Study On Synthesis,Metal Modification And Performance Of Methanol Olefinization Of SAPO-34 Molecular Sieve With Hierarchical Pore

In this paper,methanol olefination(MTO)is used as the object,using static hydrothermal synthesis method,XRD,SEM,BET characterization methods and MTO evaluation experiments to investigate the combination of microporous template and mesoporous template,synthesis conditions and metal modification effects SAPO-34 molecular sieve performance impact.Using microporous template(MOR,TEA,TEAOH)+mesoporous template(TPOAC,CTAB,PEG-6000)as a composite template to synthesize 9 kinds of molecular sieves.Spectroscopy analysis shows that:the molecular sieve synthesized with MOR as the microporous template and any mesoporous template is amorphous structure;the molecular sieve synthesized with TEAOH+PEG-6000 composite template has the highest crystallinity and specific surface area,and the crystal structure is the best Regularity.The MTO evaluation results show that the synthesis of molecular sieves with TEAOH+PEG-6000 composite template has the best catalytic performance:lifetime 480 min,C2=+C3=yield 85.85%.Therefore,the follow-up work is based on the composite template.Using dual-microporous template(TEAOH+MOR,TEAOH+TEA,TEA+MOR)+mesoporous template(TPOAC,CTAB,PEG-6000)as a composite template,9 molecular sieves were synthesized.Spectroscopy analysis shows that:the molecular sieve synthesized with TEAOH+MOR+CTAB composite template has the highest crystallinity,the largest specific surface area,and the smallest crystal size;the synthesis of TEAOH+MOR+PEG-6000 composite template has the largest number of mesopores;the synthetic molecular sieve of TEA+MOR+TPOAC composite template is a spherical large particle SAPO-5 molecular sieve.Single factor experiments were used to investigate the influence of the amount of micro-mesoporous template agent,the ratio of silicon to aluminum,the crystallization time and the crystallization temperature synthesis conditions on SAPO-34 molecular sieve.The final suitable synthesis conditions were determined as follows:the molar ratio of synthetic raw materials Al:P:Si:TEAOH:PEG-6000:H2O=2:2:0.4:2:0.1:100,crystallization at 200℃for 72 h.Under the synthesis conditions,the catalytic life of molecular sieve MTO was 480 min,and the yield of C2=+C3=was 85.85%.Based on the above molecular sieve synthesis conditions,the metal modification was carried out,and the single metal ions(Ba,Zn,Cu),double metal ions(Ba+Zn,Ba+Cu,Zn+Cu),and the amount of metal ions(molar ratio:Cu/P2O5=0.005,0.01,0.015,0.02)on the catalytic performance of SAPO-34 molecular sieve MTO.The results show that under single metal ion,Cu ion synthesis molecular sieve life can reach 450 min,and the yield of diolefin is 81.76%;under double metal ion,Ba ion is beneficial to increase the catalytic life and ethylene selectivity,and Cu ion is beneficial to increase the yield of diolefin;Under the ion content,the catalytic life of the molecular sieve with Cu/P2O5=0.01 reaches 450 min,and the yield of the diolefin with the molecular sieve of Cu/P2O5=0.02 reaches 82.60%.Under the condition of metal ion modification,the catalytic life and product yield of MTO are slightly reduced,but the stability of the catalyst is improved.The product yield can be maintained at about 80%within 4 h,and the range of change is within 1%.