Preparation Of Pt/SSZ-32 By Interface Regulation For Catalytic Hydroisomerization

The hydroisomerization of paraffins plays an important role in petroleum industry.In order to reduce the freezing point and pour point of jet fuel and lubricating oil,the isomerization of long-chain alkane in these products into isomers is required.It is of great practical significance to prepare high-performance hydroisomerization catalysts.In this paper,the preparation and metal-carrier interface regulation of Pt catalysts supported on SSZ-32 molecular sieve with straight channels（Pt/SSZ-32）were studied,in order to improve the catalytic activity and isomers selectivity.Furthermore,suitable Pt/SSZ-32 was selected to explore the optimum process conditions to provide basic data and theoretical guidance for hydroisomerization of long-chain alkanes in industry for the production of high-performance jet fuel and lubricating oil.Firstly,a series of Pd catalysts supported on carbon nanotubes modified by polydopamine（PDA）were prepared,and the interface of metal-carrier was regulated by high-temperature carbonization of PDA interlayer.The effects of different strategies of interface regulation on the hydrogenation performance of catalysts were evaluated by 4-nitrophenol（4-NP）hydrogenation.The results show that the SiO₂coating can prevent the metals from agglomeration during high-temperature carbonization,which can significantly improve the hydrogenation activity.The effects of metal load,SiO₂ coating,calcination temperature and time on the catalyst properties and corresponding hydrogenation performance were investigated.The conversion of 4-NP hydrogenation is 98.08%over the catalyst with 1.0%of Pd loading after the carbonization regulation under SiO₂ coating（55.34%over the ordinary catalyst）.Then,the above strategy of interface regulaiton was applied to the preparation of Pt/SSZ-32 to improve the catalytic performance of n-hexadecane hydroisomerization.The influences of different interface regulation methods on the catalytic hydroisomerization performance of Pt/SSZ-32 was studied,and a series of Pt/SSZ-32catalysts regulated by PDA coating were prepared.The effects of PDA-coating thickness,calcination temperature and time and non-noble metal doping on the hydroisomerization performance of catalysts were explored.It is shown that the increase of Weak acid/Strong acid and the decrease of Bronsted acid/Lewis acid after thiol grafting on SSZ-32 surface are beneficial to improving the isomers selectivity of catalysts.The optimal amout of thiol grafting is Pt/TMSH mole ratio of 1:9,contributing to a n-hexadecane conversion of 91.40%and isomers yield of 69.50%at280?C,5 Mpa,2 h^-1 and 1000 of H₂/oil.However,PDA coating regulation at high temperature has little effect on the hydroisomerization performance of catalysts and the doping of non-noble metals reduces the hydroisomerization performance of catalysts.Lastly,the influences of different process conditions on the catalytic performance were investigated.And orthogonal experiment table was designed to evaluate the hydroisomerization performance of ordinary catalysts by incipient wetness impregnation（Pt/SSZ-IP）and thiol-grafted catalysts（Pt/S-SSZ）.Under the optimum process conditions of 270?C,1 MPa,4 h^-1 and 600 of H₂/oil for Pt/S-SSZ,a n-hexadecane conversion of 90.45%and isomers yield of 90.45%were achieved.