NL8300848A - METHOD FOR PREPARING TERT. BUTYLETHERS IN PRESENCE OF BUTADIENE. - Google Patents

Abstract

In producing t-butyl alkyl ethers by etherifying with aliphatic alcohols isobutene in a hydrocarbon feedstock containing butadiene in addition to the isobutene, the increase in the pressure drop in the etherification reactor(s) that is due to the butadiene is eliminated by feeding the reactants from the bottom upwards. The reactors preferably contain an acidic ion-exchange resin catalyst.

Description

833013 / ucü <l / dw ... 'V *

Short designation: Process for preparing tert-butyl ethers in the presence of butadiene.

The invention relates to a process for the preparation of tert-butyl alkyl ethers in the presence of butadiene.

The addition reaction of alcohols to tertiary olefins, such as isobutylene, to form tert-butyl alkyl ethers is an exothermic reaction which is catalyzed by acid.

In the presence of suitable catalysts, such as macroporous ion exchange resins, the reaction reaches equilibrium at times of industrial importance, even at relatively low temperatures (40 ° -50 ° C).

It is known that it is not necessary to work with high purity isobutene, instead any fraction containing isobutene is suitable since the alcohol addition selectively occurs on the double bonds linked to a tertiary carbon atom. The fractions from catalytic cracking and those from steam cracking, which were obtained before or after extracting butadiene, are particularly suitable.

When the C 4 fraction from catalytic cracking or from steam cracking after extraction of butadiene is used as the olefin feed and methanol or ethanol and a macroporous sulfone-20 resin, type Amberlyst 15 or Lewatit SPC 108, can be used as a catalyst, reaction is carried out industrially in a wide variety of reaction vessels and under conditions aimed at optimizing the conversion of one of the reactants. In these cases a high selectivity is always obtained, together with a good activity of the catalyst, both with regard to the catalytic activity and the service life.

When an olefin fraction having a high butadiene content is used, such as the C 1 fraction from steam cracking for butadiene extraction, the operating conditions must be accurately determined to allow a butadiene yield greater than 98-99%.

In particular, it is necessary to strictly maintain the relationship between the temperature and the spatial velocity, as described in U.S. Pat. No. 4,039,590.

8300848 t - 1 -2-

However, it has been observed that when the isobutene etherification reaction is conducted in the presence of butadiene in a tubular reaction vessel containing a macroporous resin, and the reactants are fed from the top downward in a normal manner, an increase in the pressure differentials occurs with time, even when operating under conditions that allow a high butadiene yield of more than 99%, and in addition a low conversion reduction.

However, a similar test conducted with a butadiene-free fraction 10 shows neither the increase in pressure loss nor the conversion decreases.

It has been surprisingly found, and this is the subject of the present invention, that when the butadiene-containing feeds are supplied so that they flow from the bottom upwards, under mild bed expansion conditions, the pressure losses remain constant over time.

The method of the present invention includes terting. butyl alkyl ethers prepared by isobutene or a hydrocarbon feed also containing butadiene in concentrations between 10 and 70 wt. %, react with one or more aliphatic alcohols, preferably methanol or ethanol, in one, two or more reaction vessels, preferably placed in series, and characterized in that the reactants (hydrocarbon feed containing butadiene and alcohol or alcohols) and the reaction products flow through the reaction vessel (s), filled with a macroporous acid ion exchange resin as catalyst, from the bottom upwards.

In addition to what has been noted with regard to the upward flow of the reactants and reactants, it is important to note that the linear velocity of the reactants through the reactor or reactors varies from 0.5 to 2 cm / sec. and the temperature in the reaction vessels is between 50 and 60 ° C, preferably between 50 and 55 ° C.

The invention will be further elucidated by means of the following non-limiting examples.

8300848 -3-. .. *

EXAMPLE I

A C ^ fraction with the following composition:

Prop - a 0.46 wt. %

Isobutane 6.87 wt. N 5 n-butane 11.80 wt. %

Butene-1 11.39 wt%

Isobutene 30.19% by weight

Butene-2 + 3.25 wt. %

Cis butene-2 1.55 wt. Butadiene 34.43% by weight with methanol in such a way that the molar isobutyl / methanol ratio is equal to 0.85 and the mixture is passed at two liters connected in series in an amount of 14 liters / hour and a temperature of 50 ° C. barrels, with a total capacity of 4.5 liters and filled with 4 liters of catalyst. The catalyst is a macroporous sulfonic acid resin with an exchange capacity of 4.8 meq H + / g dry. j

The reactants flow up from the bottom.

The linear speed is 1 cm / sec.

The conversion and pressure losses with respect to the time side alials follows: 20 Time (hours) 24 500 2000 ΔΡ, le reaction vessel kg / cm2 0.2 0.2 0.2 2 ΔΡ »2nd reaction vessel kg / cm 0.2 0, 2 0.2 wt. % MTBE 38.1 38 38 wt. % dimers and codimers 0.05 0.05 0.05 25 wt. % butenyl ethers 0.2 0.15 0.2 isobutene conversion 96.6 96.4 96.4 butadiene yield> 99> 99> 99 Δ P represents the pressure drop EXAMPLE II (comparative) 30 The procedure described in the previous example is carried out supply at the same temperature and spatial speed to the two reactors connected in series, but such that the direction of flow of the reactants is from the top down.

At the start of the test, the results are similar to those of 8300848 * a α "-4-j in the previous example, but over time a gradual increase in pressure loss occurs and a slight loss of conversion is observed.

Time (hours) 24 500 2000 5 ΔΡ) le reaction vessel kg / cm ^ 0.3 0.4 1.5 o AP, 2nd reaction vessel kg / cm 0.3 0.5 1.8 wt. % MTBE 38 37.9 36 wt. % dimers and codimers 0.1 0.1 0.05 wt% butenyl ethers 0.2 0.2 0.2 10 isobutene conversion 96.4 96.1 91.3 butadiene yield> 99)> 99 99 EXAMPLE III (comparative )

Methanol is added to an alkene fraction containing 35 wt. % isobutene and 0.2 wt. % butadiene, such that the molar isobutene / methanol ratio is 0.85.

The mixture is fed at a rate of 14 liters / hour and at a temperature of 50 ° C to two series-placed reaction vessels, the flow direction of which is from the top downwards. In the absence of butadiene, no increase in pressure loss or conversion loss over time is observed.

Time (hours) 24 500 2000 o AP, le reaction vessel kg / cm 0.3 0.3 0.3 o ΔΡ, 2nd reaction vessel kg / cm 0.3 0.3 0.3 wt. % MTBE 43.1 42.9 43 25 wt. % dimers and codimers 0.3 0.3 0.2 isobutene conversion 96.8 96.6 96.6 3300348

Claims (3)

A process for preparing tert-butyl alkyl ethers by reaction of isobutene or a hydrocarbon feed, which also contains butadiene in a concentration of 10 to 70 wt. % with one or more aliphatic alcohols, preferably methanol or ethanol, and one, two or more reaction vessels, preferably placed in series, characterized in that the reactants or the reaction products are raised from the bottom by the reaction vessel or the reaction vessels let it flow. Method according to claim 1, characterized in that the reaction means have a linear speed of 0.5 to 2 cm / sec. own 10 Process according to claim 1, characterized in that the temperature in the reaction vessel (s) is between 50 and 60 ° C, preferably between 50 and 55 ° C. i | 8300848