KR800000338B1 - Separatin of catalyst particles from a suspension of these particles in an aqueous hydroyl-ammonium solution - Google Patents

Abstract

The suspension of catalyst particles in the aq. hydroxylammonium salt soln. is treated with 0.25-2 mg polyacrylamide per g suspended catalyst to obtain a more easily filtered sediment.

Description

How to separate catalyst particles from suspension of aqueous solution containing hydroxyl-ammonium salt

The present invention relates to a method for separating catalyst particles from a suspension of an aqueous solution containing hydroxyl ammonium salts.

Hydroxylamines and hydroxyl ammonium salts are used in caprolactam preparation. Cyclohexanone and hydroxylamine or salts thereof react to form cyclohexanone oxime and to produce caprolactam in cyclohexanone oxime.

Hydroxyl amines and hydroxyl ammonium salts can be prepared by reducing nitric oxide, nitric acid or nitrates. The method of reducing them can be obtained by reacting these compounds with a hydrogen hydride catalyst, ie platinum or palladium or mixtures thereof, as is known.

When nitrogen oxide is reduced to hydrogen with a catalyst, the catalyst particles should be removed after the reaction. When the catalyst particles are removed, they are separated by filtration. Filtering the mixture in the suspension is known to be very difficult because the reactants are in suspension when the nitrogen chloride is reduced and the suspension increases in filtration resistance over time. In some cases, the filtration resistance measured by the drainage time flowing through the filter has a very large value. Filtration resistance adversely affects the preparation and separation of hydroxylammonium salts. The increase in filtration resistance is due to the decomposition of small amounts of impurity particles. Examples of the impurities include succinic acid, hydroxycarboxylic acids, amines, toluene and the like. These organic impurities are present in the reaction mixture when the solution containing the hydroxylammonium salt reacts with the ketone to form an oxime and then removes the oxime from the reaction mixture and reuses the remaining solution for the preparation of the hydroxylammonium salt. The present invention relates to a method for separating a catalyst from a suspension of an aqueous solution containing hydroxylammonium salts, which is very important in the preparation of hydroxylammonium salts used in the preparation of caprolactam, which is a raw material of nylon 6. It has been found in the present invention that the high filtration resistance that occurs when filtration of their reaction mixtures upon reduction of nitrogen monoxide, nitric acid or nitric oxide with a catalyst is reduced by adding a coagulant to the suspension. The addition of this coagulant has no effect on the activity and selectivity of the catalyst and the reduction of the catalyst continues. According to the present invention, the catalyst particles may be removed and separated from the solution containing the hydroxyl ammonium salt without degrading the efficiency. By using the method of the present invention, it is possible to reduce the time for separating the product and the catalyst, thereby increasing the efficiency of the basic process for preparing the hydroxylammonium salt and saving time and money. The present invention can be applied to a batch process or a continuous process in the manufacture of hydroxyammonium salts or hydroxy amines. The present invention seeks to improve the production and separation of hydroxy ammonium salts (or hydroxy amines). In particular, the present invention provides hydroxy ammonium salts by reduction of nitric oxide compounds, such as nitrogen monoxide, nitric acid, and nitrates, by catalytic hydrogenation. This is useful for When these compounds are reduced by catalytic hydrogenation, the reaction mixture is in suspension, where the catalyst is dispersed in an acidic aqueous solution containing hydroxy ammonium salts. This catalyst uses platinum, palladium or carbon supported mixtures. Catalytic hydrogenation reduction is carried out in an acidic aqueous solution where the acid can be any inorganic acid that is inert, irrelevant to the reaction. In the present invention, a coagulant may be added directly to the reaction mixture. This coagulant may be added at any time before or after reduction or in the middle of the reaction step. By adding this coagulant, the filtration resistance can be lowered, and thus the product can be efficiently separated by increasing the filtration amount of the reaction mixture through the filter.

The amount of this coagulant can be added between 0.1-20 mg per g catalyst and 0.25-2 mg per g catalyst is suitable. If necessary, the addition of the coagulant may be repeated in a cycle of 1-8 hours without any disruption to the manufacturing process.

For the most efficient mixing of the suspension and the coagulant, it is recommended that the coagulant be added 0.01-1% by weight in a dilute aqueous solution. A portion of the hydroxyammonium salt solution can be used as a solvent to make this dilute aqueous solution.

The coagulant may be an anionic or nonionic polymer. Examples of suitable coagulants include starch, gelled, polyacrylamide and polyvinyl alcohol. Particularly good results are obtained with nonionic polyacrylamides having an average molecular weight of 3 × 10 ⁷ and an average degree of polymerization of 4 × 10 ⁵ . Such coagulants are commercially available under the trade name Meyprofloc P ₃ . It can be used as nonionic polyacrylamide having different average molecular weight and degree of polymerization. Since the catalyst particles have a positive charge, anionic coagulants may be suitable, but nonionic polyacrylamide has the best results. The process of the present invention is as shown in the following examples.

Example 1

In the reactor having a temperature of 60 ° C., a hydrogen pressure of 10 atm, and an effective capacity of 3 liters, four filtration tubes of sintered steel were installed while rotating the stirrer 2,000 times per minute to continuously catalytically reduce the nitric oxide compound.

The aqueous solution introduced into the reactor contained 21.6 g of phosphoric acid and 22.4 g of ammonium nitrate in 100 g and was introduced at an amount of 5 kg per hour. The catalyst used was 15 g of palladium platinum catalyst supported on porous activated carbon, with a catalyst composition of 8 weight percent palladium and 2 weight percent platinum. The solution containing 4.9 g of monohydroxy ammonium 9.3 g mill ammonium phosphate 11.7 g ammonium nitrate salt 14.4 g per 100 g of the reaction was sent to a filter tube. The capacity of this filter was such that the inflow could continue even at the highest filtration resistance.

After 10 minutes, the catalyst collected in the filter was returned to the reaction solution by a short pressure pulse. The filter was washed in this manner and immediately measured the time (drainage time) required to obtain 0.3 liters of the filtered reaction solution. Saved.

The initial filtration resistance was consistent with the drainage time of 40 seconds.

The filtration resistance gradually increased due to an organic impurity amounting to 0.04 g per 100 g of carbon-based solution added with a solution of nitrate, and the drainage time was about 100 seconds after 9 hours. Using a specially purified nitrate solution for the next comparison, the drainage time dropped to 70 seconds after 9 hours (18 hours in total). An aqueous solution containing 0.05% by weight of coagulant was then added to the suspension in the reactor. At this time, the coagulant used mayprofloc P ₃ which is a nonionic polyacrylamide having an average molecular weight of 3 × 10 ⁷ and an average degree of polymerization of 4 × 10 ⁵ . After 5 minutes, the drainage time had returned to its original value of 40 seconds, and this low filtration resistance was maintained for 17 hours without the addition of a coagulant.

Example 2

The ammonium nitrate salt solution of the same composition as that used initially in Example 1 was brought to 3.5 kg solution per hour in the same apparatus, and ammonium nitrate was continuously reduced in the same manner. Filtration resistance at initial inflow was consistent with a drainage time of 40 seconds. Next, 0.75 g of cyclohexylamine was continuously added to 1 liter of the nitrate solution to be reduced. The filtration resistance then rose to the drainage time of 70 seconds over 20 hours. Next, 0.75 g of hexasim was added to the cyclone for one liter of the solution to be reduced, and the filtration resistance was further increased to a drainage time of 100 seconds over 12 hours. Upon stopping the addition of the next impurity, over 12 hours the filtration resistance was reduced to a constant drainage time of 70 seconds. Then, 4 mg of meaprofluloc P ₃ as an aqueous 0.05% by weight solution was added to the suspension in the reactor, and the filtration resistance was reduced to a drainage time of 42 seconds over 5 minutes.

Claims (1)

Nitrogen oxide compounds such as nitrogen monoxide, nitric acid and nitrates are reduced and-from this suspension by treating the nitric oxide compound with hydrogen and a hydrogenation catalyst in an aqueous acid solution to form a suspension containing hydroxyl ammonium salts. Aqueous solution containing hydroxylammonium salt by adding a coagulant such as starch, gelatin polyacrylamide, polyvinyl alcohol to the above-mentioned water-soluble acid solution in the method for producing and separating hydroxyl amine, which is a step of separating hydroxyl ammonium salt. Improved method for separating catalyst particles from a suspension of