Application Of Micro-meso Hierarchical Porous Carbon For VOCs Adsorption Treatment

As the pillar of national economy,petrochemical industry provides indispensable petroleum and chemical products.However,the rapid development of petrochemical industry has also brought serious environmental problems.Organic waste gases emitted from petrochemical industry can cause severe air pollution even at low concentration,thus it is significant to solve the problems caused by organic waste gases.Significant scientific and technological efforts have been dedicated regarding organic compounds removal.The most extensively used method is adsorption.Therefore,it is imperative to develop effective adsorbents.In this paper,template synthesis technique is used to obtain micro-meso hierarchical porous carbon as adsorbents for toluene.Synthesis.The synthesis is performed using mesoporous molecular sieve MCM-41 as template,sucrose?MC-1??furfuryl alcohol?MC-2?and phenolic resin?MC-3?as carbon source,respectively.Characterization.The morphologies of the samples are observed by SEM.The samples are observed by TEM.And the surface areas are calculated through the BET method.Toluene adsorption properties on micro-meso hierarchical porous carbon are studied.And effects of toluene initial concentration,temperature and bed height on adsorption capacity are also researched.The carbon material MC-1 was modified by nitric acid.And the effects of nitric acid concentrate,modification temperature and time on the adsorption properties of MC-1 are discussed.The optimal modification conditions are studied by orthogonal test according to the results of single factor experiments.The modified micro-meso hierarchical porous carbon is characterized by SEM?TEM?BET?FI-IR.And the relationship between carbon pore structure and toluene adsorption amount is analyzed.The conclusions obtained from the experiment are as follows:The specific area and average volume of MC-1 are 1052.44 m²·g^-1 and 0.52cm³·g^-1,respectively.The equilibrium adsorption amount by MC-1 was 185.30mg·g^-1,when the toluene concentration is 1750 mg·m^-3,adsorption temperature is 25?,bed height is 10 mm,and gas speed is 200 mL·min^-1.The specific area of MC-2 is 754.84 m²·g^-1.And the average volume is 0.41 cm³·g^-1.Under the same adsorption condition,the equilibrium adsorption amount of toluene is only108.56 mg·g^-1.Under the same adsorption condition,equilibrium amount of toluene adsorbed is 358.8mg·g^-1 by MC-3.And the specific area and average volume of MC-3 are 859.82 m²·g^-1 and0.43 cm³·g^-1,respectively.The adsorption isotherms of toluene can fit both Langmuir Isotherm and Freundlich Equation.For the R² of Langmuir Equation are larger,adsorption isotherms of toluene on carbon fit Langmuir Isotherm better.The results of single factor experiments showed that,the optimal nitric acid concentrate?temperature and modification time are 20%?60?and 12 h,respectively.The optimal modification conditions are studied by orthogonal test according to the results of single factor experiments.And the results are nitric acid concentrate 20%,modification time 16 h and temperature 60?,the adsorption value of toluene is 0.687 g·g^-1.The effect of total surface area?micropore surface area?pore volume and micropore surface area on toluene adsorption amount is studied.The results showed that toluene adsorption amount is closely related to the four factors.And large surface area,large volume of narrow microporosity and proper average pore size are the desired parameters to achieve strong toluene adsorption capacities.