A Study On Near-critical Water Oxidation Characteristics And The Basic Structure Of Houma Lignite

Lignite is rich in China's coal reserves,that accounted for 13% of the proportion.Lignite contains a lot of ash.The air pollution caused by combustion is much larger than other coal.Lignite oxidation liquefaction in the process of experiment will not produce dust and other pollution.The product of benzene carboxylic acid and a variety of small molecular acid has a large market demand.And most of these products are petrochemical products,so looking for an effective path of lignite oxidation liquefaction,not only to clean the use of coal resources but also ease the pressure of oil supply.Near critical water has good solubility,diffuse and catalytic.Compared with supercritical water,there are many obvious technical and economic advantages.In recent years,more and more researchers at home and abroad have started to study near-critical water as a solvent for liquefaction process such as organic waste,biomass and waste plastics.But near-critical water about coal liquefaction solvent research is rarely reported.The main contents of this study include the construction of HM lignite's macromolecule structure model based on the experimental data.The influence of near-critical oxidation of lignite and the effect of reaction temperature and time on the yield of the product.At the same time,the influence of oxygen and pressure on the near-critical oxidation of lignite was discussed from the gas atmosphere.Finally,the distribution of the final product was deduced in combination with the reaction characteristics to guide the industrial production.(1)In this study,the lignite structure was characterized by modern analytical technique.The average molecular formula of Houma lignite was calculated by elemental analysis.At the same time,the infrared spectrum of Houma lignite was analyzed by software,and the aromatic structure of Houma lignite was obtained.Using ChemDraw 2016 software to draw the molecular model,and constantly adjust the structure,and finally put forward a lignite structure model.The molecular weight is 2794 and the formula is C165H162N2O33S3.Using the Gaussian software to construct the lignite macromolecule structure model to optimize and calculate the frequency to obtain its infrared spectrum,and match the experimental map,the model is constructed reasonably.The model accurately reflects the structural characteristics and experimental parameters of Houma lignite.(2)In this article,the oxidation characteristics of lignite under low temperature catalytic oxidation conditions and near critical water conditions were observed by XRD,SEM and FTIR.The results show that the weaving degree and elongation of the solid residue under the near-critical water condition are greatly reduced,the degree of polymerization of the aromatic structure is weakened,and the aromatic structure of the lignite is quickly and effectively degraded in a short time,which proves that the near-critical water oxidation and catalytic oxidation of lignite play a significant role.The surface of lignite is composed of rich folds and lamellar form,which is dominated by flocculent structure,and the proportion of mineral content is dominated.It also shows that near-critical water degrades liquefaction of lignite in a short time.The concentration of carboxyl group,phenolic hydroxyl group,aromatic ether and alkyl ether in the low temperature group increased with the increase of the reaction temperature.Under this condition,the formation rate of the oxygen functional group was higher than that of the reaction rate,Under the critical water conditions,the concentration of alkyl ether in the sample remained unchanged,the others were greatly reduced.Lignite dissolved into water-soluble substances.The hydroxyl groups,OH-N,OH-? and OH-OH were observed.The concentration of hydroxyl groups in the near-critical water decreased with the increase of temperature.(3)The stability of functional groups during the oxidation of lignite is alkyl ether> aryl ether,phenolic hydroxyl,OH-? and OH-OH> cyclic hydroxyl> fatty chain terminal methyl> carboxyl.(4)At the same time,most of the residue in the oxygen atmosphere is oxidized.The free radical theory of supercritical water is suitable for near-critical water oxidation,and the outside oxygen is the main source of oxidizing raw materials.(5)The reaction temperature and the reaction time have a significant influence on the yield of the product under near-critical water condition.The oxygen pressure has little effect on the degradation reaction of coal in near-critical water.The optimum reaction conditions for near-critical oxidation of liquefaction with Houma lignite as raw materials were reaction temperature 300 ?,reaction oxygen initial pressure 5MPa,reaction time 5Min.(6)At the same time,the reaction path of lignite molecular structure to decompose water-soluble acid under near-critical water condition is deduced,and the reaction product is predicted to provide guidance for industrial production.