University of Tennessee, Knoxville Trace: Tennessee Research and Creative Exchange Doctoral Dissertations Graduate School 5-2011 Roles of Non-thermal Plasma in Gas-phase Glycerol Dehydration Catalyzed by Supported Silicotungstic Acid Lu Liu [email protected] Recommended Citation Liu, Lu, "Roles of Non-thermal Plasma in Gas-phase Glycerol Dehydration Catalyzed by Supported Silicotungstic Acid. " PhD diss., University of Tennessee, 2011. https://trace.tennessee.edu/utk_graddiss/992 This Dissertation is brought to you for free and open access by the Graduate School at Trace: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of Trace: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a dissertation written by Lu Liu entitled "Roles of Non-thermal Plasma in Gas- phase Glycerol Dehydration Catalyzed by Supported Silicotungstic Acid." I have examined the final electronic copy of this dissertation for form and content and recommend that it be accepted in partial fulfillment of the requirements for the degree of Doctor of Philosophy, with a major in Biosystems Engineering. Xiaofei Ye, Major Professor We have read this dissertation and recommend its acceptance: Douglas G. Hayes, Joseph J. Bozell, Igor Alexeff Accepted for the Council: Dixie L. Thompson Vice Provost and Dean of the Graduate School (Original signatures are on file with official student records.) To the Graduate Council: I am submitting herewith a dissertation written by Lu Liu entitled “Roles of Non-thermal Plasma in Gas-phase Glycerol Dehydration Catalyzed by Supported Silicotungstic Acid” I have examined the final electronic copy of this dissertation for form and content and recommend that it be accepted in partial fulfillment of the requirements for the degree of Doctor of Philosophy, with a major in Biosystems Engineering. Xiaofei P. Ye, Major Professor We have read this dissertation and recommend its acceptance: Douglas G. Hayes Joseph J. Bozell Igor Alexeff Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original Signatures are on file with official student records.) Roles of Non-thermal Plasma in Gas- phase Glycerol Dehydration Catalyzed by Supported Silicotungstic Acid A Dissertation Presented for the Doctor of Philosophy Degree The University of Tennessee, Knoxville Lu Liu May 2011 Copyright © 2011 by Lu Liu All rights reserved. ii Acknowledgements I would like to thank my advisor, Dr. X. Philip Ye, who conceived and guided the research in this dissertation. Also, this dissertation would not have been completed without the valuable input from my committee members, Dr. Joseph Bozell, Dr. Douglas Hayes, and Dr. Igor Alexeff. I also wish to express my thanks to my lifelong friends, Dr. Leming Cheng, and Dr. Javier Gomez del Rio; without their companionship and continuous encouragement, I would not have been able to proceed this far. Most importantly, I feel a great appreciation to my parents and Brian; their understanding and support helped me maintain the strength to face and overcome the difficulties in the process of researching and writing this document. iii To my family iv Abstract Acrolein is an indispensable chemical intermediate with a rising demand in recent years. The concern of the increase of propylene prices due to the shrinking supply of nonrenewable crude oil makes the acid-catalyzed gas-phase glycerol dehydration to acrolein a prime candidate for research. The analysis showed that the sustainable acrolein production from glycerol was both technically and economically viable. Alumina2700 ® (Al) and Silica1252 ® (Si) loaded with silicotungstic acid (HSiW) possessed distinct features while provided equally good acrolein yield (73.86mol% and 74.05mol%, respectively) optimally. Due to the unique non-equilibrium characteristics, non-thermal plasma (NTP) could promote a variety of chemical reactions; however, its application in a dehydration process remained blank. This study used the reaction of glycerol dehydration to acrolein to probe whether NTP could 1) improve acrolein yield during dehydration, 2) suppress the coke formation and regenerate the catalyst, and 3) modify the properties of the catalyst. The dielectric barrier discharge configuration was used to generate NTP; various NTP field strengths and also their interaction with temperature and the catalyst were investigated. The results showed that NTP improved the glycerol conversion and that NTP with a proper field strength increased acrolein selectivity. The optimal acrolein yields of 83.6 mol% and 83.1 mol% were achieved with 3.78 kV/cm NTP and 4.58 kV/cm NTP at 275°C for HSiW- Al and HSiW-Si, respectively. The application of NTP-O2 (5% oxygen in argon, 4.58 kV/cm) during glycerol dehydration significantly suppressed coke formation on HSiW-Si. NTP-O2 could regenerate the deactivated HSiW-Si at low temperatures by removing both soft and hard coke at various rates. NTP-O2 with higher field strength, at medium operation temperature (150ºC) and in argon atmosphere was more effective for coke removal/catalyst regeneration. Applying NTP to the catalyst fabrication showed some capabilities in modifying catalyst properties, including enlarging surface area, preserving mesopores, increasing acid strength and Brønsted acidity. NTP with argon as the discharge gas performed better in these modifications than NTP with air as the discharge gas. v Table of Contents Introduction............................................................................................................................... 1 Chapter 1 A comparative review of petroleum-based and bio-based acrolein production....... 3 1.1 Introduction............................................................................................................... 4 1.1.1 Acrolein---an important and versatile chemical intermediate ........................... 4 1.1.2 Overview of acrolein synthesis methods .............................................................. 6 1.1.3 Going toward the bio-based route......................................................................... 7 1.2 Technical aspects of synthetic acrolein approaches.................................................. 9 1.2.1 Aldol condensation of acetaldehyde and formaldehyde ....................................... 9 1.2.2 Current manufacturing method: partial oxidation of propylene ......................... 10 1.2.3 Partial oxidation of propane................................................................................ 14 1.2.4 Promising bio-based route---glycerol dehydration ............................................. 18 1.3 Discussion of the economic and industrial potential .............................................. 31 1.4 Conclusions............................................................................................................. 43 Chapter 2 Non-thermal plasma physics & chemistry: fundamentals & applications ............. 44 2.1 NTP physics............................................................................................................ 45 2.2 NTP chemistry ........................................................................................................ 49 2.3 NTP applications..................................................................................................... 50 Objectives ............................................................................................................................... 55 Chapter 3 Glycerol dehydration to acrolein catalyzed by supported silicotungstic acid........ 56 3.1 Introduction............................................................................................................. 57 3.2 Materials and Methods............................................................................................ 58 3.3 Results and Discussion ........................................................................................... 67 3.4 Conclusions............................................................................................................. 76 Chapter 4 Synergic effects of non-thermal plasma and solid acid catalyst in glycerol dehydration ............................................................................................................................. 77 4.1 Introduction............................................................................................................. 78 4.2 Materials and Methods............................................................................................ 81 4.3 Results..................................................................................................................... 84 4.3.1 NTP field-strength effect .................................................................................... 84 4.3.2 Temperature & NTP effects................................................................................ 87 4.3.3 Byproducts .......................................................................................................... 89 4.3.4 Long-term stability test....................................................................................... 93 4.3.5 Blank test (no solid acid catalyst) with/without NTP ......................................... 94 4.4 Discussion............................................................................................................... 95 4.4.1 Temperature effect.............................................................................................