Liquefaction Conversion Research Articles

Transport fuels from two-stage coal liquefaction

Four Spanish lignites and their vitrinite concentrates were evaluated for coal liquefaction. Correlationships between the content of vitrinite and conversion in direct liquefaction were observed for the lignites but not for the vitrinite concentrates. The most reactive of the four coals was processed in two-stage liquefaction at a higher scale. First-stage coal liquefaction was carried out in a continuous unit at Clausthal Universität at a temperature of 400°C at 20 MPa hydrogen pressure and with anthracene oil as a solvent. The coal conversion obtained was 75.41% being 3.79% gases, 2.58% primary condensate and 69.4% heavy liquids. A hydroprocessing unit was built at the Instituto de Carboqumica for the second-stage coal liquefaction. Whole and deasphalted liquids from the first-stage liquefaction were processed at 450°C and 10 MPa hydrogen pressure, with two commercial catalysts: Harshaw HT-400E (Co-Mo/Al2O3) and HT-500E (Ni-Mo/Al2O3). The effects of liquid hourly space velocity (LHSV), temperature, gas/liquid ratio and catalyst on the heteroatom liquids, and levels of 5 ppm of nitrogen and 52 ppm of sulphur were reached at 450°C, 10 MPa hydrogen pressure, 0.08 kg H2/kg feedstock and with Harshaw HT-500E catalyst. The liquids obtained were hydroprocessed again at 420°C, 10 MPa hydrogen pressure and 0.06 kg H2/kg feedstock to hydrogenate the aromatic structures. In these conditions, the aromaticity was reduced considerably, and 39% of naphtas and 35% of keroseno fractions were obtained.

Evaluation of a novel mixed pyrite/pyrrhotite catalyst for coal liquefaction

Iron compounds are known to be active catalysts for direct coal liquefaction. We have synthesized ferric sulfide (Fe 2S 3) and have used it as a precursor for the preparation of specific mixtures of pyrite and pyrrhotite in intimate contact, to be used as liquefaction catalysts. By varying the gas phase, time and temperature of the disproportionation of ferric sulfide, the relative amounts of pyrite and pyrrhotite are controlled. The effects of the pyrite/pyrrhotite ratio on conversion and yields of coal liquefaction are experimentally evaluated. The coal sample used is a high-volatile bituminous coal, carefully chosen for its very low pyritic sulfur content. A conventional shaken tubing-bomb reactor is used. The best conversion and yield are associated with a presulfided catalyst containing roughly equal amounts of pyrite and pyrrhotite. Increasing the temperature of liquefaction increases the total conversion and significantly increases the selectivity to desired products. Presulfiding has little effect, except at low temperatures and for the catalyst with equal amounts of pyrite and pyrrhotite.

移動性水素量による石炭液化および前処理の評価

In order to clarify the effect of pretreatment on liquefaction reactivity of coal, transferable hydrogen (TH) of coal cleaned by gravity separation method was assessed using anthracene as hydrogen acceptor. The amount of TH in River King coal decreased with increasing ash content. The amount of TH was not necessarily correlated with H/C atomic ratio. Organic part of IR spectra of coals was hardly changed by gravity separation. It was recognized that the higher the vitrinite content and the lower the inertinite content, the larger is the amount of TH. Correlations between the amount of TH and the liquefaction yields for the cleaned coal were observed. Except for River King coals, no simple correlation exists between the amount of TH and the total conversion in liquefaction of various coals. On the other hand, good correlation was obtained between the amount of TH and (Asphaltene+Oil) yield. TH is a desirable parameter in evaluating the liquefaction reactivity of coal. The amount of hydrogen requisite to depolymerization of coal was examined on the basis of the model assuming that coal is a simple polymer and was compared with the amount of transferable hydrogen.

The petrographic approach to coal liquefaction

The procedure for quantitative estimation of a maceral liquefaction reactivity is outlined in terms of the regression analysis which takes into account petrographic composition and coal rank. The procedure is based on an additive model for maceral liquefaction and includes a mathematical/statistical analysis of conversion and/or kinetic data for coals characterized by simplified petrographic composition, i.e. by contents of liptinite (exinite), vitrinite and inertinite. The procedure was applied to long contact time liquefaction data for low sulphur high volatile bituminous coals of different rank and to kinetic analysis of short contact time liquefaction data for subbituminous and bituminous coals. On average, inertinite reacts with tetralin three times slower than vitrinite which itself is only half as reactive as liptinite. This is the reason for a decreasing apparent rate constant with extent of conversion in liquefaction of petrographically inhomogeneous coals. The activation energies in liquefaction with tetralin of subbituminous and bituminous coals are respectively 11.4 and 125 kJ mol −1 for vitrinite, and 63.3 and 98 kJ mol −1 for inertinite. Shortcomings and possible modifications of the model are discussed.

The application of Mössbauer spectroscopy to the study of coal liquefaction with iron catalysts

The catalytic effects of five iron compounds on the hydroliquefaction of Zalarroure lignite in a microautoclave are investigated with a Mössbauer spectrometer. The tetrahydrofuran-insoluble residue of liquefaction products is analysed by 50 m Ci 57Co/Pd Mössbauer spectroscopy at room temperature. It is observed that under conditions of coal liquefaction, FeS 2 is transformed into pyrrhotite, and Fe 2O 3-S or Fe 3O 4-S is transformed into pyrrhotite directly or indirectly via the inrtermediate state of FeS 2 · FeSO 4 · 7H 2O-S could be transformed into pyrrhotite only under severe conditions. Pyrrhotite is also formed from FeS-S, but its activity is low when thus formed. The relationship of transformation of iron catalysts to the quantity of sulphur added, and to temperature and reaction time have been investigated with Mössbauer spectroscopy. It is found that the quantity of the formed pyrrhotites increases with increasing quantity of sulphur added, reaction temperature, reaction time and the hydrogen-donor ability of the solvent; net liquefaction conversion increases as the quantity of Fe 1 − x S increases. It is inferred that catalytic activity in coal liquefaction is attributed to Fe 1 − x S and active H 2S when an iron-based catalyst is used.

ベンチプラントを用いた各種原料炭の液化試験

The effect of properties of 12 kinds coals such as C‰, H/C ratio, O/C ratio, fuel ratio on liquefaction conversion and product yield has been investigated.The main conclusions from this work are: 1. The linear correlation between carbon contents, fuel ratio of coals and liquefaction conversion did not recognized.2. The yield of gaseous product are increased with decrease of carbon contents of coals. 3. Produced oil from the coals which have high value of H/C, contains high portion of light fraction (b.p-220°C).

Effect of mobile phase properties and macromolecular network reactivity on liquefaction behavior of bituminous coals

The effects of quantity of mobile phase, viscosity of mobile phase, and network reactivity were evaluated on the liquefaction conversion of four coals. Reactions were carried out at 275°C for 10 and 30 minutes, and in a temperature-staged configuration for 30 minutes each at 275 and 425°C. Coals were impregnated with a sulfided ammonium molybdate catalyst. If all other factors were held reasonably comparable, it was found that a coal having lower viscosity mobile phase produced higher conversions at 275°C than a similar coal having a more viscous mobile phase. This effect is attributed to easier transport of the mobile phase from the interior of a coal particle to the catalyst on the particle's surface. For coals having comparable viscosities of mobile phase and comparable network reactivities, the coal having the greater quantity of mobile phase produced higher conversions. When network reactivity was the principal difference, the coal having the less reactive network resulted in lower conversion. Thus for good liquefaction conversions at relatively mild conditions, a coal having a large amount of fluid (low viscosity) mobile phase and a reactive network is desirable. These differences among coals are much less apparent in temperature-staged liquefaction; the much more severe reaction conditions appear to overwhelm the subtle differences of mobile phase and network properties.

Enhanced extractability in coal liquefaction by alkali metal-liquid ammonia pretreatment

Pretreatment of two bituminous coals with alkali metal in liquid ammonia followed by protonation with NH 4Cl resulted in an improvement of the conversion in thermal coal liquefaction. Experiments were performed at 400 and 425 °C, without catalyst in n-dodecane (inert) as well as in tetralin (H-donating) as the solvent. Coal liquefaction products that were soluble in tetrahydrofuran were analysed by g.p.c., 13C and 1H n.m.r. The material extracted with n-dodecane without pretreatment of the coal is highly aromatic, but metal-ammonia pretreatment decreases both the 13C- and 1H-aromaticity. A mechanism for the increase in conversion in relation to coal structure is discussed.

Mathematical Analysis of Noncatalytic Coal Dissolution Using Tetralin and the Prediction of Coal Conversion, SRC Yield and Aromatidty of SRC

Abstract Mathematical analyses of noncatalytic coal dissolution using tetralin at 350–460 °C were carried out. Coal conversion, SRC yield and aromaticity of SRC could be predicted fairly well by regression equations using liquefaction conditions as explanation variables. The equation derived from coal conversions in 67 experiments using the C% and volatile matter of 6 coals and liquefaction conditions could predict coal conversions fairly well (R=0.972). The conversions predicted by the proposed equation were also compared with those reported by previous investigators. Although it was suggested that long heating-up period was detrimental to coal conversion, the equation was a good indication of the conversion in solvent extract liquefaction.

Coal liquefaction yields in tetralin — their prediction from heat measurements of coal hydrogenation in H 2 by DSC

Given et al. 1, in this laboratory, measured the liquefaction behaviour of coals at 673 K in the presence of tetralin but with no added catalyst or molecular hydrogen. Use of a stepwise multiple regression analysis led to a number of linear equations relating liquefaction conversion simultaneously to various coal characteristics. It was concluded that liquefaction yields can only be adequately accounted for by consideration of at least three coal properties. Properties found to be most important were total sulphur, total reactive macerais, and total carbon from ultimate analysis. Concurrently with liquefaction studies, we were measuring in this laboratory exothermic heats involved during hydrogenation of coals in H 2 using differential scanning calorimetry (DSC) 2. This communication examines the possibility of using d.s.c. to predict coal liquefaction behaviour.

石炭の膨潤率と液化率との関係

In order to clarify swelling effect on liquefaction of coals, swelling ratios, liquefaction yield, heats of wetting, and water contents of coals with various carbon contents have been studied in methanol, tetralin, and mixtures of them.The swelling ratios of Yallourn coal in all solvents we used were increased up to 60 minutes, and then became a consatant. The more coal swelled in the same solvent, the higher conversion of liquefaction became. The conversions of liquefaction of all dry coals were larger in mixtures of methanol and tetralin (1: 1 by weight) than in tetralin alone. Moreover, the conversion of liquefaction of wet Yallourn coal was also larger in the mixtures of methanol and tetralin than in tetralin alone. This may be contributed that, water molecules which exist in pore parts of Yallourn coal are replaced with methanol molecules; these methanol molecules increase penetration of tetralin into pore parts of it; as a result, the swelling ratio of Yallourn coal is considerably increased.

Coal conversion and hydrogen utilization in catalytic liquefaction at low temperatures

The initial stages of coal liquefaction have been investigated in small batch autoclaves at moderate to low liquefaction temperatures. Conventional liquefaction in an organic recycle solvent was compared with liquefaction of coal in water. In conventional liquefaction, the majority of the tetrahydrofuran conversion ultimately obtained at long reaction times had already appeared before 15 minutes or less had elapsed at the set temperature. Addition of ammonium molybdate had a beneficial effect on conversion at lower temperatures as revealed by a decrease in the demands placed on the liquefaction solvent. The use of a catalyst under hydrogen pressure may compensate for the suppression of conversion values normally associated with using substantially smaller amounts of liquefaction solvent. The utilization of hydrogen was determined by elemental and NMR analyses of the organic portion of the entire charge fed to and taken from the autoclave. The net change in hydrogen per 100 carbons was calculated for four categories: hydrogen gas make, heteroatom removal, change in aromaticity (hydrogenation/dehydrogenation), and matrix bond cleavage/condensation. Hydrogen consumption is observed below 400°C in the hydrogenation of aromatic carbon. However, above 400°C, dehydrogenation reactions predominate and hydrogen is released in this category rather than consumed. These results show that the choice of liquefaction temperature, catalyst, solvent, and pressure of reducing gas may be used to control the pattern of hydrogen utilization.

A semi-continuous flow reactor technique for coal liquefaction studies

A novel semicontinuous tubular reactor flow technique was used to study liquefaction of a typical Venezuelan coal. The technique allows a simple procedure to calculate coal liquefaction conversion. This was found to be increased by various catalysts only if the appropriate amount with the proper particle size was employed. Nickel—molybdate and cobalt—molybdate catalysts were found to be better catalysts than copper—chromite for desulfurizing the coal; however, the latter catalyst produced the largest liquefaction conversion.

Effect of Wyodak coal properties on hydroliquefaction reactivity

The effect of Wyodak coal properties on liquefaction reactivity as measured by distillate yield and cyclohexane conversion has been investigated. Spot samples of four Wyodak subbituminous coals from the Anderson and Canyon coal seams in the Powder River Basin of NE Wyoming were liquefied in microautoclave and batch reactor experiments. Runs were made using two different Wyodak coal-derived solvents. Emphasis in this work was directed toward correlation of C 4-700 K distillate yield and cyclohexane conversion as functions of measurable physical, chemical and petrographic properties of the feed coal. Reactivity rankings were found to be the same using either measure of coal reactivity. However, the data indicated that distillate yields were a function of both solvent quality and feed coal properties. For each solvent studied, selected coal properties, including carbon content, total and organic sulphur content, vitrinite content and total reactive maceral (vitrinite plus exinite) content, were found to give statistically significant correlations with distillate production and cyclohexane conversion. Pyritic and sulphate sulphur contents did not appear to enhance liquefaction yield or conversion at the reaction conditions studied. However, any catalytic effects due to pyrite or sulphate sulphur may have been masked by the use of two high quality liquefaction solvents.

Primary liquefaction behavior of KY #9 and KY #11 washed coal

The conversion of moisture and ash free (maf) coal to pyridine solubles and gas was investigated in a microautoclave batch reactor. Two washed Kentucky coal samples (KY #9 and KY #11) were studied in liquefaction solvents of various donor strength. The liquefaction solvent hydrogen donor strength was varied by changing the tetralin content of a mixed 1-methylnaphthalene-tetralin mixture. Primary liquefaction conversions in excess of 90 wt% in 10 minutes of reaction time @ 700° K (427° C or 800° F) were achieved with liquefaction solvents of moderate donor strength, i. e. 40% tetralin. A modified irreversible first order rate expression (eq. 1) described the experimental data: (1) $$x\, = \,\alpha - (\alpha - \beta )\,e{\,^{ - {x_1}\,\theta }}$$ where: α is the intrinsic reactive fraction of the maf coal, β is the pyridine solubles of the starting maf coal, κ is a specific reaction velocity constant, Θ is reaction time, and x is the primary liquefaction fractional coal conversion. Primary liquefaction rates as measured by κ1 were found to be quite temperature sensitive and independant of coal when liquefaction solvents containing ≥ 40 wt% tetralin were used. Both α and κ1 appear to depend on solvent donor strength when the liquefaction solvent contained less than 40 wt% tetralin. The intrinsic reactives fraction a appears to be about equal to the reactive macerals content for the two coals studied in liquefaction solvents with a tetralin content ≥ 40 wt%.

Radicals in coals during pyrolysis in relation to liquefaction conversion

The increase in radical concentration as measured by e.s.r. on pyrolysis of nine lignites, two subbituminous coals and one bituminous coal was studied. No correlation was found between the net quantity of radicals produced on thermolysis and the percentage conversion to THF-soluble material using either a hydrogen donor solvent or a non-hydrogen donor solvent. Decker lignite produced a high steady state radical concentration at all temperatures used (150–450 °C). Wyodak subbituminous coal and Martin Lake lignite gave large steady state radical concentrations at lower reaction temperatures and low to modest levels at the higher temperatures. Zap, San Mighel and Gascoyne lignites exhibited reduced levels of steady state radical concentrations at the lower temperatures and increasing levels at the higher temperatures.

Contribution of vitrinite macerals to the liquefaction of subbituminous coals

Four Alberta subbituminous coals were selected to investigate the contribution of vitrinite macerals to liquefaction. There are indications of a rectilinear correlation between conversion yields of different density fractions of coal and their vitrinite content, but it is too early to discern any conversion factor by which any maceral group may be used to predict the liquefaction behaviour of a subbituminous coal. Contrary to common belief, not all the vitrinite fraction of the feed coal is reactive. There seems to be a definite positive correlation between the percent vitrinite reacted and the liquefaction conversion yield. Much more research work is needed to further understand the contribution of vitrinite macerals to liquefaction of a subbituminous coal.

Effect of oxidative weathering on the thermoplastic and liquefaction behaviors of four coals

Using a Gieseler plastometer to measure the thermoplastic behavior, a systematic study of the change in fluid properties with progressive oxidative weathering of three high volatile A bituminous and one low volatile bituminous coal was performed. The degree of fluidity was found to decrease rapidly with initial oxidation and then more slowly with additional oxidation. The effect of oxidation on liquefaction behavior also was studied. A level of oxidation, which significantly reduced Gieseler fluidity, had no detrimental effect on the liquefaction conversion determined as ethyl acetate soluble material, of three of the four coals tested.

Characterization of vitrinite concentrates: 3. Correlation of FT-i.r. measurements to thermoplastic and liquefaction behaviour

Measurements of aliphatic C–H content by FT-i.r. have been correlated to the plastic properties and liquefaction behaviour of a set of coals and vitrinite concentrates obtained from the Lower Kittaning seam. It has been found that for vitrinites a measure of total aliphatic C–H content correlates with Gieseler fluidity, displaying an abrupt change over a narrow range of aliphatic C–H content. Liquefaction conversion does not correlate with FT-i.r. measurements of total aliphatic C–H content but does correlate with the intensity of a band that is a measure of CH 2 content. These results confirm the general relationship between the mechanism of liquefaction conversion and plastic development, but also suggests there are some subtle differences.

Relative activity of transition metal catalysts in coal liquefaction

The catalytic activity of transition metals in coal liquefaction was studied and compared. Impregnation of coal with transition metals significantly increased oil production and asphaltene and preasphaltene conversion in coal liquefaction. Overall, coal conversion increased marginally and hydrocarbon gas production decreased slightly with metals. Iron impregnation was more active than cobalt, nickel, and molybdenum in preasphaltene conversion, whereas the other metals were more active than iron in asphaltene conversion. Hydrogen consumption decreased with all metals. The quality of generated solvent decreased with iron, but increased with other metals. Significant benefits were observed by using iron and molybdenum together; simultaneous impregnation of coal with iron and molybdenum significantly increased coal, asphaltene, and preasphaltene conversion, as well as oil production compared to individual metals. In addition, a mixture of iron and molybdenum decreased hydrocarbon gas production and increased hydrogen consumption and the quality of generated solvent over iron alone.