Patented Mar. 29, 1949 2,465,834 UNITED STATES PATENT OFFICE 2,465,834 PREPARATION OF LEWISITE Paul D. Bartlett, Weston, and Hyp Joseph Dau ben, Jr., Cambridge, Mass., and Leonard J. Rosen, Canberland, Md. No Drawing. Application May 22, 1944, Serial No. 536,848 6 Clairs. (C. 260-440) 2 The invention described herein may be manu of arsenic trichloride and a solution of mercuric factured and used by or for the Government for chloride in hydrochloric acid reacts with the governmental purposes without the payment to arseraic trichloride to form a mixture of beta US of any royalty thereo. chlorovinyldichloroarsine, bis (beta-chlorovinyl) This invention relates to a method of improv chloroarsine, and tris (beta-chlorovinyl) arsine. ing catalytic syntheses typified by a union of an Vinyl chloride and small amounts of acetalde organic compound, such as an unsaturated hydro hyde are formed as by-productS., carbon, with a polar or inorganic compound. The arsine derivatives differ by the Successive It is particularly concerned with increasing the addition to the arsenic ?trichloride of 1, 2, or 3 efficiency of catalysts having moderate or low 10 rinolecules of acetylene. The reactions are repre activity in the syntheses reactions for obtaining sented as follows: higher yield rates of desired specific products with O ease of operating control. / Narrowly considered for the purpose of elucida CE -- As Cl3 = ClCE:C.As tion, an object of this invention is to provide a Yol suitable agent for promoting the catalytic ac (Chlorovinyldichloroarsine) tivity of a mercuric chloride catalyst in the ad (Primary lewisite) dition reaction of an unsaturated aliphatic hy drocarbon, acetylene, with the polar inorganic orch:CH compound, arsenic trichloride, to substantially in 2(CH2) + AsCl3= Aso crease the yield and output rate of chlorovinyldi ClcH:CH chloroarsine a War gas known as leWisite. (Dichlorovinylchloroarsine) As in various other syntheses, the early method (Secondary lewisite) of preparing lewisite involved the use of anhy orch:CH drous aluminum chloride as a catalyst. This 25 3(CH2) - As Class ClCH:CH-As catalyst has an intense activity which makes the olototy reactions complicated and at times dangerous. (Trichlorovinylarsine) With the excessively vigorous catalyst, many un (Tertiary lewisite) desired side reactions occur, such as fission and polymerization, resulting in a degradation of the 30 The rate of fixation of acetylene depends on product. In the production of lewisite with an the concentrations of the mercuric chloride and hydrous aluminum chloride, considerable heat is hydrogen chloride, the temperature, rate of inflow eWolved and Violent explosions may occur. The of acetylene, and rate of stirring. When these reaction leads to the formation in large quanti factors are made constant, the inclusion of any ties of undesired secondary and tertiary products, 35 of several metallic chlorides, as SbCl3, SbCl5, tar, and some naterials which are also explosive. FeCl3, ZnCl2, SnCl4, and CdCl2, in the reaction Accordingly, efforts have been made to find mixture leads to increased rates of acetylene fix catalysts less active than anhydrous aluminum ation. With corresponding increases in the rate of chloride, as, for example, halides of other metals formation of the products and by-products. With as Weil as the double salt, sodium-aluminum a catalytic solution of 60% HgCl2-8% HCl-32% chloride. These catalysts With noderate or low H2O, approximately saturated with the separate activity, on the other hand, give too low a rate of ninetallic chlorides, rates of acetylene fixation at reaction in a number of reactions, especially at 50° C. Were increased up to threefold over that of temperatures which are sufficiently moderate for an unpromoted Control run. The effectiveness proper control and avoidance of undesired side 45 of the promotion in increasing absorption rate is reactions. directly proportional to the molar concentration Prior to the discoveries leading to this inven of the promoters in the reaction mixture. tion, it was generally SUSpected that various metal The metallic chloride promoters are not acetyl salts present, as impurities in the reactants might ene-fixation catalysts When dissolved in hydro have a detrimental or inhibiting effect on the ac 50 chloric acid and, accordingly, do not function as tivity of a noderate catalyst. For example, ar such in the nixture, nor are they acetylenated. Senic trichloride Was found to contain chlorides of The promoters function by abstracting chloride iron, silicon, aluminum, antinony, mercury, bis ions from combination with the mercuric chloride, nuth, tin, etc. in Small amounts. On investigat Mercuric chloride in hydrochioric acid exists in ing the effects of these inpurities in the lewisite 55 the forms Hght, HgCl, HgCl2, HgCl3, HgClar and reaction, Surprisingly a number of these same the corresponding dinneric species. The species compounds proved to be promoters of catalytic containing the lower ratios of Cl to Hg function as activity when present in adequate amounts. the nore effective acetylene-fixation catalysts as In the example of the lewisite reaction, acetyl was shown by the use of different amounts of 20% ene gas passed into a stirred and heated mixture 60 hydrochloric acid to dissolve the same amount of 2,465,834 3. 4. s (gC2, solutions containing the lower Cl/Hg being in the primary lewisite reaction. The addition . t ise best catalysts. In the presence of the metallic of such a salt as antinaony, tin, zinc, or iron chioids promoters, all being good chioride ioil a C chloride is one way of reducing the chloride ion ceptors, the chloride ions are extracted from the conceintration without reducing the acidity, Since dissolved mercuric chloride species to estaiolish a 5 aii these salts form stable complex ions with new equilibriurin mixture having a great propor- C-: tion of the members with lower Cl/Hg ratios. SbCl3--Clé-2SbC4" The promoters are not consumed by the reaction and the chloride and hydrogen ion balance is not ZnCl2--Cla2ZnCl3 sufficiently altered to lead to increased hydrolysis 10 A similar result, can be achieved by the partial of the arsenic trichloride and its acetylenated replace.heist of the hydrochloric acid by Sulfuric products in the favorable cases. Increases of c;g in the catalytic solution, but the chloride ion 10-20% in the amount of vinyl chloride formed concentration is of some inport&nce izi govelin occurs with the more easily hydrolyzed pro- ing the hydrolysis of arsenic trichloride aid of moters. 15 the primary levisite produced in the reaction, Extensive studies have been made of the effects and his chioride ion concentration is more easily of the various promoters and their concentrations controlled by the use of a Salt of the SbCl3 type, upon the rates and results of the reactions. which yields back chloride ion when he equilix It was observed that with concentrations of rium is disturbed. about 1% and higher, based on the Weight of 20 Solutions containing systems of this SOrt the catalyst, the inetal halides known to func- togethe: vyith arsenic trichloride tend, on reuse, tion as chloride-acceptors made a real increase to assuine a hydrochloric acid concentration in the accelerating absorption of the unsatu- chalacteristic of the equilibria, present. In the rated hydrocarbon by the catalyst solution. The systerns under discussion, this acid concentration following table lists observed absorption rates 25 is lower than that initially present. and primary lewisite yield rates obtained When Characteristics of the effective promoters are 60% HgCl2-8%, HCl-32% H2O catalytic layers suniciarized as follows: The promoters are salts were saturated or almost Saturated with the or compounds of multivalent metals, preferably metal chloride promoters at 25° C. and the ab- of metals which exist in more than one Stage Sorptions run at 45° C. : 30 of oxidation. The promoters having the higher

Met. Chlor. Promoter None SbCls SbCls FeCl3 ZnCl2 SnCl4 CdCl2

g. Promoterfl00g. cat. Soln------None 65.4 32.0 30.9 15.6 20.4 8.0 Av. rate in lihr./100g. HgCl) ------11, 8 35.9 8 20, 0, 9, 2 17.8 5.0 g. Primary lewisiteihr.1100 g. HgCl2-- 68.0 205.3 102.4 95.0 97.0 91.2 92.3 g. Primary lewisite/hr.?.l. reactor space 245 739 369 342 349 32S 332 There are three poSSible ways in which the inolar Solubility in the catalyst Solution exhibit promoters might function: (1) the promoters 40 proportionally higher absorption promoting rates. might themselves be acetylenated; (2) they might They do not precipitate out the catalyst more function as independent catalysts, supplementing than a Smali and unt. They do not in dalgo ly the action of the mercuric chloride catalyst preS- drolysis to more than a Small extent. They con ent; (3) they might Serve as adjunctS, or tain a netal or positive constituent Which is promoters, for the mercuric chloride catalyst. 45 more electropositive than the positive metal or The first possibility is ruled out by the observa- constituent of the catalyst and also more elec tion that in the absence of arsenic trichloride, tropositive than the positive metal or positive the only product is chlorovinylmercuric chloride, constituent of the polar reactant. They do not and the promoter remains alonst entirely in absorb, cornbine or react With the organic re the aqueous phase. The second possibility is 50 actant as readily as the catalyst. eliminated since no reaction occurs Without the The foi'egoing considerations are in accord mercuric chloride catalyst present. Therefore, With the facts that antimony trichloride is a the chlorides of the other metals, such as anti- Superior prooter, zinc, Stannic, and cadmium mony chloride, act strictly as promoters for chlorides are favorable Over antimony pentachlo the line:culic chloride catalyst. 55 ride and ferric chloride in pronoting a mercuric There is evidence to show that the rate- chloride catalyst in the lewisite reaction, while determining step in the preparation of primary phosphorus trichloride gives negative results. Jewisite is the union of acetylene with the ner- Desirable properties of the promoter System curic chloride to give chlorovinylnercuric chlo- besides a low vinyl chloride loSS are a high rate ride, and that this reaction is the faster, the 60 cf absorption accompanied by Small loss of greater the fraction of mercuric chloride in forms promoter, ease of Separation of the catalyst and other than HgCl4. The equilibria, promoter from the product, and homogeneity of ---> the catalytic Solution at the end of the run. Hg++--C-->HgCl+ The absorption rate promoting effectiveness HgClt--Cl-a-2HgCl2 65 of a good promoter, such as antimony trichloride, HgCl2--Cl-a->HgCl3- Varies linearly with the concentration of the pro - --> - moter even up to about a saturation concentra HgCl3---Cl-a-2HgCla= tion in the catalyst solution. Concentrations of can all be shifted to the left by any method antimony trichloride, expressed as grams of pro of lowering the chloride ion concentration. Since 70 moter per 100 grams of catalytic solution em the potency of these mercuric species as acetyl- ployed, were 2.2, 10.8, 26.0, 51.8, and 65.4. Over ene-fixation agents decreases With increasing this concentration range there was no increase number of chlorines attached to the mercury, a in vinyl chloride formation over that of an un general shift of these equilibria, to the left is promoted controlled run, within experimental attended by an increased catalytic effectiveness 75 error. However, in obtaining optimum results, 2,465,884 5 6 other factors should be balanced against the in groupings from the catalyst and thereby cause creased rate of reaction. An increased promoter the latter to become a more effective catalyst. concentration slightly increases the proportion of Reactions such as addition, condensation, Sub less desirable secondary lewisite and tends to stitution, and rearrangement, in which the increase the loss of promoter. Also increasing catalyst exhibits its action as the result of a the ratio of the polar compound to the promoted transient coordination with a negative or elec catalytic solution increases the loss of the pro tron-donating group, are subject to this type of moter. Accordingly, it is desirable to keep the promoter action. The promoters may function concentration of the promoter and of the polar in either homogeneous or heterogeneous catalysis reactant within optimum limits. In the mercuric O and either in liquid or vapor phase reactions. chloride catalyzed lewisite reaction, satisfactory Catalysts susceptible to the type of promoter results are obtained by using about 1% of anti action herein described include organic and in mony trichloride in the catalytic solution and organic derivatives (such as halides, cyanides, having a ratio of about 1 gram of antimony tri sulfates, phosphates, hydroxides, nitrates, ace chloride to 162 grams of arsenic trichloride. 15 tates and oxides) of metals or metalloids (such In the event higher absorption rates are desir as A, B, Fe, Hg, Cd, Cu, Ag, Sb, Sn, Zn), but able, consequently with higher promoter concen are not limited by these examples. The pro trations, the promoter loss may be reduced by moters are compounds of the same type but certain expedients. For instance, it is possible preferably bear a certain relationship to the to recover all or a large part of the promoter from 20 catalyst under the reaction conditions, as pre the product by using an extraction with a solvent, viously explained, for instance, being less re Such as 18% to 20% hydrochloric acid. The active with the unsaturated hydrocarbon or hydrochloric acid solvent has the advantage of organic reactant and containing a more electro reducing the sludge cointent, and continued reuse positive metal or positive constituent. of the Wash Solution furnishes a fairly pure re 25 More specifically, promoters may be used in covered antimony trichloride. As another ex the following reactions which are catalyzed by pedient, the arsenic trichloride may be used With nercury compounds: (a) addition of hydrogen an Organic solvent, e. g., methylcyclohexane, halides and organic acids to acetylene in form Which reduces the solubility of the promoter in ing vinyl halides and vinyl esters; (b) addition the arsenic trichloride. 30 of Water (hydration) to acetylene in forming Other types of moderate catalysts besides mer acetaldehyde. curic chloride having the property of absorbing For example, using the same conditions as the unsaturated hydrocarbon, acetylene, and those used for lewisite production, if the arsenic which are Subject advantageously to a promoting richloride is Onitted, chlorovinylmercuric chlo action are cuprous cyanide, cuprous chloride, and 35 ride is formed as the main product and vinyl mercuric cyanide. These catalysts give about the chloride as a by-product; and an inert Organic Same rate of acetylene absorption as mercuric solvent may be used in the process. Omission of chloride in 8% hydrochloric acid at 25° C. When the organic solvent leads to the formation of vinyl they are used respectively at 95°, 95° and 33° C. chloride and acetaldehyde as principal products They likewise may be used in hydrochloric acid 40 in having the chlorovinylmercuric chloride react Solutions or in Solutions with other solvents as, With aqueous hydrogen chloride as the polar re for example, ethanolanine hydrochloride. actant to give varying amounts of these products, In using any of the catalysts, the proportions of depending on the concentration of the acid. In the reactants, the proportions of the catalyst these syntheses, the promoter is able to increase chosen, the kinds and proportions of the promoter 45 the rate of reaction as it does in the production and Solvents, and the temperature may be varied of Jewisite by speeding up the absorption of Within wide linits but depending upon the nature the acetylene by the catalyst. of the materials used, the product desired, and In a like manner, the promoter may be used rate desired. For example, in test runs that con With the catalyst, in a two-step process wherein sistently demonstrated the promoting effect of 50 first an unsaturated hydrocarbon is absorbed at antimony trichloride on mercuric chloride, the a promoted rate by the catalyst, and Selectively so amount of acetylene used was varied from 8,210 if desired at a suitable temperature, after which cc. to 2,90 cc., the mercuric chloride concern the catalyst absorbed hydrocarbon may be re tration in the hydrochloric acid solution was acted with another compound. varied from 30 to 60%, the antimony trichloride 55 Promoter action of the type described is also was varied from about 2% to 52% by weight of of considerable industrial importance in the addi the Solution, the amount of arsenic trichloride tion of alcohols, ethers, anhydrides, esters, or was varied from about 108 g. to 323 g., and the ganic acid halides, hypochlorites, amines and temperature was varied from 24 C. to 45° C. other polar organic compounds to alkenes, al To Sunnarize the characteristics of the 60 kadienes and alkynes. catalysts: they are polar Substances capable of Although the meanings of such terms as polar, readily absorbing the Unsaturated hydrocarbon non-polar, electropositive and electronegative reactant and preferably contain a multivalent are Well established, a brief explanation is given metal or positive constituent which is more elec herewith for clarification. It is Well recognized tronegative than the metal or positive constituent 65 that elements and groups of elements can be ar of the polar reactant. ranged in order starting with the most electro The specific results obtained have indicated positive elements, the alkali metals, at one end that the efficiency of any catalyst which func and ending with the most electronegative ele tions by virtue of its electron-accepting ability ments, e. g., fluorine, at the other end, as in the may be increased by the addition of a promoting 70 electromotive force series. The greater the sep Substance, which possesses the same kind of aration betWeen the eleinents or groups on this electron-accepting property, preferably to a Scale, the greater is the ionic character of the higher degree. The promoter may or may not bond between Such elements Or groups. On this operate as a catalyst for the original reaction, but basis there is little ionic character in C-C bonds, its principal function is to absorb negative ions Or 5 Some in the C-H bond, still more in C-O and C-Cl 2,465,834 7 8 bonds. Accordingly, the hydrocarbons are Sub Curic chloride, further increasing the rate of re stantially non-polar, and many Substituted Orr action by adding to the solution antimony tri ganic compounds are relatively polar. A polar chloride to the extent that some of the antimony compound is a compound having ionic character. trich cride becomes dissolved in the chlorovinyl Also, from the described Scale each eleinent or 5 dichloroarsine product, and recovering dissolved group has a certain relationship of electroposi antimony trichloride from said product by ex tivity or electronegativity to the others. The traction. With hydrochloric acid. trivalent arsenic ion in connparison to the di 2. In the Synthesis of chlorovinyl dichloro valent mercuric ion is more electropositive, but arSine from acetylene and arsenic chloride, the nore electronegative compared to ions of Zinc, 10 steps comprising catalyzing the reaction with iron, cadmiurn, tin and antinony. Arsenic is an aqueous hydrochloric acid Solution of mer imoire electropositive than piosphorus. Al curic chloride, further increasing the rate of re though arsenic trichloride is a poiar Compound, action by adding to the solution antimony tri it is less polar than the described polar pro: Otters chloride to the extent that some of the antimony since a 'senic is closer in electronegativity to 5 trichioride becomes dissolved in the chlorovinyl chlorine than the metals of the promoters. AC dichloroarsine product and recovering dissolved cordingly, arsenic trichloride, even though in Or. antimony trichloride from Said product by ex ganic, teads to exhibit, properties of polar organic traction. With hydrochloric acid, said antimony compounds and has a higher Solubility in orgasic chloride remaining mostly dissolved and unhy solvents tian the promoters. Likewise, the pre 20 drolyzed in Said solution. ferred catalysts are less polar than the preferred 3. The method of preparing chlorovinyl dichlo promoters, thus tending to be more soluble in roarsine Which comprises reacting a mixture of Organic Solvents than the preferred pioioisers. acetylene and arsenic trichloride at a suitable On the basis of the foregoing description, it is reaction temperature with an aqueous solution to be noted that an improved Synthesis of this in 25 of a mercuric chloride catalyst and a promoter vention involves a reaction of a substantially nOin selected from the group consisting of antimony polar Organic compound, such as an uri Saturated trichloride, antimony pentachloride, cadmium hydrocarbon, and a relatively polar organic or chloride, zinc chloride, stannic chloride, and inorganic compound, such as chloroviilyldi ferric chloride which remains mostly dissolved chloroarsine or arsenic trichloride, with the in 30 and unhydrolyzed in said solution. tervention of a catalyst of low polarity, such as 4. The method of claim 2, wherein the pro mercuric chloride, and a promoter of higher po moter is Zinc chloride. larity, such as antinony trichloride. 5. The method of claim 2, wherein the pro While the relationship of polarity of the re noter is stannic chloride. actants, catalyst and promote is a main factor 35 6. The method of claim 2, wherein the pro of the Suitability of a Substance as a proligotter in moter is antimony trichloride. the reaction, there are other factors to be coin sidered, as already explained. For instance, in PAUL, D. BARTLETT. an aqueoul.S catalytic Solution, the promoter is HYP JOSEPH DAUBEN, JR. preferably a substance which does not hydrolyze 40 LEONARE) J. ROSEN. too much, does not precipitate out too much of the catalyst, and does not react readily with the REFERENCES CETEO non-polar reagtant. While each of these factors he following references are of record in the also has a relationship to polarity, the selection file of this patent: Of a particular profiloter depends upon the par 45 UNITED STATES PATENTS ticular reactant, catalyst and conditions of re action, Nurnber Name Date It is to be understood that the invention is not 1926,638 Toussaint ------Sept. 12, 1933 limited by the Specific examples given for the pur 1934,324. Perkins ------Nov. 7, 1933 pose of illustration nor by any theory on the 50 2,183,240 Jung ------Dec. 12, 1939 mechanism of the promoter action and that FOREIGN PATENTS Various modifications come within the spirit and Scope of the invention. Number Country Date We claim: 21,134 Great Britain ------1913 1. In the synthesis of chlorovinyldichloro 55 238,520 Great Britain ------1925 arsine from acetylene and arsenic chloride, the Oi HER REFERENCES steps comprising catalyzing the reaction with Mann and Pope, “Jour. Chem. Soc.’ (London), an aqueous hydrochloric acid solution of mer Vol. 121 (1922).