J. Cleaner Prod., Vol. 2. Na. 3-4, pp. 181-184, 1W4 Elccvicr Scicncc Lid Prinicd in Greai Briiitin 0959-6526(95)00024-0 W59-6526194 $10.00 -+ 0.00 Clean technology in the production of epichlorohydrin Jowi W. Bijsterbosch, A. Das+ and F.P.J.M. Kerkhof* RIZA, Institute for Inland Water Management and Waste Water ïreatment, Ministry of Transport, Public Works and Water Management, PO Box 17, 8200 AA Lelystad, The Netherlands *Comprimo Consulting Services, PO Box 58026, 7040 HA Amsterdam, The Netherlands The conventional production of epichlorohydrin takes place via allyl chloride and dichlorohydrin. A major disadvantage of this chemica1 process is the formation of a large amount of chiorinated organic by-products, which are found panially in the voiuminous effluent. In order to reduce thic emicsion to surface water, measures have to be taken. Technica( measures varying from end-of-pipe techniques to alternative processes have been evaluated. Application of end-of- pipe techniques is not the optimal solution for emission reduction, either technically or economically. Results from in-proces measures focused on reduction of the amount of waste water and contaminants are more promising. However, the development of an alternative route is necessary in order to obtain a process with minimal emiscions and minimal costs. Keywords: clean technology; epìchlorohydrin; chemica1 industry Introduction water treatment facilities. However, the EOCI reduction obtained is considered to be insufficient In the early 19SOs, the first industrial production of from an environmental point of view. epichlorohydrin (ECH) took place. Nowadays, therc Within the frlimework of the Dutch government are about 20 production locations worldwide at which programme SPA (focused on pollution prevention, ECH is produced by the conventional route starting clean technoiogy and advanced waste water treatment) , with propenc and chlorine via allyl chloride (AC) and u project has been set up by RIZA (Tnstitute for Inland dichlorohydrin (DCH) to ECH. The world production Water Management and Waste Water Treatrnent) capacity of arnounts to about kton per year. ECH 800 ond Comprimo Consulting Services (engineering and is mainly used for the production of epoxy resins ECH consulting company). in which the possibilities of end- (about 50% of the ECH produced) and glycerin (about of-pipe techniques, in-process measures and clean 20%). The primarily chlorine-free epoxy resins are production processes for reduction of the EOCI applied in paints, electric circuits, construction, gum, emission to surface water are compared'. and so on. Important properties of epoxy rcsins are chemica1 inertness, insensitivity to corrosion and aggressive chemicals, and good electrical isolation and adhesion properties. ECH is considered US an Conventional production of ECH irreplaceablc chemica1 compound for the production of epoxy resins at tlie moment. The chernistry of ECH production is briefly discussed. A major problem with the conventional production Details about technica1 ospects of this production process for ECH is the formation of a large arnount process can be found elsewhere'. The synthesis of of chlorinated by-products, which are found purtially ECI-I can be divided into four steps: in the voluminous effluent. The amount of by-products is about 0.3 kg per kg ECH produced. The by-products e synthesis of allylchloride (AC) are generally considered as waste and incinerated. 0 synthesis of dichiorohydrin (DCH) Without waste water treatment facilities, about 1 to synthesis of epichlorohydrin (ECH) 3 g EOCI (extractable organochíorine cornpounds) per synthesis of hypochlorite (HOCI) kg ECH produccd is present in the effluent. In western countries, ECH production plants usually have waste The main reaction equations are given in Scheme 1. J. Cleaner Prad. Volume 2 Nurnber 3-4 181 Clean technology in ECH production: J. W, Bijsterbosch et al. H2C = CH-CH-j + Cl2 + H2C = CH-CH2CI + HCI propene chlorine allyl chloride hydrochloric acid H2C = CH-CHICI + HOCI + CHZCl-CHOH-CH2Cl + CH20H-CHCCCH2CI allyl chloride h ypochlorite 1,3-dichlorohydrin 1,2-dichlorohydrin CH2CCCHOH-CH2CI + kCa(OH)2 .+ CH2CI-HC-CH2 f fCaC12 + H20 b' 13-dichlorohydrin calcium hydroxide epichlorohydrin calcium chloride Scheme 1 Reaction equations for the synthesis of (1) allyl chloride, (2) dichlorohydrin, and (3) eipichlorohydrin Synthesis of AC 40 m3 per ton ECH) originates from the DCH synthesis. The effluent contains not only CaCl, in high concen- The synthesis of AC takes place by reaction of propene tration, but also EOCI compounds. Typical concen- with chlorine at a temperature of 500-520"C (equation trations are 25-75 I-], which corresponds to an (1) in Scheme I). The selectivity of this reaction is mg EOCl ernission of 1-3 kg per ton ECH produced. In rather low; by-products such as mono- and dichloropro- some cases, the effluent of the ECH plant is biologically pene and mono- and dichloropropane are formed. treated before it is emitted to surface water. Generally the compounds are only partially removed by Synthesis DCH EOCI of biological treatrnent. Therefore, additional measures "he reaction of AC and HOC1 to form DCH is are necessary . performed in water at a temperature of 30°C (equation In this paper, three points of view for ernission (2) in Scheme I). Excess water has to be used in order reduction are considered: (i) end-of-pipe techniques to prevent formation of an organic phase, as the and combinations of end-of-pipe techniques; (ii) in- undesirable side-reaction of AC to form 1,2,3-trichloro- process measures; and (iii) alternative, cleaner pro- propane (TCP) takes place in the organic phase. The cesses. It wil1 be shown that for the production of low solubility of AC in water makes the large arnount ECH, application of most end-of-pipe techniques is of water necessary2. Besides TCP, chlorinated ethers insufficient for reaching an EOCI level of 0.1 mg I-'. are forrned as by-products. They originsite from From both an environmental and an economic point the reaction of the reactive intemediate species of view, in-process measures and especially alternative (chloronium ions) with DCH. Their formation is process routes are much more promising. suppressed by the large arnount of water. Application of end-of-pipe techniques Synthesis of ECH Several end-of-pipe techniques and combinations of ECH is forrned by dehydrochlorination of DCH with these techniques are theoretically considered for treat- Ca(OH)* in water at a temperature of 90°C (equation ment of the ECH effluent. These include (i) biological (3) in Scheme 1). ECH is irnrnediately rernoved treatment, (ii) biological treatrnent, reverse osmosis from the solution in order to prevent formation of and evaporation of the concentrate flow, (iii) biological monochlorohydrin and consequently glycerol3. (MCH) treatment and active-carbon adsorption, (iv) biological treatment, active-carbon adsorption and wet-air oxi- Syiithesis of HOC1 dation for regeneration of the carbon, and (v) evapor- The HOC1 solution is used in the DCH synthesis is ation. prepared by the reaction of chlorine and calcium Table I shows the assumed removal levels and a hydroxide (Ca(OH)2). HOCI is partially converted rough estirnate of the costs of the techniques for a into other chlorine-containing inorganic compounds, typical production plant with a capacity of 24 kton which play a role in the formation of chlorinated per year. By biological treatment, about 50% of the organic by-products. EOCl is removed. Additional application of reverse osmosis or active-carbon adsorption results in EOCI Environmental aspects of the conventional removal of 90%. Evaporation yields 100% EOCI process removal. Only by application of evaporation can the desired EOCl level of 0.1 mg I-' be reached. The As mentioned earlier, the conventional production costs of this technique are estimated to be about 800 process for ECH is characterized by a large arnount guilders (fl) per ton ECH produced, which is high of by-products and a voluminous waste water flow. In compared to the cost price of ECH (about 3000 nearly al1 processes, the by-products (-0.3 kg per kg guilders per ton). Application of the other techniques ECH produced) have to be considered as waste and is cheaper, but their performance is insufficient. are incinerated. About 80% of the effluent (about It is concluded that application of end-of-pipe 182 J. Cleaner Prod. Volume 2 Number 3-4 - Clean technology in ECH production: J. W. Bijsterbosch et al. 'ïnhle I EOCI rcmoviil :iiid estimute i)Iihe costs for end-af-pipe techiiiques applied at an ECH plant with a production capacity of 24 kton per ycar' EOCI Costs Costs Costs 'ïcchniquca removal ('70) (film3) (iüton ECH) (Wkg EOCI) -- - - ____._I_ - -~. Biological triiatriiclii 50 6 240 400 Biologica1 trciiitncni iictivc-carbon adsorption 90 9 360 330 Biologiciil trcatrneiii . aciivc-carbon adsorption + wet-air oxidaiion 90 6 320 300 Biolagicol ticatincnt + reverse osmoris + cvaporation 90 16 640 590 Ev:ipor:iiioii 100 20 800 670 techniques is not thc optima1 solution for EOCI the effect of a measure on the final EOCI emission, as cmissioi? rcduction. This is caused by the large amount a measure can result in different effects. The effect of of waste water which has to be treated (-40 m3 per the desired minimization of the amount of water is ton ECH produced). It is advisable to reduce the discussed as an example. amount of waste water first by in-process measures Excess water is prìmarily applied for preventing the iind subsequently treat the smaller waste water flow. formation of by-products. With excess water, formation of the organic phase is prevented. So, TCP formation In-process measures onginating from AC in the organic phase does not occur. Excess water also limits the formation of ether In-proccss mcasures are airned at reducing the arnount and TCP. Minimizing the amount of water wil1 result of wiistc water and the rtmount of EOCI in the effluent.