John W. Diehl

Elucidation of aliphatic structures in low-rank coals with ruthenium tetroxide oxidations☆

Abstract The oxidation of low-rank coals with ruthenium tetroxide was investigated with the objective of elucidating the aliphatic bridging groups and hydroaromatic groups present in the organic structure. The reaction was carried out in a two-phase system with a phase transfer catalyst. An accurate quantitative method was developed for the analysis of the carboxylic acid products. Six of the products were determined by isotope dilution with standard acids followed by gas chromatography-mass spectrometry of methyl esters prepared from the acid mixture. A suite of low-rank coals were oxidized in this system and product yields were compared. Higher yields of the aliphatic acids were obtained from the higher-rank subbituminous coals. A series of lithotypes of Beulah lignite were oxidized. The yields of the aliphatic acids obtained from lithotypes were in the order: vitrain > durain > fusain, and aromatic acids were obtained from the lithotypes in the opposite order. A method was developed to distinguish whether the aliphatic acids originated from hydroaromatic or bridging groups. A prior-dehydrogenation experiment resulted in a 50% change in the amount of succinic acid obtained in the oxidation but very little change in the amount of adipic acid. This finding implies that half of the succinic acid originates from hydroaromatics and half from bridging groups, whereas very little of the adipic acid results from hydroaromatic groups.

Molecular weights of solubilized lignite macromolecules

Abstract The determination of molecular weights and molecular weight distributions in humic acids derived from lignite by base extraction has been successfully carried out by low-angle laser light scattering (LALLS) photometry and by coupling size exclusion chromatography (SEC) with LALLS photometry. Since light scattering techniques give absolute molecular weight values, no error-prone calibrations of the size exclusion column were necessary. Reduction of soluble derivatives of the humic acids with zinc in acetic anhydride was required to reduce the optical absorbance so that a linear scattering response was observable. Weight average molecular weights of ≈ 1.3 × 10 6 and low polydispersity ratios were obtained for humic acid derivatives of Beulah, ND, lignite. Extension of this technique to the study of the more highly crosslinked humin which comprises the major portion of the lignite was investigated by treatment of the lignite with sodium hydroxide solution in a blender. This treatment converted up to 90% of the lignite into humic acids, which could be derivatized and studied by the LALLS techniques. The molecular weights of the products from lowtemperature solubilization of the lignite are inversely proportional to the per cent conversion.

Size exclusion chromatography-low angle laser light scattering photometry of lignite macromolecules

Abstract The determination of molecular weight distribution in humic acids, derived from lignite, has been successfully carried out by the application of size-exclusion chromatography, coupled with low-angle laser light-scattering photometry. Reduction of soluble derivatives with zinc in acetic anhydride was required to reduce the absorbance so that a linear scattering response was obtained. A benzyl derivative and a methyl derivative exhibited the best chromatographic results, giving weight average molecular weights of about 1 500 000.

Hydrosols from low-rank coals: 1. Preparation and properties

The nature of the sodium humates from low-rank coals and the factors that determine their yields are reported in this paper. The sodium humate from Beulah lignite was shown to consist of a colloidal dispersion with a particle distribution in the submicron range, with a Z-average size of 411 nm. Yields for conversion of Beulah lignite to the dispersed humate form (hydrosol) in a sodium hydroxide medium have been increased from 4%, using magnetic stirring to 89%, using a high-speed blender at temperatures less than 45 °C. When carried out in a nitrogen dry bag, the high shear, high mass flow blending gave a 45% conversion of Beulah (North Dakota) lignite to the hydrosol. Other low-rank coals also gave high conversions (Big Brown lignite, 73%; Wyodak, 69%) but bituminous coals gave no conversion to hydrosol. The mineral content of the humic acid resulting from acidification of the Beulah hydrosol was <1%, whereas the residue of material that did not disperse in the basic solution was more concentrated in mineral matter and liptinite macerals. The ash analysis data were consistent with photoacoustic FT-i.r. and 13C n.m.r. spectroscopic studies. These instrumental techniques also substantiated an increase in carboxylic groups in the humic acid products. Significantly lower conversions were observed when bases other than sodium hydroxide and nonaqueous media were used in the blending.

Structural features of low-rank coals important in liquefaction, bioconversion and gasification

Molecular weight determinations have been performed using low-angle laser light scattering photometry on derivatives of a series of humic acid macromolecules derived from lignite. The humate derivatives obtained from Beulah lignite by base extraction were shown to have molecular weights ranging from 1.3 × 106 to 4.3 × 105 daltons, low and high yield extractions respectively. Mild oxidation with p-nitroperbenzoic acid gave humic acids with slightly larger molecular weights, again inversely proportional to the yields. The nature of the aliphatic bridging groups in low-rank coals have been investigated by ruthenium tetroxide oxidations using isotope dilution GC/MS methods for analysis of the product carboxylic acids derived from oxidation of the aromatic portions of the coal.

Characterization of coal liquefaction products by gas chromatography—fourier transform infrared spectroscopy—mass spectrometry

Abstract An integrated gas chromatography—Fourier transform infrared spectroscopy—mass spectrometry system was utilized in the analysis of a neutral and acidic fraction obtained from the aqueous portion of the low-severity coal liquefaction products. Reconstructed selected-ion chromatograms along with reconstructed absorbance chromatograms over elected ranges were useful in discriminating between the types of organic compounds in the complex mixtures. A series of γ-lactones and a series of ketones were characterized, the ring size and unsaturation being determined by the absorbance frequency of the carbonyl stretching band.

Kinetics of hydantoin formation

Abstract The reaction of lignite in a slagging gasifier produces reactants which in turn form 5,5-dimethylhydantoin (DMH) as a major constituent in the condensate water. Variations in plant operating conditions made it impossible to accurately study the kinetics of formation of DMH in the actual gasifier water, and thus a model system was chosen. The reaction of acetone cyanohydrin in the presence of excess ammonium carbonate at concentrations approaching those obtained in the condensate water were studied at 50,70, and 90 °C. Secondorder kinetics were obeyed, and the pseudo second-order rate constants at the respective temperatures were 1.86, 3.6, and 4.62 dm 3 mol − 1 h − 1 . Independent variation of the concentration of either acetone, cyanide, ammonia or carbonate gave results consistent with the interpretation that the formation of DMH is first order in all reactants: rate of formation of DMH = k [acetone][HCN][NH 3 ][CO 2 ]. The pseudo second-order rate constant is a complex rate constant including several rapid equilibria. A mechanism consistent with the kinetic data is presented.

Non-aqueous enzymatic solubilization of coal-derived materials

Abstract 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.

Anisotropy in dilute solutions of coal-derived materials☆

Abstract Rayleigh light-scattering measurements of dilute solutions of coal macromolecules were carried out with polarizing analysers. These experiments showed large intensities of depolarized light scattered normal to the initial plane of polarization. The depolarization is caused by the highly anisotropic nature of coal-derived materials. This effect is generally negligible in synthetic polymers. Because of nonidentical polarizabilities on all axes of the coal macromolecules, light is scattered more intensely. Thus, corrections of the Rayleigh scattering are needed to obtain accurate molecular weights from the reciprocal Rayleigh factor plot. The required correction factors (Cabannes factors) can be calculated from the depolarization ratios observed. The depolarization ratios of material from different ranks were found to increase in proportion to the rank of the coal.