ABSTRACT CATALYTIC PERFORMANCE AND CHARACTERIZATION OF ZN-DOPED CRYPTOMELANE-TYPE MANGANESE DIOXIDE FOR ETHANOL OXIDATION by Lulu Jiang Cryptomelane (KMn8O16) was prepared by two methods: 1) a sol-gel method, and 2) a proprietary method that uses alkaline battery waste as a starting material. These cryptomelane materials were investigated as volatile organic carbon (VOC) oxidation catalysts and compared. To better understand the roles of processing steps on the physical characteristics and catalytic activity, the effects of zinc dopant and calcination temperature were studied with the sol-gel cryptomelane materials. Zinc dopant was included as a test variable because it is present in alkaline battery waste, and cyrptomelane prepared from battery waste also contains zinc (<5 wt%). The oxidation of ethanol was used to assess catalytic activity of the cryptomelane materials. It was found that cryptomelane-based manganese dioxide prepared by both the sol-gel method and from battery waste can be used as catalysts in the catalytic oxidation of ethanol in air. The zinc dopant (<5 wt%) has very little impact on catalytic activity, although it has some impact on the morphology and crystallinity of the materials. Calcination temperature, however, which impacts the surface area of the material, has a much more significant role, where the higher the calcination temperature, the lower the surface area, and hence, the lower the catalytic activity. CATALYTIC PERFORMANCE AND CHARACTERIZATION OF ZN-DOPED CRYPTOMELANE-TYPE MANGANESE DIOXIDE FOR ETHANOL OXIDATION A Thesis Submitted to the Faculty of Miami University In partial fulfillment of the requirements for the degree of Master of Science Department of Paper and Chemical Engineering by Lulu Jiang Miami University Oxford, Ohio 2012 Advisor: Dr. C. Almquist Dr. M. Krekeler Reader: Dr. S. Lalvani Reader: Dr. Lei Kerr Contents List of Tables .................................................................................................................................... iv List of Figures .................................................................................................................................... v ACKNOWLEDGEMENTS ............................................................................................................. vii I. Introduction .............................................................................................................................. 1 II. Literature Review ...................................................................................................................... 3 2.1 Preparing methods ........................................................................................................ 3 2.1.1 Overview .............................................................................................................. 3 2.1.2 Reflux Method .................................................................................................... 3 2.1.3 Sol-gel Method ................................................................................................... 3 2.1.4 Solid-State/Milling Method ........................................................................... 4 2.1.5 Dopant Methods ................................................................................................ 4 2.2 Catalytic property of cryptomelane ........................................................................ 4 2.2.1 Catalytic Mechanism ........................................................................................ 5 2.2.3 Effect of calcination temperature ............................................................... 6 2.2.4 Transition metal doped cryptomelane as a catalyst ........................... 6 2.2.4 Catalytic deactivation ...................................................................................... 7 III Hypothesis ................................................................................................................................... 8 3.1 Synthesis ............................................................................................................................ 8 3.2 Characterization ............................................................................................................. 9 3.3 Catalysis ........................................................................................................................... 10 IV. Experiment................................................................................................................................ 12 4.1 Catalyst Synthesis ........................................................................................................ 12 4.2 Characterization ........................................................................................................... 13 4.2.1 BET ....................................................................................................................... 13 4.2.2 XRD ....................................................................................................................... 14 4.2.3 SEM EDS .............................................................................................................. 14 4.2.4 TEM EDS ............................................................................................................. 14 4.3 Catalysis ........................................................................................................................... 14 4.3.1 Preparation ....................................................................................................... 14 4.3.2 Performance experiment ............................................................................. 15 V. Results and Analysis ............................................................................................................... 17 5.1 Characterization ........................................................................................................... 17 ii 5.1.1 BET surface area ............................................................................................. 17 5.1.2 X-ray Diffraction .............................................................................................. 18 5.1.3 SEM ....................................................................................................................... 21 5.1.4 TEM ...................................................................................................................... 28 5.2 Catalytic Performance ................................................................................................ 32 5.2.1 The effect of calcination temperature on catalytic activity for ethanol oxidation. ...................................................................................................... 32 5.2.3 Battery-derived cryptomelane performance ....................................... 33 5.2.4 Activation Energy............................................................................................ 34 5.2.3 Mass balance in catalytic reaction ............................................................ 37 5.2.4 Temperature at which ethanol half decomposed ............................... 38 References ....................................................................................................................................... 41 iii List of Tables Table 4.1 Summary of chemicals used in this study. ....................................................... 12 Table 5.1 Summary of BET surface areas of cryptomelane samples ........................ 17 Table 5.2 Crystal length and width estimated from SEM pictures. ........................... 24 Table 5.3 Summary of carbon balances conducted at each reaction temperature for a selected experimental trial. ............................................................................................ 37 iv List of Figures Figure 3.1 Schematic of test system used for the catalytic oxidation of ethanol. 11 Figure 4.1 Procedure for synthesizing cryptomelane using the sol-gel method . 13 Figure 4.2 Schematic diagram of the reaction system .................................................... 15 Figure 5.1 Effect of zinc dopant and calcination temperature on the BET surface area of cryptomelane. .................................................................................................................. 17 Figure 5.2 Comparison of X-ray diffraction patterns for four Zn-doped cryptomelane samples calcined at 350℃ , 400℃ , 500℃, and 600℃.................... 19 Figure 5.3 XRD crystal structures at different calcination temperatures with pure cryptomelane (upper) and 2.5 weight % Zn/cryptomelane (lower). Cryptomelane peaks have been marked above. # Refers to birnessite crystal peaks. ................................................................................................................................................. 20 Figure 5.4 SEM image of pure cryptomelane under (a) 350℃ (b) 400℃ (c) 500℃ (d) 600℃calcination temperatures with the same magnification of 100,000x (e) 400℃ (f) 500℃ under 50,000x .............................................................................................. 22 Figure 5.5 An overview of the crystal quantity that grows from the sample rock following calcination at 400℃ (left) and 600℃ (right). ............................................... 23 Figure 5.6 Calcination temperature vs. crystal length (a, upper) and crystal width (b, lower) .........................................................................................................................................