Gas-phase metathesis of 1-hexene over a WO3/SiO2 catalyst: Search for optimal reaction conditions

The performance of an 8 wt% WO3/SiO2 catalyst has been investigated for the metathesis of 1-hexene in a gas-phase fixed-bed reactor. The operating conditions (reaction temperature, feed composition and space time) were optimized for the yield of decene, the primary metathesis product, using a full factorial experimental design and a probabilistic two-factor search. A combined sequence of oxidative and reductive catalyst pre-treatments, followed by a nitrogen purge, led to the best yields of decene. It was found that at 380 deg C, with 55 mol% 1-hexene in the feed and at 2874 g min mol-1, a decene yield of 12.8% can be obtained, with a 1-hexene conversion of 94%. Pre-treatment of the catalyst with only hydrogen and nitrogen resulted in a lower conversion of 1-hexene, selectivity and yield of primary products, possibly due to over-reduction of the active tungsten surface phase. Under the experimental conditions employed, the reaction was neither limited by extra- nor intraparticle mass transfer resistance effects.