Supported Metal Sulfate Catalysts FexZny/SiO2 for Selective Dimerization of Isobutene in Mixed C4 to Isooctenes

Isobutene dimerization is an important route to properly utilize mixed C-4 and further produce isooctane with a high-octane number to replace MTBE in gasoline. A highly selective catalyst, which is effective for isobutene dimerization but ineffective for other olefins in the C-4 mixture, is necessary for industrial implementation. In this work, a series of supported metal sulfate catalysts FexZny/SiO2 were prepared and characterized by XRD, SEM, N-2 physical adsorption-desorption, NH3-TPD, Py-FTIR, and XPS. Fe0.2Zn1.8/SiO2 can achieve isobutene conversion up to 89 % with 0 % conversion of n-butene, and the selectivity of isooctenes (C-8(=)) product is 57 % (10 h on stream). Furthermore, isobutene conversion can sustain above 80 % after 50 h. It is found that these supported catalysts contain Zn2+, Zn+, Fe3+, and Fe2+ species, and there is a synergetic effect between Zn2+ and Fe2+. Zn2+ is beneficial to improve the conversion of isobutene, and Fe2+ facilitates the formation of C-8(=), resulting in a high C-8(=) yield.