Influence Of Different Reaction Conditions On Lignite Liquefaction Products And The Generation Path Analysis Of Benzene Carboxylic Acid

Oxidizing and liquefying coal to be a hot research to obtain useful chemical or liquid fuel.It can react under lower temperature and lower pressure than traditional coal liquefaction.The main product of the coal oxidation is benzene carboxylic acid.Benzene carboxylic acid is an important chemical raw materials and chemical intermediates,it has a widespread application in many fields.Coal oxidation liquefaction is mainly studied by the effect of reaction conditions on benzene carboxylic acid production rate,it is seldom studied by reaction conditions on coal liquefaction reaction mechanism and benzene carboxylic acid of the generated paths.So,understanding the effect of reaction conditions on the formation of benzene carboxylic acid and the formation mechanism of benzene carboxylic acid is well worth to study.In order to make up for the lack of research on benzene carboxylic acid yield and benzene carboxylic acid generation path,the influence of reaction conditions on the oxidation of coal liquefaction products and explore the benzene carboxylic acid generated path is explored in this paper.The different reaction temperature,pressure,alkali-coal ratio,oxygen concentration of reaction conditions on oxidation of coal liquefaction reaction product and benzene carboxylic acid generated path are analyzed by control variable methods.TG analysis,elemental analysis,and FTIR analysis and Gas analysis are used to explore coal oxidation liqufication under different conditions and optimum reaction conditions.Besides,the reaction path of C₆H₂?OH?₃ CH₃ and C₆H₄OHCH₂CH₂OH oxidizing into hydroxybenzoic acid are studied by DFT.The research results following by:?1?Changes of reaction conditions has great influence on the yield ofcarboxylic acid,the yield of carboxylic acid will achieve highest under alkali–coal ratio 2/1,reaction temperature 300?,reaction pressure 3 MPa,70%oxygen concentrations.Alkali-coal has a significant impact for the yield of carboxylic acid,but too much alkali caused the salting out effect,it will inhibit the production of carboxylic acid.When temperatures rised,the dehydrogenation reaction rate increased,reaction temperature will cause the depth oxidation of the carboxylic acid.Reaction pressure too low is not conducive to the molecular structure methyl and methylene oxidizing into carboxyl.Pressure too high will lead to carboxyl further oxidizing into carbon dioxide.?2?The oxidation liquefaction reaction has a significant effect on the rates of H/C and O/C in the molecular structure of coal.Liquefaction reaction promoted the shedding of small molecular side chain?-CH₃?or hydrogen in macromolecular aromatics edge joint,and the benzene carboxylic acid with branched chain of benzoic acid and phthalate are mainly parts in the solid.The solid material of H/C value by the coal sample with 0.89,it rise from 1.25 to 2.36 after coal liquefaction reaction.It means that the molecular structure of unsaturated degree reduced.O/C value rising from 0.23to 0.40,it means that the number of structure with branched chain of benzoic acid and phthalate in the solid material increased.?3?The main reaction path of C₆H₂?OH?3CH33 oxidized to carboxyl group is that three hydrogen atoms on the methyl group forming hydroxyl groups,and then three hydroxyl groups are easily dehydrated to form carboxyl groups directly.It need to overcome 14.372 kJ/mol for forming the three hydroxyl on the methyl,then it need to overcome anther 129.859 kJ/mol for three hydroxyl dehydrated into forming carboxyl.The reaction process of C₆H₂?OH?₃CH₃ oxidizing into hydroxyl benzoic acid is C₆H₂?OH?₃CH₃+3O?C₆H₂?OH?₃C?OH?₃?C₆H₂?OH?₃COOH+H₂O,the reaction controlling step for the pathway is the hydroxyl oxidizing into carboxyl.?4?The main path of C₆H₄OHCH₂COOH oxidizing into carboxyl is hydrogen atom oxidizing into hydroxyl on the methylene,and the hydroxyl group continues to be oxidized to ketone,the ketone is hydrolyzed into carboxyl finally.It need to overcome 21.899 kJ/mol for forming hydroxyl on the methylene,it need to overcome anther 9.556 kJ/mol for hydroxyl oxidizing into forming ketone.The ketone need to overcome 58.881 kJ/mol forming carboxyl.The reaction process of C₆H₄OHCH₂COOH oxidizingintohydroxylbenzoicacidis C₆H₅OCH₂COOH+O?C₆H₅OCH?OH?COOH,C₆H₄OHCHOHCOOH+O?C₆H₄OHCO COOH+H₂O?C₆H₄OHCOOH+HCOOH,the reaction controlling step for the pathway is the keto oxidizing into carboxyl.?5?The production of benzene carboxylic acid is mainly derived fromC₆H₄OHCH₂CH2OH.During the oxidation reaction,C₆H₄OHCH₂CH₂ needs to overcome 90.364kJ/mol reaction potential barrier to obtain benzene carboxylic acid,while C₆H₂?OH?₃CH₃ needs to overcome 144.228kJ/mol reaction potential barrier to get benzene carboxylic acid.