LU84166A1 - PROCESS FOR THE PREPARATION OF DIMETHYLETHER - Google Patents

Description

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j 1. Process for the preparation of methyl ether.

The present invention relates to a process for the preparation of methyl ether.

£ The dlmethylether subsequently designated by DME

is generally prepared in two stages, by synthesizing methanol from CO and and optionally from CO ^, then by dehydrating the methanol thus obtained to obtain DME.

However, certain processes are known in which the synthesis of DME is carried out in a single stage, by coupling the catalyst for the synthesis of methanol with a dehydration catalyst which is generally alumina.

In known processes, the methanol synthesis catalyst is a composition consisting of Cu, Zn, Cr 15 or Cu, Zn, Al while the dehydration catalyst is generally alumina.

One embodiment described in patent application [German 2757778 (US patent 4I77I67) comprises a catalyst for the synthesis of DME, consisting of metal oxides and / or metal salts which have been stabilized by treatment with a silicon compound, the stabilization consisting in making the material, obtained after treatment, capable of withstanding thermal and mechanical forces, and the action of steam at high temperature. The metal oxides and / or the 2% metal salts used according to the above patent application are generally oxides of Al, Cr, La, Mn, Cu or Zn and / or 1 'of the salts of these metals or their mixtures. The problem presented by catalysts of the known type and therefore by the catalyst of the above-mentioned German patent application is related to the fact that the dehydrating agent used msnisfete its activity in a significant manner only at relatively high temperature s uxc ue11e ε the methanol synthesis catalysts based on copper, capable of operating at low temperature and low pressure, are unstable, giving rise to sintering phenomena and consequently to loss of activity in the long run.

The optimum temperature for dehydration according to the mentioned patents is of the order of 28 · 0 to 30 Gcc, while copper-based catalysts only have a long life if they are used at a temperature between 200 and 260 ° C.

? The author of the present invention has discovered i 5 quite surprisingly that it was possible; to operate at a much lower average temperature, while obtaining rather high DNS conversion yields, using a catalyst formed by intimately mixing powdery crystalline siliceous materials substituted by aluminum and oxides or salts of CU, Zn and Cr (or Al) powder.

The process according to the present invention consists in feeding CO and Hg and optionally CO ^, a reaction zone filled with the catalyst consisting of a mixture of the following substances: a) crystalline silica in which certain silicon atoms in the crystal lattice of the silica have been replaced by aluminum and which satisfies the following general formula: 20 1S1 (0.0012-0.0050) Al Oy where y varies between 2.0018 and 2.0075 b) a mixture of oxides and / or salts of Cu, Zn, Cr or Cu, Zn, Al; or aluminum can also be present at the same time. The crystalline silica used in the present invention and its preparation are described in German patent application 2924 & 70 to which reference will be made.

40 a of all the metallic atoms present in the above-mentioned catalytic composition fa ^ fc) are these silicon atoms.

The percentage of copper atoms in tct = ί (a ~ b) as defined above, is by calculating only the metal atoms, varies from Ig said, r-ir-e νς · chromium from 0 to 10% (the value 0 being obtained when aluminum is present) and aluminum from 0.1 to 10%.

The process for preparing ΒΜΞ according to the reverse.-3g tior. is carried out at a temperature between I5G eu 250 ^ -and under a pressure between 4000 and 1500Q KPa.

The present invention is illustrated by the following descriptive and nonlimiting examples.

t · 'EXAMPLES 1 and g «

A catalyst based on Cu, Zn, Al and silica modified with aluminum is prepared according to the following process h.

5 676 g of Cu (N0 ^) 2.3H20, 327 g of Zn (N03) 2.6H20 and 57 g of sodium alumlnate are dissolved in 10 liters r of water. The solution is heated to 85 ° C and a 10/6 solution of NaOH in water is added while stirring until the pH reaches 7 * 5. The precipitate is allowed to settle during cooling, the liquid is decanted and the precipitate is washed repeatedly with water until the sodium and the nitrates have disappeared, operating by decantation and finally by filtration.

The precipitate is dried in an oven at 120 ° C. in air. The material is ground into granules which do not separate the ASTM mesh of 8 ^ 0 pm, and is mixed with 325 g of aluminum-modified silica, prepared as described in Example 5 ce German patent application No. 292I87O ,; The powder is compressed into granules having a diameter of 4 mm and a length of 6 mm.

Cu, Zn, Al and Si are present in the catalyst in the atomic ratios of 28: 11: 7: 5¾.

100 cm “·’ of catalyst are placed in a tubular reactor with a diameter of 2.5¾ cm.

2.5 A 6 & ine with an outside diameter of 8 mm for a thermocouple is placed axially in the center of the reac-j '. tor. The temperature is gradually increased while supplying the reactor with a mixture of H, - and in order to reduce f 2 2 I the catalyst under controlled conditions.

I 30 When the temperature reaches 220 ° C. and the reduction of the catalyst is complete, the pressure is brought back to 7000 EPa and the mixture of this PL and K is rerr.nl was renewed.

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by a 1: 1 mixture of CG and at an hourly sDial speed -1 c these GHSV gases of 2100 h.

The temperature of the catalyst is stabilized I at 200cC (example 1} and at 230cC (example 2).

f. The water, methanol and part of the dimethyl ether formed in the reaction are condensed in a converter placed downstream from the reactor.

The condensed water, metbanol and DME are drawn off under pressure and analyzed by gas chromatography.

5 The gas leaving the reactor is sent to an I sampling valve of a gaseous S phase α ehromatograph and analyzed, then sent to a totalizing counter i in order to measure the quantity of gas.

. Table 1 shows the results obtained under 2Q the above conditions. By-products present in an amount less than 1% have not been mentioned.

TABLE 1 i GHSV RTF Conversion Selectivity of -1 H / CO ° c KPa molar CO converted in 15 h 2 DME CH ^ OH C02 EXAMPLE 1 2 100 1 200 7000 22 61.8 4.1 34.1 ί EXAMPLE 2 2 100 1 230 γΟΟΟ 69 63.4 3.0 33.6

20 —— J

EXAMPLES 3 and 4

A catalyst like lndlaué based on

Cu, Zn, Cr, SI and Al, the constituents being present in the atomic ratios of 20: 12: 8: 60: 0.2.

op. 1 ^ 00 £ öe Cu (N0_.) 3K ^ 0, 1182 g of Ζη (ΝΟ,) ^.

oHgO and 1060 g of Cr (NO ^^^ HgO are dissolved in 20 liters of distilled water. The solution is heated to 95 ° C and 20 liters added.,,, ^ 1300g. of * 2'jriC'ts / cl an aqueous current / LaOH solution is then added while stirring. The precipitate is cooled, washed with water by decantation, filtered and washed repeatedly with water.

: the precipitate is dried like an oven at 1206C. The material is ground into granules lower than the AETM 6aC μm mesh, then mixed with 1192 g of silica modified with aluminum (example 5 of the German patent application 2,924,870).

„Granules with a diameter ce t mrr and a length of 6 mm are produced. 100 eir. "Of the catalyst are: examined under the same conditions as in Examples 1 and 2, the results being given in Table 2.

I TABLE 2 rucvvr R T P Selectivity conversion of GH? , we molar CO converted to h'1 Hg / CO C KPa ^ dme ^ ^ ^ EXAMPLE 3 2 100 1 200 'JOOO 12 62.6 3.8 33.6 EXAMPLE 4 2 100 1 230 JOOO 45 64.7 1j8 ^ 3, 5 10 EXAMPLES 5 and 6 (comparative)

The catalyst of Example 1 of the U, S patent.

4,177,167, in which the atomic ratios Cu: Zn: Cr: Al are 20: 12: 8: 60, is examined under the same conditions as in Examples 1 and 2.

15 The results are given in table 3, TABLE 3 GHSV R T P Conversion Selectivity of h'1 Η, / CO ° c KPa molalre c0 converted into

2 ° 2% DME CH, OH CO

3 2 EXAMPLE 5 2,100 1,200 7,000 11 11.9 54.0 34.1 EXAMPLE 6 2,100 1,230 7,000 42 18.5 47.0 35.0 2 * 5

These comparison examples show that at low operating temperatures, the stabilized aluminum-based catalyst does not exhibit sufficient dehydrating activity, so that DME is present only in small amounts.

30

Claims (3)

6 I. \ Λ * 1. Process for the preparation of dimethyl ether from CO, H0 and optionally CO, characterized in that the methyl ether is formed in the presence of a composition consisting of: a) a crystalline silica in which * certain silicon atoms in the crystal lattice are replaced by aluminum, and which satisfies the general formula K 'ray:! 10 1S1 (0.0012-0.0050) Al 0y where y varies between 2.0018 and 2.0075. b) a mixture of oxides and / or salts of Cu, Zn, Cr or of Cu, Zn, Al in which Al can also be present at the same time as Cr. I5 2. Method according to claim 1, characterized in that the percentage of atoms of the various elements of the overall composition is as follows: 40 to 70 $ of all the metallic atoms for Si 15 to 30 $ of all of the metal atoms for Cu 20 8 to $ 15 of all the metal atoms for Zn 1 0 to $ 10 of all the metal atoms for Cr 0.1 to $ 10 of all the metal atoms for Al. 3. Catalytic composition for the preparation! tion of dlmethylether from C0, ïL · and possibly 2 2à de C02jcharacterized by the fact that it consists of I the following elements: 40 to 70 $ of all the metal atoms for Si 15 to 30 $ of all the metal atoms for Cu 8 to $ 15 of all the metal atoms for Zn 30 0 to $ 10 of all the metal atoms for Cr 0.1 to $ 10 of all these metal atoms for Ai. 1 _. ... It .. - ·. * -