Method of obtaining tertiary ethyl butyl ether

(54) NAME Process for the preparation of tertiary alkyl ethers (56) PUBLICATIONS REFERRED TO: EP 8860, US 3,506,408, US 3,634,535 (57) SUMMARY:

A process for the preparation of tertiary alkyl ethers of isoolefins and aliphatic alcohols in the presence of a catalyst in the form of sulfonated styrene-divinylbenzene resin, characterized in that both the reaction leading to the formation of the tert-alkyl ether and the separation of the tert-alkyl ether from the hydrocarbons and subsequent compounds take place in a single fractionation device with bottoms; wherein some of the bottoms are provided with catalyst beds in the form of spheres suitable for preparing this tert-alkyl ether, the resulting ether being taken out as a substantially pure bottom product.

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The numbers in brackets indicate international identification code, INID code. Letters in clamps indicate international document code.

459 175

The present invention relates to a process for the preparation of tertiary alkyl ethers of isoolefins and aliphatic alcohols. In particular, the invention relates to the preparation of methyl tert-butyl ether or methyl tert-amyl ether of isobutene and methanol, respectively, isopentene and methanol.

In the following description, for simplicity, reference is made to the preparation of methyl tert-butyl ether, but the process is also fully applicable to the preparation of all other tert-alkyl ethers, since the difference between the boiling points of the starting materials and the products is of the same order of magnitude.

Methyl tert-butyl ether (MTBE) is prepared, according to the prior art, by reaction between isobutene, which is generally present in a varying percentage amount in a C at a temperature that can vary from room temperature to about 100 ° C.

In practice, isobutene is not available on an industrial scale, so reference will be made to the above C 2 hydrocarbon fraction containing isobutene. The reaction is an equilibrium reaction, and if the amount of methanol used is close to the stoichiometric amount, the conversion of isobutene is 90% or slightly more at the temperatures which give a reasonable reaction rate. If a higher conversion is required, an excess of methanol must be used and this must then be separated from the reaction product and recycled, achieving a conversion of slightly more than 95% under reasonable conditions, or alternatively the reaction product must be separated and the remaining mixture transferred to a second reaction step. , which again under almost stoichiometric conditions allows a conversion of about 99% to be achieved.

One problem herewith, however, is that in order to carry out the operation, the C2 components must be evaporated twice and use two reactors and two distillation columns, which increase the investment and operating costs. According to the latest technology (European patent application published on March 19

1980 under No. 8860), these problems are overcome by adding a mixture containing isobutene and methanol to a distillation column filled with catalyst suitable for preparation of MTBE, wherein the catalyst also acts as distillation gasket, thereby separating MTBE and separating MTBE from the C walk.

However, the method described in the claimed patent application has some serious drawbacks associated with the fact that the catalyst acts as gasket in the desaltion column and therefore must meet certain requirements, especially the requirement for a small pressure reduction. For this reason, it is usually placed in bags which form a band, which provides ample space for the passage of steam and liquid, but which, on the other hand, are difficult to manufacture and fill the column with.

Another disadvantage of the method described in the specified European application is that the continuous phase inside the column is the vapor phase, while the dispersed phase is the liquid phase, which results in low yields of MTBE, when the reaction takes place in practice in the vapor phase. . This also means that considerable amounts of dimer can be formed when there is a deficit of alcohol in the vapor phase.

It has now surprisingly been found to be possible to avoid all of the disadvantages mentioned above by allowing both the reaction leading to the formation of the tert-alkyl ether (MTBE) and the separation thereof from the hydrocarbons and subsequent compounds to take place in a single fractionation device having bottoms in which some of the the bottoms are provided with beds of catalysts in the form of spheres based on sulfonated styrene-divinylbenzene resin suitable for the preparation of tert-alkyl ether (MTBE).

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The process of the present invention comprises: supplying the hydrocarbon feedstock containing the isoolefin to a bottom fractionation column, wherein some of the bottoms are provided with catalyst beds consisting of sulfonated styrene-divinylbenzene resin separated from each other by groups of fractionation bottoms or single fractions; supply of the alcohol itself near the top of the column, preferably over the last catalyst bed and some bottoms (between 4 and 8) below the point at which the reflux is applied; reaction between the isoolefin and the alcohol on the bottoms provided with catalyst beds, which are immersed in the liquid containing the alcohol and thereby the steam bubbles; and separating the formed ether from the other components at the fractionating bottoms and at the bottoms provided with catalyst beds to obtain the substantially pure ether as a bottom product and the added hydrocarbons and optionally the alcohol in the form of an azeotrope with the added hydrocarbons as a top product or distillate.

The process of the present invention with respect to MTBE comprises: supplying the C C hydrocarbon starting material containing isobutene to a fractionation column having bottoms wherein some of the bottoms are provided with catalyst beds consisting of sulfonated styrene-divinylbenzene resins suitable for preparation of MTBE and separated from each other by fractionation bottoms or single fractionation bottoms; supplying the methanol itself near the top of the column and preferably over the last catalyst bed and between 4 and 8 bottoms below the point at which the reflux is applied; reaction between isobutene and methanol on the bottoms provided with catalyst beds which are immersed in the liquid containing methanol and thereby the steam bubbles; and separating formed MTBE from other components both at the fractionation bottoms and at the bottoms provided with catalyst beds, whereby as a bottom product, substantially pure MTBE is obtained and as a top product the C

459 175 is isobutene, plus methanol in an amount corresponding to the azeotrope.

The process of the present invention is carried out at a pressure between 500 and 1000 kPa.

The hydrocarbon starting material containing the isoolefin is supplied to the column with bottoms according to the invention in such a position that at least two bottoms having catalyst beds are above this feed and at least one bottom with a catalyst bed is below the feed. The steam formed by the reheater in the fractionation column bubbles through the catalyst beds, which are preferably not less than three in number, and the methanol and isobutene react there in the liquid phase covering each catalyst bed.

The catalyst is in the form of spheres having a diameter between 0.5 and 1 mm, and the thickness of each catalyst bed is of the order of 1 m.

The liquid present on each bottom containing catalyst flows down to the lower distillation bottom via one or more conventional overflow edges, and the catalyst always remains immersed in the liquid.

The catalyst is retained on each bottom by means of mesh at least above and below the bed, which prevents it from flowing away.

The invention will become more apparent from the accompanying drawing which shows a non-limiting embodiment thereof. Reference numeral 1 denotes fractionation bottoms, and 2 a fractionation bottom having a catalyst bed 3 held by meshes 4 and 5. The liquid follows the path indicated by arrows 6 and passes through the catalyst bed.

The meadow follows the upward path indicated by arrows 7.

A non-limiting embodiment of the method of the invention is described below.

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EXAMPLE

A distillation column was made using flanged tube sections 10 cm in diameter and 100 cm in length, containing six distillation bell bottoms (two bells per bottom). The column was constructed by alternating pipe sections of 1 m filled with catalyst with sections comprising six bottoms, to a total of six sections above the supply and two sections below. The column was fed 2 kg / h containing 50% isobutene.

A reflux ratio of 1: 1 was maintained and 575 g of methanol were added along with the reflux. The pressure of the process was 800 kPa and the temperature 60 ° -150 ° C. The top product 15 was made up of 1035 g containing 30 g methanol and 5 g isobutene. 1540 g of practically pure ΜΤΒΞ was obtained as a bottom product.

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