Autocatalytic model for the reduction of nickel chloride with hydrogen gas
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192--VOLUME 12B, MARCH 1981
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Autocatalytic Model for the Reduction of Nickel Chloride with Hydrogen Gas D. T. WILLIAMS, S. K. EL-RAHAIBY, A N D Y. K. RAO The mechanism of hydrogen reduction of nickel chloride consists of formation of nuclei of nickel followed by the growth of these nuclei. The incubation period observed at the start of the reduction ~is usually associated with nuclei formation. The growth of the nuclei corresponds to the acceleratory period. In the case of hydrogen reduction of nickel oxide, Benton and Emmett 2 observed autocatalytic behavior. The autocatalysis was attributed to the nickel. The acceleratory period observed in the hydrogen reduction of nickel chloride is also probably due to the autocatalytic behavior of nickel. Let us suppose that a represents the fractional reduction at time t. Then (1 a) denotes the fraction of the unreacted nickel chloride. The reaction may be represented as follows: -
Ni
NiC12(s ) + H2(g ) ~ Ni(s) + 2HCI(g)
[1]
The rate law for this autocatalytic reaction may be written as follows: da
d-)- = Ka c~(1 - c0
[21
where K~ is the rate constant for the autocatalytic reduction. Equation [2] may be integrated as follows: da ~(1 -
~)=
K.dl
or da -- +
a
da
(1 -
a)
-
K~dt
D. T. WILLIAMS, S. K. EL-RAHAIBY, and Y. K. RAO are Undergraduate Research Assistant, Graduate Research Assistant, and Professor, respectively, at the Division of Metallurgical Engineering, FB-10, University of Washington, Seattle, W A 98195. Manuscript submitted July 7, 1980.
ISSN 0360-2141 t 8110311-0192500.75 f0 9 1981 AMERICAN SOCIETY FOR METALS AND THE METALLURGICAL SOCIETY OF AIME
METALLURGICAL TRANSACTIONS B
Table I. Data for the Autocatalytlc Reduction of NlCl 2 with Hydrogen Run Number
Temperature, ~
T, K
IO00/T
Ka, m i n - 1
3 6 19 16 22 2 20 15 21 4 5
260 282 290 294 300 310 322 331 345 353 375
533 555 563 567 573 583 595 604 618 626 648
1.8762 1.8018 1.7762 1.7637 1.7452 1.7153 1.6807 1.6556 1.6181 1.5974 1.5432
5.846 X 10 -3 0.0143 0.0197 0.0195 0.0299 0.0470 0.0626 0.0672 0.1227
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