DE945326C - Process for the alkylation of aromatic hydrocarbons - Google Patents

Description

Process for the alkylation of aromatic hydrocarbons It is known, the alkylation of aromatic hydrocarbons using olefins and in particular by means of gaseous olefins under normal temperature and pressure conditions to be carried out in the presence of catalysts of the Friedel-Crafts type. These The reaction always gives a mixture of mono- and polyalkylated derivatives. That is particularly the case in the synthesis of monoethylbenzene.

It has been recognized that using the known methods, for example of the process described in U.S. Patent 2,222 OI2, the percentage of the polyalkylated products obtained versus the monoalkylated compound, which is technically only interesting, is such that this process for industrial recycling is practically ruled out. The aim of the invention is accordingly the improvement of this process in order to reduce the proportion of polyalkylated Products to achieve.

It has now been recognized that the proportion of polyalkylated components increases as the catalyst ages. In an alkylation of benzene by means of ethylene in the presence of aluminum chloride, which is carried out at a temperature of 83 ° until the catalyst is completely exhausted, the following result is obtained: Table I Age of the composition of the alkylated crude product Catalyst Monoalkylbenzene polyalkylbenzene o up to 3 hours 85% I5% 3 - 6 - 80 010 20% 6 - 9 75 o / 0 25% If no separation of the alkylation products is undertaken during the reaction period, it is found that after g hours the total of the alkylation products contains only 640/0 of monoalkylbenzenes.

It was further found that the polysubstituted derivatives form all the more easily than the concentration of monoalkylated products in the reaction mixture increases.

According to the invention, these observations have led to the monoalkylated Separate products to the extent of their formation, without up to them with the catalyst to keep in touch with his exhaustion.

It has also been found that the proportion of polyalkylated components increases as the reaction temperature falls. This results in the following picture: Table 2 Reaction ratio of the monoalkylbenzene temperature to the total alkylated ° C derivatives 45 53% 65 670/0 85 77% It is therefore of interest to work at an elevated temperature, and for this purpose the work is carried out at least towards the end of the reaction at the boiling temperature.

Finally, it was found that the yield of monoalkylated Products if you add those in the previous work steps polyalkylated derivatives sent back into the cycle, under the express The prerequisite is that work is carried out at a sufficiently high temperature. That is illustrated by the examples of Table 3 below, which shows the results obtained with different mixing ratios and temperatures can be obtained.

Table 3 Mixture 1 i 1 ii 1 III mixture Benzene ................. 100 90 90 100 Polyethylbenzene ........ 0 10 10 0 Temperature ............. 83 ° 83 ° 65 ° 65 ° Mol. C2Ho 0.43 0.39 0.39 0.33 Mol. C6H6 Parts by weight converted benzene Parts by weight of the react Benzene fed in 39% 39% 21% 250/0 Monoalkylbenzene Total alkylbenzene ... ... 77% 86 ° / o 62% 67% Benzene as monoethyl benzene Total alkylated Benzene .. .. 79% 870/0 78010 740/0 Ethylene as monoethyl benzene Total bound Ethylene .................. 720/0 870/0 400/0 54% From the last two lines of this table it can be seen that the conversion coefficient of benzene does not increase at low temperature, but that the conversion coefficient of ethylene decreases considerably, due to the formation of a large proportion of hexaethylbenzene. The recirculation of the polyalkylated derivatives will therefore have to be carried out at an elevated temperature, as will the reaction itself, and one will have to work under conditions such that it is possible to control the percentage of recirculated polyalkylbenzene at will to regulate that maximum yields are achieved which are to be reconciled with the desired mean life of the catalyst.

The method according to the invention is thus characterized by the following features marked: a) The work is carried out immediately at the boiling point of the mixture, obtained alkylated body carried out by. Otherwise you can use this temperature by using solvents or by changing the pressure or by appropriate Adjust control of excess benzene appropriately; b) go through the products the reaction zone in a relatively short time, based on the service life, which the catalyst would show if the mode of operation was discontinuous; c) the alkylated products are immediately separated from the catalyst complex. Of the the latter will. sent back into circulation; d) the monoalkylated Products are immediately separated from the polyalkylated products and the latter wholly or partially sent back into the cycle.

In the following the invention is illustrated by means of practical embodiments with reference to Figures I to 3 of the drawings.

In dilesen shows: Fig. 1 a general scheme of a system according to the invention, Fig. 2 is a schematic partial representation of a modified one Embodiment and Fig. 3 a representation corresponding to Fig. I with additions.

As Fig. 1 shows, the aromatic hydrocarbon from the Charge vessel A through the siphon to the top of reaction column B at one rate fed, which is controlled by the slide b, simultaneously with the Catalyst (complex: hydrocarbon-AlCl3), which flows in through pipe C. The olefin or the gas mixture containing it is passed through column B below the pipeline d is fed at a speed determined by the valve e is regulated. If necessary, gaseous hydrogen chloride is released through the Pipeline f added, in a monitored and regulated by the valve g Lot. In column B the temperature is automatically increased by the mixing of the liquids regulated, the olefin runs in countercurrent to the aromatic hydrocarbon and the catalyst to, forming alkylilerte derivatives of the same, which are in the Collect the foot of the column, so that a temperature gradient is established at which the Temperature gradually rises from top to bottom, which means maximum formation of monoalkylated derivative is advantageous. The ratio of hydrocarbon to the catalyst is regulated as well as the feed of olefin so that in the foot the column the desired concentration of alkylated derivative and at the top of the Column as complete exhaustion of the olefin as possible is achieved. In the cooler c the hydrocarbon is separated from the gases, which in turn are separated by the pipeline i are discharged and then subjected to any required washing can to recover entrained hydrocarbons. The hydrocarbon is sent back into the circuit through the pipeline 11.

At the bottom of column B, the mixture of catalyst is unreacted Hydrocarbon and the alkylated reaction products in the decanter D separately, optionally with cooling to reduce the solubility of the hydrocarbon-AlCl3 complex compound.

This complex compound, which is deposited in the lower layer, is returned to the reaction circuit through pump E and pipe C. The mixture of aromatic hydrocarbons that forms the top layer is through the pipe 1? sent to the column 17, where it is washed and in which it meets the washing water in countercurrent, which enters through tube j. The washing water is discharged through the pipe k, while the hydrocarbons after washing out and removing the traces of entrained catalyst by the Pipeline I get into fractionation column G. The in the form of an azeotropic Mixtures of vapors withdrawn from column G are condensed in condenser H, the unreacted hydrocarbon in decanter I from the small amounts separated from water, which is entrained during passage through the wash column have been. The hydrocarbon is transported through the pipeline rn and h via a Valve returned to the reaction column B. A small amount of the hydrocarbon is fed to the column G by the lifter n via a slide.

At the bottom of the column G, the mixture of alkylated hydrocarbons is withdrawn, which is fractionated in column 1. Receives at the top of this column the pure monoalkyl product, which condenses in the cooler K and through the pipeline o is withdrawn or partly returned through the pipelinep. At the foot the column 1, the polyalkylated derivatives are withdrawn through the pipe system r, which are partially discharged through the pipeline, while the rest through the Pipeline t and the pump N is sent back into the reaction column B. Of the Catalyst used can be either periodic or continuous through the tube u would be derived from the decanter D and hydrolyzed to produce the alkylated To pull out derivatives, which then arrive in column G for separation. As a replacement is now supplied through the pipe v fresh catalyst, for example is obtained by repeatedly passing over from the decanter I deposited Benzene over aluminum chloride in column L. This passing or passing through happens by means of the pump M or with the help of any other means. One has the possibility of regulating the reaction temperature in column B by the Pressure in this column changes. The claimed process can also be used in the presence run from solvents.

Avoid placing the catalyst in the foot of column B, where it is is in contact with the reaction products, to overheat.

The method of operation described above can also be carried out by means of the arrangement according to Fig. 2 can be improved in the following way.

In the foot of the reaction column B, the complex compound is decanted essentially on a deep intermediate floor w. The lower layer is now optionally an auxiliary decantile vessel D supplied, from which the pump E the catalyst is again filled into the reaction column B through the pipe C.

The mixture of alkylated derivatives at the foot of the Reaction column and exit at the decanting vessel D, is now through the pipe system R of the wash column 17 (Fig. 1) and then fed to the distillation.

The details of the implementation of the process and the apparatus can be modified in many ways.

For example, you can go through column B with the intermediate trays Replace a reaction vessel with or without a stirrer is used while the other devices remain unchanged. One forgives in this way, however, the advantage of separating the polyalkylated compounds in the column according to their volatility on the different trays of the column. Likewise Instead of column B, a contact column working according to the countercurrent principle could be used put, such as such. B. in the aforementioned U.S. Patent 2,222 OI2 is described. In this case you lose, even if you increase Temperature works under overpressure, for example, the advantage of self-regulation, which occurs through boiling; however, there will be all of the other advantages of the invention retained, namely - not recycling the monoalkylated product and the regulated recycling of the polyalkylated products.

The invention also includes an improvement on the above Probably which is used with particular advantage when it comes to alkylation of benzene with propylene or butylene, which makes it possible to increase the proportion to depress polyalkylbenzenes even further. The alkylated products that are obtained as by-products or waste products in the reactions described above, such as the products withdrawn at S (Fig. i), can be replaced by an excess worked up by benzene in the presence of a new amount of catalyst of the same type will; but that requires an additional consumption of catalyst. on the other hand prevents re-cycling in the alkylation zone itself even if it improves the yield, it does not result in the formation of new amounts of polyalkylated ones Products; this sending back can only be partially done.

But it has now been found that in the Falbe the alkylation of Benzene by higher olefins than ethylene alkylation at ordinary temperature more advantageous. At elevated temperature, for example at boiling point, the formation of the polyalkylated derivatives comes to the fore.

So if you have the polyalkylated derivatives in the reaction mixture from the alkylation in the cold back into the cycle, it can be determined that that new amounts of polyalkylated derivatives arise, as if sending them back again did not take place in the cycle.

If, on the contrary, the reaction mixture from the alkylation in the heat returns, it is found that the effectiveness of the catalyst decreases much faster, and this results in a new formation of polyalkylated ones Derivatives that can be attributed to the aging of the catalytic converter and which are only can be stopped by using significantly larger amounts of the catalyst.

It was also found that sending back the entire polyalkylated derivatives are possible and effective if one does the following works in two different phases: one is subjected to the action of the olefin a mixture of aromatic hydrocarbons and the polyalkylated derivatives, that you want to put back into the cycle, in the presence of suitable amounts of one Friedel-Crafts type catalyst, for example A1 C13, at ordinary Temperature and preferably avoiding any increase in temperature by a careful dissipation of the heat released by the reaction, because the Realtion is strongly exothermic. After a certain amount of olefin is formed, it becomes the mixture is brought to the boil and, after hydrolysis of the aluminum chloride, the distillation subject. The excess of unreacted aromatic hydrocarbon is now recovered and the mono- and polyalkylated derivatives. If the amount added is polyalkylated Derivatives and the fixed amount of olefin in the equilibrium of the products At the end of the reaction, it can be seen that the whole bound Olefin is implemented as monoalkylated derivatives and the amount of polyalkylated Derivatives are found unchanged.

A modified embodiment of the method which also gives good results provides, consists in the alkylation in the absence of polyalkylated derivatives to perform in the cold. After the desired amount of olefin has been absorbed added the polyalkyl compounds to be sent into the circuit and the temperature increased to Sileden. Under these conditions, those in the first phase will still be available The polyalkyl compounds formed are converted into monoalkyl compounds, and one finds at the end of the reaction ur the polyalkyl compounds that were added in the second phase and are intended to be put back into the cycle.

The advantages of the method are clear from the following table 4, in which the results of numerous tests and experiences are presented for comparison are, according to the above statements in the alkylation of benzene by butylene. In the. Table are entered: In column A is the ratio of the polyalkyls formed to the monoalkylenes formed and in Column B shows the consumption of AlCl3 per 100 kg of monoalkylated product.

The invention can be used in batch or continuous processes Table 4 AWAY Non-cycle alkylation Ordinary temperature .. 0.925 I, 440 / o Non-cycle alkylation 85 to 900 o.365 0.365 1.88% Alkylation without cycle in the cold; Separation of poly alkyls and conversion of same in a special one Operation ...................... 0.033 4.7001o Alkylation with cycle of Polyalkyls at ordinary Temperature ...................... 0.258 3.07010 Alkylation with cycle of Polyalkyls at 85 to 90 ° ... 0.287 3.09% Alkylation with cycle in the Cold with subsequent heating to 85 to 90 ° ... 0 1.80% Alkylation without cycle in the cold with subsequent Circulation and heating up 85 to 90 ° ...................... ° 0 1,700 / 0 to pure olefins or to olefins in a mixture with saturated hydrocarbons or inert gases, such as those obtained when cracking petroleum products at normal or elevated pressure.

Example I In a 300 liter vessel filled with 109 kg of benzene, 20.1 kg of polybutylbenzene from a previous operation and 1 kg anhydrous aluminum chloride is charged, it is left at ordinary temperature absorb an amount of 24.9 kg of butylene. The absorption is complete in 35 minutes. The mixture is then brought to the boil for 15 minutes, washed with water and dried the product by azeotropic distillation followed by rectification.

74.3 kg of unreacted benzene, 59.6 kg of monobutylbenzene are obtained, 20.1 kg of polybutylbenzene that you send back in a new cycle can.

This gives a quantitative conversion of the butylene involved and the reacted benzene in monobutylbenzene. The consumption of catalyst 1.68 kg of AlCl3 is monobutylbenzene produced on Iookg.

Example 2 100 kg of benzene are added in the presence of 0.92 kg of Al Cl3 ordinary temperature with 22.7 kg of butylene alkylated. Then you put 18.4 kg of add polybutylbenzene to be recycled and heat for 15 minutes to simmer.

After washing and drying, rectification gives 68.9 kg unreacted benzene, 53.8 kg monobutylbenzene, 18.4 kg polybutylbenzene, the can be sent back into the cycle.

Example 3 A reaction vessel with a useful capacity of 100 liters, which is attached to a Butylene gasometer is connected, is fed with in a continuous operation 96 kg / hour of a mixture of 84.50 / 0 benzene and 15.5% intended for circulation Polybutylbenzene containing 740 g of anhydrous aluminum chloride in suspension. While the reaction vessel is kept at ordinary temperature, absorption occurs of 18.5 kg / hour butylene.

The reaction mixture is continuously withdrawn and continued for 15 minutes heated to 930 in a simple steam coil heater, then in continuous Operation washed with water and distilled.

This gives 44 kg of monobutylbenzene, 15 kg of polybutylbenzene per hour, 55.5 kg of benzene; the last two derivatives are after addition of 25.5 kg / hour fresh benzene sent back into the cycle.

Example 4 This procedure generally works in two phases; Both reaction stages are carried out in column B, which of course has a slightly larger number of Contains intermediate floors. The apparatus essentially corresponds to that of the one-step process, however, there are certain differences in the treatment steps adapted deviations also required in the apparatus. These differences and Deviations are described in more detail below with reference to Fig. 3, with the parts that have remained unchanged compared to Fig. I have the same reference numerals are designated, unless there is a designation of the same parts at all unnecessary.

There are two reaction zones formed in that the olefin, optionally in a mixture with HCl, instead of entering the lower part of the column, into the middle part is introduced through the pipeline dz with the slide el.

Some of the benzene enters column B through line such as in the case of Fig. I, but it can also be partly in the middle part of the column B are introduced through the supply line kl.

The upper part of this column B becomes once and for all with a third Body of very low boiling point, for example butane, charged.

The effect of this third body is particularly evident, when it is the alkylation of aromatic hydrocarbons by reaction with Olefins longer chains than ethylene. The presence of the third body allows a perfect monitoring of the slow and steady reaction and avoids the occurrence of heat build-up, especially at the beginning of the treatment.

The circulation of the given in the column B before starting the process third body is regulated in such a way that, as soon as it is. a certain Reaction equilibrium has established, at the level of the intermediate floors of the upper Part of the column holds where z. B. sets a temperature of 300. Under under these conditions, the alkylation in the upper part of column B goes under normal conditions Temperature in front of you, and the conversion of the polyalkylated products into monoalkylated ones Products, however, takes place in the lower part of the column, which is at a temperature of is held at about 90 °. The polyalkylbenzenes are in their entirety by the Pipeline t is fed back into column B, from where it either goes into the head or fed back into the middle part of the column by means of the pipeline tl can be.

In certain applications, especially when the converted olefin Butylene is the third body that can be used for charging from the outset the alkylation plant provided olefin mixture be included. This is with one particularly advantageous embodiment of the method of the case where for loading Mixtures of butylene and butane are used as they come from the refineries. here if the third body, i.e. the butane, is automatically included in the charge contain. These mixtures are then immediately put into the central section of the column B introduced through line dl.

During the treatment, the butane collects in the upper part of the Column B at where it plays the role of the third body mentioned It is however necessary to continuously withdraw an amount of butane equal to that Amount contained in the starting mixture so that the equilibrium is not disturbed will. This excess of butane is continuously withdrawn in a vaporous state, for example through the pipeline i.

Claims (4)

PATENT CLAIMS: I. Process for the alkylation of aromatic hydrocarbons by reaction with olefins in the presence of Friedel-Craftsscher catalysts, thereby characterized in that the reaction at least at the end of the reaction at boiling temperature of the reaction mixture carried out and the reaction products in good time before exhaustion the catalyst then sent back into the circuit is separated from it and on the one hand in the monoalkylated and on the other hand in the polyalkylated products are divided, of which only the polyalkylated in a controllable amount in the Reaction cycle are returned. 2. The method according to claim 1, characterized in that. kenmeichnet that the reaction products be passed through the reaction zone for a relatively very short time compared to the life of the catalyst when it is discontinuous Would own way of working. 3. The method according to claim I and 2, characterized in that the Alkylation of aromatic hydrocarbons with an olefin or a mixture of olefins in dilution with a gaseous paraffin hydrocarbon or inert gas is carried out. 4. The method according to claim I to 3, characterized in that in a first phase of alkylation of the hydrocarbon and the olefin, more usually or even lower temperature brought to reaction in the presence of the catalyst are and that then in a second phase the reaction products to boiling temperature are heated, whereupon the polyalkylated products after the thermal adhesion deposited and returned to the alkylation phase or to the degradation phase. Cited publications: C. A. Thomas, Anhydrons Aluminum Chloride in Organic Chemistry, 1941, pp. 459 to 461, 690, 691 and 714; Journal of the American Chemical Society, 49 (1927), pp. 3150 to 3156.