The catalytic hydrodeoxygenation (HDO) of dibenzofuran was examined on a presulfided NiMdyAlzOa catalyst. Based on the reaction intermediates identified in the present study a reaction network for the removal of oxygen from dibenzofuran has been established. In view of the failure to detect certain key reaction intermediates an approximate network has been proposed for kinetic analysis. Using the approximate network the effects of temperature in the range 616-6491(, hydrogen pressure in the range 6.89-13.78 MPa and initial concentration of dibenzofuran in the range 9.78 X g moVg oil were examined upon the individual steps.The removal of oxygen from dibenzofuran under the above conditions proceeded via direct oxygen extrusion without hydrogenation of the adjacent benzene rings as well through the formation of hydrogenated intermediates, with the catalyst showing selectivity towards the latter mode of oxygen removal. Presulfiding the catalyst as well as addition of CS2, to maintain a partial pressure of H2S during the reaction, enhanced the activity of the catalyst. The effect of initial concentration of dibenzofuran indicated a retarding influence on its HDO, possibly due to the formation of refractory reaction intermediates.The HDO of two key reaction intermediates in the network for dibenzofuran, namely, o-phenyl phenol and o-cyclohexyl phenol, was also examined on a presulfided NiMolyAlzOS catalyst to establish the reaction network for dibenzofuran.The primary mode of oxygen removal from both the phenols, in the temperature range of 561-64K and 10.34 MPa hydrogen pressure, was through the formation of highly reactive hydrogenated intermediates. All the primary reactions for o-phenyl phenol were catalytic in nature, whereas, o-cyclohexyl phenol was found to crack to phenol and cyclohexane even under purely thermal conditions. The rates of decomposition of the above phenols were fairly rapid and highly temperature sensitive, thereby explaining their absence in the reaction products of dibenzofuran.-21.39 X SCOPEThe catalytic hydrodenitrogenation (HDN) and hydrodesulfurization (HDS) of coal-derived liquids is carried out to provide a fuel that is low in nitrogen and sulfur content. The unusually high oxygen content of coal-derived liquids has recently caused a growing interest into the interactive effects between oxygen, sulfur and nitrogen compounds during their removal. Under conditions that favor HDN and HDS, HDO can also occur, with the formation of H 2 0 which is a known catalyst poison. The reactions involved in the removal of oxygen during hydroprocessing is poorly understood at the present time. The purpose of this paper is to clarify the reaction network for oxygen removal from dibenzofuran, which is known to exist significantly in coal liquids, using a presulfided NiMo/ ?-A1203 catalyst. The effects of temperature, hydrogen pressure and initial concentration of dibenzofuran on the individual steps in the reaction network have been examined.Two key reaction intermediates in the HDO of dibenzofuran, namely...

No abstract

A mathematical model to describe backmixing in a bubble column with a side gas stream is developed from fundamental considerations. With the aid of experimental data the dispersion coefficients above and below the quench are evaluated. Results indicate that injection of a fraction of the total gas as a sidestream Is not as effective in axially dispersing the liquids as bubbling all the gas from the bottom of the column.

Baker, C. G. J.; Bergougnou, M. A. Can. J . Chem. Eng. 1972, 50, 695. Kim, S. D.; Baker, C. 0. J.; Bergougnou, M. A. Can. J. Chem. Eng. 1975, 53, 134. KO&, K.; MarWka, S.; Ueyama, K.; Matsurra, A.; Yamashlta. F.; Iwamoto, S.; Kato, Y.; Inoue. H.; Shloeta. M.; Suzuki, S.: Akehata, T. J . Chem.The effect of pH on the removal of pyritic sulfur in airlwater chemical coal cleaning was investigated. The pH was varied by adding sulfuric acid or sodium carbonate to a coal-water slurry. The effect of nearby neutral pH (-7) was determined in a buffer solution of sodium dihydrogen phosphate and disodium hydrogen phosphate. Data were taken in the temperature range of 130 to 190 OC, oxygen partial pressure of 0.32 to 1.36 MPa, and reaction times up to 3600 s. The rate of pyrite oxidation was found to be minimum at the nearby neutral conditions. Under otherwise identical conditions, the rate of pyrite oxidation was greater in basic pH than in acidic pH. The enhancement in the rate of pyrite oxidation is explained on the basis of electrochemil reactions. Under nearly neutral conditions, the overall reaction is shown to be controlled by the surface reaction, whereas under acidic as well as basic conditions, diffusion of oxygen through the product ash layer as well as the surface chemical reaction seems to be important.

A bituminous coal (Powhatan No. 5 ) and a subbituminous coal (Belle Ayr) were liquefied in the presence of hydrogen donor solvents. Statistical analyses of the data showed that for contact times up to 10 min, the coal conversion, measured in terms of tetrahydrofuran solubles, was not significantly different for the two coals. However, the subbituminous coal gave more asphaltenes than the bituminous coal.The hydrogen-donating capacity of the solvent was varied by the addition of hydrogenated phenanthrene to SRC-I1 recycle solvent. The results indicated that there are two routes for the formation of oils from coal. One is by adduct formation giving asphaltenes and preasphaltenes, which in turn gives oils, and the other is direct oil formation from coal. The preferred route depends on the hydrogendonating capacity of the solvent, The kinetic model, proposed in Part I of this paper, is extended to account for the change in the donor capacity of the solvent. SCOPECoal liquefaction can be characterized as occurring in three stages, namely dissolution, hydrogen transfer, and hydrogenation. In each of these stages the nature of the solvent can affect the rate of reaction and the selectivity of the products. Solvent components which affect the behavior of coal liquefaction processes can be classified as hydrogen donors, hydrogen shuttlers, and components that aid in solubilization. Recent studies have shown that poor bydrogendonating solvents form adducts with coal to give insoluble products. This appears to occur to a lesser extent with good donor solvents. It is likely that for the case of good hydrogen donor solvents the formation of soluble products compensate for the adduct formation. Kinetic measurements at short contact times (up to 10 min) with solvents of varying hydrogen donor capacity have been made to provide a better understanding of the processes of liquefaction and adduct formation. CONCLUSIONS AND SIGNIFICANCEIn a stirred tank batch reactor, there appears to be no significant difference in the conversion of Powhatan No. 5 bituminous and Belle Ayr subbituminous coal to pentane and tetrahydrofuran (THF) solubles for contact times up to 10 min. More asphaltenes are recovered from the liquefaction of Belle Ayr coal than from that of Powhatan coal. Both the coals, when contacted with SRC-I1 recycle solvent, show an initial effective loss of solvent.The initial depletion of oils progressively decreases with an increase in the hydrogen-donating capacity of the solvent, indicating that the initial loss of solvent is independent of the nature of coal, but it is dependent on the hydrogen-donating capacity of the solvent. Oils can be formed either directly from coal or by an indirect route via asphaltenes and preasphaltenes through adduct formation. The latter results in an initial loss of solvent. The former route gains preference over the latter as the hydrogen-donating capacity of the solvent is increased. A single kinetic model entailing both direct and indirect routes is shown to adequately represent the data o...