Charles B. Muchmore

Coliquefaction of coal and newsprint-derived lignin

Abstract When lignin derived from newsprint is coliquefied with Illinois coal in tetralin under mild reaction conditions (initial hydrogen pressure of 1.07 MPa), up to 90% enhancement in coal conversion is observed. The enhancement in coal conversion is a function of liquefaction temperature. It increases from 50 to 90% as the temperature is increased from 300°C to 325°C; however, with a further increase in temperature, the enhancement declines. This behavior is explained in terms of reaction chemistry that postulates that intermediates formed during lignin depolymerization react with coal via a parallel coal depolymerization pathway. The quality of liquid products was assessed by examining the boiling point fraction data. Data clearly show synergism in terms of product quality when lignin is added to coal during depolymerization.

Coal liquefaction in lignin-derived liquids under low severity conditions

It is found that lignin-derived liquids when reacted with coal under mild reaction conditions (375 °C and 2.17 × 106 − 3.55 × 106 N m−1) enhance the rate of coal depolymerization. Up to 30% enhancement in coal conversion rate is achieved using lignin-derived liquids. The influence of time of reaction and temperature on the degree of reaction was investigated. The lignin liquid-assisted coal depolymerization products (liquid) are observed to contain a significant amount of the desirable pentane-soluble fraction. Influence of the time of storage of lignin-derived liquids on coal conversion was also determined. Also reported are data on elemental analyses of the solid and liquid products. The liquid product analyses using n.m.r. and s.e.c. techniques are also presented. Based upon the experimental data collected, it is hypothesized that enhancement in coal depolymerization rate can be explained by a reaction pathway involving intermediates formed from lignin-derived lignin liquids. A mathematical model describing the reaction chemistry has been developed. Computed rate constants are also reported. The analysis indicates that the lignin-derived intermediates are short-lived as compared to the time needed for complete coal depolymerization.

Supercritical extraction and desulfurization of coal with alcohols

Abstract An investigation of extraction of coal with alcohols has been performed under a wide range of supercritical conditions. It was found that sulfur materials in coal were selectively removed from coal matrix. An empirical rate equation with first order kinetics can be used to fit the experimental data. The desulfurization selectivity ratio is between 2 and 4.4 for four coal samples studied. A pretreatment of coal with KOH solution demonstrated an enhancement of the desulfurization efficiency.

Coliquefaction of coal and black liquor to environmentally acceptable liquid fuels

Previous work in the laboratories has demonstrated that addition to lignin to coal during liquefaction significantly increases the depolymerization of coal and enhances the quality of the liquid products. It is believed that thermolysis of the lignin results in the formation of phenoxyl and other reactive radicals at temperatures too low for significant thermolysis of the coal matrix; such radicals are effective and active intermediates that depolymerize coal by cleaving methylene bridges. It has been reported that alkali is also effective for extraction of liquids from coal. The work presented here combines these two reactive agents by utilizing the black liquor waste stream from the Kraft pulping process for coal depolymerization. That waste stream contains large amounts of lignin and sodium hydroxide, as well as other components. To permit comparative evaluations of the extent of coal depolymerization by coprocessing coal and black liquor, reference runs were performed with tetralin alone, sodium hydroxide in tetralin, and lignin in tetralin. Results indicated that the sodium hydroxide-tetralin system resulted in almost 67% conversion at 375 C, 1 hour. The black liquor system exhibited a lower conversion of 60%, indicating some inhibition of the depolymerization reactions by components in the black liquor.

Microscopic characterization of coal residues from supercritical desulfurization of Illinois coal

Abstract An investigation of the microscopic properties of residues produced from Illinois coal treated under various supercritical alcohol extraction conditions has been conducted. The objective of this investigation was to obtain a better understanding of the supercritical alcohol/coal desulfurization system. It was found that pyrite is converted progressively to pyrrhotite and then to troilite. Also, coal particles tended to become fluid and form coke. The degree of coke formation and size of anisotropic units (optical texture) were found to correspond to the extent of desulfurization. These correlations were found to be solvent dependent. Zoning effects were also observed in both the organic and inorganic phases. These effects appear to be mass or heat transfer limited and related to the operation of the batch reactors employed in obtaining samples for this study. The investigation is continuing, employing smaller reactors with improved heat and mass transport properties. Attempts will be made to determine if desulfurization is enhancing fluidity or if fluidity is enhancing desulfurization.

Supercritical desulfurization kinetics of illinois no. 5 coals

Abstract This paper describes a desulfurization process to remove both organic and inorganic sulfur from coal employing alcohols under supercritical conditions. The overall objective of this study was to gain a better understanding of the kinetics of the supercritical alcohol/coal desulfurization process. A microreactor system was developed to examine in detail the reaction kinetics of coal desulfurization under supercritical conditions. The microreactors provide a uniform temperature within the reactor and allow precise measurement of temperature. Desulfurization tests were conducted to obtain solid residues for sulfur analysis (% in product), as well as optical microscopic examination. The results of the analysis indicate that the desulfurization process is highly temperature dependent. Generally, with increased reaction temperature, desulfurization is increased. For all isothermal reactions there is at least one stage at which sulfur is reincorporated into the product. Pretreatment of coal with 5% KOH is desirable to prevent coke formation, but under the conditions studied, had little effect on ultimate desulfurization levels. Additions of KOH increased the rate at which ultimate desulfurization levels were reached.

Stability of liquids derived from reaction of coal and lignin

Abstract Addition of lignin to coal is synergetic in that it significantly improves the quality and yield of the liquid products produced from coal under relatively mild condition of pressure and temperature. This paper describes the stability of coal- and coal-lignin-derived liquid, because the usefulness of coal-derived liquids is dependent to a certain extent on their stability during storage. The stability of liquid products was characterized by determining their solubility in pentane and benzene, and by analyzing the change of boiling point and molecular weight distributions with aging condition. Percent of conversion, and individual atomic mass balances on various experiments conducted with coal, lignin and coal-lignin mixtures are also reported.

Liquefaction of newsprint and cellulose in tetralin under moderate reaction conditions

Abstract Liquefaction of newsprint and cellulose in tetralin at 350°C and pressure of 1.07–2.51 MPa for 1 h resulted in their 37% and 40% by weight conversion to organic liquids, respectively. A significant amount of water was also formed. The gases produced consisted of mainly CH 4 and CO. The total amount of gases produced was about 3–5% of the original amount of solid charged to the reactor. A first order kinetic model was proposed for the conversion of newsprint and cellulose. Rate constants and Arrhenius parameters were also calculated. Material balance for the process showed a good correlation between the carbon and oxygen contents of the reactant solid and products. Data indicate that most of the hydrogen supplied to the products is supplied by the solvent (tetralin). Fractionation of liquid products show that a major portion can be classified as pentane-soluble and asphaltenes with negligible benzene-insoluble fraction. The molecular weight distribution of the three fractions for the liquids obtained from newsprint and cellulose liquefaction was determined by size exclusion chromatography.

Electrolytic pretreatment of coal for enhanced liquefaction

Abstract Mild oxidation of coal can result in enhanced coal liquefaction yields, presumably due to the formation and decomposition of carbonyl or hyperoxide groups from the benzylic groups of alkyl bridges in the coal structure. Due to the ability to closely control the oxidizing or reducing conditions at the electrode, electrochemical routes for coal pretreatment have attracted considerable interest. Electrolysis of an Illinois coal in NaOH and H 2 SO 4 electrolytes at potentials of between 1.0 and 1.3 V vs. saturated calomel electrode (SCE) resulted in hydrogen production at current efficiencies of about 100% while a significant amount of sulfur was removed from the coal. Liquefaction of the coal was carried out in tetralin at 375°C with an initial hydrogen pressure of 140 psig (10.5 bar). The data obtained clearly indicate that electrochemical oxidation of coal slurries results in significant enhancement (up to 27%) in coal liquefication yields. The products (liquid) obtained from the liquefication of the electrolyzed coal contained substantially larger amounts of the more desirable pentane soluble fraction, while the undesirable benzene insoluble fraction content diminished. The data also show that the molecular weight of the liquid products obtained from pre-electrolyzed coal samples is very much lower than the corresponding molecular weight of the liquid products obtained from an untreated coal under the same liquefaction conditions.

KINETICS OF SULFUR CONTAINING INTERMEDIATES DURING DESULFURIZATION OF COAL WITH SUPERCRITICAL METHANOL

Publisher Summary This chapter discusses the kinetics of sulfur-containing intermediates during desulfurization of coal with supercritical methanol. Twenty-three possible reaction products were proposed that could result from the reaction of dimethyl disulfide (DMDS) in supercritical methanol. The chapter presents a thermodynamic analysis whereby the equilibrium composition was determined by minimization of the total Gibbs free energy for the reaction mixture at reaction conditions. The fugacity coefficients necessary for the calculation were determined by use of the Redlich–Kwong equation of state. The resulting equations were solved employing a matrix procedure, utilizing a Lotus 1-2-3 spreadsheet for the trial and error solution to the equation set. The results of the calculation indicated that about 99.3% of the sulfur will be H2S when equilibrium is attained. The thermodynamic analysis implies that the reaction pathway cannot involve H2S as an intermediated product, because if it were formed, it would remain. At longer reaction times at 400°C, there is a trend toward formation of very high concentrations of hydrogen sulfide, as predicted by the thermodynamic analysis.