Peter G. Stansberry

Temperature-staged catalytic coal liquefaction

Abstract An investigation has been made of the liquefaction of a bituminous and a subbituminous coal under conditions where reaction is conducted in successive stages of increasing temperature and in the presence of a dispersed sulphided Mo catalyst. This sequence has been found to lead not only to high coal conversion but to greatly increase the selectivity of the liquefied products to oils at the expense of asphaltenes. These gains are made with marginal increases in the production of light hydrocarbon gases. Although no systematic attempt has yet been made to determine the specific influence of reaction parameters upon liquefaction behaviour, preliminary results show that there is substantial potential for further improvement through the suitable choice of solvent and reaction conditions in the two stages. The reasons for the effectiveness of temperature staged liquefaction are discussed in terms of the balance between hydrogenation and condensation reactions. Examination of the liquefaction residues by optical microscopy has provided strong supporting evidence to show that the staged reaction sequence favours hydrogenative processes. Moreover, the microscopic examination has proved to be a powerful diagnostic technique, showing, for example, that the first stage temperature should be lower for the subbituminous than the bituminous coal, and providing insight into the processes of catalysed liquefaction.

Characteristics and carbonization behaviors of coal extracts

Abstract N -methyl pyrrolidone (NMP) raw coal extract (EXT), hydrogenated coal extract (HEXT) and the blend of EXT and HEXT in NMP (BLD), from two bituminous coals, were studied. The extracts were carbonized in both tube-bomb and a temperature programmable furnace. Elemental analysis, FTIR spectroscopy and optical microscopy techniques were employed to characterize the extracts and the carbonization residues. It was found that the extracts resembled petroleum-derived pitches in the hydrogen content and (C/H) atomic ratio. Higher oxygen and nitrogen contents differentiated the coal extracts from commercial petroleum pitch. More carbon and hydrogen, and lesser oxygen and sulfur differentiated HEXT from EXT. The ratios of integrated IR band intensity for aromatic and aliphatic CH stretching indicate that the relative content of aliphatic hydrogen in EXT is higher than in HEXT. HEXT contains comparatively more aromatic hydrogen, a feature necessary for thermal stability and fluidity during carbonization. BLD materials are at a place somewhere in between. Kinetic modeling of the aliphatic hydrogen change during carbonization reveals that EXT has high carbonization rate and low apparent activation energy. This can be related to the optical texture size of carbonization residues. The residues made from EXTs exhibited fine mosaic optical texture and limited mesophase development. HEXTs were readily converted into highly anisotropic coke. BLDs produced carbonization residues with intermediate properties. Extracts with similar activation energies produced similar residues in the same coal series. The degree or extent of anisotropy displayed by the carbonization residues was found to be dependent on the relative distribution of aromatic and aliphatic hydrogen.

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

Abstract Iron compounds are known to be active catalysts for direct coal liquefaction. We have synthesized ferric sulfide (Fe 2 S 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.

Measurements and control of anisotropy in ten coal-based graphites

Abstract Using a solvent extraction process to produce high-purity extracts from untreated and hydrogenated coal, ten coal-based graphites with different levels of anisotropy have been produced. Anisotropy of these graphites and that of H-451 (a petrocoke-based commercial graphite) has been assessed by means of the intensity of the (002) line in X-ray diffraction (XRD), by magnetic susceptibility (χ), by the coefficient of thermal expansion (α), and by electrical conductivity (σ) studies. Measurements were made along directions longitudinal ( l ) and transverse (t) to the extrusion direction. The XRD ratio R for the (002) line varies between 0.23 for the most anisotropic and 0.94 for the least anisotropic of the graphites. χ l χ t and α l α t for various graphites increase systematically as R increases, although the variations are not linear over the extended range. It is argued that measurements of R , χ l χ t , and α l α t provide reliable techniques for the measurements of anisotropy in graphites. Examination of the relationship of the anisotropy to the nature of the precursors used in producing graphites shows that hydrogenation of coal prior to the extraction process produces anisotropic graphites, the anisotropy being controlled by the degree of hydrogenation. Furthermore, it is shown that by blending appropriate amounts of hydrogenated and nonhydrogenated coal extracts, graphites of desired anisotropy can be produced.

RESEARCH ON CARBON PRODUCTS FROM COAL USING AN EXTRACTIVE PROCESS

This report presents the results of a one-year effort directed at the exploration of the use of coal as a feedstock for a variety of industrially-relevant carbon products. The work was basically divided into three focus areas. The first area dealt with the acquisition of laboratory equipment to aid in the analysis and characterization of both the raw coal and the coal-derived feedstocks. Improvements were also made on the coal-extraction pilot plant which will now allow larger quantities of feedstock to be produced. Mass and energy balances were also performed on the pilot plant in an attempt to evaluate the scale-up potential of the process. The second focus area dealt with exploring hydrogenation conditions specifically aimed at testing several less-expensive candidate hydrogen-donor solvents. Through a process of filtration and vacuum distillation, viable pitch products were produced and evaluated. Moreover, a recycle solvent was also isolated so that the overall solvent balance in the system could be maintained. The effect of variables such as gas pressure and gas atmosphere were evaluated. The pitch product was analyzed and showed low ash content, reasonable yield, good coking value and a coke with anisotropic optical texture. A unique plot of coke yield vs. pitch softening point was discovered to be independent of reaction conditions or hydrogen-donor solvent. The third area of research centered on the investigation of alternate extraction solvents and processing conditions for the solvent extraction step. A wide variety of solvents, co-solvents and enhancement additives were tested with varying degrees of success. For the extraction of raw coal, the efficacy of the alternate solvents when compared to the benchmark solvent, N-methyl pyrrolidone, was not good. However when the same coal was partially hydrogenated prior to solvent extraction, all solvents showed excellent results even for extractions performed at room temperature. Standard analyses of the extraction products indicated that they had the requisite properties of viable carbon-product precursors.

COAL DERIVED MATRIX PITCHES FOR CARBON-CARBON COMPOSITE MANUFACTURE/PRODUCTION OF FIBERS AND COMPOSITES FROM COAL-BASED PRECURSORS

The Consortium for premium Carbon Products from Coal, with funding from the US Department of Energy, National Energy Technology Laboratory continue with the development of innovative technologies that will allow coal or coal-derived feedstocks to be used in the production of value-added carbon materials. In addition to supporting eleven independent projects during budget period 3, three meetings were held at two separate locations for the membership. The first was held at Nemacolin Woodlands Resort on May 15-16, 2000. This was followed by two meetings at Penn State, a tutorial on August 11, 2000 and a technical progress meeting on October 26-27.

CHAPTER 7 – Coal-Derived Carbons

This chapter reviews the class of coal-derived carbons. In recent years, researchers at West Virginia University have developed coal derived pitches on a laboratory scale in quantities sufficient to make 1 kg samples of calcined coke for fashioning graphite test specimens. The pitches were derived by utilizing solvent extraction with N-methyl pyrrolidone (NMP). This solvent is able to isolate coal-based pitches in high yield and with low mineral matter content. The chapter demonstrates that a solvent-extraction procedure with N-methyl pyrrolidone is capable of producing coal-derived extract pitches with low-ash contents. Moreover, the properties of the pitches can be varied by partial hydrogenation of the coal prior to extraction. The yield of the pitches along with the physical and chemical properties of the cokes and graphites vary. By a combination of pitch blending and hydrogenation, the properties of calcined cokes and their subsequent graphites can be controlled in a predictable manner. Thus, by altering processing conditions, graphites ranging from very isotropic to very anisotropic can be produced from a single coal source.