Study On Heavy Crude Oil Upgrading Visbreaking Reaction

With the economic development and population growth in the world,the demand for crude oil is becoming increasingly great. The reserves and production of conventional crude oil,however,is falling off with no stop. Under this circumstance, heavy crude oil,which is considered as non-conventional crude oil will occupy an important position in national energy strategy of our country.The geological reserves of heavy crude oil is about three times as large as conventional crude oil all around the world,and the pay-gross thickness ratio is low. But it is very difficult to store and transport heavy crude oil because of the high viscosity,relative density and poor liquidity.Heavy crude oil upgrading visbreaking reaction is a processing method of crude oil with low extent of reaction. This reaction contains aquathermolysis , thermal cracking ,condensation reaction and so on. Macromolecules in crude oil such as colloid and asphaltine would decompose into middle fraction with small molecular weight by upgrading visbreaking reaction which can bring about an irreversible decrescence of the viscosity. This action has the capability to decrease the viscosity fundamentally,improve the liquidity and reduce the difficulty of long-distance transportation and storage. In this paper,the feasibility of upgrading visbreaking reaction was researched and the catalyst that suit for ShengLi Oilfield also be screened out. Besides,we discussed effects of all kinds of reaction conditions on upgrading visbreaking reaction under the existence of catalyst and hydrogen donor. The reaction mechanism of upgrading visbreaking reaction was discussed in the paper yet.The main research contents:(1) Research on the feasibility of upgrading visbreaking reaction.In terms of the feasibility of upgrading visbreaking reaction,we chose three typical kinds of heavy crude oil with different viscosities from ShengLi Oilfield to find how temperature and reaction time of upgrading visbreaking reaction affect the viscosity-temperature characteristics and fraction of the viscous crude oil. Besides, we studied the rate of crack and condensation of the viscous oil reaction under these conditions which were mentioned above. The experimental result indicates that after reacting between 300℃and 380℃, between 20min and 60min, the viscosity decreased obviously. We also discovered that the viscosity break results are better with high temperature and long time. At the same time, heavy crude oil changed into heavier fraction and less light fraction. These changes show that under experimental conditions the heavy crude oil upgrading visbreaking reaction can happen.(2) Research on the effects of catalyst and hydrogen donor.Based on the feasibility research, we chose three catalysts and used high temperature vapour as hydrogen donor to study upgrading visbreaking reaction. We also discussed the effects of the kind of catalyst, reaction time, temperature and hydrogen donor on the viscous crude oil composition, viscosity-temperature characteristics and gas from the reaction. The result shows that the existence of catalyst and hydrogen donor could speed up upgrading visbreaking reaction and reduce the reaction temperature effectively. It is evident that the outcome which brings about more middle fraction is notable.(3) Research on the reaction mechanism of upgrading visbreaking reaction.We could obtain these conclusions by analyzing the variety of the fraction and the composition of the gas after upgrading visbreaking reaction. The bridge bond which is composed of heteroatoms especially the S is the weakest point in the molecular structure. When undergoing heat, this bridge bond could crack easily to creat free radical which can be used as induced fission. Cracking reaction also accompany with condensation reaction. The existence of the hydrogen donor can restrain condensation reaction and improve the effect of upgrading visbreaking reaction.