Study On Preparation Of BTX By Selective Hydrogenation Of Low-Temperature Coal Tar

Coal tar is a by-product produced during the pyrolysis of coal and is also an important raw material for crude oil substitutes.The international oil price shocks and the promotion of new energy vehicles,coal tar to produce gasoline and diesel profits fell sharply,Therefore,it is very necessary to make full use of the substances in coal tar.The coal tars are rich in naphthenes,aromatic hydrocarbons,and other potential resources,and are converted into aromatics and naphthenics chemical products,which can better reflect the utilization value of coal tar.At present,the source of BTX is mainly obtained from the catalytic reforming of naphtha,steam cracked naphtha,or high-temperature coal tar.The main source of China's triphenyl is introduced,and domestic production is insufficient to support the demand.Therefore,taking coal tar as raw material and using its aromatic rich feature to produce high value-added chemicals such as BTX have also attracted people's attention.In this dissertation,firstly,phenol model compounds were used as raw materials,and four hydrogenation catalysts with different cobalt and molybdenum ratios were used to carry out the hydrodeoxygenation tests in a fixed bed reactor.The results showed that under the effect of FTO-b catalyst,the conversion of phenol was up to 96%,the selectivity of benzene in the product was 65.2%,the specific surface area of the catalyst was 261.52 m2/g,the average pore size was 10.82 nm,and it had a high content.Co O and more acid sites,Co and Mo active components are uniformly dispersed,which is beneficial to increase hydrodeoxygenation activity.The process conditions of hydrodeoxygenation of phenol were explored using FTO-b catalyst.The results showed that with the increase of temperature,the conversion of phenol increased and the selectivity of benzene increased.With the increase of pressure,the conversion of phenol increased,the selectivity of benzene increased first and then decreased.When the pressure reached 6Mpa,the conversion of phenol was increased.to reach maximum.In addition,the reaction path was initially obtained from the product distribution of phenol hydrodeoxygenation.Second,the hydrodeoxygenation process was studied using crude phenol as raw material.The results show that the increase of temperature can promote the positive activation energy of the endothermic reaction pathway DDO,which is beneficial to the removal of functional groups in the aromatic hydrocarbon(phenol deoxygenation and demethylation reaction),resulting in the selective increase of BTX;when the space velocity is small The contact time of the material with the catalyst can be increased,the conversion of crude phenol and the content of BTX increase.In addition,the carbon number change and conversion pathway of crude phenol hydrogenation process were preliminary explored.Finally,the hydrodeoxygenation process was studied using coal tar distillate oil below260 ? as raw material.The results showed that with the increase of temperature,the yield of BTX increased,and the content of sulfur and nitrogen in the product also decreased significantly.With the decrease of airspeed,the content of BTX increased.The optimum process conditions are temperature 380?,pressure 6MPa,and volume velocity 0.4h-1.At a certain S/N content,the catalyst has better stability activity and longer life.Comparing the results of hydrodeoxygenation under various raw materials,the decrease of phenol content in coal tar can relieve the competitive adsorption of various types of reactions on the catalyst surface,and also enable the hydrodesulfurization,hydrodenitrogenation and aromatic saturation and cracking of coal tar.This promotes the selectivity of BTX in crude phenol hydrodeoxygenation products to be significantly higher than that of BTX in the hydrodeoxygenation of coal tar distillates.