Patent Application
20070282135
1.1 mol of isobuyraldehyde were stirred with 1 mol of formaldehyde in the form of a 40% strength solution and 4 mol % of trimethylamine, based on isobutyraldehyde, at 75° C. for 1 hour. The reaction solution was concentrated by distilling off low boilers such as isobutyraldehyde and part of the water at atmospheric pressure. The bottoms obtained comprised 75% by weight of hydroxypivalaldehyde, 20% by weight of water and about 5% by weight of other organic secondary components.
All percentages given under this subitem are, unless indicated otherwise, percentages by weight. The percentage compositions indicated are based on the oxidic constituents of the finished catalysts.
Starting materials were a 20% strength by weight sodium carbonate solution and an aqueous solution I comprising 2.67% by weight of Al and 5% by weight of Cu in the form of their nitrates.
In the precipitation, solution I and sodium carbonate solution were metered into a precipitation vessel at 80° C. in such a way that a pH of 5.6 was established. The precipitation mixture was transferred to a larger stirred vessel and was there brought to a pH of 7.9 at 80° C. by means of sodium carbonate solution. The suspension was then conveyed to a filter press.
The mixture was then filtered and washed with water until free of nitrate. The filter paste was suspended in water and dried in a spray drier by means of hot air at an outlet temperature of 130 -150° C. A calcination was subsequently carried out at a temperature of 375-390° C. The powder was subsequently tabletted together with 3% by weight of graphite as auxiliary to give pellets having dimensions of 5×5 mm. The pellets obtained were then calcined at a temperature of 600° C. for 60 minutes in a heated rotary tube.
The catalyst produced in this way comprised 55% of CuO and 45% by weight of Al2O3, had a specific surface area (BET) of 95 m2/g, an Hg porosity of 0.44 ml/g and a tapped density of 952 g/l.
205 g of this Cu/Al2O3 catalyst were activated by passing a mixture of 5% by volume of hydrogen and 95% by volume of nitrogen (total volume: 150 standard l/h) over the catalyst at 190° C. under atmospheric pressure for 24 hours in a tube reactor.
The mixture described above as hydrogenation feed served as starting solution. From 0 to 15% by weight (based on the hydrogenation feed) of a 15% strength by weight aqueous solution of trimethylamine were added to this mixture in order to set a pH of the hydrogenation output of greater than 8. The hydrogenation input obtained in this way was pumped over the catalyst at 37 bar and 105° C. in the dow now mode at a WHSV of 0.32 kgHPA/kgcat×h in a hydrogenation reactor having a liquid circuit (recycle:input=16:1) (hydrogen/hydroxypivalaldehyde molar ratio: about 1.5). A pH meter model 766 from Knick with a glass electrode N1041A from Schott was used for measuring the pH.
A mean conversion of 95.3% by weight at a mean pH of 8.8 was achieved over a number of days.
Example 1 was repeated under the conditions indicated but 1% of CO was mixed into the hydrogen.
The mean conversion at this setting was 70.0% by weight at a mean pH of 8.2.
The hydrogenation feed as described in example 1 was used.
The catalyst from example 1 was used.
The hydrogenation input was passed in the downflow mode at an H2 pressure of 37 bar through the reactor which was heated to 105° C. The WHSV was 0.32 kg of HPA/(kgcat*h). From 0 to 17% by weight (based on the hydrogenation feed) of a 50% strength by weight aqueous solution of trimethylamine were added to this mixture in order to set a pH of the hydrogenation output of greater than 8 (hydrogen/hydroxypivalaldehyde molar ratio: about 1.5). Part of the hydrogenation output was mixed back into the input (recycle mode). The ratio of recycle to input was 16:1. A mean conversion of 88.1% at a mean pH of 8.4 were achieved over a number of days.
Example 2 was repeated under the conditions indicated but 10% of CO2 was mixed into the hydrogen. Hydrogen/hydroxypivalaldehyde molar ratio: about 1.5.
To keep the H2 partial pressure constant, the plant pressure was increased to 41 bar. The mean conversion at this setting was 75.3% at a mean pH of 8.0.
The hydrogenation feed as described in example 1 was used.
The catalyst described in example 1 was used, but 3×3 mm pellets were produced.
The catalyst comprised 55% of CuO and 45% by weight of Ak2O3, had a specific surface area (BET) of 95 m2/g, an Hg porosity of 0.38 ml/g and a tapped density of 1042 g/l.
The hydrogenation input was passed through the reactor in the downflow mode at an H2 pressure of 40 bar. The temperature in the upper half of the reactor was 96° C., and that in the lower half was 106° C. The WHSV was 0.37 kg of HPA/(kgcat*h). Together with the liquid input, about 110 mol % of H2 (based on methyolalkanals used) were metered in, corresponding to a hydrogen/starting material molar ratio of 1:1. Part of the hydrogenation output was mixed back into the input (recycle mode). The ratio of recycle to input was 16:1. A mean conversion of 95.9% at a mean pH of 8.3 was achieved over a number of days.
Example 3 was repeated under the conditions indicated but the amount of hydrogen was doubled to a hydrogen/starting material molar ratio of 2.2 and the temperature was reduced to 93° C. in the upper half of the reactor and 103° C. in the lower half of the reactor. A mean conversion of 95.6% at a pH of 8.4 was achieved.
The hydrogenation feed was prepared as described in example 6 of PCT/WO 98/28253.
5.3 l of a Cu/TiO2 catalyst B of PCT/WO 02/85825 were activated by passing a mixture of 2.5% by volume of hydrogen and 97.5% by volume of nitrogen (total volume: 600 standard l/h) over the catalyst at 190° C. under atmospheric pressure for 144 hours in a tube reactor.
The mixture described above as hydrogenation feed served as starting solution. The hydrogenation input was passed through the reactor in the downflow mode at 110° C. and an H2 pressure of 90 bar. The WHSV was 0.2 kg of DMB/(Icat*h). Together with the liquid input, from 125 to 200 mol % of hydrogen (based on methyolalkanals) were fed in, corresponding to a hydrogen/methylolalkanal molar ratio of from 1.25 to 2.0. The plant pressure was kept constant at 90 bar (offgas mode). Part of the hydrogenation output was mixed back into the input (recycle mode). The ratio of recycle to feed was 6.5:1.
Table 1 shows the conversion over a period of 2112 hours and the amount of hydrogen metered in.
The analysis of the dimethylolbutanal content of the polyhydric alcohol obtained was carried out by means of gas chromatography (GC) on an HP5 column from J&W, injector: 280° C.; detection was effected by means of an FID (flame ionization detector).
It can clearly be seen that during the time periods during which only a small excess of hydrogen was used, a more rapid decrease in activity was observed than during periods with a large amount of offgas.
