Table 1 GBH–EDB SSTD reaction productsa
generating sufficiently high pressure to burst vessels if confined. Our
safety tests show GBH powder is insensitive to impact and friction
initiation but was found to be sensitive to initiation by electrostatic
discharge. At high wt% EDB, the reaction of GBH–EDB mixtures in
air will consistently ignite the mixture and hydrogen product and
should be avoided.
b
mol H2 generated
mol ðGBHþEDBÞ
wt% GBH wt% EDB wt% H2 yield mol% NH3
100
89.5
60.0
46.0
40.0
0
10.6
10.4
10.4
9.60
10.1
4.1
2.7
0.10
0.069
0.026
3.94
3.89
4.11
3.87
4.12
11.5
40.0
54.0c
60.0d
1 N. Desgardin, C. Perut and J. Renouard, US Pat., 7 094 487, 2006.
2 (a) C. W. Hamilton, R. Tom Baker, A. Staubitz and I. Manners,
Chem. Soc. Rev., 2009, 38, 279–293; (b) F. H. Stephens, V. Pons
and R. Tom Baker, Dalton Trans., 2007, 2613–2626;
(c) T. B. Marder, Angew. Chem., Int. Ed., 2007, 46, 8116–8118.
3 G. D. Artz, Grant and R. Louis, US Pat., 4 673 528, 1987.
4 G. Soloveichik, J.-H. Her, P. W. Stephens, Y. Gao, J. Rijssenbeek,
M. Andrus and J.-C. Zhao, Inorg. Chem., 2008, 47, 4290–4298.
5 Our attempts to isolate borohydride salts of the conjugate acids of
a
b
For pellets compressed to approximately 60% TMD. NH3
c
d
concentration in gas stream. Stoichiometric mix. Mixture is not
self-sustaining, external heat supplied (reaction initiated by a 120 1C
oil bath).
identified guanidinium and ethylenediammonium salts as the
major products indicating that the C–N skeletal structure of
the cations remains mostly intact during the hydrogen
elimination reaction.
other strong bases, either formamidinium, [HC(NH2)2]+ (pKa
=
11.5), or acetamidinium [CH3C(NH2)2]+ (pKa = 12.52), have so
far been unsuccessful. As yet uncharacterized viscous liquids were
obtained devoid of [BH4]ꢀ perhaps containing borane adducts of
acetamidine and formamidine.
While no special precautions were taken in the storage of
GBH during our investigation, and only a slight odor was
noted after a year, mixtures of GBH–EDB stored unprotected
in air underwent a slow reaction and became inactive after
several months. Samples of the mixture stored under dry
nitrogen for the same period, however, were still reactive.
In conclusion, GBH was found to reliably undergo a
tractable SSTD reaction when initiated by a heated bridge
wire providing a chemical hydrogen storage material with a
lower adiabatic reaction temperature (B450 1C) and a higher
gravimetric storage density than previous borohydride
compositions that used, for example, mixtures of sodium
borohydride with an oxidizer.1 The only gaseous products
identified from the SSTD reaction of GBH were H2 and NH3
where the hydrogen yield was nearly quantitative (above
10 wt%). The SSTD reaction of mixtures of GBH and EDB
rapidly produces a H2 gas stream suitable for PEM fuel cell
applications with minimal NH3 scrubbing required.
6 (a) W. H. Schechter, C. B. Jackson and R. M. Adams, Boron
Hydrides and Related Compounds, Callery Chemical Co., Callery,
PA, 1954; (b) R. M. Adams and A. R. Siedle, in Boron, Metallo-
Boron Compounds and Boranes, ed. R. M. Adams, John Wiley &
Sons, New York, 1964, pp. 461–462.
7 (a) L. V. Titov, M. D. Makarova and V. Ya. Rosolovskii, Dokl.
Akad. Nauk SSSR, 1968, 180, 381–382; (b) L. V. Titov and
M. D. Levicheva, Zh. Neorg. Khim., 1969, 14, 2886–2887;
(c) E. P. Kirpichev, Yu. I. Rubtsov and L. V. Titov, Zh. Neorg.
Khim., 1971, 16, 56–60; (d) L. V. Titov, M. D. Levicheva and
G. N. Dubikhina, Zh. Neorg. Khim., 1972, 17, 1181–1182.
8 Crystal data for GBH. CH10BN3: M = 74.93, tetragonal,: I4(1)/
amd, a = 6.7433(8) A, b = 6.7433(8) A, c = 24.195(3) A, a = 901,
b = 901, g = 901, V = 1100.2(2) A3, Z = 8, absorption coefficient:
0.060 mmꢀ1, wavelength: 0.71073 A, T: 296(2) K, F(000): 336,
reflections collected: 4900, independent reflections: 287 [R(int) =
0.0179, GOF on F2: 1.180, final R indices: [235 data; I 4 2s(I)]
R1 = 0.0545, wR2 = 0.1461; [all data] R1 = 0.0597, wR2 = 0.1559.
9 R. Custelcean and J. E. Jackson, Chem. Rev., 2001, 101,
1963–1980.
10 (a) H. J. Emeleus and F. G. A. Stone, J. Chem. Soc., 1951,
840–841; (b) F. C. Gunderloy, Jr., Inorg. Synth., 1967, 9, 13–16;
(c) L. R. Grant and J. E. Flanagan, US Pat., 4 381 206, 1983.
11 (a) H. C. Kelly and J. O. Edwards, J. Am. Chem. Soc., 1960, 82,
4842–4846; (b) H. C. Kelly and J. O. Edwards, Inorg. Chem., 1963,
2, 226–227; (c) H. Y. Ting, W. H. Watson and H. C. Kelly, Inorg.
Chem., 1972, 11, 374–377.
Notes and references
z Caution! The decomposition reaction of GBH is rapid, producing
heat and large amounts of combustible gas. The reaction is capable of
ꢁc
This journal is The Royal Society of Chemistry 2009
Chem. Commun., 2009, 3089–3091 | 3091