IL33552A - A process for the manufacture of alkali metal bicarbonates - Google Patents

Description

This invention relates to the manufacture of alkali metal bicarbonates by the reaction of an alkali metal chloride with carbon dioxide in the presence of an amine as acceptor for hydrochloric The most widely used conventional process for the manufacture of sodium bicarbonate is the Solvay process in which carbon dioxide is introduced into an ammoniated sodium chloride solid sodium bicarbonate is separated from the reaction mixture and from the residual ammonia is recovered in that the ammonium which has formed in the course the is decomposed by of the liquor with calcium Apart from well known teohnical inconveniences this process has the economic drawback that of the sodium is lost since the conversion yield is normally not higher than and all the chlorine introduced into the system is lost apart from the unconverted of the calcium chloride produced in the end is not utilisable0 this process be applied to the manufacture of potassium bicarbonate whioh is much more readily than sodium bicarbonate and remains mostly dissolved in the reaotion mixture0 It has already been suggested in the British Patent Specification to use amines as hydrogen chloride acceptors instead of According alkali metal or ammonium salts are prepared by the reaction of an or ammonium chloride with an carbonic or phosphoric in the presence of water and a chain primary iLhydrogen ions and chloride ions are into the organic and the latter is separated from the aqueous The amine is regenerated from its hydrochloride b treating the organic an alkaline The amines used in this known process are strongly preferably diluted with organic regeneration of the amines is mainly effected wit hydroxide though use of magnesium oxide has been mentioned in this connections Under the particular conditions described in the British Specification in view the strong basicity of the he of magnesium oxide for the regeneration the amines is not conducive to an efficacious decomposition of the amine hydrochlorides and the formation of a concentrated magnesium chloride On the recovery of in a commercially useful not been disclosed in that the object to integrated process manufacture of alkali metal bloarbonates in oth the alkali metal ions chloride ions are virtually in a conversion in a commercially useful The consists in a process for the manufacture of alkali metal wherein a saturated aqueous alkali metal metal bicarbonate brine reacted with carbon dioxide in presence of an organic liquid or solvent phase containing a selected herein amine dissolved in an organic solvent ith the the separated from the aqueous precipitated alkali metal bicarbonate is removed from a the residual a ueous hase is e not tend form complexes with magnesium amine hydrochloride must be of decomposition with magnesium The solvent together with the constitutes the solvent phase of the reaction also selected with a view to performance0 The solvent should increase the solubility in the organic phase so that the latter may serve as medium in the required amount of can be The solvent phase enables the separation of the JSfa and values the sodium as an but analogous considerations apply to other alkali metals especially the and shifts is usually totally on the left towards the side of the The ollowing Table the solubility in various solvents compared with and saturated and solutions Solvent at 1 p Water Saturated alcohol Chlorobenzene Carbon tetrachloride V Nitrobenzene Propyl alcohol Chloroform Amyl acetate Isobutyl acetate Alamine 336 Alamine alcohol i amin is a commercial tertiary or mixture of tertiary in which the alkyl radicals are or and have to carbon Even from knowledge of the properties of the selected and preferred solvents by themselves the behaviour o the solvent phase plus in the of this invention is not obvious and to be ascertained empirically under conditions of particular The solvent phase has to have a optimal basicity both brings about the reaction enables the regeneration the amine the amine hydrochloride with magnesium oxide so as to produce a concentrated having preferably a concentration above of For of weight each of trioctylamine and when tacted with an equal volume of a saturated aqueous brine the presence of CO atmospheric pressures precipitates solid from aqueous and produces amine hydrochloride in the solvent solvent can be regenerated with magnesium oxide latter is transformed into a concentrated brine If is used yield of and amine concentration in the solvent phase with a much lower concentration of brine is obtained i stage and will be extracted into solvent If nitrobenzene cyolonexanone or chloroform are and the corresponding amount of amine is converted into amine whereas with x or in the absence of any solvent a negligible of the same amine is converted into hydrochloride the yield of sodium is Low conversions are achieved comparable conditions with and The aforesaid amine can be influenced choice of of the solvent and of the composition the solvent phase as as by increasing or reducing pressure of the the NaCl and raising or lowering the For a solvent consisting of Alanine and nitrobenzene equilibrated a saturated NaCl rine at pressure solid and hydrochloride releases on addition of xylene reaction of the amine equilibrium be shifted to the left of the if the partial pressure the is decreased by blowing air the the reaction temperature is not necessarily have to be to dissolve the amount amine circulating the reaction and sys it has a Sufficient dissolving power for all amine hydrochloride by the For if nitrobenzene is used t consists of two nitrobenzene saturated and an amine phase saturated with and the reaction system will comprise altogether three liquid the solvent phase the amine and the aqueous According to the phase such an gem nt reduces the degree of and this is apt to be vantage in continuous operation as it makes it to operate with invariant phase The regeneration 2 2 s equilibrium reaction which can influenced by the choice of the the the compositio of the solvent phase well as by the of the brine In continuous operation the recycle organic phase tain some amount of amine de ending on efficiency of the the recycle urine contains some sodium The phase ratio is so chosen that the of into will give a brine of not less than depletion of the concentration in brine increases the solubility in the brine and decreases the rate of The phase ratio selected shoul a proper phase Instead of allowing the brine to become of in of the solid may be added t the saturated brine at the beginning whereby the saturation in j i the reaction pressure of the was at the above atmospheric as high as 9 gauge or it drops in the course reaction it is kept at a predetermined level the addition CO to the reaction The amine hydrochloride concentration in the solvent phase and accordingly the conversion per cycle as as the reaction rate are increased creasing The reaction temperature is so that a reaction rate is achieved and that an undesired the solubility of in the brine is Temperatures o 10 to for the formation cycle for the formation are The effect of decreasing the temperature to the effect of increasing the The solvent phase is separated the aqueous se and precipitated The solid is filtered off and the brine is resaturated with and The separated solvent is treated with amount or an excess of magnesium oxide ted o the amine in such a manner that a brine is produced and the amine hydrochloride ii posed almost The concentrated brine above is decomposed to and or which are in the regeneration solvent phase may be used as a it may be w ith before being contacted the aqueous In that case it is not necessary to the in gaseous form directly into reaction mi This arrangement avoids the entrainnient of droplets of liquid phases of the reaction mixture with the the solvent may be cooled before being contacted with the reaction mixture and thus to dissi ate the heat invention is illustrated b following to which A recycle solvent phase consisting of of nitrobenzene and of decanol was stirred with saturated recycle brine weight of of at while contained each of Alamine 336 and alcohol and was saturated at Each of the fed to the at a of with a total contact time of chloride content of the solvent phase passing through the system rose from zero to of β Simultaneously the COg pressure in the reactors decreased from 2 to The phases issuing from the to vessel for separation The solvent phase withdrawn from the top of the brine with suspended flowed from the bottom to a brine containing of was with and returned eaction The reaction yielded g of er solvent the separating vessel was fed continuously in to a slurry in water a regeneration system taining 4 The combined contact time i the mixing stages was The chloride content of the phase leaving the regeneration system was and the aqueoue regeneration weight of This Clg brine was withdrawn from the solvent phase was recharged wit and recycled at was to a unit consisting of a in series with a decomposition chamber in which the hydrothermal decomposition the as The liberated HOI was withdrawn from the The unit was operated at to yield for The process was carried out as operation with a saturated brine at a reaction temperature of and with a solvent phase composed of each of name and Isoamyi The reacted solvent contained of amine hydrochloride and Q of unreacted amine0 the same but with kerosene as the solvent of isoamyi alcoholp the reacted solvent contained as as of amine This Example shows the importance of the nature of the in the solvent EXAMPLE The importance of the nature of the solvent is brought out still more clearly by the results series experiments in which batch operations were carried with a saturated brine at and a pressure of 2 atmospheres solvent phase consisted in each case of 50 millimoles of and 15 ml of The Table lists the rate of conversion of amine to amine which is a measure of the sodium bicarbonate Isoamyi alcohol 89 Nitrobenzene 89 Octanol 75 Cyclohexanone phosphate 20 Methyl i30butyl ketone Kerosene A heavier organic phase constituting about of the organic liquids introduced and containing the amine hydrochloride formed in the reaction in an amount equivalent to the full conversion of the solid sodium chloride A bottom aqueous brine phase A solid phase by 1 kg of sodium the conversio of the solid sodium chloride The solid product from aqueous phase which was refused in a next batche The heavier organic phase was withdrawn from the and to regeneratio with slurry of of in wate in countercurrent treatment During the as the amine was bein it agai formed a lighter consisting of amine with nitrobenzene dissolved in In both stages of this treatments three liquid phases were presentc At the end of the kg of brine o concentration was obtained from stage the two organic phases issuing from stage contained substantially all the amine and nitrobenzene initially insufficientOCRQuality

Claims (1)

1. 2. CLAIMS ' ' '■ : " ' · ' "' '.' " . ' lo A process for the manufacture of alkali metal. bi~ , ·¾·..■ carbonates, wherein a saturated aqueous alkali metal chloride- alkali metal bicarbonate brine is reacted. with oarbon dioxide.. 1 in the presence of an organic liquid or solvent phase containing a selected (as herein defined) water—insoluble amine ' dissolved in an organic solvent' immiscible with the brine; the solvent phase is separated from the aqueous phase, precipitated alkali metal .bicarbonate is removed from the aqueous phase, the oxychloride in order to decompose the · dissolved- amine hydro- ' : chloride and' " to produce a concentrated aqueous magnesium chloride brine; the regenerated solvent phase is recycled for contact With the replenished alkali metal chloride-bicarbonate brines and the concentrated' magnesium chloride brine is ■· subjected, to hydrothermal decomposition in order' to produce, . ■ free hydrochloric acid and a residue of magnesium oxide or : „ magnesium oxychloride which? if desired,' is recycled to the ,,<· ' amine decomposition stage* . '*·. 2o A process according to Claim 1, wherein, the amines used '·■ · are aliphatic long-chain secondary or. tertiary, amines, having : · •more than 12 carbon atoms, or. diamines, triamines or polyamines having a CsN atomar ratio of 8 or above, being insoluble loth in the '■ '"· ■· · ■ ' ; . .· .' '4j ' ■: ". · ·'. ..· ·: · · . · '··· .. ' .·'. free state and as hydrochlorides in. the alkali, metal: :salt ' .·■ -■.>·.. '^. reaction brine, and having a low tendency to form .'carbonates and a high affinity to hydrogen chlorideV ; . · ' '.':; .;\ i'W 3.· A process according to Claims 1 or 2, wherein the solvent used' for the. solvent phase is one, or a mixture of ■ ' more', of the following! alkanols having 4 or more carbon atoms, ketones, halogenated hydrocarbons, nitrobenzene, 4. A process according to Claims 1, 2 or 3# wherein the /, organic liquid contacted with the saturated brine is comprised of two phases, .the one being a solution of the amine in a solvent, and the second phase being constituted by the amine containing some amount of the solvent « 5. A process according to any of Claims 1 to 4» wherein the carbon dioxide required for the reaction is fed to the reaction mixture by being dissolved in the organic liquid before the latter is- contacted with the aqueous brine. ' ■'■"[ " ' 6. A process according to any of Claims 1 to 5» wherein the organic- liquid is cooled before being contacted.jkvith the : -aqueous brine. . ·' 7. · A process according to any of Claims 1 to 6, wherei the saturated aqueous brine contains solid alkali metal chlo- , ride for maintaining the saturation in' such chloride in the course of the reaction. 8. . A process according to any. of Claims 1. to 7» being .' applied to the manufacture of sodium bicarbonate. , ■'" ■ 9. A process according t,o any of Claims 1 to '7, being applied to the manufacture of potassium' bicarbonate.' ' : 10. A process for the manufacture of alkali metal bicar-.. bonates, substantially as described herein with reference' > to the Examples. ·■ .' :'.' \ y.; j '■;■ '■ , . ''·.· ·, For the Applicants " '· 1 DR. REINH¾Li> QOHN PARSERS /