Green synthesis of SAPO-34 molecular sieve using rice husk ash as a silica source: Evaluation of synthesis and catalytic performance parameters in methanol-to-olefin reaction

Abstract

Reducing synthesis costs in the petrochemical industry leads to decreasing financial value of final products from raw materials. In this paper, SAPO-34 molecular sieve as a main catalyst of methanol-to-olefin process is newly synthesized by rice husk. The silica source of SAPO- 34 synthesis is achieved from this agricultural waste material by calcination and leaching methods with the purity of 97% based on XRF analysis. Between the series of samples synthesized, the sample with the highest crystallinity and textural properties is obtained by Si = 0.6 M concentration and hydrothermal synthesis at 200◦C for 18 h which has been proved by XRD, SEM, BET, EDX and NH3-TPD analyses. Also, this sample showed that has relatively higher selectivity toward light olefins compared to other samples. In the case of operating conditions, using methanol/water (20 wt%) instead of pure methanol as feed increased light olefins selectivity and reached the maximum value of 83.5% at 375 ◦C, however, highest light olefins mass (26 wt%) from the consumed feed acquired at 425 ◦C.