The present invention relates to the field of chemical technology of organic substances, namely the method for producing ethyl acetate and the catalysts used in its producing, namely, the ethanol dehydrogenation catalyst, and the hydrogenation catalyst of side organic substances of ethanol dehydrogenation reaction.

Ethyl acetate is a widely used solvent that is used in the production of paint materials, medicines, in the food industry, etc. Ethyl acetate is widely used as a solvent due to its low cost, low toxicity, and acceptable odor. In 1986, annual world production was 450-500 thousand tons, and in 2014, the production of ethyl acetate reached about 3.5 million tons. In 2018, the world market for ethyl acetate was estimated at about $ 3.3 billion, which makes its production quite promising for development and investments.

One of the most promising methods for synthesis of ethyl acetate is a method for producing ethyl acetate by dehydrogenation of ethanol in accordance with the following reactions:

C ₂ H ₅ OH C ₂ H ₄ O + H ₂

C ₂ H ₅ OH + C ₂ H ₄ O <-► CH ₃ COOC H ₂ CH ₃ + H ₂

The above reactions are reversible and their equilibrium may vary depending on the reaction conditions, namely, pressure, temperature, presence of by-products.

The prospects of this method are due to the rapid growth of bioethanol production, its availability, low cost and simplicity of the method. The advantage of this method is the use of ethanol (bioethanol) only as a raw material and this refers the method to the "green chemistry" of the production method and has a positive effect on public perception.

A number of ethanol dehydrogenation catalysts for producing ethyl acetate and methods for producing ethyl acetate have been proposed in the art. The most promising from the point of view of the authors of the present invention are ethanol dehydrogenation catalysts based on Cu, Zn, Cr, Al and Zr and their oxides, characterized by low cost of both production and use of such catalysts. For example, the patent RU2451007 describes a method for producing ethyl acetate by dehydrogenation of ethanol in the presence of a copper-zinc catalyst modified with chromium oxide at elevated temperature of 270-290 °C and pressure of 10-20 atm. In this case, the largest conversion of ethanol in 57-58% is achieved at temperature of 290 °C and 20 atm. The disadvantages of the proposed method include the high temperature and pressure of ethanol dehydrogenation reaction that cause significant energy consumption and high technological requirements for equipment operating at high pressure that significantly increases the cost of production.

The patent US70911155 describes a Cu-ZnO-Al ₂ O ₃ -ZrO ₂ catalyst for producing ethyl acetate from ethanol containing, per mol of copper, 0.05-1 mol of zinc oxide, 0.1-1 mol of alumina and 0.1-1 mol of zirconium oxide obtained by reduction by hydrogen, calcined precipitate obtained by hydrolysis reaction by alkali metal hydroxide of copper nitrate, zinc nitrate, aluminum nitrate and zirconyl nitrate.

In the case of use of ethanol with a low water content of less than 1%, preferably less than 0.5%, the yield of ethyl acetate when using the catalyst according to US70911155 was on average from 40 to 65%. But in the case of use of non-absolute ethanol (95%), the yield of ethyl acetate did not exceed 39%. That is, for this catalyst it is preferable to use dry ethanol or dehydrated ethanol, which ensures optimal performance of this catalyst and high yields of ethyl acetate. As known, technical-grade ethanol is usually produced in the form of an azeotrope with water, the concentration of which in alcohol is not less than 5%. Dehydration of ethanol usually requires significant energy costs that ultimately affects the cost of production of ethyl acetate. That is, the method proposed in US70911155 cannot be considered optimal for production of ethyl acetate from technical-grade ethanol.

The patent US9079851 also provides various catalysts containing CuO/SiO ₂ , CuO/SiO ₂ -Al ₂ O ₃ , CuO/ZnO, CuO/ZrO ₂ , CuO/SiO ₂ -ZrO ₂ , CuO/ZnO/Al ₂ O ₃ , CuO/Cr ₂ O ₃ /BaO, CuO/Cr ₂ O ₃ , and CUO/A1 ₂ O ₃ and optional other metal oxides for producing ethyl acetate from ethanol, and a method for producing ethyl acetate from ethanol is proposed. However, although the catalyst can be used at relatively low temperatures of 200-240 °C, the yield of ethyl acetate when using technical-grade ethanol (96%) did not exceed 42.6%, and in the case of pure ethanol was it was 47.9%. In addition, the disadvantages of this method for producing ethyl acetate also include the relatively high pressure of the dehydration reaction in the range of 20-36 atm that puts high demands towards the equipment used.

The patent UA116827 provides a method for producing ethyl acetate comprising a vapor-phase heterogeneous catalytic conversion of ethanol in the presence of a copper- containing catalyst at elevated temperature and pressure in the first reactor to form the target product and the reaction by-products, hydrogenation of the reaction carbonyl- containing by-products in the presence of the catalyst at reduced temperature in the second reactor to form the corresponding alcohols and subsequent separation of the target product, where the process is carried out at the temperature of 240-270 °C in the first reactor and the reduced temperature of 140-160 °C in the second reactor at the same pressure of 0.4-0.6 MPa, and with the use of, as a catalyst, a mixture of CuO-ZnO-ZrO ₂ - AI ₂ O ₃ oxides with the following ratio of CuO - 55; AI ₂ O ₃ - 18; ZnO - 7; ZrO ₂ - 20.

The disadvantage of the proposed method is also the low yield of ethyl acetate not exceeding 40% and the need to use dry ethanol (ethanol was pre-dried on calcium oxide and distilled). The possibility of using technical-grade ethanol containing from 4% water and more is not mentioned in this patent UA116827.

Therefore, today there is a topical issue in providing the method for producing ethyl acetate by ethanol dehydrogenation reaction, which would meet the following conditions:

1. The possibility of using technical-grade ethanol with a water content of from 4 to 10 wt.%;

2. High selectivity for ethyl acetate (more than 50%);

3. Low temperature of ethanol dehydrogenation reaction (in the range of 210-240 °C);

4. Low pressure of ethanol dehydrogenation reaction (in the range of 8-15 atm).

Accordingly, the aim of the present invention is to develop a method and a catalyst for producing ethyl acetate by dehydrogenation of technical-grade ethanol that allows increasing ethanol conversion and selectivity for ethyl acetate with the use of ethanol with a water concentration of up to 10 wt.% and carrying out the process at low temperature and pressure.

The put problem is solved by the developed catalyst for vapor-phase heterogeneous catalytic dehydrogenation of ethanol to ethyl acetate containing a mixture of CuO, ZnO, ZrO ₂ and AI ₂ O ₃ oxides and which further contains from 0.1 to 20 wt.% metal oxide of formula MeO, where Me is Ce, Ga, La or In.

In the preferred embodiment of the invention, the ethanol dehydrogenation catalyst contains CuO, ZnO, ZrO ₂ , AI ₂ O ₃ and MeO with the following ratio of components, wt.%:

CuO 60-70

ZnO 4-8

ZrO ₂ 15-20 AI ₂ O ₃ 9-15

MeO 1-5.

In other preferred embodiment of the invention, the ethanol dehydrogenation catalyst contains CuO, ZnO, ZrO ₂ , AI ₂ O ₃ and MeO with the following ratio of components, wt.%::

CuO 64

ZnO 5.5

ZrO ₂ 16.5 AI ₂ O ₃ 1 1

MeO 3.

In other preferred embodiment of the invention, the ethanol dehydrogenation catalyst contains cerium oxide (CeO ₂ ) as MeO.

In other preferred embodiment of the invention the catalyst for vapor-phase heterogeneous catalytic dehydrogenation of ethanol to ethyl acetate is used to dehydrogenate technical-grade ethanol with a water content of up to 10 wt.%.

Due to the optimal selection of components of the proposed catalyst the authors succeeded to ensure selectivity of producing ethyl acetate about 94% with the use of ethanol containing up to 10 wt.% water that makes the proposed catalyst particularly advantageous for large-scale production with the use of technical-grade ethanol (bioethanol), which has not undergone special preparation, namely drying. Also, the advantages of the proposed catalyst and the method in which it is used include the low temperature of ethanol dehydrogenation reaction - about 235 °C and the relatively low pressure of the reaction - about 1.3 MPa.

Accordingly, another object of the proposed invention is a method for producing ethyl acetate comprising vapor-phase heterogeneous catalytic dehydrogenation of ethanol in the presence of the ethanol dehydrogenation catalyst containing a mixture of CuO, ZnO, ZrO ₂ and AI ₂ O ₃ oxides at elevated temperature and pressure in the first reactor to form the target product and reaction by-products, hydrogenation of reaction carbonyl-containing by- products in the presence of the hydrogenation catalyst at reduced temperature in the second reactor to form the corresponding alcohols and subsequent separation of the target product, where the ethanol dehydrogenation catalyst further contains from 0.1 to 20 wt.% metal oxide of the formula MeO, where Me is Ce, Ga, La or In, and the process is carried out at temperature of 200-240 °C and pressure of 0.9- 1.5 MPa in the first reactor and temperature of 150-200 ⁰ C and pressure of 0.4-1.4 MPa in the second reactor.

In the preferred embodiment of the invention, the method for producing ethyl acetate comprises use of the ethanol dehydrogenation catalyst containing CuO, ZnO, ZrO ₂ , AI ₂ O ₃ and MeO with the following ratio of components, wt.%:

CuO 60-70

ZnO 4-8

ZrO ₂ 15-20 AI ₂ O ₃ 9-15

MeO 1-5.

In other preferred embodiment of the invention, the method for producing ethyl acetate comprises use of the ethanol dehydrogenation catalyst containing CuO, ZnO, ZrO ₂ , AI ₂ O ₃ and MeO with the following ratio of components, wt.%:

CuO 64

ZnO 5.5 ZrO ₂ 16.5 AI ₂ O ₃ 11

MeO 3.

In other preferred embodiment of the invention, the method for producing ethyl acetate comprises use of the ethanol dehydrogenation catalyst containing cerium oxide (CeO ₂ ) as MeO.

As found during the tests, the catalysts of the same composition may be used at ethanol dehydrogenation stage and at the hydrogenation stage of the reaction products obtained after ethanol dehydrogenation. However, in the preferred embodiment of the invention, the best yield of the method is provided when the catalysts of the stages of dehydrogenation and hydrogenation are different. Thus, in the most preferred embodiment of the invention, the catalyst having the following composition, wt.%, is used as a dehydrogenation catalyst:

CuO 64

ZnO 5.5

ZrO ₂ 16.5 AI ₂ O ₃ 11

CeO ₂ 3 while at the hydrogenation stage the catalyst having the following composition, wt.%, is used as a hydrogenation catalyst:

CuO 64

ZnO 5.5

ZrO ₂ 16.5

A1 ₂ O ₃ 11

Ga ₂ O ₃ 3

Typically, specially prepared metals such as nickel, cobalt, iron, platinum, palladium or oxides are used as hydrogenation catalysts. The catalysts of this type are characterized by high hydrogenation capacity. Raney nickel is one of the widely used catalysts.

However, Raney nickel is not always safe to use at high temperatures and excessive pressure. This catalyst is particularly active in hydrogenation processes at low pressure and temperatures not exceeding 100 °C. At higher temperatures and pressures, the amount of catalyst should not be more than 5% of the total amount of hydrogen acceptor. The presence of water vapor in the reaction medium leads to passivation of the catalyst surface and its activity drops significantly. Therefore, a hydrogenation catalyst, which is not being poisoned by water and retains its catalytic properties in its presence for a long time, was required to remove impurities from ethanol dehydrogenation reaction. A method for removing impurities from ethanol dehydrogenation reaction with the use of such a catalyst was also required.

Impurities within the scope of the present invention are understood as various aldehydes, ketones, esters, ethers, and alcohols formed during ethanol dehydrogenation, such as acetaldehyde, methyl ethyl ketone, butanols, crotonic aldehyde, isobutyl acetate, ethyl butyrate, butyl acetate, and the like. The presence of these impurities complicates separation of the reaction mixture and separation of pure ethyl acetate, since the boiling points of these volatile by-products are close to the boiling point of ethyl acetate. Accordingly, their catalytic transformation is necessary to facilitate the release of ethyl acetate.

To this end, in the developed method for producing ethyl acetate a catalyst that is not passivated by water vapor was proposed and the choice of the inventors turned to copper oxide systems that allow avoiding these difficulties in the operation of hydrogenation catalysts and proposing a method for removing impurities from ethanol dehydrogenation reaction.

Therefore, another object of the proposed invention is a method for removing impurities from ethanol dehydrogenation reaction in the method for producing ethyl acetate.

Unexpectedly, the authors of the present invention have found that a catalyst similar in composition to the catalyst used at the dehydrogenation stage can be used as a hydrogenation catalyst.

Therefore, another object of the proposed invention is a method for removing impurities from dehydrogenation reaction of ethanol to ethyl acetate, comprising a vapor- phase heterogeneous catalytic conversion of carbonyl-containing by-products of dehydrogenation reaction of ethanol to ethyl acetate in the presence of the hydrogenation catalyst containing a mixture of CuO, ZnO, ZrO ₂ and AI ₂ O ₃ oxides, at reduced temperature and subsequent separation of the target product, where the hydrogenation catalyst further contains from 0.1 to 20 wt.% metal oxide of formula MeO, where Me is Ce, Ga, La or In, and the process is carried out at temperature of 150- 200 °C and pressure of 0.4- 1.4 MPa.

In preferred embodiment of the invention, the catalyst of the method for removing impurities from dehydrogenation reaction of ethanol to ethyl acetate contains CuO, ZnO, ZrO ₂ , AI ₂ O ₃ and MeO with the following ratio of components, wt.%:

CuO 60-70

ZnO 4-8

ZrO ₂ 15-20 AI ₂ O ₃ 9-15

MeO 1-5. In other preferred embodiment of the invention, the catalyst of the method for removing impurities from dehydrogenation reaction of ethanol to ethyl acetate contains CuO, ZnO, ZrO ₂ , AI ₂ O ₃ and MeO with the following ratio of components, wt.%:

CuO 64

ZnO 5.5

ZrO ₂ 16.5 AI ₂ O ₃ 11

MeO 3.

In other preferred embodiment of the invention, the catalyst of the method for removing impurities from dehydrogenation reaction of ethanol to ethyl acetate that contains gallium oxide (Ga ₂ O ₃ ) as MeO.

Another advantage of the proposed method for producing ethyl acetate is the use of the catalysts of the above composition for dehydrogenation and hydrogenation that greatly simplifies and reduces the cost of their production.

According to the invention, the process for producing ethyl acetate from ethanol is carried out at temperature of 200-240 °C, preferably 235 °C, in the first reactor of ethanol dehydrogenation and pressure of 0.9- 1.5 MPa, preferably 1.3 MPa, and the second reactor of hydrogenation of the obtained reaction mixture at reduced temperature of 150-200 °C, preferably 190 °C, and pressure of 0.4 to 1.4 MPa, preferably 1.3 MPa. In the most preferred embodiment, as a catalyst for dehydrogenation and hydrogenation, a mixture of oxides with a ratio of components, wt.%: CuO - 64; ZnO - 5.5; AI ₂ O ₃ - 11; ZrO ₂ - 16.5 and MeO - 3 (where Me is Ce, Ga, La or In) is used.

In the reactor of dehydrogenation, the dehydrogenation catalyst of the following composition, wt.%: CuO - 64; ZnO - 5.5; AI ₂ O ₃ - 11; ZrO ₂ - 16.5 and CeO ₂ - 3, is preferably used as a dehydrogenation catalyst, and in the reactor of hydrogenation, the catalyst of the following composition, wt.%: CuO - 64; ZnO - 5.5; AI ₂ O ₃ - 11; ZrO ₂ - 16.5 and Ga ₂ O ₃ - 3 is used as a hydrogenation catalyst.

The dehydrogenation and hydrogenation catalysts were prepared in a conventional manner. The methods for preparing dehydrogenation and hydrogenation catalysts are shown below in the Examples section.

Catalysts can be used in the form of granules without a binder or with a binder or filler, for example, with graphite. The proposed invention is illustrated by drawings, where

FIG. 1A shows the reactor of dehydrogenation with the indicated direction of movement of the raw material;

FIG. 1 B shows the reactor of dehydrogenation 5 and the reactor of hydrogenation 7 with the indicated direction of movement of the raw material;

FIG. 2 shows a pilot plant for carrying out the method for producing ethyl acetate of the invention.

The proposed invention is further illustrated by examples of preparation of the catalysts of a certain composition and examples describing the results of tests of the catalysts in the method for obtaining ethyl acetate by dehydrogenation of ethanol in the presence of the developed catalysts.

Example 1

Synthesis of dehydrogenation and hydrogenation catalyst

The calculated amount of Cu(NO ₃ )2*3H ₂ O, Zn(NO ₃ )2*6H ₂ O, A1(NO ₃ )3*9H ₂ O and ZrO(NO ₃ )2*3H ₂ O salts was dissolved in distilled water. Subsequently, the mixture was heated to 90 °C with stirring and a stoichiometric amount of dissolved urea CO(NH ₂ )2 was added. The feed rate was selected so that the temperature of the reaction mixture did not decrease by more than 10 °C. This mixture was kept at 90 °C for 48 hours with constant stirring. The resulting solid was separated by filtration, washed 5 times with distilled water and dried for 12 hours at 110 °C. The resulting gel was dried at 130 °C and calcined at 350 °C.

The obtained catalyst, in the form of granules with a size from 2 to 3 mm formed from 2% graphite pre-reduced with a mixture of argon and 1-10 vol.% hydrogen, was studied in a flow reactor, as shown in FIG. 1 A. Ethanol (99.8%) in the vapor phase was fed from the bottom up at temperature of 210-240 °C and pressure of 1.3 MPa, the weight of the catalyst is 0.1 kg. The volumetric flow rate of ethanol was 0.07-0.09 kg/h. The reaction products were analyzed chromatographically. The results of catalyst tests are provided in Table. 1.

Example 2

It is similar to Example 1. The difference is that during catalyst synthesis Ce(NO ₃ )3*6H ₂ O was added in the amount of 3 wt.% in terms of oxide and the amount of A1(NO ₃ )3*9H ₂ O was reduced accordingly. Example 3

It is similar to Example 1. The difference is that during catalyst synthesis Ga(NO ₃ )3*9H ₂ O was added in the amount of 3 wt.% in terms of oxide and the amount of A1(NO ₃ )3*9H ₂ O was reduced accordingly. Example 4

It is similar to Example 1. The difference is that during catalyst synthesis La(NO ₃ )3*6H ₂ O was added in the amount of 3 wt.% in terms of oxide and the amount of A1(NO ₃ )3*9H ₂ O was reduced accordingly.

Example 5 It is similar to Example 1. The difference is that during catalyst synthesis

In(NO ₃ )3*5H ₂ O was added in the amount of 3 wt.% in terms of oxide and the amount of A1(NO ₃ )3*9H ₂ O was reduced accordingly.

In Table 1 below, the results of catalyst tests of the ethanol dehydrogenation reaction on the synthesized catalysts depending on the composition of the catalyst are provided.

Table 1

The results of catalyst tests of producing ethyl acetate by dehydrogenation of ethanol (99.8%) on the synthesized catalysts depending on the composition of the catalyst.

Table. 1 shows that the introduction of oxides of cerium, gallium, lanthanum, indium in the composition of the catalyst leads to increase in conversion of ethanol and increase in selectivity of the catalyst for the target product - ethyl acetate. These data indicate that the proposed catalyst allows carrying out of dehydrogenation of ethanol to ethyl acetate at lower temperatures and with higher selectivity than the known catalyst. Thus, the proposed catalyst allows increasing productivity of the ethanol dehydrogenation catalyst and change its selectivity.

Based on the results of catalyst tests, catalyst CuO-ZnO-Al ₂ O ₃ -ZrO ₂ modified with CeO ₂ was chosen as the most active catalyst for technological tests on the pilot plant.

Table 2 below shows the operating parameters of the process of catalytic producing of ethyl acetate on the technological scheme according to FIG. IB. The dehydrogenation catalyst CuO-ZnO-Al ₂ O ₃ -ZrO ₂ modified with CeCh, reactor 5, and the hydrogenation catalyst CuO-ZnO-Al ₂ O ₃ -ZrO ₂ modified with CeCh, Ga ₂ O ₃ , La ₂ O ₃ , In ₂ O ₃ , reactor 7.

Table 2

The results of catalyst tests of hydrogenation of the reaction mixture (reactor 7, FIG. IB) on the synthesized catalysts depending on the composition of the catalyst.

Parameters of the catalytic process of ethyl acetate synthesis: ethanol (99.8%) with a volumetric flow rate of 0.07 - 0.09 kg/h in the vapor phase was fed from the bottom up at dehydrogenation temperature of 235 °C, pressure 1.3 MPa, the weight of the catalyst is 0.1 kg. Hydrogenation temperature is 190 °C, pressure is 1.3 MPa. Feeding the steam mixture into the reactor from top to bottom, the weight of the catalyst is 0.1 kg.

Table. 2 shows that the modification of the catalyst composition by CeO ₂ , Ga ₂ O ₃ , La ₂ O ₃ , In ₂ O ₃ oxides facilitates increase in hydrogenation activity of the catalysts. Further, CuO-ZnO-Al ₂ O ₃ -ZrO ₂ modified with Ga ₂ O ₃ is proposed as the most active hydrogenation catalyst.

As part of the development of the method for producing ethyl acetate, a pilot plant was created to implement the method shown in FIG. 2.

According to FIG. 2, the plant contains:

1. Container for raw material 2. High pressure pump 3. Evaporator

4. Superheater

5. Thermostated reactor of dehydrogenation

6. Pressure maintenance valve

7. Thermostated reactor of hydrogenation

8. Pressure maintenance valve

9. Refrigerator

10. Centrifugal separator for separation of gas-liquid flow

11. Siphon

12. Reboiler

13. Refrigerator

14. Distillation column

15. Siphon

16. Refrigerator

17. Reboiler

18. Distillation column

According to the method for producing ethyl acetate from ethanol according to the invention, ethanol (or bioethanol) with a water content of from 4 to 10 wt.% from the container for raw material 1 is fed to the evaporator 3 by means of a high pressure pump 2. The formed vapor enters the superheater 4, where it is heated to the temperature of the reaction medium and then fed to the reactor of dehydrogenation 5 with temperature of 235 °C. In the reactor, on the surface of the catalyst, dehydrogenation of ethanol is carried out to form ethyl acetate and hydrogen. After the reactor of dehydrogenation, the formed reaction mixture is fed to the reactor of hydrogenation 7, where temperature of 190 °C and pressure of 1.3 MPa are maintained. After hydrogenation, the resulting mixture after the refrigerator is fed to the separator for separation of the gas-liquid flow of reaction products 8, in which the formed hydrogen is separated from the reaction mixture. After separating the gaseous products, the reaction mixture is fed to distillation columns 14 and 18 to separate the ethyl acetate and separate the obtained by-products.

Table. 3 below shows the operating parameters of the process of catalytic production of ethyl acetate at key points on the technological scheme according to FIG. 2. The dehydrogenation catalyst, reactor 5, CuO-ZnO-Al ₂ O ₃ -ZrO ₂ modified with CeOz, and hydrogenation catalyst, reactor 7, CuO-ZnO-AlzCh-ZrO ₂ modified with Ga ₂ O ₃ .

Table 3 Operating parameters of the process of catalytic production of ethyl acetate at key points on the technological scheme according to FIG. 2. The dehydrogenation Catalyst CuO-ZnO-Al ₂ O ₃ -ZrO ₂ modified with CeOz, the hydrogenation catalyst CuO-ZnO-Al ₂ O ₃ - ZrO ₂ modified with Ga ₂ O ₃ . Parameters of the catalytic process of ethyl acetate synthesis: feed of the raw material (ethanol/water - 93/7%) is 7.5 kg/h, dehydrogenation temperature is 235 °C, pressure is 1.3 MPa, weight of the dehydrogenation catalyst is 11 kg. Hydrogenation temperature is 190 °C, pressure is 1.3 MPa, weight of the hydrogenation catalyst is 5 kg. The data provided in Table 3 are averaged for technical-grade ethanol with different water content from 4 to 10 wt.%. As follows from these data, the average yield of ethyl acetate in terms of pure ethanol reaches about 50%, which is a much better result compared to known methods for producing ethyl acetate with the use of earlier disclosed catalysts. The proposed catalyst and the method can be recommended for the industrial production of ethyl acetate from technical-grade ethanol.