EP1051256A1

EP1051256A1 - Method for regenerating supported catalysts covered with gold particles and used for oxidising unsaturated hydrocarbons

Info

Publication number: EP1051256A1
Application number: EP99901588A
Authority: EP
Inventors: Markus Weisbeck; Ernst-Ulrich Dorf; Gerhard Wegener; Christoph Schild; Bernhard Lücke; Herbert Dilcher; Ulrich Schülke
Original assignee: Bayer AG
Current assignee: Covestro Deutschland AG
Priority date: 1998-02-06
Filing date: 1999-01-07
Publication date: 2000-11-15
Also published as: CA2319612A1; JP2002502687A; CN1144621C; AU2164699A; HUP0100768A2; WO1999039827A1; TW513326B; DE19804711A1; BR9907661A; CN1290194A; HUP0100768A3; ID25615A; KR20010040709A

Abstract

The invention relates to a method for regenerating supported catalysts covered with gold particles, based on titanium dioxide or titanium dioxide hydrate and used for oxidising unsaturated hydrocarbons in a gas phase. The invention is characterised in that the catalyst is regenerated by contacting it with water, a diluted acid or a diluted hydroperoxide solution, to restore its catalytic activity. The invention also relates to the use of regenerated catalysts for oxidising ethene, propene, 1-butene or 2-butene in the gas phase.

Description

Process for the regeneration of supported catalysts with gold particles for the oxidation of unsaturated hydrocarbons

The invention relates to a process for the regeneration of catalysts for the catalytic production of epoxides from unsaturated hydrocarbons

Oxidation with molecular oxygen in the presence of molecular hydrogen in the gas phase and the use of the regenerated catalysts for the oxidation of unsaturated hydrocarbons.

Direct oxidations of unsaturated hydrocarbons with molecular oxygen in the gas phase normally do not proceed below 200 ° C., even in the presence of catalysts, and it is therefore difficult to process oxidation-sensitive oxidation products such as e.g. B. selectively produce epoxides, alcohols or aldehydes, since the further reaction of these products often proceeds faster than the oxidation of the olefins used themselves.

As an unsaturated hydrocarbon, propene oxide is one of the most important basic chemicals in the chemical industry. With a share of over 60%, the application area is in the plastics sector, especially for the production of polyether polyols for the synthesis of polyurethanes. In addition, even larger market shares in

The area of glycols, especially lubricants and antifreezes, is occupied by propene oxide derivatives.

Today, around 50% of the propene oxide is synthesized worldwide using the "chlorohydrin process". Another 50%, with increasing tendency, is supplied by the "Oxiran-V" process.

In the chlorohydrin process (F. Andreas et al; Propylenchemie, Berlin 1969), the reaction of propene with HOCl (water and chlorine) first forms the chlorohydrin and then the propene oxide by splitting off HC1 with lime. The process is cost-intensive, but has the appropriate optimization high selectivity (> 90%) with high sales. The loss of chlorine in the chlorohydrin process in the form of worthless calcium chloride or sodium chloride solutions led early to the search for chlorine-free oxidation systems.

Instead of the inorganic oxidizing agent HOCl, organic compounds were chosen to transfer oxygen to propene (oxirane process). Indirect epoxidation is based on the fact that organic peroxides such as hydroperoxides or peroxycarboxylic acids in the liquid phase can selectively transfer their peroxide oxygen to olefins to form epoxides. The hydroperoxides are converted into alcohols and the peroxycarboxylic acids into acids. Hydroperoxides or

Peroxycarboxylic acids are generated from the corresponding hydrocarbon or aldehyde by autoxidation with air or molecular oxygen. A serious disadvantage of indirect oxidation is the economic dependence of the propene oxide value on the market of the co-product.

With titanium silicalite (TS 1) as a catalyst (Notari et al., US 44 10 501 (1983) and US 47 01 428), it was possible for the first time to epoxy propene with hydrogen peroxide in the liquid phase under very mild reaction conditions with selectivities> 90%. dieren (Clerici et al, EP-A 230 949).

The propene oxidation takes place with low yield in the liquid phase on platinum metal-containing titanium sieves with a gas mixture consisting of molecular oxygen and molecular hydrogen (JP-A 92/352771).

EP-A 0 709 360 AI (Haruta et al.) Describes for the first time a gas-phase direct oxidation of propene to propene oxide with 100% selectivity. It is a catalytic gas phase oxidation with molecular oxygen in the presence of the reducing agent hydrogen. Special titanium dioxide with an anatase modification, which is coated with nanoscale gold particles, is used as the catalyst. The propene conversion and the propene oxide yield are given as a maximum of 1%. The described Au / TiO ₂ catalysts reach the approx. 1% pro pen turnover only for a very short time; z. B. the typical half-lives at moderate temperatures (40-50 ° C) are only 100-200 min.

The regeneration of gold-coated catalysts based on titanium silicalite by dilute hydroperoxide solution was previously known (Thiele et al., J. Mol.

Cat. 117, pp. 351-356, 1997).

For the development of an economically interesting propene oxidation process, it is crucial to have the option of efficient catalyst regeneration.

Surprisingly, it has been found that catalytic activities of up to 80% of the original activity can be restored when treating inactive catalysts with water dilute acid or dilute hydroperoxide solution. The catalysts which have become inactive are preferably washed with dilute acids (for example dilute H ₂ SO ₄ or HF) at pH values of 4 to 7.5, preferably 5.5 to 6.

The invention therefore relates to a process for the regeneration of supported catalysts with gold particles based on titanium oxide or titanium oxide hydrate for the oxidation of unsaturated hydrocarbons, in which the catalytic activity of the catalyst is regenerated by contacting it with dilute hydroperoxide solution, water or dilute acid.

The treatment in the sense of the invention can be at room temperature or higher

Temperature. In embodiments of the invention, increased pressures and / or the use of water vapor can also be advantageously implemented.

The treatment can be carried out separately after removal of the catalysts from the reactor or in the reactor if the catalytic oxidation of Propene in the presence of hydrogen and the catalyst regeneration with water or water vapor can follow one another. In one embodiment of this variant, it is advantageous to carry out the catalysis and regeneration processes simultaneously in a plurality of reactors connected in parallel in a spatially separate manner. These cycles can be switched alternately.

Agitation of the regeneration mixture can be advantageous, but is not a condition for the use according to the invention.

According to the invention, supported catalysts based on titanium dioxide or titanium oxide hydrate can be regenerated with nanoscale gold particles. The catalysts are preferably produced by the “deposition-precipitation” method.

The concentration of dilute aqueous hydroperoxide solution is usually in the range from 1 to 10% by weight, preferably 1 to 4% by weight.

When using the catalysts regenerated according to the invention for the oxidation of unsaturated hydrocarbons, the amount of catalyst used and the amounts of gas used are not limited. The “space velocity” of the gas flow through the catalyst bed should normally be about 0.5 to 20 l / g cat. X h.

The use of the regenerated catalysts according to the invention is carried out in the presence of the gases oxygen and hydrogen. In the presence of these gases, the main products are water, propane and CO ₂ at 150 ° C

Oxygenate found propene oxide and acetone. When the reaction temperature is reduced to <100 ° C., preferably 30-60 ° C., the water formation becomes strong and the CO ₂ formation is completely suppressed. At a temperature between 30-60 ° C, in addition to the main product propylene oxide (approx. 4-5% yield), only traces of other components (approx. 1% based on propene oxides) are found. The water content is twice (molar) the propene oxide content. The composition of the gas phase, containing propene, oxygen, hydrogen and possibly an inert gas, is not only important for the space-time yield, but also for safety. In theory, all molar compositions of the gases propene / oxygen / hydrogen / inert gas, eg nitrogen, can be used. Preferred gas ratios for the oxidation reaction are the following ratios: H ₂ / hydrocarbon / oxygen / nitrogen: 20-80% / 10 - 50% / 1 -10% / 0-50%; preferably H ₂ / hydrocarbon / oxygen / nitrogen: 30-75% / 15-40 / 3-8% / 0-10%. The molecular oxygen used for the reaction can be of diverse origins, for example pure oxygen, air or other oxygen / inert gas mixtures.

Examples

Direct oxidation of propene to propene oxide

Standard reaction conditions: The reactor is a fixed-bed tube reactor (1 cm in diameter, 20 cm in length) made of double-walled glass, which is heated to 46 ° C. by means of a water thermostat. A static mixing and temperature control section is connected upstream of the reactor. The gold supported catalyst is placed on a glass frit. The catalyst load is 1.8 1 / g cat. H. The reactant gases are metered into the reactor from top to bottom by means of mass flow controllers. The starting gas ratios are O ₂ / H ₂ / C ₃ H ₆ : 0.1 / 1.3 / 0.4 1 / h. The reaction gas mixture is analyzed by means of gas chromatography with a FID (all oxygen-containing organic compounds, except CO ₂ ) and TCD detector (Ermanentgase, CO, CO ₂ , H ₂ O). The system is controlled by a central data acquisition system.

The catalysts are examined with TEM (Trasmission Elctron Microscopy) for the gold particle size.

Catalyst preparation 1

100 mg of H (AuCl ₄ ), dissolved in 100, are stirred at RT to stir 10 g of titanium oxide hydrate (BET surface area of 380 m2 / g, 0.6% sulfate content, 12% water) in 0.3 l of demineralized water ml deionized water, added dropwise within 60 min. To precipitate the gold hydroxide, the pH is adjusted to 8 using a 0.5 molar Na ₂ CO ₃ solution; the pale yellow suspension becomes discolored. The suspension is stirred at RT for 3 h, the solid is separated off and washed 4 times with 25 ml of demineralized water. For drying, the solid is kept at 150 ° C. for 2 hours and at 200 ° C. for 1 hour, and then the dried contact is calcined in air at 250 ° C. for 2 hours and at 400 ° C. for 5 hours. A catalyst with 0.5% by weight of gold is obtained. Characterization with TEM results in nanoscale gold particles with average particle diameters of approx. 1 -6 nm. Results of the catalytic reaction analogous to the standard reaction conditions (Example A) are summarized in Table 1.

Catalyst preparation 2:

A solution of 0.104 g HAuCl ₄ x 4 H ₂ O in 400 ml distilled water is heated to 70 ° C., brought to pH 7.5 with an aqueous 0.1 N NaOH solution and 5 g titanium dioxide (anatase- Rutile mixed oxide; P25 from the company

Degussa) added in one portion and stirring continued for 1 h. The solid is washed 5 times with 3 liters of distilled water, dried at room temperature in vacuo for 12 hours and calcined at 400 for 4 h. A gold-titanium dioxide catalyst with 1% by weight of gold is obtained.

Results of the catalytic reaction analogous to the standard reaction conditions (Example B) are summarized in Table 1.

Examples 1 to 10 Catalyst Regeneration and Catalytic Activity of Inactivated Gold

Supported catalysts with water, dilute acids or dilute hydrogen peroxide solutions:

example 1

Catalyst which has become inactive by reaction (2 g; 0.6% propene oxide yield) and which was prepared after catalyst preparation 1 is suspended in 100 ml of H ₂ O, stirred for 1 h at room temperature, separated and dried at 150 ° C. for 1 h. The contact thus obtained is used for propene oxidation according to the standard procedure. Results of the catalytic reaction are summarized in Table 1.

Example 2

Catalyst which has become inactive by reaction (2 g; 0.6% propene oxide yield) and which was prepared according to catalyst preparation 1 is suspended in 100 ml of H ₂ O, stirred at 80 ° C. for 1 h, separated and at 150 ° C. for 1 hour dried. The contact thus obtained is used for propene oxidation according to the standard procedure.

Example 3

Catalyst which has become inactive by reaction (2 g; 0.6% propene oxide yield) and which was prepared after catalyst preparation 1 is suspended in 100 ml of H ₂ O, stirred for 3 h at room temperature, separated and dried at 150 ° C. for 1 h. net. The contact thus obtained is used for propene oxidation according to the standard procedure.

Results of the catalytic reaction are summarized in Table 1.

Example 4

Catalyst which has become inactive by reaction (2 g; 0.6% propene oxide yield), which was prepared after catalyst preparation 1, is suspended in 100 ml of 3% H ₂ O ₂ solution, stirred for 1 h at room temperature, separated and 1 h dried at 150 ° C. The contact thus obtained is used for propene oxidation after

Standard driving style used.

Results of the catalytic reaction are summarized in Table 1. Example 5

Catalyst that has become inactive by reaction (2 g; 0.6% propene oxide yield), which was prepared according to catalyst preparation 1, is suspended in 100 ml of 6% H ₂ O ₂ solution, stirred for 1 h at room temperature, separated and 1 h dried at 150 ° C. The contact thus obtained is used for propene oxidation according to the standard procedure.

Results of the catalytic reaction are summarized in Table 1.

Example 6

Catalyst which has become inactive by reaction (2 g; 0.6% propene oxide yield) and which was prepared according to catalyst preparation 1 is suspended in 100 ml of 3% H ₂ O ₂ solution, stirred at 50 ° C. for 1 h, and separated off and dried at 150 ° C. The contact thus obtained is used for propene oxidation according to the standard procedure.

Results of the catalytic reaction are summarized in Table 1.

Example 7

Catalyst which has become inactive by reaction (2 g; 0.6% propene oxide yield), which was prepared according to catalyst preparation 1, is adjusted to pH = 6 in 100 ml of H ₂ O which is adjusted by 0.05 molar H ₂ SO ₄ was suspended, stirred at room temperature for 3 h, separated, dried at 150 ° C. and calcined at 400 ° C. for 2 h. The contact thus obtained is used for propene oxidation according to the standard procedure. Example 8

Catalyst which has become inactive by reaction (2 g; 0.6% propene oxide yield), which was prepared according to catalyst preparation 1, is dissolved in 100 ml of H ₂ O, which is brought to pH = 6.5 by 0.05 molar H ₂ SO ₄ , was set, suspended, stirred at room temperature for 3 h, separated, dried at 150 ° C. and calcined at 400 ° C. for 2 h. The contact thus obtained is used for propene oxidation according to the standard procedure.

Example 9

Catalyst which has become inactive by reaction (2 g; 0.2% propene oxide yield), which was prepared according to catalyst preparation 2, is suspended in 500 ml of water, stirred for 1 h at room temperature, separated and dried at 150 ° C. for 1 h. The contact thus obtained is used for propene oxidation according to the standard procedure.

Results of the catalytic reaction are summarized in Table 1.

Example 10

Catalyst which has become inactive by reaction (2 g; 0.2% propene oxide yield), which was prepared according to catalyst preparation 2, is suspended in 100 ml of 3% H ₂ O ₂ solution, stirred at room temperature for 1 h, separated and 1 h dried at 150 ° C. The contact thus obtained is used for propene oxidation after

Standard driving style used.

Results of the catalytic reaction are summarized in Table 1.

10 Table 1

Catalyst- propene oxide-from propene oxide selective preparation 1 (min) loot (%) vity (%)

Example A (active 30 5.3> 97

Example A (inactive) 0.6> 97

Example 1 30 3.7> 97

Example 2 30 3.8> 97

Example 3 30 3.8> 97

Example 4 30 3.9> 97

Example 5 30 3.6> 97

Example 6 30 3.8> 97

Example 7 30 4.2> 97

Example 8 30 4.0> 97

Catalyst - propene oxide - from propene oxide - selective preparation 2 (min) loot (%) vity (%)

Example B (active) 30 1.4> 97

Example B (inactive) 0.2> 97

Example 9 30 0.9> 97

Example 10 30 1.0> 97

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Claims

claims

1. A process for the regeneration of a supported catalyst with gold particles based on titanium dioxide or titanium oxide hydrate for the oxidation of unsaturated hydrocarbons in the gas phase, characterized in that the

Catalyst is regenerated in its catalytic activity by contact with water or dilute acid or a dilute hydroperoxide solution.

2. The method according to claim 1, characterized in that a catalyst produced by the "deposition-precipitation" method is regenerated.

3. The method according to any one of claims 1 to 2, characterized in that the catalyst is optionally regenerated under pressure with steam.

4. The method according to any one of claims 1 to 2, characterized in that an aqueous to 10% hydroperoxide solution is used.

5. Use of a carrier regenerated according to one of claims 1 to 4

Catalyst for the epoxidation of unsaturated hydrocarbons in the gas phase.

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