New insight into the mechanism of isomerization of C-5-C-7 alkanes over MoO3/FST

Molybdenum trioxide doped on fibrous silica-titania (MoO3/FST) has been synthesized and evaluated in the catalytic isomerization of C-5-C-7 for the first time. The structure characterization, functional group, and acid distribution of MoO3/FST were assessed via XRD, N-2-physisorption, FTIR, and Py-IR analysis. The IR spectra revealed that MoO3/FST was occupied by a moderate-to-strong Bronsted and Lewis acid sites distribution. By adding MoO3, intense metal-support interactions were formed, lessening Bronsted acid sites' intensity in contrast to the increasing Lewis acid sites' intensity. The isomerization test demonstrated that maximum conversions of 50.0, 80.0, and 84.0% were acquired at 300 degrees C corresponding to n-C-5, n-C-6, and n-C-7, respectively. As the isomerization temperature rose from 150 to 350 degrees C, the yield of n-C-5 to n-C-7 isomers increased to similar to 70.0%. The high activity of MoO3/FST was ascribed to the effective interaction between MoO3 with perturbed silanol groups, which led to enrichment in protonic acid site formation via H-2 spillover. This finding proves that the isomeri-zation catalysts should possess great Lewis acid and Bronsted acid sites to enrich the protonic acid side, resulting in high performance in isomerization.