DE2154074B2 - Process for the production of methanol by reacting carbon monoxide and hydrogen over a catalyst and catalyst composition for carrying out the process - Google Patents

Description

It is known that methanol can be produced by reacting carbon monoxide and hydrogen over catalysts to produce which contain a metal oxide. A commercially available catalyst that can be used for this purpose contains zinc oxide and another metal compound as a promoter. For example, in US-PS 29 04 575 described a suitable catalyst which contains a mixture of zinc oxide and chromium oxide However, the production of methanol using such catalysts has the disadvantage that high temperatures in the range from about 350 to 400 ° C and high pressures in the range from about 277 to 380 bar are absolutely necessary to achieve good yields of methanol. Attachments for working at however, such high temperatures and pressures require a large capital outlay, and besides the operating costs are also very high.

It has been known for a long time that you can get through Combination of a hard reducible metal oxide with copper oxide in some cases quite effective Can produce catalysts. For example, in US-PS 18 18 165 combinations of copper oxide and zinc oxide are described as catalysts for the production of methanol. From US-PS 16 25 924 are other metal compounds known which can be combined with copper oxide, in particular Metal halides. The US-PS 17 91 568, 20 61 470 and 04 575, however, describe earth metal oxides as Katafysatorkoinponentea In US-PS 17 07 331 Fluorides of rare earth metals are used as a catalyst component recommended, and US-PS 33 26 956 deals with the utility of chromium oxide. A more detailed discussion of the prior art dealing with copper-containing catalysts for the production of methanol can be found in the well-known book "Catalysis", Volume III, "Hydrogenation and Dehydrogenation, ”edited by Paul H. Emmet

ι ο (1955), Chapter 8, by G. Natta, "Synthesis of Methanol", being found. However, such catalysts have the disadvantage that when used relatively low temperatures only moderately high to low yields of methanol can be obtained.

For example, the catalyst described in US Pat. No. 3,326,956, which contains oxides of copper, zinc and chromium, certainly still has the highest activity of the known copper-containing catalysts. At an operating temperature of 250 to 260 ^° C. and a pressure of about 43 bar absolute, however, the yield of methanol when using this catalyst is only about 036 to 0.61 kg per liter of catalyst per hour.
Surprisingly, it has now been found that these difficulties in the manufacture of methanol can be eliminated by using a new type of catalyst.

A major advantage of the method according to the invention is the relatively very high activity of the catalyst used. This high activity is reflected in the relatively high degree of conversion of the Reactant and in the ability to work even at relatively low temperatures and pressures work. Another major advantage of the invention Process is that relatively high methanol yields can be achieved and that in spite of the formation of undesired by-products is practically negligibly small The inventive method for the production of methanol, wherein carbon monoxide and hydrogen are reacted on a catalyst that contains the oxides of copper and zinc, is characterized by that m ^ n the implementation in the presence of a Carries out catalyst, in addition to copper and zinc oxide corresponding to a weight ratio of Copper to zinc in the range of 1: 0.05 to 1: 1 in addition to 1.0 to 25 percent by weight didymoxide (i.e. Oxides of a mixture of at least two rare earth metals, with the exception of cerium, in their in the Naturally occurring proportion), calculated as metal and based on the total catalyst composition made of copper, zinc and didymium oxide. The one used in the process according to the invention novel catalyst can be used as a mixture

γ, of copper oxide and zinc oxide, which is modified by the addition of didymium oxide.

The term "dydym" is often used to denote a mixture of all of them rare earth metals, with the exception of cerium, in which

The proportions also occurring in nature contains. This definition is in accordance with the information in the known monograph von Kirk-Othmer, "Encyclopedia of Chemical Technology", 2nd Edition, Volume 4, page 843. For example

(i5 Didymoxide mixtures contain the following oxides of rare earth metals in the specified proportions: La2U3 up to 80 percent by weight; Nd2Ü3 up to 80 percent by weight; ΡΓβΟη up to 40 percent by weight;

Sm ₂ O ₃ up to 30 percent by weight; Gd ₂ O ₃ up to 30 percent by weight and other rare earth metal oxides up to 30 percent by weight Ia typical didymic oxide mixtures - the various earth metal oxides are present, for example, in the following weight ratios: La ₂ O ₃ 40 to 50 percent by weight; Nd ₂ O ₃ 25 to 40 percent by weight; PreOn 5 to 15 percent by weight; Sm ₂ O ₃ 2 to 10 weight percent; Gd ₂ O ₃ 2 to 10 percent by weight and other rare earth metal oxides 1 to 10 percent by weight.

In the present description and in the patent claims, however, the term "didymium" is understood in a broader framework, and it is intended to include any mixture which contains at least 2 rare earth metals, but practically no cerium, in naturally occurring proportions The term "rare earth metals" encompasses 15 elements of the periodic system with the atomic numbers 57 up to and including 71. Therefore, one or more rare earth metals in the didymium components used according to the invention may have been completely or partially removed from a naturally occurring mixture, with the remaining rare earth metals in spite of the fact that they are present in this mixture in a ratio to one another, as also occurs in nature. In many examples of didymium mixtures, lanthanum and neodymium are the most common rare earth metals, and then only smaller proportions of praseodymium and samarium are present. Such didymium mixtures have, for example, the following composition: La ₂ O ₃ 45 percent by weight; Nd2O ₃ 38 weight percent; Pr & Oii 11 weight percent; Sm ₂ O ₃ 4 percent by weight and other rare earth metal oxides 7th percent by weight. In yet other didymium mixtures, neodymium and praseodymium are mainly present, and these then contain only smaller proportions of the other rare earth metals. Such didymium mixtures have, for example, the following typical composition: La2O ₃ less than 1 percent by weight; Nd ₂ O ₃ 72 weight percent; PrtOn 27 percent by weight; Sm ₂ O ₃ less than 1 percent by weight and other rare earth metal oxides only in traces. Another typical didymium mixture has the following composition, for example: La ₂ O ₃ 70 percent by weight; Sm ₂ O ₃ 15 weight percent; Gd ₂ O ₃ 13 percent by weight and other rare earth metal oxides 2 percent by weight.

Although the mechanism of the special influence of didymoxide is not known with certainty, it can however, it is found that the presence of didymium oxide has a significant influence on that a high activity catalyst for the production of methanol from carbon monoxide and hydrogen or the corresponding precursors can be obtained at relatively low temperatures and pressures can. For example, catalysts show which copper oxide, zinc oxide and only individual rare earth metals contain, at a temperature of 300 ° C and a pressure of 53 bar absolutely only one Activity that the methanol yield is about 0.40 to 0.49 kg per liter of catalyst per hour. Such Catalysts show only a slight improvement in relation to a catalyst that contains only copper oxide and zinc oxide, as the last-mentioned catalyst among comparable Reaction conditions gives a methanol yield of 0.32 kg per liter of catalyst per hour. if however, a catalyst is used which consists of copper oxide, zinc oxide and didymium oxide the methanol yield is 1.01 kg per liter of catalyst per hour; that is, the methanol yield is practical twice as high as can be achieved with the known catalysts.

The catalyst preferably contains didymoxide in an amount in the range from 4 to 15 percent by weight, calculated as Metal! and based on the total catalyst composition of copper oxide, zinc oxide and ίο didymoxide.

Also the ratio of copper oxide and zinc oxide in

the catalyst can be varied. The catalyst used preferably contains copper oxide and Zinc oxide corresponding to a weight ratio of copper to zinc in the range from 1: 0.1 to 1: 1.

The process according to the invention is carried out in the vapor phase, carbon monoxide or a mixture of carbon oxides with hydrogen being intimately mixed in the presence of the catalyst at such a temperature and pressure that a reaction between carbon monoxide and hydrogen takes place. The temperature and pressure used are not critical. In general, carbon monoxide and hydrogen are allowed to react with one another, preferably at a temperature in the range from 200 to 350 ^° C. and in particular in the range from 225 to 300 ^{° C.}

It is believed that methanol formation is likely to occur in the process of the present invention according to the following reaction equation:

CO + 2 H ₂ ^ CH ₃ OH

Instead of carbon monoxide and pure hydrogen, however, other carbon oxides and hydrogen-containing Compounds are used as precursors for carbon monoxide and hydrogen. For example the following reactions also take place at elevated temperature:

CO + H ₂ O - * CO ₂ + H ₂
CO ₂ + K ₂ -CO + H ₂ O

A mixture of an excess of carbon monoxide can therefore also be used for the production of methanol and water or a mixture of carbon dioxide with

an excess of hydrogen can be used. The use of such mixtures of precursors for carbon monoxide and hydrogen, however, offers no particular advantage. Be accordingly according to the invention, carbon monoxide and hydrogen themselves are preferred for the production of methanol used. In some cases, however, the activity of the copper oxide, zinc oxide and didymoxide containing Catalyst by the presence of some carbon dioxide in the reaction mixture of carbon monoxide and hydrogen are increased. For this reason it can be advantageous when in the gaseous Some carbon dioxide is also present in the reaction mixture, for example in amounts up to about 50 percent by weight, based on the total carbon oxide-containing mixture.

On the basis of the above stoichiometric reaction equations, 2 moles of hydrogen must also be included react one mole of carbon monoxide to form methanol. If carbon dioxide is present, they show

b5 above reaction equations that 3 moles of hydrogen per mole of any carbon dioxide present are required to form methanol! in practice however, other stoichiometric quantity

Ratios of the reaction components give satisfactory results and are therefore under certain Circumstances preferred. In general, molar ratios of hydrogen to carbon oxides are about 2: 1 to 10: 1 satisfactory, the best yields being achieved when the hydrogen in the Excess over the stoichiomei.nsch required Amount is used.

The working pressure at which the reaction is carried out depends mainly on the temperature used and also on the amount and the molar ratio of the reactants. As is customary in such reactions in the gas phase, the total pressure corresponds approximately to the sum of the partial pressures of the individual reaction components used. It can be seen from the reaction equations given above that the production of methanol is favored by high pressures. For economic reasons, however, it is more often advisable to carry out the relevant implementation of Yei lower pressures. It has already been pointed out above that the high activity of the catalysts used according to the invention, which contain copper oxide, zinc oxide and didymium oxide, makes it possible to carry out the reaction even at relatively low temperatures, which results in significant economic advantages. Although the catalyst according to the invention can be used with advantage at pressures in the range from 2 to 345 bar absolute, it is particularly expedient to carry out the reaction at a pressure in the range from 35 to 104 bar absolute.

The process according to the invention is advantageously carried out continuously at space velocities in the range from 5000 to 50,000 parts by volume of the reactants per part by volume of catalyst per hour. each measured under normal conditions at a pressure of 1 bar. and a temperature of 0 ^° C. If desired, however, lower or higher space velocities can be used.

According to one embodiment of the process according to the invention, in addition to the reactants, an inert diluent is also present, for example argon, helium, nitrogen or methane or other such substances which are gaseous at the reaction temperature. Such diluents do not damage the catalyst. Sulfur and other catalyst poisons and reactive substances, v _; 'ie oxygen, however, would impair the desired conversion and their presence is therefore appropriately avoided. According to a preferred embodiment of the process according to the invention, however, the reactants and the catalyst are reacted with one another in virtually the absence of added inert diluents and in an inert reaction environment.

The inventive method can be carried out in batches by, for example, a Autoclave or a corresponding pressure reactor charged with the reactants and the catalyst and then holding the reactor at the reaction temperature until the reaction is complete. Preferably however, the process is carried out continuously, for example by passing the reactants through a tubular reactor which tien contains catalyst and is kept at the relevant llmset / ungsteniperatur. According to a Another embodiment can also be a respondent be added in small portions to the reaction mixture, for example by adding the Mixture passed through a reactor suitable for continuous operation and then a

-, Reaktton component at certain time intervals do adds to this mixture But it is quite possible also to mix the total amount of the reactants with one another at the beginning of the reaction.

After completion of the implementation, the obtained

ίο the product mixture is separated and the methanol is isolated therefrom by means of conventional measures, for example by selective condensation, selective adsorption or other appropriate separation processes.
A particular advantage of the invention

ι -, method consists in the fact that it can be carried out at practically the same pressure at which the as Starting components used gases hydrogen and carbon monoxide through non-catalyzed partial combustion generated by hydrocarbons, preferably with the addition of steam. The one for one such partial combustion required oxygen is either in practically pure form or as air supplied, the additional oxygen has been added. In some cases, oxygen cannot be used either

2 "> enriched air can be used. The pressure can range from atmospheric pressure to about 121 bar vary. However, the pressure is preferably in the range from 20 to 61 bar. The combustion gases are cooled and then it becomes the soot and

if desired, other impurities are removed. After converting part of the carbon monoxide with water into hydrogen and carbon dioxide, it can do so obtained gas can be brought into direct contact with the catalyst according to the invention, which

r> Contains copper oxide, zinc oxide and didymium oxide.

The invention also relates to those used to carry out the methanol synthesis new catalyst compositions of copper oxide, zinc oxide and didymium oxide according to claim 3.

4M In the finished catalyst must be copper, zinc and Didym exist in the oxide form. Compounds can also be used for the preparation of the catalyst which can easily be converted into the corresponding oxides, for example the corresponding

4> Metal carbonates, because such metal carbonates leave for example by pretreating the initially prepared catalyst in the corresponding Transfer oxides.

Such a catalyst combination is preferably

iii composition thereby established. that one is concerned Metals from a solution of their nitrates by mixed precipitation in the form of one or more Compounds precipitates that can easily be converted into oxides. For example, you can use a mixture of the

Γ) Nitrates are mixed with a solution of a carbonate, which then causes the metals in question to be precipitated together in the form of their carbonates. This precipitation is preferably carried out at a temperature in the range of 85 to 90 ⁰ C. The precipitation

w) consists of a mixture of the respective carbonates, basic carbonates and hydroxides. He is separated, so washed until it contains no more electrolytes, then dried and then calcined at a temperature in the range of about 200 to 400 ⁰ C.

H'i, and preferably calcined in the range of about 250 to 300 ⁰ C. The calcined material can then be formed into any shape, for example by pelletizing under pressure using

Graphite as a lubricant. In some cases, the oxide mixture is pretreated in order to increase its activity raise. Such a pretreatment can be carried out by a stream of hydrogen or conducts a stream of hydrogen and carbon monoxide over the catalyst

In some cases it may be useful to support the catalyst on an inert, neutral carrier apply, for example silica or aluminum oxide. However, the catalyst is preferably ι ο used without such a carrier

The examples illustrate the invention.

example 1

A gaseous mixture of hydrogen and carbon monoxide in a molar ratio of 2: 1 is ^{fed into a reactor for continuous conversion at a temperature of 270 °} C. and a pressure of 53 bar absolute. In the reactor there is a catalyst composition which contains 4 parts by weight of 2 » didym ( Composition: La2O3 45 percent by weight; NdA 38 percent by weight; ΡΓβΟιι 11 percent by weight; Sm2O3 4 percent by weight; other rare earth metal oxides 2 percent by weight), 40 parts by weight of copper and 18 parts by weight of zinc, each as oxides, and which has been pretreated with hydrogen The weight ratio of Cu to Zn (calculated as metals) is 2.2. The reactants are ji at a space velocity of 10,300 parts by volume; Part of the volume of catalyst passed over the catalyst per hour, measured under standard conditions. The carbon monoxide used is converted into methanol in an amount of 17.5 percent by weight

The reactor effluent is collected and condensed and the liquid product separated off is analyzed The yield of liquid product is 0.812 kg per liter of catalyst per hour and it contains 99.1 percent Methanol. The concentration of organic impurities is less than 0.9 percent.

Example 2

The procedure of Example I is repeated using a gas mixture containing 66.1 Weight percent hydrogen, 19.5 weight percent carbon monoxide and 14.4 weight percent carbon dioxide contains. The same catalyst is used as in Example 1, and one works under the same reaction conditions. 21.0 percent by weight of the carbon oxides used are in methanol converted The yield of liquid product is 1.05 kg per liter of catalyst per hour, and this liquid product consists of 92.9 percent methanol. The concentration of organic impurities is less than 0.1 percent

Example 3

A number of test runs are carried out, the copper-zinc-didymium oxide catalyst according to the invention being compared with catalyst mixtures which each contain only two of the catalyst components in question. For comparison purposes, commercially available catalyst compositions are also tested. The copper-zinc-didymium catalyst according to the invention shows an increased activity at 300 ^° C. and is also ^{significantly more effective at 250 °} C. than the other catalysts, which only have a relatively low activity at this temperature. The results of these runs are summarized in Table I below

Dragonfly i temperature Hourly Conversion Ethanol Composition. Weight percent - 98.2 - 93.0 - 92.6 - 97.6 Ethanol - 3.5 - 1.3 - 1.1 higher
organic 0.2 - 1.4 - water catalyst Gas room
speed lung Bulge Methanol 99.6 traces <0, l Connection - age - <0, l ⁰ C l / l / hx 10 ^! Weight kg / l / h (iew ilN- percent M'iliiillnis McUiIIc (respectively as oxides 0.2 1.1 0.3 present) 300 10.9 20.5 1.01 98.4 traces traces traces Cu-Zn-Di 250 11.5 13.4 0.69 -100 1.2 - 1.2 (40: 18: 4) 300 10.8 8.2 0.40 97.6 - - Cu-Di 250 10.8 ~ 0 traces traces 1.8 (58:21) 300 8.0 2.9 0.12 - - Zn-Di 250 8.0 ~ 0 traces 3.3 (49: 25) 300 13.9 5.5 0.32 - Cu-Zn *) 250 11.0 ~ 0 traces 4.7 (47: 20) 350 7.6 3.6 0.13 - Cu-Cr **) 250 7.6 ~ 0 traces 1.3 (36:21) 300 10.4 13.4 0.63 0.3 Cu-Zn-Cr ***) 250 10.4 7.2 0.34 (41: 14: 4)

*> The exothermic methane formation reaction takes place at temperatures above 300 ° C. ") Commercially available copper chromite analyzer (according to Harshaw). ***) Catalyst, manufactured! according to U.S. Patent 3,326,956 (ICI).

Example 4

10

Another series of tests was carried out, with the didymium content of the copper oxide and catalyst containing zinc oxide was varied in the range of 0 to 23.8 percent by weight. Furthermore the same procedure and the same reaction conditions were used as in Example t. The experimental results obtained are summarized in Table II below. These numerical values confirm that already 4 percent by weight Didymoxide are sufficient to obtain a catalyst with respect to the conversion of Carbon oxides and hydrogen to methanol is extraordinarily active and the generation is very high Methanol yields enabled.

Table II temperature
° C Hourly gas
Space velocity
speed x 10 ³ conversion
Weight percent Bulge
kg / l / h Weight percent
Uidym
(Cu / Zn ratio.
each as oxides
present) 250 -14 0 traces 0 (47: 20) 300 13.9 5.5 0.32 0 (47: 20) 250 10.4 13.8 0.65 0 (44: 16) 300 10.9 20.5 1.01 4.0 (44: 16) 250 9.7 23.5 1.07 8.0 (40:18) 300 10.6 15.2 0.72 13.0 (38: 17) 300 10.6 12.5 0.64 23.8 (30:11) Example 5

A number of test runs were carried out, wherein the ratio of copper to zinc in the catalyst according to the invention was varied while the didymium content was kept constant at 4 percent by weight, the rest of the procedure were and the working conditions are the same as described in Example 1.

The results obtained are summarized in Table III below in J5

The experimental data confirm that the catalysts of the invention in a wide range of Ratios of copper to zinc are active, with the best results being obtained when the copper to zinc ratio is at least 1: 1.

Table III temperature Stiindl. Gas- conversion yield Cu / Zn ratio, ii.s. Space velocity ⁰ C speed X 10 " ³ Weight percent kg / l / h 275 11.2 15.7 0.796 68/5 300 15.7 14.8 1.037 60/9 270 ! 0.3 17.5 0.812 40/18 275 * i, 5 16.6 0.634 30/30 275 7.7 5.1 0.180 21/41 Example 6

A number of test runs were carried out, the catalysts containing individual earth metal oxides and not a mixture of didymium oxide. in the Otherwise, the working conditions were the same as the catalyst composition according to the invention Contains copper oxide, zinc oxide and didymium oxide in combination, with respect to the methanol production one This shows superior catalytic effect

described in example 1. The 65 achieved in particular for a reaction temperature of

Results are summarized in Table IV below- 250 ^° C to where the remaining catalysts are essential

collectively show lower catalytic activities. These test results confirm that the invented

11

Table IV

catalyst Temperature hourly Conversion Melhanol Composition, weight percent water Gas room lung Training Methanol ethanol higher speed organic age Associate. Weight "C l / l / hx OK ^! Weight kg / l / h relationship percent Metals (each as oxides present)

Cu-Zn-Nd
(40: 18: 4)

300 250 300 250 300 250 300 250 300 250

10.9

11.5

5.5

7.6

11.1

11.4

8.9

9.3

13.9

14.0

20.5 1.01 98.4 0.2 1.1 0.3 16.4 0.69 -100 traces traces traces 10.0 0.49 97.4 0.2 !, 9 0.5 13.3 0.45 99.3 0.2 0.2 0.3 8.1 0.40 98.2 0.9 traces 0.9 3.2 0.33 98.7 0.2 traces 1.1 10.3 0.47 97.3 1.3 - 1.4 6.2 0.25 97.4 0.4 0.8 1.4 5.5 0.32 93.0 3.5 0.2 3.3 -0 traces - - - -

Claims (3)

Patent claims: 1. Process for the production of methanol, wherein carbon monoxide and hydrogen over a catalyst which contains the oxides of copper and zinc, characterized by that the reaction is carried out in the presence of a catalyst which, in addition to copper and Zinc oxide corresponding to a weight ratio of copper to zinc in the range from 1: 0.05 to 1: 1 additionally 1.0 to 25 percent by weight didymoxide (i.e. oxides of a mixture of at least two rare earth metals, with the exception of cerium, in their naturally occurring proportions), calculated as metal and based on the total catalyst composition of copper, Zinc oxide and didymium oxide 2. The method according to claim 1, characterized in that the reaction is carried out in the presence carries out a catalyst, the 4 to 15 weight percent didymoxide and copper and Zinc oxide corresponding to a weight ratio of copper to zinc in the range from 1: 0.1 to 1: 1 contains 3. Copper oxide / zinc oxide catalyst composition for carrying out the process according to either of claims 1 and 2 having a weight ratio of copper to zinc in the range of 1: 0.05 to 1: 1, the additional 4 to 15 percent by weight Didymoxide (oxides of a mixture of at least two rare earth metals, with the exception of of cerium, in its naturally occurring proportion), calculated as metal and referenced on the total catalyst composition of copper, zinc and didymium oxide