Method of preparation of aluminium oxide-platinum catalyst for neutralization vibronic gases from organic substances, carbon monoxide and oxides of nitrogen

 

(57) Abstract:

The invention relates to catalytic chemistry, in particular the preparation of aluminium oxide-platinum catalyst, for neutralization vibronic gases from organic substances, carbon monoxide and nitric oxide. Goal - increase the activity and thermal stability of the catalyst at simplifying the process and avoiding harmful emissions. Preparation lead the introduction of carrier - Al2O3supplementation of cerium or rare earth elements using their deposition from nitrate solution of cerium or concentrate the amount of rare earth elements in the pulp of active aluminum hydroxide at pH 9 to 9.2 and 50 -70 C. Then conduct the calcination of the carrier at 500 - 550 C, the introduction of platinum from a solution of hexachloroplatinic acid in a quantity of 0.2 - 0.5 %, processing of 0.5 - 2% solution of NA(O)HE at room temperature for 5 to 15 min and activation-recovery-mode-drying at 60 to 180 C for 4 - 6 hours These conditions increase the activity of the catalyst (the rate of methane oxidation at 550 C reaches 12,3 103cm3CH4/ g c against 2,8102cm3CH4/GS; the degree of conversion of nitrogen oxides, WITH 61,2 and 70% vs. 54 and 65.5% and thermal stability (up to 1000 - 1 is s relates to methods for producing catalysts for neutralization of toxic organic impurities, And NOxin the gas emissions.

Known method of preparing catalysts REE - alumina - platinum group metal [1], and with the addition of transition metal oxides [2] , which as one of the main stages of preparation involves the impregnation of the support with solutions of salts of rare-earth elements and additives, with subsequent drying and calcination of not lower than 750aboutIn order to completely decompose the deposited salt. Followed by the stage of deposition of the noble metal and high-temperature activity at 400-600aboutC. This method is one of the most widely used in practice, however, it has some significant drawbacks. These include several (at least two) high-temperature treatment of the carrier and catalyst, which reduces the specific surface, porosity of the medium and the dispersion of the noble metal, so it does not always ensure the desired activity of the samples. In order to avoid several of the high-temperature prokalivanii, additives REE and the active component is injected simultaneously from a solution of salts during the impregnation of the support [1]. In this case, it is difficult to obtain a catalyst with the desired distribution of the noble metal grain media. Decreases activatelink cases after application of the active component and modifier wet catalyst is treated at room temperature with gaseous hydrogen sulfide to secure platinum dispersed state (in the form of sulphides) [3] . However, the catalyst before use, you must activate at T 350aboutWith air to remove the sulfur content of the samples and the formation of an active form of the metal platinum, which, on the one hand, requires energy, and on the other, may lead to sintering of the active component. In [4] proposed a method wet recovery of the catalyst without heating solutions of hydrazine, hydroxylamine, reducing sugars together with impregnation dissolving salts of alkaline-earth elements, however, the dispersion of the platinum metals is obtained is not high enough. There is a method of coprecipitation from solutions of mixtures of soluble salts of Al, Ce, Cr, Zr ammonia solution at pH 5-9 [5]. After stage filtration, washing and drying should high-temperature annealing at 920aboutC. Then the resulting mixture is ground, treated with a solution of nitric acid is applied on the honeycomb carrier as an intermediate layer. This method is not used for the preparation of granular catalysts based on alumina, as in the coprecipitation of hydrogels aluminum and REE unable to get media with large surface and the desired pore size of the media.

The closest in technical essence and the achieved effect of the present invention is a method for preparing the rare earth-containing catalyst afterburning described in [6].

The catalyst is prepared by impregnation of the granules or powder of the active alumina with solutions of nitrate salts of cerium in the amount of 5-20 wt.% according to CeO2. After drying at 110aboutWith the media being annealed in air in the temperature range of not lower than 750aboutWith that required for complete decomposition of salt and get a stable media. Then follows the stage of deposition of the noble metal in an amount of 0.1 to 1.0 wt.% and again annealed in air at 400-600aboutC. In some examples, prototype, in order to eliminate the secondary calcination to obtain a catalyst with a high dispersion of platinum, it is treated with gaseous hydrogen sulfide.

The disadvantages of this method are:

high temperature calcination of the carrier and catalyst, which significantly reduces the specific surface, porosity of the aluminum oxide, the dispersion of the deposited platinum and does not provide the desired activity of the samples;

selection by calcination of harmful nitrogen oxides by decomposition of Nitra is an urn activation in air catalyst before work, it highlighted the harmful oxides of sulfur.

The aim of the invention is to develop a method of preparation of REE-containing aluminium oxide-platinum catalyst for neutralization vibronic gases from harmful organic impurities, CO and NOxproviding high activity , thermal stability of the catalyst under the conditions of the cleaning process, simplifying the technology and eliminating harmful emissions.

The catalyst according to the present method is prepared in several stages. The introduction of modifying additives cerium or amount of REE (4-5 wt.% according to CeO2and 8-10 wt.% the sum of REE) carry out the deposition of the additive under stirring and the pH from 9.0 to 9.2 heated to 70-50aboutWith a diluted slurry of active aluminum hydroxide with the generated structure. The precipitation of REE in these conditions occurs, the nitrate ions remain in solution and are easily washed. After stage wash filter press modified mass ekstragiruyut in the form of cuttings, rings with partitions of different sizes and diameter, dried and calcined at temperatures of 500-550aboutC. the resulting carrier has a surface 220-180 m2/Supplements, cerium and/or the amount of REE evenly distributed along the radius of the grain socialiniai thermal stability of the catalyst after completion of cooking. Next is the stage of impregnation of the modified carrier with a solution of hexachloroplatinic acid to make platinum in the amount of 0.2-0.5 wt.% . Before applying platinum, if you want more uniform distribution of grains, the carrier is impregnated with a solution of acetic acid. After applying the required quantity of platinum catalyst at room temperature, treated with 0.5-2% formic acid, so that then drying the catalyst in the temperature range 60-180aboutWith was an additional stage of activation - recovery deposited platinum. Stage of high-temperature treatments catalysts are absent. The high activity of this catalyst in the reaction of deep oxidation due to the stabilization of platinum on the modified sections of the media dispersed in the metallic state.

Distinctive features of this method of preparation of the catalyst are:

1. Deposition of REE ions at pH 9.0 to 9.2 and T 50-70aboutWith in the pulp of active aluminum hydroxide.

2. Processing of wet catalyst is 0.5-2% solution of formic acid and subsequent activation-recovery of platinum in drying mode when 60-180aboutC.

Test conditions

The temperature oxidation of methane 500aboutWith the methane concentration of 0.5 vol.%, the rest is air. For measure activity take the rate of the reaction at Ctechmethane and 0.25 vol.%. The oxidation of butane 300aboutWith the concentration of butane 0,1 vol.%. The activity is determined at the current concentration of butane to 0.05 vol.%. The reaction CO+NO2+O2-395aboutC, the concentration of NO and CO are at 0.9 and 1.3 vol.% accordingly, the oxygen concentration change from 0 to 0.45%. Activity evaluate the degree of conversion of NO. The selectivity for N2determined from the relations [N2] /[N2]+[N2O], where [N2] and [N2O] is the concentration of nitrogen and nitrous oxide.

The essence of the method is illustrated by the following examples.

P R I m e R 1. The pulp industrial aluminum hydroxide obtained by mixing about 3. hydroxide Al continuous cold deposition and about 1. hot deposition ("mixed method"), humidity 84-86% by weight of 667 g placed in a glass container with a capacity of 5-10 l, dilute with water to about 3.5 liters, stirred for about 2 hours while heating to 70aboutC. the pH of the solution is regulated addition of a 12% ammonia solution until the value is 00 ml of a solution of cerium nitrate (III), containing 10.0 g of salt. When prilivnyi pH sedimentation control at the level of 9.2% After adding the solution of the modifier spend additional stirring for 0.5 h and the mass is filtered on a Buechner funnel. The precipitate is dried to a moisture content of 50-70% and ekstragiruyut in the form of granules with a diameter of 2.0-2.8 mm or in the form of rings 5 x 5 mm, the Carrier is dried at 150aboutC, then calcined at 550aboutWith on the air. The mass of the obtained carrier is about 105,

Then in another capacity conduct phase deposition of platinum from a solution of hexachloroplatinic acid. Medium weight 100 g treated with 750 ml of 2% aqueous solution of acetic acid for 45 minutes and add a solution of N2PtCl6a volume of 300 ml with a concentration of platinum 1.8 mg/ml After 1.5 h impregnating solution is drained, the excess water is removed by vacuum suction and then for 15 min, the catalyst was treated with 300 ml of a 1.0% solution of formic acid. After removal of excess solution, the catalyst was activated in the mode of drying at 60aboutC in air for 4 hours Final drying to remove water sorption is carried out at 180aboutC. the resulting catalyst has the composition: 0,5-of 0.54 wt.% Pt (average particle size d 20-25 ), 5.0 wt.% CeO2(d 70 ) OS is Riya along the radius of the grains of the catalyst is uniform.

P R I m m e R 2. Similar to example 1, but differs in that the deposition of cerium ions in the slurry of aluminum hydroxide is carried out at pH 9.0 and at a temperature of 50aboutC. the resulting catalyst has the composition: of 0.52 wt.% Pt (d 20-25 ), 5.0 wt. % CeO2(d 70 ), the rest-Al2O3(d 60 ). The specific surface of the catalyst is 200 m2/,

P R I m e R 3. Similar to example 1, but differs in that the processing of the catalyst HCOOH lead 10 min, and the activation is at a temperature of 120aboutC. the resulting catalyst has the composition: 0,5-of 0.54 wt.% Pt (d 20-25 ), 5.0 wt. % CeO2(d 60-70 ), the rest-Al2O3(d 50-60 ). The specific surface is 180-200 m2/,

P R I m e R 4. Similar to example 1, but differs in that the catalyst after the application of Pt treated with a 2.0% solution of HCOOH 5 minutes composition of the obtained catalyst: 0.5% Pt (d 30-40 ), 5.0 wt.% CeO2(d 60-70 ), the rest-Al2O3. Specific surface area of 180 m2/,

P R I m e R 5. The method of preparation of the catalyst is similar to example 1, but differs in that the catalyst after the platinum plating process 1,5% HCOOH solution for 10 min, and the activation mode of drying is carried out at 80aboutC. the Composition of the obtained catalyst: 0.50 wt.% Pt (d P R I m e R 6. The method of preparation is similar to 1, but differs in that the catalyst after the application of platinum treated with 0.5% solution of HCOOH, and the activation is carried out at 120aboutC for 6 hours composition of the obtained catalyst: 0.50 to 0.52 in wt.% Pt, 5.0 wt.% CeO2the rest - -Al2O3. The specific surface of the catalyst 180-200 m2/,

P R I m e R 7. Similar to example 1, but differs in that before applying the platinum modified carrier calcined at 500aboutWith and treated for 25 min with 1% solution of formic acid with a volume of 700 ml Secondary processing of wet catalyst of 0.5% HCOOH is carried out after applying the required amount of Pt for 10 minutes activation-recovery of the catalyst is carried out at a drying temperature of 160aboutAt 6 a.m. the Catalyst has korosnoe distribution of platinum on the radius of the grains with an average particle size of the metal platinum 30-35 . The specific surface of the catalyst is 180 m2/,

P R I m e R 8. Similar to example 1, but the carrier is calcined at 500aboutWith and impregnating a solution of hexachloroplatinic acid has a concentration of platinum 0.7 mg/ml After application of the active component wet catalyst is treated with a 2.0% p is (d 40 ), the rest - Al2O3(d 50-70 ). The distribution of platinum in the catalyst of uniform.

In examples 9-10 describes the method of preparation of catalyst using industrial solution concentrate amounts of nitrates of rare-earth elements (REE).

P R I m e R 9. The pellet of aluminum hydroxide ("mixed method" of cooking) humidity 85% by weight of 6.1 kg diluted with water in ratio 1:3, stirred and heated to 60aboutC for 1.5 hours and Then added slowly to 0.39 l nitrate solution industrial concentrate the amount of rare earth elements with a concentration on the amount of REE oxides 220 g/l When adding solution REE carry out continuous stirring and the pH of the environment support to 9.2 by addition of a 12% solution of aqueous ammonia. After deposition of REE ions to the slurry additionally stirred for 1.5 h and filtered on a Buechner funnel. The resulting mass is dried at room temperature for 16 h and ekstragiruyut in the form of granules, rings, rings with partitions. The carrier is dried at 130aboutWith 3 hours and calcined at 550about6 PM Mass of the obtained carrier is 1.0 kg

Then follows the stage of deposition of platinum from a solution of hexachloroplatinic acid. Noitem 2.5 l with the concentration of platinum 2.0 g/L. After 1.5 h impregnating solution is drained, the excess water is removed by vacuum and within 10 min the catalyst was treated with 1% solution of formic acid, a volume of 2.5 L. After removal of excess solution, the catalyst restore mode drying at 120aboutAt 6 a.m. the Final drying is carried out at 160-180aboutC. the resulting catalyst has the composition: 0.5. % Pt, 8.5 wt.% oxides of rare-earth elements, the rest is aluminum oxide. The specific surface is 200-215 m2/,

P R I m e R 10. Similar to example 9, but differs in that the deposition amount of the REE in the slurry of active aluminum hydroxide is carried out at 50aboutC and a pH of 9.0, and the stage of recovery of the catalyst, after processing HCOOH for 5 min, carried out at 180oC 6 hours, the Catalyst has the composition: 0.5% Pt, 8.5 wt.% oxides of rare-earth elements, the rest-Al2O3. The specific surface 200-210 m2/,

P R I m e R 11 (prototype). 5000 g of spherical particles of the active alumina is immersed in a solution containing 700 g of Ce(NO3)36H2O and 5050 ml of N2O. After drying at 110aboutC for 16 h carrier was calcined at 950aboutWith air 2 hours After cooling, 3500 g of the carrier is placed in a solution of hexachloroplatinic acid with a volume of 1400 ml, containing the P>14 including the Final annealing is conducted in air at 500aboutTo complete removal of chloride and sulfide ions. The composition of the obtained catalyst: 0.5% Pt, 5 wt.% CeO2the rest -()- Al2O3. The specific surface 130-140 m2/,

In table. 1 presents variable conditions of the present method of preparation of the catalyst.

In table. 2 shows the specific surface of the carrier, the phase composition of the samples of the catalyst, the average particle size of the components after high temperature treatments.

In table. 3 and 4 shows the results of catalysts in model reactions.

Thus, the obtained results indicate that this method allows to prepare the catalyst afterburning of harmful impurities in the gas emissions with higher activity (3-6 times in the oxidation of hydrocarbons) and selectivity (recovery of nitrogen oxides by carbon monoxide), and with high thermal stability (up to 1000-1050aboutC) than known methods. In the present method, when receiving and activating the catalyst there is no discharge of harmful oxides of nitrogen and sulfur. The use of industrial solution amount REE is more efficient than using IU, excludes high-temperature calcination of the catalyst).

METHOD of preparation of aluminium oxide-platinum CATALYST FOR NEUTRALIZATION VIBRONIC GASES FROM ORGANIC SUBSTANCES, CARBON MONOXIDE AND OXIDES of NITROGEN, including the introduction of modifying additives - cerium or the amount of rare earth elements in alumina carrier, drying, calcining, media, application of platinum from a solution of hexachloroplatinic acid in amount of 0.2-0.5. percent , activation-recovery and drying of the catalyst mass, characterized in that, in order to obtain a catalyst with high activity, stability, simplifying the technology and eliminating harmful emissions, additives cerium or rare earth elements can be added by deposition from nitrate solution of cerium or industrial concentrate the amount of rare earth elements in the pulp of active aluminum hydroxide at a pH of from 9.0 to 9.2, a temperature of 50-70oWith the annealing medium is carried out at 500-550oAfter deposition of platinum catalytic mass is further treated 0.5 to 2.0% solution of formic acid at room temperature for 5-15 min and activation-recovery is carried out in a drying mode when 60-180oWith for the

 

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