Research On The Preparation And Efficiency Of Crystalline Through Porous Polymer Pour Point Depressant

Polyoctadecyl acrylate(POA)is a commonly used waxy crude oil pour point depressant(PPD),and the technology of introducing micro-nano particles into the POA matrix to improve its performance has also been developed rapidly.However,the introduction of inorganic particles will have potential adverse effects on the subsequent processing of crude oil.Based on the unique structure and performance advantages of porous polymer materials,in this paper,three PPDs of porous POA particles,crosslinked porous polyoctadecyl acrylate(C-POA),through porous polyoctadecyl acrylate(TP-POA),and through porous polyoctadecyl acrylate-vinyl acetate(TP-POA-VA),were prepared by traditional solution radical polymerization and high internal phase emulsion template methods.The pore structure,crystallization performance and oil phase dispersibility of porous POA particles were investigated,and the mechanism of the influence of porous POA particles on the rheological properties of the waxy oil were studied through rheological measurement and wax precipitation characteristics analysis.The conclusions of the paper are as follows:(1)The PPDs of C-POA particles were successfully prepared by the traditional solution free radical polymerization method,and the influence of C-POA with different crosslinking agent divinylbenzene(DVB)dosage on the rheological properties of model waxy oil was explored.The results showed that C-POA were uniformly dispersed in the oil phase in the form of micron-sized particles.With the increase of DVB concentration,the solid surface area,swelling and oil absorption capacity of C-POA gradually increased,and heterogeneous nucleation sites for wax molecules increased.But at the same time,the gradual deterioration of crystallization ability led to the weakening of co-crystal effect with wax molecules.These two aspects jointly affect the improvement effect of C-POA on the flowability of model waxy oil.The C-POA2 with a DVB dosage of 2wt% monomer has the best effect on improving the low-temperature flowability of model waxy oil at a dosage of 500 ppm,and reduced the pour point of model waxy oil by 3℃ on the basis of POA.(2)The PPDs of TP-POA particles were successfully prepared by the high internal phase emulsion template method,and the effects of TP-POA with different polymerization initiation sites,emulsifier concentration and crosslinking concentration on the rheological properties of waxy oil were respectively explored.The results showed that TP-POA-I2 polymerized by water phase initiator KPS has better crystallization ability than TP-POA-I1 polymerized by oil phase initiator AIBN.Therefore,it has a better reduction effect on the pour point,apparent viscosity,and yield value of waxy oil.The solid specific surface area,swelling and oil absorption capacity of TP-POA-S1～5(that is,the emulsifier Span 80 concentration gradually increases)gradually increased,and the crystallization ability was basically unchanged,but when the Span 80 was too high,the pore structure strength decreased significantly.At this time,TP-POA-S4 led to better flowability of waxy oil.The crystallization ability of TP-POA-D1～5(that is,the concentration of crosslinking agent DVB gradually increases)gradually weakened,but the solid specific surface area,swelling and oil absorption capacity were greatly increased.TP-POA-D1 with the amount of crosslinking agent and emulsifier for polymerization initiated by KPS of 0.5wt% and 15wt% of OA has the best effect on improving the flowability of waxy oil.It can further reduce the pour points of model waxy oil and Changqing crude oil by 11°C and 4°C on the basis of POA at a dosage of 500 ppm.Through the analysis of the exothermic heat of the oil samples and the observation of the microscopic morphology of the wax crystals,it is found that the addition of TP-POA-D1 resulted in a more compact structure and larger size of the wax crystals precipitated by the waxy oil.This is because TP-POA-D1 has a good co-crystal effect with wax molecules,and it also fully functions as a crystallization template for wax molecules owing to having the larger specific surface area.(3)The binary copolymer porous PPDs of TP-POA-VA particles were successfully prepared by the high internal phase emulsion template method,and the influence of TP-POA-VA with different VA content on the rheological properties of wax oil was explored.The results showed that with the increase of VA content,the polarity of TP-POA-VA gradually increased,and the dispersibility in model waxy oil gradually deteriorated.However,TP-POA-VA with appropriate polarity could be adsorbed on polar components such as asphaltenes in crude oil,so that the dispersibility of the PPD particles became better.But at the same time,the crystallization ability of TP-POA-VA gradually decreased with the increase of VA content,and the specific surface area began to decrease obviously when the molar ratio of OA to VA was less than 5:1.TP-POA-VA0 without VA has the best effect on improving the flowability of model waxy oil,while TP-POA-VA2 with a molar ratio of OA to VA of 7:1 has the best effect on improving the flowability of Changqing crude oil.The pour point could be reduced by 5℃ on the basis of POA.It’s caused by the crystallization ability of TP-POA-VA and the difference in dispersion in model waxy oil and Changqing crude oil.