SE457506B - Catalyst for ammoxidation of olefin(s) and alkyl-substd. aromatic(s) - Google Patents

Abstract

The olefins may also be halide-substd., and the catalyst also produces total combustion of hydrocarbons in the presence of atmos. contg. oxygen, the oxidn. of CO to CO2 in the presence of the same atmosphere, the oxidn. of olefins, pref. ethylene and propylene to epoxides,. Further possible action of the catalyst is the redn. of nitrous oxides to nitrogen in the presence of atmosphere contg. ammonia and oxygen. The compsn. of the catalyst is at AB2C306+delta in which O is less than or equal to delta is less than or equal to 1. A is Y, any of the rare earth metals (57 La - 71 Lu) or Bi, or mixtures of them. B is Ba, Ci or Sr or mixtures of them, C is Ca, Ni, or Co, or mixtures of them, and O is oxygen. The catalyst is introduced on a carrier which is Al203, SiO2, TiO2 or ZrO2.

Description

457 506 10 15 20 25 30 35 2 the known catalysts are often complex, but usually one or more oxides of vanadium, bismuth, tungsten, molybdenum, antimony and tin are included. The known catalysts may also contain promoters, and phosphorus, such as potassium and the active phase, may be fixed on a support.

Non-selective catalytic oxidation of hydrocarbons to carbon oxides and water is of interest from an environmental point of view. Flue gases from stationary sources as well as emissions from motor vehicles can be purified by this type of oxidation.

As catalysts, precious metals are supported. Metal oxides often used here have lower activity, but CuO and Cr2O3 can be used when purifying flue gases.

With regard to the purification of emissions containing nitrogen oxides, precious metal catalysts have been used in motor vehicles in particular, while in the case of flue gas purification, catalysts based on vanadium oxides have preferably been used. The object of the present invention is to provide a catalyst for - ammonoxidation of olefins and alkyl-substituted aromatics, which may also be halide-substituted, corresponding to nitriles in the presence of atmosphere containing oxygen and ammonia, - total combustion of hydrocarbons in a nitrogen atmosphere, - oxidation of carbon monoxide to carbon dioxide in the presence of an oxygen-containing atmosphere, - oxidation of olefins, preferably ethylene and propylene, to epoxides, preferably ethylene oxides and propylene oxides, - reduction of nitrogen oxides to nitrogen gas in the presence of an atmosphere containing ammonia and oxygen.

The catalyst according to the invention is characterized in that it has the composition AE2C306 + ¿wherein o5a <1, 10 15 is 457 ^ 506 3 A is yttrium, any of the rare earth metals <57La to 71B is barium, -calcium or strontium or mixtures Lu ) or bismuth, or mixtures thereof, thereof, C is copper, nickel or cobalt or mixtures thereof, O is oxygen, and in that it has any of the following crystal structure types: or transition forms between them.

The catalyst according to the invention may also be present as Al 2 O 3, SiO 2, TiO 2 or ZrO 2.

A known material with this atomic structure, YBa2Cu3O6 + ¿, is part of the recently developed high-temperature superconducting oxide systems. However, it is quite surprising and not previously described that materials of this type, even supported by a support, can be used as catalysts.

The properties of a catalyst are related to its atomic structure. Different phases thus have more or less different catalytic properties. Even one and the same phase can, depending on the manufacturing method, exhibit different catalytic properties. This may be because different production methods give products that expose 457 506 10 15 20 25 30 35 4 different crystallographic planes of the same phase. It is not possible to see directly from the crystal structure of a material whether this can be used as a catalyst or not.

The fact that one or more of the elements included in the structure are found in other catalysts which can be used in similar fields as the present catalyst is no proof whatsoever that the material is used as a catalyst for these purposes. The catalyst according to the present invention differs from previously known catalysts with the same use both in terms of its atomic structure. and composition The catalyst of the present invention has the above composition. The typical thing about this catalyst is that it can vary its content of oxygen atoms. The oxygen content can thus vary from 6 oxygen atoms per unit cell to 7 oxygen atoms. Up to an oxygen number of about 6.5 atoms, the catalyst has the above atomic structure type I. There is one A atom per unit cell and two B atoms, as shown in the figure. The three C atoms are coordinated to oxygen so that one type has two oxygen neighbors while the other type has five oxygen neighbors. is tetragonal.

This atomic structure Examples of materials with this type of structure include YBa2Cu3O6, and characteristic unit cell data for this compound are given in Table 1.

The oxygen content of the catalyst crystals is determined, among other things, by the ambient temperature and the redox properties of the environment. When the two-coordinated copper position in the exemplified structure type has reached a certain oxygen coordination (close to 4), the atomic structure switches to a new phase with almost the same atomic structure, gene structure type II above. This structure now has partially four-coordinated C atoms in a plane and is orthorombic.

Unit cell data for this structure type, with YBa namely-exemplified 2Cu307, are also given in Table 1. 10 15 20 25 30 35 457 50.6 Table 1 Crystal data for the structure types exemplified by YBa2Cu3O6 and YBa2Cu3O7 (from Swinnea, JS & Jf Steinfink, H. Mater, Res. 2, 424 (1987)) and Beech, F. et al, Phys. Reef. gåâ, 8778 (1987) Cell contents YBa2Cu3O6 YBa2Cu3O7 Crystal system tetragonal orthorhombic Space group P4 / mmm Pmmm Unit cell dimensions a = b = 3.863 (2) a = 3.8l98 (l) (Å)) = ll, 830 (4) b = 3.8849 (l) c = ll, 6762 (3) This structure type can also be expressed in the following ways: Structure description Atm- Fractional coordinates Number of subscribers per Number of atrns per type in the unit cell cell in YBa2Cu3O6 cell in YBa2CU3O7 Y l / 2 l / 2 l / 2 1 l Ba 1/2 l / 2 i !! 0.19 2 2 Cul 0 0 0 1 1 Cu2 0 0 now 0.36 2 2 01 O O Q! 0.15 2 2 02 1/2 0 Q! 0.38 2 2 03 0 1/2 Raw 0.38 2 2 04 0 l / 2 0 O l In YBa2Cu3O6, O2 and O3 are combined to a position due to the higher symmetry. In the case of intermediate oxygen compositions, a certain content of oxygen atoms also occurs in the position (05: 1/2 O 0).

The fact that the catalytically active compound according to the invention has the specified structure type has been verified by several methods: Atomic resolution transmission electron microscopy.

This has verified that the catalyst has the specified atomic structure in that each metal atom can be identified in direct images of crystals examined before and after catalytic reactions in a reactor. 2 Quantitative chemical analysis by means of energy dispersive 457 506 10 15 6 analysis of characteristic X-rays generated in a scanning electron microscope or transmission electron microscope. Both before and after the reaction, the catalyst exhibits the typical 1: 2: 3 composition with respect to the three positive metal ion layers. Analytical spectra before and after use of a catalyst according to the invention as nitrile-selective catalyst are shown in Fig. 1. Data analysis of these spectra gave, within experimental standard deviations, the formula YBa2Cu3O6 + ¿. The oxygen content cannot be determined with this method. The catalyst phases have also been examined by powder X-ray diffraction. with help Accurate distances between atomic lattice planes have been determined and the intensity of the X-ray lines has been investigated. Table 2 below shows that these values show good agreement with the literature data and it can therefore be concluded with complete certainty that the catalysts have the specified atomic structure. 5 10 15 20 25 30 35 457 506 7 Tabe11 2 Powder X-ray data a) Fresh catalyst b) Reference data for YBa2Cu3O6,9x aOBS (A) 1/16 <8) hp 1 d0BS (Å) 1 / IQ (3) 11,809 1 0 0 2 5,844 2 5,878 2 0 0 3 3,893 11 3,903 10 1 0 0 3,822 3,830 3 0 1 2 3,235 3,240 1 0 2 3,198 3,199 0 1 3 2,750 60 2,924 1 0 3 2,726 100 2,754 53 1 1 0) 2,728 100 1 1 1 2,653 2 2,657 1 1 1 2 2,469 2,471 3 0 0 5 2,336 11 2,338 15 1 0 4 2,321 3 2,234 17 1 1 3 2,232 13 '1,994 1 0 2 0 1,946 23 1,946 23 0 0 6J 1,911 13 2 0 0 1,911 10 1,774 4 1 ~ 1 5 1,775 3 1,741 2 0 1 6 1,741 2 1,735 2 0 2 3} 1,716 2 1 0 6 1,734 2 1,669 2 1 2 o} '1,659 1 2 0 3 1,645 1 2 1 0} 1,716 2 1,583 35 1 2 1 1,569 14 1 2 2 1,662 1 1,529 1 1 2 3 1,584 24 1,494 2 1 1 6] 1,478 3 2 1 3 1,569 11 1,423 2 1,375 4 1,363 13 “58, 1676 (1987) RJ Cava et al., Phys. Reef. Easy. 457 506 8 4 The length of the c-axis of the unit cell changes continuously with the content of oxygen atoms in crystals of, for example, YBa2Cu3O6 + ¿(0 3 6 5 1). The difference in the length of the c-axis between the end components is 0.15 Å (see Table 1). This length has been used to calculate the result by extrapolation is shown in Table 3. 457 506 ^ mvmmNæ. ~ H ^ Hvwmæ \ HH ^ HV «wß.HH ^ Hvoæw. ~ H ^ <. Omum H mu ^ wvmwæw_m ^ <. N ^ Nvmwmw.m ^ mvowmæ \ m ^ mVHæmm.m ^ vVmmHm.m ñævm umco fi mcwä fl v | HHmUwuw: cm Hmcommuuwu Hmcommuumu Hmcommuuwu xm fl naououuo fl nuwääæw O. ~ om: u om ~ u ~ mm: u. u ~ mmw mc fl nuuwwsmeewm m flfl umwwmnn Aco fl uxø fi mu umuwwv ^ C0 fl vMøUwH Hwvwwv Acø fl vx fl wmu W% muv uoßmwæ fi mwmx uoumwæ fi mumx uoummæ fl mwm fl mwm um mwm> Oo> HuxmHwm | H fl uu fl Z> fl uxwHww | oo xwnmm boum HÜGOH WGÜEHÜHHQUWPUÃCmH m fifi wßmä 457 506 10 15 20 25 30 35 10 Taken together, these analyzes thus provide a confirmation of the specified structure.

The catalyst of the present invention has the unique property of functioning both as a selective ammonia oxidation catalyst and as a total combustion catalyst. As a selective ammonia oxidation catalyst, it has the above-mentioned structure I, i.e. its oxygen content is in the range closest to 6 oxygen atoms.

As a total combustion catalyst, the catalyst has an oxygen content in the range up to 7 oxygen atoms.

The catalyst can thus be used for the selective ammonium oxidation of olefins and alkyl-substituted aromatic compounds, which can also be halide substituents for the corresponding nitriles. It can also be used for the total combustion of hydrocarbons in the absence of ammonia to carbon dioxide and water. Thus, since carbon monoxide is an intermediate in the total oxidation of hydrocarbons to carbon dioxide, the catalyst can also be used to oxidize carbon monoxide to carbon dioxide.

The first step in the total oxidation of aromatic compounds and olefins is an attack on the double bond (s) of the reactant molecule and thus the catalyst can also be used in the epoxidation of olefins to epoxides. f In selective ammonia oxidation, the catalyst exhibits better activity and selectivity than hitherto known catalysts. It also has a very high activity under total combustion conditions. Due to the catalyst's ability to activate ammonia, it can also be used to advantage for the reduction of nitrogen oxides by reaction with ammonia.

The selectivity of the catalyst, ie its ability to convert hydrocarbons to nitriles, carbon dioxide, epoxides, respectively, is mainly controlled by careful control of the partial pressure of the oxygen in the reaction atmosphere.

As examples of aromatic oxidation in the presence of ammonia, so-called ammonia oxidation, where the catalyst 10 15 20 25 30 35 4-57 506 ll according to the present invention can be used for the production of nitriles, may be mentioned ammonoxidation of toluene and xylenes (ortho, meta and para-) to benzonitrile and toluene and dinitriles, respectively. Another example is ammonium oxidation of alkyl-substituted pyridine rings, eg α-picoline, β-picoline and γ-picoline, to corresponding nitriles. Olefins can also react with ammonia in the presence of oxygen to nitriles. An example is ammonium oxidation of propylene to acrylonitrile.

Oxidation of olefins can also be carried out in the absence of ammonia as a so-called epoxidation. In this case, the double bond of the olefin reacts with oxygen, whereby an epoxide is formed. Examples of such reactions are epoxidation of ethylene to ethylene oxide and propylene to propylene oxide.

Reduction of nitrogen oxides, such as NO and NO 1, can take place in the presence of oxygen and ammonia. In this case, the nitric oxide is converted to N2, by reaction with ammonia to form water.

In the accompanying drawings: Fig. 1 shows the intensity of X-ray spectrum from the catalyst according to the invention before and after use as a nitrile selective catalyst, Fig. 2 shows the rate of formation of benzonitrile and CO 2 as a function of the partial pressure of oxygen.

The invention will be described in more detail in the examples below, which are partly examples of the preparation of catalysts according to the invention and partly are examples which show the use of the catalysts according to the invention. In all of the synthetic examples below, yttrium (Y) can be replaced by the rare earth metals (elements 57La to 7lLu) without changing the atomic structure of the catalyst. Yttrium can also be replaced with Bi. Barium can be replaced in whole or in part by strontium or calcium with the same atomic structure of the catalyst as the end result. The copper atoms in the catalyst can be exchanged for cobalt and / or for nickel 457 506 10 15 20 25 30 35 12 12 so that a copper atom of the three in structure b Example 1 1/2 mol of yttrium oxide (YZO lir replaced. 3), 2 moles of barium carbonate (BaCO3) and 3 moles of copper (II) oxide (CuO) are mixed under acetone in a ball mill for 2 hours and then compressed under a pressure of about 600 MPa. The compressed material is calcined during air access at 900 ° C for at least 24 hours. The sample is then pulverized again and mixed well in a mortar or ball mill. Compression then takes place again under a pressure of about 600 MPa. The material is reheated to 900 ° C and then allowed to cool very slowly for at least 8 hours down to 600 ° C under pure oxygen or with rapid flow of air. The temperature is then lowered for 8 hours down to 200 ° C, under pure oxygen. still The catalyst formed has a composition of YBa Cu O. Example 2 Using the same starting material and in the same amounts as in Example 1, a mixing, compression and calcination is carried out as in Example 1.

The catalyst is then ground and mixed and then compressed and heated in a flowing gas atmosphere of argon or nitrogen to 900 ° C and then allowed to cool very slowly for at least 24 hours to 200 ° C. This gives a catalyst with the composition YBa2Cu3O6.

Example 1 - 1 mole of yttrium nitrate (Y (NO 3) 3,4H 2 O), 2 moles of barium nitrate (Ba (NO 3) 2) and 3 moles of copper nitrate (Cu (NO 3) 2,3H 2 O) are dissolved in 10 ml of water. Then slowly add a solution of oxalic acid (HOZCCOZH) in excess (more than 6 mol). The resulting precipitate of yttrium, barium and copper oxalate is filtered off and dried at 150 ° C. The oxalate mixture is compressed under a pressure of about 600 MPa and heated slowly for 8 hours to 900 ° C in air. Then proceed in accordance with Example 1 or 2. This gives a product with the composition YBa Cu O 2 3 7 according to Example 1 and 10 15 20 25 30 35 457 506 13 YBa Cu 0 according to Example 2, respectively. mol of yttrium carbonate (Y2 (CO3) 3.3H2O), 2 mol of barium carbonate (BaCO3) and 1 1/2 mol of basic copper (II) carbonate (CuCO3.Cu (OH) 2) are mixed with a molar excess (more than 4 mol) of solid citric acid (HOC (CH 2 CO 2 H) 2 CO 2 H) and 1/2 ml of water per gram of mixture are added with stirring. The solution is then heated to 70 ° C, whereby a clear bluish viscous liquid is finally obtained.

This solution is homogeneous and can be stored for a long time.

Further synthesis of the catalyst takes place by evaporating the solution at 150 ° C. Calcination of the powder is then carried out at 850-880 ° C for at least 8 hours in air.

The powder is then compressed into a tablet under a pressure of about 600 MPa and heated to 900 ° C in oxygen for at least 24 hours. Cooling and tempering in oxygen takes place in accordance with Example 1.

Example 5 A catalyst with the composition YBa 2 Cu 3 O 7 is prepared by mixing stoichiometric amounts of 2 3, BaCO 3 mortar in the presence of acetone. The mixture was pressed by Y and CuO. This mixture was ground in another tablet, which was then heated at 950 ° C for 17 hours. The mixture was ground and tableted and the resulting tablets were treated in a stream of oxygen at 950 ° C for a further 17 hours. The prepared catalyst was cooled in a stream of oxygen for 8 hours to 180 ° C.

The tablets were then crushed into smaller particles, which were charged into a tube reactor.

The catalyst prepared was used in the ammonium oxidation of toluene at 400 ° C. During the experiment, constant partial pressures of ammonia and toluene were maintained in the incoming gas stream of 2.58 kPa and 0.767 kPa, respectively.

The partial pressure of oxygen varied from 26 kPa down to 9 kPa. The rates of formation of benzonitrile and CO2 (Fig. 2, curves 1 and 2). was independent of the partial pressure of the oxygen (see 457 5 10 15 20 25 30 35 506 14 After a reductive treatment for 1 hour with a gas stream consisting of ammonia and toluene (same partial pressure as above), the partial pressure of the oxygen increased.

The catalyst was now selective for nitrile formation up to an oxygen partial pressure of 8.65 kPa. The reaction rate for the formation of benzonitrile was at most 2.10_5 mol / (min, m2 catalyst surface) (Fig. 2, curve 3).

If the oxygen partial pressure increased, mol / (min, m2 catalyst surface area). This rate was 3-4 times higher than the corresponding rate before the reductive treatment.

The composition of the catalyst used was analyzed and found to be YBa2Cu3O6 + ¿(0 § 6 3 1). The stoichiometry, 6, was dependent on the reaction conditions and the reductive treatment. The composition of the selective and most active catalyst corresponded to 6 '~ 0, and the most efficient total combustion catalyst had a composition corresponding to a slightly larger value of 6.

Example § YBa 2 Cu 3 O 7 was prepared as described in Example 5. This catalyst was used for the total combustion of toluene to carbon oxides. The test temperature was 400 ° C and the partial pressures of toluene and 0.767 kPa and 17.3 kPa, respectively. of carbon oxides was 6,8.10_6 The ratio CO 2 / CO was 11 oxygen was the rate of formation mol / (min, g catalyst).

After reductive treatment with toluene and ammonia (according to Example 5), the activity increased significantly. The rate of formation of carbon oxides was now 50.10_6 mol / (min, g catalyst) at 400 ° C if the partial pressures of toluene and oxygen were 0.767 kPa and 4, respectively. , 3 kPa.

The CO 2 / CO ratio was greater than 100. The stoichiometry of the catalyst was YBa 2 Cu 3 O 6 + ¿, where 5> 0. In Example 5, the rate of total combustion in the presence of 10 mol / (min, m2 of catalyst surface) 12.10 "6 g of catalyst). The combustion corresponds to 12.10 mol / min, the rate of reaction in the absence of ammonia was thus 4 times greater. §Rsm2sl_l A catalyst having the composition YBa2Cu3O6 was prepared according to the method described in Example 5, except that the the first sintering was performed in air at 900 ° C and the second sintering was performed in an argon flow at 700 ° C.

Crushed catalyst was charged to a tube reactor.

The partial pressures of oxygen, ammonia and toluene were 2.15 kPa, 2.58 kPa and 0.767 kPa, respectively. The catalyst selectivity for benzonitrile was greater than 90%. The rate of addition of benzonitrile was measured to be 3, s. 10 "mol / (min, g catalyst).

The experiment was repeated with the following partial pressures: oxygen 17.2 kPa, ammonia 0 kPa and toluene 0.767 kPa.

The selectivity for the formation of CO 2 exceeded 99% and 5 mol / (min, the rate of formation thereof being 20.10 g of catalyst). §Rsm2sl_§ A catalyst containing samarium instead of yttrium was charged to a tube reactor. It was run under total combustion conditions with only toluene, oxygen and inert nitrogen in the incoming gas stream. The activity of CC2 formation decreased by 30% during the first hour and was then constant.

For the corresponding catalyst containing yttrium, it took at least 6 hours to achieve constant activity. Samaria thus has a stabilizing effect. 6

Claims (3)

457 506 10 15 20 25 16 PATENT REQUIREMENTS Catalyst for: ammonoxidation of olefins and alkyl-substituted aromatics, which may also be halide-substituted, to the corresponding nitriles in the presence of atmosphere containing oxygen and ammonia, total combustion of hydrocarbons in the presence of oxygen-containing atmosphere, oxidation of carbon monoxide to carbon dioxide in the presence of oxidation of olefins, to epoxides, oxides, preferably ethylene and propylene, preferably ethylene oxides and propylene reduction of nitrogen oxides to nitrogen in the presence of an atmosphere containing ammonia and oxygen, which catalyst is characterized by having the composition ABZC 0 3 6 + 6 wherein 0 S 6 5 l, A is yttrium, (57La to 71 B is barium, any of the rare earth metals Lu) or bismuth, or mixtures thereof, calcium or strontium or mixtures thereof, C is copper, nickel or cobalt or mixtures thereof , 0 is oxygen, _ and because it has any of the following crystal structure types: or transitional form r between these. Catalyst according to claim 1, in that it is applied to a support. n a d n a d Catalyst according to claim 2, in that the support is Al 2 O 3, SiO 2, TiO 2 or ZrO2.