WO2009147008A1 - Method for separating polymeric byproducts from 1,4-butynediol - Google Patents

Abstract

The invention relates to a method for purifying 1,4-butynediol, wherein 1,4-butynediol is continuously fed to a disk separator that is operated with an acceleration factor of 6000 to 12000 and the purified butynediol is continuously removed, and to a method for hydrogenating 1,4-butynediol to produce 1,4-butenediol and 1,4-butanediol using the purified 1,4-butynediol.

Description

 Process for the separation of polymeric by-products from 1, 4-butynediol

description

The invention relates to a process for the purification of a 1, 4-butynediol-containing material stream, which was obtained by reacting formaldehyde with acetylene in the presence of a catalyst by separation of impurities in the form of polymeric by-products and catalyst components and a process for the preparation of 1, 4- Butenediol and 1, 4-butanediol by hydrogenation of the purified 1, 4-butynediol, which comprises the separation of polymeric by-products.

The synthesis of 1, 4-butynediol from acetylene and formaldehyde is industrially operated several times and is described for example in K. Weissermel, H. -J. Arpe, Industrial Organic Chemistry, 5th Ed., 1998, Wiley-VCH, pages 110 and 11 1). In addition to copper, the catalysts customarily used may optionally contain bismuth and silicates (hereinafter called SiC "2) or aluminum oxide. [Cup Während] During the synthesis of 1,4-butynediol, the formation of oligomeric or polymeric substances (referred to below as cuprene) occurs as a side reaction. These cuprene usually arrive together with soluble and insoluble constituents of the catalyst used in the hydrogenation stage, in the first

1, 4-butenediol is formed, which can be hydrogenated in a further hydrogenation step to 1, 4-butenediol more significant intermediate 1, 4-butanediol.

The hydrogenation of 1, 4-butynediol to 1, 4-butanediol has been operated for decades and is described in many ways. For example, US Pat. No. 5,068,468 describes the hydrogenation of

1,4-Butanediol on solid supported nickel-copper catalysts, while US-A 4,153,578 describes a two-step process for the hydrogenation of 1,4-butynediol on suspended Raney nickel molybdenum catalysts at a pressure of 21 bar. DD-A 272 644 discloses the suspension hydrogenation of aqueous butynediol on nickel-SiO 2 catalysts and EP-B 0 319 208, the

DE-A 19 41 633 and DE-A 20 40 501 disclose general hydrogenation processes which can be used inter alia for 1,4-butynediol.

Cuprene and catalyst constituents from butynediol synthesis disturb its hydrogenation to 1,4-butenediol or 1,4-butanediol and markedly impair the hydrogenation result. Thus, cuprene deposits on the catalyst and inhibits the contact of butynediol with the catalyst surface, with the result that the reaction slows down. Catalyst components such as copper, bismuth and / or SiO 2 also deposit on catalyst and thus change the catalyst activity and selectivity. Furthermore, disadvantages here include an increase in the pressure loss and an increased formation of undesired by-products, which adversely affect the efficiency of the process. If the catalyst is heavily soiled, it must be be removed and washed. This measure is usually done about six to seven times during the life of the catalyst. However, this has the further disadvantage that the purification of the catalyst results in a large amount of wastewater, which, because of its content of heavy metals, is correspondingly expensive to clean.

Even without the removal of the catalyst, these adverse effects on the formation of the by-product butanol can be traced, since its formation is accelerated by the catalyst poisons mentioned above.

There has been no lack of attempts to purify 1, 4-butynediol. The simple purification of 1,4-butynediol, e.g. by filtration is hardly possible because in particular the cuprene and SiC "2 are partly colloidal or very finely distributed and thus clog common filters quickly, so that the filter either constantly replaced or laboriously backwashed.

Even attempts to purify by flotation proved to be hardly feasible. In the case of membrane flotation experiments, the cuprene present, on the basis of their properties, meant that purification in this way could not be successfully achieved.

WO 2007/028716 A1 describes a process for the purification of 1,4-butynediol. According to this method, separation is possible. However, here the phase separation described in the process proves to be disadvantageous in a calming zone within which a period of one to five hours is waited for.

It is an object of the invention to provide a process which, in a process-technically simple and rapid manner, permits separation of the essential portion of the solid which hinders the subsequent hydrogenation from

Butindiol, which was obtained by synthesis of formaldehyde and acetylene in the presence of a catalyst to allow. In this case, the solid contained should be reduced to such an extent that the purified 1, 4-butynediol can then be fed directly to a hydrogenation, in which by hydrogenation of 1,4-butenediol or 1, 4-butynediol in high selectivity and with good catalyst life can be won.

It has now surprisingly been found that a process in which one feeds technical 1, 4-butynediol a Tellerseparator, which is operated with an acceleration factor of 6,000 to 12,000, to a separation of undesirable in the hydrogenation components from technical 1, 4-butynediol 1 and 4-butynediol and 1, 4-butynediol are hydrogenated in each case in high selectivity and with good catalytic activity. lysatorstandzeit become accessible. In this application, technical 1,4-butynediol is understood as meaning 1, 4-butynediol prepared from acetylene and formaldehyde, customary catalysts which have not been purified by distillation, for example, and generally from 10 to 70% by weight of butynediol , preferably 30 to 60% by weight of butynediol, 0.2 to 4% by weight of propynol 0.1 to 2% by weight of formaldehyde and 1 to 2000 ppm, preferably 3 to 500 ppm, particularly preferably 10 to 200 ppm Cuprene and catalyst components as well as <0.1% contains other contaminant traces.

The disk separators used for the process according to the invention are known in their basic structure and their mode of operation and are described, for example, in "Solid-Liquid Filtration and Separation Technology", A. Rushton, 2nd edition 2000, WILEYVCH Verlag, pages 312-313 and in "Handbuch der mechanical solid-liquid separation ", Klaus Luckert, 2004 Vulkan-Verlag GmbH, pages 350-351 described. The disclosure of this document is incorporated by reference in its entirety (incorporated by reference). They are usually used for the separation of liquid and solid materials, such. in the concentration of sludge. In their basic structure, they have a rotor that rotatably supports a plurality of conical plates axially spaced apart from each other and a stator that contains a dirt collecting space in which the rotor is disposed. The plates increase the clarification area and reduce the sedimentation height, thus reducing the time for deposition. In operation, the plates attached to the rotor rotate at high speed and thus a centrifugal field is generated, which is utilized for deposition. To quantify the generated centrifugal field, one can specify an acceleration factor. This is defined as the ratio of the centrifugal acceleration generated in the plate separator in the outer diameter of the plate to the gravitational acceleration. For plate separators, this acceleration factor is usually around 6000 to 12000, so they are classified as ultracentrifuges.

For the present task of cleaning the technical 1, 4-butynediol, the skilled person would not have considered the use of a Tellerseparators for successful separation of the contained solid. So far, as described above, because of the difficulties in separating the cuprene, it is quite possible to repeatedly expand and wash the catalyst because of the difficult-to-handle impurity in the downstream catalytic hydrogenation.

In a further variant, the method described in WO 2007/028716 is used, but as already mentioned, during the phase separation in the settling zone it is necessary to wait several hours in order to successfully carry out the separation in this complex system.

The cuprene contained are filamentous polymers, which presumably consist of highly condensed aromatic systems. Because of this threadlike structure formed in the attempted separation processes quickly larger, networked structures, which could be due to their stability, other separation experiments such as the flotation and filtration failed. Even when using a plate separator, a failure had to be expected in the case of this difficult-to-handle material system. Thus, in this apparatus, the plates are arranged at a very small distance, it is usually less than 0.5mm, often less than 0.3mm. Here, in the present material system, a rapid caking of the cuprene and the other solid impurities contained had been expected, which should lead a short time later with increasing growth to disruption in the separation process. Contrary to this expectation, however, the technical 1,4-butynediol could be successfully and permanently depleted to a high degree of solids.

To carry out the process according to the invention, the technical 1,4-butynediol obtained in the synthesis stage by reaction of formaldehyde and acetylene is passed directly into the plate separator for separation of the solid. The Tellerseparator is preferably operated with an acceleration factor of 6000 to 12000, more preferably 8000 to 9000 and the plate angle range of the plate in Tellerseparator is 45 ° to 55 ° (measured on the horizontal). The distances between the individual plates in the plate separator used in the method according to the invention are preferably less than 0.6 mm, more preferably less than 0.5 mm and also distances of less than 0.3 mm may be particularly recommended. Through the outlet on the shaft, the depleted of the solid 1, 4-butynediol is withdrawn and at intervals, the separated solid is discharged from the plate separator by briefly opening the two drum halves. A further significant advantage of the process according to the invention is that both the technical 1,4-butynediol to be purified and the 1,4-butynediol depleted of solids and withdrawn via the shaft of the plate separator can be continuously supplied or removed ,

The solids content in the feed of the plate separator is usually about 50 to 2000 ppm and it can be achieved by means of the inventive method, a depletion of solids from 80Gew .-% to 98Gew .-%, preferably 90Gew .-% to 95Gew .-%. In the event that in the inventive method, the pulp separator a stream is fed, which contains 100 ppm of solids, this means, for example, that in the case of depletion of 95% corresponding 95 ppm of solid are deposited and the remaining 5 ppm in the Substance stream (also referred to as "clear run") substantially freed from the solid material is withdrawn via the shaft of the plate separator.

The solids-rich phase removed at intervals contains predominantly the cuprene as well as considerable amounts of copper, bismuth or SiC "2 -containing undesired catalyst components Combustion supplied, but can be treated previously, for example by distillation, to remove residual amounts of 1, 4-butynediol and due to the process of the invention. The phase largely freed from cuprene and unwanted catalyst constituents and discharged via the shaft of the plate separator (clarified water) is preferably fed directly to the hydrogenation to 1,4-butenediol or 1,4-butanediol.

The present invention furthermore relates to a process for the hydrogenation of 1,4-butynediol to 1,4-butenediol and preferably to 1,4-butanediol in which purified 1,4-butynediol is used according to the process of the invention.

The hydrogenation of 1,4-butynediol is known per se and is preferably carried out in the liquid phase on fixed and / or suspended catalysts. The hydrogenation can be carried out up to 1, 4-butanediol, but also only up to 1, 4-butenediol.

For the hydrogenation of purified 1,4-butynediol, use is made of catalysts which are capable of hydrogenating C-C triple and double bonds to single bonds. They usually contain one or more elements of the I., VI, VII or VIII subgroup of the Periodic Table of the Elements, preferably the elements copper, chromium, molybdenum, manganese, rhenium, iron, ruthenium, cobalt, nickel, platinum and palladium. Particular preference is given to using catalysts which have at least one

Element selected from copper, chromium, molybdenum, iron, nickel, platinum and palladium.

The metal content of these catalysts is generally between 0.1 to 100 wt .-%, preferably 0.2 to 95 wt .-%, particularly preferably 0.5 to 95 wt .-%.

The catalyst preferably additionally contains at least one element selected from the elements of II., III., IV. And VI. Main group, the II, III, IV and V subgroups of the Periodic Table of the Elements and the lanthanides as a promoter for increasing activity.

The promoter content of the catalyst is generally up to 5 wt .-%, preferably 0.001 to 5 wt .-%, particularly preferably 0.01 to 3 wt .-%.

As catalysts precipitation, carrier, or Raney type catalysts can be used, the preparation of which is described for example in Ullmanns, Encyclopedia of Industrial Chemistry, 4th Edition, 1977, Volume 13, pages 558-665.

As carrier materials, aluminum oxides, titanium oxides, zirconium dioxide, silicon dioxide, clays, for example montmorillonites, silicates such as magnesium or aluminum silicates, zeolites and activated carbons can be used. Preferred support materials are aluminas, titanium dioxides, silica, zirconia and activated carbons. Selbstver- It is also possible to use mixtures of various carrier materials as carriers for catalysts which can be used in the process according to the invention.

These catalysts can be used either as shaped catalyst bodies, for example as spheres, cylinders, rings, spirals, or in the form of powders.

Examples of Raney type catalysts are Raney nickel, Raney copper, Raney cobalt, Raney nickel / molybdenum, Raney nickel / copper, Raney nickel / chromium, Raney nickel / chromium / iron or Rhenium sponge suitable. Raney nickel / molybdenum catalysts can be prepared, for example, by the method described in US Pat. No. 4,153,578. However, these catalysts are also marketed, for example, by the company Degussa, 63403 Hanau, Germany. A Raney nickel-chromium-iron catalyst is sold, for example, under the trade name Catalyst Type 11 112 ^W® by Degussa.

In the use of precipitated or supported catalysts, these are reduced at the beginning of the reaction at 150 to 500 ⁰ C in hydrogen or hydrogen / inert gas stream. This reduction can be carried out directly in the synthesis reactor. If the reduction is carried out in a separate reactor, the catalysts can be surface-passivated at 30 ^° C. with oxygen-containing gas mixtures before being removed. The passivated catalysts can be activated in this case in the synthesis reactor before use in a nitrogen / hydrogen stream at 180 ° C or used without activation.

The catalysts can be used in a fixed bed or in suspension. When the catalysts are arranged in the form of a fixed bed, the reactor is operated not in the usual trickle mode, but in an upward direct flow of liquid and gas so that the liquid and not the gas is present as a continuous phase.

Suspended catalysts are used with a particle size generally of 0.1-500 .mu.m, preferably 0.5 to 200 .mu.m, particularly preferably 1 to 100 .mu.m.

When working with suspended catalysts, the use of packed bubble columns will also work with an upward direct flow of liquid and gas such that the liquid and not the gas will be in a continuous phase. The ratio of gas leaving the reaction vessel to the amount of gas supplied is 0.99: 1 to 0.4: 1 when using fixed bed reactors and when using packed bubble columns with a catalyst suspended in the reaction medium. The ratio to be maintained in the packed bubble columns in the case of fixed bed reactors and catalysts suspended in the reaction medium can be adjusted in a simple manner by metering the appropriate amount of hydrogen either as a fresh gas or technically preferably recirculating recycle gas and only supplemented by chemical consumption and exhaust gas-related hydrogen loss by fresh hydrogen.

The molar ratio of hydrogen to 1,4-butynediol in the reactor is at least 3: 1, preferably between 4: 1 and 100: 1.

The process according to the invention is carried out on fixed-bed catalysts with cycle gas operation, i. the gas leaving the reactor is recycled in the circulation, optionally after addition of fresh hydrogen, via a compressor in the reactor. It is possible to lead the entire cycle gas quantity or a subset thereof via a propulsion jet compressor. In this preferred embodiment, the cycle gas compressor is replaced by a low-cost nozzle. The compression work is introduced via the likewise circulated liquid. The required pressure increase of the liquid for operating the jet compressor is about 3 to 5 bar.

For carrying out the process according to the invention with a catalyst suspended in the reaction medium, jet nozzle reactors, stirred tanks and bubble columns with packings which have a packing surface area of at least 500, preferably 1000 to 2000 m ² / m ³ are suitable. Jet nozzle reactors can be used in various designs if they can ensure the high mass transfer from the gas phase to the liquid with the suspended catalyst particles which is essential for the invention by a sufficiently high energy input, which experience has shown is above 2 kW / m ³ . Particularly suitable are jet nozzle reactors which are equipped with a momentum exchange tube. An industrially widespread design of a jet nozzle reactor is, for example, the reactor described in EP-A 0 419 419. At values for the energy input of 3 to 5 kW / m ³ , with this reactor a separation of the gas phase is still possible in simple separators, without having to use additional apparatus such as foam centrifuges or cyclones.

Stirring containers are only suitable for carrying out the method according to the invention if the energy input is in a range from 2 to 10 kW / m ³ .

Jet nozzle reactors with suspended catalysts require volume-related energy inputs of more than 2 kW / m ³ , preferably 3 - 5 kW / m ³ . 1, 4-butanediol is used in large quantities in the art, for example in THF production or as a diol component in polyesters.

Examples

A plate separator of the type Westfalia SA 6, whose plates had a distance of 0.3 mm and wherein the plate diameter was 123.5 mm and which was operated according to the method according to the invention with an acceleration factor of 9400, led continuously technical 1, 4-butynediol in Form a 54 wt% aqueous solution based on the butynediol content at 250 liters per hour or 350 liters per hour. Over a period of about 8 days in the case of adding 250 L / h or 40 days in the case of adding 350 L / h, the possible depletion by the method of the present invention was measured. The results are shown in the diagrams in FIGS. 1 and 2. Over the running time (indicated on the abscissa axis in days), the solid concentration in the feed of the plate separator in ppm and line 2 the solid concentration in clear flow of the Tellersepara- sector in ppm are shown here by line 1. Line 3 shows the percentage depletion achieved according to the invention. The numbers for the curves 1 to 3 can be found on the left ordinate axis. The line 4 shows the projected for the operating scale, cumulatively separable amount of solids, the numerical value can be found in the diagram on the right axis of ordinate. It can be stated that, surprisingly, a high depletion was possible over the entire period of time and, with respect to the technical 1,4-butynediol introduced, it was possible to achieve a clear-flow which obtained only small amounts of solid. The arithmetic mean depletion was 96.7% for the case of addition of 250 L / h at a mean feed concentration of 123 ppm. The arithmetic mean depletion was 87.5% for the case of addition of 350 L / h at a mean feed concentration of 95 ppm.

The advantages of the process according to the invention with regard to the selectivity in the downstream hydrogenation are explained in more detail with reference to the following examples. Unless otherwise stated, technical 1, 4-butynediol was used in the form of a 54 wt .-% aqueous solution. The percentages of the reaction effluents in the examples, unless otherwise stated, represent anhydrous calculated percentages by weight which have been determined by gas chromatography.

Comparative example: technical 1, 4-butynediol

190 ml of a Ni catalyst according to Example 1 of US Pat. No. 5,068,468 were introduced into a 1 2 m-length hydrogen rector. Technical 1, 4-butynediol in the form of a

54 wt .-% aqueous solution based on the butynediol content was added in an amount of 100 g / h in the reactor. At a temperature of 140 ⁰ C. was hydrogenated at a hydrogen pressure of 200 bar and a liquid circulation 800 ml / h was 2 weeks.

Within the experimental period (2 weeks), butynediol turnover was always complete. The average increase in n-butanol was about 0.06% per day. After removal of the catalyst, solid deposits were found on the catalyst. The yield of 1,4-butanediol, based on butynediol used, at the beginning 98.3% by weight, however, decreased by 0.06% by weight each day.

Example 1: Purification of the 1, 4-butynediol

Cleaning:

Technical butynediol in the form of a 54% by weight aqueous solution was fed to a Westfalia SA 6 disk separator of 0.3 mm diameter and 123.5 mm diameter in a stream of 250 L / h and substantial portions of the solid contained therein separated the process of the invention. The mean arithmetic depletion was 94.5%. The butynediol thus purified was fed to the hydrogenation reactor.

hydrogenation:

The hydrogenation was carried out analogously to the comparative example, with the difference that the prepurified according to the invention 1, 4-butynediol was used. The average increase in n-butanol was about 0.04% per day. After removal of the catalyst, no deposits were found. The yield of 1,4-butanediol, based on butynediol used, was 98.3% by weight at the beginning and decreased by 0.04% by weight each day.

Claims

claims 1. A process for the purification of a 1, 4-butynediol-containing stream, which was obtained by reacting formaldehyde with acetylene in the presence of a catalyst, characterized in that the 1, 4-butynediol-containing stream continuously fed to a Tellerseparator, with an acceleration factor of 6000 to 12000 is operated and wherein the solids contained in the stream is substantially separated and continuously discharged from the solids substantially freed stream. 2. The method according to claim 1, characterized in that one operates the Tellerseparator continuously. 3. The method according to claim 1 or 2, characterized in that the distance between the plates is less than 0.5 mm. 4. The method according to claim 1 to 3, characterized in that one depletes the solids content contained in the stream by more than 90Gew.% By means of the Tellerseparators. 5. A process for the catalytic hydrogenation of 1, 4-butynediol, characterized in that hydrogenated by the process according to any one of claims 1 to 4 purified 1, 4-butynediol. 6. The method of claim 5 for the preparation of 1, 4-butenediol. 7. The method of claim 5 for the preparation of 1, 4-butanediol.