Design And Optimization Of Toluene Liquid Phase Reaction System

Selective oxidation of liquid phase toluene to prepare high value-added products is important,such as benzyl alcohol,benzaldehyde,benzoic acid and benzyl benzoate.It is significant because not only obtaining huge economic benefits,but also solving the problem of excessive toluene production capacity.Here,we designed a liquid phase reaction system to improve the catalytic performance of selective oxidation of toluene.A photothermal catalytic autoclave was designed,and TiO₂-based catalytic materials were synthesized,which will be used in the reaction system.Our results confirmed that this reaction system met the requirements of clean production.?1?We put a sapphire window on the top of autoclave as a light-transmissive window,which is applicable to high-temperature and high-pressure.A xenon lamp was used as light source in the photo-thermal catalytic autoclave.The sampling device was connected with a detachable tube and this tube can reach to the bottom of autoclave.Thus,this sampling device can sample both gas products and liquid products.The autoclave is applicable to thermalcatalytic,photocatalytic and photothermal catalytic selective oxidation of toluene.?2?The effect of reaction time,temperature,excitation light wavelength,and the amount of catalyst on the catalytic performance of selective oxidation of toluene has been studied.It is indicated that the best catalytic performance can be obtained in 30 hours,160°C,illumination with 200-800nm,and using 100mg catalysts.?3?Nitrogen-doped TiO₂?N-TiO₂?and boron-doped TiO₂?B-TiO₂?catalysts were synthesized by grinding methods and were used for selective oxidation of toluene in our designed reaction system.The N-TiO₂-1.5?1.5 represented the mass ratio of urea and TiO₂?catalyst showed the best catalytic performance.The selectivity of high value-added products including benzyl alcohol,benzaldehyde,benzoic acid and benzyl benzoate under photothermal conditions was 84.3%,and the product yield was 109mmol?g^-1_cat.?4?The TiO₂?001?catalyst with high percents of?001?crystal plane was successfully synthesized by hydrothermal method.The ratio of the?001?crystal plane increased could significantly improve the selectivity and yield of benzyl benzoate.Compared to TiO₂,the selectivity of benzyl benzoate over TiO₂?001?catalyst under thermocatalytic conditions increased from 0.9%to 24.5%,and the yield increased from 0.3mmol?g^-1_cat to 52 mmol?g^-1_cat.Under photothermal conditions,the selectivity of benzyl benzoate increased from 1.0%to20.7%,and the yield increased from 2mmol?g^-1_cat to 56mmol?g^-1_cat.In summary,we have successfully designed a liquid phase reaction system for selective oxidation of toluene.The experimental parameters and the catalyst have been optimized to obtain the high yield of high value-added products including benzyl alcohol,benzaldehyde,benzoic acid and benzyl benzoate.This reaction system will be helpful for the clean production technology.