CS205778B1 - Method of making the styrene - Google Patents

Description

The present invention finds use in obtaining styrene by catalytic dehydration of methylphenyl carbinol in the co-production of propylene oxide and styrene. Styrene is mainly used in the production of polystyrene and in the production of butadiene-styrene rubber.

Most of the known methods for dehydrating alkylaromatic alcohols are carried out in the vapor phase on catalysts with the addition of water vapor. As catalysts, titanium oxide, silica, alumina and other suitable substances are used. The dehydration is carried out at temperatures ranging from 180 ° C to 280 ° C. (In the styrene extraction process, the product yield does not exceed 80% by weight and / or the yield of high-boiling by-products ₍ ranging from 2 to 4% by weight) (French Patent Nos. 1,459,796; 1,460,574; 1,469,326; U.S. Patent Nos. 3,363,035, 3,351,635 and 3,442,963).

. It is known to produce styrene from methylphenylcarbimiol and adiabatidic conditions such as alumina or titanium dioxide as catalysts and the presence of water vapor at atmospheric pressure and at a temperature in the range of 270 ° C to 300 ° C (French Patent (U.S. Pat. 1,460,520).

As the dehydrogenation reaction of methylphenylcarbino205778 lu proceeds with higher heat consumption (it is necessary to introduce a greater amount of superheated water vapor) (/ 15 moles of water per .1 moles of methyl ifenyltoarboline) to achieve complete conversion of methylphenyl / arbinol. higher energy consumption and the need to 'take in consideration' water purification and steam generation.

In the course of this process, overheating of the methylphenylcarbinol, which leads to the formation of large min / s of high-boiling by-products, necessarily reduces the yield of the final product.

It is therefore an object of the present invention to increase the yield of styrene while simultaneously reducing energy consumption.

It is an object of the present invention to improve the catalytic dehydration technology in the vapor phase of methylphenylcartotool, which would make it possible to reduce the rt / rarity in the high-boiling by-products and to increase the selectivity of the method considered.

According to the present invention, the problem is solved by the dehydration of methylphenylcarbiriol according to the present invention in a gas-phase process, wherein the process for producing styrene by dehydrating methylphenylknthinol in the vapor phase with a dehydration / ratation catalyst in the presence of water vapor and adiabialtic conditions. that leaves the first ribbon and comes to the second htupni is regulated so that

Jettro temperature o and ivfetuplu to the first dehydration trace (it is the same or near.

As the dehydration catalyst, for example, aluminum oxide, silicon dioxide, titanium dioxide, and aluminide are used.

One preferred aspect of the method according to the invention is that the dehydration is carried out n ^! and an alumina at a contact gas temperature of 260 DEG C. to 300 DEG C. at the inlet of each stage. The methylphenylcarbinol-water vapor molar ratio is at 11:10 in the first stop.

The volume velocity of methylifeinylcarbiinol, in both dehydration stages, is in the range of 0.5 to 3 deg · ¹ .

The main advantage of the process according to the present invention (lies in the fact that the formation of by-products of boiling-by-boiling products is virtually completely eliminated, whereby the selectivity of the process is thereby increased to 99%.

Another important advantage (is the reduction in steam consumption from 15 moles to 10 moles per 1 mol of methylphenylcarbinolium, thereby reducing the energy requirement for the entire process).

The following examples serve to illustrate the method of the invention in more detail:

.Example 1

The process is carried out under admixture conditions in a two-stage reaction apparatus equipped with a heat exchanger, which is located between the two stages. Each reactor reactor contains 10 liters of alumina. It is 10 kg / h of methylphenylcarbiinolium with 15 kg / h of water vapor. The resulting mixture was heated to 275 ° C and fed to the first reactor. Due to the reaction heat of the external thermo-dehydration reaction, the temperature of the outgoing contact gas decreases to 24.5 ° C. The contact gas is heated again by passing through a heat exchanger to a temperature of < 275 [deg.] C. and is introduced at this temperature into the second dehydration stopper. The reaction products disperse the second reaction stage (a) (the mixtures (with water vapor are led to a heat exchanger and then to a separator) where they are recovered and irradiated.

The organic portion is analyzed by chromatography.

0.3 kg / h of methylphenylcarbiinol is obtained,

7.7 kg / ^H of styrene, 0.035 kg / h ethyibenzenu. High-boiling by-products were not detected. The yield was 90% conversion and corresponds to 99.55% selectivity to Istyrene.

Example 1 a d 2

The process is carried out in a separate two-stage apparatus such as that of Example 2.

. 15 kg / h of methylphenylcarlbiniolium are mixed with 22 kg / h of water vapor, the reaction mixture is heated to 290 DEG C. and fed to the reactor stage. On the basis of the reaction heat, the endothermic dehydration reaction underway, the temperature at the outlet of the first stage (260 DEG C.) is reduced. The vapors are further heated on the heat exchanger surface to 290 DEG C. and introduced into the second stage of the reactor. (The vapors exiting the second reactor are collected and separated in the separating apparatus.

It is obtained: 1.5 kg / h of methylphenylcarbinol, 11.4 kg / h of styrene, 0.095 kg / h of ethylibenzene, corresponding to 90% (conversion to 99.2% (selectivity to styrene.) was not detected.

Example 3. The process is carried out in a one-stage atiiaibatic reactor (anamous process).

kg / h of melthylphenylcarbtool is mixed with 15.5 kg / h of water vapor, the reaction mixture is heated to a temperature of 280 ° C (and fed to an alumina-containing reactor). The vapors leaving the reactor are fed to a separator where collides and splits.

The organic fraction obtained is analyzed by chromatography. Yields: 0.6 (kg / h of methylphenylglybinol, 5.2 kg / h of styrene, 0.03 kg / h of ethylbeinsene and 0.245 kg / h of high-yielding products, c: b representing 91% conversion, 95.5% selectivity to styrene and 4.0% selectivity in the case of vylsloiko, boiling products.

Comparison of Examples 1 and 2 (with Example 3 of the well-known example) will show that the present invention increases selectivity by avoiding the formation of high-boiling products to 99% and decreasing the methyl femylcarbimol molar ratio to 1:10, which umbžňulfe reduce energy consumption.

Claims (4)

A process for the production of styrene (by dehydration of methylphenylcarbniol in steam, phthalate on thihydration catalysts in the presence of Iodine steam and adiaibaltic conditions, characterized in that the dehydration of methylphenylcarbinol is carried out in one step, the contact gas coming from the second stage and it is set so that it is the same as it approaches the temperature of the contact gas entering the first stage. 2. Process according to claim 1, characterized in that the dehydration is carried out on alumina at the temperature of the inlet of the two stages in the range of 1260 ° C to 300 ° C. 3. The method of claim 1, wherein the contact gas is heated to the temperature it had at the inlet of the first stage before entering the second stage. 4. The method of claim 1, wherein black and white are introduced by introducing methylphenylcarboline and water vapor to the first stage at a 1:10 molar ratio.