(58f) Reactor Performance Assessment Using Experimental Studies and Multiscale Modeling: Liquid Phase Ethylene Production By Hydrogenation of Acetylene

Trickle bed and two-phase upflow packed bed reactors have found extensive applications in petroleum, petrochemical, chemical and environmental industries especially for processes involving complex mechanisms. Assessing the reactor performance for these reactors needs extensive experimentation complemented by validation by a reliable mathematical model at different scales. Various factors like incomplete catalyst wetting, liquid maldistribution, interphase mass transfer, intraparticle diffusion are necessary to predict the reactor performance. Moreover, accounting the variation in the overall effectiveness factor across the reactor axis due to the change in the local reactant concentrations is also significant. A one-dimensional mathematical axial dispersion flow model integrated with a pellet scale model has been developed. The kinetics and the related parameters involved in the processes were accounted in the model along with different particle to liquid wetting conditions and correlations. The model was validated using different experimental studies at a range of operating conditions from literature. The hydrogenation of acetylene in the liquid phase for ethylene production will be considered as the model reaction to assess the reactor performance and help in obtaining meaningful scaleup parameters. Gas phase catalytic hydrogenation of acetylene to produce ethylene is commonly practiced in industries to increase the ethylene yield from the cracker. This process has green oil formation which leads to catalyst deactivation and sometimes reactor runaway risks. To overcome this issue as well as to increase the selectivity and conversion liquid phase hydrogenation is under current research. The catalyst life and stability increases by reducing the green oil formation. The solvent (liquid) selectively absorbs acetylene from the cracked effluent, and this liquid phase improves heat transfer in the reactor. The kinetics studies were investigated in a stirred tank reactor in both slurry and basket modes with liquid in batch and gas as continuous using a Pd/Al₂O₃ catalyst . N-Methyl Pyrrolidone (NMP), a polar solvent, was used as the liquid phase. The reaction was conducted at a pressure of 250 psig and temperatures ranging between 60-120^oC. In order to estimate the kinetic parameters, a model was developed based on Langmuir-Hinshelwood-Hougen-Watson approach. The dispersion parameter and liquid holdup obtained from the residence time distribution studies by conducting cold flow experiments using a liquid tracer will be integrated into the model. At Multiphase Flows and Reactors Engineering and Applications laboratory (mFReal), a high-pressure, high temperature unit has been built to conduct sensitive reaction experiments. This unit is equipped with a blast shield and has laboratory scale reactors with thermowell and gas-liquid distributors. The unit will be tested for selected operating conditions for the acetylene hydrogenation in the liquid phase to demonstrate the safe experimentation as well as improving the conversion of the process. The experimental data will be validated using the developed multiscale model to assess the reactor performance and further optimize the operating parameters, process time and number of trials.