DD201671A5 - PROCESS FOR PREPARING MIXTURES OF METHANOL AND HIGHER ALCOHOLS - Google Patents

Abstract

The invention relates to a process for the preparation of mixtures of methanol and higher alcohols, which can be used in particular alone or in admixture with gasoline as propellants. It is characterized by reacting H 2 and CO, optionally in the presence of CO 2, with a molar ratio H 2: CO of 0.1 to 20, preferably 0.5 to 5 at a temperature of 300 to 500 degrees C. , preferably 350 to 450 degrees C under a pressure of 2000 to 16000 kPa in the presence of a catalyst based on chromium, zinc and at least one alkali metal, wherein the weight ratio of Zn to Cr, calculated as oxides, 5: 1 to 1: 1 and the alkali metals, calculated as oxides, are present in an amount of from 0.5 to 5% by weight, based on the total weight of the elements, calculated as oxides.

Description

Process for the preparation of methanol and higher alcohols

Field of application of the invention

The invention relates to a process for the preparation of methanol and higher alcohols and the mixtures obtained by this process. Inabesondere aind mixtures of the invention are suitable as a substitute for gasoline and can be added to this as a fuel for internal combustion engines in various amounts.

Characteristic of the known technical solutions

It is known that methanol is never used alone in admixture with gasoline and mixtures of methanol and higher alcohols are made to be added to gasoline. The reason for this lies in the fact that a certain amount of water is always present in the gasoline, which usually comes from the washing out of the lines in the refineries or from atmospheric moisture. When methanol is used alone, it mixes with the water present in the gasoline and water separates from the _3enzin} so that two layers are formed in the tanks of motor vehicles, namely a gasoline layer and a layer of methanol and water. Therefore, the engines run with great difficulty only when the layer of methanol and water is supplied in place of the gasoline.

It is known that the presence of higher allows methanol to be solubilized in the presence of water in the gasoline, giving rise to completely homogeneous mixtures.

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With the hitherto conventional mixtures containing higher alcohols generally 10 weight-IOE, it is possible to tolerate water contents of 1000 ppm water, at -18 ⁰ C at a ratio of alcohols to hydrocarbons of 20: 80. In the same ratio of 20: 80 and at -18 ⁰ G, it is possible using the mixtures of the invention to tolerate water contents of 2 500 to more than 5, 000 ppm.

There are numerous known processes for the preparation of methanol mixed with higher alcohols. However, they have the disadvantage that relatively high working pressures are required, which are generally between 17,000 and 35,000 kPa and this is obviously a disadvantage both in terms of investment costs and running costs. On the other hand, it has been found from the literature that it is necessary to work under high pressures. 2. B. Liatta in "Catalysis", vol. V, Reinhold Publishing Corp., £ iew York (1957) at page 136, clearly states that, because of the substantial decrease in volume which occurs in the formation of higher alcohols, the synthesis under Obviously, the higher the alcohols should be made, the more pressure should be exerted to favor their formation. Hatta's comments are supported by Table VII of a publication published by? .G. Laus: presented at the International Symposium on Alcohol Fuel Technology in Wolfsburg from 21 to 23 November 1977 entitled "The catalytic production and mechanism of formation of methyl fuel" according to which the quantity of isobutanol was 1.86 % 390 ⁰ G and 17 26O k? A (176 μg / cm ² ) to 6.14 %

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at 390 ⁰ G and 2β 91 β kPa (302 kg / cm ² ) is increased.

From the state of the art, it is clear that the formation of mixtures of methanol and higher alcohols is only possible when working under high pressures, according to the rules of thermodynamics. "

Object of the invention

The object of the invention is to provide an improved process, with the use of lower pressures mixtures of methanol and a considerably larger. Share of higher alcohols can be produced.

Presenting the essence of the Brf charge

The invention has the object augrunde to find a catalyst with which it is possible to produce a mixture of methanol and higher alcohols at lower pressures »

According to the invention, the process for forming a mixture of methanol and higher alcohols containing 35 to 75% by weight of methanol on an anhydrous basis is characterized by introducing into a reaction zone comprising a catalyst based on chromium, zinc and at least an alkali metal, hydrogen and carbon monoxide and optionally carbon dioxide and inert constituents having a ratio H ₂ : CO between 0.1 and 20, preferably between 0.5 and 5 at a temperature in the range of 300 to 500 ⁰ G, preferably between 350 and 450 C under a pressure between 2,000 and 16,000 kPa, preferably between 5,000 and 13,000 kPa initiates.

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The catalyst used according to the invention consists, as stated above, of chromium and zinc and at least one alkali metal and the weight ratio of Zn to Gr, calculated as oxides, is preferably between 5: 1 and 1: 1. The alkali metal is preferably potassium and the amount of alkali metals, calculated as oxides, is 0.5 to 5% by weight, based on the total weight of the elements, calculated as oxides.

The preparation of the catalyst can be carried out in various ways.

For example, precipitation from solutions of chromium and zinc nitrate with MHo or the action of chromic acid on aqueous suspensions of zinc oxide should be mentioned. The catalyst can be dried or atomized in an oven and then fired. The catalyst may be extruded, pelletized or granulated into products of different shape and size depending on the characteristics of the reactor in which it is to be used, the porosity being controlled accordingly *

The alkali metals are introduced by impregnating a preformed Zn-Cr catalyst with preformed solutions of hydroxides, carbonates, acetates, formates, and other organic salts. Optionally, the catalyst may also be prepared by reacting zinc oxide with mixtures of bichromates of ammonium or alkali metals in such a ratio that the resulting catalyst contains the desired amount of alkali oxides.

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Particularly careful should be carried out the reduction of the catalyst, which is carried out before or after the introduction of the alkali metals, by diluting the reducing gas, which is preferably hydrogen, with an inert gas such as nitrogen and controlling the temperature of the catalyst bed so that they never go beyond 350 ⁰ G.

It is also an object of the present invention to provide mixtures of methanol and higher alcohols for aeration au. The mixtures according to the invention have a methanol content of between 35 and 75% by weight, an ethanol content of 2 to 5% by weight, a content of n-propanol of 3 to 12% by weight, a content of isobutanol from 10 to 30% by weight and the remainder other higher alcohols having more than 5 carbon atoms (G (- + - alcohols) in an amount of 5 to 25% by weight All percentages are calculated on an anhydrous basis, ie neglected as a product of love formed in the reaction and present in the mixture.

With regard to the concentration ranges given above, it should be noted that the lower values for the higher alcohols and, correspondingly, the higher values for the methanol were obtained with higher pressures within the stated range.

Consequently, the higher alcohol content higher values and thus the lowest methanol content values were obtained with the lower pressures within the stated range.

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Bs has now, surprisingly, shown that the preparation of mixtures of methanol and. According to the invention higher alcohols can also be carried out under lower pressure and that such mixtures have a content of higher alcohols, which is substantially higher than that which can be achieved under the high pressures according to the state of the art. The mixtures thus obtained are better than the known mixtures in solubilizing water because of their high content of higher alcohols and act in the same way as known mixtures when added to gasoline, while their production costs are much lower due to low Stress, under which they are formed.

The mixtures obtained according to the invention have a content of higher alcohols between 25 and 65 wt .-%. This makes it possible to solubilize the methanol even if the water content of the gasoline is extremely high.

embodiment

The invention is further illustrated by the following examples.

example 1

242.5 g of chromium trioxide were dissolved in distilled water to a concentration of 30 wt .-%. Separately, an aqueous slurry of 736 g. Zinc oxide in 2 liters of distilled water was prepared and stirred vigorously. The solution of chromium trioxide was added to the zinc oxide slurry with stirring and stirring was continued for a few hours to obtain a complete solution.

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to achieve constant homogenization. The basic zinc chromate was filtered off and the dry powder was mixed with a binder of zinc stearate and the mixture was pelletized. The 6 mm diameter pellets were treated with an aqueous solution of potassium acetate in an amount such that the content of KgO in the finished reduced catalyst was about 2.5% by weight.

After drying to remove the water introduced by the impregnation step, the catalyst was ready for reduction, which was carried out in the same reactor in which the synthesis was then to be carried out. 100 cm pellets were introduced into a tubular stainless steel reactor which was immersed in a fluidized bed of sand and heated in a nitrogen stream containing approximately 2% hydrogen to 300 ⁰ G, was being careful that the temperature during reduction not more than 350 ° rose. The reduction requires a relatively long time, ie about 24 hours. After being reduced, the catalyst should no longer be exposed to the air. The chemical analysis of the catalyst thus reduced gave the following values: ZnO = 77.3% by weight Fs-Cr ₂ Or ₃ = 19.0% by weight / Fe-K "0 = 2.4% by weight fraction loss at 400 ⁰ G = 1.3 wt .-%. The specific surface area was 125 m ² / g.

The catalyst thus obtained was used to prepare methanol and higher alcohols as indicated in the following example. »

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Example 2

-

In the reactor described in Example 1, which contained 100 cm of the catalyst prepared as indicated above, a synthesis gas of the following composition was introduced:

H ₂ = 69.0 mol%

CO = 30.5 mol%

CO ₂ = 0.1 mol%

GH. '= 0.1 mol%

U ₂ = 0.3 mol%

The Tgergeratiir of the catalyst bed was maintained between 390 and 420 ⁰ C. In each case four experiments were carried out at pressures of 5,000, 7,000, 9,000 and 13,000 kPa respectively In each experiment the liquid reaction product was separated from the gas by wetting and condensation were gas chromatographed on an anhydrous product and gave the values given in the following table.

CaJ CaJ

Pressure (kPa) " ^ΛΛΛ "" * ~ """" ^^^

Temperature ( ⁰ G)

GHSV (h ~ ¹ )

He THANOL (wt -.%)

At hano1 (% by weight)

n-propanol (wt%)

Isobutanol (wt.%):;, " ~ _Z _t \ Z ~ _t \ ".!,.

Alcohols with more than 5 carbon atoms (% by weight ) χ 21.0 17.7 13.8 9.7

GHSV = Moody gas churning per hour u) ^ltxi ,

table 9,000 13,000 5,000 7,000 400-415 390-410 409-415 410-422 14,400 14,400 5,500 11,700 57.2 68.8 43.0 46.3 3.4 2.9 3.7 3.9 8.2 6.5 9.1 9.7 27.4 12.1 23.2 22.4

Ausdruck = The term "higher alcohols" as used herein should be understood to include small amounts of other oxygen-containing compounds which, when used in fuels for internal combustion engines, such as alcohols, behave in the same way

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* F AP G 07 G / 232 313/4

(59 716/18)

The total amount of G ₂ + alcohols (alcohols with two and more carbon atoms) in the mixture with methanol is 57 # at 5 000 kPa, 53.7% at 7 000 kPa, and 42.8 % at 9 000 icPa. and at 13,000 kPa, 31.2 %.

Claims (5)

Claim for invention 1. A process for the preparation of mixtures of methanol and higher alcohols, which can be used in particular as a gasoline substitute or in admixture with gasoline as propellants for internal combustion engines, by reacting H ₂ and CO, optionally in the presence of GOo imcL inert gases, at a molar ratio H ₂ : GO in the range of 0.1 to 20, preferably between 0.5 and 5 at a temperature of 300 to 500 ⁰ G preferably 350 to 400 G, characterized in that at a pressure of 2,000 to 16,000 kPa, preferably from 5,000 to 13,000 kPa with a catalyst based on chromium, zinc: and at least one alkali metal works. 2. The method according to item 1, characterized in that the resulting mixtures have a methanol content of 35 to 75% by weight on an anhydrous basis « 3. The method according to item 1 or 2, characterized in that the weight ratio of zinc to chromium, calculated as oxides, in eggs catalyst is 5: 1 to 1: 1. 4. The method according to item 1 or 2, characterized in that the alkali metals, calculated as ozides, are present in the catalyst in an amount of 0.5 to 5 wt .-> S based on the total weight of the elements calculated as oxides. 5. The method according to item 1 to 4, characterized in that aas alkali metal in the catalyst is potassium.