DE10138967B4 - Process for the preparation of 3-alkoxypropanol - Google Patents

Abstract

Process for the preparation of 3-alkoxypropanol by:
(a) alkoxylation of acrolein or an acrolein precursor in the presence of a heterogeneous catalyst with an alcohol,
(B) separating the reaction mixture from step (a) from the catalyst and optionally separating starting materials and
(c) hydrogenating the product from step (b) in the presence of a hydrogenation catalyst,
characterized in that
as catalyst in the alkoxylation step (a) an acidic ion exchanger is used, wherein in the alkoxylation step (a) acrolein or acrolein precursor with alcohol in a molar ratio of 1: 1 to 1:20 at 30 ° C to 120 ° C and a pressure in the range 1 to 20 bar is implemented.

Description

The The invention relates to a process for the preparation of 3-alkoxypropanol by Addition of an alcohol to acrolein in the presence of an acidic ion exchange resin with subsequent catalytic hydrogenation of the alkoxylation product.

It It is known to produce 3-alkoxypropanol by adding acrolein Alkoxylated 3-alkoxypropionaldehyde and then hydrogenated to 3-alkoxypropanol.

So describe R.H. Hall and E.S. Stern, Journal of Chemical Society, 1954, 3388 ff, the catalyzed reaction of acrolein with alcohols. It was found that in addition to the 3-alkoxypropionaldehyde dependent on the related catalyst system also 1,1,1-Trialkoxypropan and the acetal of acrolein is formed. In the experimental part will be investigated different catalyst systems and achieved thereby Yields of desired Product indicated. So leads the alkoxylation of acrolein with ethanol in the presence of sodium hydroxide as a catalyst, buffered by the addition of acetic acid and phosphoric acid was 3-ethoxypropionaldehyde in a yield of 40%.

at the reaction of ethanol with acrolein in the presence of hydrogen chloride The main product produced as catalyst is 1,1,3-triethoxypropane in a yield of 17%. When using hydrogen chloride and calcium chloride as a catalyst also produces 1,1,3-triethoxypropane as the main product in a yield of 28.7%. When using Ammonium chloride as a catalyst is 1,1,3-triethoxypropane in one Yield of 38.4%. Hall and star have a variety tested by catalyst systems, but have in all cases very unsatisfactory results regarding the product yield achieved for a commercial process is far from sufficient.

task It is therefore the object of the present invention to provide a process for the preparation of 3-alkoxypropanol by alkoxylation of acrolein with the following to provide catalytic hydrogenation, which in the Alkoxylation be carried out with good selectivity and high yield can. Furthermore, the reaction mixture obtained from the alkoxylation should the hydrogenation catalyst as possible deactivate little to reuse the hydrogenation catalyst to allow in subsequent batches or to extend the service life of a fixed bed hydrogenation catalyst, and thus improving the cost-effectiveness of the process.

• a) Alkoxylierung von Acrolein oder eines Acroleinvorläufers in Gegenwart eines heterogenen Katalysators mit einem Alkohol,
• b) Trennen des Reaktionsgemisches aus Schritt a) von dem Katalysator und gegebenenfalls Abtrennen von Edukten und
• c) Hydrieren des Produkts aus Schritt b) in Gegenwart eines Hydrierkatalysators gelöst, wobei als Katalysator im Alkoxylierungsschritt a) ein saurer Ionenaustauscher verwendet wird und wobei im Alkoxylierungsschritt (a) Acrolein oder ein Acroleinvorläufer mit Alkohol in einem molaren Verhältnis von 1:1 bis 1:20 bei 30°C bis 120°C und einem Druck im Bereich von 1 bis 20 bar umgesetzt wird.

This object is achieved by a process for the preparation of 3-alkoxypropanol by:

• a) alkoxylation of acrolein or an acrolein precursor in the presence of a heterogeneous catalyst with an alcohol,
• b) separating the reaction mixture from step a) from the catalyst and optionally separating starting materials and
• c) hydrogenating the product from step b) in the presence of a hydrogenation catalyst, using as catalyst in the alkoxylation step a) an acidic ion exchanger and wherein in the alkoxylation step (a) acrolein or an acrolein precursor with alcohol in a molar ratio of 1: 1 to 1 : 20 is reacted at 30 ° C to 120 ° C and a pressure in the range of 1 to 20 bar.

Especially It is advantageous to use the alcohol in molar excess, based on acrolein or the acrolein precursor, use. Preferred molar ratios are therefore within the range from 1: 2 to 1:10, and more preferably from 1: 3 to 1: 6. The reaction temperature in the alkoxylation step is preferably in a range of 40 ° C to 90 ° C, especially preferably from 50 ° C up to 80 ° C. The reaction leaves Although at temperatures below 40 ° C perform. However, this leads to extend Reaction times. Temperatures above 90 ° C are less preferred since here already a reduced selectivity and a trächtigung the lifetime of the ion exchange catalyst can occur.

at a reaction temperature below the boiling point of the acrolein the reaction can be carried out at atmospheric pressure or moderate pressure. At reaction temperatures around or above the boiling point of acrolein, it is preferred to work under a pressure in the range of 2 to 20 bar. In the preferred Temperature range of 40 ° C up to 90 ° C a pressure in the range of 2 to 5 bar has proved to be advantageous.

The acrolein / alcohol mixture may preferably contain polymerization inhibitors such. B. Hydrochi non, hydroquinone monomethyl ether or butylated phenols in an amount of 100 to 2,000 ppm.

The Alkoxylation may be batchwise or continuous in itself known reactors, such as. B. stirred reactors, Loop reactors, fluidized bed, fluidized bed or fixed bed reactors carried out become. The cited reactors are compared with the Loop and stirred reactors prefers. The flow rate through a fixed bed reactor, containing the ion exchanger and provided with a heatable jacket, and the reaction temperature it is preferable to match each other so that by one-time Passage of the reaction mixture through the reactor reaches the desired acrolein conversion becomes. The alkoxylation is generally up to an acrolein conversion in the range of 30 to 95% or more. One Turnover of 40% to 95% and in particular from 50% to 95% prefers.

Of the Alkoxylation step a) may be continuous or batchwise with a catalyst suspended in the reaction mixture. In this case, the catalyst becomes after completion of the reaction with a solid-liquid separation process separated. For separation is contemplated by sedimentation or filtration.

To completed separation of the reaction mixture from the catalyst it is advantageous to remove unreacted acrolein. The separation the acrolein can be known, in particular by distillation, preferably under reduced pressure and temperature below 80 ° C, are performed. The recovered Acrolein can again optionally after stabilization be traced back to the process. The obtained, almost acroleinfreie alkoxypropionaldehyde solution can before hydrogenation z. B. over a thin film evaporator be concentrated again.

The alcohols used may preferably be C ₁ -C ₅ -alcohols, for example these are the alcohols methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, isopentanol, with methanol, ethanol and propanol being particularly preferred.

Instead of of acrolein also acrolein precursors such as As vinyl dioxolane can be used under reaction conditions for the execution of the alkoxylation step to acrolein and ethylene glycol. The ethylene glycol reacts only negligibly under the conditions with methanol.

It was surprisingly found that when using acidic ion exchange resin in Compared to other known from the prior art acidic Catalysts at high acrolein conversions a high selectivity for 3-alkoxypropanol or 1,1,3-trialkoxypropane, both in the subsequent hydrogenation step can be achieved to the 3-alkoxypropanol can be achieved.

in the Generally can all acidic ion exchange resins used in the process according to the invention become. Suitable organic or inorganic acidic ion exchangers, in particular ion exchange resins with sulfonic acid, phosphonic acid or Carboxylic acid groups. Exchange resins with sulfonic acid groups, in the case when strong acid exchangers are desired and with carboxylic acid groups, in case medium / weak-acid exchangers are desired, are particularly preferred.

An exchange resin derived from a polyamine resin based on a crosslinked polyacrylamide matrix has been found to be particularly suitable. The polyamine resin can be prepared by reacting a polyacrylate precursor, e.g. As polyacrylate with tetraethylene or triethylenetetramine prepared. One of the amino groups forms an amine bond for anchoring to the polyacrylate matrix. The remaining amino groups are free and characterize the polyamine functionality of the resin. The polyamine resin is initially unsuitable for the Acroleinalkoxylieruag because it is present as an anion exchanger in the OH or Cl form and catalyses under these conditions, only the unwanted Acroleinpolymerisation. However, reaction with acrylic acid, acrylic acid derivatives or the salt of an ω-halocarboxylic acid (sodium 2-chloroacetate, sodium 3-bromopropionate) gives resins coated with carboxylic acid groups which have high H ⁺ capacities. The synthesis of the inventively employable Polyaminpolycarbonsäureharzes is carried out schematically according to the following equations, wherein for reasons of clarity, only the reaction is depicted on an amino group:

Reaction with acrylic acid

Reaction with a ω-halocarboxylic acid salt

in the In the first case, amino groups are added to the double bond of acrylic acid or their derivatives added, wherein amino, or Iminodipropionsäuregruppen arise. In the second case can by condensation (HX cleavage) amino, or Iminodicarbonsäuren different chain lengths being constructed. Characteristic of these derivatizations is the polarity reversal of the resin, d. h., it becomes the anion exchanger in converted a cation exchanger.

The for the Resin derivatization temperature used in the implementation with acrylic acid at 0 ° C to 150 ° C, preferably 20 ° C to 130 ° C. Of the Use of acrylic acid / methacrylic acid takes place in stabilized form in the absence or presence of water. When implemented in an acid-water mixture can the acrylic acid / methacrylic acid moiety between 5 wt% to 100 wt%, preferably 30 wt% to 90 Wt .-%, amount. As acrylic acid derivatives can for example, acrylic acid esters, Acrylic acid anhydride, acrylic acid chloride and / or acrylic acid amide be used. By subsequent saponification, the carboxyl function -released (deprotect).

The Reaction with salts of ω-halogenated carboxylic acid takes place at 0 ° C up to 60 ° C, preferably 10 ° C to 60 ° C and is in the literature R. Hering "chelating ion exchangers" (Akademie-Verlag, Berlin 1067) for the synthesis of so-called "chelation exchangers" are described Sodium 2-chloroacetate and sodium 3-chloropropionate, as well as higher homologs.

The Polyaminpolycarbonsäureharze show surprisingly only very small change in volume the transfer of the sodium in the catalytically active H-form and vice versa.

Other preferred exchange resins are those based on sulfonated Polystyrene matrices. Examples include Lewatit 5100 and S200 Bayer AG, which are sold in the Na form and before use in the inventive method by treatment with acid be converted into the acid form.

One particular advantage of the method is that due the use of the acidic ion exchangers as catalysts in the Alkoxylation step 3-alkoxypropanol and 1,1,3-Trialkoxypropan with high selectivity arises. From both classes of compounds arises in the catalytic Hydrogenation the desired 3-alkoxypropanol, so that a complicated separation of the reaction mixture from the alkoxylation stage a) is not necessary. As already described above, it is sufficient if the heterogeneous Catalyst is separated and optionally, if any, unreacted acrolein is removed from the reaction mixture. Since acrolein as a low-boiling compound simply by distillation under reduced Pressure can be removed, are not consuming processing steps for purifying the reaction mixture from the alkoxylation step necessary, leading to the economy of the method according to the invention contributes.

The catalytic hydrogenation of the reaction product from the alkoxylation step, which essentially comprises alkoxypropionaldehyde and 1,1,3-trialkoxypropane, is carried out in the gaseous or liquid phase, preferably in the liquid phase, in a manner known per se and in customary hydrogenation apparatuses. The catalyst can be used either in a suspended form per se or carrier-bound, or in a fixed bed reactor. Homogeneous catalysts can be used. As Suspensionska catalysts are Raney nickel, which can be doped with various other metals, as well as finely divided platinum on a support material such. As activated carbon particularly suitable. Fixed bed catalysts may be those mentioned in US Pat. No. 2,434,110. Ruthenium catalysts have proven to be particularly effective catalysts. To achieve a high conversion rate, the hydrogenation is carried out under pressure and at elevated temperature, the alcoholic solution having a pH in the range from 3.0 to 8.5, preferably by 6. Pressures of 20 to 250 bar, in particular 40 to 140 bar and temperatures of 40 ° C to 140 ° C, in particular 60 ° C to 100 ° C are preferred.

The The present invention will now be explained in more detail by way of examples.

example 1

A reaction solution of 20% commercially available acrolein in technical grade methanol was passed at a LHSV of 1 h ^-1 over a catalyst bed filled with 14 l of Lewatit VPOC 1505 (BAYER AG, acidic ion exchange resin based on a carboxyalkylated polyamine resin). In this case, a conversion in the range of 50% to 60%, based on acrolein on the temperature in the catalyst bed is set. The temperature in the alkoxylation reactor was increased from 52 to 57 ° C within 100 hours of operation. The pressure at the reactor head was adjusted to 1.8 bar. In addition to the primary product 3-methoxypropanol, 1,1,3-trimethoxypropane and the dimethylacetal of acrolein were formed. The composition of the reaction product was determined by gas chromatography. The three products mentioned were produced in a ratio of about 10: 1: 0.1 and, together with acrolein and methanol, gave 90 to 95%. The reaction mixture was distilled to remove acrolein and other low boilers at 50 ° C bottom temperature and 300 mbar pressure at the top, whereby a mixture of essentially acrolein and methanol was removed, which can be at least partially recycled back into the synthesis. The bottom product of the distillation described above is hydrogenated in two stages at a pressure of 80 bar and a LHSV of 1, 6 h ^-1 . In the first stage, a first ruthenium catalyst, 3% ruthenium on SiO ₂ and in the second stage another ruthenium catalyst, 2% ruthenium on activated carbon is used. The temperature was adjusted so that methoxypropanal was almost completely reacted in the first stage at 90% and after the second stage. 1,1,3-Trimethoxypropane was converted to over 90% to the desired end product 3-Methoxypropanal. The hydrogenation product was worked up by two stages by distillation, wherein in the first stage, solvents and low boilers were removed via a falling film evaporator and in a second stage, a purifying distillation was carried out. 3-Methoxypropanal was prepared in a yield of 93%, based on converted acrolein, in a purity of 99.7%. The analysis was carried out by gas chromatography.

Example 2

The Alkoxylation in the batch process was carried out in injection vials carried out, which is attached to a stirrer in a thermostatted bath were moved. The reaction vials were mixed with a 20 wt .-% methanolic Acroleinlösung and the investigated alkoxylation catalyst in the volume ratio 1: 1 filled. The reaction took place at 50.degree in an hour. The acrolein turnover and the selectivities at the Michael adduct 3-methoxypropanal (MPAL) and the acetal thereof 1,1,3-trimethoxypropanol (TRMP) were determined by gas chromatography. The results are in table 1 summarized.

Table 1:

Example 3:

The Alkoxylation was carried out analogously to Example 1. When Catalyst was used Lewatit 5120 in H form. The temperature was gradually adjusted in the range of 40-53 ° C (0-144h 45 ° C, 144-318h 40 ° C, 318-401h 45 ° C, 701-893h increase from 45 ° C to 53 ° C, 893-1033h 53 ° C). The Selectivity the wished Products were gas chromatographed during the course of the reaction determined and is in GC area percent as an average over specify the total reaction time. The selectivity to 1,1,3-trimethoxypropane was 90 area% and those attached to 3-methoxypropanal 10 area%.

Claims (8)

A process for preparing 3-alkoxypropanol by: (a) alkoxylating acrolein or an acrolein precursor in the presence of a heterogeneous catalyst with an alcohol, (b) separating the reaction mixture from step (a) from the catalyst and optionally separating starting materials and (c) Hydrogenating the product from step (b) in the presence of a hydrogenation catalyst, characterized in that the catalyst used in the alkoxylation step (a) is an acidic ion exchanger, wherein in the alkoxylation step (a) acrolein or acrolein precursor with alcohol in a molar ratio of 1: 1 to 1:20 is reacted at 30 ° C to 120 ° C and a pressure in the range of 1 to 20 bar. Method according to claim 1, characterized, that the alkoxylation step (a) continuously in one Reactor is carried out with fixed catalyst bed and the reaction product is separated from the catalyst after leaving the reactor. Method according to claim 1, characterized in that the alkoxylation step (a) is continuous or batchwise is carried out with a catalyst suspended in the reaction mixture and the catalyst after completion of the reaction with a solid-liquid separation process is separated. Method according to one of the preceding claims, characterized in that in the alkoxylation step (a) a C ₁ to C ₅ -alcohol is used. Method according to one of the preceding claims, characterized characterized in that the acrolein precursor is vinyl dioxolane. Method according to one of the preceding claims, characterized in that the acidic ion exchanger is a polyamine polycarboxylic acid resin is. Method according to Claim 6, characterized that the polyamine polycarboxylic acid resin by reacting a polyamine resin based on a crosslinked Polyacrylamide matrix with acrylic acid, Acrylic acid derivatives or the salts of an ω-haloalkanoic acid is available. Method according to one of the preceding claims, characterized in that prior to the hydrogenation step (c) only the Catalyst and an acrolein-containing fraction for the removal of Acrolein is separated from the reaction mixture from step (a).