Pyrolysis of methyl chloride into ethylene over catalyst SAPO-34 in the forms initial and modified by metals

Abstract

The process of pyrolysis of methyl chloride is investigated over various silicoaluminophosphates: pure SAPO-34 phase; modified Fe2O3 (SAPO-34Fe); modified SiO2 (SAPO-34Si); modified by magnesium (SAPO-34Mg). Methyl chloride to ethylene reaction was carried out using a fixed bed reactor with the following conditions. The feed rate (WHSV, equivalent to the mass of methyl chloride) was in the range of 2.52–8.52 h−1, time on stream (TOS) = 2 h, and temperature 425 and 450º С . It is shown that in the presence of these catalysts the process of pyrolysis of methyl chloride is carried out with selective formation of ethylene. It was observed that the initial activity of the catalysts decreases with TOS. The same order of deactivation of catalysts is practically observed: SAPO-34Mg > SAPO-34Fe> SAPO-34Si> SAPO-34. The positive effect of coke buildup on the selectivity of ethylene formation was observed for all samples of the catalyst. The observation was made for an increase in selectivity to ethylene when the feed rate was increased. Catalyst SAPO-34 gives high initial activity (degree of methyl chloride conversion: 80%), it has longer lifetime as compared to the other samples of the tested catalysts. Selectivity of ethylene formation over this catalyst is up to 50–54% mol.

Keywords

• light olefins, ethylene, catalyst sapo, selectivity, methyl chloride, conversion.