Influence of reaction parameters and comparison of fluorinated alumina and silica supports in the heterogeneous alkylation of isobutane with olefins Original Research Article

The heterogeneous alkylation of i-C4 with mixed olefins from FCC refinery streams was realized using acid-modified Al2O3 and SiO2 as catalysts. The surface acidity was determined by I.R. (pyridine), Hammett indicators and NH3-TPD, while catalytic properties were determined in a 300-ml well-mixed batch-type reactor at 0°C. The Fsingle bondAl2O3 series was active only when mixed with acidic agents (BF3·2H2O), but the Fsingle bondSiO2 series was active by itself. At 0°C, the alumina based catalysts yield 13.4 wt.-% trimethylpentane (TMP) and 69.9% of C9–C10+ alkylate. The Fsingle bondSiO2 catalysts are more selective to C7–C8 alkylate, i.e. 23.7% TMP against 55.5 wt.-% C9–C10+. In comparison, the sulfuric acid catalyst yielded 48.8% C9–C10+ and 31.3% TMPs. For the solid catalysts, the increasing i-C4C/4= ratio lowers the TMP fraction, i.e. for i-C4C4= = 10, the TMP proportion is only 10.2 wt.-% and C9–C10+ fraction reaches 76.4 wt.-% When i-C4C4= = 5, the TMP fraction is 16.9 wt.-% and C9–C10+ alkylate is 64.9 wt.-% At those low ratios the olefin dimerization could be promoted, rather than isoparaffin alkylation reactions. The surface acidity of the catalysts, i.e. those values close toH0= −9.6, and high pore volume (1.18 to 1.2 cm3/g) might be the most important factors for the heterogeneous reaction.