Catalytic Coal Liquefaction Using Synthesis Gas

Abstract

High sulfur bituminous coal is liquefied and desulfurized effectively by hydrotreating with synthesis gas at temperatures of 400-450 °C and operating pressures of 3000-4000 psi in the presence of cobalt molybdate and sodium carbonate catalysts, steam, and a recycle oil. Comparison with coal liquefaction using pure hydrogen and cobalt molybdate catalyst has shown that, in both systems, the optimum liquefaction temperature is in the range of 425-450 °C and there is no significant difference in the coal conversion and the oil yield. The sulfur content and the viscosity of the oil product both decrease with the amount of hydrogen consumed in each system, but less total hydrogen is required for the same oil product quality in the synthesis gas than in the hydrogen system. The catalytic hydrotreating of coal using synthesis gas, unlike that using hydrogen, removes large amounts of the oxygen in coal as carbon dioxide. The off-gas, with increased H2:CO ratio, is a low-Btu gas which could be burned or utilized for methane production or methanol synthesis. The cost of hydrogen production is saved.

Conceptual Design of Pyrolytic Oil Upgrading Process Enhanced by Membrane-Integrated Hydrogen Production System

“…The application of syngas HT was investigated by Fu et al [14] and the results showed promising potentials. They employed syngas to hydrotreat the liquefied coal, and the conversion was similar to pure hydrogen; they suggested that the water content showed significant impacts on the performance, which could reduce hydrogen consumption by an in-situ WGS reaction.…”

“…In addition, the water, CO and CO2 are generated in pyrolytic oil upgrading reactions as byproducts, which could contribute to hydrogen production through an in-situ WGS reaction; therefore it is feasible to employ syngas (a raw product output from SMR reactor) as a hydrogen supplier for the pyrolytic oil hydrotreating (HT) process. The application of syngas HT was investigated by Fu et al [14] and the results showed promising potentials. They employed syngas to hydrotreat the liquefied coal, and the conversion was similar to pure hydrogen; they suggested that the water content showed significant impacts on the performance, which could reduce hydrogen consumption by an in-situ WGS reaction.…”

Effects of Sodium Carbonate Additive on the Hydroliquefaction of a Sub-bituminous Coal with Fe-Based Catalyst under Mild Conditions

“…Therefore, this paper is devoted to enhance the catalytic activity of an Fe-based catalyst for the hydroliquefaction of low-rank coals under mild conditions. It is well-known that low-rank coals (lignite and sub-bituminous coal) are rich in oxygen and contain a variety of functional groups, and the liquefaction of low-rank coals can be effectively promoted by alkaline catalysts in CO (or synthesis gas)/water (or mixture of hydrogen donor solvent and water) system. − Cassidy et al reported that NaAlO 2 , NaSiOx, and Mg­(OAC) 2 can significantly promote the liquefaction of partially dried Victorian brown coal catalyzed by Cu, Ni, and Co catalysts with synthesis gas in the presence of tetralin, and compared with over 0.30 Cu­(OAc) 2 /kg dry coal alone, the conversion and oil yield increased from 66% and 29% to 74–94% and 33–46% with the addition of 0.33–1.14 mol NaAlO 2 /kg dry coal. Hulston et al reported that the treatment of Victorian coal with alkali solution (NaAlO 2 or NaOH) before Ni-Mo impregnation led to a significant increase in oil yield without solvent or added sulfur.…”

Roles of Na 2 CO 3 in lignite hydroliquefaction with Fe-based catalyst

“…Likewise, this paper focused on the investigation on lignite hydroliquefaction with Fe-based catalyst. It is well-known that the lignite contains abundant oxygen-containing moieties, which can be more easily hydrolyzed due to the promotion of alkali carbonates such as Na 2 CO 3 [26][27][28][29][30][31][32][33]. Thus, it is suggested that if alkali carbonate is added into the lignite hydroliquefaction system with Fe-based catalyst, it probably affects the lignite hydroliquefaction process.…”

“…Eom et al [28] reported that in the phenethyl phenyl ether (PPE) hydrolysis reaction with Na 2 CO 3 , the formed Na + -PPE adduct was a pivotal intermediate, which was dissociated to produce phenol, styrene and ethylbenzene through the parallel routes of heterolytic β-ether bond cleavage and α-hydrogen abstraction. Fu et al [29,30] found that under both synthesis gas-Co/Mo and hydrogen-Co/Mo systems with Na 2 CO 3 , the average oil yield increased and the oil product was quite fluid at room temperature (even after many recycles). Cassidy et al [31] reported that the alkali interacted with acidic groups in coals and also simultaneously combine with traditional catalysts to promote the brown coal liquefaction with synthesis gas and water.…”