DOCSLIB.ORG

Heavy-Water Production Using Amine-Hydrogen Exchange

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Heavy-Water Production Using Amine-Hydrogen Exchange HEAVY-WATER PRODUCTION USING AMINE-HYDROGEN EXCHANGE Development of the amine-hydrogen process for heavy-water production involves a large research and development program at CRNL supplemented by contracts with industry and universities. Four major areas of work are: — process design and optimization — process chemistry — deuterium exchange in gas-liquid contactors — materials for construction This article, which is the third in a series to appear in this publication, describes the development of equipment for efficient exchange of deuterium between hydrogen gas and amine liquid. The process flowsheet and the chemistry of aminomethane solu- tions of potassium methylamide catalyst were described previously^ >2). Efficient countercurrent, multistage contacting of liquid amine and hydrogen gas in hot and cold towers are required in this process. The unusually large separation factors possible with amine-hydrogen exchange are an important advantage. A major development program is aimed at the full exploitation of this advantage by achieving rapid exchange in the cold tower. Increasing the difference between the hot and cold tower temperatures decreases the required gas flow rate and number of theoretical plates. As the cold tower temperature is lowered plate efficiency falls, tower fabrication is more expensive and refrigeration costs rise; the range of interest is -100 to 0°F. The upper limit on hot column temperature is set by the vapor pressure of the aminomethane and chemical stability of the catalyst solution. Temperatures up to 160°F are attractive. The exchange reaction HD + CH3NH2 „ » H2 + CH3NHD occurs in the liquid phase a^d consists/of two steps: physical absorption and chemical ^reaction. Mass transfer is controlled by the diffusion of hydrogen in a thin liquid reaction zone near the gas-liquid interface. The mass transfer coefficient, enhanced by chemical Figure 1 Concurrent gas-liquid contactor for amino- reaction, is large but the hydrogen solubility is very methane-hydrogen exchange. Figure 2 Circulating equipment and piping. 3 low. Henry's law constant is 6240 atm ft /lb mole at Part of a column with deep beds is shown in -40°F. The deuterium content of the liquid is many Figure 1. Gas and liquid How cocurrently. providing hundreds of times larger than the dissolved HD contact times of a few seconds for beds which are content so that, to appreciably alter the CH3NHD several feet deep. A packing, such as wire gau/e, in concentration, a long contact time is required to the bed breaks up coalescing gas bubbles, producing allow the deuterium atoms to pass from the gas to small bubbles and large interfacial areas. This type of liquid as HD and then exchange. Pressures of 1000 gas-liquid contactor has been patented by AEClJ-1). psig or more can be used to increase the amount of Note that while flows are cocurrent in each bed, they dissolved hydrogen, but even at these pressures the are countercurrent in the column as a whole. driving force for deuterium exchange is small. As the A test facility for circulating hydrogen and liquid temperature increases, the exchange rate increases aminomethane through a 6-inch diameter column has because both the solubility and the chemical reaction been operated at cold tower conditions. Figure 2 is a rate constant increase. photograph of some of the components. The effects For the hot columns conventional sieve trays of gas and liquid velocity, temperature, catalyst should- be adequate but testing is required to confirm concentration, and bed depths have been studied this. For the cold columns none of the usual types of using packings of wire gau/e, Pall rings, and cylin- gas-liquid contactor performs satisfactorily. Deep drical screens. The deuterium concentration in the beds appear attractive because they provide a high hydrogen is measured by online mass spectrometry at ratio of mass-transfer volume to total column volume. the column inlet and outlet and in equilibrium with Much of the' research and development has been the aminomethane liquid leaving the column to concentrated on cold columns because of the lack of determine bed efficiency. Hydrogen deuteride is information on performance of this type of contactor injected into the hydrogen to maintain a driving force and because the cold columns contribute greatly to between the gas and liquid. The CH3NHD content of the capital cost of the plant. the latter rises very slowly during an experiment. Figure 3 Effect of gas velocity on stage efficiency. 3 - 90 80 70 N 1 RCE UI 0.9 60 Q_ 0.8 0.7 50 P" Figure 4 Effect of temperature on stage effi- 0.6 , ciency. 0.5 40 ENCY o 0.4 I 30 EFF 0.3 UJ CO 20 CO 0.2 TEMPERATURE, °F 0.1 I I I I I 10 20 -20 -40 -60 -80 10 Figures 3 and 4 show the stage efficiency, 77, as a Information obtained with this equipment is being function of superficial gas velocity and temperature. used for the detailed design of a 25 ton per year Tests of sieve trays in a 10-inch diameter column at aminomethane-hydrogen prototype heavy - water temperatures up to 100°F have begun. plant. W.E. Lockerby REFERENCES For further information see: 1. R.S. Jickling, "AECL Research in Engineering", AECL-3787(1971). H.K. Rae, "Heavy Water in Canada", AECL-3866 2. W.J. Holtslander, "AECL Research in Engi- (1971). neering", AECL-3990 (1971). A.R. Bancroft and H.K. Rae, "Heavy Water Pro- 3. J. Chrones and H.K. Rae, Canadian Patent No. duction by Amine-Hydrogen Exchange", AECL-3684 835227 (1970). (1970). 11.
Load more

Recommended publications
  • Selective Production of Phase-Separable Product from a Mixture of Biomass-Derived Aqueous Oxygenates
    ARTICLE DOI: 10.1038/s41467-018-07593-0 OPEN Selective production of phase-separable product from a mixture of biomass-derived aqueous oxygenates Yehong Wang 1, Mi Peng2, Jian Zhang1, Zhixin Zhang1, Jinghua An1,3, Shuyan Du1, Hongyu An1,3, Fengtao Fan1, Xi Liu 4,5, Peng Zhai2, Ding Ma 2 & Feng Wang1 1234567890():,; Selective conversion of an aqueous solution of mixed oxygenates produced by biomass fermentation to a value-added single product is pivotal for commercially viable biomass utilization. However, the efficiency and selectivity of the transformation remains a great challenge. Herein, we present a strategy capable of transforming ~70% of carbon in an aqueous fermentation mixture (ABE: acetone–butanol–ethanol–water) to 4-heptanone (4- HPO), catalyzed by tin-doped ceria (Sn-ceria), with a selectivity as high as 86%. Water (up to 27 wt%), detrimental to the reported catalysts for ABE conversion, was beneficial for producing 4-HPO, highlighting the feasibility of the current reaction system. In a 300 h continuous reaction over 2 wt% Sn-ceria catalyst, the average 4-HPO selectivity is main- tained at 85% with 50% conversion and > 90% carbon balance. This strategy offers a route for highly efficient organic-carbon utilization, which can potentially integrate biological and chemical catalysis platforms for the robust and highly selective production of value-added chemicals. 1 State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China. 2 College of Chemistry and Molecular Engineering and College of Engineering, BIC-ESAT, Peking University, Beijing 100871, China.
    [Show full text]
  • Effects of Heavy Water (D2O) on Human Pancreatic Tumor Cells
    ANTICANCER RESEARCH 25: 3407-3412 (2005) Effects of Heavy Water (D2O) on Human Pancreatic Tumor Cells JOHANNES HARTMANN1, YVONNE BADER1, ZSUZSANNA HORVATH1, PHILIPP SAIKO1, MICHAEL GRUSCH1, CHRISTOPH ILLMER1, SIBYLLE MADLENER1, MONIKA FRITZER-SZEKERES1, NICOLE HELLER2, RUDOLF-GIESBERT ALKEN2 and THOMAS SZEKERES1 1Clinical Institute of Medical and Chemical Laboratory Diagnostics, Medical University of Vienna, General Hospital of Vienna, Waehringer Guertel 18-20, A-1090 Vienna, Austria; 2BDD Berolina Drug Development GmbH, Fontanestrasse 84-89, D-15366 Neuenhagen, Germany Abstract. Background: Pancreatic cancer constitutes an carcinomas be removed by surgery. Individuals suffering entity which is difficult to treat and, therefore, mostly fatal. from inoperable tumors receive palliative therapy, including Since heavy water (deuterium oxide, D2O) was shown to be chemotherapy and radiation therapy. However, the active in various cancer cell lines in vitro and in vivo, we now treatment options are very limited and most patients die investigated its effects in human pancreatic tumor cells. within months after diagnosis. Materials and Methods: The cytotoxic effects of D2O were Incubation of tumor cells with various concentrations of examined in three pancreatic cancer cell lines (AsPC-1, D2O leads to inhibition of cell proliferation and might, BxPC-3 and PANC-1). Induction of apoptosis was therefore, help in the chemotherapeutic treatment of human determined by Hoechst/propidium iodide double staining and tumors (1). D2O, known as heavy water, contains a neutron cell cycle distribution was investigated by FACS analysis. and a proton in its hydrogen atoms and shows a variety of Results: Employing a clonogenic assay, D2O yielded IC50 different biological activities from normal (light) water.
    [Show full text]
  • Deuterium As a Research Tool in the Physical and Biological Sciences
    DEUTERIUM AS A RESEARCH TOOL IN THE PHYSICAL AND BIOLOGICAL SCIENCES HERRICK L. JOHNSTON Ohio State University The discovery (1) of deuterium and the production of "heavy water," its chief compound, in a nearly pure state (2), are among the more important scientific achievements of recent years. In less than two years from the production of heavy water in nearly pure condition over three hundred papers reporting investigations on or with deuterium have appeared in scientific journals. While most of these investiga- tions have been of a physical or chemical nature significant results have been reported in investigations of biological character. It is probable that the principal role of deuterium, in future research in all of these fields, will be more that of a research tool than as an object of investigation. Deuterium is not a new chemical element, as the name might imply, but is a special variety of hydrogen atom. It differs from the ordinary (or light) hydrogen, chiefly, in mass. The atomic weight of the ordinary hydrogen is one while that of deuterium, or heavy hydrogen, is two. It resembles the ordinary hydrogen atom in possessing just one unit of positive charge on its nucleus (equal to the number of electrons in the neutral atom) and it is this latter property which determines the chemical character of an atom, and hence its position in the family of elements. The existence of atoms which differ in mass although alike in nuclear charge is common among the elements, and atomic species which are related in this manner are called isotopes.
    [Show full text]
  • HEAVY WATER and NONPROLIFERATION Topical Report
    HEAVY WATER AND NONPROLIFERATION Topical Report by MARVIN M. MILLER MIT Energy Laboratory Report No. MIT-EL 80-009 May 1980 COO-4571-6 MIT-EL 80-009 HEAVY WATER AND NONPROLIFERATION Topical Report Marvin M. Miller Energy Laboratory and Department of Nuclear Engineering Massachusetts Institute of Technology Cambridge, Massachusetts 02139 May 1980 Prepared For THE U.S. DEPARTMENT OF ENERGY UNDER CONTRACT NO. EN-77-S-02-4571.A000 NOTICE This report was prepared as an account of work sponsored by the United States Government. Neither the United States nor the United States Department of Energy, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or useful- ness of any information, apparatus, product or process disclosed or represents that its use would not infringe privately owned rights. A B S T R A C T The following report is a study of various aspects of the relationship between heavy water and the development of the civilian and military uses of atomic energy. It begins with a historical sketch which traces the heavy water storyfrom its discovery by Harold Urey in 1932 through its coming of age from scientific curiosity to strategic nuclear material at the eve of World War II and finally into the post-war period, where the military and civilian strands have some- times seemed inextricably entangled. The report next assesses the nonproliferation implications of the use of heavy water- moderated power reactors; several different reactor types are discussed, but the focus in on the natural uranium, on- power fueled, pressure tube reactor developed in Canada, the CANDU.
    [Show full text]
  • The Tritium Beta-Ray Induced Reactions in Deuterium Oxide Vapor and Hydrogen Or Carbon Monoxide and the Exchange of H-Atoms with Water Molecules
    This dissertation has been microfilmed exactly as received 66-6232 BIBLER, Ned Eugene, 1937- THE TRITIUM BETA-RAY INDUCED REACTIONS IN DEUTERIUM OXIDE VAPOR AND HYDROGEN OR CARBON MONOXIDE AND THE EXCHANGE OF H-ATOMS WITH WATER MOLECULES. The Ohio State University, Ph.D., 1965 Chemistry, physical University Microfilms, Inc., Ann Arbor, Michigan THE TRITIUM 3ETA-RAY INDUCED REACTIONS IN DEUTERIUM OXIDE VAPOR AND HYDROGEN OR CARBON MONOXIDE AND THE EXCHANGE OF H-ATOMS WITH WATER MOLECULES DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Ned Eugene B ib le r , B .S ., M.S * * * * * The Ohio S ta te U n iversity 1965 Approved by Adviser Department of Chemistry ACKNOWLEDGMENTS Several groups were influential in the completion of this work and the culmination of my graduate career at the Ohio State University. I have singled out two who deserve special acknowledg­ ment. I wish to express my appreciation to the members of my family for their understanding and sympathetic guidance during this demanding period. In particular, I thank my wife, Jane, who was a source of encouragement, for her devotion, scientific advice, and unswervingly honest criticism ; and my mother in law, Mrs. Pauline Pycraft, who typed a major portion of the first draft of this thesis. I am indebted to the stimulating research group headed by Dr. R. F. Firestone for many fruitful discussions and altercations on an array of subjects, including the radiation chemistry of water vapor. Specifically, I thank Dr. Firestone for his keen interest and set of high scientific standards which, when applied to the course and completion of this study, made it a maturing and g r a tify in g experience.
    [Show full text]
  • Tritium Immobilization and Packaging Using Metal Hydrides
    AECL-71S1 ATOMIC ENERGY flPnSy L'ENERGIE ATOMIQUE OF CANADA LIMITED V^^JP DU CANADA LIMITEE TRITIUM IMMOBILIZATION AND PACKAGING USING METAL HYDRIDES Immobilisation et emballage du tritium au moyen d'hydrures de meta! W.J. HOLTSLANDER and J.M. YARASKAVITCH Chalk River Nuclear Laboratories Laboratoires nucl6aires de Chalk River Chalk River, Ontario April 1981 avril ATOMIC ENERGY OF CANADA LIMITED Tritium Immobilization and Packaging Using Metal Hydrides by W.J. Holtslander and J.M. Yaraskavitch Chemical Engineering Branch Chalk River Nuclear Laboratories Chalk River, Ontario KOJ 1J0 1981 April AECL-7151 L'ENERGIE ATOMIQUE DU CANADA, LIMITEE Immo ;ilisation et emballage du tritium au moyen d'hydrures de mëtâT par W.J. Holtslander et J.M. Yaraskavitch Résumé Le tritium provenant des réacteurs CANDU â eau lourde devra être emballé et stocké de façon sûre. Il sera récupéré sous la forme élémentaire T2. Les tritiures de métal sont des composants efficaces pour immobiliser le tritium comme solide non réactif stable et ils peuvent en contenir beaucoup. La technologie nécessaire pour préparer les hydrures des métaux appropriés, comme le titane et le zirconium,a été développée et les propriétés des matériaux préparés ont été évaluées. La conception des emballages devant contenir les tritiures de métal, lors du transport et durant le stockage à long terme, est terminée et les premiers essais ont commencé. Département de génie chimique Laboratoires nucléaires de Chalk River Chalk River, Ontario KOJ 1J0 Avril 1981 AECL-7151 ATOMIC ENERGY OF CANADA LIMITED Tritium Immobilization and Packaging Using Metal Hydrides by W.J. Holtslander and J.M.
    [Show full text]
  • RADIOLYTIC GENERATION of GASES in REACTORS by V
    S 2-8 BAR.C-1438 OO ti*ici tjmn RADIOLYTIC GENERATION OF GASES IN REACTORS by V. Ramshcsh und K. S. Vcnkateswurlu Water Chemistry Division 1988 B.A.R.C. - 1438 GOVERNMENT OF INDIA ATOMIC ENERGY COMMISSION CO •3- U RADIOLYTIC GENERATION OF GASES IN REACTORS by V. Ramshesh and K.S. Venkateswarlu Water Chemistry Division BHABHA ATOMIC RESEARCH CENTRE BOMBAY, INDIA 1988 B.A.R.C. - 1438 IN1S Subject Category : B1400; E3100; E3400 Descriptors WATER RADIOLYSIS G VALUE OXYGEN HYDROGEN HYDROGEN PEROXIDE GASES PHV/R TYPE REACTORS BWR TYPE REACTORS GADOLINIUM NITRATES BORIC ACID ABSTRACT Water or heavy water is used in different circuits in a reactor.Their most common use is as a moderator and/or as a coolant.Light water is used at other places such as in end shield,calandria vault etc,.In the process they are exposed to intense ionizing radiation and undergo radiolytic degradation.The molecular products of radiolysis are hydrogen,hydrogen peroxide and oxygen.As is commonly known if hydrogen is formed beyond a certain level,in the presence of oxygen it may lead to combustion or even explosion.Thus one should comprehend the basic principles of radiolysis and see whether the concentration of these gases under various conditions can be worked out.This report attempts to analyse in depth the radiolytic generation of gases in reactor systems. RADIOLYTIC GENERATION OF GASES IN REACTORS BY V.Ramshesh and K.S.Venkateswarlu \ 1.PRODUCTS OF RADIOLYSIS \ When water* is exposed to radiation,the first step is the production of excited water molecules which then
    [Show full text]
  • Annual Report 1951 National Bureau of Standards
    Annual Report 1951 National Bureau of Standards Miscellaneous Publication 204 UNITED STATES DEPARTMENT OF COMMERCE Charles Sawyer, Secretary NATIONAL BUREAU OF STANDARDS A. V. Astint, Director Annual Report 1951 National Bureau of Standards For sale by the Superintendent of Documents, U. S. Government Printing Office Washington 2 5, D. C. Price 50 cents CONTENTS Page 1. General Review 1 2. Electricity 16 Beam intensification in a high-voltage oscillograph 17, Low-temperature dry cells 17, High-rate batteries 17, Battery additives 18. 3. Optics and Metrology 18 The kinorama 19, Measurement of visibility for aircraft 20, Antisubmarine aircraft searchlights 20, Resolving power chart 20, Refractivity 21, Thermal expansivity of aluminum alloys 21. 4. Heat and Power . 21 Thermodynamic properties of materials 22, Synthetic rubber and other high polymers 23, Combustors for jet engines 24, Temperature and composition of flames 25, Engine "knock" 25, Low-temperature physics 26, Medical physics instrumentation 28. 5. Atomic and Radiation Physics 28 Atomic standard of length 29, Magnetic moment of the proton 29, Spectra of artificial elements 31, Photoconductivity of semiconductors 31, Radiation detecting instruments 32, Protection against radiation 32, X-ray equipment 33, Atomic and molecular ions 35, Electron physics 35, Tables of nuclear data 35, Atomic energy levels 36. 6. Chemistry 36 Radioactive carbohydrates 36, Dextran as a substitute for blood plasma 37, Acidity and basicity in organic solvents 37, Interchangeability of fuel gases 38, Los Angeles "smog" 39, Infrared spectra of alcohols 39, Electrodeposi- tion 39, Development of analytical methods 40, Physical constants 42. 7. Mechanics 42 Turbulent flow 43, Turbulence at supersonic speeds 43, Dynamic properties of materials 43, High-frequency vibrations 44, Hearing loss 44, Physical properties by sonic methods 44, Water waves 46, Density currents 46, Precision weighing 46, Viscosity of gases 46, Evaporated thin films 47.
    [Show full text]
  • Synthesis of Phosphine-Functionalized Metal
    DISS. ETH NO. 23507 Understanding and improving gold-catalyzed formic acid decomposition for application in the SCR process A thesis submitted to attain the degree of DOCTOR OF SCIENCES of ETH ZURICH (Dr. sc. ETH Zurich) presented by MANASA SRIDHAR M. Sc. in Chemical Engineering, University of Cincinnati born on 12.12.1987 citizen of India accepted on the recommendation of Prof. Dr. Jeroen A. van Bokhoven, examiner Prof. Dr. Oliver Kröcher, co-examiner Prof. Dr. Christoph Müller, co-examiner 2016 “anything can happen, in spite of what you’re pretty sure should happen.” Richard Feynman Table of content Abstract .............................................................................................................................. II die Zusammenfassung ..................................................................................................... VI Chapter 1 Introduction .......................................................................................................... 1 Chapter 2 Methods ............................................................................................................ 15 Chapter 3 Unique selectivity of Au/TiO2 for ammonium formate decomposition under SCR- relevant conditions ............................................................................................................. 25 Chapter 4 Effect of ammonia on the decomposition of ammonium formate and formic acid on Au/TiO2 .............................................................................................................................
    [Show full text]
  • Deuteriodesilylation: a Mild and Selective Method for the Site- Specific Incorporation of Deuterium Into Drug Candidates and Pharmaceutical Structures
    DEUTERIODESILYLATION: A MILD AND SELECTIVE METHOD FOR THE SITE- SPECIFIC INCORPORATION OF DEUTERIUM INTO DRUG CANDIDATES AND PHARMACEUTICAL STRUCTURES Kimberly N. Voronin A Thesis Submitted to the University of North Carolina Wilmington in Partial Fulfillment of the Requirements for the Degree of Master of Science Department of Chemistry and Biochemistry University of North Carolina Wilmington 2012 Approved by Advisory Committee Chris V. Galliford Pamela J. Seaton John A. Tyrell Chair Accepted by Dean, Graduate School TABLE OF CONTENTS ABSTRACT ................................................................................................................................... vi ACKNOWLEDGEMENTS .......................................................................................................... vii DEDICATION ............................................................................................................................... ix LIST OF TABLES .......................................................................................................................... x LIST OF FIGURES ...................................................................................................................... xi LIST OF ABBREVIATIONS ...................................................................................................... xiii LIST OF SCHEMES .....................................................................................................................xv CHAPTER 1: INTRODUCTION ....................................................................................................1
    [Show full text]
  • A New Generation of Chemical Sensors
    A New Generation of Chemical Sensors Dr Simon Humphrey Sam Dunning A NEW GENERATION OF CHEMICAL SENSORS Dr Simon Humphrey and Sam Dunning at the University of Texas at Austin have created a new lanthanide-based chemical sensor that can identify trace levels of water in many different solvents, and can even distinguish between normal water and ‘heavy water’. The team’s new material could potentially be applied to medical imaging and for cleaning up chemical spills. Lanthanides – the Ideal Due to their light-emitting – or This means that lanthanide-based Photoemitters ‘photoluminescent’ – properties, chemical sensors can be tuned to detect molecules containing lanthanide a specific impurity. From your schooldays, you may (Ln) ions (charged atoms) have been remember using universal indicator or increasingly explored as chemical Exciting Lanthanides litmus paper to measure pH. While sensors. The term ‘lanthanide’ refers these simple tests are well known and to the group of elements with atomic For an element to exhibit widely available, more sophisticated numbers 57 to 71, from lanthanum (La) photoluminescence, it must first chemical sensors are needed to to lutetium (Lu). When grouped together become ‘excited’ by absorbing light help tackle issues such as cleaning with the chemically similar elements energy. However, lanthanide ions are up chemical spills, remediating yttrium and scandium, you may have difficult to excite by directly absorbing old industrial sites, and detecting heard them described as ‘rare earth light. In a molecule, excitation of radioactive contamination in water elements’, and they have applications lanthanide ions is commonly achieved supplies. Although many techniques are in electronics, high-strength magnets by surrounding them with light- available for these applications, very and catalysis.
    [Show full text]
  • Interactions and Diffusion of Methane and Hydrogen in Microporous Structures: Nuclear Magnetic Resonance (NMR) Studies
    Materials 2013, 6, 2464-2482; doi:10.3390/ma6062464 OPEN ACCESS materials ISSN 1996-1944 www.mdpi.com/journal/materials Article Interactions and Diffusion of Methane and Hydrogen in Microporous Structures: Nuclear Magnetic Resonance (NMR) Studies Yu Ji, Neil S. Sullivan *, Yibing Tang and Jaha A. Hamida Department of Physics, University of Florida, Gainesville, FL 32611, USA; E-Mails: [email protected] (Y.J.); [email protected] (Y.T.); [email protected] (J.A.H.) * Author to whom correspondence should be addressed; E-Mail: [email protected]; Tel.: +1-352-846-3137; Fax: +1-352-392-0523. Received: 9 May 2013; in revised form: 4 June 2013 / Accepted: 5 June 2013 / Published: 17 June 2013 Abstract: Measurements of nuclear spin relaxation times over a wide temperature range have been used to determine the interaction energies and molecular dynamics of light molecular gases trapped in the cages of microporous structures. The experiments are designed so that, in the cases explored, the local excitations and the corresponding heat capacities determine the observed nuclear spin-lattice relaxation times. The results indicate well-defined excitation energies for low densities of methane and hydrogen deuteride in zeolite structures. The values obtained for methane are consistent with Monte Carlo calculations of A.V. Kumar et al. The results also confirm the high mobility and diffusivity of hydrogen deuteride in zeolite structures at low temperatures as observed by neutron scattering. Keywords: nuclear resonance; spin-lattice relaxation; heat capacity; mesoporous structures 1. Introduction There is currently wide interest in the thermodynamic properties of light gases constrained to the interior of microporous structures that include metal organic frameworks [1–3] and classical zeolitic structures [4] because of the potential use of these structures for storage and transport [5–8], and catalytic conversion [9] of light molecular gases (H2, CH4, CO2, CO, etc.).
    [Show full text]