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

Under $\text{CO}\text{H}{}_2\text{O}$ 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 $\text{H}{}_2\text{CO}{}_2$ 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 $\text{CO}\text{H}{}_2\text{O}$ systems are useful for coal studies.     

Flash pyrolysis of coals. Devolatilization of bituminous coals in a small fluidized-bed reactor

The devolatilization behaviour of ten bituminous coals was investigated under rapid heating conditions using a small-scale fluidized-bed pyrolyser. The pyrolyser operated continuously, coal particles being injected at a rate of 1–3 g h^?1 directly into a heated bed of sand fluidized by nitrogen. Yields of tar, C₁–C₃ hydrocarbon gases, and total volatile-matter and an agglomeration index are reported for all coals. Maximum tar yields were obtained at about 600 °C and were always substantially higher than those from the Gray-King assay. Total volatile-matter yields were also substantially higher than the proximate analysis values. The maximum tar yields appear to be directly proportional to the coal atomic $\text{H}\text{C}$ ratio. The elemental analysis of the tar is strongly dependent on pyrolysis temperature. The tar atomic $\text{H}\text{C}$ ratio is proportional to that of the parent coal. The effect on the devolatilization behaviour of two coals produced by changes in the pyrolyser atmosphere and the nature of the fluidized-bed material were also investigated. Substituting an atmosphere of hydrogen, helium, carbon dioxide or steam for nitrogen, has no effect on tar yield and, with one exception, little effect on the hydrocarbon gas yields. In the presence of hydrogen the yield of methane was increased at temperatures above 600 °C. Tar yields were significantly reduced on substituting petroleum coke for sand as the fluid-bed material. A fluidized bed of active char virtually eliminated the tar yield.     

Internal rearrangement of hydrogen during heating of coals with phenol

Heating either Bruceton or Wyodak coal with phenol results in the thermal depolymerization of the coal yielding pyridine-soluble products and an insoluble residue. The depolymerization is accompanied by extensive rearrangements of hydrogen within the coals producing a soluble material enriched in hydrogen and a residue which is hydrogen poor. The hydrogen shuttle in Wyodak coal has a different temperature dependence than does the depolymerization, being favoured at higher temperatures. The $\text{H}\text{C}$ ratio of the soluble products increased with increasing conversion. Relatively small amounts (ca. 5%) of the products at high conversion are derived from phenol.     

Hydroliquefaction of Kentucky 914 coal using bottoms recycle

Kentucky $\text{9}\text{14}$ bituminous coal has been liquefied in a batch reactor using blends of distillates and SRC or SRC fractions as the solvent. The most effective solvents contained either mildly hydrogenated SRC or the cyclohexane-soluble oil fraction of SRC. Approximately 65 wt% of Kentucky $\text{9}\text{14}$ coal was converted to C₄-700K liquids using these solvents. This yield can be compared to a yield of ≈40 wt% C₄-728K produced in the SRC-II process from Kentucky $\text{9}\text{14}$ coal.     

Liquefaction of coal and related materials

Bituminous coal, lignite, peat and more recent biogenic materials were reacted as water slurries at 380 °C for short periods with hydrogen, directly and from the water-gas shift reaction, without organic solvents or catalysts. Conversion increases with $\text{H}\text{C}$ and $\text{O}\text{C}$ ratio of the input material and reaches 90%. For benzene-soluble products $\text{O}\text{C}$ is always lower and $\text{H}\text{C}$ usually higher than for the original material.     

Electrochemical reduction of polymeric carbon

It was found that the electrochemical reduction of poly (tetrafluoroethylene) with lithium amalgam leading to the mixture of polymeric carbon and lithium fluoride as solid product is followed by a consecutive electrochemical reaction via a polymeric anion radical, [$\text{(}\text{?}$C_n$\text{)}\text{?}$^?]_m. The value of n was determined as 4.75 and was found to be independent of the reaction conditions. The charge of this radical is during the reaction neutralised with Li⁺ ions diffusing through the solid phase to form a chemical compound $\text{(}\text{?}$C_nLi$\text{)}\text{?}$_m whose CLi bonds have a localized character. Therefore, this compound does not evolve hydrogen in contact with water as the intercalation compounds C_nLi, but hydrolyses to a solid hydrocarbon $\text{(}\text{?}$C_nH$\text{)}\text{?}$_m.     

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

Isopropyl alcohol can act as a hydrogen donor to coal, as can tetralin. In contrast to tetralin, however, the transfer of hydrogen by the alcohol can be promoted by the presence of either potassium isopropoxide or KOH. Acetone is formed from the alcohol in quantities that accord with the amounts of hydrogen transferred to the coal. In runs at 335 °C for 90 min, coal was converted with isopropyl alcohol in the presence of either the alkoxide or KOH to a fully pyridine-soluble product with $\text{H}\text{C}$ ratios from 0.88 to 1.13, in contrast to coal (0.79). The organic sulphur content of the coal was reduced from 2.1% to 1%. Model-compound studies with anthracene and diphenyl ether showed that the anthracene was reduced in the system to 9,10-dihydroanthracene, but the ether was recovered unchanged. The coal products from the alcohol/base treatment are very rich in aliphatic hydrogen and have number-average molecular weights in the 450–500 range. The scheme suggested to explain the conversion at 335 °C includes initial hydrogenation of anthracene-like structures in the coal, followed by thermolysis of the dihydro-intermediate.     

Flash pyrolysis of coals: behaviour of three coals in a 20 kg h−1 fluidized-bed pyrolyser

Flash pyrolysis of Loy Yang brown coal, and Liddell and Millmerran bituminous coals has been studied using a fluidized-bed reactor with a nominal throughput of 20 kg h^?1. The apparatus and its performance are described. The yields of tar and hydrocarbon gases are reported for each coal in relation to pyrolysis temperature, as also are analytical data on the pyrolysis products. The peak tar yields for the dry, ash-free Loy Yang and Millmerran coals were respectively 23% wt/wt (at ≈ 580 °C) and 35% wt/wt (at $\text{\$}\text{?}$600 °C). The tar yield from Liddell coal was 31% wt/wt at ≈ 580 °C. Hydro-carbon gases were produced in notable quantities during flash pyrolysis; e.g. Millmerran coal at 810 °C gave 6% wt/wt (daf) methane, 0.9% wt/wt ethane, 6% wt/wt ethylene, and 2.5% wt/wt propylene. The atomic $\text{H}\text{C}$ ratios and the absolute levels of hydrogen in product tars and chars decreased steadily with increasing pyrolysis temperature.     

Relation between coal aromatic carbon concentration and proximate analysis fixed carbon

Good agreement has been obtained between measured proximate analysis values for fixed carbon (FC) and the predictions of a thermal decomposition model. The model provides a basis for understanding the relation between FC and coal structure and between FC measured under proximate analysis conditions and coke or char measured in other thermal decomposition experiments. The key parameters in the model are the aromatic carbon concentration (C_ar) and the tar yield. C_ar has been determined for 43 coals using quantitative infrared analysis. The aliphatic hydrogen concentration is measured from the absorption near 2900 cm^?1 and the aliphatic carbon concentration is computed assuming a stoichiometry of CH_1.8 C_ar is then computed by difference. The results verify the good correlation between C_ar and FC discussed by van Krevelen. To explain this correlation, use has been made of a coal thermal decomposition model which has been successful in simulating the quantity and composition of volatile components yielded under vacuum pyrolysis conditions. To apply the model to proximate analysis, it was necessary to estimate the tar yields obtained with thick beds and the amounts of O, N, H, and S which remain with the FC. The tar yields for proximate analysis conditions have been estimated to be $\text{1}\text{3}$ to $\text{1}\text{4}$ the yields for thin beds in vacuum. To determine the composition of the FC, measurements were made on a lignite and a bituminous char produced in a thin bed heated by a wire grid for the time (7 min) and temperature (950 °C) used in the proximate analysis, and on the FC residues from a proximate analysis volatile matter determination. Both residues give similar results, showing that approximately 10% of the ‘fixed carbon’ is not carbon. Values of FC computed with the model adjusted for the above conditions are in good agreement with the measured values.     

Characterization of organic fractions in solvent-refined coal by quantitative n.m.r. spectroscopy

A solvent-refined coal product obtained from Pittsburgh No. 8 coal has been preparatively separated into four sized fractions by gel permeation chromatography. Quantitative ¹H and ¹³C Fourier-transform nuclear-magnetic-resonance results for the separated fractions are reported along with elemental and molecular weight analysis data. Observed trends for several average molecular parameters for these fractions (e.g. $\text{(}\text{H}\text{C}\text{)}{}_{\mathrm{alp}}$, $\text{(}\text{H}\text{C}\text{)}{}_{\mathrm{aro}}$, etc.) are discussed. The absence of certain organic functional groups, such as carbonyls, is also noted.     

Hydrogen mass transfer and mixing energy effects in SRC-II coal liquefaction reactors

This paper summarizes the experimental work performed on a bench-scale pre-pilot unit for investigating hydrogen mass transfer and mixing energy effects in SRC-II coal liquefaction reactors. Experiments were carried out with an Ireland Mine coal where the effects of mixing energy level (150–1000 rpm), method of hydrogen introduction (preheater flow and direct reactor sparging) and hydrogen treat rate (4 to 6 g of hydrogen/100 g of feed slurry) were investigated. Several runs using Powhatan No. 6 coal were also carried out where the effect of mixing energy level (200–1000 rpm) was investigated. Other run conditions were fixed to correspond to those likely to be used in commercial operation. The experimental results clearly indicated that below a mixing energy level corresponding to 400 rpm a significant cement-like solid deposition within the reactor (hydrogen mass transfer limitation) occurred. Below this mixing energy level the C₅+ liquid yield decreases, and the selectivity of the reaction changes, resulting in an increase in the C₁C₄ yield. This critical mechanical mixing level corresponds to a mixing energy per unit of reactor volume of ≈3500 ergs/cm³ s (350 watts m^?3). For the run conditions employed, increasing the preheater hydrogen flow from 4 to 6 g of $\text{H}{}_2\text{100 g}$ of slurry prevented the formation of solid deposits at a mechanical mixing energy level as low as that corresponding to 200 rpm. Furthermore, the highest C₅+ yield in the entire data set occurred when the preheater hydrogen flow was at the higher level.     

Heavy media separation of SRC-II feedstocks: 1. Effect on coal properties

The objectives of this investigation were to determine the effects of coal preparation on the properties of Run-of-Mine (ROM) and washed Powhatan and Ireland Mine coals and to assess the potential effects on SRC-II liquefaction yields. The effect of washing on the two coals was found to be quite similar. For both coals, the properties were altered more significantly by changes in separation media gravity than by changes in the coal size. The elemental composition of the Powhatan and Ireland washed coals was correlated with carbon content. It was shown that both the hydrogen and oxygen levels increased linearly with the carbon content of the coal samples. However, the $\text{H}\text{C}$ and $\text{O}\text{C}$ ratios were not changed significantly by coal cleaning. Only small variations in the nitrogen and organic sulphur levels were observed while the sulphate sulphur and chlorine levels were not affected by coal cleaning. The major impact of the coal cleaning was to reduce the pyritic sulphur (and hence the total sulphur) content of the coals. Most of the pyritic sulphur was shifted into the middling coal and refuse fractions while the clean coals had much lower contents and the pyritic sulphur level decreased with increasing carbon content. Coal cleaning did not significantly alter the maceral contents of vitrinite, exinite, total reactive macerals (TRM), or the reflectance of vitrinite; all these parameters varied over a very narrow range, probably within the precision of the measurement technique.     

Constitution of tars from flash pyrolysis of Australian coals: 3. A structural study of Millmerran asphaltene components by hydrogenolysis

Asphaltenes derived from tar from the flash pyrolysis of Millmerran coal have been separated into acid, base, polyfunctional and neutral fractions by ion-exchange chromatography. Each fraction was studied by high-pressure catalytic hydrogenolysis followed by g.c.-m.s. analysis of the volatile products. The high content of n-alkanes from C₉ to C₃₂ in the organic products highlights the unusual maceral composition of Millmerran coal and its high $\text{H}\text{C}$ ratio. The results show that most of the asphaltenes are made up of small 1 — or 2-ring aromatic units probably linked by methylene chains bonded through intermediate functional groups. In some cases, the asphaltene structures appear to be ‘simpler’ than the corresponding coal-tar resin structures in the maltenes. Because no amphoteric molecules were detected these results support the concept of an acid-base structure for coal-derived asphaltenes.     

Oxidation of carbonaceous matter—I: Elemental analysis (C,H, O) and IR spectrometry

Products of various elemental composition ($\text{1.56 ? (}\text{H}\text{C}$) at ? 0.45 and $\text{0 < (}\text{O}\text{C}$) at < 0.45) were oxidized under an air flow at various temperatures (from 150 to 280°C) and for various times (from half an hour to one week). When plotted in a Van Krevelen diagram ($\text{H}\text{C}$ vs $\text{O}\text{C}$), their elemental composition follows an oxidation path, the slope of which depends only on the original ($\text{O}\text{H}$) atomic ratio and on the oxidizing temperature. Oxidation reactions have an “apparent activation energy” of 20–40 kcal/mole. Cross-linking may be due either to ether bonding or to hydrogen bonding as indicated by IR spectrometry. The final product, named “oxychar”, has a constant composition ($\text{H}\text{C ～}\text{-}\text{O}\text{C}\text{～- 0.5}$).     

Study of the early hydration of Ca3SiO5 by X-ray photoelectron spectrometry

C₃S pastes (W/S = 0.5), have been studied from 5 seconds to 4 hours by X-ray Photoelectron Spectrometry. XPS reveals surface transformations of C₃S grains from very early ages of hydration. The modifications have been evidenced by a change in the environment of Si atoms and a variation of the Ca/Si ratio. A Primary Hydrate (C/S << 3), a Secondary Hydrate ($\text{C/S}\text{?2}$) and a Tertiary Hydrate (CSH type I) have been identified. XPS is a sensitive and reproducible method for the study of the surface C₃S hydration.     

Tetracalcium aluminoferrite hydration in the presence of lime and gypsum

The influence of lime and/or gypsum on the C₄AF hydration was examined and the results were compared with those obtained for the C₃A hydration. Gypsum is more effective than CH in retarding the hydration of C₄AF. Ettringite produced in the C₄AF hydration in the presence of C$\text{S}$·H₂ seems to be more stable than that produced in the C₃AC$\text{S}$·H₂H₂ system. The consumption of gypsum, the transformation of ettringite into monosulfate and the hydration of C₄AF in the C₄AFC$\text{S}$·H₂H₂O system are much slower than those in the C₃AC$\text{S}$·H₂H₂O system. The retardation of hydration of C₄AF or C₃A in the presence of C$\text{S}$·H₂ is further increased by the add$\text{i}$tion of CH.     

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 $\text{CO}\text{H}{}_2\text{O}$ 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 $\text{H}\text{C}$ 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.     

The characterization of asphaltenes and preasphaltenes obtained under various coal liquefaction conditions

A CP-MAS ¹³C NMR study of asphaltenes and preasphaltenes obtained under various coal liquefaction conditions is reported. The carbon aromaticity, f_a, of the solid extracts from the reaction products has a close relation with the reaction conditions. By plotting f_a against the atomatic $\text{H}\text{C}$ ratio for these solid products on the characterization chart for model polycyclic aromatic compounds, the molecular structures with relation to the liquefaction pathway from coal to oil can be proposed.     

A mechanistic study of hydrogenation of coal. 2.

In Part 1 the authors reported that liquefaction of coal by hydrogenation in the presence or absence of vehicle and with or without catalyst progresses with characteristic variations of the reaction order. In the present paper, the roles of temperature, hydrogen, vehicle and catalyst have been studied using a free-radical scavenger such as p-benzoquinone or iodine. Based on these results, a set of characteristic reactions has been identified from which the following overall rate equation has been derived: $\text{d[P}{}_{\mathrm{m}}\text{]}\text{dt}\text{= β}{}_1\text{[C] + β}{}_2\text{[C]}{}^2\text{+ β}{}_3$ where [P_m] denotes gas, and benzene-soluble products, [C] represents the percentages of organic matter in coal and benzene insoluble intermediates, and β₁, β₂ and β₃ are constants. The rate equation thus explains the experimentally observed variation of the reaction order, which depends on the predominance of a particular group of reactions. It has been postulated that pyrolysis is the main driving force, and that hydrogenation of coal either with gaseous hydrogen or by hydrogen-donating vehicle is basically influenced by reactions involving free radicals.     

Flash pyrolysis of coals: comparison of results from 1 g h−1 and 20 kg h−1 reactors

The performances of 1 g h^?1 and 20 kg h^?1 flash pyrolysers are compared for three Australian coals: Loy Yang brown coal (Victoria), Liddell bituminous coal (New South Wales), and Millmerran sub-bituminous coal (Queensland). The two reactors gave comparable yields of tar, char and C₁–C₃ hydrocarbon gases over a range of operating conditions for each particular coal. The yield of total volatile matter from Millmerran coal was similar from both reactors, as were the compositions of chars from Loy Yang coal and tars from the Liddell and Millmerran coals. For Millmerran coal, the yields of tar, C₁–C₃ gases and volatiles from the large reactor below 650 °C, were slightly lower than for the small reactor, possibly owing to a shorter retention time of Millmerran coal particles in the large-scale reactor. At a temperature near 600 °C tar yields were independent of tar concentration in the effluent gas, over a range 0.0025–0.1 kg m^?3 for Liddell coal, 0.005–0.26 kg m^?3 for Millmerran coal and 0.0045–0.09 kg m^?3 for Loy Yang coal. The tar yields from Millmerran and Liddell coals at 600 °C in the large reactor, correlate directly with the atomic $\text{H}\text{C}$ ratio of the parent coal, in the same manner as that found for a wider range of bituminous coals in the small-scale reactor.