Method of preparing oxide catalysts using microwave emission (options)

FIELD: oxide catalyst preparation methods.

SUBSTANCE: invention relates to preparation of oxide-structure catalysts and provides a method for preparing oxide catalyst characterized by mixing two or more salt precursors of catalyst components followed by melting resulting mixture to achieve homogenous melt, cooling this melt to room temperature and subsequent decomposition of salts and calcination, wherein salt precursors of catalyst components are selected from d-metal nitrates (Ce and Y nitrates), melting of mixture is effected at 90 to 170°C in presence of ammonium nitrate used at ratio (2-10):1 to metal nitrate mixture, and decomposition of the melt into oxides is performed under effect of microwave emission. In a preferred embodiment of invention, microwave emission is used for 0.5-5 min at working frequency 2.45 GHz and power 600-1900 W. A method of preparing oxide catalysts involving introduction of oxide structure carrier into resulting melt at continuous stirring is also described.

EFFECT: enabled preparation of oxide catalysts and spinel-structure catalysts characterized by high degree of uniformity, lack of harmful impurities in catalyst composition, high-developed surface, and high heat resistance.

8 cl, 2 tbl

 

The invention relates to the field of carriers of catalysts and catalysts oxide structure.

A known method of producing catalyst for the oxidation of propylene, comprising a mixture of metal salt solutions of precursors of the catalyst components, coprecipitation, drying, decomposition of salts and calcination of a catalyst mass (U.S. Pat. EN 2236292 C1 from 20.09.2004). As salt solutions using solutions of nitrates of lithium, potassium, iron, bismuth, cobalt and heptamolybdate ammonium. Obtained by co-precipitation and drying of the catalyst powder decompose to oxides for 10 hours while gradually raising the temperature from 150 to 200°C.

The disadvantages of this method include the need for the preparation of solutions of the original substances, the presence of wash water and wastewater, as well as insufficient thermal stability and porosity of the obtained catalyst.

A method of obtaining Nickel catalyst in which the catalyst carrier make when mixing in the melt of Nickel nitrate, followed by calcination of a catalyst mass at 400-600°C, followed by pelletizing (A.S. SU 420327 A1 from 25.03.1974). As media use superfine aluminum oxide, magnesium oxide and calcium aluminate.

There is a method of preparation of the catalyst, which consists in introducing under stirring but what of Italia catalyst in the molten salt metal precursor components of the catalyst and calcining the catalyst mass (patent EP 1224968 A1 from 24.07.2002). As the metal salt precursor using nitrates of alkali, alkaline-earth, rare-earth metals and nitrate of silver.

The disadvantages of these methods include the stage of the laundering of the samples. In addition, even repeated washing does not completely get rid of the contamination of the reaction products mixed cations of alkali metals in the composition of the nitrate melt.

Problem to be solved in the invention is to develop a method of producing oxide catalysts and catalysts spinel structure, which allows to obtain catalysts having a high degree of homogeneity, absence of harmful impurities in the catalyst, the highly developed surface of the catalyst and high thermal stability.

To solve this problem, a method of obtaining oxide catalysts, in particular catalysts spinel structure, which consists in mixing two or more salts precursor of the catalyst components, melting the resulting mixture until a homogeneous melt, cooling the melt to room temperature and subsequent decomposition of the salts to oxides, salts precursor catalyst components use nitrates d-metals, nitrates of CE and Y, melting the resulting mixture is carried out at 90-170°in the presence of nitrate is of mania, taken in a molar ratio of 2-10:1 with respect to the mixture of metal nitrates, and decomposition of the resulting molten salts to oxides of lead under the action of microwave radiation. In a preferred embodiment, the microwave radiation is applied at the operating frequency of 2.45 GHz and power 600-1900 W for 0.5-5 minutes In the case of the preparation of the catalyst, which should have high thermal stability, after the stage of decomposition of the salts to oxides, the catalyst was calcined at 400-700°C for 1-4 hours

The term "nitrate d-metals" should be understood nitrate, and their hydrates of metals 4-6 periods I-VIII groups of the side of the subgroups. Preferably the use of nitrates and nitrate hydrates Mn, Co, Ni, Zr, Zn, Cr, Fe, Mo, Ru, W, Re. Particularly preferably the use of nitrates nitrate hydrates the following formula Mn(NO3)2, Mn(NO3)2·6N2O, With(NO3)2With(NO3)2·6N2O, Ni(NO3)2, Ni(NO3)2·6N2O, ZrO(NO3)2·2H2O, Cu(NO3)2, Cu(NO3)2·3H2O, Cr(NO3)·N2O, (NH4)2Cr2O7, Zn(NO3)2·4H2O, Fe(NO3)3, Fe(NO3)3·9H2O, MoO2(NO3)2, VO2NO3, Ru(NO3)2·6H2O, ReO3NO3W(NO3)3·9 the 2O, Y(NO3)3·6H2Oh, CE(NO3)3·6N2O.

In one embodiment of the invention, possible to use this method of producing oxide catalysts, in particular catalysts spinel structure on the native oxide structure, which consists in mixing two or more salts precursor of the catalyst components, melting the resulting mixture until a homogeneous melt, which is under continuous stirring contribute media, cool the mixture to room temperature and perform the subsequent decomposition of the salts to oxides, in the form of salts precursor catalyst components use nitrates d-metals, nitrates of CE and Y, melting the resulting mixture is carried out at 90-170°in the presence ammonium nitrate taken in a molar ratio of 2-10:1 mixture of metal nitrates, and decomposition of the mixture on the oxides of lead under the action of microwave radiation. In a preferred embodiment, the microwave radiation is applied at the operating frequency of 2.45 GHz and power 600-1900 W for 0.5-5 minutes

As a native oxide structure, you can use the oxides of aluminum, titanium, zirconium, various modifications, silicon dioxide, magnesium oxide, various spinels, zeolites and mixtures thereof.

In the case of receiving the applied AC is alistore, which should have high thermal stability, after the stage of decomposition of the oxide catalyst annealed at 400-700°C for 1-4 hours

EXAMPLES

For carrying out the synthesis we used the following reagents: Mn(NO3)2·6H2O, Co(NO3)2·6H2O, Ni(NO3)2·6N2O, ZrO(NO3)2·2H2O, Cu(NO3)2·3H2O, Cr(NO3)3·N2O, (NH4)2Cr2O7, Fe(NO3)3·N2O, MoO2(NO3)2, VO2NO3W(NO3)3·N2O, Y(NO3)3·N2O, CeO(NO3)2·2H2O, NH4NO3(all reagents brand "HTC").

The synthesized oxide powders can be divided into two groups:

group I - oxide phase with a spinel structure on the basis of d-metals and the following relationship cations: Mn:Co:Cu=3:2:2, Mn:Co:Cu=3:2:2 (Cr), Mn:Co:Ni=3:2:2, Co:Cr=3:2, Co:Cu=2:1, Co:Mn=2:1, Cu:Cr=1:2, Cu:Cr=1:4, Cu:Fe=1:2, Cu:Fe=1:2 (Cr), Cu:Mn=2:3, as well as complex oxides of Ce:Zr=1:1, Ce:Zr=1:2, Mo:Zr=1:1 (use the same abbreviations samples). The symbol (Cr) means that in the original mixture was added bichromate of ammonia (NH4)2Cr2O7in the amount of 0.5 mol.% of the total metal content;

group II samples of CuO/ZrO2(containing CuO 25, 40, 90 mol.%), NiO/ZrO2(with NiO content 10, 15, 0, 25, 40 mol.%). Y2O3/ZrO2(containing Y2About35, 10 mol.%), WO3/ZrO2(containing WO310, 20 mol.%).

Sample hydrates nitrates d-metals and Zirconia was mixed with ammonium nitrate in a molar ratio of 1:2 (table 1 No. of experiments 1-5), 1:3 (table 1, No. 6, table 2 No. 1-10), 1:5 (table 1 No. 8-13), 1:10 (table 1, No. 7, 14-17). Then the mixture was melted with stirring until a homogeneous transparent melts. In the case of the samples of the first group of homogeneous transparent liquid was formed at a temperature of 90-120°and, in the case of the samples of the second group to complete dissolution was required to heat up to 150-170°and the reaction mixture was injected a small amount of water. In the case of obtaining samples of the catalyst supported on a carrier, then make with continuous stirring to melt the granular carrier oxide structure. As carriers were used t-ZrO2that γ-Al2About3, TiO2. The resulting melt was cooled to room temperature, and then subjected to microwave radiation.

All experiments on microwave processing was performed in a microwave oven (Multilabor 2.45/2.0) 600 watts and an operating frequency of 2.45 GHz (table 1, No. 1-6, table 2 No. 1-10) and 1900 watts and an operating frequency of 2.45 GHz (table 1 No. 7-17).

The processing time for the samples to full the th decomposition of nitrates ranged from 30 s (table 1 No. 1-5) up to 3 min (table 1, No. 7, 14-17). After decomposition, the samples were subjected to heat treatment in a muffle furnace at a temperature of 500°C for 2 hours. Temperature measurement samples during microwave treatment was performed by introduction of platinum thermocouples in a powder sample immediately after microwave treatment.

X-ray phase analysis of the samples before and after calcination was carried out on the device STADI/P (Stoe, Germany) using Cu radiation-Kα1with a coordinate detector (Ge-monochromator) and on the device DRON-3M (plant Burevestnik, Russia) using Cu-Kαradiation in the interval of angles 2θ 5-80° when the speed of rotation of the goniometer 1-2 deg/min Powdered samples were pressed into a cell without a binder. Identification of phases was carried out using the data Bank PCPDFWIN (Version 2.2, June 2001, JCPDS-ICDD).

The morphology and surface structure of the catalysts was studied using scanning electron microscope Supra50vp (Leo, Germany). To conduct a local x-ray spectral analysis (LRA) used the console to electronic microscope INCA x-sight (Oxford instruments, UK). Powdered samples were pressed into tablets, the surface of which is to provide the necessary conductivity of the deposited gold.

Specific surface area of the catalysts was determined by the method of heat is sorbcii nitrogen on the instrument GC-1.

To study the catalytic activity of the samples in the reaction of deep oxidation of methane investigated powders were pressed into pellets under a pressure of 5 ATM, then tablets were crushed and selected fraction of particles of size 0.5-1 mm Height Sands of the samples in a quartz tube was 3.5 cm Weight hanging was 200-300 mg. Before the experiment lasted activation of the samples by heating them in a stream of nitrogen at a temperature of 400°C for 1 hour. After that, the reactor was cooled to 200°C. the Source gas mixture was a mixture of methane and oxygen in a volume ratio VCH4:VO2=1:4. In all experiments, the transmission rate of the gas mixture was 12 ml/min, and the contact time with the catalyst - 2 C. Before feeding into the reactor a gas mixture sample thermostatically at each temperature for 20 minutes, the Composition of the final gas mixture passed through the reactor was determined by gas chromatography on the device Chromatograph GC-17A" (Shimadzu, Japan).

Table 1.
The phase composition of the samples according to the XRD and the temperature of 50% (T50%) and 95% (T95%) methane conversion on the received samples.
No.SampleThe phase composition is (according to XRD) T50%that °CT95%that °
Before annealingAfter annealing
1Cu:Cr=1:2x-ray amorphous phaseCuCr2O4360440
2Cu:Fe=1:2CuFe2O4CuFe2O4385440
3Cu:Fe=1:2 (Cr)CuFe2O4CuFe2O4385440
4Mn:Co:Cu=3:2:2Cu2Co2Mn3AboutxCu2Co2Mn3Aboutx335369
5Mn:Co:Cu=3:2:2 (Cr)Cu2Co2MnCAboutxCu3Co2Mn3Aboutx336385
6Mn:Co:Ni=3:2:2Ni2Co2Mn3AboutxNi2Co2Mn3Ox310334
7CuO/ZrO2(25 mol.% CuO)x-ray amorphous phaset-ZrO2, CuO435520
8CuO/ZrO2(40 mol.% CuO)roentgenology is phase (t-ZrO2, CuO)450540
9CuO/ZrO2(90 mol.% CuO)x-ray amorphous phaseCuO, t-ZrO2385440
10NiO/ZrO2(with NiO content 10, 15, 20, 25, 40 mol.%)x-ray amorphous phaset-ZrO2, NiO43714871
11Ce:Zr=1:1x-ray amorphous phaseCe0.5Zr0.5O2--
12Ce:Zr=1:2x-ray amorphous phaseCe0.33Zr0.67O2--
13Mo:Zr=1:1x-ray amorphous phaseZr(MoO4), t-ZrO2443502
14Y2O3/ZrO2(5 mol.% Y2About3)x-ray amorphous phaset-ZrO2--
15Y2O3/ZrO2(10 mol.% Y2O3)x-ray amorphous phaset-ZrO2--
16WO3/ZrO2(10 mol.% WO3)x-ray amorphous phase t-ZrO2441514
17W03/ZrO2(20 mol.% WO3)x-ray amorphous phaset-ZrO2411489
1- data for sample NiO/ZrO2with NiO content of 20 mol.%.

Table 2.
The rate of oxidation of methane at 300°on mixed-oxide catalysts, referred to the surface area of the sample (R1) or mass (R2), specific surface area of sample (Sbeatsweight hanging the catalyst and the temperature of 50% (T50%) methane conversion.
No.SampleSbeatsm2/gmcatmgR1×105mmol·m-2·min-1R2×104mmol·g-1·min-1T50%that °
1aCu:Cr=1:43538435124362
2aCu:Cr=1:497321989395
3aCu:Mn=1:1134 4362688380
4bCu:Mn=1:11284002673380
5bCu:Mn=2:3125277791386
6cCu:Co=1:21087769576375
7cCo:Cr=3:210533925261370
8dCo:Mn=2:18836244213350
9dMn:Ni:Co=3:2:29424481648310
10dMn:Cu:Co=3:2:29630456335335
asamples containing 50 wt.% γ-Al2About3,
bsample containing 60 wt.% γ-Al2About3,
withsamples containing 50 wt.% TiO2,
dsample containing 60 wt.% t-ZrO2

From the tables after the duty to regulate, the obtained samples have highly developed surface and exhibit high catalytic activity in the reaction of deep oxidation of methane. According to XRD. and LRSA, the samples are single phase and does not contain any impurities. Annealing at a temperature of 600°does not lead to the destruction of the samples, indicating a relatively high thermal stability.

1. The method of obtaining oxide catalysts, in which mix two or more of salt, precursor of the catalyst components, melting the resulting mixture to obtain a homogeneous melt, cooling the melt to room temperature and perform the decomposition of the salts to oxides, characterized in that as the salt precursor catalyst components use nitrates d-metals, nitrates of CE and Y, melting the resulting mixture is carried out at 90-170°in the presence of ammonium nitrate taken in a molar ratio of 2-10:1 with respect to the mixture of metal nitrates, and decomposition of the resulting molten salts to oxides of lead under the action of microwave the radiation.

2. The method according to claim 1, characterized in that the microwave radiation is applied at an operating frequency of 2.45 GHz and power 600-1900 W for 0.5-5 minutes

3. The method according to claims 1 and 2, characterized in that after the stage of decomposition of the salts to oxides carry out the calcination at 400-700°in ECENA 1-4 hours

4. The method of obtaining oxide catalysts, in which mix two or more of salt, precursor of the catalyst components, melting the resulting mixture to obtain a homogeneous melt, characterized in that the resulting melt contribute with continuous stirring carrier oxide structure, cooling the melt to room temperature and perform the decomposition of the salts to oxides, in the form of salts precursor catalyst components use nitrates d-metals, nitrates of CE and Y, melting the resulting mixture is carried out at 90-170°in the presence of ammonium nitrate taken in a molar ratio of 2-10:1 with respect to the mixture of nitrates metals, and decomposition of the resulting molten salts to oxides of lead under the action of microwave radiation.

5. The method according to claim 4, characterized in that the microwave radiation is applied at an operating frequency of 2.45 GHz and power 600-1900 W for 0.5-5 minutes

6. The method according to claims 4, 5, characterized in that as a native oxide structures use the oxides of aluminum, titanium, zirconium, various modifications, silicon dioxide, magnesium oxide and mixtures thereof.

7. The method according to claims 4, 5, characterized in that after the stage of decomposition of the salts to oxides carry out the calcination at 400-700°C for 1-4 hours

8. The method according to claim 6, characterized in that after the stage of decomposition of the salts to oxides provocativelyvideo at 400-700° C for 1-4 hours



 

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