DD151741A5 - METHOD FOR PRODUCING ETHANOL FROM CARBON MONOXIDE AND HYDROGEN - Google Patents

Abstract

The invention relates to a process for the production of ethanol from carbon monoxide and hydrogen over cobalt catalysts. According to the invention, the catalyst contains cobalt as metal or compound nor at least one of the elements gold, silver and rhenium as metal or compound. Preferably, the catalysts are applied to carriers.

Description

Berlin, November 5, 198O 57 591 11

Process for the production of ethanol from synthesis gas

Field of application of the invention;

The present invention relates to a process for producing ethanol by reacting carbon monoxide with hydrogen on a gold and / or silver and / or rhenium-modified cobalt catalyst.

Characteristic of the known technical solutions

Processes for the production of alcohols from synthesis gas are already known.

Thus, it is known that shodium catalyzers with certain promoters direct the Syntbesegasreaktion in the direction of oxygen-containing compounds (DE-AS 25 03 2CXl-). The disadvantage is the relatively high price of rhodium. It is also known that cheaper cobalt catalysts (Fischer-Tropsch) are used in the synthesis gas reaction. However, this results in a variety of products, mainly hydrocarbons and only small amounts of oxygenated compounds.

Although the modification of cobalt catalysts by copper, chromium, zinc, alkaline earth metals, alkali metals, aluminum, rare earths or iron provides a number of products from methanol to butanol, but the ethane oil content is only about 30 wt .- % (DE-PS 857 799, DE-PS 544-665, FR-PS 660 678, FR-PS 1 074 045, FR-PS 2 748 097). Moreover, these catalysts are very sensitive

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Dear, as far as production, commissioning and ongoing operation are concerned. They are therefore usually not durable.

Object of the invention

The aim of the invention is to provide a process for the production of ethanol from synthesis gas with high selectivity to robust and durable catalysts.

Loan of the essence of the invention;

The invention has for its object to find suitable catalysts for the process.

It has now been found that the selectivity of ethanol over cobalt catalysts is considerably increased by the addition of the promoters gold and / or silver and / or rhenium.

The invention therefore provides a process for preparing ethanol from carbon monoxide and hydrogen over cobalt catalysts, characterized in that the catalyst contains, in addition to cobalt as metal or compound, at least one of the elements gold, silver and rhenium as metal or compound. Preferably, the catalyst contains gold other than cobalt, but especially the combination of gold / silver. The finding that the selectivity of the synthesis gas reaction to ethanol is significantly increased by the addition of said elements - with good Haumzeitleistung - is extremely surprising and unpredictable, since gold

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and silver are known as catalyst poisons in hydrogenations, while hydrogenations with rhenium generally go as far as the hydrocarbon stage.

In addition to ethanol, which is produced in high selectivity in the process according to the invention, small amounts of methanol, propanol and butanol and some acetaldehyde are formed as by-products. ,

The catalysts for the process of the invention are preferably prepared by impregnating a catalyst support with a solution of cobalt, gold and / or silver and / or rhenium salts and then drying, wherein the salts can be applied together or in succession. Suitable salts are all soluble cobalt, gold, silver and rhenium salts, e.g. As the chlorides, bromides, nitrates, acetates, propionates, lactates, citrates of cobalt, the chlorides, acetates, propionates of gold, as well as aurates (such as barium acetoaurate or barium propionoaurate), further the acetate, propionate, butyrate, lactate and nitrate of silver , as well as rhenium heptoxide, perrhenates and rhenates.

The salts mentioned are dissolved in suitable solvents. -

Suitable solvents are, for example, water, aqueous carboxylic acids and anhydrous carboxylic acids, in particular water and acetic acid.

As the carrier, the usual carrier materials with different specific surface areas and pore volumes can be used. However, carriers are using

specific surface of 50 to 1000 m. 7g and pore

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Volumes above 0.3 ml / g preferred.

Suitable z. As silicic acid, natural or synthetic silicates of elements of the II to VIII. Group of the Periodic Table (for example, the silicates of magnesium, aluminum or manganese), also alumina, thorium oxide and spinels.

However, it is also possible to prepare suitable catalysts by precipitation of cobalt oxide together with gold and / or silver and / or rhenium or by subsequent impregnation of cobalt oxide with salts of gold and / or rhenium.

Preferably, one reduces the catalyst before use with a suitable reducing agent such as hydrogen, carbon monoxide or methanol, advantageously, in the synthesis gas reactor itself. In general, operates below 400 g, preferably between 200 and 3OO ⁰ C. It is often expedient, the reduction not with the undiluted reducing gases, but with an additional proportion of inert gases such . As nitrogen, carbon dioxide and noble gases to perform.

The concentration of cobalt in the catalysts can be varied within very wide limits, it being possible to use carrier-free cobalt compounds, for example cobalt oxide, as well as supported catalysts having at least 1% by weight of cobalt.

The concentration of the promoters is chosen as a function of the cobalt concentration, in such a way that per mole of cobalt from 0.001 to 0.5 mol, preferably 0.02 to 0.2 mol

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each individual promoter.

To carry out the process according to the invention, gas mixtures which consist entirely or predominantly of carbon monoxide and hydrogen and optionally may additionally contain other components, such as nitrogen, argon, carbon dioxide or methane, are passed over the catalyst. The volume ratio of carbon monoxide to hydrogen can be varied within wide limits. Preference is given to ratios between 5: 1 and 1: 5, in particular 3: 1 to 1: 3. The reaction temperatures are generally between 175 and 375 C, preferably between 200 and 350 ⁰ C.

The reaction pressures are between 1 and 300 bar, preferably between 20 and 200 bar.

For the implementation of the method, the gas phase is preferred. For this, the conventional pest bed reactors can be used. Furthermore, reactors with a moving catalyst bed or fluidized bed reactors are also suitable.

But you can also carry out a reaction of the synthesis gas in the presence of the solid and finely divided catalyst suspended in inert solvents and / or reaction products.

A particularly preferred embodiment of the invention consists in carrying out the reaction in a gas-phase recycle gas apparatus, in which, after separation of the condensable reaction products, the unreacted gas mixture is returned to the reactor.

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This procedure is particularly economical and makes possible by dilution of the fresh gas with the recycled in the circulation hydrogen-poor residual gas higher. Reaction temperatures and thus higher space-time yields with unchanged selectivity. As Ereisgasapparaturen. in this case, those with inner or outer gas circulation come into consideration. ,.

Exporting to I

The invention will be illustrated by the following examples, which are not intended to be limiting in any way.

Examples General experimental description;

The apparatus consists of a heated reaction tube of 20 cm length and 14 mm inner diameter of corrosion-resistant steel and a centrally mounted sleeve for temperature measurement with a thermocouple.

This x 'reactor is located in a heating bath of Woodscheia metal, in which at the same time a preheating of Syntfaesegases is made. The l'emperature in the reactor as well as the metal bath can be tracked on a recorder. For the case of catalyst overheating, an N 2 purge is present.

The reduction of the freshly filled into the reactor

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Catalyst is in proportion with a Hp / Fp mixture

ο 1: 4 at normal pressure and 300 C made.

The synthesis gas mixture (CO: L = 1: 1) is taken from a compressed gas bottle, wherein the amount of the pressure drop, measured by a Feinmeßmanometer, is determined.

For pressure adjustment and pressure maintenance provides a pressure regulator. Before this, the condensable fractions of the reaction mixture are liquefied in a separator and fed to the GC analysis.

Following this procedure, the catalysts described below are tested. The following table summarizes the experimental conditions and the tree-time yields of oxygen-containing Cp products per liter of catalyst per hour and the selectivities for ethanol.

B) Catalyst description

The percentages given are always by weight.

example 1

There are 40 g of a commercially available silica gel carrier

with a specific surface area of 400 in / g, a pore volume of 1.2 ml / g and a bulk density of 0.4 g / ml with a solution of 16.3 g of cobalt acetate, 3t5 S barium acetoaurate and 0.5 g of silver acetate in one Soaked mixture of 35 ^ l of water and 5 ¹ ^ l of acetic acid and dried at 60 C in a vacuum of 250 mbar. The catalyst contains 8.4% Co, 2.8% Au, 0.7% Ag and

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1% Ba in the form of acetates

Example 2

35 ο <3 s in Example 1 mentioned carrier are impregnated with a solution of 16.3 g of cobalt acetate, 1.7 S Bariumace toaurat and 2.0 g Rheniuiaheptoxid in 43 ml of a 7% acetic acid and at 110 C under atmospheric pressure: dried. The finished catalyst contains 9.4 % Co, 1.5 % Au, 3.7% He and 0.6 % Ba.

Example 3

35 S cles mentioned in Example 1 carrier are impregnated with a solution of 16.3 g of cobalt acetate and 2 g of rhenium heptoxide in 43 ml of a 7 / acetic acid and dried at 80 ⁰ C in a stream of nitrogen. The finished catalyst contains 9.5 % Co and 3.8% Re.

Example 4

There are 40 g of a commercially available silica carrier (250 m / s surface, 0.8 ml / g pore volume, 0.7 ml / g bulk weight) with a solution of 16.3 g of cobalt acetate, 1.9 g of gold acetate in 40 ml of a 12 5% acetic acid in two stages, drying to constant weight after each impregnation. The finished catalyst contains 8.3% Co and 2 % Au.

C) Yery search results

The test results are shown in the following table:

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examples print temperature- Hem- Space-time yield (g> i Etha Per Bu Selek sp. (bar) pe overall Metha nol pa ta tivi ra vibration nol nole nole * speed to ( ⁰ C) (Nl / l "h: Etha 16.5 4.5 0 nol 1 100 280 1200 7.2 33 9.9 1.6 60 2 80 275 6000 9.9 2715 6.7 0.7 62 3 100 260 8050 8.5 19.7 5.6  1.3 65 4, 150 280 7000 14.6 12:04 12:03 0.0 ' 52 encryption 100 280 6500 0.5 gl. examples sp. lcet- aldehyde-   hyd 0.05 O - O 1.0 1 0.03

Definition of selectivity: Mol CO converted to eth anole

Mol CO total implemented

$% Comparative example with pure cobalt; Catalyst otherwise prepared as in Example 1.

The remaining reaction products consist of saturated and unsaturated hydrocarbons.

Claims (2)

-ί-- 222 5r 11. 1980 57 591 11 Claim for invention Process for the preparation of ethanol from carbon monoxide and hydrogen over cobalt catalysts, characterized in that the catalyst contains, in addition to cobalt as metal or compound, at least one of the elements gold, silver and rhenium as metal or compound. 2. Method according to item 1, characterized by,,. that the catalysts are applied to carriers.