Ni/Si O_2 and bimetallic Ni_xGa/SiO_2 catalysts with different Ni/Ga atomic ratios(x = 10～2) were investigated for the selective hydrogenation of acetylene.It was found that Ni_xGa/SiO_2 showed higher selectivity to ...Ni/Si O_2 and bimetallic Ni_xGa/SiO_2 catalysts with different Ni/Ga atomic ratios(x = 10～2) were investigated for the selective hydrogenation of acetylene.It was found that Ni_xGa/SiO_2 showed higher selectivity to ethylene than Ni/Si O_2.This is attributed to the formation Ni-Ga alloy and Ni3 Ga intermetallic compound(IMC) where there was a charge transfer from Ga to Ni,which is favorable for reducing the adsorption strength and amount of ethylene on Ni atoms.As a result,the over-hydrogenation,the C–C bond hydrogenolysis and the polymerization were suppressed,and subsequently the selectivity to ethylene was enhanced.With the decrease of Ni/Ga atomic ratio,the activity and stability of the Ni_xGa/SiO_2 catalysts increased first and then decreased,while the ethylene selectivity tended to increase.Ni_5 Ga/SiO_2 exhibited the best performance.Under the conditions of 180 °C,0.1 MPa,and a reactant(1.0 vol% acetylene,5.0 vol% H_2 and 94 vol% N_2) with the space velocity of 36,000 m L h^(-1) g^(-1),the acetylene conversion maintained at 100% on Ni_5 Ga/SiO_2 during 120 h time on stream and the selectivity to ethylene was 75%～81%after reaction for 68 h.It was also found that the formation of Ni-Ga alloy and Ni_3 Ga IMC suppressed the incorporation of carbon to form NiCx,subsequently enhancing the catalyst stability.Additionally,with increasing the Ga content,the catalyst acid amount and strength tended to increase,which promoted the polymerization and carbon deposition and so the catalyst deactivation.展开更多
对Ni Cr Fe V Ga系合金进行了X射线衍射和热机械分析(TMA)。结果表明,在室温至940℃范围内,合金的晶格点阵参数逐渐增大,线胀系数为正;在940～1150℃范围内,合金的晶格点阵参数逐渐降低,线胀系数为负,进行了K效应转变。用热力学理论对...对Ni Cr Fe V Ga系合金进行了X射线衍射和热机械分析(TMA)。结果表明,在室温至940℃范围内,合金的晶格点阵参数逐渐增大,线胀系数为正;在940～1150℃范围内,合金的晶格点阵参数逐渐降低,线胀系数为负,进行了K效应转变。用热力学理论对实验结果进行了解释。展开更多
New experimental measurements of the phase diagram and the mixing enthalpy of liquid phase along with the previous experimental data were used in a reassessment of the Ni–Ga system. A set of self-consistent thermodyn...New experimental measurements of the phase diagram and the mixing enthalpy of liquid phase along with the previous experimental data were used in a reassessment of the Ni–Ga system. A set of self-consistent thermodynamic parameters of the Ni–Ga system is obtained using the calculation of phase diagram (CALPHAD) technique, and the available phase diagram and thermodynamic data are reproduced well within experimental error limits. Some noticeable improvements are obtained in the present work compared with the previous assessment: (1) the calculated Ga-rich liquidus is more reasonable; (2) Ni<sub>3</sub>Ga<sub>7</sub> is adopted as the most Ga-rich compound rather than NiGa<sub>4</sub>; (3) the Ni<sub>5</sub>Ga<sub>3</sub> phase is treated as the nonstoichiometric compound with consideration of its narrow homogeneity range; (4) the phase transformation between B8<sub>1.5</sub>_Ni<sub>3</sub>Ga<sub>2</sub> and Ni<sub>13</sub>Ga<sub>9</sub> is considered instead of treating them as Ni<sub>3</sub>Ga<sub>2</sub> phase simply; (5) the latest experimental data of mixing enthalpy for the liquid phase are adopted. The present study can be used as a basis for the development of a thermodynamic database of the Ni-based semiconductor alloy systems.展开更多
基金supported by the National Natural Science Foundation of China (21576193)
文摘Ni/Si O_2 and bimetallic Ni_xGa/SiO_2 catalysts with different Ni/Ga atomic ratios(x = 10～2) were investigated for the selective hydrogenation of acetylene.It was found that Ni_xGa/SiO_2 showed higher selectivity to ethylene than Ni/Si O_2.This is attributed to the formation Ni-Ga alloy and Ni3 Ga intermetallic compound(IMC) where there was a charge transfer from Ga to Ni,which is favorable for reducing the adsorption strength and amount of ethylene on Ni atoms.As a result,the over-hydrogenation,the C–C bond hydrogenolysis and the polymerization were suppressed,and subsequently the selectivity to ethylene was enhanced.With the decrease of Ni/Ga atomic ratio,the activity and stability of the Ni_xGa/SiO_2 catalysts increased first and then decreased,while the ethylene selectivity tended to increase.Ni_5 Ga/SiO_2 exhibited the best performance.Under the conditions of 180 °C,0.1 MPa,and a reactant(1.0 vol% acetylene,5.0 vol% H_2 and 94 vol% N_2) with the space velocity of 36,000 m L h^(-1) g^(-1),the acetylene conversion maintained at 100% on Ni_5 Ga/SiO_2 during 120 h time on stream and the selectivity to ethylene was 75%～81%after reaction for 68 h.It was also found that the formation of Ni-Ga alloy and Ni_3 Ga IMC suppressed the incorporation of carbon to form NiCx,subsequently enhancing the catalyst stability.Additionally,with increasing the Ga content,the catalyst acid amount and strength tended to increase,which promoted the polymerization and carbon deposition and so the catalyst deactivation.
基金financially supported by the National Natural Science Foundation of China(Nos.50934011 and51274034)the Fundamental Research Funds for the Central Universities(No.FRF-SD-12-010A)
文摘New experimental measurements of the phase diagram and the mixing enthalpy of liquid phase along with the previous experimental data were used in a reassessment of the Ni–Ga system. A set of self-consistent thermodynamic parameters of the Ni–Ga system is obtained using the calculation of phase diagram (CALPHAD) technique, and the available phase diagram and thermodynamic data are reproduced well within experimental error limits. Some noticeable improvements are obtained in the present work compared with the previous assessment: (1) the calculated Ga-rich liquidus is more reasonable; (2) Ni<sub>3</sub>Ga<sub>7</sub> is adopted as the most Ga-rich compound rather than NiGa<sub>4</sub>; (3) the Ni<sub>5</sub>Ga<sub>3</sub> phase is treated as the nonstoichiometric compound with consideration of its narrow homogeneity range; (4) the phase transformation between B8<sub>1.5</sub>_Ni<sub>3</sub>Ga<sub>2</sub> and Ni<sub>13</sub>Ga<sub>9</sub> is considered instead of treating them as Ni<sub>3</sub>Ga<sub>2</sub> phase simply; (5) the latest experimental data of mixing enthalpy for the liquid phase are adopted. The present study can be used as a basis for the development of a thermodynamic database of the Ni-based semiconductor alloy systems.
