Study On Kinetic Model And Mechanism Of Coke Formation In Catalytic Conversion Of Biomass Pyrolysis Derivates

In modern society with fossil fuel depletion and ecological environment deterioration, countries around the world pay high attention to the development and utilization of clean and renewable energy. Due to widely distributed, abundant, less pollution, zero carbon dioxide emissions, and the exclusive organic carbon source, biomass energy is expected to provide petroleum products to partly replace petroleum as feedstock in the future.Catalytic pyrolysis of biomass is regarded as the most effective technology to produce high quality liquid fuels and chemicals, while it is confined because of high coke deposition and catalyst deactivation which lead to the low yields and selectivity of products. Therefore, it is necessary to study the behavior of coke formation to reduce coke formation in catalytic conversion of biomass derivates.The catalytic conversion of biomass pyrolysis derivates is a complex reaction process. In order to study the reaction mechanism of different oxygen-containing functional groups, furfural and guaiacol were selected as model compounds to study the coke formation using a fixed-bed reactor. The effects of temperature, weight hourly space velocity and partial pressure on the yield and the selectivity of products were investigated. Temperature has a significant influence on the product distribution. Based on the product distribution in the catalytic conversion of model compounds, the possible catalytic reaction pathway was speculated to explain the formation of the products. A kinetic model of coke formation was set up which related the coke amount to the main operation parameters which can be used to estimate the coke amount on catalyst in reaction process.The coked catalysts with different reaction time were characterized by thermogravimetric analysis, nitrogen isotherml adsorption-desorption, programmed desorption of ammonia. X-ray diffraction and scanning electron microscop to study the mechanism of coke formation.The results indicated that due to a large amount of acid sites were exposed on the catalyst in initial stage, the rate of coke deposition was quick and most of acid sites were coverd by coke. The surface area and pore volume of catalyst were decreased rapidly. In the late stage, the amount of coke increased slowly and the species of coke transformed to polycyclic aromatic hydrocarbons.The feed and product in catalytic conversion of biomass derivates were divided into six virtual assemblies by using the lumped method. The reaction conditions including temperature, WHSV, partial pressure, reaction time and coke effect on the catalytic activity were researched, lumped kinetic model has been built considering catalyst deactivation caused by coke. The kinetic parameters of the model were calculated through mathematical simulation and reliability of the model has been analyzed. The calculated data has a good agreement with the experimental data, and the average relative errors are below 15%.