(SANITIZED)UNCLASSIFIED SOVIET BLOC PAPERS ON CATALYSIS(SANITIZED)

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP80-00247A004200080001-5
• Release Decision: RIPPUB
• Original Classification: C
• Document Page Count: 126
• Document Creation Date: December 27, 2016
• Document Release Date: February 28, 2014
• Sequence Number: 1
• Publication Date: January 1, 1964
• Content Type: REPORT

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STAT ,
MECHANISM OF OXIDATION OF METHYL ALCOHOL
TO FORMALDEHYDE ON OXIDE CATALYSTS
P. JIRU, B.WICHTERLOVPI and J. TICHY
Institute of Physical Chemistry, Czechoslovak Academy of Sciences
Prague, Czechoslovakia
Abstract: In this paper a mechanism is proposedfor the oxidation of methyl al-
cohol to formaldehyde on a Fe203-Mo03 catalyst. The oxidation process can be
described by an oxidation-reduction mechanism. The rate of the oxidation of
methyl alcohol at a temperature of 2700C is given by the expression:
pme
- 1 + 0.5(kilk2)(pmelp02) ?
The ideas on the oxidation-reduction mechanism are confirmed in a later part
of this paper by results of the investigations: a) by the rate of interaction be-
tween methyl alcohol and catalyst without participation of oxygen in the gaseous
phase, b) by the rate of interaction between oxygen and partially reduced cata-
lyst without participation of methyl alcohol in the gaseous phase. The discussion
presents a more detailed analysis of the ideas on the course of partial processes
In catalytic oxidation of methyl alcohol with the participation of lattice oxygen of
the catalyst. A comparison of the experimentally determined rate constants for
the partial processes and for the oxidation shows that the suggested mechanism
is of physical significance. ?
1. INTRODUCTION
The mechanism of oxidation of methyl alcohol to formaldehyde on oxide
? catalysts has so far not been dealt with in the literature-1,2). There are
neither experimental data nor theories as regards to the course of partial
processes involved in this industrially important catalytic reaction. The
experimental work of Peterson and Adkins 1) is only concerned with the
study of a suitable Composition of oxide catalysts on the basis of Fe203 and
Mo03 and with the verification of their catalytic activity in the oxidation of
methyl alcohol. The authors arrived at the conclusion that the most suitable
catalyst is a mixture containing both oxides in equimolecular amounts. The
results of this work served as the basis for a number of patents 2) relating
to the preparation of these catalysts. A property common to all Fe203-
111?03 catalysts is their high activity at relatively low reaction temperatures
of 200 - 330?C and their selectivity in the oxidation of methyl alcohol to
formaldehyde.
The opinions of various authors 3, 4) about the mechanism of catalytic
oxidation differ. Some workers 5-8) prove on the basis of their experiments
that the lattice oxygen of oxide catalysts participates in the catalytic process,
while others 943) refute this idea.
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1.2
Mars and Krevelen14,15) }Ave recently published interesting results
of a study on the mechanism of oxidation of various organic compounds (ben-
zene, naphthalene, anthracene) on vanadium pentoxide. They have proposed
a kinetic equation for a two-stage oxidation-reduction mechanism on the
basis of an analysis of data on the over-all oxidation rate, but without pre-
senting any further proof to support this mechanism.
In view of the existence of such divergent opinions as regards the mech-
anism of catalytic oxidation processes it was interesting to study in detail
the mechanism of another oxidation reaction, namely the oxidation of methyl
alcohol to formaldehyde on a mixed Mo03-Fe203 catalyst, in order to obtain
some experimental proofs and ideas concerning the mechanism of oxidation-
reduction processes involved in the oxidation of methyl alcohol.
2. EXPERIMENTAL
2.1. Starting materials
For all our measurements we employed a catalyst containing 17.5% by
weight of Fe203 and 82.5% by weight of Mo03. The grain size of the catalyst
was in the range from 0.3 to 0.6 mm., The bulk weight of the catalyst amount-
ed to 1.02 g/ml. The surface area of the catalyst, as determined by the BET
? method from the adsorption of krypton at 76?K, for the surface of the kryp-
ton molecule of 21 A2, was 6.9 mz/g. The mean radius of the pores of the
catalyst, determined by means of a high-pressure mercuryporometer, was
950 A. The pore volume in the range of radii of 100 - 3.5 x 106 A amounted
to 0.39 ml/g.
The methyl alcohol was of p. a. purity, refractive index 40? = 1.3295,
vapour tension at 20?C 98.0 mm Hg. Its water content was 2.5 x 10-3 % by
weight.
2.2. Measurement of oxidation rate
, The rate of catalytic oxidation of methyl alcohol to formaldehyde was
measured in a throughflow integral reactor at atmospheric pressure. The
accuracy of dosing the individual substances (CH3OH, N2, 02), expressed
by the standard deviation, was 3% of the respective value.
By preliminary experiments and calculations we found that the rate of
oxidation of methyl alcohol on the catalyst is neither influenced by internal
nor by external diffusion. The temperature gradient between the main gas
strewn and the surface of the catalyst was likewise negligible. The form-
aldehyde content in the reaction products after absorption in water was
determined titrimetrically by means of sodium bisulphite. The content of
by-products-(CO3 CO2, CH4) was estimated chromatographically 16).
4 Under experimental conditions of kinetic measurements, no oxidation by-
products of the reaction were found.
2.3. Measurement of the rate of oxidation-reduction processes
'The rate of interaction of methyl alcohol and catalyst without participa-
tion of oxygen in the gaseous phase and the interaction of oxygen and partially
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r
Fig. 1. Microcatalytic chromatographic pulse apparatus.
1. Copper wire heated to 300?C. 8. Chromatographic column.
2. Freezing trap (-76?C). 9. Temperature-controlled methyl
3. Heat conductivity cells, alcohol saturator.
4. Dosing cock with free volumes 10. Flow meter.
- of 5.2 and 8.4 ml. 11,12. Seals of silicone rubber for
5,6. Two-way cocks. dosing with a syringe.
7. Microcatalytic reactor.
reduced catalyst without participation of methyl alcohol in the gaseous phase
were investigated by means of a microcatalytic chromatographic pulse
method 17), adjusted to our experiments. The diagram of the apparatus is
presented in fig. 1. The carrier gas, nitrogen, was freed from traces of
oxygen on copper wire at 300?C in the reactor 1 (02 content