A series of 3.0Mo/(Hβ+γ-Al_2O_3) samples with γ-Al_2O_3 contents in the range of 0_100%(mass fraction) was studied by means of XRD, NH_3-TPD, TPR and BET determinations for characterizing their structures. The Hβ ...A series of 3.0Mo/(Hβ+γ-Al_2O_3) samples with γ-Al_2O_3 contents in the range of 0_100%(mass fraction) was studied by means of XRD, NH_3-TPD, TPR and BET determinations for characterizing their structures. The Hβ zeolite structure in the 3.0Mo/Hβ sample can be effectively stabilized by adding some γ-Al_2O_3 to Hβ zeolite. γ-Al_2O_3 mainly favors the formation of polymolybdate or multilayered Mo oxide, while Hβ mainly forms the Al_2(MoO_4)_3 species, as evaluated by the TPR technique. When used as the catalyst for the metathesis of butylene-2 and ethylene to propylene, there exists a close correlation between the specific surface area and stability of the catalyst. The specific surface area of the catalyst shows the maximum when {(Hβ+}γ-Al_2O_3) contains 30%γ-Al_2O_3, which is in agreement with that of the time needed for the reaction stablization. In the case of maximum surface area, the rate of coke deposition is the minimum.展开更多
Conventional oven drying (COD) and supercritical drying (SCD) methods wereapplied to the preparation of Mn-substituted hexaaluminate (BaMnAl_(11)O_(19-α)) catalysts. Theeffect of drying methods on phase composition, ...Conventional oven drying (COD) and supercritical drying (SCD) methods wereapplied to the preparation of Mn-substituted hexaaluminate (BaMnAl_(11)O_(19-α)) catalysts. Theeffect of drying methods on phase composition, specific surface area, pore structure, reductionbehavior of Mn^(3+) ions, and combustion activity of the samples was investigated. The homogenousmixing of the components in the sol-gel process could be maintained by SCD, and the hexaaluminatephase was almost the only phase of the resulting materials after calcination. H_2-TPR revealed thatthe Mn^(3+) ions in the sample obtained by SCD were easier to be reduced than that by COD. Moreover,the samples obtained by SCD have higher surface area, narrower pore size distribution, and highercombustion activity than those obtained by COD.展开更多
A series of Mo-impregnated H\%β\% samples, with MoO\-3 loading in H\%β\% zeolite in the mass fraction range of 0\^5%\_6\^0%, were studied by means of XRD and IR in order to characterize their structures. Mo/H\%β\% ...A series of Mo-impregnated H\%β\% samples, with MoO\-3 loading in H\%β\% zeolite in the mass fraction range of 0\^5%\_6\^0%, were studied by means of XRD and IR in order to characterize their structures. Mo/H\%β\% samples′ crystallinity almost linearly decreases with increasing the amount of MoO\-3 loaded. The IR spectra and XRD patterns suggest that the progressive destabilization of the H\%β\% zeolite structure is caused by increasing Mo loading in (MoO\-3+H\%β\% zeolite). During the calcination, Al\-2(MoO\-4)\-3 formed from the dealumination of H\%β\% zeolite, causes the substantially partial breakdown of the zeolite framework when the Mo loading in MoO\-3+H\%β\% is relatively high.展开更多
文摘A series of 3.0Mo/(Hβ+γ-Al_2O_3) samples with γ-Al_2O_3 contents in the range of 0_100%(mass fraction) was studied by means of XRD, NH_3-TPD, TPR and BET determinations for characterizing their structures. The Hβ zeolite structure in the 3.0Mo/Hβ sample can be effectively stabilized by adding some γ-Al_2O_3 to Hβ zeolite. γ-Al_2O_3 mainly favors the formation of polymolybdate or multilayered Mo oxide, while Hβ mainly forms the Al_2(MoO_4)_3 species, as evaluated by the TPR technique. When used as the catalyst for the metathesis of butylene-2 and ethylene to propylene, there exists a close correlation between the specific surface area and stability of the catalyst. The specific surface area of the catalyst shows the maximum when {(Hβ+}γ-Al_2O_3) contains 30%γ-Al_2O_3, which is in agreement with that of the time needed for the reaction stablization. In the case of maximum surface area, the rate of coke deposition is the minimum.
文摘Conventional oven drying (COD) and supercritical drying (SCD) methods wereapplied to the preparation of Mn-substituted hexaaluminate (BaMnAl_(11)O_(19-α)) catalysts. Theeffect of drying methods on phase composition, specific surface area, pore structure, reductionbehavior of Mn^(3+) ions, and combustion activity of the samples was investigated. The homogenousmixing of the components in the sol-gel process could be maintained by SCD, and the hexaaluminatephase was almost the only phase of the resulting materials after calcination. H_2-TPR revealed thatthe Mn^(3+) ions in the sample obtained by SCD were easier to be reduced than that by COD. Moreover,the samples obtained by SCD have higher surface area, narrower pore size distribution, and highercombustion activity than those obtained by COD.
基金Supported by the National Natural Science Foundation of China(No.2 0 30 30 19) and the National"973"Project of China(No.2 0 0 3CB6 15 80 2 )
文摘A series of Mo-impregnated H\%β\% samples, with MoO\-3 loading in H\%β\% zeolite in the mass fraction range of 0\^5%\_6\^0%, were studied by means of XRD and IR in order to characterize their structures. Mo/H\%β\% samples′ crystallinity almost linearly decreases with increasing the amount of MoO\-3 loaded. The IR spectra and XRD patterns suggest that the progressive destabilization of the H\%β\% zeolite structure is caused by increasing Mo loading in (MoO\-3+H\%β\% zeolite). During the calcination, Al\-2(MoO\-4)\-3 formed from the dealumination of H\%β\% zeolite, causes the substantially partial breakdown of the zeolite framework when the Mo loading in MoO\-3+H\%β\% is relatively high.
