Phosphotungstic acid immobilized on mixed-ligand-directed UiO-66 for the esterification of 1-butene with acetic acid to produce high-octane gasoline

Abstract

This article proposes a novel strategy for producing highly dispersed H3PW12O40 (HPW) on metal-organic frameworks (MOFs) via the anchoring action of amino groups originating from 2-amino terephthalic acid (APTA) in the MOF ligand. Under this method, amino groups are introduced into the linker of UiO-66 materials through a one-pot synthesis to disperse supported HPW, which has a negligible impact on the crystal structure of UiO-66. The acidic densities in the HPW/UiO-66 catalysts are effectively modified by adjusting the molar APTA/PTA (terephthalic acid) ratio in the mixed ligand and HPW loading. Consequently, the dispersion and stability of supported HPW are significantly enhanced, which make the as-prepared catalyst with 40 wt% of HPW present superior sec-butyl acetate (SBAC) yield (38.6 wt%) and selectivity (98 wt%) for the direct esterification of olefins. This strategy provides a new approach for preparing supported HPW with high dispersion and stability to be applied in olefin esterification.