The 'acids used can contain the various organic and inorganic impurities normally associated with the commercially available materials, and such impurities can be permitted to remain or can be removed as one desires.
Unreacted acids containing impurities indigenous to the process can be recovered and recycled. Reaction products The product of greatest value obtained by the process of this invention is the diester of ethylene glycol.
Obviously, the glycol moiety is attributable to the olefin reactant, while the acyl moiety of the ester corresponds to the carboxylic acid reactant or reactants. However, in the reaction, substantial amounts of valuable materials other than the diester are formed, valuable because they are precursors of the primarily desired diester product.
Such precursors include glycol monoeste'r, ethylene glycol itself and higher-boiling ether-alcohols diethylene glycol, triethylene glycol and ether-alcohol monoand di-esters.
Halogenated products are also fonmed, the halogen being a component of the catalyst system. To illustrate: assuming the carboxylic acid reactant to be acetic acid and the halogen to be bromine, the reaction products include 1,2-diacetoxyethane; 2-acetoxyethane-lol; ethylene glycol; diethylene glycol; triethylene glycol; the monoand di-acetate derivatives of diethylene glycol and triethylene glycol; ethylene bromohydrin; 2-bromoethyl acetate; 1,2-dibromoethane and brominated derivatives of the higher-boiling materials.
The liquid phase reaction medium The liquid phase reaction medium, confined within the oxidation zone, is the environment in which the ester formation reaction occurs. This medium contains the carboxylic acid reactant, the catalyst system employed, the ester products of the reaction and precursors of the desired ester products of the reaction.
Of course, dissolved ethylene and oxygen are also present. The normal composition of the reaction medium would comprise from 5 to 60 mole percent of carboxylic acid and from 5 to 60 mole percent of reaction products. The catalyst system employed The process of this invention requires an essentially two-component catalyst system. The first of these two components is cationic selenium. The second of these two components is bromide ion or chloride ion or mixtures of bromide and chloride ions.
The selenium cation can be supplied to the system in any form which in solution or suspension under the oxidation conditions will yield at least some soluble cationic selenium.
Thus, the selenium can be supplied to the system in the finely divided elemental form. Other suitable forms include the selenic acids and selenious acid as well as the inorganic salts of these acids, such as the ammonium salts and the alkali metal and alkaline earth metal salts. The oxide, oxyhalides, hydrides selenine and nitrides of selenium can also be used. Organoselenium compounds such as the alkyl or aryl selenine and haloselenines can be employed; thus, for example, such materials as methylene selenine, dimethyl selenine, dimethoxy selenene oxide, dimethoxy selenene dioxide, diethyl selenine, diethoxy selenene oxide, phenyl selenine and the halogenated derivatives thereof, such as p-chlorophenyl selenine phenyltrihydroxy selenene, diethoxy selenane dioxide, diphenyl selenine, diphenyl selenene oxide and the like are suitable.
The use of elemental selenium, selenium oxide and the selenium acids both selenic and selenious is preferred since these are the most readily available forms. The halogen component of the catalyst system can be supplied in elemental form which quickly reacts to produce chloride and bromide ion within the reaction system. Alternatively, one can use bromineor chlorine-containing compounds which are capable of yielding the corresponding ions in solution under reaction conditions.
Such compounds include the hydrohalic acids gaseous or aqueous but preferably in the concentrated aqueous form , metal halides such as the alkali metal or alkaline earth metal halides or heavy metal bromides or chlorides. Organo-halogen-containing compounds can be employed including such materials as the alkyl halides, dihalides and trihalides.
Particularly suitable organic forms include the halogenated derivatives of ethylene and the halogenated derivatives of the reaction products. For example, these materials include assuming bromine to be the halogen employed 1,2-dibromoethane; ethylene bromohydrin and 2-bromoethyl carboxylate.
Reaction conditions The various reactants employed in the oxidation reaction may be effectively used over a wide range of concentrations. The effective minimum concentrations of catalyst will depend upon temperature, residence time and the type of halogen used.
The amount of halogen elemental or as a halogen compound, collectively referred to as halogenated substance , expressed in wt.
The concentration of selenium cation present expressed in terms of equivalents of cation per equivalent of halogen can suitably vary from about The temperatures maintained in the oxidation zone may vary from about 50 C. Total pressures within the oxidation zone can be sub-atmospheric, atmospheric, or super-atmospheric, with pressure up to about 5, p. Pressures from about 20 p.
The mole ratio of oxygen to ethylene is not critical and, therefore, any suitable ratio can be used. For example, such ratios as to Of course, care should be taken to avoid formation of flammable mixtures.
Reaction time, i. Flow rates are preferably adjusted so that the rate of formation of product, measured as rate of formation of glycol diester, is from about 0. As hereinbefore indicated, the process of this invention can readily be employed in continuous operation, with the olefin reactant and molecular oxygen reactant being continuously introduced to the oxidation Zone and being continuously reacted therewithin.
In such a system, the carboxylic acid reactant normally would also be fed continuously to the oxidation zone, and the liquid phase reaction medium would normally be continuously withdrawn therefrom, the liquid phase reaction medium containing the desired ester products and their precursors.
However, it should be noted that the carboxylic acid reactant can be introduced intermittently and the liquid phase reaction medium, containing the reaction products, can be withdrawn intermittently without thereby rendering the process other than a continuous one.
The reaction can conveniently be carried out in one reaction vessel although, if desired, the reaction can be carried out in two or more vessels connected in series, parallel or both.
High-boiling ether-alcohols and their derivatives can also be recycled. The esters prepared by the process of this invention find ready use as solvents :and plasticizers. For eaxmple, ethylene glycol diacetate may be used as a solvent or an intermediate to prepare ethylene glycol or vinyl acetate. Unless otherwise stated, all parts and percents in the following examples are on a weight basis.
Example I To a one-liter titanium autoclave, fitted with an agitator, are charged grams of acetic acid, 20 grams of lithium bromide, 20 grams of water and 5 grams of selenium dioxide. After charging, the autoclave is pressured to p.
Following pressurization, a gas flow of 40 liters per hour oxygen, 60 liters per hour ethylene and liters per hour of ethane is started. Gas flow rates are measured at 0 C. Upon commencement of gas flow, heat is applied to the autoclave, and gas flow is continued while the autoclave is heated to a temperature of C. The autoclave is maintained at C. After cooling, the autoclave is depressured, and the liquid contents of the autoclave are removed and analyzed.
Analysis shows concentration of glycol moieties ethylene glycol diacetate, ethylene glycol monoacetate, ethylene glycol, diethylene glycol, triethylene glycol and the acetates of diethylene glycol and triethylene glycol expressed as equivalents of ethylene glycol diacetate of 53 wt. Example II Example I is repeated except that 2. Analysis shows a glycol moiety concentration on the same basis as that defined in Example I of Analysis shows a concentration on the same basis as that defined in Example I of Included among the suitable acids of my invention are, aliphatic acids, alicyclic mono carboxylic acids, heterocyclic acids and 3 aromatic acids, both substituted and unsubstituted.
For example, the invention contemplates the use of lower mono aliphatic acids of one to four carbon atoms such as: formic, acetic, propionic, butyric and isobutyric; intermediate mono aliphatic acids of from five to car- 'bons such as: valeric, isovaleric, caproic, enanthic, caprylic, pelargonic and capric; higher mono aliphatic acids of from 1 carbons such as: lauric, myristic, palmitic, stearic, hexacosanoic and tricosanoic; dialiphatic acids of from two to six carbons, such as: oxalic, malonic, succinic, glutaric and adipic.
The invention further contemplates the use of substituted mono aliphatic acids containing one or more functional substituents such as lower alkoxy methoxy, propoxy , chloro, cyano, lower alkylthio methylthio, ethylthio, butylthio and the like, examples of which may be cited as acetoacetic, chloroacetic, chloropropionic, cyanoacetic, methoxyacetic acid and 3- methylthiopropionic acid. Among the aromatic acids contemplated may be mentioned acids containing one or more carboxyl groups such as: benzoic, l-naphthoic, 2-naphthoic, o-toluic, -m-toluic, p-toluic, ochlorobenzoic, m-chlorobenzoic, p-chlorobenzoic, onitrobenzoic, m-nitrobenzoic, p-hydroxybenzoic, anthranilic, m-aminobenzoic, p-aminobenzoic, phenylacetic, 2,4-dichlorophenyoxyacetic, hydrocinnamic, 2-phenylbutyric, l-naphthaleneacetic, and phthalic.
The alicyclicmono carboxylic acids may contain from three to six carbons in the ring, bothsubstituted and unsubstituted, and containing one or more carboxyl groups such as: cyclopropanecarboxylic, cyclopentanecarboxylic and hexahydrobenzoic, The heterocyclic acids may contain from one to three fused rings both substituted and unsubstituted, contain one or more carboxylgroups and containing at least one and less than four hetero atoms such as oxygen, sulphur or nitrogen, examples of which may be cited as: picolinic, nicotinic, 3 -indoleacetic, furoic, 2-thiophenacarboxylic, quinolinic, 2-methylindoleacetic, 3 -chloro furoic, and 4'-nitronicotinic.
In the more preferred aspects of this invention, the carboxylic acid is an aliphatic acid or aromatic acid, but especially the monophenyl aromatic acids and the lower aliphatic acids such as the lower unsubstituted mono aliphatic acids or benzoic acid and more especially acetic acid. Theinvention further contemplates the use of mixed carboxylic acids in any desired ratio, although it is preferred to employ the same acid as solvent and acid moiety of the subsequently desired ester.
It is also within the contemplation of this invention that the final ester product may be used as the solvent.
The carboxylic acid employed may suitably be any commercially available acid, such as aqueous acids. It is preferred however, to employ commercial acids having no more than percent water, and especially less than 5 percent water, such as 98 percent acetic acid.
The acids used may suitably contain the various organic and inorganic impurities normally associated with the various commercial acids and for the purpose of this invention may remain as impurities or removed as one desires. The variable valent metal compound metal cation employed in this invention may be a single salt or mixtures.
The valence state of the metal in the initial reaction may be at any valence state normally associated'with the metaLFor example, one may initially employ the manganous, or manganic cation, the cuprous or cupric cation, cobaltous or cobaltic cation and the like. For the purpose of this invention, the only critical feature for the metals is that they have a variable valence, with I any initial valence state being applicable.
If desired, the variable metal cation may be added'in anyform which in solution, under reaction conditions, will yield at least some soluble metal ions. If it is desired to employ one variable. In its preferred aspect, the metal compound is added as its oxide, hydroxide or salt of the acid solvent. In the most preferred aspects of this invention, the carboxylic acid salt of the metal compound is employed and preferably contains the anion of an aromatic acid or aliphatic acid, particularly the anion of the unsubstituted monolower aliphatic acids such as acetic acid, propionic acid and butanoic acid, or benzoic acid, but especially acetic acid, and in the case of Te, the metal is also preferably used as the metal itself or its oxide.
The metal compound employed may desirably contain impurities normally associated with the commercially available metal compounds, and need not be purifled any further. In the preferred aspect of this invention, the commercially available compound is employed. When it is desired to use a bromine or chlorine containing compound in the initial phase of the reaction instead of bromine or chlorine itself, one may employ any compound capable upon oxidation or by other means, of producing bromide or chloride ions in solution.
For example, one may use hydrohalic acids gaseous or aqueous, preferably concentrated aqueousacid any metal halide such as the alkali, alkaline earth or heavy metal bromides or chlorides, potassium bromide, calcium chloride, manganese bromide and the like the metal bromides or chlorides corresponding to the operable metals of my invention or organic halides such as alkyl trihalides, lower aliphatic halides propylhalide, pentylhalide , cyclo lower aliphatic halides cyclohexylhalide or lower aliphatic dihalides, ethylene di-chloride, di-bromoethylene all of which are considered for nomenclature purposes to be compounds capable of producing bromide or chloride anions.
The invention also contemplates the use of a mixture of two or more halogen producing compounds, containing the same or different halogen, as well as mixtures wherein the cation of the halide compound may be the same or different from the cation of the other metal compound employed.
In the most preferred aspects of this invention, the reaction carried out in the presence of bromine or chlorine or the halogen acid, the alkaline or alkaline earth metal halides or mixtures of both chloride and bromide and especially concentrated hydrobromic acid, concentrated hydrochloric acid or potassium bromide.
The halogen employed may suitably contain impurities therein, normally associated with the commercially available halogen and in the preferred aspect of this invention the commercially available materials are employed. Accordingly, in the preferred aspect of this invention: the carboxylic acid is used as a solvent as well as the moiety for the subsequent ester, and is a lower mono aliphatic acid, especially acetic acid; the halogen is in the form of molecular bromine or chlorine or hydrohalic acid; and the metal cations are Te, Ce, Sb, or Mn such as Te and bromine or hydrobromic acid, in the bromine system and Ce, Mn or C0 in the chlorine system.
The various reactants may be employed over a wide range of concentration, the effective minimum concentrations will depend upon the temperature, time and type of halogen and metal employed. Generally, the concentration of halogen expressed in weight percent of bromine or chlorine to total solution, may be from 0. The mole ratio of oxygen to ethylene is not critical and, therefore, any suitable ratios may be used.
For example, such ratios as to The source of oxygen may be oxygen gas, or a mixture of oxygen and an inert gas such as found in air. If the carboxylic acid is to be used as the solvent as well as acid moiety, it is used in excess of the theoretical amount needed for reaction.
When an inert solvent is employed, the amount of carboxylic acid, for practical reasons, should be at least equivalent to that needed to prepare the final product from ethylene.
The temperature of reaction may vary from 80C. The time of reaction will depend to a great extent upon the concentration of reactants, and therefore, may suitably be between 1 minute to one or more days.
However, under the more preferred conditions, the reaction time may be from 10 minutes to 4 hours. As the other aspect of my invention, vinyl acetate can be prepared in both high yield and selectivity by reacting ethylene under the conditions described above to form ethylene glycol diacetate and converting this compound by any known means to form vinyl acetate.
For example, this latter reaction may be carried out by reacting ethylene glycol diacetate under pyrolyzing conditions with or without a catalyst. For example, suitable catalysts may be those with large surface areas such as porous plate chips. The esters prepared from ethylene and the various carboxylic acid compounds of this invention find ready use as solvents and plasticizers. For example, ethylene. Similarly, ethylene glycol di-benzoate may be used as a solvent or as an intermediate to prepare ethylene glycol or vinyl benzoate.
For example, the ester may be saponified with an aqueous alkali or alkali earth base, at elevated temperatures, to form the mono or di-salt and subsequent acidification to form the desired products. Alternatively, the ethylene glycol ester may be hydrolyzed with water at elevated temperatures, and preferably in the presence of at least a catalytic amount of an acid.
RUNS l To a glass lined reactor containing 10 gms. The reaction vessel is then pressurized with p. The reaction mixture is then heated with agitation, for 2 hours at C. Ethylene glycol diacetate EGDA is obtained in yields as indicated below. When using a chloride alonewithout any of the variable metals of my invention, runs 3 and 4 no ethylene glycol diacetate EDGA is formed. Further, when a bromide such as KBr run 1. Similarly, when any of the operable metals of my, invention is.
However, when employing the metals of my invention with a chloride or bromide source runs substantial yields of EGDA are observed. In fact, this combination leads to yields far in excess of the simple additive effect of the halogen and metal, and in many instances leads to yields of 5 to more than times of that which would be expected from a simple additive effect. When run 5, 13, 29 or 33 is carried out with caproic acid, palmitic acid, succinic acid, chloroproplonic acid, cyanoacetic acid, methoxyacetic acid, 3- methylthiopropionic acid, benzoic acid, p-toluic acid, 2-napthoic acid, m-chlorobenzoic acid, o-nitrobenzoic acid, salicyclic acid, p-hydroxybenzoic acid, maminobenzoic, phenylacetic, 2-phenylbutyric, 1- napthtaleneacetic, hexahydrobenzoic, picolinic, nicotinic, 3-indoleacetic, furoic, 2-thiophenaca'rboxylic or quinolinic in place of acetic acid there is obtained the corresponding ethylene glycol carboxylate compound.
Similarly, when run 8, 22 or 24 is carried out using equivalent amounts of cobalt bromide, cerium hydroxide, copper carbonate, cerium methalate, copper phenoxlate, in place of the metal compound shown, similar results are obtained. Similarly, when equivalent amounts of chlorine, lead bromide, potassium tribromide, l-chloropropane, cyclohexyl bromide, or ethylene dibromide are used in place of halogen source in runs 5 or 14, there is obtained similar results.
Similarly, when any one of runs 5,8,12,16 or 29 is in run 5, similar results are obtained. The gaseous effluent is condensed and the vinyl acetate is distilled from the liquid at C. The temperature is raised successively to C.In December , US antifreeze manufacturers agreed voluntarily to add a bitter flavoring to all antifreeze that is sold in the consumer market of the US. A process for preparing an ethylene glycol ester which comprises intimately contacting ethylene, with oxygen, a hydrocarbon carboxylic acid having up to 30 carbon atoms an effective amount of a halogen selected from at least one member of the group consisting of bromine, hydrogen bromide, alkali metal bromides, al- equivalents of halogen is from to to form the desired ester. However, in the reaction, substantial amounts of valuable materials other than the diester are formed, valuable because they are precursors of the primarily desired diester product.
Such precursors include glycol monoeste'r, ethylene glycol itself and higher-boiling ether-alcohols diethylene glycol, triethylene glycol and ether-alcohol monoand di-esters. The selenium cation can be supplied to the system in any form which in solution or suspension under the oxidation conditions will yield at least some soluble cationic selenium. The process of claim 10 wherein the variable valence metal cation is Ce, Mn, Cu or Co; the wt. Precursor to polymers[ edit ] In the plastic industry , ethylene glycol is an important precursor to polyester fibers and resins. Ethylene glycol is used as a protecting group in organic synthesis to protect carbonyl compounds such as ketones and aldehydes. Following pressurization, a gas flow of 40 liters per hour oxygen, 60 liters per hour ethylene and liters per hour of ethane is started.
There is a difference in the mixing ratio, depending on whether it is ethylene glycol or propylene glycol. A process for preparing an ethylene glycol ester which comprises intimately contacting ethylene with a hydrocarbon carboxylic acid having up to 30 carbon atoms, oxygen, an effective amount of at least one of a halogen selected from the group consisting of chlorine and a chlorine containing compound yielding chloride ions during reaction; and an effective amount of at least one of a variable valence metal cation selected from the group consisting of Ce, Sb, Mn, V, Ga, As, Co, Cu, Ag and Cr; at temperatures from 80C. Many of these involve the use of oxygen as the oxidant, with the reaction being catalyzed by noble metals of Group VIII of the Periodic Table, typically palladium. It is also within the contemplation of this invention that the final ester product may be used as the solvent. Gas flow rates are measured at 0 C. A process for preparing an ethylene glycol ester which comprises intimately contacting ethylene, with oxygen, a hydrocarbon carboxylic acid having up to 30 carbon atoms an effective amount of a halogen selected from at least one member of the group consisting of bromine, hydrogen bromide, alkali metal bromides, al- equivalents of halogen is from to to form the desired ester.
However, it should be noted that the carboxylic acid reactant can be introduced intermittently and the liquid phase reaction medium, containing the reaction products, can be withdrawn intermittently without thereby rendering the process other than a continuous one. As a still further fea ture of my invention, I have also found that vinyl acetate can be prepared in high yield and selectivity, by reacting ethylene as noted above, to form ethylene glycol diacetate and subsequently cracking this compound to form the vinyl acetate. The normal composition of the reaction medium would comprise from 5 to 60 mole percent of carboxylic acid and from 5 to 60 mole percent of reaction products. For example, ethylene feedstocks containing up to 10 mole percent ethane are employable. Further, when a bromide such as KBr run 1.
The temperatures maintained in the oxidation zone may vary from about 50 C. Particularly suitable organic forms include the halogenated derivatives of ethylene and the halogenated derivatives of the reaction products.
It is preferred however, to employ commercial acids having no more than percent water, and especially less than 5 percent water, such as 98 percent acetic acid. I have still further found that my process, unlike prior processes can be successfully employed with a variety of acids.
Upon commencement of gas flow, heat is applied to the autoclave, and gas flow is continued while the autoclave is heated to a temperature of C. It enters the environment through the dispersal of ethylene glycol-containing products, especially at airports, where it is used in deicing agents for runways and aeroplanes. Flow rates are preferably adjusted so that the rate of formation of product, measured as rate of formation of glycol diester, is from about 0. A process for preparing an ethylene glycol ester which comprises oxidizing ethylene with molecular oxygen in the presence of a liquid phase reaction medium containing a C -C hydrocarbyl aliphatic monobasic carboxylic acid, said oxidation being carried out in the presence of cationic selenium and at least one halogenated substance selected from the group consisting of elemental bromine, elemental chlorine, a bromine-containing compound yielding bromine ions during reaction and a chlorine-containing compound yielding chlorine ions during reaction. The glycol and water are separated, and the glycol recycled. The amount of organo-halogen added is equivalent on a molar basis to the amount of halogen employed in Example I.
The use of ethylene glycol not only depresses the freezing point of aqueous mixtures, but also elevates their boiling point. Obviously, the glycol moiety is attributable to the olefin reactant, while the acyl moiety of the ester corresponds to the carboxylic acid reactant or reactants.
It is important that the mixture is frost-proof at the lowest operating temperature. The reaction mixture is then heated with agitation, for 2 hours at C. Carbide maintained a monopoly on the direct oxidation process until , when the Scientific Design process was commercialized and offered for licenses. The liquid phase reaction medium The liquid phase reaction medium, confined within the oxidation zone, is the environment in which the ester formation reaction occurs.