Engelhard Industries, Inc. Technical Bulletin, Thomas Graham Commemorative Issue, High Resolution version

62 Pages·1966·101.087 MB·English

by  T.B. Flanagan (Ed.)

ENGELHARD INDUSTRIES, Inc.
TECHNICAL BULLETIN
Volume vII Numbers 1/2
JUNE/SEPTEMBER 1966
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ENGELHARD INDUSTRIES, Inc.
TECHNICAL BULLETIN
Volume VII Numbers 1/2
JUNE/SEPTEMBER 1966
THOMAS GRAHAM COMMEMORATIVE ISSUE
Ted B. Flanagan, Guest Editor

Engelhard Industries Technical Bulletin
CONTENTS
VOL. VII, NOS. 1/2 JUNE/SEPTEMBER, 1966
FOREWORD
E. F. Rosenblatt .............................................................................................................. . 7
INTRODUCTION TO THE COMMEMORATION OF THE CENTENNIAL OF
THOMAS GRAHAM'S DISCOVERY OF THE ABSORPTION OF
HYDROGEN BY PALLADIUM
Ted B. Flanagan (University of Vermont) .................................................................... 9
THERMODYNAMIC STUDIES ON THE HYDROGEN-PALLADIUM SYSTEM
John G. Aston (Pennsylvania State University) ............................................................ 14
LOW TEMPERATURE ELECTRONIC EFFECTS AND NEUTRON
DIFFRACTION STUDIES OF PALLADIUM CONTAINING
ABSORBED HYDROGEN
A. 1. Schindler (U.S. Naval Research Laboratory) ...................................................... 21
LATTICE-DISTENSION AND THE MAGNETIC SUSCEPTIBILITY OF
PALLADIUM HYDRIDE
Thomas R. P. Gibb, Jr. (Tufts University) ................................................................ 28
USE OF CHANGES OF THE ELECTRICAL RESISTANCE OF PALLADIUM
AS A GUIDE TO CHANGES OF HYDROGEN CONTENT
R. Burch and F. A. Lewis (Queen's University) ........................................................ 36
SOLUBILITY AND DIFFUSION OF HYDROGEN AND DEUTERIUM IN
PALLADIUM AND PALLADIUM ALLOYS
H. Brodowsky and E. Wicke (Universit~it Munster) .................... ............................... 41
DIFFUSION OF HYDROGEN THROUGH PALLADIUM
A. C. Makrides and D. N. Jewett (Tyco Laboratories, Inc.) ...................................... 51
PERMEATION OF DEUTERIUM AND HYDROGEN THROUGH
PALLADIUM AND 75 PALLADIUM-25 SILVER AT ELEVATED
TEMPERATURES AND PRESSURES
Leonard R. Rubin............. ............................................................ .................................. 55
ABSTRACTS OF SELECTED U.S. PATENTS
JANUARY 1966 - JUNE 1966
1. Patents Assigned to Engelhard Industries, Inc. ......................... ........... ............... 63
n. Othcr Patents on Applications of Platinum Metals and Gold ...... ... .................. 65
Physical Applications .................................................................... ......... ............ 65
Electrochemistry and Surface Coating ...................................... ........................ 69
Catalytic Hydrogenation ...................................................................................... 73
Catalytic Petroleum Processing .......................................................................... 75
Other Catalytic Processing .................................................................................. 81
Refining, Analysis and Miscellancous ......................................... ...... ................. 86
INDICES TO VOLUMES I-VI ............................................................................................. 89
Please address all correspondence to
Laura A. Magistrate, Editor
Enge1hard Industries, Inc.
Research and Development Division
497 De1ancy Street
Newark, N. J. 07105
COPYRIGHT 1966, ENGELHARD INDUSTRIES, INC.
PRINTED IN THE UNITED STATES OF AMERICA
-------------------
FOREWORD
T
HE present issue of Engelhard Industries Technical Bulletin has been devoted
to commemorate the centennial of Graham's discovery of the unique proper
ties of the palladium-hydrogen system, notably the high solubility of hydrogen in
palladium and its mobility in and through palladium. Since that time extensive
research has been and continues to be carried out in this field. However, only
during the past ten years has the status of the palladium-hydrogen system changed
from one of academic interest to only one of considerable technical significance
for either the extraction of hydrogen from various gas streams or for the production
of ultra-pure hydrogen on an industrial scale.
The preparation of a commemorative Graham issue was suggested by Professor
Ted B. Flanagan of the University of Vermont. Professor Flanagan was also kind
enough to serve as editor for the present issue. He has enlisted outstanding experts
in the field who have contributed comprehensive surveys as well as critical
discussions on the palladium-hydrogen and palladium-deuterium systems or on
the corresponding systems with palladium alloys. Areas discussed include the
thermodynamics, physical properties such as electrical resistivity, magnetic sus
ceptibility, thermal electromotive force, etc., the structure and the nature of the
bond in palladium-hydrogen or palladium-deuterium alloys, as well as the kinetics
and the models of diffusion and permeation through palladium or palladium
alloys. We gratefully acknowledge the efforts of Professor Flanagan and of the
contributors which have made this issue possible.
Newark, New Jersey E. F. Rosenblatt
July 29, 1966 President
7
Introduction to the Commemoration of the
Centennial of Thomas Graham's Discovery
of the Absorption of Hydrogen by Palladium
TED B. FLANAGAN
T
HIS year, 1966, marks the centennial of istry; for example, in 1833 he discovered the
the discovery by Thomas Graham of the three different forms of phosphoric acid.2
phenomenon of the absorption of hydrogen by Graham did pioneering research with colloids
palladium. This collection of papers by well and, in fact, invented the word colloid.3 The
known workers in the field was assembled to terms sol and gel were also coined by Graham.
commemorate the centennial of his discovery. In keeping with his century he was keenly in
The contributions in this Bulletin attest to the terested in problems of technology; one exam
continued fascmation of this system. It should ple of this interest was his invention of a
be added that these papers appear at a useful life saving jacket.
time because the hydrogen-palladium system Graham published his observations of the
has not been reviewed for many years and much phenomenon of hydrogen absorption by palla
important work has appeared recently. dium when he was sixty-onc years old-ex
actly one hundred years ago.4 In the same year
he investigated the absorption of hydrogen by
Thomas Graham
a silver-palladium aIloy.4 It is of interest that
Thomas Graham (1805-1869) was a key fig Graham happened to choose the palladium al
ure in the development of modern chemistry loy system of perhaps the greatest current in
in the British Isles. A student at the Univer terest in connection with hydrogen absorption
sity of Glasgow, he obtained his M.A. there in both from the theoretical and the technological
1826. His scientific studies were continued at point of view. Also in 1866 Graham made the
Edinburgh. In 1828 he was admitted to the observation that a palladium membrane could
Royal Society and two years later was ap be employed to purify hydrogen. Two years
pointed Professor of Chemistry at the Univer later he found that palladium could be charged
sity of Glasgow. In 1841 Graham joined with electrolytically with hydrogen.5 Further re
some friends to form the Chemical Society of searches on this system were published by
London; he was elected its first president. Graham in 1869 (the year of his death); in
Graham was appointed Master of the Mint in these publications he described measurements
1855 where, in addition to his other duties, he of the electrical resistivity and magnetic prop
continued his chemical investigations. As erties of hydrogen-containing palladium and
Master of the Mint he contributed significantly coined the word "hydrogenium."6 In this year
to problems of coinage and the first bronze coin he also measured diffusion rates of hydrogen
age in the British Isles was introduced under his in palladium.
supervision. Graham did not believe that a definite stoi
His publications span a large part of the nine chiometric compound was formed between hy
teenth century (1826 to 1869) and include sev drogen and palladium; he believed rather that
eral influential textbooks, e.g., "Elements of a homogeneous alloy resulted in which the ab
Chemistry" (1833). Primarily his interests cen sorbed gas acts like a quasi-metal ("hydrogen
tered on diffusion phenomena in gases and ium"). Although the nature of the bonding of
liquids. From expcriments on the diffusion the hydrogen atoms to the palladium lattice re
rates of gases1 Graham concluded that the rates mains controversial, it is fair to say that the
of diffusion were inversely proportional to the most widely accepted model is not too far from
square root of their densities; this is, of course, Graham's "hydrogenium."
now known as Graham's law of diffusion. He With regard to Graham's work on this sys
contributed significantly to other areas of chem- tem two facts stand out in the reviewer's mind:
the advanced age at which Graham did his
pioneering experiments and his choice of key
From the Chemistry Department. University of Ver experiments.
mont, Burlington, Vermont.
9
Thus Graham set the stage for the multitude ceptibility change with hydrogen content above
of investigations of the system which followed the critical temperature. An additional effect
in the next one hundred years. Physical chem ought to be considered, as Gibb points out,
ists, physicists and metallurgists have all con namely that the expansion of the lattice itself
tributed to the present understanding of the in the transition from pure palladium to the
system but it must be emphasized that despite hydride phases would be expected to decrease
the efforts of the last one hundred years many the susceptibility.
problems remain to be solved. Although it had been postulated earlier that
The many facets of the hydrogen-palladium the hydrogen atoms which enter the palladium
system will be illustrated Ly the following brief lattice ionize into protons and electrons, Mott
historical survey which emphasizes the role that and Jo nes16 specified that the electrons enter
the system has played in the application of the partially empty d-band of palladium. This
theories and experimental techniques which appears to have been the first application of
have been developed since 1866. the band theory of metals to a process of chem
ical interest. Mott's suggestion was undoubtedly
Review of the a forerunner of the more recent applications of
Hydrogen-Palladium System electronic band theory to the two-dimensional
problem of chemisorption and catalysis on
In 1887 Roozeboom pointed out the utility transition metals. It can be forcefully argued
of the phase rule which until then had been that this is yet the best extant example of the
obscured in the abstract work of Gibbs. Not role of the electronic band structure of metals
long after (1895) Roozeboom and Hoitsema7 on a process of chemical interest. Although the
applied the phase rule to the hydrogen-palla value of 0.6 holes in the d-band of palladium
dium system and concluded that two solid is supported by a series of diverse experiments,
phases were formed, although the isotherms this value nonetheless depends on one of the
were not perfectly horizontal and the issue re following assumptions: the validity of the rigid
mained somewhat in doubt. band model; analogies with the behavior of
The great interest in nonstoichiometric com nickel; or approximate theories of paramagnet
pounds is fairly recent despite the fact that an ism. It appears to the author and to others
extreme example of such a system, i.e., one ex (see Gibb's article in this volume) that the
hibiting large deviations from stoichiometry, magnetic behavior of the hydrogen-palladium
hydrogen-palladium, dates back one hundred system in terms of holes in the d-band has, since
years. Anderson8 recently pointed out that this 1936,16 subtly and unjustifiably changed from
was probably the first nonstoichiometric system a reasonable explanation of a phenomenon to
for which equilibrium measurements were avail strong evidence in favor of 0.6 holes. Recent
able.7.9-10 Early attempts to force onto the evidence, in fact, suggests that there may only
~-phase the stoichiometry of Pd2H were, of be 0.36 holes in the d_band17-18 (see also
course, doomed to failure. Schindler's article in this volume). The model
As early as 1877 R. Blondlotll made the ob of electron donation is not invalidated by this
servation that the paramagnetism of palladium recent finding, only the rigid-band approxima
decreased as hydrogen was absorbed. More tion. Schindler and co-workers have recently
quantitative investigations followed.12-15 It is obtained direct evidence in favor of the elec
generally accepted that at room temperature tron donation model by utilizing low tempera
the magnetic susceptibility falls to a diamag ture electronic heat capacity measurements on
netic value at HjPd;:::0.6. Many investigators the hydrogen-palladium system. This signifi
have also observed that the addition of noble cant research is discussed in this volume.
metals to palladium leads to a similar decrease Ten years after von Laue's discovery that
in the susceptibility.16 The apparent continu x-rays are diffracted by crystalline substances,
ous decrease in susceptibility when hydrogen is McKeehan19 used x-ray diffraction to confirm
added to palladium has been frequently misin the existence of two phases in the hydrogen
terpreted (as has been pointed out in this vol palladium system. This was the start of many
ume by both Schindler and Gibb) because the x-ray investigations of the system which, while
two-phase nature of the system is ignored. In useful, did not resolve the crucial question of
fact, the often-obtained magnetic data imply the location of the hydrogen atoms. Neutron
merely that the ~-phase has approximately zero diffraction subsequently was employed to locate
paramagnetism. In this connection it would be the positions of the hydrogen atoms (see
of interest to examine the paramagnetic sus- page 11).
10
In 1937 J. R. Lacher20 applied statistical co-workers.40 Aston and co-workers have ex
mechanics to the hydrogen-palladium equili tended their calorimetric studies of this system
brium isothermal data obtained by Gillespie to below 1 ° K;38 in this vicinity they have noted
and co-workers.10 This was a step of consider an activated process. This represents the lowest
able importance for two reasons: it constituted temperature at which a chemical process has
an important example of a genuine three been observed in the solid state.
dimensional lattice gas to which statistical me The extreme usefulness of new physical tools
chanics could be successfully employed, and it in the elucidation of a system can be well illus
was the first statistical mechanical treatment of trated by neutron scattering experiments on
nonstoichiometry. At the least Lacher's original hydrogen-palladium. The ~-phase was found
treatment can be said to have been semi to consist of randomly arranged hydrogen
quantitatively very successful. More recent atoms occupying octahedral positions about the
treatments have included specifically the change palladium atoms.4!.42 The positions of the hy
in the approximate density of states relation drogen atoms have not been located in the
ship in the d-band with added hydrogen2!.22 a-phase but Maeland43 has found that the octa
thereby explaining the decline in the heat of hedral positions are occupied in the a-phase of
absorption at high hydrogen contents.23-25 25% gold-palladium (weight percent gold)
Lacher did not specify the nature of the hydro alloy. Neutron scattering experiments, in addi
gen-hydrogen attractive interaction which must tion, have yielded mean vibrational amplitudes
be included in the model to explain the forma of both hydrogen and palladium and the fre
tion of the ~-phase. Recently Makrides,26 quency spectrum of the hydrogen.42 Schindler
Stackelberg,27 Brodowsky and co-workers22,28 describes in this Bulletin some exceedingly im
and Aston29 have discussed possible origins of portant results from recent experiments using
this interaction. neutron diffraction at low temperatures where
Diffusion of hydrogen in palladium was in evidence is found for an octahedral tetrahedral
vestigated first by Graham himself. Interest in transition near 45 OK. This ties in beautifully
this diffusion problem has continued because of with Aston's calorimetric data.
its technological interest and because of its
The electrical resistivity of the hydrogen
fundamental importance as the most well palladium system is very useful as a convenient
defined example of interstitial diffusion within tool for the determination of the specimen's
a transition metal. hydrogen content, and in addition has some
Many papers have been published on the dif inherent interest. The former aspect of the re
fusion of hydrogen in pure a-phase, ~-phase sistivity is discussed in this volume in detail by
and the mixed phase region. One example Burch and Lewis. A recent interesting applica
which stands out is the elegant work of Jost and tion of resistivity for the determination of hy
Widmann.3o They employed spheres of palla drogen content was utilized by Burke, Kemball
dium with activated surfaces under conditions and Lewis44,45 in following catalytic processes
where the complete diffusion equation could be at palladium electrodes. Because of the near
solved. Their value for the activation energy, impossibility of making quantitative calcula
5,740 cal./mole H, in the a-phase compares tions on transition metals, resistivity is usually
favorably with recent determinations in the not one of the more useful solid state properties
a-phase.S!. 32 This low value is noteworthy from the fundamental point of view; however,
because it possibly represents the smallest ob in certain cases useful quantitative results have
served activation energy for interstitial diffu been obtained. For example, Coles and Tay-
sion in a metal. Recent research in this field 10r46 have quantitatively accounted for the
has extended the diffusion studies to palladium electrical conductivity of a series of silver
rich alloys. Contributions in this area have been palladium alloys. Since relative resistivity in
made by Makrides and co-workers33 and Wicke the hydrogen-palladium system, i.e., the ratio
and his co-workers34.35 and are discussed in of the resistivity at any hydrogen content to the
this Bulletin. hydrogen-free resistivity, may be determined as
Low-temperature heat capacity determina a function of hydrogen content, quantitative
tions on the hydrogen-palladium system were a priori calculations of the resistivity are not
not done until the work of Aston and his co required - only the effects of the added hydro
workers.36-39 They observed a heat capacity gen. Simons and Flanagan47 have examined
peak in the vicinity of 55°K, the detailed ex recently the relative resistivity changes of pal
planation of which followed later from the ladium in the a-phase (0° to 90°C) (see also
neutron diffraction studies of Schindler and his Ref. 48); some limited progress was made in
11
the interpretation of the data in terms of Mott's dium-rich alloys is to determine whether the
theory of the resistance of transition metals. model of electron donation to the empty metal
The hydrogen-palladium system holds a bands is capable of explaining the absorption
unique position in the investigation of the elec behavior of palladium alloys. Although reliable
trochemical mechanisms of hydrogen reactions. data are just now being obtained, the interpre
Hydrogen atoms can be deposited electrochem tation of the results in terms of the model ap
ically at the surface of palladium and instead pears very encouraging (see Brodowsky and
of recombining on the surface to yield gaseous Wicke in this volume). The author would like
hydrogen, as is the case of platinum, gold, etc., to point out that these results and their inter
the hydrogen atoms enter the metal. At equili pretation should be of great interest to workers
brium with respect to the surrounding hydrogen in the field of heterogeneous catalysis and
pressure, the hydrogen-palladium electrode chemisorption. If this model is capable of ex
functions as a reversible hydrogen electrode. plaining the behavior of absorption by palla
Frumkin has recently reviewed this area of dium and its alloys, then the more difficult
research.49 two-dimensional problem of catalysis and
chemisorption may be understandable in terms
Absorption isotherms of palladium and its
of the electronic structure of the metals when
alloys have been obtained electrochemically.
the nature of surface states is understood more
One technique is to charge or discharge the
fully.
specimen and to record electrode potentials at
various hydrogen contents. The Russian work
Acknowledgments
ers have used this technique extensively with
electrolytically co-deposited palladium-rich al The author's research in this area is spon
loy samples. 50 An alternate procedure is to sored by the V.S. Atomic Energy Commission
bubble hydrogen gas through an acidic solution for which he is most grateful. Drs. Arnulf
containing the sample and to record the spon Maeland and John Simons are thanked for
taneous resistivity and electrode potential many stimulating discussions. Thanks are also
changes as the specimen absorbs hydrogen from extended to Engelhard Industries, Inc., for pub
solution (e.g., see Refs. 51-54). A somewhat lishing this special edition of Engelhard Indus
modified version of the latter technique has tries Technical Bulletin and to the authors of
been utilized to obtain equilibrium isothermal the articles for their cooperation and valuable
data. The slow step in the absorption process contributions.
is diffusion of dissolved hydrogen up to the
References
surface. In order to attain equilibrium within
the specimen, the over-all rate of absorption is 1. Graham, T. Phil. Trans. Roy. Soc. (London)
136,349,573 (1846).
reduced by decreasing the partial pressure of
2. Graham, T. Phil. Trans. Roy. Soc. (London)
hydrogen gas in hydrogen-helium streams so
123,253 (1833).
that time is allowed for internal equilibration 3. Graham, T. Phil. Trans. Roy. Soc. (London)
to occur. This technique has been successfully 151, 183 (1851).
applied to obtain data in the a-phase of pure 4. Graham, T. Phil. Trans. Roy. Soc. (London)
palladium;55 arguments based on diffusion 156,415 (1866).
5. Graham, T. Proc. Roy. Soc. (London) 16,
measurements support the equilibrium nature
422 (1868); Phil. Mag. 36, 63 (1868).
of the data obtained. Equilibrium data below
6. Graham, T. Proc. Roy. Soc. (London) 17,
120°C have been difficult to obtain in the past 212, 500 (1869); Comptes rend. 68, 101,
on either palladium or palladium-rich alloys 1511 (1869); Ann. Chem. Phys. (Paris) 16,
using conventional gas phase techniques. The 188 (1869); Ann. Chem. 152, 168 (1869).
7. Hoitsema, C. and H. W. B. Roozeboom.
technique described above has proved success
Z. physik. Chem. 17, 1 (1895).
ful in obtaining such data because special pro 8. Anderson, J. S. "Current Problems in Non
cedures to insure surface activity can be carried stoichiometry," in Nonstoichiometric Com
out in solution. pounds, Advances in Chemistry Series No.
39, Am. Ch em. Soc., Washington (D.C.),
An alternate procedure has been recently
1963, p. 1.
developed by Wicke, Brodowsky and their col 9. Sieverts, A. Z. physik. Chem. 88, 451
leagues for the obtaining of equilibrium iso (1914).
thermal data below 120°C. Their important 10. Gillespie, L. J. and F. P. Hall.]. Am. Ch em.
hydrogen transfer-catalyst technique is de Soc. 48,1207 (1926).
11. Blondlot, R. Compt. rend. 85,68 (1877).
scribed in detail by these authors in this volume
12. Biggs, H. F. Phil. Mag. 32,131 (1916).
where pertinent references are given.
13. Oxley, A. E. Prac. Ray. Soc. (London)
The main purpose of the research with palla- AlOl, 264 (1922).
12