Vapor-phase transport synthesis of ZnAPO-34 molecular sieve

ZnAPO-34 molecular sieve can be synthesized by the vapor-phase transport technique using triethylamine as a structure-directing agent

Coal Pyrolysis

Prompted by the need of non-petroleum-based fuels, coal research has reemerged to center stage after a lengthy dormant period. Pyrolysis research, in particular, has gained considerable momentum because of its close connection to combustion, hydropyrolysis and liquefaction. Spectroscopic and other instrumental techniques are currently producing prodigious information about coal structure and pyrolysis mechanisms, while modeling efforts are breaking new ground in sorting out chemical and physical phenomena to provide a fundamental although simplified description. The continuing generation of experimental data will lead to revisions, in some cases drastic, of current structural and kinetic precepts. Yet, the postulates and assumptions of current work provide a meaningful starting point in elaborating theoretical descriptions of greater validity and applicability. This monograph was written to organize recent results of pyrolysis research. Experimental and theoretical aspects, given approximately equal weight, are discussed in the light of basic chemical and physical mechanisms. With this orientation the monograph should be useful to chemists, engineers and graduate students with interests in coal research. I would like to express my appreciation to the copyright holders for permission to reproduce various figures: to the American Institute of Chemical Engineers for Figs. 4.21, 5.7, 5.14; to the Combustion Institute for Figs. 4.3, 4.14, 4.15; to IPC Science and Technology Press, Ltd. for Figs. 4.16-4.18, 4.20, 5.1-5.6, 5.8, 5.9, 6.1, 6.6, 7.10-7.13; to Dr. W. R. Ladner for Figs. 7.6-7.9; to Dr. P. R. Solomon for Fig. 4.1; to Mr. M. Steinberg for Figs. 7.14-7.16 and to Dr. E. M. Suuberg for Figs. 5.10, 5.11, 6.2-6.5, 7.1-7.4. I would also like to thank Lenore Kerner and Majda Andlovec for typing the manuscript and Heather Marr for drawing the figures. G. R. GAVALAS Pasadena, California April, 198

Comparison of effective conductivities calculated by the effective medium approximation and the self consistent approximation for core-shell particulate composites

The effective conductivity of composites containing simple or core-shell particles has been estimated in the literature using the Mean Field Approximation (MFA) and the Self-Consistent Approximation (SCA) among other techniques. It is shown here that for both simple and core-shell particles the two approximations agree to first order in the particle volume fraction but differ at the second order term. For simple particles the coefficient of the second order term calculated by SCA is at much better agreement with previous exact results than the coefficient calculated by MFA. For core-shell particles the results of the two approximations are almost identical up to particle volume fraction 0.20 but diverge with increasing volume fraction and particle-to-matrix conductivity ratio

Synthesis of Porous Inorganic Membranes

Here we will attempt a brief overview of recent synthetic efforts for micropore and lower-end mesopore membranes. We will not address the very important classes of nonporous membranes, such as dense metals and solid electrolytes with applications in H_2 and O_2 separations, or meso- and macroporous membranes, which find applications in food processing and water treatment. Microporous materials provide high permselectivities for molecules encountered in the chemical-processing industry but suffer from low intrinsic permeabilities. Therefore, in order to bring microporous membrane materials to commercial applications, functional composites with small effective thicknesses (in the micron or submicron range) must be developed. For example, to achieve economical membrane-reactor sizes, fluxes as high as 0.1 mol/(m^2 s) are desirable. Approaches to microporous membranes include modification of mesoporous membranes by sol-gel and chemical-vapor-deposition (CVD) techniques, carbonization of polymers to form molecular-sieve carbon, and polycrystalline-film growth of zeolites and other molecular sieves

Comparison of effective conductivities calculated by the effective medium approximation and the self consistent approximation for core-shell particulate composites

The effective conductivity of composites containing simple or core-shell particles has been estimated in the literature using the Mean Field Approximation (MFA) and the Self-Consistent Approximation (SCA) among other techniques. It is shown here that for both simple and core-shell particles the two approximations agree to first order in the particle volume fraction but differ at the second order term. For simple particles the coefficient of the second order term calculated by SCA is at much better agreement with previous exact results than the coefficient calculated by MFA. For core-shell particles the results of the two approximations are almost identical up to particle volume fraction 0.20 but diverge with increasing volume fraction and particle-to-matrix conductivity ratio

New Development in Hydrogen Perm Selective Membranes

The objectives of the original project was to develop silica hydrogen permselective membranes and evaluate the economic feasibility of these membranes in hydrogen production from coal gas. The objectives of the work reported here were to increase the membrane permeance by developing new precursors or deposition conditions, and to carry out fundamental permeability measurements of the membrane at different stages of pore narrowing

Calcium impregnation of coal enriched in CO.sub.2 using high-pressure techniques

Methods are described for impregnating coal with calcium carbonate by utilizing an aqueous phase ionic reaction between calcium acetate, calcium hydroxide, and water with CO.sub.2 contained within the coal. The coal is enriched in CO.sub.2 by contacting it with CO.sub.2 at high pressure, in either a continuous or pulsed mode. The inclusion of CO.sub.2 in the coal during the process does not involve evacuating the coal and subsequently absorbing CO.sub.2 onto the coal as in prior methods. Rather, the coal is treated with carbon dioxide at high pressure in a practical and viable approach. The impregnation of coal by calcium compounds not only reduces sulfur emissions by effectively tying up the sulfur as calcium sulfide or sulfate, but also increases the gasification or combustion rate. The invention also encompasses the use of other Group IIA elements, as well as the coal products resulting from the methods of treatment described

High temperature regenerative H.sub.2 S sorbents

Efficient, regenerable sorbents for removal of H.sub.2 S from high temperature gas streams comprise porous, high surface area particles. A first class of sorbents comprise a thin film of binary oxides that form a eutectic at the temperature of the gas stream coated onto a porous, high surface area refractory support. The binary oxides are a mixture of a Group VB or VIB metal oxide with a Group IB, IIB or VIII metal oxide such as a film of V-Zn-O, V-Cu-O, Cu-Mo-O, Zn-Mo-O or Fe-Mo-O coated on an alumina support. A second class of sorbents consist of particles of unsupported mixed oxides in the form of highly dispersed solid solutions of solid compounds characterized by small crystallite size, high porosity and relatively high surface area. The mixed oxide sorbents contain one Group IB, IIB or VIIB metal oxide such as copper, zinc or manganese and one or more oxides of Groups IIIA, VIB or VII such as aluminum, iron or molybdenum. The presence of iron or aluminum maintains the Group IB, IIB or VIIB metal in its oxidized state. Presence of molybdenum results in eutectic formation at sulfidation temperature and improves the efficiency of the sorbent

A New Algorithm for Automatic History Matching

History-matching problems, in which reservoir parameters arc to be estimated from well pressure data, are formulated as optimal control problems. The necessary conditions for optimality lead naturally to gradient optimization methods for determining the optimal parameter estimates. The key feature of the approach is that reservoir properties are considered as continuous functions of position rather than as uniform in a certain number of zones. The optimal control approach is illustrated on a hypothetical reservoir and on an actual Saudi Arabian reservoir, both characterized by single-phase flow. A significant saving in computing time over conventional constant-zone gradient optimization methods is demonstrated

Alkali-Alumina Sorbents for Regenerable SO_2 Removal in Fluidized-Coal Combustion

Sodium and sodium-lithium oxides supported on porous alumina have been investigated as regenerable SO_2 sorbents for fluidized coal combustion. In adsorption the oxides are converted to sulfates. In regeneration, carried out by reduction with CO, the sulfates are converted back to oxides while sulfur is removed in elemental form (S_2), SO_2 and COS. The transient composition of sorbent and gaseous products was measured in a thermogravimetric analyzer and a packed-bed microreactor in order to delineate the basic chemistry of regeneration and determine conditions that maximize the yield of elemental sulfur