Metal-foam body and method for the production thereof and the use thereof as a catalyst
The invention relates to a method for producing a metal-foam body, comprising the steps of (a) providing a metal-foam body A, which consists of nickel, cobalt, copper, or alloys or combinations thereof, (b) applying an aluminum-containing material MP to metal-foam body A so as to obtain metal-foam body AX, (c) thermally treating of metal-foam body AX, with the exclusion of oxygen, to achieve the formation of an alloy between the metallic components of metal-foam body A and the aluminum-containing material MP so as to obtain metal-foam body B, wherein the duration of the thermal treatment is chosen in dependence on the temperature of the thermal treatment and the temperature of the thermal treatment is chosen in dependence on the thickness of the metal-foam body AX. The invention also relates to the metal-foam bodies obtainable by the methods according to the invention and to the use thereof as catalysts for chemical transformations.
1 . A process for producing a metal foam body, comprising the following steps:
(a) providing a metal foam body A made of nickel, cobalt, copper, alloys thereof or combinations thereof;
(b) applying an aluminum-containing material MP to metal foam body A so as to obtain metal foam body AX;
(c) treating metal foam body AX thermally, with exclusion of oxygen, in order to form an alloy between the metallic components of metal foam body A and the aluminum-containing material MP so as to obtain metal foam body B;
wherein the duration H of the thermal treatment (in minutes), depending on the temperature T of the thermal treatment (in ° C.), is chosen as follows:
H min <H<H max , wherein:
maximum duration H max =d1+(a1−d1)/(1+(T/c1){circumflex over ( )}b1); and
minimum duration H min =d2+(a2−d2)/(1+(T/c2){circumflex over ( )}b2);
wherein:
a1=366.1; b1=129.0; c1=650.9; d1=8.7;
a2=33.5; b2=235.5; c2=665.8; d2=1.8;
and wherein the metal foam body AX has a thickness D of 10-30 mm and the temperature T of the thermal treatment, depending on the thickness D of the metal foam body AX, is chosen as follows:
when D=10 mm, 600° C.<T≤680° C.;
when 10 mm<D≤20 mm, 600° C.<T≤675° C.;
when 20 mm<D≤30 mm, 600° C.<T≤665° C.
2 . The process of claim 1 , wherein the aluminum-containing material MP is an aluminum-containing powder, and an organic binder is applied to metal foam body A together with, or before, the aluminum-containing powder.
3 . The process of claim 1 wherein metal foam body A consists of nickel.
4 . The process of claim 1 , wherein metal foam body A has an apparent density in the range of from 100 to 1500 kg/m 3 .
5 . The process of claim 1 , wherein metal foam body A has a specific BET surface area of 100 to 20 000 m 2 /m 3 .
6 . The process of claim 1 , wherein metal foam body A has a porosity of 0.50 to 0.95.
7 . The process of claim 1 , wherein the aluminum-containing material MP in step (b) contains metallic aluminum in an amount of 80% to 100% by weight.
8 . The process of claim 1 , wherein the aluminum-containing material MP is a powder composed of particles, 95% of which have a diameter in the range from 5 to 75 μm.
9 . The process of claim 1 , further comprising the following step:
(d) activating the metal foam body B by treatment with a leaching agent.
10 . The process of claim 9 , wherein the treatment of the metal foam body B with leaching agent is performed for a period of 5 minutes to 8 hours at a temperature of 20 to 120° C., and wherein the leaching agent is an aqueous NaOH solution having an NaOH concentration of 2% to 30% by weight.
11 . The process of claim 9 , further comprising the following step:
(e) post-doping the activated metal foam body B with a promoter element selected from the group consisting of: Mo, Pt, Pd, Rh, Ru, Cu and mixtures thereof.
12 . The process of claim 1 , wherein metal foam body A has an apparent density of 300 to 600 kg/m 3 .
13 . The process of claim 12 , wherein metal foam body A has a specific BET surface area of 1000 to 6000 m 2 /m 3 .
14 . The process of claim 13 , wherein metal foam body A has a porosity of 0.50 to 0.95.
15 . The process of claim 14 , wherein the aluminum-containing material MP in step (b) contains metallic aluminum in an amount of 90% to 99.5% by weight.
16 . The process of claim 15 , wherein the aluminum-containing material MP is a powder composed of particles, 95% of which have a diameter in the range from 5 to 75 μm.
17 . The process of claim 16 , further comprising the following step:
(d) activating the metal foam body B by treatment with a leaching agent.
18 . The process of claim 17 , wherein treatment of the metal foam body B with leaching agent is performed for a period of 5 minutes to 8 hours at a temperature of 20 to 120° C., and wherein the leaching agent is an aqueous NaOH solution having an NaOH concentration of 2% to 30% by weight.
19 . The process of claim 1 , wherein the thermal treatment of step c) takes place in a belt furnace and wherein during thermal treatment, the temperature is first increased from room temperature to about 300 to 350° C. and this temperature is maintained for a period of about 2 to 30 minutes to remove moisture and organic constituents from the coating.
20 . The process of claim 19 , wherein, after the alloy formation, the metal foam body is cooled to a temperature below 200° C., wherein cooling is achieved in a cooling zone of the furnace.