DE1960139A1 - Process for the catalytic hydration of ethylene or propylene - Google Patents

Description

Process for the catalytic hydration of

The invention relates to a method for catalytic hydration of ethylene or propylene on a fixed bed catalyst to the corresponding alcohols in the gas or Gas-plus phase

It is known to produce alcohols by direct gas-phase hydration of olefins. The usual technique for doing this exists in that, due to unfavorable equilibrium at the reaction temperatures to be used, except at elevated Pressure must also work with very large amounts of gas circulating.

In the known method, it is customary to increase the concentration of the circulating gas at a level of about 85 vol. #. This is because of the fact that the higher the concentration of circulating gas Although the conversion at the catalyst increases and energy and investment costs are reduced, at the same time, however, the amount of gas to be discharged increases considerably, since the impurities are in the circulating gas can enrich only slightly. If, on the other hand, you work with a lower concentration of olefin in the circulating gas, i.e. With a much higher concentration of impurities in the circulating gas, the amount of gas to be discharged decreases considerably. Working with circulating gas concentrations significantly below 85 V0I.J6 is therefore out of the question, because the olefin conversion per pass is otherwise constant Conditions practically proportional to the decrease in olefin concentration decreases in the circulating gas.

The impurities that are discharged from the cycle gas are on the one hand substances that are introduced with the olefin used and on the other hand by-products that arise during the hydration of olefins. The one with the

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In the case of ethylene, the impurities introduced into the olefin are substances that have a lower boiling point than the olefin (Ethanol production) ZoB. Methane, nitrogen and some boiling higher, such as ethane and C -, - hydrocarbons; with propylene (Isopropanol production) in the case of substances with a lower boiling point than propylene, apart from methane and nitrogen, there is also ethylene and for the higher-boiling impurities, propane and CH hydrocarbons. The by-products formed during hydration are in particular low molecular weight olefin polymers, such as dimers, trimers and tetramers, the corresponding alcohols during the reaction on the catalyst can form, and the corresponding saturated hydrocarbons. ·

There is a separation of these alcohols from the main alcohol product not easy. The low molecular weight olefin polymers can, however, also polymerize further to form higher hydrocarbons, which in The form of the finest mists can be carried along with the circulating gas and are extremely difficult to separate. By occupying the catalyst, the latter cause a decrease in its activity and a reduction in service life *

The discharged gas has so far either been burned or in a plant that allows the utilization of olefins of lower concentration is used (e.g. alkylation of benzene) or returned to the olefin recovery or else by distillation on site worked up.

The work-up by distillation is carried out in accordance with the prior art at low to moderate pressures and correspondingly low temperatures, ie under conditions which are far below the critical data for the olefins. The disadvantage of this procedure can be seen, among other things, in the fact that multi-stage refrigeration units have to be used for the condensation and columns with a larger radius; in addition, because of the higher heat of evaporation of the olefins at lower temperatures, a higher expenditure of energy is required for evaporation and condensation. According to the previously customary distillative separation processes (Ulimann, Enzyklopadie der Techninischen Chemie,?. Edition, Volume lo, pages 150-161) for low-boiling olefins are for the separation of lower and

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higher-boiling impurities two columns required, wherein the low-boiling impurities are separated in the first column, while in the second column the higher-boiling impurities in the bottom of the column and the concentrated olefin are drawn off at the top of the column.

It has now been found that contrary to the general rules the kinetics according to which, with increased concentration, an increased coincidence of the reaction participants and thus in the present If an increased polymer formation would also have to occur, the formation of the lower polymers with increasing olefin concentration would occur decreases in the circulating gas.

Accordingly, the invention consists in that one of the the The mixture which leaves the reaction space is separated off after condensation and freed from alcohol by washing so concentrated that after the oasis has been returned a Circulation s & sk concentration of more than 90 VoI · #, preferably of 95 - 97 Vol. # Sets.

It has also been shown, surprisingly, that one can counter this the prejudice existing in technology, the low molecular weight olefins such as ethylene and propylene with advantage under operating conditions can purify and concentrate close to the critical data of these olefins. This makes it possible to use the circulating gas to purify from olefin hydration at higher "pressures and temperatures than previously usual. With this method of operation it was surprisingly found that some of the Contaminants with a lower boiling point than the olefin to be purified are located in the bottom of the column and are thus already separated here can be.

In the case of the corresponding procedure according to the invention, there is no need the column to separate these low-boiling impurities. Another surprising advantage of the procedure under distillation conditions close to the critical point of the olefin can be seen in the fact that the column can be increased to a multiple of the design load without that the energy consumption must be increased. Despite that

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reduced reflux is the separation effect of the column still very good. So far through those in technology usual separation devices for oil mist or not only highly imperfectly separable products can thus be easily and completely separated from the circulating gas will. As a result, these oil mists in the olefin used again for hydration are now in accordance with FIG Pollution of the concentration of lesser amounts present; the hydration catalyst is protected accordingly. the distillative concentration according to the invention under conditions so near the critical point of the olefins takes place in the presence of oils formed during hydration or non-process detergents. In the case of the Hydrar In addition to ethers and lesser oils, the resulting oils Amounts of higher alcohols mainly around hydrocarbons with a boiling range up to 35o ° C. As alien to the procedure Detergents come into consideration, for example, paraffin oils with a similar boiling point.

It is assumed that in the method according to the invention a wash extraction for olefin purification of the distillation by the oil mist in the circulating gas, which is in the Mainly consist of higher molecular hydrocarbons, is superimposed, whereby the excellent separation effects achieved will. This assumption is supported by experiments in which a synthetic mixture of pure gases is appropriate the composition of the cycle gas is subjected to distillation once with and once without injected oil. Included it is found that the amount of impurities withdrawn in the bottom of the column by a factor of 8 when oil is injected is greater than in the case of distillation without the addition of oil.

The advantages of the measures according to the invention are considerable. This means that the lower-boiling impurities that are always in the feed olefin can no longer be gas-circulated.

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enrich. They are removed in a simple manner together with the higher-boiling impurities and the hydrocarbon oils via the bottom of the distillation column, which means that special columns for separating off the low-boiling components are not required. Ethers and other alcohols can also be obtained from the mixture in the bottom of the column * It is also possible to dimension the concentration columns considerably smaller, the energy consumption is significantly lower due to the lower heat of evaporation in the vicinity of the critical point, and liquefaction is relatively easy by low heat extraction at a relatively high temperature, so that cheaper coolants can be used. For the recirculation of the purified olefin, provided that * it is withdrawn in gaseous form at the top of the column to the operating pressure of the Hydratationsanlage only a correspondingly small amount of energy is also required because of the higher operating pressure of the separation column. In addition, the water content of the olefin to be distilled does not have to meet too high requirements, since the risk of the formation of solid hydrates, which lead to blockages, is correspondingly lower at a higher temperature.

When the procedure according to the invention is used, the hydration process is also more advantageous, since with the same olefin content in the cycle gas, when the measures according to the invention are used, a significantly lower content of oil mist results is located. Since some of these oil mists are deposited on the catalyst and thus block its active centers, the decrease in the activity of the catalyst is largely prevented. The increased separation of oil mist from the circulating gas reduces its density. The advantage of this for the hydration process is that the energy requirement for both the circulation compressor and the superheater is reduced

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example 1

In a plant, the circulation compressor (3) via line (12) 45, ooo Nnr ethylene (85 #ig) together with 2.100 NmVh prishethylene (99.9 #ig) from the fresh ethylene compressor (1) via line (lo ) into the heat exchanger (4). "With the process water purape (2) 16 nr / h of degassed deionized water are fed in via line (11). The reactants are in the heat exchangers (4) in countercurrent through the reactor (6) leaving the product '-products warmed and vaporized, then in the superheater * is brought to the reaction temperature of 265 ⁰ C (5) and then fed to the reactor (6) via line (13). the pressure at the Reaktoreintritit is 7o atm. the reactor with 38 ar catalyst filled, which was produced by leaching a spherical cracking catalyst of approx. 5 now 0 based on bentonite (manufacturer Süd-Chemie, trade name K 3o6) with hydrochloric acid and subsequent impregnation with phosphoric acid in such a way that the AlgO ^ content is 3. » 7 $> » the pore volume 0.85 nl / g of catalyst and the inner surface area 185 m / g of catalyst and the E ₅ PO content after impregnation and drying is 41.5%, based on the total weight. The reaction products are fed to the heat exchangers (4) via line (14) where they warm up the reactants with cooling and partial condensation. The gas-liquid mixture is separated in the sump of the washer (7), the rising gas is in the counter- _; current at a temperature of 60 ⁰ C by washing with 4.5 myh ^: water freed from alcohol and then fed to the circulation compressor (3) via line (15). The in the sump of the washer (7) j. Accumulating liquid is depressurized in line (I7) and stored in the raw alcohol storage tank | 8). From here it is fed to the distillation via line (19) _. Released gas 0.8) - approx. 75 Nm-Vh - is fed to the combustion. '!

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In (8) there are 23, ο t raw alcohol per hour as follows Composition to:

■ 7.4 * Ethanol o, 32 Diethyl ether o, o3 acetaldehyde o, o5 % Butanols 0.09 Hydrocarbons rest water

The raw alcohol contains 195 ppm phosphoric acid, which before entry (14) into the washer (7) by adding caustic soda | is neutralized. As a supplement, 4.5 kg per hour are required Phosphoric acid (calculated loo #ig) in the free space of the Sprayed reactor above the catalyst.

The raw alcohol (19) becomes 4, ο t / h by distillation Ethanol obtained, which corresponds to a yield of 95 * ο #

The density of the circulating gas on the pressure side of the circulating compressor O) is 168 g / liter. (75'atil and 76 ° C). For every t of alcohol produced (calculated as loo #Lg) the energy requirement for the superheater (5) is 1.725 * Io kcal and for the drive of the circulation compressor it is 0.11 * lo "kcal.

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Example 2

In the operating system described in Example 1, the following amounts are per hour over the catalyst in the reactor drove: -

57,000 Nm- * propylene (85 #ig) in the circuit (I5) 2,000 Nnr fresh propylene (99.6 J & Lg) (lo) "

8.5 nr degassed deionized process water (11) 36 atmospheric pressure at reactor inlet (I5) '178 ⁰ C temperature at reactor inlet (I3)

38 m of catalyst are used. The phosphorus acidity of the catalyst is 26.5 wt.

The partially freed by cooling in (4) from the formed isopropanol recycle gas is at a temperature of 95 ° C in the scrubber (7) in counter-current with 24.5 nr water having a temperature of 98 ⁰ C washed .. As the washing water is a part of the used in the distillation of the crude isopropyl alcohol in the bottom of the rectifying column water.

That which is released during the relaxation of the alcohol formed in (8) Some of the gas (18) is returned to the process! 12o Nnr are discharged per hour and incineration fed

By distillation, ² ^, 9 t isopropyl alcohol is obtained from the crude isopropyl alcohol (I9), which corresponds to a yield of 95/8 #

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In (8), about 56.6 t of crude isopropyl alcohol of the following composition are produced per hour:

13.45 Jb isopropyl alcohol ο, 15 % Diisopropyl ether ο, οο5 # Acetone ο, οδ % n-propanol ο, ο4 % Hexanols ο, ο3 % Hydrocarbons rest water

The energy consumption for driving the rotary compressor (5) is 0.09. Io kcal and at the superheater (5) 0.86 · lo ^ kcal per t of isopropanol produced (calculated at 100%). the The density of the circulating gas on the pressure side of the circulation compressor (3) was measured at 45.6 atmospheres and lo6 ° C. to be 128 g / ltr.

Example 3

You do not, as described in Example 1, discharge 75 Nm / h Ural gas from the system via line (18), but instead compresses this amount with the fresh ethylene compressor (1) and thus returns it to the system via line (11). For this, from the Ural inlet gas to the scrubber (7) via line (16) per Sturide 4oo Nnr of the distillation column (9) fed. The concentrated head product is transferred via line (2o) admixed again with the cycle gas «while in the sump Io Nm of a gas with the following composition is obtained:

Nitrogen 0.2 vol. J6

Methane o.4 vol. #

Xthane 19.5 % by volume ', ■

Ethylene 47.1 vol. #

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Isobutane) ΐ- ν » _ftl « j

η-butane) 15.6 % by volume

Butene 12.1 % by volume

Butadienes ο, 2 vol. $>

unknown 5.0 vol. %

(see example Jb for more details)

This procedure results in a circulating gas concentration of 95.1VoI. # Ethylene one. The ethylene conversion on the catalyst rises to 2,4oo NmVh and the ethylene yield, based on converted ethylene, to 97.4 % . (75 atü and 76 ⁰ C). The energy consumption for the Uralauf compressor (3) has decreased to ο, οβ · lo ⁶ kcal and for the superheater (5) to 0.56 · Io kcal per ton of ethanol produced (calculated loo "$ 6ig).

Under the conditions of Example 3, the catalyst has only 12.7 # of activity in a 5 month period lost, which the catalyst has lost under the conditions of Example 1.

b) Separation of the impurities from the circulating gas of the ca

In a sieve tray column (9), 380 mm inner diameter, 78 trays, bottom level 16ö mm, with a reflux condenser flanged to the column and from the ethanol synthesis via line (16) per hour 400 Nnr circulation gas with an ethy lengehält 95.1 Vol. % Together with 0.5 ltr. Ethylene glycol - to prevent hydrate formation - fed into the 44th floor. The operating pressure at the top of the column is 42 atmospheres, the top temperature + 2 ° C. and the bottom temperature 116 ° C. The steam consumption is 0.048 · Io kcal / h.

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At the top of the cooler (2o) 39o only gaseous are withdrawn per hour and fed into the circulating gas via the fresh ethylene compressor (1). The ethylene concentration at the top is 96.5% . The liquid withdrawn from the bottom of the column (9) via line (21) is separated into gas and liquid after the expansion. The resulting gas - Io Nnr / h, composition see Example 3 - is burned. The liquid is separated into two layers in the decanter. The water is separated from the lower layer by distillation: ■ The ethylene glycol returns to the column (9). The upper layer, about 40 l / h, can be worked up to diethyl ether by distillation * The upper layer contains approx. 38 # diethyl ether, 5.5 S ^ Cg-C ^ -carbons, 0.3 $ ethanol and 2 7 J6 butanols. The rest are higher alcohols and hydrocarbons having a boiling range up to 315 ⁰ C. By elemental analysis it was established as Suraraenformel for the above 115 ° C boiling point mixture.

Example 4

The system is operated as in example 2. By discharging of 4oo Nm circulating gas from the pressure side of the circulating grain compressor (3), before frozen water (11) and fresh propylene (lo) I. are fed into a sieve tray column of loo trays / the operated at a pressure of 22 attt, gas is in circulation set a mirror of 96.2 #. That while relaxing The gas released by the crude isopropanol in (8), on the other hand, is completely returned to the cycle gas via the compressor (1). The propylene conversion rises to 2.25o Nnr / h and the Yield of isopropanol, based on converted propylene, to 97.6 # · The density of the circulating gas is now at Pressure side of the circulation compressor (3) at 45.6 atmospheres and lo6 ° C

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12ο, 5 g / ltr. The energy consumption for the compressor is O) o, ö5. lo ⁶ kcal for the superheater (5) ο, 4δ · lo ⁶ kcal per ton of alcohol produced (calculated loo J ^ ig). The decrease in activity of the catalyst over the period of 7 months was only 27.3 % of the decrease in activity of the catalyst in Example 2.

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Claims (2)

.l.) j Process for the catalytic hydration of ethylene C s or propylene on a fixed bed catalyst to the corresponding alcohols in the gas or gas-liquid phase, characterized in that the mixture leaving the reaction chamber after condensation The olefin which has been separated off and freed from alcohol by washing is concentrated by distillation in such a way that after recirculation of the gas, a circulating gas concentration from more than 9o VoI. #, preferably from 95 - 97 VoI. #, adjusts. 2.) The method according to claim 1, characterized in that the distillative concentration under conditions near the critical point of olefins in the presence of oils produced during hydration or those that are foreign to the process Detergents takes place, except for the higher than Olefin-boiling impurities and the more highly polymerized Hydrocarbons also have lower-boiling impurities than the olefin via the sump Distillation column are separated. BADOHIOINAL 109823/2204 Blank page