Molecular Weight Control Of Maleic Anhydride Copolymers And Its Effect On Oil Flowability Improvement

In order to find the effect of polymerization conditions on molecular weight of poly (maleic anhydride-α-octadecylene), orthogonal experiment was designed. Two series of comb-type copolymers (MAC and NMAC which were amidated by octadecylamine and 1-naphthylamine) with different molecular weight (Mw) were synthesized. Both of them could improve the flowability of model oil and crude oil well. The mechanism of flowability improvement was studied based on the result of model oil and crude oil. The main results are as follows:Maleic anhydride-α-octadecylene copolymers with different molecular weight were synthesized. The molecular weight of anhydride-α-octadecylene copolymers were determined by GPC. The heat-resistance of maleic anhydride-α-octadecylene copolymers was determined by TGA. Molecular weights of those anhydride-α-octadecylene copolymers were ranged from 4500g/mol to 7800g/mol and their heat-resistance were ranged from 144 to 166℃.二,MAC with different molecular weights were synthesized by octadecylamine amination. Their effects on model oil yield stress were evaluated by addition in model oils. Amination degree of MAC was determined by 1H NMR. With the amination degree of MAC and the molecular weight of anhydride-α-octadecylene copolymers, Mws of MAC were calculated ranging from 6400 to 11000g/mol. Effects of MAC with different Mws on crystallization of paraffin in crude oil were characterized by rheology and polarizing light microscopy. Yield stress of model oil was decreased about 99.7 percent by MAC1 with additive amount of 0.5wt%. MAC with higher Mw showed a better result in reducing the size of crystals the yield stress of model oil.三,NMAC with different molecular weights were synthesized through 1-naphthylamine amination. Their effects on model oil yield stress were evaluated by addition in model oil and Shenyang crude oil. Amination degree of NMAC was determined by 1H NMR. With the amination degree of NMAC and the molecular weight of anhydride-α-octadecylene copolymers, Mws of NMAC were calculated ranging from 5400 to 9000g/mol. Effects of NMAC with different Mws on crystallization of paraffin in crude oil were characterized by rheology and polarizing light microscopy. Heat-resistance of NMAC was determined by TGA ranging from 169 to 230℃. Because of the high aromaticity of NMAC, it was sensitive to asphaltene in oils. NMAC reduced the yield stress of model oil with high content of asphaltene than that with low content of asphaltene. Yield stress of model oil with 1wt% asphaltene was reduced about 99.9 percent by NMAC1 with additive amount of 0.5wt%. Yield stress of Jing crude oil was reduced about 93.2 percent by NMAC1 with additive amount 0.5wt%. The experimental results of XRD and polarizing light microscopy showed that NMAC could depress the size of the wax crystals.Basic on the above results, the mechanism of flow improvement was summarized:Comb-type copolymers MAC and NMAC have hydrophilic group (side chain) and hydrophobic group (carbon skeleton). Hydrophobic group not only makes comb-type copolymers soluble in oils but also interacts with wax in oils, which can modify the morphology and reduce the size of wax crystals. At the same time, hydrophilic group hinders the growth of wax crystals from forming three dimensional network structures. Because of the polarity of asphaltene in oils, it can interact with hydrophilic group of comb-type copolymers, which makes asphaltene dispersive, which improves the flowability of crude oils.