DE10005775A1 - Catalyst for the hydrogenation of unsaturated hydrocarbons - Google Patents

Abstract

In a catalyst for hydrogenation of unsaturated hydrocarbons, which contains a catalytically-effective amount of palladium (Pd) and optionally silver (Ag) on a support which is a molding with trilobal cross-section and holes through the lobes. In a catalyst for hydrogenation of unsaturated hydrocarbons, which contains a catalytically-effective amount of palladium (Pd) and optionally silver (Ag) on a support, the support is a molding with trilobal cross-section and holes through the lobes. An independent claim is also included for the production of the catalyst.

Description

The invention relates to a catalyst for the hydrogenation of unsaturated hydrocarbons.

From EP-A-0 686 615 is a method for catalytic Hydrogenation of acetylenic compounds with 2 or 3 Koh lenstoffatomen to the corresponding ethylenic Verbindun gene, wherein a supported catalyst in the form of spheres or extrudates, the palladium and silver contains. At least 80% of palladium and at least 80% of silver are close to the periphery of the catalyst in front. The catalyst preferably contains alumina Carrier and 0.01 to 0.5% by weight of palladium and 0.001 to 0.002% by weight Silver. Due to the shape of the carrier is the weight related activity and selectivity relatively low. also  can only with a relatively low Raumgeschwindig be worked, and the pressure losses in the catalyst Bed are relatively high.

From EP-A-0 689 872 there is a Kata contained in Pd and Ag lysator for the selective hydrogenation of acetylene. The Catalyst is prepared by using a support material (preferably alumina), in the form of spheres or cylin drical tablets (pellets) with an alkaline solution a reducing agent for Pd and Ag is treated.

From EP-A-0 693 315 a supported catalyst for the di olefin hydrogenation known, the palladium, silver and a Contains alkali fluoride. As a carrier are preferably sphä used in pellets or cylindrical extrudates.

From EP-A-0 738 540 a catalyst for the hydrogenation of C ₂ - to C ₁₀ -alkynes (preferably acetylene) to the ent speaking alkenes in the presence of sulfur compounds be known, the palladium, silver, at least one chemically gebun denes Alkali metal (preferably K) chemically bonded fluorine and an inorganic carrier (preferably aluminum oxide), in the form of tablets.

Further, by the applicant under the designations G-58 and G-83 Catalysts for the Selective Hydrogenation of Dio lefins and alkynes to mono-olefins or alkenes, the palladium and silver on a spherical support or on a carrier in the form of massive tablets or Extruda contained. (see data sheets "Girdler Catalyst G-58 C, G 58D, G-58H, G-58I and G-83 for Selective Hydrogenation ", from January 1998).

Catalysts on such supports generally have the Disadvantage that their activities and selectivities behave are reasonably low and the hydrogenation is only at a relatively low level  low space velocities can be performed. In addition, these catalysts have a relatively high Flow resistance.

The present invention was based on the object, this To fix disadvantages. It has surprisingly been found that these disadvantages by using a catalyst be can be lifted, whose carrier has a certain shape.

The invention thus provides a catalyst for the Hy drierung of unsaturated hydrocarbons containing catalytically effective amounts of Pd and optionally Ag a carrier; the catalyst is characterized in that the carrier is a shaped body with a trilobal cross section represents, with the lobes provided with through openings are.

The catalyst usually has a geometric surface area of about 0.9 to 1.5 cm ² per shaped body.

Preferably, the Pd is present in amounts of about 0.01 to 1.0% by weight. and the Ag in amounts of about 0.1 to 0.5 wt .-%, be attracted to the support material, before, and the weight ratio between Pd and Ag is about 0.1 to 5.0.

The support is preferably alumina, in particular 6- Alumina, used. This is generally not in pure form, but may also contain other alumina Modifications such as α-alumina. But it can also titanium oxide, zirconium oxide, silicon dioxide, zinc oxide, silicium ciumcarbide or talc.

The BET surface area of the support is about 1 to 300 m ² / g, in particular about 30 to 80 m ² / g. The BET surface area is determined by the one-point method by adsorption of nitrogen according to DIN 66132.

About 40% of the BET surface area is in pores with one Diameters of about 1570 nm to 80 nm and about 60% are located in pores with a diameter of about 80 to 14 nm Pore volume and the distribution of specific surface areas to certain pore sizes according to DIN 66133 (Hg-Porosi metrics).

The trilobal form used according to the invention as a carrier Body are explained in the attached drawing. With (d) is the diameter, with (l) the length of the trilobal shaped body designated. With d1 the diameter is a lobe and with d2 the diameter of the opening in a lobe called.

Preferably, the diameter (d) is the trilobal Shaped body about 3 to 10 mm, the length (L) about 3 to 15 mm and the diameter of an opening in a lobe (d2) is about 0.5 up to 5 mm.

The catalysts of the invention preferably contain even small amounts of alkali and / or alkaline earth metals, in particular about 0.01 to 0.1 wt .-% (calculated as oxides).

Compared to the known catalysts are the inventions catalysts according to the invention by a high activity and Se selectivity. In addition, higher space velocities can from about 12,000 to 15,000 (parts by volume of reactants in the gaseous State per volume of catalyst and hour = GHSV) (compared to a space velocity of only about 3000 to 8000 when using balls, massive tablets or extrudates. In addition, the kata invention lysatoren lower pressure losses (up to 60% compared to ball shaped or tablet shaped carriers (115 or 100%)).

The invention further provides a process for the preparation of the above-defined catalysts, wherein the Trä ger with a solution of the salts of Pd and optionally Ag (PdCl ₂ , H ₂ PdCl ₄ or AgNO ₃ ) is impregnated and the salts with the aid of a Reducing agent (eg, Na-formate, NaBH ₄ , hydrazine, formaldehyde, ascorbic acid, citric acid, etc.) can be reduced. The impregnated carrier is generally washed, dried and calcined. If the reduction is not complete and Pd and Ag are still partly present in the form of their oxides, they are reduced to the corresponding metals by heating in a hydrogen-neutral atmosphere (formation). But the formation can also follow it in the reactor, wherein before introducing the compounds to be hydrogenated connec tions initially only hydrogen is introduced.

The moldings are generally prepared by the carrier material with water, a binder (such as carboxy methylcellulose) and / or a lubricant (eg an Erdal potassium or aluminum stearate).

The production of the shaped body takes place in a Tablettenpres se with a turntable, at the periphery of several openings are arranged with trilobal cross section. In these openings (Matrices) the mixture is filled in and from below a stamp held by the during the rotation of the Turntable three pins, which in the places of the Openings are to be pushed upwards. At the other Rotation of the turntable engages from above a stamp with trilo balem cross-section, which is provided with openings in the the pins in the lower punch when pushing down the upper Penetrate punch. The pressed moldings are at the further rotation of the turntable after retraction of the un teren stamp and pushing the upper punch out pushed out of the dies. The "green" shaped body will be dried and calcined. This occurs in the molding Pores of the desired size.

The moldings are then treated with a solution of the salts of Pal and optionally impregnated silver, wherein after  an alkaline solution is added to the potion to give the Pal ladium and the silver in the form of the corresponding oxides cases. Then, the solution of a reducing agent is added which reducts the oxides to the corresponding metals ed. But it is also possible, an alkaline reduction medium solution to use.

After the precipitation of the oxides or of the metals of the catalytically active component (s), the shaped bodies are washed in order to remove soluble salts (eg NaCl and NaNO ₃ ). Then, the moldings are dried and calcined, whereupon the remaining oxides of the catalytically active component (s) are reduced to the corresponding metals. The reduction is generally carried out in a hydrogen atmosphere at Tem temperatures of about 20 to 450 ° C. The reduction can also be carried out in the reactor by introducing hydrogen or a hydrogen-containing gas before introducing the compounds to be hydrogenated.

The invention is finally the use of above-mentioned catalysts for the hydrogenation of unsaturated hydrocarbons, in particular for the selective hydrogenation of diolefins to monoolefins or of Acetylenes to olefins.

The invention is illustrated by the following examples:

example 1

1000 parts by weight of boehmite are mixed with 10 parts by weight of water and 40 parts by weight of magnesium stearate to form a homogeneous, compressible mass. This mass is placed in the openings of the rotary plate of the above-described tablet press ge, whose cross sections correspond to the shape shown (d = 6 mm, d1 = 4 mm, D2 = 1.5 mm, l = 6 mm). Then, as described above, the molded bodies are pressed and ejected from the tab lette press. The resulting moldings are dried for two hours at 120 ° C and calcined for 4.5 hours at 1075 ° C, the boehmite for the most part in θ-aluminum oxide (next to some α-alumina) is converted. The geometric surface is 1.3 cm ² per shaped body. At closing the BET surface according to DIN 66132 is determined to be 30 m ² / g. Furthermore, according to DIN 66133, the pore volume is determined to be 0.35 ml / g and the pore distribution. 40% of the BET surface area is accounted for by the pores with a diameter of 1750 to 80 nm, 60% of the BET surface area accounts for pores with a diameter of 80 to 14 nm.

To 1000 parts by weight of the moldings, a H ₂ PdCl ₄ solution (0.345 parts by weight of Pd) in 1150 parts by weight of distilled water is added rapidly and 5 min. mixed slowly. The mixture is left for about 60 minutes. rest and then drain the decolourised solution.

The moist product is immediately heated to about 40 ° C, 5% sodium formate solution and stand for 2.5 hours calmly. Thereafter, the formate solution is drained, and the Product is washed free of chloride with distilled water. Subsequently, the product at 540 ° C for two hours cal ciniert.

1000 parts by weight of the calcined product are added to a solution of 3.13 parts by weight of AgNO ₃ in 1150 parts by weight of distilled water and slowly added for 5 minutes. mixed. The mixture is allowed to rest for two hours and then allowed to drain the solution. The product is calcined at 540 ° C for 2.5 hours.

The resulting shaped bodies are ge in a tubular reactor filled, which is first purged with nitrogen. Then 8 Hours of hydrogen at a temperature of 400 ° C through passed, causing the palladium and the silver on the moldings  be completely reduced. Then a mixture from 1.1% by volume of acetylene and 1.5% by volume of hydrogen in ethylene at a temperature of 50 ° C, a pressure of 2.5 MPa and a space velocity of 14000 liters of mixture per kg of Ka catalyst and hour passed through the reactor. The acetylene is 84% with a selectivity of 93% in ethylene transformed.

Comparative Example 1

A spherical catalyst support of θ-Al ₂ O ₃ with a diameter of 2 to 4 mm, a geometric surface of 0.3 cm ² , a BET surface area of 30 m ² / g, a pore volume of 0.39 ml / g and a pore volume distribution of 40% between 1750 and 80 nm and 60% between 80 and 14 nm is impregnated with the H ₂ PdCl ₄ / AgNO ₃ solution of Example 1 and in the same manner as in Example 1, reduced, ge dried, calcined and formed. The catalyst is used as in Example 1 for the selective hydrogenation of acetylene in ethylene using the same process conditions. At a space velocity of 8,000 (liters of reactants per liter of catalyst per hour), the acetylene was converted to 57% with a selectivity of 65% in ethylene.

Comparative Example 2

The procedure of Comparative Example 1 was with the Ab repeated that a catalyst in the form of 4 × 4 mm Tablets was used, all other conditions un changed. The acetylene was 48% with a Selek 76% of ethylene converted into ethylene.

The catalysts of Example 1 and Comparative Examples  1 and 2 were in a separate pressure loss tube measured (with nitrogen as the measuring gas), the following pressure loss ratio was determined: Example 1: 60%; comparison Example 1: 115%; Comparative Example 2: 100%.

Example 2

The procedure of Example 1 was repeated except that the carrier was calcined at 1020 ° C. for 4.5 hours and the carrier thus treated was coated with 0.3% by weight of palladium. The catalyst had a BET surface area of 70 ± 5 cm ² / g, a pore volume of 0.4 ml / g with 4.71% of the surface in pores of diameter 1750 to 80 nm and 76% in pores of diameter from 80 to 14 nm. The remainder of the surface accounted for pores with a diameter of <14 nm.

The shaped catalyst bodies were formed as in Example 1 in a tubular reactor for 8 hours at 400 ° C and with a mixture of hydrogen and dienhaltigem pyrolysis gasoline (2 moles H ₂ , 1 mole of diene) first at 30 ° C and then at 60 ° C. , a pressure of 3.0 MPa and a space velocity of 8 volumes of liquid pyrolysis gasoline per volume of catalyst and hour (LHSV) acted upon. The composition of pyrolysis gasoline prior to selective hydrogenation is given in Table I.

Table I

mol% benzene 38.6 toluene 22.6 o-xylene 1.7 p-Xylene 4.1 m-xylene 2.0 ethylbenzene 2.0 styrene 6.0 cyclohexane 0.7 methylcyclohexane 1.5 hexadiene 1.2 cyclohexadiene 0.3 witches 10.2 heptane 1.4 heptene 8.9

The styrene and diene conversions as well as the diene selectivity after of selective hydrogenation are given in Table II.

TABLE II

Comparative Example 2

The procedure of Example 2 was repeated with the exception that a catalyst in the form of spheres with a diameter of 2 to 4 mm, with a palladium coverage of 0.3%, a geometric surface of 0.3 cm ² , a BET surface area of 70 ± 5 cm ² / g, a pore volume of 0.5 ml / g and a pore distribution as in the catalyst of Example 2, with pyrolysis gasoline having the composition set forth in Table I at a temperature of initially 30 ° C. and later of 60 ° C, a pressure of 3.0 MPa and a LSHV of 4 beauf. The styrene and diene conversions as well as the diene selectivity after the selective hydrogenation are given in Table III.

Table III

Example 3

Following the procedure of Example 1 of EP-0 314 024-A1, a commercial titanium dioxide (P-25 Degussa) in an intensive mixer with the addition of about 55 wt .-% water and 14 wt .-% isopropyl titanate 45 min. homogenized. After several hours of drying at 110 ° C, the TiO ₂ mass is crushed, mixed with aluminum stearate as tabletting ver and pressed as in Example 1 to give moldings with trilobal cross-section (dimensions as in Example 1).

The TiO ₂ shaped bodies were calcined for 3 hours at 550 ° C. in an oxidizing atmosphere.

The geometric surface of the support was 1.3 cm ² per molding, the BET surface area was 36 m ² / g, the pore volume was 0.39 ml / g. 3.7% of the BET surface area was accounted for by pores having a diameter of 1750 to 80 nm, 95.8% by pores having a diameter of 80 to 14 nm.

The TiO ₂ carrier was spray-impregnated with an 8% aqueous sodium formate solution (on 100 g of carrier 30 ml of formate solution). Then, the thus pretreated carrier was spray-impregnated with the same volume of a 2.5% aqueous PdCl ₂ solution. For complete reduction of the precious metal WUR the carrier moldings were overcoated with formate solution, filtered off with suction and washed free of chloride. After drying at 100 ° C was 6 hours until a final temperature of 400 ° C calcined. Subsequently, the promotion was made with silver. For this purpose, the palladium-containing TiO ₂ -formkörper were impregnated at room temperature with silver nitrate solution, dried at 110 ° C and calcined again for 6 hours to a Tempe temperature of 360 ° C. The palladium content was 0.21 wt .-%, the silver content 0.12 wt .-%.

The catalyst was at a pressure of 0.15 MPa, a temperature of 120 ° C and a LHSV of 15 h ^-1 with a molar ratio H ₂ / diene of 2: 1 for the selective hydrogenation of a liquid dienhaltigen mixture with the composition

• - 85.7 mol% paraffins
• 11.1 mol% of mono-olefins
• - 0.85 mol% serve  
• - 2.40 mol% of aromatics

used.

The diene conversion was 80% with a selectivity of 85%.

Comparative Example 3

The procedure of Example 3 was repeated with the exception that instead of the trilobal shaped body massive tablets are used with the dimensions 4.5 × 4.5 mm, which were occupied in the same manner as in Example 3 with the catalytically effective metals , The support had a BET surface area of 33 m ² / g and a pore volume of 0.2 ml / g. 51% of the BET surface area was accounted for by pores having a diameter of 1750 to 80 nm, 87.3% by pores having a diameter of 80 to 14 nm. The catalyst contained 0.213% by weight of Pd and 0.27% by weight. Ag.

The catalyst was used for the selective hydrogenation of the diene-containing mixture used in Example 3 (LHSV = 10 h ^-1 , T = 120 ° C, pressure = 0.15 MPa, molar ratio H ₂ : diene = 4: 1).

The diene conversion was 70% with a selectivity of 60%

Claims (9)

1. A catalyst for the hydrogenation of unsaturated hydrocarbons, comprising catalytically effective amounts of Pd and optionally Ag on a support, characterized in that the carrier is a shaped body with trilobal cross-section, wherein the lobes are provided with through openings. 2. Catalyst according to claim 1, characterized in that the Pd in amounts of about 0.01 to 1.0 wt .-% and the Ag in Amounts of about 0.1 to 0.5 wt .-%, based on the carrier material, is present, and that the weight ratio between Pd and Ag is about 0.1 to 5.0. 3. Catalyst according to claim 1 or 2, characterized the support comprises aluminum oxide, in particular θ-aluminum oxide, represents. 4. Catalyst according to one of claims 1 to 3, characterized in that the BET surface area of the carrier is about 1 to 300 m ² / g, preferably about 30 to 80 m ² / g. 5. Catalyst according to one of claims 1 to 4, characterized characterized in that about 40% of the BET surface area in pores with a diameter of about 1,750 to 80 nm, and about 60% turns into pores with a diameter of about 80 to 14 nm is located. 6. Catalyst according to one of claims 1 to 5, characterized characterized in that the diameter (d) of the trilobal Shaped body about 3 to 10 mm, the length (L) about 3 to 15 mm and the diameter of an opening in a lobe (d2) is about 0.5 to 5 mm.   7. Catalyst according to one of claims 1 to 6, characterized characterized in that the catalyst also small amounts Alkali and / or alkaline earth metals, preferably about 0.01 to 0.1 wt .-% (calculated as oxides). 8. A process for the preparation of the catalyst according to one of Claims 1 to 7, characterized in that the carrier with a solution of the salts of Pd and optionally Ag impregnates these salts with the aid of a reducing agent redu ciert, whereupon the so impregnated carrier washed, dried and calcined and, if the reduction is not complete is, the remaining oxides of Pd and Ag by heating in a hydrogen-containing atmosphere to the corresponding Metals are reduced. 9. Use of the catalysts according to one of claims 1 to 7 for the hydrogenation of unsaturated hydrocarbon substances, in particular for the selective hydrogenation of Dio olefins to monoolefins or from acetylenes to olefins.