Doping B2O3 to Cu/SiO2 catalyst significantly improved activity and long-term performance for glycerol hydrogenolysis to 1,2-propanediol. The strong correlation between 1,2-propanediol yield and Cu ...surface area gave direct evidence that Cu surface area was a key parameter for developing fundamental mechanistic insight into the performance of glycerol hydrogenolysis over Cu-based catalyst.
•B2O3 can promote the dispersion of copper species and stabilize copper particles.•Addition of B2O3 to Cu/SiO2 greatly enhanced activity and stability.•100% Conversion and 98.0% 1,2-propanediol selectivity were achieved over 3CuB/SiO2.•1,2-Propanediol yield was proportional to Cu specific surface area.•Glycerol hydrogenolysis is a structure-sensitive reaction.
Cu/SiO2 catalyst has been extensively applied in glycerol hydrogenolysis for its high selectivity to 1,2-propanediol, while suffering from severe deactivation easily. B2O3 is frequently used as an additive for stabilizing active species. Thus, a series of Cu/SiO2 catalysts with various B2O3 loadings for glycerol hydrogenolysis were prepared via precipitation-gel method followed by impregnation with boric acid. These catalysts were fully characterized by ICP, BET, XRD (in situ XRD), N2O chemisorption, H2-TPR, NH3-TPD, IR, Raman, XPS, and TEM. Addition of B2O3 to Cu/SiO2 can greatly restrain the growth of copper particles and promote the dispersion of copper species upon calcination, reduction and reaction, which resulted in the enhanced catalytic activity and stability. The optimal 3CuB/SiO2 reached complete conversion with 98.0% 1,2-propanediol selectivity. The strong correlation between 1,2-propanediol yield and Cu surface area gave direct evidence that the active Cu species were the primary active sites for glycerol hydrogenolysis.
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•WOx species existed as monotungstate, polytungstate and crystalline m-WO3 phase.•Addition of WOx to Pt/Al2O3 induced hydrogen spillover.•42.4% 1,3-propanediol yield was achieved over ...Pt–10WOx/Al2O3.•1,3-Propanediol yield was proportional to the concentration of Brønsted acid sites.•1,2-Propanediol yield was proportional to the concentration of Lewis acid sites.
Despite 1,3-propanediol possessing high economic value, its production from glycerol hydrogenolysis is a challenging task. Herein, a series of WOx promoted Pt/Al2O3 catalysts with various WOx contents were prepared and investigated for selective production 1,3-propanediol from glycerol hydrogenolysis. To explore the structure feature, these catalysts were fully characterized by BET, CO chemisorption, HRTEM, XRD (in situ XRD), Raman, NH3–TPD, Py–IR, H2–TPR, and XPS. Among them, Pt–10WOx/Al2O3 achieved the highest 1,3-propanediol yield up to 42.4%, which was ascribed to the large concentration of Brønsted acid sites, strong electronic interaction between Pt with WOx and hydrogen spillover. The strong correlation between 1,3-propanediol yield and Brønsted acid site indicated its essential role for the formation of 1,3-propanediol. Meanwhile the linear correlation between 1,2-propanediol yield and Lewis acid site gave direct evidence that Lewis acid site preferentially generated 1,2-propanediol.
In the catalytic conversion of lignocellulose to valuable products, the first entry point is to break down these biopolymers to sugar units or aromatic monomers, which is conventionally achieved by ...hydrolysis in water medium. Recent years have seen tremendous progress in the alcoholysis process, which has remarkable advantages, such as the avoidance of treating waste water, suppression of humins or chars, and enhancement of reaction rate and product yield. Advances have been focused on the alcoholysis of cellulose, hemicellulose, and lignin to alkyl glucosides, xylosides, and aromatic monomers, respectively. Alcoholysis of the platform molecule furfuryl alcohol (FAL) to alkyl levulinate (AL) and integrated alcoholysis of cellulose and furfural into AL are also summarized. This Minireview highlights the comparisons between alcoholysis and hydrolysis, the reaction mechanism of alcoholysis, and future challenges for industrial applications.
High‐functioning alcoholysis: This Minireview focuses on the alcoholysis of cellulose, hemicellulose, lignin, and furfuryl alcohol to give alkyl glucosides, xylosides, aromatic monomers, and alkyl levulinate, respectively. The comparisons between alcoholysis and hydrolysis, the alcoholysis reaction mechanism and future challenges for industrial applications are also highlighted.
Partially silver-exchanged phosphotungstic acid (Ag1PW) presented exceptionally high activity for glycerol esterification with acetic acid to produce valuable biofuel additives, with 96.8% conversion ...even just 15min. The TON of Ag1PW is up to 2189.9h−1, which is the best catalytic activity ever reported for glycerol esterification. Display omitted
•Ag1PW presented the best activity for glycerol esterification with acetic acid.•The TON of Ag1PW was up to 2189.9h−1.•Ag-exchanged HPW exhibited outstanding water-tolerant property.•A mechanistic scheme for glycerol esterification with acetic acid was proposed.•Ag1PW catalyst did not suffer from deactivation in five consecutive reaction tests.
A series of highly active, selective, and stable silver-exchanged phosphotungstic acid (AgPW) catalysts were prepared, characterized, and evaluated for bio-derived glycerol esterification with acetic acid to produce valuable biofuel additives. The structures, morphologies, acidities, and water tolerance of these samples were determined by FTIR, Raman, XRD, SEM-EDX, FT-IR of pyridine adsorption, and H2O-TPD. Several typical acidic catalysts were also performed for comparison. Among them, partially silver-exchanged phosphotungstic acid (Ag1PW) presented exceptionally high activity, with 96.8% conversion within just 15min of reaction time and remarkable stability, due to the unique Keggin structure, high acidity as well as outstanding water-tolerance property. A plausible reaction mechanism was also proposed. In addition, this Ag1PW catalyst exhibited universal significance for esterification, holding great potential for a wide range of other acid-catalyzed reactions.
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•Highly dispersed Cu nanoparticles on SBA-15 were facilely fabricated.•Well-dispersed Cu nanoparticles resulted from finely dispersed copper precursor.•Reactivity of 10% Cu/SBA-15(G) ...was about seven times that of 10%Cu/SBA-15(IM).•CuOSiO interfacial structures boosted the TOF.•CuOSiO structures were the primary active dehydration sites.
Metal–support interaction is a hot topic in catalysis, but attention has seldom been drawn to the promotional effect of metal–irreducible SiO2 interfaces. Here, Cu/SBA-15 catalysts with CuOSiO interface structures were prepared by simple grinding, and showed high activity and selectivity to 1,2-propanediol above 97% in liquid-phase glycerol hydrogenolysis. Glycerol conversion of ground Cu/SBA-15 with 10% Cu loading was about seven times that of its impregnation counterpart. The linear relationship between turnover frequency and (CuOSiO induced Lewis acid sites)/Cu0 ratio indicated that CuOSiO structures were crucial for achieving excellent hydrogenolysis performance. More importantly, in situ Fourier transform infrared spectroscopy of glycerol adsorption and density functional theory calculation results confirmed that CuOSiO species were the dominant active dehydration sites of glycerol hydrogenolysis, while the adjacent Cu sites were involved in subsequent hydrogenation of the generated hydroxyacetone.
•Copper-support interactions significantly influence the hydrogenation activity.•Nature of supports influences selectivity in dimethyl oxalate hydrogenation.•Selective synthesis of ethylene glycol or ...ethanol via tuning solvent and support.•A possible reaction route of dimethyl oxalate hydrogenation was proposed.
The catalytic performances of co-precipitated copper catalysts supported on SiO2, ZrO2 and Al2O3 for dimethyl oxalate hydrogenation were studied. Systematic characterizations showed that copper species formed on different supports as a result of different metal-support interactions influenced the activity and stability, while the nature of supports was closely related to the products distribution in dimethyl oxalate hydrogenation. Mainly large Cu particles were detected over Cu/SiO2 catalyst which exhibited a low activity and stability. For the Cu/ZrO2 catalyst, the highly dispersed Cu particles and the strong metal-support interaction are in favor of its superior activity and stability. Among the catalysts, Cu/SiO2 exhibited maximum ethylene glycol selectivity while Cu/Al2O3 showed a 2-methoxyethanol selectivity of 53.5% in methanol solvent. As tuning the solvent into 1,4-dioxane, an ethanol yield up to 95.5% was received in Cu/Al2O3. The significant difference of selectivity is mainly due to the acidity of the catalysts. Thus, the highly selective synthesis of ethylene glycol and ethanol could be realized by regulating the supports and solvents, and a proper reaction route was proposed.
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► H4SiW12O40/ZrO2 is an effective catalyst for glycerol esterification. ► A 93.6% combined selectivity of glyceryl diacetate and triacetate is achieved. ► H4SiW12O40/ZrO2 can be ...reused up to four consecutive runs without deactivation. ► H4SiW12O40/ZrO2 can be resistant to the impurities present in bulk glycerol.
The synthesis of bioadditives for biofuels from glycerol esterification with acetic acid was performed over zirconia supported heteropolyacids catalysts using H4SiW12O40 (HSiW), H3PW12O40 (HPW) and H3PMo12O40 (HPMo) as active compounds. The as-prepared catalysts were characterized by N2-physisorption, XRD, Raman spectroscopy, NH3-TPD, FTIR of pyridine adsorption and H2O-TPD. Among the catalysts tested, HSiW/ZrO2 achieved the best catalytic performance owing to the better combination of surface Brønsted acid sites and hydrothermal stability. A 93.6% combined selectivity of glyceryl diacetate and glyceryl triacetate with complete glycerol conversion was obtained at 120°C and 4h of reaction time in the presence of HSiW/ZrO2. This catalyst also presented consistent activity for four consecutive reaction cycles, while HPW/ZrO2 and HPMo/ZrO2 exhibited distinct deactivation after reusability tests. In addition, HSiW/ZrO2 can be resistant to the impurities present in bulk glycerol.
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► Heteropolyacids modified Pt/ZrO2 catalysts was effective in glycerol hydrogenolysis. ► 1,3-Propanediol yield was proportional to the concentration of Brønsted acid sites. ► ...1,2-Propanediol yield was proportional to the concentration of Lewis acid sites. ► A possible reaction route was proposed for glycerol hydrogenolysis and degradation.
Hydrogenolysis of glycerol to 1,3-propanediol was conducted over zirconia supported bifunctional catalysts containing Pt and heteropolyacids using H4SiW12O40 (HSiW), H3PW12O40 (HPW) and H3PMo12O40 (HPMo) as active compounds. Pt/ZrO2 was also examined for comparison. The as-prepared catalysts were characterized by BET, CO chemisorption, XRD, Raman spectra, NH3-TPD and FTIR of adsorbed pyridine. Compared with Pt/ZrO2, heteropolyacids modified Pt/ZrO2 catalysts showed higher acidity and better catalytic performance of glycerol hydrogenolysis to 1,3-propanediol. Among them, Pt-HSiW/ZrO2 exhibited superior performance due to the high Brønsted acid sites and good thermal stability. Independent of the heteropolyacid type, the concentration of Brønsted acid sites appeared as a key to the selective formation of 1,3-propanediol from glycerol hydrogenolysis, whereas the concentration of Lewis acid sites was related to the formation of 1,2-propanediol. We also investigated the reaction network and proposed a possible reaction pathway.
Graphene oxide (GO) has proved to be a highly active and reusable solid acid catalyst for glycerol esterification with acetic acid in the synthesis of bioadditives diacylglycerol (DAG) and ...triacylglycerol (TAG). The effects of reaction temperature, molar ratio of acetic acid to glycerol, catalyst amount and reaction time were investigated. A 90.2% combined selectivity of DAG and TAG with complete glycerol conversion was achieved at 120°C for 6h over GO. Final characterization shows that the active site of GO is the remaining SO3H group.
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•GO is a highly active, selective and reusable catalyst for glycerol esterification.•A 90.2% combined selectivity of glyceryl diacetate and triacetate was achieved.•GO can reuse four consecutive runs without obvious deactivation.•SO3H groups of GO were identified as the active species for glycerol esterification.
Evidence is presented for graphene oxide (GO), prepared by modified Hummers method, as a highly active, selective and reusable solid‐acid catalyst for the production of alkyl levulinates via ...alcoholysis or esterification. 95.5 % yield of ethyl levulinate was achieved by GO in furfuryl alcohol alcoholysis. Moreover, the surface SO3H groups were identified as the primary active sites, while the surface carboxyl groups worked synergistically to adsorb furfuryl alcohol.
Magic graphene oxide! GO has been discovered as a highly active, selective and reusable solid‐acid carbocatalyst for the production of alkyl levulinates via furfuryl alcohol alcoholysis or levulinic acid esterification. The surface SO3H groups were identified as the primary active sites, while carboxyl groups worked synergistically to adsorb furfuryl alcohol.
