CS243445B1 - Process for preparing mixed oxide catalysts for the oxidation of unsaturated aldehydes - Google Patents

Abstract

Method for preparing mixed oxide catalysts for the oxidation of unsaturated aldehydes into gaseous products from catalysts that are distilled for industrial production and are unusable, such that a deactivated catalyst containing at least 60 wt. % of the catalytically active component and at most 40 wt. % of the catalyst is obtained. inert tableting additives are gradually dissolved at a temperature of 20 to 120 °C in aqueous solutions of MH^OH, tartaric acid, nitric acid or their mixtures, separated and mixed with aqueous solutions of active catalyst components, adjusted to pH 6 by adding NH^OH and the thus-strained solution is concentrated at a temperature of 120 C to a paste consistency, this __ „_ ... is dried, the heated salts are thermally decomposed at a temperature of up to 320 °C and the saturated mass is stabilized after the addition of these tableting additives.

Description

The present invention relates to a process for the preparation of puffy oxide catalysts for the oxidation of unsaturated aldehydes into gaseous fuels and deactivated for the production of non-useful catalysts which are no longer usable.

for the pro-industrial production of unsaturated carboxylic acids such as acrylic acid or aetecrylic acid by oxidation of the corresponding unsaturated aldehydes, such as acrolein or non-aecrolaline, in a gaseous phase, and employing oxidation catalysts whose catalytically active allo- and I., V, or Vlil. groups of Mend * Leyev's periodic system such as Cu, Bi, Greek, Co or Mi.

The catalytically active component of this type of oxidation catalysts is usually at least 60% of the total catalyst mass, the remainder up to a total of 40% by weight. then, inert substances such as SiO ₂ , Al ₂ O 4, TiO ₂ , graphite or their emission may act as diluent of active components or as a means of facilitating the formation of catalysts.

The known processes for the preparation of these catalysts are based on aqueous solutions of the salts of the individual active constituents (usually enonic salts or nitrates) which, together with the emission and the resulting auspenae or rostok and eventually thicken, dry, contain the salts thermally and then recover the mass thus obtained. The additives stabilize and calcine to obtain the desired catalytic properties.

The cost of the catalysts for the oxidation of unsaturated aldehydes Considering the high content of the catalytically active component, which is made up of oxides of deficient metals, is considerable. The raw materials for their preparation - salts of the individual active components - it is generally necessary to import the cost of raw materials abroad, therefore they represent the decisive part of the cost of production of the catalyst.

It is generally known that the useful life (life) of industrial catalysts is limited. The ee cesene catalysts deactivate, which means that their efficacy for the Henkel reaction due to a number of physical and chemical jits will drop over time to such an extent that their further use in the production process is not economically viable.

The life span of industrial catalysts for the oxidation of unsaturated aldehydes in the gas phase is about three years. After this time, the catalysts and process must be discarded and replaced with fresh ones.

In seeking an economically advantageous use of discarded deactivated catalysts from the process of yielding unsaturated acids by oxidation of unsaturated aldehydes in gaseous fuels, which are waste gas, it has been found that such degraded catalysts can be advantageously reused as a raw material for catalysts whose catalytic properties in aldehyde oxidation they are fully comparable and catalysts of the same composition prepared and pure salts of the individual active components.

The process for preparing enriched oxide catalysts for the oxidation of unsaturated aldehydes in gaseous phase and solved deactivated catalysts according to the present invention is characterized in that the deactivated catalyst is an active component consisting of a molybdenum and vanadium oxide with one or more other metal oxides from X. V. or VIII. The groups of the MendCleev periodic system are dissolved in MH @ 2 O, tartaric acid, nitric acid and water *, optionally in their dreams, and catalytically ineffective pain substances, diluent or teblet additives are separated as a non-permeable portion.

In this way, solutions are gradually obtained which, after decanting and possibly adjusting the pH with KHHOH to a pH of 6 to 8, give a homogeneous solution of all the active components of the catalyst which can then be thickened into a paste which and drying, the contained aoll is thermally ground and the mass thus obtained after the addition of tableting ingredients becomes pelletized and calcined, thereby obtaining the desired catalytic properties

The basic amount of NH 4 OH, tartaric acid, nitric acid and water to dissolve the deactivated catalyst is proportional to the analytically determined content of the individual active components in the optimum case being equal to the amounts of NH 4 OH, tartaric acid and water added in the solutions Equal amounts by weight of catalyst of the same composition when prepared from solutions of pure salts of the individual active components.

In general, however, NH 4 OH and water to dissolve the deactivated catalyst can be used in excess, the amount of tartaric acid β nitric acid must be retained.

The dissolution of the catalyst can be carried out at a temperature of 20 to 120 ° C, preferably at a temperature of 20 to 70 ° C, in which the dissolution proceeds at a reasonable rate and does not cause intense NH 2 leakage from solutions or undesirable nitrous gas evolution.

Losses of active components when using the inventive method are nininal and are practically limited to those resulting from handling. The newly prepared catalyst therefore has practically the same ratio of active components as the dissolved deactivated catalyst.

If the deactivation of the catalyst was caused by a change in the chemical composition during operation, the composition of the solutions obtained by dissolving it can be adjusted by addition of solutions or solid salts, ammonium salts or nitrates, individual active components, to obtain a catalyst of the desired composition.

The example below explains the preparation of the catalyst according to the invention.

Example 1

Into a Keller flask fitted with an addition, heat transfer and reflux condenser and introduced 640 ml of 26% NH4OH and, with vigorous stirring, gradually introduced 300 g of deactivated catalyst Mo, 2 ^V 3 ^Cu 2 ^Fe 0 5 ^{8 content} of kaolin and graphite as tableting of the ingredients and the mixture is stirred at normal temperature for about 1.5 hours at which time the tablets disintegrate.

The suspension was then diluted with 3000 mL of distilled water and stirred at room temperature for a further 1 hour. After this time, 109 g of tartaric wine are added to the flask, the temperature is raised to 70 ° C over one hour, the suspension is filtered at this temperature, and the filter cake is washed with 450 ml of 70 ° C distilled water. Solution A is thus obtained.

The filter cake is transferred back to the flask, stirred and 350 ml of distilled water, 50 ml of 65% HNO 4 are added and the suspension is stirred at 70 ° C for 1 hour. After this time aa the undissolved residue, which forms the tabletting ingredients, is hot filtered and washed with 450 ml of distilled water (70 ° C). Thus ae solution B is obtained.

Solutions A and B are combined, pH aa is adjusted to pH 7-8 with NH 4 OH (thereby dissolving any precipitate) to give a homogeneous solution of the active catalyst components, which is then further concentrated to a temperature of up to 120 ° C. consistency of the paste, which is dried and contained aol at a temperature of up to 320 ° C thermally decomposed. The resultant aa after addition of 5 wt. with a mixture of kaolin and graphite, homogenize, blend and calcine at 325 ° C for 6 hours.

Claims (2)

SUBJECT OF THE INVENTION A process for the preparation of gas-phase oxide catalysts for the oxidation of unsaturated aldehydes in a gas phase from a deactivated catalyst for the production of non-bulky catalysts, characterized in that it is a deactivated catalyst containing at least 60%, a catalytically active component consisting of a mixture of molybdenum and other metal oxides from I., V. or Vlil. groups of Mendilejev's periodic system such as something, bismuth, iron, cobalt or nickel are not more than 40% by weight. inert tabletting agents or diluents, successively by swirling at 20 to 120 ° C in aqueous solutions of ammonium tartaric acid, nitric acid or mixtures thereof, the insoluble fraction which forms the inert tabletting additive or diluent is gradually separated, the soaked aqueous active solutions The pH of the mixture is adjusted to 6-8 by the addition of ammonium hydroxide and the homogeneous solution thus obtained at a temperature of up to 120 [deg.] C. or, after the addition of the diluent, is thickened to a consistency of the paste. The thermally decomposes and the sieved mass becomes scarlet and calcined at a temperature in the range of 300 to 400 ° C after addition of the tabulating agents. 2. Process according to claim 1, characterized in that the composition of the solutions obtained from the reactants of the deactivated catalyst is adjusted by the addition of ammonium salts and / or nitrates of the hardened metals and the solutions thus obtained are treated in the same way.