Effects of sugars on the structure of SAPO-34 and its MTO performance

Hierarchical SAPO-34 zeolites were successfully synthesized using cheap xylose, sucrose, starch and glucomannan as hard template and characterized by means of XRD, BET, SEM, TEM, ICP and NH₃-TPD. The effects of sugar hard template on the structure and MTO properties of as-prepared SAPO-34 zeolites were studied on a fixed bed. The results showed that introduction of carbohydrate hard template could increase the specific surface area, microporous and mesoporous volume of SAPO-34 zeolites. The olefin selectivity and lifetime of SAPO-34 were both higher than those of ordinary SAPO-34. The SAPO-34-z with the largest mesoporous volume, the least acidity amounts and the weakest acidity showed the longest lifetime (130 min), which was 30% longer than that of ordinary SAPO-34 (100 min). The lifetime of zeolites decreased in the order of SAPO-34-z > SAPO-34-h > SAPO-34-d > SAPO-34-m > SAPO-34 > SAPO-34-p. The olefin selectivity of hierarchical SAPO-34 zeolites is higher than that of conventional SAPO-34 zeolites.