Sonochemical synthesis of SAPO-34 catalyst with hierarchical structure using CNTs as mesopore template.

A combination of carbon nanotubes (CNTs) and diethylamine (DEA) was used as a multitemplate in sonochemical synthesis of silicoaluminophosphate (SAPO)-34 hierarchical catalyst. The results show that such use of CNTs as mesopore template in sonochemical synthesis generates catalysts with hierarchical structure and remarkably different external surface area and particle morphology; on addition of CNTs, nanoparticles with spherical hierarchical are formed, having much larger external surface area compared with the common, cubic shape of SAPO-34 particles. Comparing the performance of the improved hierarchical nanocatalyst obtained using the CNT template with the base catalyst (without use of CNTs) in the methanol to light olefins (MTO) process, it was observed that the improved catalyst remained active for a longer time. Also, a larger amount of light olefins could be produced using this nanocatalyst compared with the base catalyst. Additionally, the effect of crystallization time and amount of DEA as a micropore template on the physicochemical features and performance of SAPO-34 crystals in the MTO process was evaluated. Very low amounts of DEA and short crystallization time resulted in very low crystallinity of the synthesized SAPO-34. However, large amount or long time resulted in synthesis of agglomerated, large SAPO-34 catalysts. Neither of these is desirable, and intermediate values were found to be favorable for catalyst synthesis. [ABSTRACT FROM AUTHOR]