Preparation of Pt-MOR / MCM-41 catalyst and evaluation of hydroisomerization

Hydroisomerization of the low carbon straight chain alkanes in the products of F-T synthesis,which could be used in high quality gasoline with high octane number,is promising to realize clean utilization of coal resources. Here- in,a series of MOR / MCM-41 micro-mesoporous composites are prepared by in-situ recrystallization method,with the degree of alkali dissolution of MOR zeolite crystals being controlled and the mesoporous MCM-41 being synthesized by using zeolite solution as Si and Al sources. A series of Pt-loaded catalysts are obtained by ion exchange and impregna- tion of metal active components,and n-hexane is selected as the model compound of F-T low carbon n-alkanes for hydroisomerization performance evaluation. TEM, SEM, XRD, BET, Pyridine-IR, and N2 adsorption-desorption iso- therms measurements are introduced to characterize the morphologies,structures and chemical and physical properties of the hybrids. After in-situ recrystallization modification,the grain size of MOR crystals decrease,the outer surface of MOR is coated with MCM-41,and the adsorption performance of MOR is improved,which indicates that appropriate al- kali treatment could reduce the particle aggregation of MOR zeolite and adjust the ratio of Brönsted acid to Lewis acid. In catalytic performance evaluation,the conversion rate of n-hexane increases when the reaction temperature is in- creased from 200 ℃ to 280 ℃ . With the increasing of the alkali treatment concentration,the selectivity of isomer prod- ucts is improved,and the degree of cracking is reduced,mainly due to the composite alkali treatment effect on MOR particle dispersion. Additionally,the synthesis method of MCM-41 could expand the channels through adjusting the cat- alyst pore structure and shorten the mass transfer path between the reactant molecules and the active center,also con- tributes to the selectivity improvement. The selectivity of n-hexane hydroisomerization can be improved by preparing micro-mesoporous composites and setting up a modified system. This study will provide reference for more efficient conversion of low carbon n-alkanes hydroisomerization.