Synthesis And Catalytic Cracking Properties Of Hierarchical Zeolite Y

Zeolite Y plays an important role in fluidized catalytic cracking(FCC)catalysts due to its unique properties.However,the microporous structure with the pore openings of 7.4 A imposed diffusion limitations and limited the conversion of the larger hydrocarbon molecules in FCC process.Therefore,the internal active sites are difficult to be accessible.Synthesis of hierarchical zeolites which contain interconnected mesopores with the micropore network,was considered an effective way to reduce the diffusion limitations.Hierarchical zeolite Y was synthesized using TPHAC as mesotemplate and the optimized conditions were obtained.And the FCC catalytic performance of hierarchical zeolite Y was evaluated in an Advanced Catalytic Evaluation(ACE)unit.As presented,the yields of light oil,heavy oil,dry gas,and coke are 66.56,5.81,2.61,and 5.43%,respectively.The heavy oil and coke yields of the hierarchical zeolite Y catalysts are much lower than those of the conventional zeolites catalyst.It is indicated that the presence of mesopores in the hierarchical zeolite Y greatly reduce the secondary cracking and condensation polymerization reactions.The catalytic results demonstrated the diffusion limitation of the microporous molecular sieve was solved by the introduction of mesopores.Gemini organosilane has two quaternary ammonium centers along with double-hydrolyzable-Si(OCH3)3 fragments,which can significantly enhance the interaction between this mesoporogen and the silica-alumina gel in the synthesis system.The properties of organosilane surfactants have been altered by the introduction of two quaternary ammonium groups.When added the anionic surfactant in the system,the organosilane template linked with assistant-template by interacting between positive charge in the organosilane and the negative charges in the anionic surfactant.The mesoporous specific surface area of the hierarchical zeolite Y was 71 m2·g-1.The sodium alginate was used as the mesoporous template to synthesize hierarchical zeolite Y.Sodium alginate is characterized by unique structure of polyhydroxy.Therefore,it is a good candidate as the mesoprogen in synthesis of hierarchical zeolite Y.The total surface area of the hierarchical zeolite Y was 733m2 · g-1 and the mesopore specific surface area was 126 m2 · g-1.Synthesis of hierarchical zeolite Y was scaled up on the basis of above investigation.It had been shown that the total surface area of the product was 694 m2 · g-1 and the mesopore specific surface area was 139 m2 · g-1.The retaining ratio of the total surface area of the the scaled-up zeolite was 44%after hydrothermal treatment in 100%water vapor at 800 ? for 4 h.These results indicated that the product had excellent hydrothermal stability.