DE19804711A1 - Process for the regeneration of supported catalysts with gold particles for the oxidation of unsaturated hydrocarbons - Google Patents

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

The invention relates to a method for the regeneration of catalysts for 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 oxidation of unsaturated hydrocarbons with molecular acid Substances in the gas phase usually run - even in the presence of catalyst ren - not below 200 ° C, and it is therefore difficult to be sensitive to oxidation Oxidation products, such as. B. selectively produce epoxides, alcohols or aldehydes len, since the further reaction of these products is often faster than the oxidation of one set olefins itself.

As an unsaturated hydrocarbon, propene oxide is one of the most important reasons chemicals of the chemical industry. The area of application lies with a share of over 60% in the plastics sector, especially for the production of polyether polyols for the synthesis of polyurethanes. In addition, even larger market shares in Range of glycols, especially lubricants and antifreeze, of which Propenoxide derivatives documented.

Today around 50% of the propene oxide worldwide is produced using the "chlorohydrin process" synthesized. A further 50%, with increasing tendency, are provided by the "Oxiran processes.

In the chlorohydrin process (F. Andreas et al .; Propylenchemie, Berlin 1969) by reaction of propene with HOCl (water and chlorine) first the chlorohydrin and then the propene oxide is formed from this by splitting off HCl with lime. The process is cost-intensive, but has one if optimized accordingly high selectivity (<90%) with high sales. The chlorine loss in chlorhy process in the form of worthless calcium chloride or sodium chloride solutions led to the search for chlorine-free oxidation systems at an early stage.  

Instead of the inorganic oxidizing agent HOCl, organic compounds selected for the transfer of oxygen to propene (oxirane process). The indirect Epoxidation is based on the fact that organic peroxides such as hydroperoxides or peroxycarboxylic acids in the liquid phase selectively select their peroxide oxygen on oils can be transferred fine to form epoxides. The hydroperoxides go in alcohols, the peroxycarboxylic acids in acids. Hydroperoxides or peroxycar bonic acids are removed by autoxidation with air or molecular oxygen corresponding hydrocarbon or aldehyde generated. A serious disadvantage Indirect oxidation is the economic dependence of the propene oxide value from the co-product market.

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

The propene oxidation is achieved with low yield in the liquid phase on platinum tall titanium silicalites with a gas mixture consisting of molecular acid substance and molecular hydrogen (JP-A 92/35277 1).

EP-A 0 709 360 Al (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 Au / TiO ₂ catalysts described achieve the approx. 1% propylene conversion only for a very short time; e.g. B. the typical half-lives at moderate temperatures (40-50 ° C) are only 100-200 min.

The regeneration of gold-coated catalysts on the Basis of titanium silicalite by dilute hydroperoxide solution (Thiele et al., J. Mol. Cat 117 pp. 351-356, 1997).

For the development of an economically interesting propene oxidation process it is vital about the possibility of efficient catalyzing sator regeneration.

Surprisingly, it was found that when catalysts which have become inactive are treated with water dilute acid or dilute hydroperoxide solution, catalytic activities of up to 80% of the original activity can be restored. 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 method for the regeneration of gold supported catalysts on the basis of titanium oxide or titanium oxide hydrate for the oxidation of unsaturated hydrocarbons, in which the catalyst by contacting with dilute hydroperoxide solution, water or diluted Acid regenerates in its catalytic activity.

The treatment in the sense of the invention can be at room temperature or higher Temperature. In embodiment variants of the invention also increased pressures and / or the use of water vapor advantageous for Execution come.

Treatment can be done separately after removing the catalysts from the reactor take place or in the reactor, if one cyclically the catalytic oxidation of Propene in the presence of hydrogen and 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 in several parallel switched reactors spatially separated at the same time. These bars can be switched in alternating operation.  

Agitation of the regeneration mixture can be an advantage, but is not a requirement supply for use according to the invention.

According to the invention, supported catalysts coated with nanoscale gold particles be regenerated on the basis of titanium dioxide or titanium oxide hydrate. Prefers the catalysts are produced using the "deposition-precipitation" method poses.

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

When using the catalysts regenerated according to the invention for oxidation unsaturated hydrocarbons is the amount of catalyst used and the the amount of gas used is not limited. Usually the "space velocity" of the Gas flow through the catalyst bed be about 0.5 to 20 l / g cat. × 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 water, propane and CO ₂ as well as the oxygenates propene oxide and acetone are found at 150 ° C. 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, besides 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, e.g. B. 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 many wrinkled origins, e.g. B. 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 tubular 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 l / 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 l / h. The reaction gas mixture is analyzed by means of gas chromatography with an FID (all oxygen-containing organic compounds, with the exception of CO ₂ ) and a TCD detector (permanent gases, CO, CO ₂ , H ₂ O). The system is controlled by a central data acquisition system.

The catalysts are used with TEM (Trasmission Electron Microscopy) the gold particle size.

Catalyst preparation 1

100 mg of H (AuCl ₄ ), dissolved in, are stirred at RT to stir 10 g of titanium oxide hydrate (BET surface area of 380 m ² / g, 0.6% sulfate content, 12% water) in 0.3 l of deionized water 100 ml of demineralized 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 containing 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 × 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 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 inactive gold Supported catalysts with water, dilute acids or dilute hydrogen peroxide solutions example 1

Catalyst that 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 H ₂ O, stirred for 1 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 2

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 H ₂ O, stirred at 80 ° C. for 1 h, separated and at 150 ° for 1 h C dried. The contact thus obtained is used for propene oxidation according to the standard procedure.

Example 3

Catalyst that 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 H ₂ O, stirred for 3 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 4

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 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 5

Catalyst that 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 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), which was prepared after 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 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 7

Catalyst which has become inactive by reaction (2 g; 0.6% propene oxide yield), which was prepared after 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. for 1 h and calcined at 400 ° C. for 2 h. The contact thus obtained is used for propene oxidation according to the standard driving.

Example 8

Catalyst which has become inactive by reaction (2 g; 0.6% propene oxide yield), which was prepared after 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 for 3 h at room temperature, separated, dried for 1 h at 150 ° C. and calcined at 400 ° C. for 2 h. The contact thus obtained is used for propene oxidation according to the standard driving.

Example 9

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

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) and which was prepared according to catalyst preparation _{2 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 according to the standard procedure.

Results of the catalytic reaction are summarized in Table 1.  

Table 1

Claims (5)

1. A method for the regeneration of a carrier coated 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 by contacting it with water or dilute acid or a dilute hydroperoxide solution in its catalytic activity . 2. The method according to claim 1, characterized in that one after the "Deposition-precipitation" method produced catalyst is regenerated. 3. The method according to any one of claims 1 to 2, characterized in that the If necessary, catalyst is 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.