Catalysts

Open AccessReview

Tunable Late-Transition-Metal-Catalyzed Polymerization for Controlled Polymer Synthesis

by

,

,

,

and

Catalysts 2023, 13(4), 670; https://doi.org/10.3390/catal13040670 (registering DOI) - 29 Mar 2023

Abstract

As a powerful protocol for the preparation of common polymers, such as polyolefins, polyesters, and polycarbonates, late-transition-metal-catalyzed polymerization can be carried out by controlling the reaction conditions or developing dynamic catalytic systems that use external stimuli to influence the performance of the active [...] Read more.

As a powerful protocol for the preparation of common polymers, such as polyolefins, polyesters, and polycarbonates, late-transition-metal-catalyzed polymerization can be carried out by controlling the reaction conditions or developing dynamic catalytic systems that use external stimuli to influence the performance of the active sites, resulting in well-defined polymeric materials. In particularly, under the latter conditions, ‘one catalyst’ can provide more than one kind of polymer with a controlled sequence from the monomer mixture, making full use of the prepared catalyst. In this review, tunable modes, including reaction conditions, redox, light or electrochemical properties, Lewis acids, and alkali metal cations, of late-transition-metal-complex (especially iron, cobalt, and nickel)-catalyzed polymerization were collected and thoroughly discussed. Full article

(This article belongs to the Special Issue Catalysis with Earth-Abundant Metals Iron, Cobalt, Nickel and Copper for Sustainability)

► Show Figures

Figure 1

Open AccessArticle

Optimization Study on Synergistic System of Photocatalytic Degradation of AR 26 and UV-LED Heat Dissipation

by

Chen Wang

,

Haoliang Bai

and

Xue Kang

Catalysts 2023, 13(4), 669; https://doi.org/10.3390/catal13040669 (registering DOI) - 29 Mar 2023

Abstract

In this work, a novel UV-LED/TiO₂ photocatalytic system, having a single layer with ten LED beads, was designed to simultaneously achieve UV-LED cooling and wastewater degradation, to deal with heat dissipation problems of high-power UV-LEDs. To gain more insight into this system, [...] Read more.

In this work, a novel UV-LED/TiO₂ photocatalytic system, having a single layer with ten LED beads, was designed to simultaneously achieve UV-LED cooling and wastewater degradation, to deal with heat dissipation problems of high-power UV-LEDs. To gain more insight into this system, the parameters affecting both cooling and photocatalytic performance were first optimized using AR 26 as a basis. With respect to sewage, sewage with a flow rate of 80 mL/min and a temperature of 20 °C helped to keep a lower temperature of UV-LED, which benefits the long-term operation stability of LED beads. For parameters affecting the photocatalytic performance only, the experiments showed that TiO₂ with moderate dosing (0.75 g/L) under strong acid conditions (pH = 2) helped to further improve photocatalytic activity when the initial concentration of AR 26 was 45 mg/L. Lastly, to illustrate the advantages of this novel system, the performance of the synergistic system was compared with a conventional photocatalytic reactor with respect to degradation performance, optical quantum efficiency, and energy consumption. The results showed that the degradation efficiency and light source utilization ratio of this coupled system were, respectively, 2.1 times and 1.5 times as much as those of a conventional reactor. As the unit power consumption of the synergistic system was only 0.18-fold more than that of a conventional reactor, our work suggests that this synergistic system with the advantage of LED lamp beads has a bright future in dealing with refractory organic pollutants of sewage. Full article

(This article belongs to the Special Issue Frontiers in Catalytic Emission Control)

► Show Figures

Figure 1

Open AccessArticle

Synthesis of Ce and Sm Co-Doped TiO₂ Nanoparticles with Enhanced Photocatalytic Activity for Rhodamine B Dye Degradation

by

Yassine Slimani

,

Munirah A. Almessiere

,

Mohamed J. S. Mohamed

,

,

,

,

and

Catalysts 2023, 13(4), 668; https://doi.org/10.3390/catal13040668 (registering DOI) - 29 Mar 2023

Abstract

One of the major concerns that receive global attention is the presence of organic pollutants (dyes, pharmaceuticals, pesticides, phenolic compounds, heavy metals, and so on), originating from various industries, in wastewater and water resources. Rhodamine B is widely used in the dyeing of [...] Read more.

One of the major concerns that receive global attention is the presence of organic pollutants (dyes, pharmaceuticals, pesticides, phenolic compounds, heavy metals, and so on), originating from various industries, in wastewater and water resources. Rhodamine B is widely used in the dyeing of paints, plastics, textiles, and other fabrics, as well as biological products. It is highly persistent, toxic, and carcinogenic to organisms and humans when directly released into the water supply. To avoid this hazard, several studies have been conducted in an attempt to remove Rhodamine B from wastewater. Metal oxide semiconducting materials have gained great interest because of their ability to decompose organic pollutants from wastewater. TiO₂ is one of the most effective photocatalysts with a broad range of applications. Several attempts have been made to improve its photocatalytic activity. Accordingly, we have prepared in this work a series of cerium (Ce) and samarium (Sm) co-doped TiO₂ nanoparticles (x = 0.00, 0.25, 0.50, 1.00, and 2.00%) using a sol–gel auto-combustion approach. The influence of Ce–Sm concentrations on the structural, morphology, electronic, and optical properties, as well as the photocatalytic activity, was investigated. Structure and elemental mapping analyses proved the presence of Ce and Sm in the compositions as well as the development of the TiO₂ anatase phase with a tetragonal structure and crystallite size of 15.1–17.8 nm. Morphological observations confirmed the creation of spherical nanoparticles (NPs). The examination of the electronic structure properties using density functional theory (DFT) calculations and of the optical properties using a UV/Vis diffuse spectrophotometer showed a reduction in the bandgap energy upon Ce–Sm co-doping. The photocatalytic activity of the synthesized products was assessed on the degradation of Rhodamine B dye, and it was found that all Ce–Sm co-doped TiO₂ nanoparticles have better photocatalytic activities than pristine TiO₂ nanoparticles. Among all of the prepared nanoparticles, the sample with x = 0.50% demonstrated the best photocatalytic activity, with a degradation efficiency of 98% within 30 min and a reaction rate constant of about 0.0616 min⁻¹. h⁺ and •O₂⁻ were determined to be the most important active species in the photocatalytic degradation process. Besides the high photocatalytic degradation efficiency, these photocatalysts are highly stable and could be easily recovered and reused, which indicates their potential for practical applications in the future. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Photocatalytic Nanomaterials)

► Show Figures

Figure 1

Open AccessFeature PaperArticle

Undoped and Fe-Doped Anatase/Brookite TiO₂ Mixed Phases, Obtained by a Simple Template-Free Synthesis Method: Physico-Chemical Characterization and Photocatalytic Activity towards Simazine Degradation

by

,

,

,

and

Catalysts 2023, 13(4), 667; https://doi.org/10.3390/catal13040667 (registering DOI) - 29 Mar 2023

Abstract

For the first time, Fe-doping (0.05, 1.0, and 2.5 wt.% Fe) was performed on a high-surface-area anatase/brookite TiO₂ by adopting a simple template-free sol-gel synthesis followed by calcination at a mild temperature. The powders’ textural and surface properties were characterized by following [...] Read more.

For the first time, Fe-doping (0.05, 1.0, and 2.5 wt.% Fe) was performed on a high-surface-area anatase/brookite TiO₂ by adopting a simple template-free sol-gel synthesis followed by calcination at a mild temperature. The powders’ textural and surface properties were characterized by following a multi-technique approach. XRD analysis showed that the anatase/brookite ratio slightly varied in the Fe-doped TiO₂ (from 76.9/23.1 to 79.3/22.7); Fe doping noticeably affected the cell volume of the brookite phase, which decreased, likely due to Fe³⁺ ions occupying interstitial positions, and retarded the crystallite growth. N₂ sorption at −196 °C showed the occurrence of samples with disordered interparticle mesopores, with an increase in the specific surface area from 236 m² g⁻¹ (undoped TiO₂) to 263 m² g⁻¹ (2.5 wt.% Fe). Diffuse Reflectance UV-Vis spectroscopy showed a progressive decrease in the bandgap energy from 3.10 eV (undoped TiO₂) to 2.85 eV (2.5 wt.% Fe). XPS analysis showed the presence of some surface Fe species only at 2.5 wt.% Fe, and accordingly, the ζ-potential measurements showed small changes in the pH at the isoelectric point. The photocatalytic degradation of simazine (a persistent water contaminant) both under UV and simulated solar light was performed as a probe reaction. Under UV light, Fe-doping improved simazine degradation in the sample at 0.05 wt.% Fe, capable of degrading ca. 77% simazine. Interestingly, the undoped TiO₂ was also active both under UV and 1 SUN. This is likely due to the occurrence of anatase/brookite heterojunctions, which help stabilize the photogenerated electrons/holes. Full article

(This article belongs to the Special Issue Advances in the Synthesis and Applications of Transition/Noble Metal Oxide Photocatalysts)

► Show Figures

Figure 1

Open AccessArticle

Highly Efficient Self-Assembled Activated Carbon Cloth-Templated Photocatalyst for NADH Regeneration and Photocatalytic Reduction of 4-Nitro Benzyl Alcohol

by

,

,

,

,

,

,

,

,

,

,

and

Catalysts 2023, 13(4), 666; https://doi.org/10.3390/catal13040666 - 29 Mar 2023

Abstract

This manuscript emphasizes how structural assembling can facilitate the generation of solar chemicals and the synthesis of fine chemicals under solar light, which is a challenging task via a photocatalytic pathway. Solar energy utilization for pollution prevention through the reduction of organic chemicals [...] Read more.

This manuscript emphasizes how structural assembling can facilitate the generation of solar chemicals and the synthesis of fine chemicals under solar light, which is a challenging task via a photocatalytic pathway. Solar energy utilization for pollution prevention through the reduction of organic chemicals is one of the most challenging tasks. In this field, a metal-based photocatalyst is an optional technique but has some drawbacks, such as low efficiency, a toxic nature, poor yield of photocatalytic products, and it is expensive. A metal-free activated carbon cloth (ACC)–templated photocatalyst is an alternative path to minimize these drawbacks. Herein, we design the synthesis and development of a metal-free self-assembled eriochrome cyanine R (EC-R) based ACC photocatalyst (EC-R@ACC), which has a higher molar extinction coefficient and an appropriate optical band gap in the visible region. The EC-R@ACC photocatalyst functions in a highly effective manner for the photocatalytic reduction of 4-nitro benzyl alcohol (4-NBA) into 4-amino benzyl alcohol (4-ABA) with a yield of 96% in 12 h. The synthesized EC-R@ACC photocatalyst also regenerates reduced forms of nicotinamide adenine dinucleotide (NADH) cofactor with a yield of 76.9% in 2 h. The calculated turnover number (TON) of the EC-R@ACC photocatalyst for the reduction of 4-nitrobenzyl alcohol is 1.769 × 10¹⁹ molecules. The present research sets a new benchmark example in the area of organic transformation and artificial photocatalysis. Full article

(This article belongs to the Special Issue Catalytic Methods for the Synthesis of Carbon Nanodots and Their Applications)

► Show Figures

Figure 1

Open AccessArticle

Manganese Salan Complexes as Catalysts for Hydrosilylation of Aldehydes and Ketones

by

Nora Almutairi

,

Srikanth Vijjamarri

and

Guodong Du

Catalysts 2023, 13(4), 665; https://doi.org/10.3390/catal13040665 - 29 Mar 2023

Abstract

Manganese has attracted significant recent attention due to its abundance, low toxicity, and versatility in catalysis. In the present study, a series of manganese (III) complexes supported by salan ligands have been synthesized and characterized, and their activity as catalysts in the hydrosilylation [...] Read more.

Manganese has attracted significant recent attention due to its abundance, low toxicity, and versatility in catalysis. In the present study, a series of manganese (III) complexes supported by salan ligands have been synthesized and characterized, and their activity as catalysts in the hydrosilylation of carbonyl compounds was examined. While manganese (III) chloride complexes exhibited minimal catalytic efficacy without activation of silver perchlorate, manganese (III) azide complexes showed good activity in the hydrosilylation of carbonyl compounds. Under optimized reaction conditions, several types of aldehydes and ketones could be reduced with good yields and tolerance to a variety of functional groups. The possible mechanisms of silane activation and hydrosilylation were discussed in light of relevant experimental observations. Full article

(This article belongs to the Special Issue The Role of Catalysts in Functionalization of C-H and C-C Bonds II)

► Show Figures

Figure 1

Open AccessArticle

Supported Ionic Liquid Catalysts for the Oxidation of S- and N-Containing Compounds—The Effect of Bronsted Sites and Heteropolyacid Concentration

by

,

,

,

and

Catalysts 2023, 13(4), 664; https://doi.org/10.3390/catal13040664 - 28 Mar 2023

Abstract

In this article, a series of effective catalysts based on betaine and sulfuric or phosphomolybdic acids was obtained. These compositions were characterized by various physicochemical methods and tested in the oxidation of sulfur- and nitrogenous-containing compounds by H₂O₂. An [...] Read more.

In this article, a series of effective catalysts based on betaine and sulfuric or phosphomolybdic acids was obtained. These compositions were characterized by various physicochemical methods and tested in the oxidation of sulfur- and nitrogenous-containing compounds by H₂O₂. An increase in the amount of heteropolyacid (HPA) leads to a non-linear change in acidity, and the degree of removal of sulfur-containing compounds correlates with the concentration of Bronsted acid sites on the surface. On the contrary, the degree of pyridine removal is determined primarily by the content of heteropolyacids in the catalyst. Full article

(This article belongs to the Special Issue Heterogeneous Catalysts for Petrochemical Synthesis and Oil Refining II)

► Show Figures

Figure 1

Open AccessFeature PaperArticle

Effect of MnO₂ Crystal Type on the Oxidation of Furfural to Furoic Acid

by

,

,

,

,

and

Catalysts 2023, 13(4), 663; https://doi.org/10.3390/catal13040663 - 28 Mar 2023

Abstract

The base-free oxidation of furfural by non-noble metal systems has been challenging. Although MnO₂ emerges as a potential catalyst application in base-free conditions, its catalytic efficiency still needs to be improved. The crystalline form of MnO₂ is an important factor affecting [...] Read more.

The base-free oxidation of furfural by non-noble metal systems has been challenging. Although MnO₂ emerges as a potential catalyst application in base-free conditions, its catalytic efficiency still needs to be improved. The crystalline form of MnO₂ is an important factor affecting the oxidation ability of furfural. For this reason, four crystalline forms of MnO₂ (α, β, γ, and δ-MnO₂) were selected. Their oxidation performance and surface functional groups were analyzed and compared in detail. Only δ-MnO₂ exhibited excellent activity, achieving 99.04% furfural conversion and 100% Propo._FA (Only furoic acid was detected by HPLC in the product) under base-free conditions, while the furfural conversion of α, β, and γ-MnO₂ was below 10%. Characterization by XPS, IR, O₂-TPD and other means revealed that δ-MnO₂ has the most abundant active oxygen species and surface hydroxyl groups, which are responsible for the best performance of δ-MnO₂. This work achieves the green and efficient oxidation of furfural to furoic acid over non-noble metal catalysts. Full article

(This article belongs to the Special Issue Recent Trends in Catalysis for Syngas Production and Conversion)

► Show Figures

Graphical abstract

Open AccessArticle

Transcriptomic Analysis of Differentially Expressed Genes in Arabidopsis thaliana Overexpressing BnMYB2 from Boehmeria nivea under Cadmium Stress

by

,

,

and

Catalysts 2023, 13(4), 662; https://doi.org/10.3390/catal13040662 - 28 Mar 2023

Abstract

Boehmeria nivea (ramie) is an important fiber crop with strong tolerance to cadmium (Cd). In our previous study, a novel MYB transcription factor gene from ramie, BnMYB2, was found to positively regulate Cd tolerance and accumulation in the transgenic Arabidopsis thaliana lines. [...] Read more.

Boehmeria nivea (ramie) is an important fiber crop with strong tolerance to cadmium (Cd). In our previous study, a novel MYB transcription factor gene from ramie, BnMYB2, was found to positively regulate Cd tolerance and accumulation in the transgenic Arabidopsis thaliana lines. Herein, transcriptome sequencing was performed to identify the differentially expressed genes involved in cadmium response between the wild-type (WT) and BnMYB2 overexpressed lines; 1598 differentially expressed genes (DEGs) were detected in the shoot. GO and KEGG analysis indicated that the majority of DEGs belonged to the categories of transcription factors, plant hormone signal transduction and nitrogen metabolism. The expression level of the Ib subgroup bHLH genes (AtbHLH38, AtbHLH39, AtbHLH100 and AtbHLH101) and nitrogen assimilation-related genes (AtNIA1, AtNIA2, AtNIR1 and AtASN2) were significantly higher than that of WT, accompanied with the positive changes in iron (Fe) and total nitrogen content in the shoot of BnMYB2 overexpression lines. Several DEGs belonging to the bZIP transcription factor family or SAUR family were also found up-regulated in the transgenic plants. These results provide important clues for elucidating how the molecular mechanisms of BnMYB2 regulate plant response to Cd stress. Full article

(This article belongs to the Special Issue Advances in Photocatalysis and Electrocatalysis Applications)

► Show Figures

Figure 1

Open AccessArticle

Activation of Peroxymonosulfate Using Spent Li-Ion Batteries for the Efficient Degradation of Chloroquine Phosphate

by

,

,

,

,

,

and

Catalysts 2023, 13(4), 661; https://doi.org/10.3390/catal13040661 - 28 Mar 2023

Abstract

Recycling and reusing spent lithium-ion batteries (LIBs) have gained a lot of attention in recent years, both ecologically and commercially. The carbon nanotube-loaded CoFe₂O₄ (CoFe₂O₄@CNTs) composite was made using a solvothermal technique utilizing wasted LIBs as [...] Read more.

Recycling and reusing spent lithium-ion batteries (LIBs) have gained a lot of attention in recent years, both ecologically and commercially. The carbon nanotube-loaded CoFe₂O₄ (CoFe₂O₄@CNTs) composite was made using a solvothermal technique utilizing wasted LIBs as the starting material and carbon nanotubes as support, and it was used as an efficient peroxymonosulfate (PMS, HSO₅⁻) activator to degrade chloroquine phosphate (CQP). Scanning electron microscopy (SEM), transmission electron microscopy (TEM), an energy dispersive spectrometer (EDS), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), and X-ray photoelectron spectroscopy (XPS) were utilized to characterize the physical and chemical properties of the catalyst generated. The impacts of CoFe₂O₄@CNTs dosage, PMS concentration, reaction temperature, initial pH value, starting CQP concentration, and co-existing ions have undergone extensive experimental testing. In comparison to bare CoFe₂O₄, the CoFe₂O₄@CNTs demonstrated increased catalytic activity, which might be attributed to their super electron transport capacity and large surface area. In ideal conditions, the mineralization efficiency and removal efficiency of 10 mg/L CQP approached 33 and 98.7%, respectively. By employing external magnets, the CoFe₂O₄@CNTs catalyst may be simply recycled and reused several times. The potential reaction mechanism in the CoFe₂O₄@CNTs/PMS system was also investigated. In summary, this study indicates that CoFe₂O₄@CNTs generated from spent lithium-ion batteries have a high potential in PMS activation for CQP and other pollutant degradation. Full article

(This article belongs to the Special Issue Catalytic Conversion of Municipal Solid Wastes(MSW) for the Efficient and Clean Utilization of All Components)

► Show Figures

Figure 1

Open AccessArticle

Synthesis of Co,Ce Oxide Nanoparticles Using an Aerosol Method and Their Deposition on Different Structured Substrates for Catalytic Removal of Diesel Particulate Matter

by

,

,

,

and

Viviana Guadalupe Milt

Catalysts 2023, 13(4), 660; https://doi.org/10.3390/catal13040660 - 28 Mar 2023

Abstract

The synthesis of Co and Ce oxide nanoparticles using precipitation of precursor salt solutions in the form of microdroplets generated with a nebulizer proved to be an efficient, fast and inexpensive method. Different morphologies of single oxides particles were obtained. Ceria nanoparticles were [...] Read more.

The synthesis of Co and Ce oxide nanoparticles using precipitation of precursor salt solutions in the form of microdroplets generated with a nebulizer proved to be an efficient, fast and inexpensive method. Different morphologies of single oxides particles were obtained. Ceria nanoparticles were almost cube-shaped of 8 nm average size, forming 1.3–1.5 μm aggregates, whereas cobalt oxide appeared as rounded-edged particles of 37 nm average size, mainly forming nanorods 50–500 nm. Co₃O₄ and CeO₂ nanoparticles were used to generate structured catalysts from both metallic (stainless steel wire mesh monoliths) and ceramic (cordierite honeycombs) substrates. Ceria Nyacol was used as a binder to favor the anchoring of catalytic particles thus enhancing the adhesion of the coating. The resulting structured catalysts were tested for the combustion of diesel soot with the aim of being used in the regeneration of particulate filters (DPFs). The performance of these structured catalysts was similar to or even better than that exhibited by the catalysts prepared using commercial nanoparticles. Among the catalysts tested, the structured systems using ceramic substrates were more efficient, showing lower values of the maximum combustion rate temperatures (T_M = 410 °C). Full article

(This article belongs to the Special Issue Nanoparticles in the Catalysis)

► Show Figures

Graphical abstract

Open AccessArticle

Enhanced Visible-Light Photocatalytic Activities of CeVO₄-V₂O₃ Composite: Effect of Ethylene Glycol

by

,

,

,

,

,

,

and

Catalysts 2023, 13(4), 659; https://doi.org/10.3390/catal13040659 - 27 Mar 2023

Abstract

CeVO₄-V₂O₃ composites were prepared by simple hydrothermal method, and the effects of ethylene glycol(EG) on the products were studied by XRD, N₂ adsorption–desorption, SEM, EDS, XPS, PL and UV-vis spectra. The characterization reveals a slight decrease in [...] Read more.

CeVO₄-V₂O₃ composites were prepared by simple hydrothermal method, and the effects of ethylene glycol(EG) on the products were studied by XRD, N₂ adsorption–desorption, SEM, EDS, XPS, PL and UV-vis spectra. The characterization reveals a slight decrease in surface area and a slight enhancement of visible light absorption in the final sample, while the crystalline phase, morphology and separation efficiency of the collective carriers are severely affected by the EG. At the same time, the photocatalytic effect of CeVO₄-V₂O₃ composites was evaluated by the degradation rate of methylene blue (MB) under simulated visible light. The sample for 10 mL EG obtained the highest efficiency of 96.9%, while the one for 15 mL EG showed the lowest efficiency of 67.5% within 300 min. The trapping experiments and ESR experiment showed that the contribution of active species to the photocatalytic degradation of MB was ∙OH > h⁺ > ∙O²⁻ in descending order, and a possible degradation mechanism was proposed. Full article

(This article belongs to the Special Issue Advanced Oxidation Catalysts)

► Show Figures

Figure 1

Open AccessArticle

One-Pot Synthesis of Benzoxazole/Benzothiazole-Substituted Esters by Michael Addition: A Selective Construction of C-N/C-S Bonds

by

,

,

,

and

Catalysts 2023, 13(4), 658; https://doi.org/10.3390/catal13040658 - 27 Mar 2023

Abstract

An efficient and convenient synthesis of benzoxazole/benzothiazole-substituted esters in a one-pot strategy is reported. In this investigation, a selective construction of C-N and C-S bonds via simple addition is performed. Thus, using substituted 2-aminophenols/2-aminobenzenethiols, TMTD (tetramethylthiuram disulfide) and α,β-unsaturated esters [...] Read more.

An efficient and convenient synthesis of benzoxazole/benzothiazole-substituted esters in a one-pot strategy is reported. In this investigation, a selective construction of C-N and C-S bonds via simple addition is performed. Thus, using substituted 2-aminophenols/2-aminobenzenethiols, TMTD (tetramethylthiuram disulfide) and α,β-unsaturated esters as starting substrates, C-N and C-S bonds can be selectively constructed by means of the Michael addition reaction. This protocol features high selectivity, high atomic economy, mild conditions, good functional tolerance and good to excellent yields, showing the potential value for the preparation of some biologically and pharmaceutically active compounds. Full article

(This article belongs to the Special Issue Catalytic Annulation Reactions)

► Show Figures

Graphical abstract

Open AccessReview

Engineering Strategies for Efficient Bioconversion of Glycerol to Value-Added Products by Yarrowia lipolytica

by

Eleni Theodosiou

Catalysts 2023, 13(4), 657; https://doi.org/10.3390/catal13040657 - 27 Mar 2023

Abstract

Yarrowia lipolytica has been a valuable biotechnological workhorse for the production of commercially important biochemicals for over 70 years. The knowledge gained so far on the native biosynthetic pathways, as well as the availability of numerous systems and synthetic biology tools, enabled not [...] Read more.

Yarrowia lipolytica has been a valuable biotechnological workhorse for the production of commercially important biochemicals for over 70 years. The knowledge gained so far on the native biosynthetic pathways, as well as the availability of numerous systems and synthetic biology tools, enabled not only the regulation and the redesign of the existing metabolic pathways, but also the introduction of novel synthetic ones; further consolidating the position of the yeast in industrial biotechnology. However, for the development of competitive and sustainable biotechnological production processes, bioengineering should be reinforced by bioprocess optimization strategies. Although there are many published reviews on the bioconversion of various carbon sources to value-added products by Yarrowia lipolytica, fewer works have focused on reviewing up-to-date strain, medium, and process engineering strategies with an aim to emphasize the significance of integrated engineering approaches. The ultimate goal of this work is to summarize the necessary knowledge and inspire novel routes to manipulate at a systems level the yeast biosynthetic machineries by combining strain and bioprocess engineering. Due to the increasing surplus of biodiesel-derived waste glycerol and the favored glycerol-utilization metabolic pathways of Y. lipolytica over other carbon sources, the present review focuses on pure and crude glycerol-based biomanufacturing. Full article

(This article belongs to the Section Biocatalysis)

► Show Figures

Figure 1

Open AccessReview

A Comparative Review of Binder-Containing Extrusion and Alternative Shaping Techniques for Structuring of Zeolites into Different Geometrical Bodies

by

,

,

,

,

Paul H. M. Van Steenberge

and

Khaled O. Sebakhy

Catalysts 2023, 13(4), 656; https://doi.org/10.3390/catal13040656 - 27 Mar 2023

Abstract

Zeolites are crystalline metallosilicates displaying unique physicochemical properties with widespread applications in catalysis, adsorption, and separation. They are generally obtained by a multi-step process that starts with primary mixture aging, followed by hydrothermal crystallization, washing, drying, and, finally, a calcination step. However, the [...] Read more.

Zeolites are crystalline metallosilicates displaying unique physicochemical properties with widespread applications in catalysis, adsorption, and separation. They are generally obtained by a multi-step process that starts with primary mixture aging, followed by hydrothermal crystallization, washing, drying, and, finally, a calcination step. However, the zeolites obtained are in the powder form and because of generating a pressure drop in industrial fixed bed reactors, not applicable for industrial purposes. To overcome such drawbacks, zeolites are shaped into appropriate geometries and the desired size (a few centimeters) using extrusion, where zeolite powders are mixed with binders (e.g., mineral clays or inorganic oxides). The presence of binders provides good mechanical strength against crushing in shaped zeolites, but binders may have adverse impacts on zeolite catalytic and sorption properties, such as active site dilution and pore blockage. The latter is more pronounced when the binder has a smaller particle size, which makes the zeolite internal active sites mainly inaccessible. In addition to the shaping requirements, a hierarchical structure with different levels of porosity (micro-, meso-, and macropores) and an interconnected network are essential to decrease the diffusion limitation inside the zeolite micropores as well as to increase the mass transfer through the presence of larger auxiliary pores. Thus, the generation of hierarchical structure and its preservation during the shaping step is of great importance. The aim of this review is to provide a comprehensive survey and detailed overview on the binder-containing extrusion technique compared to alternative shaping technologies with improved mass transfer properties. An emphasis is allocated to those techniques that have been less discussed in detail in the literature. Full article

(This article belongs to the Special Issue Zeolites and Porous Materials: Insight into Catalysis and Adsorption Processes)

► Show Figures

Graphical abstract

Open AccessReview

Plant-Biomass-Derived Carbon Materials as Catalyst Support, A Brief Review

by

Antonina A. Stepacheva

,

Mariia E. Markova

,

Yury V. Lugovoy

,

Yury Yu. Kosivtsov

,

Valentina G. Matveeva

and

Mikhail G. Sulman

Catalysts 2023, 13(4), 655; https://doi.org/10.3390/catal13040655 - 27 Mar 2023

Abstract

Carbon materials are widely used in catalysis as effective catalyst supports. Carbon supports can be produced from coal, organic precursors, biomass, and polymer wastes. Biomass is one of the promising sources used to produce carbon-based materials with a high surface area and a [...] Read more.

Carbon materials are widely used in catalysis as effective catalyst supports. Carbon supports can be produced from coal, organic precursors, biomass, and polymer wastes. Biomass is one of the promising sources used to produce carbon-based materials with a high surface area and a hierarchical structure. In this review, we briefly discuss the methods of biomass-derived carbon supported catalyst preparation and their application in biodiesel production, organic synthesis reactions, and electrocatalysis. Full article

(This article belongs to the Special Issue Transition-Metal-Containing Bifunctional Catalysts: Design and Catalytic Applications)

► Show Figures

Figure 1

Open AccessArticle

Secondary Amines from Catalytic Amination of Bio-Derived Phenolics over Pd/C and Rh/C: Effect of Operation Parameters

by

,

,

,

,

and

Luis E. Arteaga-Pérez

Catalysts 2023, 13(4), 654; https://doi.org/10.3390/catal13040654 - 27 Mar 2023

Abstract

The production of renewable chemicals using lignocellulosic biomass has gained significant attention in green chemistry. Among biomass-derived chemicals, secondary amines have emerged as promising intermediates for synthetic applications. Here, we report a systematic study on the reductive amination of phenolics with cyclohexylamine using [...] Read more.

The production of renewable chemicals using lignocellulosic biomass has gained significant attention in green chemistry. Among biomass-derived chemicals, secondary amines have emerged as promising intermediates for synthetic applications. Here, we report a systematic study on the reductive amination of phenolics with cyclohexylamine using Pd/C and Rh/C as catalysts. The catalytic tests were performed in batch reactors under different reaction conditions (various: amine concentration (0.1–0.4 mol/L), hydrogen pressure (0–2.5 bar), temperature (80–160 °C), and substituted phenols (phenol, o-cresol, p-cresol, and methoxyphenol)) and using tert-amyl alcohol as a solvent. The experimental observations were consistent with a multi-step mechanism, where hydrogenation of phenol to cyclohexanone is followed by condensation of the ketone with cyclohexylamine to form an imine, which is finally hydrogenated to produce secondary amines. In addition, there was evidence of parallel self-condensation of the cyclohexylamine. The study also supported a limited dehydrogenation capacity of Rh/C, unlike Pd/C, which increases this capacity at higher temperatures generating a higher yield of cyclohexylaniline (up to 15%). The study of the alkylated phenols demonstrated that the nature and propensity of hydrogenation of the phenolic controls their amination. Kinetic analysis revealed reaction orders between 0.4 and 0.7 for H₂, indicating its dissociative adsorption. Meanwhile, phenol’s order (between 1–1.8) suggests a single participation of this compound in the hydrogenation step. The order of 0.4 for cyclohexylamine suggests its participation as a surface-abundant species. The apparent activation energies derived from a power law approximation were of 37 kJ/mol and 10 kJ/mol on Pd/C and Rh/C, respectively. Full article

(This article belongs to the Special Issue Heterogeneous Catalysis for Environmentally Compatible Reactions and Processes)

► Show Figures

Figure 1

Open AccessArticle

Dynamic EPR Studies of the Formation of Catalytically Active Centres in Multicomponent Hydrogenation Systems

by

Yuliya Yu. Titova

Catalysts 2023, 13(4), 653; https://doi.org/10.3390/catal13040653 - 27 Mar 2023

Abstract

The formation of catalytically active nano-sized cobalt-containing structures in multicomponent hydrogenation systems based on Co(acac)₂ complex and various cocatalysts, namely, AlEt₃, AlEt₂(OEt), Li-n-Bu, and (PhCH₂)MgCl, has been studied for the first time in detail [...] Read more.

The formation of catalytically active nano-sized cobalt-containing structures in multicomponent hydrogenation systems based on Co(acac)₂ complex and various cocatalysts, namely, AlEt₃, AlEt₂(OEt), Li-n-Bu, and (PhCH₂)MgCl, has been studied for the first time in detail using dynamic EPR spectroscopy. It is shown that after mixing the initial components, paramagnetic structures are formed, which include a fragment containing Co(0) with the electronic configuration 3d⁹, as well as a fragment bearing an aluminium, lithium, or magnesium atom, depending on the nature of the used cocatalyst. Such bimetallic paramagnetic sites are stabilized by acetylacetonate ligands. In addition, the paramagnetic complex contains the arene molecule(s), and the cobalt atom is bonded with the atom of the corresponding non-transition through the alkyl group of the co-catalyst, in particular through the carbon atom in the α-position with respect to the atom of the non-transition element. Due to the high reactivity of the described intermediates, they, under the conditions of hydrogenation catalysis, are transformed into nano-sized cobalt-containing structures that act as carriers of the catalytically active sites. Furthermore, because of the high reactivity and paramagnetism, such intermediates can be detected only by the EPR technique. The paper describes the whole experimental way of interpreting the EPR signals corresponding to the intermediates, precursors of catalytically active structures. In addition, a possible mathematical model based on the obtained experimental EPR data is presented. Full article

(This article belongs to the Special Issue Feature Papers in Catalysis in Organic and Polymer Chemistry)

► Show Figures

Figure 1

Open AccessArticle

Effects of the Acidic and Textural Properties of Y-Type Zeolites on the Synthesis of Pyridine and 3-Picoline from Acrolein and Ammonia

by

,

,

,

,

Deyanira Angeles-Beltrán

,

Beatriz Zeifert

,

Juan Navarrete-Bolaños

and

Naomi N. González-Hernández

Catalysts 2023, 13(4), 652; https://doi.org/10.3390/catal13040652 - 26 Mar 2023

Abstract

A set of Y-type zeolites with Si/Al atomic ratios between 7–45 were studied as catalysts in the aminocyclization reaction between acrolein and ammonia to produce pyridine and 3-picoline. The catalytic activity tests at 360 °C revealed that the acrolein conversion increased in the [...] Read more.

A set of Y-type zeolites with Si/Al atomic ratios between 7–45 were studied as catalysts in the aminocyclization reaction between acrolein and ammonia to produce pyridine and 3-picoline. The catalytic activity tests at 360 °C revealed that the acrolein conversion increased in the order Z45 < ZY34 < ZY7 < ZY17, in agreement with the increase of the total acidity per gram of catalyst. In all cases, pyridine bases and cracking products (acetaldehyde and formaldehyde) were detected in the outflow from the reactor. The total yield of pyridines was inversely proportional to the total acidity for the catalysts, which presented large surface areas and micro- and mesoporosity. The selectivity towards 3-picoline was favored when using catalysts with a Brønsted/Lewis acid sites ratio close to 1. The formation of pyridine occurred more selectively over Lewis acid sites than Brønsted acid sites. The deactivation tests showed that the time on stream of the catalysts depended on the textural properties of zeolites, i.e., large pore volume and large BET area, as evidenced by the deactivation rate constants and the characterization of the spent catalysts. The physicochemical properties of the catalysts were determined by XRD, UV-vis, and Raman spectroscopies, infrared spectroscopy with adsorbed pyridine, N₂ physisorption, and SEM-EDXS. After the reaction, the spent catalysts were characterized by XRD, Raman spectroscopy, TGA, and SEM-EDXS, indicating that the uniform deposition of polyaromatic species on the catalyst surface and within the porous system resulted in the loss of activity. Full article

(This article belongs to the Special Issue Zeolites and Porous Materials: Insight into Catalysis and Adsorption Processes)

► Show Figures

Figure 1

Journal Description

Catalysts

Latest Articles

Journal Menu

Journal Browser

Highly Accessed Articles

Latest Books

E-Mail Alert

News

Topics

Conferences

Special Issues

Topical Collections

Further Information

Guidelines

MDPI Initiatives

Follow MDPI