Tar steam reforming for synthesis gas production over Ni-based on ceria/zirconia and La0.3Sr0.7Co0.7Fe0.3O3 in a packed-bed reactor.

In this work, NiO level was varied from 5 to 40% whereas CexZr1-xO2 (x = 0.5, 0.7 and 0.9) (CZO) and La0.3Sr0.7Co0.7Fe0.3O3 (LSCF) were chosen as two different kinds of support. Regardless the type of support, the surface NiO (at 40%) was completely reduced at 600 °C, giving the amount of activated Ni at 8950 μmol/gcat. The reducibility of the updoped LSCF was found to be much better than that of the undoped CZO, evidenced by the H2-TPR of the both materials at 600 °C where the oxygen storage capacity (OSC) of LSCF and CZO was determined at 4273 and 307 μmol/gcat, respectively. In contrast, the OSC of 40%Ni-CZO (where x = 0.7, 0.9) was found to be higher than that of the LSCF, implying that the addition of Ni more enhanced both electronic defect and oxygen mobility in CZO than in LSCF, according to the H2-TPR results. Coke resistant of CZO is presumable more satisfying than that of LSCF, thus, the longer lifespan of the CZO catalyst system is expected. The catalytic performance of 40%Ni-CZO (x = 0.9) was however comparable with 40%Ni-LSCF as they accommodate the same number of active sites. The slightly better catalytic performance of the 40%Ni-CZO (x = 0.9) could be due to its smaller crystallite size (CZO = 26.83, LSCF = 35.73), rendering more access for the relative gaseous reactants. The best catalyst amongst all was 5%Ni-CZO (x = 0.9), giving 89% toluene conversion, 46% H2 yield, 71% CO selectivity, and 25% CO2 selectivity at optimum reaction temperature of 700 °C.