Study On The Shape-Selective SAPO-based Catalysts For Hydroisomerization Of Long-chain Paraffins

Paraffin isomerization is involved in the refining processes of producing environmentally benign high octane gasoline, high-cetane diesel fuel, and high viscosity lubricant base stocks with low pour points. With the increasingly strict environmental legislation and continual consumption of unregenerative petroleum resource, the importance of paraffin isomerization for improving motor fuel properties is growing. Therefore, the development of the hydyisomerization catalyts with high selectivity and activities is of great interest and significance.In the thesis, the molecular sieves with different pore structures, pore size and acidity, e.g. SAPO-11, SAPO-41, SAPO-34, ZSM-23, MCM-41, were synthesized through hydrothermal and/or solventhermal methods, and the hydroisomerization of the dodecane over the bi-functional molecular sieve supported Pt catalysts were also evaluated. By using NH3-TPD, H2-chemisorption, BET, 29Si NMR, Pyridine-IR, XRD, and SEM, etc., the influence of acidity, pore structures, crystal size and hydrogenation-dehydrogenation property on the hydroisomerization performance of the catalysts were investigated.Among the above molecular sieves, SAPO-11 and SAPO-41 supported Pt catalysts exhibited the highest hydroisomerization selectivity due to their mild acidity and monodimensional 10-member ring pore structures. A silanization process could selectively passivate the acide sites on the exterior surface of SAPO-11, and thus suppress the unselective hydrocracking reactions. Meanwhile, the silanization could also narrow the pore mouth size of SAPO-11, resulting in a...