Obtaining cyclopentanone from acidic wastewater of caprolactam production


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Tsvetkova I. V., Golovanov A. A., Reznikova N. S., Chirkunova N. V.
Chimica Techno Acta. 2020. Vol. 7, no. 4. P. 177–179.

ISSN 2409–5613

Obtaining cyclopentanone  
from acidic wastewater of caprolactam production

I. V. Tsvetkova*, A. A. Golovanov,  
N. S. Reznikova, N. V. Chirkunova

Togliatti State University, 14 Belorusskaya st.,  
Tolyatti, Samara region, 445020, Russia

*email: irina.cvetkova.56@mail.ru

Abstract. It has been shown that adipic acid released from the by-products of cap-
rolactam production is a promising raw material for the production of cyclopentanone. 
The thermal stability of calcium adipate was investigated by the derivatographic method 
and the conditions were selected that ensure the yield of at least 50% of the target 
cyclopentanone with a purity of at least 99%.

Keywords: wastes from caprolactam production; adipic acid; cyclopentanone; derivatography; 
calcium adipate; gas chromatography

Received: 22.10.2020. Accepted: 08.12.2020. Published:30.12.2020.

© Tsvetkova I. V., Golovanov A. A., Reznikova N. S., Chirkunova N. V., 2020

Results and discussion
The process of oxidation of cy-

clohexane with oxygen from air, carried 
out in  the  production of  caprolactam 
as a separate step is characterized by a large 
amount of oxygen-containing side-prod-
ucts concentrated in  acidic wastewater. 
One of these compounds is adipic acid [1].

The adipic acid is converted to a cal-
cium salt, and the calcium salt decomposes 
to cyclopentanone during the high-temper-
ature treatment (Fig. 1). Cyclopentanone 
is an important intermediate in the pro-
duction of insecticides, pharmaceuticals, 
and fragrance chemistry (synthesis of jas-
mon). In  the  pharmaceutical industry, 

cyclopentanone is a precursor in the pro-
duction of cyclopentobarbital, a sedative 
barbiturate derivative. Cyclopentanone 
is  also used to  produce cyclopentamine, 
which is an intermediate in the synthesis 
of fungicides such as pencycuron [2].

The solid concentrate of acidic waste-
water was methylated with diazomethane 
to obtain methyl esters of carboxylic acids. 
The  analysis of  the  methylated products 
was carried out on a  Kristallux 4000M 
chromatograph with a  flame ionization 
detector (capillary column, helium car-
rier gas, quartz, DB-WAX (PEG), 30 m / 
0.32 mm / 0.5 µm, maximum thermostat 
temperature is 240 °C) showed that the sol-
id residue of the acidic wastewater from 
the production of caprolactam contains up 
to 94% of adipic acid (Fig. 3). 

Calcium adipate was synthesized from 
the resulting product. The thermal stability 

(CH2)4(CO2
-)2Ca

2+
∆

O

+ CaCO3

Fig. 1. Decomposition reaction  
of calcium adipate



178

of the calcium adipate was studied on a Shi-
madzu DTG-60/60H thermal analyzer, and 
the initial temperature of its decomposi-
tion was determined as 400 °C. Th e ther-
mal eff ect of the decomposition reaction 
is 5.68 kJ/g (Fig. 3).

The  pyrolysis of  calcium adipate 
in  a  quartz reactor was carried out, and 
the yield of cyclopentanone was calculated 
as 51%.

Th e  resulting product was subjected 
to chromatographic analysis. Th e retention 
time of the technical sample of cyclopen-

tanone (96.4% purity) is 6.24 minutes ver-
sus 6.20 minutes for the standard sample 
of cyclopentanone of 99.6% purity. Th e dif-
ference in the retention times of the stand-
ard sample (Fig. 4) and the technical one 
(Fig. 5) may be due to the presence of im-
purities in the second one. 

As a result, the possibility of obtaining 
cyclopentanone from by-products of cap-
rolactam production with good yield and 
high concentration in liquid products has 
been shown.

Fig. 2. Chromatogram of the content of dimethyladipate in methylation products

Fig. 3. Th e derivatogram of calcium adipate



179

References
1. Kisil IM, Preobrazhensky VA, Zolin VS, Gorodetskaya NI, Davydov YuI, Polikar-

pov AV, Salomykov VI. Method of utilization of acidic wastewater of caprolactam 
production: Pat. 2039740 Rus. Federation. 93009600/04; declared 02.24.1993; publ. 
07.20.1995

2. Carbonyl compounds in the synthesis of heterocycles: K82 Coll. scientific. tr. / Ed. 
prof. A. P. Krivenko. Saratov: Publishing house “Scientific book”, 2008. 324 p.

Fig. 4. Chromatogram of the standard sample of cyclopentanone

Fig. 5. Chromatogram of the technical sample of cyclopentanone