The Synthesis and Characterization of Novel Group 13 Nanostructured Building Block Heterogeneous Silicate Catalysts

University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Doctoral Dissertations Graduate School 8-2012 The Synthesis and Characterization of Novel Group 13 Nanostructured Building Block Heterogeneous Silicate Catalysts Joshua G. Abbott Follow this and additional works at: https://trace.tennessee.edu/utk_graddiss Part of the Catalysis and Reaction Engineering Commons, Inorganic Chemistry Commons, and the Materials Chemistry Commons Recommended Citation Abbott, Joshua G., "The Synthesis and Characterization of Novel Group 13 Nanostructured Building Block Heterogeneous Silicate Catalysts. " PhD diss., University of Tennessee, 2012. https://trace.tennessee.edu/utk_graddiss/1430 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 Joshua G. Abbott entitled "The Synthesis and Characterization of Novel Group 13 Nanostructured Building Block Heterogeneous Silicate Catalysts." 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 equirr ements for the degree of Doctor of Philosophy, with a major in Chemistry. Craig E. Barnes, Major Professor We have read this dissertation and recommend its acceptance: Craig E. Barnes, Zi-ling Xue, Michael Best, Joseph J. Bozell Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) The Synthesis and Characterization of Novel Group 13 Nanostructured Building Block Heterogeneous Silicate Catalysts A Dissertation Presented for the Doctor of Philosophy Degree The University of Tennessee, Knoxville Josh G. Abbott August 2012 Dedication To Julia. Without your unwavering support and unconditional love the completion of this journey would not have been possible. ii Acknowledgements No endeavor this large can be the work of one person. As such, a great number of individuals have shared in the incredible journey that has led to the completion of this body of work. In doing so they have placed their collective imprint, not only on the dissertation presented here, but on the way I see and interact in the laboratory, and the surrounding world. Foremost among these is my advisor Dr. Craig E. Barnes. It is through him that I have become the chemist I am today. His never ending curiosity and his attention to detail are infectious while his calm persona and sustained patience have shown me that great chemistry can happen in a low stress, relaxed atmosphere. I must thank my committee members, Dr. Michael Best, Dr. Zi-ling Xue, and Dr. Joseph J. Bozell for agreeing to commit their time and energy to be a part of my committee in addition to the time they have spent expanding my knowledge of chemistry through their classes and collaborative efforts. I would also like to thank Dr. Carlos Steren for his sustained involvement in my education as an NMR operator. His knowledge has led to my sincere affection for the technique and pushed me to see how deep ones understanding of an analytical technique can go. I am eternally grateful to current and former group members, Dr. Ming-Yung Lee, Dr. Richard Mayes, Dr. Michael Peretich, Dr. Shujian Chen, Dr. Jiri Pinkas, Nan Chen, James Humble, Austin Albert, Daniel Taylor, Matt Dembo, Lena Elenchin and Desta Bume for helpful discussions about research, generally keeping the mood in the lab light, and for certainly making life interesting. Thanks are also in order for the staff of the Department of Chemistry. The staff of the stock room and business office has helped in immeasurable ways. Special thanks to Sharon Marshall, Gail Cox, Darrel Lay, Beverly Rosenbalm, Tray Allen, and Sherri Dugger. Art Pratt is a wizard with glass, and a patient and understanding soul. I can’t imagine how difficult things would have been without his services. Tim Free, Gene French, and Eddie Wilson of the Machine Shop were instrumental to the production, modification, and maintenance of a great number of things that keep the lab running. iii Bill Gurley, Johnny Jones, and Gary Wynn of the Electronics shop were instrumental in assisting with electronic and computer issues throughout my tenure. I owe a great deal of thanks to the Department of Energy Office of Basic Energy Sciences and C3Bio EFRC for funding my research the past six years. Finally I must thank my wife and family for believing in me and never doubting my success. Even when I had doubts, their strength and support pushed me to continue to strive for success. iv Abstract A building block approach and sequential addition methodology was utilized to prepare heterogeneous silicate catalysts containing atomically dispersed group 13 metal (B, Al, Ga) centers. The octa(trimethyltin) silsequioxane, Si8[sub]O12[sub](OSnMe3[sub])8[sub], was used as the building block for the synthesis of these materials. Reaction of the building block with a variety of group 13 metal chlorides led to the formation of cross-linked matrices. All prepared materials were characterized by gravimetric analysis, gas absorption, IR, and NMR. In addition, aluminum and boron samples where characterized by 27[sup]Al and 11[sup]B solid state NMR, and gallium samples were studied using x-ray absorption techniques. Studies found the nature of the reaction for the aluminum and gallium species to be more complex than expected. This was manifested most prominently in the formation of tetramethyltin, Me4[sub]Sn, an unexpected byproduct that led to unpredictably high connectivity of the metal centers to the silicate matrix. This in turn gave rise to questions regarding the true structural nature of the metal sites. Characterization of the aluminum systems indicated that multiple types of aluminum sites (4, 5 and 6 coordinate) were present in the matrix. Increased coordination was found to result in part from the in situ formation and reaction of the [Me3[sub]Sn][AlCl4[sub]] species. It was determined that the trimethyltin cation in this ionic species was responsible for formation of Me4[sub]Sn through abstraction of a methyl group from unreacted –OSnMe3[sub] groups remaining on the corners of the silicate building block. While the gallium analogues showed similar behavior, XANES and EXAFS analyses showed that in nearly every material, gallium had achieved 4-coordinate tetrahedral geometry. The boron systems behave quite differently than Al and Ga, producing no secondary byproduct, and forming stable 3-coordinate trigonal geometries. Pyridine adsorption studies showed that these trigonal species could at least in part be converted back and forth to pseudo tetrahedral structures. v Table of Contents 1. Introduction & Review of Heterogeneous Catalysis ................................................................. 1 1.1 Introduction ....................................................................................................................... 1 1.2 Definition of a catalyst ....................................................................................................... 2 1.3 Heterogeneous vs. Homogeneous Catalysts .................................................................... 4 1.4 Classes of Heterogeneous Catalysts ................................................................................ 5 1.4.1 – Pure Metals ............................................................................................................. 5 1.4.2 – Metal Oxides ........................................................................................................... 5 1.4.3 – Supported Homogeneous Analogues ...................................................................... 7 1.4.4 – Solid Acids .............................................................................................................11 1.5 Aluminosilicates ...............................................................................................................14 1.5.1 – Industrial Applications ............................................................................................14 1.5.2 – Classes of Aluminosilicates ....................................................................................17 1.5.3 – Nature of the Active Sites in Aluminosilicates .........................................................21 1.5.4 – Methods for the Synthesis of Aluminosilicates ........................................................25 1.6 Building Block Approach to Aluminosilicate Synthesis .....................................................28 1.7 Gallium, Boron, & POSS Analogues ................................................................................39 1.8 Characterization Methods ................................................................................................40 1.8.1 – Gravimetric Analysis...............................................................................................40 1.8.2 – Gas Adsorption Measurements ..............................................................................42 1.8.3 – Infrared Spectroscopy (IR) .....................................................................................42 1.8.4 – Inductively Coupled Plasma – Optical Emission Spectroscopy (ICP-OES) .............42

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