Methanol-to-olefin conversion over H-MCM-22 catalyst

Abstract

a b s t r a c t H-MCM-22 zeolites with different Si/Al ratios were hydrothermally synthesized, also the parent sample was dealuminated by ammonium hexafluorosilicate (AHFS). Then all of the samples were characterized and evaluated for the methanol-to-olefin (MTO) conversion. The correlation of structural and acidic properties of H-MCM-22 with catalytic performance was investigated. The H-MCM-22 (Si/Al = 35.1) exhibits best catalytic stability in all the samples because of its suitable acid site amount and distribution. As for the H-MCM-22 (Si/Al = 35.1) after dealumination by AHFS, most of the extra-framework Al species were selectively removed, the selectivity of light olefin was enhanced further and the coke deposition seems to be inhibited.

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

“…Figure (a) shows methanol conversion in the MTO reaction over the parent and dealuminated H‐MCM‐22 zeolites at 450 °C as a function of time on stream. All the samples gave a conversion of 100% at the initial stage, the catalytic stability is estimated using the reaction time for methanol conversion with 100% at a certain WHSV . Obviously, the catalytic lifetimes, were different from one another.…”

“…Obviously dealumination with different methods will influence the catalytic lifetime. Another parameter related to the catalyst stability to deactivation is the conversion capacity that is the methanol amount converted over per gram of catalyst during the catalyst lifetime . Obviously, H‐MCM‐22 (10 A) has the highest conversion capacity of 54 g g −1 as listed in Table .…”

“…wileyonlinelibrary.com/jctb 10 20 30 40 50 The liquid product, consisting of oil phase and aqueous phase, was collected in a cool trap and then separated. The oil phase was analyzed by Agilent 7820A gas chromatogragh equipped with an OV-101 column and an FID.…”

“…The propene selectivity in the MTO reaction increased over H‐MCM‐22 zeolite modified with both phosphorus and oxalic acid, due to the reduction of acid sites. In our previous study, H‐MCM‐22 zeolite was dealuminated with ammonium hexafluorosilicate (AHFS), the aluminum content in H‐MCM‐22, especially the extra‐framework aluminum, was reduced significantly, with propene selectivity and P/E ratio increased …”

“…In our previous study, H-MCM-22 zeolite was dealuminated with ammonium hexafluorosilicate (AHFS), the aluminum content in H-MCM-22, especially the extra-framework aluminum, was reduced significantly, with propene selectivity and P/E ratio increased. 30 In this work, H-MCM-22 (Si/Al = 44.3) was synthesized and dealuminated with nitric acid, oxalic acid and different concentrations of AHFS solution. The distribution of the framework aluminum (Al F ) species, which dominates the distribution of Brőnsted acid sites in a zeolite and the distribution of product during MTO reaction, was investigated by 27 Al magic angle spinning nuclear magnetic resonance ( 27 Al MAS NMR), and the acidity of the samples were characterized by the temperature programmed desorption of ammonia (NH 3 -TPD) and pyridine-infrared (Py-IR).…”