Hydrotalcite-precursor based catalyst with improved performance for LTS reaction
The present invention relates to a novel catalyst for LTS processes, the method of its preparation and LTS process by use of this catalyst.
1 . Catalyst for an LTS reaction, comprising an amorphous Cu—Zn—Al mixed oxide, wherein the catalyst is present as a tableted shaped body.
2 . Catalyst according to claim 1 , whereby it comprises domains of CuO, ZnO and a Zn spinel, as determined by Pair Distribution Function (PDF) analysis.
3 . Catalyst according to claim 1 , wherein the catalyst is present as a tableted shaped body with a side crush strength of from 40 to 250 N.
4 . Catalyst according to claim 1 , wherein the amount of Cu is in the range of from 30 to 50 mol-%, the amount of Zn is in the range of from 15 to 45 mol-%, and the amount of Al is in the range of from 15 to 50 mol-%, in relation to the overall amount of Cu, Zn and Al in the catalyst.
5 . Catalyst according to claim 1 , wherein the phase content in weight percent, as determined by PDF analysis, of CuO is in the range of from 10 to 20, of ZnO is in the range of from 1 to 10, and of the Zn spinel of gahnite structure is in the range of from 70 to 89.
6 . Process for the preparation of the catalyst according to claim 1 , comprising the following steps:
a) Providing an aqueous solution comprising solved Cu, Zn and Al compounds
b) Providing an aqueous solution comprising a carbonate and additionally an alkali metal hydroxide or alkaline earth metal hydroxide, having a pH value of 8 or higher
c) mixing the solution obtained in step a) and the carbonate solution and additionally an alkali metal hydroxide or alkaline earth metal hydroxide obtained in step b) to obtain a mixture comprising a precipitate of mixed Cu—Zn—Al hydroxide-carbonate
d) Ageing the mixture obtained after step c)
e) Separating the precipitate from the solution and optionally washing and/or drying the precipitate
f) Calcining the precipitate at a temperature in the range of from 200° C. to 600° C., for a duration in the range of from 15 minutes to 8 hours,
wherein the pH value after step c) is 8 or higher and wherein the precipitate after step f) is formed to obtain a shaped catalyst body in a step g).
7 . Process according to claim 6 , wherein the pH value after step c) lies within a range of from 8 to 9.