Study On Hydrogenation Processes Of Heavy Oil Derived From Biomass Alcoholysis

As petorleum resources dry up, people put emphasis on liqiud bio-oil derived from renewable biomass. Bio-oil is of easy restoration and transportation and high energy density, which is easy to make bio-oil commercial productin and high value utilization. At present, there are two main technologies to pruduce bio-oil, fast pyrolysis and solvent degradation. There are a lot of efforts on fast pyrolysis bio-oil. However, the reaction temparature of fast pyrolysis is relatively high (300⁵00℃), and it requires the heat transfer rate higher than 500℃/s that makes the degradation products quite complex and contain more than 400 kinds of components that can be identified. Moreover, fast pyrolysis oil contains plenty of water and acids, and the water content is up to 35⁶0%. All of these problems hinder the development of fast pyrolysis technology. Instead, alcoholysis technology especially n-octanol as the solvent can reduce the react-ion temparature to 130¹70℃. And the reactive solvent promotes directional depolymerization which can produce light oil abundant in esters and ethers. The study used acidified n-octanol as the solvent under relatively low temperature 130¹50℃to make Eucalyptus wood powder liquefaction. The liquefaction product was separated into three parts by solvent extraction: light oil, heavy oil and residue. Light oil only contains five simple components and is benefitable to be used as feedstocksof high-vaue chemicals. Heavy oil that its maximum yield is 36.72% (based on crude biomass) can be burned directly in heavy oil boiler. However, heavy oil is not stable and sticky. There will be many problems if heavy oil is burned directly. To improve heavy oil's quality, catalytic upgrading is necessary. The results are listed below:1. In this research, Eucalyptus wood powder was the feedstocks with acidified n-octanol as the solvent that the liquid ratio (the amount of 1-octanol to that of biomass) was 2:1. The Eucalyptus wood powder was liquefied at 130¹50℃in 60 min. Heavy oil which was black and sticky was separated from the liquefaction product. The analysis on heavy oil indicated that the acidity was 0.963 mgKOH/g, heating value was 36 MJ/Kg, density was 0.82 kg/m3, and ash content was 0.095%. Heavy oil was mainly the degradation of lignin in biomass and comprised aromatic or phenolic compounds containing hydroxyl, carbonyl, ether and other oxygen-containing functional groups. Through GPC analysis on the molecular weight, heavy oil mainly contained two parts, macromolecular part was 2805 and small molecuar part was 242.2. Heavy oil was hydrotreating with Pd/C as catalyst at 90²10℃. The reaction time was 30⁹0 min in atmospheric pressure with H2. The result showed that reaction temparature exerted the greatest influence on heavy oil hydrotreating. At 90℃, heavy oil conversion rate was the lowest, only 9.1%. However, when the reaction temparature was increased to 180℃, heavy oil conversion rose to maximum in the series experi-ments, 40.5%. FTIR, GPC and ultimete analysis on heavy oil and its hydrotreating products indicated that the amounts of hydroxyl groups and ethers increased obviously in heavy oil. When reaction temparature was 120℃, the molecular weight of heavy oil decreased dramatically about 50%. After hydrogenation, oxygen content decreased 55.4% while hydrogen increased 16.2%. GC-MS analysis on light part showed that light parts mainly contained small aromatic molecules, phenols and benzoic acid esters, such as 1-Ethyl-2-methyl-benzene, Phenol, Dioctyl phthalate, Isophthalic acid 1-butyl ester 3-phenyl ester.3. Heavy oil was hydrotreating with V-W-Mo-Cu/γ-Al₂O₃ as catalyst at 330⁴50℃. The reaction time was 10⁵0 min in initial H2.pressure 2⁸ MPa. And the maximun heavy oil conversion rate was 93.3%. FT-IR analysis on heavy oil before and after hydrogenation shows that when the catalytic hydrogenation reaction temperature higher than 420℃, ethers disappeared in heavy oil, carbonyl and hydroxyl absorption peaks also decreased significantly. GC-MS analysis on light part showed that after hydrogenation and separation, light parts mainly contained single ring aromatics such as 1-Ethyl-4-vinyl-benzene. In addition, there were some benzoic acid esters such as Isophthalic acid 1-butyl ester 3-phenyl ester.4. Heavy oil was hydrotreating with FeS₂ as catalyst at 330⁴50℃. The reaction time was 10⁵0 min in initial H2.pressure 2 to 8 MPa. The result showed that when the reaction temperature was below 390℃, light part from heavy oil hydrogenation contained only a little amount of single ring aromatics such as 1-Ethyl-2-methyl-benzene, Isobutyl-benzene. But when the reaction temperature increased to above 390℃, the material type of components in light parts increased significantly. Apart from 1-Ethyl-2-methyl-benzene, light parts also contained 1,2,3-Trimethoxy-5-vinyl-benzene, Isopropenyl-benzene, Phenol, etc. When the reaction temperature was above tetralin's critical temperature (417℃), conversion rate of heavy oil would increase to 89.4%. The reaearch also indicated that reaction time exerted little impact on heavy oil hydrogenation.5. In this study, the three catalysts have advantages and disadvantages. Such as Pd/C, though iht reaction conditions are mild, it is very expensive and is difficult to be recycled after reaction. Although the price of FeS₂ is extremely low, it required harshreaction conditions. Although the preparation process of V-W-Mo-Cu/γ-Al₂O₃ is complex,it have high catalytic activity andthe advantages of reuse. It is beneficial to large-scale use, and therefore the most suitable of the three catalysts in the hydrogenation of heavy oil.