Studies on the structure-function relationship of polyether-type demulsifiers based on density functional theory
The use of chemical demulsifiers in the treatment process of crude oil dehydration can greatly improve work efficiency and save costs.Among them,polyether demulsifiers are the most widely used,and studies on their structure-function relationship are crucial for the development and application of new demulsifiers.In this work,the demulsification effects of several polyether demulsifiers and reverse demulsifiers were evaluated and compared.Then corresponding model molecules were selected according to the structural characteristics of asphaltene molecules and the categories of polyether demulsifiers and reverse demulsifiers.Their optimal molecular geometries and electrostatic potential distribution diagrams were obtained through the B3LYP/6-31G basis set in density functional theory(DFT).The interaction energy between a polyether demulsifier model molecule and an asphaltene model molecule,and the interaction energy between a polyether demulsifier model molecule and a water molecule,were both calculated using the functional M062X/6-31G basis set for several kinds of polyether demulsifiers.Combined with the evaluation results of demulsification performance of polyether demulsifiers and reverse demulsifiers,their structure-function relationships were analyzed.It shows that the difference in the demulsification performance of demulsifiers deduced from theoretical chemical calculation is consistent with their demulsification effects experimentally measured.Those polyether demulsifiers with branched structure and higher polymerization degree have better demulsification effects than those with linear structure and lower polymerization degree.In addition,polyether-grafted phenolic resin has better demulsification effect than polyether-grafted phenol-amine resin.Among the inverse demulsifiers investigated,polyol polyether inverse demulsifier has the best demulsification effect.Therefore,it is feasible to study the structure-function relationship of demulsifiers with DFT method,which can provide theoretical basis and reference for the preparation and selection of new demulsifiers in future.
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