Hydrogen production from methane via chemical looping reforming on NiO/CeO2  Apichaya Yahom1, Varong Pavarajarn2, Patiwat Onbhuddha3, Sumittra Charojrochkul3, Suttichai Assabumrungrat1 *   1 Center of Excellence in Catalysis and Catalytic Reaction Engineering, Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Pathumwan, Bangkok, 10330 Thailand 2 Center of Excellence in Particle Technology (CEPT), Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Pathumwan, Bangkok, 10330 Thailand 3 National Metal and Materials Technology Center (MTEC), 114 Paholyothin Road, Klong 1, Klongluang, Pathumthani, 12120 Thailand *E-mail: Suttichai.A@chula.ac.th

Outline Hydrogen production Chemical looping reforming Metal oxides and supports Carbon dioxide sorption Objectives Experimental Results and discussion Conclusions Acknowledgements

Hydrogen production Steam reforming CH4 + H2O CO + 3H2 ΔH298K = 206.1 kJ/mol CO + H2O CO2 + H2 ΔH298K = -41.2 kJ/mol Highly endothermic Partial oxidation CH4 + 1/2O2 CO + 2H2 ΔH298K = -35.7 kJ/mol Exothermic but less hydrogen

Hydrogen production Autothermal reforming CH4 + H2O CO + 3H2 ΔH298K = 206.1 kJ/mol CO + H2O CO2 + H2 ΔH298K = 206.1 kJ/mol CH4 + 1/2O2 CO + 2H2 ΔH298K = -35.7 kJ/mol Combined steam reforming with partial oxidation to need less energy for hydrogen production

Chemical looping reforming Like autothermal reforming But has two reactors which air (oxygen) does not contact directly with methane that this process does not need energy for separating gas.

Chemical looping reforming H2, CO, CO2 N2 Fuel Reactor (Reducer) Me Air Reactor (Oxidizer) MeO Fuel, H2O Air (O2,N2)

Metal oxides and supports NiO is the most popular oxygen carrier (metal oxide) because of its high reactivity and oxygen transport capacity[1,2]. Support of oxygen carrier is the important factor to boost the reactivity. [1] N.V. Gnanapragasam, B.V. Reddy, M.A. Rosen. Hydrogen production from coal using coal direct chemical looping and syngas chemical looping combustion systems: Assessment of system operation and resource requirements. International journal of hydrogen energy 2009;34: 2606-2615. [2] Alberto Abad, Juan Adánez, Francisco García-Labiano, Luis F. de Diego, Pilar Gayán, Javier Celaya. Mapping of the range of operational conditions for Cu-, Fe-, and Ni-based oxygen carriers in chemical-looping combustion. Chemical Engineering Science 2007;62:533-549.

Metal oxides and supports Alumina support (Al2O3) is often used because it is low cost and has less tendency to agglomeration. However, solids for chemical looping should be used many times, and one of problems is carbon formation on solids that deactivates the oxygen carriers[3]. [3] Meng Ni, Dennis Y.C. Leung, Michael K.H. Leung. A review on reforming bio-ethanol for hydrogen production. International Journal of Hydrogen Energy 2007;32:3238-3247.

Metal oxides and supports Ceria support (CeO2) is famous in high oxygen storage that will release carbon on solid easier[4]. [4] A. Iriondo, V.L. Barrio, J.F. Cambra, P.L. Arias, M.B. Guemez, M.C. Sanchez-Sanchez, R.M. Navarro, J.L.G. Fierro. Glycerol steam reforming over Ni catalysts supported on ceria and ceria-promoted alumina. International journal of hydrogen energy 2010;35:11622-11633.

Carbon dioxide sorption CaO increases hydrogen purity and makes methane conversion higher because CO2 which is adsorbed allows equilibrium of the reactions shifted[5]. [5] Shiyi Chen, Dong Wang, Zhipeng Xue, Xiaoyan Sun, Wenguo Xiang. Calcium looping gasification for high concentration hydrogen production with CO2 capture in a novel compact fluidized bed: Simulation and operation requirements. International journal of hydrogen energy 2011;36:4887-4899.

Objectives Extend life of solid (metal oxide) used in chemical looping reforming. Produce more purity of hydrogen by using CO2 sorbent.

Total flow = 50 ml/min @ 600oC, 1 bar Experimental H2O = 6 ml/min CH4 = 3 ml/min Total flow = 50 ml/min @ 600oC, 1 bar Carrier gas 21 vol% Fixed bed reactor

Experimental No sorption : 1 g NiO/Al2O3 + 1 g SiC 1 g NiO/CeO2 + 1 g SiC Sorption : 1 g NiO/Al2O3 + 1 g CaO 1 g NiO/CeO2 + 1 g CaO

Results and discussion Reduction Oxidation

Chemical looping reforming H2, CO, CO2 N2 Fuel Reactor (Reducer) Me Air Reactor (Oxidizer) MeO Fuel, H2O Air (O2,N2)

Reactions in reduction reactors R1 : CH4 + 4NiO CO2 +2H2O+4Ni ΔH298K = 174.9 kJ/mol R2 : CH4 + NiO CO +2H2+Ni ΔH298K = 208.6 kJ/mol R3 : CH4 + 2NiO CO2 +2H2+2Ni ΔH298K = 169.9 kJ/mol R4 : CH4 + H2O CO + 3H2 ΔH298K = 206.1 kJ/mol R5 : CH4 + CO2 2CO + 2H2 ΔH298K = 357.8 kJ/mol R6 : H2O + CO CO2 + H2 ΔH298K = -41.2 kJ/mol In case of using CaO: R7 : CaO + CO2 CaCO3 ΔH298K = -178.8 kJ/mol

Reduction 1 g NiO/Al2O3 + 1 g SiC H2 = 60.8 %

Reduction 1 g NiO/CeO2 + 1 g SiC H2 = 65.7 %

Reduction 1 g NiO/Al2O3 + 1 g CaO H2 = 65.45 %

Reduction 1 g NiO/CeO2 + 1 g CaO H2 = 72.36 %

Chemical looping reforming H2, CO, CO2 N2 Fuel Reactor (Reducer) Me Air Reactor (Oxidizer) MeO Fuel, H2O Air (O2,N2)

Reactions in oxidation reactors R8 : Ni + ½O2 NiO ΔH298K = -244.3 kJ/mol In case of using CaO R7 : CaO + CO2 CaCO3 ΔH298K = -178.8 kJ/mol

Oxidation 1 g NiO/Al2O3 + 1 g SiC

Oxidation 1 g NiO/CeO2 + 1 g SiC

Oxidation 1 g NiO/Al2O3 + 1 g CaO

Reduction 1 g NiO/CeO2 + 1 g CaO

Results and discussion solids maximum hydrogen purity (percent) NiO/Al2O3 + SiC 60.8 NiO/CeO2 + SiC 65.7 NiO/Al2O3 +CaO 65.45 NiO/CeO2 + CaO 72.36

Results and dicussion EDX Oxygen carrier % Weight carbon NiO/Al2O3   NiO/Al2O3 2.83 NiO/CeO2 1.79

Conclusions Chemical looping reforming using Ni-based oxygen carrier on ceria support can produce hydrogen higher than alumina support because ceria support can release oxygen by itself to react with methane together with oxygen on metal oxide.

Conclusions Moreover, after regeneration of Ni by oxidation, NiO/CeO2 has less carbon than NiO/Al2O3 that will prolong its age.

Conclusions CaO as CO2 sorbent is proposed. CaO does not only adsorb CO2 from product stream but also can shift reaction, resulting in higher methane conversion and hydrogen purity.

Acknowledgements The authors would like to thank the ceria support from The Thailand research fund (TRF).