HUNGARIAN JOURNAL 
OF INDUSTRIAL CHEMISTRY 

VESZPREM 
Vol. 30. pp. 257- 259 (2002) 

THE INFLUENCE OF WATER SOLUBLE VARNISHES ON THE CATALYST 
DURING ENAMELLING PROCESS 

J. BALGARANOVA 

(Department of Fundamentals of Chemical Technology, University of Chemical Technology and Metallurgy, 
Kl.Ohridski 8, Sofia, 1756, BULGARIA) 

Received: August 21,2002 

During the drying process of enamel wires production, enamel varnishes lib~rate large amounts of. vapour from solven~s 
and diluents, as well as other products from the destruction of the varn1sh base. An appropnate method for their 
destruction is catalytic combustion. This requires certain characteristics of the catalysts. The use of the new so-called 
water soluble enamel varnishes, increases the possibilities for catalyst poisoning. 
The catalytic activity of Pd-laid catalyst in destructive oxidat~on of organic substances in .the presence of water vapour 
was studied on a large-scale production trials. It was established that the greater quantity of. water vapour do~s not 
decrease the conversion degree. On the contrary, it is slightly increased (by 9-10 %). These c~ntnbute to not only diluent 
economy and environmental protection, but as well retain the existing technology of enamel wrres. 

Keywords: catalytic combustion, catalyst poisoning, water vapour, water-soluble varnish 

Introduction 

During drying and polycondensation processes of 
enamel wires production, enamel varnishes liberate 
fairly large amounts of vapour from solvents and 
diluents, as well as other products from the destruction 
of the varnish base, mainly cresols and di-, and 
tetramethylbenzenes. These are strong toxins and 
environmental pollutants. [ 1 J An appropriate method for 
their destruction is catalytic combustion. The obtained 
heat, through recirculation of the exhaust gasses, is used 
in the drying process. [2] This requires certain 
characteristics from the catalysts, i.e. action at 
comparatively high temperatures as well as in the 
presence of multicomponent mixtures of substances, 
some of which may act as contact poisons. These 
problems become more important with the use of the 
new so-called water soluble enamel varnishes~ where 
.the quantity of water vapour in the exhaust gases 
inevitably increases. 

The literature shows at length that during 
exploitation, the activity of the catalyst is changed under 
the influence of various factors. Generally. this means 
decrease of the active surface because of sintering or 
blocking due to precipitation as well as poisoning. T~e 
most important factor for deactivation is poisoning. It IS 
a process, which lead to catalytic activity decrease and 
in diffusion limited reactions to activation energy and 

selectivity changes. It is known that the action of the 
poison is specific for a particular catalyst and a 
particular reaction. 

It is interesting to point out that at times, when the 
concentration of the poison is not high, instead of 
deactivating a certain catalyst or reaction, it may have 
an opposite activating effect [3]. 

In the SICME (Italy) and PGZ (Hungary) horizontal 
enamel machines, the catalytic elements of KA TEC 
Company {Germany) are widely used for air 
purification process. They have a square shape and look 
like a metal air filter. The active phase, palladium is laid 
on a chromium steel crimped band. According to the 
database of the producer, soot or high molecular 
compounds could deactivate the catalyst. It is sensitive 
to halogens, sulphur dioxide, and phosphorous 
compounds. The catalyst loses about 25 % of its activity 
after around 8000 hours use [4]. 

The literature review shows that a number of oxide 
catalytic systems are sensitive to the comparativel_y 
weak contact poisons of H 20 and C02 [5]. What ts 
more, a reversible poisoning is detected after the initial 
action of the poison has ceased. Comparatively few data 
exist on the influence of these poisons on platinum and 
other catalysts containing noble metals. It is pointed out 
that usuaHy, water in a reduetion conditions acts as a 
poison on the metal type catalyst [5}. 

Contact information: E-mail: petkov@uctm.edu; Tel: ( +359) 2 6254 585 



258 

Table 1 Dependence of combustion degree from the 
concentration and temperature 

Machine Varnish Cm, Coul Tin Tout ilT Combustion 
type type (mg/m3) (mglm3) ("C) ("C) ("C) degree,(%) 

PGZ P~940 8.29 4.81 450 525 75 41.98 
PGZ P-940 7.38 4.46 450 520 70 39.50 
PGZ HB-91 5.07 2.42 450 515 60 52.26 
PGZ HB-91 4.95 3.36 450 510 60 52.32 

SICME P-940 7.60 4.79 450 520 70 36.97 

SICME P-940 8.10 5.18 450 520 70 36.00 

SICME HB-91 5.18 2.85 450 500 60 44.98 

SICME HB-91 5.34 2.95 450 500 60 44.75 

Because of this, as well as the development of a new 
class of water soluble enamel varnishes which meet 
ecological aims, it is of interest to investigate the 
catalytic activity of palladium laid catalysts in the 
destructive oxidation of organic substances in the 
presence of water vapour. 

Experimental 

The investigation was carried out with varnishes P-940, 
esterimide, and the water soluble HB-91, produced in 
test series, containing dry substance, respectively 
27.5% and 41.0 %, with PGZ and SICME horizontal 
machines working with catalyst used for over a year. 
Their activity in the combustion reaction was assessed 
by determining the total amount of burning organic 
substances in recycled air, expressed as a content of 
total organic carbon, 'before and after the catalyst at 
equal constant volume velocity, by the absorption 
method [6]. 

Results and Discussion 

Results are shown on Table 1. Clearly the concentration 
of burning toxic substances in the air using the HB-91 
decreases compared to the estherimide varnish. as well 
as showing smaller temperature differences (Tin - T ouU 
in the catalyst layer at the adiabatic temperature 
increase. The comparatively small temperature 
difference points to a certain degree of deactivation of 
the catalysts over the one-year period of work. The main 
conclusion is that the greater quantity of water vapour 
does not decrease the catalytic combustion degree, i.e. 
the degree of activity. On the contrary~ it is slightly 
increased (by 9-10 % ). 

This can onty be explained by the regeneration of 
the catalyst surface owing to the coke deposits from 
carbohydrates of unknown composition laid on it. as 
wen as some high-molecular compounds released by the 
decomposition of the varnishes. 

In support of this conclusion. the results of other 
authors regarding the regeneration of Pt catalyst may be 
referred to. Usually~ a catalyst containing laid on coke is 

Table 2 Characteristics of the water varnish enamelling 
process 

Varnish Dry Wire Wire Productivity Energy Varnish 
mass diameter velocity (kg/hlp ass) expense expense 
(%) (mm) (mls) (kWh/day/ (g/kg) 

pass) 

BH-91 41 0.016 1.83/1.80 1.173 57.09 170 
±0.02 

P-940 27.5 0.016 1.8311.83 1.173 51.36 157 

±0.02 

regenerated by its combustion in airflow at high 
temperatures. To obtain the necessary oxygen 
concentration, it is suggested that the air be diluted with 
inert gases. or steam where the reaction of the latter 
with carbon plays an essential role [6]. 

Productivity, energy and varnish expenses for both 
varnish experiments are given on Table 2. In 
comparison, it can be seen only a slight increase of the 
energy expenses when working with the water-soluble 
varnish. This could be explained by the lower heat 
amount released in the catalyst layer, which can be 
completely compensated by the electrical heaters if 
necessary. 

According to these and to the good quality 
characteristics of the produced wires we consider that 
the enameling process with the studied water-soluble 
varnish does not infringe the catalytic combustion of the 
exhaust gases and fully correspond to the existing 
technology. 

Conclusions 

The investigation is of interest in view of the possibility 
of using water soluble enamel varnishes for production 
of enamel wires. It was established that the greater 
quantity of water vapour does not decrease the 
destruction oxidation degree. On the contrary, it is 
slightly increased (by 9-10 %). These contribute to not 
only diluent economy and environmental protection, but 
correspond with the existing technology of enamel 
wires. 

Acnowledgement 

The author expresses her thanks to Professor Dr.D. 
Klisurskii from the Bulgarian Acad. of Science for the 
valuable discussions and support. 

SYMBOLS 

C in• C out the inlet and outlet concentration of 
combustible organic substances. expressed 
as total organic carbon 

Tin· T ()Ul the inlet and outlet temperature of the 
catalyst layer 



REFERENCES 

1. SMITH S.R.: Prog. In Environ., 2000,2, 129-146 
2. BROECHERHOFF P. and EMONTS B.: Catalytic 

combustion, a possibility for low emission heat 
production., Proc, Intersoc. Energy Con. Vers. 
England, Conf., 29th (Pt.3), 1146 - 1150, 1994 . 

3. PIPEROV B. B.: Ph.D.Thesis, IONH, Bulganan 
Academy of Science, 175, 1992 

259 

4. KATEC-booklet, Hasselroth neuenhassland metall. 
Katalysatoren fur wirtschaftliche drahtlackierung, 
BRD, 1989 

5. SEITERFILD Ch.: Practical course on heterogeneous 
Catalysis. Edit. Mir., Moskow, p. 520,1984 

6. BALGARANOVA J.: Ph.D. Thesis, University of 
Chemical Technology and Metallurgy, Sofia, 145, 
1984 

7. Patent GDR, 234799, (1986) 


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