WO2010136297A1

WO2010136297A1 - Production of 3-methyl-1-butene

Info

Publication number: WO2010136297A1
Application number: PCT/EP2010/055813
Authority: WO
Inventors: Markus Winterberg; Alfred Kaizik; Armin Rix; Michael Grass; Wilfried Büschken
Original assignee: Evonik Oxeno Gmbh
Priority date: 2009-05-29
Filing date: 2010-04-29
Publication date: 2010-12-02
Also published as: TW201105608A; DE102009026586A1

Abstract

The invention relates to a method for producing 3-methyl-1-butene, according to which a feed material containing 3-methyl-1-butanol is provided, the feed material is subjected to a catalytic dehydration, whereby a reaction product is created, the reaction product containing at least the following constituents: 3-methyl-1-butene, di-(3-methylbutyl)-ether, water and non-reacted 3-methyl-1-butanol, the reaction product is separated by distillation and water separation into a low-boiling fraction, a high-boiling fraction and a water fraction, the low-boiling fraction containing 3-methyl-1-butene, the high-boiling fraction containing di-(3-methylbutyl)-ether and non-reacted 3-methyl-1-butanol, and the water fraction containing essentially water, and the high-boiling fraction is at least partially guided back into the dehydration process.

Description

Preparation of 3-methyl-1-butene

The present invention relates to a process for the preparation of 3-methyl-1-buten according to the preamble of claim 1.

3-Methyl-1-butene belongs to the group of methyl butenes, which in turn belong to the C ₅ olefins. The name 3-methyl-1-butene is synonymous with 3-methylbut-1-ene. 2-Methyl-1-butene and 2-methyl-2-butene are also methylbutenes. Synonyms analog.

3-Methyl-1-butene can be used as monomer or comonomer for the preparation of polymers or copolymers.

"High boilers" in the context of the invention are a group of components of a liquid mixture whose respective boiling point in comparison to the boiling points of the other components of the mixture at higher temperatures, or whose vapor pressure is lower than the vapor pressure of the other components.

The terms "high boilers" and "high boiling components" are used synonymously with the term "high boilers".

"Low boilers" within the meaning of the invention are a group of components of a liquid mixture whose respective boiling point is lower than the boiling points of the other components of the mixture at lower temperatures, or whose vapor pressure is higher than the vapor pressure of the other components.

The inventors start from WO 2008/006633 A1 as closest prior art. WO 2008/006633 A1 describes the preparation of 3-methyl-1-butene via three process steps based on isobutene. Isobutene is first hydroformylated in this process, the hydroformylation product 3-methylbutanal hydrogenated to 3-methyl-1-butanol and then cleaved from the resulting alcohol water. For the dehydration of 3-methyl-1-butanol to 3-methyl-1-butene, basic modified aluminas are preferably used. In the example described dehydration at 340 ⁰ C and 0.15 MPa in the gas phase is used as a catalyst with 1, 5 mass% barium compounds (calculated as barium oxide) modified γ-alumina. The product contained - anhydrous - in addition to 94.5% by mass of 3-methyl-1-butene as desired product additionally 3.2% by mass of 2-methyl-2-butene, 0.7% by mass of 2-methyl-1 - butene and 0.2% by mass of di- (3-methylbutyl) ether and 0.5% by mass of high-boiling by-products and 0.9% by mass of unreacted 3-methyl-1-butanol. At a conversion of 99.2%, the yield is 92.2%, corresponding to a selectivity of 92.8%. The methylbutene fraction consists of 96% 3-methyl-1-butene and 4% of isomers.

In the generic process known from WO 2008/006333 A1, after optional removal of water, a distillative separation of the reaction mixture into starting alcohol (3-methyl-1-butanol), olefins (3-methyl-1-butene, 2-methyl-2 -butene, and 2-methyl-1-buten) and by-products (di (3-methylbutyl) ether and high-boiling by-products). It is proposed to return the unreacted alcohol to the dehydration.

With regard to its material efficiency (yield), the process discussed above needs to be improved.

The present invention is therefore based on the object to form a method of the type mentioned so that it has a higher material efficiency. This problem is solved in that in addition to the unreacted 3-methylbutanol and the di- (3-methylbutyl) ether is recycled into the dehydration. It has been found that the di (3-methylbutyl) ether can be selectively split back to 3-methyl-1-butene and 3-methyl-butanol. Accordingly, the return of the di- (3-methylbutyl) ether to the dehydration increases the yield of 3-methyl-1-butene and thus the material efficiency of the overall process.

The invention therefore provides a process for the preparation of 3-methyl-1-butene, a) in which a starting material containing 3-methyl-1-butanol is provided; b) in which the feedstock is subjected to catalytic dehydration to form a reaction product; c) wherein the reaction product contains at least the following components: 3-methyl-1-butene, di (3-methylbutyl) ether, water and unreacted 3-methyl-1-butanol; d) in which the reaction product is separated by distillation and a water separation by phase separation, in particular by simple phase separation, in a low boiler fraction, in a high boiler fraction and in a water fraction; e) wherein the low boiler fraction contains 3-methyl-1-butene; f) wherein the high boiler fraction contains at least di (3-methylbutyl) ether and unreacted 3-methyl-1-butanol; g) wherein the water fraction contains substantially water; h) and wherein the high boiler fraction is at least partially recycled to the dehydration.

The separation of the reaction product into the three fractions low boiler fraction (with the target product 3-methyl-1-buten), high boiler fraction (for recycling in the dehydration) and water fraction (process water auszuschleusendes) is carried out according to the invention in two steps distillation and water separation Distillation from the reaction product, the low boiler fraction be separated. The low boiler fraction containing the target product then constitutes the top stream of the distillation. Bottom stream of the distillation is a mixture of two liquid phases, namely high boiler fraction and water fraction. This liquid / liquid mixture can then be subjected in the second step to a simple phase separation, which separates the water from the high boilers.

Likewise, it is possible to first phase-phase the reaction product to separate out the water fraction and then to carry out distillation in the second step. The low boiler fraction containing the target product then again represents the top stream of the distillation, the bottom stream of the distillation forms the high boiler fraction.

If high-boiling components are formed as by-products of the dehydration in the reactor and / or if such high-boiling components are already contained in the starting material containing 3-methyl-1-butanol, they should be removed from the circulation on recycling, in order to enrich for undesirably high concentrations and, where appropriate, to avoid product contamination.

The separation of these high-boiling components can be done, for example, by discharging a smaller portion of the recovered from the water separation high boiler fraction from the circulation. Alternatively, a second distillation is provided, by means of which high-boiling components contained in the starting material and / or formed during the dehydration are separated from the high-boiling fraction and discharged. This optional distillation will hereafter be called secondary distillation for its verbal distinctiveness, in contrast to which the former distillation is referred to below as primary distillation. The prefixes "primary" and "secondary" have no connection with the technical execution of the distillation.

In a particularly preferred variant of the process according to the invention, high-boiling components are thus produced in a further process step discharged by secondary distillation of the high boiler fraction. In this case, a bottom stream is obtained, in which the high-boiling components are enriched. This bottom stream is discharged from the process. The overhead stream is then largely free of the high-boiling components and can then be recycled to the dehydration.

Advantageously, the secondary distillation is carried out after mixing with the starting material. Thus, even in the feed containing high boiler can be removed. Preferably, the secondary distillation is carried out at a pressure which is at least 0.05 MPa above the operating pressure of the dehydration. Without energy-intensive compression then the top stream of the distillation can be returned to the reactor.

Preferably, the secondary distillation is carried out in a distillation column whose top product is taken off in gaseous form and fed to the dehydration. As a result, hardly any energy is lost at this point in the process.

In order to further increase the energy efficiency of the process, process steam can be generated by means of the heat of condensation of the top product of the secondary distillation. The process steam is used in the process itself or in another process which is operated in the vicinity of the process according to the invention.

Advantageously, the primary distillation is carried out at a pressure which is at least 0.05 MPa below the operating pressure of the dehydration. Thus, no compressor work needs to be introduced at this point in the process.

Preferably, the reaction product is at least partially supplied in gaseous form to the primary distillation. A heat input is then not required at this point. The process according to the invention is preferably followed by a process for the preparation of 3-methyl-1-butanol,

The process for the preparation of 3-methyl-1-butanol as the last process step involves a distillation whose top product contains 3-methyl-1-butanol,

Wherein said distillation of the process for producing 3-methyl-1-butanol is carried out at a pressure which is at least 0.05 MPa above the operating pressure of the dehydration,

• and wherein the overhead of said distillation of the process for the preparation of 3-methyl-1-butanol is withdrawn in gaseous form and then fed as a feed to the dehydration.

The transition from the process for producing 3-methyl-1-butanol to the process for the preparation of 3-methyl-1-butene can then be carried out at the same enthalpy level.

Preferably, the water separation is carried out as a simple phase separation in a liquid-liquid separator.

Preferably, the distillations discussed here are each operated as fractional distillation.

In the following, the invention will be described by way of example, without the invention, whose scope of protection is apparent from the claims and the description, should be limited thereto. The claims themselves belong to the disclosure of the present invention. Given below ranges, general formulas, or classes of compounds, the disclosure is intended to cover not only the corresponding regions or groups of compounds explicitly mentioned, but also all sub-regions and sub-groups of compounds by omitting individual values (ranges) or compounds receive without explicit mention for reasons of clarity.

In the process according to the invention, pure 3-methylbutanol or 3-methylbutanol can be used in industrial grade. 3-methylbutanol is u. a. obtained by hydroformylation of isobutene and subsequent hydrogenation of the hydroformylation products. From the Hydriergut 3-methyl-1-butanol is separated by distillation.

3-methyl-1-butanol can be fed in gaseous or liquid form into the 3-methyl-1-butene plant.

If both a 3-methyl-1-butanol and a 3-methyl-1-butene plant is present at a production site, and at the same time the 3-methyl-1-butanol in the 3-methyl-1-butanol plant In the last step of the process, it may be desirable to remove the 3-methyl-1-butanol from this distillation step in vapor form and to introduce it in vapor form into the 3-methylbut-1-ene plant.

dehydration:

The dehydration of 3-methyl-1-butanol can be carried out in the presence of solid catalysts in the gas / liquid mixed phase or in the gas phase on suspended or lumpy catalysts arranged in a fixed bed. In the process according to the invention, the dehydration is preferably carried out on solid catalysts arranged in a fixed bed in the gas phase.

Oxides of the alkaline earth metals, aluminum, silicon, titanium, zirconium and thorium and the rare earths can be used as catalysts. It is also possible to use mixed oxides and combinations of the above oxides. For some catalysts, for. B. based on aluminum oxides, a certain acidity can be adjusted by the addition of alkali oxides. Preferably, the Selection of the catalysts and the reaction conditions such that the formation of by-products, such as di (3-methylbutyl) ether or high-boiling by-products and the isomerization of the formed 3-methyl-1-butene, for example, 2-methyl-2 butene or 2-methyl-1-butene, is largely avoided. Therefore, the dehydration of the process according to the invention is preferably carried out on catalysts modified with basic metal oxides. The catalysts used may contain as main component aluminum oxide (Al 2 O 3) and / or zirconium oxide (ZrO 2) as well as alkali metal and / or alkaline earth oxides. Titanium dioxide, silicon dioxide and / or thorium oxide may be present as further components in the catalyst at 0.1 to 3% by mass, preferably 0.5 to 5% by mass.

The proportion of basic metal oxides (hydroxides are converted into oxides) in the catalyst is preferably 0.01 to 10% by mass, more preferably 0.1 to 5% by mass, particularly preferably 0.1 to 3% by mass. Preferred alkali metals are sodium and / or potassium oxide. As alkaline earth metals magnesium and / or barium oxide are preferably used. As the dehydration catalyst, very particular preference is given to using a barium oxide (BaO) -modified γ-alumina, which is formally composed of barium oxide and aluminum oxide. Preference is given to using γ-aluminum oxides having a BET surface area of from 80 to 350 m ² / g, preferably from 120 to 250 m ² / g (determined by N ₂ adsorption in accordance with DIN 66131). The catalysts are prepared by known methods. Common methods are, for example, precipitation, impregnation or spraying of an aluminum oxide body with an appropriate salt solution and subsequent calcining.

Preferably, catalysts are used for dehydration, as described in WO 2008/006633 A1 and WO 2005/080302 A1.

In the process according to the invention, preference is given to using catalysts having a defined geometric shape, which have a hydraulic diameter of 0.1 to 10 mm, preferably 0.5 mm to 5 mm, particularly preferably 1, 5 to 3 mm. In the process according to the invention, the catalyst can be used as a shaped body. The moldings can take any shape. The catalyst is preferably used as a shaped body in the form of spheres, extrudates, cylinders or tablets. Particular preference is given to using catalysts in spherical form. The mold body preferably have the above-mentioned hydraulic diameter.

Preferably, dehydration of 3-methyl-1-butanol using said catalysts in the temperature range of 200 to 500 ⁰ C, preferably in a temperature range of 240 to 360 ⁰ C and more preferably in a temperature range of 250 to 310 ⁰ C. The dehydration can be carried out under reduced pressure, overpressure or at atmospheric pressure, wherein the reaction pressure is preferably in the range between 0.1 to 15 MPa (absolute), preferably in the range between 0.15 and 0.95 MPa (absolute). The dehydration is preferably carried out at a WHSV (weight hourly space velocity) of from 0.01 to 30 h ^-1 , preferably from 0.1 to 10 h ^-1 (kg of 3-methyl-1-butanol per kg of catalyst per hour).

With the preferred catalysts and under the preferred reaction conditions, total conversions of 3-methyl-1-butanol can be achieved in a straight pass. However, in order to achieve the highest possible selectivity towards 3-methyl-1-butene, it has proved to be advantageous if only a partial conversion of the alcohol used is aimed for in a straight pass. The straight-through 3-methyl-1-butanol conversion is preferably 50 to 95%, in particular 70 to 95%. Nevertheless, in the process according to the invention, a total conversion of 3-methyl-1-butanol close to 100% can be achieved since unreacted 3-methyl-1-butanol in the reactor is separated from the target product 3-methyl-1-butene in the course of the phase separation and within the framework of Return is returned to the reactor. The di- (3-methylbutyl) ether present in the cleavage product is likewise recycled together with 3-methyl-1-butanol into the cleavage reactor. This is particularly advantageous on catalysts to which the (Methylbutyl) ether already at temperatures below 300 ⁰ C to 3-methyl-1 - butanol and 3-methyl-1-butene back cleaved.

By recycling the unreacted 3-methyl-1-butanol and its ether, the yield of 3-methyl-1-butene based on Fhsch-3-methyl-i-butanol in the range of 85 to 99%, in particular in the range of 95 to 98%.

The dehydration can be carried out in conventional reactors, such as. B. in a tubular reactor, shell-and-tube reactor, shaft furnace or fluidized bed reactor or a combination thereof. Preferably, the dehydration in the process according to the invention in a reactor which is equipped with a heating jacket and which is heated with a liquid heat carrier, carried out, wherein the dehydration is carried out so that the temperature drop in the catalyst zone / reaction zone at any point with respect the inlet temperature of less than 50 ⁰ C, preferably less than 40 ⁰ C and particularly preferably from 1 to 30 ⁰ C, that the reaction mixture in the reactor and the heat transfer in the jacket in the DC flow through the reactor and that the temperature difference of the heat carrier between feed point to the reactor and effluent from the reactor is less than 40 ⁰ C. The maximum temperature drop can be due to numerous parameters, such. B. by the temperature of the heat carrier used for heating and by the speed at which the heat carrier flows through the jacket can be adjusted.

Preferably, the inlet temperature of the gaseous educt, in particular in this preferred embodiment of the dehydration step of the invention, is above 200 ^° C., preferably above 230 ^° C. and more preferably above 250 ^° C. The inlet temperature of the educt can be adjusted in a heater upstream of the reactor. When using fresh catalyst, the inlet temperature is preferably between 250 to 310 ⁰ C. In the course of operation, it may be advantageous with increasing deactivation of the catalyst to keep constant the input temperature up to 400 ⁰ C. Can the turnover on reaching 400 ⁰ C is no longer maintained be so it may be advantageous to replace the catalyst in whole or in part. In addition to low activity, a reduction in selectivity over service life may possibly also be a reason for a possible catalyst change.

The reactor may, in particular in this preferred embodiment of the dehydration of the process according to the invention, be arranged in any desired spatial direction. If the reactor has reactor tubes, these can also point in any direction in space. Preferably, however, the reactor is set up such that the reactor or the reactor tubes are aligned vertically. In a vertically oriented reactor, the heat carrier is preferably supplied at the highest point or near the highest point of the jacket and withdrawn at the lowest point or in the vicinity of the lowest point of the reactor or vice versa. The reaction mixture in the reaction zone and the heat transfer medium in the jacket preferably flow through the reactor in the same direction. Particularly preferably, the heat carrier and the reaction mixture flow through the jacket of the reactor or the reaction zone of the reactor from top to bottom.

As a heat carrier salt melts, water or heat transfer oils can be used. For the temperature range of 200 to 400 ⁰ C, the use of heat transfer oils is advantageous because heating circuits require less capital investment with them compared to other technical solutions. Heat transfer oils which can be used are, for example, those sold under the trade names Marlotherm (for example Marlotherm SH from Sasol Olefins & Surfactants GmbH), Diphyl (Bayer), Dowtherm (Dow) or Therminol (Therminol ) to be expelled. These synthetically produced heat transfer oils are based essentially on thermally stable ring hydrocarbons.

Preferably, the heat transfer medium at a temperature which is 10 to 40 ⁰ C, preferably 10 to 30 ⁰ C higher than the temperature of the reactant flowing into the reactor, passed into the heating jacket of the reactor. The temperature difference of the liquid heat carrier over the reactor, ie between the inlet temperature of the Heat carrier at entry into the heating jacket and the outlet temperature of the heat carrier at the outlet from the heating jacket is preferably less than 40 ⁰ C, preferably less than 30 ⁰ C and particularly preferably from 10 to 25 ⁰ C. The temperature difference can be by the mass flow of the heat carrier per unit time (Kilograms per hour) are set by the heating mantle.

The preferred embodiment of the dehydration can be carried out in all suitable reactors which are equipped with a heating jacket and which can be heated with a liquid heat carrier. Such reactors have a catalyst-containing reaction zone (catalyst zone), which is spatially separated from a heating jacket through which the heat transfer medium flows. The process according to the invention is preferably carried out in a plate reactor, in a tubular reactor, in several tubular reactors or plate reactors connected in parallel or in a tube bundle reactor. The process according to the invention is preferably carried out in a tube bundle reactor or several tube bundle reactors connected in parallel.

It should be noted that the hollow bodies in which the catalyst is located, not only pipes in common usage must be. The hollow bodies may also have non-circular cross-sections. For example, they can be elliptical or triangular.

The materials used for the construction of the reactor, in particular the material which separates the reaction zone from the heating jacket, preferably has a high coefficient of thermal conductivity (greater than 40 W / mK). Preferred as a material with a high coefficient of thermal conductivity iron or an iron alloy, such as. B. steel used.

If the process according to the invention is carried out in a tube bundle reactor, the individual tubes preferably have a length of from 1 to 15 m, preferably from 3 to 9 m and particularly preferably from 4 to 9 m. The individual tubes in a tube bundle reactor used in the method according to the invention preferably have an inner diameter of 10 to 60 mm, preferably from 15 to 40 mm and particularly preferably from 20 to 35 mm. It may be advantageous if the individual tubes of the tube bundle reactor used in the method according to the invention have a thickness of the tube wall of 1 to 4 mm, preferably from 1, 5 to 3 mm.

In a tube bundle reactor used in the preferred embodiment of the method according to the invention, the tubes are preferably arranged in parallel. Preferably, the tubes are arranged uniformly. The arrangement of the tubes can, for. B. square, triangular or rhombic. Particularly preferred is an arrangement in which the virtual connected centers of three mutually adjacent tubes form an equilateral triangle, i. H. the tubes are the same distance. The process according to the invention is preferably carried out in a tube bundle reactor in which the tubes have a spacing of 3 to 15 mm, particularly preferably 4 to 7 mm, from one another.

The main reaction of the process according to the invention is the dehydration of 3-methyl-1-butanol to 3-methyl-1-butene and water. Depending on the adjusted 3-methyl-1-butanol conversion, the reaction product after the reactor preferably has a residual 3-methyl-1-butanol content of 1 to 50% by mass, preferably from 5 to 30 and particularly preferably from 5 to 20% by mass. The water content in the reaction product is preferably from 8 to 20% by mass, preferably from 12 to 18% by mass.

The 3-methyl-1-butene content in the reaction product is preferably from 40 to 78% by mass, preferably 55 to 74% by mass. As side reactions, the formation of di-methylbutyl ether and optionally traces of the formation of high-boiling components can occur as well as the isomerization of the formed 3-methyl-1-butene to 2-methyl-2-butene or 2-methyl-1-butene occur. By recycling the high boiler fraction separated from the reaction product, di (3-methylbutyl) ether is also recycled to the reactor. Among the preferred Reaction conditions and on the preferred catalyst system di (3-methylbutyl) ether is split back proportionately to methylbutene and 3-methyl-1-butanol.

Water separation and primary distillation:

Dehydration is followed by water separation and primary distillation. In this case, the resulting from the dehydration reaction product in a predominantly methylbutenes contained low boiler and a predominantly unreacted 3-methyl-1-butanol and di- (methylbutyl) ether and optionally high-boiling components contained high boiler fraction by fractional distillation and a predominantly water-containing Fraction separated by simple phase separation in a liquid-liquid separator.

The reaction product decomposes in complete condensation in two liquid phases, the light phase predominantly the organic components methylbutenes, 3-methyl-1-butanol and di (methylbutyl) ether and optionally high-boiling organic components and the heavy phase contains predominantly water. Light and heavy in this case refers to the specific gravity of the phases, i. H. the heavy, aqueous phase has a higher density than the light, organic phase.

For separation of the heavy, aqueous phase from the light, organic phase separators can be used, which allow the phase separation with the sole use of gravity. These so-called gravitational separators can also be designed with internals as a coalescence-promoting measure to increase the separation efficiency. The use of internals accelerates the coalescence and sedimentation process. By means of these design measures, the capacity expansion of existing facilities or the reduction of the investment volume in new construction is possible. As coalescence aids z. As plates, random packings, tissue packs or Faserbettabscheidern be used. Gravity separators can be designed as horizontal tanks or as standing tanks. As an alternative to gravitational separators, separators based on the centrifuge principle can also be used for liquid-liquid separation. By centrifugal forces in a rotating drum while the heavy phase is separated.

In order to separate off the heavy, aqueous phase, gravitational separators are preferably used in the process according to the invention, preferably gravity separators, designed as horizontal containers with internals.

By liquid-liquid separation, the water can be separated from the organic components to its physical solubility limit. The water solubility of methyl butenes decreases with decreasing temperature, at the same time the solubility of water in methylbutenes decreases, so that the liquid-liquid separation should be carried out as low as possible, preferably in a temperature range of less than 70 ⁰ C, preferably less than 60 ⁰ C. , more preferably at a temperature of less than 50 ⁰ C. The pressure should be chosen so that no evaporation occurs, preferably in a range of 0.3 and 2.0 MPa (absolute).

The separation of the water from the reaction product formed in the dehydration can be carried out before or after the primary distillation to separate the reactor discharge into low and high boiler. A separation before the primary distillation has the advantage that the stream to be worked up is depleted by the free water content and thus a smaller stream must be worked up. On the other hand, a separation of the water from the high-boiler stream after the primary distillation can have energy advantages, since in this case the reactor discharge does not have to be cooled and completely condensed, but can be fed to the fractional distillation in whole or in part in gaseous form.

The reaction product is in the primary distillation in a predominantly methylbutenes contained low boiler and a predominantly unreacted Separated 3-methyl-1-butanol and di (methylbutyl) ether and optionally high-boiling components high-boiling fraction. This separation is preferably carried out in at least one column, preferably in exactly one distillation column.

A distillation column which is preferably used in the primary distillation for fractionating the reactor output into low and high boilers preferably has from 5 to 50 theoretical plates, preferably from 5 to 40 and particularly preferably from 5 to 25 theoretical plates. The reflux ratio is, depending on the number of stages realized, the composition of the reactor effluent and the required purities of distillate and bottom product, preferably less than 5, preferably less than 0.5. The operating pressure of the column may preferably be adjusted between 0.1 and 2.0 MPa (absolute). If the removal of water by liquid-liquid separation is carried out after the primary distillation, it may be advantageous to drive the reactor discharge in the column completely or partially in gaseous form. In this case, it may be advantageous, in order to save a compressor, to operate the column at a lower pressure than the pressure at which the reactor is operated for dehydration. To condense 3-methyl-1-butene against cooling water, a pressure of about 0.25 MPa (absolute) is necessary. If the cleavage is operated, for example, at a pressure of 0.4 MPa (absolute), it may be advantageous if the distillation column is operated at an operating pressure of 0.3 to 0.35 MPa (absolute). For heating the evaporator, for example, steam or hot water can be used. The separated high boiler fraction preferably contains unreacted 3-methyl-1-butanol, di-methylbutyl ether and optionally in the reaction in traces formed high-boiling components. The low boiler fraction preferably contains methylbutenes having a purity greater than 95% by mass, based on the total overhead product. In this case, the low-boiling fraction contains the target product 3-methyl-1-butene and the isomers 2-methyl-2-butene and 2-methyl-1-butene and water. The low boiler fraction obtained by fractional distillation, which is preferably greater than 95% by mass of methyl butenes, can be used directly as a commercial product or further purified.

Return:

In the course of recycling, the high boiler fraction separated by water separation is recycled to the dehydration of the process according to the invention. The high boiler fraction may be separately fed to the reaction part or previously mixed with the 3-methyl-1-butanol-containing feed and then fed to the reaction part. Preferably, the high boiler fraction is mixed with the 3-methyl-1-butanol-containing feed before being returned to the reactor.

According to the invention, the recycle stream also contains di (3-methylbutyl) ether in addition to the unreacted 3-methylbutanol. By selective cleavage of the di (3-methylbutyl) ether to 3-methyl-1-butene and 3-methyl-butanol in the dehydration, the yield of 3-methyl-1-buten increases and thus the material efficiency of the overall process.

If, in the dehydration of the process according to the invention, high-boiling components are formed as by-products in the reactor and / or if such high-boiling components are already present in the 3-methyl-1-butanol-containing feedstock, they must be removed from the cycle during the recirculation in order to obtain a Enrichment to undesirably high concentrations and, where appropriate, to avoid product contamination. High-boiling components in this context are meant substances which boil higher than di- (3-methylbutyl) - ether, ie have a normal boiling point greater than about 175 ⁰ C. The separation of these high-boiling components can be carried out, for example, by discharging a smaller part ("discharge part") of the high-boiling fraction from the cycle., However, in order to keep this discharge flow as small as possible, it is advisable, the discharge of the high boilers by a secondary distillation of the To carry out high boiler fraction. The process thus has a primary distillation and a secondary distillation. In the secondary, a bottom stream is obtained, in which the high-boiling components are enriched and is discharged from the process. The overhead stream is then largely free from the high-boiling components and can then be recycled to the reaction. The secondary distillation to remove the high-boiling components can also be carried out in the high-boiling fraction after mixing with the feedstock 3-methyl-1-butanol.

In a particularly preferred variant of the process according to the invention, therefore, high-boiling components formed in the dehydration or optionally already present in the 3-methyl-1-butanol-containing starting material are removed in a secondary distillation by fractional distillation of the high boiler fraction. In this case, a bottom stream is obtained, in which the high-boiling components are enriched. This bottom stream is discharged from the process. The top stream is then largely free of the high-boiling components and can be returned.

The discharge of the high-boiling components is preferably carried out in a distillation column in the recirculated high-boiling fraction after mixing with the feedstock 3-methyl-1-butanol. Preferably, the addition of the recirculated high boiler fraction and the feedstock at different place in the column. The distillation column used in this case preferably has from 5 to 50 theoretical plates, preferably from 5 to 35 and more preferably from 5 to 20 theoretical plates. The reflux ratio is, depending on the number of stages realized, the composition of the recirculated high-boiling fraction and the starting material and the required purities of distillate and bottom product, preferably less than 5, preferably less than 0.5.

The operating pressure may preferably be from 0.1 to 2.0 MPa (absolute). If the dehydration of the overhead product in the gas phase takes place at elevated pressure, It may be advantageous to carry out the distillation at a higher pressure, in which case the top condenser is preferably operated as a partial condenser and the overhead product is taken off in vapor form. For example, if the reaction pressure in the cleavage reactor is 0.4 MPa (absolute), the distillation pressure in the secondary distillation should preferably be at least 0.45 MPa (absolute). At operating pressures of greater than 0.15 MPa (absolute), the condensation heat can be used to generate low-pressure steam, with which other columns of the process can be heated. To heat the column can be used depending on the selected operating pressure, steam or heat transfer oil. The bottom product, in addition to the separated high-boiling components and 3-methyl-1 - butanol and di (3-methylbutyl) ether. This mixture can be used thermally, used as starting material for a synthesis gas plant or optionally used as a solvent or fuel additive.

Be used in the process according to the invention columns, such. B. in the figures 1 to 4 with K1, K2, columns, so they can with internals, z. B. from soils, rotating internals, random beds and / or ordered packs are provided.

In the column bottoms z. B. the following types are used:

- Soils with holes or slots in the bottom plate.

- Soils with necks or chimneys covered by bells, caps or hoods.

- Floors with holes in the bottom plate, which are covered by movable valves.

- floors with special constructions.

In columns with rotating internals of the return z. B. sprayed by rotating funnel or spread using a rotor as a film on a heated pipe wall. In the process according to the invention, as already stated, columns can be used which have random beds with different packing. The packing can from almost all materials, in particular z. Example of steel, stainless steel, copper, carbon, earthenware, porcelain, glass or plastics and have a variety of forms, in particular the shape of balls, rings with smooth or profiled surfaces, rings with inner webs or wall openings, wire mesh rings, caliper body and spirals.

Packages with regular / ordered geometry may e.g. B. consist of sheets or tissues. Examples of such packages are Sulzer metal or plastic BX packages, Mellapak sheet metal Sulzer laminations, Sulzer high performance packages such as Mella-pakPlus, structural packings from Sulzer (Optiflow), Montz (BSH) and Kühni (Rombopak).

Based on the figures, the present invention will be explained in more detail below, without the invention being limited to the illustrated embodiments. Show it:

1 shows a circuit diagram of a plant for carrying out a first process variant according to the invention; FIG. 2 shows a circuit diagram of a system for carrying out a second variant of the method according to the invention; FIG. 3 shows a circuit diagram of a plant for carrying out a third process variant according to the invention; 4 shows a circuit diagram of a system for carrying out a fourth process variant according to the invention.

A block diagram of a first embodiment according to the invention of a plant in which the process according to the invention can be carried out is shown in FIG. The feed stream (1) containing 3-methyl-1-butanol is mixed with the recycle stream (7b) and reacted in reactor R1 for the most part in methylbutenes and water (dehydration). The in the recycle stream (7b) contained di- (3-methylbutyl) ether is reacted proportionally to methylbutenes and 3-methyl-1-butanol. From the obtained from the dehydration carried out in reactor R1 reaction product (4) is separated in this system, after complete condensation of the reaction product (4), first by liquid-liquid separation in the separator D1, the majority of the water. In this case, the heavy, aqueous phase (5) is discharged and the light, organic phase (4a) of the column K2 supplied. The water is separated up to its physical solubility. In the column K2 the largely anhydrous reactor discharge into a low-boiling fraction as the top product (6), which predominantly contains the resulting in the reaction methylbutenes and a high boiler fraction as the bottom product (7), the at least unreacted 3-methyl-1-butanol and in the Reaction resulting di- (3-methylbutyl) ether and optionally in the reaction resulting high-boiling components, fractionated. The bottom product (7) from the distillation in the context of recycling in the reactor R1 recycled. Optionally, streams (1) and (7) may be passed separately or together into reactor R1. If high-boiling components are formed as by-products in the reactor R1 or if such high-boiling components are contained in the starting material (1) containing 3-methyl-1-butanol, they can optionally be discharged with stream (8) in order to enrich for undesirably high concentrations and, where appropriate, to avoid product contamination.

Optionally, the separated water phase (5) can be distilled in Figure 1 to reduce the cargo of organic substances and the distillate, consisting of water and low boilers, are recycled to the separator D1.

A block diagram of a second embodiment according to the invention of a plant in which the process according to the invention can be carried out is shown in FIG. The embodiment of Fig. 2 differs from that of Fig. 1 in that by dehydration of 3-methyl-1-butanol in water formed in only after the separation of the low boiler fraction (6) from the high boiler fraction (7) behind the column K2 Will get removed. In doing so, the vast majority of Water again separated by liquid-liquid separation in the separator D1. The heavy, aqueous phase (5) is discharged and the light organic phase (7a) is returned to the reactor R1. The water is separated again up to its physical solubility. The separation of the water from the high-boiler stream (7) after the fractional distillation in the column K2 therefore has energetic advantages, since in this case the reactor discharge (4) does not have to be cooled and completely condensed, but completely or partially gaseous fractional distillation in column K2 can be supplied. If high-boiling components are formed as by-products in the reactor R1 and / or if such high-boiling components are contained in the starting material (1) containing 3-methyl-1-butanol, they can optionally be discharged again with stream (8).

A block diagram of a third embodiment of a plant in which the method according to the invention can be carried out is shown in FIG. The embodiment of FIG. 3 differs from that of FIG. 2 in that high-boiling components which are formed in the dehydration of the process according to the invention as by-products in the reactor R 1 and / or as secondary components 3-methyl-1-butanol-containing feedstock contained are discharged. The discharge of the high-boiling components is carried out in Fig. 3 by fractional distillation of the largely anhydrous recycle stream (7a) in column K1. In this case, the recycle stream (7a) is separated into a top stream (7b) which is largely free of high-boiling components and a bottom stream (3). The bottom stream (3) contains, in addition to the enriched high-boiling components, di (3-methylbutyl) ether and 3-methyl-1-butanol. The top stream (7b) of the column K1 is fed back to the reactor R1 for dehydration.

A block diagram of a fourth embodiment of a plant in which the method according to the invention can be carried out is shown in FIG. 4. The embodiment of FIG. 4 differs from that of FIG. 3 in that high-boiling components are formed as by-products in the reactor R1 and / or are already contained as minor components in the 3-methyl-1-butanol-containing feed, be discharged in a column K1 as the bottom stream (3). The feedstock (1) and the recycle stream (7a) are fed to the column K1. In the column K1, these streams are separated into a head stream (2) which is largely free of high-boiling components and a bottom stream (3). The bottom stream (3) contains, in addition to the enriched high-boiling components, di (3-methylbutyl) ether and 3-methyl-1-butanol. The top stream (2) of the column K1 is fed back to the reactor R1 in. In this case, the column K1 is preferably operated at an operating pressure above the operating pressure of the reactor R1. The top condenser of the column K1 is operated in this case preferably as a partial condenser. The top product (2) is then withdrawn in vapor form and fed to the reactor R1.

The following examples are intended to illustrate the invention without restricting the scope of application that results from the description and the claims.

Example 1: Cleavage of 3-methyl-1-butanol

99.81 mass% of 3-methyl-1-butanol was used in an electrically heated flow fixed bed reactor on the B44 / 1 c spherical catalyst (1.7 to 2.1 mm spheres) with a bulk density of 0, 58 g / cm ³ reacted. The catalyst is a 0.48% barium oxide-modified γ-alumina catalyst, whose preparation is described in a patent application of the same Applicant of the same date. Before entering the reactor, the liquid educt was completely evaporated in an upstream evaporator at 230 ⁰ C. At reaction temperatures of 280-300 ⁰ C, 18.5 g of 3-methyl-1 were passed in the gas phase -butanol passed through 29.0 g of catalyst, corresponding to a WHSV of 0.64 h ^'1. The liquid hourly space velocity WHSV ( Weight hourly space velocity) is expressed in grams of starting material per gram of catalyst per hour, and the reaction pressure was 0.15 MPa (absolute). The gaseous product was cooled in a condenser and cooled in collected a steel template. The product had, calculated anhydrous, the composition shown in Table 1.

Table 1: Composition of the reactor effluent upon dehydration on B44 / 1 c catalyst for Example 1.

Table 1 lists, in addition to the composition of the product, the distribution of the methylbutylene isomers normalized to 100%. As can be seen, the formation of desired product 3-methyl-1-buten increases with increasing reaction temperature. As an intermediate and by-product of the 3-methyl-1-butanol cleavage is mainly the ether of 3-methyl-1-butanol, di (3-methylbutyl) ether formed. With the increase of the temperature from 280 to 290 ⁰ C or to 300 ⁰ C, the proportion of 3-methyl-1-butene in the isomer mixture decreases by the isomerization. The highest proportion of 3-methyl-1-butene of about 97.4% was determined at a reaction temperature of 280 ⁰ C, but under these reaction conditions forms appreciably Di (3 methylbutyl) ether, so that without a return of the ether, the resulting yield of 3-methyl-1-butene in single pass is unsatisfactory.

Example 2: Cleavage of di (3-methylbutyl) ether

As shown in Example 1, in the cleavage of 3-methyl-1-butanol to 3-methyl-1-butene as an intermediate and by-product di (3-methylbutyl) ether is formed. In Example 2, the cleavage of di (3-methylbutyl) ether on the same catalyst as in Example 1 is shown.

Di- (3-methylbutyl) ether with a purity of 99.63% by mass was reacted in an electrically heated flow-fixed bed reactor on the same catalyst as in Example 1. Before entering the reactor, the liquid educt was completely evaporated in an upstream evaporator at 230 ⁰ C. At reaction temperatures between 270 and 300 ^° C. and a reaction pressure of 0.15 MPa (absolute), 18.5 g of the di- (3-methylbutyl) ether per hour were mixed with 29.0 g of catalyst in the gas phase, corresponding to a WHSV value 0.64 h ^"1, passed through. the gaseous product was cooled in a condenser and collected in a steel template. After GC analysis of the product discharge had expected anhydrous the composition shown in table 2. at the same time in table 2 again beside the composition. of Product also lists the 100% normalized distribution of methyl isobutene isomers.

Table 2: Composition of the reactor effluent with cleavage of di (3-methylbutyl) ether on B44 / 1 c catalyst for Example 2.

As can be seen from Table 2, the di-3-methylbutyl ether is selectively converted to 3-methyl-1-butene. In parallel, the second product of the ether cleavage, 3-methyl-1-butanol, is also converted to 3-methyl-1-butene. The conversion increases with increasing temperature, at 300 ⁰ C almost full conversion of di-3-methyl butyl ether is achieved. In the isomer mixture, however, the proportion of the desired target product 3-methyl-1-butene decreases with increasing temperature.

Example 3: Cleavage of a 3-methyl-1-butanol / di (3-methylbutyl) ether mixture

The feedstock used in Example 1, nearly pure 3-methyl-1-butanol, and the feedstock used in Example 2, nearly pure di- (3-methylbutyl) ether mixed together in a ratio such that a mixture of about 30.0% by mass of di (3-methylbutyl) ether and about 70.0% by mass of 3-methyl-1-butanol was formed. This mixture was reacted in an electrically heated flow fixed bed reactor on the same catalyst as in Example 1 and Example 2. Before entering the reactor, the liquid educt was completely evaporated in an upstream evaporator at 230 ⁰ C. At reaction temperatures between 280 and 300 ^° C., 18.5 g of 3-methyl-1-butanol were passed through 29.0 g of catalyst per hour in the gas phase, corresponding to a WHSV of 0.64 h ^-1 Analysis anhydrous calculated the composition shown in Table 3. At the same time Table 3 again lists the normalized to 100% distribution of the methyl isomers.

TABLE 3 Composition of the reactor effluent in the case of cleavage of a 3-methyl-1-butanol / di (3-methylbutyl) ether mixture on the B44 / 1 c catalyst for example 3. As can be seen from Table 2, the di- (3-methylbutyl) ether is already selectively reacted at a reaction temperature of 280 ⁰ C to the desired product 3-methyl-butene-1. At this temperature, the content of the ether in the product with about 23% by mass in the same order of magnitude as in Example 1 (about 19% by mass at 280 ⁰ C) in driving with pure 3-methyl-1-butanol as starting material , With increasing reaction temperature, the content of ether in the product decreases, at 300 ⁰ C, the ether is almost completely implemented. However, the proportion of 3-methyl-1-butene in the mixture of isomers decreases simultaneously with the increase in temperature. The highest proportion of 3-methyl-1-butene of about 97% was determined at a reaction temperature of 280 ⁰ C. Thus, for the content of target product in the isomer almost the same value is achieved as in Example 1 (about 97% by mass at 280 ⁰ C) in driving with pure 3-methyl-1-butanol as starting material.

With these experimental examples could be shown that, for a driving at a lower reaction temperature below 300 ⁰ C, the proportion of the target product, 3-methyl-1-butene in the C ₅ -lsomerengemisch principle increases. Upon separation and recycling of the unreacted 3-methyl-1-butanol and the resulting di- (3-methylbutyl) ether, the total conversion and the corresponding yield can be increased to very high values, since the ether with high conversions and very selective to Target product can be implemented, even at lower reaction temperatures below 300 ⁰ C.

It could thus be clearly demonstrated that the process according to the invention, in which not only unreacted 3-methyl-1-butanol but also di- (3-methylbutyl) ether is recycled to the dehydration, a process in which only the unreacted Alcohol is recycled, is superior in terms of material efficiency.

In addition to the experimental work shown below, example calculations for the overall process with distillation steps and recirculations are intended to illustrate the process according to the invention. These Invoices were performed with the stationary simulation program ASPEN Plus (version 2006.1 of the company AspenTech). In order to generate transparent, reproducible data, only generally accessible material data was used. As a material data model, the property method "UNIFAC-DMD" (see J. Gmehling, J. Li, and M. Schiller, Ind. Eng. Chem. Res., 32, (1993), pp. 178-193) was used. This makes it easy for the skilled person to understand the calculations.

For the reactor R1, a reactor volume of 37.5 m ^{3 is} modeled in each case, assuming a filling with a catalyst as used in Examples 1 to 3. For the reactor modeling, a kinetic reactor model was used in the calculations, which is based on extensive experimental data with this catalyst. In the examples, therefore, each of the reaction temperatures are called, which were assumed in the reactor modeling. Since in each case the composition of the incoming and outgoing streams of the reaction stage are called, it is possible for the skilled worker by adjusting the reactors with fixed predetermined conversions to recalculate the example, without knowing the exact equations for the kinetics.

Example 4: Process for the preparation of 3-methyl-1-butene according to FIG. 1

Example 4 corresponds to the non-inventive variant shown in Fig. 1. As feed stream (1) is assumed according to Figure 1, a current of 10 t / h, consisting of pure 3-methyl-1-butanol. Stream (1) is mixed with the recycle stream (7b). The recycle stream (7b) is the bottom stream of the column K2 after separation of the discharge stream (8). The composition of the feedstock (1), the recycle stream (7b) and the feed stream (2) resulting from the mixture to the reactor R1 are shown in Table 4. As can be seen, an inlet stream containing about 16% by mass of di (3-methylbutyl) ether and 82% by mass of 3-methyl-1-butanol arises at the chosen process conditions.

Table 4: Composition of the feedstock (1), the recycle stream (7b) and the reactor feed (2) for Example 4.

The stream (2) is evaporated, heated up to the reaction temperature and fed in vapor form to the reactor R1. The reactor is operated at 275 ^° C. and 0.40 MPa (absolute). Under these reaction conditions, the formal result is a 3-methyl-1-butanol conversion of about 78%. The composition of the reactor effluent (4) is shown in Table 5. In addition to 3-methyl-1-butene and its isomers, di- (3-methylbutyl) ethers and high boilers are formed as by-products. By way of example, the formation of a C ₅ -olefin as the by-product of 3-methyl-1-butanol was assumed to be a high boiler. It should be noted that in parallel there is also a conversion of the di (3-methylbutyl) ether contained in stream (2). The di (3-methylbutyl) ether is split proportionally to 3-methyl-1-butene and 3-methyl-1-butanol, so that the content of di- (3-methylbutyl) ether in the reactor effluent (4) only moderately increases to about 17% by mass.

Table 5: Composition of the reactor effluent (4) and the organic phase (4a) and the aqueous phase (5) of liquid-liquid separator D1 for Example 4.

The reactor effluent (4) is completely condensed, cooled to 45 ⁰ C, and fed to the liquid-liquid separator D1. In the separator D1, the water is separated to its physical solubility limit and discharged as a heavy phase (5). The then largely anhydrous stream (4a) is moved to the distillation column K2. The mass flows and the compositions of the organic phase (4a) and the aqueous phase (5) are listed in Table 5.

Table 6: Composition of the distillate (6) and the bottom product (7) of the column K2 and of the discharge stream (8) for Example 4.

The organic phase (4a) is fed in liquid form to the column K2. The column has 22 theoretical stages and is operated at a reflux ratio of 0.06 and at a pressure of 0.40 MPa (absolute). The addition of the feed takes place above stage 17, counted from above. The top temperature is 51, 7 ⁰ C, the bottom temperature 170.7 ⁰ C. The top product (6) is 3-methyl-1-butene% 3-methyl-1-butene with a purity of greater than 95 mass, see Table 6 As secondary components are also the isomers 2-methyl-1-butene and 2-methyl-2-butene, 3-methyl-1-butanol and water. Thus, the top product may already be a sales product. However, the secondary components are preferably separated off in further process steps and the 3-methyl-1-butene is purified to purities greater than 99% by mass.

The bottom product (7) of the column K2 consists predominantly of unreacted 3-methyl-1-butanol (about 49% by mass) and di (3-methylbutyl) ether (about 47% by mass). In addition, high boilers, water and methyl butenes are included. In order to avoid an undesirable Aufkonzentherung the high boilers in the circuit, with stream (8) a smaller part of the bottom product (7) is separated and discharged. The mass larger stream (7b) is mixed with the feed (1) and fed back to the reactor R1.

In Example 4, the total yield of methylbutenes calculated from the alcohol content in stream (1) and the methylbutene content in stream (6) is 96.4%, the yield of 3-methyl-1-butene is 94.2%. These high yields of material are achieved by recycling and cleavage of the unreacted alcohol and the ether formed.

Example 5: Process for the preparation of 3-methyl-1-butene according to FIG. 4

Example 5 corresponds to the variant shown in FIG. As feed stream (1) is again assumed, analogously to Example 4, a current of 10 t / h, consisting of pure 3-methyl-1-butanol. Stream (1) and the recycle stream (7a) are fed to the column K1. The recycle stream (7a) is the bottom stream of the column K2 after separation of the aqueous phase (5) in the liquid-liquid separator D1. The composition of the feedstock (1) and recycle stream (7a) are shown in Table 7. As can be seen, the recycle stream at the selected process conditions in addition to unreacted 3-methyl-1-butanol substantially still di- (3-methylbutyl) ether and high boilers.

Table 7: Composition of the feedstock (1), the recycle stream (7a) and distillate (2) and bottom product (3) of the column K1 for Example 5.

The column K1 in Example 5 is used for separating and discharging the high boilers formed in the reactor R1. The column K1 has 10 theoretical stages and is operated at a reflux ratio of 0.07 and at a pressure of 0.40 MPa (absolute). The addition of stream (1) and stream (7a) into the column takes place above stage 9, counted from above. The head temperature is 179.2 ° C, the bottom temperature 195.0 ⁰ C. The top condenser is operated as a partial condenser, the overhead product (2) is taken off in the vapor. The top product (2) contains about 85% by mass of 3-methyl-1-butanol and about 13% by mass of di (3-methylbutyl) ether and is largely free of high boilers with about 140 ppm, see Table 7 The bottom product (3) of the column K1 consists predominantly of 3-methyl-1-butanol (about 33% by mass), di (3-methylbutyl) ether (about 37% by mass) and high boilers (ca. 29% by mass).

The top product (2) of the column K1 is further heated up to the reaction temperature and fed in vapor form to the reactor R1. The reactor is operated at 282 ⁰ C and 0.35 MPa (absolute). With these reaction conditions results formally a 3-methyl-1-butanol conversion of about 81%. The composition of the reactor effluent (4) is shown in Table 8. In addition to 3-methyl-1-butene and its isomers, as in Example 4, as by-products di- (3-methylbutyl) ether and high boilers (Ci ₅ -olefins) are formed. In parallel with the 3-methyl-1-butanol cleavage, the reaction of the di (3-methylbutyl) ether contained in the stream (3) to 3-methyl-1-butene and 3-methyl-1-butanol takes place again. The content of di (3-methylbutyl) ether in the reactor discharge (4) increases only moderately to about 13.6% by mass.

Table 8: Composition of the reactor discharge (4), distillate (6) and bottom product (7) of the column K2 and the aqueous phase (5) of liquid-liquid separator D1 for Example 5.

The reactor discharge (4) is partially condensed at a temperature of 88.6 ⁰ C and two-phase fed to the column K2. The column has 18 theoretical stages and is operated at a reflux ratio of 0.47 and at a pressure of 0.30 MPa (absolute). The addition of the feed takes place above stage 13, counted from above. The head temperature is 53.3 ⁰ C, the bottom temperature 119.2 ⁰ C. The top product (6) is 3-methyl-1-butene-butene with a purity of greater than 96% by mass of 3-methyl-1, see Table 8 As minor components are also the isomers 2-methyl-2-butene and 2-methyl-1-butene, 3-methyl-1-butanol and water.

The bottom product (7) of the column K2 consists predominantly of unreacted 3-methyl-1-butanol (about 37% by mass), di- (3-methylbutyl) ether (about 30% by mass) and water (ca. 33% by mass). Besides these are high boilers and methylbutenes contain. Stream (7) is cooled to 40 ⁰ C and fed to the liquid-liquid separator D1. In the separator D1, the water is separated to its physical solubility limit and discharged as a heavy phase (5). The then largely anhydrous stream is recycled as recycle stream (7a) in the distillation column K1. The mass flow and the composition of the organic phase (7a) are shown in Table 7 and those of the aqueous phase (5) in Table 8.

In Example 5, the total yield of methylbutenes - calculated from the alcohol content in stream (1) and the methylbutene content in stream (6) - is 98.7%, the yield of 3-methyl-1-butene is 96.2%. These high yields of material are again achieved by recycling and cleavage of the unreacted alcohol and the ether formed. Compared to Example 4, the material efficiency is significantly increased by the fact that the stream (3) is significantly depleted before removal by distillation in column K2 recyclables 3-methyl-1-butanol and di (3-methylbutyl) ether.

Claims

claims:

A process for the preparation of 3-methyl-1-buten, a) in which a feedstock containing 3-methyl-1-butanol is provided; b) in which the feedstock is subjected to catalytic dehydration to form a reaction product; c) wherein the reaction product contains at least the following components: 3-methyl-1-butene, di (3-methylbutyl) ether, water and unreacted 3-methyl-1-butanol; d) in which the reaction product is separated by distillation and a water separation by phase separation in a low boiler fraction, in a high boiler fraction and in a water fraction; e) wherein the low boiler fraction contains 3-methyl-1-butene; f) wherein the high boiler fraction contains at least di (3-methylbutyl) ether and unreacted 3-methyl-1-butanol; g) wherein the water fraction contains substantially water; h) and wherein the high boiler fraction is at least partially recycled to the dehydration.

2. The method according to claim 1, characterized in that the high boiler fraction is divided into a return part and a discharge part, and that only the return part is returned to the dehydration, during which the discharge part is discharged from the process , wherein the return part is larger than the discharge part.

3. The method according to claim 1, characterized in that the high boiler fraction is subjected to a distillation, by means of which contained in the feedstock and / or formed during the dehydration, high-boiling components are separated from the high boiler fraction and discharged.

4. The method according to claim 3, characterized in that the distillation of the high boiler fraction is carried out after mixing with the feedstock.

5. The method according to claim 3 or 4, characterized in that the distillation of the high boiler fraction is carried out at a pressure which is at least 0.05 MPa above the operating pressure of the dehydration.

6. The method according to claim 5, characterized in that the distillation of the high boiler fraction is carried out in a distillation column whose top product is withdrawn in gaseous form and fed to the dehydration.

7. The method according to any one of claims 3 to 6, characterized in that by means of the heat of condensation of the overhead product of the distillation of the high boiler fraction process steam is generated.

8. The method according to any one of claims 1 to 7, characterized in that the distillation for the separation of the reaction product in low-boiling fraction and high-boiling fraction is carried out at a pressure which is at least 0.05 MPa below the operating pressure of the dehydration.

9. The method according to claim 8, characterized that the reaction product is at least partially supplied in gaseous form to the distillation for separating the reaction product into low boiler fraction and high boiler fraction.

10. The method according to any one of claims 1 to 9, characterized in that it is followed by a process for the preparation of 3-methyl-1-butanol, a) wherein the process for the preparation of 3-methyl-1-butanol as the last process step a (B) where said distillation of the process for producing 3-methyl-1-butanol is carried out at a pressure which is at least 0.05 MPa above the operating pressure of dehydration, c) and wherein the overhead product of the said distillation of the process for the preparation of 3-methyl-1-butanol is withdrawn in gaseous form and then fed as a feedstock for dehydration.

11. The method according to any one of claims 1 to 10, characterized in that the water separation is carried out as a simple phase separation in a liquid-liquid separator.

12. The method according to one or more of the preceding claims, characterized in that the dehydration is carried out with a conversion of 3-methyl-1-butanol in the straight pass of 50 to 98%.

13. The method according to one or more of the preceding claims, characterized in that are used in the dehydration as catalysts with barium oxide modified γ-aluminum oxides.

14. The method according to one or more of the preceding claims, characterized in that the dehydration in the gas phase in the temperature range of 250 to 400 ⁰ C and in the pressure range of 0.15 to 0.95 MPa is performed.

15. A process for the modification of polypropylene or polyethylene using 3-methyl-1-butene as comonomer, characterized in that the 3-methyl-1-butene was prepared according to one of the preceding claims.