Role of surface Ni and Ce species of Ni/CeO2 catalyst in CO2 methanation

Ni‐Ce/Zeolites for CO2 Hydrogenation to CH4: Effect of the Metal Incorporation Order

“…[44] This could be due to the reductiono ft he CeO 2 species, ap rocess happening at higher temperatures on unsupported cerium oxide.T his indicates that the reducibility of Ce is enhanced when supported on the USY zeolite, probably owing to the higher oxygen mobility. Additionally,i n the 5Ni/3Ce/Na-USY(3), where Ni was incorporated after Ce, [24] can be seen at low temperatures (200-300 8C), confirming the presenceo fN iO species interacting more strongly with the CeO 2 than with the zeolite. This multiplicity of reduction processes indicatest he presence of Ni and Ce oxide species interacting with the supports or even between them at different strengths.…”

“…In the case of the 3Ce/Na-USY(3) sample, am ain reductionp rocess occurs at approximately 460 8C, in agreement with the results reported for a similar sample in our former studies. Zhou et al [24] reported three reduction processes for NiO supported on CeO 2 catalyst at 250, 300,a nd 400 8C, attributed to highlyd ispersed NiO species over CeO 2 ,N iO species on the subsurface of the NiO/CeO 2 sample, and bulk NiO species, respectively.Considering that the reduction of NiO species located on the surfaceo ft he zeoliteso ccurs at 400-420 8Ci n all the Ni-Ce samples, the peaks found in those samples at 370-400 8Cc ould be related to the reduction of bulk NiO species weaklyi nteracting with the CeO 2 particles. [44] Concerning the three Ni-Ce samples, two reduction processes take place below 470 8Ca nd three above the pre-reductiont reatment.…”

“…For the 15Ni/Cs-USY(38) sample, one can verify that mainly two reduction process happen: one below 450 8Ca ttributed to the reductiono fN iO speciesl ocated on the external surface of the zeolite and the second one above 500 8Ca scribed to the reductiono ft he NiO speciesl ocated inside the zeolite mesopores and/or Ni 2 + ion-exchanged in the zeolite lattice. [24] In the range 370-420 8C, where reduction peaks attributed to NiO supported on CeO 2 and on the zeolite were found for the Na-USY(3) based samples, no possible distinction could be carried out for the Cs-USY(38) zeolite catalysts, probably owing to the higher metal contentst hat increaset he complexity of the reduction processes.A dditionally,t he sample where Ni was incorporated first presentsareduction process at about 750 8C, which could be attributed to the reduction of bulk CeO 2 .T he same peak cannotb ec learly seen in the co-impregnated sample, where a reduction processo ccurs at 600 8C, indicating that the CeO 2 speciescould be more dispersed in this sample. In addition, the sample prepared by introducing Ni beforeC e( 20Ce/15Ni/Cs-USY(38)) presentsm ainly ar eduction process at low temperature (below the pre-reductiont reatment temperature of about 470 8C), indicating that most NiO speciesw ill be reduced during the pre-treatment.F or the sample preparedb ys imultaneous impregnation, there will be, however,ahigherf raction of unreduced metal species.…”

“…[1][2][3][4][5][6] Ni and Ru-based materials have been commonly used for this reaction, on different supports, such as Al 2 O 3 , [7][8][9][10][11][12][13][14][15] SiO 2 , [16][17][18][19][20] Ce and Zr oxides, [21][22][23][24][25][26][27][28] hydrotalcites and hydrotalcite-derived materials, [21,[29][30][31][32] carbon nanotubes, [33][34][35][36][37] mesoporous materials, [38][39][40][41][42][43] and zeolites. [1][2][3][4][5][6] Ni and Ru-based materials have been commonly used for this reaction, on differen...…”

Supported Catalysts for CO2 Methanation: A Review

“…Ceria was also studied as a single support for efficient Ni catalysts in CO 2 methanation [81,[151][152][153][154], although its synergic effect with zirconia seems to increase the nickel performance.…”