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Title: Thermal decomposition of t-butylamine borane studied by in situ solid state NMR

Abstract

Development of suitable materials to store hydrogen for automotive use has received pointed attention over the past decade. Significant progress has been made with the discovery of novel chemical hydrides, complex metal hydrides, and adsorption substrates which continue to optimize both thermodynamics and kinetics of hydrogen sorption. Chemical hydrides typically offer the largest theoretical gravimetric capacities. Autrey et al. have recently shown that mechanical milling of alkali metal hydrides with ammonia borane can further lower the decomposition temperature. In all cases, however, many challenges remain in order to meet the current US DOE performance targets. Amine boranes are being considered for hydrogen storage materials since they contain significant quantities of hydrogen which potentially can be released at low temperatures (80-150 C) via chemical reactions. Ammonia borane, NH{sub 3}BH{sub 3}, is one of the most promising in this class as it decomposes to release greater than two moles of pure hydrogen gas (14 wt%) below 160 C. Although isoelectronic to ethane, NH{sub 3}BH{sub 3} is a solid at room temperature due to the di-hydrogen bonding network formed between the amine protons and boron hydrides in the solid state lattice. Further, it has been shown that the hydrogen release mechanism involves transformationmore » and isomerization to an ionic dimer where a hydride migrates from one boron to the adjacent boron in the dimer. The greatest challenge to the use of ammonia borane as a hydrogen fuel is the regeneration path from spent fuel to ammonia borane again. The proposed chemical synthesis involves complicated organometallic reactions to form boron hydrogen bonds from the thermodynamically stable polyimidoborane products (BNH){sub n}. Recent theoretical calculations suggested that incorporation of carbon atoms into the (BNH)n product would be less thermodynamically stable. These (CBNH)n compounds are potentially less energy intensive making regeneration of the amine borane fuel more feasible [22]. In the present study, tert-butylamine borane is investigated by heteronuclear in situ solid state NMR to understand hydrogen release from a hydrocarbon containing amine borane. tbutylamine borane has similar physical properties to amine borane with a melting point of 96 C. A single proton has been replaced with a t-butylamine group resulting in a weakening of the dihydrogen bonding framework. t-butylamine borane has a theoretical gravimetric hydrogen density of 15.1%; however, isobutane can also be evolved rather than hydrogen. If decomposition yields one mole isobutane and two moles hydrogen, 4.5 wt% H2 gas will be evolved. More importantly for the present work, the resulting spent fuel should be comprised of both (BNH)n and (CBNH)n polyimidoboranes.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Oak Ridge Y-12 Plant (Y-12), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Defense Programs (DP)
OSTI Identifier:
977147
Report Number(s):
Y/DZ-3078
Journal ID: ISSN 1042-1122; CETREW; TRN: US1002798
DOE Contract Number:  
DE-AC05-00OR22800
Resource Type:
Journal Article
Journal Name:
Ceramic Transactions
Additional Journal Information:
Journal Name: Ceramic Transactions; Journal ID: ISSN 1042-1122
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; 11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; 2-METHYLPROPANE; ALKALI METALS; AMMONIA; BORON; BORON HYDRIDES; CHEMICAL REACTIONS; HYDRIDES; HYDROGEN; HYDROGEN FUELS; HYDROGEN STORAGE; ISOMERIZATION; MELTING POINTS; PHYSICAL PROPERTIES; PYROLYSIS; SPENT FUELS; THERMODYNAMICS; US DOE

Citation Formats

Feigerle, J, Smyrl, N R, Morrell, J S, and Stowe, A C. Thermal decomposition of t-butylamine borane studied by in situ solid state NMR. United States: N. p., 2010. Web. doi:10.1002/9781118019467.ch7.
Feigerle, J, Smyrl, N R, Morrell, J S, & Stowe, A C. Thermal decomposition of t-butylamine borane studied by in situ solid state NMR. United States. doi:10.1002/9781118019467.ch7.
Feigerle, J, Smyrl, N R, Morrell, J S, and Stowe, A C. Thu . "Thermal decomposition of t-butylamine borane studied by in situ solid state NMR". United States. doi:10.1002/9781118019467.ch7. https://www.osti.gov/servlets/purl/977147.
@article{osti_977147,
title = {Thermal decomposition of t-butylamine borane studied by in situ solid state NMR},
author = {Feigerle, J and Smyrl, N R and Morrell, J S and Stowe, A C},
abstractNote = {Development of suitable materials to store hydrogen for automotive use has received pointed attention over the past decade. Significant progress has been made with the discovery of novel chemical hydrides, complex metal hydrides, and adsorption substrates which continue to optimize both thermodynamics and kinetics of hydrogen sorption. Chemical hydrides typically offer the largest theoretical gravimetric capacities. Autrey et al. have recently shown that mechanical milling of alkali metal hydrides with ammonia borane can further lower the decomposition temperature. In all cases, however, many challenges remain in order to meet the current US DOE performance targets. Amine boranes are being considered for hydrogen storage materials since they contain significant quantities of hydrogen which potentially can be released at low temperatures (80-150 C) via chemical reactions. Ammonia borane, NH{sub 3}BH{sub 3}, is one of the most promising in this class as it decomposes to release greater than two moles of pure hydrogen gas (14 wt%) below 160 C. Although isoelectronic to ethane, NH{sub 3}BH{sub 3} is a solid at room temperature due to the di-hydrogen bonding network formed between the amine protons and boron hydrides in the solid state lattice. Further, it has been shown that the hydrogen release mechanism involves transformation and isomerization to an ionic dimer where a hydride migrates from one boron to the adjacent boron in the dimer. The greatest challenge to the use of ammonia borane as a hydrogen fuel is the regeneration path from spent fuel to ammonia borane again. The proposed chemical synthesis involves complicated organometallic reactions to form boron hydrogen bonds from the thermodynamically stable polyimidoborane products (BNH){sub n}. Recent theoretical calculations suggested that incorporation of carbon atoms into the (BNH)n product would be less thermodynamically stable. These (CBNH)n compounds are potentially less energy intensive making regeneration of the amine borane fuel more feasible [22]. In the present study, tert-butylamine borane is investigated by heteronuclear in situ solid state NMR to understand hydrogen release from a hydrocarbon containing amine borane. tbutylamine borane has similar physical properties to amine borane with a melting point of 96 C. A single proton has been replaced with a t-butylamine group resulting in a weakening of the dihydrogen bonding framework. t-butylamine borane has a theoretical gravimetric hydrogen density of 15.1%; however, isobutane can also be evolved rather than hydrogen. If decomposition yields one mole isobutane and two moles hydrogen, 4.5 wt% H2 gas will be evolved. More importantly for the present work, the resulting spent fuel should be comprised of both (BNH)n and (CBNH)n polyimidoboranes.},
doi = {10.1002/9781118019467.ch7},
journal = {Ceramic Transactions},
issn = {1042-1122},
number = ,
volume = ,
place = {United States},
year = {2010},
month = {3}
}