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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]

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]

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]

Furfural (FF) has a high potential to become a major renewable platform molecule to produce biofuels and bio-based chemicals. The catalytic performances of AuxPty and AuxPdy bimetallic nanoparticulate systems supported on TiO2 were studied in a base-free aerobic oxidation of furfural to furoic acid (FA) and maleic acid (MA) in water. The characterization of the catalysts was performed using standard techniques. The optimum reaction conditions were also investigated, including the reaction time, the reaction temperature, the metal ratio, and the metal loading. The present work shows a synergistic effect existing between Au, Pd, and Pt in the alloy, where the performances of the catalysts were strongly dependent on the metal ratio. The highest selectivity (100%) to FA was obtained using Au3-Pd1 catalysts, with 88% using 0.5% Au3Pt1 with about 30% of FF conversion at 80 °C. Using Au-Pd-based catalysts, the maximum yield of MA (14%) and 5% of 2(5H)-furanone (FAO) were obtained by using a 2%Au1-Pd1/TiO2 catalyst at 110 °C. [ABSTRACT FROM AUTHOR]

2,5-furandicarboxylic acid (2,5-FDCA) is a biomass derivate of high importance that is used as a building block in the synthesis of green polymers such as poly(ethylene furandicarboxylate) (PEF). PEF is presumed to be an ideal substitute for the predominant polymer in industry, the poly(ethylene terephthalate) (PET). Current routes for 2,5-FDCA synthesis require 5-hydroxymethylfurfural (HMF) as a reactant, which generates undesirable co-products due to the complicated oxidation step. Therefore, direct CO2 carboxylation of furoic acid salts (FA, produced from furfural, derivate of inedible lignocellulosic biomass) to 2,5-FDCA is potentially a good alternative. Herein, we present the primary results obtained on the carboxylation reaction of potassium 2-furoate (K2F) to synthesize 2,5-FDCA, using heterogeneous catalysts. An experimental setup was firstly validated, and then several operation conditions were optimized, using heterogeneous catalysts instead of the semi-heterogeneous counterparts (molten salts). Ag/SiO2 catalyst showed interesting results regarding the K2F conversion and space–time yield of 2,5-FDCA. [ABSTRACT FROM AUTHOR]

The heterogeneous catalytic partial oxidation of alcohols and aldehydes in the liquid phase usually needs the addition of a homogeneous base, which in turn makes the products' recovery cumbersome, and can further induce undesired side reactions. In the present work, we propose the use of novel catalysts based on metallic Au, Pd and bimetallic AuPd nanoparticles embedded in a titanosilicate matrix. The as-prepared catalysts showed good efficiency in the base-free partial oxidation of furfural and 5-hydroxymethylfurfural. Au4Pd1@SiTi catalyst showed high selectivity (78%) to monoacids (namely, 5-formyl-2-furancarboxylic acid and 5-hydroxymethyl-2-furancarboxylic acid) at 50% 5-hydroxymethylfurfural (HMF) conversion. The selectivity even reached 83% in the case of furfural oxidation to furoic acid (at 50% furfural conversion). The performances of the catalysts strongly depended on the Au–Pd ratio, with an optimal value of 4:1. The pH of the solution was always below 3.5 and no leaching of metals was observed, confirming the stabilization of the metal nanoparticles within the titanosilicate host matrix. [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]

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]