United States Patent (19) [11] 3,887,695 Plentovich et al. (45) *June 3, 1975

54 PRODUCTION OF SODUM HYDROSULFTE FROM FORMATES 56 References Cited (75) Inventors: Jack Plentovich, Nansemond UNITED STATES PATENTS County; Charles Ellis Winslow, Jr., 3,41 1,875 1 / 1968 Yoshikaww et al...... 2311 16 Norfolk; Mearl A. Kise, Portsmouth, 3,576,598 4/1971 Plentovich et al...... 2311 16 all of Va. FOREIGN PATENTS OR APPLICATIONS (73) Assignee: Virginia Chemicals Inc., 1,148,248 4/1969 United Kingdom...... 2311 16 Portsmouth, Va. * Notice: The portion of the term of this Primary Examiner-Earl C. Thomas patent subsequent to Apr. 27, 1988, Attorney, Agent, or Firm-David H. Semmes has been disclaimed. 57. ABSTRACT 22 Fed: Nov. 16, 1970 Method for the production of anhydrous sodium hy 21 Appl. No.: 89,720 drosulfite (Na2SO4) by feeding together solutions of Related U.S. Application Data sulfur dioxide (SO) and methyl alcohol (CHOH) and sodium hydroxide (NaOH), sodium formate 63 Continuation-in-part of Ser. No. 9,078, Feb. 5, 1970, (HCOONa) and water into a reactor containing a wa Pat. No. 3,576,598. ter-miscible alcohol; stirring and heating under pres sure, while venting carbon dioxide (CO); cooling and 52 U.S. C...... 4231515 recovering by filtering hydrosulfite solids. 51 int. Cl...... C0b 17/98 58) Field of Search...... 2311 16; 4231515 6 Claims, 2 Drawing Figures

FIRST FEED SOLUTION: SECOND FEED SOLUTION THIRD FEED SOLUTION: COMPLETEY DISSOLWMG MEHY ACOHOL ABSORBING S02 IN NOOH AND HCOONG IN AND METHYL. ALCOHO H20 AND HEATING METHYL FORMATE

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VENTING FEEDING TOGETHER, WHE STRRING C02 AND HEATING E areer --ScotNTsCOOING REACTOR ...... 3,887,695 SHEET 1

FIRST FEED SOLUTION: SECOND FEED SOLUTION THIRD FEED SOLUTION: ABSORBING SO2 IN COMPLETELY DISSOLVING METHY ALCOHOL 2 NaOH AND HCOONC N ARD METHYL ALCOHOL H2O AND HEATING METHYL FORMATE B ry C

FEEDING TOGETHER, VENTING WHE STRRING C02 AND HEATING COOLNG REACTOR y F - coNTENTs

G RECOVERNG BY FILTERING No. S2 04

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3,887,695 2 PRODUCTION OF SODIUM HYDROSULFITE ing to the process described in U.S. Pat. No. 2,010,615 FROM FORMATES yielded sodium hydrosulfite with a maximum purity of 85% and yields of 50 to 60% based on sulfur dioxide CROSS-REFERENCES TO RELATED and 30 to 35% based on sodium formate. The dried APPLICATIONS 5 product appeared to be more dusty and less stable. A continuation-in-part of PRODUCTION OF SO Since only low reactant concentrations can be em DIUM HYDROSULFITE FROM FORMATES (Ser. ployed, a maximum of only 125 gm/ of product is ob No. 9,078), filed Feb. 5, 1970, now U.S. Pat. No. tained, and the reaction time is approximately eight 3,576,598. The present application differs from the hours. parent application in that the methyl formate recov 10 Belgian Pat. No. 698,427 (Mitsubishi Edogawa) is a ered with methyl alcohol, as the anhydrous sodium hy further improvement on U.S. Pat. No. 2,010,615. Ac drosulfite product is removed, is re-cycled as part of cording to this patent the three raw materials, sodium the reactant feed solution. formate, sodium hydroxide, and sulfur dioxide are maintained in three separate solutions or suspension; BACKGROUND OF THE INVENTION 5 the formate in an alcohol-water suspension in the reac 1. Field of the Invention tor, the sodium hydroxide as an aqueous solution, and A great deal of recent attention has been given to the the sulfur dioxide as an alcohol solution. The three are production of anhydrous alkaline metal hydrosulfites, brought together for batch reaction by simultaneously using formates. This attention is due to the contempo feeding the latter two into the first. Experiments per rary by-product availability of the formates. Earlier in formed according to the process described in this pa ventors have addressed themselves to laboratory pro tent yielded sodium hydrosulfite with a maximum pu duction of hydrosulfites from formates; however, these rity of 91% and yields of 60 to 65% based on sulfur di earlier methods did not address themselves to the criti oxide and 40 to 45% based on sodium formate. The cality of commercial yield nor the adaptability of the maximum production was 50 gm/l, and the reaction laboratory process for commercial use. For the most 25 required a minimum of three and one-half hours. part, the earlier inventors batch-reacted the alkaline Yoshikawa U.S. Pat. No. (3,41 1875) related to Bel metal hydroxides, and gaseous sulfur dioxide with the gium Pat. No. (698,427), has been issued to the as formates, achieving somewhat less than optimum yield. signee Mitsubishi Edogawa and concerns the produc According to the present method, there is obtained tion of HYDROSULFITES FROM FORMATES. from cheaper raw materials a high yield of hydrosulfite 30 As in Belgium Pat. No. 698,427, Yoshikawa U.S. Pat. of high purity and great stability. No. (3.41 1,875) is a batch reaction process wherein 2. Description of the Prior Art sulfur dioxide containing methanol and an alkaline Great Britain Pat. No. 1 1,010 Kinzlberger, (corre agent are batch-reacted with an aqueous solution of al sponding to U.S. Pat. No. 1,166,160 and Germany Pat. kali metal formates. In U.S. Pat. 3,41 1,875 dependent No. 343,791) featured the production of anhydrous hy 35 claim 2 the alkaline agent is defined as sodium hydrox drosulfite by reacting formic acid or formates with sul ide and the alkaline metal formate is designated as so furous acid or salts, while excluding the presence of Wa dium formate. ter. In one example, sodium formate and formic acid However, according to the present invention, sulfur are mixed in alcohol to which is added sodium pyrosul dioxide-methanol is not added to the total aqueous al fite, while heating and stirring. In another example, So 40 kali metal formate solution within the reactor, as dis dium formate and formic acid are mixed in alcohol to closed in U.S. Pat. No. (3,41 1,875). Rather, applicants which is added sodium pyrosulfite, while heating, then have found that better efficiencies and substantially passing a current of sulfur dioxide into the mixture. greater productivity per unit volume of the reaction Great Britain Pat. No. 1 1,906 Casella teaches the system and per unit of the solvent alcohol can be production of sodium hydrosulfite by mixing formalde 45 achieved by separately dissolving the sodium hydroxide hyde, sodium sulphoxylate, sodium bisulphite and com and sodium formate reactant, prior to simultaneous mon salt in solution, while heating. feeding with the methanolic SO. Great Britain Pat. No. 25,872 Kinzlberger is an im provement upon Great Britain Pat. No. 1 1,010 teach SUMMARY OF THE INVENTION ing the production of anhydrous hydrosulphites by dis 50 The present method is an improvement over U.S. solving formic acid in alcohol, while heating and adding Pat. No. 2,010,615; Belgium Pat. No. 698,427; and sulfurous acid. The hydrosulfite is recovered by filter U.S. Pat. No. 3,411,875. According to the present in 1ng. vention, sulfur dioxide (SO) is absorbed in methyl al U.S. Pat. No. 1,036,705 (Portheim, apparently a cohol (CH3OH) as a first feed solution, sodium hydrox Kinzlberger employee) teaches reacting a bi-sulfite so 55 ide and sodium formate are completely dissolved in lution with formic acid in the absence of Water, so as water by heating, as a second feed solution, and a small to obtain the anhydrous hydrosulfites. Either ammo amount of methyl alcohol is fed, as a third feed solu nium or potassium may be employed. tion. The third feed solution is fed into the reactor U.S. Pat. No. 2,010,615 (Victor Chemical) is an im while stirring and heating under pressure, then the first provement over earlier Kinzlberger patents, both U.S. 60 and second solutions are simultaneously fed together, and foreign, for producing anhydrous sodium hydrosul while continuing stirring and heating within the reactor fite from sodium formate and sulfur dioxide. Alkali under pressure. CO is vented, the reaction contents metal sulfites are reacted with alkali formates and Sul are cooled, and the hydrosulfite yield is filtered out and fur dioxide in a solution of either ethyl or methyl alco dried. By using higher temperatures and pressures in hol and water. U.S. Pat. No. 2,010,615 distinguishes the reaction process, applicants are able to use high re from the prior art in the use of larger quantities of actant concentrations. As a result, there is a high pro water in the reaction. Experiments performed accord duction per unit of reactor volume, per unit of alcohol 3,887,695 3 4 volume, and per unit of time. The over-all result is a sig dioxide first feed solution was adjusted so that the re nificant improvement in the reactant to product yields. maining 26 percent was fed in an additional 104 minute By this process, sodium hydrosulfite of a high degree period, again maintaining the agitation, the tempera of purity may be produced, with yields in excess of 67% ture of 83°C. and the pressure of 25 psig, Continuing based on formate, in excess of 80% based on sulfur di- 5 these conditions after the conclusion of all feeding of oxide, and in excess of 74% based on sodium hydrox reactants for an additional 76 minute period resulted in ide. The high purity product has a large crystal size of completion of the desired reaction. good appearance, is devoid of dust, and is quite stable At this point the reactor contents were cooled to and readily soluble. 70°C. and the anhydrous sodium hydrosulfite produced was separated from the solution by filtration. The solids BRIEF DESCRIPTION OF THE DRAWINGS were rinsed with 1200 parts methyl alcohol and dried FIG. 1 is a flow sheet depicting applicant's method of by heating to 70°C. under vacuum. The resulting dry producing sodium hydrosulfite; and product, 2269 parts by weight, assayed 92.0 percent FIG. 2 is a schematic view of a proposed reactor, anhydrous sodium hydrosulfite, and was of large crystal used according to present method. 15 size containing no obnoxious dust and of excellent sta bility, ready solubility, and good appearance. DESCRIPTION OF THE PREFERRED In that a portion of the sodium formate fed to the re EMBODIMENTS actor will be converted to methyl formate via a side re A proposed reactor which may be used, according to action, the filtrate resulting from the removal of the an the present method, is illustrated in FIG. 2. Reactor 10 20 hydrous sodium hydrosulfite from the slurry will con is illustrated as having exterior cooling coils 12, stirrer tain methyl formate in addition to methyl alcohol. 20 extending axially into the reactant mix and feeding When the methyl alcohol is recovered via distillation solution input conduits 14, 16, and 18. A thermometer from the filtrate it will unavoidably contain all of the probe 26 may be employed to maintain heating at the . methyl formate originally contained in the filtrate. It desired optimum. CO, is vented via conduit 24 into re- 25 has been found that this methyl formate can be effec flux condensers 22 and 29 which are sufficient to strip tively utilized as a raw material for the reaction in place all the methyl formate from the effluent carbon diox of sodium formate, provided that an additional mole of ide. sodium hydroxide be fed to the reactor for each mole Upon completion of the reaction, the mix is dis of methyl formate added and each mole of sodium for charged through conduit 28 to a filter system (not illus- 30 mate subtracted. A portion of the methyl formate and trated) for recovery of the hydrosulfite solids. additional sodium hydroxide react in situ to achieve the The sulfur dioxide-methyl alcohol feeding conduit 18 same sodium formate - methyl formate equilibrium is a bottom feeding conduit, so as to prevent undesired which exists in the absence of methyl formate in the heating of the inlet solution. Pre-heating of the inlet so feed. lution as occurs in a dip tube feeding device has the del The following is an actual example of this mode of eterious result of evolving sulfur dioxide gas, leading to operation utilizing recovered methyl alcohol contain process difficulties. ing methyl formate: The following in an actual production example: EXAMPLE II - two feed solutions were prepared. EXAMPLE I - Two feed solutions were prepared. A first feed solution was obtained by absorbing 1920 A first feed solution was two by absorbing 1920 parts 40 parts of sulfur dioxide in 2700 parts of methyl alcohol. of sulfur dioxide in 2700 parts of methyl alcohol. A sec A second feed solution was made by adding 650 parts ond feed solution was made by adding 550 parts of so of sodium hydroxide and 1 190 parts of sodium formate dium hydroxide and 1360 parts of sodium formate to to 880 parts of water and heating the resulting slurry to 880 parts of water and heating the resulting slurry to approximately 160°C. to effect complete solution of all approximately 160°C. to effect complete solution of all solids. These solutions were fed to a reactor exactly as solids. These solutions were fed to a stirred reactor described in Example I and in the same exact manner, equipped with a heating and/or cooling coil, a water and again maintaining the same pressures and tempera cooled reflux condenser, a refrigerated brine cooled tures as in Example I. Initially, however, 1100 parts of reflux condenser, and a thermometer. Initially, 1 100 methyl alcohol containing 150 parts of methyl formate parts of methyl alcohol as a third feed solution was 50 as a third feed solution was added to the reactor. added to the reactor and heated with agitation to a tenn At the completion of the desired reaction the reactor perature of 83°C. at a pressure of 25 pounds per square contents were cooled, filtered, rinsed, and dried as in inch gauge. Feed of the sodium hydroxide-sodium for Example I. The resulting dry product, 2265 parts by mate second feed solution was initiated and maintained weight, assayed 92.0% anhydrous sodium hydrosulfite at a rate such that it was completely fed to the reactor and was of a quality equal to that of Example I. in 60 minutes. Six minutes after commencing this feed, a flow of the methyl alcohol-sulfur dioxide solution was COMPARISON OF APPLICANT'S PROCESS WITH initiated and maintained at a rate such that 74 percent U.S. PAT. NO. 341 1875 of this solution was fed to the reactor in 54 minutes. 60 In that both the U.S. Pat. No. 34l 1,875 and the Vir The mixture in the reactor resulting from the simulta ginia Chemical's application, (Ser. No. 9,078) involve neous addition of the first and second solutions was agi the same raw materials, any comparison designed to tated all the while and the temperature maintained at show the advantages of one process relative to the 83°C. The pressure of the system was maintained at 25 other involves essentially two criteria; yield efficiencies pounds per square inch gauge. The pressure was con- 65 in producing the desired end product from each of the trolled by the appropriate venting of the carbon dioxide raw materials, the production efficiency in rate of out gas formed in the reaction. At the end of this primary put of the desired end product per unit of reactor vol feed period, the flow rate of the methyl alcohol-sulfur ume and per unit of time. The first of these two criteria 3,887,695 S 6 relates only to the cost of raw materials needed to make centrations. The dissolved sodium formate apparently the product, while the second relates to the operating serves as an acidity buffer by suppressing the ionization cost and the cost of the plant required to make a given of the formic acid formed by the reaction between so quantity of product. Note that in either process a nee dium formate and Sulfur dioxide (sulfurous acid). Thus, essary part of the operating cost is that of the recovery 5 the hydrogen ion concentration is maintained at a low for reuse of the considerable quantity of methyl alcohol level, minimizing the decomposition of already formed involved in the reaction. A quantitative comparison fol sodium hydrosulfite. These conditions can be obtained lows: only by feeding sodium formate to the reactor in a dis solved state. As previously noted, this completely dis O solved condition of the sodium formate, along with the U.S. sodium hydroxide, can be achieved only by heating the 34,875 Applicant mixture of the two or the two individually with the al % yield based on sodium formate 49.1 67.7 lowable quantity of water to a temperature very much % yield based on sulfur dioxide 69.4 8().3 % yield based on sodium hydroxide 7.3 74.6 in excess of that permitted in the reactor itself. It is ob vious that this condition cannot be achieved in the U.S. Pounds of production per gallon Pat. No. 3,411,875 process. of reactor volume per hour (). 95 ().65) The preferred reaction temperature range is 60 to Pounds of production per gallon 90° C. Below 60°C. the desired reaction forming so of alcohol used 83 45) dium hydrosulfite does not occur, while above 90° C. the decomposition of the sodium hydrosulfite already The yield for each of the raw materials is considera formed becomes so rapid as to detract substantially bly enhanced for the applicant's process as compared from the yield. The selection of a single operating tem to that of U.S. Pat. No. 3,41 l,875. The improvement perature within this range is a compromise between in is such that raw material costs for the former would be creasing speed of reaction with increasing temperature, 82% of those for the latter. The improvement in pro on the one hand, and increasing decomposition losses duction rate is even more dramatic. Applicant's pro with increasing temperature, on the other. cess will yield over three times the hourly production The pressure at which the reactor is operated must be for a given reactor size than that of the U.S. Pat. No. at least sufficient to allow the selected reaction temper 3.41 1,875 process. The saving in the cost of a plant is ature to be achieved. The atmospheric boiling tempera obvious. Further, the applicant's process yields over ture of the mixture within the reactor is approximately twice the production per gallon of alcohol as does the 70 C., so that, if the selected reaction temperature is U.S. Pat. No. 3.41 1,875. Here again, a saving in plant in the range of 60 to 70° C., operation may be had at cost results since the alcohol recovery facilities can be atmospheric pressure. A superatmospheric pressure is much more modest. Also, a reduction in operating cost mandatory to achieve reaction temperatures in the is achieved because of the lesser quantity of alcohol to 3 5 range of 70° to 90° C. However, a superatmospheric be recovered. pressure in the reactor is to be preferred in that higher In order to achieve the very high production rate per pressures aid in retaining, in the reactor, the highly vol unit of reactor volume reported in applicant's process atile methyl formate formed via a side reaction. Such example, it is essential to use very high concentrations retention suppresses further side reaction forming still of raw materials. In order that these high starting con 40 more methyl formate. No upper limit on the superat centrations result in an acceptable efficiency in con mospheric pressure exists other than the economical verting raw materials to product, it is absolutely essen limit of reactor cost. The preferred operating pressure tial that the sodium hydroxide and sodium formate be range is 10 to 50 psig. completely dissolved prior to reacting with the sulfur Manifestly, the control temperatures, pressures, and dioxide. They can be dissolved in the limited quantity times permitted for reaction may be varied extensively of water permissible in the reaction only by heating to without departing from the spirit of the invention. quite high temperatures, as 160°C. in the example. This We claim: w can only be done outside the reactor, in that the per 1. Method of preparing sodium hydrosulfite (Na2S missible reaction temperature range is 60 to 90°C. O) from formates comprising: Thus, in the U.S. Pat. No. 3,41 1,875 process, whereby 50 A. absorbing sulfur dioxide (SO) in methyl alcohol all of the sodium formate is placed in the reactor ini (CHOH) as a first feed solution: tially, it is completely impossible to dissolve high con B. dissolving sodium hydroxide (NaOH) and sodium centrations of sodium formate prior to reaction with formate (HCOONa) in water (HO) and heating to sulfur dioxide. effect complete solution of all solids, as a second As should be obvious to one versed in the art, it is feed solution; also possible to dissolve the two components, Sodium C. feeding a small amount of methyl alcohol hydroxide and sodium formate, individually, making (CHOH) and methyl formate (HCOOCH) to a two separate solutions rather than the one mixed Solu reactor, as a third feed solution, while heating in tion. Again, the same limitation on the allowable quan the range 60' to 90° C. and stirring under superat tity of water applies, and substantially elevated temper 60 mospheric pressure within said reactor; atures are still required. The two seaprate solutions D. sequentially feeding together under pressure said should be fed to the reactor substantially simulta first and second feed solutions as a reaction liquid neously to achieve essentially the same effect as feed into said reactor while stirring and heating in the ing a single mixed solution. 65 range 60 to 90° C. under a superatmospheric pres it would appear that the presence of a maximum Sure, quantity of dissolved sodium formate in the reactor is E. venting carbon dioxide (CO) from said reaction essential for successful operation at high reactant Con liquid within said reactor; 3,887,695 7 8 F. cooling said reactor and contents; 2700 parts of methyl alcohol (CHOH) as a first G. recovering by filtering sodium hydrosulfite (NaS feed solution; Os) solids from said reaction liquid; and B. dissolving 650 parts of sodium hydroxide (NaOH) H. recovering methyl formate (HCOOCH) together and 1 90 parts of sodium formate (HCOONa) in with methyl alcohol (CHOH), sequentially of fil 5 880 parts of hot water (HO) as a second feed solu tering said hydrosulfite from said reaction liquid, tion, and recycling both said methyl formate C. heating said second feed solution to approximately (HCOOCH) and said methyl alcohol (CHOH) 160° C. so as to effect complete solution of all into said third feed solution. solids, 2. Method of preparing sodium hydrosulfite (NaS () D. feeding 1 100 parts of methyl alcohol (CHOH) O) from formates as in claim 1, including varying and 150 parts of methyl formate (HCOOCH) to a amounts of sodium hydroxide (NaOH) and sodium for reactor as a third feed solution, while heating in the mate (HCOONa) dissolved in said second feed solution range 60 to 90° C. and stirring under a superat proportionately to the amount of methyl formate mospheric pressure in the range of 10 to 50 psig (HCOOCH) in said third feed solution. 5 within said reactor; 3. Method of preparing sodium hydrosulfite (NaS E. sequentially feeding together under pressure said O) from formates as in claim 1, including increasing first and second solutions as a reaction liquid into the amount of sodium hydroxide (NaOH) while de said reactor while stirring and heating in the range creasing the amount of sodium formate (HCOONa) in 60 to 90° C. under a superatmospheric pressure in said second feed solution proportionately to the the range of 10 to 50 psig, amount of methyl formate (HCOOCH) in said third F. venting carbon dioxide (CO) from said reaction feed solution. liquid within said reactor; 4. Method of preparing sodium hydrosulfite (Na2S G. cooling said reactor and contents; and O) from formates as in claim 3, wherein one addi H. recovering by filtering sodium hydrosulfite (Na2S tional mole of sodium hydroxide (NaOH) is added and O) solids from said reaction liquid. one mole of sodium formate (HCOONa) is subtracted 6. Method of preparing sodium hydrosulfite (Na2S for each mole of methyl formate (HCOOCH) in the O) from formates as in claim 1, wherein said sodium third feed solution. hydroxide (NaOH) and sodium formate (HCOONa) 5. Method of preparing sodium hydrosulfite (Na2S are dissolved individually prior to feeding into said re O) from formates comprising: 30 actOr. A. absorbing 1920 parts of sulfur dioxide (SO) in k k K sk

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