SE193192C1 - - Google Patents

Description

Inventors: R Johnson and CR Campbell Priority Required from June 23, 1960 (USA) This invention relates to a catalyst recovery process, and more particularly to the recovery of a specific blan.dk catalyst system from the "waste" solutions obtained in the manufacture of adipic acid by oxidation of cyclohexanol and / or cyclohexanone with nitric acid. An electrifying commercial method for the production of adipic acid, a valuable () and widely used chemical, involved a series of various steps, including (1) the oxidation of liquid phase eykloheman with air or other molecular oxygen-containing gas to a mixture of eyklohexanol and cyclohexanone with a fairly low conversion rate but high yields, (2) the separation of the non-oxidized cyclohexane from the reaction intermediates cyclobexanol and cyclohexanone (3) the final oxidation of the intermediates with a strong oxidizing agent, such as nitric acid, to adipic acid and other organic, dibasic acids, such as glutaric acid and succinic acid, and (4) isolation of adipic acid from the by-products of organic acids. A proposed method of carrying out the nitric acid oxidation of said intermediates in the reaction involves the use of a mixed catalyst system composed of vanadium and copper compounds. The adipic acid thus produced is crystallized from the product from the nitric acid oxidation, and the mother liquor of the adipic acid is separated from Iran. In the mother liquor are the valuable catalyst compounds and soluble by-products in the form of organic tvabasic acids. Hitherto the economics of the process have required that the mother liquor must be disposed of as waste, as by burning the remaining hydrocarbons and thereby losing the precious catalyst compounds. Nth. If vanadium compounds are used in catalyst mixture one, it has previously been proposed to recover such compounds by adjusting the pH of the waste solution to a value exceeding 1.0, by adding some inorganic base, such as sodium carbonate or hydroxide. The precipitated organic vanadium complex can be recovered by filtration, and returned to the nitric acid oxidation step. However, such a procedure obviously involves the addition of metal ions to the system, thereby giving rise to considerable processing durations. In accordance with another age procedure, it has been proposed to add sulfur to the waste solution, and to heat the resulting mixture until substantially all of the nitric acid and water has been evaporated therefrom. The catalysts and by-products are then isolated from the residue. This latter method is unsatisfactory, since one has to introduce foreign substances into the system, and in addition expensive steps must be taken to separate the catalysts from the by-products isolated in connection with armed. If the recovery of the copper and vanadium of these valuable catalysts is attempted by first evaporating the waste solutions to dryness, a vigorous oxidation reaction sets in, which makes recovery in this way very dangerous.

A further object of the present invention is to provide an improved method for recovering and recycling a copper-vanadium catalyst from waste disposal obtained in the manufacture of adipic acid by oxidation of cyclohexanol and cyclohexanone mixtures with nitric acid, the problems usually associated with The clay recovery of said catalysts is eliminated. A further object of the present invention is to provide for the recovery and re-use of the aforementioned copper-vanadium catalyst, without introducing into the nitric acid oxidation system described above foreign chemicals which could accumulate and be damaged by further recirculation thereof. These and other objects according to the invention will become further apparent from the following detailed description. In the process of this invention, the above objects are generally achieved by subjecting the waste solutions obtained by the production of adipic acid by nitric acid oxidation of cyclohexanol and cyclohexanone in the presence of mixed copper-vanadium catalyst, at the time the adipic acid is crystallized and the organic acid is crystallized. , dibasic acids, such as glutaric acid and succinic acid, such controlled conditions which cause the nitric acid in the solutions to evaporate to such an extent that the pH of the evaporated residue, matt after dilution with water, is increased to between 1.0 and 2.2. The residue from the evaporation can then be diluted with water. Upon cooling of the diluted residue, the vanadium component from the above-mentioned mixed catalysts is selectively precipitated in the form of an organic vanadium complex. Appropriately, the vanadium precipitate is isolated from the mother liquor of diluted residue for possible reuse in the nitric acid oxidation of cyclohexanol and cyclohexanone. The vanadium precipitate can thus be dissolved in dilute nitric acid or the like, and recycled to the starting material for the aforementioned nitric acid oxidation step. Preferably, the mother liquor Iran diluted the vanadium precipitate and the separation further with water and cooled. This cooled, diluted mother liquor is brought into intimate contact with a polymerized cation exchange properties to effect substantially complete removal of the ionized copper from this mother liquor. The polymer with the copper ions bonded thereby is separated from the liquid medium in an appropriate manner. Finally, the copper ions are eluted from the ion exchange polymer, for example by contacting the polymer with dilute nitric acid or other suitable eluents. The eluted copper ions can be recycled to the starting material for the above-mentioned nitric acid oxidation steps.

In more detail, referring to the preferred embodiment of the invention, the first step comprises reducing the nitric acid present in the mother liquor from the adipic acid precipitate and separation, with the adipic acid produced by nitric acid oxidation of cyclohexanol or cyclohexanone of copper varysanate in a narvaro system. The nitric acid reduction or disposal can take place by batch, semi-continuous or continuous distillation under such pressure and temperature conditions that the nitric acid is evaporated from the broken mother liquor. Preferably, the mother liquor, which of course contains the vanadium copper catalyst to be deposited, is passed continuously through a steam distillation apparatus or similar vessel used for distilling water shoes at a temperature of between 90 and 150 ° C, and at a pressure of 10 to 400 mm Hg, mainly all nitric acid and alit water go over and condense. This recovered nitric acid can be passed to an acid recovery system, or used in whole or in part to, if desired, regenerate the ion exchange resin, soul used for the recovery of the copper component. The deposition of the nitric acid was continued without complete evaporation to dryness until a pH after dilution is obtained which is at least 1.2, but preferably not greater than 2.2. The liquid residue from the nitric acid evaporation can be diluted with water so that it can be handled more easily. While the quantity of the dilution water can be varied considerably, it is preferred that the amount of water should be from 0.75 to 4.0 times the weight of the residue from the evaporation. The precipitation of vanadium as an organometallic complex occurs, for example, by cooling the diluted residue to a suitable, low temperature, preferably below 100 ° C but above 30 ° C, and by retaining it in a storage vessel for a sufficiently long time to provide a essentially complete precipitation. The preferred precipitation temperature is in the vicinity of 60 ° C. The vanadium precipitate is separated from its surrounding mother liquor by filtration, centrifugation or by other optional separation procedures. The vanadium compound can then be dissolved in nitric acid at room temperature and the resulting solution after concentration if so. Desired in metered doses to the step where the cyclohexanol and cyclohexanone mixture are catalytically oxidized with nitric acid to adipic acid. The mother liquor from the vanadium precipitate was further diluted with water if necessary, and further cooled with a flake lamp device, such as by using a heat exchanger or by initially drawing cold water or the like to a temperature preferably below 35 ° C. In this case, the preferred temperature range is in the vicinity of 20 to 30 ° C. The cooled liquid, which contains the copper catalyst, dissolved, organic dibasic acids, water and some nitric acid at a temperature of 20 to 30 ° C, is passed through a column containing a cation exchange resin or brought into some other suitable salt in intimate contact therewith, whereby the copper ions removed from the solution. The organic, dibasic acids and the other substances which pass through the column can be burned or disposed of in any suitable manner. The copper component is eluted at a temperature of 20 to 30 ° C Iran cation exchange resin for reuse. The dilute nitric acid recovered from the distillation of the mother liquor can be used to regenerate the resin and to remove the copper component from said resin. The eluent of obvious distinction is preferably nitric acid, alien or other pineapple can be used. The elution solution containing the dissolved copper compound may, if desired, be returned to the nitric acid oxidation step after first concentrating. It is to be understood that the temperature at which the solution is brought into contact with the cation exchange resin and the temperature at which the copper component is eluted are not critical, but may vary from one kind of resin to another, the main thing being that the temperature does not become sufficiently high to substantially probe the resin.

In order to obtain a more complete picture of the present invention, reference will now be made to the accompanying drawing, which is a schematic representation of a process system suitable for recovering the catalyst mixture. The mother liquor of adipic acid is fed to a liquid container for storage 10 of the line 12. It supplies the material to said zone for the aqueous waste liquor obtained in the production of adipic acid by nitric acid oxidation of cyclohexanol and cyclohexanone in the presence of a copper and copper catalyst with cocatalyst to the system as a soluble salt, for example as copper nitrate or the like and the vanadium added as ammonium vanadate or the like. The liquid also contains a quantity of organic, dibasic acids, such as glutaric acid and succinic acid, which are formed in by-products in the aforementioned nitric acid oxidation process. Due to the differences between the phenadipic acid and the other so-called homologous dicarboxylic acids, the adipic acid Hit can be isolated therefrom by simple crystallization and separation methods. The aqueous mother liquor from the adipic acid crystallization is the starting material for the present process, from which valuable catalyst compounds are recovered. Fran lag-. zone 10, the aqueous mother liquor is drained batchwise, continuously if necessary, and passed via a line 16 to a conventional stripper, adapted to remove the resulting lion concentrate and the released gases, such as a steam evaporator 14. by the solution which is fed into the evaporator, with said milord to the evaporator through line 18. This water distillation was continued until essentially all the nitric acid had been removed from the mother liquor.

The residue after evaporation is a free-flowing liquid above 110 ° C, and has melting points from 80 to 100 ° C, depending on the content thereof of dibasic acids, including glutaric acid and succinic acid, as well as some adipic acid. The other constituents of the residue are the catalyst components and a small amount of water and the saving amount of nitric acid. It falls within the scope of this invention to remove the nitric acid from the solution by other methods, such as by inhalation of vacuum and heating as long as the pH of the solution. chemicals. Not introducing any foreign chemicals into the pH adjustment system enables the recovery of the catalyst components from the adipic acid mother liquor with improved quality, while at the same time reducing the liabilities that normally accompany the known catalyst recovery operations.

From the evaporator 14, the evaporation residue is passed through the tube 20. During the passage through this tube, water was added to the residual material through the conduit 22, and the whole stream was then led into a filling zone, provided by the precipitation tank 24. The addition of water serves to ensure that the residual material of the organic, dibasic acids, small amounts of nitric acid and copper compounds remain in solution as desired, and the vanadium component precipitates at an appropriate temperature, thereby facilitating material handling. In the tank or on the way there, the temperature of the evaporated residue must be lowered, in order to cause the vanadium to be formed as an organic vanadium complex. It is clear that the temperature to which the evaporated residue is adjusted depends, inter alia, on the specific composition of the diluted residue, as the optimum precipitation temperature may vary from time to time, with the preferred temperature indicated above. The diluted material, which now contains the vanadium precipitate, is filtered or otherwise separated after this precipitation, in order to effect removal of the vanadium-containing substase. This can be accomplished by feeding the diluted material through line 26 to filter 28, the aqueous phase being separated from the vanadium-containing precipitate. Any of several types of filters can be used for this step in the process. A rotary filter, or a quick filter, such as a centrifuge can be used, or a pressure filter can also be used. The vanadium precipitate is removed from the filter 28 in a conventional manner, and then the deposited material is passed through the conduit 30 to an effluent container 32. It is preferred to dissolve the precipitated vanadium-containing material with dilute nitric acid. The dissolved material can then be recirculated through the tube 34 to the step in the production of adipic acid, where cyclohexanol and cyclohexanone are oxidized to adipic acid - - nitric acid. The subsequent treatment of the liquid passing through the filter 28 depends on the concentration of the dissolved material and its temperature. It is usually preferred to spit out the solution by adding water. This can be accomplished by supplying water through line 36, while the solution is led through pipe 38 to cooler 40. Cooling and spouting have been proposed so that ordinary, commercial ion breaker resins can be used in a conventional manner, although it is worth noting that steps may be omitted when the selected resin is adapted to precipitate copper ions from the solution at other concentrations and temperatures. The cooled solution is then passed through either of the ion exchange columns 42 or 44, which contain a cation exchange resin in such a form as a compact bath of beads. When two or more columns are used, the process can be adjusted to be continuous. While a column can be used in a semi-continuous process, two or more columns of easy-to-understand shells are preferred. A solid cation exchange material against which the cooled solution is inert, in order to remove the copper ions therein. The ion exchange material may be a synthetic polymer, which reacts with the copper ions in the solution, and deposits them therefrom. The material should also be able to conveniently regenerate to at least some of its original activity, so that it can be anyandas Hera times, and it should be insoluble in the liquid containing the copper ions. A suitable ion exchange material is a water-insoluble polymer of a mixture of a sulfonated polyvinyl aryl compound and a monovinyl aryl compound. Such materials are sold under the tradenames IR-120 and DOW-50W and can be chemically identified as sulfonated polystyrene containing various amounts of divinylbenzene and crosslinking agents. The cooled liquid is passed from the cooler 40 to the ion exchange columns through lines 45-46 or 45-48, as needed. The Risning which emerges at the bottom of column 42 or column 44, contains essentially the remaining dibasic acids, comprising glutaric acid, succinic acid and adipic acid, together with some water and nitric acid. The solution is disposed of in a somewhat appropriate manner, which in some cases involved burning of the remaining acids. The copper is eluted from the ion exchange resin in an appropriate manner. It is preferred that dilute nitric acid be passed down through the resin in columns 42 and 44 from acid reservoir 50 through lines 52-54 or 52-56. The elution solution, containing the recovered copper catalyst component, can then be recycled through line 58-61 or 60-61. to the step via the addition of adipic acid, where the mixture of cyclohexanol and cyclohexanone is oxidized with nitric acid. A suitable cold for dilute nitric acid for the reservoir 50 Or the distillate recovered from the evaporator 11. The nitric acid in the distillate can either be wholly or partly led to a recovery system with the aid of line 62. Alternatively, the Overgaende was diluted with water using a mixer 64. , provided with a water intake 66. The diluted acid is then led to the reservoir 50, through the line 68. Columns 42 and 44 can be rinsed with water supplied through the pipes 70 and 72 respectively, and can be emptied through the pipes 74 and 76 respectively.

In order to better illustrate the invention, the following examples will be given, which exemplify the invention but joke intend to delimit it. The parts and percentages used hereinafter ayse weight, savida joke otherwise stated.

Example. For the feed, mother liquor Iran adipic acid was used. Adipic acid produced generic nitric acid oxidation with cyclohexanol and cyclohexanone in the presence of a copper-vanadium catalyst was recovered from the two-step oxidation reaction product. First, adipic acid was crystallized from strong nitric acid and separated therefrom. In the second step, the first mother liquor was concentrated by precipitating nitric acid, followed by the addition of water. The diluted, evaporated residue was cooled to form a second batch of adipic acid crystals. The mother liquor from this second batch was the input material, which was used in delta examples. The removal of nitric acid from a starting material took place by semi-continuous as well as continuous one-step distillation as well as by water-distillation.

The average composition of the feed material on an aqueous basis was 9.7 nitric acid, 4.42% adipic acid, 17.0% glutaric acid, 6.17% succinic acid, 1.9% copper nitrate and 0.2% vanadium compound. During the semi-continuous evaporation, the mother liquor was fed continuously into a three-liter flask, which was heated with a surrounding electric heating mantle. A pressure of 144 mm Hg is maintained during evaporation. The feed rate was controlled at the vessel temperature, as Mils yid 110 ± 5 ° C. The water and nitric acid vapors that passed over were condensed and analyzed for total acidity. The residue lick accumulates in the coal to the end of the nitric acid distillation. The remaining residue in the flask was a lark, free-flowing liquid at 90 ° C. This substance was cooled to solidification, pulverized, and analyzed for nitric acid, organic dibasic acids and catalyst. Continuous evaporation of the feed material was done in a unit consisting of an electrically heated glass boiler, with devices for continuous feeding of the mixture and continuous disposal of the titer column. The distillate was condensed in a glass master over above the feed section. The working pressure was 140 mm Hg and the feed rate was adjusted to maintain a base temperature of 105-110 ° C. Water vapor distillation of the feed material was done in a conventional unit. The operating pressure during steam distillation was 140 mm Hg and the feed rate was adjusted to maintain a base temperature of 120 ° C. The residues remaining after evaporation, as indicated above, were free-flowing water shoes above 110 ° C. They had melting points varying 60 ° C and 100 ° C depending on the pH composition of the organic dibasic acids. A typical composition for the residues was 0.47% copper, 0.17% vanadium, 3.2% water, 23.4% adipic acid, 36.7% glutaric acid and 29.7% succinic acid. An equal weight of water was added to the residue, and the mixture was heated and stirred at 60 ° C to dissolve the residue, except for the vanadium component. Below 60 ° C crystallization of organic disbasic acids enters at this concentration and such crystallization should be avoided. The joke-dissolved, vanadium-containing material is an organic vanadate complex, which is extracted by filtration in a conventional manner. It was found that a pH of the residue corresponding to 1.5 at 25 ° C resulted in the greatest yield of vanadium compound. The effect on pH on the recovery percentage of vanadium compound and the vanadium content in the joke dissolved residue is shown in Table I below.

Table I pH% atenine. V 1.4 70.0 1.72.7 1.8 64.4 2.0 12.0 At a pH below 1.2, the recovery decreases markedly. The recovered vanadium compound was used as a catalyst component in the conventional nitric acid oxidation of cyclohexanol and cyclohexanone. No significant variations were observed between the oxidations catalyzed with recovered vanadium and those catalyzed with fresh ammonium metavanadate. The oxidation reaction catalyzed by the recovered vanadium material proceeded normally, resulting in equivalent yields of adipic acid. The recovered vanadium precipitate was relatively insoluble in% nitric acid, but was easily dissolved in nitric acid. The dissolved vanadium compound can then be processed to recirculate the nitric acid oxidation step. The solution from the vanadium separation was diluted to a content of organic dibasic acids of about 30% by weight in order to prevent crystallization of the dibasic acids at the normal operating temperature of 30-35 ° C. A 90% copper recovery is obtained by passing the solution through a bath of Rohm and Haa's cation exchange resin I R-120 (the cotton mold). The bath was contained in a 25.4 mm (I. D.) glass column packed to a bath depth of 60 mm riled for the aforementioned resin. The flow rate through the column was controlled by the liquid tank above the bath and through valves at the bottom of the column. The reaction rate between the copper ions and the resin was high. An interesting phenomenon was noted during the copper absorption. The copper elements were substantially quantitatively absorbed into the resin, with a sharp green band, easily visible against the normal brown color of the resin. No loading of copper ions from the column could be detected before the edge reached a point at the bottom of the bath. After the resin bath was matte, the copper ions were eluted and the resin was regenerated by passing a stream of dilute nitric acid through the column. The concentration of the eluent acid was about 8% oiler less, to prevent flagon nomdvard aggregation of the resin. The recovered copper compounds, copper nitrate, were used as a catalyst component in the conventional nitric acid oxidation of cyclohexanol and cyclohexanone. The oxidation of the copper catalyst catalyzed by the recovered copper proceeded normally and resulted in good yields of adipic acid. In applying the invention as described above, several advantages have been found to arise. Firstly, the indicated process recovers the valuable catalyst mixture of copper and vanadium compounds and nitric acid, which would normally be removed and lost from the system. Second, the catalytic material is recovered as a product with high reactivity and purity. Third, an economic gain arises through the recycling of the catalyst mixture and nitric acid from the system. Furthermore, the process described above can proceed without any waste disposal problem arising in Iran from the recovered items.

Various modifications of the invention described above will be apparent to those skilled in the art. It is to be understood, however, that the invention is not limited by the foregoing description or the accompanying drawing, but only by the appended patent claims.

Claims (3)

Patent claim: The process for removing and recovering copper-vanadium mixed catalyst from the mother liquor obtained after crystallization and precipitation of adipic acid, which is prepared by oxidation of cyclohexanol and cyclohexanone with nitric acid in the presence of the said mixed catalyst. Provided that its nitric acid content is reduced so much that the pH of the evaporated residue after dilution is between 1.2 and 2.2 at 25 ° C, that the residue just mentioned is diluted, that the vanadium component of the catalyst is selectively selected in the form of an organic vanadium complex. by cooling, that this complex is separated from the mother liquor, that the mother liquor is brought into intimate contact with a polymer having cation exchange properties, so that the copper component of the catalyst is chemically bonded to the polymer, and that the copper ions are recovered by elution from the polymer. 2. Process according to claim 1, characterized in that the nitric acid is evaporated by heating the first-mentioned mother liquor and that the heating is continued until the nitric acid content has dropped to such a level that the pH value of the residue after dilution is between the stated values. 3. Process according to claim 1 or 2, characterized in that the nitric acid is evaporated by means of water vapor. Request publications: