MXPA00007651A - Method for regenerating supported catalysts covered with gold particles and used for oxidising 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

A METHOD FOR THE REGENERATION OF SUPPORTED CATALYSTS, COATED WITH GOLD PARTICLES, USED FOR THE OXIDATION OF UNSATURATED HYDROCARBONS.

FIELD OF THE INVENTION The invention relates to a method for the regeneration of catalysts for the gas phase catalytic production of epoxides from unsaturated hydrocarbons by oxidation with molecular oxygen in the presence of molecular hydrogen as well as the use of catalysts regenerated for the oxidation of unsaturated hydrocarbons.

BACKGROUND OF THE INVENTION Normally, direct oxidations of unsaturated hydrocarbons with molecular oxygen take place in the gas phase - even in the presence of catalysts - it does not proceed below 200 ° C, and it is therefore difficult to selectively produce oxidation products sensitive to oxidation, such as epoxies, alcohols or aldehydes, since the subsequent reactions of these products often take place faster than the REF. : 122273 oxidation of the olefins themselves used.

As an unsaturated hydrocarbon, propene oxide represents one of the most important basic chemicals in the chemical industry. The field of application is found with a proportion of more than 60% in the plastics sector, especially for the manufacture of polyether polyols for the synthesis of polyurethanes. In addition, propene oxide derivatives also cover the largest market share in the field of glycols, especially in lubricants and antifreeze.

Currently around the world approximately 50% of the propene oxide is synthesized by the "chlorohydrin method". The other 50%, with a tendency to rise, is provided by the "oxirano methods".

In the chlorohydrin method (F. Andreas et al., Propylenchemie, Berlin 1969), chlorohydrin is first formed by the reaction of propene with H0C1 (water and chlorine) and then propene oxide is formed from it. dissociation of HCl with lime. The method is very economically expensive, but has a high selectivity (> 90%) with high yields with a corresponding optimization. The loss of chlorine in the chlorohydrin method in the form of solutions of calcium chloride or sodium chloride without value has led early to the search for oxidation systems without chlorine.

In place of the inorganic oxidant H0C1, organic compounds have been chosen for the transfer of oxygen to propene (oxirane method). Indirect epoxidation is based on the fact that organic peroxides such as hydrogen peroxide or peroxycarboxylic acids in liquid phase can selectively transfer their peroxygen to olefins, forming epoxides. The hydrogen peroxide is converted here into alcohols, the peroxycarboxylic acids into acids. Hydrogen peroxide and peroxycarboxylic acids are obtained by auto-oxidation with air or molecular oxygen of the corresponding hydrocarbon or aldehyde respectively. One drawback that affects indirect oxidation is the economic dependence of the propene oxide value on the market value of the coupling product.

Using titanium silicate (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 epoxidize propene with hydrogen peroxide in liquid phase and under very high reaction conditions. soft with selectivities > 90% (Clerici et al., Document EF-A 230 949).

Oxidation of propene is also achieved with lower yield in liquid phase on titanium silicates containing platinum with a gaseous mixture composed of molecular oxygen and molecular hydrogen (JP-A 92/352771).

In EP-A 0 709 360 Al (Haruta et al.) A direct oxidation in the gas phase of propene to propene oxide with a 100% selectivide is described for the first time. This involves catalytic oxidation in the gas phase with molecular oxygen in the presence of the hydrogen reductant. As a catalyst, special titanium dioxide is used with an anatase modification coated with nanometer-scale gold particles. The transformation of the propene and the yield of propene oxide are specified with a maximum of 1%. The described Au / Ti02 catalysts achieve propene transformation of approximately 1% only for a very short time; for example, typical half-life periods at moderate temperatures (40-50 ° C) amount to only 100-200 minutes.

Until . It is now known to regenerate titanium silicate-based catalysts coated with gold by a dilute solution of hydrogen peroxide (Thiele et al., J. Mol.

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

For the development of an economically interesting propenoid oxidation process, it is of decisive significance to have the possibility of an efficient regeneration of the catalyst.

Surprisingly it has been found that in the treatment of acid-inactivated catalysts diluted with water or dilute hydrogen peroxide solution, catalytic activities of up to 80% of the original activity are recovered. Preferably the inactivated catalysts are washed with dilute acids (for example H 2 SO 4 or t HF diluted) at pH values from 4 to 7.5, preferably from 5.5 to 6.

DESCRIPTION OF THE INVENTION It is therefore the object of the invention, a method for the regeneration of supported catalysts based on titanium oxide or titanium oxide hydrate coated with gold particles, for the oxidation of hydrocarbons, unsaturated, in which the catalyst is regenerated in its catalytic activity by contacting it with diluted solution of hydrogen peroxide, water or dilute acid.

In the sense of the invention, the treatment can be carried out at room temperature or at an elevated temperature. In embodiments of the invention, high pressures can also be applied and / or water vapor advantageously used.

The treatment can be carried out separately after the extraction of the catalyst from the reactor or also in the reactor if the catalytic oxidation of the propene in the presence of hydrogen and the regeneration of the catalyst with water or steam are consecutively carried out in a cyclic manner. In an embodiment of this variant it is advantageous to carry out the steps of catalysis and regeneration in several reactors connected in parallel spatially separated at the same time. These cycles may be connected in alternative operation.

An agitation of the regeneration mixture may 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 coated with nanometer-scale gold particles can be regenerated. Preferably the catalysts are prepared in this respect by the "deposition-precipitation" method.

The concentration of the dilute aqueous solution of hydrogen peroxide is usually in the range of 1 to 10% by weight, preferably 1 to 4% by weight In the use of the regenerated catalysts according to the invention for the oxidation of unsaturated hydrocarbons the amounts of catalyst used and the amounts of gas used are not limited. Usually the "Spatial velocity" of the gas flow through the catalyst bed should reach from 0.5 to 20 1 / g of the catalyst x h_1 approximately.

The use according to the invention of the regenerated catalysts is carried out in the presence of the oxygen and hydrogen gases. In the presence of these gases, at 150 ° C in addition to the main products' water, propane and C02 are also oxygenated products propene oxide and acetone. Lowering the reaction temperature to < 100 ° C, preferably at 30-60 ° C the formation of water and totally the formation of C02 is strongly restrained. At a temperature between 30-60 ° C, in addition to the main product are propylene oxide (approximately 4-5% yield) only traces of other components (approximately 1% based on OP). The proportion of water reaches twice (molar) of the proportion of propene oxide.

The composition of the gas phase, composed of propene, oxygen, hydrogen and optionally an inert gas, is not only important for space-time performance but also for safety. Theoretically, all the molar compositions of propene / oxygen / hydrogen / inert gas, for example nitrogen, can be used. The preferred gas ratios for the oxidation reaction are the following ratios: H2 / hydrocarbon / oxygen / nitrogen: 20-80% / 10-50% / l-10% / 0-50%; preferably H2 / hydrocarbon / oxygen / nitrogen: 30-75% / 15-40% / 3-8% / 0-10%. The molecular oxygen used for the reaction can be from multiple sources, for example pure oxygen, air or other mixtures of oxygen / inert gas.

Examples Direct oxidation of propene to propene oxide Standard reaction conditions: The reactor is a stationary bed reactor (1 cm diameter, 20 cm long) of double-walled glass, thermally conditioned with a water thermostat at 46 ° C. A mixing and thermal conditioning path is pre-connected to the reactor. The gold supported catalyst is placed on a glass filter plate. The catalyst loading amounted to 1.8 1 / g catalyst / hour. The reactant gases were metered into the reactor from top to bottom by a mass flow regulator. The ratios of reactant gases were 02 / H2 / C3H6: 0.1 / 1.3 / 0.4 1 / h. The reaction gas mixture was analyzed by gas chromatography with an FID detector (all organic compounds containing oxygen except C02) and one WLD (permanent gases, CO, C02, H20). The installation was controlled through a central system for recording measurement values.

The catalysts were analyzed by TEM (Transmission Electron Microscopy) with regard to the size of the gold particles.

Preparation of catalyst 1 To the suspension of 10 g of titanium oxide hydrate (BET surface of 380 m2 / g, 0.6% of sulphate, 12% of water) in 0.3 ml of fully deionized water were added dropwise to RT and with stirring in the course of 60 minutes 100 mg of H (AuCl4) dissolved in 100 ml of fully deionized water. For the precipitation of the gold hydroxide, the pH value was adjusted to 8 with a 0.5 molar solution of Na C03; the weakly yellow suspension became discolored. The suspension was stirred at room temperature for 3 hours, the solid matter was separated and washed 4 times with 25 ml of fully deionized water. For drying the solid matter was kept for 2 hours at 150 ° C and 1 hour at 200 ° C, and then the dry contact material was calcined in the air for 2 hours at 250 ° C and 5 hours at 400 ° C.

A catalyst with 0.5% by weight of gold was obtained. The TEM characterization gave nano-scale gold particles with average particle diameters of approximately 1-6 nm. The results of the catalytic reaction are summarized analogously to the standard reaction conditions (Example A) in Table 1.

Preparation of catalyst 2: A solution of 0.104 g of water was heated to 70 ° C.

HAÚCl 4 x H20 in 400 ml of distilled water, it was brought to pH 7.5 with a 0.1 N aqueous solution of NaOH and 5 g of titanium dioxide (mixed anatase-rutile oxide; Signature 'Degussa) and continued stirring for 1 hour. The solid matter was washed 5 times with 3 liters of distilled water, dried at room temperature under vacuum for 12 hours and calcined for 4 hours at 400 ° C. A gold-titanium dioxide catalyst with 1.0% gold was obtained.

The results of the catalytic reaction are summarized analogously to the standard reaction conditions (Example B) in Table 1. 1 to 10 Regeneration of the catalyst and catalytic activity of gold-inactivated supported catalysts treated according to the invention with water, diluted acids or diluted solutions of hydrogen peroxide: Use 1 It was suspended in 100 ml of H20 catalyst inactivated by the reaction (2 g, 0.6% yield in propene oxide) that had been prepared according to the catalyst preparation 1, stirred for 1 hour at room temperature, separated and it was dried for 1 hour at 150 ° C. The contact material thus obtained was used for the oxidation of propene according to the standard procedure.

The results of the catalytic reaction are summarized in Table 1.

Example 2 It was suspended in 100 ml of H20 catalyst inactivated by the reaction (2 g, 0.6% yield in propene oxide) which had been prepared according to the preparation of catalyst 1, stirred for 1 hour at 80 ° C, separated and it was dried for 1 hour at 150 ° C. The contact material thus obtained was used for the oxidation of propene according to the standard procedure.

Example 3 It was suspended in 100 ml of H20 catalyst inactivated by the reaction (2 g, 0.6% yield in prspene oxide) that had been prepared according to the preparation of catalyst 1, stirred for 3 hours at room temperature, separated and dried for 1 hour at 150 ° C. The contact material thus obtained was used for the oxidation of propene according to the standard procedure.

The results of the catalytic reaction are summarized in Table 1.

Example 4 It was suspended in 100 ml of 3% H202 solution catalyst inactivated by the reaction (2 g, 0.6% yield in propene oxide) that had been prepared according to the preparation of catalyst 1, stirred for 1 hour at room temperature , separated and dried for 1 hour at 150 ° C. The contact material thus obtained was used for the oxidation of propene according to the standard procedure.

The results of the catalytic reaction are summarized in Table 1.

Example 5 It was suspended in 100 ml of H202 solution at 6% catalyst inactivated by the reaction (2 g, 0.6% yield in propene oxide) that had been prepared according to the preparation of catalyst 1, was stirred for 1 hour at room temperature , separated and dried for 1 hour at 150 ° C. The contact material thus obtained was used for the oxidation of propene according to the mode. to proceed standard.

The results of the catalytic reaction are summarized in Table 1.

Example 6 It was suspended in 100 ml of 3% H202 solution, catalyst inactivated by the reaction (2 g, 0.6% yield in propene oxide) that had been prepared according to the preparation of catalyst 1, stirred for 1 hour at 50 °. C, separated and dried for 1 hour at 150 ° C. The contact material thus obtained was used for the oxidation of propene according to the standard procedure.

The results of the catalytic reaction are summarized in Table 1.

Example 7 It was suspended in 100 ml of H20 which had been adjusted to pH = 6 with H S04 0.05 molar catalyst inactivated by the reaction (2 g, 0.6% yield in propene oxide) that had been prepared according to the preparation of catalyst 1, it was stirred for 3 hours at room temperature, separated, dried for 1 hour at 150 ° C and calcined for 2 hours at 400 ° C. The contact material thus obtained was used for the oxidation of propene according to the standard procedure.

Example 8 It was suspended in 100 ml of H20 which had been adjusted to pH = 6.5 with H2SO4 0.05 molar catalyst inactivated by the reaction (2 g, 0.6% yield in propene oxide) that had been prepared according to the preparation of catalyst 1, stirred for 3 hours at room temperature, separated, dried for 1 hour at 150 ° C and calcined for 2 hours at 400 ° C. The contact material thus obtained was used for the oxidation of propene according to the standard procedure.

Example 9 It was suspended in 500 ml of catalyst water inactivated by the reaction (2 g, 0.6% yield in propene oxide) that had been prepared according to the catalyst preparation 2, stirred for 1 hour at room temperature, separated and dried for 1 hour at 150 ° C. The contact material thus obtained was used for the oxidation of propene according to the standard procedure.

The results of the catalytic reaction are summarized in Table 1.

Example 10 It was suspended in 100 ml of H202 solution to the catalyst inactivated by the reaction (2 g, 0.2% yield in propene oxide) that had been prepared according to the catalyst preparation 2, stirred for 1 hour at room temperature, separated and dried for 1 hour at 150 ° C. The contact material thus obtained was used for the oxidation of propene according to the standard procedure.

The results of the catalytic reaction are summarized in Table 1. Table 1 C C It is noted that in relation to this date, the best method known to the applicant, to carry out the aforementioned invention is that which is clear from the manufacture of the objects to which it relates.

Having described the invention as above, the content of the following is claimed as property.

Claims (5)

1. A method for the regeneration of a supported catalyst based on titanium oxide or titanium oxide hydrate coated with gold particles, for the oxidation of unsaturated hydrocarbons in gas phase, characterized in that the catalyst is regenerated in its catalytic activity by putting it in contact with water or dilute acid or a diluted solution of hydrogen peroxide.

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

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

4. Method according to one of claims 1 to 2, characterized in that an aqueous solution of up to 10% hydrogen peroxide is used.

5. Use of a regenerated supported catalyst according to one of claims 1 to 2 for the epoxidation of unsaturated hydrocarbons in the gas phase.