Study On The Development Of New Catalysts For Hexadecane Hydroisomerization And Its Reaction Performance

In this work, one-dimensional ZSM-22 zeolites with different Si O2/Al2O3 under various ion exchange conditions had been prepared, bifunctional catalysts had been prepared by incipient wetness impregnation technique. The topology, morphology,composition and acidity had been investigated by XRD, SEM, XRF, N2 physical adsorption, 29 Si MAS NMR, 31 P MAS NMR, 27 Al MAS NMR, NH3-TPD, Py-IR and H2 chemisorption methods. The hydroisomerization of n-hexadecane over the catalysts were evaluated on the fixed bed micro-reaction apparatus. The results indicated that Pd/ZSM-22 catalysts with one-dimensional pore channel enhanced the selectivity for mono-branched i-C16. Based on the research results, the optimized condition for preparation catalysts was that Si O2/Al2O3 was 70, without ion exchange, and the protonic samples was extruded with adding quasi-boehmite(25 wt.%) as the binder,then impregnated into a solution of Pd(NO3)2. The catalysts prepared above0.5Pd/Z22-C possessed the highest i-C16 yield of 71.0%.Series of SAPO-31, SAPO-11, SAPO-5 molecule sieves with different silicon content were successfully synthesized. The bifunctional catalysts Pd/SAPO-n(n=11, 31,5) had been prepared by impregnation. The physical and chemical performance research results showed that the Br?nsted acid sites of molecule sieves synthesized with the same Si O2/Al2O3 ration in the mixture gel decreased as the order, SAPO-5 > SAPO-31 >SAPO-11. The lack of active metal sites of Pd/S5 led to the low activity, while the non-shaped pore strcture of SAPO-5 and low CPd/CH+ resulted in low i-C16 selectivity.Pd/SAPO-11 and Pd/SAPO-31 exhibited better activity and i-C16 selectivity due to onedimensional pore structure. The circle pore structure of SAPO-31 molecule sieves was similar to the size of mono-methy i-C16, thus the limination of diffusion of isomers had been declined, and better balance between metal sites and acid sites, 0.5Pd/SAPO-31 possessed the higher i-C16 yield. The reaction conditions had been optimized over0.5Pd/S31-0.6, it was the pressure of 2MPa, the weight hourly space velocity of 4h-1,the H2/hydrocarbon(volume) ratio of 500.The effect by species of noble metal, metal precursors and the metal loading on the properties and catalytic performance of bifunctional catalysts had been investigated.The results stated clearly that the catalysts with Pt exhibited higher catalytic activity, but low selectivity. The catalysts with Pd(NH3)4(NO3)2 promoted the dispersion of Pd with less blockage of micropore, more multi-branched isomers had been achived. The balance between metal sites and acid sites had been quantified of CPd/CH+, a series of CPd/CH+ had been obtained with various Pd loading content, the catalysts with 0.5wt.%of CPd/CH+ 0.189 showed better catalytic activity with high i-C16 selectivity due to best balance between metal and acid sites, when the conversion of n-C16 was 92.0%, the i-C16 yield reached 88.1%.