| Coal/heavy oil hydrogenation replaces the hydrogen supply solvent in the traditional direct coal liquefaction with heavy oil to realize the process of coal liquefaction and heavy oil lightening.Existing studies have shown that coal/heavy oil hydrogenation can obtain a higher conversion rate of dry-based ashless coal(>95%),but the yield of light oil(gasoline,diesel)in its liquefaction products is lower(<20%).Affect the economics of the technology.Therefore,exploring the lightening process of coal/heavy oil hydroliquefaction products and improving the yield of light oil can provide strong support for the further development of this technology.In this paper,the coal/heavy oil hydrogenation reaction of Xinjiang and Mengdong lignite was first carried out in an autoclave.The distribution of liquefied products and the hydrogenation activity of solid products were analyzed,and the coal/heavy oil hydrogenation conditions were determined.As the reference condition,the liquefied product is used as the raw material for the lightening reaction.Furthermore,on the basis of the benchmark conditions,the reaction temperature and reaction time were further increased,and the influence of the two key lightweight process parameters of temperature and time on the yield of lightweight products was investigated,and better lightweight process conditions were optimized.Finally,through elemental analysis,XRD,1H-NMR,SEM,determination of relative molecular weight(VPO)and other characterization methods,the composition and morphology of the asphaltene and solid residue in the lightweight products were characterized,and they were compared with coal/The distribution of heavy oil hydroliquefaction products was correlated.Studies have shown that the lightening reaction temperature and time have similar effects on the distribution of the lighter products of Xinjiang lignite/heavy oil hydroliquefaction products(XJ)and Mengdong lignite/heavy oil hydroliquefaction products(MD).As the reaction temperature rises If the reaction time is high or the reaction time is prolonged,the light oil yield will increase,the asphaltene yield will decrease,and the solid residue yield will decrease first and then increase.Both XJ and MD lightweight process conditions are: reaction temperature 440°C(reference +20°C),reaction time 75 min.Under these better conditions,the yield of light oil in the XJ lightweighting reaction product was 21.95%(reference + 10.72%),the yield of asphaltene was 11.89%(reference-5.37%),and the yield of solid residue was 6.01%(Benchmark-0.93%).The yield of light oil in the MD lightening reaction product was 11.76%(reference +2.34%),the yield of asphaltene was 7.49%(reference-2.42%),and the yield of solid residue was 11.40%(reference-4.15%).Asphaltene is a compound with aromatic ring and heterocyclic ring.It is centered on fusedring aromatic hydrocarbon,and its side chain is dominated by shorter alkyl side chains such as methyl,ethyl,and propyl.The solid residue is composed of carbonaceous components,mineral particles and fused-ring aromatic hydrocarbon organic matter,and has an obvious layered accumulation structure,in which the carbonaceous components can still be transformed.As the lightening reaction temperature increases or the reaction time prolongs,the side chain of the asphaltene alkyl continues to break,the carbon fraction of the alkyl decreases,the relative molecular weight and the degree of condensation decrease,and the convertible carbon components in the solid residue decrease This leads to an increase in the yield of light oil in the lightening reaction product and a decrease in the yield of asphaltenes and solid residues.When the reaction temperature or reaction time is too high or too long,the relative molecular weight and condensation degree of the asphaltenes will increase,resulting in an obvious accumulation structure.The phenomenon of polycondensation between asphaltene macromolecules is obvious,and the increase of spherical particles on the surface of the solid residue leads to a decrease in the yield of asphaltene in the light-weight reaction product and an increase in the yield of solid residue. |
PDF Full Text Request