Wendell H. Wiser

A comparison of the carbon-13 n.m.r. spectra of solid coals and their liquids obtained by catalytic hydrogenation

Abstract High-volatile bituminous and lignite coals have been studied by means of carbon-13 n.m.r. employing cross-polarization and magic-angle-spinning techniques. The solids spectra have been compared to those of the coal-derived liquids. By artificially broadening the high-resolution spectra of the liquids, a striking similarity in line shape and position is observed when the liquid spectra are compared with those of the corresponding solid coal. It is noted however that certain bands visible in the solid are no longer present in the liquefied state. The significance of these results is discussed in terms of carbon skeletal structures present in the solids but not in the liquids.

New procedure for molecular-weight determination by vapour-phase osmometry

Abstract Inconsistent results on molecular weights determined by different methods reported in the recent literature prompted this study. A detailed investigation of the behaviour of benzil-chloroform solutions and fourteen other systems resulted in a major revision of the experimental procedure used in the VPO method for molecular-weight determination. The revision was based on a clear recognition of a ‘rectilinear region’ and a ‘curved region’ in the relation between the osmometer readout (ΔV) and non-volatile solute concentration. Only the rectilinear region shows a direct relation between ΔV and the number of solute molecules in an infinitely dilute concentration range, a fact which has not been clearly identified before. A method of determining a concentration range for the rectilinear region was devised and used to develop a simpler experimental procedure. Molecular weights of eleven model compounds were checked using the new procedure. Molecular weights of two coal-derived liquid fractions were also determined and the presence of association in their mixture was examined. Shortcomings in the present theory and two other experimental procedures are pointed out. Molecular weights of model compounds including those in the experiments quoted ranged from 122 to 1238.

Structural characterization of coal-hydrogenation products by proton and carbon-13 nuclear magnetic resonance

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.

Rate data of tar hydrocracking

Abstract The rate data of the hydrocracking reaction of low-temperature tar are presented. The overall order of the reaction was found to be second order below 1500 psi and first at and above 1500 psi ∗ . The rate of gasoline formation from tar was found to be represented by k1g = 0.14 k1N.O + 0.16 k1S + 0.14 k1O + 0.12 k1N + 0.08 where k1N.O′k1S′k1O′ and k1N are first order rate constants for the hydrocracking of hydrocarbons, and sulphur, oxygen and nitrogen compounds present in tar respectively.

Conversion of Bituminous Coal to Liquids and Gases: Chemistry and Representative Processes

Bituminous coal consists principally of condensed ring structures containing aromatic and hydroaromatic rings. The condensed units are connected mainly by short aliphatic chains and ether linkages. Coal liquefaction reactions in the usual temperature range (400–500°C) proceed chiefly via a free radical mechanism, thermally produced radicals being stabilized mostly by hydrogen from available sources. Several approaches to achieve liquids production are illustrated with specific processes. Gasification of coal to yield a gas of low heating value and one of high heating value is discussed and the principles illustrated with specific processes.

Kinetics of coal liquefaction: effect of catalyst, H2 concentration and coal type

Abstract A process for dry coal hydrogenation—liquefaction has been developed that permits short residence times (seconds) and achieves notably high space rate utilization factors. The purpose of the work reported here is to identify more precisely the process variables that determine space rate utilization factors, and to express them in a kinetic scheme, in the hope of establishing more effective control of these variables in the process. A kinetic analysis of work done in a 3 mm i . d . × 1 m long reactor is presented. Some data from a 4.5 mm i . d . × 34 m long reactor is also included. A correlation of hydroaromatic, catalyst and hydrogen concentration is considered. Parameters considered important for an optimum space rate utilization factor are both chemical and physical in nature. Of special importance are heat transfer, catalyst concentration and hydrogen concentration. A large space rate utilization factor is important from the standpoint of reduced reactor volume.

Thermodynamic probability of the conversion of multiring aromatics to isoparaffins and cycloparaffins

Thermodynamic properties were shown to provide a good estimation for product selectivity, thereby reducing the number of screening tests with respect to reaction temperature. Equilibrium constants for the conversion of aromatics to isoparaffins and cycloparaffins were calculated to determine reaction conditions for the production of high octane gasoline components without aromatics from hydrogenation/hydrocracking of 1-methylnaphthalene. These calculations, combined with screening studies of different catalysts, determined optimum hydrotreatment conditions.

Production of high octane gasoline components by hydroprocessing of coal-derived aromatic hydrocarbons

The main objective of this work + was to convert aromatic compounds, representative ofcoal-derived liquids, into high octane compounds low in aromatics. For this study, 1-methyl-naphthalene was chosen as a model compound. Experiments were performed in single and two-stage systems. The model compound was treated with various catalysts at different reaction conditions in the single-stage operation. The highest conversion to isoparaffins and substituted cyclohexanes and cyclopentanes, 40.1% was achieved with a NiW/SiO 2 -Al 2 O 3 catalyst at 325°C and 1000psig in 10h with a feed to catalyst ratio of 10 to 1. In the two-stage operation, 1-methylnaphthalene was hydrogenated to methyldecalins at 325°C with almost 100% conversion in the first stage, using a NiMo/TiO 2 -Al 2 O 3 catalyst. In the second stage, the methyldecalins underwent hydrocracking reactions at different reaction conditions using various catalysts. Pd/REX exhibited the best result for the production of high octane gasoline components without aromatics at 300–325°C.

High conversion (98%) for the hydrogenation of 1-methylnaphthalene to methyldecalins

This work presents results from the hydrogenation of 1-methylnaphthalene. Experiments were conducted in a stirred batch reactor with commercial as well as previously tested non-commercial catalysts under different reaction conditions. The data show that a NiMo catalyst supported on titania-alumina produced high yields of methyldecalins at 325°C and 1000 psig. The products were analyzed by GC/MS and 1H-NMR, 13C-NMR and FT-IR spectroscopies. Conversion to methyldecalins was 98%. Previous methods yielded considerably lower conversion.

Residence time measurements in a coal hydrogenation process

Abstract Residence time of coal in the University of Utah “coiled tube” coal hydrogenation reactor has been measured. This has been done with an electronic device which detects a tracer (usually iron) as it passes specific places at the beginning and end of the reactor. The measured coal solids residence time in the reactor has varied from a few seconds to a few minutes. Calculated vapor and gas residence times are one or two seconds. Short vapor residence time terminates further hydrogenation of vapors and thus reduces gas production and hydrogen consumption. The relatively longer coal solids residence time permits further hydrogenation which increases liquid yields.