Catalysts

12 pages, 3757 KiB

Open AccessCommunication

Mechanistic Details of the Titanium-Mediated Polycondensation Reaction of Polyesters: A DFT Study

by Zhenyu Guan, Jialong Zhang, Wenle Zhou, Youcai Zhu, Zhen Liu, Yumei Zhang and Yue Zhang

Catalysts 2023, 13(10), 1388; https://doi.org/10.3390/catal13101388 - 23 Oct 2023

Cited by 1 | Viewed by 1060

In this work, the mechanism of polyester polycondensation catalysed by titanium catalysts was investigated using density functional theory (DFT). Three polyester polycondensation reaction mechanisms, including the Lewis acid mechanism (M1), the coordination of the ester alkoxy oxygen mechanism (M2) and the coordination of [...] Read more.

In this work, the mechanism of polyester polycondensation catalysed by titanium catalysts was investigated using density functional theory (DFT). Three polyester polycondensation reaction mechanisms, including the Lewis acid mechanism (M1), the coordination of the ester alkoxy oxygen mechanism (M2) and the coordination of the carboxy oxygen mechanism (M3), were investigated. Three reaction mechanisms for the polycondensation reaction of diethyl terephthalate (DET) were investigated using Ti(OEt)₄ and cationic Ti(OEt)₃⁺ as the catalyst. The results show that the polycondensation reaction of the Lewis acid mechanism exhibits similar energy barriers to the catalyst-free condition (42.6 kcal/mol vs. 47.6 kcal/mol). Mechanism M3 gives the lowest energy barrier of 17.5 kcal/mol, indicating that Ti(OEt)₄ is the active centre for the polycondensation reaction. The catalytic efficiency of Ti(OEt)₃⁺ is lower than that of Ti(OEt)₄ catalysts due to its higher DET distortion energy (67.6 kcal/mol vs. 37.4 kcal/mol) by distortion–interaction analysis. Full article

(This article belongs to the Section Computational Catalysis)

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21 pages, 3983 KiB

Open AccessArticle

Exploring Long Range para-Phenyl Effects in Unsymmetrically Fused bis(imino)pyridine-Cobalt Ethylene Polymerization Catalysts

by Yizhou Wang, Zheng Wang, Qiuyue Zhang, Song Zou, Yanping Ma, Gregory A. Solan, Wenjuan Zhang and Wen-Hua Sun

Catalysts 2023, 13(10), 1387; https://doi.org/10.3390/catal13101387 - 23 Oct 2023

Cited by 1 | Viewed by 952

Abstract

Unsymmetrical 11-phenyl-1,2,3,7,8,9,10-heptahydrocyclohepta[b]quinoline-4,6-dione, incorporating a para-phenyl substituted pyridine unit fused by both 6- and 7-membered carbocyclic rings, has been prepared on the gram-scale via a multi-step procedure involving cyclization, hydrogenation and oxidation. Templating this diketone, in the presence of cobalt(II) chloride [...] Read more.

Unsymmetrical 11-phenyl-1,2,3,7,8,9,10-heptahydrocyclohepta[b]quinoline-4,6-dione, incorporating a para-phenyl substituted pyridine unit fused by both 6- and 7-membered carbocyclic rings, has been prepared on the gram-scale via a multi-step procedure involving cyclization, hydrogenation and oxidation. Templating this diketone, in the presence of cobalt(II) chloride hexahydrate, with the corresponding aniline afforded in good yield five examples of doubly fused bis(arylimino)pyridine-cobalt(II) chlorides, Co1 (aryl = 2,6-dimethylphenyl), Co2 (2,6-diethylphenyl), Co3 (2,6-diisopropylphenyl), Co4 (2,4,6-trimethylphenyl) and Co5 (2,6-diethyl-4-methylphenyl). Structural characterization of Co1, Co2 and Co3 highlights the flexible nature of the inequivalent fused rings on the NNN’-ligand and the skewed disposition of the para-phenyl group. On activation with MAO, Co1–Co5 exhibited high activity for ethylene polymerization at 30 °C (up to 5.66 × 10⁶ g (PE) mol⁻¹ (Co) h⁻¹) with the relative order being as follows: Co4 > Co1 > Co5 > Co3 > Co2. All polyethylenes were strictly linear, while their molecular weights and dispersities showed some notable variations. For Co1, Co2, Co4 and Co5, all polymerizations were well controlled as evidenced by the narrow dispersities of their polymers (M_w/M_n range: 1.8–2.7), while their molecular weights (M_w range: 2.9–10.9 kg mol⁻¹) steadily increased in line with the greater steric properties of the N-aryl ortho-substituents. By contrast, the most hindered 2,6-diisopropyl counterpart Co3 displayed a broad distribution with bimodal characteristics (M_w/M_n = 10.3) and gave noticeably higher molecular weight polymer (M_w = 75.5 kg mol⁻¹). By comparison, the MMAO-activated catalysts were generally less active, but showed similar trends in molecular weight and polymer dispersity. End group analysis of selected polymers via ¹³C and ¹H NMR spectroscopy revealed the presence of both saturated and unsaturated polyethylenes in accordance with competing chain transfer pathways. Notably, when comparing Co3/MAO with its non-phenyl substituted analogue (E_2,6-iPr2Ph)CoCl₂/MAO, the former, though less controlled, displayed higher activity and molecular weight, a finding that points towards a role played by the remote para-phenyl group. Full article

(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members and Topical Advisory Panel Members of Catalysts in Section "Catalysis in Organic and Polymer Chemistry")

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23 pages, 9202 KiB

Open AccessArticle

Acid-Catalyzed Etherification of Glycerol with Tert-Butanol: Reaction Monitoring through a Complete Identification of the Produced Alkyl Ethers

by Alfonso Cornejo, Inés Reyero, Idoia Campo, Gurutze Arzamendi and Luis M. Gandía

Catalysts 2023, 13(10), 1386; https://doi.org/10.3390/catal13101386 - 23 Oct 2023

Viewed by 1222

Abstract

Higher tert-Butyl glycerol ethers (tBGEs) are interesting glycerol derivatives that can be produced from tert-butyl alcohol (TBA) and glycerol using an acid catalyst. Glycerol tert-butylation is a complex reaction that leads to the formation of five tBGEs [...] Read more.

Higher tert-Butyl glycerol ethers (tBGEs) are interesting glycerol derivatives that can be produced from tert-butyl alcohol (TBA) and glycerol using an acid catalyst. Glycerol tert-butylation is a complex reaction that leads to the formation of five tBGEs (two monoethers, two diethers, and one triether). In order to gain insight into the reaction progress, the present work reports on the monitoring of glycerol etherification with TBA and p-toluensulfonic acid (PTSA) as homogeneous catalysts. Two analytical techniques were used: gas chromatography (GC), which constitutes the benchmark method, and ¹H nuclear magnetic resonance (¹H NMR), whose use for this purpose has not been reported to date. A method for the quantitative analysis of tBGEs and glycerol based on ¹H NMR is presented that greatly reduced the analysis time and relative error compared with GC-based methods. The combined use of both techniques allowed for a complete quantitative and qualitative description of the glycerol tert-butylation progress. The set of experimental results collected showed the influence of the catalyst concentration and TBA/glycerol ratio on the etherification reaction and evidenced the intrinsic difficulties of this process to achieve high selectivities and yields to the triether. Full article

(This article belongs to the Special Issue Biomass Derived Heterogeneous and Homogeneous Catalysts, 2nd Edition)

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16 pages, 4236 KiB

Open AccessArticle

S_{2} O_{8}^{2 -}

/CeO₂ Solid Superacid Catalyst Prepared by Radio-Frequency Plasma-Assisted Hydrothermal Method

by Kaiqiang Wang, Changhui Zhu, Xudong Zhang, Baohe Tian, Wenchao Zhu and Bangdou Huang

Catalysts 2023, 13(10), 1385; https://doi.org/10.3390/catal13101385 - 22 Oct 2023

Viewed by 1245

Abstract

CeO₂ was prepared using a hydrothermal method, modified by radio-frequency plasma in the form of glow discharge, and then the solid superacid

S_{2} O_{8}^{2 -}

/CeO₂ was prepared by the impregnation method. A series of properties such as [...] Read more.

CeO₂ was prepared using a hydrothermal method, modified by radio-frequency plasma in the form of glow discharge, and then the solid superacid

S_{2} O_{8}^{2 -}

/CeO₂ was prepared by the impregnation method. A series of properties such as pore structure was characterized by N₂ adsorption–desorption experiments, surface morphology was characterized by TEM, crystal phase was characterized by XRD, and surface acidity of the catalyst was characterized by Py-IR and Hammett titration. The methyl esterification reaction of tryptophan was used to evaluate the activity of the solid superacid. The results showed that the catalyst modified by radio-frequency plasma had a larger specific surface area, more surface oxygen vacancies, smaller particle size, and higher total acid content. The yield of tryptophan methyl ester reached a higher level of 94.5% (150 °C, 1 MPa, 2 h), catalyzed by the modified

S_{2} O_{8}^{2 -}

/CeO₂. This work verified the feasibility of plasma technology in the field of catalytic activity enhancement of solid superacid. Full article

(This article belongs to the Section Catalytic Materials)

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13 pages, 6826 KiB

Open AccessFeature PaperArticle

The Evolution of Hexagonal Cobalt Nanosheets for CO₂ Electrochemical Reduction Reaction

by Qingyu Li, Yichao Hou, Jie Yin and Pinxian Xi

Catalysts 2023, 13(10), 1384; https://doi.org/10.3390/catal13101384 - 21 Oct 2023

Viewed by 1297

Abstract

The CO₂ electrochemical reduction reaction (CO₂RR) is one of the most promising methods to reduce carbon dioxide emissions and store energy. At the same time, the pathways of CO₂ reduction reaction are diverse and the products are abundant. Converting [...] Read more.

The CO₂ electrochemical reduction reaction (CO₂RR) is one of the most promising methods to reduce carbon dioxide emissions and store energy. At the same time, the pathways of CO₂ reduction reaction are diverse and the products are abundant. Converting carbon dioxide to C₂₊ products, a critical feedstock, requires a C–C coupling step with the transfer of more than 10 electrons per molecule and, hence, is kinetically sluggish. The production of some key adsorptions is conducive to the formation of C₂₊ products. In this work, we used in situ techniques to figure out the reason why hexagonal-close-packed (hcp) Co nanosheets (NSs) have high activity in CO₂RR to ethanal. According to the in situ Raman spectra, the high local pH environment on the catalyst surface is favorable for CO₂RR. The high pH at low potentials not only suppresses the competing hydrogen evolution reaction but also stimulates the production of COCO* intermediate. The isotopic labeling experiment in differential electrochemical mass spectrometry (DEMS) provides a possible sequence of the products. The ¹³CO is generated when we replace ¹²CO₂ with ¹³CO₂, which identifies the origin of the products. Besides, in situ electrochemical impedance spectroscopy (EIS) shows that the hcp Co at −0.4 V vs. RHE boosts the H₂O dissociation and proton transfer, feeding sufficient H* for CO₂ to *COOH. In the end, by analyzing the transmission electronic microscopy (TEM), we find that the Co (002) plane may be beneficial to the conversion of CO₂ and the adsorption of intermediates. Full article

(This article belongs to the Special Issue CO₂ Capture and/or Its Catalytic Transformation into Fuels or Valuable Chemicals II)

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14 pages, 7794 KiB

Open AccessArticle

The Synthesis of a Pt/SAPO-11 Composite with Trace Pt Loading and Its Catalytic Application in n-Heptane Hydroisomerization

by Zhen Jiang, Liduo Chen, Yanhong Cui, Huijie Gao, Yisi Zhou, Wei Zhang, Yanhua Suo and Yingjun Wang

Catalysts 2023, 13(10), 1383; https://doi.org/10.3390/catal13101383 - 20 Oct 2023

Viewed by 1394

Abstract

n-Alkane hydroisomerization over bifunctional catalysts is an effective approach for clean fuel production. However, achieving metal–acid synergy and enhancing the catalytic performance by the preparation of bifunctional catalysts with suitable proximity between the metal sites and Brønsted acid sites are still challenging. [...] Read more.

n-Alkane hydroisomerization over bifunctional catalysts is an effective approach for clean fuel production. However, achieving metal–acid synergy and enhancing the catalytic performance by the preparation of bifunctional catalysts with suitable proximity between the metal sites and Brønsted acid sites are still challenging. In this work, a series of Pt/SAPO-11 catalysts with different Pt loading applied in n-heptane hydroisomerization was synthesized. SAPO-11 was synthesized by the Instant Exactness Synthesis (IES) method, which, with unique morphology and pore structure, was chosen as support for the hydroisomerization catalysts; Pt/SAPO-11 was synthesized with the impregnation method, Pt nanoclusters with trace loading were fabricated over the SAPO-11 support, and the as-synthesized catalysts with different Pt loading were labeled as xPt/SAPO-11 (x = 0.1, 0.3, 0.5, 0.8 and 1.0). Various characterizations, including XRD, nitrogen adsorption–desorption, SEM, TEM, NH₃-TPD and XPS, were carried out on catalysts to obtain deep insights into the microstructure and valence states of xPt/SAPO-11. The catalytic performance of xPt/SAPO-11, including catalytic selectivity and conversion, was investigated in the n-heptane hydroisomerization in detail. Pt loading affected the catalytic properties of xPt/SAPO-11 in the hydroisomerization of n-heptane. The selectivity of 0.5Pt/SAPO-11 toward isomers was about 65% with a conversion of 77% at 310 °C, which was obviously higher than other xPt/SAPO-11 catalysts. Full article

(This article belongs to the Section Catalytic Materials)

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19 pages, 11692 KiB

Open AccessArticle

Thermo-Catalytic Decomposition Comparisons: Carbon Catalyst Structure, Hydrocarbon Feed and Regeneration

by Mpila Makiesse Nkiawete and Randy Vander Wal

Catalysts 2023, 13(10), 1382; https://doi.org/10.3390/catal13101382 - 20 Oct 2023

Viewed by 986

Abstract

Thermo-catalytic decomposition (TCD) activity and stability depend upon the initial carbon catalyst structure. However, further transitions in the carbon structure depend on the carbon material (structure and composition) originating from the TCD process. In this article, reaction data are presented that illustrates the [...] Read more.

Thermo-catalytic decomposition (TCD) activity and stability depend upon the initial carbon catalyst structure. However, further transitions in the carbon structure depend on the carbon material (structure and composition) originating from the TCD process. In this article, reaction data are presented that illustrates the time-dependent TCD activity as TCD-formed carbon contributes and then dominates conversion. A variety of initial carbon catalysts are compared, including sugar char, a conductive carbon black (AkzoNobel Ketjenblack), a rubber-grade carbon black (Cabot R250), and its graphitized analogue as formed and partially oxidized. Regeneration of carbon catalysts by partial oxidation is evaluated using nascent carbon black as a model, coupled with subsequent comparative TCD performance relative to the nascent, non-oxidized carbon black. Activation energies for TCD with nascent and oxidized carbons are evaluated by a leading-edge analysis method applied to TCD. Given the correlation between nanostructure and active sites, two additional carbons, engine soots, are evaluated for regeneration and dependence upon nanostructure. Active sites are quantified by oxygen chemisorption, followed by X-ray photoelectron spectroscopy (XPS). The structure of carbon catalysts is assessed pre- and post-TCD by high-resolution transmission electron microscopy (HRTEM). Last, energy dispersive X-ray analysis mapping (EDS) is carried out for its potential to visualize oxygen chemisorption. Full article

(This article belongs to the Special Issue Catalysis and Carbon-Based Materials, 2nd Edition)

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20 pages, 3931 KiB

Open AccessFeature PaperReview

Research Progress of the Selective Catalytic Reduction with NH₃ over ZSM-5 Zeolite Catalysts for NO_x Removal

by Wangxiang Pan, Jingping He, Guanlin Huang, Wentao Zhang and De Fang

Catalysts 2023, 13(10), 1381; https://doi.org/10.3390/catal13101381 - 19 Oct 2023

Cited by 1 | Viewed by 1231

Abstract

Nitrogen oxides (NO_x) are very common air pollutants that are harmful to the environment and human bodies. Selective catalytic reduction with ammonia (NH₃-SCR) is considered an effective means to remove NO_x emissions due to its good environmental adaptability, [...] Read more.

Nitrogen oxides (NO_x) are very common air pollutants that are harmful to the environment and human bodies. Selective catalytic reduction with ammonia (NH₃-SCR) is considered an effective means to remove NO_x emissions due to its good environmental adaptability, high catalytic activity, and remarkable selectivity. In this paper, the preparation methods, types, advantages, and challenges of ZSM-5 catalysts are reviewed. Special attention is paid to the catalytic properties and influence factors of ZSM-5 catalysts for NH₃-SCR. The SCR performances of ZSM-5 catalysts doped with single or multiple metal ions are also reviewed. In addition, the environmental adaptabilities (sulfur resistance, alkali resistance, water resistance, and hydrothermal stability) of ZSM-5 catalysts are discussed, and the development of ZSM-5 catalysts in denitrification is summarized. Full article

(This article belongs to the Special Issue Zeolites as Catalysts: Applications in Chemical Engineering, Energy Sources and Environmental Protection)

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19 pages, 4579 KiB

Open AccessFeature PaperArticle

A New Ammonia Kinetic Model in Ru-Catalyzed Steam-Reforming Reaction Containing N₂ in Natural Gas

by Chulmin Kim, Juhan Lee and Sangyong Lee

Catalysts 2023, 13(10), 1380; https://doi.org/10.3390/catal13101380 - 19 Oct 2023

Viewed by 1372

Abstract

Hydrogen for building fuel cells is primarily produced by natural-gas steam-reforming reactions. Pipeline-transported natural gas in Europe and North America used to contain about 1% to 5% N₂, which reacts with H₂ in steam-reforming reactions to form NH₃. [...] Read more.

Hydrogen for building fuel cells is primarily produced by natural-gas steam-reforming reactions. Pipeline-transported natural gas in Europe and North America used to contain about 1% to 5% N₂, which reacts with H₂ in steam-reforming reactions to form NH₃. In the case of Ru, one of the catalysts used in natural-gas steam-reforming reactions, the activity of the NH₃-formation reaction is higher than that of Ni and Rh catalysts. Reforming gas containing NH₃ is known to poison Pt catalysts in Polymer Electrolyte Membrane Fuel Cells (PEMFCs) and also poison catalysts in preferential oxidation (PROX). In this study, Langmuir–Hinshelwood-based models of the NH₃-formation reaction considering H₂ and CO were proposed and compared with a simplified form of the Temkin–Pyzhev model for NH₃-formation rate. The kinetic parameters of each model were optimized by performing multi-objective function optimization on the experimental results using a tube-type reactor and the numerical results of a plug-flow one-dimension simple SR (steam-reforming) reactor. Full article

(This article belongs to the Topic Hydrogen Production Processes)

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20 pages, 8272 KiB

Open AccessFeature PaperArticle

Industrial Scale Direct Liquefaction of E. globulus Biomass

by Irina Fernandes, Maria Joana Neiva Correia, José Condeço, Duarte M. Cecílio, João Bordado and Margarida Mateus

Catalysts 2023, 13(10), 1379; https://doi.org/10.3390/catal13101379 - 19 Oct 2023

Viewed by 941

Abstract

This work presents the study of Eucalyptus globulus bark and sawdust direct liquefaction. Laboratory scale experiments were carried out to assess the impact of several variables on the reaction yield and the sugar content of the bio-oil. These variables were the biomass type [...] Read more.

This work presents the study of Eucalyptus globulus bark and sawdust direct liquefaction. Laboratory scale experiments were carried out to assess the impact of several variables on the reaction yield and the sugar content of the bio-oil. These variables were the biomass type and concentration, the solvent, and the reaction time. The results show that E. globulus sawdust presented the highest yields (>95%), but the highest sugar content after water extraction was obtained for E. globulus bark (~5.5% vs. 1.2% for sawdust). Simultaneously, industrial-scale tests were carried out at the ENERGREEN pilot plant using the same reaction variables, which resulted in reaction yields of nearly 100%. The reagents and raw materials used, as well as the products obtained (bio-oil, reaction condensates, polyols, and sugar phases) were characterized by elemental analysis, infrared spectroscopy, thermogravimetry, and high-performance liquid chromatography with mass spectrometry. The heating value of the bio-oils is higher than the original biomass (higher heating value of E. globulus sawdust bio-oil 29 MJ/kg vs. 19.5 MJ/kg of the original E. globulus sawdust). The analyses of the bio-oils allowed us to identify the presence of high-added-value compounds, such as levulinic acid and furfural. Finally, a study of the accelerated aging of liquefied biomass showed that the biofuel density increases from 1.35 to 1.44 kg/dm³ after 7 days of storage due to the occurrence of repolymerization reactions. Full article

(This article belongs to the Special Issue Catalytic Processes in Biofuel Production and Biomass Valorization, 2nd Edition)

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14 pages, 4179 KiB

Open AccessFeature PaperArticle

Noble Metal Single-Atom Coordinated to Nitrogen, Oxygen, and Carbon as Electrocatalysts for Oxygen Evolution

by Jianhua Wang, Jiangdong Bai, Yaqi Cang, Qing Li, Xing Fan and Haiping Lin

Catalysts 2023, 13(10), 1378; https://doi.org/10.3390/catal13101378 - 19 Oct 2023

Viewed by 1120

Abstract

Tuning the coordination environment centering metal atoms has been regarded as a promising strategy to promote the activities of noble metal single-atom catalysts (SACs). In the present work, first-principle calculations are employed to explore the oxygen evolution reaction (OER) performance of Ir and [...] Read more.

Tuning the coordination environment centering metal atoms has been regarded as a promising strategy to promote the activities of noble metal single-atom catalysts (SACs). In the present work, first-principle calculations are employed to explore the oxygen evolution reaction (OER) performance of Ir and Ru SACs with chemical coordination being nitrogen (M-N₄-C), oxygen (M-O₄-C), and carbon (M-C₄-C) in graphene, respectively. A “three-step” strategy was implemented by progressively investigating these metrics (stability, catalytic activity, structure–activity relationship). A volcano plot of reactivity is established by using the adsorption-free energy of O* (∆G_O*) as a theoretical descriptor. The intrinsic OER activity is IrN₄-C > IrO₄-C > RuO₄-C > RuN₄-C > IrC₄-C > RuC₄-C. The in-depth tuning mechanism of ∆G_O* can be indicated and interpreted by the d-band centers of the active sites and the crystal orbital Hamilton population analysis of metal-oxygen bonds, respectively. Full article

(This article belongs to the Special Issue Theory-Guided Electrocatalysis and Photocatalysis)

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17 pages, 5110 KiB

Open AccessArticle

Cu-Doped SrTiO₃ Nanostructured Catalysts for CO₂ Conversion into Solar Fuels Using Localised Surface Plasmon Resonance

by Lorenzo Rizzato, Jonathan Cavazzani, Andrea Osti, Marco Scavini and Antonella Glisenti

Catalysts 2023, 13(10), 1377; https://doi.org/10.3390/catal13101377 - 19 Oct 2023

Cited by 1 | Viewed by 1354

Abstract

Carbon dioxide valorisation is one of the most discussed topics amongst researchers; indeed, finding a way to significantly reduce CO₂ concentration in the atmosphere is crucial in order to mitigate climate change effects in the next decades. In this study, SrTiO₃ [...] Read more.

Carbon dioxide valorisation is one of the most discussed topics amongst researchers; indeed, finding a way to significantly reduce CO₂ concentration in the atmosphere is crucial in order to mitigate climate change effects in the next decades. In this study, SrTiO₃-supported Cu nanoparticles are exploited as Localised Surface Plasmon Resonance (LSPR)-mediated catalysts for CO₂ reduction. The materials were prepared via sol–gel citrate route methodology, inserting Cu as a dopant in the perovskite structure; reducing treatments at different temperatures were performed to promote copper atom exsolution, thus forming nanostructures upon the surface. The perovskitic structure was confirmed via ex situ and operando XRD analysis, while compositional analysis was carried out through XPS and EDS; SEM and TEM images revealed morphological changes with different reducing treatments, and bulk reducibility was analysed with H₂-TPR, revealing different Cu species in the material. Band gap analysis via DRS showed the successful incorporation of copper in the perovskite, affecting the light absorption properties. Finally, catalytic tests showed that copper nanoparticles play a role in CO₂ activation with sunlight, proving that LSPR could be exploited for catalytic means. Full article

(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members and Topical Advisory Panel Members of Catalysts in Section "Catalytic Materials")

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15 pages, 1904 KiB

Open AccessFeature PaperArticle

Synergistic Effects of Ionizing Radiation Process in the Integrated Coagulation–Sedimentation, Fenton Oxidation, and Biological Process for Treatment of Leachate Wastewater

by Sha Liu, Arindam Sinharoy, Ga-Young Lee, Myun-Joo Lee, Byung-Cheol Lee and Chong-Min Chung

Catalysts 2023, 13(10), 1376; https://doi.org/10.3390/catal13101376 - 18 Oct 2023

Cited by 1 | Viewed by 1127

Abstract

This study evaluated the feasibility of ionizing radiation combined with coagulation–sedimentation and Fenton oxidation as a treatment method for landfill leachate. The experiments revealed a positive correlation between pollutant removal efficiency and increased ionizing radiation intensity. Remarkable pollutant removal efficiencies were achieved under [...] Read more.

This study evaluated the feasibility of ionizing radiation combined with coagulation–sedimentation and Fenton oxidation as a treatment method for landfill leachate. The experiments revealed a positive correlation between pollutant removal efficiency and increased ionizing radiation intensity. Remarkable pollutant removal efficiencies were achieved under ionizing radiation at 50 kGy, with a maximum of 27% removal of total organic carbon (TOC), 61% removal of total nitrogen, 51% removal of total phosphorus, and an impressive 93% removal of NO₃⁻-N. With the addition of coagulation–sedimentation and Fenton oxidation, the treatment efficiency further increased by 33% nitrogen, 18% SCOD, and 8% phosphate. The most significant observation from the study was that for all the different treatment methods, the results were always better for leachate samples treated with ionizing radiation than for the untreated samples. Subsequently, biological treatment was applied as a post-treatment method to remove residual organic carbon and nitrogen, which found that the best removal efficiencies were only for the low salt concentration (0.5%) and the removal decreased with increasing salt concentration. These experimental results conclusively demonstrated that when treating leachate wastewater, it was more appropriate to employ physicochemical methods rather than a biological treatment, primarily due to the high salt concentration present. Full article

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12 pages, 3242 KiB

Open AccessArticle

The Synthesis of Ginsenoside Compound K Using a Surface-Displayed β-Glycosidase Whole-Cell Catalyst

by Lianxia Guo, Tao Li, Gege Guo, Zhaoxing Liu and Ning Hao

Catalysts 2023, 13(10), 1375; https://doi.org/10.3390/catal13101375 - 18 Oct 2023

Cited by 1 | Viewed by 1011

Abstract

Ginsenoside compound K (CK) has garnered considerable attention due to its versatile pharmacological properties, including anti-inflammatory, anti-allergic, anti-aging, anti-diabetic, and hepatoprotective effects, along with neuroprotection. The conventional approach to synthesizing ginsenoside CK involves enzymatic conversion. However, the purification of enzymes necessitates effort and [...] Read more.

Ginsenoside compound K (CK) has garnered considerable attention due to its versatile pharmacological properties, including anti-inflammatory, anti-allergic, anti-aging, anti-diabetic, and hepatoprotective effects, along with neuroprotection. The conventional approach to synthesizing ginsenoside CK involves enzymatic conversion. However, the purification of enzymes necessitates effort and expense, and enzymes are prone to inactivation. Additionally, whole-cell catalysis suffers from inefficiency due to limited cell permeability. To address these challenges, we harnessed the YiaT protein as an anchoring motif, establishing a surface display system for β-glycosidase Bgp3. This innovative system served as a whole-cell catalyst for the efficient synthesis of ginsenoside CK. We further optimized the YiaT-Bgp3 system, enhancing display levels and significantly increasing ginsenoside CK production. Optimal conditions were achieved at an IPTG concentration of 0.5 mM, an induction temperature of 16 °C, a ginsenoside substrate concentration of 15 mg/mL, and a catalytic temperature of 30 °C. Ultimately, the YiaT-Bgp3 system synthesized 5.18 ± 0.08 mg/mL ginsenoside CK within 24 h, with a conversion of 81.83 ± 1.34%. Furthermore, the YiaT-Bgp3 system exhibited good reusability, adding to its practicality and value. This study has successfully developed an efficient whole-cell Bgp3 biocatalyst, offering a convenient, highly productive, and economically viable solution for the industrial production of ginsenoside CK. Full article

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15 pages, 2829 KiB

Open AccessArticle

Pd+Al₂O₃-Supported Ni-Co Bimetallic Catalyst for H₂ Production through Dry Reforming of Methane: Effect of Carbon Deposition over Active Sites

by Anis H. Fakeeha, Dharmesh M. Vadodariya, Mohammed F. Alotibi, Jehad K. Abu-Dahrieh, Ahmed A. Ibrahim, Ahmed E. Abasaeed, Naif Alarifi, Rawesh Kumar and Ahmed S. Al-Fatesh

Catalysts 2023, 13(10), 1374; https://doi.org/10.3390/catal13101374 - 18 Oct 2023

Cited by 2 | Viewed by 981

Abstract

Dry reforming of methane (DRM) is gaining global attention due to its capacity to convert two greenhouse gases together. It proceeds through CH₄ decomposition over active sites (into CH_4−x) followed by CH_4−x oxidation by CO₂ (into syngas). Furthermore, [...] Read more.

Dry reforming of methane (DRM) is gaining global attention due to its capacity to convert two greenhouse gases together. It proceeds through CH₄ decomposition over active sites (into CH_4−x) followed by CH_4−x oxidation by CO₂ (into syngas). Furthermore, CH_4−x oligomerization into coke cannot be neglected. Herein, xNi(5−x)Co/Pd+Al₂O₃ (x = 5, 3.75, 2.5, 1.25, 0) catalysts are prepared, investigated for DRM, and characterized with X-ray diffraction, UV-Vis, transmission electron microscopy, temperature-programmed reduction/desorption techniques, and thermogravimetry. Fine-tuning among stable active sites, graphitic carbon deposits, and catalytic activity is noticed. The total reducibility and basicity are found to decrease upon increasing the Co proportion up to 2.5 wt% in the Ni-Co bimetallic Pd+Al₂O₃-supported catalyst. The active sites derived from strong metal–support interaction species (NiAl₂O_x or dispersed CoO_x) are found to be promising in higher levels of activity. However, activity is, again, limited by graphitic carbon which is increased with an increasing Co proportion in the Ni-Co bimetallic Pd+Al₂O₃-supported catalyst. The incorporation of 1.25 wt% Co along with 3.75 wt% Ni over Pd+Al₂O₃ results in the generation of fewer such active sites, extensive oxidizable carbon deposits, and inferior catalytic activity compared to 5Ni/Pd+Al₂O₃. The 2.5Ni2.5Co/Pd+Al₂O₃ catalyst has lower crystallinity, a relatively lower coke deposit (than the 3.75Ni1.25Co/Pd+Al₂O₃ catalyst), and a higher number of stable active sites. It attains a 54–51% H₂ yield in 430 min TOS and 0.87 H₂/CO (similar to 5Ni/Pd+Al₂O₃) Full article

(This article belongs to the Section Catalytic Materials)

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14 pages, 7217 KiB

Open AccessFeature PaperArticle

Kinetics of Hydrogen Evolution Reaction on Monometallic Bulk Electrodes in Various Electrolytic Solutions

by Goitom K. Gebremariam, Aleksandar Z. Jovanović and Igor A. Pašti

Catalysts 2023, 13(10), 1373; https://doi.org/10.3390/catal13101373 - 18 Oct 2023

Viewed by 1198

Abstract

The hydrogen evolution reaction (HER) holds pivotal significance in electrochemical energy conversion. In this study, we present essential HER kinetic parameters encompassing nine metals (Ag, Au, Co, Cr, Fe, Ni, Pt, W, and Zn) evaluated within seven distinct electrolytes (0.1 mol dm⁻³ [...] Read more.

The hydrogen evolution reaction (HER) holds pivotal significance in electrochemical energy conversion. In this study, we present essential HER kinetic parameters encompassing nine metals (Ag, Au, Co, Cr, Fe, Ni, Pt, W, and Zn) evaluated within seven distinct electrolytes (0.1 mol dm⁻³ HClO₄, 0.1 mol dm⁻³ HCl, 0.5 mol dm⁻³ NaCl, 1 mol dm⁻³ KH₂PO₄, 0.1 mol dm⁻³ KOH, 0.1 mol dm⁻³ LiOH, and 1 mol dm⁻³ KOH). Through careful measures to restrain oxide formation, HER activity was measured on clean electrodes, while the assessment of HER activity on oxidatively treated metals was also performed. By correlating HER exchange current densities with calculated hydrogen binding energies, we show that the shape of HER volcano curves is largely preserved in studied electrolytes, at least around their apexes. Additionally, depending on the metal–electrolyte combination, the presence of surface oxide can have both positive and negative effects on HER kinetics. Finally, we collated HER kinetic data for bulk surfaces from diverse literature sources, offering a comprehensive overview of the kinetic parameters governing hydrogen evolution across distinct electrolytic environments. These insights have practical significance, guiding the development of new catalytic materials for different water electrolysis technologies, optimizing electrolyte formulations for boosting HER, and enhancing energy efficiency and catalytic performance through catalyst–electrolyte synergies. Full article

(This article belongs to the Special Issue Electrocatalysts for the Production of Hydrogen, Oxygen and Syngas)

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18 pages, 3270 KiB

Open AccessArticle

Synthesis and Characterization of Acid-Activated Carbon Prepared from Sugarcane Bagasse for Furfural Production in Aqueous Media

by Thiago Alves Lopes Silva, Adilson Candido da Silva and Daniel Pasquini

Catalysts 2023, 13(10), 1372; https://doi.org/10.3390/catal13101372 - 17 Oct 2023

Viewed by 1589

Abstract

Furfural is a platform molecule obtained from hemicellulosic monosaccharides present in lignocellulosic biomass. Due to the possibility of converting this molecule into several value-added chemicals and the need to search for more sustainable production processes, the present work aimed to produce and characterize [...] Read more.

Furfural is a platform molecule obtained from hemicellulosic monosaccharides present in lignocellulosic biomass. Due to the possibility of converting this molecule into several value-added chemicals and the need to search for more sustainable production processes, the present work aimed to produce and characterize different sulfonated activated carbons (AC-S) from sugarcane bagasse (SCB) for application in furfural production in aqueous media. ACs were produced by chemical activation using salts of ZnCl₂, NiCl₂, and CuCl₂ and a temperature and activation time of 550 °C and 3 h under nitrogen flow, respectively. Sulfonation was carried out with H₂SO₄ (98%) at a solid/liquid ratio of 1:10 at 160 °C for 2 h. Catalytic tests were performed using 5% catalyst mass regarding xylose, a temperature of 180 °C, and a reaction time of 2 h. ACs with high surface areas, ranging from 290 to 1100 m² g⁻¹, were produced. All catalysts had an increased sulfur content and total acidity after sulfonation, indicating the successful attachment of the sulfonic group (-SO₃H) in the carbon matrix of the CAs. The AC-S/CuCl₂ catalyst achieved the best catalytic performance compared to AC-S/ZnCl₂, AC-S/NiCl₂, and other acidic solids reported in the literature, achieving yield and selectivity of 55.96% and 83.93%, respectively. These results evidence the importance of the synergy between the Lewis and Brønsted acid sites on selective xylose dehydration and make AC-S/CuCl₂ a promising acid catalyst for converting xylose to furfural in an aqueous medium. Full article

(This article belongs to the Special Issue Catalytic Conversion of Biomass to Biofuels)

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14 pages, 4222 KiB

Open AccessArticle

Nickel Glycerolate Overcoming a High-Entropy Configuration for High-Performance Oxygen Evolution Reaction

by Irlan S. Lima, Rafael S. Pereira, Timothy G. Ritter, Reza Shahbazian-Yassar, Josué M. Gonçalves and Lúcio Angnes

Catalysts 2023, 13(10), 1371; https://doi.org/10.3390/catal13101371 - 16 Oct 2023

Viewed by 1416

Abstract

In response to the requirement for alternative energy conversion and storage methods, metal-glycerolates (MG) and their analogs are considered promising classes of electrode material that can be synthesized in various designs. Recently, the concept of high-entropy configuration and multimetallic systems has gained attention [...] Read more.

In response to the requirement for alternative energy conversion and storage methods, metal-glycerolates (MG) and their analogs are considered promising classes of electrode material that can be synthesized in various designs. Recently, the concept of high-entropy configuration and multimetallic systems has gained attention in the field of electrocatalysis. In fact, the presence of five or more metals in a single-phase material can produce unique and unexpected properties. Thus, it becomes crucial to explore different metal combinations and evaluate their synergistic interaction as a result of these combinations. Therefore, in this work, a scalable solvothermal method was used to synthesize a high-entropy glycerolate (HEG) containing Ni, Zn, Mn, Mg, and Co ions (HEG) and their respective sub-systems such as NiG, NiMnG, and NiMnZnG. The SEM-EDS images showed the excellent distribution of the metal cations in the obtained microspheres. Surprisingly, our experiments demonstrated that even in reaching a single-phase HEG, the oxygen evolution reaction (OER) performance measured in 1 M KOH electrolyte did not surpass the benefit effect observed in the NiG-based carbon paste with an overpotential of 310 mV (@10 mA cm^–2), against 341 mV (@10 mA cm^–2) of HEG. Moreover, the NiG shows good stability toward OER even after 24 h, which is attributed to the NiOOH active phase generated during the electrochemical cycling. Full article

(This article belongs to the Special Issue Polyoxometalates (POMs) as Catalysts for Biomass Conversion)

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10 pages, 2578 KiB

Open AccessCommunication

Aminocyclopropenium as a New Class of Hydrogen Bonding Catalyst in Friedel–Crafts Alkylation

by Xuesuo Ma, Jiaxi Xu, Jingjing Liu, Jun He, Tong Chang, Qingbiao Yang, Ning Li, Dong Qian and Zhenjiang Li

Catalysts 2023, 13(10), 1370; https://doi.org/10.3390/catal13101370 - 16 Oct 2023

Viewed by 1049

Abstract

H-bonding has achieved massive advancements by utilizing an H-bond donor (HBD) to interact with the electron-rich site of the substrate, and an H-bond acceptor (HBA) to coordinate with the electron-deficient site. Rapid transformation is often correlated with the acidity of HBD, namely the [...] Read more.

H-bonding has achieved massive advancements by utilizing an H-bond donor (HBD) to interact with the electron-rich site of the substrate, and an H-bond acceptor (HBA) to coordinate with the electron-deficient site. Rapid transformation is often correlated with the acidity of HBD, namely the degree of charge deficiency of the hydrogen proton. In addition, the positive cations were employed to enhance the HBD; the electron-withdrawing groups were also a dissimilar approach for increasing the capability of the H-bond donor. We first introduced the H-bonding organic ion pair tris(phenylamino)cyclopropenium (TPAC·Cl) into the Friedel–Crafts alkylation of indoles with nitroalkenes, which was implemented via vicinal positive charges on the cyclopropenium core. The counter ion chloride anion became a potential HBA to activate the electron-deficient part of the substrate. X-ray analyses of a single crystal of TPAC·Cl described the 3D architecture and the delocalized cationic charge in the solid state. The aromatic cyclopropenium endowed the N–H moieties with the ability of the H-bond donor to activate the nitroalkene; meanwhile, the chloride anion acted as the H-bond acceptor to activate the indole. The amino-cyclopropenium-offered HBD and HBA displayed cooperative organocatalysis in the Friedel–Crafts alkylation of indole with nitroalkene. A new class of hydrogen bonding catalysis and a working mechanism were proposed. Full article

(This article belongs to the Special Issue Organocatalysis in the Chemical Transformations, 2nd Edition)

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29 pages, 8060 KiB

Open AccessReview

Recent Developments in the Synthesis of Organoselenium Compounds Based on the Reactions of Organic Diselenides with Acetylenes

by Maxim V. Musalov, Vladimir A. Potapov, Maria V. Musalova, Svetlana V. Amosova and Leonid B. Krivdin

Catalysts 2023, 13(10), 1369; https://doi.org/10.3390/catal13101369 - 15 Oct 2023

Cited by 1 | Viewed by 1225

Abstract

The last decade has witnessed significant progress in the development of novel synthetic methods for the preparation of a variety of new functionalized and condensed compounds via reactions of organic dichalcogenides with acetylenic derivatives. The present review highlights recent developments in the synthesis [...] Read more.

The last decade has witnessed significant progress in the development of novel synthetic methods for the preparation of a variety of new functionalized and condensed compounds via reactions of organic dichalcogenides with acetylenic derivatives. The present review highlights recent developments in the synthesis of organoselenium compounds based on the reactions of organic diselenides with acetylenes over the past few years. The discussion mainly focuses on the literature data for the last 5 years. It is worth noting that the lion’s share of this material is devoted to catalytic and electrophile-mediated reactions with aromatic compounds, containing a triple bond and nucleophilic functional groups. Full article

(This article belongs to the Special Issue Recent Advances in Catalytic Synthesis and Application of Heterocyclic and Heteroatom Compounds)

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21 pages, 8237 KiB

Open AccessArticle

Detection of Ciprofloxacin Based on BPN/TDNA Photoelectrode

by Jiangnan Yuan, Shusheng Wei, Zhiheng Ji and Juan Wang

Catalysts 2023, 13(10), 1368; https://doi.org/10.3390/catal13101368 - 15 Oct 2023

Viewed by 805

Abstract

The photoelectrochemical (PEC) process has been demonstrated to exert enormous potential in the fields of analysis, and the rational design of PEC sensors are vital for practical applications. In this study, Titanium Dioxide Nanoarrays (TDNA) and black phosphorus nanosheets (BPN) were prepared, and [...] Read more.

The photoelectrochemical (PEC) process has been demonstrated to exert enormous potential in the fields of analysis, and the rational design of PEC sensors are vital for practical applications. In this study, Titanium Dioxide Nanoarrays (TDNA) and black phosphorus nanosheets (BPN) were prepared, and a BPN/TDNA composite was proposed as the photoelectrochemical sensing material for the detection of ciprofloxacin (Cip). The formation and excellent optoelectronic properties of BPN/TDNA composite materials have been demonstrated through a series of characterization methods. Moreover, the measurement of PEC properties exhibited that the introduction of BPN and natural light would improve the electron migration efficiency and the separation of photogenerated electron–hole pairs, thereby displaying the synergistic effect to promote photoelectric performance. More importantly, the current density of BPN/TDNA was linearly proportional to the concentration of Cip ranging from 1.14 to 438.86 ng/mL, and the detection limit (3S/N) was 7.56 ng/mL. In addition, such a PEC sensor demonstrated long-term stability, good reproducibility, and selectivity. Finally, the real commercial sample detection was measured to confirm the possibility of practical applications. Thus, the BPN/TDNA photoelectrocatalyst provides a new method for Cip detection with high selectivity and sensitivity. Full article

(This article belongs to the Special Issue Advances in Two-Dimensional Photocatalysts)

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34 pages, 5147 KiB

Open AccessArticle

Optimization of ZnO Nanoparticles’ Synthesis via Precipitation Method Applying Taguchi Robust Design

by Maria-Anna Gatou, Katerina Kontoliou, Eleni Volla, Konstantinos Karachalios, Grigorios Raptopoulos, Patrina Paraskevopoulou, Nefeli Lagopati and Evangelia A. Pavlatou

Catalysts 2023, 13(10), 1367; https://doi.org/10.3390/catal13101367 - 13 Oct 2023

Cited by 2 | Viewed by 1551

Abstract

Zinc oxide (ZnO) possesses exceptional potential to be utilized in water and wastewater treatment applications, either as a photocatalyst or in membrane incorporation. In the present study, ZnO nanoparticles were synthesized using the precipitation method. The Taguchi approach with the L_32b orthogonal [...] Read more.

Zinc oxide (ZnO) possesses exceptional potential to be utilized in water and wastewater treatment applications, either as a photocatalyst or in membrane incorporation. In the present study, ZnO nanoparticles were synthesized using the precipitation method. The Taguchi approach with the L_32b orthogonal array was utilized in order to optimize the experimental conditions for the synthesis of the nanoparticles and to ensure that relatively smaller-sized particles were obtained. The design was characterized by ten factors, where nine of them possessed four levels, while one had two levels. This study’s design factors were the type of Zn precursor, the concentration of the Zn precursor, the type of precipitating agent, the precipitation agent’s concentration, the type of utilized solvent, the pH value of the solvent, the temperature used during the synthetic procedure, the calcination temperature, the time of stirring during synthesis, as well as the stirring speed. The influences of those factors on the selected response parameters (the average crystallite size, degree of crystallinity, energy band gap (E_g), and photodegradation constant (k)) were then evaluated. XRD analysis and the calculated E_g values indicated that the hexagonal wurtzite structure was the only crystalline phase present in the produced samples. The photocatalytic efficiency of all ZnO nanoparticles was examined in the degradation of rhodamine B under UV light irradiation. The optimal conditions were achieved using zinc acetate dihydrate as the Zn precursor at a concentration equal to 0.3 M, sodium hydroxide as the precipitating agent (1.5 M), methanol as the solvent (the pH value of the solvent was equal to 13), a temperature during the synthetic procedure of 70 °C, 600 °C as calcination temperature, a 90 min stirring time, and 700 rpm as the stirring speed. The optimized ZnO sample was synthesized based on the aforementioned conditions and thoroughly characterized. The acquired results confirmed the prediction of the Taguchi approach, and the most enhanced k-value was observed. Full article

(This article belongs to the Special Issue Recent Advances in Photocatalytic Degradation of Pollutants in Wastewater)

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12 pages, 3489 KiB

Open AccessArticle

Ni-Doped La_0.6Sr_0.4CoO₃ Perovskite as an Efficient Electrocatalyst for Oxygen Reduction and Evolution Reactions in Alkaline Media

by Ronghua Yuan, Weina Xu, Liquan Pan, Ruibin Li, Chuanying Xiao and Xiaochang Qiao

Catalysts 2023, 13(10), 1366; https://doi.org/10.3390/catal13101366 - 13 Oct 2023

Viewed by 917

Abstract

The Co-based perovskite La_0.6Sr_0.4CoO₃ has received significant attention as a potential electrocatalyst for its oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) due to its abundance, facile synthesis, and high oxygen kinetics. However, research on the catalytic [...] Read more.

The Co-based perovskite La_0.6Sr_0.4CoO₃ has received significant attention as a potential electrocatalyst for its oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) due to its abundance, facile synthesis, and high oxygen kinetics. However, research on the catalytic performance of Ni-doped La_0.6Sr_0.4Co_1−xNi_xO₃ as a bifunctional cathode catalyst for Zn-air batteries (ZABs) is still scarce. In this work, lanthanum strontium cobalt-based perovskite catalysts with various Ni contents (La_0.6Sr_0.4Co_1−xNi_xO₃, x = 0, 0.2, 0.5, and 0.8) were synthesized using a simple combustion method. The effects of Ni doping on the morphology, structure, surface oxygen-related species, and valence states of the transition metals of the perovskite were characterized. The electrochemical behaviors of the perovskite catalysts in both ORR and OER were also assessed. The characterization results revealed that proper Ni doping can decrease particle size, increase surface oxygen vacancies, and create mixed valence states of the transition metal and, thus, lead to improvement of the electrocatalytic activity of perovskite catalysts. Among the different perovskite compositions, La_0.6Sr_0.4Co_0.8Ni_0.2O₃ exhibited the best ORR/OER activity, with a higher limiting current density, smaller Tafel slope, higher half-wave potential, lower overpotential, and lower potential difference than the other compositions. When La_0.6Sr_0.4Co_0.8Ni_0.2O₃ was applied as the cathodic catalyst in a primary ZAB, it delivered a peak power density of 81 mW cm⁻². Additionally, in rechargeable ZABs, the La_0.6Sr_0.4Co_0.8Ni_0.2O₃ catalyst exhibited a lower voltage gap (0.94 V) and higher stability during charge–discharge cycling than the commonly used catalyst Pt/C. These results indicate that Ni-doped La_0.6Sr_0.4Co_0.8Ni_0.2O₃ is a promising bifunctional electrocatalyst for ZAB. Full article

(This article belongs to the Special Issue Oxygen Evolution Reaction (OER) and Oxygen Reduction Reaction (ORR) Electrocatalysis)

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16 pages, 12029 KiB

Open AccessArticle

New BaTi_0.96Cu_0.02X_0.02O₃ (X = V, Nb) Photocatalysts for Dyes Effluent Remediation: Broad Visible Light Response

by Ghayah M. Alsulaim

Catalysts 2023, 13(10), 1365; https://doi.org/10.3390/catal13101365 - 12 Oct 2023

Viewed by 781

Abstract

The problem of industrial dyes depollution has pushed the scientific research community to identify novel photocatalysts with high performance. Herein, new photocatalysts composed of BaTiO₃, BaTi_0.96Cu_0.04O₃, BaTi_0.96Cu_0.02V_0.02O₃ and [...] Read more.

The problem of industrial dyes depollution has pushed the scientific research community to identify novel photocatalysts with high performance. Herein, new photocatalysts composed of BaTiO₃, BaTi_0.96Cu_0.04O₃, BaTi_0.96Cu_0.02V_0.02O₃ and BaTi_0.96Cu_0.02Nb_0.02O₃ powders were prepared by solid-state reaction. The structural analysis of the samples confirmed the formation of the BaTiO₃ structure. The splitting of (002) and (200) planes verified the formation of the tetragonal phase. The XRD peaks shifted, and the unit cell volume expansion verified the substitution of the Ti⁴⁺ site by Cu²⁺, V⁴⁺ and Nb⁵⁺ ions. The morphological measurements showed that the addition of (Cu, V) and (Cu, Nb) ions changes the particles’ morphology of BaTiO₃, reducing its grains size. After the incorporation of (Cu, V) and (Cu, Nb) ions, the band gap of BaTiO₃ was reduced from 3.2 to 2.84 and 2.72 eV, respectively. The modification of BaTiO₃ by (Cu, Nb) ions induced superior photocatalytic properties for methyl green and methyl orange with degradation efficiencies of 97% and 94% during 60 and 90 min under sunlight irradiation, respectively. The total organic carbon results indicated that the BaTi_0.96Cu_0.02Nb_0.02O₃ catalyst has a high mineralization efficiency. In addition, it possesses a high stability during three cycles. The high photodegradation efficiency of Bi_0.96La_0.02Gd_0.02FeO₃ was related to the wide-ranging visible light absorption. Full article

(This article belongs to the Section Photocatalysis)

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21 pages, 4893 KiB

Open AccessFeature PaperArticle

Zn-Cr Layered Double Hydroxides for Photocatalytic Transformation of CO₂ under Visible Light Irradiation: The Effect of the Metal Ratio and Interlayer Anion

by Dolores G. Gil-Gavilán, Daniel Cosano, Juan Amaro-Gahete, Miguel Castillo-Rodríguez, Dolores Esquivel, José R. Ruiz and Francisco J. Romero-Salguero

Catalysts 2023, 13(10), 1364; https://doi.org/10.3390/catal13101364 - 12 Oct 2023

Cited by 1 | Viewed by 1247

Abstract

Carbon dioxide is the main gas responsible for the greenhouse effect. Over the last few years, the research focus of many studies has been to transform CO₂ into valuable products (CO, HCOOH, HCHO, CH₃OH and CH₄), since it [...] Read more.

Carbon dioxide is the main gas responsible for the greenhouse effect. Over the last few years, the research focus of many studies has been to transform CO₂ into valuable products (CO, HCOOH, HCHO, CH₃OH and CH₄), since it would contribute to mitigating global warming and environmental pollution. Layered double hydroxides (LDHs) are two-dimensional materials with high CO₂ adsorption capacity and compositional flexibility with potential catalytic properties to be applied in CO₂ reduction processes. Herein, Zn-Cr LDH-based materials with different metal ratio and interlayer anions, i.e., chloride (Cl⁻), graphene quantum dots (GQDs), sodium dodecyl sulfate (SDS) and sodium deoxycholate (SDC), have been prepared by a co-precipitation method and characterized by different techniques. The influence of the interlayer inorganic and organic anions and the metal ratio on the application of Zn-Cr LDHs as catalysts for the photocatalytic CO₂ reduction reaction under visible light irradiation is unprecedentedly reported. The catalytic tests have been carried out with Ru(bpy)₃²⁺ as photosensitizer (PS) and triethanolamine as sacrificial electron donor (ED) at λ = 450 nm. All LDHs materials exhibited good photocatalytic activity towards CO. Among them, LDH3-SDC showed the best catalytic performance, achieving 10,977 µmol CO g⁻¹ at 24 h under visible light irradiation with a CO selectivity of 88%. This study provides pertinent findings about the modified physicochemical features of Zn-Cr LDHs, such as particle size, surface area and the nature of the interlayer anion, and how they influence the catalytic activity in CO₂ photoreduction. Full article

(This article belongs to the Special Issue Photocatalysis in Air Purification)

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30 pages, 5413 KiB

Open AccessFeature PaperReview

Hydroisomerization Catalysts for High-Quality Diesel Fuel Production

by Yamen Aljajan, Valentin Stytsenko, Maria Rubtsova and Aleksandr Glotov

Catalysts 2023, 13(10), 1363; https://doi.org/10.3390/catal13101363 - 11 Oct 2023

Viewed by 1927

Abstract

Upgrading the properties of diesel fractions is considered one of the crucial processes in the petrochemical industry; and for this purpose in laboratory-scale researching it is studied on the base of the hydroisomerization of n-hexadecane as a main model reaction. Recently, zeolite-based bifunctional [...] Read more.

Upgrading the properties of diesel fractions is considered one of the crucial processes in the petrochemical industry; and for this purpose in laboratory-scale researching it is studied on the base of the hydroisomerization of n-hexadecane as a main model reaction. Recently, zeolite-based bifunctional catalysts have proven their efficiency due to their remarkable acidity, shape-selectivity and relative resistance to deactivation. In this review, different topological-type zeolite-based catalysts, the mechanism of their catalytic effect in n-C₁₆ isomerization, and the principles of shape-selectivity are reviewed. A comparison of their structural-operational characteristics is made. The impact of some feedstock impurities on the catalyst’s performance and deactivation due to carbonaceous deposits as well as various modern eco-friendly cost-effective synthesis techniques are also discussed. Full article

(This article belongs to the Special Issue Feature Papers in "Industrial Catalysis" Section)

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19 pages, 3495 KiB

Open AccessFeature PaperArticle

Study on the Hydrogenation of Ethyl Stearate to the Fatty Alcohol 1-Octadecanol over Ru on Tungstated Zirconia

by Diego Quintero-Ramos, Manuel Checa, Jose Luis Jordá and Maria J. Sabater

Catalysts 2023, 13(10), 1362; https://doi.org/10.3390/catal13101362 - 11 Oct 2023

Viewed by 1212

Abstract

Fatty alcohols are important products in the chemical industry, given that they are frequently used in the formulation of surfactants and lubricants. In this context, this work describes a catalytic heterogeneous approach for the production of 1-octadecanol (C₁₈OH) from ethyl stearate [...] Read more.

Fatty alcohols are important products in the chemical industry, given that they are frequently used in the formulation of surfactants and lubricants. In this context, this work describes a catalytic heterogeneous approach for the production of 1-octadecanol (C₁₈OH) from ethyl stearate (ES) using nanosized Ru-supported on tungstated zirconia (W/Zr). The activity and selectivity of this series of catalysts have been studied during the hydrogenation of ES in a batch reactor at 175 °C and P_H2 = 40 bar. The so-prepared catalysts were characterized by a sort of characterization techniques (i.e., X-ray diffraction, H₂-TPR, etc.), confirming the high dispersion and higher reducibility of Ru nanoparticles on the W/Zr surface (primarily tetragonal zirconia) with respect to pure zirconia. Overall, the catalysts were significantly active. In addition, a strong synergistic effect was revealed between Ru and W species, according to catalytic data. Finally, the reaction sequence towards fatty alcohol has also been elucidated, pointing to the ester hydrogenolysis to the aldehyde and ulterior hydrogenation of the latter as the main route for fatty alcohol formation. Full article

(This article belongs to the Special Issue Nanotechnology in Catalysis, 2nd Edition)

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12 pages, 1960 KiB

Open AccessArticle

Thermal Degradation Kinetics of Vacuum Residues in the Presence of Chrysotile Supported Ni-Ti Catalyst

by Nazerke Balpanova and Murzabek Baikenov

Catalysts 2023, 13(10), 1361; https://doi.org/10.3390/catal13101361 - 11 Oct 2023

Cited by 1 | Viewed by 979

Abstract

For the first time, thermal decomposition of vacuum residue and a mixture of vacuum residue with binary nanocatalysts based on leached and non-leached chrysotile with applied active metals was studied using the thermogravimetry method. It is shown that the thermokinetic parameters of decomposition [...] Read more.

For the first time, thermal decomposition of vacuum residue and a mixture of vacuum residue with binary nanocatalysts based on leached and non-leached chrysotile with applied active metals was studied using the thermogravimetry method. It is shown that the thermokinetic parameters of decomposition of vacuum residue and its mixture with binary nanocatalyst are different. The phase composition of the binary nanocatalyst was established through X-ray phase analysis (XRD): (Mg₃Si₂O₅ (OH), NiO and Ti (SO₄)₂). The quantitative content of elements on the chrysotile surface was determined using X-ray fluorescence analysis: (Ni (4.88%), Ti (7.29%), Si (24.93%), Mg (7.83%), Fe (0.69%) and S (3.89%)). Using atomic emission spectral analysis, the gross quantitative content of supported metals on chrysotile was determined: Ni (4.85%) and Ti (4.86%). A transmission electron microscope showed the presence of finely dispersed particles adsorbed on the surface of and possibly inside chrysotile nanotubes with sizes ranging from 5 to 70 nm. The acidity of the nanocatalyst obtained from the leached active-metal-supported chrysotile was 267 μmol/g and the specific surface area of the nanocatalyst was 54 m²/g. The Ozawa–Flynn–Wall (OFW) method was used to calculate the kinetic parameters of the thermal degradation of vacuum residue and the mixture of vacuum residue with nanocatalysts. Using the isoconversion method, the average values of activation energies and the pre-exponential factor were calculated: 147.55 kJ/mol and 3.37·10¹⁶ min⁻¹ for the initial vacuum residue; 118.69 kJ/mol and 1.54·10¹⁸ min⁻¹ for the mixture of vacuum residue with nanocatalyst obtained from non-leached chrysotile with applied metals; 82.83 kJ/mol and 2.15·10¹⁹ min⁻¹ for the mixture of vacuum residue with nanocatalyst obtained from leached chrysotile with applied metals. The kinetic parameters obtained can be used in modeling and designing the processes of thermal degradation and hydroforming of heavy hydrocarbon raw materials. Full article

(This article belongs to the Special Issue Heterogeneous Catalysts for Petrochemical Synthesis and Oil Refining, 2nd Edition)

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19 pages, 2357 KiB

Open AccessFeature PaperArticle

Production of Prebiotic Galacto-Oligosaccharides from Acid Whey Catalyzed by a Novel β-Galactosidase from Thermothielavioides terrestris and Commercial Lactases: A Comparative Study

by Athanasios Limnaios, Maria Tsevdou, Elena Tsika, Nausika Korialou, Anastasia Zerva, Evangelos Topakas and Petros Taoukis

Catalysts 2023, 13(10), 1360; https://doi.org/10.3390/catal13101360 - 11 Oct 2023

Cited by 3 | Viewed by 1022

Abstract

The steadily increasing global popularity of Greek strained yoghurt has necessitated alternative valorization approaches for acid whey, the major straining process effluent. In this context, prebiotic galacto-oligosaccharides can be enzymatically synthesized from acid whey lactose, via either commercial or novel β-galactosidases. A comparative [...] Read more.

The steadily increasing global popularity of Greek strained yoghurt has necessitated alternative valorization approaches for acid whey, the major straining process effluent. In this context, prebiotic galacto-oligosaccharides can be enzymatically synthesized from acid whey lactose, via either commercial or novel β-galactosidases. A comparative study of galacto-oligosaccharide production from acid whey was carried out, employing two commercial β-galactosidases (from Kluyveromyces lactis and Aspergillus oryzae) and one novel, in-house produced (from Thermothielavioides terrestris), as a function of the initial lactose content and enzyme load. Selected reaction conditions for β-galactosidases from K. lactis, A. oryzae, and T. terrestris were 35 °C at pH 7.2, 45 °C at pH 4.5, and 50 °C at pH 4.0, respectively. Maximum galacto-oligosaccharide yields equal to 23.7, 23.4, and 25.7% were achieved with, respectively, 0.13 U/mL of K. lactis β-galactosidase in non-concentrated acid whey, 4 U/mL of A. oryzae β-galactosidase, and 8 U/mL of T. terrestris β-galactosidase in acid whey concentrated to 20% w/v initial lactose content. The increased galacto-oligosaccharide productivity of the thermophilic β-galactosidase from T. terrestris can be a determining asset in a combined concentration and oligomerization industrial process. This will allow for high galacto-oligosaccharide yields for efficient, cost-effective production of valuable prebiotics from acid whey. Full article

(This article belongs to the Special Issue New Trends in Industrial Biocatalysis)

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28 pages, 7972 KiB

Open AccessReview

Enzymatic Glycosylation Strategies in the Production of Bioactive Compounds

by Alicia Andreu, Marija Ćorović, Carla Garcia-Sanz, A. Sofia Santos, Ana Milivojević, Clara Ortega-Nieto, Cesar Mateo, Dejan Bezbradica and Jose M. Palomo

Catalysts 2023, 13(10), 1359; https://doi.org/10.3390/catal13101359 - 11 Oct 2023

Cited by 2 | Viewed by 1789

Abstract

Enzymatic glycosylation is a versatile and sustainable biotechnological approach that plays a pivotal role in the production of bioactive compounds. This process involves the enzymatic transfer of sugar moieties onto various acceptor molecules, such as small molecules, peptides, or proteins, resulting in the [...] Read more.

Enzymatic glycosylation is a versatile and sustainable biotechnological approach that plays a pivotal role in the production of bioactive compounds. This process involves the enzymatic transfer of sugar moieties onto various acceptor molecules, such as small molecules, peptides, or proteins, resulting in the synthesis of glycosides. These glycosides often exhibit enhanced bioactivity, improved solubility, and enhanced stability, making them valuable in pharmaceuticals, nutraceuticals, and the food industry. This review explores the diverse enzymatic glycosylation strategies employed in the synthesis of bioactive compounds. It highlights the enzymatic catalysts involved, including glycosyltransferases, glycosidases, glycophosphorylases, and glycosynthases. It considers the advantages and disadvantages of these biocatalysts in the stereoselective and regioselective synthesis of different types of glycosylated molecules, phenolic and aliphatic alcohols, oligosaccharides, polysaccharides, glycoderivatives, glycopeptides, and glycoproteins with a clear focus on food and pharmaceutical chemistry. Furthermore, the review outlines various sources of sugar donors, activated glycosides, and sugar nucleotides, as well as the utilization of engineered enzymes and microorganisms for glycosylation reactions. The advantages of enzymatic glycosylation, including its high regioselectivity, stereoselectivity, and sustainability, are emphasized. Therefore, these approaches combining the use of different catalytic systems, the improvement of tools such as immobilization technology or chemical or genetic modification to improve the glycosylation process, could be useful tools in continuous biotechnological advancements. Full article

(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members and Topical Advisory Panel Members of Catalysts in Section "Biocatalysis")

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Catalysts, Volume 13, Issue 10 (October 2023) – 72 articles

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