A shaped binderless and two binder‐containing ZSM‐11 zeolite catalysts were prepared and characterized by powder X‐ray diffraction, N2 adsorption‐desorption, and pyridine adsorption‐infrared measurements. The bin...A shaped binderless and two binder‐containing ZSM‐11 zeolite catalysts were prepared and characterized by powder X‐ray diffraction, N2 adsorption‐desorption, and pyridine adsorption‐infrared measurements. The binderless catalyst was synthesized using a dry‐gel conversion technique, inwhich 1,6‐hexanediamine and tetrabutylammonium bromide were used as structure‐directingagents and no other alkaline materials were added. The catalytic performance of the zeolites in the direct amination of isobutene to tert‐butylamine was evaluated in a fixed‐bed reactor. By virtue of its high crystallinity as well as its good mechanical strength, the shaped binderless ZSM‐11 catalyst showed a higher rate of formation of tert‐butylamine than did the binder‐containing catalysts.展开更多
Methanol-to-olefins(MTO)is industrially applied to produce ethylene and propylene using methanol converted from coal,synthetic gas,and biomass.SAPO-34 zeolites,as the most efficient catalyst in MTO process,are subject...Methanol-to-olefins(MTO)is industrially applied to produce ethylene and propylene using methanol converted from coal,synthetic gas,and biomass.SAPO-34 zeolites,as the most efficient catalyst in MTO process,are subject to the rapid deactivation due to coke deposition.Recent work shows that steam regeneration can provide advantages such as low carbon dioxide emission and enhanced light olefins yield in MTO process,compared to that by air regeneration.A kinetic study on the steam regeneration of spent SAPO-34 catalyst has been carried out in this work.In doing so,we first investigated the effect of temperature on the regeneration performance by monitoring the crystal structure,acidity,residual coke properties and other structural parameters.The results show that with the increase of regeneration temperature,the compositions of residual coke on the catalyst change from pyrene and phenanthrene to naphthalene,which are normally considered as active hydrocarbon pool species in MTO reaction.However,when the regeneration temperature is too high,nitrogen oxides can be found in the residual coke.Meanwhile,as the regeneration temperature increases,the quantity of residual coke reduces and the acidity,BET surface area and pore structure of the regenerated samples can be better recovered,resulting in prolonging catalyst lifetime.We have further derived the kinetics of steam regeneration,and obtained an activation energy of about 177.8 kJ·mol^(-1).Compared that with air regeneration,the activation energy of steam regeneration is higher,indicating that the steam regeneration process is more difficult to occur.展开更多
To improve oil quality,ZSM-22/SAPO-11 composite molecular sieves were synthesized by adding ZSM-22 into a synthetic gel of SAPO-11 for n-decane hydroisomerization.The mass ratios of ZSM-22/(ZSM-22+SAPO-11)in the compo...To improve oil quality,ZSM-22/SAPO-11 composite molecular sieves were synthesized by adding ZSM-22 into a synthetic gel of SAPO-11 for n-decane hydroisomerization.The mass ratios of ZSM-22/(ZSM-22+SAPO-11)in the composite molecular sieves were optimized and the optimal ZSM-22/SAPO-11 composite(ZS-9)was obtained.The electrostatic repulsions between the ZSM-22 precursors and the SAPO-11 crystalline nuclei produced small ZSM-22 and SAPO-11 crystallites in ZS-9,which increased the specific surface area and mesopore volume and thereby exposed more acid sites.In comparison with conventional SAPO-11,ZSM-22 and their mechanical mixture,ZS-9 with smaller crystallites and the optimal medium and strong Brønsted acid centers(MSBAC)content displayed a higher yield of branched C_(10) isomers(81.6%),lower cracking selectivity(11.9%)and excellent stability.The correlation between the i-C_(10) selectivity and the MSBAC density of molecular sieves indicated that the selectivity for branched C_(10) isomers first increased and then decreased with increasing MSBAC density on the molecular sieves,and the maximum selectivity(87.7%)occurred with a density of 9.6×10^(−2)μmol m^(−2).展开更多
A defect-free SAPO-44 zeolite membrane firmly anchored the porous α-Al2O3 plate substrate was successfully synthesized. The separating results showed that the H2/N2 and H2/CO permselectivities were higher than those ...A defect-free SAPO-44 zeolite membrane firmly anchored the porous α-Al2O3 plate substrate was successfully synthesized. The separating results showed that the H2/N2 and H2/CO permselectivities were higher than those of the corresponding Knudsen diffusion and the substrate, attaining 5.78 and 7.15 respectively.展开更多
The dispersion behavior of MoO_3 on ZSM-11 and effect of dispersed MoO_3 on the fram ework structure of ZSM-11 have been studjed using X-ray diffraction and infrared spectroscopy
基金supported by K.C.Wong Education Foundation, Hong Kong (201611)Youth Innovation Promotion Association, CAS (20120155)~~
文摘A shaped binderless and two binder‐containing ZSM‐11 zeolite catalysts were prepared and characterized by powder X‐ray diffraction, N2 adsorption‐desorption, and pyridine adsorption‐infrared measurements. The binderless catalyst was synthesized using a dry‐gel conversion technique, inwhich 1,6‐hexanediamine and tetrabutylammonium bromide were used as structure‐directingagents and no other alkaline materials were added. The catalytic performance of the zeolites in the direct amination of isobutene to tert‐butylamine was evaluated in a fixed‐bed reactor. By virtue of its high crystallinity as well as its good mechanical strength, the shaped binderless ZSM‐11 catalyst showed a higher rate of formation of tert‐butylamine than did the binder‐containing catalysts.
基金the National Natural Science Foundation of China(91834302)。
文摘Methanol-to-olefins(MTO)is industrially applied to produce ethylene and propylene using methanol converted from coal,synthetic gas,and biomass.SAPO-34 zeolites,as the most efficient catalyst in MTO process,are subject to the rapid deactivation due to coke deposition.Recent work shows that steam regeneration can provide advantages such as low carbon dioxide emission and enhanced light olefins yield in MTO process,compared to that by air regeneration.A kinetic study on the steam regeneration of spent SAPO-34 catalyst has been carried out in this work.In doing so,we first investigated the effect of temperature on the regeneration performance by monitoring the crystal structure,acidity,residual coke properties and other structural parameters.The results show that with the increase of regeneration temperature,the compositions of residual coke on the catalyst change from pyrene and phenanthrene to naphthalene,which are normally considered as active hydrocarbon pool species in MTO reaction.However,when the regeneration temperature is too high,nitrogen oxides can be found in the residual coke.Meanwhile,as the regeneration temperature increases,the quantity of residual coke reduces and the acidity,BET surface area and pore structure of the regenerated samples can be better recovered,resulting in prolonging catalyst lifetime.We have further derived the kinetics of steam regeneration,and obtained an activation energy of about 177.8 kJ·mol^(-1).Compared that with air regeneration,the activation energy of steam regeneration is higher,indicating that the steam regeneration process is more difficult to occur.
基金The authors gratefully acknowledge the financial support of Science Foundation of China University of Petroleum,Beijing(Grant No.KYJJ2012-03-03).
文摘To improve oil quality,ZSM-22/SAPO-11 composite molecular sieves were synthesized by adding ZSM-22 into a synthetic gel of SAPO-11 for n-decane hydroisomerization.The mass ratios of ZSM-22/(ZSM-22+SAPO-11)in the composite molecular sieves were optimized and the optimal ZSM-22/SAPO-11 composite(ZS-9)was obtained.The electrostatic repulsions between the ZSM-22 precursors and the SAPO-11 crystalline nuclei produced small ZSM-22 and SAPO-11 crystallites in ZS-9,which increased the specific surface area and mesopore volume and thereby exposed more acid sites.In comparison with conventional SAPO-11,ZSM-22 and their mechanical mixture,ZS-9 with smaller crystallites and the optimal medium and strong Brønsted acid centers(MSBAC)content displayed a higher yield of branched C_(10) isomers(81.6%),lower cracking selectivity(11.9%)and excellent stability.The correlation between the i-C_(10) selectivity and the MSBAC density of molecular sieves indicated that the selectivity for branched C_(10) isomers first increased and then decreased with increasing MSBAC density on the molecular sieves,and the maximum selectivity(87.7%)occurred with a density of 9.6×10^(−2)μmol m^(−2).
文摘A defect-free SAPO-44 zeolite membrane firmly anchored the porous α-Al2O3 plate substrate was successfully synthesized. The separating results showed that the H2/N2 and H2/CO permselectivities were higher than those of the corresponding Knudsen diffusion and the substrate, attaining 5.78 and 7.15 respectively.
文摘The dispersion behavior of MoO_3 on ZSM-11 and effect of dispersed MoO_3 on the fram ework structure of ZSM-11 have been studjed using X-ray diffraction and infrared spectroscopy
