DE4332790A1 - Process for producing methanol - Google Patents

Abstract

To produce methanol from carbon dioxide and hydrogen, the starting substances carbon dioxide and hydrogen are fed to a thermal reactor and are converted into methanol therein at elevated pressure and in the presence of a catalyst. Particularly high conversion rates are achieved by the mixture of carbon dioxide and hydrogen being introduced into the thermal reactor from the top and then passing through the catalyst in the lower section of the reactor. The catalyst used is one based on copper. The residence time in the catalyst depends upon the temperature in the reaction department in such a way that the value of the quotient of residence time sv and temperature T is between 10 and 50, the residence time sv being defined as the gas volume/hour divided by the total amount of gas and the temperature T being measured in degrees celsius. <IMAGE>

Description

TECHNICAL AREA

The invention relates to a method of manufacture of methanol from carbon dioxide and hydrogen, in which a mixture of carbon dioxide and hydrogen a thermi be fed to the reactor and there under excess pressure and converted to methanol in the presence of a catalyst become.

The invention relates to a state of the art, as it is for example from the magazine "HITACHI REVIEW", December 1990, Vol. 39-No. 6, pages 318 and 319, in particular Fig. 8 on page 318, or the publication by N. Kanoun et al. "Catalytic properties of new Cu based catalysts containing Zr and / or V for methanol synthe sis from a carbon dioxide and hydrogen mixture" in CATALYSIS LETTERS 15 (1992), 231-235.

TECHNOLOGICAL BACKGROUND AND PRIOR ART

The carbon dioxide emissions from fossil combustion processes reached a level that global changes in the together the atmosphere and the greenhouse boss can lead to serious climate changes. To Information from the IPCC Commission, which is the World Climate Conference in Geneva in October / November 1990, one would have to  immediately reduce the emission of carbon dioxide by 60% stabilize the carbon dioxide content of the atmosphere.

There are currently only a few applications that use larger amounts need for carbon dioxide and at the same time to reduce emissions contribute to reduction, e.g. B. tertiary oil production (Enhanced Oil recovery). The proposed disposal concepts (Sea, natural gas fields) are hardly re in this century can be and could be z. B. from biological Always remain closed for reasons. On the other hand, there is Converting carbon dioxide into chemical compounds, which are sold in large quantities, e.g. B. as fuel for Transportation or incinerators. To this Compounds primarily belong to methanol too Methane.

In principle, the synthesis of these substances according to fol overall reaction:

CO₂ + 3H₂ → CH₃OH + H₂O
CO₂ + 4H₂ → CH₄ + 2H₂O

In classic chemical process engineering, these reactions only under increased pressure using spe ziale catalysts, e.g. B. rhodium plus metal oxides, cup fer / zinc plus chrome, aluminum, manganese, silver or vanadium or copper / nickel compounds, at temperatures of 230 - Carry out at 280 ° C.

In the above-mentioned publication "HITACHI REVIEW" loc. Cit., Fig. 8, the classic processes for the synthetic production of methane and methanol are summarized alongside two new ones, in which water or hydrogen react directly with carbon dioxide.

In one method ("Photo-electric chemical conver sion ") the water molecules are disso  adorns. The resulting protons (H⁺) reduce this Carbon dioxide to methane or methanol. The one achieved However, efficiency (energy conversion efficiency) is un ter 1%. In addition, very large electrode areas are not necessary are agile.

In the other known method, carbon dioxide is used Hydrogen generated by solar energy catalytically hydrogenated ("hydrogenation"), a process that already at the hydrogenation of carbon monoxide carried out commercially becomes. Besides providing cheap water the necessary high pressures and high pressures Temperatures are the main problems for an economic Application.

Finally, from DE-A-42 20 865 a method for Synthesis of methane or methanol known, which already at low temperatures and low pressures economically is feasible. There is a reaction chamber Mixture of carbon dioxide and one containing hydrogen Quiet substance exposed to electrical discharges.

In the known catalytic processes only vague information about the pressure and temperature in the reaction chamber, Residence times of the mixture in the catalyst (bed) and also about the pretreatment of the catalyst. The vote these process variables are of crucial importance for the achievable methanol yield.

SUMMARY OF THE INVENTION

The invention has for its object a method for To create production of methanol that already at low temperatures and low pressures economically is feasible and enables a high methanol yield.  

This object is achieved in that the a mixture of carbon dioxide and hydrogen from above the reaction space is introduced and then the catalyst penetrates in the lower section of the reaction space that a copper-based catalyst is used, and that the residence time in the catalyst depending on the temperature in the reaction chamber is such that the numerical value of the quotient of residence time sv and tem temperature t lies between the values 10 and 50, whereby the Residence time sv as gas volume / hour divided by total amount of gas is defined and the temperature in Celcius degrees is to be taken.

Applying this teaching makes it possible for the first time to use methanol Manufacture in large quantities within reasonable times and this way the greenhouse gas carbon dioxide, so to speak to recycle. It has proven to be particularly advantageous proven to use a copper-based catalyst the one that previously had a mixture of nitrogen and Hydrogen was conditioned for several hours. Essentially all come in as the catalyst material initially cited publication "Catalytic properties of new Cu based catalysts. . . "The above-mentioned substances in Consider, which are usually traded as pellets.

The starting substance hydrogen can according to one of the today common processes are manufactured, e.g. B. by electro lysis, with nuclear or renewable energy sources Serve energy sources (sun, wind, hydropower, biomass) can. In addition, the hydrogen can be split by Hydrogen sulfide (H₂S) using microwaves, using stil electrical discharges, through thermal dissociation or generated by electrolytic dissociation. Hydrogen sulfide drops at certain chemical Process as a waste product; he is also a By-product of the natural gas processing industry. The Extraction of hydrogen from hydrogen sulfide has to do this  the advantage that its binding energy is less than that of water.

The CO₂ required for the synthesis of methanol falls at Burning fossil fuels as an unwanted compo abent. Before such carbon dioxide with hydrogen mixed and then fed to the thermal reactor, However, it must be from other combustion residues become free. There are already numbers for this purpose rich technologies available that contain either carbon dioxide for food applications (food-grade applications) or chemical applications (chemical-grade applications) ready (see company lettering from ABB Lummus Crest, 12141 Wickester, Houston, TX 77079-9570 U.S.A. "CO₂ Recovery from Flue Gas "undated).

The method according to the invention is described below of an embodiment with reference to the drawing tert.

BRIEF DESCRIPTION OF THE DRAWING

The drawing shows:

Figure 1 is a schematic representation of a device for performing the inventive method for methanol synthesis on a laboratory scale.

Fig. 2 is a diagram to illustrate the influence of temperature and pressure in the thermal reactor on the methanol yield for a given dwell time.

WAYS OF CARRYING OUT THE INVENTION

In the schematic laboratory setup of a device for the synthesis of methanol (CH₃OH), pure hydrogen and pure carbon dioxide are fed via a high-pressure flow controller 1 or 2 to a mixer 3 .

The mixer 3 is equipped with a safety valve 4 . The H₂ / CO₂ mixture passes from the mixer 3 into a cylindrical thermal reactor 5 . A catalyst 6 is loosely heaped up in the bottom region of the reactor 5 . It extends about 1/10 of the container height in the laboratory setup. The catalyst - it comes on the market in the form of pellets - was ground beforehand, and only catalyst material with particle sizes between 250 and 500 µm was used. It is a Cu-based catalyst which is sold under the type designation MK-101 by Haldor Topsoe A / 5 , Nymollevej, DK-2800 Lyngby. The reactor has a Heizvor direction 7th The pressure inside the reactor 5 can be set within wide limits by means of a pressure regulator 8 in the course of the line leading out of the reactor. Tem temperature and pressure in the reactor 5 are detected with a pressure meter 9 and a temperature meter 10 .

From the pressure regulator 8 leads a heated line 11 - the heating is denoted by 12 and prevents the condensation of the methanol generated in the reactor 5 - to a multi-way valve 13 . This multi-way valve allows the gas mixture flowing through line 11 to be fed once to a gas chromatograph 14 or a condensing device 15 . In the gas chromatograph 14 , the composition of the gas mixture leaving the reactor 5 can be determined qualitatively and quantitatively. The methanol 16 condensing at about 60 ° C. is collected in the condensation device 15 . The unreacted H₂ / CO₂ mixture and (in this laboratory setup) is left outside.

In the diagram according to FIG. 2, the dependence of the percent methanol conversion rate CR on the pressure P inside the reactor 5 is plotted at different temperatures. In general, the conversion rate CR increases with increasing pressure. The conversion rate CR also initially increases with increasing temperature; it reaches a maximum at values between 220 and 250 ° C and falls again with increasing temperature.

According to the knowledge of the applicant, opti for this responsible for two competing processes:

Methanol essentially forms in reactor 5 after the following total reaction:

CO₂ + 3H₂ → CH₃OH + H₂O (1)

Methanol synthesis leads to at lower temperatures higher conversion rates; however, the processes then run much slower, and the residence time in the catalyst bed must be increased accordingly. The effect of In contrast, the catalyst increases with increasing temperature towards the specified maximum working temperature (310 ° C for type MK-101).

In the laboratory, the methanol synthesis with H₂ / CO₂-Gemi with molar ratios of 1: 1 to 10: 1, with dwell times between 1/10 and 10 sec, press between 1 and 30 bar and temperatures between 140 and 300 ° C carried out. Optimal yield was obtained with a molar ratio of 3: 1, a residence time of about 1 sec, a pressure of 20 bar and a temperature of 240 ° C. CO₂ sales (Percentage of converted moles of CO₂ supplied Molen CO₂) was about 10%, the selectivity (percentage Share of moles CH₃OH formed to the number converted Mole CO₂) was over 50%.  

The invention has been described above with reference to a laboratory setup and using a specific one Described catalyst. With a large-scale reali The method according to the invention would come from coal dioxide e.g. B. from a plant, as in the ge called company name "CO₂ Recovery from Flue Gas" will.

As hydrogen sources come e.g. B. nuclear or solar powered water electrolysis systems in question. As what Hydrogen sulfide is also an option.

Reference list

1 , 2 flow regulator
3 mixers
4 safety valve
5 thermal reactor
6 catalyst
7 heater
8 pressure regulators
9 pressure gauges
10 temperature meters
11 line
12 line heating
13 multi-way valve
14 gas chromatograph
15 condensing unit
16 methanol

Claims (8)

1. A process for the production of methanol from carbon dioxide and hydrogen, in which a mixture of carbon dioxide and hydrogen are fed to a thermal reactor ( 5 ) and converted there under pressure and in the presence of a catalyst ( 6 ) into methanol, characterized that the mixture of carbon dioxide and hydrogen of is here introduced above in the ther mixing reactor (5) and then the Ka talysator in the lower portion of the thermal reactor (5) penetrates, that such is used copper-based catalyst, and that the Residence time sv in the catalyst as a function of temperature T in the reaction chamber is such that the numerical value of the quotient of residence time sv and temperature T is between values 10 and 50, the residence time sv being defined as the gas volume / hour divided by the total amount of gas and the temperature T in degrees Celsius is to be taken. 2. The method according to claim 1, characterized in that the temperature in the reaction chamber ( 5 ) is kept at values between 220 and 250 ° C. 3. The method according to claim 1 or 2, characterized net that the molar ratio of hydrogen to Carbon dioxide between 1 and 10, preferably by 3. 4. The method according to any one of claims 1 to 3, characterized in that the pressure in the reaction chamber ( 5 ) is kept at values between 1 and 30 bar, preferably 20 bar. 5. The method according to any one of claims 1 to 4, characterized in that the residence time of the mixture in the reaction chamber ( 5 ) is between 0.1 and 10 seconds, preferably before by 1 second 6. The method according to any one of claims 1 to 5, characterized ge indicates that the carbon dioxide by treatment of the exhaust gas from fossil-fired energy generation plants is won. 7. The method according to any one of claims 1 to 6, characterized characterized in that the hydrogen by dissociation is obtained from water or hydrogen sulfide. 8. The method according to claim 7, characterized in that the hydrogen by dissociation of sulfur water fabric by means of microwaves, silent electrical discharge dungs, thermal dissociation and / or electrolyti dissociation is won.