David S. Ross

Alcohols as H-donor media in coal conversion. 1. Base-promoted H-donation to coal by isopropyl alcohol

Abstract At 400 °C in 20 min runs, coal was converted by methanol/KOH systems to a product which was extractable by pyridine fully, and 15–25% by methanol. The methanol-sotuble fraction is significantly enriched in hydrogen relative to the starting coal, reduced in both N and organic S, and was fluid at room temperature. It was established that this liquid product was derived from the coal, and not the methanol. The liquid was distillable at 300 °C/133 Pa (1 torr), and an analysis of the liquid by gas chromatography/mass spectrometry techniques shows it to consist of significant quantities of butyrolactone, polymethyl phenols, and some unidentified compounds having major C4H7O and C4H7O2 MS fragments. The methanol-insoluble products were hydrogen-enriched also, but to a lesser degree. The suggested conversion scheme is similar to that proposed for isopropyl alcohol, where alkoxide ion donates hydride to the coal, followed by proton abstraction by the anionic intermediate from the alcohol medium. In model-compound studies at 400 °C with the system, it was found that phenyl ether was converted in 33% yield to a collection of polymethyl phenols, similar to those found in the coal distillate. Anthracene was converted in about 80% yield to 9,10-dihydroanthracene. Biphenyl, phenanthrene and bibenzyl were found to be unreactive in our system.

Conversion of bituminous coal in COH2O systems: 2. pH Dependence

Under COH2O systems at initial pH values s> 12.6, an Illinois No. 6 coal, PSOC-26, was converted to a fully pyridine-soluble product, with benzene and hexane solubilities of 50% and 18%, respectively. The product gases were H2 and CO2. However, the expected H2CO2 ratio of 1.0 based on the water gas shift reaction was not observed, but the deficit in hydrogen was found in the increased hydrogen content of the coal product. 95% coal carbon recovery and good hydrogen balances were obtained, and the coal products were found to be very similar to those from conventional tetralin systems. The results suggest an efficient base-catalysed process, and that COH2O systems are useful for coal studies.

Hydrothermal treatment and the oxygen functionalities in Wyodak coal

The effects of hydrothermal treatment (liquid water) at 350 °C on Argonne-supplied Wyodak coal previously ‘dried’ at 60 °C under 1 torr for 18 h were studied. Control experiments were conducted in the absence of added water, and with n-undecane replacing water. All runs were conducted in batch reactors with quartz liners for periods of 30 min or 5 h with added N2 (500 psi cold), and product workups and all manipulations were conducted in an N2 glove bag. A tar representing 5–7% of the starting coal was deposited on the quartz walls solely for hydrothermal conditions. In all cases the coal lost oxygen, the O-losses being in the order: undecane < no added water (30 min) = added water (30 min) = no added water (5 h) < added water (5 h). Thermal gravimetric and field ionization mass spectrometer (f.i.m.s.) analyses (ambient to 500 °C at 2.5 °C min−1) showed little difference between the experiments with undecane and those with no added water. By contrast, hydrothermal treatment yielded a volatiles fraction that was at the same time more volatile and had a greater weight average molecular weight. Phenol, catechol, and their C1-, C2-, and C3-derivatives were the two most prominent families in the f.i.m.s.-volatiles spectra, and the f.i.m.s. responses showed that under added water conditions the catechols response was increased. With undecane in place of water, the precursors to the f.i.m.s.-volatile arenols engaged primarily in regressive chemistry. The exhaustive (5 h) hydrothermal treatment resulted in virtual elimination of both phenol and catechol signals, demonstrating extensive hydrolysis of the coal structure. The results are consistent with a scheme in which water promotes the production of the tar, removing it from the coal matrix. The organic medium, on the other hand, suppresses the diffusion of thermally generated fragments, and they become irreversibly reincorporated. The O-losses are due primarily to CO2- and H2O-evolution. The data suggest that the latter is largely due specifically to catechol dehydroxylation.

Conversion of bituminous coal in COH2O systems: 3. Soluble metal catalysis

The oxyanions of the highest oxidation states of several transition metals, including W, Mo, Cr and Mn, were found to catalyse the liquefaction of Illinois No. 6 coal in COH2O systems at 400°C. Unlike the high pH (s> 12) required in the base-catalysed system, the effective range for these metal-mediated conversions extend down to pH < 5.0. The benzene-soluble product was found to have a higher HC ratio than the starting coal, and the metals were reduced to water-insoluble, lower oxidation states during conversion. A chain scheme is suggested as an explanation for the data.

Comments on the source of petroleum hydrocarbons in hydrous pyrolysis

Abstract The D-isomer distribution of alkanes isolated following hydrous pyrolysis of Messel shale in D2O by Hoering is much more broad than that predicted by statistical, sequential D/H exchange. This result is in contrast to the D-isomer profile for deuterated alkane generated in the system through the purposeful addition of alkene, which yields a profile in agreement with calculation. Thus, the generation of the alkanes from kerogen involves precursors which can undergo simultaneous deuteration at several sites, or accumulation and linking of smaller, preexchanged units. These scenarios receive some support from Hoerings data for recovered pristane, which displayed a bimodal D-isomer distribution. In this case the distribution was very well matched by the sums of two distributions calculated on the basis of two separate H/D exchanges taking place at different sites at different rates.

Supercritical water/CO liquefaction and a model for coal conversion

Abstract Studies of Illinois No. 6 coal in CO/water at 400°C over a range of conversions to toluene-soluble (TS) products show product yields in D2O consistently superior to those in H2O, the yields leveling off respectively at 60% and 50%. These findings are compelling toward a conversion scheme in which coal is partitioned in parallel, competitive steps to TS and toluene insoluble (TI) fractions, with the TS/TI ratio determined by the reduction potential of the system. Conversion is thus limited by the kinetics of conversion rather than by coal structure, this limitation applying to conversion generally, including conventional donor conversions. The CO/water system has been successfully modeled with a numerical simulation scheme on a microcomputer, the model showing that the key limiting feature of the CO/water system is irreversible consumption of OH− by CO2. The major source of CO2 is the water gas shift reaction, which operates in parallel to the conversion chemistry.

Coal Conversion in Carbon Monoxide–Water Systems

Publisher Summary This chapter discusses the conversions of bituminous coals in water systems and several aspects of the process, including the kinetics and mechanism of the conversions. The mineral matter in coals includes abundant quantities of silica, several aluminosilicates, pyrite (FeS2) as the major sulfide, and smaller quantities of oxides and carbonates. Conversion in H2/H2O systems is very sensitive to the mineral content of the coal, with the conversion falling in the absence of the mineral material. FeS2, a major component in coal mineral matter, can be very reactive under hydrothermal conditions. The effectiveness of the CO/water system in conversion has been discussed in the chapter. The increase in the level of ultimate coal conversion upon switching to D2O as the medium shows that the interplay of subtle kinetic features of the reducing system can substantially affect the convertibility of a given coal.

Regular coal structure and conversion severity

In two separate coal conversion studies, one dealing with CO-water conversions of Illinois No. 6 coal, and the other with H2S addition to conventional tetralin conversions of the lower-rank Wyodak 2, data have been collected over a range of conversion levels. For both studies the degrees of conversion were increased by increasing the reducing power of the medium, while the conversion temperature was kept constant at 400 °C for all runs. The conversion levels for the CO-water runs ranged from 29 to 60%, while the tetralin-H2S runs yielded conversions from 44 to 67%. Sequential elution solvent chromatography and field ionization mass spectrometry were used for analyses of toluene-soluble fractions from the CO-water runs and THF-soluble fractions from the H2S-tetralin runs, respectively. The analyses showed that the fraction compositions remained constant with increasing degrees of conversion. This finding suggests that there may be some gross regularity in the structure of coal. Moreover, the results here are in contrast to work reported earlier, in which increased conversion levels, reached through greater conversion temperatures, yielded products with successively increased condensation and aromatization. It is thus suggested that severity be considered in terms of two components. Thermal severity reflects the temperature/time component of conversion chemistry, and derives from simple Arrhenius behaviour of competing reactions, while reduction severity reflects only on the reducing power of the system.

Synthesis of polynaphthoquinone

Abstract The synthesis of polynaphthoquinone in nitric acid was found to require N(III) catalysis.

Catalysis of aromatic nitration by the lower oxides of nitrogen

In the absence of nitrous acid traps, the nitration of phenol in 56·2% sulphuric acid displays autocatalytic behaviour; on the other hand, the isomer ratio of the products is inconsistent with the commonly accepted prior nitrosation scheme, and some other route for the promotion of nitration must be operative.