Cu/SiO2 catalysts prepared by a convenient and efficient method using the urea hydrolysis deposition-precipitation (UHDP) technique have been proposed focusing on the effect of copper loading.The texture,structure a...Cu/SiO2 catalysts prepared by a convenient and efficient method using the urea hydrolysis deposition-precipitation (UHDP) technique have been proposed focusing on the effect of copper loading.The texture,structure and composition are systematically characterized by ICP,FTIR,N 2-physisorption,N2O chemisorption,TPR,XRD and XPS.The formation of copper phyllosilicate is observed in Cu/SiO2 catalyst by adopting UHDP method,and the amount of copper phyllosilicate is related to copper loading.It is found the structure properties and catalytic performance is profoundly affected by the amount of copper phyllosilicate.The excellent catalytic activity is attributed to the synergetic effect between Cu0 and Cu +.DMO conversion and EG selectivity are determined by the amount of Cu0 and Cu+,respectively.The proper copper loading (30 wt%) provides with the highest ratio of Cu + /Cu0,giving rise to the highest EG yield of 95% under the reaction conditions of p=2.0 MPa,T=473 K,H2/DMO=80 and LHSV=1.0h-1.展开更多
The efficient synthesis of methanol and ethylene glycol via the chemoselective hydrogenation of ethylene carbonate(EC) is important for the sustainable utilization of CO_2 to produce commodity chemicals and fuels. I...The efficient synthesis of methanol and ethylene glycol via the chemoselective hydrogenation of ethylene carbonate(EC) is important for the sustainable utilization of CO_2 to produce commodity chemicals and fuels. In this work, a series of β-cyclodextrin-modified Cu/SiO_2 catalysts were prepared by ammonia evaporation method for the selective hydrogenation of EC to co-produce methanol and ethylene glycol. The structure and physicochemical properties of the catalysts were characterized in detail by N_2 physisorption, XRD, N_2O titration, H_2-TPR, TEM, and XPS/XAES. Compared with the unmodified 25 Cu/SiO_2 catalyst, the involvement of β-cyclodextrin in 5β-25 Cu/SiO_2 could remarkably increase the catalytic activity—excellent activity of 1178 mgEC g_(cat)^(–1) h^(–1) with 98.8%ethylene glycol selectivity, and 71.6% methanol selectivity could be achieved at 453 K. The remarkably improved recyclability was primarily attributed to the remaining proportion of Cu~+/(Cu^0+Cu~+). Furthermore, the DFT calculation results demonstrated that metallic Cu^0 dissociated adsorbed H_2, while Cu~+ activated the carbonyl group of EC and stabilized the intermediates. This study is a facile and efficient method to prepare highly dispersed Cu catalysts—this is also an effective and stable heterogeneous catalyst system for the sustainable synthesis of ethylene glycol and methanol via indirect chemical utilization of CO_2.展开更多
The Cu/SiO2catalysts were in situ synthesized by the hydrolysis of tetraethyl orthosilicate(TEOS)in one phase solution using ethanol as co-solvent or TEOS/H_2O two phases solution,followed by the precipitation of c...The Cu/SiO2catalysts were in situ synthesized by the hydrolysis of tetraethyl orthosilicate(TEOS)in one phase solution using ethanol as co-solvent or TEOS/H_2O two phases solution,followed by the precipitation of copper on SiO2by ammonia evaporation.In the hydrogenation of dimethyl oxalate,the catalyst prepared by one phase hydrolysis exhibited higher activity and ethylene glycol(EG)selectivity at lower temperature than that of two phases due to its larger BET surface area and multimodal pore distribution.At 488-503 K,the catalyst prepared in one phase solution with water/ethanol(W/E)volume ratio of 3:1 exhibited 90-95%EG selectivity,while catalyst prepared by two phase hydrolysis reached 90%EG selectivity only at 498-503 K.展开更多
Copper supported over silica exhibited very high activity and selectivity for the direct synthesis of indole at atmospheric pressure. Under the reaction temperature of 325C,the yield of indole could obtain 88%.
摘要Cu/SiO2 catalysts prepared by a convenient and efficient method using the urea hydrolysis deposition-precipitation (UHDP) technique have been proposed focusing on the effect of copper loading.The texture,structure and composition are systematically characterized by ICP,FTIR,N 2-physisorption,N2O chemisorption,TPR,XRD and XPS.The formation of copper phyllosilicate is observed in Cu/SiO2 catalyst by adopting UHDP method,and the amount of copper phyllosilicate is related to copper loading.It is found the structure properties and catalytic performance is profoundly affected by the amount of copper phyllosilicate.The excellent catalytic activity is attributed to the synergetic effect between Cu0 and Cu +.DMO conversion and EG selectivity are determined by the amount of Cu0 and Cu+,respectively.The proper copper loading (30 wt%) provides with the highest ratio of Cu + /Cu0,giving rise to the highest EG yield of 95% under the reaction conditions of p=2.0 MPa,T=473 K,H2/DMO=80 and LHSV=1.0h-1.
摘要The efficient synthesis of methanol and ethylene glycol via the chemoselective hydrogenation of ethylene carbonate(EC) is important for the sustainable utilization of CO_2 to produce commodity chemicals and fuels. In this work, a series of β-cyclodextrin-modified Cu/SiO_2 catalysts were prepared by ammonia evaporation method for the selective hydrogenation of EC to co-produce methanol and ethylene glycol. The structure and physicochemical properties of the catalysts were characterized in detail by N_2 physisorption, XRD, N_2O titration, H_2-TPR, TEM, and XPS/XAES. Compared with the unmodified 25 Cu/SiO_2 catalyst, the involvement of β-cyclodextrin in 5β-25 Cu/SiO_2 could remarkably increase the catalytic activity—excellent activity of 1178 mgEC g_(cat)^(–1) h^(–1) with 98.8%ethylene glycol selectivity, and 71.6% methanol selectivity could be achieved at 453 K. The remarkably improved recyclability was primarily attributed to the remaining proportion of Cu~+/(Cu^0+Cu~+). Furthermore, the DFT calculation results demonstrated that metallic Cu^0 dissociated adsorbed H_2, while Cu~+ activated the carbonyl group of EC and stabilized the intermediates. This study is a facile and efficient method to prepare highly dispersed Cu catalysts—this is also an effective and stable heterogeneous catalyst system for the sustainable synthesis of ethylene glycol and methanol via indirect chemical utilization of CO_2.
基金supported by the International Science and Technology Cooperation Program(No 2009DFA61050)National High Technology Research and Development Program of China(863 program)(Nos 2007AA05Z334&2009AA05Z407)National Basic Research Program of China(No2007CB210200)
摘要The Cu/SiO2catalysts were in situ synthesized by the hydrolysis of tetraethyl orthosilicate(TEOS)in one phase solution using ethanol as co-solvent or TEOS/H_2O two phases solution,followed by the precipitation of copper on SiO2by ammonia evaporation.In the hydrogenation of dimethyl oxalate,the catalyst prepared by one phase hydrolysis exhibited higher activity and ethylene glycol(EG)selectivity at lower temperature than that of two phases due to its larger BET surface area and multimodal pore distribution.At 488-503 K,the catalyst prepared in one phase solution with water/ethanol(W/E)volume ratio of 3:1 exhibited 90-95%EG selectivity,while catalyst prepared by two phase hydrolysis reached 90%EG selectivity only at 498-503 K.
摘要Copper supported over silica exhibited very high activity and selectivity for the direct synthesis of indole at atmospheric pressure. Under the reaction temperature of 325C,the yield of indole could obtain 88%.