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Propylene-based elastomers (PBEs) have received widespread attention and research in recent years due to their structural diversity and excellent properties, and are also an important area for leading chemical companies to compete for layout, but efficient synthesis of PBEs remains challenging. In this paper, we review the development of PBEs and categorize them into three types, grounded in their unique chain structures, including homopolymer propylene-based elastomers (hPBEs), random copolymer propylene-based elastomers (rPBEs), and block copolymer propylene-based elastomers (bPBEs). The successful synthesis of these diverse PBEs is largely credited to the relentless innovative advancements in homogeneous catalysts (metallocene catalysts, constrained geometry catalysts, and non-metallocene catalysts). Consequently, we summarize the catalytic performance of various homogeneous catalysts employed in PBE synthesis and delve into their effect on molecular weight, molecular weight distribution, and chain structures of the resulting PBEs. In the end, based on the current academic research and industrialization status of PBEs, an outlook on potential future research directions for PBEs is provided. [ABSTRACT FROM AUTHOR]

Biodiesel has received tremendous attention as a sustainable energy source. This review presents an overview of various catalysts utilized in biodiesel production and compares their potential for producing biodiesel. Presented here are the excellent features of the various catalysts while highlighting their drawbacks. For instance, production of biodiesel with homogeneous base catalysts is easy but it can only be used with refined oils having low levels of free fatty acid (FFAs). When homogeneous acid is used in esterification, it causes reactor corrosion. Water and FFAs do not affect heterogeneous acid catalysts. Thus, transesterification of triglycerides into biodiesel and converting FFAs into biodiesel through esterification can be catalyzed more efficiently using a heterogeneous acid catalyst. Biocatalysts are also being used to produce biodiesel from oils with high FFAs. However, heterogeneous acid catalysts and biocatalysts are not suitable for industrial application due to serious mass transfer limitations. Biodiesel yield and conversion were compared over various catalysts in this paper. Also presented are the effects of different reaction parameters on biodiesel yield over different catalysts. The correct interplay of factors like reaction temperature, time, alcohol-to-oil molar ratio, and catalyst loading produces optimal process conditions that give the highest biodiesel yield. [ABSTRACT FROM AUTHOR]

The extensive use of biodiesel leads to the excess of glycerol as a by‐product. But as a carbon resource, it has been increasingly used in organic synthesis of high value‐added derivatives in recent years. Among them, solketal is one of the most important derivatives of glycerol, which is generated by the reaction of glycerol and acetone. Based on a large number of relevant literatures, this paper systematically summarized the relevant researches in recent ten years. We systematically summary the latest research progress on the synthesis of solketal by glycerol and acetone. We have focused on a systematic study of four different reaction mechanisms for the ketonation reaction of glycerol and acetone. And the types of catalysts were classified into two categories, homogeneous catalysts and non‐homogeneous catalysts, and the non‐homogeneous catalysts were further classified in more details for the study. This review provides a more comprehensive reference for the ketal reaction of glycerol and acetone, and develops some new ideas for the transformation. [ABSTRACT FROM AUTHOR]

Iron porphyrins are known to provide CH4 as an eight-electron reduction product of CO2 in a photochemical reaction. However, there are still some aspects of the reaction mechanism that remain unclear. In this study, we synthesized iron porphyrin dimers and carried out the photochemical CO2 reduction reactions in N,N-dimethylacetamide (DMA) containing a photosensitizer in the presence of 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole (BIH) as an electron donor. We found that, despite a low catalytic turnover number, CH4 was produced only when these porphyrins were facing each other. The close proximity of the cyclic dimers, distinguishing them from a linear Fe porphyrin dimer and monomers, induced multi-electron CO2 reduction, emphasizing the unique role of their structural arrangement in CH4 formation. [ABSTRACT FROM AUTHOR]

Linear α-olefins (LAOs) are linear alkenes with double bonds at the ends of the molecular chains. LAOs with different chain lengths can be widely applied in various fields. Ethylene oligomerization has become the main process for producing LAOs. In this review, different homogeneous or heterogeneous catalysts recently reported in ethylene oligomerization with Ni, Fe, Co, Cr, etc., as active centers will be discussed. In the homogeneous catalytic system, we mainly discuss the effects of the molecular structure and the electronic and coordination states of complexes on their catalytic activity and selectivity. The Ni, Fe, and Co homogeneous catalysts are discussed separately based on different ligand types, while the Cr-based homogeneous catalysts are discussed separately for ethylene trimerization, tetramerization, and non-selective oligomerization. In heterogeneous catalytic systems, we mainly concentrate on the influence of various supports (metal–organic frameworks, covalent organic frameworks, molecular sieves, etc.) and different ways to introduce active centers to affect the performance in ethylene oligomerization. Finally, a summary and outlook on ethylene oligomerization catalysts are provided based on the current research. The development of highly selective α-olefin formation processes remains a major challenge for academia and industry. [ABSTRACT FROM AUTHOR]

The recent developments of the synthesis of bio-based long-chain aliphatic polyesters by the acyclic diene metathesis (ADMET) polymerization of α,ω-dienes, derived from plant oils and bio-based chemicals, like bis(10-undecenoate) with isosorbide, using ruthenium-carbene catalysts are reviewed. The development of subsequent (one-pot) tandem hydrogenation produced saturated polyesters under mild conditions. The polymerizations under bulk (without solvent, 80–90 °C) or in ionic liquids (50 °C) under vacuum conditions enabled the synthesis of high molar mass polymers (Mn > 30,000 g/mol). The polymerization performed by the molybdenum-alkylidene catalyst afforded the highest-molecular-weight polyesters (44,000–49,400 g/mol, in toluene at 25 °C) exhibiting promising tensile properties (strength and elongation at break) compared to polyethylene and polypropylene. Depolymerizations of these polyesters, including closed-loop chemical recycling, were also demonstrated. Catalyst developments (more active, under mild conditions) play a key role in the efficient synthesis of these materials. [ABSTRACT FROM AUTHOR]

Massive waste tires unrecycled will pose a significant threat to the urban environment. Hydrothermal gasification (HTG) is a promising technology converting polymer wastes into H 2 -rich syngas. The homogeneous catalytic hydrothermal gasification behavior of natural rubber (NR) and styrene-butadiene rubber (SBR) was estimated based on reactive force field molecular dynamics (ReaxFF-MD). KOH had the highest catalytic performance in enhancing the degradation efficiency (22.5 %) and H 2 yield (27.4 %) in HTG of NR, and K 2 CO 3 demonstrated the most optimal alkaline catalyst for SBR to enhance the degradation efficiency (27.2 %) and H 2 yield (37.9 %). K 2 CO 3 loading with 6 wt% manifested the optimum amount for lifting DE and H 2 yield in HTG of SBR, while 10 wt% K 2 CO 3 loading represented the best effect for lifting DE (26.5 %) and H 2 yield (42.6 %) in HTG of NR. The activation energy of SBR in HTG was about 259 kJ/mol, which was about 72 kJ/mol higher than that of NR. With 6 wt% K 2 CO 3 , the activation energy of SBR and NR in HTG decreased to about 143 kJ/mol and 122 kJ/mol, respectively. The present work could provide essential theoretical support and fundamental data for the application of the homogeneous catalysts in HTG recycling of waste rubber materials. • Catalytic HTG of rubber polymeric wastes was examined by ReaxFF-MD. • K 2 CO 3 was the optimum catalyst to improve the H 2 yield of SBR in HTG. • K-based catalyst was better than Na-based one for hydrothermal gasification of NR. • A better catalystic effect was realized by promoting the formation of OH radicals. • The lowest activation energy of SBR was 143 kJ/mol with K 2 CO 3 addition. [ABSTRACT FROM AUTHOR]

Iron porphyrins are known to provide CH4 as an eight-electron reduction product of CO2 in a photochemical reaction. However, there are still some aspects of the reaction mechanism that remain unclear. In this study, we synthesized iron porphyrin dimers and carried out the photochemical CO2 reduction reactions in N,N-dimethylacetamide (DMA) containing a photosensitizer in the presence of 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole (BIH) as an electron donor. We found that, despite a low catalytic turnover number, CH4 was produced only when these porphyrins were facing each other. The close proximity of the cyclic dimers, distinguishing them from a linear Fe porphyrin dimer and monomers, induced multi-electron CO2 reduction, emphasizing the unique role of their structural arrangement in CH4 formation.

This chapter summarizes recent advances of group 10 transition metal hydrosilylation catalysts from 2015 onward. Since the discovery of Speier's catalyst in 1957, homogeneous Pt catalysts have been mainly used for the hydrosilylation reaction of C-C multiple bonds. Although research on homogeneous Pt hydrosilylation catalysts has still been intensive, recent trends of research that meet the demands for sustainable development significantly increased the research on heterogeneous and non-precious metal hydrosilylation catalysts including Ni catalysts. Although Pd catalysts are very popular in organic transformation, its usefulness in hydrosilylation reaction is relatively limited, except for several special cases such as asymmetric hydrosilylation. [ABSTRACT FROM AUTHOR]

The development of selective aromatic oxidation catalysts based on non-noble metals has emerged over the last decades, mainly due to the importance of phenol products as intermediates for the generation of pharmaceuticals or functional polymers. In nature, metalloenzymes can perform a wide variety of oxidative processes using molecular oxygen, including arene oxidations. However, the implementation of such enzymes in the chemical industry remains challenging. In this context, chemists have tried to mimic nature and design synthetic non-noble metal catalysts inspired by these enzymes. This review aims at providing a general overview of aromatic oxidation reactions catalyzed by metalloenzymes as well as synthetic first-row transition-metal complexes as homogeneous catalysts. The enzymes and complexes discussed in this review have been classified based on the transition-metal ion present in their active site, i.e., iron, copper, nickel, and manganese. The main points of discussion focus on enzyme structure and function, catalyst design, mechanisms of operation in terms of oxidant activation and substrate oxidation, and substrate scope. [ABSTRACT FROM AUTHOR]

Concern about environmental problems and climate change has led to increasing efforts toward a transition of the global energy matrix to renewable sources. In this sense, biodiesel is a renewable and alternative biofuel proposal and castor bean and jatropha are interesting non-edible raw materials for its production owing to their high fatty acid content. Transesterification is the most common process applied to industrial-scale biodiesel production owing to its attractive economic characteristics. This process can be catalyzed by chemical (homogeneous or heterogeneous) or biochemical (enzymatic) catalysts. The choice of raw material, as well as the production route of biodiesel, will significantly influence the process parameters. Considering the importance of biodiesel production in Brazil, the present work explores biodiesel production routes focusing on these non-edible raw materials (jatropha and castor bean) and compares them with the process using soy bean, as this is one of the most used worldwide raw materia. In addition, an extensive literature review was performed and the software Microsoft Power BI Desktop was used to model and analyze the selected works, grouping them according to the pattern of each route's influence on process parameters. In addition, the technical scores of each route were determined. The homogeneous chemical route presented better scores and the most interesting parameters for all raw materials; however, considering the technical and environmental advantages related to biochemical and heterogeneous routes, application of environmental impact studies such as life cycle analysis can help decision-making in the search for the most appropriate production route. [ABSTRACT FROM AUTHOR]

Addressing the lithium polysulfide shuttle is critical for the high‐energy‐density lithium–sulfur pouch cells in practical applications, especially under high sulfur loading and lean electrolyte conditions. In contrast to previously reported heterogeneous adsorption catalysis within cathode or separator with slow catalytic kinetics and limited adsorption area, herein, lithium difluorophosphate (LiPO2F2) is demonstrated as a homogeneous catalyst in electrolyte which mitigates polysulfide diffusion. The Li–S pouch cell with LiPO2F2 in the electrolyte has record‐breaking shelving stability of two months, significantly improved capacity retention from 37.0% to 81.4% after long cycling, and electrical‐car‐level energy density over 400 Wh kg−1. A minimal amount of 1 wt% LiPO2F2 tends to facilitate lithium polysulfide disproportionation on the S/C cathode instead of in the electrolyte, which initiates the fast transformation of soluble lithium polysulfide to insoluble solid S8 and Li2S2/Li2S. The reliable mechanism of polysulfide disproportionation via biradicals is further proposed by both density functional theory calculation and experiments. To best of the authors' knowledge, this is the first report on mechanism of polysulfide disproportionation via biradical intermediates. It is believed that this new insight into homogeneous catalytic mechanisms in electrolytes may pave the way for the commercialization of high‐energy‐density Li–S batteries. [ABSTRACT FROM AUTHOR]

The valorization of coffee cherry waste through hydrothermal carbonization (HTC) was investigated using various organic and inorganic acid catalysts to produce platform chemicals. This study aimed to evaluate the effectiveness of these catalysts for enhancing reaction rates, improving yields, and promoting selectivity. The results showed that sulfuric acid and adipic acid were the most effective, each resulting in a 20% increase in the total yield, demonstrating the potential of organic acids as efficient catalysts in HTC. Other catalysts, such as benzoic acid and phenylacetic acid, also showed promising results, while butyric acid significantly decreased the total yield. The most abundantly produced platform chemicals were sugars, followed by formic acid, levulinic acid, HMF, and furfural. These findings highlight the potential of coffee cherry waste as a valuable resource for producing key chemicals, and the feasibility of hydrothermal carbonization as a sustainable approach for biomass valorization. This study emphasizes the importance of selecting the appropriate catalysts to optimize the conversion process and maximize the extraction of valuable chemicals. The environmental and economic implications of these findings are significant, as they can contribute to the development of sustainable and efficient biomass utilization technologies that could transform agricultural waste into high-value products while reducing waste and promoting a circular economy.

Abstract The production of biodiesel through chemical production processes of transesterification reaction depends on suitable catalysts to hasten the chemical reactions. Therefore, the initial selection of catalysts is critical although it is also dependent on the quantity of free fatty acids in a given sample of oil. Earlier forms of biodiesel production processes relied on homogeneous catalysts, which have undesirable effects such as toxicity, high flammability, corrosion, by‐products such as soap and glycerol, and high wastewater. Heterogeneous catalysts overcome most of these problems. Recent developments involve novel approaches using biomass and bio‐waste resource derived heterogeneous catalysts. These catalysts are renewable, non‐toxic, reusable, offer high catalytic activity and stability in both acidic and base conditions, and show high tolerance properties to water. This review work critically reviews biomass‐based heterogeneous catalysts, especially those utilized in sustainable production of biofuel and biodiesel. This review examines the sustainability of these catalysts in literature in terms of small‐scale laboratory and industrial applications in large‐scale biodiesel and biofuel production. Furthermore, this work will critically review natural heterogeneous biomass waste and bio‐waste catalysts in relation to upcoming nanotechnologies. Finally, this work will review the gaps identified in the literature for heterogeneous catalysts derived from biomass and other biocatalysts with a view to identifying future prospects for heterogeneous catalysts.

The relevance of heterogeneous catalysis in biodiesel production cannot be overemphasized, as heterogeneous catalysts have eliminated the demerits associated with a homogeneous catalysts. Some heterogeneous catalysts experience drawbacks such as partial recoverability and reusability, energy and waste conservation issues during biodiesel processing and leaching of active catalyst sites. This paper highlights and summarizes several heterogeneous catalysts used in biodiesel production. The catalyst preparation, reaction conditions, feedstock, and biodiesel yield for the heterogeneous base and acid catalysts were emphasized. The inability of heterogeneous base catalysts to trans-esterify low-grade oil with high free fatty acid (FFA) is a primary concern; the cost of processing low-grade oil with high FFA using heterogeneous acid catalysts is also a big issue. Nano-doped heterogeneous catalysts with unique properties were recommended because they can process oil with high FFA transesterification, improve reaction efficiency, simplify production, reduce the leaching of active sites, enable better biodiesel yield by minimizing energy and waste, and increase catalyst recoverability, activity, selectivity and durability.

Peroxymonosulfate (HSO 5 −, PMS) is a well-known oxidant for water treatment. It needs to be activated to form strong oxidizing agents of organic pollutants like sulfate radical (SO 4 •−), hydroxyl radical (•OH), superoxide ion radical (O 2 •−), and the non-radical singlet oxygen (1O 2). Recently, the removal of synthetic organic dyes from waters by PMS upon homogeneous and heterogeneous catalysts has received a great research attention due to their high effectiveness and oxidation rate determined by simple treatments centered at bench scale in the laboratory. The present review summarizes and analyzes the recent trends of this topic over the period 2020–2023. Homogeneous catalysts with transition metal ions like iron ions and Cu2+, and heterogeneous catalysts with single or mixed transition metals such as Co, Cu, Fe, and Mn, MOFs, and carbonaceous and other materials, have been examined. The action of these catalysts has been detailed for the generation of oxidizing agents from PMS activation. Selected examples describe the discoloration rate of synthetic waters contaminated with organic dyes and the influence of the operating variables on process performance. The production of oxidants via radical and non-radical mechanisms of PMS reduction has been confirmed by specific scavengers and EPR analysis. In some cases, the effect of the aqueous matrix on the dye discoloration has been analyzed and the detection of its by-products has been described with proposal of pathways for the degradation/mineralization of dyes to better know their oxidation process. A final section proposes the future development of dyes remediation with catalytic activators of PMS. [Display omitted] • Recent catalytic activation of peroxymonosulfate (PMS) for azo dye removal is summarized. • PMS activated by homogeneous, single and mixed transition metals, MOFs and carbonaceous catalysts. • Greater discoloration rate of azo dyes with Co catalysts than with Fe ones. • Non-radical ones with 1O 2 and radical mechanisms mainly with SO 4 •− and •OH are described. • Removal in real waters < in pure waters: Cl−, SO 4 2−., H 2 PO 4 −, HCO 3 −, CO 3 2−, and NOM as inhibitors. [ABSTRACT FROM AUTHOR]

Herein, the design, synthesis, supramolecular interactions and structural analysis of a novel bidentate carboxylate chelating N-heterocylic carbene (NHC) ligand is presented. The NHC structure was modified to strategically incorporate adamantyl moiety for the formation of a supramolecular complex with host molecules such as cucurbiturils. The adamantyl modified NHC ligand could potentially be used in recoverable homogeneous catalysts when Immobilized on a solid support via host–guest chemistry. As a versatile precursor, NHC ligand (8) was synthesized and characterized by 1H-NMR, 13C-NMR, FTIR, single crystal X-ray crystallography and elemental analysis. A proof-ofprinciple non-covalent immobilization of the NHC ligand (8) with a Cucurbit[7]uril (CB7) host was demonstrated using 1H-NMR titration. [ABSTRACT FROM AUTHOR]

Recent knowledge in chemistry has enabled the material utilization of greenhouse gas (CO2) for the production of organic carbonates using mild reaction conditions. Organic carbonates, especially cyclic carbonates, are applicable as green solvents, electrolytes in batteries, feedstock for fine chemicals and monomers for polycarbonate production. This review summarizes new developments in the ring opening of epoxides with subsequent CO2-based formation of cyclic carbonates. The review highlights recent and major developments for sustainable CO2 conversion from 2000 to the end of 2021 abstracted by Web of Science. The syntheses of epoxides, especially from bio-based raw materials, will be summarized, such as the types of raw material (vegetable oils or their esters) and the reaction conditions. The aim of this review is also to summarize and to compare the types of homogeneous non-metallic catalysts. The three reaction mechanisms for cyclic carbonate formation are presented, namely activation of the epoxide ring, CO2 activation and dual activation. Usually most effective catalysts described in the literature consist of powerful sources of nucleophile such as onium salt, of hydrogen bond donors and of tertiary amines used to combine epoxide activation for facile epoxide ring opening and CO2 activation for the subsequent smooth addition reaction and ring closure. The most active catalytic systems are capable of activating even internal epoxides such as epoxidized unsaturated fatty acid derivatives for the cycloaddition of CO2 under relatively mild conditions. In case of terminal epoxides such as epichlorohydrin, the effective utilization of diluted sources of CO2 such as flue gas is possible using the most active organocatalysts even at ambient pressure. [ABSTRACT FROM AUTHOR]

Tungsten bipyridyl tetracarbonyl complexes were shown to reduce CO2 to CO in acetonitrile [Chem. Sci., 2014, 5, 1894–1900]. Here, we employ density functional theory (DFT) calculations to investigate the electronic structure and reactivity of a series of tungsten electrocatalysts, [W(bpy-R)(CO)4] (where R = H, CH3, tBu, OCH3, CF3, and CN), for the CO2 reduction reaction (CO2RR). Our proposed mechanism suggests that initial reduction of the starting material by two electrons is required to access the active catalyst upon CO dissociation, which is slightly endergonic, consistent with the slow product release observed experimentally. The doubly reduced species, which has a closed-shell singlet ground state, can bind CO2 via an η2-CO2 binding mode to yield the metallocarboxylate intermediate. Based on the energy span model, CO2 addition is the TOF-determining transition state (TDTS) in the presence of water as the proton source. Different substituents at the 4,4'-positions of the bipyridine ligand in [W(bpy-R)(CO)4] (R = H, CH3, tBu, OCH3, CF3, and CN) were considered to comprehend the substituent effects for CO2RR. DFT results show that electron-withdrawing substituents, such as CN and CF3, do not yield efficient CO2 reduction catalysts due to the necessity of forming high energy intermediates for the protonation steps, resulting in low TOFs and high overpotentials. Among electron-donating groups, the parent compound and tert-butyl substituted complex are the most active catalysts for CO2RR due to higher TOFs at low overpotentials. Overall, based on the energy span model and theoretical Tafel plots, our computational approach provides quantitative information for designing CO2 reduction electrocatalysts. [ABSTRACT FROM AUTHOR]

The production of biodiesel through chemical production processes of transesterification reaction depends on suitable catalysts to hasten the chemical reactions. Therefore, the initial selection of catalysts is critical although it is also dependent on the quantity of free fatty acids in a given sample of oil. Earlier forms of biodiesel production processes relied on homogeneous catalysts, which have undesirable effects such as toxicity, high flammability, corrosion, by‐products such as soap and glycerol, and high wastewater. Heterogeneous catalysts overcome most of these problems. Recent developments involve novel approaches using biomass and bio‐waste resource derived heterogeneous catalysts. These catalysts are renewable, non‐toxic, reusable, offer high catalytic activity and stability in both acidic and base conditions, and show high tolerance properties to water. This review work critically reviews biomass‐based heterogeneous catalysts, especially those utilized in sustainable production of biofuel and biodiesel. This review examines the sustainability of these catalysts in literature in terms of small‐scale laboratory and industrial applications in large‐scale biodiesel and biofuel production. Furthermore, this work will critically review natural heterogeneous biomass waste and bio‐waste catalysts in relation to upcoming nanotechnologies. Finally, this work will review the gaps identified in the literature for heterogeneous catalysts derived from biomass and other biocatalysts with a view to identifying future prospects for heterogeneous catalysts. [ABSTRACT FROM AUTHOR]

In this article, the current state and future perspectives in the application of complexes of Lewis acids with ethers in the synthesis of highly reactive polyisobutylene (HR PIB) were critically reviewed. The complexes of metal halides with ethers showed good activity and regioselectivity in the synthesis of HR PIB only in polar solvents due to their poor solubility in hydrocarbons. In strong contrast, HR PIB with high exo-olefin end group content was synthesized in non-polar n-hexane using fully soluble in hydrocarbons complexes of alkylaluminum dichlorides as catalysts. The further improvement in the synthesis of HR PIB was achieved using heterogeneous catalysts (acidic ionic liquids or liquid coordination complexes), which provides polyisobutylenes with high exo-olefin end group content in conjunction with low polydispersity. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (H2O2) is an environmentally friendly oxidant, finding widespread use across the chemical industry, in sanitation and environmental remediation. Currently, H2O2 is manufactured via the anthraquinone process which has a number of disadvantages including nondistributed production, high‐energy consumption, substantial organic by‐product waste, and the need to transport the obtained H2O2 to the point‐of‐use. Accordingly, the electrochemical synthesis of H2O2 is now attracting a lot of interest as an alternative, cost‐effective, small‐scale, and distributed technology for H2O2 manufacture. This review summarizes recent advancements in the development of Homogeneous and Heterogeneous catalysts for electrocatalytic O2 reduction reaction (ORR) to H2O2. The basic principles of the ORR, and methodologies for investigating the ORR to H2O2 are first introduced. Next, H2O2 production over Homogeneous catalysts is discussed, with a focus on the reaction mechanisms and the factors that influence activity, selectivity, and reaction kinetics. Subsequently, recent breakthroughs in H2O2 synthesis over Heterogeneous catalysts, including nonnoble metal‐based nanomaterials, carbon materials, and single‐atom catalysts are described. The latter are given special attention, since they serve as a bridge between Homogeneous catalysis and Heterogeneous catalysis, while also offering excellent performance. Finally, the challenges and opportunities for electrochemical ORR to H2O2 are critically discussed. [ABSTRACT FROM AUTHOR]

The incorporation of abiotic transition metal catalysis into the chemical biology space has significantly expanded the tool kit of bioorthogonal chemistries accessible for cell culture and in vivo applications. A rich variety of homogeneous and heterogeneous catalysts has shown functional compatibility with physiological conditions and biostability in complex environs, enabling their exploitation as extracellular or intracellular factories of bioactive agents. Current trends in the field are focusing on investigating new metals and sophisticated catalytic devices and toward more applied activities, such as the integration of subcellular, cell- and site-targeting capabilities or the exploration of novel biomedical applications. We present herein an overview of the latest advances in the field, highlighting the increasing role of transition metals for the controlled release of therapeutics. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, we investigated the improvement of thermal properties of Vietnam deproteinized natural rubber (DPNR) via graft copolymerization of styrene/acrylonitrile and transfer hydrogenation. The graft copolymerization was achieved successfully in the latex stage using tert‐butyl hydroperoxide and tetraethylenepentamine as radical initiators at 30°C. The obtained graft copolymer was hydrogenated by a diimide reduction system in the presence of different copper (II) homogeneous catalysts. The effects of styrene to acrylonitrile on the total conversion and the grafting efficiency have been studied. The structural characterization of the obtained copolymers was made by 1H NMR and ATR‐FTIR. The graft DPNR was then characterized by gel permeation chromatography (GPC). The effects of different copper (II) catalysts on the system have been evaluated by the hydrogenation degree of each hydrogenated sample. The improvement of the thermal properties of the graft copolymers was confirmed by thermal gravimetric analysis/differential thermal analysis. The core‐shell arrangement was obtained in both DPNR‐graft‐PS/PAN and hydrogenated‐DPNR‐graft‐PS/PAN by transmission electron microscopy. [ABSTRACT FROM AUTHOR]

Herein, the design, synthesis, supramolecular interactions and structural analysis of a novel bidentate carboxylate chelating N-heterocylic carbene (NHC) ligand is presented. The NHC structure was modified to strategically incorporate adamantyl moiety for the formation of a supramolecular complex with host molecules such as cucurbiturils. The adamantyl modified NHC ligand could potentially be used in recoverable homogeneous catalysts when Immobilized on a solid support via host–guest chemistry. As a versatile precursor, NHC ligand (8) was synthesized and characterized by 1H-NMR, 13C-NMR, FTIR, single crystal x-ray crystallography and elemental analysis. A proof-of-principle non-covalent immobilization of the NHC ligand (8) with a Cucurbit[7]uril (CB7) host was demonstrated using 1H-NMR titration.

Carbon dioxide (CO2) is one of the most important materials as renewable chemical feedstock. In this review, the Co- and Rh-catalyzed transformation of CO2 via carbon–carbon bond-forming reactions is summarized. Combinations of metals (cobalt or rhodium), substrates, and reducing agents realize efficient carboxylation reactions using CO2. The carboxylation of propargyl acetates and alkenyl triflates using cobalt complexes as well as the cobalt-catalyzed reductive carboxylation of α,β-unsaturated nitriles and carboxyamides in the presence of Et2Zn proceed. A Co complex has been demonstrated to act as an efficient catalyst in the carboxylation of allylic C(sp3)–H bonds. Employing zinc as the reductant, carboxyzincation and the four-component coupling reaction between alkyne, acrylates, CO2, and zinc occur efficiently. Rh complexes also catalyze the carboxylation of arylboronic esters, C(sp2)–H carboxylation of aromatic compounds, and hydrocarboxylation of styrene derivatives. The Rh-catalyzed [2 + 2 + 2] cycloaddition of diynes and CO2 proceeds to afford pyrones.

Non-thermal plasma exhibits unique advantages in biomass conversion for the sustainable production of higher-value energy carriers. Different homogeneous catalysts are usually required for plasma-enabled biomass liquefaction to achieve time-and energy-efficient conversions. However, the effects of such catalysts on the plasma-assisted liquefaction process and of the plasma on those catalysts have not been thoroughly studied. In this study, an electrical discharge plasma is employed to promote the direct liquefaction of sawdust in a mixture of polyethylene glycol 200 and glycerol. Three commonly used chemicals, sulfuric acid, nitric acid and sodium p-toluene sulfate, were selected as catalysts. The effects of the type of catalyst and concentration on the liquefaction yield were examined; further, the roles of the catalysts in the plasma liquefaction process have been discussed. The results showed that the liquefaction yield attains a value of 90% within 5 min when 1% sulfuric acid was employed as the catalyst. Compared with the other catalysts, sulfuric acid presents the highest efficiency for the liquefaction of sawdust. It was observed that hydrogen ions from the catalyst were primarily responsible for the significant thermal effects on the liquefaction system and the generation of large quantities of active species; these effects directly contributed to a higher efficacy of the plasma-enabled liquefaction process. [ABSTRACT FROM AUTHOR]

To achieve a safe, efficient, and sustainable (even fully automated) production for the continuous‐flow hydrogenation reactions, which is among the most often used reactions in chemical synthesis, new catalyst types and immobilization methods as well as flow reactors and technologies have been developed over the last years; in addition, these approaches have been combined with new and transformational technologies in other fields such as artificial intelligence. Thus, attention from academic and industry practitioners has increasingly focused on improving the performance of hydrogenation in flow mode by reducing the reaction times, increasing selectivities, and achieve safe operation. This Minireview aims to summarize the most recent research results on this topic with focus on the advantages, current limitations, and future directions of flow chemistry. [ABSTRACT FROM AUTHOR]

The increased demand for more efficient, safe, and green production in fine chemical and pharmaceutical industry calls for the development of continuous‐flow manufacturing, and for chiral chemicals in particular, enantioselective catalytic processes. In recent years, this emerging direction has received considerable attention and has seen rapid progress. In most cases, catalytic enantioselective flow processes using homogeneous, heterogeneous, or enzymatic catalysts have shown significant advantages over the conventional batch mode, such as shortened reaction times, lower catalysts loadings, and higher selectivities in addition to the normal merits of non‐enantioselective flow operations. In this Minireview, the advancements, key strategies, methods, and technologies developed the last six years as well as remaining challenges are summarized. [ABSTRACT FROM AUTHOR]

Catalytic conversion of microcrystalline cellulose (MCC) to nanocellulose involves a one-pot homogeneous reaction carried out by the cleavage of β-1,4-glycosidic bonds within the cellulose network. Through this work, the synergistic combination of ultrasonication and catalyst has been proved to be effective in the controlled depolymerisation process of cellulose. Iron oxide being a Lewis acid catalyst has been used to abstract the single electron from the electron-rich C-O bond in cellulose. The iron oxide, maghemite (-Fe2O3) shows the highest activity as determined by the increase of crystallinity index (CrI%) from 80.62% to 85.63%. The other phases of iron oxide also showed catalytic activity with hematite (Fe2O3) at 84.05% and magnetite (Fe3O4) at 83.39%. Morphology and particle size analysis clearly show that the nanocellulose have been obtained in the range 78 nm to 220 nm due to the structural dimension measurement of both thickness (diameter) & length. Spectroscopy analysis via Fourier transform infrared and Raman shows no changes to the functional group, hence the chemical composition and integrity of cellulose remains intact. Nanocellulose suspension obtained using maghemite exhibited the highest colloidal stability and surface tension making it more suitable for application. [ABSTRACT FROM AUTHOR]

Efficient Mizoroki-Heck couplings were obtained using a very easily synthesizable palladium(II) complex of hemilabile N-O ligand (picolinate), with high turnover frequencies up to >10,000 h−1, in just 15 min, with high selectivity of >99% to the desired products. Wide applicability of the simple-looking palladium complex catalyst was established with differently functionalized substrates. Catalyst screening studies revealed intricate details of dependence of catalyst performance on different reaction parameters and conditions and arriving at the optimized facile methodology. [ABSTRACT FROM AUTHOR]

Magnetic nanoparticles are a highly valuable substrate for the attachment of homogeneous inorganic and organic containing catalysts. This review deals with the very recent main advances in the development of various nanocatalytic systems by the immobilisation of homogeneous catalysts onto magnetic nanoparticles. We discuss magnetic core shell nanostructures (e.g., silica or polymer coated magnetic nanoparticles) as substrates for catalyst immobilisation. Then we consider magnetic nanoparticles bound to inorganic catalytic mesoporous structures as well as metal organic frameworks. Binding of catalytically active small organic molecules and polymers are also reviewed. After that we briefly deliberate on the binding of enzymes to magnetic nanocomposites and the corresponding enzymatic catalysis. Finally, we draw conclusions and present a future outlook for the further development of new catalytic systems which are immobilised onto magnetic nanoparticles.

Hydrothermal liquefaction (HTL) is a thermal depolymerization process used to convert wet biomass such as microalgae into bio-crude oil. Four main products, gas, bio-crude oil, an aqueous phase, and solid residue, are generated through HTL. In this study, various HTL conditions were investigated to enhance the phosphorus content in the aqueous phase as well as the yield of bio-crude oil. Tetraselmis sp. was used as the microalgae feedstock, and the product yields according to catalyst type were explored. The phosphate ion (PO43−) content in the aqueous phase was significantly enhanced when acetic acid was added because of the effect of pH. In addition, it was found that both the bio-crude oil yield and the ammonium ion content could be increased by recycling the post-HTL aqueous phase, while the phosphate content was not. [ABSTRACT FROM AUTHOR]

Syntheses of ethanol based biodiesel fuel fatty acid ethyl esters (FAEEs) from corn oil were conducted at subcritical ethanol conditions (T: 175–225 °C, P: 80–200 bar) with the presence of trace amount of catalysts (0.1 wt% sulfuric acid, 0.05 and 0.1 wt% potassium ethoxide, based on oil mass). Experiments were conducted in a continuous tubular 316SS reactor. Potassium ethoxide showed a stronger catalytic ability than sulfuric acid at the same temperature of 225 °C, as the reaction yield reached 95% in five minutes with potassium ethoxide while only 25% yield was achieved for sulfuric acid. A three-step partially reversible model was determined to best fit the kinetic data for both catalytic reactions. To investigate the effect of water and free fatty acids (FFA) impurities on reaction yield under subcritical conditions, 10 vol% water (based on ethanol volume) and 30 wt% oleic acid (based on oil mass) were added to the reaction systems. For sulfuric acid, the reaction yield benefitted from the presence of these impurities. On the contrary, for reactions catalyzed by potassium ethoxide, the yield decreased from 96.8% to 15.3% and 2.6% when adding 10 vol% water and 30 wt% oleic acid, respectively. A pressure range of 80–200 bar at 225 °C was investigated to study the pressure effect on reaction yield. The reactions at these pressures were observed to occur in the homogeneous phase, and the yields at all pressures were in the range of 94–96%, which implies that when the reactions are performed in the homogeneous state, pressure will have little effect on the yield. [ABSTRACT FROM AUTHOR]

Bifunctional ZnII porphyrin catalysts bearing tributylammonium bromide groups at the meta positions of the meso-phenyl groups showed high catalytic activity for the synthesis of cyclic carbonates from epoxides and CO2. Herein, several substituents with different electronic properties were introduced at the para positions. Introduction of electron-donating groups decreased the catalytic activity, whereas the introduction of electron-withdrawing groups increased the activity. The substituents modulated the Lewis acidity of the zinc center, which was confirmed by binding constant experiments. The bifunctional catalyst bearing cyano groups showed the highest catalytic activity with a turnover frequency of up to 42 000 h−1. [ABSTRACT FROM AUTHOR]