Promoter MgO on 10% CeO2/Al2O3 oxygen carrier was investigated for direct partial oxidation of methane to syngas in molten salt. The MgO content of 0.5%, 1%, 2%, 3% and 4% on the 10%CeO2/Al2O3 oxygen carriers in exper...Promoter MgO on 10% CeO2/Al2O3 oxygen carrier was investigated for direct partial oxidation of methane to syngas in molten salt. The MgO content of 0.5%, 1%, 2%, 3% and 4% on the 10%CeO2/Al2O3 oxygen carriers in experiments were prepared at the temperature of 750℃, respectively. The methane conversion, H2 and CO selectivity was measured on these prepared oxygen carriers at different reaction temperature. The results showed that the 3% MgO on 10%CeO2/Al2O3 had the best activity, and the CH4 conversion and CO selectivity reached 92.58% and 87.64% at 875℃, respectively. The effect of different calcination temperature on 3% MgO as promoter on 10% CeO2/Al2O3 oxygen carrier was investigated. The results of BET indicated that oxygen carrier had the largest surface area at 750℃. When the calcined temperature was too high there would be a negative effect on oxygen carrier activity.展开更多
Ultrathin zeolite membranes are of paramount importance in accelerating gas transport during membrane separation,and lowering down their membrane thicknesses to submicron scale is deemed to be very challenging.Herein,...Ultrathin zeolite membranes are of paramount importance in accelerating gas transport during membrane separation,and lowering down their membrane thicknesses to submicron scale is deemed to be very challenging.Herein,we develop an advanced approach of surface gel conversion for synthesis of submicron-thick pure silica MFI(silicalite-1)zeolite membranes.Viscous gel is prepared by finely adjusting the precursor composition,enabling its reduced wettability.The unfavorable wetting of the support surface can effectively prevent gel penetration into alumina support voids.Aided by the seeds,the surface gel is directly and fully crystallized into an MFI zeolite membrane with minimal water steam.A membrane with a thickness of 500 nm is successfully acquired and it is free of visible cracks.Additionally,the as-synthesized membranes exhibit rapid and selective separation of hexane isomers by virtue of unprecedentedly high n-hexane permeance of 24.5×10^−7 mol m^−2 s^−1 Pa^−1 and impressive separation factors of 13.3-22.6 for n-hexane over its isomers.This developed approach is of practical interest for sustainable synthesis of high-quality zeolite membranes.展开更多
基金Acknowledgments： The work was supported by the National Nature Science Foundation of China （No. 50574046, 50164002） and National Natural Science Foundation of Major Research Projects （No. 90610035）, Natural Science Foundation of Yunnan Province （No. 2004E0058Q）, High School Doctoral Subject Special Science and Research Foundation of Ministry of Education （No. 20040674005）.
文摘Promoter MgO on 10% CeO2/Al2O3 oxygen carrier was investigated for direct partial oxidation of methane to syngas in molten salt. The MgO content of 0.5%, 1%, 2%, 3% and 4% on the 10%CeO2/Al2O3 oxygen carriers in experiments were prepared at the temperature of 750℃, respectively. The methane conversion, H2 and CO selectivity was measured on these prepared oxygen carriers at different reaction temperature. The results showed that the 3% MgO on 10%CeO2/Al2O3 had the best activity, and the CH4 conversion and CO selectivity reached 92.58% and 87.64% at 875℃, respectively. The effect of different calcination temperature on 3% MgO as promoter on 10% CeO2/Al2O3 oxygen carrier was investigated. The results of BET indicated that oxygen carrier had the largest surface area at 750℃. When the calcined temperature was too high there would be a negative effect on oxygen carrier activity.
基金the National Natural Science Foundation of China(21531003,21501024 and 21971035)Jilin Scientific and Technological Development Program(20170101198JC and 20190103017JH)+2 种基金Jilin Education Office(JJKH20180015KJ)“111”Program(B18012)open projects from the State Key Laboratory of Inorganic Synthesis&Preparative Chemistry and State Key Laboratory of Heavy Oil Processing(2018-8,SKLOP201902003)。
文摘Ultrathin zeolite membranes are of paramount importance in accelerating gas transport during membrane separation,and lowering down their membrane thicknesses to submicron scale is deemed to be very challenging.Herein,we develop an advanced approach of surface gel conversion for synthesis of submicron-thick pure silica MFI(silicalite-1)zeolite membranes.Viscous gel is prepared by finely adjusting the precursor composition,enabling its reduced wettability.The unfavorable wetting of the support surface can effectively prevent gel penetration into alumina support voids.Aided by the seeds,the surface gel is directly and fully crystallized into an MFI zeolite membrane with minimal water steam.A membrane with a thickness of 500 nm is successfully acquired and it is free of visible cracks.Additionally,the as-synthesized membranes exhibit rapid and selective separation of hexane isomers by virtue of unprecedentedly high n-hexane permeance of 24.5×10^−7 mol m^−2 s^−1 Pa^−1 and impressive separation factors of 13.3-22.6 for n-hexane over its isomers.This developed approach is of practical interest for sustainable synthesis of high-quality zeolite membranes.
