DE102009055928A1 - Process for the continuous production of glycerine tertiary butyl ethers - Google Patents

Abstract

The present invention relates to a process for the preparation of a higher glycerine tertiary butyl ether comprising mixture of substances, comprising the steps: acid-catalyzed conversion of isobutene with glycerol to form a reaction mixture and the extraction of at least part of the reaction mixture from step a with at least one solvent, the solvent or the Solvent mixture has an E (30) value of .0 35.0.

Description

The present invention relates to a process for the preparation of a higher Glycerintertiär-butyl ethers comprehensive substance mixture. The invention further relates to a fuel obtainable by this process.

Glycerin is a very versatile starting material, which is mainly produced from renewable raw materials. If the demand for biodiesel, which produces glycerine as a coproduct by transesterification, will increase in the next few years, glycerine could be available at too low a price in quantities that make sense for use in large-scale products.

A distillative separation of a product mixture of glycerol and a mixture of high boilers is therefore not useful for energetic and technical reasons. The range of GTBE (glycerol tertiary butyl ethers) ranges over three different etherification stages, of which only the higher ethers (di- and triethers), also called h-GTBE, can be used as octane enhancers in the fuel. The monoether shows less good combustion properties and also tends to settle in the fuel.

In US 573 1476 describes a homogeneous with sulfonic acids catalyzed etherification. The reaction is carried out only up to a low conversion, in which the reaction mixture is still biphasic. Unreacted glycerin, the catalyst and portions of the resulting monoether are separated in a decanter and recycled. From the organic phase, the isobutene is stripped and the liquid phase extracted with water. The extract is thereby discarded and the raffinate is recovered from higher ethers at the top of the extraction unit.

The method has the disadvantages that the reaction is carried out with low conversions to ensure the two-phase nature of the stream at the reactor exit. In addition, less than half of the incoming stream in the extraction process consists of monoethers and therefore nearly half of the discharged reaction products are discarded.

It is therefore an object to provide an improved process for the preparation and / or purification of glycerol tertiary-butyl ethers, which at least partially eliminates the present disadvantages and in particular is able to provide a higher yield in many applications.

• a) Säurekatalysierte Umsetzung von Isobuten mit Glycerin zu einem Reaktionsgemisch;
• b) Extraktion zumindest eines Teils des Reaktionsgemisches aus Schritt a mit mindestens einem Lösungsmittel, wobei das Lösungsmittel oder das Lösungsmittelgemisch einen E_T(30)-Wert von ≤ 35.0 aufweist.

The invention therefore proposes a process for the preparation of a higher mixture of glycerol tertiary butyl ethers comprising the steps:

• a) acid-catalyzed conversion of isobutene with glycerol to a reaction mixture;
• b) extraction of at least part of the reaction mixture from step a with at least one solvent, wherein the solvent or the solvent mixture has an E _T (30) value of ≦ 35.0.

• – der bei dem Verfahren entstehende Glycerinether kann mit einem Kraftstoff extrahiert werden kann und als Gemisch für Verbrennungsmotoren verwendet werden kann.
• – der Glycerinether direkt gewonnen werden kann, wenn man einen weiteren Aufreinigungsschritt anschließt.
• – das Auftreten von (letztendlich wegzuwerfenden) Nebenprodukten wie Monotert.butyl-ethern kann (ggf. durch geeignete zusätzliche Maßnahmen) deutlich veringert werden,
• – Vermeidung der aufwändigen thermischen Trennung von Wasser und Glycerin
• – Vermeidung der aufwändigen Trennung der Monoether von den h-GTBE

When using the method according to the invention, at least one of the following advantages can be achieved for a multiplicity of applications:

• - The resulting in the process glycerol ether can be extracted with a fuel and can be used as a mixture for internal combustion engines.
• - The glycerol ether can be obtained directly, if followed by another purification step.
• The occurrence of (ultimately disposable) by-products such as monotertiary butyl ethers can be significantly reduced (possibly by appropriate additional measures),
• - Avoiding the time-consuming thermal separation of water and glycerin
• - Avoiding the complicated separation of the monoethers from the h-GTBE

For the purposes of the present invention, higher glycerol tertiary butyl ethers are the ethers which can be formed from the reaction of isobutene with glycerol. In particular, isobutene and glycerol may be present as pure substances. In this case, by means of a catalyst, an acceleration of the reaction can be achieved. Glycerol tertiary butyl ethers comprise in particular ethers selected from the group consisting of 3-tert-butoxypropane-1,2-diol, 2-tert-butoxypropane-1,3-diol, 1,3-di-tert-butoxypropane. 2-ol, 2,3-di-tert-butoxypropan-1-ol, 1,2,3-tri-tert-butoxypropane. From the spectrum of these ethers, the diethers and triethers are referred to as so-called higher ethers.

In the present invention, the mixture of substances may consist of at least one component of the glycerol tertiary butyl ether, a solvent and / or another compound. The mixture of substances may be both homogeneous and heterogeneous. Preferably, the mixture is present as a solution.

The first step of the process of the invention involves the acid-catalyzed reaction of isobutene with glycerol to form a reaction mixture. In the context of the present invention, an acid-catalyzed reaction is understood as meaning, in particular, a sub-stoichiometric use of a proton donor with the corresponding starting materials isobutene and glycerol. The catalyst may be present in a molar concentration, based on the starting concentration of glycerol, in a range of ≥ 0.5 mol% to ≦ 10 mol%, preferably in a range of ≥ 2 mol% to ≦ 8 mol% and especially preferably in a range of ≥ 3 mol% to ≤ 6 mol%. The catalyst may be homogeneous or heterogeneous. Preferably, the proportion of glycerol and monoether in the substance mixture in a range ≥ 0% by weight to ≤ 5% by weight, preferably in a range of ≥ 0.1% by weight to ≤ 3% by weight and more preferably in a range of ≥ 0.5 % By weight to ≦ 2% by weight.

For the purposes of the present invention, the reaction mixture formed in this case is in particular the reaction mixture from the beginning of the reaction to the equilibrium state and / or until the reaction is stopped. The reaction mixture can be both homogeneous and heterogeneous. For the purposes of the present invention, the educts in the process for preparing glycerol tertiary butyl ethers in the liquid phase are preferably selected from the group comprising the raw materials of the educts, glycerol and an isobutene-containing material stream, crude glycerol and isobutene or crude glycerol and an isobutene-containing material stream. Particularly preferred may be the reaction of pure glycerol with pure isobutene or isobutene-containing streams.

The reaction can be carried out in a reaction unit. In particular, the reaction unit comprises a stirred tank, a stirred tank cascade, a tubular reactor, a liquid jet mixer and / or a static mixer. Particularly preferred may be a single or stirred in a cascade stirred tank.

In a variant of the invention, the substance mixture, after it has been at least partially reacted, freed as the reaction unit leaving the flow of material by stripping and / or by flashing of the unreacted isobutene. In this case, the separated isobutene can, according to a preferred embodiment of the invention, be at least partially recycled to the reaction. Also, the isobutene or isobutene-containing gas stream may be passed out of the plant according to an alternative preferred embodiment of the invention.

In step b of the process according to the invention, the extraction of at least part of the reaction mixture from step a comprises at least one solvent, wherein the solvent or the solvent mixture has an E _T (30) value of ≦ 35.0.

In this case, extraction means in particular the selective extraction, washing or leaching of certain substances as transition components from solid or liquid substance mixtures with the aid of liquid solvents. In particular, for the purposes of the present invention, extraction may be understood to mean a liquid-liquid extraction.

It should be noted at this point that in the event that in step b) a solvent mixture is used, individual components of this mixture (depending on the application of the method) may also have a higher E _T (30) value. These mixtures are expressly also covered by the method according to the invention as long as the E _T (30) value of the mixture as a whole has a value of ≦ 35.0

For the purposes of the present invention, a mixture of solvents is understood as meaning a mixture of at least two partially miscible components. In this case, one component in the other can dissolve to a proportion of ≥90 vol.%, Preferably ≥98 vol.% And particularly preferably ≥99 vol.%. Preferably, the resulting solvent mixture has an E _T (30) value of ≤ 35.0.

The liquid-liquid extraction (FFE) involves two liquid phases. In this case, the substance to be extracted, the valuable substance S, is dissolved out of an existing carrier liquid mixture with the aid of a solvent L. A mechanical phase separation after completion of mass transfer of valuable material between the delivery and receiving solvent provides the valuable material raffinate R and the rich extract phase E. In contrast to other separation methods is obtained in the FFE no individually separated mixture component, but a solvent-loaded mixture. This mixture can usually be further separated in subsequent process steps.

The term "E _T (30) value" is understood to mean the polarity of a solvent, the values referred to in US Pat Reichart; Dimroth Fortschr. Chem. Forsch. 1969, 11, 1-73 . Reichart Angew. Chem. 1979, 91, 119-131 as well as cited in March, Advanced Organic Chemistry, 4th Edition, J. Wiley & Sons, 1992, Table 10.13, p. 361 have been published.

Preferably, an extraction is carried out with at least one solvent, which has an E _T (30) value of ≤33 and / or wherein the solvent preferably has a miscibility gap with water.

Preferably, an extraction is carried out with at least one solvent which has an E _T (30) value of ≦ 32.0, more preferably ≦ 31.5. Particularly preferred solvents are those selected from the group of alkanes, cycloalkanes, alkenes, cycloalkenes, alkynes, Cycloalkynes and / or the C-6 to C-14 carbon aromatics.

In particular, for the purposes of the present invention, solvents from the group comprising 2-methylbutane, n-pentane, n-hexane, 1-hexene, 1-hexyne, n-heptane, n-octane, n-nonane, benzene, methylbenzene, toluene, (Trifluoromethyl) benzene, 1,4-dimethylbenzene, p-xylene, 1,3,5-trimethylbenzene, n-decane, n-dodecane, cyclohexane, cyclohexenes, cis-decahydronaphthalene, 1,2,3,4-tetrahydronaphthalene, vinylbenzene, diethyl ether , Bis (2-chloroethyl) ether, tetrahydrofuran, ethyl vinyl ether, di-n-propyl ether, diisopropyl ether, di-n-butyl ether, tert-butyl methyl ether, tert-amyl methyl ether, 2-methoxy-2-methylbutane and / or carbon disulfide.

In one variant, the solvent can be selected from the group of diesel fuel, kerosene, gasoline, light gasoline, synthetic gasoline, alkylate gasoline, biodiesel, ethanol fuel, cellulosic ethanol, butanol, liquefied petroleum gas, methanol, vegetable oil, heavy fuel oil, benzene, gasoline-benzene mixture , Gas oil, motor petrol are selected.

In one embodiment of the process according to the invention, the volume ratio of the solvent to the reaction mixture from step a) is in a range of ≥ 0.8: 1 to ≦ 1.5: 1. In the case of a liquid-liquid extraction, in this case the monoether compounds can be separated off more easily from the mixture by means of the glycerol phase, so that the monoether can preferably remain in the polar phase.

In a further variant of the invention, the molar ratio (mol: mol) of the educts isobutene to glycerol in a range of ≥ 1: 0.5 to ≦ 1: 5, preferably in a range of ≥ 1: 1 to ≦ 4, and particularly preferred a range of ≥1: 1.5 to ≤1: 3.5. As a result, the conversion of isobutene can be increased. In particular, this proves advantageous for mixtures such as raffinate I. An advantage is that the gas outlet contains little isobutene, because for example in an ethyl tertiary-butyl-ether production, an isobutene conversion of 99% only by very complex double Reactive rectification can be achieved.

For the purposes of the present invention, "raffinate I" is understood as meaning, in particular, a mixture which, in addition to isobutene, also contains at least one of the substances selected from isobutane, n-butane, 2-butene (cis and / or trans), 1-butene and butadiene contains.

In a further alternative embodiment of the process according to the invention, the molar ratio (mol: mol) of isobutene to the higher glycerol tertiary-butyl ethers from step a is in a range of ≥ 0.1: 1 to ≦ 1: 1. As a result, the conversion of isobutene can be increased. In particular, this proves advantageous for mixtures such as raffinate I. An advantage is that the gas outlet contains little isobutene, because for example in an ethyl tertiary-butyl-ether production an isobutene conversion of 99% only by very complex double Reactive rectification can be achieved.

In a further embodiment of the method according to the invention, the temperature of the reaction mixture from step a) is between ≥ 60 ° C to ≤ 130 ° C, preferably in a temperature range between ≥ 70 ° C to ≤ 120 ° C and particularly preferably in a temperature range between ≥80 ° C to ≤ 110 ° C. At this temperature, many applications lead to improved reaction behavior in terms of yield and reaction time.

In a further embodiment of the process according to the invention, the reaction is carried out at a pressure of ≥ 10 bar to ≤ 20 bar. Advantageously, it is possible in this pressure range to liquefy the compounds present under normal conditions as gases and to use them as solvent. Another advantage in many applications of the inventions is that this pressure range is favorable for the economic operation of the plant, since it corresponds to the autogenous pressure of the system and therefore does not have to be generated by compression or pumping power

In a further embodiment of the process according to the invention, the acid from step a) has a pks value of ≦ 2. In the context of the present invention, the term "acid" encompasses those substances which can function as proton donors. It may also be a mixture of acids having a pks ≤ 2. In particular, the acid comprises hydrochloric acid, sulfuric acid and / or sulfonic acid. Preferably, p-toluene sulfonic acid, methanesulfonic acid and / or benzenesulfonic acid can be used.

In a further embodiment of the process according to the invention, the higher ethers are extracted from the liquid reaction product with a carbon-containing stream. In this case, the carbon-containing stream may be a gasoline, pure hydrocarbon, and / or a naphtha.

In one variant, the higher ethers with gasoline with the addition of a glycerol-containing stream or with pure hydrocarbon under Addition of a glycerol-containing stream to be extracted. The extraction unit can be realized by a plurality of mixer-settler units, by extraction columns or by interconnecting both. The current flow can be carried out in cross-flow, countercurrent or by countercurrent distribution.

In a further variant, the extract stream can be worked up thermally and the extractant can be returned to the extraction. Advantageously, there is thus a saving of the extractant, which leads to a more cost-effective production of the mixture of substances according to the invention.

In a further embodiment of the process according to the invention, the acid-catalyzed reaction is a homogeneous catalysis. In this case, at least during the catalytic step during the reaction, the catalyst and the reactants may be in solution.

The invention furthermore relates to a fuel obtainable by the process according to the invention, comprising at least part of the reaction mixture from step a and at least one solvent.

Another object of the invention relates to the use of fuel for internal combustion engines, turbines or combustion plants.

The aforementioned method as well as the claimed method described in the exemplary embodiments is not subject to any particular exceptional conditions in terms of its size, shape design, material selection and technical conception, so that the selection criteria known in the field of application can be used without restriction.

Further details, features and advantages of the subject matter of the invention will become apparent from the subclaims and from the following description of the accompanying drawings, in which - by way of example - several embodiments of the method according to the invention are shown.

The present invention will be further explained with reference to several specific embodiments of the method with reference to the following drawings, without being limited thereto. Show it:

1 a process for producing a higher ether comprising fuel; such as

2 an alternative method for producing higher ethers

1 shows an arrangement of the various process steps according to a preferred embodiment of the method. The starting material isobutene is after a possible pre-cleaning on the stream ( 1 ) together with recycled isobutene ( 4 ) and recycled glycerol, monoether and catalyst ( 14 ) to a suitable reaction unit (A) ( 2 ). In a downstream process step, in a stripping column (B) (or alternatively a flash), the reaction product ( 3 ) is liberated from unreacted isobutene which is recycled to the reaction ( 4 ).

The liquid phase removed from the stripping column (B) ( 5 ) is supplied to a liquid-liquid extraction process step in a continuous extraction unit (C). As extractant, fed via electricity ( 7 ), the quality of the fuel can be used directly.

To enhance the polar phase of the extraction, it is necessary to use electricity ( 6 ) at least a portion of the plant supplied glycerol the continuous extraction unit (C) added, although this is not absolutely necessary for the process depending on the application. From the extraction unit (C), the mixture ( 8th ) conveyed into the settling part (C '). Depending on the design, this can be done by pumping from one container to another (mixer-settler) or simply by an overflow weir (decanter).

The head stream ( 10 ) of the continuous extraction unit is fed in this embodiment of the extraction column and with another stream of fresh glycerol ( 11 ) extracted. The head stream ( 13 ) of the plant part (D) can be used directly as fuel or diluted to the corresponding volume fraction of higher ether. The glycerol-rich extracts ( 9 ) 12 ) are in turn passed into the reactor ( 14 ).

It should be noted that the top stream ( 10 ) depending on the application can also be used directly without further extraction.

2 Figure 4 shows a variant of the process according to an alternative preferred embodiment of the invention for isolating the higher ethers. The currents and plant components correspond to the 2 the process 1 Unless otherwise specified.

In the process lt. 2 becomes the non-polar raffinate ( 13 ) for the recovery of the extractant in a retention unit (E), optionally also a flash, for the thermal separation of the extractant fed. The separated, low-boiling extractant is passed over the stream ( 7 ) into the continuous extraction unit (C) and the higher ether over the stream ( 15 ) won as high boilers.

The individual combinations of the components and the features of the already mentioned embodiments are exemplary; the exchange and substitution of these teachings with other teachings contained in this document with the references cited are also expressly contemplated. Those skilled in the art will recognize that variations, modifications and other implementations described herein may also occur without departing from the spirit and scope of the invention. Accordingly, the above description is illustrative and not restrictive. The word used in the claims does not exclude other ingredients or steps. The unanimous article "a" does not exclude the meaning of a plural. The mere fact that certain measures are recited in mutually different claims does not make it clear that a combination of these dimensions can not be used to advantage. The scope of the invention is defined in the following claims and their equivalents. Furthermore, the reference numerals used do not limit the claimed scope of the invention.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• US 5731476 [0004]

Cited non-patent literature

• Reichart; Dimroth Fortschr. Chem. Forsch. 1969, 11, 1-73 [0020]
• Reichart Angew. Chem. 1979, 91, 119-131 [0020]
• March, Advanced Organic Chemistry, 4th Edition, J. Wiley & Sons, 1992, Table 10.13, p. 361 [0020]

Claims (10)

A process for the preparation of a higher mixture of glycerol tertiary butyl ethers comprising the steps of: a) acid catalyzed conversion of isobutene with glycerol to a reaction mixture; b) extraction of at least part of the reaction mixture from step a with at least one solvent, wherein the solvent or the solvent mixture has an E _T (30) value of ≦ 35.0. The method of claim 1, wherein the volume ratio of the solvent to the reaction mixture from step a) in a range of ≥ 0.8: 1 to ≤ 1.5: 1. The method of claim 1 or 2, wherein the molar ratio of the reactants isobutene to glycerol in a range of ≥ 1: 0.5 to ≤ 1: 5. Method according to one of claims 1 to 3, wherein the temperature of the reaction mixture from step a) is between ≥ 60 ° C to ≤ 130 ° C. Method according to one of claims 1 to 4, wherein the reaction takes place at a pressure of ≥ 10 bar to ≤ 20 bar. The method of any one of claims 1 to 5, wherein the acid of step a) has a pks value of ≤ 2. The process of any one of claims 1 to 6, wherein the higher glycerol tertiary butyl ethers are extracted from the liquid reaction product with a carbon-containing stream. Method according to one of claims 1 to 7, wherein the acid-catalyzed reaction in step a) is a homogeneous catalysis. A fuel obtainable by a process according to any one of claims 1 to 8, comprising at least part of the reaction mixture from step a) and at least one solvent. Use of the fuel according to claim 9 for internal combustion engines, turbines or combustion plants.

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