Coal and model compounds were hydrogenated and desulfurized in the presence of petroleum solvents and catalyst under coprocessing condition by using hydrogen or syngas (H2+CO) with steam in place of hydrogen. The catalysts used include NiMo, CoMo, synthetic pyrite and ZnCl2 catalysts. In general, the catalyst activities are somewhat lower with the use of syngas than with hydrogen. Nickel molybdate and cobalt molybdate catalysts impregnated with potassium carbonate, however, exhibited good activities for coal conversion as well as hydrogenation and desulfurization of model compounds with the use of syngas. Better results were obtained at a mild temperature of 400°C for the coprocessing of coal with petroleum solvents using syngas. It was observed, with the solvents containing decalin, that decalin underwent dehydrogenation and isomerization, and that the extent of hydrodesulfurization increased with the increase of trans/cis ratio of the remaining decalin after the reaction. The addition of or 1-methylnaphthalene with decalin in the solvent mixtures increased the extent of conversion even though these compounds are nonhydrogen donors, suggesting that these compounds could be acting as hydrogen shuttlers to transfer hydrogen from decalin to coal or model compounds.
Victorian brown coal was hydroliquefied with two kinds of solvents in the presence of iron/sulfur catalyst using a process development unit (PDU) with three stirred tank reactors in series. The effects of solvent properties on the progress of the liquefaction reaction and the actual state in the plural reactors were investigated by analysing product yields and liquid samples from each reactor. Vaporization of solvent fraction and actual residence time of the liquid phase in the reactors were also determined by using the results of these analyses. The solvents used were a creosote oil and a recycling solvent recovered from other PDU operations. Oil yield with the recycling solvent in the first reactor was higher than that with the creosote oil although the liquefaction reactions mainly took place in the first reactor with both solvents. However, oil yield through three reactors was almost the same with both solvents. These results indicate that the hydrogen donation from the solvent was effective at the early stages of liquefaction, and the hydrogen shuttling by solvent with catalyst was effective for hydroliquefaction of heavy products such as preasphaltenes derived from the coal. These conclusions were supported by analyses of the amount of transferred hydrogen to the products and liquid phase in the reactor. These results show that the vaporization and actual residence time of hydrogenated solvent were larger than that of non-hydrogenated solvent such as creosote oil.
Catalytic effects of limestone on oxidation of NH3 and HCN were investigated with a quartz fixed bed reactor at temperatures between 923K and 1123K. Limestone was found to be an active catalyst of oxidation of NH3 and HCN. The major product of NH3 oxidation was NO.N2O was not detected as a product of NH3 oxidation. The intrinsic selectivity of NH3 to N2O was calulated by eliminating the effect of secondary decomposition of N2O by coexisting limestone. The intrinsic selectivity of NH3 to N2O was no higher than 3%. The major products of HCN oxidation were NO and N2. Selectivity of HCN to N2O for catalytic oxidation was 3 to 10%, which are considerably lower than the reported value of selectivity for homogeneous HCN oxidation.
Catalytic activity of uncalcined limestone to decompose N2O was evaluated with a quartz fixed bed reactor at 1123K under elevated CO2 partial pressure conditions to suppress decomposition of CaCO3. The rate of SO2 capture was also measured for uncalcined limestone. The rate of N2O decomposition over uncalcined limestone was found to be more than two order of magnitude lower than that of SO2 capture. The rate of N2O decomposition over uncalcined limestone was more than three order of magnitude lower than N2O decomposition rate over calcined limestone.