Liquefaction Of Low-rank Coals Research Articles

95/00378 Liquefaction of low-rank coals as a potential source of specialty chemicals

95/00378 Liquefaction of low-rank coals as a potential source of specialty chemicals

Fossil Energy. Liquefaction of Ishikari Coal using Supercritical Water.

The liquefaction of low-rank coal with supercritical water has been studied at 400°C and 25.3 MPa using a semi-batch microreactor. Liquid yield up to 41wt% is attained in less than 7 min. Subsequent gasification of residue takes place. 2D-n. m. r. spectral analysis of liquids products in supercritical and the results of mass balance suggests that both hydrolysis and condensation reactions contribute to oxygen removal during supercritical water liquefaction of coal.

Effect of exchangeable cations on liquefaction of low rank coals

Exchangeable alkali and alkaline earth metal cations such as, Na +, K + and Ca 2+, have been found to reduce conversion and product quality during liquefaction of a Wyodak subbituminous coal and a North Dakota lignite. The adverse effect, which increases in the order Na + < K + ⪡ Ca 2+, is probably due to these cations inhibiting hydrogen transfer from the donor solvent or H 2 gas to the coal free radicals, thus promoting retrogressive reactions. The deleterious effect of metal cations may be significantly reduced by preswelling coals prior to liquefaction. Preswelling enhances both the liquefaction yield and product quality. The magnitude of the enhancement is determined by the type of cations present on the coal surface. We have also found that the catalytic activity of iron deposited on a lignite by ion exchange is far superior to the same iron species deposited by slurry mixing.

Data on low rank coal liquefaction from DRIFT analysis

A Spanish low rank coal was hydrogenated without solvent in the presence of a molybdenum catalyst. The asphaltenes and derived residues were analysed to obtain an understanding of the behaviour of the coal under hydrogenation conditions and the influence of a previous extraction with chloroform, as well as reaction time and temperature, on the structure of the products obtained. Under the reaction conditions used, with tubing bomb reactors and an initial hydrogen pressure of 7 MPa, the data obtained for this coal show that an increase in temperature from 350 to 400 °C, and of reaction time from 5 to 60 min gives, in general, lower content of organic matter in the residues. The two variables have opposing effects on the aromatic content of the asphaltenes. Increasing reaction time reduces the aromaticity, whereas increasing the temperature will increase aromaticity. Prior extraction of the low molecular weight chloroform-soluble compounds increased conversion, and resulted in asphaltenes with higher content of aromatic- and oxygen-containing groups.

SEARCH FOR LOW SEVERITY LIQUEFACTION CONCEPT

ABSTRACT Numerous process-configurations are presently being investigated to produce hydrocarbon liquid from coal. The common step in all the variants is thermal decomposition-dissolution of the coal in a liquid hydrocarbon vehicle; this common step is generally referred to as liquefaction. Unfortunately, up to now, no precise relationship has been established between liquefaction behaviour and coal composition or chemical structure. Extensive Study of the process indicates that liquid yield is high when the fluidity of the feed coal is high or d.a.f. hydrogen content is greater than 5%. The world resource of high-fluidity coal is limited, but in many countries easily mineable subbituminous or lignitic coals are abundant. The little investigation that has been done on the chemistry of liquefaction of low rank coals leaves room to search for an inexpensive method of producing a high yield of liquid from these resources. This paper discusses some relevant experimental data which may lead to development of n...

Determination of low-rank coal liquefaction light oils by chromatography and nuclear magnetic resonance spectrometry

Light oils from liquefaction of lignite were separated by extraction into dimethyl sulfoxide (Me/sub 2/SO) insoluble hydrocarbon, aromatic, phenolic, and basic fractions and by silica gel column chromatography into 11 fractions of increasing polar content. The fractions were characterized by 200-MHz /sup 1/H NMR, 50-MHz /sup 13/C NMR, and capillary gas chromatography. Forty hydrocarbons and six phenolic compounds were identified, and their quantity was determined. Analysis and comparison of process-derived samples are possible by use of these methods.