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Dynamic differential thermal analysis (DDTA) will be described and its application to the study of the glass transition interval of polystyrene will be discussed. The mode of operation involves reproducible cooling from the molten state through the glass transition interval and subsequent heating, both at reproducible linear rates of temperature change. Data on the temperature of half-freezing on cooling and on the temperature of the peak and (or) minimum in the heat capacity have been collected and will be compared with theoretical expressions derived on the basis of the hole theory of liquids. From the half-freezing temperature on cooling; which is taken to be a mean fictive temperature, properties of a mean hole are calculated for polystyrene. (Mean molar hole volume = 21.9 cm.3, energy 1600 cal., activation energy 157,600 cal.; relaxation time at the fictive temperature 5.5 min,) DDTA will be shown to be applicable to the determination of the second freezing-in process of polystyrene which occurs over a range of 230 to 350°K. and is thought to involve the librational motion of the phenyl rings.

The densities of the Argonne Premium Coal samples were measured using H 2 , He, and a H 2 -He mixture (49.13 vol% of H 2 in He) in a gas pycnometer. Significant differences between the apparent hydrogen densities and helium densities were observed. The larger H 2 densities observed in the tests are attributed to H 2 gas adsorption/absorption on coal. The H 2 gas adsorption coefficient increases with increasing carbon content. The «true» or intrinsic densities of coals extrapolated from plots of the measured density versus H 2 gas partial pressure are very close to the He-densities. The organic coal density (dmmf coal density) was obtained after a correction for the mineral matter in the coals. It decreases with increasing carbon content initially, reaches a minimum at about 82 wt% carbon, and then increases with increasing carbon content

The electrochemical behavior of mineral and coal pyrites in basic borate/sulfate solutions was investigated using cyclic voltammetry with both stationary and rotating disk electrodes. Emphasis was centered on transpassive oxidation. In the transpassive region, 0.4 to 0.8 V (SCE), aggressive oxidation of pyrite occurred. The reaction products in this region are Fe(III) oxides, sulfate ion, and partially oxidized sulfur intermediates. The formation of sulfur and polysulfides was identified by in situ Raman spectroscopy. Exposure of pyrite to anodic potentials higher than the transpassive region resulted in rapid oxidation of sulfur intermediates to sulfate ion. The effect of electrode rotation speed, electrode precondition time, and upper potential of the scan in the transpassive region was observed to be critical to the formation of sulfur intermediates. Sulfur intermediates, formed in the transpassive region, dramatically affected subsequent oxidation reactions occurring in the lower potential region. The magnitude of two dominant oxidation peaks, a ferrous hydroxide peak and an iron sulfide peak, observed in this region correlated directly with the quantity of sulfur intermediates formed in the transpassive region. This effect was less pronounced for coal pyrites compared to mineral pyrite.

An optical multichannel apparatus was used to obtain Raman spectra from electrochemically oxidized pyrite in a neutral solution. The pyrite Raman spectra are compared with the spectra from electrochemically oxidized galena and sulfur electrodeposited on platinum. Elemental sulfur and polysulfides are found in the range 0.42–1.0 V vs. the saturated calomel electrode (SCE) for pyrite and 0.13–1.0 V(SCE) for galena.

The surface products of electrochemically oxidized pyrite (FeS(2)) are investigated as a function of applied potential by using Raman spectroscopy. The parameters necessary for sulfur formation on the pyrite surface were determined. An optical multichannel apparatus, consisting of an argon laser, a triple spectrograph, and a charge-coupled-device detector, was utilized for the Raman measurements. The advantages of this system for surface characterization include high resolution and high sensitivity as well as the capability of identifying compounds and making in-situ measurements.

Recent international events have demonstrated the need for additional energy sources to supplement or replace petroleum and natural gas in the United States. Petroleum and natural gas provide over 75‰ of the energy. Supplies of these fuels have not kept pace with demand and in recent years the gap between supply and demand has been widening, resulting in a search for alternate fuels and in the importation of petroleum.Vast reserves of coal make it an attractive fuel, but problems of environmental pollution and inconvenience in handling have restricted its use. Processes for conversion of coal are receiving much attention from Government and Industry. Coal conversion processes under study include liquefaction by hydrogenation, by pyrolysis and by solution in solvents ; gasification and methanation to produce high B. t. u. gas; and gasification to produce low B. t. u. gas. Processes for production of liquids or semisolid products and for the production of high B. t. u. gas are being tested at the pilot plant level and are being scaled-up as rapidly as possible. Low B. t. u. gasification processes will receive increased support during fiscal 1975.The University of Utah has been involved in the study of coal properties and coal conversion processes for over ten years. A liquefaction process under study involves the direct hydrogenation of dry coal, impregnated with catalyst, at moderately high pressures and at short residence times. Hydrogenation occurs in small diameter tube reactors. Both free-fall and entrained-flow designs have been investigated. In the entrained flow reactor coal is fed into the reaction zone by a hydrogen stream at a flow rate in the turbulent range of flow.Metal halides such as ZnCl2 and SnCl2·2H2O have been found to be effective catalysts when impregnated on the coal from aqueous solution. A temperature range of 450°C to 650°C has been found to be effective for hydrogenation. Conversions to liquid and gaseous products of up to 85‰ are attainable, while 60-65‰ conversion isattainable at less severe conditions. Over 60‰ conversion is achieved in a 5mm diameter by 35m reactor tube at 510°C and 135kg/cm2 hydrogen pressure at feed rates of 10kg/hour. Residence times are estimated to be 4-6 seconds, giving a relatively high space utilization rate.Studies on the mechanism of coal hydrogenation by impregnated metal halide catalysts indicate that these catalysts react with coal to form a site which is active for hydrogenation. Pyrolysis of matal halide impregnated coals results in dehydrogenation of hydroaromatic structures in the coal and a subsequent decrease in the evolution of tars and gases. The Lewis acid properties of the metal halide are lost on heating the impregnated coal samples to 400°C. An increase in the surface areas and the develop-ment of a capacity to chemisorb hydrogen indicate that the micropore structure of the coal in enlarged upon heating the impregnated coals . Unimpregnated coals show a different behavior.Although zinc halides and stannous chloride are very effective catalysts, they present problems in terms of expense, corrosion of the system by the catalyst and the recovery of the catalyst. Up to 93.8‰ of the zinc can be recovered by extraction from the liquid products and char.

The total recovery of zinc chloride decreases from 94.4 wt% to 75.4 wt%, on the basis of ZnCl 2 catalyst added, with the progress of the liquefaction reaction. Over 90 wt% of zinc and chlorine found in the liquid and solid products is present in the toluene insolubles. The contents of zinc and chlorine in the other products are below 1 wt% and 5 wt%, respectively, of the ZnCl 2 added.

The formation and chemical structure of preasphaltenes in short residence time coal hydrogenolysis were investigated. In short residence time coal hydrogenolysis, preasphaltenes are the major product. The maximum yield for this parametric study was obtained under reaction conditions of 500 °C and 21 s. The formation of preasphaltenes reached the maximum value in the initial stage of the liquefaction reaction. As the liquefaction reaction continued, the deoxygenation of preasphaltenes proceeded. However, the decrease in aromatic atoms bound to the hydroxy, methoxy and oxygen atoms of the diphenyl ether group (Arz.sbnd;O) is small, and the ArO functionality still remains abundant in preasphaltenes. Preasphaltene-I is characterized by carbon aromaticity (fa) of 0.6–0.7, aromatic rings of from 1 to 3–5 per condensed aromatic ring system, 55–70% substitution of aromatic ring carbons and C2–3 aliphatic substituents. The molecular weight ranges from 500 to 650, and is not much different from that of the asphaltenes. The fa values based on the Brown-Ladner method and on solid state CP/MAS 13C n.m.r. spectra data agree closely.

Heavy oil derived from hydrogenolysis of Hiawatha, Utah, coal was separated by dual packed silica alumina liquid chromatography in accordance with the respective hydrocarbon types and each compound type was fractionated by gel permeation chromatography by the magnitude of their molecular size. It may be assumed that the molecular ion sensitivity coefficient for low-voltage mass analyses are not so largely different among components constituting the respective LC-GPC subfractions inasmuch as the structure of compound types and carbon numbers of alip hatic substitution are limited. Therefore, the structural analyses of GPC subfrac-tions from Fr-D-1 to Fr-D-7 of diaromatic compound were investigated by gas chromatography-mass spectrometry of a low resolution and low energy voltage (10eV) method, and by direct injection for higher molecular weight GPC subfractions eluted earlier. Mass spectra were measured with the integrating multiscan technique. Integrated mass spectra of molecular ion calculated by a computer were dealt with to esimate the hydrocarbon type and carbon numbers of alkyl groups substituted on the basis of Z values which indicates the deficiency of hydrogen in the compounds.From these results, it was shown that Fr-D-2 to Fr-D-7 consist mainly of homologous naphthalene derivatives with less amounts of mono-and triaromatic ring series. With regard to the respective type of naphthalen derivatives constituting each LC-GPC subfraction, the carbon number of alkyl substitution was found to decrease gradually with the increasing GPC fraction numbers from Fr-D-2 to Fr-D-7. For carbon numbers of alkyl substitution of the respective types of naphthalene de-rivatives, alkylnaphthalene series were found to have a range of 0 to 21, 0 to 18 for mononaphthenonaphthalene, 0 to 13 for dinaphthenonaphthalene, 0 to 8 for trinaphthenonaphthalene, respectively.

Heavy oil derived from coal hydrogenation was separated into saturated fractions, neutral aromatic oil, and asphaltene, and these materials were subsequently fractionated according to the magnitude of their respective molecular sizes by gel-permeation chromatography. These GPC subfractions were analysed by proton and carbon-13 n.m.r. spectroscopy and by an additional procedure using gas chromatography for the paraffinic GPC subfractions. 13C-n.m.r. spectra for the GPC subfraction of saturated material showed typical long straight-chain paraffin spectral patterns accompanied by iso-and cycloparaffinic carbon signals. The results from gas-chromatographic measurement for the paraffinic GPC subfractions agree fairly well with the trends of average carbon numbers and contents of straight-chain paraffins obtained by varying the fraction numbers, estimated from 13C-n.m.r. analyses. The ratios of aromatic carbon to total carbon (fa) for aromatic oil and asphaltene GPC subfractions obtained directly from 13C-n.m.r. spectra are slightly lower than the results from the 1H-n.m.r. method assuming x = y = 2 in the Brown—Ladner equation. Peak intensities of the respective carbon species in 13C-n.m.r. spectra were compared with the peak intensities of correspondingly bonded species obtained from 1H-n.m.r. measurement. Some inadequacy was recognized in both measurements. It is assumed that there are two reasons for the discrepancy, one of which is the inaccuracy of 13C-n.m.r. results owing to the long relaxation times and the effect of Nuclear Overhauser Enhancement, and another is the application of unsuitable values of x and y for calculations from the Brown—Ladner equation. New analytical treatments for 13C-n.m.r. results in combination with 1H-n.m.r. analyses are suggested in this study to avoid these uncertainties in structural analyses. From this procedure, it is believed that the actual contents of aromatic and aliphatic carbon and appropriate values of x and y can be derived.

Asphaltenes produced by hydrogenolysis of coal were further hydrogenated in a batch autoclave at 400°C and 22 MPa hydrogen pressure. Red-mud was used as a catalyst and sulfur as promoter. The hydrogen content of the residual asphaltene increases and the fraction of aromatic carbon and the fraction of protons bound to aromatic carbons decrease as the reaction proceeds, indicating that hydrogenation of aromatic rings occurs. Aromatic ring systems of more than 2 rings are relatively easily hydrogenated to 2 rings. However, 2 ring systems are not easily hydrogenated. The heteroatoms-to-carbon ratios are similar for both the oil and the residual asphaltene, but less than that of the original asphaltene. The main differences in the chemical structure between the oil and the residual asphaltene are the hydrogen-to-carbon ratio, the fraction of aromatic carbon, the molecular weights and the average degrees of crosslinking. The residual asphaltene is composed of trimers and/or oligomers of unit structures of two or more condensed aromatic rings bound together by crosslinks. The size and composition of the condensed ring systems varies about the average properties measured in these experiments. Cleavage of the crosslinks by hydrogenation and heteroatom removal produces oil, composed for the most part of monomers of unit structures of two condensed aromatic rings. Coals of different rank show similar behavior although the magnitude of the changes depends on rank.

Oil product from the hydrogenolysis of a high-volatile bituminous coal was separated by solubility, fractionated by gel permeation chromotography and characterized by structural analysis. The average structural unit in the hexane-soluble, aromatic oil fraction consists of 1–3 aromatic rings with 0.3-0.5 of the ring carbons substituted by alkyl groups and oxygen containing groups. Molecular weights vary from 200 to 500. The larger molecular weight fractions have longer alkyl chains and lower carbon aromaticities. The molecules are mainly of single unit structures. The average structural units in asphaltene fractions contain from 2.5-4 aromatic rings, are of higher carbon aromaticities and contain shorter alkyl groups. The asphaltene molecules consist of two or more structural units, crosslinked together, and have molecular weights of 300–1400. The oxygen content of the fractions decreases with decreasing molecular weight. Increasing the amount of ZnCl2 catalyst during hydrogenolysis resylts in an increased yield of lower-molecular-weight material, but no change in the structural properties of the product. This is interpreted to mean that ZnCl2 is active in the scission of covalent bonds between structural units during liquefaction and that the hydrogenolysis reaction is mostly cleavage of crosslinks between structural units with minimal reaction of the units themselves.

Free radicals produced as intermediates during the radiolysis of polyethylene have been most frequently studied by ESR techniques. We have now used ultraviolet absorption spectroscopy because the uv absorption bands of the allyl, dienyl, and trienyl conjugated free radicals are well separated on the wavelength scale and do not overlap as do the ESR signals from these intermediates. Stable polyenes are also produced by the radiolysis and these groups can also be studied quantitatively by ultraviolet spectroscopy. In contrast to the diene groups whose concentration grows linearly with the dose, the allyl and dienyl free radicals as well as conjugated trienes grow with increasing rates as the irradiation proceeds. In fact, a statistical calculation of the triene growth reaction rate constant in terms of the diene concentration and a probability factor based on the vinylene growth rate has been quite successful. From this result and others it is concluded that trienes and allyl, dienyl, and trienyl free radicals are not primary products of the irradiation. The effect of ultraviolet light on the allyl and dienyl free radicals has also been studied. In agreement with others we find that uv light decreases the allyl free radical concentration; however, the dienyl and trienyl concentrations increase. On standing after the uv irradiation the allyl groups recover practically their initial abundance—but the dienyl and trienyl free radical concentrations continue to grow. Various mechanisms are discussed.

Equations for the apparent heat capacity in the glass‐transition interval as functions of temperature, heating rate, and thermal history have been developed and programmed for computation. The hole theory of liquids was used as basis for the analysis of the glass transition. Experimental information was derived from dynamic differential thermal analysis, DDTA, on polystyrene.The maximum of the apparent heat capacities found experimentally agrees with the theory. The peak temperatures Tm can be expressed over four decades of heating rates by logq = A′ − B/Tm, where q is the heating rate, A′ is an approximate constant, and B is the activation energy for hole formation. Higher cooling rates lead to higher activation energies on subsequent heating, indicating the need to recognize a hole size distribution.The minimum in the heat capacity that precedes the maximum on heating through the glass‐transition interval could be detected on quenched samples. Mathematical expressions for the minimum temperature and mag...

When polyethylene has been irradiated with high‐energy radiations ultraviolet absorption bands having peaks at 229, 236, 245, 258, 264, 275, 285, 288, 307, 323, 340, 359, and 396 mμ can be observed. The bands are most clearly distinct at liquid‐nitrogen temperature, but some can only be observed after the decay of free radicals on admission of oxygen at room temperature. The assignment of these bands to conjugated polyene and polyenyl free‐radical groups is given and discussed.

Samples of high-density polyethylene were irradiated with x-rays and oxidized with concentrated nitric acid to determine the location of unsaturated groups. Vinyl groups initially present in the polymer were rapidly oxidized to the extent of 85% and are assumed to be excluded from the crystals. Vinylene groups show a rapid oxidation followed by slow oxidation. The initial oxidation is about 35%, which is slightly greater than the 25% amorphous content of the polymer prior to irradiation. Diene groups are rapidly oxidized by nitric acid but are formed at about the same rate in crystalline and amorphous samples. This is interpreted to indicate that diene groups are formed throughout the polymer but form large defects in crystalline regions and are accessible to oxidation. Defects formed in crystalline regions during irradiation lower the melting point to a greater extent than predicted by the mole fraction of noncrystallizable units.

Coal undergoes changes during the hydrogenation process which depend on the balance between carbonization and hydrogenation reactions, which in turn depend on various experimental conditions, i.e. hydrogen availability, heating rate etc. If carbonization conditions prevail, semicoke is formed, whereas liquid hydrocarbons are formed under hydrogenation conditions. This model is applicable to hydrogenation reactions carried out under a wide range of experimental conditions.