Bifunctional catalyst of mordenite- and alumina-supported platinum for isobutane hydroisomerization to n-butane

n-Butane has higher value-added applications than isobutane in the petrochemical process. To improve the catalytic performance of isobutane isomerization catalysts, catalysts of mordenite- and alumina-supported platinum were prepared. The intimacy between metal and acid sites and platinum content was investigated. The effect of reaction conditions on the catalytic performance of the catalyst was analyzed by response surface methodology. The characterization results of X-ray diffraction (XRD) patterns, specific surface area, and transmission electron microscope (TEM) confirmed high dispersion of platinum on the catalysts. The results of temperature-programmed desorption of ammonia (NH3-TPD) indicated that more acid sites existed on millimetre scale and centimetre scale catalysts than on Pt-HM/Al2O3 and Pt-Al2O3/HM, which led to low selectivity of n-butane. The best yield of n-butane was attained on microscale samples, as the larger diffusion distance inhibited the cracking reaction. The dispersion of reaction products indicated that the increase of platinum content slightly increased the selectivity of n-butane. Compared with Pt-HM/Al2O3, Pt-Al2O3/HM showed high stability due to fewer carbon deposits in the catalytic reaction process. The optimal reaction condition in isobutane isomerization was T = 413.4 degrees C, liquid hourly space velocity (LHSV) = 5.31 h(-1), and P = 2.57 MPa.