Steam Reformation & Water Gas Shift. Team 1 Gabrielle Carbone, Kathleen Cooley, David Hessler, and Jacob Prucnal

Transcription

1 Steam Reformation & Water Gas Shift Team 1 Gabrielle Carbone, Kathleen Cooley, David Hessler, and Jacob Prucnal

2 Overall Process CH 4 + H 2 O CO + 3H 2 Steam Reforming of Methane H = +206 kj/mol CH 4 + 2H 2 O CO 2 + 4H 2 Side Reaction H = +165 kj/mol CO + H 2 O CO 2 + H 2 Water Gas Shift Reaction H = -41 kj/mol Operated at bar and high temperatures up to 1000 degrees C

3 Use of Synthesis Gas Synthesis gas, or syngas, is composed of carbon monoxide and hydrogen gas Syngas can be used to produce many different organic compounds, including: Fuel Hydrocarbons, such as diesel Solvents, such as methanol or dimethyl ether Ammonia

4 Steam Reformation Mechanism Dissociative adsorption of methane is rate determining step

5 Water Gas Shift Mechanism Using Au/CeO 2 as catalyst Formal mechanism does not exist yet Activation of water to release H 2 Activation of CO combines with the O left Releases CO 2

6 Problems with Steam Reformation The desired steam reformation reaction is unfavored at STP Therefore reaction conditions must avoid side reactions Extreme temperature/pressure Reaction-specific catalyst

7 Catalyst Selection and Usage Late transition metals are the best catalysts Nickel is most frequently used due to economic feasibility Blends have been shown to improve stability Poisoning, thermal degradation and coking are concerns Current reactors are fixed-bed Experiences thermodynamic equilibrium that leads to low conversion of WGS reaction Ni/Au Blend Catalyst Surface

8 Coking and Coke Prevention Techniques? What is coking? Carbon deposition on the surface of the catalyst which poisons it CH 4 C + 2H 2 CO + H 2 C + H 2 O 2CO C + CO 2 Coke Prevention Selective poisoning by sulphur Use of alloys

9 Use in Fuel Cells Fuel cells require large amounts of hydrogen, which is difficult to transport No extensive infrastructure exists Tanks would be large and bulky Steam reformation/wgs could alleviate this problem by using methane as a source for hydrogen Methane is much easier to transport with current infrastructure Current technology favors NGVs over this combination but that could change

10 Looking Ahead; Emerging Technology Another form of Methane Steam Reformation is using carbon dioxide instead of water to react with methane over a fixed bed catalyst reactor. This reactor involves several different catalysts that allow the oxidation of methane and reduction of water

11 Super-dry Reforming of Methane

12 Conclusion The MSR reaction converts methane to syngas, an important building block for other chemical processes Due to the endothermic nature of the steam reformation reaction and the prevalence of side reactions, catalysts are used to facilitate the reaction The WGS reaction converts the syngas into a hydrogen-rich product Current technology is inefficient, but there is potential for many applications

13 Works Cited Chorkendorff, I., and J. W. Niemantsverdriet. Concepts of Modern Catalysis and Kinetics. Weinheim: Wiley-VCH, Print. Navarro, R. M., M. C. Sánchez-Sánchez, M. C. Alvarez-Galvan, F. Del Valle, and J. L. G. Fierro. "Hydrogen Production from Renewable Sources: Biomass and Photocatalytic Opportunities." Hydrogen Production from Renewable Sources: Biomass and Photocatalytic Opportunities - Energy & Environmental Science (RSC Publishing). The Royal Society of Chemistry, 22 Oct Web. 31 Jan Rodriguez, Jose A. "V.N.12 Active Sites and Mechanism for the Water-Gas Shift Reaction on Metal and Metal/Oxide Catalysts." DOE Hydrogen and Fuel Cells Program (2013): n. pag. Print. Liu, James A. Kinetics, Catalysis and Mechanism of Methane Steam Reforming. Thesis. WORCESTER POLYTECHNIC INSTITUTE, N.p.: n.p., n.d. Print. Super-dry reforming of methane intensifies CO2 utilization via Le Chatelier sprinciple, Science, 2016, 354 (6311), Liu, Dongxia. CHBE486 Lecture 23 Fall 2016