Study On The Preparation And Adsorption Properties Of Activated Carbon Paper Based Adsorption Composites

With improvement of residents'living standards,air quality regulations have become increasingly strict.In order to control vehicle emission,China has issued more stringent emission limits.The hydrocarbon emission limits for vehicles have been tightened by 65%among the sixth national emission standards of vehicles.The development of vehicle activated carbon fiber paper is mainly aimed at the hydrocarbon evaporation emission control of the air intake system of light vehicles,and its dynamic adsorption performance to hydrocarbons is the essential performance.Suitable pore structure is the key to the excellent adsorption performance of activated carbon fiber paper for hydrocarbons.Many researchers have investigated the adsorption of related adsorbate by a large number of activated carbon raw materials with different pore structures,but there is a lack of in-depth and systematic research on the adsorption performance and adsorption behavior of activated carbon products to hydrocarbons.On the basis of a large number of pre-experiments,this paper first built a hydrocarbon adsorption test system which can characterize the dynamic adsorption properties of activated carbon fiber paper for hydrocarbons.Then we made a series of activated carbon paper and sisal-based activated carbon fiber paper,which were used to characterize the dynamic adsorption properties for n-butane,a representative gas of hydrocarbons.The effects of papermaking process,carbonization activation process and secondary activation process on the pore structure and adsorption properties of activated carbon paper based composites were studied.The properties of the self-made activated carbon paper based adsorption composites are similar to those of the expensive monopoly products abroad,and the import substitution was realized.Then,the adsorption behavior of n-butane gas on activated carbon paper-based adsorption composites was discussed to guide the understanding and application of dynamic adsorption performance.The main contents and results of this paper are as follows:(1)With reference to several foreign advanced adsorption test standards,the hydrocarbon adsorption test system was built and the corresponding test steps for n-butane adsorption were established.The accuracy of the test system was verified by the deviation analysis,and the environmental conditions of the test were determined.The relative deviation between the measured adsorption rate and the saturated adsorption capacity was less than 10%.R-Squared and applicability of Thomas models and Yoon-Nelson models were studied.(2)The effects of beating degree,retention aid and reinforcing resin on the preparation of powdered activated carbon paper were systematically studied.The optimum preparation process of powdered activated carbon paper was determined based on the experimental data.BET adsorption model,t-plot Method and H-K theory were used to analyze the pore structure of three kinds of powder activated carbon.Compared with their dynamic adsorption properties for n-butane,it was found that powdered activated carbon 3#PAC with both microporous and mesoporous was more suitable for n-butane adsorption than microporous powdered activated carbon 1#PAC and mesoporous powdered activated carbon 2#PAC.(3)The thermal stabilization mechanism of diammonium hydrogen phosphate on sisal paper was analyzed by FTIR and TGA.The comprehensive yield and SEM diagram analysis showed that the thermal stabilization effect of diammonium hydrogen phosphate was remarkable when sisal-based activated carbon fiber papers were activated with phosphoric acid and carbon dioxide and zinc chloride.The activation mechanism of carbon dioxide and zinc chloride and the different pore forming effects of different activation processes on sisal fiber were analyzed.Then we discussed the influence of activation temperature of CO₂and concentration of zinc chloride on the intensity of activation reaction.(4)Sisal-based activated carbon fiber paper was prepared by secondary activation method,and its pore structure was observed by SEM and TEM.The BET specific surface area of the paper is 1482.03 m²·g^-1,and the dynamic adsorption performance of n-butane was better than the self-made powdered activated carbon paper,especially the adsorption rate was nearly three times that of self-made powdered activated carbon paper.Compared with commercial activated carbon paper ACS-310X,its adsorption rate and adsorption attenuation rate are also more competitive.It was found that the surface of the reactivated sisal-based activated carbon fiber paper was uneven,there were many nanoscale grooves and scratches,which proved the micropore structure in the material is well developed.(5)The adsorption behavior of n-butane on powdered activated carbon paper and sisal-based activated carbon fiber paper was analyzed and discussed using Weber-Morris intra-particle diffusion model.And the dynamic adsorption properties of powdered activated carbon paper and sisal-based activated carbon fiber paper were analyzed by Clark dynamic adsorption model.It was judged that a large number of micropores of sisal-based activated carbon fiber paper are distributed on the outer surface.Moreover,due to the high proportion of effective microporous adsorption sites for n-butane,the overall dynamic adsorption strength of sisal-based activated carbon fiber paper for n-butane was greater than the powdered activated carbon paper.