Chemistry of Coal Conversion

Chemistry of Coal Conversion

Chemistry 0/ Coal Conversion Edited by Richard H. Schlosberg Exxon Chemical Company Linden, New Jersey Springer Science+Business Media, LLC

Main entry under title: Library of Congress Cataloging in Publication Data Chemistry of coal conversion. Includes bibliographical references and index. 1. Coal liquefaction. 2. Co al gasification. 1. Schlosberg, Richard H. TP352.C48 1985 662/.6622 85-16977 ISBN 978-1-4899-3634-9 ISBN 978-1-4899-3632-5 (ebook) DOI 10.1007/978-1-4899-3632-5 1985 Springer Science+Business Media New York Originally published by Humana Press, New York in 1985. Softcover reprint ofthe hardcover Ist edition 1985 All rights reserved No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, microfilming, recording, or otherwise, without written permission from the Publisher

Contributors Frank Hershkowitz, Corpora te Research, Exxon Research and Engineering Company, Clinton Township, Route 22 East, Annandale, NJ 08801 Peter S. Maa, Ken L. Trachte, and Richard D. Williams, Exxon Research and Engineering Company, P. O. Box 4255, Baytown, TX 77520 Richard H. Schlosberg, Exxon Chemical Company, P. O. Box 536, Linden, NJ 07036 Peter R. Solomon and David G. Hamblen, Advanced Fuel Research, Inc., 87 Church Street, East Hartford, CT 06108 Stephen E. Stein, Chemical Kinetics Division, Center for Chemical Physics, National Bureau of Standards, Washington, DC 20234 Leon M. Stock, Department of Chemistry, University of Chicago, Chicago, IL 60637 Eric M. Suuberg, Division of Engineering, Brown University, Providence, RI02912 v

Preface The impetus for this book is twofold. First, in response to the welldocumented oil shocks of the 1970s there arose a resurgence of research activity in the synthetic fuels area. This book attempts to capture some of the leading edge advances which have been made over the past decade in the area of the chemistry of coal conversion. The second driving force behind this book is to jog people's memories about the fundamental truths of the energy industry, i.e., there IS a finite amount of liquid hydrocarbons on and under the earth's surface, most of the easy to find, produce, and use liquid hydrocarbons have been exploited, and the real need continues to be for liquid hydrocarbons for use as transportation fuels. The uncertainty is not if synthetic liquids will be needed, but rat her when they will be needed. The inability to answer that question accurately caused many of the financial and research disruptions following the double shocks of the 1970s. Since future projections can only be based upon the historical record, they cannot anticipate major disruptions such as, e.g., discovery of huge easily producible oils fields, or, on the other side, global or regional economic disruptions such as warfare. With this level of uncertainty, then, the second impetus is to point out how much research remains to be done at a time when fiscal support for fossil fuels research in the Uni ted States is rapidly spiraling downward. I would like to acknowledge the contribution of each of the authors in this book. Their research eftorts have shed considerable light on our understanding of the challenges and opportunities present in coal conversion chemistry research. We look forward to their continued contributions toward our progress to ultimate energy independence. R. H. SCHLOSBERG vii

Contents 1. Introduction Richard H. Schlosberg 1. Pyrolysis... 3 2. Liquefaction... 5 References... 11 2. Free Radicals in Co al Conversion Stephen E. Stein 1. Introduction... 13 2. Resonance Stabilization Energies (RSE)-An Update... 14 3. Elementary Reactions... 17 3.1. Unimolecular Reactions... 18 3.2. Bimolecular Reactions................................................... 20 4. C1asses and Reactions of Coal Radicals... 22 4.1. Highly Reactive Radicals................................................. 23 4.2. Reactive Delocalized Radicals............................................. 27 4.3. Inert Radicals... 41 References... 42 3. Mass Transfer Effects in Coal Conversion Chemistry Frank Hershkowitz 1. Introduction... 45 1.1. Observed Reaction Control by Mass Transfer............................... 46 2. Fundamentals of Mass Transfer in Co al Reaction Systems... 47 2.1. Molecular Diffusion..................................................... 47 2.2. Diffusion in Porous Solids................................................ 48 2.3. Mass Transfer in Fluid-Solid Systems...................................... 49 2.4. Coal Reactivity......................................................... 50 2.5. Internal vs. External Resistance to Mass Transfer... 50 2.6. Testing for Mass Transfer Effects.......................................... 51 2.7. Combined Reaction with Mass Transfer.................................... 52 ix

x Contents 3. Theory and Mode1ing of Coal-Gas Systems..................................... 53 3.1. Modeling of Pore Transport Processes... 53 3.2. Modeling Mass Transfer with Reaction..................................... 57 3.3. Gasification........................................... 61 4. Reaction vs. Mass Transfer for Coal Liquefaction.......................... 61 5. ConcIusions................................................................ 63 References... 64 4. Mass Transfer Effects in Pyrolysis of Coals: A Review of Experimental Evidence and Models Eric M. Suuberg 1. Introduction... 67 2. Experimental Evidence for the Role of Mass Transfer in Rapid-Rate High-Temperature Coal Pyrolysis... 68 3. External Mass Transfer Limitations... 72 4. Internal Mass Transfer Limitations......................................... 77 4.1. Softening Coals......................................................... 78 4.2. Nonsoftening coals...................................................... 85 5. Pyrolysis Models Which IncIude Mass Transfer Limitations....................... 89 5.1. Models Mainly Designed to Predict Weight Loss and Swelling Behavior....................................................... 90 5.2. Models Which Predict Yields ofindividual Products... 103 6. Mass Transfer Effects in Liquefaction Systems................................... 113 7. ConcIusions... 114 Table of NomencIature... 115 Greek Letters... 117 References... 117 5. Pyrolysis Peter R. Solomon and David G. Hamblen 1. Introduction... 121 1.1. Background... 121 1.2. A Proposed View of Coal Pyrolysis-Rank-Insensitive Phenomenon... 122 1.3. Rank-Dependent Phenomena... 126 1.4. Pyrolysis Conditions... 131 2. Experimental............................................................... 138 2.1. Entrained Flow Reactor... 139 2.2. Flash Pyrolysis Experiments... 149 2.3. Constant-Heating-Rate Experiments....................................... 151 2.4. Fourier-Transform Infrared (FT -IR) Analysis of Solids... 153 3. Theory... 161 3.1. Model Assumptions... 161 3.2. Aspects of Pyrolysis Not Considered in the Model... 172 3.3. Functional-Group Pyrolysis Model........................................ 173 3.4. Model for Depolymerization.............................................. 177 3.5. Coal ParticIe Temperature... 187 3.6. Swelling........................................................ 195 4. Application of Pyrolysis Theory... 203 4.1. Entrained Flow Reactor... 204

Contents xi 4.2. Flash Pyrolysis... 219 4.3. Programmed Slow-Heating-Rate Pyrolysis... 232 5. Conclusions... 246 References... 248 6. Hydrogen-Transfer Reactions Leon M. Stock 1. Introduction... 253 2. Mechanism of Coal Liquefaction... 254 3. Liquefaction in Labeled Reagents and Co al Liquids... 260 3.1. Introduction... 260 3.2. Experiments Using Deuterium-Tracer Techniques... 263 3.3. Experiments Using Coal Liquids as Solvents... 279 4. Behavior of Representative Compounds... 289 5. Overview of Hydrogen-Transfer Reactions... 308 References... 313 7. Solvent Effects in Exxon Donor-Solvent Coal Liquefaction Peter S. Maa, Ken L. Trachte, and Richard D. Williams 1. Introduction... 317 2. EDS Process Configuration... 318 3. Solvent-Quality Effects on Co al Conversion... 319 3.1. Solvent-Quality/Hydrogen-Pressure Interactions... 321 3.2. Solvent-Quality Effects on Product Selectivity... 321 3.3. Solvent-Quality Effects on Hydrogen Consumption... 325 3.4. Solvent-Quality/Mineral Matter Interactions... 325 4. Effects of Coal Rank on Solvent Composition................................... 327 5. Interactive Effects of Solvent Hydrogenation and Liquefaction... 327 6. Conclusions... 330 References... 330 Index... 333