KR20090009153A - Pd/c hydrogenation catalyst, preparation and use thereof - Google Patents

Abstract

A palladium/carbon hydrogenization catalyst is provided to increase catalyst stability by reducing loss of the palladium through additional optimization of dispersion of the palladium during operation and to extend lifetime of catalyst without injuring activity of catalyst. A palladium/carbon hydrogenization catalyst comprises carbon granules activated a supporting material and metallic palladium as active component. A content of the metallic palladium is 0.1-5 weight% based on a total weight of the catalyst. The palladium of 45 weight% is contained within an external layer of which a depth is 0.2-20mum of the supporting material. The palladium less than 10 weight% is contained within an outermost layer of which a depth is less than 0.2mum of the supporting material. The palladium of rest weight% is contained within an inner layer of which a depth is 20-40mum of the supporting material.

Description

Palladium / carbon hydrogenation catalyst, and preparation method and use thereof {Pd / C hydrogenation catalyst, preparation and use}

The present invention relates to a method and use of the palladium / carbon hydrogenation catalyst and the palladium / carbon hydrogenation catalyst.

Palladium / carbon catalysts are selective hydrogenation catalysts that can be used to selectively hydrogenate aldehydes, especially aromatic aldehydes. Specifically, the palladium / carbon catalyst selectively selects an aromatic aldehyde having a compositional formula of X-aromatic ring-CHO to X-aromatic ring-CH ₂ OH, or additionally X-aromatic ring-CHO to X-aromatic ring-CH ₃ . It can be used to hydrogenate, where X is methyl or carboxyl, aromatic ring is benzene ring or naphthalene ring, aromatic aldehyde is hydrogenated in acidic solution or aqueous solution at a temperature of 100-300 ° C. in the presence of hydrogen.

Based on the foregoing, the palladium / carbon catalysts are hydropurification of low purity terephthalic acid and low purity 2,6-naphthalenedicarboxylic acid as well as low purity 4- (hydrides such as aromatic aldehydes. It can be used to purify low purity 4- (hydroxymethyl) benzoic acid by selectively hydrogenating impurities in oxymethyl) benzo acid. Specifically, 4-carboxybenzaldehyde (hereinafter referred to as '4-CBA' in low purity terephthalic acid) is hydrogenated to methyl benzoic acid through two stages of hydrogenation, and 4-CBA in low purity 4- (hydroxymethyl) benzoic acid is Hydrogenated to 4- (hydroxymethyl) benzoic acid via one-step hydrogenation, 2-formyl-6-naphthoic acid in low purity 2,6-naphthalenedicarboxylic acid Is hydrogenated with 2-methyl-6-naphthoic acid.

However, since palladium is used as a single active ingredient for palladium / carbon catalysts, the distribution of metal palladium relative to the support material has a significant effect on the hydrogenation properties of the catalyst.

Furthermore, since the selective hydrogenation of aromatic aldehydes is a high speed primary reaction, it is not easy for the reactants to diffuse into the catalyst during the reaction, so that the active metal inside the particles cannot fully function. Therefore, active metal palladium should be contained in the outside of the catalyst particles as much as possible. In addition, the greater the surface area where palladium contacts the reactants, the better the activity of the catalyst.

Thus, in the context of a palladium / carbon catalyst, US Pat. No. 4,476,242 proposes to contain all active metal palladium in a surface layer at a depth of less than 70 to 80 μm of the particles; US Pat. No. 6,066,589 discloses less than 50% by weight of metal palladium in the outer layer at a depth of less than 50 μm of the support material and the remaining weight% of metal palladium in the inner layer at a depth of 50 to 400 μm of the support material. It is proposed to contain; Canadian Publication No. 1,457,922A produced a catalyst, which exhibits, for example, high conversion of 4-CBA during the hydrogenation of low purity terephthalic acid, but up to 30% by weight of palladium. Contained within the outermost layer at a depth of less than 0.2 μm of the support material, resulting in a large loss of palladium in the surface layer of the support material due to direct wear.

Based on the prior art palladium / carbon catalysts, under the condition that there is no impairment of catalytic activity, the present invention provides that the palladium contained in the outermost layer of the support material can be contained in the outer and inner layers of the support material as much as possible. The amount of p is further reduced to reduce the loss of palladium due to wear during use.

Specifically, the present invention provides a palladium / carbon hydrogenation catalyst containing activated carbon particles as a support material and containing metal palladium as an active ingredient, wherein the content of the metal palladium is based on the total weight of the catalyst. 0.1 to 5% by weight, preferably 0.2 to 3.5% by weight, more preferably 0.3 to 0.8% by weight, and at least 45% by weight of the palladium is in the outer layer at a depth of 0.2 to 20 μm of the support material. And less than 10% by weight of the palladium is contained in an outermost layer at a depth of less than 0.2 μm of the support material, and the remaining weight% of the palladium is at a depth of 20 to 400 μm of the support material. Contained within the inner layer.

According to the palladium / carbon catalyst of the present invention, the activated carbon particles have a specific surface area of 600 to 1800 m ² / g, preferably 800 to 1500 m ² / g, and a pore volume of 0.30 to 0.85 ml / g. natural or shaped particles having a pore volume, preferably natural or shaped coconut charcoal particles, and also at least 90% by weight of the particles Has a size of 4 to 8 mesh.

According to the palladium / carbon catalyst of the present invention, preferably 45 to 60% by weight of the palladium is contained in the outer layer at a depth of 0.2 to 20 μm of the support material; Preferably the remaining weight percent of the palladium is contained in an inner layer at a depth of 20-180 μm of the support material.

The present invention is the following steps

(a) selecting activated carbon particles suitable as support material particles;

(b) competing adsorbate the activated carbon particles at 0 to 50 ° C., preferably at room temperature for 5 to 60 minutes, preferably 10 to 30 minutes to obtain pre impregnated activated carbon particles. ), Where the competitive adsorbent material is an aqueous solution of a lower organic acid having 1 to 6 carbon atoms at a concentration of 0.01 to 0.5 N (normal), preferably 0.05 to 0.2 N. impregnating), filtering and drying;

(c) a weakly acidic solution containing a palladium precursor and a surfactant by impregnation or spray coating to obtain a supported catalyst, wherein the weakly acidic solution is from 3 to 6 palladium on the pre-impregnated activated carbon particles having a pH, wherein palladium is 0.1 to 5% by weight, preferably 0.2 to 3.5% by weight, more preferably 0.3, based on the total weight of the catalyst Supported in an amount of from 0.8% by weight;

(d) aging the supported catalyst in air for 1 to 24 hours to obtain a aged catalyst; And

(e) reducing the aged catalyst with a reducing agent at a temperature of 0 to 200 ° C., preferably 50 to 120 ° C. for 0.5 to 10 hours, preferably 1 to 4 hours, to obtain an activated catalyst

Including,

The next step,

(b ') removing dust and loose portions from the surface of the particles prior to step (b), washing the particles with an inorganic acid, with deionized water until neutral. Preprocessing comprising washing the particles, and drying the particles

Optionally containing

Further provided is a method of making a palladium / carbon catalyst.

According to the process for preparing the palladium / carbon catalyst of the present invention,

In step (a), the selected activated carbon particles have a specific surface area of 600 to 1800 m ² / g, preferably 800 to 1500 m ² / g, and 0.30 to 0.85 ml / g, preferably 0.40 to 0.60 ml / g. Natural or some form of particles, preferably natural or some form of coconut charcoal particles having a pore volume of, wherein at least 90% by weight of the particles mesh);

In the step (b '), the inorganic acid used in the washing step has a concentration of 0.1 to 0.5 N, and is selected from the group consisting of hydrochloric acid, nitric acid, phosphoric acid, and mixtures thereof. The purpose of washing is to condition functional groups on the surface of the activated carbon particles, and the drying step is carried out at 100 to 200 ° C, preferably 110 to 150 ° C;

In step (b), the low molecular weight organic acid is selected from the group consisting of citric acid, maleic acid, oxalic acid, lactic acid, and mixtures thereof, preferably citric acid, and the temperature of the drying step is 100 to 200 ° C, Preferably 110 to 150 ° C;

In step (c), the palladium precursor is palladium chloride (palladium chloride), palladium oxide (palladium oxide), palladium acetate (palladium acetate), palladium nitrate (palladium chloride), palladic chloride (palladic chloride), palladic Alkaline salts of chloride (palladic chloride), complexes of palladium with amines, and mixtures thereof, preferably palladic chloride; The surfactant has a concentration of 0.2 to 5% by weight, preferably 0.5 to 1.5% by weight; The surfactants are used to modify the distribution and / or dispersion properties of the palladium and the surfactants are cationic surfactants, preferably polyoxyethylene aliphatic ether sulphate alkali metal salts and poly Oxyethylene aliphatic ether phosphate alkali metal salts, specific examples are sodium polyoxyethylene dodecyl ether sulfate, potassium polyoxyethylene dodecyl ether sulfate, sodium polyoxyethylene dodecyl ether phosphate and potassium polyoxyethylene dodecyl ether phosphate Is; The pH of the solution is adjusted by the addition of carbonates, hydrocarbonates or hydroxides of alkali metals, and specific examples of the alkali metal compounds are sodium carbonate, potassium carbonate, sodium hydrocarbonate, potassium hydrocarbonate, sodium hydroxide, potassium hydro Oxides and the like; Supporting palladium on the pre-impregnated activated carbon particles is impregnated with the solution at 0-50 ° C., preferably at room temperature for 0.5-6 minutes, preferably 1-3 minutes, or 0-70 ° C. Preferably, by spray coating the solution onto the pre-impregnated activated carbon particles at a rate of 5 to 20 ml / min (min) at room temperature;

In step (e), the reducing agent is selected from the group consisting of formic acid, sodium formate, formaldehyde, hydrazine hydrate, glucose, hydrogen and mixtures thereof, preferably sodium formate.

  According to the process for producing the palladium / carbon catalyst of the invention, the support material, ie the activated carbon particles, are pre-impregnated with a competing adsorbent material and some adsorption sites on the support material are filled so that only 10 wt% of the palladium Only below is contained in the outermost layer at a depth of less than 0.2 μm of the support material, thus reducing the loss of the palladium due to wear. Therefore, the palladium / carbon catalyst of the present invention has advantages such as excellent stability and long life.

As mentioned above, the present invention also provides the use of the palladium / carbon catalyst for the purification of low purity 4- (hydroxymethyl) benzoic acid as well as hydrogenation purification of low purity terephthalic acid and low purity 2,6-naphthalenedicarboxylic acid. The low purity streams in the presence of the palladium / carbon catalyst at a temperature of 100 to 300 ° C. to convert impurities in the aromatic aldehyde contained therein to obtain hydrogenated purified or purified in said use. Acidic solution or aqueous solution is contacted with hydrogen.

All catalysts prepared according to the invention significantly reduce the amount of palladium contained in the outermost layer (0.2 μm or less) and these amounts are controlled to less than 10% by weight so that all catalysts have a very low loss of palladium even after 1000 hours of operation. Have only.

In addition, palladium is mainly contained in the outer layer (0.2-20 μm) to ensure the initial activity of these catalysts (ie high conversion of 4-CBA can be obtained in a batch reaction), and this activity is 1000 A very low decrease in activity was found to still remain after operation for hours.

In addition, the catalyst according to the present invention further reduces the loss of palladium during operation through further optimization of palladium distribution, thus increasing catalyst stability and extending the life of the catalyst without compromising the activity of the catalyst.

The invention is now described in further detail by the following non-limiting examples.

Preparation of the catalyst

Example  One

Weighing 50 g (grams) coconut charcoal particles in the flake state having a particle size of 4 to 8 mesh, a specific surface area of 1078 m ² / g and a pore volume of 0.47 ml / g; Removing dust and loose portions from the surface of the particles, washing the particles with nitric acid at a concentration of 0.5N in a vessel for one hour at 80 ° C., removing the retainers until neutral Washing the particles with deionized water, and finally drying the particles at 120 ° C. for two hours; Pre-impregnating the coconut charcoal particles with an aqueous solution of citric acid at 0.1 N concentration for 15 minutes at room temperature, then filtering, and drying at 120 ° C. for two hours; Injecting 1.25 g of an aqueous solution of palladium chloride containing 20% by weight of palladium, adding 15 g of deionized water to the aqueous solution to form an impregnation solution, and 0.45 g of potassium polyoxyethylene dode Adding additional real ether phosphate, adjusting the solution to pH 5.5 by adding the required amount of sodium carbonate, and finally 5 g of the solution such that the solution has a volume in which the coconut charcoal particles can only be dipped Replenishing deionized water, and then impregnating the coconut charcoal particles with the solution for approximately one minute to obtain the palladium / carbon catalyst; Aging the palladium / carbon catalyst in air for 24 hours, thereafter reducing the palladium / carbon catalyst with an aqueous solution of sodium formate at 80 ° C. for 4 hours, and with deionized water until neutral. Washing the palladium / carbon catalyst and finally drying the palladium / carbon catalyst to obtain catalyst A.

Example  2

Example 1 is repeated except to inject 2.00 g of an aqueous solution of palladic chloride containing 20% by weight of palladium, wherein the competitive adsorbent material is lactic acid.

Example  3

To obtain the catalyst C, the coconut char particles are not washed with nitric acid, pre-impregnating the coconut char particles with an aqueous solution of citric acid at a concentration of 0.2 N for 20 minutes, and palladic chloride containing 20% by weight of palladium. Example 1 is repeated except that 2.50 g of an aqueous solution of.

Example  4

Example 1 is repeated except to inject 6.25 g of an aqueous solution of palladic chloride containing 20% by weight of palladium to obtain catalyst D.

Example  5

Example 1 is repeated except to inject 0.50 g of an aqueous solution of palladium nitrate containing 20% by weight of palladium to obtain catalyst E.

Example  6

To obtain catalyst F, pre-impregnating the coconut charcoal particles with an aqueous solution of lactic acid at a concentration of 0.4 N for 5 minutes, and injecting 3.50 g of an aqueous solution of palladium nitrate containing 20% by weight of palladium And Example 1 is repeated.

Example  7

To obtain catalyst G, pre-impregnating the coconut charcoal particles with an aqueous solution of lactic acid at a concentration of 0.04 N for 30 minutes, and injecting 8.75 g of an aqueous solution of palladic chloride containing 20% by weight of palladium And Example 1 is repeated.

Example  8

In order to obtain catalyst H, the competitive adsorbent material is an aqueous solution of a mixture of citric acid and lactic acid, injecting 11.25 g of an aqueous solution of palladic chloride containing 20% by weight of palladium, and a rate of 10 ml / min (minutes) Example 1 is repeated except for supporting palladium on the coconut charcoal particles by furnace spray coating.

compare Example  One

Example 1 is repeated except that the coconut char particles are not pre-impregnated to obtain catalyst I.

compare Example  2

Example 1 is repeated except that potassium polyoxyethylene dodecyl ether phosphate is not added to the aqueous solution of palladic chloride to obtain catalyst J.

compare Example  3

In order to obtain catalyst K, Example 1 is repeated except that the coconut char particles are not pre-impregnated and no potassium polyoxyethylene dodecyl ether phosphate is added to the aqueous solution of palladic chloride.

In the context of the present invention, the weight percent of supported palladium relative to the palladium / carbon catalysts prepared in all of the examples and comparative examples is inductively coupled plasma spectrophotometer (ICP-AES), and the distribution of the supported palladium Is determined as follows: the amount of palladium contained at a depth of 20 μm or less and the amount of palladium contained at a depth of 180 μm or less is determined by electron microprobe analysis (EMPA) and contained at a depth of 20 μm or less. The proportion of palladium atoms is determined by X-ray photoelectron spectroscopy (XPS).

Furthermore, all the palladium / carbon catalysts prepared in all of the above examples and comparative examples are inspected through hydrogenation purification of low purity terephthalic acid. The samples are analyzed by HPLC.

For initial activity, i.e. the final conversion of 4-CBA, each catalyst is examined by batch reactions in an autoclave under the following conditions: the amount of each catalyst is 2.0 g; The amount of terephthalic acid is 30.0 g; The amount of 4-CBA was 1.0 g; The reaction pressure is 8.0 MPa (gauge); The reaction temperature is 280 ° C.

For operating activity and final palladium loss, each catalyst is checked by continuous reaction in a continuous apparatus under the following conditions: The amount of each catalyst is 200.0 g; The rate of the slurry is 3 Kg / h; The content of terephthalic acid is 5% by weight; The content of 4-CBA is 0.35% by weight; The reaction pressure is 8.0 MPa (gauge); Reaction temperature is 280 ° C; The reaction time is 1000 hours except that the reaction time of Catalyst A is 6000 hours.

The conversion of 4-CBA during the test is calculated as follows.

Transformation: (initial amount of 4-CBA-amount of 4-CBA after reaction) x 100% ÷ initial amount of 4-CBA

Evaluation of the supported palladium, palladium distribution and initial activity of each palladium prepared in all the above examples and comparative examples is shown in Table 1.

catalyst Supported Pd (wt%) Pd distribution (% by weight) Conversion of 4-CBA (%) 0-0.2mm 0.2-20mm 20-180mm 180-400mm A 0.50 9.1 60.5 30.4 0 99.0 B 0.80 9.4 62.3 28.3 0 99.2 C 1.00 8.3 53.1 38.6 0 99.3 D 2.49 9.2 60.3 30.5 0 99.5 E 0.20 9.1 61.5 29.4 0 85.7 F 1.40 8.2 51.0 40.8 0 99.4 G 3.49 9.5 70.6 19.9 0 99.6 H 4.48 8.8 62.8 28.4 0 99.7 I 0.50 16.3 59.9 23.8 0 99.8 J 0.50 8.5 40.5 36.3 14.7 94.3 K 0.49 14.3 37.2 34.9 13.6 99.2

The supported palladium, loss of palladium and operating activity of each catalyst prepared in all examples and comparative examples after 1000 hours of operation in a continuous apparatus are shown in Table 2.

catalyst Pd weight supported (after 1000 hours of operation) Loss of Pd (wt%) Conversion of 4-CBA (%) % Reduction in conversion A 0.48 0.02 97.9 1.1 B 0.76 0.04 98.0 1.2 C 0.96 0.04 98.3 1.1 D 2.43 0.06 98.5 1.0 E 0.18 0.02 84.5 1.2 F 1.36 0.04 98.1 1.3 G 3.44 0.05 98.2 1.4 H 4.40 0.08 98.3 1.4 I 0.40 0.10 95.5 4.3 J 0.49 0.01 93.2 1.1 K 0.42 0.07 97.2 2.0

The supported palladium, loss of palladium and operating activity of Catalyst A prepared in Example 1 after 6000 hours of operation in a continuous apparatus are shown in Table 3.

catalyst Pd weight supported (after 6000 hours of operation) Loss of Pd (wt%) Conversion of 4-CBA (%) % Reduction in conversion A 0.43 0.07 97.6 1.4

As can be seen from the data in Table 1 and Table 2 above, all catalysts prepared according to the present invention significantly reduced the amount of palladium contained in the outermost layer (0.2 μm or less), ie these amounts were 10% by weight. Controlled to less than all catalysts have only a very low loss of palladium even after 1000 hours of operation; Furthermore, palladium is mainly contained in the outer layer (0.2-20 μm) so that the initial activity of these catalysts can be ensured, ie high conversion of 4-CBA can be obtained in a batch reaction, and this activity is 1000 hours It was found to remain still after operation, ie a very low decrease in activity.

Furthermore, as can be seen from the data in Table 3, even after 6000 hours of operation, Catalyst A still has 0.43% by weight of supported palladium, the loss of palladium is only 0.07%, and the conversion of 4-CBA is Still at 97.6%, for example, the loss of conversion is only 1.4%,

Thus, the catalyst according to the invention reduces the loss of palladium during operation through further optimization of palladium distribution, thus increasing catalyst stability and extending the life of the catalyst without compromising the activity of the catalyst.

As various modifications may be made to the constructions and methods described and illustrated herein without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings be exemplary, and not intended to limit the invention. It is not. Therefore, the scope of the present invention should not be limited by the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims (17)

In the palladium / carbon hydrogenation catalyst, Contains activated carbon particles as support material and contains metal palladium as active ingredient, The content of the metal palladium is 0.1 to 5% by weight based on the total weight of the catalyst, At least 45% by weight of the palladium is contained in an outer layer at a depth of 0.2-20 μm of the support material, and less than 10% by weight of the palladium is an outermost layer at a depth of less than 0.2 μm of the support material. ) And the remaining weight percent of the palladium is contained in the inner layer at a depth of 20 to 400 μm of the support material. Palladium / carbon hydrogenation catalyst. The method of claim 1, The activated carbon particles are natural or shaped particles, preferably palladium / carbon hydrogenation catalysts of natural or shaped coconut charcoal particles. The method according to claim 1 or 2, The activated carbon particles have a specific surface area of 600 to 1800 m ² / g, preferably 800 to 1500 m ² / g, and a pore volume of 0.30 to 0.85 ml / g, More than 90% by weight of the activated carbon particles has a size of 4 to 8 mesh (mesh) Palladium / carbon hydrogenation catalyst. The method according to claim 1 or 2, The content of the metal palladium is 0.2 to 3.5% by weight, preferably 0.3 to 0.8% by weight based on the total weight of the catalyst. The method according to claim 1 or 2, 45 to 60% by weight of the palladium is contained in the outer layer at a depth of 0.2 to 20 μm of the support material. The method according to claim 1 or 2, The remaining weight percent of the palladium is contained in the inner layer at a depth of 20-180 μm of the support material. In the method for producing the palladium / carbon hydrogenation catalyst according to any one of claims 1 to 6, (a) selecting activated carbon particles suitable as support material particles; (b) competing adsorbate the activated carbon particles at 0 to 50 ° C., preferably at room temperature for 5 to 60 minutes, preferably 10 to 30 minutes to obtain pre impregnated activated carbon particles. ), Where the competitive adsorbent material is an aqueous solution of a lower organic acid having 1 to 6 carbon atoms at a concentration of 0.01 to 0.5 N (normal), preferably 0.05 to 0.2 N. impregnating), filtering and drying; (c) a weakly acidic solution containing a palladium precursor and a surfactant by impregnation or spray coating to obtain a supported catalyst, wherein the weakly acidic solution has a pH of 3 to 6; Palladium on the pre-impregnated activated carbon particles, wherein palladium is from 0.1 to 5% by weight, preferably from 0.2 to 3.5% by weight, more preferably from 0.3 to 5% by weight, based on the total weight of the catalyst Supported in an amount of 0.8% by weight; (d) aging the supported catalyst in air for 1 to 24 hours to obtain a aged catalyst; And (e) reducing the aged catalyst with a reducing agent at a temperature of 0 to 200 ° C., preferably 50 to 120 ° C. for 0.5 to 10 hours, preferably 1 to 4 hours, to obtain an activated catalyst Method of producing a palladium / carbon hydrogenation catalyst comprising a. The method of claim 7, wherein The method for producing the palladium / carbon hydrogenation catalyst (b ') removing dust and loose portions from the surface of the particles prior to step (b), washing the particles with an inorganic acid, with deionized water until neutral. Preprocessing comprising washing the particles, and drying the particles Containing additional Process for preparing palladium / carbon catalyst. The method according to claim 7 or 8, The method for producing the palladium / carbon hydrogenation catalyst In step (a), the selected activated carbon particles have a specific surface area of 600 to 1800 m ² / g, preferably 800 to 1500 m ² / g, and 0.30 to 0.85 ml / g, preferably 0.40 to 0.60 ml / g. Natural or shaped particles, preferably natural or shaped coconut charcoal particles having a pore volume of More than 90% by weight of the particles have a size of 4 to 8 mesh (mesh) Process for preparing palladium / carbon catalyst. The method according to any one of claims 7 to 9, The method for producing the palladium / carbon hydrogenation catalyst In step (b), the low molecular weight organic acid is selected from the group consisting of citric acid, maleic acid, oxalic acid, lactic acid, and mixtures thereof, preferably citric acid, The temperature of the drying step is 100 to 200 ℃, preferably 110 to 150 ℃ Process for preparing palladium / carbon hydrogenation catalyst. The method according to any one of claims 7 to 10, The method for producing the palladium / carbon hydrogenation catalyst In the step (c), the palladium precursor is palladium chloride, palladium oxide, palladium acetate, palladium nitrate, palladium chloride, palladic Alkaline salts of chloride (palladic chloride), complexes of palladium with amines and mixtures thereof, preferably palladic chloride Process for preparing palladium / carbon hydrogenation catalyst. The method according to any one of claims 7 to 11, The method for producing the palladium / carbon hydrogenation catalyst In step (c), The surfactant has a concentration of 0.2 to 5% by weight, preferably 0.5 to 1.5% by weight, The surfactant is a cationic surfactant selected from the group consisting of polyoxyethylene aliphatic ether sulphate alkali metal salts and polyoxyethylene aliphatic ether phosphate alkali metal salts, The pH of the solution is adjusted by the addition of carbonates, hydrocarbonates or hydroxides of alkali metals. Process for preparing palladium / carbon hydrogenation catalyst. The method of claim 12, The method for producing the palladium / carbon hydrogenation catalyst The cationic surfactants are sodium polyoxyethylene dodecyl ether sulphate, potassium polyoxyethylene dodecyl ether sulphate, sodium polyoxyethylene dodecyl ether phosphate and potassium polyoxyethylene dodecyl ether phosphate Process for preparing palladium / carbon hydrogenation catalyst. The method according to any one of claims 7 to 13, The method for producing the palladium / carbon hydrogenation catalyst In step (c), supporting palladium on the pre-impregnated activated carbon particles is carried out with the solution at 0-50 ° C., preferably at room temperature for 0.5-6 minutes, preferably 1-3 minutes. Impregnation or spray coating the solution with the pre-impregnated activated carbon particles at a rate of 5-20 ml / min (min) at 0-70 ° C., preferably at room temperature. Process for preparing palladium / carbon hydrogenation catalyst. The method according to any one of claims 7 to 14, The method for producing the palladium / carbon hydrogenation catalyst In step (e), the reducing agent is selected from the group consisting of formic acid, sodium formate, formaldehyde, hydrazine hydrate, glucose, hydrogen and mixtures thereof, preferably sodium formate Process for preparing palladium / carbon hydrogenation catalyst. The method according to any one of claims 8 to 15, The method for producing the palladium / carbon hydrogenation catalyst In the step (b '), the inorganic acid used in the washing step has a concentration of 0.1 to 0.5N, and is selected from the group consisting of hydrochloric acid, nitric acid, phosphoric acid, and mixtures thereof, The drying step is carried out at 100 to 200 ℃, preferably 110 to 150 ℃ Process for preparing palladium / carbon hydrogenation catalyst. Palladium / In the use of the palladium / carbon hydrogenation catalyst prepared by a carbon hydrogenation catalyst or a method for producing a palladium / carbon hydrogenation catalyst according to any one of claims 7 to 16, Contacting the acidic solution or aqueous solution of the low purity streams with hydrogen in the presence of the palladium / carbon catalyst at a temperature of 100 to 300 ° C. to convert impurities of the aromatic aldehyde contained therein. Use of palladium / carbon hydrogenation catalysts.