LU84665A1 - PROCESS FOR THE PREPARATION OF ALKYLIC TERTIO-BUTYL ETHERS IN THE 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

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Process for the preparation of tert-butyl-alkyl ethers in the presence of butadiene

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

The reaction for adding alcohols to tertiary olefins such as isobutene to obtain tert-butyl alkyl ethers is an exothermic reaction which is catalyzed by an acid.

In the presence of suitable catalysts such as macroporous ion exchange resins, the reaction continues until equilibrium in times which are advantageous industrially, even at relatively low temperatures (40-50 ° C).

It is known that it is not necessary to operate with isobutene of high purity, and instead, any cut which contains it is appropriate, since the addition of alcohol takes place selectively on the double bonds which engage a tertiary carbon atom. These cuts from catalytic cracking and those from steam cracking, the latter either before or after extraction of butadiene, are particularly suitable.

If the C4 fraction from catalytic cracking or that from steam cracking after extraction of butadiene is used as the olefin feedstock, and methanol or ethanol is used as the alcohol and iS // a macroporous sulphonic resin of the Amberlyst 15 or * Levâtit SPC 108 "type as catalyst, the reaction can be carried out industrially in a wide range of reactor designs and operating conditions aimed at optimizing the conversion of one or more other reagents.

* In these cases, a high selectivity is always obtained, as well as a good performance of the catalyst both in% in terms of catalytic activity and of life.

Jj If we operate with a cut of olefins having a content

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2 high in butadiene, such as the C4 cut coming from steam cracking before extraction of butadiene, the operating conditions must be exactly defined in order to be able to recover more than 98 to 99 of butadiene · In particular, it is necessary to maintain a strict relationship between temperature and space velocity as described in US Patent No. 4,039,590.

However, it has been noted that if the isobutene etherification reaction is carried out in the presence of butadiene in a tubular reactor containing a macroporous resin, and the reagents are fed from top to bottom in a conventional manner, pressure drop increases over time, even when operating under conditions which allow recovery of butadiene at 99 and further the conversion decreases slightly.

However, an identical test carried out with a cut without butadiene shows neither an increase in the pressure drop nor a reduction in the conversion. The author of the present invention has now surprisingly discovered, and this is the object of the present invention, that by feeding the charge containing butadiene so that it circulates from bottom to top, under low bed expansion conditions, pressure drops remain constant over time "" | The process according to the present invention consists in preparing tert-butyl alkyl ethers by reaction of isobutyrene with a hydrocarbon feedstock which also contains butadiene at concentrations of between 10 and 70% by weight. , with one or more aliphatic alcohol (sj ^), preferably methanol or ethanol, in one, two or more | 30 of two reactors, preferably in series, and this process is characterized in that the reactants (feedstock of hydrocarbons containing butadiene and alcohol or alcohols) and the reaction products pass through the or the S reactors loaded] with a catalyst based on exchange resin—

Fj 35 (} geuse of macroporous acid ions, from bottom to top · Ί 1 · In addition to what is indicated concerning the ascending direction of the flow of reactants and reaction products, it is important to note that the linear speed of the reactants through the reactor (s) varies from 0.5 to 2 cm / s, and that the temperature in the reactors is between 50 and 60UC; preferably between 50 and 55 ° C * The present invention is illustrated by the descriptive and nonlimiting examples ‘below, I Example 1 10 A section is mixed in C4 having the following composition:

Propylene 0.46 c / o by weight

Isobutane 6.87 c / ° by weight j n-butane 11.80 e / o by weight

Butene-1 11.39% by weight 15 Isobutene 30.19 by weight JButene-2 + 3.25 C / D by weight

Cis butene-2 1.55% by weight

Butadiene 34.43 by weight with methanol such that the isobutene / methanol molar ratio is equal to 0.85, and the mixture is fed with a flow rate of 14 l / h and a temperature of 50 ° C in two reactors connected in series, having a total capacity of 4.5 liters and packed with 4 liters of catalyst. The catalyst is a macroporous sulfonic resin having an exchange capacity of 4.8 meq H + / g / sec,

Reagents flow from bottom to top Linear speed is 1 cm / s *

The reduction in conversion and the pressure drops as a function of time are as follows: 30 - 'time in hours 24 500 2000 - ΔΡ in the 1st reactor, bar 0.2 0.2 0.2 v - ΔΡ in the 2nd reactor, bar 0.2 0.2 0.2 - CP of tertiary butyl methyl ether 38.1 38 38 (MTBE), by weight 35 / - fo of dimers and codimers, 0.05 0.05 0, 05 by weight! r 4 s a [JÜ ”. $.

- $ of butenyl ethers, by weight 0.2 0.15 0.2 - conversion of 1 * isobutene 96.6 96.4 96.4 - recovery of butadiene> 99> -99> -99 - Ap represents the fall pressure 5 Example 2 (comparative)

The feedstock described in the previous example is supplied, under the same conditions of temperature and space speed, in the two reactors connected in series, but so that the direction of the flow of the reactants is from top to bottom ·

At the start of the test, the results are similar to those of the previous example, but as time passes we observe a gradual increase in pressure drop and a slight decrease in conversion · 15 - Time in hours 24 500 2000 - ΔΡ in the 1st reactor, bar 0.3 0.4 1.5 - ΔΪ in the 2nd reactor? bar 0.3 0.5 1, 8 -% of HTBE, by weight 38 37.9 36 - ° / o of dimers and codimers, by weight 0.1 0.1 0.05 20 - $ of butenyl ethers , by weight 0.2 0.2 0.2 - conversion of isobutene 96.4 96.1 91.3 - recovery of butadiene> 99> 99> 99

Example 3 (comparative)

Methanol is added to a section of olefins containing 25% of isobutene and 0.2% butadiene, by weight, so that the isobutene / methanol molar ratio is 0.85 ·

The mixture is fed with a flow rate of 14 l / h and at a temperature of 50 ° C. in two reactors connected in series, the direction of the flow being descending. In the absence of butadiene, no increase in pressure drop or increase in conversion was observed over time "| »- Time in hours 24,500 2,000! - ΛΡ of the 1st reactor ^ bar 0.3 0.3 0.3 I "- Δ P of the 2nd reactor j bar 0.3 0.3 0.3 1 35 - fe of MTBE, by weight 43.1 42.9 43 ** Λ 5 = · r -% of dimers and codimers, by weight 0.3 0.3 0.2 - conversion of isobutene 96.8 96.6 96.6 '\

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Claims (3)

6 I v 1 "Process for the preparation of alkyl tertio-butyl 1 ethers by reacting isobutylene with a hydrocarbon feedstock, which also contains" 5 butadiene at a concentration of between 10 and 70 $ by weight, with one or more aliphatic alcohols, preferably with methanol or ethanol, in one, two or more than two reactors, preferably in series, this process being characterized in that the reactants and the reaction products are passed through the reactor (s) from bottom to top · 20 Method according to claim 1, characterized in that the reactants have a linear speed between 0.5 and 2 cm / s. 3. Method according to claim 1, characterized in that the temperature in the reactor (s) is between 50 and 60 ° C, preferably between 50 and 55 ° C0 \ N, î '* ΙΛ I? \ I 1 P