JPH0160294B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a catalyst for the selective hydrogenation of acetylene compounds in olefins. In the petrochemical industry, large amounts of ethylene or propylene are produced by thermal decomposition of naphtha, natural gas, etc., but each olefin fraction obtained contains small amounts of acetylene compounds such as acetylene and methylacetylene. There is. In chemical reactions using these olefins as raw materials, contamination with acetylene compounds is often avoided.
It is usually purified by selectively hydrogenating an acetylene compound using a catalyst in which palladium is supported on a refractory carrier such as alumina. However, in the purification of such olefins, since the reaction is carried out in the presence of more than an equivalent amount of hydrogen to the acetylene compound in the olefin atmosphere, the excess hydrogen is added to the olefins, producing low-value paraffins. Undesirable side reactions are induced. In order to suppress the by-product of paraffin, it is required to make the supply ratio of hydrogen to the acetylene compound as close to equimolar as possible, but as the amount of excess hydrogen is reduced, the removal rate of the acetylene compound decreases. In order to solve this dilemma, there is a long-awaited development of highly active and highly selective catalysts that can selectively hydrogenate and remove acetylene compounds while reducing the amount of excess hydrogen. A proposal has been made. For example, catalysts in which a second component such as chromium is added to palladium, and palladium catalysts using alumina as a carrier with pore diameters controlled within a predetermined range have shown some improvement effects. The present inventors conducted a study to improve the activity and selectivity of a palladium catalyst for selectively hydrogenating and removing acetylene compounds in olefins, and found that at least a portion of the palladium catalyst is a θ-type crystal. A catalyst in which palladium is supported on a support mainly composed of alumina and having a specific surface area of 55 to 120 m ² /g.
The total volume of pores from 37.5 Å to 75000 Å is 0.4 to 1.0 cc/
g, and the pore volume with a radius of 37.5 Å to 150 Å and the pore volume with a radius of 150 Å to 3000 Å are both at least 0.1 cc/g, and the pore volume with a radius of 40 Å to 150 Å
We have discovered that a catalyst characterized by a pore distribution with one distinct peak in the radius range from 150 Å to 3000 Å has high activity and excellent selectivity in removing acetylene compounds from olefins. , this invention has been achieved. The present invention will be explained in detail below. The catalyst according to the present invention has a specific surface area of 55 to 120 and is mainly composed of alumina, at least a part of which is θ-type crystal.
m ² /g, preferably 55 to 110 m ² /g, is a catalyst in which palladium is supported on a carrier, and the radius is 37.5 Å to 37.5 Å.
The total capacity of the 75000 Å pores is 0.4 to 1.0 cc/g,
and radius 37.5 Å to 150 Å pore volume and radius 150 Å
Pore volume between 3000 Å and at least 0.1 cc/
g, preferably 0.1 to 0.5 cc/g, and radius 40 Å
It shows a pore distribution with one clear peak at radius from 150 Å to 3000 Å, and one at radius from 150 Å to 3000 Å. The carrier preferably has an alumina component of 60% by weight or more, and of course a carrier containing 100% alumina can also be used. Components other than alumina that can constitute the carrier include refractory oxides such as silica, titania, zirconia, and magnesia. One feature of the catalyst according to the present invention (hereinafter referred to as the present catalyst) is that at least a part of the crystal type of alumina, which is the main component of the carrier, is the θ type, and this carrier has the above-mentioned 55- It has an intermediate surface area of 120 m ² /g and a large number of pores at both micro and meso positions. Generally, when hydrogenating and removing acetylene compounds in olefins, a catalyst with a large carrier specific surface area has high activity but poor selectivity, and a catalyst with a small carrier surface area tends to have high selectivity but low activity. However, the catalyst carrier used in practical use is α-
It has a small specific surface area of 5 to 30 m ² /g, which also contains alumina, or it is made of γ-alumina.
It is limited to those having a large specific surface area of 150 to 300 m ² /g, and either activity or selectivity is often sacrificed. This is due to the fact that it is difficult to produce an alumina support having an intermediate specific surface area, and at the same time, the performance of the catalyst obtained from such a support is not necessarily satisfactory. In contrast, the carrier used for this catalyst has a 55 to 120
It has an intermediate specific surface area of m ² /g, and holds a considerably larger pore volume than alumina-based supports that usually have a specific surface area of this level, and has a radius of 37.5 Å.
Relatively microscopic pores from 150 Å and from 150 Å
Pores are distributed in both meso-macro pores of 3000 Å. A catalyst in which palladium is supported on such a carrier surprisingly achieves extremely high activity and high selectivity at the same time. The reason for this is not entirely clear, but it is assumed that the relatively high specific surface area improves the dispersion of palladium, imparting activity, and at the same time improving selectivity due to its special pore structure. be done. In order to produce an alumina support having the above-mentioned physical properties, which is used as a support for the present catalyst, γ-alumina,
Carbon black is mixed with an alumina raw material such as activated alumina such as η-alumina or alumina hydrate such as boehmite, pseudoboehmite, cipsite, etc. or rehydratable transition alumina, and water and a forming aid are added as necessary. It can be produced by adding, kneading and shaping, and then firing in an oxygen-containing air stream to burn off the carbon plaque. The carbon black to be mixed with the alumina raw material has a particle size ranging from 150 to 3000 Å. Generally, individual particles of carbon black aggregate to form a large chain-like higher-order structure (hereinafter referred to as "structure"), and the position and width of the bore distribution in the resulting alumina support depend on the particle size of the carbon black and the size of the structure. It is greatly influenced by the weather. The size of the structure is expressed by the oil absorption capacity of the carbon black (eg, DBP absorption capacity; capacity of dibutyl phthalate absorbed by 100 g of carbon black, unit: ml/100 g).
And in normal carbon black, its DBP
Absorption amount is about 60-300ml/100g, special type
There are also over 300ml/100g. There are no particular restrictions on the type of carbon black that can be used, and commercially available carbon blacks such as channel blacks such as Mitsubishi Carbon Black #100 and #600 (manufactured by Mitsubishi Chemical Industries, Ltd.), Diablack A, and Diablack H ( Mitsubishi Chemical Industries, Ltd.
), Asahi Thermal FT, etc.
(manufactured by Asahi Carbon Co., Ltd.), Denka Acetylene (manufactured by Denki Kagaku Kogyo Co., Ltd.), and Ketsutien Black EC (manufactured by Akzochemy Co., Ltd.). During molding, the alumina raw material and carbon black should be mixed as uniformly as possible to obtain better physical properties. The amount of carbon black added to the alumina raw material is 5 to 120
% by weight, preferably 10 to 100% by weight. When using additives that disappear upon firing, the upper limit of the amount of additives is approximately 10% by weight to avoid impairing the strength and other physical properties of the resulting molded product. Compared to the usual case, in the present invention, when producing an alumina carrier, the amount of carbon black added is extremely large. Moreover, it is quite surprising that such a large amount of addition can impart controlled locations and amounts of pores, while not compromising the required physical properties. The raw material alumina and carbon black that have been uniformly mixed in this way are further mixed and kneaded by adding water and other forming aids if necessary.
Molded into desired shape. Well-known molding methods include tableting, extrusion, and extrusion.
There are methods such as the Marmo method, rolling granulation method, and briquetting method, among which extrusion molding method is easy and versatile. The molding method will be described by taking as an example a case where pseudoboehmite (an X-ray analysis thereof shows a broad boehmite structure - hydrated alumina) is used as a raw material. For example, 30 to 100 parts of pseudoboehmite
After adding carbon black and mixing uniformly with a mixer, transfer to a kneader, add water and auxiliary agents, and knead. Preferred auxiliaries include inorganic acids,
Examples include organic acids or basic nitrogen compounds such as ammonia, hydracine, aliphatic amines, aromatic amines, and heterocyclic amines, and organic substances such as polyvinyl alcohol. The kneaded material thus obtained is then extruded using an extruder through a die hole of a desired size. The molded product can also be aged in a closed container if desired. The alumina molded bodies formed by various methods as described above are then dried and then oxidized and calcined to finally have properties as a carrier. However, oxidative calcination must be accomplished with great care.
This is because carbon black is flammable, and the amount added is relatively large, so if the removal of combustion air is insufficient, the desired temperature cannot be controlled and there is a great possibility that the temperature will become high. A rapid temperature rise is not desirable even if the temperature is below the upper limit temperature. The firing temperature required to burn off the carbon black as described above is about 500°C or higher, and the final firing temperature to obtain the alumina used in the present invention is 1000 to 1250°C. Further, the firing time is not particularly limited, but is usually about 1 hour to 1 day. Thus, an alumina support is obtained which has excellent mechanical strength, abrasion resistance and physical properties such as large surface area, large pore volume, and characteristic pore distribution. Although there are no particular limitations on the size of the carrier, hydrogenation of acetylene compounds in olefins is usually carried out using
Since the process is carried out in a fixed bed, the size of the mesh is preferably about 4 to 25 meshes. In addition, the shape of the carrier is cylindrical,
It may be in any shape, such as spherical, tablet-shaped, or crushed products thereof. The amount of palladium supported on the above-mentioned carrier is
Usually 0.01 to 1% by weight based on the carrier, preferably
It is 0.02 to 0.4% by weight, and in many cases it is supported intensively on the surface layer of the carrier. As raw materials for palladium used in producing this catalyst, common palladium compounds such as palladium chloride, palladium nitrate, potassium chloropalladate, sodium chloropalladate, palladium oxide, and palladium ammine complex salts are used. . Supporting of palladium can be carried out by dissolving the palladium compound in a solvent such as water, supporting the palladium compound by a known supporting method such as a dipping method, a spraying method, or a precipitation method, followed by reduction. The catalyst supporting the palladium compound can be used in the reaction as is after drying, or if there are residual substances harmful to the reaction, such as chlorine radicals or nitrate radicals, it can be subjected to heat treatment, reduction treatment, or washing with water. It is used after applying. Moreover, a catalyst with even higher performance can also be obtained by the method described below. That is, after a carrier is impregnated with a solution of a palladium compound, it is dried, calcined and reduced as necessary, and further (1) immersed in an oxygen-containing organic compound or its aqueous solution or a hydrocarbon having 5 to 30 carbon atoms. and then calcined at 300 to 600°C in a molecular oxygen-containing gas atmosphere, or (2) 100 to 600°C in a methanol-containing gas atmosphere.
and then under a molecular oxygen-containing gas atmosphere.
By oxidizing at 100 to 600°C, the amount of carbon monoxide adsorbed by palladium on the carrier at 25°C is adjusted to 5 to 75 mg per gram of palladium. In the above treatment (1), examples of the oxygen-containing organic compound include aliphatic alcohols such as methanol and ethanol, aliphatic carboxylic acids such as acetic acid and propionic acids, and starch. Aliphatic carboxylic acids and starches are usually used as aqueous solutions, while aliphatic alcohols may be used as such or as aqueous solutions. As the hydrocarbon having 5 to 30 carbon atoms, aliphatic hydrocarbons are used, preferably aliphatic unsaturated hydrocarbons, especially α-olefins having 6 to 28 carbon atoms. The immersion temperature is arbitrarily selected within the range of room temperature to about 200℃, and the immersion treatment is carried out for 1 hour to 10 days.
A long-time immersion treatment under mild conditions will give better results in terms of catalyst life. The immersed catalyst is then calcined at 300 to 600° C. in an atmosphere of molecular oxygen-containing gas such as air to oxidize and remove attached oxygen-containing organic compounds or hydrocarbons. The above process (1) can be repeated two or more times if desired. In the process (2) above, gaseous methanol diluted with an inert gas such as nitrogen to contain 0.1% by volume or more of methanol is used as the methanol-containing gas, and the molecular oxygen-containing gas is , oxygen gas diluted to 1 to 60% by volume with an inert gas such as nitrogen is used. The treatment time for both of these reduction and oxidation treatments is not particularly limited, but a treatment time of about 1 to 10 hours is usually sufficient. Moreover, the process (2) above can be repeated two or more times if desired. In the present invention, the catalyst prepared by the method described above is more accurately called a catalyst precursor, and although the palladium in the catalyst is not completely in the form of metallic palladium, it is directly converted into an acetylene compound. When used for hydrogenation removal, it is quickly reduced within the reaction system and exhibits a catalytic action, so it can be used in the reaction without any special reduction treatment. However, in order to maintain the initial reaction stably, it is preferable to use the catalyst after previously reducing it. The reduction treatment is carried out at a temperature of room temperature to 300° C. in an atmosphere of a reducing gas such as hydrogen gas. This catalyst is used for the reaction of hydrogenating acetylene compounds up to the olefin stage, particularly for the selective hydrogenation of acetylene compounds in olefins such as ethylene and propylene obtained by thermal decomposition of hydrocarbons such as naphtha and natural gas. It is effective for When the reaction is carried out by the so-called post-hydrogenation method, the amount of hydrogen gas required for the reaction is 1 to 5 times the mole of the acetylene compound in the raw material gas, and if the amount of hydrogen gas is increased more than this, the amount of baraffin by-produced will increase. Not only does this increase, but also the heat of reaction is large, making it difficult to control the reaction temperature. The reaction temperature varies depending on the required removal rate of the acetylene compound and the molar ratio of hydrogen gas to the acetylene compound, but it is preferably as low as possible, and is usually selected within the range of room temperature to 200°C. The reaction pressure is selected within the range of normal pressure to about 30 atmospheres. Since the above reaction has an extremely high reaction rate, the space velocity can be increased. Usually, the gas hourly space velocity is within the range of 100 to 10,000 Hr ^-1 in terms of standard conditions. Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it departs from the gist thereof. In addition, in the following examples, the amount of carbon monoxide adsorbed by palladium on the carrier was measured by the following method. Approximately 0.2 g of catalyst was weighed into a quartz U-shaped tube with an inner diameter of 5 mm, and heated in an electric furnace in a hydrogen gas flow (50 ml/min).
Reduce at 300℃ for 1 hour. Then 15ml/min of He
Switch to gas flow and cool to room temperature. The gas flow path at the front and rear of the U-shaped tube is connected in advance to a thermal conductivity cell of a gas chromatograph so that it can be recorded. Next, in the He gas flow, take 50μ of CO gas with a microsyringe and pulse inject it from the injection port. Record the peaks before and after adsorption on the catalyst, and use the difference as the amount of CO adsorbed on the catalyst. C.O.
Repeat the pulse two or three more times and confirm that no CO is adsorbed after the second pulse. Finally, accurately weigh the amount of catalyst and calculate the amount of CO adsorption per catalyst. In addition, a reaction test using the prepared catalyst was conducted in the following manner. 15 ml of the prepared catalyst was packed into a SUS316 reactor with an inner diameter of 20 mm, heated to 60°C, and hydrogen gas was passed through it for 1 hour to reduce the catalyst.
%, nitrogen 18.5%, acetylene 0.5%, hydrogen 1.0%,
Gas with a composition of 0.001% carbon monoxide (unit: volume %) at 60°C, 75Nl/hour at 25Kg/cm ² G
(GHSV5000hr ^-1 ) to remove acetylene from ethylene by hydrogenation. The reactor outlet gas was analyzed by gas chromatography, and the selectivity was calculated according to the following formula. Selectivity = △ [C ₂ ] / [H ₂ ] _io − [H ₂ ] _put ×100 However, [ ] _io ... Reactor inlet concentration [ ] _put ... Reactor outlet concentration [C ₂ ] ... Acetylene concentration [H ₂ ]...Hydrogen concentration △ [C ₂ ] = [C ₂ ] _io − [C ₂ ] The pore distribution and amount in the _put examples were measured using a mercury intrusion type borosimeter. After use, use Carlo Erba's Polysimeter Series 2000 to obtain a maximum pressure of 2000 kg/
^cm2 gauge. Therefore, the measurement range of the pore is the radius
The range is from 37.5 Å to 75000 Å. The surface area was calculated using the BET method using the nitrogen adsorption method.
After use, use Carlo Erba Soap Tomatics 1800.
It is. For the compressive strength, the radial breaking load (Kg/piece) of the extrusion molded product was measured using a Honya type hardness tester, and the average value of 20 pieces was adopted. Further, Table 1 shows the physical properties of carbon black used in the following examples.

[Table] Example 1 Boehmite powder Pural SB manufactured by Condea (Al ₂ O ₃
75%) 225g and carbon black
After dry mixing 67.5 g of A (30% by weight based on boehmite) in a mixer for 60 minutes, transfer it to a Patsch type kneader (inner capacity 2) and add 220 g of 4.3% nitric acid aqueous solution.
g was added while kneading over about 5 minutes, and kneading was continued for an additional 25 minutes. Then add 21% ammonia water to the mixture.
After adding 128 g and kneading for 25 minutes, it was extruded to a diameter of 3.5 mm using a screw extruder. After drying the molded product at 120° C. for 3 hours, the temperature was gradually raised in an electric furnace under flowing dry air, and it was fired at 600° C. for 3 hours, and then at 1100° C. for 3 hours to obtain an alumina support. The diameter of the extrudate after firing is approx.
2.4 mm, and the average compressive strength was 25 kg/ke. Further, the specific surface area was 100 m ² /g. The analysis results of this alumina support by X-ray diffraction were consistent with the data for theta alumina described in the Catalyst Society of Japan's Handbook of Catalysts by Element (Jijinshokan), pages 27-28. The pore volume and pore distribution of this alumina carrier were as follows. Pore capacity from radius 37.5Å to 150Å 0.471cc/g Pore capacity from radius 150Å to 3000Å 0.205cc/g Total pore volume (37.5Å to 75000Å) 0.685cc/g Modest pore radius (distribution is maximum) radius)
90 Å and 230 Å The pore distribution curves of this alumina support are shown in FIG. Next, 200 g of this alumina carrier was immersed in 600 ml of an aqueous solution containing 0.17 g of palladium chloride and 0.2 ml of hydrochloric acid for 1 hour, drained, and dried at 120°C for 24 hours to reduce the amount of palladium chloride to 0.05 in terms of palladium.
A catalyst (catalyst-10) supported on wt% alumina was obtained. The CO adsorption amount of Catalyst-10 was 78 mg/g-Pd, and the pore distribution curve was almost the same as that of the alumina support. Catalyst-10 was immersed in a mixed α-olefin having 12 to 14 carbon atoms at 100°C for 3 hours, and then the liquid was drained.
Fill a glass tube and heat at 400℃ for 1 hour under air circulation.
It was calcined at 450°C for 3 hours to obtain catalyst-11. Catalyst-
The CO adsorption amount of No. 11 was 48 mg/g-Pd. When the reaction test was conducted using Catalyst-10 and Catalyst-11, the results shown in Table 2 were obtained. Example 2 An alumina carrier was produced in the same manner as in Example 1 except that the final firing temperature was changed to 1200°C, and θ
An alumina support containing type and α type crystal forms was obtained. Various physical property values of the obtained alumina carrier were as follows. Compressive strength 3.1Kg/ke Specific surface area 63m ² /g Pore capacity (37.5~150Å) 0.160cc/g 〃 (150~3000Å) 0.300 〃 〃 (37.5~75000Å) 0.465 〃 Modest pore radius 93Å and 920Å This alumina The pore distribution curve of the carrier is shown in FIG. Next, palladium chloride was supported on this alumina carrier in the same manner as in Example 1, and the loading rate in terms of palladium was
0.05% by weight catalyst-20 was prepared. Catalyst - 20
The CO adsorption amount was 85 mg/g-Pd, and the pore distribution curve was almost the same as that of the alumina support. In addition, catalyst-20 was prepared in exactly the same manner as in Example 1, and α-
Catalyst-21 was obtained by immersion in olefin and calcination. The CO adsorption amount of Catalyst-21 was 17 mg/g-Pd. When the reaction test was conducted using Catalyst-20 and Catalyst-21, the results shown in Table 2 were obtained. Comparative Example 1 An alumina carrier was produced in the same manner as in Example 1 except that the final firing temperature was changed to 1000°C. The physical properties of the obtained carrier were as follows. Compressive strength 2.0Kg/ke Specific surface area 135m ² /g Pore capacity radius (37.55~150Å) 0.619cc/g 〃 (150~3000Å) 0.151 〃 〃 (37.5~75000Å) 0.772 〃 Modest pore radius 80Å and 200Å Then, palladium was supported on this carrier in the same manner as in Example 1, and finally catalyst-01 having a palladium loading rate of 0.05% by weight was prepared. When the above reaction test was conducted using this catalyst, the results shown in Table 2 were obtained. Comparative Example 2 An alumina carrier was produced in the same manner as in Comparative Example 1, except that carbon black was not used. The physical properties of the obtained carrier were as follows. Compressive strength 3.4Kg/ke Specific surface area 110m ² /g Pore capacity (radius 37.5~150Å) 0.470cc/g 〃 (150~3000Å) 0.008 〃 〃 (37.5~75000Å) 0.498 〃 Modest pore radius 81Å Next, this Palladium was supported on the carrier in the same manner as in Example 1, and finally catalyst-02 with a palladium loading rate of 0.05% by weight was prepared. When the reaction test was conducted using this catalyst, the results shown in Table 2 were obtained. Comparative Example 3 Alumina carrier SCS-79 (3
m/mφ sphere) was fired at 1150°C. The physical properties of the obtained carrier were as follows. Specific surface area 25 m ² /g Pore capacity (37.5 to 150 Å radius) 0.048 cc/g (150 to 3000 Å) 0.453 (37.5 to 75000 Å) 0.534 Modest pore radius 940 Å Next, this carrier was coated in the same manner as in Example 1. Catalyst-03 was prepared by supporting palladium and finally having a palladium support rate of 0.05% by weight. When the reaction test was conducted using this catalyst, the results shown in Table 2 were obtained.

【table】

【table】

【table】 [Brief explanation of drawings]

Figures 1 and 2 are pore distribution state diagrams of the alumina supports produced in Examples 1 and 2, respectively, where curves 1 and 3 are curves showing the state of pore distribution, and curves 2 and 4 are curves showing the state of pore distribution. This is an integration curve of pore capacity.

Claims (1)

[Scope of Claims] 1. A catalyst in which palladium is supported on a support having a specific surface area of 55 to 120 m 2 /g and having a specific surface area of 55 to 120 m ² /g, the main component of which is alumina, at least a part of which is a θ-type crystal, and which has a radius of 37.5 Å to 37.5 Å.
The total capacity of the 75000 Å pores is 0.4 to 1.0 cc/g,
and pore volume and radius from 37.5 Å to 150 Å radius
Both pore volumes from 150 Å to 3000 Å are at least 0.1
cc/g, radius 40 Å to 150 Å and radius 150
A selective hydrogenation catalyst for hydrogenating an acetylene compound in an olefin to the olefin stage, characterized by exhibiting a pore distribution having one distinct peak in the range from Å to 3000 Å. 2 Palladium content is 0.02 to 0.02 to the carrier
Catalyst according to claim 1, which is 0.4% by weight.