Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B3/00—Electrolytic production of organic compounds
  • C25B3/20—Processes
  • C25B3/25—Reduction

Definitions

• ABSTRACT In the cathodic reduction of oxalic acid to glyoxylic acid production of hydrogen is reduced when the catholyte contains oxalic acid and 0.001 percent 1 percent of an adjuvant 'which isa tertiary amine or quaternary ammonium derivative having more than 1 1 carbon atoms and, the nitrogen of which is not part of an unsaturated heterocyclic ring, or a heterocyclic tertiary amine or quaternary ammonium derivative thereof, the heterocyclic ring being unsaturated, containing a nitrogen atom and at least five carbon atoms.
• an adjuvant ' which isa tertiary amine or quaternary ammonium derivative having more than 1 1 carbon atoms and, the nitrogen of which is not part of an unsaturated heterocyclic ring, or a heterocyclic tertiary amine or quaternary ammonium derivative thereof, the heterocyclic ring being unsaturated, containing a nitrogen atom
• the present invention provides a process for the preparation of glyoxylic acid by the cathodic reduction of oxalic acid which consists of carrying out an electrolysis in an electrolysis cell comprising a cathode. a cathode compartment, a separating diaphragm, an anode compartment, and an anode, the said cathode compartment containing a catholyte comprising an aqueous so lution of oxalic acid, and 0.00005 to 1 percent by weight of an adjuvant which is:
• a tertiary amine or quaternary ammonium compound which has a total of more than I 1 carbon atoms and the nitrogen atom of which is not part of an unsaturated heterocyclic ring.
• a heterocyclic tertiary amine or quaternary ammonium compound derived therefrom the heterocyclic ring structure of which is unsaturated,contains nitrogen and possesses at least five carbon atoms.
• the adjuvants defined above generally have less than 40 carbon atoms in all.
• y g N Preferred adjuvants are those having the formulae:
• R R R R R R and R which may be the same or different, represents a saturated or unsaturated, linear or branched, aliphatic hydrocarbon radical, or any pair from R,, R ,R and R or any pair from R R and R together forms a saturated alkylene or oxydialkylene radical, or a radical containing at least 2 oxyalkylene groups, for example, a radical of the for- 2 or 3 and m is an integer of l to 10,
• ferred amines of the formula [ll or IV are pyridine, dipyridyl, quinoline, phenanthroline and their derivatives carrying alkyl substituents, especially picolines and lutidines.
• R represents an alkyl radical of up to 20 carbon atoms.
• y is equal to 1, 2 or 3.
• A is the hydroxyl radical or an anion such that AH represents an inorganic or organic acid.
• A can be varied widely and any particular anion can be replaced by another according to the conventional techniques of ion exchange; examples of anions represented by A in addition to the hydroxyl radical, are nitrate, sulphate, phosphate, sulphonate, bicarbonate and oxalate.
• the adjuvants used in the invention are preferably those which are soluble in water at the concentration considered, and in particular it is preferred to choose A so that the salts have this solubility.
• Examples of preferred adjuvants are tetrabutylammonium, tributyl-lauryl-ammonium, trimethyllauryl-ammonium, trimethyl-myristyl-ammonium, trimethyl-palmityl-ammonium, trimethyl-stearylammonium, trimethyl-oleyl-ammonium, trimethyllinoleyl-ammonium, trimethyl-linolenyl-ammonium, trimethyl-arachidyl-ammonium, trimethyl-behenylammonium, trimethyl-erucyl-ammonium, triethylstearyl-arnmonium and triethyl-hexyl-ammonium salts, especially the halides and bicarbonates and the hydroxides; pyridinq quinoline and 2,2' -dip yridyl.
• the temperature of the catholyte is generally between and 70C., and preferably between and 35C.
• Examples of metallic materials which are capable of forming the cathodes used in the process of the invention are lead, cadmium, mercury and amalgams, as well as the alloys of these metals, particularly with silver, tin or antimony.
• the anode of the electrolysis cells consists of an electrically conducting material which is electrochemically stable in the anolyte and under the operating conditions considered.
• electrically conducting material examples include metals and metalloids such as platinum, platinised titanium, graphite, lead and its alloys, particularly with .silver, antimony or tin.
• the separating diaphragm of the anode and cathode compartments is preferably a cation exchange membrane.
• Any known membrane can be used, but membranes of the homogeneous type and membranes of the heterogeneous type are preferred. These membranes can optionally be reinforced with a screen.
• membranes which do not swell and which are stable to the action of the various constituents of the catholyte and the anolyte. Examples of such membranes are those described in the following specifications. United States Patent No. 2,681,320 and French Patent Nos. 1,568,994, 1,575,782, 1,578,019, 1,583,089, 1,584,187 and 2,040,950.
• the permeation selectivity of the membranes used is preferably greater than 60%.
• the catholyte used in the process according to the invention can comprise water, oxalic acid,glyoxylic acid, one or more adjuvants having one of the formulae 1 to V and, optionally, a strong inorganic acid such as sulphuric acid; however, the strong acid is preferably absent.
• the catholyte can contain oxalic acid without glyoxylic acid only at the start of electrolysis; in the same way, the catholyte can contain glyoxylic acid without oxalic acid only at the end of electrolysis.
• concentrations of the oxalic and glyoxylic acid can be either constant when the reaction is carried out continuously, or variable when the reaction is carried out discontinuously or at the start of a continuous operation. In all cases, the concentration of oxalic acid is less then the saturation value at the temperature of electrolysis; generally, this concentration is greater than 2 percent by weight, this value relating particularly to the constant concentration when the reaction is carried out continuously and to the final concentration when the reaction is carried out discontinuously.
• the concentration of glyoxylic acid is usually between 3 and 25 percent by weight, and preferably between 5 and 15 percent by weight, these values relating particularly to the constant concentration of glyoxylic acid when the reaction is carried out continuously and to the final concentration of this acid when the reaction is carried out discontinuously.
• the oxalic acid can be the commercially available material, or if preferred the acid recrystallised from this can be used. Oxalic acid produced by any known process can be used with apparatus in which no special precautions are necessary to remove harmful ions.
• the concentration of adjuvant in the catholyte is usually 0.00005 to 1 percent by weight. This concentration is preferably between 0.0001 and 0.5 percent; the use of these small amounts has the value of avoiding the need to remove the adjuvant from the glyoxylic acid produced, as the adjuvant in these amounts hardly exerts any harmful effect on the properties of the acid.
• the adjuvant helps to reduce the amount of hydrogen produced at the cathode and improves the electrical yield.
• the catholyte can also contain reaction byproducts in small amounts, e.g. generally less than 1 percent.
• An aqueous acid solution is preferably used as the anolyte, though any other anolyte capable of providing electrical conductivity between the two electrodes can be used.
• Aqueous solutions of sulphuric or phosphoric acids are usually employed in a concentration generally of 0.1 to 5 mols/ litre, and preferably 0.5 to 2 mols/ litre.
• the current density at the cathode is preferably 3 to 50 A/dm, and especially 10 to 35 Aldm
• electrolysis cells of any known type can be used, for example, those disclosed in the patent specifications mentioned above and especially Belgian Patent Specification No. 751 0.
• electrolysis cells with solid electrodes, which makes it possible to produce a compact apparatus, especially of the filter press type.
• the electrodes and the separating diaphragm are advantageously located in parallel planes.
• either or both of the catholyte and the anolyte can be circulated in their respective compartments, which makes it possible to achieve better results.
• spacers for example, woven fabrics or grids, can be located between the electrodes and the separating diaphragm.
• concentrations of solutions expressed as a percentage denote, unless otherwise stated, the number of grams of solute per 100 cm of solution; however, these concentrations in g/l cm differ only slightly from concentrations in (weight/Weight) because the solutions employed in the Examples generally have a density of about 1.
• the commercial oxalic acid used in the Examples is an acid prepared according to the techniques described in French Patent Specification No. 331,498 and British Patent Specification No. 11,487/1915, the various reactions carried out leading to an oxalic acid solution which is dried in vacuo and then crystals separated from mother liquor.
• the product is an oxalic acid dihydrate with a degree of purity of about 99.2 percent.
• the recrystallizations mentioned in the Examples were carriedout from water.
• Both the electrodes are rectangular plates of lead with a usable surface area of these electrodes being 2.5 40
• the cation exchange membrane is of the heteroge neous type consisting of a crosslinked sulphonated styrene/divinylbenzene copolymer dispersed in a polyvinyl chloride matrix, and is reinforced with a screen in the form of a woven fabric.
• Catholyte introduced initially: 7 1 of a 3.28% oxalic acid solution.
• This solution is electrolysed for 7 hours 15 minutes, supplying 0.510 l/hour of a 15.6 percent strength aqueous solution of oxalic acid and removing the taining 10.5 percent of oxalic acid. During this entire period, the volume of the catholyte is kept constant at 7 1.
• the catholyte was found to contain 4.4 percent glyoxylic acid and 4.2 percent oxalic acid.
• Table 1 shows the development of the instantaneous current yield (yield for the production of hydrogen) during the various time intervals studied.
• Two pumps cause the catholyte and the anolyte to flow in the corresponding compartments of the cell.
• the catholyte removed during the 40 hours represents 33.990 1.
• the material balance for the40 hour period considered is as follows:
• oxalic acid employed 3,423 g oxalic acid consumed 2,220 g glyoxylic acid produced 1,674 g current yield 86.6% yield of glyoxylic acid relative to the oxalic acid consumed 91.7%
• Electrolysis is carried out under the following conditions:
• the catholyte is degassed with a stream of nitrogen of 100 l/hr.
• Catholyte introduced initially: 1.630 1 of a 5.8% aqueous solution of oxalic acid (commercial oxalic acid, recrystallised once from water). This solution is electrolysed for 1 hour and recrystallised oxalic acid containing 172g of pure oxalic acid is then introduced again into the catholyte. This addition is repeated every 30 minutes during the first 9 hours ofelectrolysis. The volume of catholyte is kept constant at 1.600 I. After a total electrolysis time of 9 hours, the hydrogen, which is liberated from the catholyte, represents an instantaneous current yield of 10.7 percent.
• the catholyte is found to contain 8.5 percent glyoxylic acid and 4.35 percent oxalic acid.
• This solution was found to contain 435 g glyoxylic acid and 207 g. oxalic acid.
• EXAMP 3 The apparatus described in Example 2 is used and electrolysis is carried out under the following conditions:
• Catholyte introduced initially: 1 litre of a 3.57 percent aqueous solution of oxalic acid (commercial acid recrystallised once from water).
• Electrolysis is carried out for 1 hour 45 minutes, supplying the catholyte with 0.110 l/hour of a 35.7 percent hot (C) solution of oxalic acid and removal as in previous Examples to keep the volume constant.
• the hydrogen produced at this instant represents an instantaneous electrical yield of 3.9 percent.
• Electrolysis is continued for 4 hours 15 minutes with the same rate of feed catholyte as above; 2 g of the tetra-butyl-ammonium hydroxide solution mentioned above are then added. Electrolysis is continued under the same conditions for 1 hour 30 minutes. The volume of the catholyte is brought to 1.600 1 and electrolysis is continued for 6 hours, keeping the volume of the catholyte at 1.6 l by suitable removal.
• the catholyte is supplied with a 19.1 percent aqueous solution of oxalic acid, at the rate of 0.230 l/hour.
• the evolution of hydrogen represents an electrical yield which is constant and substantially equal to 1 percent.
• the apparatus is emptied and the liquid obtained is combined with the liquid removed.
• Glyoxylic acid was obtained with an average current yield of 91% and a yield of 93.2 percent relative to the oxalic acid used up.
• the electrolysis conditions are as follows:
• Catholyte introduced initially: 2 l of a 5.85 percent aqueous solution of oxalic acid (commercial acid which has not been recrystallised. This solution is electrolysed for 1 hour 15 minutes and 17.9 g of oxalic acid are then added to the catholyte every 30 minutes until the end of the experiment. After a total electrolysis time of 4 hours, the hydrogen produced represents a current yield of 10.5 percent. 4 cm of an aqueous solution containing 0.5 mol of tributyl-lauryl-ammonium hydroxide/litre are then added. Electrolysis is continued for 2 hours and the hydrogen evolved, which then represents a current yield of 0.1 percent, is measured.
• EXAMPLE 5 The reduction of commercial oxalic acid is carried out in a cell similar to that of Example 1.
• the electrolysis conditions are as follows:
• Catholyte introduced initially: 10 l of a percent aqueous solution of oxalic acid (commercial acid recrystallised once from water).
• This solution is electrolysed for 29 hours, adding 114 g of oxalic acid to the catholyte every hour. After operating for 18 hours, 0.500 1 of water is added every hour at the same time as the oxalic acid, and the volume of the catholyte is kept at 1.
• the catholyte contains 9.55 percent glyoxylic acid and 4.55 percent oxalic acid.
• Example 4 0.2 cm of the solution containing 0.36 mol of triethyl-(n-stearyl)-ammonium hydroxide/litre is then added to the catholyte. During the 14 hours which fol- EXAMPLE 6 The procedure of Example 4 is followed, using, as the quaternary ammonium derivative, 5 cm of a solution containing l mol of triethyl-(n-hexyl)-ammonium bicarbonate/litre.
• the hydrogen produced represents a current yield of 3.7 percent.
• the solution of triethyl -(n-hexyb ammonium bicarbonate is added to the catholyte, the volurneof which is 2 1.
• the current yield corresponding to the hydrogen produced beqme 9-9 per nt;
• EXAMPLE 7 The procedure of Example 4 is followed, using pyridine as the adjuvant. After v .0 h9ur .5.mia t s 9 sls rqlysi vygh u a adjuvant, the hydrogen produced represents a current Y ld of 6.2 why99115 One g of pyridine is then added to the catholyte; at the end of minutes the current yield for the hydrogen is no more than percent; 1 cm of pyridin e is again added to the catholyte and electrolysis is continued for a further 3 hears n te "Marth same conditions. During all this time, the instantaneous current yield corresponding to the hydrogen produced remains constant and equal to 4 percent.
• EXAMPLE 8 The procedure of Example 4 is followed, using quinoline as the adjuvant. After 5 hours of electrolysis without an adjuvant, the hydrogen produced represents a current yield of 6.5 percent. 0.25 cm of quinoline is added to the catholyte, the volume of which is 2 l. The current yield corresponding to the hydrogen produced after the addition of the adjuvant is n o more than 4.1 percent.
• the hydrogen produced represents a current yield of 21 percent. 0.25 g of 2,2-dipyridyl is then added to the catholyte, the volume of which is 2 l. The current yield corresponding to the hydrogen produced after the addition of the adjuvant is no more than 2.2 percent.
• EXAMPLE l0 Electrolysis is carried out in an apparatus similar to that of Example 1, under the following conditions.
• Anolyte 10 percent by weight aqueous solution of sulphuric acid.
• Catholyte during the first 10 hours, the apparatus is supplied at the rate of 0.27 l/hour with an aqueous solution, at C, containing 57.2 percent by weight of oxalic acid and 0.007 g/l of trimethyl-stearylammonium chloride.
• the apparatus is supplied at the rate of 0.68 l/hour with a solution, at 60C, containing 25.3 percent by weight of oxalic acid and 0.014 g/l of trimethyl-stearylammonium chloride.
• the catholyte is removed at the rate of 0.74 l/hour.
• the anolyte and the catholyte are degassed with a stream of nitrogen l/hour) Speed of flow of the electrolytes I m/second.
• oxalic acid (dihydrate) employed- 18.025 kg oxalic acid (dihydrate) recovered-3.855 kg glyoxylic acid produced-7.747 kg chemical yield mols of glyoxylic acid produced qts za sasgx lishiiea p e prising an aqueous solution of oxalic acid, and 0.00005 to 1 percent by weight of an adjuvant which is:
• a trt i ary airline or quaternary ammonium compound which has a total of more than 11 carbon i atoms and the nitrogen atom of which is not part of an unsaturated heterocyclic ring
• a heterocyclic tertiary amine or quaternary ammonium compound derived therefrom the heterocyclic ring structure of which is unsaturated, contains nitrogen and possesses at least 5 carbon atoms.
• each of R R R R4, R R and R independently represents a saturated or unsaturated, linear or branched,”aliphiifiFTfl diOEHJGi radical, or any pair from R R R and R4, or any pair from R R and R together forms a saturated alkylene or an oxydialkylene radical, or a radical containing at least two oxyalkylene groups (1 represents a hydrogen atom, or an alkyl radical of up to 20 carbon atoms, or a radical of the formula or two adjacent (1 symbols together form a radical of the formula ace: (2
• R8 represents an alkyl radical of up to 20 carbon atoms.
• y is equal to l, 2 or 3
• A is the hydroxyl radical or an anion such that AH represents an inorganic or organic acid.
• the adjuvant is selected from the group consisting of tetrabutylammonium, tributyl-lauryl-ammonium, trimethyllauryl-ammonium, trimethyl-myristyl-ammonium, trimethyl-palmityl-ammonium, trimethyl-stearylammonium, trimethyl-oleyl-ammonium, trimethyllinoleyl-ammonium, trimethyl-linolenyl-ammonium, trimethyl-arachidyl-ammonium, trimethyl-behenylammonium, trimethyl-erucyl-ammonium, triethyle rx pniyln and F 1 -hexx -anmeniu 7,5 and hydroxide, pyridine, quinoline and 2,2-dipyridyl.

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  • BE BE787771D patent/BE787771A/fr unknown
• 1971
  • 1971-08-20 FR FR7130396A patent/FR2151151A5/fr not_active Expired
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  • 1972-08-17 JP JP8185972A patent/JPS5324406B2/ja not_active Expired
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