Study On Kinetics Of Hydrolysis And Hydrocarbon Generation Of Mixed Esters Catalyzed By Minerals At Low Tempereture

Fatty acids and its ramifications are regarded as important precursors of low-mature oil. It has been found that immature oil source rocks are rich in fatty acids. Fatty acids have different distribution of carbon number and mainly exist in form of fatty acid ester in immature oil source rocks. In this paper, mixed esters were chosen as the model reactant. Study on kinetics of hydrolysis and hydrocarbon generation of mixed esters catalyzed by minerals at low temperature was carried out, with considering complex effect of factors. The mechanism of hydrocarbon generation of fatty acid ester and its contribution to the formation and accumulation of immature oil were also discussed. This research subject has important significance both in theory and practice.Firstly, the effects of several important influential factors on the hydrolysis and hydrocarbon generation of mixed esters catalyzed by minerals were investigated: (1) The effects of reaction temperature, reaction pressure, pH value and salinity were investigated by orthogonal experiments. By the range analysis and gray relation analysis based on the experimental data, the significance of influential factors was evaluated. The results show that the effect of reaction temperature is most important, the next is pH value, the third is reaction pressure and the fourth is salinity. (2) The effects of some inorganic salts on hydrolysis and hydrocarbon generation of mixed esters catalyzed by minerals at low temperature were investigated. The effects of inorganic salts were distinguished and their effect mechanism was analyzed too. The different inorganic salts have different effect on the reaction. Magnesium chloride exhibited inhibitive effect on hydrolysis and sodium sulfate inhibited hydrocarbon generation. The others promoted the reaction (sodium chloride inhibited the hydrolysis of mixed esters catalyzed by clay minerals). Furthermore, the catalytic activity of minerals can be influenced by inorganic salts.Secondly, the catalytic activity of immature oil source rocks was evaluated and the interaction among esters was also investigated: (1) The catalysis of clay minerals is the main influential factor in the hydrolysis of mixed esters catalyzed by immature oil source rocks in which the clay is dominant component at low temperature. Carbonate minerals have better catalytic effect on the hydrocarbon generation of mixed esters at low temperature. The immature oil source rocks whose carbonate and clay content is in a suitable ratio have better catalytic effect on hydrocarbon generation of mixed esters catalyzed by minerals at low temperature. These conclusions haven't been reached in the similar study. Furthermore, the trend of hydrocarbon generation rate of mixed esters catalyzed by immature oil source rocks at low temperature is similar to the weighted contents of minerals in it. These minerals include calcite, dolomite, pyrite, montamorillonite and illite. (2) The activity of hydrolysis and hydrocarbon generation reaction of fatty acid ester is different because of their different carbon number. In the process of hydrolysis and hydrocarbon generation of mixed esters catalyzed by mineral at low temperature, the hydrolysis rate and hydrocarbon rate of each ester in reaction of mixed esters is lower than those of single ester. It can attribute to the competition for active sites among fatty acid esters.Finally, kinetics study on hydrolysis and hydrocarbon generation of mixed esters catalyzed by minerals at low temperature was carried out. Time and quantity of converting fatty acid esters into hydrocarbons were also accounted based on the kinetic parameters. Meanwhile, the mechanism of hydrolysis and hydrocarbon generation from fatty acid ester catalyzed by carbonate minerals at low temperature was preliminary discussed: (1) Both the hydrolysis reaction and hydrocarbon generation reaction of mixed esters catalyzed by minerals at low temperature can be described by first order global reaction kinetic model. To natural mineral samples, the order of activation energy is E_carbonate﹤E_pyrite﹤E_clay. Moreover, with the increase of temperature, the difference of minerals'influence on hydrocarbon generation reaction decreased. (2) The reaction pathway was proposed based on experiment results and research results of previous investigators. Moreover, water has an important role in the reaction.