Heterogeneous catalyst synthesis and obtaining hydrogen rich gaseous product from tea waste by thermochemical processes

In this study, tea waste was gasified in an updraft gasifier in order to obtain H2 rich gaseous product using air and air+steam as gasifying agents. K2CO3 was used as a catalyst. Ni/Al2O3, Ni-CeO2/Al2O3 catalysts were synthesized by impregnation and sol-gel methods. Synthesized catalysts were characterized by XRD, XRF, SEM, BET and TGA techniques. The activity of catalysts was determined by performing gasification experiments of tea waste. Effect of parameters such as temperature (450, 650, 850°C), reaction time (10, 15, 20 min), catalyst ratio (0, 10, 20, 30, 40, 60% by weight), air flow rate (2, 3, 4 L/h), synthesis method and CeO2 loading (0-40%) on gaseous product yield and composition was investigated. Maximum H2 yield was achieved as 6.26 mol H2/kg tea waste at 850°C, 15 min, 20% catalyst ratio and 3 L/h air flow rate in the presence of Ni-CeO2/Al2O3 which was synthesized by sol-gel method and contained 40% CeO2 in air gasification, while this value equals to 3.54 mol H2/kg tea waste in the presence of K2CO3. When steam was added to gasifying medium, H2 yield reached at 48.76 and 29.71 mol H2/kg tea waste in the presence of K2CO3 and Ni-CeO2/Al2O3 catalysts, respectively. Tar yield was decreased by using Ni-CeO2/Al2O3 at 850°C from 9.14% to 4.46%. The liquid products obtained from the air gasification reactions were characterized by GC-MS. The liquid product was composed of mostly phenolic compounds and caffeine.