Catalyst for low-temperature oxidation of carbon monoxide and preparation method thereof

FIELD: chemistry.

SUBSTANCE: disclosed catalyst for low-temperature oxidation of carbon monoxide, which is silver deposited on a silicon dioxide surface in amount of 1-16% of the weight of the catalyst. The catalyst contains silver in the form of nanoparticles with a size smaller than 6 nm, which are uniformly distributed on the surface of mesoporous silica gel with specific surface area of 50-200 m2/g and pore size of 3-60 nm, which is used as a support. The invention also relates to a method of using the catalyst to remove carbon monoxide from air, which is carried out using the catalyst by passing a stream of moist air containing up to 100-115 mg/m3 CO through the catalyst bed at room temperature.

EFFECT: improved catalyst properties.

4 cl, 1 tbl, 4 dwg, 5 ex

 

The invention relates to the field of heterogeneous catalysis, namely the low-temperature oxidation of CO (carbon monoxide, carbon monoxide), and can be used for cleaning air in enclosed spaces (for example, the interior of motor vehicles), industrial, office and residential spaces.

Catalytic oxidation of air pollutants (carbon monoxide, formaldehyde and other volatile organic compounds) to harmless CO2and water recently attracted special attention as an effective and promising method of air purification. Carbon monoxide is one of the most dangerous and widespread pollutants. It is produced from the combustion of various materials, forest fires, operation of internal combustion engines or in the untimely closure of the flue of the heating furnace. The maximum allowable concentration of CO in the air of working zone is not more than 20 mg/m3(GN 2.2.5.1313-03), and for premises of a valid daily average concentration is 3 mg/m3(GN 2.1.6.1338-03). The main difficulty of air purification from impurities CO is that CO catalytic oxidation must occur at room temperature and ambient humidity no less than 50%.

Most active in low-temperature CO oxidation are applied to�talesfore, containing as an active ingredient gold, palladium and platinum [RF №2506988 from 20.02.2014, RF 2339446 from 27.11.2008, RF 2464086 from 20.10.2012]. In the literature one can distinguish two main groups of catalysts. The first group consists of the catalytic composition constituting the noble metal deposited on an inert media, such as Al2O3[X. Zou, S. Qi et al. Activity and deactivation of Au/Al2O3catalyst for low temperature CO oxidation //Catalysis Communications. - 2007. - V. 8. - P. 784-788; A. Satsuma, K. Osaki, M. Yanagihara et al. Activity controlling factors for low-temperature oxidation of CO over supported Pd catalysts //Applied Catalysis B: Environmental. - 2013. - V. 132-133. - P. 511-518; K. Arnby, A. Törncrona et al. Investigation of Pt/γ-Al2O3catalysts with locally high Pt concentrations for oxidation of CO at low temperatures //Journal of Catalysis. - 2004. - V. 221. - No. 1. - P. 252-261] or SiO2[H. Zhu, Z. Ma, Jason C. Clark et al. Low-temperature CO oxidation on Au/fumed SiO2-based catalysts prepared from Au(en)2Cl3precursor //Applied Catalysis A: General. - 2007. - V. 326. - P. 89-99; J. L. Margitfalvi, I. Borbáth, M. Hegedűs. Low temperature oxidation of CO over a tin-modified Pt/SiO2catalysts //Catalysis Today. - 2002. - V. 73. - №3-4. - P. 343-353].

The second group is represented by catalysts, in which the media are oxides of transition metals, e.g., cerium oxide [A. Satsuma, K. Osaki, M. Yanagihara et al. Activity controlling factors for low-temperature oxidation of CO over supported Pd catalysts //Applied Catalysis B: Environmental. - 2013. - V. 132-133. - P. 511-518; X. Huang, H. Sun, L. Wang et al. Morphology effects of nanoscale ceria on the activity of Au/CeO2catalysts for low temperature CO oxidation //Applied Catalysis B: Environmental. - 2009. - . 90. - P. 224-232], iron [S. Kudo, T. Maki et al. A new preparation method of Au/ferric oxide catalyst for low temperature CO oxidation //Chemical Engineering Science. - 2010. - V. 65. - No. 1. - P. 214-219; L. Liu, F. Zhou, L. Wang et al. Low-temperature CO oxidation over supported Pt, Pd catalysts: the Particular role of FeOxsupport for oxygen supply during reactions //Journal of Catalysis. - 2010. - V. 274. - No. 1. - P. 1-10], manganese [Q. Ye, J. Zhao, F. Huo et al. Nanosized Au supported on three-dimensionally ordered mesoporous b-MnO2: Highly active catalysts for the low temperature oxidation of carbon monoxide, benzene, and toluene //Microporous and Mesoporous Materials. - 2013. - V. 172. - P. 20-29].

However, these catalytic systems are not sufficiently stable in the presence of CO2and water vapor. The cause of deactivation may be the adsorption of water, the formation of adsorbed carbonates and hydroxocobalamin, blocking the active sites of the catalyst surface. To increase the stability of the catalyst requires additional cleaning of the air, which complicates the design of the entire air-scrubbers. So, in [H. Zhu, Z. Ma, Jason C. Clark et al. Low-temperature CO oxidation on Au/fumed SiO2-based catalysts prepared from Au(en)2Cl3precursor //Applied Catalysis A: General. - 2007. - V. 326. - P. 89-99] used a dry mixture based on the air with the water vapor content less than 4 ppm. However, even in these conditions, the catalyst Au/SiO2were subjected to decontamination (after 20 hours, the conversion decreased from 85 to 70%). The authors other work [Y. Shen, G. Lu, Y. Guo. An excellent support of Pd-Fe-Oxcatalyst for low temperature CO oxidation: CeO2with rich (200) facets //Catalysis Communicaions. - 2012. - V. 18. - P. 26-31] a study was conducted on the stability of the catalyst Pd-FeOx/CEO2at 25°C. it is Established that when using a mixture of CO+air water vapor content less than 10 ppm, the catalyst begins to lose activity after 2 hours of work.

Because of these disadvantages and high cost of catalysts based on Au, Pd and Pt (even when they are sufficiently small content), more stable and cheap silver system could potentially be used in the systems of purification of air in enclosed spaces.

In the patent [EP 2191884 from 26.06.2013] described the catalyst Ag/Al2O3obtained by impregnation of boehmite aqueous solution of silver nitrate, followed by drying at 100°C, the annealing of catalyst at 900-1000°C in air and the recovery at 100-500°C in a stream of a mixture of 1% H2/He. However, this catalyst has no activity in CO oxidation at room temperature.

Known silver-containing catalyst, which is inert substrate used active oxide media such as CeO2[US 8360073 from 29.01.2013]. This catalyst was developed as an additive to cigarette filter to reduce the concentration of carbon monoxide in the inhaled smoke, but can potentially be used for air purification. However, the low-temperature activity of the catalyst �ri relatively low silver content (10 wt. % in terms of Ag2O) is not high enough. With increasing silver content to 40 wt. % (in terms of Ag2O) low-temperature activity increases, however, decreases significantly for several minutes. To return activity to the initial level requires heating of the catalyst layer 110aboutC. it Should also be noted that increasing the silver content in the catalyst is disadvantageous from an economic point of view.

The closest to the claimed technical essence is a CO oxidation catalyst based on silver nanoparticles stabilized in mesoporous silica gel described in [CN 101890349 from 24.11.2010] and selected as a prototype.

The catalyst containing 1-16 wt. % Ag/SiO2receive a one-step synthesis using silver nitrate (AgNO3) as a precursor of the silver particles, tetraethoxysilane (Si(OC2H5)4, TEOS) as a source of silicon, formaldehyde (HCHO) as a reductant and dodecylamine (C12H25NH2) as a template. The molar ratio of the reactants TEOS:C12H25NH2:C2H5OH:AgNO3:HCHO:H2O=1:0,2965:7,593:0,0055-0,088:0,131:24,58. After the completion of the recovery of silver and of gelation (24-48 h) the resulting product was washed with deionized water, dried p�and 80-120°C and calcined at 400-600°C. The catalytic properties of the catalyst (loading 200 mg) in the reaction of CO oxidation was evaluated by the degree of conversion of CO at various temperatures using a gas mixture containing 1%CO, 0.5 TO 20% O2, 98,5-79 He (volumetric feed rate of 30 ml/min). The catalyst provides 100% conversion of CO at 60°C for 12 hours of continuous operation.

A feature of the catalyst of the prototype is the high value of specific surface area (878-1142 m2/y) with a pore size of 2.2-2.8 nm. Materials with similar textural characteristics have low strength characteristics and are highly dispersed powders, poorly pressed or hard-molded to obtain pellets of a given size and shape [A. P. Karnaukhov Adsorption. The texture of dispersed and porous materials. Novosibirsk: Nauka, 1999. - 470 p.]. The catalyst in this form seems to be inconvenient for use in real systems cleaning air WITH.

Given that the pore size of the catalyst of the prototype is 2.2-2.8 nm is expected to have low stability of the catalyst in the presence of water vapor, i.e., in the humid air. Adsorption of water vapor with subsequent condensation in high humidity conditions will lead to blocking of the active surface (the inner part of the granule or block parts of the porous space) and decontamination catalysate�.

It is also important to note that the study of the activity and stability of the catalyst was carried out using a gas mixture of He/O2/CO, free from water vapor, so nothing is known about the activity of the catalyst of the prototype in the presence of water vapor and the change in the activity of the catalyst in continuous operation for more than 12 hours.

The technical problem to be solved by the present invention is to develop a catalyst with high efficiency oxidation of carbon monoxide to carbon dioxide (CO2, carbon dioxide) over a long period of time at temperatures close to ambient, atmospheric air containing water vapor (humidity not less than 50%).

To solve this problem we used a catalytic oxidation of carbon monoxide containing as an active ingredient silver (1-16 wt. % ) deposited on silicon dioxide (silica gel) with a specific surface area of 50-200 m2/g and a pore size of 3-60 nm, and can also contain oxides of cerium, zirconium, manganese or a mixture of these oxides in an amount up to 10% by weight of the catalyst.

We offer the silver-containing catalyst prepared by impregnation from an aqueous solution of silver nitrate (the most affordable and cheap precursor of the active component), followed by those�chemical treatment to (400-700)°C. The proposed method is easy to implement in laboratory conditions and can be used for industrial (semi) obtaining a catalyst.

The technical result according to the method of applying the catalyst is to increase the stability of the catalyst due to thermal pre-treatment media and additives oxide modifier, and also due to the uniformity of application and small size of the particles of the active ingredient is silver.

The problem is solved in that a method of using the catalyst for purification of air from carbon monoxide is carried out using a catalyst according to claims. 1-3 of the formula by passing the stream of humid air containing CO (up to 100-115 mg/m3), through the catalyst bed at room temperature.

As a carrier can be used silica gels of various grades, including those available on the Russian market technical silicagel XKG. The technical problem is solved due to the special conditions of pretreatment of the carrier, consisting of a hydrothermal treatment of silica gel in the presence of an aqueous solution of ammonia to modify the porous structure and providing additional strength to the pellets, followed by high temperature treatment at temperatures of 500-1000°C.

The catalyst has the form of spherical granules, the size of which op�Adelaide the size of grains of the original media. Also the catalyst may be obtained in the form of granules of different size and shape depending on the requirements of the air treatment device in which it will be used.

The essence of the invention is as follows.

The low-temperature oxidation catalyst WITH contains silver as an active ingredient in a number (1-16) % by weight of the catalyst, silicon dioxide as the carrier and may contain oxides of cerium, zirconium and manganese in an amount up to 10% by weight of the catalyst. The catalyst is characterized in that it has a mesoporous structure with a developed system of transport pores (3-60 nm), providing efficient transfer of reagents, including water vapor. The isotherms of adsorption-desorption of nitrogen and the distribution of pore size for the catalysts described in examples 1-3, are shown in Fig. 1 and Fig. 2, respectively. It is seen that for all samples the main distribution of pores is in the area of 15-40 nm.

Another feature of the catalyst is that the silver is in the form of particles smaller than 6 nm. Fig. 3 shows a PAM image as well as the distribution of the silver particles size of the catalyst described in example 2. It is seen that the silver is evenly distributed along the surface of the carrier, and the particle size of silver is 1-6 nm with an average particle size of 2.8 nm.

Clean air�ha from WITH carried out by passing a stream of moist air containing 100-115 mg/m3WITH, through the catalyst bed at temperatures close to room. Observed in this technical effect is to make more than 80% of CO in CO2and this conversion for a long time (at least 20 hours).

The proposed catalyst was obtained by the following method.

Pre-calcined at 500-900°C, the silica gel was impregnated with an aqueous solution containing a predetermined amount of silver nitrate or ammonia complex of silver nitrate, then the resulting samples were dried at 70°C without access of light during the day and calcined to 500°C in air. Catalysts containing the oxides of transition metals, obtained by impregnating silica gel with an aqueous solution of nitrates of the respective metals and silver nitrate followed by heat treatment under similar conditions.

The essence of the claimed invention is illustrated by the description, the drawings and table:

Fig. 1 shows the isotherms of adsorption-desorption of nitrogen for the catalysts described in examples 1-3;

Fig. 2 shows the distribution of pore size for the catalysts described in examples 1-3;

Fig. 3 shows the PAM image and the distribution of the silver particles size of the catalyst described in example 2;

Fig. 4 shows the dependence of the degree of conversion of CO from time to Cathal�congestion, the compositions described in examples 1-4;

Table 1 provides data on the porous structure of catalysts and a comparison of the CO oxidation process in real conditions, clean the air with humidity not less than 50% for the catalysts described in examples 1-4.

The efficiency of the catalyst characterized by the following values: degree of transformation WITH at 29°C, expressed in percent, the lifetime of the catalyst in a stream of air with a humidity of not less than 50%.

The present invention is illustrated by examples of specific performance.

Example 1. The catalyst composition of 8 wt. % Ag, SiO2- the rest.

Commercial silica gel brand XCG (GOST 3956-76, Sbeats=268 m2/g, Vthen=0,95 cm3/g, Dthen=10 nm) was used as a carrier. The silica gel was subjected to a hydrothermal treatment in an aqueous solution of ammonia at 120°C for 3 hours. Further, the silica gel was dried in air at 120°C for 3 h. the resulting carrier has a specific surface area of 98 m2/g. Silica gel (2,76 g) soaked in water holding capacity (water volume 2.0 ml) with an aqueous solution of silver nitrate (0,378 g), then the sample is dried at 70°C overnight, calcined in air atmosphere at 500°C.

Is characterized in that as the carrier used technical silicagel XCG (GOST 3956-76, Sbeats=28 m 2/g, Vthen=0,95 cm3/g, Dthen=10 nm), in the form of spherical granules with a diameter of 3-6 mm or in the form of granules of irregular shape smaller size.

Example 2. The catalyst composition of 8 wt. % Ag, SiO2- the rest.

Similar to example 1. The difference is that the silica gel used as the carrier was subjected to additional high-temperature treatment at 700°C before applying the active component.

Example 3. The catalyst composition of 8 wt. % Ag, 10% wt. MnOx(calculated as MnO2), SiO2- the rest. Similar to example 2, the difference lies in the fact that in its composition contains oxides of manganese in an amount of 10 wt%. in the calculation of MnO2.

Example 4. The catalyst composition of 8 wt. % Ag, 10 wt. % Ce0,5Zr0,5O2, SiO2- the rest.

Similar to example 2. The difference lies in the fact that in its composition contains the oxides of zirconium and cerium in an amount of 10 wt%.

Example 5. Method of air purification from WITH is passing moist air containing 100 to 115 ppm of CO, through the catalyst bed described in p. 1-4.

In table 1 and Fig. 4 shows the results of catalytic testing of the proposed catalysts in conditions close to real operating conditions of air-cleaning devices, as well as their comparison with catalyst-prototype (CN 101890349 from 24.11.2010). The air humidity not less than 50% contained�of ASI 100-115 ppm CO, was passed through the quartz reactor with a catalyst made of PP. 1-4 (volume of catalyst 0.5 cm3) at a flow rate of 100 ml/min at a temperature of 29°C. the Residual concentration was measured WITH an electrochemical sensor.

Analysis of the results of experimental determination of the efficiency of catalysts, the composition of which is listed in Table 1, in the cleaning process of moist air from impurities of carbon monoxide, showed that the catalysts provide efficient removal of 100-115 mg/m3CO (conversion not less than 80%) within an extended period of time (20 hours).

All described in the examples, the catalysts contain not more than 8.0 wt. % of silver, and a method of producing the present catalyst is more simple in comparison with the prototype.

The use of pre-calcination of silica gel and applying the composition of oxides of transition metals makes the catalyst more resistant to the adsorption of water vapor and CO2that allows to increase the activity and prolong its service life.

Thus, the above data confirm that the implementation of the use of the claimed invention, the following set:

- the claimed method and the catalyst is intended for use in catalytic purification of moist air from impurities of carbon monoxide;

- for the claimed invention in the form as it is characterized in the independent claims, confirmed the possibility of its implementation using the described in the application of tools and methods.

1. The catalyst of low-temperature oxidation of carbon monoxide, representing the silver deposited on the surface of silicon dioxide in amounts of 1 to 16% by weight of the catalyst, characterized in that it comprises silver nanoparticles with size<6 nm, which are uniformly distributed on the surface of mesoporous silica having a specific surface area of 50-200 m2/g and a pore size of 3-60 nm, used as a carrier.

2. The catalyst according to claim 1, characterized in that in its composition contains oxides of manganese in an amount up to 10 wt.% in the calculation of MnO2.

3. The catalyst according to claim 1, characterized in that in its composition contains the oxides of zirconium and cerium in an amount up to 10 wt.%.

4. A method of using the catalyst for purification of air from carbon monoxide, characterized in that it is carried out using a catalyst according to claims. 1-3 by passing the stream of humid air containing CO (up to 100-115 mg/m3), through the catalyst bed at room temperature.



 

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2 cl, 4 tbl, 4 ex

FIELD: chemistry.

SUBSTANCE: invention relates to a method of filling a longitudinal section of a contact pipe with a homogeneous part of a solid catalyst bed. The method of filling a longitudinal section of a contact pipe with a homogeneous part of a solid catalyst bed, the active mass of which is at least one multielement oxide which contains a) elements Mo, Fe and Bi, or, b) elements Mo and V, or c) element V, and additionally P and/or Sb, or the active mass of which contains elementary silver on an oxide support-article, and which consists of only one type Si, or a homogenised mixture of various types Si of catalytically active moulded articles of a defined geometrical shape or catalytically active moulded articles and inert moulded articles of a defined geometrical shape, wherein the median of the maximum longitudinal dimensions Lsi of the articles of a defined geometrical shape of type Si is characterised by the value Dsi, at least within one type Si of moulded articles of a defined geometrical shape, the following set of conditions M is satisfied, such that 40 to 70% of the total number of moulded articles of a defined geometrical shape belonging to S1, have a maximum longitudinal dimension Lsi, for which the inequality 0.98·Dsi≤Lsi≤1.02·DSi holds, at least 10% of the total number of moulded articles of a defined geometrical shape belonging to Si have a maximum longitudinal dimension Lsi, for which the inequality 0.94·Dsi≤Lsi<0.98·Dsi holds, at least 10% of the total number of moulded articles of a defined geometrical shape belonging to S1 have a maximum longitudinal dimension Lsi for which the inequality 1.02·Dsi<Lsi≤1.10·Dsi holds, less than 5% of the total number of moulded articles of a defined geometrical shape belonging to Si have a maximum longitudinal dimension Lsi for which the inequality 0.94·Dsi>Lsi holds, and less than 5% of the total number of moulded articles of a defined geometrical shape belonging to Si have a maximum longitudinal dimension Lsi for which the inequality 1.10·Dsi<Lsi holds, wherein the sum of all moulded articles of a defined geometrical shape belonging to Si is 100%; described also is a method of loading a contact pipe with a solid catalyst bed, a shell-and-tube reactor, a method for oxidation of an organic compound and a method for synthesis of separate organic compounds.

EFFECT: high selectivity of moulding the final synthesis product.

17 cl, 3 ex

FIELD: chemistry.

SUBSTANCE: catalyst is characterised by the following content of components: 30-70 wt % (Mo5-12Sb>6.0-15Bi0.2-3M10.1-10M20.05-0.5M30.01-2On) and 70-30 wt % SiO2, where M1 is one or more elements selected from Co, Ni, Fe, Cr, Cu; M2 is one or more elements selected from Na, K, Cs, Mg, Ce, La, M3 is an element selected from P, B, n is a number defined by the valence and number of elements other than oxygen. The invention also relates to a method of producing butadiene-1,3 using said catalyst.

EFFECT: catalyst enables to achieve high butadiene selectivity in oxidative dehydrogenation of n-butenes and provides high output of butadiene.

3 cl, 1 tbl, 7 ex

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