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Home , Sulfur trioxide

United States Patent (19) [11] 3,929,964 Thoma (45) Dec. 30, 1975

54) PROCESS FOR THE CONVERSION OF 3,846,535 l l 1974 Fonseca...... 4231422 SULFTE 76 Inventor: Matthias Thoma, Primary Examiner-Oscar R. Vertiz Johann-Strauss-Strasse 8, 8264 Assistant Examiner-Gary P. Straub Waldkraiburg, Germany 22 Filed: Sept. 23, 1974 57 ABSTRACT 21 Appl. No.: 508,401 The sodium obtained as a byproduct in the pro duction of hydroxy aromatic compounds from aro 30 Foreign Application Priority Data matic hydrocarbons, trioxide and sodium hy Oct. 5, 1973 Germany...... 2350.191 droxide, is converted into sulfur trioxide and sodium hydroxide for recirculation of same in said production 52 U.S. Cl...... 423/183; 4231166; 423/242; of hydroxy aromatic compounds, by a process 423/428; 423/438; 438/532; 4231555; wherein: (a) the sodium sulfite is reacted with 423/642; 260/628 chloride to form sodium chloride and zinc sulfite; (b) 51 Int. Cl."...... C01D 1120 the zinc sulfite is heated to form zinc and sulfur 58 dioxide and the is oxidized to sulfur tri 4231190, 422, 423, 424, 426, 427, 491, 499, oxide; (c) the sodium chloride is reacted with ammo 512,539, 541 A, 532,533, 622, 642, 643; nium bicarbonate to form ammonium chloride and so 260/628 dium bicarbonate; (d) the is reacted with the ammonium chloride to form zinc chloride and am 56 References Cited monia; (e) the ammonia is reacted in the Solvay Pro UNITED STATES PATENTS cess to form ammonium bicarbonate; and (f) the so 2,180,755 1 1/1939 Carrels et al...... 423/643 dium bicarbonate is heated to form sodium carbonate 2,259,409 10/1941 Wenzel et al...... 4231622 and dioxide, and the sodium carbonate is re 2,927,001 3/960 McCulloush...... 4231532 acted with oxide to form sodium hydroxide. 3,329,479 7/1967 Hustinx...... 423190. 3,535,083 10/1970 Smith...... 423/242 6 Claims, No Drawings 3,929,964 2 Thus the progress of the present invention represents

PROCESS FOR THE CONVERSION OF SODIUM a technical and economical progress also in this re SULFITE spect. The sodium carbonate obtained during the conver This invention relates to a process for converting sion step represents no problem concerning the pollu sodium sulfite into sulfur trioxide and sodium hydrox tion laws. Sodium carbonates are harmless and further ide. . . . . more sodium carbonates are required by numerous It is well-known that during the production of hy branches of industry. droxy aromatics from aromatic sulphonic acids with During the conversion of sodium sulfite by means of Sodium hydroxide equivalent quantities of sodium sul 10 zinc chloride on one hand sodium chloride is obtained fite are obtained as a by-product. which can be converted into soda by the generally On the basis of the present pollution regulations, known Solvay process or possibly, when using calcium hydroxide, also into sodium hydroxide. On the other sodium sulfite may be used in the production of cellu : hand the zinc sulfite formed in the conversion of so losic material only in a very small extent. For this rea 15 dium sulfite by means of zinc chloride is decomposed Son Sodium sulfite has to be utilized or removed in a on heating into sulphur dioxide and zinc oxide which is form corresponding to the pollution laws. reacted together with the ammonium chloride obtained A well-known method for processing sodium sulfite is in the Solvay process and which is used for the recovery its oxidation into sodium or its neutralization, by of zinc chloride. The reaction is practically quantita means of suitable acids, into sodium salts that can be 20 tive. The resulting ammonia, in turn, is used in the re-used. These procedures, however, are costly and Solvay process. Sulphur dioxide is oxidized into sulphur time-consuming and furthermore additional chemicals trioxide and is employed as such or as sulphuric acid are consumed. Moreover it has to be mentioned that up for the sulfonation step. to now no possibility has been found for the removal of This means: in this process the formation of unde Sodium sulfate simultaneously solving the pollution 25 sired by-products is completely prevented as the mate problem satisfactorily. rials required for the processing of sodium sulfite are The present invention is based on the task of supply recovered completely, i.e. practically quantitatively ing a non-pollution processing of sodium sulfite which during the process and the by-products obtained in the can be carried out simply without obtaining any by-pro conversion are consumed again completely, too... ducts. • 30 As already mentioned in the conversion of sodium According to this invention this aim is reached by sulfite according to the present invention exactly those converting sodium sulfite into sodium hydroxide and materials are recovered which are required in the man sulphur trioxide and re-using it in a circulation step for ufacture of hydroxy aromatics from aromatic sulphonic the production of hydroxy aromatics, whereby acids with sodium hydroxide, namely sulphur trioxide a... sodium sulfite is converted into sodium chloride 35 and sodium hydroxide...... and zinc sulfite by means of zinc chloride, The process of this invention for the conversion of b. Zinc sulfite is converted into zinc oxide and sulphur sodium sulfite is thus combined with the well-known dioxide by heating and the latter is processed into process for the production of hydroxy aromatics from sulphur trioxide by oxidation, aromatic sulphuric acids and sodium hydroxide in the c. sodium chloride is converted by means of ammo 40 form of a circulation process in such a way that the nium bicarbonate in order to form ammonium sodium sulfite obtained as a by-product in the produc chloride and sodium bicarbonate, , tion of hydroxy aromatics is converted according to d. Zinc oxide with the ammonium chloride obtained this process into the initial products sulphur dioxide in (c) is converted into zinc chloride in order to and sulphur trioxide and alkali hydroxide respectively recover the zinc chloride consumed in the conver 45 required for the production of the hydroxy aromatics. sion of sodium sulfite, . . , , .. Details of this invention are given in the below de e. the ammonia liberated in (d) is used for the forma scription of illustrative examples to which, however, tion of ammonium bicarbonate, and the invention is not limited. f. the sodium bicarbonate is processed into sodium 50 EXAMPLE carbonate and by heating, and so An about 15-20% aqueous solution of sodium sulfite dium carbonate is processed into sodium hydroxide from a melt of sodium hydroxide and aryl sulphonic by means of . t acid is mixed with zinc chloride. The process of the present invention is carried out in sodium sulfite 126 kilos the form of a circulation process and has the advantage 55 water 500 kilos that the reactants required for the different, necessary zinc chloride 36 kilos chemical conversions are reformed in the course of the The conversion takes place at 25-30°C. The hereby single steps of the process and the resulting by-products practically quantitatively obtained 145 kgs zinc sulfite are consumed again so that after completion of a pro are separated from the about 19% sodium chloride cess cycle no by-products have to be removed. 60 solution. By heating zinc sulfite in usual manner, 64 kgs The conversion of zinc oxide with ammonium chlo sulphur dioxide are liberated and 81.5 kgs zinc oxide ride into zinc chloride and ammonia is practically are obtained. quantitative. Moreover in the conversion of sodium Converting the sodium chloride solution with ammo sulfite according to the present invention exactly those nium bicarbonate into sodium carbonate and further materials are formed or may be converted into such 65 into sodium hydroxide according to the Solvay process, without any particular problems, which are required the ammonium chloride formed during this process will for the production of hydroxy aromatics from aromatic be left. Zinc oxide, together with ammonium chloride, sulphonic acids and sodium hydroxide. will give zinc chloride and ammonia. Whereas ammo 3,929,964 3 4 nia is recirculated for the conversion of sodium chlo sulphuric acid or sulphur trioxide and subsequent con ride, zinc chloride is reused for conversion. version by means of sodium hydroxide. This example clearly proves that by means of zinc The following is added: chloride alkali sulfite may be converted into alkali hydroxide and sulphur dioxide - the latter will give the 1.9 moles = 258 grs ZnCl2) reaction is complete after required sulphur trioxide without causing any troubles Water 30 minutes at about 20°C - and no by-products are obtained which could be re moved only with great difficulties due to the pollution Composition of the combined solution: laws. 10 By this fact the process of the present invention com 1.8 moles = 260 grs ZnSO pares favourably to the Solvay process during which 3.6 moles = 211 grs NaCl 0.1 moles = 14 grs ZnCl calcium chloride in quantities equivalent to those of the 0.1 moles = 14 grs NaSO converted sodium chloride are obtained and which 0.1 moles = 13 grs NaSOa have been removed into waters in the past and caused 4 grs phenolic substances considerable pollution. 15 1, 20 grs water Below are the chemical conversions in the form of l,636 grs chemical reaction equations obtained during the pro cess of example 1: the insoluble ZnSO is filtered off and washed with a 1. NaSOa - ZnCl2 = 2 NaCl -- ZnSO part of the distillate to be recovered later until it is 2. 2 NaCl + 2 NHHCO = 2 NaHCO+ 2 NHCl 20 free of . 3. 2 NaHCO = NaCO + CO -- HO 260 grs ZnSO, moist, are introduced by a pipe 4. NaCO3 + CaO + HO = CaCO + 2 NaOH heated externally at about 320°C from the top 5. CaCO = CaO + CO successively so that there is no considerable loss in 6. ZnSO = ZnO + SO temperature. 7. ZnO + 2 NHCl = ZnCl + 2 NH + HO 25 The conversion into ZnO and SO is carried out at Herefrom it can be realized that the process of this more than 96% and with correspondingly long periods invention gives a conversion of sodium sulfite into so ZnSO may be converted practically quantitatively. dium hydroxide and sulphur dioxide without by-pro Whereas the resulting ducts are obtained or consumed. On the contrary, all 30 reactants are recovered quantitatively during the pro 46 grs ZnO and CSS. 8 grs. ZnO from the precipitation with NH, amounting to 154 grs are used for the later conversion of ammonium chloride if instead of sodium hydroxide sodium carbonate is (NHCl) obtained in the process into ZnCl2 and NH3 required, then the procedures described in equations (animides), the recovered SO, gas is oxidized in usual manner with air or into SOs and is employed as (4) and (5) may be left away without any change in the 35 such or as sulphuric acid for sulfonation again. This course of the circulation process. described way of recovering SOSOs from the NaSOs necessarily obtained in the manufacturing process is a EXAMPLE 2 part of the circulation process, i.e. the relevant sulfonation of the initial product to be sulfonated, as e.g. The initial products are the same as in example 1. toluol, is carried out with SO, (oxidized into SOs) from Only additional 3-4% of sodium sulfate are added the NaSO. which also is in general present in the aryl alkali hy 40 droxide melt in this amount. The filtrate obtained after separation of ZnSOa con After the formation of 117 kgs of sodium chloride the sists of: sodium sulfate will remain in the sodium chloride solu tion. 2.8 kgs of calcium chloride are added so that 211 grs NaCl - sodium chloride sodium sulfate is converted into sodium chloride and 14 grs ZnCl2 - zinc chloride 14 grs NaSO - sodium sulfate 3.7 kgs of which is separated from the 3 grs NaSO - sodium sulfite solution by filtration. 4 grs phenolic substances The present, purified sodium chloride solution, 120 1,300 grs water kgs of sodium chloride, are treated according to our 1,556 grs example 1 and to the Solvay process respectively. 50 The hereby obtained 107 kgs of ammonium chloride are re-converted into 136 kgs of zinc chloride by means Balance: 1,556 grs of the 81.5 kgs of zinc oxide obtained and the zinc NaSO is obtained by partial oxidation of NaSO chloride will be used in the following charge. 55 during the production of hydroxy aromatics. In order to obtain no enrichment of NaSO, the EXAMPLE 3 solution is mixed with such an amount of BaCl, so that NaSO as well as the still present NaSO are Into a flask equipped with stirrer, thermometer and precipitated as BaSO, and BaSOs. "addition flask' 42 grs BaCl 1,598 grs Adter heating and filtration a residue of 60 45 grs is obtained (consisting of BaSO and BaSOa) 1.9 moles = 240.0 grs sodium sulfite (NaSOs) 1,553 grs as well as a solution consisting of O. moles = l4.0 grs sodium sulfate (NaSO4) 235 grs NaCl 0.03 moles = 4.0 grs phenolic substances 14 grs ZnCl 1,100.0 grs water 4 grs phenolic substances 1,358.0 grs 1,339 grs water 65 1.592 grs After addition of are added. 15 grs 25% ammonia solution the resulting precipitate consisting of This solution results from the production of hydroxy 10 grs Zn(OH) - zinc hydroxide is removed by filtration, aromatics by sulfonation of toluol with concentrated and the filtrate consisting of 3,929,964 5 6 -continued Sodium hydroxide and sulphur trioxide for recircula 235 grs NaCl tion in said production of hydroxy aromatics, which 10 grs NHCl (ammonium chloride) 4 grs phenolic substances comprises: 1,400 grs water a. reacting said sodium sulfite with zinc chloride to 1,649 grs form sodium chloride and zinc sulfite, is adjusted to a 23.5% sodium chloride solution by distilling off b. heating said zinc sulfite to form zinc oxide and 650 grs water with sulphur dioxide and oxidizing said sulfur dioxide to 3.5 grs phenolic substances. sulphur trioxide, c. reacting said sodium chloride with ammonium While the distillate with the phenolic substances is 10 bicarbonate to form ammonium chloride and so re-employed for solving the subsequent fusion melt, the dium bicarbonate, solution consisting of d. reacting said zinc oxide with said ammonium chlo. ride to form zinc chloride and ammonia, 235 grs NaCl - sodium chloride e. converting said ammonia to form ammonium bi 10 grs NHCl - ammonium chloride 15 containing traces of organic substances is processed carbonate, and with carbon dioxide and ammonia into sodium f. heating said sodium bicarbonate to form sodium carbonate and sodium hydroxide respectively carbonate and carbon dioxide, and reacting said according to the Solvay process. sodium carbonate with calcium oxide to form so dium hydroxide. By filtration sodium bicarbonate is separated from 20 2. A process as in claim 1 wherein the zinc chloride the solution. Its composition is: produced in step (d) is recirculated for reaction with 79.2%, NaHCO sodium sulfite in step (a). 0.6%, NHHCO 3. A process as in claim 1 wherein the ammonium 0.5%, NaCl 25 bicarbonate produced in step (e) is recirculated for 0.4%, NHCl reaction with sodium chloride in step (c). 19.3%, water 4. A process as in claim 1 wherein calcium carbonate The filtrate containing is produced along with sodium hydroxide in step (f), said calcium carbonate is heated to form calcium oxide 28.0 grs NaCl 30 and carbon dioxide, and said calcium oxide is recircu 198.0 grs NHCl p 51.0 grs NaHCO lated for reaction with additional sodium carbonate in 38.0 grs NHHCO ... step (f). 860.0 grs water 5. A process as in claim 1 wherein sodium sulfate is 1,175.0 grs is mixed with the recovered 154.0 grs ZnO - zinc oxide and evaporated to a slurry. A part of present with sodium sulfite in the starting composition the ammonium chloride is already decomposed and 35 and is carried through step (a) in admixture with said thus ammonia excapes. The conversion of more than 95% is reached by spontaneously heating the slurry to sodium chloride, and wherein prior to step (b), said 480'C, sodium sulfate in the admixture is reacted with calcium Whereas all of the ammonia is recirculated for the conversion of NaCl into NaHCO, the residue chloride to form sodium chloride and calcium sulfate, consisting of said calcium sulfate then being separated. 200.0 grs 40 33.0 grs ZnO 6. In a process for the conversion of sodium sulfite, 64.0 grs NaCl obtained in the production of hydroxy aromatics, into 10.0 grs NHCl sodium carbonate and sulfur trioxide, for recirculation 3.07.0 grs is used for the subsequent conversions of NaSOs. in said production of hydroxy aromatics, which com prises: The by-products included in the ZnCl, residue, like 45 a. reacting said sodium sulfite wich zinc chloride to NaCl, NHCl, do not cause any troubles as the subse form sodium chloride and zinc sulfite, quent reactions are incorporating these chemicals. b. heating said zinc sulfite to form zinc oxide and From this example it can be clearly noted that beside sulphur dioxide and oxidizing said sulfur dioxide to of the usual losses incurring during operation a real sulphur trioxide, circulation is given, for NaOH as well as for SO, and 50 c. reacting said sodium chloride with ammonium SOs respectively. It is not very important to obtain bicarbonate to form ammonium chloride and so quantitative conversions in the relevant reactions as the dium bicarbonate, single components will always reappear in the circula d. reacting said zinc oxide with said ammonium chlo tion step. Only some percent of SO, are to be replaced ride to form zinc chloride and ammonia, as the oxidation product of about 4-5% of NaSO will 55 e. converting said ammonia to form ammonium bi be lost as BaSO. carbonate, and What is claimed is: f. heating said sodium bicarbonate to form sodium 1. A process for the conversion of sodium sulfite, carbonate and carbon dioxide. obtained in the production of hydroxy aromatics, into sk >k k k sk 60

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