Vinyl acetate is the main derivative of acetic acid. Its production process stems from the acetoxylation of acetylene or ethylene, with the ethylene route being the major commercial route today. As vinyl acetate is an organic precursor with wide application in the polymer industry, its synthesis and related aspects are of great interest in the scientific field. Based on theoretical and experimental evidence, this article provides an analysis of vinyl acetate production, focusing on the two main industrial routes, the catalysts used on a commercial and laboratory scale, and the reaction mechanisms involved in each synthesis pathway.

This work investigates the performance and deactivation of mono and bimetallic (Cu-Fe) catalysts supported on functionalized carbon nanotubes (CNTF) on the preferential oxidation of CO (CO-PROX), and compare in situ the structure before and after reaction. The bimetallic Cu-Fe/CNTF catalyst exhibited superior activity by reducing the reaction temperature compared to the monometallic counterparts, and achieving complete CO2 selectivity below 100 °C. However, competition with H2 oxidation limited overall CO conversion at higher temperatures. Results indicate that this enhancement is attributed to the interaction of Cu-Fe, which creates a strong interfacial synergy between Cu and Fe oxide species, as suggested by a positive shift in the Cu 2p XPS binding energy. The Cu/CNTF and Cu-Fe/CNTF catalysts demonstrated excellent thermal and catalytic stability. In contrast, the Fe/CNTF catalyst showed progressive deactivation due to sintering or partial reduction of Fe₂O₃. The iron oxide matrix provides structural and electronic anchoring sites, with the formation of carbide Fe3C and probably Fe2C enhancing the stability. The Cu-Fe/CNTF system exhibits high intrinsic activity and excellent sintering resistance, due to the surface being electronically modified through doping, which selectively inhibits the H2 oxidation pathway.

This study provides a mechanistic understanding of the enhanced catalytic performance in the preferential oxidation of CO (CO-PROX) previously demonstrated for Pt/Al2O3 catalysts promoted with CoAl2O4 and NiAl2O4 spinels [1]. Using in situ diffuse reflectance infrared Fourier transform spectroscopy coupled with mass spectrometry (DRIFTS-MS), temperature-programmed surface reaction (TPSR), X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations, we investigated the surface processes underlying the superior low-temperature activity and selectivity. The analyses reveal electron transfer from Pt to the aluminate phase, generating electron-deficient Pt species; DFT calculations quantify this electronic modification, showing increased charge transfer from the Pt cluster to the support in the presence of Ni and Co, which strengthens O2 activation at the promoter sites. These effects are consistent with a dual-site Langmuir-Hinshelwood mechanism in which CO adsorbed on Pt reacts with oxygen activated at adjacent promoter sites. The combined evidence explains the markedly lower CO oxidation onset temperatures (≈50-60 °C for Co/Ni-promoted catalysts vs. ≈100 °C for Pt/Al2O3) and provides molecular-level insight into the role of promoters in optimizing CO-PROX performance.

Integrating metallic sites with tailored acid-base and redox functionalities is sensitive to the selective hydrogenation of CO2 to methanol and DME. Herein, we designed a series of confined Cu-ZrO2@SiO2 catalysts with different Cu-Zr ratios (3:1, 3:2, 3:3), to enhance Cu–Zr interfacial interactions and regulate surface acidity by spatially confining active sites. While low Zr content retained a partial spherical morphology and high methanol selectivity (97%) at 220 °C, increasing the Zr loading induced a structural distortion into a “cotton-like” morphology. This transformation promoted a high contribution of defect-related oxygen species (62%) and total acidity (1128 μmol∙g−1) associated with distorted Zr–O–Si interfacial environments. The optimized Cu-Zr (3:3) catalyst exhibited a superior balance of functionalities, achieving 81% methanol and 17% DME selectivity, with 15% CO2 conversion (220 °C). At high temperatures (280 °C), this catalyst also maintained high selectivity for methanol (65%) and DME (20%), outperforming a conventional impregnated Cu-ZrO2/SiO2 reference catalyst, which converted only 9% CO2, with 76% methanol selectivity and negligible DME production under the same conditions. XPS and EPR revealed that this enhanced activity probably stems from a unique electronic environment: a high fraction of electronically perturbed Cu species, strongly coupled to Zr-derived sites, which facilitates CO2 activation and suppresses the reverse water-gas-shift reaction. This catalyst demonstrated 72-hour stability with a space-time-yield (223 mgMeOH∙gcat−1∙h−1) significantly higher than that of the impregnated catalyst (121 mgMeOH∙gcat−1∙h−1). These results indicate that spatially coupling Cu redox sites with Zr-derived acidity within a SiO2–confined architecture provides an effective strategy to tune product selectivity in CO2 hydrogenation.

Hydrodeoxygenation (HDO) reactions are one of the most studied oxygen removal processes and are typically carried out at high temperatures and hydrogen pressures with the aid of a solid catalyst. One of the greatest challenges is the development of effective catalysts. In this sense, this work aims to evaluate the metallic dispersion of Ni supported on carbon nanotubes and its performance as a catalyst in the hydrodeoxygenation reaction of bio-oil (using guaiacol as a model molecule). Thermally pretreated CNTs were impregnated to the wet point with a nickel acetate solution and subsequently calcined at 500 °C for 12 h. Catalysts with 2

This work presents C-H bond activation on CuCo and Zn-based catalyst metals supported on carbon nanotubes and zirconia for acetic acid, with emphasis on CH4 activation and subsequent CO2 insertion leading to acetic acid formation. Catalysts were synthesized by dry impregnation and characterized by XRD, Raman spectroscopy, N2 physisorption, and TGA. H2-TPR revealed metal-support interactions and reducibility that directly influence the formation of surface intermediates. CH4-TPSR experiments demonstrated that Cu-and Co-containing catalysts promote homolytic C-H cleavage at substantially lower temperatures than Zn-based systems, enabling earlier formation of CHx species. DRIFTS measurements confirmed that CH4 exposure generates CHx species, while the subsequent addition of CO2 leads to the formation of carbonate, bicarbonate, formate, and acetate-type species. The CNTs evidenced that the in situ generated CO2 enhanced the insertion into CHx fragments, thereby promoting C-C bond formation. DRIFTS confirm the carboxylation pathway in the temperature range where simultaneous CH4 activation occurs, with CO2 availability and H2. Post-reaction characterization shows preservation of the active sites, phases, and carbon formation associated with CH4 activation. This work confirms the methane carboxylation pathway and highlights the catalytic relevance of the reaction with CO2 to enable C-C coupling under milder conditions.

This work studies the activation of the C-H bond in methane over CuCo- and Zn-based catalysts supported on carbon nanotubes and zirconia, with emphasis on the mechanistic steps of CH4 activation and subsequent CO2 insertion leading to acetic acid formation. Catalysts synthesized by dry impregnation were characterized by XRD, Raman spectroscopy, N2 physisorption, TGA and H2TPR, revealing distinct metal–support interactions and reducibility profiles that directly influence the formation of surface intermediates. CH4TPSR experiments demonstrated that Cu- and Co-containing catalysts promote homolytic C-H cleavage at substantially lower temperatures than Zn-based systems, enabling earlier formation of CHx species. DRIFTS measurements confirmed that CH4 exposure generates the CHx species and weakly bound hydrocarbons, while the subsequent introduction of CO2 leads to the formation of carbonate, bicarbonate, formate, and acetate-type species. The CH4-TPSR results demonstrates that the ”in situ” CO2 generated from CNT decomposition plays a mechanistic role by enhancing CO2 insertion into CHx fragments, thereby promoting C-C bond formation. The temperature-dependent evolution of DRIFTS bands matches the CH4-TPSR transitions, confirming that the carboxylation pathway becomes dominant precisely in the temperature window where CH4-TPSR indicates simultaneous CH4 activation, CO2 availability and H2 formation. Post-reaction characterization shows preservation of the active site phases and coke deposition associated with CH4 activation. By integrating DRIFTS mechanistic evidence with CH4-TPSR performance, this work advances the understanding of methane carbonylation pathways in the synthesis of value-added compounds and highlights the catalytic relevance of the reaction with CO2 to enable C-C coupling under milder conditions.

Integrating metallic sites with tailored acid-base and redox functionalities is sensitive to the selective hydrogenation of CO2 to methanol and DME. Herein, we designed a series of confined Cu-ZrO2@SiO2 catalysts with different Cu-Zr ratios (3:1, 3:2, 3:3), to enhance Cu-Zr interfacial interactions and regulate surface acidity by spatially confining active sites. While low Zr content retained a partial spherical morphology and high methanol selectivity (97%) at 220 degrees C, increasing the Zr loading induced a structural distortion into a "cotton-like" morphology. This transformation promoted a high contribution of defect-related oxygen species (62%) and total acidity (1128 mu mol center dot g(-1)) associated with distorted Zr-O-Si interfacial environments. The optimized Cu-Zr (3:3) catalyst exhibited a superior balance of functionalities, achieving 81% methanol and 17% DME selectivity, with 15% CO2 conversion (220 degrees C). At high temperatures (280 degrees C), this catalyst also maintained high selectivity for methanol (65%) and DME (20%), outperforming a conventional impregnated Cu-ZrO2/SiO2 reference catalyst, which converted only 9% CO2, with 76% methanol selectivity and negligible DME production under the same conditions. XPS and EPR revealed that this enhanced activity probably stems from a unique electronic environment: a high fraction of electronically perturbed Cu species, strongly coupled to Zr-derived sites, which facilitates CO2 activation and suppresses the reverse water-gas-shift reaction. This catalyst demonstrated 72-hour stability with a space-time-yield (223 mgMeOH center dot g(cat)(-1)center dot h(-1)) significantly higher than that of the impregnated catalyst (121 mgMeOH center dot g(cat)(-1)center dot h(-1)). These results indicate that spatially coupling Cu redox sites with Zr-derived acidity within a SiO2-confined architecture provides an effective strategy to tune product selectivity in CO2 hydrogenation.

This study compares unsupported NiO nanoflowers (NiEG) and ZrO2-supported NiO (25NiZ) for methane activation and hydrogenation, focusing on the impact of catalyst morphology. The NiEG catalyst demonstrated superior performance, achieving a high methane activation rate of 1.79 mol/(s·gNiO) and unique product selectivity. It produced ethylene and ethane at 503 K and higher hydrocarbons (C4–C6) at 593 K. Furthermore, the NiEG catalyst exhibited enhanced coke resistance, forming less-deactivating carbon nanotubes compared to the filamentous coke prevalent on the 25NiZ catalyst. We attribute this performance to the nanoflower morphology, which provides highly exposed and stable Ni sites that facilitate C-H cleavage and stabilize reaction intermediates.

Rising global energy and growing environmental concerns demand cleaner production methods for fuels and platform chemicals. The Fischer-Tropsch synthesis (FTS) is a promising alternative to fossil oil sources for producing valuable hydrocarbons directly from syngas (CO and H-2) such as light olefins and middle distillates. Due to their cost-effectiveness and bifunctional properties, Fe/HZSM-5 catalysts have gained recent interest for FTS. However, research on reaction conditions and CO consumption kinetics for this catalyst remains limited. This work addresses a comprehensive study encompassing catalyst characterization, catalytic activity evaluation, and kinetic modeling of Fe/HZSM-5 catalysts for FTS. Our data showed that Fe presented multiple reduction stages and changed the moderate acidity of the evaluated zeolites upon Fe impregnation. Fe2O3 particles were also found to be transformed into iron carbides species during the catalytic reaction according to the M & ouml;ssbauer spectroscopy. The catalysts were active and stable for FTS (X-CO > 50 %) with a major production of hydrocarbons in C-2-C-4 and C-5-C-8 ranges. Pressure, temperature, feed composition and space velocity significantly influenced the CO conversion. The kinetic model for the Fe/HZSM-5 catalyst was investigated by modeling and in situ DRIFTS, aligning with the carbide mechanism considering dissociative adsorption of CO and H-2, a two-site reaction pathway, and competitive adsorption between CO and CO2 on the metal sites. These findings provide important insights for optimizing catalyst design and reaction conditions to enhance the efficiency of syngas-based fuel production.

Carbon formation is one of the major problems in methane reforming reactions, mainly in dry reforming of methane (DRM), limiting its industrial competitiveness. Thus, in this work, we investigate the oxygen mobility and carbon resistance of the LaNi-Zn perovskite in the DRM reaction. The catalysts LaNiO3 (LN) and LaNi0.5Zn0.5O3-delta (LNZn) were synthesized and characterized by XRD, H2-TPR, CH4-TPSR-MS, H2-TPHR-MS, XPS, TGA, Raman, HRTEM, and quasi-in-situ DRIFTS-MS, aiming to understand the role of the promoter in coke suppression. The CH4-TPSR-MS, H2-TPHR-MS, and Raman analyses revealed that the Zn-substituted catalyst exhibited higher oxygen mobility compared to the LN catalyst, attributed to the oxophilicity of Zn2+, which facilitates carbon gasification. XPS and HRTEM analyses of reduced samples confirmed the presence of metallic Zn0 on the surface as Ni-Zn alloying. 30 h of TOS showed higher activity for the LN catalyst than the LNZn. However, post-reaction analysis indicated that the addition of Zn increased carbon resistance by 5 times. The formation of the Ni-Zn alloying effectively prevented the removal of Ni particles from the support and their encapsulation by carbon nanotubes. Quasi-in-situ DRIFTS-MS has revealed that the LNZn catalyst promotes the formation of intermediate species responsible for carbon oxidation (CHxO, HCOO-, and HCO3-), clearing the anti-carbon behavior of the Zn-substituted catalyst.

We synthesized nickel catalysts supported on carbon nanotubes (Ni/NTC), graphene nanoplatelets (Ni/NPG), and silica (Ni/SiO2) and evaluated their performance in CO2 methanation. Ni/NTC exhibited the highest CO2 conversion (59 %) and CH4 selectivity (95.7 %) at 450 degrees C, outperforming other supports due to favorable Ni crystallinity and dispersion.". The catalytic performance for CH4 production was Ni/NTC>Ni/SiO2>Ni/NPG. The crystallinity, reducibility, and size of Ni nanoparticles were the factors that contributed to the difference in catalytic performance.

This study aimed to synthesize functionalized nanosupports via emulsion polymerization to develop new promising nanobiocatalyts via enzyme immobilizations. The co-monomers methyl methacrylate, divinylbenzene and the epoxy monomer glycidyl methacrylate (GMA) were used. The performance of the nanobiocatlysts was evaluated in hydrolysis and esterification reactions after the immobilization of lipase B from Candida antarctica (CAL B). Firstly, the nanosupports functionalized in situ with 25% and 50% w/w of GMA were successfully synthesized. In esterification reactions, the nanobiocatalysts containing 25% (w/w) of GMA were more active, achieving 254 U.g-1, or an enzyme activity per area of 2.8 U.m-2; such value was higher than the one obtained when the commercial matrix Octadecyl Sepabeads was used (328 U.g-1, 2.4 U.m-2). Such results point out that there is an optimum concentration of GMA epoxide groups that should be incorporated into the supports. The greater enzymatic activity obtained for 25% of GMA nanobiocatalyst was achieved not only because of their textural properties, but also due to a favorable interaction between the epoxide groups and CAL B. These results highlight the potential use of the heterofunctional matrices for the synthesis of new market-competitive biocatalysts. Monomers used in the synthesis of nanosupports via emulsion polymerization to produce biocatalysts. image

The main challenge for the RWGS reaction’s technological feasibility is the search for catalysts operating at low temperatures for CO2 activation and conversion and preventing secondary reactions, such as methanation. In this work, the metals Copper (Cu), Iron (Fe), Ruthenium (Ru), and Nickel (Ni) catalysts and combined metals on Cerium-Zirconia support were synthesized, characterized, and tested in the RWGS. The Fe–Ni–Cu combination was the most effective at lower temperatures (400 °C) compared to other metallic combinations 2, presenting 40

In the present paper, the effects of metal promoters (M = Fe, Co, and Cu) in Pt/M x Zr y O z catalysts and the influence of CO2 and H2O on the CO oxidation activity (PROX) were investigated. To do that, characterizations of catalyst structures and surfaces were performed and reported here. The catalyst Pt/Fe x Zr y O z (PFeZ) was the most active at low temperatures among the analyzed ones. The addition of platinum caused strong interaction with the mixed oxide, affecting the structure and the surface composition, blocking basic sites, and thus preventing catalyst deactivation. Particularly, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results evidenced the formation of carboxylate and carbonate species. Besides, the addition of CO2 and H2O in the gas feed stream affected the observed CO oxidation results, showing that CO2 competes with O2 on metallic sites. Moreover, DRIFTS and temperature-programmed desorption (TPD) analyses suggested the occurrence of OH- oxidation by CO, leading to the formation of highly reactive compounds that can be easily oxidized.

Hydrogen is a key component for a successful energy transition on a large scale since it boasts remarkable energy efficiency. Currently, H2 is mainly obtained through steam reforming of natural gas or hydrocarbons and low-carbon alcohols but contains approximately 2 % CO, a contaminant detrimental to H2 fuel cells. Herein, an N-doped carbon nanotube was prepared via the soft nitriding method to support nickel and cobalt for the PROX-CO as the main reaction for hydrogen purification. The most efficient condition was achieved when the reaction temperature reached 250 degrees C and the Ni and Co loading rate was 7.5 %. In this situation, the CO2 selectivity reached almost 33 %, and CO conversion was 61 %. Regarding CO conversion among bimetallic catalysts at 250 degrees C a minimal variation occurred and the catalyst 10Ni/N-CNTs slightly outperformed (64.4 %). The effect of N-doping on the carbon nanotube's structure was also revealed. Nitrogen atoms incorporated into the lattice of carbon nanotubes impart an electron-donor character. Consequently, Co oxide reduction to the metallic phase occurred at significantly lower temperatures compared to other supports such as SiO2, Al2O3, and graphene. For the bimetallic catalysts, the strong metal-support interaction facilitated obtaining different oxide and metallic phases at milder temperatures.

This work uses sol-gel and sonochemical methods to prepare bimetallic PdCu catalysts supported on modified ZrO2 with Ti and Al. The catalysts are tested for vinyl acetate synthesis from ethylene, acetic acid, and oxygen, varying the reaction temperature for two catalysts prepared, which show higher activity. Catalysts characterization results show bimetallic species and distort alloys with a dispersed distribution of active metal onto the support. The in situ reaction by DRIFT-MS identifies the surface formation of main intermediates like palladium acetate monomers and mono and bidentate intermediates, associated to vinyl acetate formation, like vinyl hydrogenated species over PdCu. Finally, this behavior will be attributed to the bimetallic distortions of PdCu samples, provided by interaction effects between PdCu and supports, indicating a more exposition of PdCu species suitable for the reaction, according to high-resolution transmission microscopy electron microscopy results for PdCu/ZrTi sample. Thus, this sample exhibits a minimal formation of sub-products and catalytic stability for 18 hh. These results evidence the participation of hydroxyls and oxygen vacancies of the catalyst in the catalytic reaction measured in situ, monitoring the products formed at the reactor outlet. Finally, it is proposed a reaction pathway as a function of reaction conditions.

In this work we presented the synthesis and performance of two different materials supports, silica and carbon, impregnated with 5% Nickel and the effect of reaction condition and feed compositions on the tri-reforming for the synthesis gas production. The highest conversions of CH4 and CO2 were obtained at 750 degrees C and weight hourly space velocity (WHSV) 1250 mL/g.min. The 5%Ni/MWCNT catalysts reached 90.2% and 76.5% conversions of CH4 and CO2, while the catalyst 5%Ni/SBA-15%, 87.4% and 64.7%, respectively. The conversions for the MWCNT are significantly higher than for the SBA-15 at 750 degrees C, but the yields of H2 and selectivity of CO decreased on the SBA support. The influence of the feed conditions on the activity was tested. Both catalysts demonstrated high activity and good stability. TGA results after reaction showed that the carbon nanotubes were preserved, and SBA-15 is more resistant to carbon formation under such reaction conditions.

In this study, the catalytic performance of Pt on alumina catalyst modified by adding MAl2O3 (Co and Ni) aluminates promoter has been tested for the preferential oxidation of CO in a H2-rich stream (CO-PROX). Activity and selectivity were superior compared to those of a reference Pt/alumina system, which requires higher temperatures (above 150 °C) to operate at reasonable rates. For all the modified catalysts, the maximum conversion occurs at 150 °C, a value within the acceptable working range for this process. Characterizations results indicate that the presence of aluminates oxides facilitated the electron transfer from Pt to promotes (caused by Pt and MAl2O4 close contact), resulting in the decrease of CO adsorption strength and the enhancement of low-temperature activity. The modified catalysts followed the dual-site Langmuir–Hinshelwood mechanism with CO preferentially adsorbing at the Pt sites and O2 adsorbing at the aluminates sites. Also, the excellent stability presented by modified catalysts after 30 h on stream at 200 °C demonstrates their high potential for practical CO-PROX applications.

In this work, we studied the effect of CO 2 in the feed stream of the TRM process performance of nickel supported on LaFeO 3 perovskite for hydrogen production compared to the POM reaction. The perovskite and nickel supported on LaFeO 3 were synthesized and characterized by thermogravimetric analysis (TGA/DTA), X-ray diffraction (XRD), transmission electron microscopy (TEM), and programmed reduction temperature (TPR). The catalytic tests were carried out in temperatures varying from 700 to 800 °C with feed flow of 350 cm 3 /min and 200 cm 3 /min for TRM and POM, respectively. The hydrogen selectivity for the tri-reforming was 78%, while for the partial oxidation reaction, only 55% H 2 at 700 °C. Results showed that the hydrogen selectivity for the Ni/LaFeO 3 catalyst is significantly higher for the tri-reforming process, suggesting that CO 2 enhanced the hydrogen selectivity compared to the partial oxidation of methane. Analyses by Raman spectroscopy and thermogravimetric calculations showed structural modifications of the catalysts after the reaction. The Raman spectrum showed segregated NiO and Fe 3 O 4 and low carbon formation at 700 °C. The proposed mechanism suggests methane and oxygen adsorption, lattice oxygen and CO 2 on surface active sites, and vacancies for both reactions.