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Patented July 23,‘ 1946 2,404,438 UNITED STATES PATENT OFFICE 2,404,438 PROCESS FOR THE MANUFACTURE OF OLEFIN OXIDES Theodore W. Evans, Oakland, Calif., assignor to Shell Development Company, San Francisco, Calif., a corporation of Delaware No Drawing. Application September 7, 1943, Serial No. 501,501 9 Claims. (Cl. ace-348.5) 1 2 This invention relates to the manufacture of ole?n oxides, and particularly pertains to a novel process and catalysts for the economical pro decomposition is eifected by subjecting the above or other suitable inorganic or organic silver com' pounds, such as the silver oxide and/or silver duction of ole?n oxides, particularly ethylene oxide, by the direct oxidation, in the presence of such novel catalysts, of the corresponding oxalate, at substantially atmospheric pressure to an elevated temperature which is substantially at or slightly above the decomposition temper ature of the organic silver compound subjected to such treatment. The silver catalysts employed in the catalytic conversion of ole?ns such as ethylene to the corresponding ole?n oxide have also been here tofore promoted by the incorporationthereinto of small amounts of various hydroxides, oxides or peroxides of alkali and alkali earth metals. ole?ns, such as ethylene. The invention is of particular value in that it provides a novel and economical process whereby ethylene may be readily converted to ethylene oxide, while the formation of undesirable by-products, particular ly carbon dioxide and water, is suppressed to a degree heretofore unattainable with known process and catalysts employed for such direct catalytic oxidation of ethylene to ethylene oxide. 15 The addition of these promoters ‘to silver cat The ole?n oxides, and particularly ethylene alysts resulted in an increase in the ole?n oxide oxide, are valuable compounds per se, as sol production. However,‘ this advantage has been vents, extractants, fumigants, insecticides, and always oifset'to a great extent by a correspond the like. In addition, they are highly valuable ing increase .in the formation of undesirable by intermediates in the preparation of a wide variety 20 products, particularly carbon dioxide. It is well of useful organic compounds such as alcohols, known that two'main reactions occur when an glycols, halohydrins, aldehydes, carboxylic acids, ole?n such as ethylene is subjected to direct ethers, esters, alkylolamines, resins, polymers, catalytic oxidation in the presence of the here and the like. tofore known promoted and/or unpromoted silver Processes have been disclosed in accordance 25 catalysts. In one of these reactions the ethylene with which ole?ns are directly catalytically oxi is converted to ethylene oxide, while in the other dized to the corresponding ole?n oxides. Gen the ethylene is oxidized completely to carbon di erally speaking, the catalytic conversion of ole oxide andwater. Aside from‘the fact that the ?ns, such as ethylene, to the corresponding ole formation of ‘carbon dioxide and water in the ?n oxides is effected by subjecting the ole?n and 30 catalytic oxidation of ethylene affects the ef? oxygen or an oxygen-containing gas, such as air, ciency of the process in that; it lowers the po tential yield of the desired product, viz. ethylene to certain elevated temperatures in the presence of ‘a silver catalyst. Although silver catalysts oxide, the production of carbon dioxide is also undesirable because the heat evolved during such conversion of ethylene to carbon dioxide is con - have been employed in the massive form, the use of such massive catalysts requires too much silver to render the process commercially attractive. siderably greater than that evolved during the Therefore, it has been the general practice to oxidation of ethylene to ethylene oxide, ‘thus employ the silver in an active ?nely divided rendering the control of the reaction temper state, in which case the active silver catalysts ature increasingly di?icult, if not impossible. As have been prepared, for example, by thermally 40 stated, the use of the heretofore known promoted decomposing suitable silver compounds such as silver catalysts, although increasing the yield of silver oxide, and particularly a suitable organic ethylene oxide (as compared to‘ the yields ob silver compound which, on being heated, will de tainable when the catalytic oxidation is, effected compose with the formation of the aforesaid under like conditions but in the presence of an active and ?nely divided silver catalytic material. 45 unpromoted silver catalyst), also causes a corre As organic silver compounds which may thus be ‘ spending if ‘not greaterincrease in the formation treated to produce the active silver catalysts, of undesirable by-products, e. g. the complete reference may be made to the silver salts of the oxidation of the ole?n to carbon dioxide. . carboxylic acids, such as formic, acetic, propionic, It is therefore the main object of the present butyric, isobutyric, valeric, oxalic, malic, malonic, 60 invention to provide an e?icient process for the maleic, lactic, and like acids. Although these compounds may be used, it is, well known that the silver oxalate is particularly suitable and will readily decompose with heat to form an ac tive silver catalytic materiah Generally, such 66 catalytic oxidation of ole?n hydrocarbons to the corresponding ole?n oxides. A further object of the invention is to provide a practical and eco nomical process for thedirect catalytic oxidation or‘ ethylene to ethylene oxide wherein the ratio 2,404,431; 3 of ethylene oxide to carbon dioxide in the reac promote the oxidation of ole?ns to the-curred tion products is substantially greater than that sponding ole?n oxides in the presence of active silver is not possessed by all oxygen-containing compounds of sodium and lithium, but is shown to a marked degree by the sodium and lithium salts of aliphatic carboxylic acids. This ability obtained by the heretofore known processes and by the use of the heretofore employed promoted. and/or unpromoted silver or silver-containing catalysts. Still another object or‘ the invention is the provision of a catalyst which is particu larly effective in selectively catalyzing the oxida tion of ole?ns, particularly ethylene, to the corre sponding ole?n oxides, which catalysts are sub‘_ 10 stantially free of any promoting effect on side is found to be present to a far lesser extent and often to a negligible degree in such oxygen-con taining compounds of sodium and lithium ‘as the oxides, peroxides and hydroxides of these two alkali metals. In this connection, reference is reactions which convert the ole?n hydrocarbons , ~ made to one of the examples, which includes the to undesirable by-products, particularly carbon results of a run using a sodium hydroxide-pro moted silver catalyst. It is seen therefrom that , I It has now been discovered that the above and 15 the selectivity factor of such catalyst is far below other objects may be attained by using certain that of a silver catalyst promoted with, for exam oxygen-containing compounds of sodium and ple, sodium oxalate or sodium formate. It is also lithium, namely the sodium and lithium salts of shown therein that the addition of sodium hy aliphatic carboxylic'acids, as promoters. It has droxide,'although it increased to a certain degree dioxide. been further discovered that the sodium and 20 the conversion of ethylene to ethyleneoxide over lithium salts of aliphatic carboxylic acids are particularly effective in promoting the catalytic the conversion obtained by the use of an unpro effect of silver in the oxidation of ole?ns to the the complete combustion of the ethylene to car moted silver catalyst, also materially increased corresponding ole?n oxides without substantially bon dioxide, the production of carbon dioxide increasing the production of undesirable oxida 25 being so great as togive a selectivity factor of only 0.9, as compared to a selectivity factor of 1.2 tion products. These new catalysts are claimed in copending application Serial No. 659,135, ?led for the unpromoted silver catalyst. In other April 2, 1946. With the use of these novel pro words, the presence of the sodium hydroxide, moted catalysts in the process of the present in although increasing the conversion of ethylene vention it is possible toconvert ole?ns, particu 30 to ethylene oxide, increased the complete com larly ethylene, to the corresponding ole?n oxide bustion of the ethylene to carbon dioxide to a with excellent results and with the attainment greater extent, thus lowering the selectivity factor of much greater ratios of ole?n oxideto carbon .of this silver catalyst containing sodium hydrox dioxide in the reaction products than is possible ide. The use of such a silver catalyst would there with catalysts and processes of the prior art. It 35 fore have but little economic advantage over the unpromoted silver catalyst. . has also been discovered that the novel promoted catalysts possess a selectivity factor which is not In a preferred method of preparing the acti possessed and cannot be attained when the here vated catalytic material for‘use in the execu tofore known catalysts are employed for the direct tion of the process of the invention, sodium catalytic oxidation of ole?ns to ole?n oxides. 40 and/or lithium salts of aliphatic carboxylic acids The “selectivity factor" of a catalyst as this term‘ are added in small quantities to active, ?nely di is employed throughout this speci?cation may be vided silver. The following are illustrative ex de?ned as the ratio or the percent of ole?n con amples of the promoters which may be used in verted to the corresponding ole?n oxide, to the the manufacture of the novel catalysts: sodium percent of ole?n completely oxidized to carbon 45 and lithium salts of formic, acetic, propionic, dioxide. The addition of the above-mentioned promoters, and particularly of the sodium salts of aliphatic carboxylic acids, to an adt've silver catalyst not only increases the conv'e sion of butyric, isobutyric, valeric. oxalic, malic, ma lonic, lactic, maleic acids, and the like. The ac tive ?nely divided silver may be prepared in any suitable manner, as for example by the precipi ethylene to ethylene oxide as compared to the 50 tation of the silver from solution of silver salts conversion attainable when using the same silver in the presence of a reducing agent. It may also catalyst without the promoter, or with the here-' be prepared in any of the many ways disclosed tofore known promoters, but also materially in in the art, comprising thermal decomposition of creases the selectivity factor of the catalyst. For an organic compound of silver, such as silver instance, as shown in one of the examples pre-‘ oxalate, or by the reduction at elevated temper sented hereinbelow, the addition of even minor atures of an oxygen-containing compound of sil amounts of sodium oxalate to an ‘active silver ver, such as for example silverv oxide or silver catalyst more than quadrupled the conversion of carbonate or any other silver compound capable ethylene to ethylene oxide. over ‘that obtained of reduction to active silver. when using the same catalyst ‘without any pro The sodium or lithium ‘salt of an aliphatic, 00 moter. Also, the presence of this sodium oxalate carboxylic acid may be added to the active, ?nely materially increased the selectivityfactor of the divided silver in quantities ranging from a frac catalyst. The same example shows that, whereas tion of a percent, e. g. 0.5%, to about 5% by the unpromoted silver catalyst had a selectivity weight of the active silver. This promoter is factor of 0.21, the addition of the minor amounts preferably added in such a quantity that the so of sodium oxalate raised the selectivity factor to dium or lithium in the added carboxylic acid salt 2.33, i. c. more than an eleven-fold increase in will amount to, for example, from 0.25% to the selectivity factor of the catalyst. It is readily about 2.5% by weight of the active silver in the catalyst mass. It must be stressed, however, that 70 the amount of the promoter material added'will ‘substantial increase of ole?n oxide in the reaction depend at least in part upon the method of apparent that an increase of even only a fraction . of a percent in the selectivity factor denotes a products, and therefore'a substantial increase in - preparing the catalyst, the specific promoter the economic value of the catalyst? and of the added, the activity and nature of the ?nal cat process employing such catalyst. alyst desired, and the invention is not limited ' ' ‘ It has been found that the ability to selectively 75 to any speci?c ratio of promoter to active silver. 8,404,488 ,It isvintended‘toi'use'the- optimum amount of promoter required i-for the particular .oxidation operation. - If ‘desired, more than :one sodium-or lithi ‘ salt of ‘an aliphatic carboxylic acid, or both so dim. and‘ ‘lithium salts- of aliphatic ‘carboxylic acids, ‘may be added as activating agents to‘ the v*Inca'rrying out the process bitithe'present in vention a stream "of ‘hydrocarbons comprising an ole?n, : particularly ‘ethylene, in admixture with ‘oxygen or an oxygeng-containin‘g gas'i‘e, 3.‘ air; ‘is ‘passed in a‘ continuous manner at elevated’ tem-. perature conditions over an active silver cata lyst‘‘ promoted ‘by-the presence of‘ a'promoting active silver. - The‘ activating agent or agents amount of sodium or lithium introduced into may be added to the catalytic material'during the ‘catalyst in the form of vthe sodium or lithium any phase of the preparation of the active silver; 10 salt vof an aliphatic vcarboxylic acid. To assure for example, either before or after conversion the attainment and maintenance of the desired of the silver‘ to the active state. An active sil reaction temperature, any‘ suitable means may ver catalyst particularly suitable for the process be resorted to in order to supply heat to the re of selectively catalytically converting ethylene actants onto the reaction zone, or to" withdraw to ethylene oxide maybe prepared, for example, 15 excess heat therefrom during the course of the in the following manner: .A mixture is prepared reaction. At the conditions of operational: which the ole ?n and oxygen are brought into contact with the mixture a small quantity or sodium or lithium in catalyst, the ole?n, e. g. ethylene, will react with the form of a salt of an aliphatic carboxylic 20 the oxygen to form the corresponding ole?n ox acid is added, and the mixture thus formed ide, for example ethylene oxide. In accordance is then heated to a temperature at which silver with the invention, the oxygen may be present oxalate decomposes to yield a ?nely divided sil as free oxygen or it may be employed in admix ver, this temperature being in the neighborhood a ture with other gaseous materials such as air, of about 230° C. The resulting mixture isthen 25 steam, nitrogen, carbon dioxide, etc. The free heated in a stream of a reducing gas, e. g., hydro oxygen may, if desired, be liberated or formed from oxygen-containing substances in situ at the gen, at a temperature of from about 200° C. to conditions of operation. about 300° C., and preferably at a temperature containingone part by weight of silver oxalate and two parts by weight of silver oxide. To this The ratio of oxygen to ole?n may vary widely of about 250° C., for a period of time su?icient to reduce any remaining silver oxide to active sil 30 within the scope of the invention, depending upon the conditions at which the operation is carried ver. The promoted catalyst prepared in this out. Although the oxidation of the ole?ns may manner is particularly suitable for the oxidation be eifected by employing the oxygen in amounts of ethylene to ethylene oxide and possesses ex less than the stoichiometrical amount necessary, ceptional selective promotional characteristics. The activated silver catalyst as prepared in ac 36 in the preferred embodiment of the invention the reaction is effected in the presence of an cordance with the present invention may be used amount of oxygen at least equal to and prefer as such, in the form of a powder, or in the form ably in excess of the stoichiometric amount of pellets, pastilles, pills or other shapes of de needed to combine with the olefin available in the sired size or form. This promoted active silver catalyst may or may not be deposited upon or 40 reaction zone. The process of the invention may be carried out mixed with any suitable carrying material such at any suitable temperature in the broad. range as clay, asbestos, activated carbon, charcoal, sil of from about 150° C. to about 500° C. How ica gel, alumina, pumice or the like. If desired, ever, one of the advantages of the process is that this supporting material may be incorporated into the catalytic material before or after the 45 it permits the ei?cient oxidation of olefins to the corresponding ole?n oxides and particularly of conversion of the silver to the active state. ethylene to ethylene oxide, with substantially in Although the promoted catalysts of the pres creased yields at temperatures not exceeding ent invention are particularly applicable to the about 350°C. For example, the oxidation of catalytic selective conversion ‘of ethylene to ethylene oxide, other ole?ns may be similarly 60 ethylene to ethylene oxide may be effected at a temperature in the range of from about 200° C. treated to produce the corresponding ole?n ox to about 350° C. and preferably from about 230° ides. The ole?ns capable of being thus oxidized‘ to the corresponding ole?n oxides in accordance C. to about 320° C., in thizpresence of silver acti vated by the presence of thium or sodium intro with the process of this invention are the nor mally gaseous as well ‘as the readily volatile nor 55 duced in the form of the corresponding salt of an aliphatic carboxylic acid, with an excellent mally liquid ole?ns such as ethyleneLpropylene, butylenes, amylenes and their homologues and ' suitable substitution products. The ole?ns-m‘ay yield of ethylene oxide and a minimum produc- tion of carbon dioxide. _ _ - Although additional inert diluent fluids, such be employed severally or in mixtures containing a plurality of different-species thereof, or resort 60 as nitrogen, carbon dioxide, steam, etc., may be added to the charge subjected to the catalytic may be made'to the use of mixtures thereof with oxidation in accordance with the‘proces's or the relatively unreactive substances, such as mix present invention, the e?icient operation of the tures of ole?ns and para?ins, which may be em process in the relatively low temperature range ployedwithout resorting to the separation of the ole?n or ole?ns therefrom prior’ to their being 65 greatly facilitates the problem of heat control. It has been found that as'a result of the selective subjected to the oxidation process. Such ole?ns promotional effect of the novel catalyst in the or ole?n-containing mixtures ‘may be obtained process, ‘the material decrease in‘ the tendency from any suitable source, for example the prod ucts resulting from any petroleum re?nery op toward destructive exothermic oxidation reac eration, e. g. the products resulting from the 70 tions leading to the formation of considerable simple distillation, thermal cracking, hydro genation, dehydrogenation, polymerization, etc., proportions of carbon dioxide in the reaction products substantially suppresses the need for of hydrocarbon ?uids. Also, these fractions may be obtained from processes encountered in the these additional diluent ?uids. natural gasoline industry, etc. Although it ispreferable to effect the process 75 of the present invention at pressures slightly in 2,404,488 8 7 excessoi atmospheric, the process may if desired be carried out at subatmospheric or superatmos pheric pressures. The optimum pressure to be employed will be governed by the conditions oi’ operation and the nature . or the materials treated. ' a - , . Reaction products resulting from the process may be subjected to any subsequent treatment to separate the desired constituent or constituents from the remaining reaction products. For ex ample, the ole?n oxide, e. g. ethylene oxide, may be separated from the remaining reaction prod ucts by any suitable method of separation, com 1. Silver oxide was heated for one hour at 2i;0° C. to obtain a ?nely divided unpromoted si ver. silver oxide and added promoter for one hour at 200° C. to obtain the promoted silver metal-con taining catalyst. The promoter and quantity thereof added to the silver oxide prior to heating, in percent by weight of silver oxide used. are in dicated in the following table opposite the re 1 spective catalyst number: prising fractionation, absorption, adsorption, and/or extraction. . For illustrative purposes only, reference is made to the several examples which describe certain methods of preparing the novel promoted silver catalysts and the preferred modes, conditions ' Three promoted silver metal-containing cata lysts were prepared by mixing the promoter with silver oxide and heating the resulting mixture of No. 2—1% sodium hydroxide. , No. 3—3% sodium oxalate. No. 4—3%.sodium formate. An ethylene-air mixture consisting of 28% by volume of ethylene and 72% by volume of air was and advantages of effecting the catalytic oxida 20 passed over the catalysts at a rate of about one liter of the gas mixture per 2 grams of catalyst tion reaction in accordance with the process of per hour at the temperature indicated in the table the present invention. presented below. In this table, the conversion of Example I ethylene to ethylene oxide, in percent by weight, Two silver metal-containing catalysts were pre pared in the following manner: 1. About one part by weight of silver oxalate was mixed with‘ about two parts by weight of sil is given in column A. The ?gures in column C indicate the ratio of the percent by weight of ethylene converted to ethylene oxide to the per cent by weight of ethylene converted to ethylene oxide and carbon dioxide. The selectivity factor of each catalyst based upon the indicated results ver oxide, and the mixture was then heated until the silver compounds were substantially com 30 is shown in column S. pletely converted to ?nely divided silver metal. 2. About one part by weight of silver oxalate was mixed with about two parts by weight of sil ‘ ver oxide. Sodium oxalate was then added in an 240° C 260° 0. Catalyst amount equal to about 3% by weight of the mix‘ 35, A C S A C S ture, which latter was then heated until the sil ver compounds were substantially completely 1 5.1 0.55 1.2 7.2 0.45 0.8 2 9.7 .47 0.9 6.3 .38 0.6 converted to ?nely divided silver. 3 8.0 .67 2.0 12.4 .67 2.0 Over each of the above catalysts there was 4 9.2 .74 2.8 13.3 .68 2.2 passed about the same volume of an ethylene-air 40 mixture consisting of 28% by volume of ethylene A comparison of the results presented in the and 72% by volume of air. This mixture was above table shows the advantages of effecting the passed over the catalysts at a rate of about one oxidation of ethylene to ethylene oxide in the liter of the gas mixture per 2 grams of catalyst presence of a silver catalyst containing minor per hour. In each case the catalyst was main 45 amounts of sodium oxalate or sodium formate tained at a temperature of about 240° C. over the unpromoted catalyst or even one con In the following table, column‘ A shows the taining sodium hydroxide. The addition of the conversion (in percent by weight) of ethylene to minor amounts of either sodium oxalate or so ethylene oxide, while column B shows the weight formate not only increased the conversion percent of carbon dioxide produced. The se 50 dium of ethylene to ethylene oxide to a very great ex lectivity factor is shown in the third column tent, but also decreased the total combustion of under “S.” > the ethylene to carbon dioxide, thus materially increasing the selectivity factor of the catalysts Catalyst A B S promoted with the sodium salts of the aliphatic 55 carboxylic acids. On the other hand, the addi» 1 2 No promoter ____ ._' ________________________ ._ NBsCrOi promoted ________ ..' .............. ._ 3. 0 l2. 2 l2. 0 5. 2 0. 21 2. 33 tion of sodium hydroxide, although it caused an increase in the conversion of ethylene to ethylene oxide when the oxidation reaction was effected at A comparison of'the results presented in this 240° C., also caused a material increase in the example shows that the addition of about 3% combustion of ethylene, so that the selec of sodium oxalate to a silver catalyst produced 60 total tivity factor of the silver catalyst containing so by the decomposition of the above mixture of dium hydroxide was even lower than that of the silver oxalate and silver oxide more than quad unpromoted catalyst. A comparison of the re rupled the conversion of ethylene to ethylene sults obtained at an operating temperature. of oxide, as compared to the conversion obtained C. with the unpromoted catalyst and the when using the same silver catalyst without the 65 260° catalyst containing sodium hydroxide clearly promoter. Also, this material increase in the shows the negative effects of the addition or in-_~ ethylene oxide was obtained with acarbon dioxide corporation of sodium hydroxide. production which amounted to only about one This application is a continuation-in-part ofv third of that obtained when using the'unpro the co-pending application, Serial No. 351,244, 70 moted silver catalyst. ' ?led August 3, 1940. Example [I I claim as my invention: ' ~ 1. A process for the production of ethylen One unpromoted and three promoted silver oxide by the direct catalytic oxidation of- ethylene metal-containing catalysts were prepared as fol lows: 76 which comprises reacting ethylene with oxygen 2,404,488 10 employed in amount less than the stoichiometric of from about 0.5% to about 5% by weight of a amount necessary to combine with the ethylene, sodium salt of an aliphatic carboxylic acid. and effecting the reaction at a temperature of 6. A process for the production of ethylene between about 230° C. and about 320° C. in the oxide by the direct catalytic oxidation of ethylene presence of a catalyst comprising silver metal 6 which comprises reacting ethylene with oxygen at activated by the presence of from about 0.5% to a temperature of between about 200° C. and about about 5% by weight of sodium oxalate. 350° C. and in the presence of a catalyst compris 2. A process for the production of ethylene ing silver metal activated by the presence of from oxide by the direct catalytic oxidation of ethylene about 0.5% to about 5% by weight of a lithium which comprises reacting ethylene with oxygen v10 salt of an aliphatic carboxylic acid. employed in an amount less than the stoichio '7. A process for the production of ethylene metric amount necessary to combine with the oxide by the direct catalytic oxidation of ethylene ethylene, and e?ecting the reaction at a tempera which comprises reacting ethylene with oxygen at ture of between about 230° C. and about 320° C. a temperature of between about 150° C. and about in the presence of a catalyst comprising silver 15 500° C. and in the presence of a catalyst compris metal activated by the presence of from about 0.5% to about 5% by weight of sodium formate. 3. A process for the production of ethylene ing silver metal activated by the presence of from about 0.5% to about 5% by weight of a compound of the group consisting of the sodium and lithium oxide by the direct catalytic oxidation of ethylene salts of aliphatic carboxylic acids. which comprises reacting ethylene with oxygen 20 8. A process for the production of an ole?n at a temperature of between about 200° C. and oxide by the direct catalytic oxidation of an ole?n about 850° C. and in the presence of a catalyst which comprises reacting an ole?n with oxygen comprising silver metal activated by the presence at a temperature of between about 150° C. and of from about 0.5% to about 5% by Weight of about 500° C. and in the presence of a catalyst sodium oxalate. 25 comprising silver metal activated by the presence 4. A process for the production of ethylene of from about 0.5% to about 5% by weight of a oxide by the direct catalytic oxidation of ethylene compound of the group consisting of the sodium which comprises reacting ethylene with oxygen and lithium salts of aliphatic carboxylic acids. at a temperature of between about 200° C. and 9. A process for the production of an ole?n about 350° C. and in the presence of a catalyst 30 oxide by the direct catalytic oxidation of an ole?n _ comprising silver metal activated by the presence of from about 0.5% to about 5% by weight of sodium formate. which comprises reacting an ole?n with oxygen in the presence of a catalyst selectively promoting the oxidation of the ole?n to the ole?n oxide 5. A process for the production of ethylene which catalyst comprises silver metal activated oxide by the direct catalytic oxidation of ethylene 35 by the presence of from about 0.5% to about 5% which comprises reacting ethylene with oxygen by weight of a compound of the group consisting at a temperature of between about 200° C. and about 350° C. and in the presence of a catalyst of the sodium and lithium salts of aliphatic comprising silver metal activated by the presence carboxylic acids. THEODORE W. EVANS.