Study Of The Process And Mechanism Of Alkylation Reaction With Toluene And Methanol In Hydrodynamic Cavitation Field

The alkylation of toluene with methanol is an important process route for preparing paraxylene.At present,the demand for paraxylene is greater than that for toluene and methanol,and the relative production of toluene and methanol is excessive.Therefore,the conversion of the two to high-value-added aromatic chemicals such as PX has become a focus of attention in the petrochemical and coal chemical industries.In this paper,toluene and methanol are used as the research system,and then the alkylation reaction of toluene and methanol is carried out under the enhancement of hydrodynamic cavitation field.The contents of the study are as follows:First of all,the CFD flow field simulation of the inclined hole plate cavitation reactor of the core device of this experiment was performed to obtain the distribution cloud diagrams such as pressure,flow velocity,vaporization rate,and turbulent kinetic energy.The results show that when the liquid flows through the orifice,the pressure gradually decreases to negative pressure,which is lower than the saturated vapor pressure of the liquid.Based on the principle of hydrodynamics and some simulation results,the design of hydrodynamic cavitation experimental device and the selection of instrumentation were carried out,and the installation of the device was completed.The methyl violet fading experiment was chosen to verify the reliability of the device.After cavitation,the methyl violet coloration was evident,indicating that the cavitation effect of the device was good.And comparing the flow rate under different pressures through the flowmeter measurement and simulation results,the relative error of the two is within5%,which proves the reliability of the device again.Then,the alkylation process of toluene with methanol was deduced.Toluene dissociated as phenyl and methyl,and methanol dissociated into methyl and hydroxyl groups.Phenols reacted with hydroxyl groups to produce phenol.At the same time,toluene reacted with the remaining methyl to form xylene.Dimethylbenzene reacted with free radical hydrogen radicals to produce corresponding two methyl cyclohexane.Hydroxyl radical and hydrogen free radical generated into water.Under the enhancement of hydrodynamic cavitation,toluene and methanol reacted to form two methyl cyclohexane,ethyl cyclohexane,ethylbenzene,p-xylene and o-xylene.No xylene generation was explained according to product distribution and Materials studio.The formation of phenol and water was proved through Carle Fischer and UV full wavelength scanning.Then the process conditions of hydraulic cavitation were optimized.The effects of reaction temperature,inlet pressure,cavitation times and toluene addition on the selectivity of products and the conversion of toluene to methanol were investigated.The results showed that when the inlet pressure was 0.5MPa,the final reaction temperature was 45,the number of cavitation was about 168 times,and the toluene amount was 37.5%,the conversion of toluene methanol reached the maximum,36.57 and 15.43%,respectively.Finally,we choose different separation methods according to the boiling point of each product,and simple separation steps were composed.The dimethylcyclohexane and phenol were separated by ordinary distillation and the salt extraction distillation.Then,the separation of ethyl cyclohexane with o-xylene was separated by a partition rectification unit.In addiotion,different adsorbents were selected to separate the dimethylbenzene and ethylbenzene.