November 14, 2011
Here’s a way to make intermediate olefins “on purpose”. C5 and C6 olefins are low-volume byproducts from ethylene steam crackers. A process for converting smaller olefins to C5 and C6 olefins “on-purpose” would have commercial value. L. A. Chewter and colleagues describe how MTT-type zeolites can catalyze the reaction of 1-butene and dimethyl ether (DME) to give mixtures of C5 and C6 olefins with good selectivity.
The patent’s examples cover the reaction of 1-butene and DME in a 2:1 mol ratio over MTT-type zeolites with Si/Al ratios of 47:1, 79:1, and 107:1. The zeolite powders were pressed into tablets, and the tablets were broken into pieces and sieved. The 30–80 mesh sieve fraction (200 mg) was loaded into a 3-mm i.d. quartz tube reactor. After the catalyst was calcined under argon at 550 °C for 1 h, a mixture of 2.0 vol% 1-butene, 0.9 vol% DME, and 1 vol% water in argon was passed over the catalyst at a flow rate of 50 mL/min at 1 bar pressure and temperatures ranging from 300 to 400 °C.
1-Butene conversions ranged from 21 to 57%. Selectivity to C5 and C6 olefins ranged from 61 to 96%. Other olefins in the product mixture included ethylene, propylene, and heptenes. (Shell Oil [Houston]. US Patent 8,049,054, Nov. 1, 2011; Jeffrey S. Plotkin)