Conversion of methanol to light olefins over H-MCM-22 dealuminated with different methods

Background In the post-oil society, the methanol-to-olefin (MTO) conversion is a successful non-oil route for the production of ethene, propene and butene, which are important chemicals in modern chemical industry. Recently, the global demand for propene increased, which makes high propene selectivity attractive in the MTO conversion. However, looking for an effective catalyst is the main challenge. Results H-MCM-22 zeolite was dealuminated with nitric acid, oxalic acid and ammonium hexafluorosilicate (AHFS). Then, the parent and dealumianted samples were examined in the MTO. The results show that the total acid amounts decreased and the distribution of Bronsted acid sites in the pores of H-MCM-22 are reregulated after the different dealumination procedures. The results of thermogravimetric (TG) of the spent samples demonstrated that H-MCM-22 (10A) dealumination with 10 mmol/L AHFS solution has the lowest coking rate and coke selectivity, which makes it exhibit the longest lifetime (54 h), and highest propene and butene selectivity (71.8%). Conclusion Dealumination with AHFS is an effective method for H-MCM-22. Because it can eliminate almost all the extra-framework aluminum species and concentrate the Bronsted acid sites in the sinusoidal channels which promotes the propene and butene formation with a resistance to carbonaceous deposition in the MTO reaction.