The methyl halide to hydrocarbon reaction over H-SAPO-34

Abstract

Methyl chloride (MeCl) and methyl bromide (MeBr) were converted to hydrocarbons over a H-SAPO-34 catalyst in a fixed-bed reactor at atmospheric total pressure. The feed rate (WHSV, equivalent to the mass of methanol) was in the range of 0.8–7.7 h −1, and the reaction temperature was varied from 300 to 450 °C. Comparative experiments were performed using methanol (MeOH). An induction period was observed for all reactants. The induction period may be overcome by adding a small amount of propene to the reactor before admission of the methyl halide feed. MeCl and MeBr were converted to the same extent under identical reaction conditions, whereas the methanol conversion was more than one order of magnitude greater than the methyl halide conversion. Product selectivities were similar for all reactants. Partial pressure variations of MeCl (0.1 vs. 1.0 bar pressure) indicated a first-order reaction rate in MeCl at 350–450 °C. Rapid catalyst deactivation was observed for all reactants at and above 350 °C. Repeated reaction–regeneration cycles using 1 bar of MeCl at 450 °C led to a loss of initial activity only, whereas the subsequent activity and product distribution with time on stream were identical for cycles 2–5. No structural changes in the catalyst were observed by X-ray diffraction after the regeneration tests.