Study On The Hydro-transformation Rule Of Long-chain Nalkane Over Multi-function Catalysts

N-paraffins hydroisomerization is an important reaction in the pour point reduce process of diesel fuel and lubricating oil.Thus,in this paper,as a bifunctional catalyst,Pt/SAPO-11 was studied to explore the influence of different composition and different modification methods of catalysts on the long-chain n-alkanes hydroconversion by modulating the match between metallicity and acidity.As to the process of the long-chain n-alkanes hydroconversion reaction,some researches were carried out,including the influence of process conditions on reaction process,the isomerization reaction rule of different chain lengths n-alkanes and its mixture on the bifunctional catalyst,the establishment of the reaction network and the catalytic reaction mechanism,as well as the structure-function relationship between catalysts,which provided theoretical guidance for industrial applications of the long-chain n-alkanes hydroconversion reactions and the design of catalyst.In the composition and modification research of Pt/SAPO-11 catalyst,it was found that acid quantity and B acid sites of the catalyst increased when enhancing SAPO-11 molecular sieve in catalyst sopporter,consequently isomerization selectivity improved.While reduction of metal component promoted the interaction between metallicity and acidity and suppress cleavage reaction,which improved isomerization reaction.The modification research of supporter using itric acid and carbon black showed that citric acid significantly improved the low temperature catalytic activity of the catalysts,while carbon black effectively promoted the mass transfer performance and monomethyl isomer selectivity of catalysts.Study of different long-chain n-alkanes hydroisomerization transformation rule indicates:Different carbon chain n-alkanes exhibited relatively high isomerization selectivity at low temperature.The isomerization selectivity of n-alkanes can reach 90%by controlling temperature to make the conversion rate less than 85%.The conversion rate of n-alkanes was increased and the selectivity of isomerization was decreased with the increase of carbon atoms number and temperature due to the occurrence of cracking reaction.The optimal isomerization reaction conditions were as following:2.0 MPa,320°C,1.0 h^-1 and hydrogen/oil volume ratio equals to 500.Bifunctional catalyst has a good product shape selective effects.The isomerization products are mainly composed of unilateral chain isomer which the methyl was located at the end and the center position of the carbon chain.At low conversion rate,the cracking reaction of the long-chain n-alkanes in the Pt/SAPO-11 catalyst was mainly metal hydrocracking,the carbon number distribution of the cracking products was uniform.However,at high conversion,the reaction was mainly acid catalytic cracking,the carbon number distribution of cracking products was obvious asymmetric distribution.