Stepanenko T., Bashevaya T.

Donbas National Academy of Civil Engineering and Architecture, Ukraine

EMISSION REDUCTION OF POLLUTANTS IN THE PETROCHEMICAL INDUSTRY

Chemical and petrochemical industries are the sources of multicomponent emissions of chemical impurities I, II, III, IV hazard class (organized process emissions, ventilation emissions, open areas with equipment) into the environment.

Work objective: to explore and study the method of emission reduction of repugnant substances in the production of phenol and acetone.

In the production of phenol and acetone, by the cumene method, which is widely used in the present time, we can distinguish three main stages: alkylation of benzene with propylene to form isopropylbenzene (the reaction proceeds at a temperature of 250°C and a pressure of 2.5 MPa in the presence of a catalyst); the oxidation of cumene by atmospheric oxygen in hydroperoxide at 100-130°C; the degradation of cumene hydroperoxide to phenol and acetone at 50-90°C [1]. At that, the degradation products of cumene hydroperoxide, passing to the atmosphere, are formed such as carbon dioxide, methane, ethylene, acetophenone, biphenyl, phenol, α-methylstyrene.

There are two ways to reduce the amount of pollutants released into the environment

· cleaning of gas-air mixture;

· prevention of pollution by optimizing the existing process flows or introduction of new unwaste technologies.

The analysis of the literature showed that to reduce emissions of the mentioned substances, we could use different methods. Absorption technique is widely used [2]. However, a significant weakness is the formation of liquid flows to be recycled. Sufficiently widely spread got the adsorption technique of pollution abatement [2]. A large specific consumption of the desorption stages and subsequent separation greatly complicates the application of this method for multicomponent mixtures. The advantage of catalytic and catalytic thermal methods is the high degree of purification (95-99%), ability to process multi-component gases with low initial emission concentrations. Along with this, these methods have a drawback - the high cost of catalysts [2].

An alternative way to reduce harmful emissions into the atmosphere is to optimize the technological process of production of phenol and acetone.

When coupled with the production of phenol and acetone by the cumene stage of cumene oxidation by air oxygen simultaneously with cumene hydroperoxide, various by-products are formed, such as: dimethylphenylcarbinol peroxide of dicumene, acetophenone, α-methylstyrene, as well as phenol and organic acids, which require disposal. The presence of these components is considered harmful for the reaction. Indeed, acid favor the splitting of hydroperoxide into phenol, which itself is an inhibitor of the oxidation reaction [3].

It should be noted that the most toxic substances are phenols (MAC = 0,003mg/m³), acetophenone (MAC = 0,003 mg/m³), α-methylstyrene (MAC = 0,04mg/m³).

Effect of the temperature on the composition of the breakdown products of cumene hydroperoxide is shown in Figure 1.

Fig. 1 – Composition of the breakdown products of cumene hydroperoxide at 110°C, 137°C and 160°C

It is known from the literary sources, that the on-process temperature affects the amount of breakdown products of cumene hydroperoxide, which enters the atmosphere (Fig. 1). The figure shows that fall of the temperature of the on-process at 50ºC (from 160ºC until 110ºC) allows a factor of two to reduce the methane content and acetophenon in flue gases. We also know that at 60°C, the decomposition reaction of cumene hydroperoxide does not proceed. Adding reagent, - the initiator of oxidation, - solves this problem and lets to reduce the oxidation temperature to 35°C [5].

We have investigated the rate of oxidation of cumene hydroperoxide (in the presence of an oxidation initiator - N-hydroxyphthalimide) at different temperatures. The introduction of the initiators of the process lets to reduce the on-process temperature to 35°C [5]. The temperature range was chosen as 35 - 60°C.

To calculate the rate of oxidation of cumene hydroperoxide, we used the data from the volume of absorbed oxygen, obtained by the experimental means. Dependence of the rate of cumene oxidation on the temperature in the presence of an initiator is shown in Fig. 2.

Fig. 2 – A plot of oxidation rate of cumene hydroperoxide on the temperature

Dependence of the rate of oxidation in the temperature range (35-60°C) is given by: . With a decrease of temperature process in 5°C, the oxidation rate falls by 1,5 times, while reducing by 10°C – 3 times. Analyzing the experimentally derived data, we can conclude that the maximum oxidation rate of cumene in the presence of oxidation initiator (N- hydroxyphthalimide) was observed at 60°C (333 K).

The comparative characteristics of the breakdown products of cumene hydroperoxide, which enters the atmosphere at a temperature of 60°C and 110°C is shown below (in mol.%):

	60 °С	110 °С
Methane	12	27
Acetyl benzene	6	30
Dicumyl	11	21
α-methylstyrene	0,35	0,7

Reducing of harmful emissions during production of phenol and acetone is achieved by introducing the catalyst N-hydroxyphthalimide, that lets to reduce the temperature from 110°C till 60°C. The decrease in temperature of oxidation process of cumene in 2 times allows to reduce the number of pollutants, released into the atmosphere: acetophenone – 5 times; Dicumyl – 1,9 times; methane – 2,25 times, α-methylstyrene – 2 times.

References:

1. Кружалов Б.Д. Совместное получение фенола и ацетона. / Б.Д. Кружалов, Б.Н.Голованенко. – M.: Химия, 1983. – 200 с.

2. Кутепов А.М. Общая химическая технология. / А.М. Кутепов, Т.И. Бондарева, М.Г. Беренгартен. – М.: Высшая школа, 1990. – 512 с.

3. Пат. 2131414 Российская Федерация, МПК⁷ С 07 С 409/10 С 07 С 407/00. Способ получения гидропероксида кумола / Рон-Пуленк Шими; заявитель и патентообладатель. – № 96105025/04; заявл. 08.08.1994; опубл. 10.06.1999.

4. Андреас Ф. Химия и технология пропилена. / Ф. Андреас, К. Гребе – Л.: Химия, 1973. – 368 с.

5. Горбатенко Н.В. Дія супрамолекулярних галоїдвмісних комплексів на розпад ацилпероксидів та ініціювання ними радикально-ланцюгового окиснення: дис. ... канд. наук: 02.00.04 / Горбатенко Наталія Валеріївна. – Донецьк, 2006. – 144с.