Synthesis Of Micro/mesoporous ZSM-5 Zeolite By Hard Template

In order to increase the yield of propylene,we introduce ZSM-5 zeolite as an additive into FCC catalyst.Due to the micropore restriction of traditional ZSM-5 zeolite,cracking performance of FCC catalyst for heavy oil moleculars is relatively poor.Mesoporous ZSM-5 zeolite as an additive can efficiently inhance the mass transfer rate and cracking reaction rate of big moleculars for FCC catalyst.We can not only augment the yield of propylene,but also increase the conversion rate of heavy oil and the yield of light oil.In this thesis,we adapt traditional and in-situ hard-templated methods to synthesize micro/mesoporous ZSM-5 zeolite.In the process of synthesizing micro/mesoporous ZSM-5 zeolite in the traditional hard-templated method,we firstly optimized synthesis conditions of SBA-16,then compared ordered mesoporous carbon with SBA-16 as a hard template to which was synthesized through solvent evaporation induced self-assembly method,and finally we prepared mesoporous ZSM-5 zeolite via opitimized mesoporous carbon.Experimental conditons such as hydrothermal temperature,the amount of TEOS and F127,additives were examined to synthesize SBA-16 which has better degree of order,however,results show that orderd mesoporous carbon cannot be gained through SBA-16 due to its unique 3-D cage-like structure.Synthesis conditions like phenolic resin,the amount of TEOS and F127,carbonization temperature and pore-expanding agent were studied to prepare mesoporous carbon with good degree of order,but as the precursor solution of ZSM-5 zeolite has large viscosity,the porous structure of ZSM-5 zeolite cannot be accessed through incipient-wetness impregnation method.In the process of in-situ hard-templated method,the soluble starch was added into the precursor solution of ZSM-5 zeolite,after carbonization,in-situ carbon template was gained to be a hard template,and then mesoporous ZSM-5 zeolite was synthesized through dry-gel synthesis.Results demonstrate that the amount of starch and temperature of drying gel are of vital importance to the final product,and the crystallization time can efficiently inhance the mesopore volume of ZSM-5 zeolite.The mesopores volume is up to 0.30cm3/g under the micropore volume stable(0.15cm3/g).Stability study indicates that mesoporous ZSM-5 zeolite has good thermal and hydrothermal stability,the micropore and mesopore volume almost keep the same after 800℃ thermal treatment.The micropore volume decreases in some extent after 800℃ hydrothermal treatment,but of note is that the mesopore volume is almost unchanged.Catalytic cracking micro-reactor evaluation result suggests that FCC catalyst with mesoporous ZSM-5 zeolite as an additive can obviously inhance the yield of propylene compared to FCC catalyst with traditional ZSM-5 zeolite as an additive,its conversion rate of heavy oil and the total liquid oil yield increase in some extent compared to control sample.