Research On Synthesis And Performance Of Compounding Of High Carbon Polymethacrylate Pour Point Depressant For Crude Oil

Polymeric pour point depressants can effectively improve the cold flow properties of crude oil,but there is a strong selectivity for waxy crude oil.Single pour point depressant is difficult to apply to different types of crude oil.In order to meet the needs of production and transportation of crude oil,compound modification is necessary to make it have a good susceptibility to crude oil,so that the performance of pour point depressants can be improved.This paper mainly discussed the synthesis and compound modification of polymethacrylate pour point depressant.Firstly,hexadecyl methacrylate was synthesized by solvent esterification method.Then,hexadecyl methacrylate/octadecyl methacrylate,oleic acid and maleic anhydride were used as monomers to synthesize binary polymers and terpolymers by solution polymerization method.The effects of the carbon number of side chain and polymerization conditions on the pour point were explored by the single-factor experiment.It was found that the performance of the polymer with eighteen carbons of side chain was better.With the change of monomer ratio,reaction temperature,reaction time and initiator dosage there exised an optimal value.Orthogonal experiment determined the optimum synthesis process of octadecyl methacrylate-maleic anhydride-oleic acid(AMO₁₈):the molar ratio of monomers was 3:2:2,the reaction temperature was 100°C,the reaction time was 8h,and initiator dosage was 1.0%.Under these conditions,the optimum dosage of pour point depressant was 800ppm and the best treatment temperature was 70°C,with the reduction on pour point by22°C.From gel permeation chromatographic analysis,it was found that the polymer with a molecular weight between 10000¹2000 had the best effect.On the basis of previous work,a variety of pour point depressants were compounded.It was found that the same type of pour point depressants or different types of pour point depressants can improve the performance of pour point depressant.The results showed that poly（stearyl methacrylate）-maleic anhydride-oleic acid（AMO）,polymethyl methacrylate-maleic anhydride（AmM）,polymethyl methacrylate-oleic acid（AmO）can match better with paraffin molecules after compounding.The depression of pour point can reach 11°C for the compounding of EVA type pour point depressants,which was better than single EVA pour point depressant.The effect was improved when AMO with sixteen and eighteen carbon number of side chain compounded with three surfactants,including Span80,AC-1810 and gemini organic surfactant OP-10,and the pour point can be reduced by 24°C for the combination of OP-10 and AMO₁₈.Additionally,differential scanning calorimetry and optical microscopy were used to explore the pour point depressant mechanism.The pour point depressant will change the thermodynamics and kinetics of crude oil.It is characterized by the change of pour point,wax precipitation point,wax precipitation peak temperature and the amount of wax precipitation.With pour point decreasing,the wax precipitation point decreased,the wax precipitation peak temperature decreased,and the amount of wax precipitation increased.Due to the eutectic,adsorption and dispersion of pour point depressant and wax crystal,the change of pour point depressant to the wax crystal is different.It may increase the size of the wax crystal or reduce the size of the wax crystal.Meanwhile,pour point depressants transformed irregular wax crystals into relatively regular ones.Therefore,the cold flow properties of the oil sample improved.