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Catalytic Material Design: Design Factors Affecting Catalyst Performance for Biomass and Fine Chemical Applications

Deshpande, Nitish
http://rave.ohiolink.edu/etdc/view?acc_num=osu154273906480973

Abstract Details

2018, Doctor of Philosophy, Ohio State University, Chemical Engineering.
Continual development of heterogeneous catalysts is important for a sustainable chemical industry. Easy to separate heterogeneous catalysts can reduce energy consumption and waste generation in chemical processes. However, typically these catalysts are non-uniform and thus less active and selective compared to their homogeneous counterparts. Herein, different design factors affecting the catalytic performance for silica-based heterogeneous catalysts are described for reactions including glucose isomerization and epoxide ring opening with alcohols. Glucose isomerization to fructose is an important step in upgrading cellulosic biomass to high valued products. Tertiary amines are selective homogeneous catalysts for this reaction. Herein, tertiary amine analogues are immobilized on mesoporous silica supports (SBA-15) to create heterogeneous catalysts. These materials are characterized using a battery of standard characterization techniques and analyzed for their ability to catalyze glucose isomerization. Preliminary results reveal that amine-support surface interactions hinder the catalytic performance. Systematic investigations of various catalyst design parameters are carried out to limit these interactions. Design parameters including active site loading, length of the amine tethers, size of substituents on the amine nitrogen, and support pore characteristics are found to affect the catalytic performance significantly. The material with a high loading of amine sites, comprising of bulky isopropyl substituents on the nitrogen atom tethered to the silica support using a methyl linker, results in fructose yields similar to those obtained for homogeneous amines. Conventional synthesis of SBA-15 support (REG) results in small amounts of micropores. Through synthesizing and analyzing the catalytic performance of amines grafted onto SBA-15 with limited to no micropores (NMP), it is observed that micropores negatively impact catalysis. This indicates that the activity of amine sites grafted within the micropores of SBA-15 is different than that of those grafted within the mesopores. To evaluate the scope of this phenomenon, other reactions of pharmaceutical importance are analyzed. For Knoevenagel condensation, tertiary amines immobilized on NMP outperform those on REG. Secondary amines follow the same trend in case of aldol condensation. This illustrates the need to understand the implications of catalytic sites of different types existing in conventionally used heterogeneous supports and devising strategies to increase the uniformity of active sites. Epoxides are versatile chemical intermediates that can be ring opened using various nucleophiles to yield synthetically and industrially important bifunctional compounds. Silica-based solid Lewis acidic catalysts are investigated for the ring opening of epoxides with alcohols. Epichlorohydrin ring opening with methanol is used as a probe reaction. While Sn incorporated in SBA-15 framework is catalytically active, significantly higher activity is obtained using zeolites Sn-Beta and Sn-MFI. The more Lewis acidic Sn-Beta is 6-7 times more active as compared to Zr-Beta and Hf-Beta. A detailed substrate study reveals that while the epoxide and the alcohol both impact the catalytic activity, the epoxide structure directs the regioselectivity. Activity of Sn-Beta remains unaffected over multiple catalytic runs indicating that Sn-Beta is a promising catalytic material for this reaction. Overall, the work identifies key design features that affect catalytic performance for heterogeneous catalysts and synthetic strategies to tune them to enhance catalytic performance.
Nicholas Brunelli, Ph.D. (Advisor)
Umit Ozkan, Ph.D. (Committee Member)
Aravind Asthagiri, Ph.D. (Committee Member)
275 p.
Chemical Engineering
Catalyst design; heterogeneous catalysis; zeolites; glucose isomerization; amine functionalized silica materials; epoxide ring opening with alcohols

Recommended Citations

Citations

  • Deshpande, N. (2018). Catalytic Material Design: Design Factors Affecting Catalyst Performance for Biomass and Fine Chemical Applications [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu154273906480973

    APA Style (7th edition)

  • Deshpande, Nitish. Catalytic Material Design: Design Factors Affecting Catalyst Performance for Biomass and Fine Chemical Applications. 2018. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu154273906480973.

    MLA Style (8th edition)

  • Deshpande, Nitish. "Catalytic Material Design: Design Factors Affecting Catalyst Performance for Biomass and Fine Chemical Applications." Doctoral dissertation, Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu154273906480973

    Chicago Manual of Style (17th edition)

osu154273906480973
382
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This open access ETD is published by The Ohio State University and OhioLINK.