PROCESS FOR PRODUCTION OF ACRYLIC ACID, PROCESS FOR THE SELECTIVE OXIDATION OF CARBON MONOXIDE, CATALYST FOR THE SELECTIVE OXIDATION OF CARBON MONOXIDE, PROCESS FOR PRODUCING

THE SAME

Field of the invention

The present invention relates to chemical industry, specifically to a process for producing acrylic acid by the partial oxidation of propane, using a step of selective oxidation of carbon monoxide in the process of recirculating unreacted propane and/or propylene, and to a catalyst for the selective oxidation of carbon monoxide, and to a process for producing thereof.

Background of the invention

Acrylic acid is used, particularly, as a monomer in the production of polymers, including polyester resins.

One of the industrially applicable processes is a process for producing acrylic acid by the heterogeneous catalytic partial direct oxidation of propane, according to which:

1 ) Gaseous streams, at least one of which comprises propane, oxygen and water, are introduced into a first reaction zone.

2) The propane introduced into the reaction zone is subjected to catalytic oxidation to form a product mixture comprising acrylic acid.

Said process for producing acrylic acid from propane is known, for example, from patents EP0529853 Bl (28.02.1996), EP0603836 Bl (20.05.1998), etc. In most cases, the reaction gas comprising propane becomes only partially converted even at elevated temperatures. Thus, it is important to recirculate the unreacted propane and/or propylene contained in the product gas mixture back to the reaction step for carrying out efficiently the heterogeneous catalytic direct oxidation so as to obtain at least one of the desired target products.

A gas containing carbon monoxide is generated as a by-product in the steps of oxidizing hydrocarbon feedstock during the industrial production of acrylic acid. The presence of carbon monoxide in the recirculation gas is highly disadvantageous as it contributes to excessive dilution of the reaction medium and, consequently, to decreasing efficiency of the acrylic acid production. Moreover, the presence of carbon monoxide in the reaction mixture may result in decrease of catalyst activity. Accumulation of carbon monoxide may also promote formation of an explosive mixture in an oxidation reactor. As a consequence, purification of the recirculation gas from carbon monoxide contained therein is of utmost importance.

Known in the art are processes for removing carbon monoxide from a recirculation stream by fractional distillation. According to the invention provided in US8431743 B2 (30.04.2013), propane is subjected to heterogeneously catalyzed dehydrogenation in the first reaction stage, wherein a product gas mixture 1 comprising propane, propylene and other components are obtained. If necessary, a partial amount of the components different from propane and propylene present in the mixture, for example, such as hydrogen and carbon monoxide, is thereafter converted from the product gas mixture 1 formed in the first reaction stage into other compounds different from propane and propylene. Then, if necessary, the components different from propane and propylene present in the mixture, for example, such as hydrogen, carbon monoxide, and water vapor, are separated from the product gas mixture 1 formed in the first reaction stage.

Such separation of propane and propylene may be carried out, for example, by absorption followed by desorption in a high-boiling, hydrophobic organic solvent. A disadvantageous feature of the disclosed process is that all compounds having a boiling point lower than the boiling point of propane and propylene are removed from the recirculation stream. Oxygen, nitrogen, water, carbon dioxide, which function as diluents in the oxidation process, relate to such compounds.

Another option of removing undesired carbon monoxide from the recirculation gas is oxidation thereof to carbon dioxide, which is then removed by adsorption, if required. It is crucial to avoid the oxidation of propane and/or more reactive propylene during said oxidation process.

Patent EP0495504 Bl (09.04.1997) teaches the use of the oxidation of carbon monoxide to carbon dioxide in the presence of a catalyst comprising a noble metal (platinum, palladium, rhodium, ruthenium), copper, cobalt, nickel, magnesium, iron, and alloys or oxides thereof supported on an inorganic carrier for the production of methacrylic acid. The inventors found that the low temperature of the oxidation of carbon monoxide does not lead to the oxidation of isobutane, although the invention is silent on the oxidation of more reactive alkenes and on a possibility of carrying out the process in the presence of water vapor.

The authors of the article «Selectively combusting CO in the presence of propylene» [Chemical Engineering and processing: Process intensification 70, 2013, pp. 162-168] disclose a process for the oxidation of carbon monoxide in the presence of propylene and propane in a process for producing acrylic acid. A noble metal, such as palladium, platinum, rhodium, ruthenium, supported on an inorganic carrier is utilized as a selective oxidation catalyst. The selective oxidation is performed in a fluidized bed catalytic reactor in order to ensure agitation of the solid and gaseous mixture and thereby provide uniform distribution of the reactor temperature. Patent application US20130131380 Al (23.05.2015) teaches oxidizing of carbon monoxide in a fluidized bed reactor in the presence of a catalyst based on noble metals. According to the examples of the invention, a recirculation gas stream may comprise up to 20 mol% of water, 50 mol% of propane, and a small amount of propylene and acrolein (less than 1 mol% of each). However, the use of fluidized bed reactors complicates the process equipment and sets certain requirements to abrasion strength of the catalyst.

An actual technical problem is to develop an industrially applicable, efficient and simple process for producing acrylic acid by the oxidation of propane, in which process a recirculation mode is provided. The recirculating of a gas stream is difficult, since the stream comprises, in addition to unreacted propane and propylene, other oxidation products, including by-produced carbon monoxide, the presence of which in the recirculation gas stream is extremely unwanted.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a process for producing acrylic acid by the oxidation of propane, comprising a recirculation step of a gas stream comprising such compounds as propane and propylene, where preliminary removal of carbon monoxide by oxidation thereof is provided.

Another object of the present invention is to provide a process for the selective oxidation of carbon monoxide, which is generated as a by-product during the production of acrylic acid by the oxidation of propane, to carbon dioxide by means of a catalyst for the selective oxidation of carbon monoxide to carbon dioxide.

A technical result of the present invention is to increase the productivity of the process for producing acrylic acid, reduce the production cost, and improve safety of said process. Also, the technical result consists in carrying out a process for the oxidation of carbon monoxide to carbon dioxide in a recirculation gas stream at a high conversion rate and selectivity for carbon dioxide, and in enhancement of stability of the catalyst for the oxidation of carbon monoxide in the presence of water vapor.

The present invention includes the following aspects set forth below.

According to one aspect, the invention relates to a catalyst for the selective oxidation of carbon monoxide in the presence of a gas mixture comprising propylene, water vapor and propane, the catalyst comprising particles of a platinum group metal supported on a surface of a porous carrier comprising a y-AhCb phase and a boehmite phase.

According to one aspect, the invention relates to a catalyst for the selective oxidation of carbon monoxide, wherein particles of a platinum group metal are applied to the outer surface of a porous carrier.

According to another aspect, the invention relates to a catalyst characterized by a specific surface area of a catalyst carrier of from 220 to 280 m /g, an average pore size of from 7 to 14 nm, and a pore volume of from 0.6 to 0.9 cmVg. According to another aspect, the invention relates to a catalyst, wherein the gas mixture comprises propylene in an amount of from 1 to 3 vol.% and water vapor in an amount of from 20 to 45 vol.%.

According to another aspect, the invention relates to a catalyst, wherein the platinum group metal is selected from: rhodium, ruthenium, platinum, and palladium, and combinations thereof.

According to another aspect, the invention relates to a catalyst, wherein the platinum group metal is palladium, the palladium content is from 0.5 to 3.0% by weight, preferably from 1.5 to 2.8% by weight, even more preferably from 2.0 to 2.4% by weight.

According to another aspect, the invention relates to a catalyst, wherein the thickness of a palladium layer applied to a surface of the porous carrier is from 10 to 250 μιη, preferably from 50 to 150 μιη.

According to another aspect, the invention relates to a catalyst, wherein the porous carrier is granules having a shape selected from spherical, cylindrical, annular, and combinations thereof.

According to another aspect, the invention relates to a catalyst, wherein a content of the boehmite phase is up to 10% by weight, preferably from 0.5 to 7.0% by weight, more preferably from 1.5 to 5.0% by weight.

According to another aspect, the invention relates to a catalyst, wherein the specific surface area of the catalyst is from 240 to 270 m ² /g.

According to another aspect, the invention relates to a catalyst, wherein the catalyst pore volume is from 0.7 to 0.8 c Vg.

According to another aspect, the invention relates to a catalyst, wherein the content of a catalyst micropores, namely pores having a size of less than 2 nm, is from 1 to 5%, preferably 1 .5%.

According to another aspect, the invention relates to a catalyst for the selective oxidation of carbon monoxide in the presence of a gas mixture comprising propylene, water vapor and propane, the catalyst comprising particles of a platinum group metal applied to a surface of a porous carrier comprising a y-AhCb phase and a boehmite phase, and the catalyst is characterized by at least the following main diffraction peaks in an X-ray diffraction pattern: 20=14°, 46°, 67°.

According to yet another aspect, the invention relates to a process for the selective oxidation of carbon monoxide by reacting a gas mixture including carbon monoxide, propylene, water vapor, propane in the presence of a catalyst for the selective oxidation of carbon monoxide. According to one more aspect, the invention relates to a process, in which the reaction of the gas mixture is carried out in a tube reactor.

According to yet another aspect, the invention relates to a process, wherein the gas mixture comprises from 2 to 4 vol.% of carbon monoxide, from 1 to 3 vol.% of propylene, from 20 to 45 vol.% of water vapor.

According to yet another aspect, the invention relates to a process, wherein the reaction of the gas mixture is carried out in a tube reactor with a tube diameter of between 10 to 60 mm, preferably between 20 and 50 mm.

According to one more aspect, the invention relates to a process, wherein the catalyst is loaded into the reactor in beds alternating with beds of an inert material so that a volume of an inert material bed is by 1.1 -2 times larger than that of a catalyst bed.

According to yet another aspect, the invention relates to a process, wherein the reaction of the gas mixture is carried out at a temperature of from 60 to 160°C, preferably from 80 to 140°C, more preferably from 80 to 120°C.

According to one more aspect, the invention relates to a process, wherein the reaction of the gas mixture is carried out in the reactor at an excess pressure of between 0.1 and 0.5 bar, preferably between 0.1 and 0.3 bar.

According to yet another aspect, the invention relates to a process, wherein the contact time between the catalyst and the gas mixture is from 0.5 to 10 sec, preferably from 1 to 3 sec.

According to one more aspect, the invention relates to a process for producing acrylic acid by the heterogeneous oxidation of propane, comprising the steps of:

a) supplying a feed gas stream comprising propane, water vapor and an oxidizing agent into a reactor comprising a catalyst for the selective oxidation of propane to acrylic acid to produce a gas mixture comprising acrylic acid, unreacted propane and propylene, carbon oxides, b) the gas mixture obtained in step a) is supplied to a separation step to recover acrylic acid and obtain a gas mixture including propane, propylene, water vapor, and carbon oxides, c) the gas mixture obtained in step b) is supplied to a carbon monoxide selective oxidation reactor comprising a catalyst for the selective oxidation of carbon monoxide, in which carbon monoxide is oxidized according to the process for the oxidation of carbon monoxide set forth above,

d) a gas mixture leaving the carbon monoxide selective oxidation reactor is supplied to a step of separating water and purifying from carbon dioxide, and

e) after step d), the gas mixture enriched in propane and propylene is recirculated to step a). According to yet another aspect, the invention relates to a process further comprising a step, in which, prior to supplying the feed gas stream into the reactor comprising a catalyst for the selective oxidation of propane to acrylic acid, said gas stream is fed into a reactor comprising a catalyst for the selective oxidation of propylene to acrolein.

According to one more aspect, the invention relates to a process, in which the gas mixture obtained in step a) comprises minor amounts of acrolein and acetic acid.

According to another aspect, the invention relates to a process, in which the oxidizing agent comprises molecular oxygen as such or in a mixture with inert gaseous diluents.

According to yet another aspect, the invention relates to a process, in which the content of the water vapor is from 20 to 45 vol.%, preferably from 20 to 35%, more preferably from 20 to 30 vol.%.

According to one more aspect, the invention relates to a process, in which the conversion of propane is from 5 mol% to 30 mol%, preferably from 20 mol% to 25 mol%.

According to yet another aspect, the invention relates to a process, in which the selective oxidation of propane to acrylic acid is performed at a temperature of from 320 to 420°C.

According to one more aspect, the invention relates to a process, in which the selective oxidation of propane to acrylic acid is performed at a pressure of from 0.5 to 5 bar, preferably from 1 to 3 bar.

According to yet another aspect, the invention relates to a process, in which step a) is carried out in one reactor.

According to one more aspect, the invention relates to a process, in which step a) is carried out in two or more reactors connected in series.

According to another aspect, the invention relates to a process, in which step a) is carried out in two or more reactors connected in parallel.

According to yet another aspect, the invention relates to a process, wherein step a) is carried out in a tube reactor.

According to one more aspect, the invention relates to a process, wherein a heat-transfer agent selected from melts of salts, fusible metals or diphenyl mixtures is used in the tube reactor.

According to yet another aspect, the invention relates to a process, wherein step a) is carried out in the presence of a catalyst which temperature exceeds the temperature of the heat- transfer agent by 40-60°C.

According to one more aspect, the invention relates to a process, wherein the temperature of the heat-transfer agent in the tube reactor is from 260 to 310°C.

According to yet another aspect, the invention relates to a process for producing a catalyst for the selective oxidation of carbon monoxide, comprising the steps of: a) providing a catalyst carrier comprising a gamma aluminum oxide phase and up 10% of a boehmite phase;

b) reducing a platinum group metal on the surface of the catalyst carrier by adding a reducing agent;

c) cooling the resulting mixture to room temperature followed by recovering the catalyst from the mixture;

d) drying the catalyst;

e) reducing the resulting catalyst in a hydrogen stream;

f) passivating the catalyst in an inert gas stream.

According to one more aspect, the invention relates to a process, wherein the platinum group metal is selected from rhodium, ruthenium, platinum, palladium, and combinations thereof.

According to another aspect, the invention relates to a process, wherein the platinum group metal is palladium.

According to yet another aspect, the invention relates to a process, wherein the step of providing a catalyst carrier comprises the following substeps:

i) preparing an aqueous suspension of y-AhCb;

ii) adding a basic precipitant to said suspension;

iii) adding a precursor comprising a platinum group metal, and subsequently agitating, heating, and maintaining the resulting mixture for a predetermined period of time.

According to yet another aspect, the invention relates to a process, in which the basic precipitant comprises potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, or combinations thereof.

According to one more aspect, the invention relates to a process, in which a pH of the medium is maintained at a constant level of approximately 9 to 1 1 , preferably 10.

According to yet another aspect, the invention relates to a process, in which the precursor comprising a platinum group metal is a palladium-containing precursor and includes compounds selected from H ₂ PdCl ₆ , [Pd(NH ₃ ) ₂ Cl ₂ ], Pd(N0 ₃ ) ₂ , H ₂ PdCU.

According to one more aspect, the invention relates to a process, in which the precursor comprising a platinum group metal is added in doses within a period of time of from 10 to 30 min at a temperature of from 70 to 80°C.

According to yet another aspect, the invention relates to a process, in which, after dosing the precursor comprising a platinum group metal, the catalyst suspension is maintained for a period of time of from 20 to 60 min at a temperature of from 70 to 100 ^C C. According to one more aspect, the invention relates to a process, in which the reducing agent includes a solution of a weak organic acid salt and a strong base.

According to yet another aspect, the invention relates to a process, in which the reducing agent is selected from the group comprising sodium formate, ammonium acetate, ammonium formate, and ammonium oxalate.

According to one more aspect, the invention relates to a process, in which the catalyst is purified from chloride ions after the recovering step.

According to another aspect, the invention relates to a process, in which the obtained catalyst is subjected to drying at temperatures of from 40 to 150°C at the atmospheric pressure and/or at a pressure that is considerably lower than the atmospheric pressure.

According to yet another aspect, the invention relates to a process, in which the reduction of the precursor to the metallic condition on the surface of the catalyst is performed in a hydrogen stream in a tube furnace within a period of time from 30 to 60 minutes at a temperature of from 100 to 200°C, preferably, from 120 to 180°C, more preferably, from 140 to 160°C.

According to one more aspect, the invention relates to a process, in which the reduced catalyst is cooled in a stream of an inert gas selected from argon, nitrogen or helium.

According to yet another aspect, the invention relates to a process, in which the molar ratio of Pd:basic precipitant:reducing agent is maintained within the range of l :(10-2):(4-l), most preferably 1 :4: 1.5.

According to one more aspect, the invention relates to a process, in which a y-AhC phase is converted into a boehmite phase by selecting the conditions of substeps i-iii so as to shift the thermodynamic equilibrium to the formation of a boehmite phase.

According to another aspect, the invention relates to a process, in which y-AhCb is maintained in the presence of water at a temperature of from 70 to 100°C within a period of time from 20 min to 60 min to shift the thermodynamic equilibrium to the formation of a boehmite phase from a y-AhCb phase.

According to yet another aspect, the invention relates to a process, in which the content of the boehmite phase is from 0.5 to 7.0% by weight, preferably from 1.5 to 5.0% by weight.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows a scheme of an installation for producing acrylic acid by the oxidation of propane.

Fig. 2 shows an X-ray diffraction pattern of a catalyst comprising a boehmite phase between 1.5 and 5% by weight obtained in Example 1.

Fig. 3 shows an X-ray diffraction pattern of a catalyst comprising a boehmite phase greater than 10% by weight obtained in Example 2. Fig. 4 shows an X-ray diffraction pattern of a catalyst comprising no boehrnite phase obtained in Example 3.

Fig. 5 shows a cross-section of a structure of a catalyst in a form of granules.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The oxidation of carbon monoxide to carbon dioxide according to the invention is difficult due to the following factors:

a) the need for the selective oxidation of carbon monoxide in the presence of propane and propylene,

b) carrying out the process at elevated temperatures in the presence of water vapor, which contributes in reducing activity and stability of the known catalysts for the oxidation of carbon monoxide.

Therefore, in order to provide an efficient process for the oxidation of carbon monoxide to carbon dioxide in the presence of a gas mixture comprising propane, propylene, water vapor, and other unreacted gases, a catalyst is required that has high selectivity to carbon monoxide and that is simultaneously characterized by high activity and stability at high temperatures in the presence of water vapor.

The authors of the invention have surprisingly found that a catalyst comprising, as an active component, particles of platinum group metals applied in the form of a thin layer to the outer surface of a porous carrier, which comprises γ-Α1 ₂ 0 ₃ and an additional phase (boehrnite), has excellent selectivity and enhanced stability at high temperatures in the presence of water vapor. Preferably, the platinum group metals are selected from rhodium, ruthenium, platinum, and palladium, and combinations thereof. The most preferable metal is palladium.

The catalyst surface may be divided into an outer surface and an inner surface. The outer surface is an "external" surface of the catalyst. The inner surface is formed by pore walls, cracks, etc. An important feature of the catalyst according to the present invention is that the active component is applied onto the outer surface of the catalyst carrier thus forming a crusted layer on the surface of the carrier.

If the catalyst has a granular form, such a surface is illustrated as variant II on Fig. 5.

Since the oxidation of carbon monoxide occurs in the gas phase, the localization of the active component on the outer surface of the catalyst prevents the reaction from running in a diffusion region that is characterized by low selectivity due to catalyst heating. If the active component is localized within the catalyst volume, the reaction rate will be determined not by a rate of the oxidation reaction as such, but rather by a rate of the diffusion of the reactant within the catalyst volume. Emergence of diffusion limitations during the localization of the active component within the catalyst volume results in a decrease in performance of the entire process. The propylene diffusion in the pore volume of the catalyst and an increase of a contact time with the catalyst will enhance the probability of the undesired reaction of propylene oxidation.

In the process of oxidation of carbon monoxide, it is preferable to use a catalyst, in which a thickness of a layer of particles of a platinum group metal, particularly, palladium, applied to the outer surface of a porous alumina carrier is from 10 to 250 μηι, more preferably from 50 to 150 μιτι.

The amount of palladium is from 0.5 to 3.0% by weight, preferably from 1.5 to 2.8% by weight, more preferably from 2 to 2.4% by weight.

According to the present invention, the oxidation of carbon monoxide runs at elevated temperatures in the presence of water vapor, thus creating the need for providing hydrothermal stability of the catalyst. For this purpose, it is preferable to use a carrier consisting of γ-Α1 ₂ 0 ₃ and an additional phase (boehmite), which is a compound having the formula AIO(OH), as the catalyst carrier. Boehmite is a phase state of alumina and, first of all, is characterized by orthorhombic symmetry. y-AhC is transformed into boehmite by changing reaction conditions to shift the thermodynamic equilibrium to the formation of boehmite. The authors of the present invention have surprisingly discovered that the presence of the boehmite phase in the structure of a carrier contributes to a significant increase in stability of the catalyst in the presence of water vapor.

A phase transition of boehmite to pseudoboehmite, which is hydrated boehmite, may take place as the reaction of oxidation of carbon monoxide in the presence of water vapor runs. Application of a platinum group metal, particularly, palladium, on the catalyst surface facilitates stabilization of the boehmite phase due to the reaction of palladium with its hydroxide groups which, in its turn, prevents further hydration of boehmite followed by the formation of pseudoboehmite, and, consequently, contributes to improvement in stability of the catalyst under reaction conditions. The content of boehmite in the catalyst carrier is up to 10% by weight. Preferably, the content of boehmite in the catalyst carrier is from 0.5 to 7% by weight, more preferably from 1.5 to 5% by weight.

Therefore, one of the advantages of the catalyst according to this invention is the enhanced hydrothermal stability in the presence of water vapor. The enhanced hydrothermal stability facilitates retention of the surface area, porosity, and pore size of the catalyst when the latter is contacted with water vapor.

The catalyst according to the invention is characterized by a specific surface area of from 220 to 280 m ² /g, preferably from 240 to 270 m ² /g.

The pore volume of the carrier in the catalyst is from 0.6 to 0.9 cm ³ /g, preferably from 0.7 to 0.8 cm ³ /g. The pore volume of less than about 0.6 cm ³ /g deteriorates transport properties of pores of the carrier and increases pore-diffusion resistance during the oxidation of carbon monoxide, which results in low conversion of carbon monoxide during its oxidation to carbon dioxide. The pore volume of greater than about 0.9 cmVg raises catalyst brittleness considerably, which does not permit using it in flow-type reactors.

The average pore size of the carrier in the catalyst is from 7 to 14 nm. Slow diffusion of propylene molecules is observed in pores having a size of less than 7 nm, which entraps propylene molecules in the pore space and makes them react with oxygen thus generating oxidation products. It is not desirable to increase the pore size to greater than 14 nm, since in this case the specific surface of the carrier is reduced dramatically, this fact significantly hinders obtaining the catalyst with the required distribution and dispersity of the active agent.

The preferred content of micropores, namely pores with a size of less than 2 nm, in the catalyst carrier is from 1 to 5% (relative), preferably 1.5% (relative).

Thus, the catalyst according to the present invention used in the selective oxidation of carbon monoxide to carbon dioxide in the presence of a gas mixture comprising from 2 to 4 vol.% of carbon monoxide, from 1 to 3 vol.% of propylene, from 20 to 45 vol.% of water vapor, the remaining part being unreacted gases, including propane, is characterized by the following parameters:

• the active catalyst component is a platinum group metal, preferably palladium, in an amount of from 0.5 to 3.0% by weight, preferably from 1.5 to 2.8% by weight, more preferably from 2.0 to 2.4% by weight;

• the platinum group metal is applied as a thin layer of from 10 to 250 μιη, more preferably from 50 to 150 μηι, onto the outer surface of the catalyst carrier;

• the catalyst carrier comprises γ-Α1 ₂ 0 ₃ and an additional phase (boehmite) in an amount of from 0.5 to 7.0% by weight, more preferably from 1.5 to 5.0% by weight;

• the specific surface area of the catalyst is from 220 to 280 m ² /g, preferably from 240 to 270 m ² /g;

• the pore volume of the catalyst carrier is from 0.6 to 0.9 cmVg, preferably from 0.7 to 0.8 cm ³ /g;

• the average pore size of the catalyst carrier is from 7 to 14 nm;

• the content of micropores, namely pores with a size of less than 2 nm, in the catalyst carrier is from 1 to 5% (relative), preferably 1.5 relative %.

Therefore, according to the present invention, high efficiency of the catalyst, which is determined by its stability in the presence of water vapor at elevated temperatures and selectivity of carbon monoxide to carbon dioxide, is achieved due to the combination of the aforementioned features, more precisely: - provision of an alumina layer having the desired phase state (boehmite) on the surface of the catalyst carrier;

- efficient distribution of the active component in the form of a thin layer on the surface of the catalyst carrier;

- provision of an optimal surface area and porous structure of the catalyst.

The catalyst disclosed in the present invention may be obtained by a process comprising the steps of:

a) providing a catalyst carrier comprising an aluminum gamma oxide and up 10% of a boehmite phase;

b) reducing a platinum group metal on the surface of the catalyst carrier by adding a reducing agent;

c) cooling the resulting mixture to room temperature followed by recovering the catalyst from the mixture;

d) drying the catalyst;

e) reducing the resulting catalyst in a hydrogen stream;

f) passivating the catalyst in an inert gas stream.

Preferably, the step of providing a catalyst carrier comprises the following substeps:

1. Preparing an aqueous suspension of γ-Α1 ₂ 03;

2. Adding a basic precipitant, which makes an alkaline medium with pH«9-l 1 , preferably 10, to the aqueous suspension of γ-Α1 ₂ 0 ₃ ;

3. Adding a precursor comprising a platinum group metal, in particular, palladium, and subsequently agitating, heating, and maintaining the resulting mixture for a predetermined period of time.

The boehmite phase is formed within the catalyst carrier in steps 2 and 3. A compound selected from the group consisting of potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, and other alkaline agents may be used as the basic precipitant that ensures the formation of an alkaline medium. Use of sodium carbonate is preferred. Sodium carbonate utilized as the basic precipitant allows generating a buffer solution, which ensures the formation of an alkaline medium having constant pH«9- l l, preferably 10, which, in its turn, permits avoiding the need for controlling pH within the entire process of preparation of the catalyst. A medium having pH«9- l l is necessary for the formation of negatively-charged functional groups on the surface of the catalyst carrier, the presence of which contributes to better adsorption of anions of platinum group metals from the solution.

In a preferred embodiment, a palladium-containing precursor, which may be represented by compounds selected from H ₂ PdCl ₆ , [Pd(NH3) ₂ Cl ₂ ], Pd(NC>3) ₂ , preferably H ₂ PdCl ₄₎ is used as a precursor comprising a platinum group metal. The palladium-containing precursor is added in doses within a period of time of from 10 to 30 min at a temperature of from 70 to 80°C. After dosing the palladium-containing precursor, the catalyst suspension is maintained for a period of time of from 20 to 60 min at a temperature of from 70 to 100°C.

A reducing agent, which is a solution of a weak organic acid salt and a strong base, for example, sodium formate, ammonium acetate, ammonium formate, ammonium oxalate, is added to the suspension so as to obtain disperse particles of palladium having a certain size (1 -3 nm) on the catalyst surface. It is preferable to use sodium formate that is free of nitrogen, which latter affects adversely the catalyst activity.

After cooling the solution to room temperature, the catalyst is recovered by any prior art method, for example, centrifugation, filtration, decantation, etc.

After the recovery step, the catalyst is purified from chloride ions, the presence of which within the catalyst reduces oxygen adsorption on its surface, which, in its turn, decreases the catalyst activity. Completeness of removal of chloride ions is controlled by a qualitative reaction between the washing solution and silver nitrate.

The resulting catalyst is subjected to drying at temperatures of from 40 to 150°C at the atmospheric pressure and/or at a pressure that is considerably lower than the atmospheric pressure, for example, drying by vacuum at 100-150°C.

The reduction of the active component to the metallic condition on the surface of the catalyst is performed in a hydrogen stream in a tube furnace within a period of time from 30 to 60 minutes at a temperature of from 100 to 200°C, preferably, from 120 to 180°C, more preferably, from 140 to 160°C. The reduced catalyst is cooled in a stream of an inert gas selected from argon, nitrogen or helium. Helium is prefened, because no processes of formation of inactive palladium-containing surface structures occur in its atmosphere. The molar ratio of Pd:basic Na ₂ C0 ₃ :HCOONa is maintained within the range of l :(10-2):(4-l), most preferably 1 :4: 1.5, during the preparation of the catalyst.

Another subject matter of the present invention is a process for the selective oxidation of carbon monoxide to carbon dioxide in the presence of a gas mixture comprising propane, propylene, water vapor, using the above-defined catalyst. The gas mixture comprises from 2 to 4 vol.% of carbon monoxide, from 1 to 3 vol.% of propylene, from 20 to 45 vol.% of water vapor, with unreacted gases, including propane, being the rest.

During the selective oxidation of carbon monoxide to carbon dioxide, there is a need for arranging efficient withdrawal of a considerable amount of heat that releases during the gas- phase catalytic oxidation reaction, in which the gas mixture reacts with oxygen in the presence of a catalyst. Such efficient withdrawal of heat protects the catalyst from local overheating and, as a consequence, from destruction and exceeding the temperature that is allowed for the reaction of selective oxidation.

Therefore, according to the invention, the oxidation of carbon monoxide is performed using a tube reactor, in tubes of which a static bed of catalyst is loaded, for the purpose of efficiently withdrawing a large amount of heat generated by the gas-phase catalytic oxidation reaction. It is preferable to employ a tube reactor with a tube diameter of between 10 and 60 mm, preferably between 20 and 50 mm. If tubes with a diameter of greater than 50 mm are used, local overheating of the catalyst bed takes place due to inefficient heat withdrawal. If tubes with a diameter of less than 20 mm are used, on one hand, technical obstacles associated with loading and unloading of the catalyst will occur, on the other hand, hydrodynamic resistance of the catalyst bed in respect to a stream of a feedstock will increase, which fact, in turn, will lead to the presence of a pressure gradient over the length of the tube, this is undesirable for the process of a direct oxidation of a propane to an acrylic acid.

In order to achieve maximum heat withdrawal, reactor tubes are arranged vertically, and the reaction mass is fed from top to bottom. Solutions of monohydric or dihydric alcohols, water, and silicone oils may be used as a heat-transfer agent circulating in the reactor.

Also, in order to provide efficient heat withdrawal, the catalyst is loaded into the reactor in beds alternating with beds of an inert material so that the volume of an inert material bed is by 1.1 -2 times larger than that of a catalyst bed. Glass, quartz and other heat-resistant materials that do not decrease indices of the target reaction may be utilized as the inert material.

A catalyst in the form of granules having a shape selected from spherical, cylindrical, annular, and combinations thereof may be used to carry out the reaction of selective oxidation of carbon monoxide.

The temperature of the CO selective oxidation reaction according to the invention is from 60 to 160°C, preferably from 80 to 140°C, more preferably from 80 to 120°C. It is not reasonable to carry out the reaction at a temperature of less than 60°C due to low conversion of carbon monoxide, and at a temperature of greater than 160°C due to high conversion of propylene.

The reasonable excess pressure in the reactor is between 0.1 and 0.5 bar, preferably between 0.1 and 0.3 bar.

The contact time during the reaction is from 0.5 to 10 sec, preferably from 1 to 3 sec. It is not feasible to allow the reaction run for a longer contact time, since large load of the catalyst is required. In the event of a shorter contact time, the catalyst bed heats up to over 160°C, which is favorable for undesired oxidation reactions of propylene and propane.

Furthermore, a subject matter of the present invention is a process for producing acrylic acid, in which recirculation of a gas stream comprising valuable unreacted components, such as propylene and propane, is provided, said recirculation comprising a step of the selective oxidation of carbon monoxide to carbon dioxide, which process comprises:

1. supplying a feed gas stream comprising propane, water vapor and an oxidizing agent to a propane oxidation reactor, which contains a catalyst for the selective oxidation of propane to acrylic acid at a temperature of from 320 to 420°C;

2. supplying the gas mixture comprising acrylic acid, propane and propylene, carbon oxides, as well as optionally minor amounts of acrolein and acetic acid, obtained at an outlet of the propane oxidation reactor to a separation step of separating liquid and gas products followed by isolating acrylic acid;

3. supplying the gas product stream comprising propane, propylene, water vapor, carbon oxides to a reactor for the selective oxidation of carbon monoxide to carbon dioxide at a temperature of from 80 to 100°C;

4. conveying the gas mixture leaving the carbon monoxide selective oxidation reactor to a step of separating water and removing carbon dioxide, thereafter returning the remaining gas mixture enriched in propane and propylene to recirculation.

In a preferred embodiment of the invention, prior to introduction of the feed gas stream to a propane oxidation reactor, said gas stream is supplied to a reactor, in which a catalyst for the selective oxidation of propylene to acrolein is present.

As an oxidizing agent according to the invention, molecular oxygen is used, which may be added to the reaction gas mixture, for example, in pure form or in a mixture with gases, advantageously inert ones.

Since the production of acrylic acid is accompanied by considerable heat release, the hydrocarbon feedstock supplied to the propane oxidation reactor is diluted by a gas, which is capable of absorbing the heat releasing during the reaction due to its heat capacity. At least one gaseous inert diluent selected from N ₂ , H ₂ 0, C0 ₂ , He, Ar, saturated Ci-C ₅ hydrocarbons (for example, as taught by DE 924431 Al and EP 293224 A, and the like) is used as such a gas.

In order to withdraw heat and control the reaction according to the present invention, water vapor is used that contributes to absorption of reaction heat and decrease in a temperature gradient along the catalyst bed. On the one hand, the heat capacity of water permits compensating the temperature of reactor hot spots, on the other hand, the dilution with water vapor decreases the partial pressure of the starting product and the end product. Also, use of water vapor is useful for extending a lifetime of the catalyst for the oxidation of propane and reducing its coke deposition. Moreover, carrying out the process in the presence of water vapor provides safety of the entire process, because the composition of the gas mixture is outside the explosive range in this instance. The content of water vapor according to the invention may be from 20 to 45 vol.%, preferably from 20 to 35 vol.%, more preferably from 20 to 30 vol.%.

According to the invention, an embodiment of the process which achieves the propane conversion of between 5 mol.% and 30 mol.%, preferably between 20 and 25 mol%, is advantageous. This is associated with the circumstance that the remaining amount of unreacted propane in a subsequent, at least one oxidation zone essentially acts as a gaseous inert diluent and may later be returned to the oxidation zone without any loss.

The aforementioned propane conversion requires, predominantly, heterogeneous catalyzed oxidation of propane at an operating pressure of from 0.5 to 5 bar, preferably from 1 to 3 bar.

The oxidation of propane so as to obtain acrylic acid is performed at a temperature of from 320 to 420°C, preferably from 350 to 390°C, in a fixed bed reactor. Consumption of the mixture through catalysts is from 1.6 to 2.2 m /hour, preferably from 1.8 to 2.2 m ³ /hour.

In order to increase the yield of acrylic acid, propane may be oxidized not in a single reactor, but in two or more reactors connected in series or in parallel.

According to the invention, the gas-phase catalytic oxidation is preferably carried out in a tube reactor. Performing oxidation processes in tube reactors allows adjusting a reaction temperature by efficient withdrawal of a considerable amount of heat releasing during a gas- phase catalytic oxidation reaction, in which a substance to be oxidized is contacted with molecular oxygen in the presence of a solid catalyst. Such a process precludes the catalyst from destruction caused by local overheating of a catalyst bed (formation of hot spots).

Heat generated by the oxidation reaction running on the catalyst is conveyed to a boiling heat-transfer agent through a wall of the reactor tube, which is required to maintain uniform temperature within the catalyst bed. Heat-transfer agent vapor is supplied to a water-cooled reflux condenser via a connecting pipe. The heat-transfer agent vapor is condensed in the reflux condenser and returns to the reactor by gravity. A nitrogen blanket with continuous supply of nitrogen through an adjustable rotameter is created in a top part of the reflux condenser. The nitrogen blanket pressure and, correspondingly, the heat-transfer agent vapor pressure are adjusted by a pressure controller. Therefore, the boiling temperature of the heat-transfer agent is adjusted by setting the pressure automatically. For the avoidance of a temperature gradient within the heat-transfer agent, a condensed heat-transfer agent supply line is heated electrically to ensure heat-transfer agent boiling. Isothermality of the liquid bed of the heat-transfer agent is controlled by thermocouples.

First of all, liquid thermostatic media are used as a heat-transfer agent. It is preferable to utilize melts of salts, such as potassium nitrate, potassium nitrite, sodium nitrite and/or sodium nitrate, or fusible metals, along with diphenyl mixtures, for example, consisting of a mixture of diphenyl and diphenyl ether (DOWTHERM).

The heat-transfer agent has a temperature of from 260 to 310°C.

The maximum temperature within the catalyst bed exceeds the heat-transfer agent temperature by 40-60°C.

Catalysts suitable for the heterogeneous gas-phase catalytic oxidation of propane to acrylic acid are represented by mixtures of metal oxides having the formula MoV _a AbB _c On, in which Mo is molybdenum, V is vanadium, Ab is tellurium (Te) or antimony (Sb), B _c is at least one element of the group including niobium (Nb), tantalum (Ta), tungsten (W), titanium (Ti), aluminum (Al), zirconium (Zr), chromium (Cr), manganese (Mn), gallium (Ga), iron (Fe), ruthenium (Ru), cobalt (Co), rhenium (Rh), nickel (Ni), palladium (Pd), platinum (Pt), lanthanum (La), bismuth (Bi), boron (B), cesium (Cs), tin (Sn), zinc (Zn), silicon (Si), and indium (In), O is oxygen.

Mixtures of metal oxides, which composition corresponds to the formula indicated above, are known over patent applications EP 0608838, EP 0529853, JP-A 7-232071, JP-A 10-57813, JP-A 2000-37632, JP-A 10-3631 1 , WO 00/29105, WO 2010014206 Al„ WO 0198246 Al .

For the avoidance of accumulation of a high content of propylene in the recirculate (over 5-10 vol.%), and for the purpose of increasing the acrylic acid yield, prior to introducing the feed gas stream into a propane oxidation reaction zone, said gas stream is supplied to a reactor in which a catalyst for the selective oxidation of propylene to acrolein is contained.

Any prior art catalyst for the oxidation of propylene, comprising oxides of metals selected from bismuth (Bi), molybdenum (Mo), cobalt (Co), nickel (Ni), iron (Fe), potassium (K), phosphorus (P), silicon (Si), etc., is used in a reactor where the reaction of oxidation of propylene to acrolein runs (SU1 141627, US2012095267 Al).

The process according to the invention becomes especially important when it is effected in a recirculation mode. In this case, the target product is separated from the gas mixture escaping the propane oxidation reaction zone, while unreacted propane remaining in this gas mixture, conventionally together with unreacted propylene contained therein, are recirculated to an oxidation step, with by-produced carbon monoxide being preliminarily removed therefrom in accordance with the process for the selective oxidation of carbon monoxide to carbon dioxide described in the present invention.

The gas containing unreacted propane and propylene, which is recirculated to the reaction medium, is introduced into the same position of the reaction zone as the other propane- containing feed gas streams, i.e. as a constituent of the starting reaction gas mixture. A detailed description of Fig. 1 , which illustrates a scheme of an installation for producing acrylic acid by the oxidation of propane (according to the preferred embodiment of the invention), is given below. In conformity with the preferred embodiment, an oxygen- containing gas with a predetermined consumption is supplied to a mixing unit (1 ) passing through a preheater. A portion of the stream is drawn off after the preheater and directed to a reactor R- l to be mixed with the stream. The installation also provides an ability to feed an additional amount of oxygen to the line between reactors R-2 and R-3. Propane enters an evaporator, it is evaporated and heated up to a temperature of from 50 to 90°C. The resulting stream is conveyed to the heated mixing unit (1), where it is mixed with the oxygen-containing gas, recirculation gases and water vapor. The gas- vapor stream from the mixing unit (1 ) is conveyed to the reactor R-l, which contains a catalyst for the selective oxidation of propylene to acrolein at a temperature of 360-400°C. The catalyst is positioned in a tube that is cooled by boiling Dowtherm. The conversion degree of propylene is 90-95%.

After the reactor R-l , fresh oxygen is admixed to the stream and conveyed sequentially to reactors R-2 and R-3. A catalyst for the selective oxidation of propane to acrylic acid at a temperature of 360-400°C is placed in the reactor R-2. The catalyst is placed in a tube that is cooled by boiling Dowtherm. The conversion degree of propane in the reactor R-2 is 10-15%. Almost all acrolein is oxidized, predominantly to acrylic acid. The reaction mixture leaving the reactor R-2 enters the reactor R-3, in which the catalyst for the selective oxidation of propane to acrylic acid at a temperature of 360-400°C is present. The catalyst is placed in a tube that is cooled by boiling Dowtherm. The total conversion of propane in the reactors R-2 and R-3 is 20- 25%. Apart from acrylic acid, significant amounts of propylene and carbon oxides, as well as minor amounts of acetic acid and acrolein, are formed. The reaction mixture leaving the reactor R-3 is fed to an acrylic acid absorber (2) between the packing part and the plate part. The absorber (2) consists of two packing parts with a plate part between them. The upper packing part is wetted, by means of a pump (3), with an aqueous solution of hydroquinone that inhibits the polymerization of acrylic acid. Warmed water is fed to a dephlegmator for cooling, thereby providing the residual content of water vapor in the effluent gas of 30-40 vol.% at a temperature of 65-75°C. The plate part of the absorber is utilized to condense the majority of acrylic acid in a liquid phase in the guaranteed presence of hydroquinone. The lower packing part of the absorber is intended for distilling off propane dissolving in the condensate. The temperature of the absorber (2) bottoms is 103-105°C. The absorber (2) bottoms, which comprise mainly a solution of acrylic acid and acetic acid in water, are withdrawn from the lower part of the absorber ("product"). Acrylic acid is recovered from the product comprising acrylic acid, acetic acid and acrolein impurities in water in an acrylic acid removal unit (not shown in Figure). This unit may be implemented by any known method, inter alia, it may represent a system of column apparatuses for the removal and concentration of commercial acrylic acid.

The gas mixture leaving the absorber (2) is supplied to a reactor R-4, which contains a catalyst for the selective oxidation of CO to CO2 (the catalyst in Example 1 ) at a temperature of 60-100°C. The catalyst is within a tube that is cooled by a boiling heat-transfer agent. The degree of CO conversion is 50-90%. A portion of said gas mixture may be withdrawn from the absorber (2) for combustion, if necessary, for the avoidance of its uncontrollable accumulation in the system. The gas mixture leaving the reactor R-4, which was removed from the condensate, is supplied to a compressor (4). A portion of the reaction mixture is blown off after the compressor. The recirculating gas mixture is fed to an absorber (5) for alkali treatment of CO2 through a gas- consumption meter. The absorber (5) has the same structure as the absorber (2). The upper packing part is wetted by an alkali solution supplied by a pump (6), while the lower packing part is used for withdrawing propane. The gas mixture leaving the dephlegmator is recirculated to the inlet of the mixing unit (1).

This process for production of acrylic acid, which comprises the step of the selective oxidation of CO to CO2, allows producing acrylic acid without accumulation of carbon oxides in recirculation gases and without loss of hydrocarbon feedstock (propane and/or propylene) due to their oxidation on the CO oxidation catalyst (see Table 9).

EXAMPLES

Crystalline phases of the catalyst were identified by grazing incidence X-ray diffraction on Shimadzu XRD-700°C diffractometer using Cu K«- radiation (λ=1 ,5418 A) and a Ni filter. Measurement conditions: the range is 10-80 2Θ, the scanning speed is 2.0 degrees/min, the voltage across the tube is 25 kV, the current is 20 MA.

The specific surface area and pore structure of the catalyst samples were calculated using the single-point and multiple-point Brunauer-Emmett-Teller (BET) method, the multiple-point STSA (Statistical Thickness Surface Area (STSA)) method according to ASTM D6556.

Example 1. Preparation of a catalyst for the oxidation of carbon monoxide

2 g of γ-Α1 ₂ 0 ₃ were added to 100 ml of distilled water. 0.192 g of sodium carbonate dissolved in 2 ml of distilled water were added to the aqueous suspension of γ-Α1 ₂ 03. An aqueous solution comprising 0.1 1 g of H ₂ PdCl4, having a volume of 5 ml, was added dropwise. The H ₂ PdCl4 solution was added under constant agitation and heating to 90°C for 20 minutes. The resulting suspension was maintained at 90°C for 40 minutes. Then 0.216 g of a 30% aqueous solution of sodium formate were added. The obtained suspension was cooled down to 25°C, and the catalyst was separated by filtration. The catalyst was loaded into a tube furnace and calcined in a hydrogen stream at a temperature of 150°C for 30 minutes. Thereafter, the catalyst was cooled down in a helium stream and discharged from the tube furnace.

As a result, a catalyst having a palladium content of 2.2% by weight was obtained, the catalyst being characterized by the textural characteristics (surface area and pore structure) set out in Table 1.

Table 1 - Textural characteristics of the catalyst obtained in Example 1.

The X-ray diffraction pattern of the catalyst obtained in Example 1 is shown in Fig. 2.

As it can be seen in Fig. 2, substantially all diffraction peaks in the X-ray diffraction pattern of the catalyst obtained in Example 1 relate to the y-AhCb phase -46 °, 67 °. Moreover, the X-ray diffraction pattern comprises a diffraction peak at 2Θ=14°, which relates to the boehmite phase. Judging by quantitative calculations, based on evaluation of intensity of diffraction peaks in the X-ray diffraction pattern, the boehmite concentration in the catalyst structure is 1.5-5%.

Example 2 (comparative). Preparation of a catalyst for the oxidation of carbon monoxide comprising a boehmite phase over 10%.

A catalyst having a palladium content of 2.2%, which is characterized by the textural features (specific surface and pore structure) set out in Table 2, was used as a comparative catalyst.

2 g of γ-Α1 ₂ 03 were placed in 100 ml of distilled water so as to obtain the catalyst. 0.192 g of basic sodium carbonate dissolved in 2 ml of distilled water were added into the aqueous suspension of γ-Α1 ₂ 03, thereby making a pH of the suspension reach 1 1-12. 5 ml of an aqueous solution, in which 0.1 1 g of H ₂ PdCl ₄ had been dissolved, were added in doses. The H ₂ PdCU solution was added under agitation and heating to 90°C for 20 minutes. The suspension was maintained at a temperature of 90°C for 110 min. Then 0.216 g of a 30% aqueous solution of sodium formate were added. The obtained suspension was cooled down to 25°C, and the catalyst was separated by filtration. The catalyst was loaded into a tube furnace and calcined in a hydrogen stream at a temperature of 150°C for 30 minutes. Thereafter, the catalyst was cooled down in a helium stream and discharged from the tube furnace.

Table 2 - Textural characteristics of the catalyst obtained in Example 2.

Surface area, m ² /g 247.4

Micropore share, % 2.6

Pore volume, cm ³ /g 0.72

Pore diameter, nm 4.5-16 The X-ray diffraction pattern of the catalyst obtained in Example 1 is shown in Fig 3.

As it can be seen in Fig. 3, the diffraction peaks of 14°, 18°, 42° and 49° at 2Θ in the X- ray diffraction pattern of the catalyst obtained in Example 2 relate to the boehmite phase. Judging by quantitative calculations, the boehmite concentration in the catalyst structure is greater than 10% by weight.

Example 3. (comparative) Preparation of a catalyst for the oxidation of carbon monoxide comprising no boehmite phase.

A catalyst having a palladium content of 2.2%, which is characterized by the textural features (specific surface and pore structure) set out in Table 3, was used as a comparative catalyst.

2 g of γ-Α1 ₂ 0 ₃ were placed in 100 ml of distilled water so as to obtain the catalyst. 0.192 g of basic sodium carbonate dissolved in 2 ml of distilled water were added into the aqueous suspension of γ-Α1 ₂ 0 ₃ , thereby making a pH of the suspension reach 1 1- 12. 5 ml of an aqueous solution, in which 0.1 1 g of PdCU had been dissolved, were added in doses. The FhPdCU solution was added under agitation and heating to 90°C for 20 minutes. The resulting mixture was maintained at a temperature of 90°C for 5 min. Then 0.216 g of a 30% aqueous solution of sodium formate were added. The obtained suspension was cooled down to 25 °C, and the catalyst was separated by filtration. The catalyst was loaded into a tube furnace and calcined in a hydrogen stream at a temperature of 150°C for 30 minutes. Thereafter, the catalyst was cooled down in a helium stream and discharged from the tube furnace.

Table 3 - Textural characteristics of the catalyst obtained in Example 3.

Surface area, m ² /g 255.5

Micropore share, % 0.2

Pore volume, cnrVg 0.69

Pore diameter, nm 5-16

The X-ray diffraction pattern of the catalyst is shown in Fig. 4.

As it can be seen in Fig. 4, all diffraction peaks in the X-ray diffraction pattern of the catalyst obtained in Example 3 relate to γ-Α1 ₂ 0 ₃ . No boehmite phase was found.

Example 4. Process for the oxidation of carbon monoxide (CO)

Composition of the reaction mixture (volume %): CO - 3%, 0 ₂ .8%, C ₃ H ₆ -2%, H ₂ 0 - 30%, diluent gas (N ₂ ) -57%. The sample obtained in Example 1 was used as a catalyst. A tube reactor with an internal diameter of 26 mm was used to carry out the process. An inert material bed of 10 mm in height was loaded onto the reactor bottom. Catalyst beds (Mbed =1.2 cm ³ , Vbed =2.02 g) alternated with inert material beds having the equal volume. A diameter of the catalyst granules was 2.5-3.0 mm. A total weight of the loaded catalyst was 1 1.9 g. The temperature 9

22 within the catalyst bed was controlled by a thermocouple. The contact time was 2 s. The formulation of the reaction products was controlled by the gas chromatographic analysis.

The results of the experiments are represented in Table 4, according to which latter the CO conversion is 61 % and the propylene conversion is less than 4% at a temperature within the catalyst bed of 102°C. Therefore, the highest CO conversion in the presence of propylene, propane and water is achieved at a temperature of 100°C or more.

Table 4 - Results of the experiments in Example 4.

Example 5. Process for the oxidation of carbon monoxide (CO)

It is the process of Example 4, in which a reactor with a diameter of 4 mm is used, while the weight of the loaded catalyst is 0.88 g. The contact time is 1.1 sec. The reaction is performed at 80-140°C.

The formulation of the starting reaction mass and the formulation of the reaction products at a temperature of 80-140°C are set out in Table 5. The results of the experiment show that the CO conversion is greater than 50% when the reaction is carried out at temperatures over 100°C. This experiment demonstrates the possibility to carry out the process on a catalyst obtained in Example 1 at the contact time of 1.1 sec.

Table 5 - Results of the experiments in Example 5.

It is apparent from Example 5 that the CO conversion effected on the catalyst obtained in

Example 1 in the reactor with an internal diameter of 4 mm is 58% at 100°C and rises to 85% as the temperature is increased to 140°C. Propylene is oxidized insignificantly in this instance.

Example 6 (comparative) Process for the oxidation of carbon monoxide (CO) It is the process of Example 4, in which the catalyst obtained in Example 2 is used, the weight of the loaded catalyst is 1 1.47 g. The contact time is 2.0 sec. The reaction is performed at 80-280°C.

The formulation of the starting reaction mass and the formulation of the reaction products at a temperature of 80-280°C is set out in Table 6. The results of the experiment show that the CO conversion is greater than 50% when the reaction is carried out at temperatures over 100°C.

Table 6 - Results of the experiments in Example 6.

The results of the experiments of Example 6 demonstrate that the catalyst obtained in

Example 2 is characterized by low activity and low selectivity in the process for the oxidation of

CO in the presence of propylene, propane, and water.

Example 7 (comparative). Process for the oxidation of carbon monoxide (CO)

It is the process of Example 4, in which the catalyst obtained in Example 3 is used, the weight of the loaded catalyst is 0.87 r. The contact time is 1.1 sec. The reaction is performed at

100-140 °C.

The formulation of the starting reaction mass and the formulation of the reaction products at a temperature of 100-140°C are set out in Table 7.

Table 7 - Results of the experiments in Example 7.

The results of the experiment reveal that it is not reasonable to use the catalyst obtained in Example 3 for the oxidation of CO in the presence of propylene, propane, and water. Example 8. Process for the oxidation of carbon monoxide (CO) (life tests)

It is the process of Example 5, in which a reactor with a diameter of 4 mm is used, while the weight of the loaded catalyst is 0.88 g. The contact time is 1.1 sec. The reaction is performed at 100°C for 50 hours. The results of the experiment are represented in Table 8, according to which the CO conversion on the catalyst obtained in Example 1 is at least 50% and the propylene conversion is less than 1 %. This experiment demonstrates the possibility to carry out the process for a long time and achieve the claimed result.

Table 8 - Results of the experiments in Example 8.

It is apparent from the results of the experiment of Example 8 that use of the catalyst obtained in Example 1 in the process for the oxidation of CO ensures stability of the catalyst performance for more than 50 hours.

Example 9. Comparative. Process for the oxidation of carbon monoxide (CO) (life tests)

It is the process of Example 5, in which a reactor with a diameter of 4 mm is used, while the weight of the loaded catalyst is 0.92 g. The contact time is 1.1 sec. The reaction is performed at 140°C. The results of the experiment are represented in Table 9, according to which the CO conversion on the catalyst obtained in Example 3 is less than 50% and the propylene conversion is greater than 1% after 29 hours of experimentation. This experiment reveals that it is not reasonable to carry out the process on the catalyst obtained in Example 3 for a long time.

Table 9 - Results of the experiments in Example 9

platinum group metal, preferably palladium, layered on a surface of a porous carrier, said catalyst most preferably is characterized by a set of the following features:

□ a catalyst carrier consisting of γ-Α1 ₂ 0 ₃ and an additional boehmite phase in an amount of not greater than 10%, preferably from 0.5 to 7% by weight, more preferably from 1.5 to 5% by weight

□ well-developed specific surface area of the catalyst of 240- 270 m ² /g

□ a pore volume of the catalyst of 0.7 to 0.8 cm ³ /g;

□ an average pore size of the catalyst of 7 to 14 nm;

□ micropore content in the catalyst of 1 ,5 -2%.

should be used for the efficient oxidation of CO to CO2 in the presence of propylene, propane, and water. The oxidation of CO should preferably be carried out at the contact time of 1-3 sec and at a temperature of 100-140°C.

Example 9. Process for production of acrylic acid by the oxidation of propane

Table 10. Formulations of the material flows during the production of acrylic acid

Continuation of Table 10

Reactor inlet R-l Reactor inlet R-2 Reactor inlet R-3

wt. vol. wt. vol. wt. vol. g/hr Nl hr g hr Nl h g hr Nl/hr

% % % % % %

1340. 681.0 37.8 1340. 681.0 37.7 1153. 45.0 585.7 32.0

Propane C3H8 52.35 52.35

81 6 1 82 6 7 10 2 6 7

Propylene

43.47 1.70 23.14 1.29 6.02 0.24 3.20 0.18 32.53 1.27 17.32 0.95

C ₃ H ₆

265.2 10.3

Acrylic acid 2.25 0.09 0.70 0.04 2.25 0.09 0.70 0.04 82.46 4.52

9 6

Acrolein 3.38 0.13 1.35 0.08 50.67 1.98 20.25 1.12 2.39 0.09 0.95 0.05

Acetic acid 1.29 0.05 0.48 0.03 1.29 0.05 0.48 0.03 23.53 0.92 8.78 0.48

C0 ₂ 0.05 0.00 0.03 0.00 1.28 0.05 0.65 0.04 19.26 0.75 9.81 0.54

CO 5.76 0.23 4.60 0.26 8.88 0.35 7.10 0.39 47.1 1 1.84 37.67 2.06

498.4 619.7 34.4 516.1 641.7 35.5 675.0 26.3 839.3 45.9

H ₃ 0 19.46 20.15

2 0 0 3 2 9 0 5 2 5

623.8 436.6 24.2 591.9 414.3 22.9 301.0 1 1.7 210.7 1 1.5

0 ₂ 24.36 23.1 1

5 7 4 5 5 8 6 5 5 4

Nitrogen 42.13 1.65 33.68 1.87 42.13 1.65 33.68 1.87 42.13 1.65 33.69 1.84 2561. 100.0 1801. 100. 2561. 100.0 1803. 100. 2561. 100. 1826. 100.

Total:

41 0 41 00 41 0 20 00 40 00 50 00

Temperature,

120.00 360.00 375.00

°C

Pressure, bar 2.53 2.53 2.03

Vapor

1 .00 1 .00 1.00

fraction

Continuation of Table 10

Continuation of Table 10

Reactor inlet R-4 Reactor outlet R-4 Absorber inlet (5) CO2

vol. vol. wt. vol. g/hr t. % Nl hr g hr wt. % Nl/hr g hr 1/hr

% % % %

1071. 544.1 38.4 1071. 544.1 39.0 1005. 70.9 5 10. 63.3

Propane C3H8 55.39 55.39

25 5 7 25 8 5 62 5 88 9

Propylene 22.1

43.88 2.27 23.36 1.65 43.88 2.27 23.36 1.68 41.55 2.93 2.74 C ₃ H ₆ 2

Acrylic acid 2.25 0.12 0.70 0.05 2.25 0.12 0.70 0.05 0.21 0.02 0.07 0.01

Acrolein 3.41 0.18 1 .36 0.10 3.41 0.18 1.36 0.10 3.1 8 0.22 1 .27 0.16 Acetic acid 1.29 0.07 0.48 0.03 1.29 0.07 0.48 0.04 0.20 0.01 0.08 0.01

109.2 108.1 55.0

C0 ₂ 27.00 1.40 13.74 0.97 5.65 55.59 3.99 7.63 6.83

2 0 3

CO 58.15 3.01 46.50 3.29 5.82 0.30 4.65 0.33 5.76 0.41 4.60 0.57

498.9 620.4 43.8 498.9 620.4

H ₂ 0 44.5 70.5

25.80 25.80 56.75 4.00 8.76 8 1 7 8 5 3 7

185.6 129.9 155.7 109.0 154.2 10.8 107. 13.4 o ₂ 9.60 9.19 8.05 7.83

6 6 7 4 4 8 98 0

33.3

Nitrogen 42.13 2.18 33.68 2.38 42.13 2.18 33.69 2.42 41.71 2.94 4.14

6

1933. 100.0 1414. 100. 1933. 100.0 1393. 100. 1417. 100. 805. 100.

Total:

99 0 34 00 99 0 50 00 32 00 95 00

Temperature,

90.52 100.00 91.75

°C

Pressure, bar 1.60 1.40 2.73

Vapor

1.00 1.00 1.00

fraction

Thus, it can be seen from the results of the experiment (Table 10) that this process for production of acrylic acid, which comprises the step of the selective oxidation of CO to C0 ₂ , allows producing acrylic acid without accumulation of carbon oxides in recirculation gases and without loss of hydrocarbon feedstock (propane and/or propylene) due to their oxidation on the CO oxidation catalyst