Experimental Study On Low-temperature Oxidation Of Heavy Oil Catalyzed By Nano-metal Oxides

Low temperature catalytic oxidation air injection is a new EOR technology to improve the effects of thermal recovery.The technology can effectively enlarge the formation energy and reduce heat loss in the late stage of thermal recovery.In addition,the rich resources,the low engineering cost and the strong injection ability,render air a broad prospects in oilfeild development.However,a suitable low-temperature oxidation catalyst is required for the technology to accelerate the reaction between the oil and 02 in the air injection so that can make effectively the O2 content of heavy oil production well non condensable gas low the safety value and ensure the safety of the production process for steam huff and puff or steam flooding recovery processes.In this thesis,five kinds of nano-metal oxide catalysts were in-situ prepared by using microemulsion method and residue as matrix,and they were characterized by DLS,XRD,SEM,TEM and EDX.The average particle size of as-perpared CuO was about 84.3nm,and the few residue adhered to the surface of particles rendered them a certain lipophilicity,which improved the dispersibility of the particles in the crude oil as well as improved the catalytic effect.The nano-metal oxides was used as the catalyst investigated the low temperature catalytic oxidation in the Liaohe B-5#heavy oil taking the oxygen consumption rate as the main evaluation index.The optimum catalyst CuO was slected as the subsequent experiment catalyst to obtain the optimal process parameters:catalytic dosage 0.1 wt%,reaction temperature 120℃,injection pressure 2.5MPa,water content 20%,reaction time 9h.Under the optimal operating parameters,the oxidation oils acid value increased from 4.22 mgKOH g-1 to 11.76 mgKOH g-1,asphaltene content increased from 0.45%to 13.73%,resin content decreased from 43.62%to 30.98%,the aromatic hydrocarbon content decreased from 30.43%to 25.98%,and saturated hydrocarbon content increased from 25.5%to 29.31%.Compared with non-catalytic oxidation of heavy oil,The 02 content in the tail gas decreased from 8.76%to 3.90%,the CO2 content increased from 4.12%to 6.03%and the average oxygen consumption rate increased by 1.4 times with nano-CuO and.Effects of temperature on the low temperature catalytic oxidation of Liaohe heavy oil was most obvious.The oxygen consumption rate increased and O2 content in the tail gas decreased with increasing temperature after the addition of nano-CuO,while the reaction temperature was more than 120℃,heavy oil tend to coke leading to properties deteriorated.The SARA analysis results showed nano-CuO had a catalytic cracking effect with a certain temperature.Kinetics analysis and thermal effect results indicated that the reaction order changed from zero-order reaction to first-order reaction and the Arrhenius activation energy decreased from 60.30 to 45.06 kJ/mol,decreased by 15.24%at the present of nano-CuO,moreover,the heat generation of the catalytic oxidation reaction was 74.93kJ at 100℃,and would rise the temperature by 24℃ under thermal isolation atmosphere that twice than that of the non-catalytic oxidation under the same conditions,which showed that nano-CuO could accelerate the low-temperature oxidation reaction rate and deepen the oxidation reaction owing to the thermal effect improved obviously.The IR,GC-MS and Elemental analysis results showed that nano-CuO could catalyze the oxygen addition reactions as well as the pyrolysis of macromolecular compounds.At high temperatures,the nature of copper is lively and the addition of nano-CuO will form Cu-heavy oil heavy component coordination complex,which could reduce the C-S,C-C and C-N bond energies in heavy oil molecules to undergo the bond scission reaction.In addition,the O2 in CuO surface chemical adsorption,could generate the active intermediate species O2-and 0-and serve as strong electrophilic reagents.They would attack such as double bonds,triple bonds and aromatic rings with high electron cloud density in the heavy oil molecules and pick up electrons to form carbon positive ions,which induced the aromatic ring side chain breaks;besides,the effects of saturated hydrocarbons of crude oil in CuO activation and dissociation adsorption could produce R·and H·free radicals which could speed up the oxidation reaction rate.