DE767297C - Process for the alkylation of aromatic hydrocarbons - Google Patents

Description

Process for the alkylation of aromatic hydrocarbons It is known that one aromatic hydrocarbons in the presence of zinc chloride, phosphorus pentoxide, Alkylate sulfuric acid or activated aluminum hydrosilicates with alcohols can. However, none of these catalysts can be used to produce toluene from benzene and methanol in an economical manner.

Performs the reaction of benzene with methanol in the presence of acid phosphates, especially heavy metals, on supports such as coke as catalysts by, it is true that higher yields of toluene are obtained. These catalysts have but unsatisfactory mechanical properties and only a short service life. In addition, a number of undesirable by-products are formed. The implementation with dimethyl ether instead of methanol is not possible with these catalysts. Also with so-called. calcined phosphoric acid, d. H. a calcined mixture of a phosphoric acid with a solid silicate adsorbent, is obtained from the reaction of Benzene with methanol and dimethyl ether has higher yields of toluene, but has this catalyst also only has a short lifespan.

It has now been found that the production of toluene from benzene and methanol can be carried out very advantageously, if in the presence of fully catalysts works which, in addition to phosphoric acid, zinc oxide as an additive contained in such an amount that the phosphoric acid in excess (of expedient 10 to 30%) above the amount necessary for the formation of secondary zinc phosphate is. and the water content not falling below @ about 4%, preferably been dried to a water content of 4.5 to 12% and preferably from 5 to 8% are. These catalysts can also be used to convert benzene with dimethyl ether to toluene. They can also be used for aromatic hydrocarbons other than renzene alkylate.

The catalysts mentioned are very effective and do too much less formation of undesirable by-products than the catalysts used hitherto. They also have a high mechanical strength and show when treated appropriately compared to the known catalytic converters a much longer service life.

In addition to zinc oxide, the catalysts can also contain other additives Oxides, e.g. B. manganese oxide. Cadmium oxide, iron oxide. Magnesium oxide or aluminum oxide, contain.

You can also mix them with carbon powder.

These additives are usually not in excess of 10 per cent Amount applied.

The phosphoric acid is advantageously mixed with the zinc oxide in a mixer brought together, the zinc oxide dry or pasted with water of the implementation is subjected. The amount of water is approximately 10% of the weight of the zinc oxide and shouldn't be bigger than this. To the dry or pasted with water Zinc oxide is first allowed to rapidly flow in phosphoric acid with the stirrer running: The Because of the heat developed in the process, implementation takes place with vigorous steam development in front of you. If about a third of the required phosphoric acid has flowed in, so if you slow down the feed rate, otherwise you will get an inhomogeneous product receives. After the second third of the phosphoric acid has been added, a homogeneous, Creamy liquid available, to which you can then with pinch-speed accelerated Stirrer lets the rest of the acid flow in again quickly, finally homogenizing the mixture for another 3 minutes. then leaves the creamy liquid on while still hot Take off the trays and immediately bring them to a temperature of at least 120 °. functional on I30 to 150 °. heated drying cabinet. Cooling down is to be avoided. otherwise the strength suffers. The sheets are expediently made of aluminum or with Phenol-formaldehyde resin coated iron.

In order to produce the water content specified above, the Catalysts useful at moderately elevated temperatures up to about 180 °, $ preferably not over 150 °. The drying can take place in the presence of additional reducing agents. Metals, z. B. zinc.

Cadmium. Aluminum. Magnesium or silicon, happen.

The drying time depends primarily on the temperature used, but then also on the type of drying cabinet and the layer thickness of the goods addicted; at 150 ° it is an average of 12 hours.

The acidic zinc phosphate can then be easily removed from the metal sheets will; it is ready for use after breaking to the desired grain size. When breaking there is less loss due to abrasion when using corrugated sheets for drying. The waste can be reprocessed with a new approach. Appropriate if you add the waste in the second third of the approach; but you can also do it add to the incoming acid or the dry zinc oxide.

The alkylation of aromatic hydrocarbons in the presence the catalysts mentioned is expediently in iron, pressure-resistant ovens Temperatures between 280 and 370 °. expediently between 310 and 340, and under pressure from 25 to 500 at or even higher. advantageously carried out at 30 to 100 at. the Throughput rate is generally from 0.1 to 0.5 l per hour and preferably 0.25 to 0.30 1 starting mixture per liter of catalyst. For the production of toluene it is advisable to start from a mixture of excess benzene and methanol (molar ratio advantageously 4: 1) or dimethyl ether (molar ratio advantageously 8: 1). One can also use mixtures of methanol and dimethyl ether as alkylating agents.

Subject to a treatment of whether about 4 to 5 weeks leaves the effectiveness of the catalytic converter gradually. if you work in the usual way. Man can then sator the Kataly by treatment with steam at an elevated temperature revive. It was found. that the life of the catalyst was kept considerable can extend. if you often change the direction of flow of the substances to be converted, z. B. every day, changes. The catalyst then still shows none even after 7 weeks Reduction is animal effectiveness.

The product formed is worked up by distillation. While in the previously known processes, the reaction of benzene with methanol and or or dimethyl ether to a yield of at most about 120 / o toluene in addition to 2.5% high-boiling aromatic hydrocarbons, one obtains after the present process 15 to 17% toluene in addition to traces of by-products.

Example I 2.2 kg of zinc oxide are mixed with 400 g of abrasion from one earlier approach in a mixer and then leaves a drip device with the stirrer running 2.2 1 85% phosphoric acid flow in. the first third of the acid is left quickly, the second third flow slowly and the last one again quickly. The whole will mixed for a further 2 minutes, then the mixture is drained onto metal sheets and dried 18 hours at I300, after which the water content is 7%.

The solid pieces made from the dried mass become brought into an iron pressure furnace, through which at 35 at and 3300 a steam mixture, containing 4 moles of benzene to 1 mole of methanol, with an hourly throughput rate of 0.251 per liter of catalyst is passed from the bottom to the top. That by cooling the condensate extracted from the furnace consists of 5% water, 75% benzene, 15% toluene, 44% xylene, 0.4% higher methylated aromatics, 0.5% Methanol and 0.1% dimethyl ether. After about 4 weeks, the Catalyst to slowly decrease.

For example 2 2 kg of zinc oxide are mixed with 200 g of manganese oxide and 0.8 kg of water intimately kneaded; 2.2 1 85% phosphoric acid is allowed to flow into the fast. The resulting cream-like liquid is then spread on aluminum sheets in a thickness 3 cm and dried at 1600 for 12 hours. The ones from the dried one Mass-made pieces who put the in an iron pressure furnace through the a vapor mixture under the conditions given in the previous example 8 moles of benzene and 1 mole of dimethyl ether is passed from top to bottom. The end The condensate obtained from the end products consists of 2% water, 78% benzo, l, 15% toluene, 3.60 / 0 xylene, 0.40 / 0 higher methylated aromatic hydrocarbons and 1 dimethyl ether. The catalyst starts to work after about 4 weeks slowly getting smaller.

Example 3 2.2 kg of tin oxide are mixed with 1.2 l of water in one with a mixer equipped with a stirrer mixed for 10 minutes. Then one leaves under continued Stir in a stream 1/2 cm thick, add 0.81 70% phosphoric acid, throttle then the feed to about half the feed rate and still leaves around 1.11 flow in. Then let about 0.81 flow in again with a full jet, - whereby the stirrer is accelerated.

The whole is then stirred for a further 3 minutes to homogenize and then lets the creamy liquid obtained through one in the bottom of the mixer with the stirrer running on a sheet metal of 1 square meter taper to a layer 3 cm thick. The mass is dried for 14 hours at 140 °, after which the water content is 60 / o. Those made from the dried mass Pieces are filled into a single pressure furnace, through the one in the example I specified conditions a vapor mixture of 4 moles of benzene and 1 mole of methanol but the direction of flow is reversed every 24 hours. That condensate obtained from the end products consists of 5% water, 74.5% benzene, 15.5% toluene, 40/0 xylene, 0.40 / 0 higher methylated aromatic hydrocarbons, 0.5% methanol and 0.1% dimethyl ether. Even after 7 weeks, the Catalyst not yet lower.

B e i s p i e l 4 About a catalyst prepared according to Example 3 in an iron pressure furnace at 40 at and 3500 a steam mixture, the I mol Contains naphthalene for 1 mole of methanol with an hourly throughput rate of 0.31 per liter of catalyst passed from the bottom to the top.

After the water of reaction has been separated off by distillation of the product obtained after separation of the naphthalene about 15% (of the weight of the product) a liquid mixture boiling between 235 and 2850 of different Obtained mono- to tetramethylnaphthalenes.

By mixing the product with a low-boiling, paraffinic one Gasoline and filtering or centrifuging can make up most of the unreacted Naphthalene can also be separated off without distillation, since naphthalene is difficult to use here is soluble, but not the methylnaphthalenes.

Unreacted methanol distilled off from the water of reaction, a small amount of dimethyl ether and the recovered naphthalene are used again passed over the catalyst.

Claims (3)

PATENT CLAIMS: I. Process for the catalytic alkylation of benzene or other aromatic Hydrocarbons with methanol and or or dimethyl ether at elevated temperature and under elevated pressure, thereby characterized in that the catalyst used is mixtures of phosphoric acid and zinc oxide used, in which the phosphoric acid in excess over that to the formation of secondary edema Zinc phosphate necessary amount is present, and which does not fall below about 4% Water content were dried. 2. The method according to claim I, characterized in that the catalyst the phosphoric acid in an excess of 10 to 30% over that for the formation of secular Contains zinc phosphate necessary amount and dried to a water content of 5 to 8% became. 3. Process according to Claims I and 2, characterized in that after short time intervals the direction of flow of the substances to be converted changes. To differentiate the subject matter of the invention from the prior art are The following publications were considered in the granting procedure: German Patent specification No. 617 990: French patent specifications No. 657 416, 681 049, 714 813; Swiss patent specification No. 207 342.