Adsorption Kinetics Of Multicomponent VOCs In Gasoline On Polymeric Resins

Gasoline volatilizes easily in the process of production,transportation and utilization.The emission of gasoline produces high concentration of hydrocarbon mixtures,which will endanger human's health,cause the environmental pollution,waste resources and lower fuel quality.Therefore,it is of great significance to use reasonable technology to recover oil gas.Nowadays,adsorption-based technology has been used widely for gasoline vapor recovery.The composition of oil and gas is complex.There are inter-adsorbate and adsorbent-adsorbate interactions in multicomponent co-adsorption.The existence of competitive adsorption between different components will lead to the different adsorption behavior for a specific adsorbate in the multicomponent from that in a single component system.In a few studies,the gasoline vapor was often simplified as pure substance or a particular component of gasoline vapor was investigated.In addition,the previous studies about multicomponent adsorption focused on equilibrium and breakthrough,seldom on the adsorption kinetics.Recently,polymeric resin has gained much attention as a potential adsorbent due to its large specific surface area,good mechanical strength,excellent adsorption and desorption ability and controllable pore structure.Therefore,in this paper,hypercrosslinked resin NDA-150 and macroporous resin NDA-1800 were selected as adsorbent.The toluene,cyclohexane and n-pentane,which are the representative components of gasoline,were chosen as adsorbates.The single,binary and ternary adsorption kinetics of n-pentane,cyclohexane and toluene onto NDA-150 and NDA-1800 were investigated.The main contents and results are shown as follow:(1)The adsorption kinetics curves of single component n-pentane,cyclohexane and toluene on hypercrosslinked resin NDA-150 and macroporous resin NDA-1800 were investigated using thermogravimetric analyzer(TG)under 303K,313K and 323K,respectively.It is found that the adsorption process is controlled by both external surface diffusion and pore diffusion.The linear driving force(LDF)model can fit the adsorption kinetics data well with R2>95%.From the adsorption rate constant k obtained by LDF model,we can know that the adsorption rate of volatile organic compounds(VOCs)on NDA-1800 is faster than that of NDA-150.Also,the adsorption rate of three VOCs on both resins has the following order:n-pentane>cyclohexane>toluene.The higher the temperature or the initial concentration of VOCs is,the faster the adsorption rate is.(2)The differential adsorption bed(DAB)method was used to measure the intra-pore diffusion of n-pentane,cyclohexane and toluene in hypercrosslinked resin NDA-150 and macroporous resin NDA-1800 under 303K,313K and 323k.Also,three models including Barrier Model,Pore Model and Dual Model were used to fit the single component kinetics data obtained from DAB experiments.The results show that the Dual model was better than the Pore model and the Barrier model for the fitting of experimental data with larger R2(>94%),indicating that the adsorption diffusion resistance existed at the micropore mouth and the mircopore interior simultaneously.(3)The differential adsorption bed method was used to measure adsorption kinetics of the binary components(toluene-cyclohexane,toluene-n-pentane,cyclohexane-n-pentane)and ternary component(toluene-cyclohexane-n-pentane)on hypercrosslinked resin NDA-150 and macroporous resin NDA-1800 under 303K,313K and 323K.The results show the adsorption kinetics curves of binary and ternary component can be predicted by combining Dual model with extended Langmuir(E-L)model according to the single component kinetics data,and the mean relative deviation between the experimental and calculated data is less than 20%.Also,increasing the concentration of adsorbates led to the reinforcement of competitive substitution phenomenon,while increasing the temperature would result in less competitive adsorption.The competitive substitution phenomenon of multicomponent VOCs on NDA-150 was more pronounced than that on NDA-1800 under the same condition.