Study On Upgrading Of Heavy Oil Model Compounds N-hexadecane And Decalin By DBD Plasma Method

Heavy oil generally refers to a fraction with boiling point greater than 350°C and its C/H ratio is between 1.4 and 1.7,which is difficult to be used directly.With the depletion of light oil resources,heavy oil upgrading is imminent.There are two main processing routes for traditional heavy oil treatment:decarbonization and hydrogenation.Although decarbonization technology has a wide range of applications,it has the disadvantages of high coking rate,low light oil yield and poor oil after treatment.Hydrogenation technology can effectively solve the problems existing in decarbonization technology,but it has the disadvantages of complex equipment structure and high operation cost.Plasma technology was used to develop a new lightweight method,which was applied to the field of heavy oil processing and stood out with the advantages of no catalyst,simple structure,high efficiency,fast speed and low cost.In this thesis,the DBD（dielectric barrier discharge）plasma was used for pyrolysis and in-situ hydrogenation of heavy oil to improve the light hydrocarbon selectivity of liquid products by studying the characteristics and mechanism of plasma pyrolysis of heavy oil.Using n-hexadecane(C₁₆H₃₄)and decahydronaphthalene(C₁₀H₁₀)as heavy oil simulants,a plate-plate DBD plasma reactor was designed to study the modification of the two substances under atmospheric pressure.During the modification of n-hexadecane,the experimental results showed that the light hydrocarbon selectivity of the liquid product is 51.6%when the discharge time is 40 s and the discharge voltage is 19 k V;The gas products of pure hexadecane discharge were collected and detected.The gas products were mainly H₂,CH₄ and C₂H₆,and C₂H₄ and C₂H₂ appeared in turn with the increase of discharge voltage.The light hydrocarbon selectivity of n-hexadecane liquid product is improved by adding hydrogen-rich substances.Two ways of adding hydrogen-rich substances were selected in the experiment:The first method is that hydrogen-rich substances were directly dropped onto the upper layer of n-hexadecane（directly added）.The results showed that the light hydrocarbon selectivity of liquid product is 74.9%under the conditions of discharge time of 40 s,discharge voltage of 19 k V and ethanol addition of 0.8 m L;The gas phase products were collected and detected.After adding different hydrogen-rich substances,the components of each gas phase product were different.Compared with methanol and water,the addition of ethanol will significantly increase the content of C₁ and C₂ substances.The second method is to heat ethanol and purge it into the n-hexadecane reaction area with carrier gas in the form of gas（purge addition）.The results show that when the discharge time is 120 s,the discharge voltage is 20 k V and the amount of ethanol is 5.6 m L,the maximum liquid product light hydrocarbon selectivity is 96.6%.In addition,during the modification of decahydronaphthalene,the experimental results showed that the liquid products after discharge of decahydronaphthalene were mainly A_12.3,A_14.2,A_14.9,A_15.2,A_17.4 and A_20.7.After adding different hydrogen-rich substances,the composition of liquid products changed.When water is added,the main liquid phase product is A_12.3;when ethanol is added,the main liquid phase product is A_20.7.