WO2008019582A1

WO2008019582A1 - Supported pd/c catalyst and the preparation methodthereof

Info

Publication number: WO2008019582A1
Application number: PCT/CN2007/002322
Authority: WO
Inventors: Bin Qian; Yanqing Chang; Dawei Chen; Weimin Yang; Xiaoli Zhu; Hong Tang; Zhongbin Xiao
Original assignee: China Petroleum & Chemical Corporation; Shanghai Research Institute Of Petrochemical Technology, Sinopec
Priority date: 2006-08-11
Filing date: 2007-08-02
Publication date: 2008-02-21
Also published as: DE102007038045B4; CN101121127A; TWI355293B; KR101424042B1; BRPI0714962A2; KR20090037949A; BRPI0714962B1; TW200906484A; DE102007038045A1

Abstract

A supported Pd/C catalyst, wherein the Pd supported to the active carbon carrier is present in the microcrystalline state, and the microcrystallines whose diameters are less than 2.5nm take up more than 80wt% of the total amount of the Pd microcrystallines. The preparation method of the supported Pd/C catalyst, wherein the solution for impregnating or spraying the active carbon carrier contains Pd compound and compound with formula I, wherein n, m or l is independently selected from the integers of 0 and 1~5, and R1, R2 or R3 is independently selected from the group consists of H, CH3, NH2, OH and COOH.

Description

Supported palladium/carbon catalyst and preparation method thereof

The present application claims priority to CN200610029964.4, filed on Aug. 11, 2006, the entire disclosure of which is incorporated herein by reference in its entirety in its entirety herein in Technical field

The present invention relates to a metal palladium catalyst supported on activated carbon (hereinafter referred to as supported palladium/carbon catalyst) and a preparation method thereof, and particularly to a method for refining crude terephthalic acid by selective hydrogenation reaction Acid-supported palladium/carbon catalyst and preparation method thereof. Background technique

Supported palladium/carbon catalysts are widely used for the selective hydrogenation of unsaturated organics. In particular, a negative-supporting palladium/carbon catalyst is suitable for the purification of crude terephthalic acid, in which some impurities in crude terephthalic acid such as p-carboxyphenyl hydrazine (cylinder called 4-CBA) are converted into hydrogenation by hydrogenation. Other compounds, followed by terephthalic acid products, can be isolated and purified by crystallization. Since the palladium/carbon catalyst usually employs a single active component, the improvement in the prior art has mainly focused on the structure of the support and the distribution of the metal Pd on the support, and these aspects do have a great effect on the performance of the catalyst. Impact.

Since the hydrotreating reaction of terephthalic acid is a first-order reaction, the reaction rate is fast, and it is difficult for the reactants to penetrate into the inside of the catalyst particles to carry out the reaction, which makes the active components inside the particles ineffective. Therefore, in order to make full use of the noble metal, the palladium/carbon catalyst is usually made into an eggshell type, that is, the active component precious metal is mainly supported on the surface of the carrier.

Since the hydrogenation reaction is carried out on the surface of the metal Pd, usually for metals The higher the dispersion of the Pd in the catalyst, the higher the dispersion of the metal Pd in the catalyst and/or the higher the crystallite content of the supported metal Pd in the catalyst and/or the better the thermal stability of the catalyst, the activity of the catalyst. The higher the life, the longer the service life.

If a solution containing a Pd-containing compound (such as sodium chloropalladate or palladium chloride) is directly loaded onto the activated carbon, a very thin and shiny metal Pd layer will appear on the surface of the activated carbon, mainly because the surface of the activated carbon contains a ruthenium. Reducing groups and free electrons, which are highly susceptible to the reduction of Pd ions to zero-valent metal Pd. Therefore, the catalyst thus obtained has a very low metal Pd dispersion. One method for overcoming this problem is to convert Pd ions in an immersion liquid containing a Pd compound into an insoluble compound before the impregnation process. For example, the water-soluble compound of Pd is hydrolyzed to insoluble Pd(OH) ₂ or PdO H ₂ 0 at room temperature, and then loaded on activated carbon, followed by reduction with formaldehyde, sodium citrate, glucose, citric acid or hydrogen. The agent is reduced, which prevents migration of Pd and grain growth. Hydrogen peroxide is added to the impregnation solution to hydrolyze the water-soluble compound of Pd to form an insoluble compound, which is then impregnated, as taught in U.S. Patent No. 3,138,560. U.S. Patent No. 4,476,242 teaches the use of an organic solvent such as decyl alcohol or pyridine to prepare an impregnating solution containing a Pd compound, which is said to be very effective in preventing the migration of Pd. In addition, it has been reported that the conversion of the chloropalladium acid solution into a palladium-containing colloidal solution by adjusting the pH value is said to prevent the reducing group on the surface of the activated carbon from directly reducing the Pd ion to the zero-valent metal Pd.

CN1698952A discloses the addition of a nitrogen-containing polycarboxylic acid agent to an impregnation liquid for preparing a palladium/carbon catalyst. Summary of invention

It is an object of the present invention to provide a new supported palladium on carbon catalyst. The metal Pd in the catalyst has a higher dispersion, a higher crystallite content, and better thermal stability. When used in the hydrofinishing of crude terephthalic acid, the catalyst can provide high conversion to p-carboxybenzaldehyde (4-CBA). Another object of the present invention is to provide a process for preparing the supported palladium on carbon catalyst. Detailed description of a preferred embodiment

In a first aspect, the present invention provides a supported palladium/carbon catalyst in which palladium supported on a supported activated carbon exists in a nanometer-sized crystal form, and wherein the crystallite having a particle size of less than 2.5 nm accounts for the total amount of palladium crystallites. 80% by weight or more, preferably 85% by weight or more, more preferably 88% by weight or more, and most preferably 90% by weight or more.

In the supported palladium/carbon catalyst of the present invention, the weight content of the metal Pd is preferably in the range of from 0.05 to 5%, more preferably in the range of from 0.2 to 3.5%, based on the total weight of the catalyst.

In a preferred embodiment, the supported palladium is concentrated in the surface layer of the supported activated carbon such that the palladium/carbon catalyst has a palladium content of 0.50 ± 0.10% by weight based on the total weight of the catalyst, under the surface of the supported activated carbon. The metal palladium in the layer having a depth of 5 nm accounts for 30% by weight or more, preferably 40% by weight or more, more preferably 50% by weight or more based on the total atomic weight in the layer; the metal palladium in the layer having a depth of 300 nm under the surface of the supported activated carbon The total atomic weight in the layer is 5% by weight or more, preferably 10% by weight or more, more preferably 15% by weight or more, and most preferably 20% by weight or more.

In the supported palladium/carbon catalyst of the present invention, the supported palladium is highly dispersed on the surface of the supported activated carbon, and its dispersion is not less than 5%, preferably not less than 10%, more preferably not less than 15%, and most preferably not less than 20 %. At 500. Under C, pass the bubble through 25. After 10 hours of calcination of the catalyst in a nitrogen stream of water of C, the supported palladium has an average grain size of not more than 10 nm, preferably not more than 8.0 nm, more preferably not more than 7.0 nm, and most preferably not more than 6.0 nm.

In a second aspect, the invention provides a method of preparing a supported palladium on carbon catalyst, the method comprising the steps of:

a) first wash the activated carbon with an aqueous solution of mineral acid, then wash it with water to neutral, And drying the washed activated carbon to obtain an activated carbon carrier;

b) impregnating or spraying the activated carbon support with an aqueous solution containing a Pd compound and an additive, and supporting the Pd compound on the activated carbon support to obtain a catalyst precursor, wherein the molar ratio of the additive to the Pd in the Pd compound is 0.01:1 -

2.0: 1, the additive is selected from the compounds represented by the following formula I:

R, -(CH ₂ ) _n -CHCOOH

R ₂ — (CH ₂ ) _m — CCOOH

I

R ₃ -(CH ₂ )i -CHCOOH

I

Wherein n, m and 1 are independently selected from 0 and an integer from 1 to 5, and R, R ₂ and R _{3 are} independently selected from the group consisting of H, CH ₃ , NH ₂ , OH and COOH; pH adjustment of the palladium solution To 7±3; and

c) The catalyst precursor is reduced with a reducing agent to obtain a supported palladium/carbon catalyst.

According to a preferred embodiment, the above method further comprises aging the catalyst precursor at a temperature of from 0 to 80 ° C for from 1 to 50 hours prior to subjecting the catalyst precursor to a reduction treatment.

There is no particular limitation on the activated carbon used in the present invention. An example of activated carbon is coconut shell char having a surface area greater than 900 m ² /g and a particle size of 4-8.

The concentration of the aqueous mineral acid solution used in the process of the present invention may be in the range of 0.01 to 5 mol/liter, preferably in the range of 0.01 to 3.0 mol/liter. Examples of the inorganic acid include, but are not limited to, hydrochloric acid, nitric acid, and phosphoric acid. The pickling time is not critical, but is preferably in the range of 0.5 - 8, hours, more preferably in the range of 0.5 - 4 hours.

The activated carbon is washed with the aqueous solution of the inorganic acid, washed with water until neutral, and then dried. Drying can usually be done at 80 ~ 150. It is dried at a temperature of C for 0.5 to 10 hours, preferably 0.5 to 6 hours.

Examples of Pd compounds useful in the present invention include, but are not limited to, halides of Pd, Palladium acetate, palladium nitrate, chloropalladium acid, a basic salt of chloropalladium acid, a palladium ammonia complex, and combinations thereof. Preferably, the Pd compound is chloropalladic acid or ethyl palladium acid. The pH of the solution containing the Pd compound and the additive is preferably in the range of 4 to 9. The concentration of the Pd compound in the solution in terms of Pd is preferably in the range of 0.01 to 20% by weight, more preferably in the range of 0.1 to 10% by weight, most preferably in the range of 0.2 to 3.6 % by weight.

The amount of the additive in the Pd solution may vary depending on the Pd compound used and the additive used, but usually the molar ratio of the additive in the solution to the Pd in the Pd compound is in the range of 0.01:1 to 2:1, and the additive The molar ratio to Pd in the Pd compound is preferably in the range of 0.05:1 to 1.5:1, more preferably in the range of 0.1:1 to 1.0:1.

Some examples of compounds of formula I useful in the present invention are as follows:

Ri -(CH ₂ ) _n -CHCOOH

R ₂ — (CH ₂ ) _m — CCOOH

I

R ₃ -(CH ₂ )| -CHCOOH

Examples of reducing agents for reducing the catalyst precursor include, but are not limited to, citric acid, sodium formate, formaldehyde, hydrazine hydrate, glucose, hydrogen, and combinations thereof. Preferably, the reducing agent is sodium formate or hydrazine hydrate. The amount of the reducing agent depends on the amount of the active component Pd, and is generally 1 to 10 times, preferably 2 to 5 times, the amount required for the reduction reaction theory. The reminder The reduction treatment of the precursor of the agent can be carried out according to procedures and conditions well known to those skilled in the art. For example, the restore process can be from 0 to 200. C, preferably at a temperature of 20 to 120 ° C for 0.5 to 24 hours, preferably 1 to 10 hours, more preferably 1 to 4 hours.

According to a preferred embodiment, the method of preparing a supported palladium on carbon catalyst of the present invention comprises the steps of:

1) washing the granular or shaped activated carbon carrier with an aqueous acid solution for 0.5 to 8 hours, the acid concentration of the aqueous acid solution is 0.01 to 3.0 moles / liter, and the acid is one selected from the group consisting of hydrochloric acid, nitric acid and phosphoric acid;

2) The acid washed activated carbon carrier is washed with water to neutrality, and then at 80 to 150. Drying under conditions of 0.5 to 10 hours gives the treated activated carbon carrier;

3) impregnating or spraying the treated activated carbon support with an aqueous solution containing a water-soluble Pd compound and an additive of the following formula I, and supporting the Pd compound on the treated activated carbon support to obtain a catalyst precursor, The content of the Pd compound in the aqueous solution is 0.1 to 10% by weight in terms of Pd, and the molar ratio of the additive to Pd is

In the range of 0.05: 1 ~ 1.5: 1, the pH of the aqueous solution is adjusted to 7 ± 3,

R, -(CH ₂ ) _n -CHCOOH

R ₂ — (CH ₂ ) _m — CCOOH

I

R ₃ -(CH ₂ )i -CHCOOH

I

Wherein n, m and 1 are independently 0 or any integer of 1 to 5; and, and are independently selected from the group consisting of OH, H, CH ₃ , NH ₂ and COOH;

4) The catalyst precursor from step 3) is from 0 to 80. C temperature aging 1 ~ 50 hours; and

5) The aged catalyst precursor is subjected to a reduction treatment with a reducing agent to reduce Pd ions in the Pd compound to metal Pd to obtain a catalyst product.

Compared with the prior art, the invention has the advantages that the prepared catalyst has higher metal Pd dispersion and higher crystallite content, and the catalyst has high activity and length. The service life. detailed description

The invention is illustrated by the following examples without restricting the scope of the invention.

In the embodiment, the following test methods are employed:

(1) Dispersion of metal palladium:

The degree of dispersion of the metal palladium was measured by a hydrogen peroxide titration method using a chemical adsorption apparatus. Degree of dispersion is calculated according to the following formula: polydispersity _{_{= ((2xV ¾ xM Pd)}} / (3x22400xW #xC Pd)) xl00% where: V represents a hydrogen absorption amount of adsorption of the sample,

M _Pd represents the atomic weight of palladium,

W sample represents the weight of the sample, and

C _Pd represents the content of palladium in the sample.

(2) Microcrystalline content:

The term "crystallite content" as used in the present invention means the content of crystal grains having a particle diameter of less than 2.5 nm.

The content of palladium in the catalyst was determined by X-ray fluorescence spectroscopy, and the particle size of the metal palladium crystallites was measured by X-ray diffractometry (XRD), and then the crystallite content was calculated by the following formula: Microcrystalline content =

(metal palladium grain weight less than 2.5 nm / total metal palladium weight) X 100 %

(3) Thermal stability:

The average particle diameter of the palladium crystal grains of the palladium/carbon catalyst was measured by an X-ray diffractometer (XRD). The catalyst was then at 500. C, in the bubble through 25. Baking in a nitrogen stream of C water After burning for 10 hours, the average particle diameter of the palladium crystal grains was measured by an X-ray diffractometer (XRD). The change in the average particle diameter of the palladium crystal grains after calcination and the average particle diameter of the palladium crystal grains before and after calcination indicates the thermal stability of the catalyst. The smaller the average particle size of the palladium grains after calcination, the better the thermal stability of the catalyst. At the same time, the smaller the change of the average particle size of the palladium grains before and after calcination, the better the thermal stability of the catalyst.

(4) The content of palladium in layers at different depths under the catalyst surface:

The catalyst surface was subjected to argon etching. After etching to a certain depth, the content of palladium in the exposed surface layer was measured by photoelectron spectroscopy XPS and Auger spectroscopy AES, and the palladium content in the layer at different depths under the catalyst surface was obtained.

[Embodiment 1]

100 g of coconut shell activated carbon passing through a 4-mesh sieve but remaining on an 8-mesh sieve at a surface of 1100 m ² /g was washed with 200 ml of a 0.4 mol/liter aqueous solution of nitric acid for 2 hours. After removing the acid solution, the activated carbon was washed with deionized water until neutral, and then dried at 120 ° C for 6 hours.

3.2 g of a 16 wt% palladium chlorohydrate solution was added, and deionized water was added to 40 ml, and 2.16 g of a 10 wt% aqueous solution of the additive A was added thereto, and deionized water was added thereto to a solution volume of 60 ml. A 3 % aqueous NaOH solution was added to adjust the pH of the palladium-containing solution to about 7. After the Pd-containing solution was stabilized for 180 minutes, the treated activated carbon was immersed in the Pd-containing solution for 3 hours to obtain a catalyst precursor. The catalyst precursor was aged at room temperature for 24 hours and then at 20 in a reducing solution prepared from 20 g of a 5% by weight aqueous hydrazine solution and 200 pure water. Immerse for 3 hours under C. After removing the liquid by filtration, the solid was washed with neutral water to neutrality and dried to obtain a catalyst product.

[Examples 2 to 24]

Pd-containing solutions were prepared using different Pd compounds and different additives, the same as in Example 1. The specific Pd compound, the content of the Pd compound in the Pd-containing solution (in terms of Pd), the specific additives, and the molar ratio of the additive to Pd are listed in Table 1.

[Examples 25 to 30] According to the procedure of Example 1, but different additives were used to prepare the Pd-containing solution (see Table 1 for the specific additives used), and the Pd-containing solution was sprayed on the activated carbon to obtain a catalyst precursor, and the other uses as shown in Table 2. The inorganic acid, the concentration of the inorganic acid, the pickling time, the drying time, the temperature, the pH of the solution containing the additive and the Pd compound, the reducing agent, the reduction treatment temperature, and the reduction treatment time.

[Comparative example]

No additives were added when preparing the Pd-containing solution, and the rest were the same as in Example 1.

The catalysts prepared in the respective examples and comparative examples were subjected to measurement of dispersity, crystallite content, thermal stability, and palladium content in layers at different depths of the catalyst surface, and the catalysts were evaluated under the following evaluation conditions. 3 and Table 4.

Catalyst evaluation conditions:

Catalyst dosage: 2.0 g

Amount of crude terephthalic acid: 30.0 g

4-CBA amount: 1.0 g

Reaction pressure: 70 Kg

Hydrogen partial pressure: 5.0 Kg

Reaction time: 1.0 hours

Reaction temperature: 270 °C Add 4-CBA amount - Remaining 4-CBA amount

4-CBA conversion rate χΐοο%

Add 4-CBA:

Table 1

EXAMPLES Pd compound Additive Pd feed amount / Activated carbon Additive /Pd (molar ratio)

(% by weight)

Example 1 Chloro palladium acid additive A 0.51 0.20 Example 2 Chloro palladium acid additive A 0.51 0.30 Example 3 Chloro palladium acid additive A 0.22 0.60 Example 4 Palladium acetate additive A 0.08 1.50 Example 5 Chloro palladium acid additive B 0.51 0.20 Example 6 Chloro palladium acid additive B 0.62 0.40 Example 7 Chloro palladium acid additive B 0.51 0.60 Example 8 Palladium acetate additive B 3.55 0.80 Example 9 Chloro palladium acid additive C 0.51 0.20 Example 10 Chloro palladium acid additive C 0.51 0.40 Example 11 Chloro palladium acid additive C 0.51 0.60 Example 12 Palladium acetate additive C 0.15 1.00 Example 13 Chloro palladium acid additive D 0.51 0.20 Example 14 Chloro palladium acid additive D 0.41 0.40 Example 15 Chloro palladium acid additive D 0.51 0.60 Example 16 Palladium acetate additive D 0.51 0.80 Example 17 Chloro palladium acid additive E 0.51 0.20 Example 18 Chloro palladium acid additive E 1.00 0.40 Example 19 Chloro palladium acid additive E 0.51 0.60 Example 20 Palladium acetate additive E 0.51 0.80 Example 21 Chloro palladium Acid additive F 4.50 0.05 Example 22 Chloro palladium acid additive F 0.51 0.40 Example 23 Chloro palladium acid additive F 0.51 0.60 Example 24 Palladium acetate additive F 0.51 0.80 Example 25 Chloro palladium acid additive A 0.51 0.20 Example 26 Chloro palladium acid additive B 0.51 0.40 Example 27 Chloro palladium acid additive C 0.51 0.60 Example 28 Chloro palladium acid additive D 0.51 0.80 Example 29 Chloro palladium acid additive E 0.51 0.50 Example 30 Chloro palladium acid additive F 0.51 0.50 Comparative example Chloro palladium acid 1 0.51 1

table 3

EXAMPLES Pd dispersion in the catalytic penalty Microcrystalline content Average grain size 500. C roasting before and after roasting 4-CBA

Content (% by weight) Degree (%) Size (nm) Back diameter Change Conversion rate

(%) Average grain size % (%)

Small (nm)

Example 1 0.50 20 90 3.5 5.9 69 99.5 Example 2 0.50 23 91 3.6 6.0 67 99.7 Example 3 0.20 29 90 3.4 5.3 56 89.2 Example 4 0.08 21 92 2.7 5.3 96 ― Example 5 0.50 20 90 3.5 5.9 69 99.4 Example 6 0.60 26 90 3.6 6.0 67 99.8 Example 7 0.50 28 93 3.8 5.8 53 99.5 Example 8 3.50 20 92 3.3 5.9 79 99.6 Example 9 0.50 20 91 2.9 5.7 97 99.6 Example 10 0.50 22 92 3.8 5.6 47 99.8 Example 11 0.49 25 90 3.6 5.8 61 99.7 Example 12 0.15 28 91 3.0 5.7 90 ― Example 13 0.50 20 90 3.6 5.9 64 99.5 Example 14 0.40 21 92 3.3 5.6 70 99.5 Example 15 0.50 26 91 3.4 5.8 71 99.8 Example 16 0.49 25 90 3.2 5.9 84 99.9 Example 17 0.50 30 94 3.6 6.0 67 99.7 Example 18 0.98 27 90 3.7 5.9 59 100 Example 19 0.50 27 91 3.4 5.8 71 99.7 Example 20 0.50 28 91 3.5 5.7 63 99.8 Example 21 4.48 27 90 3.7 6.0 62 100 Example 22 0.50 28 92 3.6 5.9 64 99.7 Example 23 0.50 30 90 3.8 5.9 55 99.9 Example 24 0.50 28 91 3.3 5.9 79 99.7 Example 25 0.50 20 91 3.3 6.0 82 99.6 Example 26 0.50 20 90 3.5 5.9 69 99.7 Example 27 0.50 22 90 3.4 6.0 76 99.8 Example 28 0.49 26 91 3.7 5.9 59 99.9 Example 29 0.50 27 90 3.8 6.0 58 99.8 Example 30 0.50 28 92 3.0 5.7 90 99.6 Comparative Example 0.50 4 52 4.6 11.1 141 66.2 Table 4

EXAMPLES Pd catalyst under the surface of the catalyst 5 nm deep under the catalyst surface 300 nm deep content (% by weight) degree of palladium content in the layer of palladium content

(% by weight) (% by weight) Example 1 0.50 50.2 22.3 Example 2 0.50 51.2 23.7 Example 3 0.20 43.1 11.8 Example 4 0.08 30.1 5.9 Example 5 0.50 52.6 20.4 Example 6 0.60 57.8 28.0 Example 7 0.50 60.1 23.5 Example 8 3.50 63.4 29.3 Example 9 0.50 54.3 24.2 Example 10 0.50 51.4 23.6 Example 11 0.49 50.3 23.2 Example 12 0.15 40.6 11.3 Example 13 0.50 52.3 23.7 Example 14 0.40 50.4 20.5 Example 15 0.50 52.9 24.9 Example 16 0.49 50.4 23.1 Example 17 0.50 56.3 23.0 Example 18 0.98 70.1 30.3 Example 19 0.50 57.8 23.6 Example 20 0.50 53.5 23.8 Example 21 4.48 83.2 40.2 Example 22 0.50 56.1 21.2 Example 23 0.50 50.6 24.7 Example 24 0.50 53.4 25.3 Example 25 0.50 54.5 23.0 Example 26 0.50 55.6 27.4 Example 27 0.50 56.4 23.7 Example 28 0.49 53.3 23.9 Example 29 0.50 50.1 20.1 Example 30 0.50 56.5 24.7

Comparative Example 0.50 30.6 12.5 The patents, patent applications, non-patent literature and test methods mentioned in the specification of the present application are hereby incorporated by reference.

While the invention has been described with respect to the embodiments of the embodiments of the invention Therefore, the invention is not limited to the specific embodiment disclosed as the best mode of the invention, but all embodiments are included within the scope of the appended claims.

Claims

A negative-supporting palladium/carbon catalyst in which palladium supported on a supported activated carbon exists in a crystallite form, and wherein crystallites of less than 2.5 nm account for more than 80% by weight of the total amount of palladium crystallites.

2. The supported palladium/carbon catalyst according to claim 1, wherein the supported palladium is concentrated in the surface layer of the supported activated carbon such that the palladium/carbon catalyst has a palladium content of 0.50 ± 0.10% by weight based on the total weight of the catalyst. In the case, the metal palladium in the layer having a depth of 5 nm under the surface of the supported activated carbon accounts for 30% by weight or more of the total atomic weight in the layer; the metal palladium in the layer having a depth of 300 nm under the surface of the supported activated carbon accounts for the total atom in the layer. More than 5% by weight of the weight.

3. The supported palladium/carbon catalyst according to claim 2, wherein the palladium/carbon catalyst has a palladium content of 0.50 ± 0.10% by weight based on the total weight of the catalyst, in a layer having a depth of 5 nm under the surface of the supported activated carbon. The metal palladium accounts for 40% by weight or more of the total atomic weight in the layer; the metal palladium in the layer having a depth of 300 nm under the surface of the supported activated carbon accounts for 10% by weight or more based on the total atomic weight in the layer.

The supported palladium/carbon catalyst according to any one of claims 1 to 3, wherein the loaded palladium is highly dispersed on the surface of the supported activated carbon, and the dispersion thereof is not less than 5%.

The supported palladium/carbon catalyst according to claim 4, wherein the supported palladium has a dispersion of not less than 10%.

The supported palladium/carbon catalyst according to any one of claims 1 to 5, wherein the catalyst is calcined at 500 ^e C for 10 hours after bubbling through a stream of 25 Torr of nitrogen. The average grain size is not more than 6.0 nm.

The supported palladium on carbon catalyst according to any one of claims 1 to 6, wherein the catalyst contains 0.05 to 5% by weight of metal Pd based on the total weight of the catalyst.

8. The supported palladium/carbon catalyst according to claim 7, wherein the catalyst contains 0.2 to 3.5% by weight of metal? (1, based on the total weight of the catalyst.

9. A method of preparing a supported palladium on carbon catalyst according to claim 1, comprising the steps of:

a) firstly, the activated carbon is washed with an aqueous solution of inorganic acid, then washed with water to neutrality, and the washed activated carbon is dried to obtain an activated carbon carrier;

b) impregnating or spraying the activated carbon support with an aqueous solution containing a Pd compound and an additive, and supporting the Pd compound on the activated carbon support to obtain a catalyst precursor, wherein the molar ratio of the additive to the Pd in the Pd compound is 0.01: 1 -

2.0: 1 , the additive is selected from the compounds represented by the following formula I:

R, -(CH ₂ ) _n -CHCOOH

R ₂ — (CH ₂ ) _m — CCOOH

I

R ₃ -(CH ₂ )i -CHCOOH

I

10. The method of claim 9, wherein the inorganic acid is at least one selected from the group consisting of hydrochloric acid, nitric acid, and phosphoric acid; the pickling time is 0.5 to 8 hours; and the acid concentration of the inorganic acid solution is 0.01 to 5.0 moles per liter; Dry at 80 ~ 150. The temperature of C is 0.5 to 10 hours.

11. The method of claim 9 or 10, wherein the Pd compound is selected from the group consisting of halides of Pd, palladium acetate, palladium nitrate, chloropalladium acid, basic salts of chloropalladium acid, palladium-ammonia complexes, and combinations thereof; The concentration of Pd in the Pd solution is 0.01-20%; the molar ratio of the additive in the solution to the Pd in the Pd compound is 0.01:1 ~ 2.0:1.

12. The method of claim 11, wherein the Pd compound is chloropalladic acid or palladium acetate; the solution containing the Pd compound and the additive has a pH of 4 - 9; the concentration of Pd in the solution is 0.1 to 10% by weight; Additives and Pd moles in Pd compounds The ratio is 0.05: 1 ~ 1.5: 1.

13. The method of any of claims 9-12, further comprising subjecting the catalyst precursor to from 0 to 80 prior to the reduction treatment. C temperature aging 1 ~ 50 hours.

The method according to any one of claims 9 to 13, wherein the reducing agent is selected from the group consisting of citric acid, sodium formate, formaldehyde, hydrazine hydrate, glucose, hydrogen, and combinations thereof; and the reduction treatment is from 0 to 200. The temperature of C is 0.5 to 24 hours.

15. The method of claim 14, wherein the catalyst precursor is aged at a temperature of from 0 to 80 ° C for 1 to 24 hours prior to the reduction treatment; the reducing agent is sodium formate or hydrazine hydrate; and the reduction treatment is carried out at a temperature of from 20 to 120 ° C. Carry out 1 to 10 hours.

16. A method of preparing a supported palladium on carbon catalyst of claim 1 comprising the steps of:

3) impregnating or spraying the treated activated carbon support with an aqueous solution containing a water-soluble Pd compound and an additive of the following formula I, and supporting the Pd compound on the treated activated carbon support to obtain a catalyst precursor. The content of the Pd compound in the aqueous solution is 0.1 to 10% by weight in terms of Pd, and the molar ratio of the additive to Pd is

In the range of 0.05: 1 - 1.5: 1, the pH of the aqueous solution is adjusted to 7 ± 3,

R,-(CH ₂ ) _n -CHCOOH

R ₂ -(CH ₂ ) _m -CCOOH

R ₃ -(CH ₂ )| -CHCOOH

I

Wherein n, m and 1 are independently 0 or any integer of 1 to 5; and R, 11, ₂ and 1 are independently selected from OH, H, CH ₃ , NH ₂ and COOH; 4) The catalyst precursor from step 3) is from 0 to 80. C temperature aging 1 ~ 50 hours; and