Study On Properties Of Pt/MOR Catalysts For N-octane Hydroisomerization

With the increasing strictness of environmental regulations on the quality of gasoline and the increasing demand for products such as clean gasoline,diesel oil and advanced lubricants.Hydroisomerization of n-alkanes as a technology for producing high-quality petroleum products has received increasing attention from researchers.The conversion of n-alkanes to monobranched and multibranched alkanes is an effective way to increase the octane number of gasoline and improve the quality of oils.At present,supported catalysts composed of acidic supporters supported metals are the research focus on the isomerization catalysts of n-alkane.Microporous MOR zeolites are widely used as catalysts or catalyst supports for alkylation and isomerization reactions because of their good acidity,thermal stability,isomerization,and alkylation properties.The conventional microporous MOR zeolites has a smaller pore size and larger diffusion resistance to reactants,while the mesoporous zeolites has a large pore size,but its acidity is small and the hydrothermal stability is poor.In order to overcome the limitations,microporous-mesoporous composite zeolites with a hierarchical pore structure,strong acidity,and good hydrothermal stability for hydroisomerization was synthesized by template method.The precious metals based catalysts with a higher n-alkane isomerization property were prepared by using microporous-mesoporous composite zeolites as supports.Additive can be introduced on the Pt-based catalyst to modulate the pore structure,acidity,and dispersion of active components,in order to improve the activity,selectivity,and thermal stability of the catalyst.Finally,the deactivation of the catalyst and the regeneration performance were examined.The addition of templates has an important influence on the properties of the MOR zeolites.The characterization results of XRD,BET and NH₃-TPD showed that the addition of the complex template can effectively introduce mesoporous.The surface area and volume percentage of the mesoporous increased from 47.7%and 50.0%to 70.4%and72.0%,respectively,and the total acid and weak acid of the zeolites were increased by adding the composite template.The evaluation results of the catalysts showed that the suitable amount of the template was 15%CTAB and 5%polyethylene glycol 20000,and the conversion of n-octane over the corresponding catalyst was increased by 23%and the selectivity of the isomerization product was increased by 13%.The modified results of additives showed that the modification effects of rare earth metal Ce and metal Cr were the best,and their suitable addition amounts were 0.4%and1%respectively（all based on the supporter mass）.The characterization results show that the addition of additives improves the dispersion of metal Pt,increases the reduction capacity of the catalyst,and increases the total acid amount and L-acid amount.The characterization results of deactivated and regenerated catalysts by TG,BET,NH₃-TPD show that carbon deposition is the main reason for the deactivation of the catalyst.Regeneration of coke combustion inside the rig can effectively restore the pore structure and acid amount of the catalyst.The performance evaluation results show that the catalytic performance of the regenerated catalyst is not significantly different from that of the fresh catalyst.The regeneration conditions of the deactivated catalyst were as follows,atmospheric pressure,regeneration time 3 hours,temperature 500℃,air flow 75 m L/min,and regeneration frequency 1 time.