Catalyst for the synthesis of methylmercaptan and method thereof

 

(57) Abstract:

The invention relates to a catalyst for the synthesis of methylmercaptan and how to obtain it. Describes the catalyst used for the synthesis of mercaptan from hydrogen sulfide and methanol, as well as the method of obtaining this catalyst. The catalyst consists of active alumina, on which deposition is applied 5 to 25 wt.% tungstate of potassium as a promoter. Thanks to the application, carried out by two-stage mechanism with intermediate drying, to obtain the catalyst in comparison with the catalysts obtained one-step method of impregnation, has much higher selectivity in the synthesis of methylmercaptan. 2 S. and 3 C.p. f-crystals, 1 tab., 3 Il.

The invention relates to a catalyst used for the synthesis of mercaptan from methanol and hydrogen sulfide, as well as to a method for producing this catalyst.

The mercaptan is an industrially important intermediate product for the synthesis of methionine, as well as for obtaining dimethyl sulfoxide and dimethyl sulfone. Currently, it is mainly obtained from methanol and hydrogen sulfide in the presence of a catalyst based on the P>oC and at a pressure of 1-25 bar.

The reaction gas mixture contains, along with the mercaptan formed unreacted educt and by-products, such in particular as dimethyl sulphide and simple dimethyl ether, as well as inert to the reaction gases, such as methane, carbon monoxide, hydrogen and nitrogen. From this reaction mixture allocate the resulting mercaptan.

If the interaction between hydrogen sulfide and methanol in the presence of a catalyst is carried out at increased pressure and thus in the process of obtaining mercaptan product is formed at high pressure (>7 bar), as described in the application DE Germany 1768826, the mercaptan can be selected, for example, by washing with methanol at a temperature in the head part of the scrubber 25oC. If the product is under normal pressure, for subsequent processing in order to obtain the mercaptan in the liquid form it is necessary to work at temperatures down to -60o(Cf. paved the application of Japan JP-OS 45-10728). Unreacted hydrogen sulfide, as described in the aforementioned application DE 1768826 again to return to the reactor.

The efficiency of the method involves Maximale methylmercaptan, because of the need to reduce logistical costs in the allocation of the resulting mercaptan from the reaction mixture to a minimum. It is primarily about such a significant factor, as the high energy intensity of the process of cooling the reaction gas mixture for separation of condensate methylmercaptan.

To improve the activity and selectivity aluminiumoxide catalyst latter usually promotirovat the potassium tungstate. The promoter when it is used usually in an amount up to 15 wt.% in terms of the total weight of the catalyst. Increased activity and selectivity reached also by increasing the molar ratio between hydrogen sulfide and methanol. In most cases, this molar ratio is 1-10. At the same time, a high molar ratio means the presence in the reaction gas mixture a large excess of hydrogen sulfide and thus the need to introduce into the circuit a significant amount of gas. Therefore, to reduce required for these purposes, energy molar ratio between hydrogen sulfide and methanol ought to choose a little more than 1. Further, to reduce heat loss in the reactor, it is desirable to carry out the reaction with m the which used catalyst on the basis of active alumina, promoted with potassium tungstate in an amount of from 1.5 to 15 wt.% in terms of the weight of the catalyst. Using this catalyst to achieve high activity and selectivity at a temperature of 400oC and a molar ratio equal to 2. According to the above U.S. patent are various possibilities for the introduction of potassium tungstate in the aluminum oxide. Thus, in particular, can use the methods of impregnation, coprecipitation and clean mix. Actually getting the same catalyst as an important indicator of the efficiency of the method of synthesis of methylmercaptan in the publication is given only a small place.

The present invention was based on the task to obtain the catalyst and to develop a method thereof, and the catalyst had to be different at low molar ratios between hydrogen sulfide and methanol higher activity and selectivity compared with the known catalysts and to provide thereby increasing the efficiency of the method.

This task is solved through the catalyst based on alumina containing this active aluminium oxide from 5 to 25 wt.% tungstate of potassium as a promoter. This catalyst was prepared si portion of the promoter by the method of impregnating, using excessive amounts of water impregnating solution, put one layer, and then at an elevated temperature dried, and then impregnated pore size of the second portion of the alumina cover with another layer after repeated drying at elevated temperature obtained at this preliminary stage of the catalyst last finally calcined at temperatures in the range from 200 to 600oC.

The quantitative ratio between the two portions of the promoter is chosen preferably such that the amount of the first portion of the promoter is between one to two thirds of the total number of promoter. As promoters can be used wolframate alkali elements Li, Na, K or Rb, or their mixtures, preferably, however, only potassium.

As aluminum oxide for the proposed catalyst is used the so-called active alumina. This material has a high specific surface area from about 10 to 400 m2/g and represents mainly the oxides of the transition modification (patterns) crystallographic phases of aluminum oxide (see , for example, Ullmann's Enzyclopedia of Industrial Chemistry, 1985, volume A1, pages 561-562). These crystalline modificati the temperature over 1100oWith moving in its thermally stable form. Active alumina is commercially available and is proposed for use in catalytic reactions with different qualities and different for deliveries. Particularly suitable for the purposes of the invention granulated or extruded aluminum oxide with a diameter of grains from 1 to 5 mm, a specific surface area of 180-4002/g total pore volume of 0.3 to 1.0 ml/g and a bulk density of 300 to 900 g/l

The promoter of the potassium tungstate precipitated on alumina by the method of impregnation carried out by two-stage mechanism, namely, at the first stage, the aluminum oxide is impregnated with the promoter or promoters, using excessive amounts of water impregnating solution, and the second stage covered by the promoter due to the impregnation of the pore volume to the rest of the number. This special two-stage method of impregnating with intermediate drying is compared with the known from the prior art one method of impregnating the advantage that this improves the activity and selectivity of the finished catalyst, especially at low molar ratios between hydrogen sulfide and methanol. The specifics of the ptx2">

For the first stage of impregnation prepare an aqueous solution of the promoter. In cases where this is required by the necessary concentration and/or limited solubility promoter compounds, the temperature of the impregnating solution can be increased to 95oC. In this case, is loaded into the corresponding capacity of the catalyst particles on the basis of aluminum oxide fill is not necessarily still hot impregnating solution, covering them all particles. After deposition promotor compounds, ongoing, typically about 20-60 minutes, excess water is drained. After draining the water particles of the catalyst for 1-10 h dried at elevated temperature in the range from 50 to 250oC, preferably from 100 to 140oWith, then within 1-5 h it is possible to carry out the process of annealing in the temperature range from 400 to 600oWith, primarily from 420 to 480oC. This drying process may be preceded by preliminary drying is carried out at room temperature over a period of time up to 20 h, preferably from 10 to 14 o'clock this improves the uniformity of impregnation throughout the cross section of the catalyst particles.

In the second stage of impregnation of the well-known also under the name of "absorption - moisture - impregnation"). With this purpose, the residual amount of the promoter is dissolved in a volume of water corresponding to about the capacity of the catalyst particles. The solution, as mentioned above, to increase the solubility of the components can be heated to 95oC. This solution was slowly distributed throughout the catalyst carrier, stir in the device apparatus for drazhirovanija. Then the catalyst carrier, and after the first stage of impregnation, is dried and finally within 1-5 h, annealed at temperatures in the range from 400 to 600oC.

Before applying the promoter on the carrier for optimal activity it is recommended that the catalyst particles be subjected to preliminary annealing for 1-10 hours and at temperatures in the range from 400 to 600oC.

Amount applied to both stages of impregnation of the promoter chosen preferably identical, however, this ratio can be varied, namely, the amount of promoter is applied to the first stage of impregnation, can be from one to two thirds of the total number of promoter.

The described technology stages impregnating have a critical ri implementation of one-step methods using excess impregnating solution, as well as one - and two-stage methods of impregnation of the pore volume leads to catalysts having a lower activity and selectivity.

Before use in the synthesis of methylmercaptan catalysts under similar reaction conditions previously sulfiderich [(see V. Yu. Mashkin, Appl. Catal. A 109 (1994) pp. 45-61]. To this end over the catalyst particles at 350oC and a pressure of 9 bar for 2 h pass a stream of hydrogen sulfide. To such processing and the catalysts according to the invention, and conventional catalysts are outside grey and white pith, whereas after sulfatirovnie there are clear differences in their coloration. Obtained by traditional methods of catalysts change color after sulfatirovnie only slightly, whereas the catalysts obtained according to the invention have after this treatment pronounced yellow color, which can be explained by increased formation of toolplate. This yellow color changes not only the surface of the catalyst particles, but also penetrates fully into their core. Compared with the known catalysts observed yellow color seen in the presence of remitting the spectrum of the powdered catalyst particles clearly vein wavelengths between 375 and 420 nm. Somewhat more weakly pronounced absorption bands are in the range of wavelengths between 270 and 290 nm and between 325 and 345 nm. Remitting spectra of the catalysts according to the invention and comparative catalysts shown in Fig. 1-3.

Fig. 1: Remitting range of catalyst from comparative example 1, measured relative to barium sulfate as a white reference.

Fig. 2: Remitting range of catalyst from example 1, measured relative to barium sulfate as a white reference.

Fig. 3: Remitting range of catalyst from example 1, measured relative to the catalyst of comparative example 1.

Example 1. 1.8 kg of Granular aluminum oxide (Spheralite 501 And firm Rhne-Poulenc; specific surface area of 320 m2/g; total pore volume of 0.45 ml/g; a bulk density of 0.8 g/cm3) for 4 h was progulivali at 455oWith on the air. Placed in the appropriate capacity of granular aluminum oxide filled in the previously prepared aqueous solution of about 8.7 wt.% the potassium tungstate, heated to a temperature of 95oWith until the solution did not cover all of the catalyst particles. After exposure for 40 min, excess water was decanted, and the wet catalyst particles are first dried in thecinemasource this treatment, the catalyst particles were deposited 7 wt.% the potassium tungstate, i.e., 126,

For carrying out the impregnation of the pores 162 g of potassium tungstate was dissolved at a temperature of 95oWith 900 ml of water in accordance with a 100% exactly specific total pore volume of the catalytic material and this solution was poured stir in the device for drazhirovanija catalyst carrier. Followed by repeated 16-hour preliminary air drying, finished with final drying for 2 h at 110oC. At the end of the catalyst particles for 4 h was progulivali at 455oWith on the air.

Thus, the finished catalyst contained a total of 288 g of potassium tungstate 1.8 kg of aluminum oxide, i.e., 16 wt.% this promoter in terms of weight used catalytic material.

Example 2. Analogously to example 1 was obtained a catalyst according to the invention, containing 16 wt.% the potassium tungstate. However, unlike example 1, the catalytic material prior to the introduction of the promoter did not progulivali.

Comparative example 1. The same as the above example 1 was obtained a catalyst containing 16 wt.% the potassium tungstate. This proceeded from 1.5 kg of aluminum oxide. Next, prepare a hot solution (95oC) to 17.4 wt. % of potassium tungstate in water and talibanisation water was poured, the catalytic material, as in example 1, was subjected to a preliminary drying, and then spent the final drying, after which he progulivali. The finished catalyst contained 16 wt.% the potassium tungstate, calculated on the weight of alumina.

Obtained in example 1 and comparative example 1, catalysts after preliminary sulfatirovnie clearly differed from each other on the colouring. The catalysts obtained in accordance with the invention, had a yellowish color, whereas the comparative catalysts had color from white to gray. For measuring the remission of both materials a number of both catalysts were crushed into powder, which is then alloy preformed. Their remission was determined using a spectrometer, Perkin-Elmer against the barium sulphate as a reference. The obtained curves of the measurements are presented in Fig.1 and 2. The catalyst according to the invention in the range below 420 nm has a distinct absorption band, which explains the presence of the observed yellow color. In Fig.3 shows the differential spectrum of both curves remission in Fig. 1 and 2. This differential spectrum of both curves is particularly clearly visible differences between the two catalysts. This prowl is similar to comparative example 1, with that, however, the difference that the entire amount of potassium tungstate was applied to the catalyst particles at one stage due to the impregnation of the pore volume. To this end 240 g of potassium tungstate (16 wt.% in terms of the amount of aluminum oxide 1.5 kg) was dissolved in 750 ml heated to 95oWith water and pour this solution stir in the apparatus for drazhirovanija catalyst particles.

Comparative example 3. Worked similarly to comparative example 2 with that, however, the difference is that the impregnation of the pore volume was performed by two-stage mechanism with intermediate drying of the catalyst particles. For each of the two stages of impregnation was dissolved in 120 g of potassium tungstate 750 cm3water.

Obtained in the above examples, the catalysts before use in the process of getting methylmercaptan was previously sliderule. After sulfatirovnie were established clear differences in the color of the catalysts obtained according to the invention and comparative catalysts. Obtained according to the invention catalysts had a yellowish color, whereas the comparative catalysts had color from white to gray.

The example application.

Kata is ode and of methanol. The synthesis process was carried out in the tube of the noble metal with an inner diameter of 14 mm and a length of 500 mm Loaded portion of the catalyst according to 32.4 ml, respectively recorded in the reaction tube on both sides of inert material, which are glass beads. Then the tube by electric heated to the desired reaction temperature 350oC. Products - mercaptan, dimethyl sulfide, dimethyl ether and unreacted methanol after cooling to 25oWith washed from the gas stream with methanol and subjected to further processing by distillation.

Conditions of carrying out of experiments: hourly average gas flow rate - 1280 h-1(in terms of standard conditions); average hourly feed rate of the liquid - 0,56 h-1(in terms of liquid Meon); the reaction temperature 357oC; molar ratio of H2S/MeOH and 1.5; the pressure is 9 bar

The measurement results obtained by gas chromatography of the reaction gas mixture in the flow shown in the table. As can be seen from this table that the catalyst according to the invention from example 1 with the same degree of conversion of methanol provides more of the same degree of conversion of methanol provides blearily 2. When carrying out the synthesis of methylmercaptan in the industrial scale, this can significantly reduce logistical costs required for separation of the target product. The presented results were achieved with a relatively low molar ratio between servodata and methanol, constituting only 1.5, and also at relatively low compared with the prior art temperatures of about 357oC.

The above justification of technical solutions of the invention are to simplify limited by the problems of synthesis of methylmercaptan. For a specialist in this obesity technique, however, it is clear that the proposed catalyst can also be applied to the total synthesis of mercaptans, carried out by the catalytic interaction of olefinic hydrocarbons with hydrogen sulfide.

1. The catalyst based on aluminum oxide for synthesis of methylmercaptan, containing the active aluminum oxide potassium tungstate as a promoter, characterized in that the catalyst contains 5-25 wt. % of potassium tungstate and it is produced by deposition of the promoter of the two portions on the active aluminum oxide, and the first aluminum oxide, the first portion of the promoter by the method of impregnovane is at an elevated temperature, and then impregnation of the pore volume of the second portion of the alumina cover with another layer after repeated drying at elevated temperature, obtained at this preliminary stage of the catalyst, the latter finally calcined at 200 - 600oC.

2. The catalyst p. 1, characterized in that the amount of the first portion of the promoter is 1/3 - 2/3 of the total number of promoter.

3. A method of producing a catalyst for the synthesis of methylmercaptan, containing the active aluminum oxide potassium tungstate as a promoter comprising impregnation of the alumina with potassium tungstate, drying, annealing, characterized in that the promoter of the two portions precipitated on the active aluminum oxide, and the first aluminum oxide, the first portion of the promoter by the method of impregnation, and the use of excessive amounts of aqueous impregnating solution is applied to one layer, and then dried at elevated temperature, and then impregnation of the pore volume of the second portion of the alumina cover with another layer after repeated drying at elevated temperature, obtained at this preliminary stage of the catalyst, the last finally calcined at 200 - 600oWith and receive the catalyst is rcii promoter is 1/3 - 2/3 of the total number of promoter.

5. The method according to p. 4, characterized in that the active aluminum oxide before applying to a promoter calcined for 1 to 10 hours at 400 - 600oC.

 

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