Supported noble metal catalyst and process for preparing the same in situ

A process for preparing in situ a supported noble metal catalyst having a composition represented by the general formula:

• Me-LDHs-Al2O3 (I)
• wherein Me is a noble metal as the active component of the catalyst, and is Ru, Rh, Pd or Pt, the noble metal element particle in the catalyst has a particle size of 10 to 60 nm, with an even and stable dispersion on or between slabs of hydrotalcite (LDHs), and the hydrotalcite is grown in situ on the surface of an Al2O3 carrier, the process consisting of the steps of:
• A) dissolving a soluble noble metal salt precursor in a solvent to prepare a noble metal salt solution with a concentration of 0.004 to 0.01 mol/L, wherein the anion in the solution is NO3−, Cl−, CH3COO− or C5H7O2− and the solvent is deionized water, ethanol, or toluene;
• B) dissolving a soluble divalent metal salt in deionized water to prepare a divalent metal salt solution in a concentration of 0.02 to 0.08 mol/L, wherein the divalent metal M2+ is one or more of Mg2+, Zn2+, Ni2+, Co2+, Cu2+ and Mn2+, and the anion in the salt solution is one or more of Cl−, NO3−, SO42− and CO32−;
• C) adding hexamethylenetetramine to the divalent metal salt solution prepared in the step B), and stirring to reach a sufficient dissolution while the temperature of the solution is maintained at 0 to 10° C., followed by adding thereto the noble metal salt solution prepared in the step A) and stirring well to obtain a mixed solution, wherein the molar ratio of M2+ to hexamethylenetetramine is 1:3 to 1:28, and the molar ratio of the noble metal to M2+ is 0.15:100 to 7.5:100;
• D) adding the Al2O3 carrier to the mixed solution as above according to a theoretcial supported amount of 0.01 to 5% of the noble metal Me on the Al2O3 carrier, subjecting the resulting material to crystallization for 1 to 6 hours at 130° C. to 180° C., discharging, washing the solid product with deionized water until the pH value of the washings becomes 7 to 8, and subsequently performing a drying for 8 to 24 hours at 30° C. to 90° C., to obtain Me-LDHs-Al2O3.