Pub Date : 2024-12-21DOI: 10.1016/j.jcat.2024.115922
Diru Liu, Mengyuan Zhang, Lin Zhao, Xueli Guo, Guangyan Xu, Hong He
Methanol steam reforming (MSR) is essential for in-situ hydrogen production, providing a clean fuel alternative for sustainable energy applications. Copper catalysts are widely applied in MSR, yet the nature of active sites and reaction pathway involved remain some debates. Herein, we reveal the crucial role of water activation and dynamic active sites on Cu/Al2O3 catalysts during the MSR reaction. Specifically, methanol was preferentially adsorbed on Al2O3 and underwent stepwise dehydrogenation to formaldehyde, while water was activated on metallic Cu, oxidizing Cu0 to form Cu+-OH species, accompanied by hydrogen migration to another Cu0 site. The Cu+-OH species further reacted with formaldehyde to generate highly reactive formate, whose dehydrogenation produced CO2. Concurrently, the Cu+ was reduced back to the Cu0 state, and H2 was continuously produced by dehydrogenation. Compared to the facile oxidation of Cu0 by water, the slow reduction of Cu+ induced by the dehydrogenation of formate predominated the overall reaction rate at low temperatures. These findings provide new insights into a dynamic Cu0/+-Cu0 site mechanism on copper catalysts in methanol steam reforming, beneficial for the design of efficient MSR catalysts.
{"title":"Mechanistic insights into methanol steam reforming on copper catalysts: Dynamics of active sites and reaction pathway","authors":"Diru Liu, Mengyuan Zhang, Lin Zhao, Xueli Guo, Guangyan Xu, Hong He","doi":"10.1016/j.jcat.2024.115922","DOIUrl":"https://doi.org/10.1016/j.jcat.2024.115922","url":null,"abstract":"Methanol steam reforming (MSR) is essential for <em>in-situ</em> hydrogen production, providing a clean fuel alternative for sustainable energy applications. Copper catalysts are widely applied in MSR, yet the nature of active sites and reaction pathway involved remain some debates. Herein, we reveal the crucial role of water activation and dynamic active sites on Cu/Al<sub>2</sub>O<sub>3</sub> catalysts during the MSR reaction. Specifically, methanol was preferentially adsorbed on Al<sub>2</sub>O<sub>3</sub> and underwent stepwise dehydrogenation to formaldehyde, while water was activated on metallic Cu, oxidizing Cu<sup>0</sup> to form Cu<sup>+</sup>-OH species, accompanied by hydrogen migration to another Cu<sup>0</sup> site. The Cu<sup>+</sup>-OH species further reacted with formaldehyde to generate highly reactive formate, whose dehydrogenation produced CO<sub>2</sub>. Concurrently, the Cu<sup>+</sup> was reduced back to the Cu<sup>0</sup> state, and H<sub>2</sub> was continuously produced by dehydrogenation. Compared to the facile oxidation of Cu<sup>0</sup> by water, the slow reduction of Cu<sup>+</sup> induced by the dehydrogenation of formate predominated the overall reaction rate at low temperatures. These findings provide new insights into a dynamic Cu<sup>0/+</sup>-Cu<sup>0</sup> site mechanism on copper catalysts in methanol steam reforming, beneficial for the design of efficient MSR catalysts.","PeriodicalId":346,"journal":{"name":"Journal of Catalysis","volume":"19 1","pages":""},"PeriodicalIF":7.3,"publicationDate":"2024-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142869979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-20DOI: 10.1016/j.jcat.2024.115916
Pranay Rajendra Chandewar, Debaprasad Shee
The direct methane to methanol (DMTM) conversion was studied in a fixed bed reactor under varying reaction parameters including temperature, and weight hourly space velocity (WHSV) and CH4:O2 over several CeO2-ZSM5, CeO2-SiO2 and CeO2-Al2O3 supported CuO catalysts prepared by wetness impregnation method and characterized by several techniques including N2 adsorption desorption, X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), ultraviolet visible spectroscopy (UV–vis), temperature programmed reduction (H2-TPR), temperature programmed desorption (CO2-TPD) and CO-diffuse reflectance infrared Fourier transform spectroscopy (CO-DRIFT) studies. The characterization results confirm the formation of bis(µ-oxo) dicopper or mono-(µ-oxo) dicopper species considered as the active sites for the DMTM reaction. Moreover, various copper (Cu2+, Cu+ and Cu0) and cerium (Ce3+ and Ce4+) species are coexisted in a redox cycle equilibrium (Cu+ + Ce4+ ⇌ Cu2+ + Ce3+) depending on CeO2 loading. XPS studies indicates the generation of lattice and adsorbed oxygen species on deposition of CeO2 and their ratio varied with the CeO2 loading. Moreover, the different cerium species induces charge unbalance, oxygen vacancies, and formation of unsaturated chemical bonds on the catalyst’s surface. The deposition of CeO2 and CuO incorporates more Lewis’s acid sites in xCu/yCe-ZSM5 composite catalysts and even formation of additional Lewis’s acid sites originated from exchanged copper species. The various copper and cerium species formed in the composite catalysts strongly influenced the methane molecule activation, and selectivity and yield of methanol. The surface Cu2+ species promotes the formation of methanol and prevents the methanol overoxidation forming oxygenates and carbon dioxide. In addition to the Cu2+ species, the lattice and adsorbed oxygen generated on deposition of CeO2 also influence the formation and oxidation of methanol. Thus, optimum surface concentration of Cu2+ and lattice to adsorbed oxygen maximizes the yield of methanol. The process parameters also the affect the methane conversion and methanol selectivity and yield. The methanol selectivity of 6.34 % with methane conversion of 37.89 % was achieved over 20Cu/15CeZ catalysts at 873 K, 1030 ml hr-1 gcat−1 and CH4:O2 = 2:1. A plausible reaction mechanism of oxidation of methane to methanol based on the activity results and in-situ DRFIT studies of methanol oxidation.
{"title":"Role of copper and cerium species in Cu/CeZSM catalysts for direct methane to methanol reaction: Insights of structure–activity relationship","authors":"Pranay Rajendra Chandewar, Debaprasad Shee","doi":"10.1016/j.jcat.2024.115916","DOIUrl":"https://doi.org/10.1016/j.jcat.2024.115916","url":null,"abstract":"The direct methane to methanol (DMTM) conversion was studied in a fixed bed reactor under varying reaction parameters including temperature, and weight hourly space velocity (WHSV) and CH<sub>4</sub>:O<sub>2</sub> over several CeO<sub>2</sub>-ZSM5, CeO<sub>2</sub>-SiO<sub>2</sub> and CeO<sub>2</sub>-Al<sub>2</sub>O<sub>3</sub> supported CuO catalysts prepared by wetness impregnation method and characterized by several techniques including N<sub>2</sub> adsorption desorption, X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), ultraviolet visible spectroscopy (UV–vis), temperature programmed reduction (H<sub>2</sub>-TPR), temperature programmed desorption (CO<sub>2</sub>-TPD) and CO-diffuse reflectance infrared Fourier transform spectroscopy (CO-DRIFT) studies. The characterization results confirm the formation of bis(µ-oxo) dicopper or mono-(µ-oxo) dicopper species considered as the active sites for the DMTM reaction. Moreover, various copper (Cu<sup>2+</sup>, Cu<sup>+</sup> and Cu<sup>0</sup>) and cerium (Ce<sup>3+</sup> and Ce<sup>4+</sup>) species are coexisted in a redox cycle equilibrium (Cu<sup>+</sup> + Ce<sup>4+</sup> ⇌ Cu<sup>2+</sup> + Ce<sup>3+</sup>) depending on CeO<sub>2</sub> loading. XPS studies indicates the generation of lattice and adsorbed oxygen species on deposition of CeO<sub>2</sub> and their ratio varied with the CeO<sub>2</sub> loading. Moreover, the different cerium species induces charge unbalance, oxygen vacancies, and formation of unsaturated chemical bonds on the catalyst’s surface. The deposition of CeO<sub>2</sub> and CuO incorporates more Lewis’s acid sites in xCu/yCe-ZSM5 composite catalysts and even formation of additional Lewis’s acid sites originated from exchanged copper species. The various copper and cerium species formed in the composite catalysts strongly influenced the methane molecule activation, and selectivity and yield of methanol. The surface Cu<sup>2+</sup> species promotes the formation of methanol and prevents the methanol overoxidation forming oxygenates and carbon dioxide. In addition to the Cu<sup>2+</sup> species, the lattice and adsorbed oxygen generated on deposition of CeO<sub>2</sub> also influence the formation and oxidation of methanol. Thus, optimum surface concentration of Cu<sup>2+</sup> and lattice to adsorbed oxygen maximizes the yield of methanol. The process parameters also the affect the methane conversion and methanol selectivity and yield. The methanol selectivity of 6.34 % with methane conversion of 37.89 % was achieved over 20Cu/15CeZ catalysts at 873 K, 1030 ml hr<sup>-1</sup> gcat<sup>−1</sup> and CH<sub>4</sub>:O<sub>2</sub> = 2:1. A plausible reaction mechanism of oxidation of methane to methanol based on the activity results and in-situ DRFIT studies of methanol oxidation.","PeriodicalId":346,"journal":{"name":"Journal of Catalysis","volume":"24 1","pages":""},"PeriodicalIF":7.3,"publicationDate":"2024-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142867269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-20DOI: 10.1016/j.jcat.2024.115904
Jared L. Barr, Kathy S. Clear, Masud M. Monwar, Mitchell Refvik, Max P. McDaniel
The initiation of the Phillips commercial polymerization catalyst, comprising simultaneous reduction and self-alkylation of the Cr(VI), has again been examined, this time by using oxygen to terminate live Cr–alkyls formed during reduction. Cr(VI)/silica catalysts were first reduced by an alkane or alkene, then exposed to oxygen, followed by immediate hydrolysis to liberate the species thus formed. The brief exposure to oxygen significantly increased the amount of oxygenated products obtained from Cr(VI) including both monomeric and oligomeric species. This suggests that Cr–alkyls formed during reduction were converted into Cr–alkoxides or other oxygenated terminal species. This approach produces an interesting insight into the state of Cr during and shortly after initiation.
{"title":"Air termination of hydrocarbon-reduced Cr(Vi)/silica","authors":"Jared L. Barr, Kathy S. Clear, Masud M. Monwar, Mitchell Refvik, Max P. McDaniel","doi":"10.1016/j.jcat.2024.115904","DOIUrl":"https://doi.org/10.1016/j.jcat.2024.115904","url":null,"abstract":"The initiation of the Phillips commercial polymerization catalyst, comprising simultaneous reduction and self-alkylation of the Cr(VI), has again been examined, this time by using oxygen to terminate live Cr–alkyls formed during reduction. Cr(VI)/silica catalysts were first reduced by an alkane or alkene, then exposed to oxygen, followed by immediate hydrolysis to liberate the species thus formed. The brief exposure to oxygen significantly increased the amount of oxygenated products obtained from Cr(VI) including both monomeric and oligomeric species. This suggests that Cr–alkyls formed during reduction were converted into Cr–alkoxides or other oxygenated terminal species. This approach produces an interesting insight into the state of Cr during and shortly after initiation.","PeriodicalId":346,"journal":{"name":"Journal of Catalysis","volume":"63 1","pages":""},"PeriodicalIF":7.3,"publicationDate":"2024-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142867270","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-20DOI: 10.1016/j.jcat.2024.115919
Jiefu Zhang, Kai Zhang, Qingqing Wang, Xiaolin Tan, Dan Wang, Xiaojun Wu, Xiang Shao
Bimetallic systems can be significantly affected in terms of the catalytic activity by their compositions as well as atomic structures. This study demonstrates that the single Pd atoms and ultrasmall clusters dispersed on the surface of Cu2O/Cu(1 1 1) exhibit significantly enhanced oxophilicity and auto-oxidizes into a checkboard-like Pd4O8 structure by grabbing oxygen atoms from the Cu2O thin film. As a comparison, the Pd ad-islands on the Cu(1 1 1) surface possess compressed lattice and present a lowered activity to oxygen, but in turn enhances the oxophilicity of the Cu substrate and leads to preferential formation of cuprous oxide overlayers on the Pd islands. The drastically different oxidative reactivity of Pd on the respective Cu2O/Cu(1 1 1) and Cu(1 1 1) surfaces dictate close correlations to their dispersion statuses. It thus provides a strategy for tuning the catalytic activities of similar bimetallic systems.
{"title":"Dispersity-dependent activity of Pd on bare and pre-oxidized Cu(1 1 1) surface","authors":"Jiefu Zhang, Kai Zhang, Qingqing Wang, Xiaolin Tan, Dan Wang, Xiaojun Wu, Xiang Shao","doi":"10.1016/j.jcat.2024.115919","DOIUrl":"https://doi.org/10.1016/j.jcat.2024.115919","url":null,"abstract":"Bimetallic systems can be significantly affected in terms of the catalytic activity by their compositions as well as atomic structures. This study demonstrates that the single Pd atoms and ultrasmall clusters dispersed on the surface of Cu<sub>2</sub>O/Cu(1 1 1) exhibit significantly enhanced oxophilicity and auto-oxidizes into a checkboard-like Pd<sub>4</sub>O<sub>8</sub> structure by grabbing oxygen atoms from the Cu<sub>2</sub>O thin film. As a comparison, the Pd ad-islands on the Cu(1 1 1) surface possess compressed lattice and present a lowered activity to oxygen, but in turn enhances the oxophilicity of the Cu substrate and leads to preferential formation of cuprous oxide overlayers on the Pd islands. The drastically different oxidative reactivity of Pd on the respective Cu<sub>2</sub>O/Cu(1<!-- --> <!-- -->1<!-- --> <!-- -->1) and Cu(1<!-- --> <!-- -->1<!-- --> <!-- -->1) surfaces dictate close correlations to their dispersion statuses. It thus provides a strategy for tuning the catalytic activities of similar bimetallic systems.","PeriodicalId":346,"journal":{"name":"Journal of Catalysis","volume":"13 1","pages":""},"PeriodicalIF":7.3,"publicationDate":"2024-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142867271","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The conversion of carbohydrates to high value-added 5-hydroxymethylfurfural (5-HMF) has aroused intensive research interest. Herein, a series of cerium phosphates was prepared by simple calcination accompanied by a hexagonal-monoclinic phase transformation. Hexagonal CePO4-200 exhibits superior catalytic activity for the conversion of glucose to 5-HMF with a yield of 73 % compared with monoclinic CePO4-800. The related characterization results confirm that hexagonal CePO4-200 possesses unoccupied and open spaces leading to favorable coordination environments, good pore structure and high acid density, which contributed to activation and catalysis of glucose. Density functional theory (DFT) calculations proves that the hexagonal CePO4-200 interface possesses a more effective charge transfer ability by comparing with monoclinic CePO4-800 interface in Lewis acidic Ce3+ sites region thus enhancing the catalytic activity. Additionally, a feasible tandem reaction mechanism through glucose-to-fructose isomerization driven by Ce3+ acidic sites and fructose dehydration to 5-HMF catalyzed by P-OH group was proposed.
{"title":"Enhanced glucose-to-5-hydroxymethylfurfural transformation activity over CePO4 catalyst: Insights into crystal structure, acidic property and reaction pathway","authors":"Yanjuan Yang, Hansheng Wang, Yuhuan Li, Zixu Yang, Jing Xu","doi":"10.1016/j.jcat.2024.115912","DOIUrl":"https://doi.org/10.1016/j.jcat.2024.115912","url":null,"abstract":"The conversion of carbohydrates to high value-added 5-hydroxymethylfurfural (5-HMF) has aroused intensive research interest. Herein, a series of cerium phosphates was prepared by simple calcination accompanied by a hexagonal-monoclinic phase transformation. Hexagonal CePO<sub>4</sub>-200 exhibits superior catalytic activity for the conversion of glucose to 5-HMF with a yield of 73 % compared with monoclinic CePO<sub>4</sub>-800. The related characterization results confirm that hexagonal CePO<sub>4</sub>-200 possesses unoccupied and open spaces leading to favorable coordination environments, good pore structure and high acid density, which contributed to activation and catalysis of glucose. Density functional theory (DFT) calculations proves that the hexagonal CePO<sub>4</sub>-200 interface possesses a more effective charge transfer ability by comparing with monoclinic CePO<sub>4</sub>-800 interface in Lewis acidic Ce<sup>3+</sup> sites region thus enhancing the catalytic activity. Additionally, a feasible tandem reaction mechanism through glucose-to-fructose isomerization driven by Ce<sup>3+</sup> acidic sites and fructose dehydration to 5-HMF catalyzed by P-OH group was proposed.","PeriodicalId":346,"journal":{"name":"Journal of Catalysis","volume":"1 1","pages":""},"PeriodicalIF":7.3,"publicationDate":"2024-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142867265","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-19DOI: 10.1016/j.jcat.2024.115908
Ziru Wang, Tian Wang, Yali Zhao, Qinghua Ye, Peilei He
The fixation of CO2 with epoxides offers a promising approach for the converting CO2 into valuable chemicals, particularly when driven by the synergistic combination of solar energy and thermal processes. Consequently, the development of innovative and efficient catalysts for photothermal CO2 cycloaddition under visible light irradiation is of critical importance. In this study, we encapsulated titanium-substituted polyoxometalates ([PTi2W10O40]7−, abbreviated as PTi2W10) within covalent organic frameworks (COFs), specifically EB-TFP. The resulting PTi2W10@EB-TFP composite exhibits outstanding performance in photothermal catalytic CO2 cycloaddition, offering a product yield of 98.62 %, which significantly exceeds those obtained with the individual components PTi2W10 (61.39 %) and EB-TFP (50.34 %). In-situ experiments and theoretical calculations indicate that the superior catalytic performance arises from the photothermal catalytic pathway, rather than a synergistic interaction between photocatalytic and thermal pathways. Notably, photogenerated electrons are transferred to PTi2W10, promoting the activation of the epoxide, while the electron-deficient EB-TFP facilitates CO2 activation. This work exemplifies the utilization of polyoxometalates as photothermal catalysts for CO2 cycloaddition, offering a sustainable and efficient strategy to chemical conversion.
{"title":"Photothermal CO2 conversion to cyclic carbonate over titanium-substituted polyoxometalate within covalent organic frameworks","authors":"Ziru Wang, Tian Wang, Yali Zhao, Qinghua Ye, Peilei He","doi":"10.1016/j.jcat.2024.115908","DOIUrl":"https://doi.org/10.1016/j.jcat.2024.115908","url":null,"abstract":"The fixation of CO<sub>2</sub> with epoxides offers a promising approach for the converting CO<sub>2</sub> into valuable chemicals, particularly when driven by the synergistic combination of solar energy and thermal processes. Consequently, the development of innovative and efficient catalysts for photothermal CO<sub>2</sub> cycloaddition under visible light irradiation is of critical importance. In this study, we encapsulated titanium-substituted polyoxometalates ([PTi<sub>2</sub>W<sub>10</sub>O<sub>40</sub>]<sup>7</sup><sup>−</sup>, abbreviated as PTi<sub>2</sub>W<sub>10</sub>) within covalent organic frameworks (COFs), specifically EB-TFP. The resulting PTi<sub>2</sub>W<sub>10</sub>@EB-TFP composite exhibits outstanding performance in photothermal catalytic CO<sub>2</sub> cycloaddition, offering a product yield of 98.62 %, which significantly exceeds those obtained with the individual components PTi<sub>2</sub>W<sub>10</sub> (61.39 %) and EB-TFP (50.34 %). In-situ experiments and theoretical calculations indicate that the superior catalytic performance arises from the photothermal catalytic pathway, rather than a synergistic interaction between photocatalytic and thermal pathways. Notably, photogenerated electrons are transferred to PTi<sub>2</sub>W<sub>10</sub>, promoting the activation of the epoxide, while the electron-deficient EB-TFP facilitates CO<sub>2</sub> activation. This work exemplifies the utilization of polyoxometalates as photothermal catalysts for CO<sub>2</sub> cycloaddition, offering a sustainable and efficient strategy to chemical conversion.","PeriodicalId":346,"journal":{"name":"Journal of Catalysis","volume":"38 1","pages":""},"PeriodicalIF":7.3,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142849519","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Oxidative cyanation of furfural (1a) to 2-furancarbonitrile (3a) by using NH3 as a nitrogen source and O2 as an oxidant is an effective strategy for biomass-based nitrile synthesis. Herein, Co catalyst supported on a nanocomposite of nitrogen-doped carbon and TiO2 (Co/NC-TiO2) was developed for the oxidative cyanation. The multiphase interface architecture of the catalyst enriched oxygen vacancies; moreover, the electron-rich NC nanocomponent facilitated Co2+/Co3+ valence transformation, thus promoting O2 activation. The kinetic analysis demonstrated the condensation of 1a/NH3-to- (2-furanyl)methanimine (2a) as the rate-determining step, which was consecutively promoted by 2a/O2-to-3a dehydrogenation over the catalyst surface. A Langmuir-Hinshelwood mechanism was suggested for the oxidative dehydrogenation of the 2a/O2-to-3a step, in which O2 is activated by an associative adsorption on the Co surface yielding a superoxide radical (O2•–) species for 2a dehydrogenation with the release of H2O2. This research highlights a kinetic and mechanic understanding of the catalytic oxidative cyanation.
{"title":"Kinetics for Co catalyzed oxidative cyanation of biomass-based furfural","authors":"Youjie Li, Chenglong Yao, Xiaomei Wang, Jinzhu Chen, Yisheng Xu","doi":"10.1016/j.jcat.2024.115915","DOIUrl":"https://doi.org/10.1016/j.jcat.2024.115915","url":null,"abstract":"Oxidative cyanation of furfural (<strong>1a</strong>) to 2-furancarbonitrile (<strong>3a</strong>) by using NH<sub>3</sub> as a nitrogen source and O<sub>2</sub> as an oxidant is an effective strategy for biomass-based nitrile synthesis. Herein, Co catalyst supported on a nanocomposite of nitrogen-doped carbon and TiO<sub>2</sub> (Co/NC-TiO<sub>2</sub>) was developed for the oxidative cyanation. The multiphase interface architecture of the catalyst enriched oxygen vacancies; moreover, the electron-rich NC nanocomponent facilitated Co<sup>2+</sup>/Co<sup>3+</sup> valence transformation, thus promoting O<sub>2</sub> activation. The kinetic analysis demonstrated the condensation of <strong>1a</strong>/NH<sub>3</sub>-to- (2-furanyl)methanimine (<strong>2a</strong>) as the rate-determining step, which was consecutively promoted by <strong>2a</strong>/O<sub>2</sub>-to-<strong>3a</strong> dehydrogenation over the catalyst surface. A Langmuir-Hinshelwood mechanism was suggested for the oxidative dehydrogenation of the <strong>2a</strong>/O<sub>2</sub>-to-<strong>3a</strong> step, in which O<sub>2</sub> is activated by an associative adsorption on the Co surface yielding a superoxide radical (O<sub>2</sub><sup>•–</sup>) species for <strong>2a</strong> dehydrogenation with the release of H<sub>2</sub>O<sub>2</sub>. This research highlights a kinetic and mechanic understanding of the catalytic oxidative cyanation.","PeriodicalId":346,"journal":{"name":"Journal of Catalysis","volume":"22 1","pages":""},"PeriodicalIF":7.3,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142858062","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-19DOI: 10.1016/j.jcat.2024.115913
Shengqiang Zhou, Tianliang Lu, Lipeng Zhou, Xiaomei Yang
Au/Sn-zeolite catalysts showed high activity for selective conversion of glycerol to methyl lactate, but suffered from poor stability under the reaction conditions in our previous report (ACS Catal. 2017, 7, 7274). Encapsulation of Au nanoparticles within zeolite is a promising strategy to enhance their stability in catalytic reaction. Herein, one-pot synthesis of Au@Snβ was achieved by a mercaptosilane-assisted hydrothermal synthesis method. The protocol involves crystallization of Snβ synthesis gels around coordinated Au precursors, resulting in Snβ framework constraining Au coordination complexes. The confinement of small (∼2.89 nm) and uniform Au particles within Snβ was achieved. The bifunctional catalyst composed of oxidative sites (Au) and Lewis acid sites (Sn) gave 77.3 % methyl lactate (MLA) yield from the base-free selective conversion of glycerol (GLY). The TOF value of Au@Snβ was higher than that of Au/Sn-zeolite in our previous report. Moreover, the special structure protects Au nanoparticles from sintering or agglomeration and improves the stability and recyclability in selective oxidation of GLY to MLA.
{"title":"Au@Snβ zeolite as stable and active catalyst for the conversion of glycerol to methyl lactate","authors":"Shengqiang Zhou, Tianliang Lu, Lipeng Zhou, Xiaomei Yang","doi":"10.1016/j.jcat.2024.115913","DOIUrl":"https://doi.org/10.1016/j.jcat.2024.115913","url":null,"abstract":"Au/Sn-zeolite catalysts showed high activity for selective conversion of glycerol to methyl lactate, but suffered from poor stability under the reaction conditions in our previous report (ACS Catal. 2017, 7, 7274). Encapsulation of Au nanoparticles within zeolite is a promising strategy to enhance their stability in catalytic reaction. Herein, one-pot synthesis of Au@Snβ was achieved by a mercaptosilane-assisted hydrothermal synthesis method. The protocol involves crystallization of Snβ synthesis gels around coordinated Au precursors, resulting in Snβ framework constraining Au coordination complexes. The confinement of small (∼2.89 nm) and uniform Au particles within Snβ was achieved. The bifunctional catalyst composed of oxidative sites (Au) and Lewis acid sites (Sn) gave 77.3 % methyl lactate (MLA) yield from the base-free selective conversion of glycerol (GLY). The TOF value of Au@Snβ was higher than that of Au/Sn-zeolite in our previous report. Moreover, the special structure protects Au nanoparticles from sintering or agglomeration and improves the stability and recyclability in selective oxidation of GLY to MLA.","PeriodicalId":346,"journal":{"name":"Journal of Catalysis","volume":"18 1","pages":""},"PeriodicalIF":7.3,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142849487","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Valorization of renewable lignin toward value-added fuels and chemicals can improve the economies of biorefinery. However, maintaining catalyst stability and preventing metal aggregation under the certain conditions of lignin hydrogenolysis remains a key challenge. Herein, hydrogenolysis of corncob enzymatic lignin was investigated using biochar-encapsulated CoTi@BC catalysts at the reaction temperature of 250 °C. Co1Ti0.5@BC catalyst with the addition of Ti species outperforms Co@BC catalyst, resulting in 82.5 % lignin liquefaction degree and 23.7 wt% yield of monophenols. Besides, the catalytic stability of Co1Ti0.5@BC catalyst is outstanding in the lignin hydrogenolysis, where almost no activity loss occurred after four recycle runs. Catalyst characterization suggests that the addition of moderate amounts of Ti species changed the reduction temperature of Co species and the interaction between metal sites and carbon layer. The uniform distribution of Ti species improves the dispersion of Co metal particles, and the carbon layer can protect the surface of metal nanoparticles from oxidation, thus maintaining the stability and the activity of Co metal sites. Furthermore, the mechanism of lignin hydrogenolysis with CoTi@BC catalysts was investigated based on the results of benzyloxyphenol hydrogenolysis. These findings demonstrate the unique advantages of biochar-encapsulated metal particles for efficient C-O bond cleavage and offer valuable insights for advancing lignin valorization and sustainable biorefinery development.
{"title":"Highly stable biochar-encapsulated CoTi@BC nanocatalysts for lignin hydrogenolysis","authors":"Bowen Luo, Zhipeng Tian, Riyang Shu, Chao Wang, Ying Chen, Jianping Liu, Yuhe Liao","doi":"10.1016/j.jcat.2024.115914","DOIUrl":"https://doi.org/10.1016/j.jcat.2024.115914","url":null,"abstract":"Valorization of renewable lignin toward value-added fuels and chemicals can improve the economies of biorefinery. However, maintaining catalyst stability and preventing metal aggregation under the certain conditions of lignin hydrogenolysis remains a key challenge. Herein, hydrogenolysis of corncob enzymatic lignin was investigated using biochar-encapsulated CoTi@BC catalysts at the reaction temperature of 250 °C. Co<sub>1</sub>Ti<sub>0.5</sub>@BC catalyst with the addition of Ti species outperforms Co@BC catalyst, resulting in 82.5 % lignin liquefaction degree and 23.7 wt% yield of monophenols. Besides, the catalytic stability of Co<sub>1</sub>Ti<sub>0.5</sub>@BC catalyst is outstanding in the lignin hydrogenolysis, where almost no activity loss occurred after four recycle runs. Catalyst characterization suggests that the addition of moderate amounts of Ti species changed the reduction temperature of Co species and the interaction between metal sites and carbon layer. The uniform distribution of Ti species improves the dispersion of Co metal particles, and the carbon layer can protect the surface of metal nanoparticles from oxidation, thus maintaining the stability and the activity of Co metal sites. Furthermore, the mechanism of lignin hydrogenolysis with CoTi@BC catalysts was investigated based on the results of benzyloxyphenol hydrogenolysis. These findings demonstrate the unique advantages of biochar-encapsulated metal particles for efficient C-O bond cleavage and offer valuable insights for advancing lignin valorization and sustainable biorefinery development.","PeriodicalId":346,"journal":{"name":"Journal of Catalysis","volume":"28 2 1","pages":""},"PeriodicalIF":7.3,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142849488","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-18DOI: 10.1016/j.jcat.2024.115910
Zhentao Zhao, Yuxin Wang, Guangwen Xu, Lei Shi
N-heterocyclic carbene CO2 adducts (NHC–CO2) are typical zwitterionic ionic liquid compounds, known for their strong nucleophilicity and significant catalytic ability. However, NHC–CO2 is sensitive to water, and its complex and polluting preparation process limits its widespread application. Furthermore, most reported NHC–CO2 compounds function as homogeneous catalysts, posing considerable challenges for separation. In this study, an in-situ green synthesis method was employed to develop a heterogeneous NHC–CO2 catalyst, PS–IMIL. This approach not only prevents direct contact between the catalyst and water but also simplifies the preparation process and mitigates environmental pollution. The synthesis conditions of PS–IMIL were optimized, and its structure and properties were analyzed. Furthermore, the synthesis mechanism of PS–IMIL was investigated, and its kinetics were also studied. The results indicate that the interaction between the material ethylene carbonate (EC) and the precursor is crucial for the in-situ synthesis of PS–IMIL. The prepared PS–IMIL not only preserves the catalytic ability of NHC–CO2 but also exhibits characteristics of being metal- and halogen-free. Remarkably, the catalytic activity and structure of PS–IMIL remain unchanged after 300 h of continuous use in dimethyl carbonate (DMC) production. Compared to similar catalysts, PS–IMIL exhibits excellent catalytic activity and stability. This study provides a solid theoretical and practical reference for the development of heterogeneous NHC–CO2 catalysts. The synthesized PS–IMIL demonstrates significant potential for the industrial production of DMC and other carbonate esters.
{"title":"In-situ synthesis of a heterogeneous NHC–CO2 catalyst for continuous DMC production","authors":"Zhentao Zhao, Yuxin Wang, Guangwen Xu, Lei Shi","doi":"10.1016/j.jcat.2024.115910","DOIUrl":"https://doi.org/10.1016/j.jcat.2024.115910","url":null,"abstract":"N-heterocyclic carbene CO<sub>2</sub> adducts (NHC–CO<sub>2</sub>) are typical zwitterionic ionic liquid compounds, known for their strong nucleophilicity and significant catalytic ability. However, NHC–CO<sub>2</sub> is sensitive to water, and its complex and polluting preparation process limits its widespread application. Furthermore, most reported NHC–CO<sub>2</sub> compounds function as homogeneous catalysts, posing considerable challenges for separation. In this study, an in-situ green synthesis method was employed to develop a heterogeneous NHC–CO<sub>2</sub> catalyst, PS–IMIL. This approach not only prevents direct contact between the catalyst and water but also simplifies the preparation process and mitigates environmental pollution. The synthesis conditions of PS–IMIL were optimized, and its structure and properties were analyzed. Furthermore, the synthesis mechanism of PS–IMIL was investigated, and its kinetics were also studied. The results indicate that the interaction between the material ethylene carbonate (EC) and the precursor is crucial for the in-situ synthesis of PS–IMIL. The prepared PS–IMIL not only preserves the catalytic ability of NHC–CO<sub>2</sub> but also exhibits characteristics of being metal- and halogen-free. Remarkably, the catalytic activity and structure of PS–IMIL remain unchanged after 300 h of continuous use in dimethyl carbonate (DMC) production. Compared to similar catalysts, PS–IMIL exhibits excellent catalytic activity and stability. This study provides a solid theoretical and practical reference for the development of heterogeneous NHC–CO<sub>2</sub> catalysts. The synthesized PS–IMIL demonstrates significant potential for the industrial production of DMC and other carbonate esters.","PeriodicalId":346,"journal":{"name":"Journal of Catalysis","volume":"201 1","pages":""},"PeriodicalIF":7.3,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142849518","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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