The Effect Of Organic Micromolecules On Coal Adsorption Characteristics Of Methane

Coal is a complex organic compound.In addition to a molecular framework composed of a large number of carbon atoms,it also contains many organic small molecules that occur in the pores and macromolecular networks of coal.The existence of organic small molecules will inevitably have a certain effect on coal adsorption of methane,but its effect and mechanism are still unknown.In this paper,molecular simulation method is used to simulate the isotherm adsorption of coal to adsorb methane,to study the effect of different concentrations and different components of organic small molecules on coal adsorption of methane.Combined with the interaction of organic small molecules on methane molecules,the mechanism of influence on coal adsorption of methane is concluded.Using molecular mechanics methods to construct a coal macromolecular model,a methane molecular model and three small organic molecules(tetrahydrofuran-2-ol,methylbenzene and nundecane)models and perform geometric optimization to obtain a stable molecular configuration.Different amounts and different components of small organic molecules are added to the macromolecular model of coal to construct different adsorbate models.According to the Monte Carlo method,the isotherm adsorption simulation of coal adsorption of methane is carried out,and the adsorption amount data of methane molecules under the influence of different concentrations and different contents of small organics molecules are obtained.The results show that when a certain concentration of methylbenzene exists alone,the adsorption capacity of methane in coal is increased,but when methylbenzene and other small organic molecules coexist,the adsorption of methane by coal is inhibited.Both n-undecane and tetrahydrofuran-2-ol can inhibit the adsorption of coal and methane when they are alone,and the mixture of the two can increase the adsorption of methane in coal.Calculate the isosteric heat of adsorption data based on the isotherm adsorption curve.The results show that two methylbenzene molecules in the adsorbate molecules can enhance the adsorption of coal and methane when they are alone,and that methylbenzene can still enhance the adsorption of coal and methane after being mixed with two other small organic molecules.When there are two n-undecane molecules or two tetrahydrofuran-2-ol molecules in the adsorbate molecules alone,the adsorption of coal and methane will be weakened.Research on the interaction between small molecular organics and methane based on DFT theory.The results show that when methane interacts with three small organic molecules:methylbenzene,tetrahydrofuran-2-ol and n-undecane,the interaction energies are-4.96 k J/mol,-3.76 k J/mol and-3.33 k J/mol,respectively.It is an exothermic process;the amount of charge transfer is the largest when methane interacts with methylbenzene,which is 0.012 e.The mechanism of small organic molecules on coal and methane adsorption has two main aspects.On the one hand,the presence of small organic molecule changes the pore structure of coal,which in turn affects the ability of coal pores to adsorb gas;on the other hand,small small organic molecules affect methane.The molecules have a certain interaction,which changes the charge structure of methane molecules,which in turn changes the van der Waals force between the methane molecules and the coal surface,that is,the strength of coal and methane adsorption.The research results are helpful for in-depth understanding of the occurrence mechanism of coalbed methane.