Kyung C. Kwon

Pyrite-catalysed coal liquefaction using quinoline/tetrahydroquinoline as an H-donor system

Abstract Pyrite catalyses the hydrogenation of the N-containing ring in quinoline (Q) to form the active H-donor, 1,2,3,4-tetrahydroquinoline, (THQ). THQ is shown to dissolve coal readily at 325 °C, a temperature lower than that commonly used in most liquefaction processes. Pyrite is effective for maintaining the H-donor capacity of the solvent by hydrogenating the Q formed after H-donation, thereby providing the high THQ/Q required for sustained operation. Qualitative observations suggest that some source of hydrogen, either molecular or donor, must be present to prevent retrogressive reactions of coal fragments.

Coal solvolysis in a series of model compound systems

Abstract A series of 23 model donor solvents was used to rank their efficacy for the dissolution of Western Kentucky No. 9 14 coal. The transfer of hydrogen from the solvent to the coal fragments, as measured by coal conversion, was examined at three levels of available hydrogen. The hydrogen donors are ranked according to their ability to convert coal to THF-solubles. Aromatic analogs of the model donors showed little ability to convert coal to THF-solubles. Factors which influence hydrogen donation include the presence of heteroatoms or substituents both internal and external to the aromatic or hydroaromatic rings, the degree of hydrogenation, the aromaticity or non-aromaticity of the hydroaromatics, and the presence of five-membered rings. A relation between heats of formation and hydrogen donor ability is shown for hydroaromatics within two ring or three ring homologous series. A model hydrogen acceptor, benzophenone, is also used to rank model donors. No correlation exists in the ranking of hydrogen donors by the model acceptor used in this work and in other experimental studies and that obtained by conversion of Western Kentucky coal at typical liquefaction conditions.

Pseudo-binary molecular diffusion of vapors into air

Abstract A novel open-tube evaporation method was developed to determine the experimental diffusion coefficients of the vapors of various liquids diffused into air. The mass losses of the volatile liquids chosen for this study were measured with a balance rather than changes in the level of the liquid in a diffusion tube for various evaporation durations and no fresh air was passed over the top end of the diffusion path by forced convection, as opposed to the conventional open-tube evaporation method. A diffusion equation was developed which is suitable for the novel open-tube evaporation method. The experimental diffusion coefficient values obtained from the novel experimental diffusion methods were in reasonable agreement with the diffusion coefficient values predicted with both the Wilke-and-Lee method and the Fuller et al. method. The experimental diffusion coefficients of n-heptane diffused into air are independent of the lengths and the evaporation areas of the diffusion paths chosen for this study. The experimental diffusion coefficients of normal alcohols and hydrocarbons in air decrease with increased number of carbon atoms in their molecular formulas. The overall root mean squares of deviation of the diffusion values of this experimental study from those predicted with the Wilke-and-Lee method and the Fuller et al. method are 5.8 and 6.0%, respectively.

Selectivity of coal minerals using cyclohexene as a probe reactant

The activity of several minerals, representative of those indigenous to coal, liquefaction residue ash and metal oxides, has been examined using a probe reaction, the hydrogenation of cyclohexene. The selectivity of the various minerals for isomerization and hydrogenation was determined from the cyclohexene products distribution. A complementary i.r. study using adsorbed pyridine to examine the surface acidity of the minerals was also performed and the results compared with those of the cyclohexene reaction. Finally, an attractive mechanism for the isomerization of cyclohexene to methylcyclopentenes is proposed. The activity and selectivity of the various minerals studied have implications for various types of reactions occurring in coal liquefaction, which may be catalysed by coal minerals.

Reactivity of Metal Oxide Sorbents for Removal of Sulfur Compounds from Coal Gases at High Temperature and Pressure

Abstract Hot-gas desulfurization for the integrated gasification combined cycle (IGCC) process has been investigated to effectively remove hydrogen sulfide with various metal oxide sorbents at high temperatures and pressures. Metal oxide sorbents such as zinc titanate oxide, zinc ferrite oxide, copper oxide, manganese oxide, and calcium oxide were found to be promising sorbents in comparison with other removal methods such as membrane separation and reactive membrane separation. The removal reaction of H2S from coal gas mixtures with zinc titanate oxide sorbents was conducted in a batch reactor. The main objectives of this research are to formulate promising metal oxide sorbents for removal of hydrogen sulfide from coal gas mixtures, to compare reactivity of a formulated sorbent with a sorbent supplied by the Research Triangle Institute at high temperatures and pressures, and to determine effects of concentrations of moisture contained in coal gas mixtures, and to determine effects of concentrations of mo...

VISCOSITY OF GLYCEROL AND ITS AQUEOUS SOLUTIONS MEASURED BY A TANK-TUBE VISCOMETER

In this paper we demonstrate several series of experiments for the measurement of viscosity of neat glycerol and its aqueous solutions using a tank-tube viscometer. Measuring viscosity of highly viscous liquids with the tank-tube viscometer is easier than other types of viscometers. This inexpensive viscometer continuously generates numerous reproducible viscosity data of highly viscous neat glycerol and its aqueous solutions under given experimental conditions such as a desired temperature and a desired concentration of water in aqueous glycerol solutions. Fabricating the tank-tube viscometer is inexpensive, since this viscometer does not need sophisticated accessories such as a high-pressure liquid pump, a sensitive pressure sensor, and an accurate flow meter. The tank-tube viscometer consists of a large-diameter reservoir and a long, small-diameter, vertical tube. The viscosity equation was developed under the following assumptions. Both the quasi steady state approach and the negligible friction loss due to a sudden contraction between the reservoir tank and the tube are valid. The kinetic energy of the emerging stream from the bottom end of the vertical tube of the tank-tube viscometer also is assumed to be negligible. Very viscous glycerol and its aqueous solutions were used to test the viscometer by comparing viscosity values from the viscometer with those from literatures. The main objective of this study is to demonstrate effects of water as well as temperature on viscosity of aqueous glycerol solutions, applying experimental data of accumulated amounts of aqueous glycerol solutions at various drain durations to the newly-developed viscosity equation for the fabricated tank-tube viscometer.

Molecular diffusion of volatile-liquid vapors into air

Diffusion coefficients of vapors diffused into stagnant air were determined at room temperature and atmospheric pressure. Experimental data on diffusion coefficients were obtained from the steady-state open-tube evaporation method modified for this study. No fresh air is passed over the top end of a diffusion tube, and amounts of volatile liquids evaporated in the diffusion tube are measured with a balance rather than a change of the liquid level in a diffusion tube. Experimental molecular diffusion coefficients are obtained by applying experimental data of mass losses of volatile liquidsversusevaporation durations to a diffusion equation developed suitable for the novel open-tube evaporation method. Three main experimental errors of the novel open-tube evaporation method are described in detail. Predicted diffusion coefficients are calculated with the Wilke-Lee method and compared with experimental values obtained from this diffusion study.

Reactivity of sorbents with hot hydrogen sulfide in the presence of moisture and hydrogen

Hot-gas desulfurization for the integrated gasification combined cycle (IGCC) process has been investigated by many researchers to remove effectively hydrogen sulfide (H2S) with various metal oxide sorbents at elevated temperatures. Various metal oxide sorbents are formulated with metal oxides such as Fe, Co, Zn, and Ti. In this article, reactivity of AHI-1 sorbent, obtained from the Research Triangle Institute (RTI), was investigated. Initial reactivity of AHI-1 sorbent with hydrogen sulfide was studied in the presence of various amounts of moisture and hydrogen at various reaction temperatures. AHI-1 sorbent consists of 20-w% Fe2O3, 10-w% ZnO, and 70-w% spent fluid cracking catalyst (FCC). The objectives of this research were to study initial reaction kinetics for the AHI-1 sorbent–hydrogen sulfide heterogeneous reaction system, to investigate effects of concentrations of hydrogen sulfide, hydrogen, and moisture on dynamic absorption of H2S into the sorbent, to understand effects of space time of reaction gas mixtures on initial reaction kinetics of the sorbent–hydrogen sulfide system, and to evaluate effects of temperature and sorbent amounts on dynamic absorption of H2S into the sorbent. Experimental data on initial reaction kinetics of hydrogen sulfide with the metal oxide sorbent were obtained with a 0.83-cm3 differential reactor. The sorbent in the form of 130-μm particles was reacted with 1000 to 4000 ppm hydrogen sulfide at 450 to 600°C. The range of space time of reaction gas mixtures is 0.03 to 0.09 s. The range of reaction duration is 4 to 14,400 s.

Comparison of anthracene and phenanthrene in coal liquefaction

Abstract A comparison of anthracene and phenanthrene as solvents was undertaken by liquefying either Wyodak or Kentucky 9/14 coal in the presence of hydrogen or nitrogen. Phenanthrene was found to be a better physical solvent than anthracene for liquefying both coals. Anthracene and its derivatives are better hydrogen-shuttling solvents than phenanthrene and its derivatives. Hydrogenation of anthracene to tetrahydro-anthracene was observed with both coals. Dihydroanthracene is a better hydrogen-shuttling solvent than dihydrophenanthrane in the liquefaction of Kentucky 9/14 coal. Anthracene is a better solvent than phenanthrene in the presence of 1-methylnaphthalene in liquefying both Wyodak coal under hydrogen and Kentucky 9/14 coal under nitrogen. The minerals in Kentucky 9/14 coal appear to be better hydrogenation catalysts than those in Wyodak coal. Labile hydrogen from coal appears to escape readily before reacting with hydrogen-shuttling solvents under the atmospheric environment.

RHEOLOGICAL CHARACTERIZATION OF NON-NEWTONIAN FLUIDS WITH A NOVEL VISCOMETER

A hydrostatic head viscometer and its novel viscosity equation were developed to determine flow characteristics of Newtonian and non-Newtonian fluids. The objective of this research is to test capabilities of the hydrostatic head viscometer and its novel non-Newtonian viscosity equation by characterizing rheological behaviors of well-known polyethylene oxide aqueous solutions as non-Newtonian fluids with 60 wt.% sucrose aqueous solution as a reference/calibration fluid. Non-Newtonian characteristics of 0.3–0.7 wt.% polyethylene oxide aqueous solutions were extensively investigated with the hydrostatic head viscometer and its non-Newtonian viscosity equation over a 294–306 K temperature range, a 0.14–40 Reynolds number range, and a 55–784 s−1 shear rate range at atmospheric pressure. Dynamic viscosity values of 60 wt.% sucrose aqueous solution were determined with the calibrated hydrostatic head viscometer and its Newtonian viscosity equation over a 3–5 Reynolds number range at 299.15 K and atmospheric pressure and compared with the literature dynamic viscosity value.