close

Вход

Забыли?

вход по аккаунту

?

Enrichment of Deuterium by Countercurrent Isotope Exchange between Hydrogen and Ammonia in a Hot-and-Cold Plant.

код для вставкиСкачать
35°C with a voltage of 20-25 V and a current of 1-3 amp
produces triphenylphosphine ( 5 ) and a-branched p-keto
esters ( 4 ) .
Received: May 17th, 1965
[Z 991/817 1El
German version: Angew. Chem. 77, 620 (1965)
of the hot column. The enrichment is expressed by the ratio
of the relative deuterium contents in the enriched hydrogen or
ammonia and in the original hydrogen, i. c. (nD/nH)product:
(nD/nH) starting hydrogen, where nD and nH are the mole
fractions of H D and Hz, or NHzD and NH?, respectively[4].
[ I ] H . J . Bestmann and H . Hartung, Angew. Chem. 75, 297
(1963); Angew. Chem. internat. Edit. 2, 214 (1963).
121 L. Horner and A . Mentrup, Liebigs Ann.Chem.646, 65 (1961).
The degrees of enrichment achieved are in agreement within the limits of error - with values calculated from
laboratory experiments with single sieve plates.
Received: May 19th, 1965
IZ 985/811 IEI
German version: Angew. Chem 77, 620 (1965)
.
Enrichment of Deuterium by Countercurrent
Isotope Exchange between Hydrogen and
Ammonia in a Hot-and-Cold Plant
[I] W . P. Bebbington and V . R. Thayer, Chem. Engng. Progr. 5 5 ,
No. 9, 70 (1959); W. P . Bebbington, J . F. Proctor, W. C . Scotton,
and V. R. Thayer, Third United Nations Internat. Conf. on the
Peaceful Uses of Atomic Energy, Geneva 1964, Paper 290.
[2] Cf. for example E. W. Becker: Heavy Water Production.
Internat. Atomic Energy Agency Rev. Ser. No. 21, Vienna 1962.
[ * ] Temperature dependence of the ideal enrichment factors CL =
(nD/nH)lic/(nD/nH)gas [41.
By Dr. S. Walter,
Friedrich Uhde GrnbH., Dortmund (Germany)
and Doz. Dr. U. Schindewolf
lnstitut fur Kernverfahrenstechnik der Technischen
Hochschule und des Kernforschungszentrums
Karlsruhe (Germany)
["cl
Heavy water is produced mainly by the hydrogen sulfide
process [ I ] which is based upon the temperature dependence
of the isotope exchange equilibrium between hydrogen sulfide
and water. Replacement of the system hydrogen sulfide/
water by ammonia/water with dissolved potassium amide as
catalyst has been frequently proposed [2,3], since here the
isotope exchange is much larger and is more dependent upon
the temperature [*I and since here there is the thermodynarnically favorable possibility [2] of using hydrogen as starting
material. However, no enrichment attempts have been published to date.
Our plant consists of two cold columns in series with a total
length of 28 m and a hot column with a total length of 17.5 m
(see Figure). The cold columns are cooled by two deep
freezers, and the hot column is heated by an electrical heating
m-Hot column
Rj!l)coi
-
---Synthesis
gas
Ammonia circulation
element. Each column has a n internal diameter 120 mm and
contains about 200 sieve plates. The upper and lower plates of
the hot column act as direct heat exchangers. Ammonia containing dissolved pgtassium amide is circulated in the system.
Synthesis gas (hydrogen-nitrogen mixture for ammonia
synthesis) which is taken directly from the producer plant,
is passed through the deuterium enricher, and then on
to the consumer. At a pressure of 200 atm and a temperature of 6OoC in the hot column and -2OOC in the cold
column, with a potassium amide concentration of 50 g
per kg of ammonia, and with a throughput of 450 m3 (S.T.P.)
of synthesis gas and 50-100 kg of ammonia per hour, a sixto sevenfold enrichment of the deuterium was achieved in
the hydrogen at the top of the hot column and an over
twentyfold enrichment in the ammonia, based o n the original
deuterium content of the hydrogen introduced at the foot
Angew. Chem. internat. Edit. / VoI. 4 (1965) / No. 7
-25
0
50
100
150
1
hydroLnjammonia
5.1
4.25
3.1
2.4
I
hydroLn sulfidelwater
2.6
2.15
1.9
1.75
131 B. Lefrancois, J. M . Lerrat, and E. Roth, Third Internat.
Conf. on the Peaceful Uses of Atomic Energy, Geneva 1964,
Paper 28/P/91; R . Haul, H. Ihle, and H. Schierholz, Chem.-1ng.Techn. 33, 713 (1961).
141 The mole fractions n relate to the reactions H D
NH3 +
Hz NH2D and H D S H20 + H2S HDO respectively.
+
+
+
+
The Quaternary Structure of Catalase
from Beef Liver
By Dr. K. Weber and Doz. Dr. H. Sund
Chemisches Laboratorium
der Universitiit Freiburg/Breisgau (Germany)
Denaturing agents cause catalase (molecular weight co.
250000 [I]) t o dissociate into subunits. Depending on the
experimental conditions, fractions are obtained with molecular weights which have been found t o be one-sixth, onethird, one-half, or two-thirds of that of native catalase [2].
However, in accordance with the iron and heme content of
catalase, dissociation into 4 or 4n subunits should be expected.
We succinylated catalase with succinic anhydride according
to [3] and obtained a dissociation product which was found
t o be monodisperse in the analytical ultracentrifuge and still
contains bonded heme. Extrapolation to infinite dilution
gives a value of 4 . 4 ~10-7 cmZ/sec for the diffusion coefficient
DY,,,v and 3 . 2 10-13
~
sec-1 for the sedimentation coefficient
s:,,~ (measured in 0.067 M potassium sodium phosphate
buffer at p H 7.6 and 20 "C). Taking a partial specific volume
of 0.73 ml/g [l], the molecular weight of this dissociation
product was calculated by the Svedberg formula to be
65000. Succinylation therefore causes dissociation of the
catalase molecule into four subunits which according t o
sedimentation and diffusion measurements are of equal
size. This finding is in agreement with the results of electronmicroscopic investigations 141. The action of dodecyl sulfate
leads t o a dissociation product with the same sedimentation
constant.
If it is assumed that each of the four heme groups in the
enzyme is located at an active site, then there must be an
active site in each of the catalase subunits. The question
whether the subunit of molecular weight 65000 is already
the polypeptide chain or whether i t contains several -
597
Документ
Категория
Без категории
Просмотров
0
Размер файла
128 Кб
Теги
hydrogen, exchanger, ammonia, hot, countercurrent, cold, enrichment, plan, deuterium, isotopes
1/--страниц
Пожаловаться на содержимое документа