Biogenic hydroxyapatite as novel catalytic support for Ni and Cu for the water–gas shift reaction

Biogenic hydroxyapatite (NHAp) was prepared by calcination of waste pork bones and investigated as catalytic support for Ni and Cu metals in the water–gas shift (WGS) reaction. Part of the doped Cu was ion exchanged with Ca ions in the NHAp structure. Also, XPS data showed that after Cu doping, nickel d-hole density increased due to adjacent Cu atoms. Upon reduction, Ni–Cu alloying was detected. For an ideal mixture (CO/H 2 O: 1/2 in vol%), the monometallic Cu assay was WGS inactive, whereas 10Ni/NHAp was the most active. However, under reformer outlet stream conditions (CO/H 2 O/CO 2 /H 2 /He = 5/46/4/31/14, in vol%), the catalyst 10Ni/NHAp showed negative H 2 yield (net hydrogen consumption), whereas selectivity and yield to H 2 by Cu-doped bimetallic catalysts reached up to 93% and 26%, respectively. Interestingly, the band-gap energy of these catalysts decreased in line with methane suppression capability (10Ni/NHAp ≫ 7.5Ni2.5Cu/NHAp > 2.5Ni2.5Cu/NHAp > 10Cu/NHAp). Long duration catalytic tests revealed that NHAp derived from pork bone can provide good stability for the WGS reaction, with negligible carbon deposition. Graphical abstract