Heterogeneous Catalysis — A Themed Issue in Honor of Prof. Dr. Avelino Corma

A special issue of Chemistry (ISSN 2624-8549). This special issue belongs to the section "Catalysis".

Deadline for manuscript submissions: closed (31 May 2023) | Viewed by 59015

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Inorganic Chemistry Department and the Materials Science Institute, University of Seville, Av. Américo Vespucio 49, 41092 Sevilla, Spain
Interests: heterogeneous catalysis; CO2; biomass
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Departamento de Quimica and Instituto Universitario de Tecnologia Quimica (CSIC-UPV), Universitat Politecnica de Valencia, Av. De los Naranjos s/n, 46022 Valencia, Spain
Interests: heterogeneous catalysis; photocatalysis
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

This Special Issue is dedicated to Avelino Corma in recognition of his long career dedicated to heterogeneous catalysis and his discovery of many fields related to catalysis. Starting with zeolites for oil refining and petrochemistry, Avelino was among the first to study the remarkable properties of all-silica zeolites and the role of silanol nests in promoting reactions. Avelino’s contributions to zeolite synthesis include the grafting of heteroatoms such as Ti and Sn on aluminosilicate lattices and the use of Ge’s tendency to form small three- and four-member rings to obtain extra-large-pore zeolites. His work on Ti zeolites and Ti-MCM-41 as solid epoxidation catalysts, utilizing the Lewis acid properties of isolated tripodal Ti atoms, was used to develop commercial epoxidation catalysts. He demonstrated that Sn-Beta behaves as a water-tolerant Lewis acid and can serve as a catalyst for biomass conversion in aqueous media. Avelino also introduced delaminated 2D zeolites and zeolites with imprinted transition states.

However, Prof. Avelino Corma’s contributions to heterogeneous catalysis goes beyond zeolites, extending into fields including other micro-/mesoporous materials, such as MOFs, as well as heterogeneous catalysts and the development of heterogeneous Au catalysis. More recently, he has focused on the catalytic activity and stability of the clusters of a few metal atoms. Biomass transformation for transportation fuels and platform chemicals are other domains in which the creativity and the research of Prof. Corma have inspired many developments.

This Special Issue recognizes the well-respected and significant work of Prof. Corma in the field of catalysis, encompassing over 1,600 articles.

Prof. Dr. José Antonio Odriozola
Prof. Dr. Hermenegildo García
Guest Editors

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Keywords

  • heterogeneous catalysis
  • zeolite synthesis and catalysis
  • catalysis by supported gold nanoparticles
  • mesoporous materials as solid catalysts
  • metal–organic frameworks as heterogeneous catalysts
  • photocatalysis
  • oil and refining
  • synthesis of fine chemicals
  • biomass valorization
  • biomass conversion for transportation fuels

Published Papers (32 papers)

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17 pages, 4430 KiB  
Article
Exploring the Effect of Sn Addition to Supported Au Nanoparticles on Reducible/Non-Reducible Metal Oxides Supports for Alkane Oxidation
by Marta Stucchi, Alessandro Vomeri, Sándor Stichleutner, Károly Lázár, Emanuela Pitzalis, Claudio Evangelisti and Laura Prati
Chemistry 2023, 5(3), 1560-1576; https://doi.org/10.3390/chemistry5030107 - 21 Jul 2023
Viewed by 1179
Abstract
Acetone-stabilized Au- and Sn-solvated metal atoms (SMAs) were used as to obtain Au- and AuSn-supported catalysts by simple impregnation on a reducible (TiO2) and a non-reducible (Al2O3) metal-oxide. Their catalytic behaviour was investigated for cyclohexane oxidation to [...] Read more.
Acetone-stabilized Au- and Sn-solvated metal atoms (SMAs) were used as to obtain Au- and AuSn-supported catalysts by simple impregnation on a reducible (TiO2) and a non-reducible (Al2O3) metal-oxide. Their catalytic behaviour was investigated for cyclohexane oxidation to cyclohexanol and cyclohexanone (KA oil), and their morphological and physical properties were studied by TEM, STEM-EDS and 119Sn-Mössbauer spectroscopy. The catalytic results firstly demonstrated that the bare supports played a role on the reaction mechanism, slowing down the formation of the oxidation products and directing the radical formation. Hereinafter, the comparison between the monometallic Au-supported catalysts and the corresponding bimetallic Au-Sn catalysts allowed for the understanding of the potential role of Sn. 119Sn-Mössbauer characterization analyses showed the presence of SnO2, which was recognized to favour the electrons’ exchange to form radicals, interacting with oxygen. Such interaction, in particular, could be favoured by the co-presence of Au. Moreover, the same metal composition on the catalyst surface resulted in a different catalytic behaviour depending on the support. Full article
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17 pages, 6208 KiB  
Article
Catalytic Performances of Co/TiO2 Catalysts in the Oxidative Dehydrogenation of Ethane to Ethylene: Effect of CoTiO3 and Co2TiO4 Phase Formation
by Hanane Mahir, Younes Brik, Abdallah Benzaouak, Eleonora La Greca, Luca Consentino, Mohamed Kacimi, Adnane El Hamidi and Leonarda Francesca Liotta
Chemistry 2023, 5(3), 1518-1534; https://doi.org/10.3390/chemistry5030104 - 06 Jul 2023
Cited by 1 | Viewed by 1237
Abstract
Co/TiO2 catalysts with different cobalt loadings (3.8, 7.5 and 15 wt%) were prepared by impregnation method of Co(NO3)2 6H2O over titania. Samples containing Co(NO3)2·6H2O and TiO2 in stoichiometric proportions in [...] Read more.
Co/TiO2 catalysts with different cobalt loadings (3.8, 7.5 and 15 wt%) were prepared by impregnation method of Co(NO3)2 6H2O over titania. Samples containing Co(NO3)2·6H2O and TiO2 in stoichiometric proportions in order to obtain CoTiO3 and Co2 TiO4 phases were also synthesized. The effect of the calcination treatment at two different temperatures, 550 and 1150 °C, was investigated. Characterizations by several techniques, such as XRD, UV–vis–NIR, DRS, Raman and XPS, were carried out. XRD showed the coexistence of three phases: CoTiO3; Co2TiO4 and Co3O4 after calcination at 550 °C, while calcination at high temperature (1150 °C) led to single-phase systems (CoTiO3 or Co2TiO4). Diffuse reflection and XPS spectroscopy showed that divalent cobalt occupies octahedral sites in the ilmenite phase, and both tetrahedral and octahedral sites in the spinel phase. The catalytic performances of the prepared catalysts were evaluated in the oxidative dehydrogenation reaction (ODH) of ethane to ethylene, as a function of the Co content for Co/TiO2 catalysts and as a function of the calcination temperatures for the CoTiO3 and Co2TiO4 phases. Co(7.5)/TiO2 was the most active, although the conversion of ethane decreased in the first 150 min of the reaction, reaching values comparable to those of Co2TiO4 and CoTiO3; however, Co(7.5)/TiO2 was confirmed as having the best selectivity to ethylene in comparison with the bulk phases, CoTiO3 and Co2TiO4. The influence of the reaction mixture composition, specifically the presence of water, at different percentages, was investigated. There is a decrease in the overall ethane conversion and an increase in the ethylene selectivity when the percentage of water increases. This behavior can likely be attributed to an increase in the surface concentration of hydroxyl species (OH), resulting in heightened surface acidity. Full article
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12 pages, 1890 KiB  
Article
Au Single Metal Atom for Carbon Dioxide Reduction Reaction
by Anna Vidal-López, Sergio Posada-Pérez, Miquel Solà and Albert Poater
Chemistry 2023, 5(2), 1395-1406; https://doi.org/10.3390/chemistry5020095 - 05 Jun 2023
Cited by 2 | Viewed by 1766
Abstract
CO2 is the gas that contributes the most to the greenhouse effect and, therefore, to global warming. One of the greatest challenges facing humanity is the reduction of the concentration of CO2 in the air. Here, we analyze the possible use [...] Read more.
CO2 is the gas that contributes the most to the greenhouse effect and, therefore, to global warming. One of the greatest challenges facing humanity is the reduction of the concentration of CO2 in the air. Here, we analyze the possible use of Au1@g-C3N4 electrocatalyst to transform CO2 into added-value products. We use density functional theory (DFT) to determine the reaction Gibbs energies for eight electron–proton transfer reaction paths of the electrochemical carbon dioxide reduction reaction (CO2RR) using a single Au atom supported on 2D carbon nitride support. Our simulations classify the Au1@g-C3N4 electrocatalysts as “beyond CO” since their formation is energetically favored, although their strong binding with a Au single atom does not allow the desorption process. DFT calculations revealed that the lowest energy pathway is CO2 (g) → COOH* → CO* → HCO* → HCOH* → CH2OH* → CH2* → CH3* → CH4 (g), where the first hydrogenation of CO to HCO is predicted as the rate-limiting step of the reaction with slightly lower potential than predicted for Cu electrodes, the most effective catalysts for CO2RR. Methane is predicted to be the main reaction product after eight proton–electron transfers (CO2 + 8 H+ + 8e → CH4 + 2H2O). The generation of formaldehyde is discarded due to the large formation energy of the adsorbed moiety and the production of methanol is slightly less favorable than methane formation. Our computational study helps to identify suitable electrocatalysts for CO2RR by reducing the amount of metal and using stable and low-cost supports. Full article
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12 pages, 1777 KiB  
Article
Probing Low-Temperature OCM Performance over a Dual-Domain Catalyst Bed
by Baoting Huang, Jin Wang, Dina Shpasser and Oz M. Gazit
Chemistry 2023, 5(2), 1101-1112; https://doi.org/10.3390/chemistry5020075 - 08 May 2023
Cited by 1 | Viewed by 1466
Abstract
The Mn-Na2WO4/SiO2 catalyst is regarded as the most promising catalyst for the oxidative coupling of methane (OCM). Despite its remarkable performance, the Mn-Na2WO4/SiO2 catalyst requires a high reaction temperature (>750 °C) to show [...] Read more.
The Mn-Na2WO4/SiO2 catalyst is regarded as the most promising catalyst for the oxidative coupling of methane (OCM). Despite its remarkable performance, the Mn-Na2WO4/SiO2 catalyst requires a high reaction temperature (>750 °C) to show significant activity, a temperature regime that simultaneously causes quick deactivation. In the current work, we show that the benefits of this catalyst can be leveraged even at lower reaction temperatures by a using a stacked catalyst bed, which includes also a small amount of 5% La2O3/MgO on-top- of the Mn-Na2WO4/SiO2 catalyst. The simple stacking of the two catalysts provides >7-fold higher activity and ~1.4-fold higher C2 yield at 705 °C compared to Mn-Na2WO4/SiO2 and La2O3/MgO, respectively. We specifically show that the enhanced OCM performance is associated with synergistic interactions between the two catalyst domains and study their origin. Full article
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13 pages, 7345 KiB  
Article
Production of Alkyl Levulinates from Carbohydrate-Derived Chemical Intermediates Using Phosphotungstic Acid Supported on Humin-Derived Activated Carbon (PTA/HAC) as a Recyclable Heterogeneous Acid Catalyst
by Nivedha Vinod and Saikat Dutta
Chemistry 2023, 5(2), 800-812; https://doi.org/10.3390/chemistry5020057 - 06 Apr 2023
Viewed by 1686
Abstract
This work reports a straightforward and high-yielding synthesis of alkyl levulinates (ALs), a class of promising biofuel, renewable solvent, and chemical feedstock of renewable origin. ALs were prepared by the acid-catalyzed esterification of levulinic acid (LA) and by the alcoholysis of carbohydrate-derived chemical [...] Read more.
This work reports a straightforward and high-yielding synthesis of alkyl levulinates (ALs), a class of promising biofuel, renewable solvent, and chemical feedstock of renewable origin. ALs were prepared by the acid-catalyzed esterification of levulinic acid (LA) and by the alcoholysis of carbohydrate-derived chemical platforms, such as furfuryl alcohol (FAL) and α-angelica lactone (α-AGL). Phosphotungstic acid (PTA) was chosen as the solid acid catalyst for the transformation, which was heterogenized on humin-derived activated carbon (HAC) for superior recyclability. Using HAC as catalyst support expands the scope of valorizing humin, a complex furanic resin produced inevitably as a side product (often considered waste) during the acid-catalyzed hydrolysis/dehydration of sugars and polymeric carbohydrates. Under optimized conditions (150 °C, 7 h, 25 wt.% of 20%PTA/HAC-600 catalyst), ethyl levulinate (EL) was obtained in an 85% isolated yield starting from FAL. Using the general synthetic protocol, EL was isolated in 88% and 84% yields from LA and α-AGL, respectively. The 20%PTA/HAC-600 catalyst was successfully recovered from the reaction mixture and recycled for five cycles. A marginal loss in the yield of ALs was observed in consecutive catalytic cycles due to partial leaching of PTA from the HAC support. Full article
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9 pages, 2987 KiB  
Communication
Defective PrOx for Efficient Electrochemical NO2-to-NH3 in a Wide Potential Range
by Shunhan Jia, Xingxing Tan, Limin Wu, Jiaqi Feng, Libing Zhang, Liang Xu, Ruhan Wang, Xiaofu Sun and Buxing Han
Chemistry 2023, 5(2), 753-761; https://doi.org/10.3390/chemistry5020053 - 29 Mar 2023
Viewed by 1770
Abstract
Electrocatalytic reduction of nitrite (NO2) is a sustainable and carbon-neutral approach to producing green ammonia (NH3). We herein report the first work on building defects on PrOx for electrochemical NO2 reduction to NH3, [...] Read more.
Electrocatalytic reduction of nitrite (NO2) is a sustainable and carbon-neutral approach to producing green ammonia (NH3). We herein report the first work on building defects on PrOx for electrochemical NO2 reduction to NH3, and demonstrate a high NH3 yield of 2870 μg h−1 cm−2 at the optimal potential of –0.7 V with a faradaic efficiency (FE) of 97.6% and excellent FEs of >94% at a wide given potential range (−0.5 to −0.8 V). The kinetic isotope effect (KIE) study suggested that the reaction involved promoted hydrogenation. Theoretical calculations clarified that there was an accelerated rate-determining step of NO2 reduction on PrOx. The results also indicated that PrOx could be durable for long-term electrosynthesis and cycling tests. Full article
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23 pages, 5972 KiB  
Article
Synthesis and Structure of COE-11, a New Borosilicate Zeolite with a Two-Dimensional Pore System of 12-Ring Channels
by Bernd Marler, Hermann Gies, Trees De Baerdemaeker, Ulrich Müller, Andrei-Nicolae Parvulescu, Weiping Zhang, Toshiyuki Yokoi, Feng-Shou Xiao, Xiangju Meng, Dirk De Vos and Ute Kolb
Chemistry 2023, 5(2), 730-752; https://doi.org/10.3390/chemistry5020052 - 28 Mar 2023
Cited by 1 | Viewed by 1597
Abstract
The new zeolite, COE-11, was synthesized at 155 °C to 168 °C by hydrothermal synthesis from a reaction mixture of SiO2/tetraethylammonium hydroxide/H3BO3/NaOH/H2O. Because tetraethylammonium is an unspecific structure directing agent, COE-11 crystallizes in all cases [...] Read more.
The new zeolite, COE-11, was synthesized at 155 °C to 168 °C by hydrothermal synthesis from a reaction mixture of SiO2/tetraethylammonium hydroxide/H3BO3/NaOH/H2O. Because tetraethylammonium is an unspecific structure directing agent, COE-11 crystallizes in all cases together with at least one impurity phase from a selection of phases: zeolite types *BEA, CHA, FER, MFI, MOR, MTW; the layered silicates magadiite and kenyaite; and searlsite and silica polymorph quartz. The crystal structure was solved from 3D electron diffraction (3D ED) data. Subsequent structure refinements of X-ray powder diffraction (PXRD) data and single crystal electron diffraction data converged to residual values of RF = 0.039, chi2 = 3.6 (PXRD) and RF = 21.81% (3D ED) confirming the structure model. COE-11 crystallizes in space group C2 with unit cell dimensions of a0 = 17.3494(11) Å, b0 = 17.3409(11) Å, c0 = 14.2789(4) Å and β = 113.762(2) °. The structure of COE-11 is characterized by a microporous borosilicate framework with intersecting, highly elliptical 12-ring channels running parallel (110) and (1–10) and forming a two-dimensional pore system. The Rietveld refinement provided a hint that boron partly substitutes silicon on three specific T sites of the framework. The idealized chemical composition of as-made COE-11 is [(CH3CH2)4N]4[B4Si62O132] per unit cell. Physico-chemical characterization using solid-state NMR spectroscopy, SEM, TG-DTA, and ATR-FTIR spectroscopy confirmed that COE-11 is a microporous borosilicate zeolite. COE-11 is structurally closely related to zeolite beta polymorph B but differs concerning the dimensionality of the pore system, which is 2D instead of 3D. Full article
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10 pages, 2354 KiB  
Article
UiO-66 MOF-Derived Ru@ZrO2 Catalysts for Photo-Thermal CO2 Hydrogenation
by Fernando Almazán, Marta Lafuente, Amaya Echarte, Mikel Imizcoz, Ismael Pellejero and Luis M. Gandía
Chemistry 2023, 5(2), 720-729; https://doi.org/10.3390/chemistry5020051 - 25 Mar 2023
Cited by 3 | Viewed by 1990
Abstract
The use of metal–organic frameworks (MOFs) as templates or precursors in the manufacture of heterogeneous catalysts is highly attractive due to the transfer of MOFs’ inherent porosity and homogeneous metallic distribution to the derived structure. Herein, we report on the preparation of MOF-derived [...] Read more.
The use of metal–organic frameworks (MOFs) as templates or precursors in the manufacture of heterogeneous catalysts is highly attractive due to the transfer of MOFs’ inherent porosity and homogeneous metallic distribution to the derived structure. Herein, we report on the preparation of MOF-derived Ru@ZrO2 catalysts by controlled thermal treatment of zirconium-based MOF UiO-66 with ruthenium moieties. Ru3+ (3 or 10 mol%) precursor was added to UiO-66 synthesis and, subsequently, the as-synthesized hybrid structure was calcined in flowing air at different temperatures (400–600 °C) to obtain ZrO2-derived oxides doped with highly dispersed Ru metallic clusters. The materials were tested for the catalytic photo-thermal conversion of CO2 to CH4. Methanation experiments were conducted in a continuous flow (feed flow rate of 5 sccm and 1:4 CO2 to H2 molar ratio) reactor at temperatures from 80 to 300 °C. Ru0.10@ZrO2 catalyst calcined at 600 °C was able to hydrogenate CO2 to CH4 with production rates up to 65 mmolCH4·gcat.–1·h–1, CH4 yield of 80% and nearly 100% selectivity at 300 °C. The effect of the illumination was investigated with this catalyst using a high-power visible LED. A CO2 conversion enhancement from 18% to 38% was measured when 24 sun of visible LED radiation was applied, mainly due to the increase in the temperature as a result of the efficient absorption of the radiation received. MOF-derived Ru@ZrO2 catalysts have resulted to be noticeably active materials for the photo-thermal hydrogenation of CO2 for the purpose of the production of carbon-neutral methane. A remarkable effect of the ZrO2 crystalline phase on the CH4 selectivity has been found, with monoclinic zirconia being much more selective to CH4 than its cubic allotrope. Full article
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14 pages, 3086 KiB  
Article
Comparison of Cu-CHA-Zeolites in the Hybrid NSR-SCR Catalytic System for NOx Abatement in Mobile Sources
by Sergio Molina-Ramírez, Marina Cortés-Reyes, Concepción Herrera, María Ángeles Larrubia and Luis José Alemany
Chemistry 2023, 5(1), 602-615; https://doi.org/10.3390/chemistry5010043 - 10 Mar 2023
Viewed by 1569
Abstract
DeNOx activity in a NSR–SCR hybrid system of two copper-containing chabazite-type zeolitic catalysts was addressed. A Pt-Ba-K/Al2O3 model catalyst was used as the NSR (NOx storage and reduction) catalyst. For the SCR (selective catalytic reduction) system, two Cu-CHA [...] Read more.
DeNOx activity in a NSR–SCR hybrid system of two copper-containing chabazite-type zeolitic catalysts was addressed. A Pt-Ba-K/Al2O3 model catalyst was used as the NSR (NOx storage and reduction) catalyst. For the SCR (selective catalytic reduction) system, two Cu-CHA zeolites were synthesized employing a single hydrothermal synthesis method assisted with ultrasound and incorporating Cu in a 2 wt.%, 2Cu-SAPO-34 and 2Cu-SSZ-13. The prepared catalysts were characterized, and the crystallinity, surface area, pore size, HR-TEM and EDX mapping, coordination of Cu ions and acidity were compared. The NH3 storage capacity of the SCR catalysts was 1890 and 837 μmol NH3·gcat1 for 2Cu-SAPO-34 and 2Cu-SSZ-13, respectively. DeNOx activity was evaluated for the single NSR system and the double-bed NSR–SCR by employing alternating lean (3%O2) and rich (1%H2) cycles, maintaining a concentration of 600 ppm NO, 1.5% H2O and 0.3% CO2 between 200 and 350 °C. The addition of the SCR system downstream of the NSR catalyst significantly improved NOx conversion mainly at low temperature, maintaining the selectivity to N2 above 80% and reaching values above 90% at 250 °C when the 2Cu-SSZ-13 catalyst was located. The total reduction in the production of NH3 and ~2% of N2O was observed when comparing the NSR–SCR configuration with the single NSR catalyst. Full article
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13 pages, 2525 KiB  
Article
Selective Styrene Oxidation Catalyzed by Phosphate Modified Mesoporous Titanium Silicate
by Rupak Chatterjee, Avik Chowdhury, Sudip Bhattacharjee, Rajaram Bal and Asim Bhaumik
Chemistry 2023, 5(1), 589-601; https://doi.org/10.3390/chemistry5010042 - 10 Mar 2023
Cited by 2 | Viewed by 1642
Abstract
Selective oxidation of organics over an efficient heterogeneous catalyst under mild liquid phase conditions is a very demanding chemical reaction. Herein, we first report the modification of the surface of mesoporous silica MCM-41 material by phosphate for the efficient incorporation of Ti(IV) in [...] Read more.
Selective oxidation of organics over an efficient heterogeneous catalyst under mild liquid phase conditions is a very demanding chemical reaction. Herein, we first report the modification of the surface of mesoporous silica MCM-41 material by phosphate for the efficient incorporation of Ti(IV) in the silica framework to obtain highly ordered 2D hexagonal mesoporous material STP-1. STP-1 has been synthesized by using tetraethyl orthosilicate, triethyl phosphate, and titanium isopropoxide as Si, P, and Ti precursors, respectively, in the presence of cationic surfactant cetyltrimethylammonium bromide (CTAB) under hydrothermal conditions. The observed specific surface area and pore volume of STP-1 were 878 m2g−1 and 0.75 ccg−1, respectively. Mesoporous STP-1 has been thoroughly characterized by XRD, FT-IR, Raman spectroscopy, SEM, and TEM analyses. Titanium incorporation (Ti/Si = 0.006) was confirmed from the EDX analysis. This mesoporous STP-1 was used as a heterogeneous catalyst for the selective oxidation of styrene into benzaldehye in the presence of dilute aqueous H2O2 as an oxidizing agent. Various reaction parameters such as the reaction time, the reaction temperature, and the styrene/H2O2 molar ratio were systematically studied in this article. Under optimized reaction conditions, the selectivity of benzaldehyde could reach up to 93.8% from styrene over STP-1. Further, the importance of both titanium and phosphate in the synthesis of STP-1 for selective styrene oxidation was examined by comparing the catalytic result with only a phosphate-modified mesoporous silica material, and it suggests that both titanium and phosphate synergistically play an important role in the high selectivity of benzaldehyde in the liquid phase oxidation of styrene. Full article
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18 pages, 5995 KiB  
Article
Ni-Mg/Al Mixed Oxides Prepared from Layered Double Hydroxides as Catalysts for the Conversion of Furfural to Tetrahydrofurfuryl Alcohol
by Abdulaziz Aldureid, Daniel Montané, Jordi Llorca and Francesc Medina
Chemistry 2023, 5(1), 571-588; https://doi.org/10.3390/chemistry5010041 - 09 Mar 2023
Cited by 1 | Viewed by 1470
Abstract
Ni-Mg/Al mixed oxide catalysts (Ni2Al, Ni2Mg1Al, and Ni1Mg1Al) obtained from layered double hydroxides (LDHs) were tested on the one-pot production of tetrahydrofurfuryl alcohol (TFA) from furfural (FF). Upon calcination at 400 [...] Read more.
Ni-Mg/Al mixed oxide catalysts (Ni2Al, Ni2Mg1Al, and Ni1Mg1Al) obtained from layered double hydroxides (LDHs) were tested on the one-pot production of tetrahydrofurfuryl alcohol (TFA) from furfural (FF). Upon calcination at 400 °C and reduction at 500 °C, the LDHs gave catalysts containing small nickel crystallites (<4 nm) dispersed on mixtures of metal oxides and spinel structures. Complete conversion of FF (>99.5%) was achieved on all the catalysts after 4 h at 190 °C and 5.0 MPa of H2 using 5 wt.% FF in ethanol and a furfural-to-catalyst mass ratio of 7.44 g/g. TFA evolved from the sequential hydrogenation of FF to furfuryl alcohol (FA) to TFA. Competing reaction routes involved decarbonylation of FF to furan (FUR) followed by hydrogenation to tetrahydrofuran (THF) or hydrogenolysis to n-butane (BU) and the hydrogenation of the carbonyl group in FF to form 2-methyl furan (mFUR) and its hydrogenation to 2-methyltetrahydrofuran (mTHF). A third competing route consisted of the nucleophilic addition of FF with ethanol and with FA to form acetals (such as 2-(diethoxymethyl)furan, FDA), which were later converted to difurfuryl ether (DFE) and tetrahydrofurfuryl ethyl ether (TFEE) as final products. Hydrogen pressure favored the production of TFA and diminished the formation of acetals, while temperature reduced the capacity of the catalyst to hydrogenate the furan ring, thus reducing TFA and increasing FA and FUR. An 80% yield to TFA was achieved with the Ni2Mg1Al catalysts after 6 h at 190 °C and 50 bar H2, but a variety of coproducts were present at low concentration. Testing of the catalysts in gas-phase hydrogenation conditions at atmospheric pressure revealed a poorer performance, with FA as the main product. Full article
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15 pages, 3864 KiB  
Article
Conversion of Ethanol to Butadiene over Binary MgO-SiO2 Mixed Oxides Prepared by the Ammonia Evaporation Method
by Ismail Bin Samsudin, Stephan Jaenicke and Gaik-Khuan Chuah
Chemistry 2023, 5(1), 544-558; https://doi.org/10.3390/chemistry5010039 - 07 Mar 2023
Viewed by 1575
Abstract
The ammonia evaporation method, originally applied for the preparation of highly dispersed silica-supported copper catalysts, was used to synthesize magnesia-silica for the one-step conversion of ethanol to 1,3-butadiene. The MgO-SiO2 catalysts obtained by this method contained a high fraction of magnesium silicate [...] Read more.
The ammonia evaporation method, originally applied for the preparation of highly dispersed silica-supported copper catalysts, was used to synthesize magnesia-silica for the one-step conversion of ethanol to 1,3-butadiene. The MgO-SiO2 catalysts obtained by this method contained a high fraction of magnesium silicate hydrates, which are associated with enhanced butadiene selectivity. These catalysts were benchmarked against those prepared by a conventional wet-kneading method. A Mg/Si molar ratio of 4 was optimal, forming butadiene with 37% yield, which is far superior to the 15% yield obtained with MgO-SiO2 formed by wet-kneading. At 475 °C and a WHSV of 3.2 h−1, a productivity of 0.612 gBD gcat−1 h−1 was measured without the catalyst suffering from deactivation, even after 52 h TOS. The catalysts were characterized by spectroscopic and thermal techniques to elucidate their physicochemical properties and explain the differences in the catalytic performance. The presence of magnesium silicate hydrates gave a balance of surface acidity and basicity, which greatly improved butadiene formation. The open morphology of MgO-SiO2 with vertically arranged platelets and the presence of large pores are proposed to contribute to the stability of the catalyst. Full article
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18 pages, 4009 KiB  
Article
Gold Clusters Immobilized by Post-Synthesis Methods on Thiol-Containing SBA-15 Mesoporous Materials for the Aerobic Oxidation of Cyclohexene: Influence of Light and Hydroperoxide
by Rafael Delgado, Carlos Márquez-Álvarez, Álvaro Mayoral, Ramón de la Serna, Javier Agúndez and Joaquín Pérez-Pariente
Chemistry 2023, 5(1), 526-543; https://doi.org/10.3390/chemistry5010038 - 07 Mar 2023
Viewed by 1411
Abstract
Gold nanospecies produced by a historically inspired two-liquid phase system were immobilized on plate-like mesoporous silica, SBA-15, functionalized with mercaptopropyl groups by a post-synthesis method, and the resulting materials were tested in the oxidation of cyclohexene with molecular oxygen at atmospheric pressure. The [...] Read more.
Gold nanospecies produced by a historically inspired two-liquid phase system were immobilized on plate-like mesoporous silica, SBA-15, functionalized with mercaptopropyl groups by a post-synthesis method, and the resulting materials were tested in the oxidation of cyclohexene with molecular oxygen at atmospheric pressure. The main purpose of this approach was to compare the physicochemical properties and catalytic performance of these materials with those of previously reported related materials functionalized by in situ methods during synthesis. In addition, catalytic tests under ambient lighting and darkness and also in the presence and absence of the initiator tert-butyl hydroperoxide (TBHP) were carried out. The samples were characterized by chemical analysis, N2 adsorption/desorption, TGA, SEM, HRTEM, UV-vis spectroscopy and XPS. Gold nanoclusters and isolated gold atoms but no AuNPs were found in the catalysts (0.31–2.69 wt.% of gold). The XPS shows that nearly 60% of the -SH groups (1.33 wt.% of S) were oxidized to sulphonic groups upon gold immobilization. The AuNCs and isolated gold atoms evolved in the the reaction medium to form AuNPs. The activity of the samples was lower than that of the catalysts supported on related S-bearing SBA-15 functionalized in situ, which was attributed to their different Au/S ratios, which in turn regulated the evolutionary process of the gold species during the reaction. The catalysts turned out to be inactive in darkness, which evidences that the cyclohexene oxidation carried out at ambient illumination is actually photocatalyzed by the AuNPs formed in situ during the reaction. The TBHP initiator is required to obtain the activity in order to counteract the inhibitors of cyclohexene auto-oxidation present in the commercial reagent. On the other hand, no major differences in the selectivity among the different catalysts and reactions were observed, with 2-cyclohexen-1-one and 2-cyclohexen-1-ol resulting from the allylic oxidation as main products (selectivity of (one + ol) ~80% at a conversion ≥ 35%; one/ol~2). Full article
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15 pages, 4126 KiB  
Article
Kinetic and Spectroscopic Studies of Methyl Ester Promoted Methanol Dehydration to Dimethyl Ether on ZSM-5 Zeolite
by Zhiqiang Yang, Benjamin J. Dennis-Smither, Zhuoran Xu, Zhenchao Zhao, Meiling Guo, Neil Sainty, Guangjin Hou, Xuebin Liu and Glenn J. Sunley
Chemistry 2023, 5(1), 511-525; https://doi.org/10.3390/chemistry5010037 - 06 Mar 2023
Viewed by 1603
Abstract
Methyl carboxylate esters have been shown to be potent promoters of low-temperature methanol dehydration to dimethyl ether (DME) using various zeolite catalysts. In the present work, catalytic kinetic studies, in-situ Fourier-transform infrared spectroscopy (FT-IR) and solid-state nuclear magnetic resonance spectroscopy (NMR) techniques were [...] Read more.
Methyl carboxylate esters have been shown to be potent promoters of low-temperature methanol dehydration to dimethyl ether (DME) using various zeolite catalysts. In the present work, catalytic kinetic studies, in-situ Fourier-transform infrared spectroscopy (FT-IR) and solid-state nuclear magnetic resonance spectroscopy (NMR) techniques were used to elucidate the promotional mechanism of methyl carboxylate esters on methanol dehydration to DME, using the medium pore zeolite H-ZSM-5 (MFI) as the catalyst. Kinetic studies were performed using the very potent methyl n-hexanoate promoter. The DME yield was dependent on both the methanol and methyl n-hexanoate partial pressures across the temperature ranges used in this study (110 to 130 °C). This is consistent with the promoted reaction being a bimolecular reaction between methanol and ester species adsorbed at the catalyst active sites, via an SN2 type reaction, as previously postulated. The in-situ FT-IR studies reveal that the Brønsted acid (BA) sites on H-ZSM-5 were very rapidly titrated by ester carbonyl group adsorption and bonded more strongly with esters than with methanol. Upon methanol addition, an even lower DME formation temperature (30 °C) was observed with methyl n-hexanoate pretreated H-ZSM-5 samples in the in-situ NMR studies, further confirming the strong promotion of this methyl ester on methanol dehydration to DME. The adsorption and reactivity of different methyl esters on H-ZSM-5 indicates that while methyl formate more easily dissociates into a surface methoxy species, [Si(OMe)Al], and carboxylic acid, it is a less potent promoter than alkyl-chain-containing methyl esters in methanol dehydration to DME, which in turn did not show this dissociative behavior in the low-temperature NMR studies. This indicates that methyl alkyl carboxylates do not need to be dissociated to a surface methoxy species to promote the methanol dehydration reaction and that a bimolecular associative mechanism plays an important role in promoting DME formation. Full article
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13 pages, 997 KiB  
Article
Conversion of Sugar Di-Ketals to Bio-Hydrocarbons through Catalytic Cracking over Beta Catalysts in Fixed and Fluidized Catalytic Beds
by Cristiane Cardoso, Yiu L. Lam, Marlon B. B. de Almeida and Marcelo Maciel Pereira
Chemistry 2023, 5(1), 479-491; https://doi.org/10.3390/chemistry5010035 - 04 Mar 2023
Cited by 1 | Viewed by 1348
Abstract
Second-generation biomass (BM) can be produced in amounts that meet worldwide fuel demands. However, BM favors parallel and undesirable reactions in its transformation chain. We circumvent this problem by first modifying BM by ketalization, giving a user-friendly liquid we named BP (bio-petroleum). This [...] Read more.
Second-generation biomass (BM) can be produced in amounts that meet worldwide fuel demands. However, BM favors parallel and undesirable reactions in its transformation chain. We circumvent this problem by first modifying BM by ketalization, giving a user-friendly liquid we named BP (bio-petroleum). This study converted a representative compound of BP, DX (1,2:3,5-di-O-isopropylidene-α-D-xylofuranose), mixed with n-hexane by beta zeolites and catalysts containing beta zeolite. Beta zeolite showed low coke and high liquid product yields in converting this mixture (having 30 wt. % DX) into hydrocarbons in a fixed-bed reactor at 500 °C with a space velocity of 16 h−1 (0.3 catalyst/feed). Its performance was further improved by steam treatment (lowering the coke yield by lowering the acid site density) or incorporation into a catalyst (improving DX participation due to the active sites in the matrix). Further, by changing the conversion process from a fixed bed to a fluidized cracking unit, a much larger amount of the deactivated catalyst could be used (catalyst/feed = 3), remarkably reducing oxygenates and fully converting DX. Additionally, the green hydrocarbon efficiency (olefin, aromatics, furans, and cyclo-alkanes) of DX was approximately 77%. Hence, beta catalysts were shown to have a great potential to provide green fuels for future bio-refineries. Full article
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16 pages, 4394 KiB  
Article
Crotonaldehyde Adsorption on Cu-Pt Surface Alloys: A Quantum Mechanics Study
by Ricardo Ruvalcaba, Jonathan Guerrero-Sanchez, Noboru Takeuchi and Francisco Zaera
Chemistry 2023, 5(1), 463-478; https://doi.org/10.3390/chemistry5010034 - 03 Mar 2023
Cited by 2 | Viewed by 1662
Abstract
The adsorption of crotonaldehyde on Cu-Pt alloy surfaces was characterized by density functional theory (DFT). Two surfaces were considered: Cu2Pt/Cu(111) and Cu3Pt/Cu(111). It was determined that the presence of Pt on the surface, even when isolated as single atoms [...] Read more.
The adsorption of crotonaldehyde on Cu-Pt alloy surfaces was characterized by density functional theory (DFT). Two surfaces were considered: Cu2Pt/Cu(111) and Cu3Pt/Cu(111). It was determined that the presence of Pt on the surface, even when isolated as single atoms fully surrounded by Cu, provides additional stability for the adsorbates, increasing the magnitude of the adsorption energy by as much as 40 kJ/mol. The preferred bonding on both surfaces is via multiple coordination, with the most stable configuration being a cis arrangement with di-σ bonding of the C=O bond across a Cu–Cu bridge and an additional π bonding to a Pt atom. The fact that Pt significantly affects the adsorption of unsaturated aldehydes such as crotonaldehyde explains why the kinetics of their hydrogenation using single-atom alloy (SAA) catalysts vary with alloy composition, as we previously reported, and brings into question the simple model in which the role of Pt is only to promote the dissociation of H2. Full article
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16 pages, 4109 KiB  
Article
How Topological Differences between Two Oxide Surfaces Determine Selectivity—The Case of the Dehydra-Decyclization of Tetrahydrofuran
by Sai Praneet Batchu, Stavros Caratzoulas and Dionisios G. Vlachos
Chemistry 2023, 5(1), 422-437; https://doi.org/10.3390/chemistry5010031 - 01 Mar 2023
Cited by 1 | Viewed by 1366
Abstract
Production of butadiene from biomass-based tetrahydrofuran (THF) is explored as an alternative to the existing petroleum-based processes. Metal oxide catalysts have been shown to exhibit varying product selectivities when reacted with THF. Among those oxides, ZrO2 showed the highest selectivity for butadiene. [...] Read more.
Production of butadiene from biomass-based tetrahydrofuran (THF) is explored as an alternative to the existing petroleum-based processes. Metal oxide catalysts have been shown to exhibit varying product selectivities when reacted with THF. Among those oxides, ZrO2 showed the highest selectivity for butadiene. In contrast, Al2O3 showed the highest selectivity for the competing retro-Prins products, C3H6 and HCHO. The reasons behind the varying selectivity across oxides are unclear. In this work, we employ periodic density functional theory and mean-field microkinetic modeling to investigate the mechanism of the reaction of THF to butadiene and retro-Prins products on t-ZrO2 (101) (dry and hydrous) and on γ-Al2O3 (110). Our simulations reproduce the experimental selectivity trends. High selectivity for butadiene is promoted by the presence of neighboring Lewis acid metal sites that facilitate E1cB hydroxyl elimination from a 3-butenoxide intermediate; on hydrous Al2O3; where such neighboring Lewis acid centers are not available, the butenoxide undergoes E2 elimination and retro-Prins products ensue. The THF ring opening is rate-determining on ZrO2, whereas the γ-proton elimination that yields the 3-butenoxide intermediate is rate controlling on hydroxylated Al2O3. We conclude that the local topology around the active site greatly influences the mechanism and selectivity. Full article
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16 pages, 3813 KiB  
Article
Vapor-Phase Oxidant-Free Dehydrogenation of 2,3- and 1,4-Butanediol over Cu/SiO2 Catalyst Prepared by Crown-Ether-Assisted Impregnation
by Enggah Kurniawan, Shuya Hosaka, Masayuki Kobata, Yasuhiro Yamada and Satoshi Sato
Chemistry 2023, 5(1), 406-421; https://doi.org/10.3390/chemistry5010030 - 28 Feb 2023
Cited by 9 | Viewed by 2184 | Correction
Abstract
A silica-supported copper (Cu/SiO2) catalyst containing highly dispersed Cu nanoparticles was prepared via a crown-ether-assisted impregnation method. A 12-crown-4-ether-assisted Cu/SiO2 catalyst outperformed several Cu/SiO2 catalysts prepared with various organic additives in the dehydrogenation of 2,3- and 1,4-butanediol. It was [...] Read more.
A silica-supported copper (Cu/SiO2) catalyst containing highly dispersed Cu nanoparticles was prepared via a crown-ether-assisted impregnation method. A 12-crown-4-ether-assisted Cu/SiO2 catalyst outperformed several Cu/SiO2 catalysts prepared with various organic additives in the dehydrogenation of 2,3- and 1,4-butanediol. It was found that the catalytic activity, i.e., the formation rate of acetoin from 2,3-butanediol and that of γ-butyrolactone from 1,4-butanediol, was proportional to the copper surface area. Full article
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13 pages, 1755 KiB  
Article
Gold(III) Chloride-Mediated Transformation of Furfural to the trans-N,N-4,5-Diaminocyclopent-2-enones in the Presence of Anilines
by Marina A. Tzani and Ioannis N. Lykakis
Chemistry 2023, 5(1), 393-405; https://doi.org/10.3390/chemistry5010029 - 27 Feb 2023
Viewed by 1649
Abstract
We investigated the efficient approach of a series of trans-N,N-4,5-substituted-diaminocyclopent-2-enones (trans-DACPs) from furfural and anilines mediated by Gold(III) chloride (HAuCl4). The present protocol required a low amount of the catalysts, 1.5 mol%, open air [...] Read more.
We investigated the efficient approach of a series of trans-N,N-4,5-substituted-diaminocyclopent-2-enones (trans-DACPs) from furfural and anilines mediated by Gold(III) chloride (HAuCl4). The present protocol required a low amount of the catalysts, 1.5 mol%, open air conditions, the absence of any additives, and short reaction times. The desired trans-DACPs were isolated in good to high yields. The protocol was also applied to secondary amines, leading to the corresponding 4,5-diamino-cyclopent-2-enones in good yields. To the best of our knowledge, this is the first gold-mediated paradigm as an efficient catalyst for the formation of the cyclopentenones core-bearing C-N bonds under mild reaction conditions. Full article
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12 pages, 2128 KiB  
Article
Solvent-Assisted Adsorption of Cellulose on a Carbon Catalyst as a Pretreatment Method for Hydrolysis to Glucose
by Abhijit Shrotri, Kiko Eguchi, Lina Mahardiani, Hirokazu Kobayashi, Masakuni Yamashita, Hiroshi Yagita and Atsushi Fukuoka
Chemistry 2023, 5(1), 381-392; https://doi.org/10.3390/chemistry5010028 - 24 Feb 2023
Viewed by 1788
Abstract
Cellulose hydrolysis to glucose using a heterogeneous catalyst is a necessary step in producing bio-based chemicals and polymers. The requirement for energy-intensive pretreatments, such as ball milling, to increase the reactivity of cellulose is one of the major issues in this area. Here, [...] Read more.
Cellulose hydrolysis to glucose using a heterogeneous catalyst is a necessary step in producing bio-based chemicals and polymers. The requirement for energy-intensive pretreatments, such as ball milling, to increase the reactivity of cellulose is one of the major issues in this area. Here, we show that by using solvent-assisted adsorption as a pretreatment step, cellulose can be adsorbed on the surface of a carbon catalyst. For adsorption pretreatment, phosphoric acid (H3PO4) performed better than other solvents such as sulfuric acid (H2SO4), tetrabutylammonium fluoride/dimethyl sulfoxide (TBAF/DMSO) and 1-butyl-3-methylimidazolium chloride ([BMMI]Cl). Hydrolysis after the adsorption of cellulose and the removal of H3PO4 produced a 73% yield of glucose. Partial hydrolysis of cellulose in H3PO4 before adsorption increased the final glucose yield. The glucose yield was proportional to the number of weakly acidic functional groups on the carbon catalyst, indicating the reaction was heterogeneously catalyzed. In a preliminary lab-scale life-cycle analysis (LCA), greenhouse gas (GHG) emissions per kg of glucose produced through the hydrolysis of cellulose were calculated. The H3PO4-assisted adsorption notably reduces GHG emissions compared to the previously reported ball milling pretreatment. Full article
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17 pages, 3017 KiB  
Article
Steering the Metal Precursor Location in Pd/Zeotype Catalysts and Its Implications for Catalysis
by Luc C. J. Smulders, Johan H. van de Minkelis, Johannes D. Meeldijk, Min Tang, Anna Liutkova, Kang Cheng, S. Tegan Roberts, Glenn J. Sunley, Emiel J. M. Hensen, Petra E. de Jongh and Krijn P. de Jong
Chemistry 2023, 5(1), 348-364; https://doi.org/10.3390/chemistry5010026 - 23 Feb 2023
Cited by 2 | Viewed by 2182
Abstract
Bifunctional catalysts containing a dehydrogenation–hydrogenation function and an acidic function are widely applied for the hydroconversion of hydrocarbon feedstocks obtained from both fossil and renewable resources. It is well known that the distance between the two functionalities is important for the performance of [...] Read more.
Bifunctional catalysts containing a dehydrogenation–hydrogenation function and an acidic function are widely applied for the hydroconversion of hydrocarbon feedstocks obtained from both fossil and renewable resources. It is well known that the distance between the two functionalities is important for the performance of the catalyst. In this study, we show that the heat treatment of the catalyst precursor can be used to steer the location of the Pd precursor with respect to the acid sites in SAPO-11 and ZSM-22 zeotype materials when ions are exchanged with Pd(NH3)4(NO3)2. Two sets of catalysts were prepared based on composite materials of alumina with either SAPO-11 or ZSM-22. Pd was placed on/in the zeotype, followed by a calcination-reduction (CR) or direct reduction (DR) treatment. Furthermore, catalysts with Pd on the alumina binder were prepared. CR results in having more Pd nanoparticles inside the zeotype crystals, whereas DR yields more particles on the outer surface of the zeotype crystals as is confirmed using HAADF-STEM and XPS measurements. The catalytic performance in both n-heptane and n-hexadecane hydroconversion of the catalysts shows that having the Pd nanoparticles on the alumina binder is most beneficial for maximizing the isomer yields. Pd-on-zeotype catalysts prepared using the DR approach show intermediate performances, outperforming their Pd-in-zeotype counterparts that were prepared with the CR approach. Full article
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14 pages, 2644 KiB  
Article
Environmental Applications of Zeolites: Hydrophobic Sn-BEA as a Selective Gas Sensor for Exhaust Fumes
by Martin Jendrlin, Julien Grand, Louwanda Lakiss, Florent Dubray, Philippe Bazin, Jaafar El Fallah, Svetlana Mintova and Vladimir Zholobenko
Chemistry 2023, 5(1), 334-347; https://doi.org/10.3390/chemistry5010025 - 21 Feb 2023
Cited by 3 | Viewed by 1980
Abstract
Environmental monitoring of pollutants, such as NOx and COx, which can be facilitated by a range of gas sensors, is of considerable fundamental and practical importance. This work has been focused on the synthesis and evaluation of zeolite β with [...] Read more.
Environmental monitoring of pollutants, such as NOx and COx, which can be facilitated by a range of gas sensors, is of considerable fundamental and practical importance. This work has been focused on the synthesis and evaluation of zeolite β with tin (Sn-BEA) and dealuminated β (DeAl-BEA) zeolites. The zeolite samples have been extensively investigated by IR, UV-VIS and NMR spectroscopy, XRD, TGA, and N2 adsorption-desorption. The prepared Sn-BEA sample is characterised by the submicron particle size, an almost defect-free structure, and high hydrophobicity. Sensors containing selective microporous layers based on Sn-BEA and DeAl-BEA zeolites have been prepared and extensively tested. Both the Sn-BEA and DeAl-BEA zeolites have been deposited in thin films and evaluated as gas sensors for CO, CO2, NO, and NO2 in the presence of water vapour at room temperature. The Sn-BEA zeolite-based sensor showed high selectivity towards NO2, while the DeAl-BEA is selective towards CO2 and NO2. Full article
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20 pages, 4183 KiB  
Article
Environmental Applications of Zeolites: Preparation and Screening of Cu-Modified Zeolites as Potential CO Sensors
by Martin Jendrlin, Julien Grand, Louwanda Lakiss, Philippe Bazin, Svetlana Mintova and Vladimir Zholobenko
Chemistry 2023, 5(1), 314-333; https://doi.org/10.3390/chemistry5010024 - 20 Feb 2023
Cited by 1 | Viewed by 1605
Abstract
This work is focused on the application of Cu-containing zeolites as potential environmental sensors for monitoring carbon monoxide. A number of commercial zeolites with different structural properties (NaX, NaY, MOR, FER, BEA and ZSM-5) were modified using CuSO4, Cu(NO3) [...] Read more.
This work is focused on the application of Cu-containing zeolites as potential environmental sensors for monitoring carbon monoxide. A number of commercial zeolites with different structural properties (NaX, NaY, MOR, FER, BEA and ZSM-5) were modified using CuSO4, Cu(NO3)2 and Cu(OAc)2 solutions as copper sources to prepare Cu+-containing zeolites, since Cu+ forms stable complexes with CO at room temperature that can be monitored by infrared spectroscopy. Zeolite impregnation with Cu(NO3)2 resulted in the highest total Cu-loadings, while the Cu(OAc)2-treated samples had the highest Cu+/Cutotal ratio. Cu(NO3)2-impregnated MOR, which displayed the highest concentration of Cu+, was subjected to a number of tests to evaluate its performance as a potential CO sensor. The working temperature and concentration ranges of the sensor were determined to be from 20 to 300 °C and from 10 to 10,000 ppm, respectively. The stepwise CO desorption experiments indicated that the sensor can be regenerated at 400 °C if required. Additional analyses under realistic flow conditions demonstrated that for hydrophilic zeolites, the co-adsorption of water can compromise the sensor’s performance. Therefore, a hydrophobic Sn-BEA was utilised as a parent material for the preparation of an impregnated Cu-Sn-BEA zeolite, which exhibited superior resistance to interfering water while maintaining its sensing properties. Overall, the prepared Cu-modified zeolites showed promising potential as environmental CO sensors, displaying high sensitivity and selectivity under representative testing conditions. Full article
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20 pages, 5604 KiB  
Article
Revisiting the Impact of Tungsten on the Catalytic Properties of Ammonia-SCR V2O5-WO3/TiO2 Catalysts: Geometric vs. Electronic Effects
by Hermann Wilfried Siaka, Christophe Dujardin, Alain Moissette and Pascal Granger
Chemistry 2023, 5(1), 294-313; https://doi.org/10.3390/chemistry5010023 - 20 Feb 2023
Viewed by 1379
Abstract
The SCR performance of V2O5-WO3/TiO2 SCR-catalysts characterized by different surface W density (2.1W/nm2 and 9.5W/nm2) and different surface V density varying in the range 1–8V/nm2 has been investigated in order to clarify [...] Read more.
The SCR performance of V2O5-WO3/TiO2 SCR-catalysts characterized by different surface W density (2.1W/nm2 and 9.5W/nm2) and different surface V density varying in the range 1–8V/nm2 has been investigated in order to clarify existing controversies on the preferential involvement of electronic and geometric effects in the catalytic properties. It was found that tungsten has a weak effect on the VOx cluster size distribution through contraction of dilution effect. In contrast, the optimal interaction between W and V, when both reach their highest composition, appears to be a relevant parameter that can enhance their acidic properties and improve the catalytic efficiency in dry conditions. On the other hand, an absence of significant interaction leads to discontinuity due to deactivation. In the presence of steam, acidic properties are averaged, lowering the impact of the V to W ratio. Finally, the critical importance of acidic properties which outperform redox properties in the definition of active site is pointed out in the light of this study. Full article
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18 pages, 4873 KiB  
Article
Operando NAP-XPS Studies of a Ceria-Supported Pd Catalyst for CO Oxidation
by Xènia Garcia, Lluís Soler, Xavier Vendrell, Isabel Serrano, Facundo Herrera, Jordi Prat, Eduardo Solano, Massimo Tallarida, Jordi Llorca and Carlos Escudero
Chemistry 2023, 5(1), 1-18; https://doi.org/10.3390/chemistry5010001 - 20 Dec 2022
Cited by 3 | Viewed by 3406
Abstract
Supported Pd/CeO2 catalytic systems have been widely investigated in the low-temperature oxidation of CO (LTO CO) due to the unique oxygen storage capacity and redox properties of the ceria support, which highly influence the structural, chemical and electronic state of Pd species. [...] Read more.
Supported Pd/CeO2 catalytic systems have been widely investigated in the low-temperature oxidation of CO (LTO CO) due to the unique oxygen storage capacity and redox properties of the ceria support, which highly influence the structural, chemical and electronic state of Pd species. Herein, operando near-ambient pressure XPS (NAP-XPS) technique has allowed the study of a conventional Pd/CeO2 catalyst surface during the CO oxidation reaction under experimental conditions closer to the actual catalytic reaction, unfeasible with other surface science techniques that demand UHV conditions. SEM, HRTEM and XRD analyses of the powder catalyst, prepared by conventional incipient wetness impregnation, reveal uniformly CeO2-loaded Pd NPs of less than 2 nm size, which generated an increase in oxygen vacancies with concomitant ceria reduction, as indicated by H2-TPR and Raman measurements. Adsorbed peroxide (O22−) species on the catalyst surface could also be detected by Raman spectra. Operando NAP-XPS results obtained at the ALBA Synchrotron Light Source revealed two kinds of Pd species under reaction conditions, namely PdOx and PdII ions in a PdxCe1−xO2−δ solution, the latter one appearing to be crucial for the CO oxidation. By means of a non-destructive depth profile analysis using variable synchrotron excitation energies, the location and the role of these palladium species in the CO oxidation reaction could be clarified: PdOx was found to prevail on the upper surface layers of the metallic Pd supported NPs under CO, while under reaction mixture it was rapidly depleted from the surface, leaving a greater amount in the subsurface layers (7% vs. 12%, respectively). On the contrary, the PdxCe1−xO2−δ phase, which was created at the Pd–CeO2 interface in contact with the gas environment, appeared to be predominant on the surface of the catalyst. Its presence was crucial for CO oxidation evolution, acting as a route through which active oxygen species could be transferred from ceria to Pd species for CO oxidation. Full article
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15 pages, 1729 KiB  
Article
Acid Site Density as a Kinetic Descriptor of Catalytic Reactions over Zeolites
by Dmitry Yu. Murzin
Chemistry 2022, 4(4), 1609-1623; https://doi.org/10.3390/chemistry4040105 - 23 Nov 2022
Cited by 4 | Viewed by 1398
Abstract
A mathematical framework for the quantitative description of site density dependence of catalytic data (activity and selectivity) was developed considering that changes in the electrostatic contribution to the Gibbs energy of an elementary reaction on the acid sites in zeolites depend on the [...] Read more.
A mathematical framework for the quantitative description of site density dependence of catalytic data (activity and selectivity) was developed considering that changes in the electrostatic contribution to the Gibbs energy of an elementary reaction on the acid sites in zeolites depend on the proximity of these sites. For the two-step sequence with the most abundant surface intermediate, an expression for turnover frequency explicitly containing the acid site density was derived. The treatment was extended to linear sequences of elementary reaction and analysis of the acid site density on selectivity in parallel and consecutive reactions, allowing to quantitatively relate the ratio between products for such reactions. Experimental data on Prins condensation of isopulegol with acetone and transformations of syngas over mesoporous H-ZSM-5 supported cobalt nanoparticles to a mixture of iso- and normal hydrocarbons were used as a show case. Full article
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Review

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14 pages, 4192 KiB  
Review
Hydrogen Evolution upon Ammonia Borane Solvolysis: Comparison between the Hydrolysis and Methanolysis Reactions
by Naixin Kang, Changlong Wang and Didier Astruc
Chemistry 2023, 5(2), 886-899; https://doi.org/10.3390/chemistry5020060 - 13 Apr 2023
Cited by 4 | Viewed by 1815
Abstract
Hydrogen (H2) production is a key challenge for green carbon-free sustainable energy. Among the H2 evolution methods from H-rich materials, ammonia borane (AB) solvolysis stands as a privileged source under ambient and sub-ambient conditions given its stability, non-toxicity, and solubility [...] Read more.
Hydrogen (H2) production is a key challenge for green carbon-free sustainable energy. Among the H2 evolution methods from H-rich materials, ammonia borane (AB) solvolysis stands as a privileged source under ambient and sub-ambient conditions given its stability, non-toxicity, and solubility in protic solvents, provided suitable and optimized nanocatalysts are used. In this paper dedicated to Prof. Avelino Corma, we comparatively review AB hydrolysis and alcoholysis (mostly methanolysis) in terms of nanocatalyst performances and discuss the advantages and inconveniences of these two AB solvolysis methods including AB regeneration. Full article
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29 pages, 15587 KiB  
Review
Cesium Heteropolyacid Salts: Synthesis, Characterization and Activity of the Solid and Versatile Heterogeneous Catalysts
by Marcio Jose da Silva, Alana Alves Rodrigues and Neide Paloma Gonçalves Lopes
Chemistry 2023, 5(1), 662-690; https://doi.org/10.3390/chemistry5010047 - 21 Mar 2023
Cited by 4 | Viewed by 2280
Abstract
Keggin-type heteropolyacid cesium salts have been regarded as potential candidates for heterogeneous catalytic reactions. This review describes the success of Keggin-type heteropolyacids cesium salts (Cs-HPA salts) as efficient catalysts in various synthesis processes. The Cs-HPA catalysts can be synthesized as solid salts through [...] Read more.
Keggin-type heteropolyacid cesium salts have been regarded as potential candidates for heterogeneous catalytic reactions. This review describes the success of Keggin-type heteropolyacids cesium salts (Cs-HPA salts) as efficient catalysts in various synthesis processes. The Cs-HPA catalysts can be synthesized as solid salts through the metathesis of a solution containing precursor HPA and another solution containing soluble Cs salt, which will give Cs-HPA salt as a solid precipitate. Alternatively, they can be also obtained from the commercial precursor HPA. In this review, all the routes to prepare the different cesium salts (i.e., saturated, lacunar, metal-doped) were described. These salts can be used in acid-catalyzed reactions (i.e., esterification, etherification, acetalization, dehydration) or oxidative transformations (oxidative esterification, oxidation, epoxidation). All of these reactions were addressed herein. Aspects related to the synthesis and characterization of these catalyst salts were discussed. This review aims to discuss the most pertinent heterogeneous catalytic systems based on Keggin HPA Cs salts. The focus was to correlate the physicochemical properties of these salts with their catalytic activity. Ultimately, the most recent advances achieved in the applications of these Cs-HPA salts as catalysts in the synthesis of industrial interest compounds were discussed. Cesium heteropoly salts are an alternative to the traditional soluble mineral acids as well as to solid-supported catalysts. Full article
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19 pages, 3864 KiB  
Review
Niche Applications of MXene Materials in Photothermal Catalysis
by Zhiyi Wu, Jiahui Shen, Chaoran Li, Chengcheng Zhang, Chunpeng Wu, Zimu Li, Xingda An and Le He
Chemistry 2023, 5(1), 492-510; https://doi.org/10.3390/chemistry5010036 - 06 Mar 2023
Cited by 7 | Viewed by 2998
Abstract
MXene materials have found emerging applications as catalysts for chemical reactions due to their intriguing physical and chemical applications. In particular, their broad light response and strong photothermal conversion capabilities are likely to render MXenes promising candidates for photothermal catalysis, which is drawing [...] Read more.
MXene materials have found emerging applications as catalysts for chemical reactions due to their intriguing physical and chemical applications. In particular, their broad light response and strong photothermal conversion capabilities are likely to render MXenes promising candidates for photothermal catalysis, which is drawing increasing attention in both academic research and industrial applications. MXenes are likely to satisfy all three criteria of a desirable photothermal catalyst: strong light absorption, effective heat management, and versatile surface reactivity. However, their specific functionalities are largely dependent on their structure and composition, which makes understandings of the structure–function relationship of crucial significance. In this review, we mainly focus on the recent progress of MXene–based photothermal catalysts, emphasizing the functionalities and potential applications of MXene materials in fields of photothermal catalysis, and provide insights on design principles of highly efficient MXene–based photothermal catalysts from the atomic scale. This review provides a relatively thorough understanding of MXene–based materials for photothermal catalysis, as well as an in–depth investigation of emerging high-prospect applications in photothermal catalysis. Full article
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14 pages, 1728 KiB  
Review
Advancements in Basic Zeolites for Biodiesel Production via Transesterification
by Guoju Yang and Jihong Yu
Chemistry 2023, 5(1), 438-451; https://doi.org/10.3390/chemistry5010032 - 03 Mar 2023
Cited by 4 | Viewed by 2122
Abstract
The excessive utilization of petroleum diesel has led to the depletion of fossil resources and severe environmental pollution. Biodiesel produced from renewable triglycerides (TGs) or waste lipids is a low-emission fuel substitute for diesel. Biodiesel is mainly produced by transesterification reactions over homogeneous [...] Read more.
The excessive utilization of petroleum diesel has led to the depletion of fossil resources and severe environmental pollution. Biodiesel produced from renewable triglycerides (TGs) or waste lipids is a low-emission fuel substitute for diesel. Biodiesel is mainly produced by transesterification reactions over homogeneous base catalysts with excellent activity and low cost. In comparison, solid base catalysts are more attractive due to their lower environmental impact and simpler production and purification processes. It remains a challenge to further improve the stability and activity of solid base catalysts. Because of the high surface area, superior stability, and tunable basicity, basic zeolites, especially two-dimensional zeolites, have emerged as promising solid basic catalysts for the transesterification of TGs. In this review, we present recent advancements in the synthesis, characterization, and catalytic performance of basic zeolites for the transesterification of TGs. Challenges and development prospects of basic zeolites for biodiesel production via transesterification are also pointed out. We expect that this review will inspire the more efficient and rational design of zeolites for sustainable fuel production. Full article
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31 pages, 4552 KiB  
Review
Development of Power-to-X Catalytic Processes for CO2 Valorisation: From the Molecular Level to the Reactor Architecture
by Luis F. Bobadilla, Lola Azancot, Ligia A. Luque-Álvarez, Guillermo Torres-Sempere, Miriam González-Castaño, Laura Pastor-Pérez, Jie Yu, Tomás Ramírez-Reina, Svetlana Ivanova, Miguel A. Centeno and José A. Odriozola
Chemistry 2022, 4(4), 1250-1280; https://doi.org/10.3390/chemistry4040083 - 08 Oct 2022
Cited by 4 | Viewed by 2861
Abstract
Nowadays, global climate change is likely the most compelling problem mankind is facing. In this scenario, decarbonisation of the chemical industry is one of the global challenges that the scientific community needs to address in the immediate future. Catalysis and catalytic processes are [...] Read more.
Nowadays, global climate change is likely the most compelling problem mankind is facing. In this scenario, decarbonisation of the chemical industry is one of the global challenges that the scientific community needs to address in the immediate future. Catalysis and catalytic processes are called to play a decisive role in the transition to a more sustainable and low-carbon future. This critical review analyses the unique advantages of structured reactors (isothermicity, a wide range of residence times availability, complex geometries) with the multifunctional design of efficient catalysts to synthesise chemicals using CO2 and renewable H2 in a Power-to-X (PTX) strategy. Fine-chemistry synthetic methods and advanced in situ/operando techniques are essential to elucidate the changes of the catalysts during the studied reaction, thus gathering fundamental information about the active species and reaction mechanisms. Such information becomes crucial to refine the catalyst’s formulation and boost the reaction’s performance. On the other hand, reactors architecture allows flow pattern and temperature control, the management of strong thermal effects and the incorporation of specifically designed materials as catalytically active phases are expected to significantly contribute to the advance in the valorisation of CO2 in the form of high added-value products. From a general perspective, this paper aims to update the state of the art in Carbon Capture and Utilisation (CCU) and PTX concepts with emphasis on processes involving the transformation of CO2 into targeted fuels and platform chemicals, combining innovation from the point of view of both structured reactor design and multifunctional catalysts development. Full article
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3 pages, 610 KiB  
Correction
Correction: Kurniawan et al. Vapor-Phase Oxidant-Free Dehydrogenation of 2,3- and 1,4-Butanediol over Cu/SiO2 Catalyst Prepared by Crown-Ether-Assisted Impregnation. Chemistry 2023, 5, 406–421
by Enggah Kurniawan, Shuya Hosaka, Masayuki Kobata, Yasuhiro Yamada and Satoshi Sato
Chemistry 2023, 5(3), 1719-1721; https://doi.org/10.3390/chemistry5030117 - 07 Aug 2023
Cited by 1 | Viewed by 644
Abstract
In the published article “Vapor-Phase Oxidant-Free Dehydrogenation of 2,3- and 1,4-Butanediol over Cu/SiO2 Catalyst Prepared by Crown-Ether-Assisted Impregnation“ [...] Full article
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