Optimisation Of The Reaction Process For Photocatalytic Reduction Of Carbon Dioxide

Currently,simulating photosynthesis in plants using solar energy to convert carbon dioxide into high value-added chemicals is an effective method to address the issues of greenhouse gas emissions and energy crisis.Improving the solar energy utilization efficiency and catalytic efficiency is the primary task of current research in photocatalysis technology,and the photocatalytic reaction environment plays an important role in the reaction efficiency and product selectivity.In this study,we first reviewed the current photocatalytic reaction environments,and analyzed the material transfer process of gas-liquid-solid and gas-solid photocatalytic environments to identify the main mass transfer resistance process.Subsequently,we improved the reaction activity of photocatalytic reduction of carbon dioxide by intrinsic reaction study,diffusion process enhancement,fluid simulation optimization and novel membrane reactor environment,achieving the following specific results:Using titanium dioxide as a catalyst,we investigated the effects of catalyst type,light source and sacrificial reagent on the intrinsic reaction of photocatalytic reduction.The results showed that P25 titanium dioxide,254 nm wavelength ultraviolet light and 6.81m W·cm^-2light irradiance produced a carbon monoxide yield of 28.69μmol·g^-1.Adding anhydrous sodium sulfate as a sacrificial reagent increased the carbon monoxide yield by1.8 times.After adding triethylamine as a sacrificial reagent,the formaldehyde yield was11.8μmol·g^-1.Under the conditions of intrinsic reaction,the effects of catalyst mass,reaction temperature,and stirring rate on diffusion processes were investigated,and response surface methodology was used for optimization.The results indicated that the optimum conditions for carbon monoxide production were 115 mg of catalyst mass,40.5°C reaction temperature,and stirring at 1000 rpm with a cross-shaped impeller,resulting in a CO generation rate of 32.62μmol·g^-1.The FLUENT computational fluid dynamics software was utilized to simulate the gas-liquid-solid reaction mode and assess the impact of fluid flow on transport processes.A fan-shaped rotor was proposed to counteract the high diameter-to-height ratio of the reactor.The results suggested that the rotor shape was a crucial factor in catalyst dispersion and that the fan-shaped rotor could significantly enhance dispersion without having to increase the speed.In light of the mass transfer characteristics of the CO₂photocatalytic reaction,a membrane-like reaction mode was proposed and tested in a reactive environment.Compared to the gas-liquid-solid suspension agitation reaction,the membrane-like reaction mode could significantly decrease energy consumption while enhancing mass transport.Response surface methodology was employed to optimize catalyst mass,gas flow rate,and reaction temperature.The highest CO generation rate obtained was 37.86μmol·g^-1at 111 mg catalyst mass,19.2°C reaction temperature,and 14.3 m L·min^-1gas flow rate,representing a 16%increase.