Supercritical alkylation and butene dimerization over sulfated zirconia and iron–manganese promoted sulfated zirconia catalysts Original Research Article

Supercritical alkylation and butene dimerization were investigated using sulfated zirconia (SZ) and iron–manganese promoted sulfated zirconia catalysts (SFMZ), as a function of iso-butane/olefin (I/O) ratio and at temperatures between 60 and 155°C. Detailed product analysis demonstrated that while C8 yields were as high as 80 wt.%, neither catalyst produced significant quantities of trimethyl pentanes, although both had high selectivities to dimethyl hexenes. A comparison of 1-butene versus 2-butene as the olefin feed charge showed that 1-butene first isomerizes to 2-butene, which then produces C8 products. In all cases, the products consisted primarily of C8 olefins, which in turn was dominated by dimethyl hexenes. The addition of water at a concentration as low as 1.4 mol% was found to increase dimethyl hexene selectivity (94 wt.%), and lowered the deactivation rate by 30%. The dimerization of a straight 2-butene charge produced a C5+ yield in excess of 90 wt.%, with a 73 wt.% selectivity to dimethyl hexenes. Subsequent regenerations of this catalyst resulted in about 10% conversion loss/generation, but with minimal change in dimethyl hexene selectivities.