DE19737190A1 - 1,3 -propanediol production, at high constant conversion with long catalyst life - Google Patents

Abstract

Production of 1,3 -propanediol comprises hydrogenating an aqueous solution of 3- hydroxypropionaldehyde at 30-180 deg C, a hydrogen pressure of 5-300 bar and pH 2.5-7 in the presence of a heterogeneous catalyst comprising 0.1-20 wt.% ruthenium on an oxide phase. Preferably the oxide phase contains titanium oxide, silicon oxide, aluminium oxide, magnesium oxide, zeolite, zirconium dioxide and/or mixed oxides. The amount of finely divided ruthenium on the oxide phase is 0.1-10 (preferably 0.5-5) wt.% and the oxide phase is impregnated with an aqueous solution of a ruthenium compound, then reduced under hydrogen for 20 minutes to 24 hours at 100-500 deg C. The hydrogenation step is carried out at a hydrogen pressure of 90 (preferably 10-60 bar) in a trickle bed reactor.

Description

The invention relates to a method for producing 1,3-propanediol by hydrogenating hydroxypropionaldehyde.

1,3-propanediol is used as a monomer unit for polyester and Polyurethanes and as a raw material for synthesis cyclic connections used.

Various processes are available for the preparation of 1,3-propanediol, either from a C ₂ and C _{1 building} block or from a C _{3 building} block, such as, for. B. Acrolein, known. When acrolein is used, it is first hydrated in the presence of an acidic catalyst, forming hydroxypropionaldehyde. The aqueous reaction mixture formed in the hydration contains after separation of unreacted acrolein in addition to 85% hydroxypropionaldehyde and about 8% oxaheptandial and other organic components in smaller proportions by weight. To produce 1,3-propanediol, this reaction mixture is hydrogenated in the presence of hydrogenation catalysts.

According to US 2,434,110 are for the hydrogenation of hydroxy propionaldehyde catalysts, which one or more hydration-effective metals, such as. B. Fe, Co, Cu, Ag, Mo, V, Contain Zr, Ti, Th, Ta, Ag, suitable. Furthermore can Raney's nickel and Adkin's copper chromium oxide as Catalysts are used.

According to DE-P 39 26 136, the catalyst can both in suspended form per se or carrier-bound or be part of fixed bed catalysts; also homogeneous catalysts can be used. As Suspension catalysts are Raney nickel, which with various other catalytically active metals can be doped, as well as specified platinum on activated carbon.  

The prior art catalytic hydrogenation carries the risk that the catalytically active Element in small amounts in the form of soluble compounds is discharged into the product stream, and thus more Steps to separate the resulting Impurities become necessary. This is particularly the case with Suspension catalysts, such as. B. Raney nickel observe. With nickel fixed bed contacts, there is also the risk of contamination of the product Nickel compounds.

Hydrogenation processes can be achieved with them Sales, selectivities and space-time yield characteri be settled.

The turnover indicates how many moles of the educt (here Hydroxypropionaldehyde) by hydrogenation into others Substances are implemented. It is usually given in Percent of the mol of the educt used.

The selectivity of the hydrogenation process, on the other hand, is a measure for how many moles of the educt in the desired product be transferred. For continuous hydrogenation processes the space-time yield is another important parameter that the achievable amount of the product per unit of time and Indicates reaction volume. In industrial hydrogenation from hydroxypropionaldehyde to 1,3-propanediol it is crucial for the economy of the Hydrogenation process and for the quality of the product that Turnover and selectivity are as close as possible to 100%. Though after the hydrogenation, the propaniol from the im Product stream containing water and remaining Hydroxypropionaldehyde and by-products Distillation separated, this distillative separation is however, by residual hydroxypropionaldehyde and by-products much more difficult or even through reactions between Residual hydroxypropionaldehyde and propanediol to acetals, whose boiling point is close to the boiling point of propanediol,  made completely impossible. The lower sales and Selectivity is so bad achievable product quality.

In order to be able to produce 1,3-propanediol economically it is also important that the catalyst for the Hydrogenation of hydroxypropanol shows high activity. The aim should therefore be to find a method in which the production of 1,3-propanediol is as low as possible Amount of catalyst is necessary. That means it should be with a small catalyst volume as high as possible Sales of hydroxypropanol to 1,3-propanediol achieved become.

Sales, selectivity and space-time yield are achieved through the properties of the catalyst and by the hydrogenation conditions such as reaction temperature, hydrogen pressure and Hydrogenation time, or in the case of continuous hydrogenations through the space velocity LHSV (Liquid Hourly Space Velocity) is affected.

In the hydrogenation of hydroxypropionaldehyde to propanediol it should be noted that the main reaction is linear from Hydrogen pressure and time (space velocity at continuous process) depends on the Reaction temperature has little influence. Against that is Formation of by-products exponentially from temperature dependent. If the conditions are otherwise the same, Doubling of by-product formation per 10 ° C too observe what leads to a corresponding deterioration that leads to selectivity. Has a positive effect on selectivity the increase in hydrogen pressure, however, the positive impact of pressure on the Selectivity less than the negative influence of a Temperature rise because of the hydrogen pressure Main reaction rate only linear, on Temperature increase the speed of the side reaction however increased exponentially.  

An essential quality criterion for the at Hydrogenation used catalysts is theirs Service life in operation. Good catalysts should be in the course constant turnover and selectivity in the hydrogenation of hydroxypropionaldehyde to propanediol guarantee. Known hydrogenation processes according to the prior art, in particular on the basis of Nickel catalysts insufficient long-term stabilities. This requires a more frequent change of the whole Catalyst packing with the known problems in the Disposal and processing of nickel-containing Links.

From the Engelhard brochure "Exceptional Technologies" 1991 it is known to aliphatic carbonyl compounds in Presence of ruthenium on alumina to the to hydrogenate corresponding alcohols (escalite).

From the brochure of Degussa "Powder Precious Metal Catalyts "(published 6/95) is known to be aliphatic Aldehydes to alcohols in the presence of ruthenium carriers to hydrogenate catalysts. As a carrier it will Alumina specified.

EP-B 535 565 describes a method for producing 1,3-propanediol by heterogeneously catalyzed hydrogenation of Hydroxypropionaldehyde in aqueous solution known which is the supported catalyst made of titanium dioxide, on which Platinum in an amount relative to the carrier from 0.1 to 5 wt .-% is in finely divided form.

The known method has the disadvantage that a relative high hydrogenation pressure must be applied.

In addition, you need because of its low activity a relatively large amount of platinum catalyst around one to achieve sufficiently large sales. By the high  The price of the platinum is, accordingly significant increase in the price of the hydrogenation process.

It is therefore an object of the present invention Hydrogenation process, which mentioned the disadvantages of the process according to the state of the art.

The invention relates to a method for producing of 1,3-propanediol by heterogeneously catalyzed hydrogenation of hydroxypropionaldehyde in aqueous solution at a Temperature from 30 to 180 ° C, a hydrogen pressure of 5 up to 300 bar and a pH of 2.5 to 7.0, which is characterized in that one as a catalyst Supported catalyst used, which consists of an oxidic Phase, preferably an oxidic phase, in acid Environment is persistent and insists on the ruthenium, preferably in an amount of 0.1 to 20% by weight on the oxidic phase, in finely divided form.

A substance from the group consisting of titanium dioxide, SiO ₂ , Al ₂ O ₃ and / or their mixed oxides and aluminum silicate, MgO, zeolites and zirconium dioxide can be used as the oxidic phase.

Such substances are described for example in Catalyst Supports and Supported Catalysts by Alvin B, Stiles Verlag, Butterworths 1987, Chapters 2 and 3.

An oxidic phase which is stable in an acidic medium is preferably used. Such oxidic phases can be substances from the group consisting of titanium dioxide, SiO ₂ and / or their mixed oxides and aluminum silicate, MgO, zeolites, zirconium dioxide. Alumina has a lower acid resistance.

In a preferred embodiment of the invention as oxidic phase oxides and mixed oxides made of aluminum and in particular titanium and / or silicon become.  

A pyrogenically produced, especially manufactured by flame hydrolysis Titanium dioxide can be used.

As titanium oxide, for example, a so-called pyrogenic titanium dioxide obtained by flame hydrolysis from titanium tetrachloride can be used with a BET surface area of 40 to 60 m ² / g and a total pore volume of 0.25 to 0.75 ml / g, which has an average size of the primary particles of 20 nm, a density of 3.7 g / cm ³ and an X-ray structure of 20 to 40% rutile and 80 to 60% anatase and the impurities in silicon dioxide, aluminum oxide and iron oxide are less than 0.5% by weight. Pyrogenic titanium oxide such as Degussa's P25 material is particularly suitable as a carrier for the catalytically active component. It has a high BET specific surface area of 50 m ² / g on average (measured according to DIN 66131).

The oxides can be used to form moldings such. B. pellets, granules or extrusions are processed.

The coating of the oxidic phase can be done by means of Incipient Wetness Method, published in "Preparation of Catalyst ", Delmon, B., Jacobs, P.A., Poncald, G. (eds.), Amsterdam Elsevier, 1976, page 13.

For this, the water absorption capacity of the carrier certainly. Then an aqueous ruthenium chloride solution with a concentration corresponding to the later one Ruthenium coating produced. The carrier will according to the water absorption capacity with aqueous Load ruthenium chloride. Then the loaded one Carrier, preferably at 20 to 100 ° C at normal pressure in Inert gas atmosphere, such as neon, helium, argon or air, dried with hydrogen, preferably at a Temperature from 100 to 500 ° C in a time from 20 minutes to 24 hours with a hydrogen concentration of 1 to 100%  reduced in a mixture with nitrogen and if necessary chloride-free, preferably <100 ppm Cl⁻, washed.

Examples

The catalysts are tested under stationary conditions in order to be able to make statements about the long-term behavior. The hydrogenation is carried out continuously in a trickle bed system with a 140 ml reactor volume. The system consists of a liquid supply, the liquid reactor and a liquid cutter. The reaction temperature is set via a heat transfer oil circuit. Pressure and hydrogen flow are controlled electronically. The aqueous hydroxypropionaldehyde solution is metered into the hydrogen stream with a pump and the mixture is added to the top of the reactor (trickle bed mode of operation). After passing through the reactor, the product formed is removed from the cutter at regular intervals. The concentration of the hydroxypropionaldehyde in the reactant solution is 10% by weight in all cases, the temperature is 40 ° C., the pressure is 40 bar and the liquid load LHSV is 1 h ^-1 . The results of the tests according to various examples are summarized in Table 1.

Manufacturing instructions for the catalysts

• 1. The water absorption of the carrier is determined in g H ₂ O per 100 g carrier.
• 2. To load 250 ml of carrier, RuCl ₃ is dissolved in distilled water (see Table 1).
• 3. 250 ml of carrier are placed in the coating pan and poured with the RuCl ₃ solution in the rotating pan.
• 4. The coated carrier is left in air for 16 h dried, then in the raw oven to 200 ° C heated up.
• 5. The catalyst is at 200 ° C for 8 h with hydrogen reduced.  
• 6. The reduced catalyst is three times with each 40 ml of distilled water washed free of chloride.

The carriers used are characterized as follows:
Carrier 1: silica gel from Grace (0.8-1.2 mm)
Designation: V432,
Carrier 2: activated carbon from Norit (diameter 2.3 mm)
Name: Norit CNR 115 (olive stones),
Carrier 3: activated carbon from Norit (diameter 0.8 mm)
Name: Norit ROX (peat coal)
Carrier 4: P25 titanium dioxide pyrogenic by flame hydrolysis manufactured by Degussa AG
Carrier 5: Al ₂ O ₃ from Rhône-Poulenc (diameter 1.1-1.3 mm)
Name: Spheralite 521.

When coating the carrier, the following are Conditions met:

Table 1

Table 2

Comparison of the results of comparative examples VB 1 and VB 2 and examples B 1 to B 6 according to the invention shows that the ruthenium according to the invention catalysts through higher activity, d. H. higher Sales, award.

The comparative examples VB 1 to VB 6 show that both the platinum as well as the ruthenium catalysts Activated carbon carriers have poor long-term behavior exhibit. Both catalyst groups are after a few deactivated for a hundred hours. In contrast, the Ruthenium catalysts according to the invention on oxidic Bearers have no deactivation whatsoever. The turnover remains constant. In particular ruthenium on SiO2 and TiO2 (Examples 1 to 4) show a very high activity.

Claims (2)

1. Process for the preparation of 1,3-propanediol by heterogeneously catalyzed hydrogenation of hydroxypropionaldehyde in aqueous solution at a temperature of 30 to 180 ° C, a hydrogen pressure of 5 to 300 bar, and a pH of 2.5 to 7 , 0, characterized in that the catalyst used is a supported catalyst which consists of an oxidic phase and on the ruthenium, preferably in an amount of 0.1 to 20% by weight, based on the oxidic phase, in finely divided form is present. 2. The method according to claim 1, characterized in that a substance from the group consisting of titanium dioxide, SiO ₂ , Al ₂ O ₃ and / or their mixed oxides and aluminum silicates, MgO, zeolites or zirconium oxide is used as the oxidic phase.