Optimization Of Fixed-bed Reactor For Ethylene Oxidation

In this thesis we can get main information about production of ethylene oxide,importance in our live and in industry.Ethylene and oxygen reacts over a silver catalyst surface.Mainly two reactions occurring in the process,partial oxidation of ethylene to ethylene oxide and total oxidation of ethylene to carbon dioxide and water.The largest economic cost in production of ethylene oxide is ethylene therefore it's important to optimize the selectivity towards ethylene oxide and thus reduce the consumption of ethylene.The aim with this thesis to create a mathematical model of the fixed-bed reactor using MATLAB that correlates with more useful assumptions.This model is then going to be a tool for future investigations of reform of best condition of reactor.Initially a literature study was made to increase the understanding of the chemical substance present and the mechanism in the reactor.Part of this project is to find a two dimensional pseudo-homogeneous and heterogeneous models that correlate with the system.Based on the literature study an equation of state model,K.R.Westerterp and K.J.Ptasinski were studied reactor model with to parallel reactions.Multiple studies have been done to discover the kinetics of the oxidation reactions of ethylene over a silver catalyst.There has been no general agreement among the kinetics equations and mechanisms described.It is agreed that silver can adsorb oxygen in a number of ways and that this phenomenon is the basis of silver's efficiency in catalyzing the oxidation of ethylene to ethylene oxide.The modeling was divided in two types of reactor condition,start of adiabatic reactor modeling,second of isothermal reactor modeling.The selectivity and activity decreases over time and the reason is increasing of the temperature that occurs due to inlet of the reactor.At the same time the selectivity for producing ethylene oxide decreases.In the processes,the solid catalyst loses activity over a period of operation time due to impurities in the feed and sintering of the catalyst.The operating temperature in the reactor is increased to compensate for the loss of activity,but an increased operating temperature favor the complete oxidation over the partial oxidation of ethylene and thus decreases the selectivity of the desired product by producing more byproducts(carbon dioxide and water).Therefore,there is a need for the optimization of the reactor operating temperature profile over the length of the operation that will improve the selectivity of the desired product thus maximizing the profitability of the process.