Study On Catalytic Characteristics Of Three Way Catalyst Based On Detailed Mechanism

Civil vehicles account for a large proportion of fossil energy consumption,which causes a certain pressure on environmental protection and energy iteration.Especially in urban environment,vehicle exhaust emission has become one of the biggest pollution sources.In order to protect the environment and respond to the increasing national emission standards,it is necessary to further improve the catalytic efficiency of three-way catalytic converters.Three way catalyst is a special catalytic purification device for hydrocarbon,carbon monoxide and nitrogen oxide in exhaust gas of gasoline internal combustion engine.The catalyst loaded on it can promote the oxidation-reduction reaction of the above pollutants to produce harmless carbon dioxide,water and nitrogen.According to the current research direction of three-way catalyst,this paper mainly studies the following problems:（1）At present,the widely used detailed catalytic reaction kinetic model has some limitations;The mainstream reaction mechanism uses C₃H₆ instead of all HC, neglecting propane,ethylene,acetylene,methane and other important components,which can not accurately describe the reaction path under dynamic catalytic reaction conditions;The existing reaction models only focus on HC,CO and no,which are not scalable.As an important alternative fuel for engine,hydrogen will inevitably affect the catalytic reaction in the catalyst.（2）The complexity of engine operating conditions leads to dynamic changes of exhaust temperature,speed and pressure.Therefore,it is an important direction to study the effect of different exhaust conditions on the catalytic performance of the catalyst.（3）The engine exhaust component concentration will be greatly affected by engine speed,load and fuel composition.The existing research of catalyst model mainly focuses on the influence of oxygen concentration on the overall catalytic performance,and the influence of hydrogen and other substances in the exhaust gas on the overall catalytic performance is also one of the research focuses.In view of the above problems,the main research work and innovation of this paper are as follows:（1）In order to solve the above problems,a new detailed kinetic model of catalytic reaction was established by adding more detailed entrance components and elementary reactions,such as propane cracking,Ethane Adsorption and desorption,and hydrogen catalytic reaction on Pt surface,The model can accurately describe both the traditional three-way catalytic reaction process and the catalytic reaction process under the condition of rich hydrogen.（2）In order to study the influence of different inlet gas temperature,velocity and pressure on catalytic reaction.One dimensional model was used to couple the new catalytic reaction mechanism,and the catalytic reaction characteristics under different steady-state inlet conditions were analyzed,which simplified the complexity of dynamic inlet conditions.（3）A two-dimensional model coupled with a new catalytic reaction mechanism is used to analyze the catalytic reaction characteristics under different component inlet conditions,and the influence of gas component diffusion on the catalytic process can also be studied to a certain extent.Using this model,we mainly study the influence of oxygen and hydrogen enrichment on the catalytic reaction,and further explore the effect of wall temperature on the catalytic efficiency.According to the simulation results,we analyze the catalytic law under the conditions of oxygen and hydrogen enrichment,and make theoretical research for improving the catalytic efficiency and expanding the adaptability of existing catalysts.The catalytic reaction in the catalyst is a complex dynamic process,and the inlet conditions such as inlet temperature,pressure,flow rate and component concentration,as well as the external conditions such as catalyst structure,catalyst life,mechanical vibration and impact will affect the catalytic effect.In this paper,the steady-state flow and structure simulation are simplified to explore the universality and general rules of existing commercial catalysts.