Method for production of methyl chloride, hydrochlorination catalyst and uses thereof

FIELD: chlororganic chemistry.

SUBSTANCE: invention relates to hydrochlorination catalyst containing aluminum η-oxide, doped with cesium chloride. Also method for methanol hydrochlorination in vapor phase using claimed catalyst is disclosed.

EFFECT: decreased selectivity to dimethyl ether and inhibited coke deposition on working catalyst.

16 cl, 6 tbl, 1 dwg, 20 ex

 

The present invention relates to catalysts for use in obtaining methyl chloride and to a process for the preparation of methyl chloride from methanol and Hcl using such catalysts. The invention relates to a method of prolonging the life of such catalysts.

In the industrial production of methyl chloride using a gas-phase catalytic process methanol and hydrogen chloride is usually served in approximately equimolar ratio in a reactor with a fixed or fluidized bed at a temperature of 250-300° C. the Reaction is strongly exothermic, and often there are large temperature increase, and easily achieved temperature above 400° C. Such high temperature or "hot spots" can lead to sintering of the catalyst and the formation of coke with subsequent loss of catalyst activity over relatively short periods of time. Working pressure industrial reactor is not critical for the process to work: use reactors of high and low pressure.

As a catalyst to obtain methyl chloride from methanol and Hcl usually use aluminum oxide. Typically, the preferred catalyst is γ -aluminium oxide, as achieved acceptable levels of activity for the formation of methyl chloride without any excess hot spots of the layer of catalyst. For example, US patent 5183797 describes the use of γ -alumina catalysts for production of methyl chloride with a depressed formation of a reaction hot spots to limit the coking of the catalyst by adjusting the surface area of the catalyst.

The main side product of the reaction of methanol with hydrogen chloride is dimethyl ether.

Applicants found that, if as a catalyst for the reaction of methanol with hydrogen chloride to use η -aluminum oxide, doped salt of an alkali metal, achieved a significant reduction in the selectivity of dimethyl ether. Selectivity for dimethyl ether tends to be about 100 times lower than the selectivity obtained with commercially available γ -alumoxane catalyst.

According to the first aspect of the present invention proposed a catalyst for the hydrochlorination of methanol, which includes η -aluminum oxide, doped alkali metal salt.

According to the second aspect of the present invention proposed a catalyst for the hydrochlorination of methanol, the preparation of which involves the step of doping η -aluminium oxide, salt of an alkali metal. After that, the processed product may be calcined.

According to a third aspect of the present invention proposed a method according to the teachings of methyl chloride, which involves the reaction of methanol with Hcl in the vapor phase in the presence of a catalyst, as defined in the first or second aspects of the present invention.

Preferably alkali metal salts of alkaline metal, which according to the present invention alloyed η -aluminum oxide, is cesium or potassium, more preferably, cesium, since decreasing the selectivity of dimethyl ether is more noticeable. It was found that there is little difference in selectivity for methyl chloride or dimethyl ether between the different salts of the same alkali metal, such as nitrate, chloride and hydroxide.

Doping η -aluminium oxide, salt of an alkali metal can be carried out with known methods of impregnation. Usually it η -aluminum oxide are added dropwise an aqueous solution of salts of alkaline metal. Then η -alumina is heated under vacuum to remove water. The doped catalyst may then be calcined.

According to further aspect of the present invention, a method for preparation of the catalyst according to the first or second aspects of the present invention, comprising a stage of impregnation η -aluminium oxide with an aqueous solution of salts of alkaline metal.

The concentration of the aqueous solution of alkali metal salt used in the method according to mark is usamu aspect of the present invention, should be selected to give the desired salt concentration of the alkali metal in the catalyst.

The salt concentration of the alkali metal in the catalyst is usually from 0.05 to 5.0 mmol × g-1, preferably 0.1 to 3.0 mmol × g-1and more preferably 0.1 to 2.0 mmol × g-1for example, 0.2 to 2.0 mmol × g-1.

The physical form of the catalyst, i.e. the shape and size chosen, taking into account, among other things, the particular reactor used in the hydrochlorination reaction, and the reaction conditions in it.

The molar ratio of Hcl : methanol used in the preparation of methyl chloride is at least 1:10 and not more than 10:1, preferably of 1:1.5 to 1.5:1, more preferably is close to stoichiometric.

This receiving process can be carried out at 200-450° C, preferably about 250° C.

This receiving process can be carried out in the reactor headspace hydrochlorination high or low pressure, typically between 100 and 1000 kPa (abs.).

The retrieval process may be performed periodically or be a continuous process. A continuous process is preferred.

Additional aspects of the invention relate to the doping η -aluminium oxide in order to delay the start of such coking of the catalyst used in the reaction hydrochloridw the Oia.

Preferably such additional aspects of the invention, the alkali metal salt of an alkali metal, wherein the doping η -aluminum oxide, is a cesium or potassium, preferably cesium. It was found that there is only a small difference in the rate of coke formation between the different salts of the same metal, for example, nitrate, chloride and hydroxide.

The present invention is additionally illustrated by reference to the following examples.

Performance of catalysts in hydrochloridebuy methanol was estimated using ordinary microreactor system operating at atmospheric pressure with a gas stream that is regulated by mass flow controllers Brooks.

In the examples, the specific surface area and the volume of pores of the catalysts was determined by absorption of nitrogen, and the activity of the catalysts was determined in a laboratory microreactor. Adsorption isotherm of nitrogen was determined using a Micromeritics ASAP2400 Gas Absorption Analyser after degassing the samples of the catalyst during the night.

General methods

Roughly 0.04 ml/min of liquid methanol gave the HPLC pump to the evaporator stainless steel, filled with glass beads with a diameter of 2-3 mm, supported at a temperature of 130° C. the resulting flow of the vaporized methanol was the equivalent of 36.3 ml/min flow PA is s of methanol at room temperature and pressure. In order to facilitate the flow of methanol through the evaporator, the evaporator simultaneously administered 25 ml/min of nitrogen gas.

The vaporized mixture of methanol/nitrogen mixed with 40 ml/min of gaseous hydrogen chloride and served in the U-shaped reactor tube made of Pyrex containing the catalyst and immersed in an oven with air circulation. The oven temperature was controlled by two thermocouples placed on the wall of the reactor in a neighborhood filled with a catalyst layer.

In examples 1-14 extrudates of catalyst was grinded and sieved to a fraction of the size of 300-500 μm and 0.07 g of ground catalyst was mixed with 0.9 g of Pyrex fractions of the same size. This mixture was placed in a reactor tube microreactor system inside a furnace at a temperature of 250° C. performance of the catalyst was evaluated by increasing the temperature of the furnace 10° C/hour to a maximum temperature of 310° C. Samples of the reactor products were analyzed by gas chromatography every 15 minutes.

Emerging from the micro-reactor gases were mixed with 5 l/min of nitrogen gas to prevent condensation of any of the reaction products or unreacted methanol, and part of this stream was analyzed by gas chromatography using a gas chromatograph NR equipped with valve for gas-sampling and capillary column PWax 52 50 m × 0,530 mm diameter (Chrompak). Obtained from gas chromatograph signal is integrated using a computer program PE Nelson Turbochrom, and the relative content of methyl chloride, dimethyl ether and unreacted methanol was obtained as a normalized percentage (about./about.) composition, using the relative response factors for these components, which were previously determined from volumetric analysis prepared standard gas mixtures.

Results temperature profiles were analyzed using the linearized form of the equation of Arrhenius equation (graph ln (% vol./about.) as a function of 1/T)to obtain the calculated values of activity on the formation of methyl chloride and dimethyl ether at 290° C.

Examples 1-3

These examples are comparative tests using the extrudates γ -aluminum oxide with a specific surface 296 m2×g-1, 196 m2×g-1and 225 m2×g-1accordingly, milled and sieved to a fraction of the size of 300-500 μm. Evaluation of their performance gave the results shown in table 1.

Table 1
# exampleCatalystSpecific surface area (m2× g-1)Dimethyl ether (% vol.)Methyl chloride (% vol.)
1γ -aluminium oxide2962,3021,6
2γ -aluminium oxide1953,1024,10
3γ -aluminium oxide2252,3018,50

From table 1 one can see that (a) these catalysts show an acceptable level of activity in relation to the formation of methyl chloride with a significant level of education by-product dimethyl ether and (b) the activity of these catalysts is not directly related to the measured specific surface area.

Examples 4-6

These examples are comparative tests in which the extrudates η -aluminum oxide with a specific surface according to BET 332 m2×g-1, 417 m2×g-1and 398 m2×g-1respectively were milled and sieved to a fraction of the size of 300-500 μm, and evaluated their performance. The results are shown in table 2.

Table 2
# exampleCatalystSpecific surface area (m ×g-1)Dimethyl ether (% vol.)Methyl chloride (% vol.)
4η -aluminium oxide3322,7053,9
5η -aluminium oxide4172,9050,60
6η -aluminium oxide3982,3054,30

From table 2 one can see that the levels of activity with respect to the formation of methyl chloride, achieved on η -alumoxane catalysts, significantly above the levels reached in γ -alumina catalysts (examples 1-3), while concentrations of dimethyl ether is similar to the observed for γ -alumina catalysts. It should be clear that with such high levels of activity with respect to the formation of methyl chloride using these η -alumoxane catalysts in the industrial process is problematic due to the occurrence of large hot spots in the catalyst bed.

Examples 7 and 8

These examples show the use of alloyed η -alumina according to the present invention. Samples η -alumoxane extrudates used in example 4 was impregnated with potassium chloride and cesium chloride as follows: η and umaczenie extrudate (approximately 10 g) were introduced into the two-neck flask, the flask was pumped out to remove air from the pores of the aluminum oxide. The salt solution of an alkali metal (approximately 30 ml) was added into the flask through an addition funnel. Then the particles of the catalyst was filtered and was dried in a rotary evaporator at 70° C under vacuum for one hour. After drying, the catalysts were grinded and sieved to a fraction with a particle size of 300-500 μm for testing. Rated input of an alkali metal in each sample of the catalyst was calculated from the measured volume of pores η -alumoxanes extrudate and the concentration of the salt solution used for each preparation. The results are shown in table 3.

Table 3
# exampleCatalystSpecific surface area (m2×g-1)Dimethyl ether (% vol.)Methyl chloride (% vol.)
7η -aluminium oxide + 1.0 mmol × g-1KCl2410,1216,20
8η -aluminium oxide + 1.0 mmol × g-1CsCl1660,0314,20

From table 3 one can see that (a) adding a salt of an alkali metal moderate activity on education is ethylchloride to acceptable levels, while the selectivity for dimethyl ether was impressively reduced, and (b) the effect of salt of cesium on the selectivity for dimethyl ether is substantially higher than that which was achieved with potassium salt.

Examples 9 and 10

These examples illustrate the catalysts of the present invention, including η -alumina doped with cesium chloride. Samples η -alumoxane catalysts used in examples 5 and 6 were saturated with cesium chloride according to the method described in examples 7 and 8. The results are shown in table 4.

Table 4
# exampleCatalystSpecific surface area (m2×g-1)Dimethyl ether (% vol.)Methyl chloride (% vol.)
9η -aluminium oxide + 1.0 mmol × g-1CsCl930,0222,0
10η -oxyl aluminum + 1.0 mmol × g-1CsCl830,0224,7

From table 4 we can see that adding salt cesium moderates the activity in relation to the formation of methyl chloride and dramatically reduces the selectivity to the formation of dimethyl ether.

Examples 11-14/p>

These examples show the other catalysts of the present invention. In these examples, samples η -alumoxanes extrudate used in example 4 was soaked in different concentrations of caesium chloride using the method described in examples 7 and 8. The results are shown in table 5.

Table 5
# exampleCatalystSpecific surface area (m2×g-1)Dimethyl ether (% vol.)Methyl chloride (% vol.)
11η -aluminium oxide + 0.1 mmol × g-1CsCl3130,5519,50
12η -aluminium oxide + 0.3 mmol × g-1CsCl2940,0914,50
13η -aluminium oxide + 0.6 mmol × g-1CsCl2320,0315,40
14η -aluminium oxide + 1.0 mmol × g-1CsCl1660,0214,7

From table 5 one can see that the impact of adding cesium chloride on observed changes in activity by methyl chloride and dimethyl ether is clearly nonlinear. A significant reduction actively the ti on the formation of methyl chloride is obtained at the input of 0.1 mmol × g-1cesium chloride, but to obtain the most complete reduction of selectivity towards the formation of dimethyl ether required higher concentrations of cesium chloride.

Examples 15-20

These examples demonstrate the coking of the catalysts over time, and example 15 is a comparative example. In examples 15-20 preparation of catalysts was carried out, soaking the caesium chloride η -alumoxane extrudates with a specific surface area according to BET of 320 m2×g-1as follows: η -alumoxanes extrudate (approximately 10 g) were introduced into the two-neck flask, the flask was pumped out to remove air from the pores of the aluminum oxide. A solution of cesium chloride (approximately 30 ml) was added into the flask through an addition funnel. Then the particles of the catalyst was filtered and was dried in a rotary evaporator at 70° C under vacuum for one hour. After drying, the catalysts were grinded and sieved to a fraction with a particle size of 300-500 μm for testing. Rated input of an alkali metal in each sample of the catalyst was calculated from the measured volume of pores η -alumoxanes extrudate and the concentration of the salt solution used for each preparation.

Coking of the catalysts in time was determined using the reactor system Rupprecht and Patashnick RMA Pulse Mass Analyser T IS Ω (TEOM are presented denotes oscillating microbalance with a wedge-shaped element). The sample (approximately 100 g) of the catalyst shown in table 6 were loaded into the reactor TEOM are presented and the sample was dried in situ in a stream of helium for 5 hours at 400° C. After drying, the sample temperature was lowered to 390° and leave the sample at this temperature overnight.



Table 6
Example (curve number)CatalystSpecific surface area (m2×g-1)Pore volume (cm3/g)
15* (1)η -aluminium oxide3200,36
16 (2)η -aluminium oxide + 0.05 mmol/g of CsCl3070,35
17 (3)η -aluminium oxide + 0.10 mmol/g CsCl3070,34
18 (4)η -aluminium oxide + 0.20 mmol/g CsCl2990,32
19 (5)η -aluminium oxide + of 0.60 mmol/g CsCl2440,27
20 (6)η -aluminium oxide + 1.00 mmol/g CsCl1810,21
15* represents comparative test

Coking of the catalyst at 390° was implemented, replacing the gas flow is Not met chloride (15 ml/min at normal temperature and pressure), supplied through the mass flow controller Brooks, and monitoring increase the weight of the catalyst over a period of several days at atmospheric pressure. The results are shown in the drawing, which shows the weight gain per gram of catalyst as a function of traveltime. In the drawing the curves marked with the numbers 1-6, corresponding respectively to examples 15-20.

From the drawing you can see that for all catalysts the rate of coke deposition as a function of time is changed by a nonlinear way. However, with the increasing input of cesium beginning of the coking delayed so that the time to achieve a given level of kokoulina impressively increased. The results show that the maximum influence on the deposition of coke is achieved when the input cesium greater or equal to 0.2 mmol/g

1. The method of producing methyl chloride, including the interaction of methanol with Hcl in the vapor phase in the presence of a catalyst, which catalyst includes η-aluminum oxide, doped alkali metal salt.

2. The method according to claim 1, in which the molar ratio of Hcl:methanol is of 1:1.5 to 1.5:1.

3. The method according to claim 1 or 2, carried out under a pressure in the range of 100-1000 kPa.

4. The method according to any one of claims 1 to 3, performed at a temperature in the range of 200-450°C.

5. The method according to any one of claims 1 to 4, in which the catalyst includes the t η -alumina, impregnated with a salt of an alkali metal.

6. The method according to any one of claims 1 to 5, in which the alkali metal is cesium or potassium.

7. The method according to claim 6 in which the alkali metal is cesium, optional caesium chloride.

8. The method according to claim 7, in which the salt concentration of cesium in the catalyst is in the range from 0.2 to 2.0 mmol×g-1.

9. The use of the catalyst of η-alumina, impregnated with a salt of an alkali metal, for the implementation of the hydrochlorination.

10. The use of the catalyst according to claim 9 to obtain methyl chloride.

11. The use of the catalyst according to claim 9 or 10, in which the alkali metal is cesium or potassium.

12. The use of the catalyst according to claim 11, in which the alkali metal is cesium, optional caesium chloride.

13. The use of the catalyst according to item 12, in which the salt concentration of cesium in the catalyst is in the range from 0.2 to 2.0 mmol×g-1.

14. The hydrochlorination catalyst, including η-alumina doped with cesium chloride.

15. The hydrochlorination catalyst for 14, including η-alumina impregnated with cesium chloride.

16. The hydrochlorination catalyst for 14 or 15, in which the concentration of cesium chloride in the catalyst is in the range from 0.2 to 2.0 mmol×g-1.



 

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