DE102019105105A1 - Process for the production of 1,2-propanediol - Google Patents

Abstract

The invention relates to a process for the preparation of 1,2-propanediol from lactic acid by catalytic hydrogenation in aqueous solution, the reaction being carried out in the presence of a base and / or a basic salt of an alkali metal and / or alkaline earth metal.

Description

The invention relates to a process for the preparation of 1,2-propanediol from lactic acid.

1,2-Propanediol is widely used in the polymer industry, in food additives and in the manufacture of pharmaceuticals. A high demand for 1,2-propanediol requires efficient production processes. With the increasing depletion of fossil resources, it is also increasingly important to develop alternative production routes to chemicals. Lactic acid is an important platform chemical that can be industrially produced in high yields by fermenting carbohydrates. The conversion of lactic acid to 1,2-propanediol is therefore seen as a promising way of adding value.

The font US 6403844 B1 discloses a chemical process for the catalytic hydrogenation of lactic acid to 1,2-propanediol in the condensed phase. The process relates to the reaction of lactic acid at elevated pressure and elevated temperature using a ruthenium catalyst on an inert support. At low temperature and low pressure, it was possible to achieve high conversion with high selectivity at the same time. However, the catalyst used is not only complex to manufacture, but also comparatively expensive due to the noble metal used. The WO 2001/016063 A1 describes a process for the catalytic reduction of carboxyl groups, for example lactic acid, to 1,2-propanediol, using hydrogen, copper being used as the catalytically active metal. The reaction can be carried out in the presence of water. However, the selectivity of the conversion of lactic acid to 1,2-propanediol is low. The DE 10 2008 013 474 A1 describes a process for the preparation of lactic acid from primary alcohols or aldehydes in the presence of a transition metal catalyst. The process allows the formation of lactic acid with high selectivity, 1,2-propanediol being formed as a by-product when glycerol is used as the starting material.

The present invention was based on the object of providing a process for the preparation of 1,2-propanediol from lactic acid which overcomes at least one of the aforementioned disadvantages of the prior art.

This object is achieved by a process for the preparation of 1,2-propanediol from lactic acid by catalytic hydrogenation in aqueous solution, the reaction being carried out in the presence of a base and / or a basic salt of an alkali metal and / or alkaline earth metal.

It has surprisingly been found that the process according to the invention allows the conversion of lactic acid to 1,2-propanediol in an aqueous medium with high selectivity. It is particularly advantageous that the method is particularly suitable for favorable transition metals of the fourth period such as copper on carriers such as SiO ₂ in the presence of a base or a salt such as Mg (OH) 2 or magnesium acetate. 1,2-Propanediol can be produced with a yield of 93%. The process thus enables 1,2-propanediol to be produced from a readily available and resource-saving starting compound.

According to the invention, the process is carried out in the presence of a base and / or a basic salt of an alkali metal and / or alkaline earth metal. It has been found that bases of the alkali and alkaline earth metals are useful in the process. The alkali metal can be selected from sodium and / or potassium. It has been shown that the process can be carried out particularly advantageously in the presence of an alkaline earth metal. A high conversion could be achieved here. In preferred embodiments, the alkaline earth metal is selected from calcium and / or magnesium. In particular, the alkaline earth metal is magnesium. Using magnesium, it was possible to achieve high yields in the implementation.

The alkali or alkaline earth metal is in an aqueous solution. A base is understood to be a compound which, in aqueous solution, is able to form hydroxide ions (OH ^- ). A basic salt is understood to mean a salt which increases the pH value of an aqueous solution. Bases such as sodium or potassium hydroxide can be used, for example. Hydroxides and basic salts of the alkaline earth metals are preferred. In preferred embodiments, the base and / or the basic salt of the alkaline earth metal is selected from the group comprising calcium hydroxide, magnesium hydroxide, calcium acetate and / or magnesium acetate. Mg (OH) 2 or magnesium acetate can preferably be used. In particularly preferred embodiments, the base is magnesium hydroxide. It was found that when using divalent cations, a higher conversion of lactic acid to 1,2-propanediol could be achieved.

The reactant lactic acid and the base and / or the basic salt of an alkali metal and / or alkaline earth metal can be fed separately to the reaction solution. However, lactic acid can also be used in the form of its salt lactate. Alkali and / or alkaline earth cations are particularly suitable as counterions for the lactate. In embodiments, the basic salt of the alkaline earth metal is selected from calcium lactate and / or magnesium lactate.

The reactant lactic acid can be used in stoichiometric amounts or preferably in deficit, based on the base or the basic salt of an alkali metal or alkaline earth metal. Lactic acid can be present in the range from> 0 equivalents (eq.) To 3.75 equivalents (eq.), Based on the base, such as hydroxide ions (OH ^- ). Lactic acid can be in the range of> 0 eq. to ≤ 2.5 eq., or from> 0 eq. up to 1.25 eq., based on Mg (OH) 2. With a deficit of lactic acid, better yields of 1,2-propanediol could be achieved.

The process in aqueous solution is preferably carried out under heterogeneous catalysis. Heterogeneous catalysts can be separated off after the reaction by simple methods such as filtration. In this way, on the one hand, the reaction mixture can be more easily separated and further processed. Heterogeneous catalysts can also be reused after purification and, optionally, activation. The transition metal of the catalyst is preferably a metal of the fourth period of the periodic table of the elements. In preferred embodiments, the reaction is carried out using a transition metal selected from the group of the fourth period comprising copper, nickel, cobalt, zinc and / or iron. In particular, the transition metal is selected from the group comprising copper and / or cobalt. The fact that the process is particularly suitable for low-cost transition metals of the fourth period such as copper is a great advantage. An advantageous combination of high selectivity and high conversion could be achieved using copper. Furthermore, an advantageous combination of high selectivity and high conversion could be achieved using cobalt, in particular even with a low loading of the catalyst support. In addition to copper and cobalt, nickel, iron and zinc can also be used as active metals. Nickel in particular also showed advantageous conversion rates.

The transition metal catalysts can be used as such, for example in the form of powders, granules, particles or else in extrudate form. Preferably the catalyst is in supported form, i. used as a so-called supported catalyst, on a suitable support material. Suitable support materials are, for example, conventional support materials such as silica, aluminum oxide, lanthanum oxide, zirconium oxide, aluminosilicates, synthetic porous materials or clay. In preferred embodiments, the catalyst is used in supported form on a support material selected from silica, aluminum oxide, lanthanum oxide, zirconium oxide and / or aluminosilicates. In particular, silica is preferred as the carrier. Using Cu / SiO2 as a catalyst, particularly good conversion rates could be achieved. Good conversion rates could also be achieved using aluminum oxide and lanthanum oxide as carriers. Suitable support materials are commercially available. Supported catalysts are also commercially available or can be produced, for example, by means of ammonia evaporation precipitation or wet impregnation processes.

In preferred embodiments, the reaction is carried out at a temperature in the range from 393 K to 773 K, preferably in the range from 493 K to 513 K. Good yields could be obtained in particular in these temperature ranges. The reaction times for the reaction can be in the range from 0.5 hour to 48 hours, preferably in the range from 2 hours to 4 hours.

The process can in principle be carried out continuously or discontinuously, in tubular reactors, stirred tanks, flow reactors or vortex reactors. It is preferred that the reaction is carried out at elevated pressure based on atmospheric pressure. For example, the process can be carried out in a reactor such as a pressure autoclave. In a pressure autoclave, the hydrogen can be injected at a suitable pressure. In preferred embodiments, the hydrogen is injected with a hydrogen pressure in the range from 1 MPa to 5 MPa, preferably in the range from 2 MPa to 4 MPa. The pressure data correspond to the applied pressure at room temperature, corresponding to 20 ± 2 ° C. It is believed that the implementation can benefit from higher hydrogen pressures in this range. In contrast, it was found that the conversion of lactic acid to 1,2-propanediol did not take place at hydrogen pressures of less than 10 bar under the conditions used. Advantageously, a hydrogen pressure of just 1 MPa is sufficient for significant amounts of 1,2-propanediol to be formed.

In a preferred embodiment, 0.5 g of lactic acid dissolved in 20 ml of deionized water is reacted with 0.4 g of Mg (OH) 2 over 0.2 g of Cu / SiO2 with a 25% load at a temperature of 513K for 4 hours.

The reaction mixtures resulting from the process for producing 1,2-propanediol from lactic acid can be purified by conventional methods, for example thermally by means of distillative or rectification processes. The process according to the invention can be used to produce 1,2-propanediol in an economical manner by reaction in an aqueous solution.

Overall, a method can be made available using a readily available, resource-saving educt allows the production of 1,2-propanediol. The conversion could be carried out with high selectivity using inexpensive fourth period transition metals such as copper on carriers such as SiO ₂ .

Unless otherwise stated, the technical and scientific terms used have the meanings commonly understood by one of ordinary skill in the art to which this invention belongs.

Examples and figures which serve to illustrate the present invention are given below.

• 1 die katalytische Aktivität an auf verschiedenen Oxiden geträgertem Kupfer.
• 2 die katalytische Aktivität verschiedener SiO2-geträgerter Übergangsmetalle.
• 3 die katalytische Aktivität in Anwesenheit verschiedener Hydroxide.
• 4 die Temperaturabhängigkeit der Kupfer-katalysierten Hydrierung.
• 5 die katalytische Aktivität in Abhängigkeit vom Wasserstoffdruck.
• 6 den zeitlichen Verlauf der Umsetzung von Magnesiumlactat (Mg(LA)2) und Calciumlactat (Ca(LA)₂) über Cu/SiO₂.
• 7 den Umsatz als Funktion der eingesetzten Menge an Milchsäure in Bezug auf Mg(OH)₂.
• 8 den zeitlichen Verlauf der Cobalt-katalysierten Umsetzung von Milchsäure

Here shows:

• 1 the catalytic activity of copper supported on various oxides.
• 2 the catalytic activity of various SiO2-supported transition metals.
• 3 the catalytic activity in the presence of various hydroxides.
• 4th the temperature dependence of the copper-catalyzed hydrogenation.
• 5 the catalytic activity as a function of the hydrogen pressure.
• 6th the time course of the conversion of magnesium lactate (Mg (LA) 2) and calcium lactate (Ca (LA) ₂ ) over Cu / SiO ₂ .
• 7th the conversion as a function of the amount of lactic acid used in relation to Mg (OH) ₂ .
• 8th the time course of the cobalt-catalyzed conversion of lactic acid

Chemicals:

Cu (NO ₃ ) ₂ • 3H ₂ O, Co (NO ₃ ) ₂ • 6H ₂ O, Ni (NO ₃ ) ₂ • 6H ₂ O, Fe (NO ₃ ) ₃ • 9H ₂ O, Zn (NO ₃ ) ₂ 6H ₂ O, ammonia solution (25%), pyrogenic silica powder, colloidal silica (40%), Al ₂ O ₃ , La ₂ O ₃ , CeO ₂ , TiO ₂ , magnesium lactate, calcium lactate, NaOH and KOH were obtained from Sigma-Aldrich . Mg (OH) ₂ , Ca (OH) ₂ , Ba (OH) ₂ and La (OH) ₃ were purchased from abcr GmbH. Mesoporous silicon dioxide SBA-15 (Puralox) and KIT-1 were obtained from Sasol GmbH. Lactic acid was purchased from Fluka.

High performance liquid chromatography (HPLC):

The liquid phase products were analyzed by HPLC using a Shimadzu system (Rezex ROA Organic Acid H + (8%) column from Phenomenex, eluent: 0.05 MH ₂ SO ₄ ).

example 1

Production of supported transition metal catalysts

The example shows the production of supported catalysts of the transition metals Fe, Co, Ni, Cu and Zn of the fourth period. Metal oxides such as MgO, Al ₂ O ₃ , La ₂ O ₃ , SiO ₂ , TiO ₂ , CeO ₂ , ZrO ₂ were selected as carriers. Ammonia evaporation precipitation and wet impregnation processes were used to make the catalysts.

Catalysts that were produced by wet impregnation are identified below by the addition “WI”, for example Cu / SiO ₂ -WI, while a designation without an addition, for example Cu / MO _x , indicates a catalyst produced by ammonia evaporation.

Ammonia evaporation precipitation:

The catalyst Cu / SiO2 was produced by ammonia evaporation precipitation. For this purpose, the respectively required amount of Cu (NO ₃ ) ₂ · 3H ₂ O was dissolved in deionized water in a 250 ml round bottom flask with stirring for 1 hour at 750 rpm. Ammonia solution was prepared by diluting a 25% ammonia solution to specific concentrations with deionized water in a 200 ml beaker. Then the dilute ammonia solution was added dropwise to the Cu solution with constant stirring. One hour after the addition of the ammonia solution had ended, a 40% strength colloidal silica suspension was added dropwise. The resulting slurry was stirred overnight before ammonia was evaporated through a 363K oil bath. The evaporation was not stopped until the pH of the slurry dropped to 7. The slurry was then filtered and washed with 2000 ml of deionized water. A residue was obtained after further removal of the water in a drying cabinet at 353 K overnight. The residue was calcined at 823 K for 4 hours with a supply of air. The catalyst was obtained after four hours of reduction under H2 at 723 K. The process was also used to make Cu / SBA-15, Cu / KIT, Fe / SiO ₂ , Zn / SiO ₂ , Ni / SiO ₂ , Co / SiO ₂ .

Wet impregnation:

Cu / SiO ₂ -WI was produced by wet impregnation. Cu (NO ₃ ) ₂ · 3H ₂ O was dissolved in deionized water in a 100 ml round bottom flask and stirred at 750 rpm for 1 hour. Solid SiO ₂ was slowly added to the solution. The slurry was stirred further overnight before water was removed on a rotary evaporator (323 K, 7 kPa and 160 rpm). The resulting materials were additionally dried overnight at 353 K in a drying cabinet. The calcination and reduction took place as described above. The process was also used for the production of Cu / -Al ₂ O ₃ -WI, Cu / La ₂ O ₃ -WI, Cu / CeO ₂ -WI and Cu / TiO ₂ -WI.

Example 2

Hydrogenation of lactic acid over copper on various supports in the presence of Mg (OH) ₂

The example illustrates the hydrogenation of lactic acid in the presence of Mg (OH) ₂ over Cu, which is supported on various oxides (MO _x ). The reaction was carried out in a 50 ml autoclave with a Teflon inlet. 0.5 g of lactic acid dissolved in 20 ml of deionized water was added along with 0.1 g of Cu / MO _x and 0.1 g of Mg (OH) 2. The closed autoclave was flushed five times and brought to 50 bar with H2. The reaction was carried out for 4 hours at 513 K with stirring at 750 rpm.

The 1 shows the catalytic performance of the individual catalysts under the following reaction conditions: 0.1 g catalyst, 25% loading, 0.5 g lactic acid, 0.1 g Mg (OH) 2, 20 ml H ₂ O, 513 K, 5 MPa H2, 4 h. How to get the 1 shows copper supported on silica, Cu / SiO2 (colloidal silicon dioxide), a conversion of 23%, by wet impregnation supported on La ₂ O ₃ (Cu / La ₂ O ₃ -WI) a conversion of 14.2%, while copper supported on Al ₂ O ₃ , pyrogenic SiO ₂ , CeO ₂ , TiO ₂ , KIT and SBA-15 showed a conversion of less than 5%. It was found that Cu supported on all oxides is effective in converting lactic acid. Of these, Cu / SiO2 produced by ammonia evaporation is the most efficient. The selectivity for conversion to 1,2-propanediol (1,2-PDO) was over 95% for all catalysts.

Example 3

Hydrogenation of lactic acid over various SiO ₂ -supported metal catalysts in the presence of Mg (OH) ₂

The example illustrates the hydrogenation of lactic acid over various non-noble metal catalysts (M) on SiO ₂ supports in the presence of Mg (OH) 2. The reaction was carried out in a 50 ml autoclave with a Teflon inlet. 0.5 g of lactic acid, dissolved in 20 ml of deionized water, was added together with 0.04 mmol of M / SiO ₂ and 0.4 g of Mg (OH) 2. The closed autoclave was flushed five times and brought to 50 bar with H2. The reaction was carried out for 4 hours at 513 K with stirring at 750 rpm.

The catalytic performance of the catalysts under the reaction conditions described: 0.04 mmol of metal, 25% loading, 0.5g of lactic acid, 0.4g of Mg (OH) 2, 20 ml of H ₂ O, 513 K, 5 MPa H2, 4 h in 2 shown. How to get the 2 taken out, 1,2-propanediol (1,2-PDO) was obtained as a desired product, accompanied by propanol (1-PO) and isopropanol (2-PO) as by-products. The conversion of lactic acid over Fe and Zn / SiO ₂ catalysts was low. A 21% conversion of lactic acid with a selectivity of 29.4% to 1,2-PDO and 70.6% to 2-propanol (2-PO) was obtained over Ni / SiO ₂ . The conversion increased to 50.8% compared to Cu / SiO ₂ , with the selectivity for 1,2-PDO also increasing to up to 98.2%. With the catalysis of Co / SiO ₂ , a further increase in sales to 94.0% was achieved. However, the selectivity to 1,2-PDO decreased to 36.3%. Two by-products were obtained with a selectivity of 17.7% for 1-PO and 46.0% for 2-propanol (2-PO).

Example 4

Hydrogenation of lactic acid on Cu / SiO2 in the presence of various bases

The example illustrates the hydrogenation of lactic acid on Cu / SiO ₂ in the presence of various bases. The reaction was carried out in a 50 ml autoclave with a Teflon inlet. 0.5 g of lactic acid, dissolved in 20 ml of deionized water, together with 0.1 g of Cu / SiO2 and 1.37 mmol of OH each ^- as NaOH, KOH, Zr (OH) 2, Sr (OH) 2, Ca ( OH) 2, Mg (OH) 2 or La (OH) 3 added. The closed autoclave was flushed five times and brought to 50 bar with H2. The reaction was carried out for 4 hours at 513 K with stirring at 750 rpm.

The dependence of the catalytic performance in the presence of different bases under the reaction conditions described: 0.1 g 25% Cu / SiO ₂ , 0.5 g lactic acid, 1.37 mmol OH ^- , 20 ml H ₂ O, 513 K, 5 MPa H2, 4 Hours is in 3 shown. A sample without base, but otherwise the same parameters of 0.1 g 25% Cu / SiO ₂ , 0.5 g lactic acid, 20 ml H ₂ O, 513 K, 5 MPa H2, 4 hours served as control (blank).

The OH ^- components introduced were identical in all cases. How to get the 3 removed, when using NaOH, KOH, Zr (OH) 2, Sr (OH) 2 or La (OH) 3, no significant conversion (<5%) was achieved. However, a 10% conversion of lactic acid to 1,2-PDO was obtained using Ca (OH) 2. A more significant increase to 50.8% took place when using Mg (OH) 2. This suggests that Mg (OH) 2 is the most promising candidate for lactic acid conversion. The selectivities for 1,2-PDO were higher than 95% in all cases.

Example 5

Investigation of the influence of temperature

The example illustrates the influence of temperature on the hydrogenation of lactic acid using Cu / SiO2 in the presence of Mg (OH) 2. The reaction was carried out in a 50 ml autoclave with a Teflon inlet. 0.5 g of lactic acid, dissolved in 20 ml of deionized water, was added along with 0.1 g of Cu / SiO2 and 0.4 g of Mg (OH) 2. The closed autoclave was flushed five times and brought to 50 bar with H2. The reaction was carried out at different temperatures of 473 K, 493 K and 513 K for 4 hours with stirring at 750 rpm.

The dependence of the catalytic performance on the temperature is in 4th shown. How to get the 4th there was a slight conversion (1.7%) of lactic acid at 473K, with the conversion increasing to 37.3% at 493K. As the temperature rises, the conversion at 513K increases to 50.4%. The temperature profile shows that a higher temperature favors the conversion of lactic acid. The selectivity for 1,2-PDO was higher than 95% at each of the temperatures examined.

Example 6

Investigation of the influence of hydrogen pressure

The example illustrates how the hydrogenation of lactic acid is influenced by varying the hydrogen pressure using Cu / SiO2 in the presence of Mg (OH) 2. The reaction was carried out in a 50 ml autoclave with a Teflon inlet. 0.5 g of lactic acid, dissolved in 20 ml of deionized water, was added along with 0.1 g of Cu / SiO2 and 0.4 g of Mg (OH) 2. The closed autoclave was flushed five times and H2 was injected at different pressures. The reaction was carried out for 4 hours at 513 K with stirring at 750 rpm.

The dependence of the catalytic performance on different H2 pressures is in 5 shown. How to get the 5 removed, the conversion of lactic acid rose from 16.0% at 1 MPa to 86.4% at 4 MPa and remained constant at higher pressure. This shows that a pressure of less than 4 MPa favors the conversion of lactic acid, but a pressure of more than 4 MPa has no influence on the conversion. The selectivity for 1,2-PDO was greater than 95% at each pressure.

Example 7

Hydrogenation of alkaline lactates over Cu / SiO2 in the absence of base

The example illustrates the hydrogenation of magnesium lactate (Mg (LA) ₂ ) and calcium lactate (Ca (LA) ₂ ) over Cu / SiO ₂ . The reaction was carried out in a 50 ml autoclave with a Teflon inlet. A corresponding amount of the alkaline salt, dissolved in 20 ml of deionized water, was added together with 0.1 g of Cu / SiO2. In each case, 5.6 mmol of lactate were used. The closed autoclave was flushed five times and brought to 50 bar with H2. The reaction was carried out at 513 K with 750 rpm stirring. Samples were taken at 0.5, 1, 2, 4 and 8 hours after the temperature reached 513K.

The transformations of the substrates over time are in 6th shown. How to get the 6th the conversion of Mg (LA) 2 was 34.8% after 0.5 hours and increased to 95% after 2 hours. The conversion of Ca (LA) 2, on the other hand, was lower, reaching 1.1% after 0.5 hours and increasing to 20.0% after 8 hours. It turned out that Mg (LA) 2 and Ca (LA) 2 were both converted to 1,2-PDO, with Mg (LA) 2 having higher efficiency. The selectivity for 1,2-PDO was higher than 95% in both cases.

Example 8

Investigation of the influence of the amount of lactate

The example illustrates how the hydrogenation of lactic acid is influenced as a function of the amount of lactic acid used in relation to Mg (OH) 2. The reaction was carried out in a 50 ml autoclave with a Teflon inlet. 1.25, 2.5 or 3.75 equivalents of lactic acid dissolved in 20 ml of deionized water were added along with 0.1 g of Cu / SiO2 (25% loading) and 0.4 g of Mg (OH) 2. The closed autoclave was rinsed five times and brought to 50 bar with H2. The reaction was carried out for 4 h at 513 K with stirring at 750 rpm.

7th shows the conversion as a function of the amount of lactic acid used in relation to Mg (OH) 2. How to get the 7th the conversion was 50.4% when 0.5 g of lactic acid was placed in 20 ml of water. With a higher amount of lactic acid, the conversion decreased. It was observed that only 0.8% lactic acid was converted when the amount charged was 1.5 g. This shows that the amount of lactic acid is another factor that significantly affects the response.

Example 9

Investigation of the cobalt-catalyzed conversion of lactic acid

The example illustrates the hydrogenation of lactic acid on cobalt as a catalyst supported on SiO ₂ with 10% loading in the presence of Mg (OH) 2. The reaction was carried out in a 50 ml autoclave with a Teflon inlet. 0.5 g of lactic acid dissolved in 20 ml of deionized water was added along with 0.1 g of 10% Co / SiO ₂ and 0.4 g of Mg (OH) 2. The closed autoclave was flushed five times and brought to 50 bar with H2. The reaction was carried out for 0.5, 2, 4, 8 or 24 hours at 513 K with stirring at 750 rpm.

8th shows the time course of the cobalt-catalyzed conversion of lactic acid. How to get the 8th deminished, a conversion of 20.7% lactic acid to 1,2-propanediol (1,2-PDO) with a selectivity of 100% was obtained after a reaction time of 0.5 hours. The conversion increased with the reaction time, while the selectivity of the conversion to 1,2-propanediol decreased and propanol (1-PO) was formed as a by-product at the expense of 1,2-PDO. A conversion of 89% with a selectivity of 84.9% to 1,2-PDO and a selectivity of 15.1% to 1,2-PO was obtained after 24 hours. This shows that using cobalt as a catalyst, 1,2-propanediol can be produced from lactic acid with high selectivity even with a 10% loading.

Overall, the results show that 1,2-propanediol can be produced from lactic acid by catalytic hydrogenation in aqueous solution in the presence of a base and / or a basic salt of an alkali metal and / or alkaline earth metal with very good selectivity and high yield .

QUOTES INCLUDED IN THE DESCRIPTION

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Patent literature cited

• US 6403844 B1 [0003]
• WO 2001/016063 A1 [0003]
• DE 102008013474 A1 [0003]

Claims (9)

Process for the preparation of 1,2-propanediol from lactic acid by catalytic hydrogenation in aqueous solution, characterized in that the reaction is carried out in the presence of a base and / or a basic salt of an alkali metal and / or alkaline earth metal. Procedure according to Claim 1 , characterized in that the alkaline earth metal is selected from calcium and / or magnesium, in particular magnesium. Procedure according to Claim 1 or 2 , characterized in that the base and / or the basic salt of an alkaline earth metal is selected from the group comprising calcium hydroxide, magnesium hydroxide, calcium acetate and / or magnesium acetate. Method according to one of the preceding claims, characterized in that the base is magnesium hydroxide. Method according to one of the preceding claims, characterized in that the basic salt of the alkaline earth metal is selected from calcium lactate and / or magnesium lactate. Process according to one of the preceding claims, characterized in that the reaction is carried out under heterogeneous catalysis using a transition metal selected from the group of the fourth period comprising copper, nickel, cobalt, zinc and / or iron, in particular copper or cobalt. Process according to one of the preceding claims, characterized in that the catalyst is used in supported form on a support material selected from silica, aluminum oxide, lanthanum oxide, zirconium oxide and / or aluminosilicates, in particular silica. Process according to one of the preceding claims, characterized in that the reaction is carried out at a temperature in the range from 393 K to 773 K, preferably in the range from 493 K to 513 K. Method according to one of the preceding claims, characterized in that the hydrogen is injected with a hydrogen pressure in the range from ≥ 1 MPa to ≤ 5 MPa, preferably in the range from ≥ 2 MPa to ≤ 4 MPa.

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