The invention relates to a method for production of dichloropropanols from glycerol using continuous method by hydrochlonnation of glycerol with hydrochloric acid dissolved in a stream of diluted dichloropropanols, and then with gaseous hydrogen chloride.

Quick development of fuels based on methyl esters of acids contained in rapeseed oil brings in a necessity to manage glycerol which is the second product of ester formation. Glycerol produced in this process on an industrial scale, is - apart from application for cosmetics industry - more and more often used for epichlorohydrin production.

Hydrochlorination of glycerol at 105 to 120°C in the presence of concentrated acetic acid as a catalyst (L.A. Oszin; Promyszliennyje chlororganiczeskije produkty, Moskwa, Izdatielstwo Chimija 1978 r.), added to the mass in the quantity of 2 do 3% wt., is a commonly known method for synthesis of dichloropropanol isomers mixture of high concentration. The technological process includes the following stages: preparation of glycerol-acetic acid mixture, synthesis of dichloropropanols, neutralization of the post-reaction mass, and separation of pure dichloropropanols by rectification.

All newer methods for synthesis of concentrated mixture of dichloropropanol isomers are based on the method mentioned above, and they differ in catalysts used, engineering solutions of the apparatus, and carrying out the reaction under pressure.

Patent application No. WO 2006/100311 teaches a raw material base for production of glycerol, and in a broader aspect, of other polyols, application No. WO 2005/021476 teaches purity of the applied glycerol, and application No. WO 2005/054167 - extension of the range of catalysts for organic mono- and dicarboxylic acids, and their anhydrides and organic derivatives. Differences in comparison to the method reported in the cited L.A. Oshin's publication concern engineering solutions and conditions of the reaction, such as application of a reactor cascade, a column reactor, a proper range of catalyst concentration in the reaction mass, method of its recovery for instance by crystallization. In patent application No. WO 2006/106154, composition of the post-reaction mass of glycerol hydrochlorination, in which contents of sum of dichloropropanol isomers is higher than 10% molar and lower than 98% molar, is claimed.

A novelty in hydrochlorination method of glycerol, claimed in application No. WO 2006/20234, consists in carrying out the reaction under pressure from 2.5 to 44 bar at 50 to 140°C, during from 2 to 5 hours. In the invention, catalysts that belong to the group of carboxylic acids, carboxylic acid anhydrides, acid chlorides, esters, lactones, lactans groups are used. From among of carboxylic acids, acids containing from 1 to 60 carbon atoms in the molecule are claimed. From among of carboxylic acid anhydrides, acetic acid anhydride, propionic acid anhydride, butyric acid anhydride etc. are claimed. From among of acid chlorides, 6-chlorohexanoic acid, 5-chloropentanoic acid, 4-chlorobutyric acid etc. are claimed. From among of esters, ester of glycerol, ester of ethylene glycol and ester of poly(propylene glycol) with carboxylic acids are claimed. From among of lactones and lactans, ε-caprolactone, γ-buthyllactone, δ-valerolactone are claimed. While the reaction is being carried out, water forming as a result of it is not carried off, and the post-reaction mixture is subjected to distillations in order to separate the unre- acted hydrogen chloride dissolved in water (hydrochloric acid), the concentrated reaction product being a mixture of 1,3- and 2,3-dichloropropanol isomers, and a residue consisting mostly of polyglycerols and their esters.

In the examples, acetic acid added to glycerol in quantity of 4% is emphasized, and pure or raw glycerol is used as a raw material, requiring precipitation formed from sodium salts introduced to the reaction medium with raw glycerol to be removed after reaction by filtration. Description of WO 2006/100317 reserves utilization of metallic and non-metallic materials resistant to chlorinating agents for production of equipment and piping for hydrochlorination reaction of polyols. Among metallic materials, tantalum, zirconium, titanium, platinum and their alloys, alloys of molybdenum, nickel and copper, and also alloys of gold and silver are claimed; and among non-metallic materials, elastomers, thermoplastics, glass, ceramic, metalloceramic laminates, fireproof materials, self-curing agents, impregnated graphite, carbon, glass, enamel, porcelain and stoneware are claimed. These materials are resistant in the temperature range from 0 to 200°C. In the method according to Polish patent application No. P-383486, a mixture of 1,3- and 2,3-dichloropropanols is obtained in a cascade of four tank reactors with intersecting feeding of each reactor with gaseous hydrogen chloride and serial flow of the liquid reacting mass through the reactors in a way ensuring that glycerol, the catalyst and part of unreacted alpha- and beta-monochlorohydrins form the cube of the column, in which concentrated dichloropropanols, containing a port of the catalyst used for the reaction in the form of mono- and diester of 1,3-dichloropropanol with adipic acid with contents in the range of 80-95% molar of its feed to the reaction and gaseous hydrogen chloride, are separated, is introduced to the first reactor of hydrochlorination; post-reaction mass from the first reactor is directed to the second reactor, and from it - successively to the third and the fourth reactor, to which gaseous hydrogen chloride is fed crosswise; the process is carried out at 115 to 125°C, and times of stay of the mixture in the first, second, third, and fourth reactors are selected from the range of 1.5 to 2.5 hours in a way ensuring at least 98% conversion level of glycerol after the second reactor, and total contents of 1,2- and 1,3-dichlopropanols after the fourth reactor not lower than 33%; water from the reaction is collected together with a part of the formed mixture of 1,3- and 2,3-dichloropropanols in vapour phase from each of the cascade reactors, and separation of the concentrated product from the fourth reactor's decoction is carried out in a rectifying column with at least 28 theoretical plates, while the decoction is introduced on the plate between 10 and 18 theoretical plates from the bottom, and unreacted alpha- and beta-monochlorohydrins are returned to the first reactors of the process of glycerol hydrochlorination.

The essence of the method of formation of a mixture of 1,3- and 2,3-dichloropropanols forming as a result of glycerol hydrochlorination with gaseous hydrogen chloride under pressure of 700 to 900 kPa, in the presence of dicarboxylic acids, for instance adipic acid, or monocarboxylic acids, for instance acetic acid, as catalysts with concentration in the reacting mass varying in the range of 0.0005 to 0.0020 mol/L, disclosed in patent application No. P-383987, consists in that hydrochlorination reactions with gaseous hydrogen chloride are started in a flow reactor with similar structure as a tubular reactor, in an adiabatic way with countercurrent flow of partially reacted glycerol and fresh hydrogen chloride, initiating them at temperature in the range of 115 to 125°C, at molar ratio of hydrogen chloride to glycerol in the range of 2.1 to 2.4, in time from 45 to 90 minutes, and terminating them in a absorption column with unreacted gaseous hydrogen chloride from the flow reactor, working adiabatically under countercurrent flow of fresh, initiating them at temperature in the range of 115 to 125°C, in time no longer than 15 minutes. Unreacted hydrogen chloride from the flow reactor is combined with hydrogen chloride from the distillate from the column dewatering the post-reaction mass from the flow reactor. Dewatering of the post-reaction mass is carried out in a rectifying column working under pressure close to atmospheric pressure, maintaining column top pressure in the range of 101.3 to 130 kPa, in a way ensuring that the column distillate contains a mixture of 1,3- and 2,3-dichloropropanols with total concentration of at least 40% wt. of dichloropropanols apart from hydrogen chloride and water, and that it does not contain components with boiling points higher than boiling point of the mixture of dichloropropanols. After dewatering, the post-reaction mass is subjected to further rectification in order to separate the rest of the obtained mixture of 1,3- and 2,3-dichloropropanols by method known in the art.

Document No. EP 2093221 teaches carrying out the reaction of glycerol hydrochlorina- tion in a column bubble reactor with glycerol and gaseous hydrogen chloride feeds from the bottom. The reaction runs in the presence of oxalic acid with concentration in the range of 0.5 to 10% wt. Separation of the mass after hydrochlorination is carried out in two rectifying columns, with products being collected at their tops, and streams from the cubes are partially recirculated to the bubble reactor, while the rest - to third rectifying column for better distilling off of useful compounds. From the cube of the third column, a waste residue is carried off. Fill level of the bubble reactor with the liquid is at least 5 m. From the top of the first rectifying column, water-dichloropropanol azeotrope is carried off, and from the top of the second rectifying column dichloropropanol is carried off.

In patent application No. WO 2008/074733, catalytic halogenation of aliphatic compounds containing at least one hydroxyl group is described. An organic polymer, containing at least one carbonyl group in its chemical structure, is a catalyst. Catalyst vapour pressure at the reaction temperature is lower than 1 mbar, and average molecular mass is not lower than 500 g/mol, the catalyst is soluble in the reaction mass. A polymer or an organic flocculant are catalysts, including polyester amide, highly branched poly- acrylamide polymer. Compounds containing at least one hydroxyl group are C ₂ - C ₄ o hydrocarbons with linear or branched chain. The reaction temperature is 20 to 160°C. Russian patent No. 2358964 discloses a method of carrying out the reaction of glycerol hydrochlorination with gaseous hydrogen chloride in the presence such catalysts as silica gel, aluminium oxide, activated carbon, ionites containing acidic groups. The reaction temperature is 100 to 140°C. Glycerol conversion reaches 96.5%, and reaction selectivity to dichloropropanols - 69.5%.

The process of glycerol hydrochlorination according to patent application No. WO 2009/066327 is carried out in a cascade of two reactors working under varied pressures, the first one - under pressure of 1 to 4 bar, the second one - under pressure of 6 to 10 bar, at 90 to 130°C. The liquid leaving the first reactor partially evaporates, and the vapour phase is fed to a column, in which dichloropropanols react to epichlorohydrins in dehydrochlorination reaction. The liquid carried off of the second reactor is subjected to two-stage evaporation; the first stage under working pressure of the first reactor of the cascade, delivering a stream containing hydrogen chloride, recirculated into the first reactor; the vapours from the second stage flow to a dehydrochlorination column, and the liquid from the evaporation second stage - to a rectifying column working under high vacuum, isolating dichloropropanols as distillate. Acetic acid and its glycerol ester, carboxylic acids are catalysts of hydrochlorination reaction.

Patent application No. WO 2009/075402 describes use of a heteropolyacidic catalyst for synthesis of dichloropropanol of glycerol. Heteropolyacidic catalysts are selected from among groups containing a eggin type heteropolyacid, in which the ratio of the central atom to the polyatom amounts to 1:12 Wells-Dawson type heteropolyacid, in which the ratio of the central atom to the polyatom amounts to 2:18. Heteropolyacid types are as follows: molybdenum-tungsten-phosphoric acids, molybdenum-vanadium-phosphoric acids, molybdenum-tungsten-siliceous acids. The reaction is carried out in homogeneous or heterogeneous phase, at 50 to 200°C, under pressure of 1 - 50 bar, for a period of from 10 minutes to 50 hours.

Process of hydrochlorination of glycerol according to application No. WO 2009/104961 consists of two stages. In the first stage, glycerol reacting with hydrogen chloride in molar ratio from 1 to 100, forms a mixture containing alpha-monochlorohydrin as the main component. Then, in the second stage alpha-monochlorohydrin contained in the mixture, reacts with hydrogen chloride in molar ration of 1 :100, forming dichloropropanols. The mixture after the first reaction stage contains at least 25% wt. of alpha- monochlorohydrin. Mono-, di- and tricarboxylic acids of Cj - C] ₂ series are catalysts. Then, American document No. US 7473809 reserves a continuous hydrochlorination of glycerol with minimum concentration of 50% wt. with gaseous hydrogen chloride in the presence of acetic acid catalyst, using continuous method, without a solvent, in at least one reactor, in temperature range of 70 to 140°C, with continuous carrying off water forming as a result of the reaction, by distillation under educed pressure. Together with water, 1,3-dichloropropanol and 2,3-dichloropropanol are partially carried off. Identical parameters of hydrochlorination with gaseous hydrogen chloride are used in the method of 1,3-dichloropropanol and 2,3-dichloropropanol synthesis from liquid stream containing at least 50% wt. of monochlorohydrins.

According to patent No. PL 198551, hydrochlorination of glycerol is carried out with dry hydrogen chloride, using formamide as catalyst. Hydrochlorination is carried out at 110 to 130°C with introduction of hydrogen chloride to the reaction mass under pressure higher than atmospheric pressure.

According to patent application No. P.383157, hydrochlorination of glycerol is carried out together with a solution containing diluted dichloropropanols, hydrochloric and acetic acids, recirculated from the dichloropropanols synthesis process.

A common feature of all quoted method consists in formation processing of dichloro- propanol isomers mixture into epichlorohydrins, apart from sodium and calcium chlorides generated in reaction of dehydrochlorination of dichloropropanols to epichlorohydrins with soda lye or whitewash, and additional quantities of chlorides in the reaction of hydrogen chloride absorbed in water in the stream from dewatering of the mass after hydrochlorination of glycerol, in the so-called acidic dichloropropanols stream. De- watering is a necessary process during isolation of dichloropropanols stream from the mass after hydrochlorination of glycerol. Chloride ions from dissolved hydrogen chloride, carried off with waste water from epichlorohydrin synthesis of dichloropropanols are an additional burden in the stream requiring purification.

The aim of the invention was to develop a method of obtaining of glycerol, dichloropropanols streams with concentration and composition allowing to use them directly in epichlorohydrin synthesis installation.

Unexpectedly, it turned out that it is possible to obtain of glycerol, dichloropropanols stream with concentration over 90 cg/g, and dichloropropanols stream with con- centration of about 10 cg/g, containing only insignificant quantities of chlorine compounds. Thanks to this, these streams may be used directly in installations of epichloro- hydrin synthesis of dichloropropanols, without a necessity of chlorine compounds removal, and also without a necessity of dewatering.

The essence of the method according to the invention consists in the fact that hydrochlorination of glycerol is carried out in two stages; in the first stage, glycerol is subjected to wet hydrochlorination, with hydrochloric acid contained in the stream of acidic dichloropropanols, then the post-reaction mass from the first hydrochlorination stage is directed to a reaction column, in which completing the reaction of residues of dissolved hydrogen chloride is carried out as well as separation of the post-reaction mixture to diluted dichloropropanols stream and decoction stream, which is directed to the second stage, pressured hydrochlorination with dry gaseous hydrogen chloride; the post-reaction mixture after the second hydrochlorination stage is directed to a distillation column, in which dewatering is carried out; the distillate from the distillation column is directed as stream of acidic dichloropropanols to the first stage of glycerol hydrochlorination, and the decoction being a stream of concentrated dichloropropanols, is subjected to rectification.

Preferably, the first stage of glycerol hydrochlorination is carried out under pressure close to atmospheric pressure in times in the range of 40 - 60 hours.

Preferably, parameters of the first stage of glycerol hydrochlorination are chosen in the way ensuring that the stream of diluted dichloropropanols after rectification column contains no more than 5 cg/g of unreacted hydrogen chloride.

Preferably, in the second stage, hydrochlorination is carried out with gaseous hydrogen chloride under pressure of 700 - 900 kPa no longer than for 90 minutes.

Preferably, to the first stage of reaction of glycerol hydrochlorination with hydrochloric acid, gaseous hydrogen chloride is introduced which was not absorbed in water during dewatering of the post-reaction mass from the second stage of hydrochlorination with gaseous hydrogen chloride.

Preferably, in the second stage of hydrochlorination, gaseous hydrogen chloride from allyl chloride production using dry method of rectification isolation of hydrogen chloride from the mass after propylene chlorination, is used. Preferably, the stream of diluted dichloropropanols is directed to epichlorohydrin installation.

Preferably, the stream of concentrated dichloropropanols is directed to epichlorohydrin installation.

Thanks to recirculation of acidic dichloropropanols stream that form as a result of dewatering of post-reaction mass from hydrochlorination with gaseous hydrogen chloride, to the system of glycerol hydrochlorination, dissolved in a stream of acidic dichloropropanols hydrogen chloride, after reaction is finished, a distillate forms in the rectifying column, being a stream of diluted dichloropropanols with spent quantity of hydrogen chloride dissolved in it, with concentration not exceeding 5% wt. Its average value amounts to 2.5% wt. Pressurized hydrochlorination of the decoction from the column of separation of dichloropropanols gaseous stream diluted with hydrogen chloride leads to a total conversion of glycerol, and selectivity of glycerol conversion to total quantity of dichloropropanol isomers exceeds 85%. Consumption of gaseous hydrogen chloride is lower than in the case of the earlier know methods by 0.09 kg per 1 kg of glycerol used in hydrochlorination.

Example 1 - comparative example

1 kg/h of glycerol with purity of 99.5% wt. and gaseous hydrogen chloride in molar ratio towards the introduced glycerol amounting to 2.19, are fed to the reactor system. Working parameters of the reactor system are as follows: reaction temperature 70 - 140°C, pressure 1 - 10 bar, reaction time from 30 minutes to 2 hours. Mass leaving the reactor expands, and the gases are absorbed in a column sparged with glycerol. The liquid is subjected to dewatering under pressure close to atmospheric pressure, at column top temperature of 102°C. Product in quantity of 0.85 kg/h is obtained, composed of:

1 ,3-dichloropropanol: 38.54 cg/g,

2,3-dichloropropanol: 1.75 cg/g,

water: 42.50 cg/g,

hydrogen chloride: 17.21 cg/g.

The distillate is a monophasic liquid, called a pseudo-azeotrope in the literature, and its formation occurs in all known methods of glycerol hydrochlorination to dichloropropanols. Decoction from dewatering of the post-reaction mass is directed to a rectifying column in order to isolate a stream of concentrated dichloropropanols from it. The col- umn works under pressure of 5 kPa, column top temperature of 91°C. from the top of the column, stream of concentrated dichloropropanols is collected in quantity of 0.86 kg/h and the following composition:

1 ,3-dichloropropanol: 91.43% wt.

2,3-dichloropropanol: 8.25

water: 0.32.

Adipic acid mixed with glycerol is a catalyst of this reaction, with acid concentration in glycerol amounting to 2.4 cg/g. Conversion of glycerol: complete, selectivity of the reaction with regard to sum of dichloropropanol isomers: 85%. Hydrogen chloride consumption in relation to 1 kg of glycerol: 0.87 kg.

Example 2

Method of glycerol hydrochlorination according to the invention is illustrated by a block diagram of processes and operations shown in the Figure.

Hydrochlorination of glycerol is carried out in two stages; the first stage being wet hydrochlorination, carried out with hydrochloric acid contained in the stream acidic dichloropropanols, and the second stage, dry hydrochlorination, is carried out using gaseous hydrogen chloride.

1 kg/h of glycerol (stream 1) with purity of 99.5 cg/g, and distillate from dewatering of the mass after the second reaction stage, called acidic dichloropropanols (stream 3) in quantity of 0.80 kg/h, are fed to the reactor system of wet hydrochlorination. Working parameters of the reactor system for wet hydrochlorination are as follows: reaction temperature 85 - 90°C, pressure close to atmospheric pressure, reaction time 40 hours. Post- reaction mass is directed to a reactive column, in which completing the reaction of dissolved hydrogen chloride is carried out. Stream of diluted dichloropropanols (stream 4) is collected as a distillate. The column works under pressure close to atmospheric pressure, column top temperature is 107°C. Decoction from the column is directed to dry hydrochlorination with gaseous hydrogen chloride (stream 2). The reaction is carried out adiabatically in the temperature range of 120 - 150°C, under pressure of 800 kPa, for 60 minutes. The post-reaction mass is dewatered in a column working under pressure close to atmospheric pressure, at the column top temperature of 106°C. Distillate of the column called acidic dichloropropanols stream, is directed as a carrier of hydrogen chloride in wet glycerol hydrochlorination, to the first stage, and a decoction is isolated from the stream of concentrated dichloropropanols (stream 5) as a distillate from the rectifying column, working under lowered pressure of 3.5 kPa, at the column top temperature of 90°C and concentrated dichloropropanols flow of 1.12 kg/h. Acetic acid is the catalyst of the reaction, and the acid's concentration in the reacting mass amounts to 0.86 cg/g. Consumption of hydrogen chloride in relation to 1 kg of glycerol amounts to 0.76 kg.

Table. Compositions of streams.

Stream number/ Compound name 1 2 3 4 5

Glycerol 99.50

Water 0.50 40.53 79.89 2.43

Hydrogen chloride 99.50 24.30 2.52 0.22

Inerts 0.50

Acetic acid 2.25 6.08 0.08

1 ,3-Dichloropropanol 31.48 11.33 91.02

2,3-Dichloropropanol 1.00 0.46 5.07 beta-Monochlorohydrin 0.08 0.85

1,3-Dichloropropanol acetate 0.28 0.02 0.15

Glycerol acetate 0.06 0.11 beta-Monochlorohydrin acetate 0.07

Polyglycerols 0.02