Integrated Process Of Oil Shale Hydropyrolysis With Shale Oil Hydrotreatment

Most forecasts of energy supply and demand show a projected shortfall in liquid hydrocarbons and considerable research has been undertaken to develop new processes for the conversion of unconventional sources of hydrocarbons, heavy oils or oil shale oils into clean liquid fuels. Liquid fuels from oil shales represent an alternative to this problem. Oil shale, an unconventional energy source with abundant reserves and wide distribution, can produce shale oil with properties similar to natural oil through heat treatment. Meanwhile, shale oils derived via pyrolysis of oil shales are characterized by high alkene contents, high heteroatomic content and higher aromaticity compared to crude petroleum oils. This dissertation focused on increasing shale oil yield and improving shale oil quality simultaneously by introducing an integrated process of oil shale hydropyrolysis with shale oil hydrotreatment. Two oil shale samples, Liushuhe (LSH) oil shale from Heilongjiang province of China and Estonia (EST) oil shale, were used in this work. The feasibility of utilizing synthetic gas to replace hydrogen during hydropyrolysis was also discussed. Besides, this dissertation has also been involved in the study of mechanism and kinetics of pyrolysis of oil shale, mainly concerning the contribution of inorganic material during pyrolysis and hyropyrolysis of oil shale.Thermogravimertric (TG) analysis and a fixed bed reactor were used to test the influence of inorganic materials during pyrolysis and hydropyrolysis. Usually, decomposition of kerogen to oil, gas, and char products is a two-stage process. First, decomposition of kerogen to pyrolytic bitumen occurs and, second, decomposition of bitumen to final products takes place. From the kinetic parameters derived from TG/DTG results, the following conclusion was achieved. Silicate minerals in LSH oil shale shifted activation energy to higher values for the first stage, however, inorganic matter caused no remarkable change during the second stage. For EST oil shale, the case was different. It was found that the second stage reaction was catalyzed by carbonate minerals while the first stage was inhibited. The results from the fixed bed reactor showed that inorganic minerals changed the product distribution during pyrolysis and hydropyrolysis of LSH and EST oil shale.Knowledge of the chemical composition of the retorted shale oil provides insight for selecting upgrading conditions. Acid-base extraction and column chromatography were used to separate shale oil to six different fractions, and GC/MS was used to identify specific compounds. The results indicated that aliphatic fraction is composed of alkane, branched alkane, cycloalkane and alkene, whereas normal alkane was main component. Aromatic fraction contains2to4ring aromatic compounds, such as, naphthalene, phenanthrene, anthracene and their alkylated derivative. Oxygen-containing compounds mainly exist as acid phenol, naphthol and their alkylated derivative, The minority of oxygen-containing compounds are neutral alkylated ketone. The majority of the nitrogen-containing compounds are pyridine, quinoline, indole, carbazole, aniline and their alkylated derivatives and aliphatic nitriles. Compared to the LSH shale oil, nitriles and aniline are not founded in EST shale oil.The integrated process of oil shale hydropyrolysis with shale oil hydrotreatment achieved the target of increasing shale oil yield and improving shale oil quality simultaneously. LSH oil shale is hydrogen deficient compared with EST oil shale and the corresponding shale oil yield produced by pyrolytic methods was much lower. The hydropyrolysis seemed particularly well suited for processing LSH oil shale since oil yield substantially increases by operating under a high hydrogen partial pressure.The results of the integrated process showed that sulfur and nitrogen in shale oil were dramatically removed; the content of light distillate increases; aliphatic and aromatic fraction increases with the reduction of heterocyclic compounds. Three and four ring polycyclic aromatic hydrocarbon decreases while single ring aromatic compounds and two ring polycyclic aromatic hydrocarbon increases. The suitability of three commercial catalysts based on Ni/Mo, Co/Mo and Ni/W were also evaluated. The Ni/Mo shows the most satisfactory performance.The results of pyrolysis of LSH oil shale under coal gas atmosphere indicated that it is feasible to use coal gas instead of hydrogen during hydropyrolysis of oil shale. The influence of gas component on the pyrolytical yield was also summarized. The increase of oil yield is mainly attributed to the hydrogen in coal gas. Methane acted as an inert role during pyrolysis. The existence of carbon dioxide significantly increases water yield due to reverse water-gas shift reaction. Carbon monoxide suppresses the reverse water-gas shift reaction of carbon dioxide and thus inhibits the formation of water.