Coal continued studies

Autoclaves provide reactors which can be used readily to acquire data from coal liquefaction studies but are less representative of likely commercial plant tyi reactors than small scale continuous bed-type reactors. Ideally comparisons between reactors are best made by carrying out experiments in various designs of reactors under similar reaction conditions, but, in order to cover the full range of designs adequately, a larger expenditure on equipment (beyond the budgets of most laboratories) would be necessary. However, steps can be taken to cover the... 

Jhe distribution of hydrogen types in coals continues to be a subject of considerable interest in coal structure studies. Published data indicate that the fraction of aromatic hydrogens usually increases with increasing rank, but the absolute values depend on the specific analytical method used (7). Hydrogen type analysis of a single coal based on the application of NMR spectroscopy to the soluble fraction from depolymerization with phenol-BFa has been reported by us (3). The conversion of coal to soluble fragments in substantial yields under very mild conditions permits a reliable determination of the hydrogen types by NMR analysis, and these results can be extrapolated to the parent coal with considerable confidence. 

Concerns about the environmental effects of emissions resulting from the combustion of fossil fuels, particularly coal, continue to increase as the utilization of these fuels grows. The large amounts of sulfur dioxide and nitrogen oxides emitted into the atmosphere and the attempts to tie these fossil-fuel-derived pollutants directly to the undeniably difficult problem of acid rain have caused heated debates, numerous research studies, government actions, and serious efforts to reduce pollution. The issues are extremely complex, and our understanding of the origin, properties, behavior, and effects of these pollutants is incomplete. Often, theories are contradictory. 

Currently there is considerable effort being expended in several institutions to continue sorption analyses to evaluate the porosity and internal surface area of coal. These studies involve studies of vapor (2, 3, 4 and liquid (5) sorption analyses. We have employed proven micro-gravimetric sorption equipment and techniques (6) for a detailed examination of the thermodynamics and mechanisms of sorption of various vapors on well-characterized coals. Specifically, the coals used for this study are classified as C-bituminous, Illinois No. 6, from the Sahara... 

The minerals found in United States coals continue to be studied with the availability of improved instrumental procedures such as x-ray diffraction, infrared absorption, and scanning electron microscopy beyond the traditional optical and chemical mineralogical techniques as applied to thin sections, polished pellets, and isolated particles. The minerals may be grouped into the silicates (kaolinite, illite montmorillonite, and chlorite), the oxides (quartz, chalcedony, hematite) the sulfides (pyrite, marcasite, and sphalerite) the sulfates (jarosite, gypsum, barite, and numerous iron sulfate minerals) the carbonates (ankerite, calcite, dolomite, and siderite) and numerous accessory minerals (apatite, phosphorite, zircon, rutile, chlorides, nitrates, and trace minerals). 

Raw materials are the precursor of a processed (virgin) plastic that combines with additives, fillers, and/or reinforcements to become a plastic matrix in RPs. The source is principally petroleum. Others include natural gas, coal, and agriculture products. Agricultural products are used they are continually studied and targeted to develop a major raw material source and one of the latest concerns corn. 

The second deviation from the HRI CTSL is the continued use of the CSD unit to remove the ash and solids. Improvements in the CSD unit have reduced organic rejection to the same levels that HRI achieves with filtration. These changes have allowed the Wilsonville plant to achieve distillate yields of up to 77 percent (maf coal) with a cleaned Ohio 6 bituminous coal. " More typical yields of 70 percent (maf coal) were found with Illinois 6 bituminous coal. " Recent studies demonstrated the beneficial effects on the distillate yield of deep-cleaning the coal, achieving a distillate yield of 74 percent with a Pittsburgh 8 bituminous coal. ... 

Alternative feedstocks for petrochemicals have been the subject of much research and study over the past several decades, but have not yet become economically attractive. Chemical producers are expected to continue to use fossil fuels for energy and feedstock needs for the next 75 years. The most promising sources which have received the most attention include coal, tar sands, oil shale, and biomass. Near-term advances ia coal-gasification technology offer the greatest potential to replace oil- and gas-based feedstocks ia selected appHcations (10) (see Feedstocks, coal chemicals). 

Replacing one carbon atom of naphthalene with an a2omethene linkage creates the isomeric heterocycles 1- and 2-a2anaphthalene. Better known by their trivial names quinoline [91-22-5] (1) and isoquinoline [119-65-3] (2), these compounds have been the subject of extensive investigation since their extraction from coal tar in the nineteenth century. The variety of studies cover fields as diverse as molecular orbital theory and corrosion prevention. There is also a vast patent Hterature. The best assurance of continuing interest is the frequency with which quinoline and isoquinoline stmctures occur in alkaloids (qv) and pharmaceuticals (qv), for example, quinine [130-95-0] and morphine [57-27-2] (see Alkaloids). 

About one half of the coal samples used in the above study (61) have been investigated by workers in Gulf Research and Development Company, using a continuous flow reactor (63). The throughput was about 1 kg./h of coal/solvent slurry, the solvent was a partly hydrogenated anthracene oil, temperatures of 440 and 455°C were used, and the system was pressurized with hydrogen to 20.69 MPa. 

The Effect of Residence Time The final parameter that was studied was the solid residence time. In the semi-continuous reactor used for this study, the volatile product is swept from the reactor by a continuous stream of hydrogen and, therefore, there is both a vapour and solid residence time. It is this latter parameter that has been studied here and the solid residence time was considered to be the time that the reactor spends at temperature. For the study of the residence time, tin (1 % of the coal) as stannous chloride was used as the catalyst and the other conditions are given in Table II. 

In a continuous reactor, particularly of the trickle bed type, intimate contact between the coal liquid and the catalyst will be maintained throughout the pass of the liquid feed. In an autoclave, particularly of the stirred design, the contact between the liquid and the catalyst will not be as intimate. The action of the stirrer will produce a centrifugal force which will tend to throw the liquid away from the catalyst surface. Consequently, it can be visualised that less strongly adsoibed molecules will spend a shorter time at the catalyst surface so that reaction rates and mechanisms could be very different from those observed in continuous reactor studies. In addition, steady state conditions can be readily investigated in a continuous reactor, whereas for a single contact in an autoclave, steady state conditions may not have been established and changes in catalyst activity will become more relevant. 

Of the many factors which influence product yields in a fluid catalytic cracker, the feed stock quality and the catalyst composition are of particular interest as they can be controlled only to a limited extent by the refiner. In the past decade there has been a trend towards using heavier feedstocks in the FCC-unit. This trend is expected to continue in the foreseeable future. It is therefore important to study how molecular types, characteristic not only of heavy petroleum oil but also of e.g. coal liquid, shale oil and biomass oil, respond to cracking over catalysts of different compositions. 

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