Study on regeneration characteristics and dust deposition mechanism of nickel based tar-cracking catalyst

The catalysis and in-situ regeneration of 1.0%NiO/0.1%MgO-Al₂O₃ catalyst were investigated in an atmospheric fixed bed reactor, in which the dust was also introduced in the feed to simulate the real dust environment of coal and biomass pyrolysis. The results show that the catalyst has a higher activity but a shorter life as the reaction temperature increases. Cycle regeneration of the catalyst exhibits a good durability, while a significant hydrothermal deactivation phenomenon happens at the regeneration temperature of 800 ℃. As a result, the preferable regeneration temperature range of 600~700 ℃ and regeneration time of 20 min are determined. The increased ratio of air/steam will gradually change the specific surface area and pore structure of the catalyst. EPMA and XRD results show that the introduction of dust does not change the composition of catalyst except the introduction of MgO that will be converted to a new phase of (Mg_0.4Al_0.6)Al_1.8O₄. MgO plays a positive anti-carbon deposition role, while SiO₂ is reverse. The negative effect of SiO₂ on the activity of catalyst can be reduced by a lower operating gas velocity.