Gas-solid Reactive Adsorption Of Typical Benzene Compounds By MCM-41-supported Sulfuric Acid

Volatile organic compounds（VOCs）are emitted from industrial processes such as fossil fuel combustion,petrochemical industry,coatings,and printing,and pose serious threats to the atmospheric environment and human health.The purification and elimination of VOCs have received widespread attention worldwide.The currently used adsorption purification methods are mainly based on the physical adsorption mechanism of porous adsorbents,which have strict requirements for temperature,pressure,humidity conditions,and regeneration performance,limiting their wider application.The author’s research group has previously demonstrated that solid-supported sulfuric acid can effectively remove gaseous o-xylene through surface sulfonation reaction and proposed that the process follows a reactive adsorption mechanism.This method is a new resource chemical adsorption treatment method that overcomes the limitations of traditional physical adsorption methods.However,the removal performance,process kinetics behavior,and mechanism of other benzene series molecules using this method are still unclear.Therefore,this paper uses MCM-41-supported sulfuric acid as the adsorbent material to study the adsorption performance and behavior of the reactive adsorption method on three typical substituted benzene compounds（cumene,anisole and chlorobenzene）,and reveal the relevant adsorption mechanism,providing experimental and theoretical basis for the development of resourceful VOCs treatment technology.The main research content and results of this paper are as follows:1.Reactive adsorption of gaseous cumene on MCM-41 supported sulfuric acidMCM-41-supported sulfuric acid（SSA/MCM-41）adsorbent was prepared by wet impregnation of MCM-41 with sulfuric acid.The effects of adsorption reaction temperature（T）,inlet concentration(C_in),bed height（h）,and flow rate（V_g）on cumene adsorption were studied through dynamic adsorption experiments.Characterization techniques such as low-temperature nitrogen gas adsorption/desorption isotherms（N₂-BET）,Fourier transform infrared spectroscopy（FTIR）,scanning electron microscopy（SEM）with cold field emission,energy-dispersive X-ray spectroscopy（EDS）,and nuclear magnetic resonance spectroscopy(¹H/¹³C NMR)were used to analyze SSA/MCM-41 and its adsorption products.The results indicated that the cumene adsorption rate of SSA/MCM-41 versus temperature curve exhibited a"U-shaped"trend,with the optimal adsorption temperature range being 120-170℃.Rising the bed height or reducing the flow rate enhanced the adsorption performance metrics,such as breakthrough time（t _B）and breakthrough adsorption capacity（Q_B）,whereas increasing the inlet concentration resulted in t _B shortening and Q_B rising.As demonstrated in this paper,the highest t _B and Q_B were 69.81 min and 316.73 mg g^-1,respectively.After four cycles of adsorption/desorption/reloading,the t _B and Q_B of cumene remained at 20.86 min and 201.77mg g^-1,which were 84.51%and 90.45%of the initial values,respectively,indicating that MCM-41,as a carrier for supported sulfuric acid,had excellent cyclic stability.The main adsorption product was identified as 4-isopropylbenzenesulfonic acid,and the byproduct was identified as4,4′-sulfonyl bis（isopropyl-benzene）through separation and purification of the adsorption products.2.Theoretical simulation of the dynamic adsorption behavior of cumene on SSA/MCM-41The penetration curves of cumene under different h,V_g,and C_in were simulated and processed using Yoon-Nelson models,Thomas models,and Dose-response models,and the corresponding model parameters and theoretical breakthrough adsorption indicators(theoretical breakthrough time(t _B,th)and theoretical adsorption capacity(Q_B,th))were obtained.The results indicated that the Dose-response model was the best fitting model for the SSA/MCM-41/cumene reactive adsorption,and the maximum t _B,th and Q_B,th predicted by the model were 69.60 min and 324.50 mg g^-1,respectively.Increasing the bed height and decreasing the flow rate appropriately can improve the adsorption performance of SSA/MCM-41 for cumene.3.Reactive adsorption of gaseous anisole on SSA/MCM-41This section investigated the dynamic adsorption penetration behavior of anisole on an SSA/MCM-41 adsorbent bed and systematically examined the effects of process conditions on anisole adsorption.The results indicated that the adsorption rate（X_a）of anisole on SSA/MCM-41 exhibited a"U-shaped"trend with temperature,and X_a could reach over 95%in the temperature range of 110-140℃.The collected breakthrough adsorption data fit the dose–response model,and the maximum values of t _B,th and Q_B,th predicted were 73.82 min and 247.56mg g^-1,respectively.In the comprehensive analysis of the process conditions,reducing the flow rate or raising the bed height enhanced t _B,th and Q_B,th,while reducing the inlet concentration resulted in a trend of first increasing and then slightly decreasing the Q_B,th.The SSA/MCM-41exhibited excellent cyclic stability,with t _B and Q_B of anisole maintained at 30.91 min and201.10 mg g^-1,respectively,after four cycles of adsorption/desorption/reloading,which were95.96%and 99.58%of the initial values,respectively.The separation and characterization of the SSA/MCM-41/anisole adsorption products demonstrated that the main adsorption product was 4-methoxybenzenesulfonic acid,and the by-product was 1-methoxy-4-（4-methoxyphenyl）sulfonylbenzene.4.Gas-solid reactive adsorption of chlorobenzene on SSA/MCM-41SSA/MCM-41(9.25 mmol g^-1)was prepared for the reactive adsorption and removal of chlorobenzene.The effects of reaction temperature and process conditions on the adsorption performance were investigated using dynamic adsorption experiments.The results showed that the adsorption rate(X_CB)of chlorobenzene on SSA/MCM-41 exhibited a"U-shaped"trend with temperature,and the optimal adsorption temperature range was 170-200℃.Increasing the bed height,decreasing the inlet concentration and gas flow rate appropriately could prolong the residence time of chlorobenzene molecules in the fixed bed,and increase the breakthrough time(t₅₀)and breakthrough adsorption amount(Q₅₀).Under the experimental conditions,the maximum t₅₀ and Q₅₀ were 49.51 min and 277.99 mg g^-1,respectively.The cyclic adsorption/desorption/reloading experiments demonstrated that SSA/MCM-41 was renewable and reusable.The structural analysis of the products showed that the main and by-products of the adsorption were 4-chlorobenzenesulfonic acid and bis（4-chlorophenyl）sulfone,respectively.