Preparation Of Chromium Based Catalyst And Numerical Simulation Of Spouted Bed Reactor For Propane Dehydrogenation

Propylene is an important chemical feedstock and its demand is rising year by year.Propane dehydrogenation processes are considered as one of the most promising ways to produce propylene.It is usually divided into two categories:direct dehydrogenation and oxidative dehydrogenation.The former has already been industrialized,with chromium-based catalysts being one of the commonly used industrial catalysts due to its advantages in cost and activity.However,the tendency of chromium species in the catalyst to agglomerate and subsequently lead to permanent deactivation of the catalyst remains to be solved.The oxidative dehydrogenation of propane is still in the research stage,focusing on catalyst screening and improvement,while little research has been reported on reactor selection and optimization of operating parameters.Therefore,in this paper,a new method for the preparation of Cr-based catalysts for the direct dehydrogenation of propane and the applicability of the oxidative dehydrogenation spray bed reactor are investigated in a focused manner.（1）Preparation of MIL-101（Cr）-derived Cr2O3@C catalysts:The effects of different carbonization temperatures on the catalyst structure and reaction performance during the preparation process were investigated.Based on the instrumental characterization by XRD,FT-IR,BET,and XPS,and the results of catalytic reactivity evaluation,the optimal carbonization temperature was 900℃.Under the reaction conditions of P=0.1 MPa,T=580℃,and GHSV=800 h^-1,the catalyst achieved optimal performance with 19.60%propane conversion and 90.74%propylene selectivity.（2）Preparation of MIL-101（Cr/Al）-derived Crx Aly@C catalysts:To address the above catalyst activity stability issues,Cr-Al bimetallic MOF-derived carbon material catalysts were prepared to investigate the effects of different Cr/Al ratios on the catalyst structure and reaction performance.From the instrument characterization and evaluation results,the optimal Cr/Al ratio was 6:4.Under the reaction conditions of P=0.1 MPa,T=580℃and GHSV=800 h^-1,the propane conversion was 19.52%and propylene selectivity was 92.01%,and the propane conversion and propylene selectivity were still maintained at 11.80%and 92.10%after 8 h of reaction.（3）Numerical simulation of spouted bed reactor:The MP-PIC method was used to compare the two-phase flow and dehydrogenation reaction processes in the spouted bed reactor with and without a draft tube,and the results showed that the propylene selectivity was higher in the spouted bed reactor with a draft tube,while the propane conversion was higher without a draft tube.The effect of reactor operating parameters on the propane dehydrogenation process in the spouted bed reactor was then investigated,and the results showed that the best performance was achieved when the catalyst static bed height of 0.3m,the particle diameter of 1.0 mm to 1.2 mm,the temperature of 500℃,the ratio of propane to oxygen of 1.0 and the oxygen content of 1%,with a propane conversion of18.01%and a propylene selectivity of 29.78%.