Dilute-phase hydrogenation

Low sulfur fuel oils were prepared from a high volatile bituminous coal by hydrogenation under high temperatures and pressures. At a coal conversion of 80%, the ratio of oiU to-gas yields was about three, and 23% of the coal sulfur was contained in the oil. Sulfur content of the oil, however, remained the same at different coal conversion levels. The data obtained in the semi-continuous, dilute phase hydrogenation system showed that the whole oil can be directly used as a fuel oil where 1% sulfur is tolerated. Fuel oils containing 0,5 and 0,25% sulfur were produced by desulfurization of the whole oil, A preliminary economic evaluation indicated that low sulfur fuel oils can be produced from coal by hydrogenation at a manufacturing cost of about 5-6 per barrel. 

Figure 4. Effect of hydrogen feed to coal ratio on increasing the heating value of gas by dilute-phase hydrogenation...

G. N. Lewis and H. Storch, "The Potential of the Bromine Electrode the Free Energy of Dilution of Hydrogen Bromide the Distribution of Bromine Between Several Phases". J. Am. Chem. Soc., 39, 2544-2554 (1917). 

Qader, et al., (4) reported work on hydrogenation in a dilute phase free fall reactor at temperatures in the order of 515°C, pressures of 2000 psi and with a heavy dose of catalyst, 15% stannous chloride by weight of coal. Up to 75% conversion was reported with a product distribution of 43% oil, 32% gas and 25% char. The residence time of the coal feed particles was estimated to be in the order of seconds, however, no measurement was made and aromatics were reported after further hydrorefining in a second stage hydrogenation. 

The concept is a dilute-phase hydrogasification process in which coal is directly reacted with hydrogen to produce maximum yield of methane in the reactor. We are not, as an organization, competitive with industry either in hardware or in process work. 

C designates the non-reactive elemental carbon contained in the char product The chemical reaction is assumed to be the rate controlling step. This assumption is justified in the Discussion of Results. The reactions are considered to be first order with respect to fraction of carbon remaining in coal as well as converted to hydrocarbons and m 1 order with respect to H2 partial pressure. The details of the development of the model is reported elsewhere ( ). The experimental data correlated was obtained from dilute phase operation in an excess of hydrogen atmosphere, so the partial pressure of hydrogen was considered to be approximately equal to the total system pressure and was assumed constant along the length of the reactor. 

Discussion of Results and Conclusions. The results of regression analysis show that a chemical reaction model, first order with respect to fractional carbon conversion, with a production and a decomposition step for each of CH4, C2H5, BTX and Oils, satisfactorily describes the dilute phase flash hydrogenation of both lignite and subbltumlnous coal. 

The piu ified activated charcoal, whose BET surface area amounted to 1140 m2/gm, was soaked with a dilute solution of PdCl2-2 HCl, left for several hours, and then filtered and washed completely. It was confirmed that all palladium ions were completely adsorbed on the charcoal and all chloride ions were completely washed out from the charcoal. The catalyst thus prepared exhibited an excellent catalytic activity for the liquid-phase hydrogenation of the benzene nucleus at room temperature without preliminary reduction with hydrogen. This catalyst, furthermore, after evacuation for several hours at 200-300°,... 

The gas phase hydrogenation of acetonitrile has been studied in a differential microflow reactor operating at atmospheric pressure. Prior to any measurements, the sample was reduced under a diluted hydrogen flow (H2/N2 10/90, vol/vol) at 723 K for 2h (ramp 2 K min i). The reaction temperature ranged from 343 to 453 K, and the H2/acetonitrile molar ratio was 6.8. The effluent was analyzed by sampling on line to a gas chromatograph (Perkin Elmer) equipped with a capillary column (30 m x 0.25 mm i.d., apolar phase) and a flame ionization detector. 

Since then, a dependable system for hydrogasifying coal in dilute phase has been developed, and experimental data are being obtained. In addition, some data have been obtained for hydrogenating dilute-phase char. These experimental results are presented, and a theoretical process is discussed which integrates these two operations for producing high B.t.u. gas on a commercial scale. 

Results and Discussion. In dilute-phase hydrogasification, the composition of the effluent gas is determined by the feed gas rate and composition and the gas yield. The feed gas rate and composition can be selected somewhat freely, but the gas yield depends on many variables, some of which interact. The most prominent variables are coal rate, hydrogen coal ratio, maximum temperature attained by the solids and the vapors, residence times of the solids and the vapors, total pressure, hydrogen partial pressure, particle size and density, gas viscosity, heat... 

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