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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]

Cu 2 O nanostructures of cubic or octahedral shape as well as decorated with gold nanoparticles were synthesized by a chemical process. The electrochemical activity of these nanostructures for the oxygen evolution reaction (OER) in alkaline media was assessed in the dark and under solar light irradiation. Electrodes modified with cubic-shaped Cu 2 O and Cu 2 O-Au nanostructures revealed both enhanced electrocatalytic OER activity over the octahedral-shaped ones, for which hydroxylation of the (111) surfaces might hinder the OER as supported by numerical computations. Illumination of Cu 2 O nanostructures with solar light did not enhance the electrocatalytic OER. Cu 2 O-Au nanostructures, however, showed improved OER activity with an overpotential of 200 mV (10 mA cm−2) and a Tafel slope of 97 mV dec−1. The enhanced OER activity was ascribed to increased light absorption due to the plasmonic properties of Cu 2 O-Au cubes. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Elucidation of the promotion with antimony and tin on iron catalysts. • 7–10 times increase in the intrinsic activity of iron surface sites. • In-situ identification of the structure of working catalysts. • Strong interaction of the promoters and iron active phase. • Iron antimony bimetallic nanoparticles in activated catalysts. Fischer-Tropsch synthesis provides an important opportunity for utilization of biomass and plastic waste. Iron catalysts are the catalysts of choice for light olefin synthesis using Fischer-Tropsch reaction. In this paper, we investigate strong promoting effects of antimony and tin on the catalytic performance of silica supported iron Fischer-Tropsch catalysts using a combination of advanced and in-situ techniques. The catalyst doping with these elements added via impregnation results in a major increase in the reaction rate and much better catalyst stability. No enhancement of iron dispersion was observed after the promotion, while somewhat higher extent of iron carbidization was observed in the antimony promoted catalysts. Iron-bismuth bimetallic nanoparticles are detected by several techniques. In the working catalysts, the promoters are located in close proximity to the iron nanoparticles. The promotion leads to the 7–10 times increase in the intrinsic activity of iron surface sites due to their interaction with the promoters. [ABSTRACT FROM AUTHOR]

This paper investigates the catalytic properties of the iridium catalysts supported on modified silicalite-1. Post-synthesis modification of silicalite-1, with solutions of ammonium compounds (NH4F and NH4OH), appeared to be an efficient method to generate the acidic sites in starting support. The modification of support led not only to changes in its acidity but also its porosity—formation of additional micro- and mesopores. The novel materials were used as supports for iridium. The iridium catalysts (1 wt.% Ir) were characterized by N2 adsorption/desorption measurements, temperature-programmed reduction with hydrogen (TPR-H2), H2 chemisorption, transmission electron microscopy (TEM), temperature-programmed desorption of ammonia (TPD-NH3), X-ray photoelectron spectroscopy (XPS) and tested in the hydrogenation of toluene reaction. The catalytic activity of iridium supported on silicalite-1 treated with NH4OH (higher porosity of support, better dispersion of active phase) was much higher than that of Ir supported on unmodified and modified with NH4F silicalite-1. [ABSTRACT FROM AUTHOR]

During recent decades, the use of enzymes or chemoenzymatic cascades for organic chemistry has gained much importance in fundamental and industrial research. Moreover, several enzymatic and chemoenzymatic reactions have also served in green and sustainable manufacturing processes especially in fine chemicals, pharmaceutical, and flavor/fragrance industries. Unfortunately, only a few processes have been applied at industrial scale because of the low stabilities of enzymes along with the problematic processes of their recovery and reuse. Immobilization and co-immobilization offer an ideal solution to these problems. This review gives an overview of all the pathways for enzyme immobilization and their use in integrated enzymatic and chemoenzymatic processes in cascade or in a one-pot concomitant execution. We place emphasis on the factors that must be considered to understand the process of immobilization. A better understanding of this fundamental process is an essential tool not only in the choice of the best route of immobilization but also in the understanding of their catalytic activity. [ABSTRACT FROM AUTHOR]

As a consequence of intense industrialization in the last few decades, the amount of agro-industrial wastes has increasing, where new forms of valorization are crucial. In this work, five residual biomasses from Maranhão (Brazil) were investigated as supports for immobilization of lipase from Thermomyces lanuginosus (TLL). The new biocatalysts BM-TLL (babaçu mesocarp) and RH-TLL (rice husk) showed immobilization efficiencies >98% and hydrolytic activities of 5.331 U g−1 and 4.608 U g−1, respectively, against 142 U g−1 by Lipozyme® TL IM. High esterification activities were also found, with 141.4 U g−1 and 396.4 U g−1 from BM-TLL and RH-TLL, respectively, against 113.5 U g−1 by TL IM. Results of porosimetry, SEM, and BET demonstrated BM and RH supports are mesoporous materials with large hydrophobic area, allowing a mixture of hydrophobic adsorption and confinement, resulting in hyperactivation of TLL. These biocatalysts were applied in the production of hexyl laurate, where RH-TLL was able to generate 94% conversion in 4 h. Desorption with Triton X-100 and NaCl confirmed that new biocatalysts were more efficient with 5 times less protein than commercial TL IM. All results demonstrated that residual biomass was able to produce robust and stable biocatalysts containing immobilized TLL with better results than commercial preparations. [ABSTRACT FROM AUTHOR]

• 29 elements tested as promoters for silica supported iron catalysts • Elucidation of selectivity trends in high temperature Fischer-Tropsch synthesis • Higher activity and better stability of Sn-, Sb-, Bi- and Pb-promoted catalysts • No effect of tin and antimony on the olefin selectivity, • Higher olefin selectivity on bismuth and lead promoted catalysts In this work, 29 elements were evaluated as promoters for silica supported iron catalysts for high temperature Fischer-Tropsch synthesis using a high-throughput experimentation unit. The selected promoters include alkali/alkaline metals, transition metals, precious metals and lanthanides. Several general selectivity trends were observed and discussed. The selectivity enhancement to light olefins requires maintaining low selectivity to methane and light paraffins and at the same time, slowing the chain growth to the C 5+ hydrocarbons. A major increase in Fischer-Tropsch rate principally due to higher intrinsic site activity, was observed over the catalysts promoted with metals with low melting points such as tin, antimony, bismuth and lead. These promoted catalysts also exhibited better stability. The effect of the promotion with tin and antimony on the olefin selectivity was not noticeable, while the presence of bismuth and lead results in the major enhancement of the selectivity to light olefins, lower methane and C 2 -C 4 paraffin selectivities. [ABSTRACT FROM AUTHOR]

[Display omitted] • New hybrid paragmanetic nanocatalysts containg Fe3O4 nanoparticles, Pd and lipase. • Easy synthesis and characterization protocols. • One-pot DKR of (rac)-1-phenylethylamine in batch and continuous flow conditions. • Higher conversions and selectivities if compared to metal-enzyme separated systems. • Good recycles potential. Recent papers estimates that about 40 % of drugs present chiral amines in their structure and their synthesis in a sustainable and cost-competitive way is still a challenge for the industry. Kinetic resolution is one of the most applied method to produce these desired compounds where the association with lipase as a catalyst is a good alternative. However, the use of separate racemization catalyst and enzymes in the reaction medium still limits recovery, recycling and can occasionally be responsible for decreasing in selectivity for the desired product. In this work we proposed the synthesis and characterization of a hybrid magnetic catalyst composed containing lipase CaL B and Pd immobilized on the same recovered nanometric magnetic support for the application on Dynamic Kinetic Resolution of (rac)-1-phenylethylamine both in batch and continuous flow conditions. As results it was possible to achieve 99 % of conversion, with 95 % of selectivity and 93 % of enantiomeric excess after 12 h in batch. For a continuous flow system, it was possible to achieve 95 % of conversion with 71 % of selectivity and ee > 99 % after 60 min of reaction. The hybrid catalyst had around 50−100 nm with nanoparticulated Pd (5−10 nm) on its surface, presented a superparamagnetic behavior without remaining magnetization and 22 emu/g of saturation magnetization. [ABSTRACT FROM AUTHOR]

Furfural (FF) is a strategic product for the development of highly valued chemicals from biomass. The oxidation product of FF, furoic acid (FA), is an important precursor for the synthesis of green esters, such as methyl furoate. Taking into account issues with the direct furfural oxidation, furfural derivatives, such as alkyl furoates, can be easily prepared via oxidative esterification. Here, Au nanoparticles that were immobilized on alkaline-earth metal oxide supports were studied for the oxidative esterification of furfural while using alcohol as both reactant and solvent. The formation of esters is favored by the presence of basic sites on catalyst surface, resulting in high selectivity, preventing the formation of the acetal as a by-product. The Au/MgO sample provided up to 95% methyl furoate (MF) yield, a fast reaction rate, and high performance for furfural:Au molar ratios between 50 and 300. Furthermore, this catalyst was stable during reuse, since both the selectivity and the activity were maintained after four cycles. Oxidative esterification products were achieved in the presence of other alcohols, leading to the formation of esters of up to C5 (isopentyl furoate) with high selectivity (>99%). Linear and branched esters were formed, but the long-chain linear alcohols resulted in higher yields, such as n-butyl furoate in 94% yield. [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]

Selective oxidation of furfural to furoic acid was performed with pure oxygen in aqueous phase under mild conditions and uncontrolled pH using hydrotalcite-supported gold nanoparticles as catalyst. Hydrotalcites with different Mg: Al ratios were tested as support. The effects of reaction time, temperature and furfural/catalyst ratio were evaluated. The catalyst Au/HT 4:1 showed the highest activity and selectivity to the desired product, achieving a complete conversion of furfural to furoic acid after 2 h at 110 °C. Further, stability tests were carried out in a continuous stirred-tank reactor and a progressive deactivation of the catalyst due to the leaching of Mg2+ cations from the support inducing changes in the pH of the reaction medium was observed. [ABSTRACT FROM AUTHOR]

The global imperative to shift towards renewable and sustainable resources has spurred significant interest in exploring and utilizing platform chemicals derived from renewable feedstocks. Among these, levoglucosenone (LGO) and Cyrene™ have emerged as promising candidates. LGO, derived from the pyrolysis of cellulose and hemicellulose, exhibits structural versatility, making it an attractive starting material for various valuable products. Its chemical transformations can yield a diverse array of derivatives, including levulinic acid, furan derivatives, and intermediates for pharmaceutical and agrochemical synthesis, as well as bio-based materials such as bioplastics and resins. Cyrene™, produced through the hydrogenation of LGO, serves as a renewable, biodegradable, and non-toxic dipolar aprotic solvent, offering sustainability advantages for green chemistry applications. Herein we report our results on the continuous-flow cascade transformation of LGO into Cyrene™ and then (R)-γ-carboxy-γ-butyrolactone in good yields with an additional mechanistic investigation for the Baeyer-Villiger oxidation of Cyrene™., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Brazil has one of the greatest biodiversities on the planet, where various crops play a strategic role in the country's economy. Among the highly appreciated biomasses is babassu, whose oil extraction generates residual babassu mesocarp (BM), which still needs new strategies for valorization. This work aimed to use BM as a support for the immobilization of Thermomyces lanuginosus lipase (TLL) in an 8.83 mL packed-bed reactor, followed by its application as a biocatalyst for the synthesis of hexyl laurate in an integrated process. Initially, the percolation of a solution containing 5 mg of TLL at 25 °C and flows ranging from 1.767 to 0.074 mL min -1 was investigated, where at the lowest flow rate tested (residence time of 2 h), it was possible to obtain an immobilized derivative with hydrolytic activity of 504.7 U g -1 and 31.7 % of recovered activity. Subsequent studies of treatment with n-hexane, as well as the effect of temperature on the immobilization process, were able to improve the activities of the final biocatalyst BM-TLLF, achieving a final hydrolysis activity of 7023 U g -1 and esterification activity of 430 U ⋅ g -1 against 142 U g -1 and 113.5 U g -1 respectively presented by the commercial TLIM biocatalyst. Desorption studies showed that the TL IM has 18 mg of protein per gram of support, compared to 4.92 mg presented by BM-TLL. Both biocatalysts were applied to synthesize hexyl laurate, achieving 98 % conversion at 40 °C within 2 h. Notably, BM-TLLF displayed exceptional recyclability, maintaining catalytic efficiency over 12 cycles. This reflects a productivity of 180 mg of product ⋅ h -1  U -1 of the enzyme, surpassing 46 mg h -1  U -1 obtained for TLIM. These results demonstrate the efficacy of continuous flow technology in creating a competitive and integrated process offering an exciting alternative for the valorization of residual lignocellulosic biomass., (© 2024 Wiley-VCH GmbH.)

Developing a process that performs the lignocellulosic biomass fractionation under milder conditions simultaneously with the depolymerization and/or the upgrading of all fractions is fundamental for the economic viability of future lignin-first biorefineries. The molten salt hydrates (MSH) with homogeneous or heterogeneous catalysts are a potential alternative to biomass pretreatment that promotes cellulose's dissolution and its conversion to different platform molecules while keeping the lignin reactivity. This review investigates the fractionation of lignocellulosic biomass using MSH to produce chemicals and fuels. First, the MSH properties and applications are discussed. In particular, the use of MSH in cellulose dissolution and hydrolysis for producing high-value chemicals and fuels is presented. Then, the biomass treatment with MSH is discussed. Different strategies for preventing sugar degradation, such as biphasic media, adsorbents, and precipitation, are contrasted. The potential for valorizing isolated lignin from the pretreatment with MSH is debated. Finally, challenges and limitations in utilizing MSH for biomass valorization are discussed, and future developments are presented. Cellulose Avicel®PH-101 ZnCl 2  ⋅ 4H 2 O, ZnBr 2  ⋅ 4H 2 O, LiCl ⋅ 8H 2 O, LiBr ⋅ 4H 2 O H 2 SO 4 , (0.2 M); H 3 PW 12 O 40 (0.067 M); H 4 SiW 12 O 40 (0.05 M) T (145-175 °C); Time (30-120 min) Organic solvent (MIBK) LA (94 %) and HMF (3.4 %) Dissolution time: ZnBr 2  ⋅ 4H 2 O<> 2 O<> 2  ⋅ 4H 2 O<> 2 O; The highest conversion of pretreated cellulose and yield of glucose were obtained with ZnBr 2  ⋅ 4H 2 O (88 % and 80 %, respectively)., (© 2024 Wiley-VCH GmbH.)

Catalytic reactions involving molecular hydrogen are at the heart of many transformations in the chemical industry. Classically, hydrogenations are carried out on Pd, Pt, Ru or Ni catalysts. However, the use of supported Au catalysts has garnered attention in recent years owing to their exceptional selectivity in hydrogenation reactions. This is despite the limited understanding of the physicochemical aspects of hydrogen activation and reaction on Au surfaces. A rational design of new improved catalysts relies on making better use of the hydrogenating properties of Au. This Review analyses the strategies utilized to improve hydrogen-Au interactions, from addressing the importance of the Au particle size to exploring alternative mechanisms for H 2 dissociation on Au cations and Au-ligand interfaces. These insights hold the potential to drive future applications of Au catalysis., (© 2024. Springer Nature Limited.)

The in situ growth of N-doped multi-walled carbon nanotubes (N-MWCNTs) from the products of graphitic carbon nitride (g-C 3 N 4 ) etching by Ni nanoparticles in a hydrogen atmosphere has been confirmed for the first time. During the etching process of g-C 3 N 4 , the building blocks, notably methane, ammonia, and hydrogen cyanide, are formed. The formation of N-MWCNTs was confirmed by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning (SEM) and transmission electron microscopy (TEM). A sponge-like carbonaceous structure was obtained with a specific surface area of 384 m 2 g -1 from initial g-C 3 N 4 (32 m 2 g -1 )., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

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 H 2 but with a change in structure and chemical ordering.

Studies involving the transformation of lignocellulosic biomass into high value-added chemical products have been intensively conducted in recent years. Its matrix is mainly composed of cellulose, hemicellulose and lignin, being, therefore, an abundant and renewable source for obtaining several platform molecules, with levoglucosan (LG) standing out. This anhydrous carbohydrate can be acylated to obtain carbohydrate fatty acid esters (CFAEs). Here, these compounds were obtained via enzymatic acylation of LG, commercially obtained (Start BioScience®), with different acyl donors in continuous flow. Through the experimental design using a model reaction, it was possible to optimize the reaction conditions, temperature and residence time, obtaining a maximum conversion at 61 °C and 77 min. In addition, there was a productivity gain of up to 100 times in all comparisons made with the batch system. Finally, CFAEs were applied in tests of interfacial tension and biological activity. For a mixture of 4- and 2- O -lauryl-1,6-anhydroglucopyranose (MONLAU), the minimum interfacial tension (IFT min ) obtained was 96 mN m -1 and the critical micelle concentration (CMC) was 50 mM. Similar values were obtained for a mixture of 4- and 2- O -palmitoyl-1,6-anhydroglucopyranose (MONPAL), not yet reported in the literature, of 88 mN m -1 in 50 mM. For a mixture of 4- and 2- O -estearyl-1,6-anhydroglucopyranose (MONEST) and 4- and 2- O -oleoyl-1,6-anhydroglucopyranose (MONOLE), CMC was higher than 60 mM and IFT min of 141 mN m -1 and 102 mN m -1 , respectively. Promising data were obtained for minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of MONLAU against Staphylococcus aureus strains at 0.25 mM., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Pt, Ru, and Ir were introduced onto the surface of graphitic carbon nitride (g-C 3 N 4 ) using the wet impregnation method. A reduction of these photocatalysts with hydrogen causes several changes, such as a significant increase in the specific surface area, a C/N atomic ratio, a number of defects in the crystalline structure of g-C 3 N 4 , and the contribution of nitrogen bound to the amino and imino groups. According to the X-ray photoelectron spectroscopy results, a transition layer is formed at the g-C 3 N 4 /metal nanoparticle interphase, which contains metal at a positive degree of oxidation bonded to nitrogen. These structural changes significantly enhanced the photocatalytic activity in the production of hydrogen through the water-splitting reaction. The activity of the platinum photocatalyst was 24 times greater than that of pristine g-C 3 N 4 . Moreover, the enhanced activity was attributed to significantly better separation of photogenerated electron-hole pairs on metal nanoparticles and structural distortions of g-C 3 N 4 .

Carbon dioxide (CO 2 ) is the iconic greenhouse gas and the major factor driving present global climate change, incentivizing its capture and recycling into valuable products and fuels. The 6H + /6e - reduction of CO 2 affords CH 3 OH, a key compound that is a fuel and a platform molecule. In this Review, we compare different routes for CO 2 reduction to CH 3 OH, namely, heterogeneous and homogeneous catalytic hydrogenation, as well as enzymatic catalysis, photocatalysis and electrocatalysis. We describe the leading catalysts and the conditions under which they operate, and then consider their advantages and drawbacks in terms of selectivity, productivity, stability, operating conditions, cost and technical readiness. At present, heterogeneous hydrogenation catalysis and electrocatalysis have the greatest promise for large-scale CO 2 reduction to CH 3 OH. The availability and price of sustainable electricity appear to be essential prerequisites for efficient CH 3 OH synthesis., (© 2021. Springer Nature Limited.)

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 CO 2 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., (© 2020 Wiley-VCH GmbH.)

This work investigates batch and continuous-flow heterogeneous catalytic hydrogenation of a mixture of cafestol and kahweol (C&K) to obtain pure cafestol. These diterpenes were extracted from green coffee beans, and hydrogenation was performed using well-established palladium catalysts (Pd/C, Pd/CaCO 3 , Pd/BaSO 4 , and Pd/Al 2 O 3 ) and a carbon black-supported Pd catalyst coated by a covalently tethered SiO 2 shell with mesoporous texture (Pd/CB@SiO 2 ), all partially deactivated with quinoline. Pd/C 10% poisoned with 1 wt % quinoline gave the best result for batch reaction, producing cafestol from kahweol with high selectivity (>99%) after 10 min. Excellent selectivity was also obtained with the catalyst Pd/CB@SiO 2 with only 1% Pd. In addition, Pd/C-quinoline adapted for continuous-flow experiments exhibited the best catalytic activity, also providing cafestol with excellent selectivity (>99%) after 9.8 s., Competing Interests: The authors declare no competing financial interest.

In this paper, Raman spectroscopy is used as a tool to study the mechanism of furfural oxidation using H 2 O 2 as a reagent on gold nanoparticles (NPs) supported on hydrotalcites (HTs). This reaction was repeated, under the same conditions, but with different reaction times in a parallel multireactor system. The reaction media were analyzed using a macro device associated with a multipass cell permitting us to enhance the Raman signal by reflecting the laser beam 3 times. The Raman spectra showed the conversion of furfural to furoic acid without any chemical intermediates, thus privileging a direct pathway. Combining the results of the catalytic tests with those of the Raman study, the mechanism of furfural oxidation to furoic acid using gold NPs supported on HTs is proposed. The key points of this mechanism were found to be as follows: (i) the in situ formation of a base, originating from the Mg leaching from the HT support, initiates the oxidation of furfural by deprotonation; (ii) H 2 O 2 used as a reagent in the solution increases the catalytic activity by its dissociation to form hydroxide ions; and (iii) the oxidation of furfural occurs on the surface of gold NPs and leads to higher furoic acid yield., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

One of the most interesting intermediates for the chemical industry is acrylic acid, which can be derived from lactic acid by catalytic dehydration in the gas phase. The realization of this reaction is complex due to a strong thermal activation leading to the formation of undesired by-products (acetaldehyde, propanoic acid…) as well as polymerization. We studied this reaction over hydroxyapatites modified by substitution of the hydroxyl groups by fluoride. This notably enabled increasing the selectivity to acrylic acid while reducing the formation of the undesired acetaldehyde. Introduction of fluoride induced a modification of the phosphate ( PO 4 3 - ) groups. In the presence of water, fluoride prevented the formation of hydrogenophosphate species ( HPO 4 2 - ), which are well-known acid sites responsible for the formation of acetaldehyde by decarboxylation/decarbonylation. Further, we evidenced an important impact of fluoride substitution on crystallinity, specific surface area and on the surface Ca/P ratio. This latter is known to be a key parameter to control the acidity and the basicity of the hydroxyapatites. Using FT-IR spectroscopy with propyne as a probe molecule, we could show that lactic acid was concertedly adsorbed on basic and acid sites, which might be at the origin of the observed superior performances., (Copyright © 2020 Wojcieszak, Bonnotte, Paul, Katryniok and Dumeignil.)

Engineering photocatalysts based on gold nanoparticles (AuNPs) has attracted great attention for the solar energy conversion due to their multiple and unique properties. However, boosting the photocatalytic performance of plasmonic materials for H2 generation has some limitations. In this study, we propose a soft-chemistry method for the preparation of a strong metal-support interaction (SMSI) to enhance the photocatalytic production of H2. The TiO2 thin overlayer covering finely dispersed AuNPs (forming an SMSI) boosts the photocatalytic generation of hydrogen, compared to AuNPs deposited at the surface of TiO2 (labelled as a classical system). The pathway of the charge carriers' dynamics regarding the system configuration is found to be different. The photogenerated electrons are collected by AuNPs in a classical system and act as an active site, while, unconventionally, they are injected back in the titania surface for an SMSI photocatalyst making the system highly efficient. Additionally, the adsorption energy of methanol, theoretically estimated using the density functional theory (DFT) methodology, is lower for the soft-chemistry SMSI photocatalyst accelerating the kinetics of photocatalytic hydrogen production. The SMSI obtained by soft-chemistry is an original concept for highly efficient photocatalytic materials, where the photon-to-energy conversion remains a major challenge.