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To make pyrolytic bio‐oil useful as a transportation fuel, the oxygen content must be reduced, and this can be carried out by using catalytic hydrodeoxygenation (HDO) reaction. The greatest challenge is associated with the removal of strongly bound oxygenated groups without saturating the aromatic ring while preserving the number of carbons. However, the development of a stable catalyst that can selectively remove such oxygenated groups with low hydrogen consumption is still challenging. In this context, a systematic study on HDO of vanillin on bimetallic Pd−Pt catalysts was carried out. It aims to study the effect of bimetallic synergy in terms of activity and selectivity to creosol. Metallic nanoparticles of Pd and Pt were synthesized by sol immobilization technique and deposited on TiO2. The conversion of vanillin was correlated to the Pd−Pt atomic ratio, while the production of the creosol was correlated to the Pd(0)/(Pd+Pt) ratio at the surface. Full conversion of vanillin was obtained at low reaction temperature (20 °C) achieving nearly 100 % selectivity to creosol. These results represent a step forward in advancing the development of more efficient and sustainable processes for bio‐oil upgrading. [ABSTRACT FROM AUTHOR]

In this work, solid-state fermentation (SSF) was applied to babassu mesocarp (BM) for the low-cost bioproduction of natural aroma compounds having Trichoderma harzianum (IOC 4042) and Geotrichum candidum (CCT 1205) as microbial agents. Fermentation was carried out using in natura babassu mesocarp (IN-BM) and defatted babassu mesocarp through soxhlet extraction (DEF-BM) as support, impregnated with hydration solutions of three and seven salts. The compounds produced were analyzed using solid phase microextraction (SPME) and gas chromatography coupled with a mass spectrometer (GC-MS). Among several aroma compounds detected, 6-pentyl-α-pyrone (6-PP)—GRAS 3696, coconut aroma; 2-phenylethanol (2-PE)—GRAS 2858, rose and honey aroma; and hexanal—GRAS 2557, green apple aroma, were the compounds that that were detected with the greatest intensity. The highest concentrations (ppm (w/w)) of 6-PP and 2-PE were obtained in DEF-BM using NS7SG (308.17 ± 3.18 and 414.53 ± 1.96), respectively, while for hexanal, the highest concentration (ppm (w/w)) was obtained in IN-BM using NS7SG (210.83 ± 2.14). The results indicate that producing aroma compounds by G. candidum and T. harzianum through BM SSF is viable, generating value-added compounds. [ABSTRACT FROM AUTHOR]

Increasing the efficiency of cellulose hydrolysis is a crucial milestone to enable its use as a platform for the production of renewable chemicals. Consequently, exploring alternative techniques for cellulose dissolution and subsequent depolymerization and hydrolysis remains a pivotal area of research. This study delves into the performance of diverse solid acid catalysts (ion-exchange resins, metal oxides, and zeolites) for cellulose depolymerization when combined with a concentrated solution of zinc chloride (ZnCl2) as the reaction medium and extractant. The influence of this molten salt hydrate on cellulose dissolution and the stability of the tested catalysts was thoroughly investigated. Optimal mild operating conditions (90 °C and 2 h) that facilitate enhanced conversion and selective glucose production were identified. The highest glucose yields (exceeding 40%) were obtained with Amberlyst-15 and HZSM-5 (SiO2/Al2O3 = 23), effectively mitigating product degradation and equaling or surpassing the traditional homogeneous system using H2SO4. Furthermore, insights into the deactivation mechanisms affecting the best catalysts are provided. [ABSTRACT FROM AUTHOR]

Strong metal–support interaction (SMSI) is a pivotal strategy in thermal catalysis; however, its application in photocatalysis leaves ample area for further development. A method inducing SMSI between earth-abundant metals, such as copper and TiO2, at room temperature, and thus hindering the agglomeration of copper species remains rarely reported. In this work, we achieved SMSI construction of TiO2 overlayers on Cu nanoparticles via a straightforward soft-chemistry method. SMSI coverage is stable even after high-temperature treatment in the air (500 °C), as demonstrated by chemical mapping and surface analysis. The method is more accurate than thermal reduction since it produces a metastable, highly active anatase phase. Interestingly, the TiO2 overlayer induces the formation of four-coordinated copper(II) species surrounded by oxygen atoms, resulting in coexisting CuO2 planes, which were monitored through high-resolution transmission electron microscopy and electron paramagnetic resonance spectroscopy. The stronger interfacial interaction by forming Ti–O–Cu bonding promotes charge carrier separation, producing twice as much H2 than the low interfacial interaction within a conventional photoactive system wherein copper was decorated onto TiO2. Our approach offers a rational design for SMSI materials in photocatalysis, which is extendable to other catalytic reactions. [ABSTRACT FROM AUTHOR]

This study investigated the oxidation of 5-hydroxymethylfurfural (HMF) to produce valuable products such as 2,5-furandicarboxaldehyde (DFF), 5-formyl-2-furancarboxylic acid (FFCA) and 2,5-furandicarboxylic acid (FDCA) through (photo) chemical and enzymatic catalysis. Laccases from different sources, including Aspergillus spp., Pseudomonas cepacea, and Trametes versicolor, were evaluated for their catalytic activity in the HMF oxidation. Laccase from Trametes versicolor (LacTV) emerged as the most effective catalyst, achieving complete conversion of HMF under specific pH conditions. The reaction mechanisms were explored, revealing a preference for the primary alcohol oxidation pathway over the aldehyde, leading to the formation of DFF and subsequent conversion to FFCA and FDCA. The impact of substrate concentration on HMF conversion was examined, revealing optimal conversion at lower HMF concentrations (<100 mM) and reduced performance at higher concentrations (>100 mM). The study also examined the influence of blue light (430 nm) on this reaction, revealing the dependence on light exposure for gC3N4 based catalysts and a negative effect for LacTV. Furthermore, the study introduces a modular flow chemical platform that utilizes Continuous Stirred Tank Reactors (CSTR) in a cascade configuration, the optimization of HMF oxidation. The implementation of this innovative approach has led to the effective synthesis of FDCA, demonstrating an impressive 40-fold increase in productivity compared to the traditional batch system. These results present significant potential for advancing green chemistry and sustainable chemical synthesis, introducing novel possibilities for environmentally friendly HMF oxidation processes. [ABSTRACT FROM AUTHOR]

In the quest to combat global warming, traditional thermal chemistry processes are giving way to selective photocatalysis, an eco-friendly approach that operates under milder conditions, using benign solvents like water. Benzaldehyde, a versatile compound with applications spanning agroindustry, pharmaceuticals, and cosmetics, serves as a fundamental building block for various fine chemicals. This study aims at enhancing benzaldehyde production sustainability by utilizing photooxidation of benzyl alcohol. Gold nanoparticle-based catalysts are renowned for their exceptional efficiency in oxidizing bio-based molecules. In this research, Au nanoparticles were anchored onto three distinct supports:  T i O 2 ,  Z r O 2 , and graphitic carbon nitride (g- C 3 N 4 ). The objective was to investigate the influence of the support material on the selective photocatalysis of benzyl alcohol. In the preparation of g- C 3 N 4 , three different precursors—melamine, urea, and a 50:50 mixture of both—were chosen to analyze their impact on catalyst performance. After 4 h of irradiation at 365 nm, operating under acidic conditions (pH = 2), the Au photocatalyst on graphitic carbon nitride support synthesized using urea precursor (Au@g- C 3 N 4 (u r e a) ) displayed the optimal balance between conversion (75%) and selectivity (85%). This formulation outperformed the benchmark Au@TiO2, which achieved a similar conversion rate (80%) but exhibited lower selectivity (55%). [ABSTRACT FROM AUTHOR]

The hydrodeoxygenation of furfural (FF) over Mo carbides in liquid phase at 200 °C, 30 bar of H2 for 4 h in 2‐butanol was investigated. Unsupported and SiO2‐supported Mo carbide with different crystallographic phases (β‐Mo2C/SiO2 and α‐MoC/SiO2), and in the presence of Cu and Ni as promoters were studied. The reactivation treatment under H2 atmosphere of the passivated Mo carbides was investigated by XAS. The results show that Mo is present in different states of oxidation in the passivated catalysts, with more severe oxidation in the bimetallic systems, in which the original carbides are not restored after reactivation. Finally, the product distribution in the HDO of furfural is modified as a function of catalyst oxidation degree. Using the less oxidized Mo carbide (β‐Mo2C), a higher yield to 2‐methylfuran is obtained, while C10 condensation products are formed for the more oxidized catalysts. [ABSTRACT FROM AUTHOR]

In recent years, the synthesis of bio‐based polymers and compounds has grown due to greater environmental concerns and the need to develop green and sustainable products as substitutes for fossil derivatives. In this context, lignocellulosic biomass is an important source of raw materials, as it is abundant and low‐cost, in addition to its chemical variety. Thus, chemical catalysis and biocatalysis have been important tools for obtaining these high value‐added compounds. With the aim of detecting the current scenario, as well as the main challenges and opportunities in the production of bio‐based polymers through the valorization of biomass, this work carried out a technological investigation of articles published in the last 10 years, establishing a relationship between the conditions of each production route and its main challenges. The results show a growing number of publications in the last 6 years involving the application of biomass‐derived molecules as monomers to obtain various classes of polymers, where polyesters and polyurethanes have been the most studied. The use of heterogeneous chemical catalysts is still the predominant production strategy, due to the extreme conditions required for production. However, the application of enzymes such as lipases to obtain polyesters and microbial biotransformation to obtain polyhydroxyalkanoates have been emerging as promising strategies within the context of biorefineries. Almost all works are at the proof‐of‐concept stage, where most of the molecules produced have been obtained from synthetic starting materials, demonstrating the need to integrate technologies for obtaining monomers directly from biomass and synthesis protocols for the advent of new processes that are more sustainable and competitive with traditional routes. [ABSTRACT FROM AUTHOR]

Exploring the potential of utilizing CO2 for commercial purposes is a promising opportunity, especially in light of the growing research efforts towards CO2 capture, storage, and utilization as well as green H2 production. This review article delves into catalyst features and other technological aspects of a plausible process for the indirect conversion of CO2 into glycolic acid, which involves the following steps: CO2 capture, water electrolysis, CO2 hydrogenation to methanol, catalytic oxidation to formaldehyde, and formaldehyde carbonylation to glycolic acid. We adopt an industrial perspective to address this challenge effectively, thoroughly evaluating different processing alternatives with emphasis on the catalytic systems to optimize glycolic acid production performance. [ABSTRACT FROM AUTHOR]

Engineering the composition and geometry of metallic sites has become a popular manner to boost reaction rate and control reaction selectivity in heterogeneous catalysis. Many studies have been devoted to enhancing the stability of metallic nanoparticles during catalytic reactions by dispersion on metal oxide supports such as TiO2, CeO2 or Nb2O5. These supports not only modulate electronic properties and dispersion/stabilization of metallic nanoparticle but also influence catalytic selectivity, resulting in the so‐called "strong metal‐support interaction" (SMSI). In this minireview, we outlined the discovery and fundamentals of SMSI, as well as its extensive development over years. In addition, we summarized recent approaches developed to induce the construction of SMSI between different metal nanoparticles and metal oxide supports. Associated characterization microscopic and spectroscopic techniques were emphasized. Despite being a prevalent concept in catalysis, the number of studies on SMSI in heterogeneous photocatalysis has been even in limitation. Herein, we highlighted the beneficial effects of SMSI on boosting photocatalytic activity for CO2 reduction and H2 evolution reactions. In general, despite some controversial aspects of the SMSI, this concept offers wide opportunities ahead and encourages researchers to rethink the local active site localization and photocatalyst design. [ABSTRACT FROM AUTHOR]

Supported gold nanoparticles have proven to be highly effective catalysts for the base-free oxidation of furfural, a compound derived from biomass. Their small size enables a high surface-area-to-volume ratio, providing abundant active sites for the reaction to take place. These gold nanoparticles serve as catalysts by providing surfaces for furfural molecules to adsorb onto and facilitating electron transfer between the substrate and the oxidizing agent. The role of the support in this reaction has been widely studied, and gold–support interactions have been found to be beneficial. However, the exact mechanism of furfural oxidation under base-free conditions remains an active area of research and is not yet fully understood. In this review, we delve into the essential factors that influence the selectivity of furfural oxidation. We present an optimization process that highlights the significant role of machine learning in identifying the best catalyst for this reaction. The principal objective of this study is to provide a comprehensive review of research conducted over the past five years concerning the catalytic oxidation of furfural under base-free conditions. By conducting tree decision making on experimental data from recent articles, a total of 93 gold-based catalysts are compared. The relative variable importance chart analysis reveals that the support preparation method and the pH of the solution are the most crucial factors determining the yield of furoic acid in this oxidation process. [ABSTRACT FROM AUTHOR]

Bio‐oil obtained from the depolymerization of lignocellulosic biomass is a potential alternative source to replace fossil fuels. However, due to high oxygen content, the bio‐oil must be upgraded. In this direction, the hydrodeoxygenation reaction (HDO) is widely applied. Considering the complex chemical composition of the bio‐oil, a variety of model molecules have been used in the literature to study the mechanism of the HDO process. In this work, we discuss heterogeneous catalysts and reaction conditions (temperature, pressure, and solvent) generally used for the HDO of dimeric aryl ethers representative of the main ether linkages present in the lignin:α‐O‐4, β‐O‐4, and 4‐O‐5. The present work aims to shed light on the role of metal and acid sites and understand the influence of the reaction conditions on the reaction pathways. [ABSTRACT FROM AUTHOR]

The effect of metal and support acidity on the hydroconversion of dimeric aryl ethers, used as model molecules for lignin, is still under debate, both in terms of hydrogenolysis (cleavage of the ether bond) and formation of by-products (coupling of aromatic monomers to dimers by alkylation reaction). Their role is investigated here in the conversion of three typical molecules representative of the α-O-4, β-O-4, and 4-O-5 ether linkages of lignin, respectively, benzyl phenyl ether (BPE), phenethoxybenzene (PEB), and diphenyl ether (DPE), at 503 K, under 18 bar of H2 in decalin. Ru- and Pd-based catalysts were synthesized on non-acidic SiO2 and on acidic HZSM5. Under these reaction conditions, the conversion of the ethers over the bare supports was observed in the presence of acidic sites; the effect decreased as the ether bond strength increased. The results also suggest that the product distribution is directly affected both by the support acidity and by the oxophilicity of Ru. Alkylated products from isomerization reactions, which are reported to be formed only over acidic sites, were also produced on the surface of the Ru nanoparticles. [ABSTRACT FROM AUTHOR]

The conversion of biomass as a sustainable path to access valuable chemicals and fuels is very attractive for the chemical industry, but catalytic conversions still often rely on the use of noble metals. Sustainability constraints require developing alternative catalysts from abundant and low-cost metals. In this context, NiFe nanoparticles are interesting candidates. In their reduced and supported form, they have been reported to be more active and selective than monometallic Ni in the hydrogenation of the polar functions of organic molecules, and the two metals are very abundant. However, unlike noble metals, Ni and Fe are easily oxidized in ambient conditions, and understanding their transformation in both oxidative and reductive atmospheres is an important though seldom investigated issue to be addressed before their application in catalysis. Three types of NiFe nanoparticles were prepared by an organometallic approach to ensure the formation of ultrasmall nanoparticles (<3.5 nm) with a narrow size distribution, controlled composition and chemical order, while working in mild conditions: Ni2Fe1 and Ni1Fe1, both with a Ni rich core and Fe rich surface, and an alloy with a Ni1Fe9 composition. Supported systems were obtained by the impregnation of silica with a colloidal solution of the preformed nanoparticles. Using advanced characterization techniques, such as wide-angle X-ray scattering (WAXS) and X-ray absorption spectroscopy (XAS) in in situ conditions, this study reports on the evolution of the chemical order and of the oxidation state of the metals upon exposure to air, hydrogen, and/or increasing temperature, all factors that may affect their degree of reduction and subsequent performance in catalysis. We show that if oxidation readily occurs upon exposure to air, the metals can revert to their initial state upon heating in the presence of H2 but with a change in structure and chemical ordering. [ABSTRACT FROM AUTHOR]

A series of zirconium-based metal–organic framework (MOF) nanocrystals (95–211 nm) displaying sulfonate functions (UiO-66-SO3H) was prepared in N,N-dimethylformamide (DMF)the conventional solventand water, and their physicochemical properties were thoroughly investigated. In particular, X-ray diffraction results suggest that upon replacing DMF with water, the resulting MOF crystal structure presents a highly defective structure belonging to the space group Im3̅ instead of typical Fm3̅m. The acid catalysts were applied to the fructose dehydration into 5-hydroxymethylfurfural (5-HMF). Complete conversion of fructose over UiO-66-SO3H prepared in water was reached after only 30 min at 100 °C, in line with its stronger Brønsted acidity. In comparison, its counterpart prepared in DMF showed only 30% fructose conversion. Moreover, the intrinsic catalytic effect at 80 °C was only observed with the water-based UiO-66-SO3H. Without reactivation of the catalyst, recycling tests demonstrated the preservation of its structural integrity upon nine consecutive cycles, while a gradual loss of the catalyst activity was attributed to the humin adsorption on the MOFs. [ABSTRACT FROM AUTHOR]

The high demand for food and energy imposed by the increased life expectancy of the population has driven agricultural activity, which is reflected in the larger quantities of agro-industrial waste generated, and requires new forms of use. Brazil has the greatest biodiversity in the world, where corn is one of the main agricultural genres, and where over 40% of the waste generated is from cobs without an efficient destination. With the aim of the valorization of these residues, we proposed to study the immobilization of laccase from Aspergillus spp. (LAsp) in residual corn cob and its application in the degradation of Remazol Brilliant Blue R (RBBR) dye. The highest yields in immobilized protein (75%) and residual activity (40%) were obtained at pH 7.0 and an enzyme concentration of 0.1 g.mL−1, whose expressed enzyme activity was 1854 U.kg−1. At a temperature of 60 °C, more than 90% of the initial activity present in the immobilized biocatalyst was maintained. The immobilized enzyme showed higher efficiency in the degradation (64%) of RBBR dye in 48 h, with improvement in the process in 72 h (75%). The new biocatalyst showed operational efficiency during three cycles, and a higher degradation rate than the free enzyme, making it a competitive biocatalyst and amenable to industrial applications. [ABSTRACT FROM AUTHOR]

The catalytic performance of the Ag/TiO2 catalyst was evaluated in the oxidation of furfural (FF) to furoic acid (FA) in an alkaline aqueous solution under 15 bar of air in a batch reactor. The catalytic activity, yield, and stability of the catalyst were compared as a function of different reaction parameters including temperature (25–110 °C), nature of the atmosphere, base equivalent (nbase/nFF = 0.25–3), and nature of the inorganic bases used (NaOH, NaHCO3, and Na2CO3). Under optimum conditions, the yield of FA (96%) was achieved at room temperature, with an excellent carbon balance (>98%). The recyclability of the catalyst was also studied and the catalytic activity of the Ag/TiO2 catalyst slightly declined due to an increase in particle size as confirmed by TEM studies. [ABSTRACT FROM AUTHOR]

The development of the future French and European bioeconomies will involve developing new green chemical processes in which catalytic transformations are key. The VAALBIO team (valorization of alkanes and biomass) of the UCCS laboratory (Unité de Catalyse et Chimie du Solide) are working on various catalytic processes, either developing new catalysts and/or designing the whole catalytic processes. Our research is focused on both the fundamental and applied aspects of the processes. Through this review paper, we demonstrate the main topics developed by our team focusing mostly on oxygen- and hydrogen-related processes as well as on green hydrogen production and hybrid catalysis. The social impacts of the bioeconomy are also discussed applying the concept of the institutional compass. [ABSTRACT FROM AUTHOR]

This work evaluates the performance of activated carbon-supported Ni and Re catalysts in the hydrogenation of furfural and levulinic acid. The increase in Re content enhances Ni dispersion, decreases Ni reducibility and increases acidity. The Lewis acidity on the catalysts was attributed to unreduced Ni and Re species, while the Bronsted acidity, to Re–OH species formed in the presence of water. In the furfural hydrogenation, all the bimetallic catalysts were more selective to furfuryl alcohol (86–91%) than the monometallic materials. Low temperature and high pressures enhance selectivity to furfuryl alcohol. Concerning the conversion of levulinic acid to γ-valerolactone, the bimetallic catalysts also showed higher performance than the monometallic materials, with rates of levulinic acid conversion around four times superior. High temperature enhances levulinic acid conversion, and the selectivity to γ-valerolactone does not depend on pressure (> 97% for all conditions). The bimetallic catalyst containing 5.0 wt% Ni and 10.0 wt% Re was the most efficient one for both reactions. In this sense, we prepared this catalyst at different calcination temperatures (350 and 500 °C) and showed this is an important parameter for the catalyst stability. After four reuse cycles, in both reactions, the catalyst calcined at 350 °C lost considerable activity (loss of activity > 50%), while the catalyst calcined at 500 °C was considerably more stable. Catalyst deactivation was caused by leaching of the metallic active phase. The bimetallic Ni–Re/C catalysts calcined at high temperatures are promising materials for the hydrogenation of furfural and levulinic acid. [ABSTRACT FROM AUTHOR]

Oxidative deamination is part of the metabolic pathways of amino acid oxidase and glutamate dehydrogenase enzymes, and enables obtaining α‐keto acid from amino compound with ammonia as a by‐product. This work presents the utilization of Pt‐based catalyst composed of small platinum nanoparticles supported on industrial silica support (Pt/SiO2). This nanozyme was tested in the oxidative deamination reaction of two amino compounds: 5‐hydroxymethylfurfurylamine (HMFA) to 5‐hydroxymethylfurfural (HMF) and glutamic acid (GA) to α‐ketoglutaric acid (KGA). This paper outlines the use of Pt nanozymes with deaminase‐like activity. We showed the ability of this nanozymes to be selective and active in liquid phase oxidative deamination of HMFA and glutamic acid in a 6 to 9 pH range at 60 °C under atmospheric pressure. Pt/SiO2 nanozyme actually plays as a deaminase mimic with high HMFA conversion (60%) and cumulative yield to the corresponding desaminated keto compounds (67%). [ABSTRACT FROM AUTHOR]

Currently, carbon dioxide in the atmosphere is the major contributor toward global climate change. Direct CO2 hydrogenation to dimethyl ether produces an important platform molecule for the synthesis of fuels and chemicals and at the same time, utilizes large amounts of this greenhouse gas. In this paper, we prepared a series of hybrid catalysts, which are composed of alumina supported copper–palladium nanoparticles and HZSM-5 zeolite for the direct synthesis of dimethyl ether from CO2. Copper active sites showed a higher intrinsic activity for CO2 hydrogenation compared to palladium. The low palladium content in the copper–palladium bimetallic catalysts was particularly beneficial for the dimethyl ether production. Undesirable methane and ethane production was completely suppressed, while the dimethyl ether selectivity was considerably increased. Extensive catalyst characterization combined with catalytic measurements was indicative of the presence of copper and palladium monometallic and bimetallic particles with different sizes and reducibility in the hybrid catalysts. The presence of even small amounts of palladium significantly improved copper reducibility and copper dispersion. Some decrease in the Brønsted acidity in the copper containing catalysts was due to the migration of unreduced copper ions in the zeolite channels during the reduction. The methanol dehydration to dimethyl ether was only slightly affected by the amounts of Brønsted acid sites in the hybrid catalysts. [ABSTRACT FROM AUTHOR]

Growing CO2 emissions lead to global warming, which is currently one of the most challenging environmental phenomena. Direct catalytic hydrogenation to dimethyl ether over hybrid catalysts enables CO2 utilization, hydrogen and energy storage and produces sustainable fuels and an important platform molecule. In this paper, we evaluated structure–performance correlations in the bifunctional hybrid copper–zinc SAPO-34 catalysts for direct synthesis of dimethyl ether via CO2 prepared using zirconia, alumina and ceria used as oxide carriers. Higher copper dispersion and higher CO2 conversion rate were uncovered over the alumina and zirconia supported catalysts followed by ceria supported counterpart. The CO2 hydrogenation seems to be principally favoured by higher copper dispersion and to a lesser extent depends on the concentration of Bronsted acid sites in the studied catalysts. Because of lower reverse water gas-shift activity, the alumina supported catalyst exhibited a higher dimethyl ether yield compared to the zirconia and ceria supported counterparts. [ABSTRACT FROM AUTHOR]

Core–shell SiO2@Au@TiO2 materials have shown excellent catalytic performances in the base-free oxidation of furfural (FF) to furoic acid (FA). The enhanced catalytic behaviour with respect to that observed over supported SiO2@TiO2@Au catalysts suggests a key role of the TiO2 shell, which could prevent Au deactivation by irreversible FA adsorption, improve metal–oxide interaction and presumably, give rise to the formation of new active sites located at the perimeter of the Au–TiO2 interface. [ABSTRACT FROM AUTHOR]

34684956 8 Hassanisaadi M., Bonjar G.H.S., Rahdar A., Pandey S., Hosseinipour A., Abdolshahi R. Environmentally Safe Biosynthesis of Gold Nanoparticles Using Plant Water Extracts. The authors studied the effect of polymeric stabilizers on gold nanoparticle size and activity in hydrogenation of 4-nitrophenol. The catalytic activity of metallic nanoparticles is very often governed by the method of preparation, which determines the particle size and structure of nanoparticles. [Extracted from the article]

The search for the optimal coupling of several types of catalysts has inspired the development of multi-catalytic hybrid materials (MCHMs) featuring chemical and biological catalysts co-immobilised on the same support. This complex interdisciplinary strategy, located at the crossroads of chemistry, biology, and materials science, calls for a wide range of skills and offers access to MCHMs with diverse catalytic properties and applications. In particular, numerous organic and inorganic supports, both rigid or flexible, have been used to develop remarkable hybrid catalysts that exhibit synergetic effects and achieve yields and enantiomeric excesses unattainable through the separate use of catalyst constituents even in one-pot/one step processes. As the spearhead of hybrid catalysis, MCHMs concentrate the very essence of this field, requiring seamless communication and collaboration between chemists, biologists, materials scientists, and modelling specialists. Future developments in this area are expected to revolutionise catalysis and make it an inter- or even transdisciplinary research area. [ABSTRACT FROM AUTHOR]

Hybrid catalysis, which combines chemo‐ and biocatalytic benefits, is an efficient way to address green chemistry principles. 5‐Hydroxymethylfurfural (HMF) is a versatile building block in numerous industrial applications. To date, few studies have described the production of its amine derivatives and their polymers. Finding a good methodology to directly transform HMF to 5‐aminomethyl‐2‐furancarboxylic acid (AMFC) therefore represents an important challenge. After selecting the best oxidation catalyst for HMF conversion to 5‐aldehyde‐2‐furancarboxylic acid and immobilizing a transaminase onto a solid carrier, we implemented the first one‐pot/two‐steps hybrid catalytic process to produce AMFC (77 % yield); this is the most efficient AMFC catalytic production method from HMF reported to date. This process also produced 2,5‐furandicarboxylic acid (21 % yield) as a major secondary product that can be applied to polymer syntheses such as polyethylene furanoate. Herein, we report a novel way to access new biosourced polymers based on HMF oxidized and aminated derivatives. [ABSTRACT FROM AUTHOR]

2,5‐furandicarboxylic acid (FDCA) is one of the most important bio‐sourced building blocks and several routes have been reported for its synthesis. FDCA is presumed to be an ideal green alternative to terephthalate, which is one of the predominant monomers in polymer industry. This Minireview concerns the synthesis of FDCA by using various carboxylation reactions and discusses the synthesis of FDCA starting from furoic acid and CO2 and using different catalytic and stoichiometric processes. This process is of high interest, as it avoids the glucose isomerization step and selectivity issues observed during the 5‐hydroxymethylfurfural oxidation step of the current alternative route to FDCA. Discussion focuses on the main parameters that govern selectivity and activity in the carboxylation processes. Moreover, various previously described processes, such as the Henkel reaction and enzymatic, homogeneous catalytic, and photoelectrocatalytic processes, are also discussed. [ABSTRACT FROM AUTHOR]

By using the most popular method of thermal condensation of dicyandiamide in a semi-closed system, graphitic carbon nitrides (gCNs) were synthesized at 500, 550, and 600 °C. The resulting materials were comprehensively analyzed via X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction (XRD)techniques. We show that the use of routine analytical methods provides an insight into the structure of the carbon nitride materials. The analysis of geometric linear structures and fully condensed structure of polymeric carbon nitrides was performed and the ranges within which the contents of different nitrogen species (pyridine, amine, imine and quaternary nitrogen) can change were determined. This analysis, in combination with quantitative XPS studies, permits to state that the carbon nitride structure prepared by the thermal condensation of dicyandiamide is closer to the structure in which poly(aminoimino)heptazine subunits are linked into chains rather than the structure involving fully-condensed polyheptazine network. The XRD analysis proved that the 3D crystal structure of carbon nitride is described more correctly by the orthorhombic cell and space group P21212 applied to condensed chains of poly(aminoimino)heptazine (melon) and not by the hexagonal cell with the space group P6m2. [ABSTRACT FROM AUTHOR]

Lignocellulosic biomass is the most abundant carbon source and it is a base of the whole biorefinery concept. Levoglucosan (1,6-anhydro-β- D -glucopyranose) (LG) is an anhydrous sugar formed as a major product during pyrolysis of cellulose. LG might be a promising chemical platform. It can be converted to different high added-value chemicals such as levoglucosenone, 5-hydroxymethylfurfural and styrene directly or through a glucose intermediate via chemical, catalytic and biochemical processes. In this critical review we focus not only on the pyrolytic methods for the synthesis of levoglucosan, but above all also on the recent scientific progress in the chemical and biochemical transformation of levoglucosan to highly valued compounds. The catalytic performances of the heterogeneous and enzymatic catalytic systems used for different reactions of LG conversion are reviewed. Specific properties of the active sites, roles of additives, and solvents and conditions are discussed in detail. We conclude on recommendations to further improve LG conversion to high added-value products. [ABSTRACT FROM AUTHOR]

Plasmon-driven chemical transformation has become a promising approach for enhancing sluggish electrocatalytic reactions. Herein, an alternative enhancement strategy employing plasmon-induced hot electrons was developed and found to be competitive with oxygen reduction reaction (ORR) on platinum electrodes. We demonstrated that, by using the intertwined plasmon-catalytic-electrochemical properties of nanoperforated gold thin film electrodes, the ORR under alkaline conditions could be significantly enhanced by careful tuning of the laser wavelength and power density. Irradiation at 980 nm and 2 W cm−2 displays maximal current densities of j = −6.0 A cm−2 at 0.95 V vs. RHE, under hydrodynamic conditions, comparable to that of commercial Pt/C (40 wt%) catalysts, with good long-term stability. The wavelength-dependent electrochemical reduction confirmed that the hot carriers formed during plasmon decay are responsible for the improved electrocatalytic performance. [ABSTRACT FROM AUTHOR]

The selective hydroconversion of 5‐hydroxymethylfurfural (HMF) to biofuels is currently highly sought‐for. While the literature has demonstrated that this reaction is possible on promoted Ni catalysts, we show here that a monometallic, non‐promoted Ni/SBA‐15 catalyst, prepared by incipient wetness impregnation, can convert HMF to 2,5‐dimethylfuran (DMF) and to 2,5‐dimethyltetrahydrofuran (DMTHF) at 180 °C, in a consecutive way. Through a control over reaction time, high yields to DMF (71 %, at conversion of 93 %) or DMTHF (97 %, at conversion of 100 %) can be achieved. Kinetic modelling suggests a preferential route to DMF via 5‐methylfurfural (MFFR) as intermediate, though the route via 2,5‐bis(hydroxylmethyl)furan (BHMF) is also present. The favored route in the experimental conditions involves the hydrogenolysis of the hydroxyl group of HMF as first step, followed by the hydrogenation of the aldehyde function, to methylfurfuryl alcohol (MFOL). It is suggested a higher reaction rate of hydrogenation or hydrogenolysis of the side group is linked to the presence of a methyl group in the molecule. No hydrogenation of the furan ring is detected on the intermediates. [ABSTRACT FROM AUTHOR]

AuPd alloyed nanoparticles are regarded as very active catalysts for oxidation of alcohols. However we found that their catalytic activity can be further improved after calcination in air, which lead to the restructuring of alloyed AuPd nanoparticles and PdO segregation on the surface. The alloyed character was partially recovered upon reduction with H2 atmosphere, but the yet Pd‐rich surface was less active in the oxidation of the model molecule benzyl alcohol. [ABSTRACT FROM AUTHOR]

The catalytic decarboxylation of fatty acids to yield hydrocarbons, for use as biofuel as a main target, is a topical reaction in which the main challenge is actually to control the selectivity while using the smallest amount of hydrogen possible (or even better, not using hydrogen at all) in order to optimize cost‐efficiency of the process. Herein, the focus is on the non‐noble mono‐, bi‐ and tri‐metallic catalysts used to carry out this reaction. Historically, several non‐noble monometallic catalysts based on Cu, Co, Ni supported on different types of supports were first studied. Among such materials, the Co‐based catalysts were not selective, while, Cu‐based catalysts were more or less selective to hydrocarbons or to olefins, depending on the support used. Among these three metals, the Ni‐based catalysts are the most widely described ones due to their specific ability to promote deoxygenation reactions. Combining Ni to a second metal yielded a synergistic effect toward better catalytic performances, with increases in both conversion and selectivity and also improvement of the resistance of the catalyst to carbon deposit, especially when adding non‐noble metals. For future prospects, it appears that the main challenge will be to be able to maintain good catalytic performances under inert gas in solvent‐free conditions, in order to yield a fully environmentally friendly and cost‐effective process. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Featured Application: The catalysts developed in this work could be potentially used industrially for green oxidations of bio-based compounds. A series of catalysts consisting of gold nanoparticles supported on MnO2 presenting different morphologies were synthesized and tested in the base-free oxidation of furfural. Ultra-small Au particles (less than 3 nm) were deposited on low (commercial MnO2) and high (NF, nanoflowers and NW, nanowires MnO2) surface area supports. High activity was observed for Au/MnO2-NF material with very high selectivity to furoic acid. The X-ray photoelectron spectroscopy (XPS) study confirmed the presence of a significant amount of highly active Auδ+ species on the surface of the Au/MnO2-NF catalyst. These species seem to be responsible for the high activity in oxidation of furfural under mild conditions (air as oxidant, 110 °C). [ABSTRACT FROM AUTHOR]

Abstract: The dehydration of lactic acid to produce acrylic acid is a renewable alternative to the mostly used production of acrylic acid from propene. In this review, the recent developments and state of the art for the dehydration of lactic acid to acrylic acid are presented and critically commented. The most recent publications on the topic are discussed inetail with respect to the observed catalysts and process performance data. Among the different catalysts developed, three main groups can be distinguished: zeolites, sulphates, and phosphates. The latter, especially hydroxyapatites, have recently attracted the attention of academics in particular. The three families of catalysts are discussed and the recent developments and technical drawbacks in the gas phase dehydration are reported. [ABSTRACT FROM AUTHOR]

Herein we report a one pot organometallic strategy to access alumina-embedded Pd nanoparticles. Unexpectedly, the decomposition of the organometallic complex tris(dibenzylideneacetone)dipalladium(0), Pd2(dba)3, by dihydrogen in the presence of aluminum isopropoxide, Al(iPrO)3, and without extra stabilizers, was found to be an efficient method to generate a Pd colloidal solution. Careful characterization studies revealed that the so-obtained Pd nanoparticles were stabilized by an aluminum isopropoxide tetramer and 1,5-diphenyl-pentan-3-one, which was produced after reduction of the dba ligand from the organometallic precursor. Moreover, calcination of the obtained nanomaterial in air at 773 K for 2 h resulted in a nanocomposite material containing Pd nanoparticles embedded in Al2O3. This stabilization strategy opens new possibilities for the preparation of transition metal nanoparticles embedded in oxides. [ABSTRACT FROM AUTHOR]

The oxidation of bio-based molecules in general, and of carbohydrates and furanics in particular, is a highly attractive process. The catalytic conversion of renewable compounds is of high importance. Acids and other chemical intermediates issued from oxidation processes have many applications related, especially, to food and detergents, as well as to pharmaceutics, cosmetics, and the chemical industry. Until now, the oxidation of sugars, furfural, or 5-hydroxymethylfurfural has been mainly conducted through biochemical processes or with strong inorganic oxidants. The use of these processes very often presents many disadvantages, especially regarding products separation and selectivity control. Generally, the oxidation is performed in batch conditions using an appropriate catalyst and a basic aqueous solution (pH 7-9), while bubbling oxygen or air through the slurry. However, there is a renewed interest in working in base-free conditions to avoid the production of salts. Actually, this gives direct access to different acids or diacids without laborious product purification steps. This review focuses on processes applying gold-based catalysts, and on the catalytic properties of these systems in the base-free oxidation of important compounds: C5-C6 sugars, furfural, and 5-hydroxymethylfurfural. A better understanding of the chemical and physical properties of the catalysts and of the operating conditions applied in the oxidation reactions is essential. For this reason, in this review we put emphasis on these most impacting factors. [ABSTRACT FROM AUTHOR]

Methyl formate (MF) is a valuable platform molecule, the industrial production of which is far from being green. In this contribution, TiO2-supported Pd( z)Pt(1− z) catalysts were found to be effective in the green synthesis of methyl formate (MF)-at T=323 K and ambient pressure-through methanol (MeOH) oxidation. Two series of catalysts with similar bulk Pd/(Pd+Pt) molar ratios, z, were prepared; one by a water-in-oil microemulsion (MicE) method and the other by an incipient wetness impregnation (IWI). The MicE method led to more efficient catalysts owing to a weak influence of z on particle size distributions and nanoparticles composition. Pd( z)Pt(1− z)-MicE catalysts exhibited strong synergistic effects for MF production but weak synergistic effects for MeOH conversion. The catalytic performance of Pd( z)Pt(1− z)-MicE was superior to that of Pd( z)Pt(1− z)-IWI catalysts despite the latter displaying synergetic effects during the reaction. The catalytic behavior of TiO2-supported Pd( z)Pt(1− z) catalysts was explained from correlations between XRD, TEM, and X-ray photoelectron spectroscopy characterizations. [ABSTRACT FROM AUTHOR]

Abstract: This work reports a 1 mol scale catalytic process to synthesize adipic acid directly from cyclohexane in solvent‐free conditions using air as oxidant. Catalysts based on vanadium phosphorus oxides were prepared, characterized and tested. They showed good activity and remarkably high selectivity to adipic acid in comparison to other already known heterogeneous catalysts. The use of solvent‐free conditions permits the easy separation of the product from the reactant mixture, which is very important from the industrial point of view. The process can be used at industrial scale for sustainable adipic acid synthesis. [ABSTRACT FROM AUTHOR]

This review paper presents the current state of the art on maleic acid synthesis from biomass-derived chemicals over homogeneous or heterogeneous catalysts. It is based on the most recent publications on the topic, which are discussed in details with respect to the observed catalytic performances. The recent developments and the technical drawbacks in the gas and the liquid phases are also reported. In addition, recent results on the mechanistic aspect are discussed giving insights into the probable reaction mechanisms depending on the starting molecule (furan, furfural and 5-hydroxymethylfurfural). [ABSTRACT FROM AUTHOR]