Study On The Interfacial Catalytic Oxidation Of Benzyl Alcohol Based On Pickering Emulsion In Microchannel Reactor

Microchannel reactor has been widely used in fine chemicals,medicine,and other fields,as its high heat and mass transfer efficiency,intrinsic safety,narrow distribution of reaction residence time,etc.Solid catalysis has been involved in many current reaction processes.However,solid catalyst particles are prone to fouling and clogging issues inside microchannels,which seriously hinders the application of microchannel reactors in the field of solid catalytic reaction processes.In this paper,a continuous flow process for the Pickering emulsion to enhance the liquid-phase oxidation of benzyl alcohol in a microchannel reactor is developed,which is based on the irreversible adsorption of solid particles at the oil-water interface in Pickering emulsions.The issues of particle adhesion and blockage caused by direct contact between solid particles and channel walls during flow are effectively avoided through using this approach.The main research contents are as follows:Firstly,the factors affecting the stability of Pickering emulsions were studied,and suitable preparation conditions of benzyl alcohol-water Pickering emulsions were selected through experiments.The results showed that the amount of silane coupling agent,catalyst particle addition amount,and dispersed phase volume all have an effect on the stability of Pickering emulsions.On this basis,Pd/Si O₂ particles modified with the optimal amount of silane coupling agent were selected as emulsifiers,and stable W/O type and O/W type Pickering emulsions were successfully prepared using benzyl alcohol as the oil phase.Secondly,the liquid-phase oxidation process of benzyl alcohol enhanced by Pickering emulsion in microchannel reactors was investigated.It was found that O/W-type Pickering systems were superior to W/O-type,and a model for the change in droplet diameter during the O/W emulsion reaction process was constructed.The effects of a series of operating parameters on the reaction were explored,including temperature,CB,dispersed phase volume,tube length,total volumetric flow rate,gas-liquid two-phase volumetric flow rate ratio,tube internal diameter,and pressure.The results show that the optimal temperature was 403 K,CB was 5 wt%,O₂/BNOH was 0.76,and the reaction tube length was 8 m,the reaction conversion was 86.53%and reaction selectivity was 99.79%.Under this condition,the effect of total flow rate on the reaction is negligible.In the case of the CB fixed,the effects of varying solid particle addition and dispersed phase volume on the reaction were identical.Reducing the microchannel diameter can enhance mixing inside the liquid phase and diffusion at the gas-liquid two-phase interface,thereby increasing the reaction rate.Finally,the mass transfer mechanism in the Pickering emulsion enhanced liquid-phase oxidation of benzyl alcohol in microchannels was discussed,and the influence of various factors on the mass transfer process was analyzed.The apparent kinetics model for the reaction was established,and it was found that the model predictions are in good agreement with the experimental results.