| Coal direct liquefaction is a kind of efficient coal clean utilization technology. Hydrogen is the feed gas of coal direct liquification process and upgrading of coal liquid, so that the thorough study of the regular pattern of hydrogen dissolved in coal liquid has important theoretical and practical meanings for coal direct liquification process and upgrading of coal liquid. This paper studies the regular pattern of hydrogen dissolved in coal liquid and the role of hydrogen during QCLHT.To research the regular pattern of hydrogen dissolved in coal liquid, the experimental device measuring gas solubility in liquid under the high temperature and high pressure was improved. The experimental device added an attemperator in the sampling system can measure hydrogen solubility in some solvents that are solid at normal temperatures. The reliability of device was verified using methylbenzene as the solvent. This paper measures hydrogen solubility in naphthalene and 1-naphthol in using this device for the first time. The regular pattern of hydrogen dissolved in the model components of coal liquid and two-component mixed solvents was studied. The model components of coal liquid consist of hexadecane, methylbenzene, naphthalene, tetrahydronaphthalene, quinoline and 1-naphthol. Two-component mixed solvents consist of different proportions of hexadecane-tetrahydronaphthalene, hexadecane-quinoline, tetrahydronaphthalene-quinoline. The results show that hydrogen solubility in all solvents increase with rising temperature and partial pressure of hydrogen. It exits a rapid stage in first 5 minutes in the process of hydrogen dissolved, then increases gradually and approaches the basic equilibrium at 30 minutes, and reaches a steady-state value with the time prolonging. The ability of hydrogen solubility in all solvents also depends on property of solvents, it reflects the laws that (1) hydrogen solubility in alkane is more than that in aromatic hydrocarbons, (2) hydrogen solubility decreases when the condensation aromatic ring number increases in aromatic compound, and (3) hydrogen solubility in organic compounds containing nitrogen is significantly lower than in that corresponding aromatic hydrocarbons without heteroatoms.Based on Pierotti method and Henry law, A new mathematical model about hydrogen solubility in all solvents is proposed by referring to Henry's law expression of hydrogen solubility in metal, the expression of the model isin which related parameters in the model are obtained by regression of a few known solubility data for different solvents. Related parameters of the hydrogen in the model components of coal liquid and coal liquid were summarized in Table.3-2.The model may accurately present the relationship between hydrogen solubility in hydrocarbons and temperature and pressure, the property of solvents is also involved. It indicates the model is suitable for numerical computer simulations of hydrogen solubility in different solvents.Based on research of the rule of hydrogen solubility in different solvents, the role of hydrogen during QCLHT is studied by using a 17ml tubular resonance agitation microautoclave reactor. It is shown that conversion under N2 during the initial high activity stage process of coal liquefaction and QCLHT without catalyst in which tetrahydronaphthalene and naphthalene are selected as solvents respectively was slightly above the that under H2. It is shown that hydrogen doesn t take part in largely the coal liquefied reaction. From research of the rule of hydrogen solubility in different solvents, hydrogen solubility within 5 min has reached more than the 76% of the maximum during initial high activity stage process of coal liquefaction and QCLHT without catalyst. It illustrates the dissolution of hydrogen is not the critical factor that hydrogen could not take part in the reaction during these coal liquefaction. When ammonium molybdate is selected as the catalyst in QCLHT in naphthalene under H2, the catalyst only promotes the transformation of the liquefied product into lighter components instead of promoting the increase of the total conversion rate. When high dispersed iron-based catalyst or impregnated Fe2S3 are selected as catalyst in QCLHT in which tetrahydronaphthalene and naphthalene are selected as solvents respectively under H2, the catalysts promote not only hydrogen to take part in coal liquefaction, but also promote the more obvious change of the liquefied product into lighter components. However, the increase of total conversion rate is limited. These results demonstrate that the addition of catalyst promotes hydrogen to take part in coal liquefaction and the various types of catalysts has the different catalytic results because of different mechanism. When solvent possess hydrogen donating abilities, active hydrogen of QCLHT come mainly from the solvent. In this paper, based on the result of this paper and the former one of our research group, the reaction mechanism of QCLHT is obtained by the comprehensive analysis. The model of reaction mechanism is shown in Figure.5-9. The features of this model are shown as follow:1) The reaction mechanism of QCLHT is connected with the coal-liquefying reaction and coal molecular structure. Bridge of basic unit in coal molecular structure will be cracked to greatest extent in the process of QCLHT.2) When hydrogen donating abilities of solvent is good and the amout of solvent is abundant In the system of reaction, hydrogen donating speed of solvent is both very large and very fast, hydrogenation is Better and faster than polycondensation during polycondensation competing with hydrogenation.3) The experiment of QCLHT at 773.15 K indicates that For direct coal liquefaction, the gases come from four parts:detachment of the original side chains in coal molecular, detachment of newly-formed side chains because of ring-opening of aromatic compound, and polycondensation of free radicals. For QCLHT, the latter two parts are restrained effectively.
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