CHROMIUM-FREE HYDROGENATION CATALYST HAVING INCREASED WATER AND ACID STABILITY

Abstract

The present invention relates to an improved catalyst on the basis of a shaped catalyst body for hydrogenating carbonyl groups in organic compounds under the effect of acids and water, characterized in that the shaped catalyst body contains copper in an amount of 17.5 to 34.5 wt. %, relative to the shaped catalyst body and the copper is present in the shaped catalyst body to at least 70% in the form of a copper spinel CuAl.sub.2O.sub.4. The invention also relates to the production of the catalyst an to the use of same in the hydrogenation of carbonyl groups in organic compounds in the presence of acids and/or water.

Claims

1. A Cu—Al shaped catalyst body, characterized in that the shaped catalyst body contains copper in a proportion by weight from 17.5% to 34.5% based on the total weight of the shaped catalyst body after loss on ignition, and in which the copper is present in the form of a copper spinel CuAl.sub.2O.sub.4 to an extent of at least 70%, preferably within a range from 70% to 98%, more preferably within a range from 70% to 95%, even more preferably within a range from 75% to 90%, most preferably within a range from 80% to 90%.

2. The shaped catalyst body as claimed in claim 1, wherein the copper is present in a proportion by weight from 25.0% to 34.5%, preferably from 27.5% to 31%, based on the total weight of the shaped catalyst body after loss on ignition.

3. The shaped catalyst body as claimed in claim 1, wherein the shaped catalyst body is in tablet form.

4. The shaped catalyst body as claimed in claim 1, wherein the side crush strength is 80 to 300 N, preferably 150 to 250 N, more preferably 170 to 230 N.

5. The shaped catalyst body as claimed in claim 1, which contains Al in an amount within a range from 21.2% by weight, preferably 21.8% by weight, more preferably 24.9% by weight, more preferably 29.0% by weight, even more preferably 29.5% by weight, most preferably 30.1% by weight, to 38.3% by weight, preferably 36.9% by weight, more preferably 36.7% by weight, more preferably 36.4% by weight, particularly preferably 35.1% by weight, most preferably 34.7% by weight, based on the total weight of the shaped catalyst body after loss on ignition.

6. The shaped catalyst body as claimed in claim 1, wherein the Cu/Al.sub.2 atomic ratio in the shaped catalyst body is less than 1, preferably less than 0.97, more preferably less than 0.94.

7. The shaped catalyst body as claimed in claim 6, wherein the Cu/Al.sub.2 atomic ratio is greater than 0.49 and less than 1, preferably greater than 0.57 and less than 0.97, more preferably greater than 0.58 and less than 0.94, particularly preferably greater than 0.79 and less than 0.94.

8. The shaped catalyst body as claimed in claim 1, wherein the side crush strength is within a range from 80 to 300 N, preferably within a range from 150 to 250 N, more preferably within a range from 170 to 230 N.

9. The shaped catalyst body as claimed in claim 1, wherein the specific BET surface area is within a range from 20 to 150 m.sup.2/g, preferably within a range from 70 to 120 m.sup.2/g.

10. A process for preparing a shaped catalyst body as claimed in claim 1 containing copper in a proportion by weight from 17.5% to 34.5%, preferably from 25.0% to 34.5%, most preferably from 27.5% to 31%, based on the shaped catalyst body after loss on ignition, comprising the following steps: a) combining (i) at least one aqueous solution A of copper compounds, aluminum compounds, and optionally transition metal compounds and (ii) at least one aqueous alkaline solution B to form a precipitate, wherein solution A and/or solution B additionally comprises 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, e) shaping the calcined precipitate from step d) to obtain a shaped body.

11. The process as claimed in claim 10, wherein the shaped body obtained from step e) is subjected in a step f) to thermal treatment at a temperature of between 200 and 800° C. for a period of between 30 min and 4 h, preferably of between 400 and 700° C. for a period of between 1 h and 3 h.

12. The process as claimed in claim 10, wherein the shaping in step e) is carried out with a binder.

13. The process as claimed in claim 10, wherein step f) is followed by reduction of the shaped body.

14. A process for hydrogenating carbonyl groups in organic compounds with the shaped catalyst body as claimed in any of claim 1 to 9 or prepared by a process as claimed in any of claim 10 to 13.

15. The process as claimed in claim 14 for hydrogenating oxo aldehydes to oxo alcohols.

Description

EXAMPLES

[0062] The loss on ignition in the context of the present invention was determined in accordance with DIN 51081 by determining the weight of about 1-2 g of a sample of the material to be analyzed and then heating it to 900° C. under ambient atmosphere and storing it at this temperature for 3 h. 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.

[0063] 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.

[0064] Chemical elements were determined by ICP (inductively coupled plasma) measurement in accordance with DIN EN ISO 11885.

[0065] The acid value was determined by mixing about 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]$\mathrm{AV}=\frac{\mathrm{Volume}\mathrm{consumed}*c*M}{\mathrm{Sample}\mathrm{weight}}=\mathrm{mg}\mathrm{KOH}/g\mathrm{sample}$

[0066] 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.

[0067] Specific BET surface areas were determined by nitrogen adsorption in accordance with DIN 66131.

[0068] 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.

[0069] The proportion by weight of copper spinel CuAl.sub.2O.sub.4 in the shaped catalyst body and the crystallite size of the copper were determined by X-ray diffractometry and Rietveld refinement.

[0070] This was done by analyzing the sample in a Bruker D4 Endeavor over a range from 5 to 90° 20 (step sequence 0.020° 2Θ, 1.5 seconds measurement time per step). The radiation used was CuKα1 radiation (wavelength 1.54060 Å, 40 kV, 35 mA). During the measurement, the sample stage was rotated about its axis at a speed of 30 revolutions/min. The resulting diffractogram of the reflection intensities was quantitatively calculated by means of Rietveld refinement and the proportion of copper spinel CuAl.sub.2O.sub.4 in the sample was determined. The proportion of the respective crystal phases was determined using the TOPAS software, version 6, from Bruker. The crystallite size of the copper was calculated by the software using the Scherrer formula on the basis of the reflection at 43.3°2Θ.

Example 1: Preparation of the Reference Powder

[0071] An aqueous solution 1 was prepared by adding 4482 g of Cu(NO.sub.3).sub.2.Math.2.5H.sub.2O to 3000 mL of demineralized water. The mixture was then mixed with 3000 mL of nitric acid (65% by weight HNO.sub.3). The acidic solution was made up to a total volume of 23 300 mL with demineralized water. The pH of the solution was −0.20. The solution was then heated to 80° C.

[0072] In addition, 1600 g of Na2CO.sub.3 and 4625 g of NaAlO.sub.2 were dissolved in 26 670 mL of demineralized water; the pH of the solution was 12.43.

[0073] 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 and the carbonate-containing solution. The dosing rate was adjusted such that the precipitation solution had a pH of approx. 6.5.

[0074] 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. The filter cake was then resuspended in 8000 mL of demineralized water and dried.

[0075] The spray-dried powder was then calcined at 750° C. for 2 h.

[0076] The relative proportions by weight were Cu=30% by weight and Al=30% by weight, based on the total mass after loss on ignition.

Example 2: Preparation of Inventive Catalyst 1

[0077] 1529 g of the calcined powder obtained in example 1 was combined with 36 g of Pural SCF binder, 5 g of demineralized water, and 31 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 450° C. for 2 h. The bulk density of the tablets thus obtained was 1111 g/I, the side crush strength of the tablets was 198 N. 84% of the copper present in the shaped catalyst body was in the form of copper spinel CuAl.sub.2O.sub.4. The crystallite size of the copper in the shaped body after reduction was 9.5 nm. The pore volume was 314 mm.sup.3/g, the BET specific surface area was 103 m.sup.2/g.

Example 3: Preparation of Inventive Catalyst 2

[0078] For the preparation of inventive catalyst 2, 360 g of the calcined powder obtained in example 1 was combined with 7.2 g of graphite and mixed for 10 minutes, affording 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 450° C. for 2 h. The side crush strength of the tablets was 155 N.

Comparative Example 1 (Catalyst A)

[0079] 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.

Comparative Example 2 (Catalyst B)

[0080] 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.3O.Math.9H.sub.2O in 9000 g of distilled H2O. Solution 2 was prepared by dissolving 1720 g of Na2CO.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 in the tablets 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.

[0081] 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, Zr=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 (Catalyst C)

[0082] The powder for catalyst C was prepared in accordance with the method for preparing the powder for catalyst B, except that 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.

[0083] A portion of the material obtained after tableting of comparative catalysts A, B, and C and of inventive catalyst 1 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 N2 at a temperature of 200° C. in order to bring about reduction of the Cu present in the oxidic state. 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

[0084] For the inventive catalyst 1 and the comparative catalysts A, B and C, the acid stability was in each case determined by combining a quantity of tableted, reduced, and stabilized samples totaling 25 g with a liquid mixture composed of 75 g of an oxo aldehyde 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 separated from the liquid mixture at the end of the test. Its side crush strength was then immediately measured.

[0085] After performance of the test, the oxo aldehyde solution was analyzed for the presence of Cu, Al, Cr, and Mn.

TABLE-US-00001 TABLE 1 Side crush strength after Side crush strength after Example reduction [N] acid/water treatment [N] Catalyst 1 137 119 Comparative catalyst A 97 86 Comparative catalyst B 93 74 Comparative catalyst C 47 not measurable, because the sample material had fractured

[0086] Table 1 shows clearly that the side crush strength of the inventive catalyst after reduction is already higher than that of the catalysts known from the prior art. The increased stability to acid and water is demonstrated even more clearly by the side crush strength values at the end of the test. The inventive catalyst still has the highest value for side crush strength here, whereas by contrast the tablets of the chromium-free CuAlMn catalyst fractured during the test and no meaningful measurement of the side crush strength was possible.

TABLE-US-00002 TABLE 2 Concentration of metals in test solution after test [ppm] Example Cu Al Cr Mn Catalyst 1 8 29 — — Comparative catalyst A 12 — 70 — Comparative catalyst B 64 43 — 5510 Comparative catalyst C 69 116 — 31

[0087] The data from Table 2 show that the inventive catalyst is largely stable to a loss of copper species under the severe test conditions, whereas this is markedly higher for the comparative catalysts. Overall, the catalyst of the invention has a low total loss of metals compared to the comparative catalysts.

Use Example 2: Hydrogenation of Oxo Aldehydes to Oxo Alcohols

[0088] A bed with a volume of 100 mL of inventive catalyst 1 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 chosen for each temperature. A liquid phase containing 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.

[0089] 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.

[0090] For comparison, a sample of comparative catalyst A and a sample of comparative catalyst B were subjected to the same conditions and the results obtained are likewise shown in Table 3.

TABLE-US-00003 TABLE 3 Alcohol fraction in Aldehyde conversion the product stream [% by weight] [% by weight] Example 120° C. 140° C. 180° C. 120° C. 140° C. 180° C. Catalyst 1 91.8 95.2 96.1 65.2 66.1 65.7 Comparative 95.6 96.0 98.2 68.0 66.2 65.5 catalyst A Comparative 92.5 96.3 97.5 69.3 71.1 70.2 catalyst B

[0091] It is clear from Table 3 that inventive catalyst 1 achieves aldehyde conversions under comparable test conditions that correspond roughly 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.

[0092] 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 prolonged period of time under the severe conditions of the reaction.