| Waxy crude oil has high solidification point and poor low-temperature fluidity, which brings many questions to the production and gathering-transportation and so on. At present, the main ways to improve low-temperature fluidity of waxy crude oil include heating, mixing dilute, emulsification, suspension conveying and pour point depressant, etc. Among these methods, heating, mixing dilute, emulsification and suspension conveying have their own disadvantages. While the oil-soluble pour point depressant method has a lot of advantages such as simple operation, less dosage, high efficiency, less equipment investment, no post-processing and so on. Thus the pour point depressant method became one of the hot spot of current study.This article mainly aims at the reality problems of high solidification point and poor low-temperature fluidity and the waxy simulation oil was selected as the investigative subject in this thesis. Combining with research situation of the oil-soluble pour point depressant and the principle of molecular structure design, undecylenic acid benzyl ester (BUA) was synthesized by direct esterification firstly, then BUA was used with maleic anhydride (MA), vinyl acetate (VA) for ternary polymerization, getting polymer BMV (undecylenic acid benzyl ester-maleic anhydride-vinyl acetate), and finally oil-soluble polymer OBMV was got through using high carbon octadecanol to BMV alcoholysis modification. The optimum synthesis condition of the monomer and the polymer were obtained by a series of single factor experiments and their structure and composition were characterized by infrared spectrum and 1H NMR spectrum, and the molecular weight of pour point depressant OBMV of the optimum synthesis conditions was determination by GPC.The optimized synthesis conditions of the pour point depressant OBMV were confirmed as follows:under the protection of nitrogen, the monomer mole ratio of BUA, MA and VA was 1:11:7, the added amount of initiator (AIBN) was 0.9% of the total mass of the monomers, the interval time of AIBN and VA was 90min, the reaction temperature was 75℃ and the reaction time was 6h, then terminated reaction and cooled it to room temperature. Then successively join octadecanol (n (MA): n (octadecanol)=1:2.1), catalyst p-toluene sulfonic acid (2% of the total quality of MA and octadecanol), the inhibitor hydroquinone (0.2% of the total quality of the monomers), the reaction temperature was 110℃ and the reaction time was 8h. By investigating a series of evaluation of the optimized pour point depressant OBMV, the experimental results show that when the dosage of pour-point depressant was 1500 ppm, the pour point of the model oil 1# was decreased up to 16.5℃, and the extent of pour point depression of the simulated oil 3# was 24.5℃; Studied the influence of simulation oil of different wax content on pour point depression, when wax content was less than 30%, the extent of pour point depression decreased with the increase of the wax content and when wax content exceeded 30%, the pour point depression was not obvious. For low waxy crude oil B8, including 9.96% wax content, the extent of pour point depression was up to 7℃,20% waxy crude oil B14, the extent of pour point depression was 1.5℃.The pour point depression mechanism of oil-soluble pour point depressant was inquiried and analysed preliminarily through contrasting the DSC, XRD and high magnification fluorescence microscope photo of the oil-samples with and without pour point depressant.The result shows that pour point depressant molecular mainly happened eutectic-adsorption with wax crystal. The molecules of the pour point depressant can depress the oil-sample wax precipitation point, change the wax crystallization process, make the wax precipitation rate slower and precipitation time extended; increase the wax precipitation amount during wax precipitation point and pour point, weaken the interaction between the wax crystals, inhibit the normal growth of wax crystal; decrease wax crystal size and wax crystal surface area, change wax crystallization ability and the wax crystal morphology. Thereby pour point depressant can reduce oil-sample pour point and improve its liquidity. |
