Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
2002-01-31
2004-01-20
Nguyen, Cam N. (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
C502S259000
Reexamination Certificate
active
06680280
ABSTRACT:
DESCRIPTION
The invention relates to a catalyst which can be used in particular for the hydrogenation of nitro groups in nitroaromatics to form the corresponding amines in the presence of water, and to a process for its production.
The catalytic hydrogenation of nitroaromatics is known. The hydrogenation reactions are generally carried out both in a fixed-bed reactor and in a batch reactor. On an industrial scale, it is most usual to carry out hydrogenation reactions in the liquid phase with a suspended catalyst, the processes differing with regard to the reaction temperature, the pressure, the catalyst, the solvents and the way in which the reaction is carried out. The catalysts used are various catalyst systems, such as for example nickel-containing catalysts. For example, JP 551 33 33 describes the hydrogenation of 2,4-dinitrotoluene and 2,6-dinitrotoluene in the presence of the catalysts Pd/C, Raney nickel, Raney cobalt and/or platinum black.
EP A 98 681 has disclosed a nickel-kieselguhr supported catalyst for the hydrogenation of dinitrobenzophenone to form the corresponding diamine.
DE-A 3 537 247 describes the hydrogenation of dinitro compounds to form the diamines in the presence of modified Raney nickel catalysts.
DD 152 065 discloses the use of a nickel-SiO
2
catalyst with a special particle size distribution for the hydrogenation of nitro compounds.
EP-A 0 335 222 discloses the use of nickel-Al
2
O
3
/ZrO
2
supported catalysts for the hydrogenation of nitrites, aromatics, nitro compounds and olefins. This document discloses, inter alia, the simultaneous precipitation of nickel, zirconium and aluminum on supports at 50 to 1200° C. and at a pH of 7.3 to 9.0, activated carbon, Al
2
O
3
, SiO
2
, kieselguhr and others being used as the supports.
SU patent 28 31 85 discloses nickel-Al
2
O
3
/ZrO
2
catalysts which have been produced by the precipitation of nickel and Al
2
O
3
on ZrO
2
.
According to the teaching of U.S. Pat. No. 2,564,331, a nickel-ZrO
2
catalyst is produced by precipitation of a nickel and zirconyl carbonate mixture with subsequent washing, drying and reduction at 250 to 3500° C., the catalyst containing at most 10% by mass of ZrO
2
.
DE-B 1 257 753 discloses the precipitation of insoluble carbonates, the precipitation operation being initiated by evaporation of CO
2
and NH
3
out of a mixed salt solution of ammonium zirconyl carbonate and nickel amine carbonate.
EP-A 0 672 452 has disclosed catalysts for the hydrogenation of organic compounds which substantially contain 65 to 80% by mass of nickel, calculated as NiO, 10 to 25% by mass of SiO
2
, 2 to 10% by mass of zirconium, calculated as ZrO
2
, and 0 to 10% by mass of aluminum, calculated as Al
2
O
3
, the sum of the SiO
2
content and of the Al
2
O
3
content being at least 15% by mass. These catalysts are produced by adding an acidic aqueous solution of Ni, Zr and, if desired, aluminum compounds to a basic aqueous solution or suspension of silicon compounds and, if desired, aluminum compounds. During the precipitation, the pH is initially reduced to 4.0 to 6.5 and is then set at 7 to 8. The precipitated product is dried, calcined and shaped.
The nickel hydrogenation catalysts which have been revealed hitherto all have the drawback that rapid aging of the catalysts takes place under the hydrothermal reaction conditions of the hydrogenation of nitroaromatics.
The technical problem on which the present invention is based is therefore that of providing nickel-containing supported catalysts which have a longer service life than the conventional catalysts in particular under the hydrothermal reaction conditions of the hydrogenation of nitroaromatics.
According to the invention, this problem is solved by the fact that a catalyst, in particular for the hydrogenation of nitro groups in nitroaromatics to form the corresponding amines in the presence of water, containing nickel on a support is provided, the catalyst being reduced and stabilized and having nickel crystallites with a bimodal nickel crystallite size distribution, a nickel content of from 60, in particular 61% by mass to 80% by mass (based on the total mass of the catalyst) and a degree of reduction of at least 70%. The degree of reduction is determined after further reduction of the stabilized catalyst for one hour at 100° C.
In a particularly preferred embodiment, the invention provides for the above-mentioned catalyst to have a bimodal nickel crystallite size distribution, the two maxima of the nickel crystallite size distribution lying at 30 to 80 Angstrom and 81 to 150 Angstrom. In a further particularly preferred embodiment, the invention provides for the proportion of nickel with a maximum of the nickel crystallite size distribution at 30 to 80 Angstrom to be≧40% (based on the total mass of the catalyst) . The proportion of metallic nickel with crystallites with a size of 30 to 80 Angstrom is therefore≧40% (based on the total mass of the catalyst).
In a further preferred embodiment, it is provided that the above-mentioned catalyst is supported on a zirconium-containing support, preferably contains or consists of ZrO
2
, ZrO
2
HfO
2
, SiO
2
.ZrO
2
, SiO
2
.ZrO
2
HfO
2
or mixtures of at least two of these substances.
In a particularly preferred embodiment, the SiO
2
content is 0 to 20% by mass (based on the total mass of the catalyst). In a further preferred embodiment, the ZrO
2
content is 20 to 40% by mass (based on the total mass of the catalyst). In a further preferred embodiment, the HfO
2
content is 0 to 4% by mass (based on the total mass of the catalyst).
In a particularly preferred embodiment of the invention, the reduced and stabilized catalysts may be used as powders with grain sizes of from 1 to 100 &mgr;m, preferably from 2 to 25 &mgr;m. Naturally, compacts can also be used.
The catalysts according to the invention are advantageously and surprisingly distinguished by their service life, which is longer than that of conventional catalysts while achieving a catalytic activity which is identical or better. Catalysts with the bimodal nickel crystallite size distribution according to the invention have a considerably longer service life than conventional catalysts, in particular under hydrothermal reaction conditions.
In the context of the present invention, the term bimodal nickel crystallite size distribution is understood as meaning a distribution of the nickel crystallites in which there are two maxima of the crystallite size distribution which can be clearly distinguished from one another.
In the context of the present invention, the term degree of reduction is understood as meaning the proportion of metallic nickel in the total nickel content of the catalyst in % after further reduction of the stabilized catalyst for one hour at 1000° C.
In a further embodiment, the invention also relates to a process for producing the above-mentioned catalyst. The invention therefore also relates to a process for producing a nickel-containing supported catalyst, in particular a catalyst for the hydrogenation of nitro groups in nitroaromatics to form the corresponding amines in the presence of water, in which, by precipitation from a solution which contains Ni
2+
and Zr
4+
with a basic solution, in particular a solution of NaOH, NaHCO
3
or Na
2
Co
3
or a mixture of at least two of these substances, to a pH of 8 to 9, a precipitated product is obtained which is calcined at temperatures of from 250° C. to 650° C., is then rendered inert if appropriate, and is then reduced with hydrogen at temperatures of from 250° C. to 555° C., in particular 300° C. to 550° C., if appropriate rendered inert and then stabilized.
In a particularly preferred embodiment, the solution which contains Ni
2+
and Zr
4+
additionally contains Hf
4+
. In a further preferred embodiment, the solution which contains Ni
2+
and Zr
4+
or the solution which contains Ni
2+
and Zr
4+
/Hf
4+
also contains silicon dioxide SiO
2
, preferably in suspended form. In a preferred embodiment, it is possible for the
Birke Peter
Geyer Reinhard
Kraak Peter
Schödel Rainer
Kataleuna GmbH Catalysts
Nguyen Cam N.
Ostrolenk Faber Gerb & Soffen, LLP
LandOfFree
Hydrogenating catalyst containing nickel and method for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hydrogenating catalyst containing nickel and method for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hydrogenating catalyst containing nickel and method for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3218364