Molten Salt Nio Oxygen Carrier Partial Oxidation Of Methane To Syngas In The Pilot Study

The reaction of partial oxidation of methane(POM) to syngas before producing fuel and other chemical products has been one of the most promising natural gas utilization approaches. Currently, the synthesis gas is typically prepared through three routes: steam reforming with methane, POM and methane catalytic reforming with carbon dioxide. The ecommercialization of steam reforming has occurred. But there are some disadvantages: it will lead to large H₂/CO ratio, and need high energy consumption. POM in catalyst bed can avoid these disadvantages, but this way needs produce pure oxygen before reaction and it will lead to hot-spot in catalyst bed for it is exothermic reaction and the mixture of CH₄ and O₂ is explosive gas, which are danger for large industrial scale. POM to syngas by lattice oxygen in molten salt medium system is introduced for utilizing reaction heat and avoiding hot spots and explosion in catalyst bed.The principle and mechanism have been studied by TG, DAT, TPD and TPR. The results showed that the molten salt medium system of wt% of Na₂CO₃-K₂CO₃ being 1 to 1 is suitable for this technique, and the best reaction temperature is about 800°C. It is suggested that reactions of POM to syngas using oxygen carriers of NiO, CeO₂, Co₃O₄ and ZnO need different conditions by thermodynamics analysis. The NiO is responsible for POM in molten salts at 800°C.Conclusions of POM in catalyst bed: pure NiO as oxygen carrier, it can loss lattice oxygen to be Ni and the lattice oxygen can react with methane to syngas, carbon deposition and agglomeration were observed by SEM and TG analyses. The NiO oxygen carrier was prepared mixed with supports such as Al₂O₃ , MgO and SiO₂. It was found that the NiO/Al₂O₃ oxygen carrier among those investigated always possess better POM performances, giving higher conversion of CH4 and higher selectivity for CO and H₂, and lower CO₂ and coke formations. NiO/NiAl₂O₄ oxygen carrier prepared by coprecipitation method showed the best cycle performance. It showed that NiO/NiAl₂O₄ would renew lattice oxygen about 100%,methane conversion, H₂and CO selectivity were kept at 99.78%, 60% and 58.21% respectively.Conclusions of POM in molten salt: SEM-EDS analysis showed that NiOoxygen carrier distributed in molten salts unevenly. The added oxygen carrier and supports would affect stability of molten salts. Obvious interstice occurred in the middle of the molten salts by leading Methane. NiO oxygen carrier would lose lattice oxygen obviously. Substance composed of different quantities of elements would show different configuration. Aagglomeration was not observed in molten salts. After reacted with CH₄, Oxygen carrier NiO/Al₂O₃ would renew lattice oxygen by reacting with oxygen in air. Methane would react with lattice oxygen firstly. Decomposition of methane would be the primary reaction when lack of lattice oxygen. Carbon deposition would affect the stability of molten salts too. The best condition of experiment is wt% of NiO/ (NiO + Al₂O₃) being 10% and flux of methane being 10ml/min at 800°C. The volume content of H₂, CO and CO₂ were kept at 63.4%, 30.25% and 6.35% respectively.In conclusion, POM to Syngas by Lattice of oxygen carriers in molten salt is a feasible and outstanding technology. NiO is appropriate for POM to syngas by Lattice of oxygen carriers in Molten Salt of wt% of Na₂CO₃ and K₂CO₃ being 1 to 1.