KR800001259B1 - Catalyst regeneration with impregration of bismuth and molybdenum - Google Patents

Abstract

Ammoxidn. catalysts were regenerated by addn. of Bi and Mo. The catalysts were used in manuf. of acrylonitrile from propene. In an example, a regenerating soln. was prepd. from MoO3, H3PO4, NHO3, Bi(NO3)35H2O, and H2O. It was used to regenerate a SiO2-supported ammoxidn. catalyst contg. Bi, P, Mo, K, Co, Ni, and O.

Description

Regeneration method of oxidation catalyst

The present invention relates to a method for regenerating a catalyst containing various metal oxides by impregnating a spent catalyst in a solution containing several metals.

In particular, the present invention provides acetonitrile from propylene, ammonia and oxygen or air by impregnating a spent catalyst in a solution of soluble molybdenum and bismuth and then calcining the treated catalyst to obtain an active catalyst ( Ammoximation ammoxidation) relates to a method for regenerating a catalyst consisting of oxides of potassium, cobalt, nickel, iron, bismuth, phosphorus, and molybdenum used.

It is known that some of the molybdenum-containing catalysts that are particularly suitable for rock moxibustion tend to be inactivated upon prolonged exposure to the reactants under reaction conditions. It was also observed that molybdenum was lost from the catalyst during the reaction.

It has been found that one of the inert pathways is due to the loss of molybdenum, and a method for reactivating the catalyst during the reaction by contacting the molybdenum particles in the fluidized bed on an inert support without removing the darkoxidation catalyst from the reactor. Also known. Optionally these particles may contain other elements useful for regeneration such as iron, bismuth or tellurium, but particles on an inert support consisting essentially of molybdenum are preferred. Preferred methods for preparing these particles include spray drying a finely divided support and an aqueous slurry containing finely divided molybdenum metal or molybdenum compound.

Another method of preparation involves combining the molybdenum compound solution with a finely divided support material and then drying and grinding the particles.

The cobalt and molybdenum are produced by impregnating the catalyst with a liquid containing bismuth, iron, tellurium compounds, or mixtures thereof, which are at least partially soluble in the liquid, and then heating the impregnated matrix under elevated temperature to produce an active catalyst. Processes for regenerating catalyst substrates containing oxides of magnesium and molybdenum, nickel and molybdenum, manganese and molybdenum or mixtures thereof are known.

A method for regenerating a catalyst containing iron and molybdenum consisting of impregnating a spent catalyst with a molybdenum amine solution (non-oxidizing compound of molybdenum), removing the solvent, and then heating the catalyst to recover the lost molybdenum It is.

It is also known to bind iron to the spent-molybdate phosphate bismuth catalyst to enhance their activity.

The present invention is represented by the general formula AaBbCcFedBieMofOx, and the catalyst is intimately contacted with molybdenum and bismuth in an aqueous solution on a support, and the contacted catalyst is separated from a solution that is not adsorbed on the catalyst, and then calcined to activate an active catalyst. It is about how to play.

Wherein A is at least one element selected from the group consisting of alkali metals, rare earth metals, tantalum and niobium, B is at least one element selected from the group consisting of nickel and cobalt, C is at least one element selected from the group consisting of phosphorus and arsenic, lowercase letters represent moles, “a” and “c” are 0-3, “b” is 0.1-20 and “d” is 0.1-8 , “E” is 0.1-6, “f” is 8-16 and “x” is determined by the balance of valences of other elements present.

In a particular embodiment, the present invention essentially consists of a catalyst in an aqueous solution containing bismuth and molybdenum, such as a solution containing at least 29 g / l molybdenum and 11 g / l bismuth at least about 0.75% molybdenum relative to the catalyst And 0.28% by weight bismuth, or 1.5% and 0.56% by weight, for catalyst elements (e.g. support) are impregnated until bound on the catalyst surface, and the treated catalyst is removed from the Represented by the general formula K (g) Co (h) Ni (i) Fe (j) Bi (k) P (l) Mo (m) O (x) consisting of plasticizing the resulting material after separation A method for regenerating a catalyst composed of elements. In the general formula, (g)-(m) indicates the number of moles, and is in the range of 0.05-0.10, 4.0-5.0, 2.0-3.0, 2.5-3.5, 0.8-1.2, 0.1-1.0, 10.9-13.2, respectively, and x is present. It is a number that matches the valence of another element. In this way about 50%, preferably at least about 90%, of molybdenum lost from the catalyst during use can be recovered and the amount of bismuth in the catalyst can be increased. The molar ratio of added molybdenum to bismuth is 0.5-20 and preferably 1-5.

In a more preferred embodiment of the invention, phosphorus or silicon is present in addition to molybdenum and bismuth in the solution. If phosphorus is present, dissolve a sufficient amount of molybdenum trioxide and phosphoric acid in water to obtain a solution containing at least 29 g / l molybdenum and 0.8 g / l phosphorus, add nitric acid to it, and add a sufficient amount of bismuth nitrate to the resulting solution. The hydrate can be dissolved to produce a solution containing at least 11 g / l bismuth.

The regeneration process of the present invention is particularly suitable for some types of catalysts, but can be widely applied to various catalysts.

The catalyst is generally represented by the general formula AaBbCcFedBieMofOx, where A is at least one element selected from the group consisting of alkali metals, rare earth metals Ta and Nb and B is at least one element selected from elements consisting of nickel and cobalt, C is phosphorus or arsenic or both, where the lowercase alphabet represents a mole, where “a” and “c” are 0-3, “b” is 0.1-20, “d” is 0.1-8, and “e” is 0.1-6, "f" is 8-16 and "x" is determined by the valence of the other elements present. The above elements are generally present on silicon oxide supports, which constitute 40-60% by weight of the catalyst.

These active catalysts are particularly effective in powder form such as powders having an average particle diameter of 50-70 microns and provide about 92% propylene conversion and a selectivity of at least about 70% in the rock seedization that converts propylene to acrylonitrile.

Where 'conversion' is the percentage of propylene consumed divided by the number of moles of propylene injected, and selectivity is the percentage of the resulting acrylonitrile divided by the amount of propylene glycol consumed.

These variables are determined by known analytical methods, such as gas chromatography, using rock seeding equipment and conditions as in Example 1. In a particular embodiment the catalyst may be represented by the general formula K (g) Co (h) Ni (i) Fe (j) Bi (k) P (l) Mo (m) O (x), where x is present (G)-(m) are in the range 0.05-0.10, 4.0-5.0, 2.0-3.0, 2.5-3.5, 0.8-1.2, 0.1-1.0, 10.8-13.2, respectively.

For example, long-term exposure of the catalyst to the reactants under similar conditions as in Example 1 to validate the regeneration in consideration of various factors in commercial operation resulted in a conversion rate of about 90% or less and a selectivity of about 69% or less. It has become apparent that the reduction in the effectiveness of the catalysts is economically viable and should replace the catalyst at this value. Catalysts with reduced effectiveness have been labeled “waste” and generally refer to a state in which the catalyst of the general formula has lost 0.4-1.2 mol of molybdenum. However, the present invention is also applicable to the case where the loss of activity and / or molybdenum is more or less than the above.

The “lung” exhibits the general formula K _0.07 Co _4.5 Ni _2.5 Fe ₃ Bi ₁ P _0.5 Mo _11.25 Ox on the silicon oxide support (x is dependent on the valence requirement of the other element) and shows 90% conversion and 69% selectivity. When the catalyst was regenerated according to a more preferred embodiment of the present invention, the resulting catalyst contained an elemental weight of approximately the general formula K _0.07 Co _4.5 Ni _2.5 Fe ₃ Bi _1.35 P _0.65 Mo _12.7 Ox, and the method of Example 1 The test showed a conversion rate of at least about 92% and a selectivity of 75%.

In the present invention, it is important to apply a combination of bismuth and molybdenum, since satisfactory regeneration is not achieved if only one metal is added to the catalyst. This is unexpected because the metal lost from the catalyst is molybdenum one.

Bismuth and molybdenum may be brought into contact with the catalyst at the same time or in turn, but preferably at the same time. In general, the molar ratio of Mo / Bi in the impregnation solution is in the range of 0.5-20, but is preferably applied in a ratio of 1-5. In a more preferred embodiment of the present invention the solution in which Bi and Mo are present preferably contains at least one metal in the oxyanion form, for example phosphorus or silicon. Bi, Mo and tertiary elements can be represented as chemical compositions of heteropoly heavy acids such as, for example, acids containing oxygen, molybdenum, phosphorus and / or silicon and bismuth. Chemical compositions can also be represented as bismuth salts of heteropolyacids containing Mo and one or more other elements. Other indications of the chemical composition should be apparent to those skilled in the art. Other catalytic elements such as, for example, iron and antimony can also be present in the impregnation solution without departing from the scope of the present invention. These additional elements are related to the integral part of the heteropolyacid or salt.

The compounds used to regenerate the catalyst are most effective in solution. The solution may be water soluble, organic or a combination thereof and depends on the form of bismuth and molybdenum used. Aqueous or near aqueous solutions such as those in which the main solvent is water are preferred. The present invention mainly relates to aqueous solutions, but other functionally equivalent systems such as, for example, vapor systems containing elements in the form that can easily adhere to the catalyst surface are within the scope of the present invention.

Molybdenum can be obtained from various substances in the aqueous system. Molybdates of molybdates, soluble alkali-, alkali metal-, ammonium- or organic amines are the basis materials such as sodium molybdate, -potassium, -lithium, -calcium, -barium, -magnesium, -ammonium and -methyl There is an amine. Molybdenum compounds such as molybdenum oxybromide, molybdenum oxychloride molybdenum oxychloride, molybdenum oxyfluoride, triphenylmolybdenum, hexacarbonyl molybdenum and molybdenum emulsified can be used as molybdenum oxides by hydrolysis and / or oxidation in the presence of water. In the presence of phosphorus, molybdenum compounds can also react to form phosphomolybdates. As a base material of molybdenum, trioxide ribon is preferable. Preferred bases of phosphorus include phosphoric acid but phosphorus pentoxide, triacid, metaphosphoric acid, phosphorus pentachloride, phosphorus obromide, phosphorus oxychloride, phosphorus oxybromide, trimethylphosphate and phosphorus triphenylphosphate, primary phosphorus Compounds capable of forming an aqueous solution of phosphoric acid may also be used.

Phosphorus and molybdenum can be fed simultaneously when they are present as phosphomolybdate salts of soluble ammonium, alkali or alkaline earth metals such as phosphomolybdic acid, sodium phosphomolybdate, potassium phosphomolybdate.

It is most preferable to treat the impregnation only with a solution, and if molybdenum and / or phosphorus are not completely dissolved, such as forming a slurry, it is preferable to filter out the solid before entering the next step in preparing the impregnation solution. Do.

As will be appreciated by those skilled in the art, in order to maximize the solubility of Bi and Mo compounds or to make them in complete solution, it is advantageous to keep the solution basic, neutral or acidic depending on the compound used. When molybdenum trioxide and aqueous phosphoric acid solution are used, it is preferable to make the solution acidic to maximize solubility.

The bismuth compound is preferably soluble in the impregnation solution. Preferred base materials of bismuth in aqueous systems can be hydrolyzed in addition to bismuth nitrate in molybdenum and / or phosphoromolybdenum solutions such as bismuth trioxide, bismuth hydroxide, bismuth oxa chloride, bismuth nitrate, bismuth sulfide, bismuth oxalate, bismuth stannate, etc. Compounds that are soluble in aqueous nitric acid solution can be used.

Silicon is conveniently supplied to molybdenum silicon in the presence of silicon, but organic silicates such as ethyl orthosilicate can be used as well as soluble ammonium and alkali metal silicon compounds such as ortho-silicate, sodium silicate and potassium silicate.

In some cases, the selected molybdenum, phosphorus bismuth or silicon compounds can attract undesirable amounts of ions such as sulfides and chlorides in the impregnation solution. However, these ions can be easily removed at any stage in the preparation of the impregnating solution by conventional methods such as treatment with adsorbents such as amorphous, molecular sieves or ion exchange resins.

Since it is desirable to eliminate or minimize solids in the impregnation solution, it is necessary to adhere to the series of additions as indicated to prevent precipitation formation reactions. In an aqueous system, molybdenum and optionally phosphorus are added to a solution, acidified by addition of 5-60% by volume, preferably 5-30% by volume, of 15.4N nitric acid, the acidified solution is cooled, and the bismuth compound is dissolved. Generally preferred.

It is also advantageous to increase the dissolution rate of the compound by heating the solution, but it is desirable to cool the solution at this time as the elevated temperature may cause precipitation. For example, when molybdenum trioxide and phosphoric acid are added to water and heated to accelerate the solution process, and then acidified by addition of nitric acid to prepare a typical "waste" catalyst impregnation solution, before adding bismuth nitrate to prevent precipitation, Is cooled to about 85 ° C. or less, more preferably 20-30 ° C.

The concentration of impregnant in solution is proportional to the amount of impregnant bound to the catalyst surface. For effective regeneration, it is necessary to add at least 0.75% molybdenum, 0.28% bismuth, and optionally 0.02% phosphorus and / or silicon based on the weight of the catalyst for the special spent catalyst. In order to combine the minimum amount of these elements by one contact of the impregnation solution with the catalyst, the solution should contain at least 29 g / l molybdenum, 11 g / l bismuth and optionally 0.8 g / l phosphorus and / or silicon. do.

When contacting the catalyst and the impregnation solution several times, the concentration of each component in the solution can be reduced in proportion to the number of contacts, without departing from the scope of the present invention. The impregnation solution may be contacted with the catalyst by a variety of methods including, for example, dropping or spray impregnation and filtration impregnation.

Dropping or spray impregnation involves improving the impregnation solution thereon while rotating the catalyst as it is meant. The volume of solution used for the drop or spray impregnation is preferably no greater than 110% of the catalyst pore volume for optimum results. In filtration impregnation, it is desirable to remove substantially excess of the impregnation solution after contact with the catalyst and before plasticizing the excess catalyst. Many effective impregnation solutions, such as, for example, solutions with high acid contents, can be reacted with the catalyst, which leads to decomposition and / or dislocation of the catalyst, which can adversely affect the catalytic effect.

Therefore, especially in filtration impregnation, it is preferable to contact an impregnation solution which can introduce a desired level of element into the catalyst and can quickly separate the catalyst from the excess impregnation solution after contact.

The impregnated catalyst must be dried and calcined independently of the impregnation method to provide an active catalyst. Drying can be effected by conventional methods such as heating at 25-125 ° C. for 24-48 hours or simultaneously with calcining. The calcining can be conveniently carried out by heating the catalyst in an oxidizing air stream in the range of 300-700 ° C., preferably 450-650 ° C., preferably at 500 ° C. for about 1 hour.

Example 1

16.40 g molybdenum trioxide, 1.31 (85%) phosphoric acid and 300 ml of water are mixed in a 500 ml glass glass flask and the mixture is periodically added to maintain a volume of 250 ml until a solution is obtained (approximately 6 hours). Boil). Water was evaporated until the solution volume reached 140 ml and the flask and its contents cooled to about 25 ° C. and then had 10 ml of nitric acid (70%). Stir the flask contents and add 14.53 g of bismuth nitrate pentahydrate. Stirring is continued until bismuth nitrate is dissolved.

The spent catalyst is on a silicon oxide support that supports up to about 50% by weight of the catalyst in powder form. The catalyst has an average particle size of about 66 microns and a pore volume of about 0.25 cc / g and approximately K _0.07 Co _4.5 Ni _2.5 Fe ₃ Bi _1.0 P _0.5 Mo _11.25 Ox (where x is the valence requirement of other elements present) Is a numerical value determined). Approximately 450 g of this spent catalyst is placed in a 1-gallon Stansence steel beaker with internal stir fins and the beaker is placed in a rotary device and the solution prepared as described above at about 30 ° from the horizontal is placed in the spent catalyst. The solution was spun at a speed of about 30 rpm and then the treated catalyst was dried at 115 ° C. and then calcined by heating to about 500 ° C. for 1 hour and held at this temperature for another hour. The resulting catalyst has a composition of approximately K _0.07 Co _4.5 Ni _2.5 Fe _3.0 Bi _1.35 P _0.65 Mo _12.7 Ox and contains 1.39 wt% Bi 0.08 wt% P and 2.43 wt% Mo.

About 400 g of such catalyst was placed in a 4 inch diameter fluidized bed reactor, and the pre-mixed ammonia, propylene and air mixture at 440 ° C., 12 psig, at a molar ratio of 1.09 / 1.0 / 10.1 at a gas velocity of 1.74 cm / sec. Send it to the fluidized bed through the stomach. The conversion of propylene was 92% and the selectivity to acrylonitrile was 76%, compared with 90% conversion and 69% selectivity for spent catalysts tested in the same way.

Example 2-13

A waste catalyst sample having almost the same composition and conditions as the waste catalyst of Example 1 was replaced with (1) the amount of Bi, P and Mo added to the waste catalyst as follows (2) the amount of impregnant was filtered Regeneration was carried out according to the method of Example 1, except that it was increased to provide an impregnation solution of 250 ml, sufficient for For convenience, divide the solution into two 125-ml portions. The liver part is contacted with the spent catalyst 225-g and the excess impregnation solution is quickly filtered off before the impregnated catalyst is dried, calcined and inspected.

The results are shown in the table below. Excess MoO ₃ , H ₃ PO ₄ and Bi (NO ₃ ) ₃ .5H ₂ O (the amount calculated from the measured pore volume of the catalyst) are added to ensure saturation of the pores.

In the table, the weight percent of impregnated elements bound to the spent catalyst is calculated from the measured pore volume. The calculated value of molybdenum added is almost the same as the amount determined by the analysis, but there is a big difference between the calculated value and the analysis value of bismuth because of the analyte. However, it is not necessary to determine the amount of element added to the catalyst according to the analysis result. For example, when the impregnating solution is brought into contact with the catalyst by drop or spray impregnation, all the compounds in a given solution are all on the catalyst since no solution is removed. Since the amount of compound used to prepare the solution is known, the amount of catalyst phase can also be determined by simple calculations. In addition, since the molybdenum, bismuth and / or phosphorus or silicon are not selectively adsorbed during the impregnation, the amount of element added to the catalyst is actually at the same ratio as in the impregnation solution. Thus, by analyzing the amount of molybdenum added, it is possible to calculate the amount of other elements added during drip or filtration impregnation. Analysis of the amount and composition of the impregnation solution removed from the catalyst during filtration impregnation can also be used to determine the amount of elements added.

Example 14-17

The impregnation process of Examples 1-13 was modified to contact 450 g of the catalyst with a solution containing molybdenum and bismuth. Molybdenum is introduced as ammonium heptamolybdate (100% of (NH ₄ ) ₆ Mo ₇ O ₂₄ 4H ₂ O) in 115 ml of an aqueous solution containing the amounts indicated in the table below. Bismuth is introduced as bismuth nitrate (100% Bi (NO ₃ ) ₃ .5H ₂ O) in 115 ml of an aqueous solution containing the amounts indicated in the table below. This solution is dipped into the catalyst according to the method of Example 1. Molybdenum was added before bismuth in Examples 14 and 15 and after bismuth was added in Examples 16 and 17. In Example 14 the catalyst is dried and calcined before and after disposing of bismuth or in Example 15 only before bismuth is added. Plasticization and / or drying are applied in the same manner as in Examples 16 and 17. The regenerated catalyst was examined as in Example 1 and the results are shown in the table.

Example 18

The method of Example 1 was repeated except that 2.70 g of sodium silicate (Na ₂ SiO ₃ .9H ₂ O) was used instead of phosphate to add 0.097% by weight of sodium and 0.06% by weight of silicon in addition to the elements shown in the table. do.

Example 19

The method of Example 1 was repeated except that 1.62 g of sodium nitrate was added together with bismuth nitrate to bind 0.097% by weight of sodium in the catalyst other than the elements shown in the table.

[Control Experiment A-D]

The method of Example 1 was repeated except using a solution containing molybdenum or bismuth alone and molybdenum and phosphorus alone as the impregnation solution of the catalyst. The results are shown in the table.

From the above examples and control experiments, it was demonstrated that molybdenum or bismuth alone did not show satisfactory regeneration and that a combination of these elements was necessary for optimal results.

[table]

(a) Amount of the enclosure in 115 ml of solution added to 450 g of catalyst by dropping according to the method of Example 1

(b) An aqueous 250 ml solution of about 37.28 g molybdorosilic acid (H ₄ SiMo ₁₂ O ₄ 07H ₂ O as 100%) was used instead of molybdenum oxide and phosphoric acid.

(c) The added molybdenum was added dropwise to 450 g of the catalyst according to the method of Example 1 to add ammonium heptamolybdate (100%, NH ₆ Mo ₇ O ₂ 4H ₂ O), expressed in grams in 115 ml solution.

(d) Nitric acid is added to the impregnation solution to make a concentration of 6.2N.

(e) Nitric acid is added to the impregnation solution to make a concentration of 1.6N.

(f) About 105 ml of solution was used.

Claims (1)

Prolonged exposure to ammoxidation conditions results in the loss of some of the molybdenum contained in the catalyst, impregnation of the partially deactivated catalyst with the solution containing molybdenum and bismuth, followed by absorption of the impregnated catalyst into the catalyst. Separated from unmolded molybdenum or bismuth solution and calcined at a temperature of 300-700 ° C. and oxidizing pressure to recover at least 50% of the molybdenum loss of the original catalyst and the molar ratio of added molybdenum to bismuth is 0.5-20 A method for regenerating an oxidation catalyst represented by the general formula AaBbCcFedBieMofOx in the range of. Wherein A is at least one element selected from the group consisting of alkali metals, rare earth metals, tantalum, niobium, B is at least one element selected from the group consisting of nickel and cobalt, and C is phosphorus and arsenic At least one element selected from lowercase alphabets represents moles, “a” and “c” are 0-3, “b” is 0.1-20, “d” is 0.1-8, “e” is 0.1-6, "F" is 8-16 and "x" is determined by the valence of other elements present).