CHROMIUM-FREE WATER- AND ACID-STABLE CATALYST FOR HYDROGENATION REACTIONS

Abstract

The present invention relates to an improved chromium-free Cu—Al catalyst for the hydrogenation of carbonyl groups in organic compounds, characterized in that the catalyst contains zirconium in a proportion of 0.5 to 30.0 wt. %. The invention also relates to the production of the catalyst and to the use of same in the hydrogenation of carbonyl groups in organic compounds.

Claims

1. A Cu—Al catalyst, wherein the catalyst contains zirconium in a proportion by weight of 0.5% to 30.0% based on the total weight of the catalyst after loss on ignition.

2. The catalyst as claimed in claim 1, wherein the zirconium is present in a proportion by weight of 5.0% to 20.0%, preferably within a range of 10% to 20% by weight, based on the total weight of the catalyst after loss on ignition.

3. The catalyst as claimed in claim 1, wherein the catalyst contains Cu in an amount within a range from 20% to 50% by weight, preferably within a range from 25% to 40% by weight, and Al in an amount within a range from 8% to 29% by weight, preferably within a range from 15% to 25% by weight, based on the total weight of the catalyst after loss on ignition.

4. The catalyst as claimed in claim 1, wherein the catalyst is present in the form of a shaped body.

5. The catalyst as claimed in claim 4, wherein the shaped catalyst body is present in tablet form.

6. The catalyst as claimed in claim 4, wherein it has a binder content within a range from 2% to 30% by weight, preferably within a range from 2% to 10% by weight, and more preferably within a range from 2% to 5% by weight, based on the total weight of the shaped body after loss on ignition.

7. The catalyst as claimed in claim 6, wherein the binder is calcium aluminate.

8. The catalyst as claimed in claim 7, wherein the proportion of calcium in the shaped body is within a range from 0.14% to 17.02% by weight, preferably within a range from 0.14% to 5.67% by weight, and more preferably within a range from 0.14% to 2.84% by weight, based on the total weight of the shaped body after loss on ignition.

9. The catalyst as claimed in claim 4, wherein the side crush strength is 80 to 500 N, preferably 150 to 250 N, more preferably 170 to 230 N.

10. The catalyst as claimed in claim 1, wherein it has a cubic zirconium dioxide phase and optionally in addition a further ZrO2 phase selected from orthorhombic and monoclinic zirconium dioxide.

11. The catalyst as claimed in claim 1, wherein the catalyst does not contain manganese in oxidized or metallic form.

12. A process for preparing a catalyst as claimed in claim 1 containing zirconium in a proportion by weight of 0.5% to 30.0% based on the total weight of the catalyst after loss on ignition, said process comprising the following steps: a) combining (i) at least one aqueous solution A comprising copper compounds, zirconium compounds, and optionally further transition metal compounds and (ii) at least one aqueous alkaline solution B to form a precipitate, wherein solution A and/or solution B additionally include(s) a dissolved aluminum compound, b) separating off the precipitate, optionally washing the precipitate, c) drying the precipitate to obtain a dried precipitate, d) calcining the dried precipitate from step c) at a temperature of between 200 and 800° C. for a period of between 30 min and 4 h.

13. The process as claimed in claim 12, comprising the following step: e) shaping the calcined precipitate from step d) to obtain a shaped body.

14. The process as claimed in claim 13, comprising the following step: f) subjecting the shaped body to thermal treatment at a temperature of between 200 and 800° C. for a period of between 30 min and 4 h.

15. The process as claimed in claim 12, wherein the thermal treatment in step f) takes place at between 400 and 700° C. for a period of between 1 h and 3 h.

16. The process as claimed in claim 12, wherein step f) is followed by reduction of the catalyst.

17. A process for hydrogenating carbonyl groups in organic compounds with the catalyst as claimed in claim 1 or prepared by a process as claimed in claim 12.

18. The process as claimed in claim 17, wherein the water content of the reaction stream is 0.1% to 5.0% by weight, preferably 0.2% to 5.0% by weight, more preferably 0.5% to 5.0% by weight, particularly preferably 0.5% to 3.0% by weight.

19. The process as claimed in claim 17, wherein the acid value of the reaction stream is within a range from 0.1 to 3.4 mgKOH/gsolution, preferably within a range from 0.2 to 1.0 mgKOH/gsolution.

20. The process as claimed in claim 17 for hydrogenating aldehydes to alcohols.

21. The process as claimed in claim 17 for hydrogenating a fatty acid methyl ester.

22. The process as claimed in claim 17 for hydrogenating ketones to alcohols.

Description

EXAMPLES

[0069] The loss on ignition was in the context of the present invention determined in accordance with DIN 51081 by determining the weight of about 1-2 g of a sample of the material to be analyzed, then heating it to 900° C. under ambient atmosphere and storing it at this temperature for 3 h.

[0070] The sample was then cooled under an inert atmosphere and the residual weight measured. The difference in weight before and after thermal treatment corresponds to the loss on ignition.

[0071] The side crush strength (SCS) was determined in accordance with ASTM 04179-01 without predrying the tablets. This was done by measuring a statistically sufficient number of tablets (at least 20 tablets) and calculating the arithmetic mean of the individual measurements. This average corresponds to the side crush strength of a particular sample.

[0072] Chemical elements were determined by ICP (inductively coupled plasma) measurement in accordance with DIN EN ISO 11885.

[0073] The acid value was determined by mixing approx. 4 g of the sample solution with 25 mL of propanol and adding phenolphthalein as indicator. The solution was titrated at room temperature with a tetrabutylammonium hydroxide solution (0.1 mol/L in 2-propanol/methanol) until the color change. The acid value AV in mg.sub.KOH/g.sub.solution is calculated according to

[00001]$\mathrm{AV}=\frac{\mathrm{Volume}\mathrm{consumed}*c*M}{\mathrm{Sample}\mathrm{weight}}=\mathrm{mg}\mathrm{KOH}/g\mathrm{sample}$

[0074] where AV=acid value, volume consumed=volume of tetrabutylammonium hydroxide solution consumed in mL, c=concentration of the tetrabutylammonium hydroxide solution, M=molar mass of KOH, and sample weight=amount of the sample solution used in g.

[0075] The pore volume of the shaped catalyst body was measured by the mercury porosimetry method in accordance with DIN 66133 in a pressure range from 1 to 2000 bar.

[0076] The water content of the solutions was determined by the Karl Fischer method in accordance with ASTM E 203 (2016).

Example 1: Production of Inventive Catalyst 1

[0077] An aqueous solution 1 was prepared by adding 3530 g of Cu(NO.sub.3).sub.2.Math.3H.sub.2O and 1843 g of (ZrO).sub.2(OH).sub.2CO.sub.3 to 5000 mL of demineralized water. Complete dissolution of the salts was then achieved by adding 1550 mL of nitric acid. The acidic solution was made up to a total volume of 20 000 mL with demineralized water. The pH of the solution was −0.70. The solution was then heated to 80° C.

[0078] In addition, 1500 g of Na.sub.2CO.sub.3 and 2140 g of NaAlO.sub.2 were dissolved in 22 000 mL of demineralized water; the pH of solution 2 was 12.23.

[0079] For the precipitation, a precipitation vessel was provided, which was filled with 8000 mL of demineralized water. Into this were introduced simultaneously the copper-containing solution 1 and the carbonate-containing solution 2. The dosing rate was adjusted such that the precipitation solution had a pH of approx. 6.5.

[0080] At the end of the addition and after precipitation was complete, the precipitate was filtered off and washed with demineralized water to remove adhering impurities until the wash water had a conductivity below 0.25 mS. The filter cake was then dried.

[0081] The dried powder was then calcined at 750° C. for 2 h.

[0082] The relative proportions by weight were Cu=29.9% by weight, Zr=17.5% by weight, and Al=20.6% by weight, based on the total mass after loss on ignition.

Example 2: Production of Inventive Catalyst 2

[0083] 1706 g of the calcined powder obtained in example 1 was combined with 51 g of Secar 71 binder (31% by weight CaO, 69% by weight Al.sub.2O.sub.3), 5 g of demineralized water, and 34 g of graphite and mixed for 10 minutes to afford a homogeneous mixture. This mixture was first compacted and granulated and then pressed in a Kilian Pressima tablet press into tablets having a width of 4.5 mm and a height of 3 mm. The tablets were then finally subjected to calcination at 600° C. for 2 h. The bulk density of the tablets thus obtained was 1175 g/L. For use examples 3 and 4, tablets were produced according to the same procedure, with the difference that the tablets had a height of 3.0 mm and a width of likewise 3.0 mm. The relative proportions by weight in the tablets were Cu=29.0% by weight, Zr=17.0% by weight, Al=21.1% by weight, and 0.6% by weight Ca, based on the total mass after loss on ignition.

Example 3: Production of Inventive Catalyst 3

[0084] 1706 g of the calcined powder obtained in example 1 was combined with 5 g of demineralized water and 34 g of graphite and mixed for 10 minutes to afford a homogeneous mixture. This mixture was first compacted and granulated and then pressed in a Kilian Pressima tablet press into tablets having a width of 4.5 mm and a height of 3 mm. The tablets were then finally subjected to calcination at 600° C. for 2 h. The relative proportions by weight in the tablets were Cu=29.9% by weight, Zr=17.5% by weight, and Al=20.6% by weight, based on the total mass after loss on ignition.

Comparative Example 1 (Comparative Catalyst A)

[0085] Catalyst A was prepared by precipitating a copper- and chromium-containing precipitate, converting it into the oxidic form by thermal treatment, and pressing it into tablets having a width of 4.5 mm and a height of 3 mm. The relative proportions by weight were Cu=37.5% by weight and Cr=23.0% by weight, based on the total mass after loss on ignition. For use examples 3 and 4, tablets were produced according to the same procedure, with the difference that the tablets had a height of 3.0 mm and a width of likewise 3.0 mm.

[0086] Comparative example 2 (comparative catalyst B) To prepare catalyst B, an aqueous solution 1 was prepared by dissolving 1250 g of Cu(NO.sub.3).sub.2.Math.3H.sub.2O, 220 g of Mn(NO.sub.3).sub.2.Math.4H.sub.2O, and 1800 g of Al(NO.sub.3).sub.3.Math.9H.sub.2O in 9000 g of distilled H.sub.2O. Solution 2 was prepared by dissolving 1720 g of Na.sub.2CO.sub.3 in 7500 g of distilled H.sub.2O. The two solutions were heated separately to 80° C. while stirring. The two solutions were then metered into a precipitation vessel with continuous stirring. The resulting precipitate was filtered off and washed with distilled H.sub.2O to remove adhering impurities until the wash water had a conductivity below 0.25 mS. The filter cake was then dried. The dried powder was then subjected to thermal treatment at 750° C. for 3 h; the relative proportions by weight were Cu=44.8% by weight, Mn=7.0% by weight, and Al=17.92 by weight, based on the total mass after loss on ignition.

[0087] 1706 g of this powder was combined with 51 g of Secar 71 binder, 5 g of demineralized water, and 34 g of graphite and mixed for 10 minutes to afford a homogeneous mixture. This mixture was first compacted and granulated and then pressed in a Kilian Pressima tablet press into tablets having a width of 4.5 mm and a height of 3 mm. The tablets were then finally subjected to calcination at 600° C. for 2 h. The relative proportions by weight in the tablets were Cu=43.5% by weight, Mn=6.8% by weight, Al=18.5% by weight, and Ca=0.6% by weight, based on the total mass after loss on ignition.

Comparative Example 3 (Comparative Catalyst C)

[0088] The powder for catalyst C was prepared in accordance with the method for preparing the powder for catalyst B, wherein the proportion of Mn(NO.sub.3).sub.2.Math.4H.sub.2O was chosen such that the relative proportion by weight of manganese in the powder thus obtained, based on the mass after loss on ignition, was 0.1% by weight. The relative proportions by weight were Cu=49.7% by weight, Mn=0.1% by weight, and Al=20.0% by weight, based on the total mass after loss on ignition. 1706 g of the powder thus obtained was combined with 5 g of demineralized water and 34 g of graphite and mixed for 10 minutes to afford a homogeneous mixture. This mixture was first compacted and granulated and then pressed in a Kilian Pressima tablet press into tablets having a width of 4.5 mm and a height of 3 mm. The relative proportions by weight in the tablets were Cu=49.7% by weight, Mn=0.1% by weight, and Al=20.0% by weight, based on the total mass after loss on ignition. The bulk density of the tablets thus obtained was 1152 g/L.

[0089] A portion of the material obtained after tableting of comparative catalysts A, B, and C and of inventive catalysts 2 and 3 was subjected to a reduction. This was done by subjecting the sample to thermal treatment in a gas mixture of 2% by volume H.sub.2 and 98% by volume N.sub.2 at a temperature of 200° C. in order to bring about reduction of the CuO present to Cu. The sample then was cooled to room temperature under nitrogen and stored under liquid isodecanol. The side crush strength of this sample was then measured and used for use examples 1 to 3.

Use Example 1 (Stability Test)

[0090] For each of the inventive catalysts 2 and 3 and for each of the comparative catalysts A, B and C, the acid stability was determined by combining a quantity of tableted, reduced, and stabilized samples totaling 25 g with a liquid mixture comprising 75 g of an oxoaldehyde solution, a water content of 1% by weight, and an acid value of 0.2 mg.sub.KOH/g.sub.solution. This mixture was heated at 120° C. under a nitrogen atmosphere for 4 days. The tableted sample was at the end of the test separated from the liquid mixture. Its side crush strength was then immediately measured.

[0091] After performance of the test, the oxoaldehyde solution was analyzed for the presence of Cu, Al, Cr, Mn, and Zr.

TABLE-US-00001 TABLE 1 Side crush strengths of the catalysts Side crush strength after Side crush strength after Example reduction [N] acid/water treatment [N] Catalyst 2 137 132 Catalyst 3 95 84 Comparative catalyst A 97 86 Comparative catalyst B 93 74 Comparative catalyst C 47 not measurable because the sample material was broken

[0092] Table 1 shows clearly that the side crush strength of inventive catalysts 2 and 3 is after reduction already higher than that of the catalysts known from the prior art. The increased stability to the effect of acid and water is demonstrated even more clearly by the side crush strength values at the end of the test. Inventive catalyst 2 still has the highest value for side crush strength here, whereas by contrast the tablets of the chromium-free CuAlMn catalyst, comparative catalyst C, broke during the test and no meaningful measurement of the side crush strength was possible.

TABLE-US-00002 TABLE 2 Metal concentrations in the test solution after the stability test Concentration of metals in test solution after test [ppm] Example Cu Al Cr Mn Zr Catalyst 2 3 27 — — 34 Catalyst 3 9 101 — — 54 Comparative catalyst A 12 — 70 — — Comparative catalyst B 64 43 — 5510 — Comparative catalyst C 69 116 — 31 —

[0093] The data from Table 2 show that the inventive catalysts are largely stable to a loss of copper species under the drastic test conditions, whereas this is markedly higher for the comparative catalysts.

[0094] These results illustrate the beneficial effect achieved by adding zirconium to a copper-containing catalyst, namely increased stability to acids and water, which is manifested both in higher mechanical stability and in lower loss of metals from the catalyst itself.

Use Example 2: Hydrogenation of Oxoaldehydes to Oxoalcohols

[0095] A bed with a volume of 100 mL of inventive catalyst 2 in the reduced and wet-stabilized form was introduced into a reactor and heated under a stream of nitrogen to temperatures within a range from 120 to 180° C., with a reaction time of 2 days at each temperature chosen. A liquid phase comprising 45% by weight of aldehyde, 25% by weight of the corresponding alcohol, and 30% by weight of by-products (paraffins, olefins, others), having a water content of 0.7% by weight and an acid value of 0.2 was then passed through the reactor.

[0096] The constituents of the product stream downstream of the reactor were analyzed by gas chromatography. The conversions and alcohol contents in the product stream calculated over the entire run time at the respective temperature are shown in Table 3.

[0097] For comparison, a sample of comparative catalyst A and a sample of comparative catalyst B were each subjected to the same conditions and the results obtained are likewise shown in Table 3.

TABLE-US-00003 TABLE 3 Conversions and alcohol fractions in the aldehyde hydrogenation at varying temperatures Aldehyde conversion Alcohol fraction in the product [% by weight] stream [% by weight] Example 120° C. 140° C. 180° C. 120° C. 140° C. 180° C. Catalyst 2 92.1 93.9 97.4 64.8 65.0 64.3 Comparative catalyst A 95.6 96.0 98.2 68.0 66.2 65.5 Comparative catalyst B 92.5 96.3 97.5 69.3 71.1 70.2

[0098] It is clear from Table 3 that the catalyst of the invention achieves aldehyde conversions under comparable test conditions that correspond approximately to those of the commercial chromium-containing catalyst A. Similar behavior is also demonstrated for the formation of the corresponding alcohol. The catalyst of the invention is thus an environmentally friendly alternative to the chromium-containing catalysts used up to now.

[0099] The data additionally show that, although comparative catalyst B achieves comparable conversions and even significantly improved alcohol formation, its low physical stability makes it unsuitable for use over a relatively long period of time under the drastic conditions of the reaction.

[0100] Comparative catalyst C was likewise used in the same test. However, the catalyst particles disintegrated during the test, which meant it was not possible to make any meaningful statement regarding aldehyde conversions and selectivities.

[0101] Use example 3: Hydrogenation of a fatty acid, e.g. through esterification and subsequent hydrogenolysis (FAME)

[0102] A bed with a volume of 5 mL of inventive catalyst 2 was introduced into a reactor in the reduced and wet-stabilized form, after which 200 mL of methyl laurate having a water content of 0.062% by weight and an acid value of 0.351 mg.sub.KOH/g.sub.solution was metered in. The reactor was then sealed pressure-tight and heated to a temperature of 280° C. under a stream of nitrogen. A stream of water at a pressure of 175 bar was then fed through a valve into the reactor until the nitrogen had been completely displaced. Hydrogenation using the catalyst was then carried out by fluidizing the hydrogen in the reactor with the methyl laurate solution by means of a stirrer.

[0103] Samples of the solution were taken at regular intervals via an outlet valve and the constituents thereof analyzed by gas chromatography. Table 4 shows the resulting conversion values for methyl laurate, the selectivity, and the yield in respect of 1-dodecanol.

[0104] For comparison, a bed having a volume of 5 mL of comparative catalyst A was subjected to the same conditions, and the results obtained thereby are likewise shown in Table 4.

TABLE-US-00004 TABLE 4 Reaction data for the hydrogenation of methyl laurate Hours Example 1 2 3 4 5 6 Catalyst 2 Conversion 11.3 28.4 43.9 57.5 70.5 80.1 Selectivity 73 56.9 56.9 59.1 61.2 66.9 Yield 8.3 16.2 25 34 43.1 53.5 Comparative Conversion 5.5 13.1 31.4 31.5 40.6 47.7 catalyst A Selectivity 98.2 63.8 42.1 41.9 39.2 42.4 Yield 5.4 8.3 13.2 13.2 15.9 20.2