Wyodak Subbituminous Coal Research Articles

Role of Pyridine in Wyodak−Pyridine Adducts

When pyridine (PYR) is added to powdered Wyodak subbituminous coal (WYO), the sample is converted to a paste, and the molecular-level adduct which is formed is stable for months. After the excess pyridine has evaporated from the WYO−PYR sample, the stoichiometry of the adduct is ca. two pyridine molecules per bilayer of WYO polycyclic units; this adduct exists even after mild vacuum treatment of the sample. The pyridine molecules in this adduct appear to be located between the bilayer lamellae and to be H-bonded to either H−O or H−N moieties attached to the poly-cyclic aromatic units of WYO. An H-bonded N- - -H−X distance of 2.6 Å has been calculated from a structural model of the WYO−PYR adduct.

Effect of Pretreatment with Carbonic Acid on “HyperCoal” (Ash-Free Coal) Production from Low-Rank Coals

The use of 'HyperCoal' (ash-free coal) as feedstock for gas turbines results in higher net power output with lower CO{sub 2} emissions. HyperCoal can be produced by thermal extraction from low-rank coals with industrial organic solvents in an inert atmosphere, providing raw materials. The pretreatment of low-rank coals with carbonic acid (CO{sub 2} dissolved in water - CO{sub 2}/H{sub 2}O) produced a strong increase in HyperCoal yields at relatively lower CO{sub 2} pressures of 0.1-0.5 MPa; the thermal extraction yields at 360{sup o}C increased by 7%-15% with extraction yields of 52% and 45% obtained for Wyodak sub-bituminous coal and Beulah-Zap lignite, respectively. In the range of 320-360{sup o}C, crude methylnaphthalene oil (CMNO) extraction yields of pretreated Wyodak coal increased significantly (by 4%-11%) over those of raw coal. The enhanced extraction yields of these low-rank coals are attributed to disruption of cation-bridging crosslinks on acid pretreatment, and the release of the hydrogen bonds by CMNO extraction. 18 refs., 4 figs., 4 tabs.

The Effects of Pretreatment and the Addition of Polar Compounds on the Production of “HyperCoal” from Subbituminous Coals

The effects of acid and hydrothermal pretreatments and the addition of polar compounds on the production of ashless-coal (HyperCoal) from subbituminous coals using cost-effective industrial solvents were investigated. The extraction yield of Wyodak subbituminous coal (C%, 75.0%) using crude methylnaphthalene oil (CMNO) at 360 °C was increased significantly by 19% following acid pretreatment; it was 41.3% for the raw coal and 60.5% for the acid-treated coal. The addition of strongly polar compounds, such as N-methyl-2-pyrrolidinone (NMP), also increased the extraction yields. For Pasir subbituminous coal (C%, 73.0%) the yield increased by 10% from 54.3% for the raw coal to 64.2% when 20% NMP was added to CMNO. The highest extraction yield of 72.2% was obtained for acid-treated Wyodak coal using CMNO with 20% NMP added. The ash content in HyperCoal tended to decrease following acid pretreatment and was less than 200 ppm in some coals. Hydrothermal pretreatment had a negative effect on the thermal extraction...

96/04797 Liquid hydrocarbons by hydrogenation of coal, biomass, plastics and domestic wastes

This chapter reviews the unusual and strong promoting effect of water on low-severity catalytic liquefaction of Wyodak sub-bituminous coal. The primary drying effect on coal conversion at 350°C is due to water removal rather than physicochemical changes within coal structure caused by drying. Prompted by this observation, the effect of water on catalytic run finds that water can have strong promoting effect on catalytic coal liquefaction with a dispersed molybdenum (Mo) sulfide catalyst at 350°C. The chapter examines the water effect using dispersed Mo catalysts generated in situ from water-soluble precursor, ammonium tetrathiomolybdate (ATTM), and an oil-soluble precursor. It describes new opportunities for developing low-severity catalytic processes for coal liquefaction that uses dispersed Mo sulfide catalysts from either water-soluble or oil-soluble precursor; adding a proper amount of water dramatically improve coal conversion at temperatures lower than the conventional processes.

Two-dimensional HPLC and GC-MS of oils from catalytic coal liquefaction

We have employed normal-phase HPLC with photo diode array detector and GC-MS techniques to characterize the oils (hexane soluble fraction) from the catalytic and non-catalytic liquefaction of Wyodak subbituminous coal at 400{degrees}C under 6.9 MPa H{sub 2} pressure. The use of a dispersed Mo catalyst afforded much higher oil yield than the non-catalytic run. HPLC reveals that the oils from the catalytic runs contain more phenolic compounds and more of heavier components as compared to the oils from non-catalytic run. On the other hand, GC-MS shows that there is a significant amount of long-chain alkanes in the oils, ranging from C{sub 11} to C{sub 35}. The analytical results from the two techniques appear to be complementary to each other. The oils contain some heavier components which are detectable by HPLC but undetectable by GC-MS. GC-MS of HPLC fractions of the oils from the catalytic run confirmed the presence of significant amount of phenols and indanols.

Surface Characterization and Liquefaction of Iron- and Molybdenum-Impregnated Subbituminous Coal

Results are presented from a study of the preparation and characterization of Wyodak subbituminous coal impregnated with iron and iron-molybdenum salts by the incipient wetness (IW) technique. X-ray photoelectron spectroscopy (XPS) was used to examine the surface composition and chemistry of coals impregnated with 0.7-2.0 wt% Fe and 500-1000 ppmw Mo. Various salts were used in preparing the impregnated coals including ferric nitrate, ferric sulfate, ferrous sulfate, and ammonium molybdate. The surface concentration of Fe increased as the amount of added Fe increased, with higher concentrations being observed for the nitrateimpregnated coals. The anions of the impregnating salts were readily removed from the samples that were treated with ammonium hydroxide solution

Use of a Novel Short Contact Time Batch Reactor and Thermogravimetric Analysis To Follow the Conversion of Coal-Derived Resids during Hydroprocessing

The conversion of two coal-derived nondistillable residua (resids) in tetralin during hydroprocessing has been examined. A novel laboratory scale batch reactor capable of operation up to 450°C and 17 MPa (2500 psi) under well-defined contact times from a few seconds to 30 min or longer was used. Thermogravimetric analyses, augmented by gas chromatography and gas chromatography/mass spectrometry, were used to follow the course of the conversion. Two resids, one derived from Wyodak subbituminous coal and another from Pittsburgh bituminous coal, were found to differ in their reactivity toward conversion to soluble or lower boiling materials. In the absence of a catalyst, the insoluble resids became solubilized in tetralin to some degree. However, even at long reaction times and high temperatures there was no indication of a breakdown in molecular weight or molecular structure as shown by thermogravimetric analysis and laser desorption high resolution mass spectrometry. In the presence of a presulfided Ni/Mo on alumina catalyst there was a much higher degree of solubilization and a definite indication of molecular breakdown

Coal liquefaction modelling: 1. Development of a kinetic model

This is the first of three papers on modelling coal liquefaction processes. In this paper a kinetic model for the thermal dissolver of the Wilsonville integrated two stage liquefaction (ITSL) process was developed using a new reaction network to describe the liquefaction of Wyodak (Clovis Point) subbituminous coal. The coal was considered to consist of two differently reactive fractions and the liquefaction reactions were assumed to occur in two distinct stages. The first stage is an instantaneous dissolution of the most reactive coal fraction to lighter products. The second stage is a rate controlled conversion of the less reactive coal fraction and thermal resid. The kinetic model was developed using bench-scale data from the variable submergence temperature control (VaSTeC) autoclave programme conducted at the Wilsonville Advanced Coal Liquefaction Research and Development Facility. The model parameters were estimated using a non-linear multiresponse parameter estimation routine. An overall average absolute deviation of 9.57% and an overall error of 3.73%, between the predicted and observed autoclave outlet composition indicated a good fit of the model to the VaSTeC data.

Effect of Temperature, Sample Size, and Gas Flow Rate on Drying on Beulah-Zap Lignite and Wyodak Subbituminous Coal

Beulah-Zap lignite and Wyodak-Anderson ([minus]100 and [minus]20 mesh from the Argonne Premium Coal Sample Program) were dried in nitrogen under various conditions of temperature (20--80[degree]C), gas flow rates (20--160 cc/min), and sample sizes (20--160 mg). An equation relating the initial drying rate in the unimolecular mechanism was developed to relate the drying rate and these three variables over the initial 80--85% of the moisture loss for the lignite. The behavior of the Wyodak-Anderson subbituminous coal is very similar to that of the lignite. The nitrogen BET surface area of the subbituminous sample is much larger than the lignite.

Effects of Drying and Oxidation of Wyodak Subbituminous Coal on Its Thermal and Catalytic Liquefaction.Spectroscopic Characterization and Products Distribution

Drying and oxidation of Wyodak subbituminous coal at 100-150° C have been shown to have significant effects on its structure and on its catalytic and noncatalytic low-severity liquefaction at 350° C for 30 min under 6.9 MPa of H 2 . Spectroscopic analyses using solid-state 13 C NMR, pyrolysis- GC-MS, and FT-IR revealed that oxidative drying at 100-150° C causes the transformation of phenolics and catechol into other related structures (presumably via condensation) and high-severity air drying at 150° C for 20 h leads to disappearance of catechol-like structure. Increasing air drying time or temperature increases oxidation to form more oxygen functional groups at the expense of aliphatic carbons

Non-aqueous enzymatic solubilization of coal-derived materials

The utilization of enzymes in non-aqueous solvents was explored for the conversion of coal-derived materials to oil-soluble derivatives for use as fuels. A novel three-step process was developed: 1. (1) an initial low-severity conversion to a form that is soluble or dispersible in a polar solvent; 2. (2) formation of an alcohol substrate with a high activity for subsequent enzymatic processing; 3. (3) lipase-catalysed transesterification to a product that is soluble in hydrocarbon solvents. The process was successful for the conversion of a first-stage liquefaction product from Wyodak subbituminous coal to an acylated product, about half of which is soluble in hexane and the remainder in toluene. Coals, humic acids and several other higher-molecular-weight coal liquefaction products, such as Chemcoal, and their derivatives inhibited the lipases, and thus the alcohol intermediates from these precursors were converted in 0–5% yields to acylated products.

Antiliquefaction: model systems for enhanced retrogressive crosslinking reactions under coal liquefaction conditions

The paper reports the liquefaction of Wyodak subbituminous coal. It has been found thaat benzyl alcohol and benzene dimethanol, which can be vieved as the precursors of benzyl-type radicals, can induce extensive retrogressive cross-linking involving themselves and solid coal

Enhancing low severity coal liquefaction reactivity using mild chemical pretreatment

We describe results from a study in which mild chemical pretreatment of coal has been used to enhance low severity liquefaction reactivity. We have found that ambient pretreatment of eight Argonne coals using methanol and a trace amount of hydrochloric acid improves tetrahydrofuran (THF)-soluble conversions by 24.5 wt% (daf basis) for Wyodak subbituminous coal and 28.4 wt% for Beulah-Zap lignite with an average increase of 14.9 wt% for liquefaction of the eight coals at 623 K (350 °C) reaction temperature and 30 min reaction time. Similar enhancement results occurred using hexane or acetone in place of methanol. Pretreatment with methanol and HCl separately indicated that both reagents were necessary to achieve maximum liquefaction improvement. Acid concentration was the most important pretreatment variable studied; liquefaction reactivity increased with increasing acid concentration up to 2vol%. No appreciable effect on reactivity was observed at higher acid concentrations. Although vapour phase alcohol/HCl mixtures have been shown to partially alkylate bituminous coals, analysis of Wyodak and Illinois no. 6 coal samples indicated that no organic phase alteration occurred during pretreatment; however, over 90 wt% of the calcium was removed from each coal. Calcium is thought to catalyse retrogressive reactions during coal pyrolysis, and thus calcium removal prior to low severity liquefaction minimizes the rate of THF-insoluble product formation.

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.

Microbial solubilization of a preoxidized subbituminous coal

Preliminary characterization of a microbial coal solubilization product has been performed. Submerged cultures ofPaecilomyces TLi orCandida ML13 were grown in defined minimal media containing preoxidized Wyodak subbituminous coal. Culture supernatants contained high-molecular-weight, acid-precipitable material that was separated by gel permeation chromatography (GPC) in aqueous and polar organic solvents. Organic GPC also separated a low-molecular-weight (<2700 daltons) fraction that was converted to higher-molecular-weight material upon acidification. Elemental analysis of the acid-precipitated material indicated an increased oxygen content as a result of the biological treatment. The biosolubilized product may undergo further microbial modification.

The pathways for thermal decomposition of aryl alkyl ethers during coal pyrolysis

Wyodak subbituminous coal was reacted with methyl- 13C iodide under basic conditions to obtain modified labelled coal. The modified coal was pyrolysed in a wire screen reactor at 700–800 °C. The distribution of the label among the gaseous products was established by g.c.-m.s.. Of all the labelled ethers that undergo thermal decomposition to form gaseous products, the 13C product distribution is as follows. Approximately 78% of the label appeared in methane, 14% in carbon monoxide, 4.5% in methanol, 1.5% in carbon dioxide and 2% in ethane. These results are examined on the basis of the reaction pathways available for the decomposition of the aryl methyl ethers in coal. The observations are compatible with the view that simple carbon-oxygen bond scisson is the dominant reaction, but they also indicate that the decomposition reactions initiated by hydrogen atom abstraction from the methyl groups play a role in the formation of carbon monoxide. The results for Wyodak coal and for Illinois No. 6 coal are also consistent with the idea that certain hindered aryl methyl ethers undergo decomposition selectively. An explanation for this finding is advanced.

Enhanced coal liquefaction with steam pretreatment

A two-step process for the liquefaction of coal, in a semiflow microreactor, was investigated. The process consisted of pretreating coal with low-temperature steam, followed by treatment with supercritical steam. The maximum observed conversion of a Wyodak subbituminous coal, using this two-step process, was 40 wt % on a moisture- and ash-free basis (MAF). The 240/sup 0/C pretreatment step resulted in a 32% increase over the conversion observed with just a 400/sup 0/C treatment. The coal liquid obtained has a number average molecular weight of 325 and a mass average molecular weight of 373, with a narrow molecular weight distribution.

Liquefaction of a subbituminous coal with steam and ammonia

Liquefaction of coal with a solvent mixture of steam and ammonia was investigated. Concentrations of ammonia in the solvent mixture ranged from 0 to 30 wt %. Ammonia was found to catalyze the conversion of coal. The highest conversion for a Wyodak subbituminous coal was obtained with 2.5% ammonia at 400/sup 0/C and 750 psig. This conversion was 42.5 wt %, on a moisture- and ash-free basis (MAF), representing a 39% increase over the conversion obtained with pure steam at these conditions. The coal liquid obtained is enriched in hydrogen and has low molecular weight (number-averaged (M/sub n/) = 293, weight-averaged (M/sub w/) = 338.

Dissolution of subbituminous coal in tetrahydroquinoline

Two different samples of Wyodak subbituminous coal from the Powder River Basin in Wyoming were liquefied in a two dm 3 batch reactor using 1,2,3,4 tetrahydroquinoline, THQ, as a solvent. Sufficient sample was produced to determine product boiling ranges by distillation and to measure THQ distribution in the product. Product distillation showed that even at cyclohexane conversions greater than 50%, net distillate yields produced using THQ as a solvent were negative. In some cases, high boiling, coal-derived resid yields were greater than the dry coal charged to the reactor. These observations have been attributed to THQ losses resulting from dimerization of the THQ and reactions between THQ and coal derived components.

Changes in composition of solvent-refined coal with severity of hydrogenation

The effects of mild and severe hydrogenation on the chemical composition of solvent-refined coal (SRC) produced from Wyodak subbituminous coal in the direct coal liquefaction SRC-I process were investigated. The yields of solvent-derived fractions of ‘oils’ and ‘asphaltenes’ increased with increasing severity of hydrogenation at the expense of ‘preasphaltenes’. Further separation of ‘oils’ and ‘asphaltenes’, each into three compound-class fractions, revealed more compositional changes. Concentrations of hydrocarbons, nitrogen compounds and hydroxyl aromatics in ‘oils’ increased with increasing severity of hydrogenation. ‘Asphaltenes’, containing nitrogen compounds and hydroxyl aromatic fractions but almost no hydrocarbons, showed an increase in nitrogen-compound concentration with increasing severity of hydrogenation. Hydroxyl aromatic concentration in ‘asphaltenes’ increased under mild but decreased under severe hydrogenation conditions. High-performance liquid chromatography followed by field-ionization mass spectrometry analysis of the hydrocarbon subfractions revealed a complex picture of structural transformations. Over fifty homologous series of aromatic and hydroaromatic hydrocarbons covering a carbon number range from about C 12 to C 50 were identified and approximate concentrations obtained. Small amounts of partly aromatized pentacyclic triterpane ‘biomarkers’ and their hydrogenation products were found.