Richard H. Schlosberg

Pyrolysis studies of organic oxygenates: 3. High temperature rearrangement of aryl alkyl ethers

Abstract Thermal chemistry pathways of aryl alkyl ethers have been investigated under coal conversion-like conditions. Anisole is a thermally reactive compound having an oxygen functionality found in such coal precursors as lignins. Pyrolysis of anisoles was carried out using small batch autoclaves. Under thermolysis conditions anisole yielded a product distribution strongly dependent upon experimental parameters. Phenol, methane, CO and benzaldehyde are the low molecular weight products and polyphenyls and polyethers are the predominant high molecular weight products. The generation of CO is explained by a high temperature rearrangement of the phenyl group from O- to C- followed by rapid thermal decarbonylation of the benzaldehyde. Carbon monoxide formation from aryl alkyl ethers can thus be an important mechanistic pathway in coal conversion processes. By investigating the rearrangement using para-fluoroanisole it was shown that this rearrangement proceeds via a three-centered intermediate to para-fluorobenzaldehyde. No meta isomer was observed.

Pyrolysis studies of organic oxygenates. 2. Benzyl phenyl ether pyrolysis under batch autoclave conditions

Benzyl phenyl ether (BPE) is a reactive organic oxygenate which contains the ether functionality believed to be present in subbituminous and bituminous coals. With an HC of 0.92 it has a hydrogencarbon ratio similar to that found in bituminous coals. Benzyl phenyl ether reacts readily at 375 °C either in the presence or absence of added donor hydrogen sources. The major products are toluene and phenol. Other, heavier products are also produced in significant quantities. In general, as available donor hydrogen is reduced, the products tend to have higher molecular weights. Conventional pyrolysis products become lighter (more desirable) materials when the pyrolysis is carried out in the presence of added hydrogen.

Pyrolysis of benzyl ether under hydrogen starvation conditions

Abstract Pyrolysis of dibenzyl ether at 450 °C, without added hydrogen, produces toluene and benzaldehyde as the major low-molecular-weight products. Additionally, carbon monoxide, biphenyl, diphenylmethane, diphenylethane, and benzyl toluenes are formed in significant amounts via secondary reaction pathways. In the absence of added hydrogen, increasing reaction severity (residence time) leads to growth/polymerization reactions ultimately leading to coke. Moderate-pressure molecular hydrogen, as an added reagent, inhibits, to some extent, the polymerization pathway.

Alkylation: a beneficial pretreatment for coal liquefaction

Abstract Several coals were alkylated employing isopropyl and methyl halides under Friedel-Crafts conditions. These alkylated coals, and corresponding untreated coals, were processed (liquefied) with tetralin in batch autoclaves (tubing bombs) at 700 K, 130 min residence time, and 10 MPa (1500 psi) hydrogen pressure. Conversion to cyclohexane-soluble liquids was found to be 10–21 percent higher (on an alkyl-group-free basis) for the alkylated coals than for untreated coals. These results are explained on the premise that alkylation beneficially disrupts the coal structure sufficiently to allow improved contacting between coal and tetralin.

Stability of adamantane and its derivatives to coal-liquefaction conditions, and its implications toward the organic structure of coal☆

Abstract Adamantane, diamantane, 2-phenyladamantane, and adamantanone were shown to be stable to H-donor conditions, under which coals are converted to liquids (425 °C; 130 min; 2:1 tetralin to substrate). Both 1-adamantanol and 1-adamantane carboxylic acid were completely converted to adamantane. The data demonstrate the remarkable stability of this class of hydrocarbon, and argue against polyamantanes as models for major structural features of coals.

Coal Science: Basic Research Opportunities

More fundamental knowledge of coal (knowledge of its structure and its behavior during conversion processes) is essential before we can generate new technologies necessary for the efficient use of coal in the future. Herein are suggested specific basic research opportunities in the areas of coal characterization, gasification, combustion, and liquefaction, along with an assessment of the impact such research programs could have. Critical characterization needs include qualitative and quantitative determination of the chemical forms of carbon, oxygen, nitrogen, and sulfur and reliable methods for the measurement of surface area, pore volume, and weight-average molecular weights. Mechanistic studies aimed at increasing understanding of the thermal breakdown of the functionalities in coal, the behavior of coal in the presence of molecular and donor hydrogen environments, and carbon gasification and hydrocarbon synthesis reactions starting from carbon monoxide and hydrogen will lay the scientific foundation for the development of new processes for converting coal into clean usable fuels and chemicals.

Effect of Friedel-Crafts alkylation on the caking properties of bituminous coal

Abstract Reaction of medium caking Illinois No. 6 and highly caking Kentucky HVB coals under mild Friedel-Crafts alkylation conditions rendered the product non-caking. Use of aluminium chloride alone with coal did not change the caking property, while this catalyst in the presence of either an alkyl chloride or benzene did suppress caking. Gaseous HCl decreased but did not eliminate agglomeration. Alkylation of a non-caking Western subbituminous coal had no effect on its non-caking property.

ANALYSIS OF A SYMMETRIC NEOPOLYOL ESTER I. Measurement and calculation of heat capacity

Quantitative thermal analysis was carried out for tetra[methyleneoxycarbonyl(2,4,4-trimethyl)pentyl]methane. The ester has a glass transition temperature of 219 K and a melting temperature of 304 K. The heat of fusion is 51.3 kJ mol -1 , and the increase in heat capacity at the glass transition is 250 J K -1 mol -1 . The measured and calculated heat capacities of the solid and liquid states from 130 to 420 K are reported and a discussion of the glass and melting transitions is presented. The computation of the heat capacity made use of the Advanced Thermal Analysis System, ATHAS, using an approximate group-vibration spectrum and a Tarasov treatment of the skeletal vibrations. The experimental and calculated heat capacities of the solid ester were compared over the whole temperature range to detect changes in order and the presence of large-amplitude motion. An addition scheme for heat capacities of this and related esters was developed and used for the extrapolation of the heat capacity of the liquid state for this ester. The liquid heat capacity for the title ester is well represented by 691.1+1.668 T [J K -1 mol -1 ). A deficit in the entropy and enthalpy of fusion was observed relative to values estimated from empirical addition schemes, but no gradual disordering was noted outside the transition region. The final interpretation of this deficit of conformational entropy needs structure and mobility analysis by solid state 13 C NMR and X-ray diffraction. These analyses are reported in part II of this investigation.

Pyrolysis studies of organic oxygenates. IV. Naphthalene methyl ether pyrolysis under batch autoclave conditions

Aryl alkyl ethers undergo two major kinds of thermal reactions at temperatures of about 450/sup 0/C. They cleave homolytically at the O-C alkyl bond to produce phenols and they cleave homolytically at the C-H alkyl bond, and rearrange to an aryloxy radical leading to carbonyl compounds and ultimately to other products. Results obtained with the methyl ethers of 1- and 2-naphthol and with anisole show clearly that relative kinetics for these pathways differ for different substrates. Unimolecular decomposition rates at 400/sup 0/C and at 450/sup 0/C show that 1-methoxy naphthalene decomposes faster than 2-methoxy naphthalene which in turn is more thermally reactive than anisole.

13C NMR study of the acid-catalyzed carbonylation of methyl tert-butyl ether (MTBE)

Methyl tert-butyl ether (MTBE) is a widely used additive in oxygenated gasoline that has recently been identified as a potential health threat to the drinking water supply due to leaking underground storage tanks. One alternate use for MTBE is the production of methyl 2,2-dimethylpropanoate (methyl pivalate) via Koch carbonylation chemistry. BF3/H2O catalysts are employed in industrial applications of Koch chemistry, but cannot be used for direct ester production because the presence of water in the system leads to the formation of carboxylic acids and lowers the selectivity to esters. Therefore, a BF3/CH3OH complex was investigated for the carbonylation of MTBE to avoid this loss in selectivity. This study used 13C NMR spectroscopy and ab initio calculations to investigate this carbonylation reaction. NMR results and ab initio calculations suggest a structure for the BF3/CH3OH acid which is in agreement with previous studies, and a Hammett acidity value of -4.2 was calculated for BF3-2.19CH3OH using the Δδ method. It is believed that these are the first reported ab initio calculations on the BF3/CH3OH system. NMR results also show that MTBE begins to react between 50 °C and 75 °C to produce oligomers of isobutene when no CO is present and carbonylated species when CO is present.