GB2203427A

GB2203427A - Method of obtaining methanol

Info

Publication number: GB2203427A
Application number: GB08806616A
Authority: GB
Inventors: Alexandr Yakovlevich Rozovsky; Galina Ivanovna Lin; Sergei Minovich Loktev; Vladimir Petrovich Mochalin; Anatoly Alexandrovic Kochetkov; Vladimir Nikiforovich Menshov; Igor Alexandrovich Ryzhak; Aida Anatolievna Lender; Viktor Andreevich Topchy; Boris Alexandrovich Bulachev; Jury Vasilievich Lender
Original assignee: INST NEFTECHIMICHESKOGO SINTEZ; AV Topchiev Institute of Petrochemical Synthesis
Current assignee: INST NEFTECHIMICHESKOGO SINTEZ; AV Topchiev Institute of Petrochemical Synthesis
Priority date: 1986-07-24
Filing date: 1987-07-23
Publication date: 1988-10-19
Anticipated expiration: 2007-07-23
Also published as: GB8806616D0; PL266975A1; CN87105309A; RO100569B1; DE3790376T1; IT1220038B; WO1988000580A1; GB2203427B; JPH01500436A; IT8741641A0

Abstract

A method of obtaining methanol consists in contacting a gas mix, containing carbon monoxide, carbon dioxide and hydrogen, with a copper-containing catalyst at a temperature of 190-290 DEG C and a pressure of 5-10 MPa in two stages. During the first stage the copper-containing catalyst is contacted with a gas mix containing 5-30 % by volume of carbon monoxide, 0.3-20 % by volume of carbon dioxide at a volume ratio between the carbon monoxide and the carbon dioxide of 0.25-87 and at a volume ratio between the hydrogen and the total of carbon oxides of 2-3.65. The first stage is carried out in one through-flow reactor or in a cascade of such reactors at a bulk speed of the initial gas mix of 4,500-100,000 h<-1>, thus obtaining, after the first stage, a gas mix containing carbon monoxide, carbon dioxide, methanol vapor and 0.02-1.38 % by volume of water vapor. The methanol and water vapors are removed from the gas mix and the remaining gas mix, which contains the carbon monoxide, the carbon dioxide and the hydrogen, is fed to the second stage which is carried out in a reactor at a bulk speed of 7,000-15,000 h<-1> thus obtaining, after the second stage, a mix containing the carbon monoxide, the carbon dioxide, the hydrogen and the methanol and water vapors, the methanol and water vapors being then removed from the gas mix.

Description

METHOD OF PREPARING METHANOL Field of the Art The present invention relates to base organic synthesis and, more particularly, to methods of preparing methanol. Methanol can be used for the synthesis of some organic products: formaldehyde, methyl terephthalate, synthetic resins, medicinal preparations, and the like.

Description of Prior Art Known in the art is a method of preparing methanol from a gaseous mixture containing carbon oxide, carbon dioxide, and hydrogen via circulation of said gaseous mixture through a copper-containing catalyst placed into a reactor at 160 - 300 OC under I - 15 MPa, the space velocity of the gaseous mixture being 5000 - 50000 h-l Methanol and water are separated from the gaseous mixture leaving the reactor and the mixture remained is mixed with the initial gaseous mixture and fed into the reactor for circulation (GB, A, 1159035).

The known method is disadvantageous in that the catalyst has a low efficiency amounting to 0.2 - 0.4 t/(m3/h) at a pressure of 5 MPa. The method is also disadvantageous in that the energy consumption for the circulation of the gaseous mixture is high.

Also known in the art is a two-stage method of preparing methanol. At the first stage a gaseous mixture containing carbon oxide, carbon dioxide, and hydrogen is brought into contact with a copper-containing catalyst in a circulation system at 160 - 300 OC under a pressure of 1 15 MPa and space velocity of the gaseous mixture of 2000 25000 h1 After separation of methanol and water the circulating gaseous mixture is mixed with the initial gaseous mixture with a C02 content of 1 - 20 vol. % and CO/CO2 volume ratio equal to 0.5 c 2.The gaseous mixture leaving the first stage, i.e. blowing-off gas, is supplied to the second stage where it is brought into contact with a copper-containing catalyst in a circulation system at the same values of temperature, pressure and space velocity as in the first stage. Methanol and water formed at the second stage are separated from the circulating gaseous mixture (GB, A, 1259945).

The method is disadvantageous in that the catalyst efficiency is low amounting under 5 MPa to 0.4 t/(m3/h) for the first stage, 0.28 t/(m3/h) for the second stage, and 0.34 t/(m3/h) for the installation as a whole. In addition, the use of high-powered compressors for circulation of the gaseous mixture at each stage is also a disadvantage of the known method.

Disclosure of the Invention It is an object of the invention to provide a method of preparing methanol, which will enhance the efficiency of a copper-containing catalyst, ensure a high degree of conversion of carbon oxides into-methanol, decrease the energy consumption for circulation of a gaseous mixture and simplify the technology and equipment of the process.

Said object is accomplished by that a method is proposed of preparing methanol in two stages by contacting a gaseous mixture containing carbon oxide, carbon dioxide, and hydrogen with a copper-containing catalyst at 190 290 OC under 5 - 10 MPa, obtaining after the first stage a gaseous mixture containing carbon oxide, carbon dioxide, hydrogen, methanol, and water vapours, said methanol and water vapours being removed from the gaseous mixture, and the remaining gaseous mixture containing carbon oxide, carbon dioxide and hydrogen is delievered to the second stage performed in the reactor upon circulation of the gaseous mixture at a space velocity of 7000 - 15000 h , obtaining after the second stage a gaseous mixture containing carbon oxide, carbon dioxide, hydrogen, methanol and water vapours, said methanol and water vapours being removed from the gaseous mixture, wherein, according to the invention, at the first stage the copper-containing catalyst is contacted with the gaseous mixture containing 5 - 30 vol. % of carbon oxide and 0.3 - 20 vol. % of carbon dioxide, the CO/CO2 volume ratio being 0.25 - 87 and the H2/(CO+C02) volume ratio being equal to 2 - 3.65, the first stage is performed in one flow-type reactor or in a cascade of flow-type reactors at a space velocity of the initial gaseous mixture of 4500 - 100000 h 1, the content of water vapours in the gaseous mixture obtained after the first stage being maintained equal to 0.02 - 1.38 vol. %.

In developing the proposed method it was shown that preparation of methanol on a copper-containing catalyst gives rise to water which, depending on the technological conditions, exerts different effects on synthesis of methanol, namely, either activates the catalyst or desactivates it, thereby hindering the formstion of methanol. For instance, the content of water in the gaseous mixture leaving the reactor at the first stage of the known method (GB, A, 1259945) attains more than 1.5 vol. % which decreases the catalyst efficiency (below 0.4 t/(m3/h)).In the proposed method the content of water in the gaseous mixture obtained after the first stage (i.e. at the output of the first stage) is maintained equal to 0.02 - 1.38 vol. % which ensures a high catalyst efficiency (0.4 - 2.4 t/(m3/h)), the conversion degree of carbon oxides being also high (86 - 97 %).

Since the first stage of the proposed method is accomplisned in flow-type reactors, the energy expenditures for circulation of the gaseous mixture can be cut down considerably and the technology of the process can be simplified.

A rise in the catalyst efficiency makes it possible to decrease the dimensions of the reactors, the preset capacity of the installation being the same. The use of the cascade of the reactors at the first stage allows one to design installations of different powers.

A water content in the gaseous mixture obtained after the first stage, hence, the catalyst efficiency, are controlled by the CO/CO2 volume ratio in the gaseous mixture.

To enhance the catalyst efficiency, it is recommended to maintain the content of water vapours in the gaseous mixture leaving the first stage equal to 0.02 - 0.8 vol. 96 % by contacting at this stage a copper-containing catalyst with the gaseous mixture in which the Co/Co2 volume ratio is 2.8 - 87 (at any space velocity of the gaseous mixture within the range from 4500 to 100000 h 1).

A water content in the gaseous mixture obtained after the first stage and, hence, the catalyst efficiency can also be controlled by the space velocity of the initial gaseous mixture. To enhance the catalyst efficiency at a water content in the gaseous mixture obtained after the first stage equal to 0.02 - 1.38 vol. %, it is recommended to perform the contact of the initial gaseous mixture with a copper-containing catalyst at the first stage with a space velocity of 60000 - 100000 h-l A combination of these two factors (the CO/CO2 volume ratio and the space velocity of the gaseous mixture) also makes it possible to enhance the catalyst efficiency if a water content in the gaseous mixture leaving the.first stage equal to 0.02 - 1.38 vol. %.For this purpose, it is recommended to perform the contact of the initial gaseous mixture with a copper-containing catalyst at the first stage at a volume ratio of carbon oxide to carbon dioxide in said gaseous mixture equal to 1 - 2.8 and a space velocity of the gaseous mixture equal to 4500 - 60000 h 1.

As was mentioned above, the contact of a gaseous mixture containing carbon oxide, carbon dioxide,and hydrogen with a copper-containing catalyst at the first and second stages is performed at 190 - 290 C.

It is inexpedient to perform the contact at temperatures below 190 OC since the process stops to be autothermal because of a low catalyst efficiency. A temperature rise above 290 OC is inexpedient becase of an unfavourable thermodynamics of methanol synthesis and the necessity to carry out the process under elevated pressures.

At the first and second stages the process is carried out under a pressure of 5 - 10 MPa. It is inexpedient to synthesize methanol on the existing copper-containing cata- lysts under pressure below 5 MPa since this decreases the rate of methanol formation and, hence, increases the dimen sions of the reactors. A pressure rise above 10 MPa is inexpedient because of a considerable growth of capital investments for the equipment.

The lower limit of the CO content in the initial gaseous mixture (5 vol. %) is determined by the equilibrium of the conversion reaction CO + H20 r CO2 + H2 since at lower content of carbon oxide the consumption of hydrogen for water formation grows considerably. The upper limit of the CO content (30 vol. %) is determined by the fact that it is expedient to retain the hydrogen content in the initial gaseous mixture at a level no less than the stoichiometric value to ensure a high conversion degree of carbon oxides.

The lower limit of the C02 content in the initial gaseous mixture (0.3 vol. %) is determined by that at lower content of CO2 the efficiency of the copper-containing catalyst drops sharply. A choice of the upper limit of the CO2 content (20 vol. %) is similar to that of the upper limit of CO content.

The CO/C02 volume ratio equal to 0.25 - 87 in the initial gaseous mixture is determined by the efficiency of copper-containing catalysts.

The lower limit of, the H2/(CO+C02) volume ratio equal to 2 is determined by that it is inexpedient to decrease the hydrogen content in the initial gaseous mixture below stoichiometric since in this case a high degree of conversion of carbon oxides cannot be attained. The upper limit of the H2/(CO+C02) volume ratio equal to 3.65 is determined by that at higher values a considerable accumulation of hydrogen in the gaseous mixture, which is delivered to the second stage, takes place and, hence, the content of hydrogen in the gaseous mixture circulating at the second stage increases which results in a greater energy consumption for circulation of excess hydrogen.

The lower limit of water vapour content (0.02 vol. %) in the gaseous mixture obtained after the first stage is determined by the water content in the initial gaseous mixture. The upper limit of the water vapour content (1.38 vol. %) is determined by the necessity to maintain a high catalyst efficiency.

It is inexpedient to perform the contact of the initial gaseous mixture at the first stage at a space velocity of below 4500 h 1 since the catalyst efficiency decreases as a result of increasing content of water formed in the gaseous mixture. The contact of the initial gaseous mixture at a space velocity above 100000 h 1 is inexpedient since at higher flow rates the volume of the reactors at the first stage is insufficient for processing the gaseous mixture into methanol as a result of which the number of the reactors must be increased, the process will be technologically more complicated, and the capital investments will grow.

It is not recommended to perform the circulation of the gaseous mixture at the second stage at a space velocity below 7000 h 1 since this decreases the conversion degree of carbon oxides. It is inexpedient to perform the circulation of the gaseous mixture at a space velocity above 15000 h because of an unreasonable energy consump- tion for circulation when the conversion degree of carbon oxides grows insignificantly.

The proposed method of preparing methanol can be accomplished in the following way.

The initial gaseous mixture containing carbon oxide, carbon dioxide and hydrogen is used. The CO content in the initial gaseous mixture is 5 - 30 vol. %, the CO2 content 0.3 - 20 vol. %, the CO/CO2 volume ratio is 0.25 - 87 and H2/(CO+C02) volume ratio is 2 - 3.65. Said gaseous mixture is fed to a heat exchanger and heated to 190 - 290 C. The heated initial gaseous mixture is supplied at a space velocity of 4500 - 100000 h'l to the first stage into a flowtype reactor with an enhanced heat removal, for instance, into a tube reactor.In the reactor the initial gaseous mixture contacts a copper-containing catalyst, for instance, copper-zinc-chromium (56 mass % CuO, 26+2 mass % ZnO, 17+2 mass % Cr203), aopper-zinc-cromium-aluminium (54 mass % CuO, 25 mass % ZnO, 3.97 mass % A1203, 12.6 mass % Cr203), copper-zinc-aluminium (53 mass % CuO, 27 mass % Zn0,8 mass % Al203; 53.2 mass % CuO, 27.1 mass % ZnO, 5.5 mass % Awl203; 53+3 mass % CuO, 26+2 mass % ZnO, 5.5+0.7 mass % Al203; 62.5 mass % CuO, 25 mass % ZnO, 7.5 mass % Al203) or copper zinc (30 mass % CuO, 68 mass % ZnO). In all the above com positions of catalysts the content of only main components is given (the impurities being the balance).

The contact of the initial gaseous mixture with a cop per-containing catalysts yields methanol and water. The heat liberated in the reaction is removed from the reaction zone and used, for instance, for preparing water steam.

The gaseous mixture leaving the flow-type reactor and con taining carbon oxide, carbon dioxide, methanol and water vapours (the content of water vapours in the gaseous mix- ture is 0.02 - 1.38 vol. %) has.a temperature exceeding only slightly the temperature of the initial gaseous mixture at the reactor input.

Said gaseous mixture leaving the flow-type reactor and containing carbon oxide, carbon dioxide, hydrogen, me thanol and water vapours is supplied to a heat-exchanger for heat withdrawal and then methanol and water vapours are removed from the gaseous mixture, for instance, by passing this mixture through a condenser and separator successively.

The gaseous mixture leaving the separator and contain ing carbon oxide, carbon dioxide, and hydrogen is delivered to the second stage which is performed in the reactor with circulation of the gaseous mixture at a space velocity of 7000 - 15000 h'l The second stage is performed at tempera tures and pressures lying within the above-mentioned ranges and with the use of any of the above copper-contain ing catalysts.

The circulating gaseous mixture leaving the reactor at the second stage and containing carbon oxide, carbon dioxide, hydrogen, methanol and water vapours is delivered to a heat-exchanger for heat withdrawal and then methanol and water vapours are removed from said mixture, for instance, by passing thereof through a condenser and separator successively.

The gaseous mixture leaving the separator and containing carbon oxide, carbon dioxide, and hydrogen is divided into two parts. A part of the gaseous mixture (blowing-off gas), the value of which is determined by the catalyst efficiency at the second stage, is fed, for instance, into reforming furnaces. The remaining part of the gaseous mixture is mixed with the gaseous mixture leaving the first stage (the separator) and supplied to the input of a circulation compressor and then to the heat exchanger and reactor of the second stage.

The methanol and water vapours can be removed from the gaseous -mixtures leaving the reactor of the first stage and the reactor of the second stage by passing preliminary mixed said gaseous mixtures through a condenser and separator successively.

It should be noted that in the case of processing a great amount of the initial gaseous mixture it is expedient to carry out the first stage in a cascade of the flowtype reactors, the conditions of the process being similar to those when the first stage is performed in one flowtype reactor.

Methanol and water vapours are removed from the gaseous mixture after each reactor of the cascade. However, methanol and water vapours in the gaseous mixture leaving the last flow-type reactor of the cascade can be removed simultaneously with methanol and water vapours contained in the gaseous mixture leaving the reactor of the second stage. This simplifies the technology and equipment of the process.

At the second stage of the proposed method the content of carbon oxides and their volume ratio (CO/CO2) in the gaseous mixture entering' the reactor are determined by the conditions at the first stage (the composition and space velocity of the initial gaseous mixture, the catalyst efficiency) and at the second stage (the space velocity of the circulating gaseous mixture and catalyst efficiency).

It should be mentioned that in the present invention by an initial gaseous mixture is meant the gaseous mixture delivered to the first stage into the only flow-type reactor or into the first flow-type reactor of the cascade.

For a better understanding of the present invention specific examples of realizing thereof are given hereinbelow by way of illustration.

Example 1 Use is made of the initial gaseous mixture of the following composition, vol. %: carbon oxide 20.7, carbon dioxide 7.5, hydrogen 67.4, and nitrogen 4.4. The CO/CO2 volume ratio is 2.80 and the H2/(CO+C02) volume ratio is 2.39. Said gaseous mixture under a pressure of 8 MPa is supplied to a heat-exchanger where the mixture is heated to 260 CC. The heated initial gaseous mixture is delivered at a space velocity of 4666 h 1 to the first stage into a flow-type tube reactor with an intence heat removal. In the reactor the initial gaseous mixture contacts a copper -zinc-aluminium catalyst containing 53.2 mass % CuO, 27.1 mass % ZnO and 5.5 mass % A1203, the amount of the catalyst being 30 m3. The flow rate of the initial gaseous mixture is 140 000 Nm /h.

The gaseous mixture leaving the reactor flow-type has the following composition, vol. %: carbon oxide 9.6, carbon dioxide 9.75, hydrogen 53.54, nitrogen 6.14, methanol 20.19, water 0.78. Said gaseous mixture has a temperature of 269 C. The mixture is fed into a heat exchanger for heat withdrawal and the temperature of the mixture decreases to 200 OC. To remove methanol and water, the cooled gaseous mixture is passed successively through a condenser and separator.

The gaseous mixture leaving the separator (79 133 Nm3/h) is delivered to the second stage which is carried out in the reactor with a circulation of the gaseous mixture at a space velocity of 10 564 h 1. The temperature of the circulating gaseous mixture at the input of the reactor is 200 OC and at the output 268 OC. The pressure in the reactor is 8 MPa. The catalyst used at the second stage is similar to that used st the first stage, the amount of the catalyst at the second stage being 60 m3.

The flow rate of the circulating gaseous mixture ii 679 133 Nm3/h.

The circulating gaseous mixture entering the reactor has the following composition, vol. %: carbon oxide 4.1, carbon dioxide 5.8, hydrogen 54,nitrogen 35.75, methanol 0.32, water 0.03.

The circulating gaseous mixture leaving the reactor has the following composition, vol. %: carbon oxide 2.9, carbon dioxide 4.7, hydrogen 50.1, nitrogen 37.7, methanol 3.16, water 1.44.

Said gaseous mixture leaving the reactor is fed into a heat exchanger for heat withdrawal and the gaseous mix ture is cooled to 200 OC. The cooled gaseous mixture is passed through a condenser and separator successively to remove methanol and water.

The gaseous mixture leaving the separator and containing carbon oxide, carbon dioxide and hydrogen is divided into two parts. The part of the gaseous mixture (blow ing-off gas) in amount 15 550 Nm3/h is delivered to reforming furnaces. The remaining part of the gaseous mix ture (600 000 Nm3/h) is mixed with the gaseous mixture leaving the first stage (the separator) and fed to the input of the circulation compressor, and then into the heat-exchanger and reactor of the second stage.

The conditions of realizing the proposed method at the first stage, according to Examples 1 through 8, and the results obtained at the first stage are given in Table 1.

The conditions of realizing the proposed method at the second stage, according to Examples 1 through 8, and the results obtained at the second stage are given in Table 2.

The total results obtained at two stages of the proposed method, according to Examples 1 through 8, are given in Table 3.

Table 1 Parameters Known method Proposed method (GB, A, 1259945) Example 1 Example 2 Example 3 2 2 3 4 5 First stage Number of flowtype reactors 1 1 1 1 Catalyst composit ion with respect to main components, mass CuO 53.2 53.2 54.0 54.0 ZnO 27.1 27.1 25.0 25.0 Cr203 - - 12.6 12.6 Al203 5.5 5.5 3.97 3.97 Catalyst volume i3 one reactor, 47.6 30 20 30 m; 47.6 30 20 30 Composition of gaseous mixture, vol. %: CO 13.35/11.67 20.7/9.6 26.0/19.8 30.0/19.39 C 2 13.74/13.41 7.5/9.75 0.3/0.36 2.0/2.98 H2 68.88/64,5 67.4/53.54 65.69/56.8 66.7/48.8 CH4 3.01/3.67 - 5.0/6.28 0.5/0.77 N2 0.63/0.67 4.4/6.14 3.0/3.78 0.8/1.23 CH30H 0.36/4.5 -/20.19 -/12.95 -/26.74 H20 0.03/1.58 -/0.78 -/0.02 -/0.09 CO/CO2 volume ratio in gaseous mixture at the reactor input 0.97 2.80 87 15 Ho/(CO+CO ) volume radio in gaseous mixture at the reactor input 2.54 2.39 2.5 2.08 Table 1 (continued) 1 2 3 4 5 Pressure, MPa 5 8 5 8 Temperature of gaseous mixture, OC input/output 240/270 260/269 257/264 245/256 Flow rate of the initial gaseous mixture, Sm /h 94000 140000 120000 135000 Space velocity of the gaseous mixture at the rector input, h 6176 4666 6000 4500 Flow rate of the circulating gaseous mixture, Nm /h 294000 Catalyst efficiency in me thanol, t/(m /h) 0.4 0.96 0.85 Amount of methanol prepared, t/h 19 28.8 17 33.6 Table 1 (continued) Parameters Proposed method Example 4 Example 5 1 6 7 First stage Number of flow-type reactors 2 3 Catalyst composition with res- pect to main components, mass % CuO 62.5 53.0 ZnO 25.0 27.0 Cr203 A1203 7.5 8.0 Catalyst volume in one rec tor, 20 10 Composition of gaseous mixture, vol. %:: input/ First Second First Second Third output reactor reactor reactor. reactor reactor Co 20.7/13.9 16.05/9.06 20X/17.16 18.56/14.55 15.9/11.56 CO2 7.5/8.68 10.0/11.16 7,5/7.89 8.53/8.99 9.85/10.25 H2 67.4/58.37 67.16/57.89 67.4/61.97 67.05/61.07 66.9/60.36 CH4 - - N2 4.4/5.5 6.37/7.92 4.4/5.04 5.45/6.31 6.7/8.05 0H30H -/12.8 0.41/12.68 -/7.24 0.4/8.2 0.44/8.59 H20 -/0.75 0.01/1.29 /0.7 0.01/0.88 0.01/1.19 CO/CO volume ratio in the gaseous mixture at the reactor input 2.80 1.605 2.80 2.18 1.61 Table 1 (continued) 1 6 7 H2 (CCeC02 ) volume ratio in the gaseous mixture at the reactor input 2,39 2.58 2.4 2.48 2.6 Pressure, MPa 8 8 8 8 8 Temperature of the gase OU8 mixture, C input/ output 254/266 252/261 251/265 255/264 258/264 Flow rate of the initial gaseous mixture, Em3/h 280000 - 280000 Space velocity of the gaseous mixture at the reactor input, h-1 14000 9728 28000 22602 17847 Flow rate of the cir culating gaseous mixture, Nm /h - - - - Catalyst efficiency in methanol, t/(m;;/h) 1.99 1.37 2.4 2.2 1.8 Amount of methanol prepared, t/h 39.8 27.4 24 22 18 Table 1 (continued) Parameters Proposed method Example 6 Example 7 1 8 8 9 First stage Number of flow-type reactors 1 I Catalyst composition with respect to main components, mass CuO 53.0 53.0 ZnO 27.0 27.0 Cr2O3 Al2O3 8.0 8.0 Catalyst volume in one reactor, m 0.5 1.5 Composition of gaseous mixture, vol. %:: input/output CO 5.0/5.21 10.0/9.64 CO2 20.0/19.14 10.0/9.34 H2 72.0/69.89 73.0/71.09 CH4 N2 3.0/3.08 7.0/7.24 CH3OH -/1.3 -/1.69 H20 -/1.38 -/1.0 CO/CO volume ratio in the gaseous mixture at the reactor input 0.25 1.0 /(C O+CO ) volume ratio in the gaseous mixture at the reactor output 2.89 3.65 Pressure, MPa 10 7 Temperature of the gaseous mixture, C input/output 230/235 240/247 Flow rate o:: the initial gaseous mixture, Em/h 50000 90000 Space velocity oi the ga seou mix - ture at the reactor input,h 100000 60000 Flow rate of th circulating gaseous mixture, Nm /h Catalyst efficiency in methanol, t/(m/h) 1.8 1.4 Amount of methanol prepared, t/h 0.9 2.1 Table 1 (continued) Parameters Proposed method Example 8 1 10 First stage Number of flowtype reactors 4 Catalyst compob sit ion with respect to main components, mass CuO 56.0 ZnO 27.0 Cr203 16.5 Al2O3 - Catalyst volume in one reactor, m 30 Composition of the gaseous mixture, vol. %:: input/ First Second Third Fourth output reactor reactor reactor reactor CO 27.49/23.98 25.98/21.59 23.94/18.27 20.78/13.52 CO2 350/3.91 4.22/4.84 5.37/6.31 7.18/8.60 H2 67.t62.27 6750/61.02 67.77/60.04 68.27l59.38 CH4 - - - - N2 1.30/1.52 1.63/1.96 2.18/2.69 3.05/3.87 CR3OR -/8.16 0.66/10.37 0.68/12.33 0.68/14.13 H20 0.01/0.16 0.01/0.22 0.06/0.31 0.07/0.50 CO/CO2 volume ratio in the gaseous mix ture at the reactor input 7.85 6.16 4.46 2.89 H /(CO+CO ) volime ratio in the gaseous mixture at the reactor input 2.18 2.23 2.31 2.44 Pressure, MPa 5 5 5 5 Table 1 (continued) 1 10 Temperature of the gase OU9 mixture, C input/ 235/246 234/244 234/243 237/242 output Flow rate of the initial gaseous mixture, Mm /h 280000 Space velocity of the gaseous mixture st the reactor input, 9333 7410 5600 4000 Flow rate of the circulating gaseous mixture, Nm /h - - - Catalyst efficiency in methanol, t/(m;/h) 0.93 0.85 0.75 0.6 Amount of methanol prepared, t/h 28.0 25.5 22.5 1 & Table 2 Parameters Known method Proposed method (GB, A 1259945) Example 1 Example 2 Example 3 1 2 3 4 5 Second stage Catalyst volume in the reactor, m 46.3 60 60 40 C omposit ion of the circulating gaseous mixture, vol. 9%:: input/output CO 11.15/10.24 4.1/2.9 7.77/5.18 13.88/10.36 CO2 11.86/10.67 5.8/4.7 1.57/1.59 2.73/2.72 H2 61.98/56.23 54.0/50.1 62.13/59.89 53.44/48.49 c 11.78/15.11 - 17.86/18.94 11.31/12.59 N2 2.68/3.44 35.75/37.7-10.27/10.95 18.09/19.98 CH3OH 0.49/2.8 0.32/3.16 0.48/3.59 0.53/5.57 H2O 0.06/1.51 0.03/1.44 0.01/0.07 0.01/0.29 Pressure, MPa 5 8 5 8 Temperature of the circulating gaseous mixture, OC input/output 240/270 200/268 210/266 220/290 Flow rate of the circulating gase ourl mixture, 600000 400000 Nm /h 464300 679133 600000 400000 Space velocity of the circulating gaseous mixture at the reactor input, 9806 11319 10000 0000 h'' 9806 11319 10000 10000 Catalyst efficiency in methanol, t/(m /h) 0,28 0,44 0.41 0.68 Amount of methanol prepared, t/h 13 26.4 25, 0 26.9 Table 2 (continued) Parameters Proposed method Example 4 Example 5 Example 6 Example 7 Example 8 1 6 7 8 9 10 Second stage Catalyst vo lume in the 60 60 zooin the reactor 60 60 30 38 65 Composition of the circu lating gase ous mixture, vol. %:: input/output CO 8.48/7.66 9.03/7.74 3.74/3.10 2.1/0.71 8.72/6.55 CO2 10.6/9.65 9.64/8.77 12.16/10.66 2.87/1.61 7.43/6.65 H2 62.89/53.1062.03/57.90 60.33/56.65 75.49/72.61 67.10/63.48 CR4 - - N2 17.6/18.7 18.95/20.26 22.3/23.62 19.20/20.21 16.15/17.55 CR3OH 0.32/3.25 0.33/3.77 0.4/3.57 0.5/3.45 0.55/4.35 1120 -0.01/1.64 0.01/1.56 0.04/2.40 0.04/1.41 0.05/1.42 Pressure, MPa 8 8 10 7 5 Temperature of the circu- lating gase ous mixture, C input/output 190/262 200/278 239/265 220/278 200/270 Flow rate of the circulating gaseous mixture, Nm /h 734628 735006 377202 570000 455000 Space veloci ty oi the circulating gaseous mix ture at the reactor input, h 1 12244 12250 12573 15000 7000 Catalyst efficiency in me thanql, t/(m /h) 0.49 0.57 0.52 0.59 0.4 imount of me- thanol pre pared, t/h 29.4 34 15.7 22.6 26 Table 3 Parameters Known me- Proposed method thod (GB,A, 1259945) Example 1 Example 2 Example 3 1 2 3 4 5 First+econd stage a Catalyst volume, m 93.9 90 80 70 Catalyst efficiency in mclthanol, t/(m /h) 0,34 0.61 0.52 0.86 Amount oi methanol prepared, t/h 32,0 55.2 42.0 60.5 Flow rate oi the circulating gaseous mixture per 1 t oi methanol, Nm /(t.h) 23698 11483 14286 6838 Conversion degree of carbon oxides, % 90*0 97.0 93.1 98.0 Table 3 (continued) Parameters Proposed method Example 4 Example 5 Example 6 Example 7 Example 8 6 7 8 9 10 First+Second stages Catalyst volume, 90 90 30.5 39.5 185 m 90 90 30.5 39.5 85 Catalyst efficiency in 0.96 1.09 0.54 methanol, 0.96 1.09 0.54 0.63 0.65 Amount of methanol prepared, t/h Flow rate of the circulating gaseous mixture per t t of methanol, Nm3/(t.h) 7605 7500 22723 23077 3792 Conversion degree oi carbon oxides, % 86.0 90.0 93.0 96,0 96.8 For the sake of comparison, Tables t and 2 list also similar data obtained in preparing methanol by the known method described in GB, A, 1259945.

In the Tables the term "input" is used for the gaseous mixture entering the reactor and the term "output for the gaseous mixture leaving the reactor. By the initial gaseous mixture is one delivered to the first stage into the only flow-type reactor or into the first flowtype reactor of the cascade. In addition, the catalysts used in the proposed method (3xamples 1 through 8) and in the known method have a similar composition both at the first and second stages.

As is seen from Table 1, the proposed method makes it possible to enhance the catalyst efficiency at the first stage 1.7 - 6 times compared to the catalyst efficiency at the first stage attained then the known method is used (G3, A, 1259945). Such an increase in catalyst efficiency at the first stage allows one to decrease a catalyst volume and, hence, the dimensions of the reactor for preparing the required amount of methanol.

Since the proposed method is accomplished at the first stage in flow-type reactors, there are no energy expenditures for circulation of the gaseous mixture at the first stage contrary to the known method and the first stage of the proposed method is technologically simpler.

The performance of the first stage under the conditions of the proposed method improves the conditions of the second stage. As is seen from Table 2, the catalyst efficiency at the second stage according to the proposed method increases 1.4 - 2.4 times as compared to that at the second stage of the known method (GB, A, 1259945).

Such an increase in the catalyst efficiency is attained at the same values of space velocity (7000 - 15000) of the circulating gaseous mixture as claimed in the known method.

As is seen from Table 3, the catalyst efficiency in methanol in all the examples (Examples 1 through 8) illustrating the proposed method is within the range from 0.52 to 1.09 t/(t3/h) which is greater than the catalyst efficiency attained in the known method 1.5 - 3 times (GB, A, 1259945). The conversion degree of carbon oxides remains high.

From Table 3 it follows that the proposed method makes it possible to decrease the flow rate of the circulating gas per ton of methanol as compared to knoun method (GB, A, 1259945). For instance, at the first stage of the proposed method carried out in the cascade of flow-type reactors the flow rate of the circulating gas per ton of methanol decreases 3.1 - 6 times (Examples 4, 5, 8). when the first stage of the proposed method is performed in one flow-type reactor, the flow rate of the circulating.gas per ton of methanol can also be considerably decreased, for instance, 3 times (Example 3). A decrease in the flow rate of the circulating gas per ton of methanol cuts down greatly the energy expenditures for circulation of the gaseous mixture.

It also follows from Table 3 that the proposed method allows one to obtain much greater amount of methanol as compared to known method on the catalyst of the same volume.

For instance, on the catalyst 90 m3 in volume (Examples 1, 4, 5) from 54 to 98 t/h of methanol is obtained by the proposed method whereas on the catalyst of almost the same volume (93.9 m3) 32 t/h of methanol is obtained by the known method which is 1.7 - 3 times less as compared to the proposed method.

Thus, the proposed method of preparing methanol makes it possible to enhance considerably the efficiency of copper-containing catalyst at a high conversion degree of carbon oxides into methanol, to cut down energy expenditures for circulation of the gaseous mixture, and simplify the technology and equipment of the process as a whole.

Industrial Applicability The present invention may find application in the or panic synthesis for the production of large-tonnege product, viz., methanol.

Claims

WE CLAIM:

1. A method of preparing methanol, by contacting a gaseous mixture containing carbon oside, carbon dioxide, and hydrogen is with a copper-containing catalyst st 190 290 OC under 5 - 10 liPa in two stages, the first stage giving a gaseous mixture containing carbon oxide, carbon dioxide, hydrogen, vapours of methanol and water vapours, said methanol and water vapours being removed from the gaseous mixture, the remaining gaseous mixture containing carbon oxide, carbon dioxide aid hydrogen being delivered to a second stage carried out in s reactor wherein said gaseous mixture circulates at a space velocity of 700 15 000 h the second stage giving a gaseous mixture containing carbon oxide, carbon dioxide, hydrogen, methanol vapours, end water vapours, said methanol and water vapours being then removed from the gaseous mixture, c h a r a c t e r i z e d in that at the first stage a gaseous mix ture being contracted with the copper-containing catalyst contains 5 - 30 vol. % of carbon ox-and 0.3 - 20 vol. % of carbon dioxide, the CO/CO2 volume ratio being 0.25 87 and the H2/(CO+C02) volume ratio being 2 - 3.65, the first stage being performed in one flow-type reactor or in a cascade of flow-type reactors at a space velocity of the initial gaseous mixture equal to 4500 - 100000 h 1, the content of water vapours in the gaseous mixture resulting at the second stage being maintained equal to 0.02 1.38 vol. %.

2. A method as claimed in Claim 1, c h a r a c t e - r i z e d in that the content of water vapours in the gaseous mixture obtained after the first stage is maintained equal to 0.02 - 0.8 vol. % by contacting said gaseous mixture with a copper-containing catalyst, the CO/CO2 vo lume ratio in said gaseous mixture being equal to 2.8-87.

3. A method as claimed in Claim 1, c h a r a c t e r i z e d in that the contact of the initial gaseous mixture with a copper-containing catalyst at the first stage is performed at a space velocity of said gaseous mixture equal to 60000 - 100000 h1

4. A method as claimed in Claim 1, c h a r a c t e r i z d in that the contact of the initial gaseous mixture with a copper-containing catalyst at the first stage is performed at a CO/C02 volume ratio in said gase ous mixture equal to I - 2.8 and a apace velocity of the gaseous mixture delivered for the contact 4500 - 60000 h-