Peter S. Maa

Alkylation: a beneficial pretreatment for coal liquefaction

Abstract Several coals were alkylated employing isopropyl and methyl halides under Friedel-Crafts conditions. These alkylated coals, and corresponding untreated coals, were processed (liquefied) with tetralin in batch autoclaves (tubing bombs) at 700 K, 130 min residence time, and 10 MPa (1500 psi) hydrogen pressure. Conversion to cyclohexane-soluble liquids was found to be 10–21 percent higher (on an alkyl-group-free basis) for the alkylated coals than for untreated coals. These results are explained on the premise that alkylation beneficially disrupts the coal structure sufficiently to allow improved contacting between coal and tetralin.

Stability of adamantane and its derivatives to coal-liquefaction conditions, and its implications toward the organic structure of coal☆

Abstract Adamantane, diamantane, 2-phenyladamantane, and adamantanone were shown to be stable to H-donor conditions, under which coals are converted to liquids (425 °C; 130 min; 2:1 tetralin to substrate). Both 1-adamantanol and 1-adamantane carboxylic acid were completely converted to adamantane. The data demonstrate the remarkable stability of this class of hydrocarbon, and argue against polyamantanes as models for major structural features of coals.

Reaction of methane with coal

Abstract The reactivities of Australian coals and one American coal with methane or methane-hydrogen mixtures, in the range 350–400°C and a range of pressures (6.0–8.3 MPa, cold) have been examined. The effects of aluminophosphates (AlPO) or zeolite catalysts, with and without exchanged metals, on reactivity have also been examined. Yields of dichloromethane extractable material are increased by using a methane rather than a nitrogen atmosphere and different catalysts assist dissolution to various extents. It appears that surface exchanged catalysts are effective, but incorporating metals during AlPO lattice formation is detrimental. Aluminium phosphate catalysts are unstable to water produced during coal conversion, but are still able to increase extraction yields. For the American coal, under methane-hydrogen and a copper exchanged zeolite, 51.5% conversion was obtained, with a product selectivity close to that obtained under hydrogen alone, and with only 2% hydrogen consumption. The conversion under methane-hydrogen was close to that obtained under hydrogen alone, while a linear dependence of conversion on proportion of methane would predict a 43% conversion under methane-hydrogen. This illustrates a synergistic effect of the methane-hydrogen atmosphere for coal liquefaction using this catalyst system.

Reactivity of methane at low temperatures (∼400°C) with ‘refractory’ bonds

Abstract The thermal cracking of benzene, toluene, diphenylmethane, biphenyl, diphenyl sulfide, diphenyl ether, phenol and dinaphthol was studied in the presence of inert gases, methane, methane-hydrogen mixtures and Cu-Beta, H-Beta and Cu-ZSM-5 catalysts at various reaction temperatures (350–480°C), pressures (3.5–9 MPa) and times (1–4 h). For some systems methane assists conversion by either methylation (benzene, biphenyl) or debenzylation and methylation (diphenylmethane). In others, where methylated materials are reactants, demethylation may occur at the same time as debenzylation. The activities of the various catalysts are compared. Their effectiveness in conversion or selectivity varies with organic substrate. Two mechanisms of conversion are identified. One involves direct addition of methyl groups, the other includes a disproportionation process probably resulting in carbon deposition.

A critical temperature threshold for coal hydropyrolysis

Abstract Pyrolysis of coals in the presence of hydrogen is known to enhance liquid yields, but this enhancement is often accompanied by increases in methane make. In many instances increased methane yields are detrimental because of the amount of hydrogen consumed to make methane. This paper will discuss the discovery of a critical temperature threshold for coal hydropyrolysis, below which little methane is formed, and above which significant methane is produced. A simple procedure is described to determine the critical temperature, which is different for each coal and pressure regime used.

Solvent Effects in Exxon Donor-Solvent Coal Liquefaction

The Exxon donor-solvent (EDS) coal liquefaction process is being developed by Exxon Research and Engineering Company (ERaE) under the joint sponsorship of the Department of Energy and private industry.* This development project includes operation of a 250-ton/day (2.27 x 105 kg) liquefaction pilot plant in Bay town, Texas and laboratory and engineering studies aimed at producing technology upon which pioneer, commercial-scale EDS plants may be built. The process handles a variety of coals ranging in rank from lignitic to bituminous and produces high-quality naphtha and distillate liquids. The laboratory component of this program includes the operation of two 75 lb (34 kg)/day coal liquefaction pilot plants and a 1-ton (910 kg)/day coal liquefaction pilot plant at the Baytown Research and Development Division of ER&E. Small batch autoclaves called tubing bombs are also used extensively in screening studies.