Preparation And Evaluation Of Catalyst In The Dehydration Of Castor Oil

Castor oil can be made into a lot of industrial products,which can be widely used in many fields.Therefore,it is an inevitable trend to increase the development of further-processing industries of castor oil.At present,the dehydration industrial chain of castor oil is matured,but there are still many problems.The dehydration reaction of castor oil is usually occurred at high temperature,it is easy to produce thermal polymerization,thermal cracking and other side reactions in the reaction process,which makes the degree of dehydration of castor oil not high.In order to improve the efficiency of the dehydration reaction of castor oil,the NaHSO4/MCM-41 catalyst was prepared by loading NaHSO4 on MCM-41,and the catalytic efficiency was improved by changing the catalyst preparation method and physical modification of the catalyst.The NaHSO4/MCM-41 catalyst was prepared by loading NaHSO4 on MCM-41 support.The samples were evaluated by XRD,nitrogen adsorption-desorption,NH3-TPD,FT-IR,TG,and pyridine-FTIR measurements.The analyses demonstrated that the mesostructure of the catalysts was maintained,and NaHSO4 was loaded onto MCM-41.The experiment results showed that the catalytic activity of the NaHSO4/MCM-41 catalyst was much higher than that of NaHSO4.The optimum parameters were as follows:reaction time 70 min,the loading amount of NaHSO4 25 wt%,reaction temperature 240?,and the amount of catalyst 4 wt%.Under this condition the iodine and hydroxyl value of product were respectively up to 134.2 g(I2)/100g and 17.3 mg(KOH)/g.N-Dodecyltriethoxysilane(DTEOS)-modified NaHSO4/MCM-41 catalysts(silanized catalysts)were synthesized by different impregnation sequences and evaluated in the liquid-phase dehydration of castor oil.The samples were evaluated by XRD,nitrogen adsorption-desorption,SEM,TEM,FTIR,XPS,29Si MAS NMR,contact angle measurements,NH3-TPD,and pyridine-FTIR.The analyses demonstrated that silanization enhanced the hydrophobicity of the catalysts,and the impregnation sequence of silanized catalysts had a significant effect on the NaHSO4 dispersion,surface area,acid distribution,and hydrophobicity of the silanized catalysts.The catalytic activity of the silanized catalysts was much higher than that of NaHSO4/MCM-41.Among the silanized catalysts,the catalyst prepared by simultaneous impregnation with DTEOS and NaHSO4 showed the highest iodine value and the lowest hydroxyl value.The NaHSO4/MCM-41-SUP catalysts were first prepared by supercritical impregnation as highly efficient catalysts in the liquid phase dehydration of castor oil.NaHSO4/MCM-41-IMG catalysts prepared by conventional wet impregnation method were also examined for comparison.The results indicated that the catalytic activity and repeatability of Cat-1 catalyst were much better than those of Cat-2 catalyst.The catalysts were studied by XRD,nitrogen adsorption-desorption,NH3-TPD,pyridine-FTIR,FTIR,TG,and CHNS elemental analyzer.According to the results of characterization,the preparation condition of SC CO2 was good for improving the dispersion of NaHSO4 supported on MCM-41,increasing the interaction sites between NaHSO4 and MCM-41,heightening the thermostability of catalyst and enhancing the amount of medium acid sites and Br(?)nsted acid sites on the catalyst.Therefore,the leaching of NaHSO4 and formation of coke were retarded,the deactivation rate of NaHSO4/MCM-41-SUP catalyst was slow,and the repeatability of NaHSO4/MCM-41-SUP catalyst was excellent.After six cycles,the iodine value of product decreased from 135.2 g(I2)/100g to 114.2 g(I2)/100g and the hydroxyl value increased from 14.7 mg(KOH)/g to 59.1 mg(KOH)/g over NaHS04/MCM-41-IMG(S element leaching ratio 51.8%and 11.5 wt%coke),while the iodine value of product slightly reduced from 137.5 g(I2)/100g to 134.5 g(I2)/100g and the hydroxyl value slightly increased from 13.1 mg(KOIH)/g to 16.5 mg(KOH)/g over NaHSO4/MCM-41-SUP(S element leaching ratio 10.9%and 4.7 wt%coke).