Study On Purification Of Toluene Based On High Gravity Coupled Adsorption And Catalytic Combustion

VOCs(Volatile Organic Compounds)seriously endanger human health and the living environment in the fields of petrochemical,coal chemical,and daily life.It not only causes discomfort to the human body,but also easily participates in chemical reactions to produce secondary pollution such as smoke and ozone.The purification of VOCs has become a research hotspot,which is closely related to environmental protection and safe and stable production.The increasingly harsh ecological environment,people's awareness of environmental protection and requirements,the rapid development of the coating automotive industry,and the extensive use of industrial organic sources all put forward better requirements for the purification of VOCs.The Ministry of Environmental Protection,the National Development and Reform Commission and other agencies jointly formulated the"13th Five-Year Plan for the Prevention and Control of Volatile Organic Pollutants",which should comprehensively strengthen the prevention and control of volatile organic pollutants and promote the continuous improvement of ambient air quality.Among the many methods for purifying VOCs,adsorption and catalytic combustion are widely used due to their high purification degree,simple operation,low investment and operating costs,and no secondary pollution.The common equipment for adsorption is a fixed bed,which has the disadvantages of low adsorption and desorption efficiency,limited service life of the adsorbent and low utilization rate.The core of the catalytic combustion method is a catalyst,and the catalyst prepared by the conventional impregnation method has the disadvantage of low active component loading,poor dispersibility and reproducibility.It is of great significance to seek for the absorption and desorption of mass transfer efficiency and the preparation of catalyst performance and technology to prolong the service life of adsorbents and catalysts and improve the purification rate of VOCs.In this paper,a high gravity coupled adsorption and catalytic combustion method and a new process for purifying VOCs was developed,which expanded the application field of high gravity technology.The high gravity technology has carried out extensive research on gas-liquid and liquid-liquid and has shown good mass transfer effects.However,it is still in the exploration stage in terms of gas-solid and liquid-solid.The high gravity rotating adsorption bed and the high gravity rotary impregnation equipment were developed to study the adsorption and catalytic combustion properties of toluene,and scientifically revealed the mechanism of action of the high gravity technology in gas-solid and liquid-solid.The high gravity adsorption technology can achieve rapid absorption and desorption,prolonged life of the adsorbent,and energy saving.The high gravity catalyst preparation technology effectively increases the catalyst loading and maintains good dispersibility,and has broad application potential.The high gravity rotating adsorption bed is used as the adsorption and desorption equipment,the activated carbon is the adsorbent,and the toluene is the adsorbate.The adsorption and desorption properties are studied under the condition of 0-50m~3/h treatment gas volume,and the adsorption and desorption effect of fixed bed and rotating bed is compared.The results show that the saturated adsorption capacity,adsorption rate,adsorption site and bed utilization of the rotating bed are higher than that of the fixed bed and exhibit excellent adsorption performance under the same working conditions.The Weber-Morris particle diffusion model shows that the adsorption of the rotating bed is divided into three processes:surface adsorption,intraparticle diffusion and adsorption equilibrium.The contribution rate of intraparticle diffusion is the largest.Compared with the fixed bed,the rotating bed can effectively realize deep pore adsorption and improve the utilization of activated carbon.The adsorption performance of the rotating bed is related to the operating conditions.High gravity factor,medium to low inlet toluene concentration,suitable inlet flow rate and bed thickness are beneficial to the increase of adsorption capacity and bed utilization.The saturated carbon was used as the experimental system to compare the desorption effect of fixed bed and rotating bed under the same working conditions.Through the desorption curve,it can be seen that the rotating bed has a higher desorption rate and a faster desorption rate,which can realize deep regeneration of saturated activated carbon and prolong the service life of the activated carbon.At the same time,the desorption performance of temperature and high gravity factor on saturated activated carbon was investigated.The temperature was the key factor of desorption.The larger the high gravity factor,the better the desorption effect.The desorption of activated carbon by rotating bed showed better adsorption performance.Desorption technology provides a new way of thinking.In order to further improve the adsorption performance of activated carbon,a high gravity alkali-modified activated carbon adsorption toluene process was developed.Through the modification of activated carbon infrared,pore structure and functional group content,the adsorption of toluene by high gravity modification and traditional stirring modification was investigated.The results showed that the content of basic functional groups on the surface of activated carbon modified by high gravity method was improved,and the alkaline material did not form an entrapped pore structure on the surface of activated carbon.The adsorption energy of high gravity modified activated carbon is higher than that of traditional stirring and effective adsorption of chemical adsorption in the same concentration of alkali solution.It is known from the adsorption model to analyze the adsorption mechanism that the adsorption of toluene by activated carbon by high gravity method belongs to the monolayer adsorption dominated by microporous adsorption,and the adsorption performance is improved by promoting chemical adsorption.Compared with the adsorption performance of modified gravity activated carbon in rotating bed and fixed bed,the adsorption performance of rotating bed is better than that of fixed bed.The process of preparing composite transition metal catalyst by high gravity method was developed to overcome the disadvantages of low loading of metal catalyst and poor dispersion of metal oxide by traditional impregnation method,combined with the characteristics of high mass transfer efficiency and uniform liquid dispersion.It not only solves the problem that the precious metal is easy to sinter and has high cost,but also effectively enhances the catalytic activity of the catalyst.The results show that the surface active metal oxide dispersion of the composite metal catalyst prepared by the high gravity method is uniform and agglomerated,and the loading is large.The amount of load increases as the rotational speed of the rotating bed increases,and increases first and then decreases as the flow rate of the active component increases.The composite metal catalyst exhibits a good catalytic activity than the single component,which is attributed to the synergy between Cu/Mn,which provides a lot of adsorbed oxygen,thereby improving the catalytic activity.Compared with the traditional impregnation method,the catalyst prepared by the high gravity method maintains the porous pore structure of the carrier,and the active component does not block the pores,and the carrier surface and the pores exist in the form of a uniform supported membrane.This paper opens up a new method for the preparation of catalytic combustion VOCs,which effectively solves the problems of low activity and poor reproducibility of traditional catalysts.The composite metal catalyst was prepared by high gravity method,and its catalytic combustion toluene performance was studied.The results show that the composite metal catalyst prepared by the same molar ratio of high gravity exhibits low temperature catalytic combustion performance.Catalytic combustion toluene kinetics results show that the catalyst prepared by the high gravity method has a high oxidation rate,which is derived from the higher loading and good dispersibility of the catalyst,and provides more adsorption sites and active sites for catalytic oxidation.The catalyst prepared by the high gravity method achieved low-temperature catalytic combustion performance,and maintained good and stable catalytic performance after 600 min.The research work provides a high-performance,low-cost catalyst preparation process to expand the application range of overweight machine technology.In summary,the high gravity equipment and adsorption and catalytic combustion processes are proposed in this paper.New techniques for coupled gravity adsorption and catalytic combustion of VOCs have been developed and explored basic research theories.The application range of the high gravity process strengthening technology has been expanded to provide an efficient,energy-saving and environmentally friendly process for purifying VOCs.