Facile preparation of PtSn-La/Al2O3 catalyst with large pore size and its improved catalytic performance for isobutane dehydrogenation

Al2O3 beads with various pore sizes were successfully synthesized by combining ammonium alginate assisted sol-gel and emulsion template methods using liquid paraffin as pore-enlarging agent and polysorbate 80 as dispersant. The great influences of textural structure of Al2O3 beads on the activity and stability of PtSn-La/Al2O3 catalyst for isobutane dehydrogenation were investigated by N2 adsorption-desorption, XRD, NH3-TPD, SEM, HRTEM, H2-TPR, XPS, isobutene transient response experiment and TG analysis. The results showed that Al2O3 beads with tunable pore sizes (7.4-13.3 nm), surface areas (294-322 m2/g) and pore volumes (0.56-1.1cm3/g) could be obtained by changing the addition amount of liquid oil. Moreover, the transient response experiment stated that the PtSn-La/Al2O3 catalysts with large pore sizes could enhance the diffusion speed of the gas molecule in the channels. With increasing the amount of liquid oil from 0 to 20%wt, the particle sizes of platinum decreased from 2.86 nm to 1.45 nm, the amount of carbon deposit declined by 30.6% and the final yield of isobutene increased from 42% to 48%. The enhancement of catalytic performance of PtSn-La/Al catalyst with larger pore size was related to its smaller Pt particles, lower surface acidity and diffusion resistance of reaction products in the pore.