I am investigating the use of activated carbon (AC) as a catalyst in place of mercury. As an example of the application of AC, see for example,
'Activated carbon for aerobic oxidation: Benign approach toward 2-benzoylbenzimidazoles and 2-benzoylbenzoxazoles synthesis' by Kai Bao, et al, at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4603700/ .
My speculated path, first, we have electrostatic interactions (for example, Coulombic interactions) between ionic salts (like Aluminum producing
positively charged Al3+) and ‘charged activated carbon pore surfaces’ (see https://www.sciencedirect.com/topics/materials-science/carbo... ). I would describe the latter below on the surface of activated carbon (note, AC
is a known photocatalyst so UV or solar light in the presence of moisture and oxygen, see https://www.sciencedirect.com/science/article/pii/S092633731... , or oxidizing agents or heating may induce radical creation):
AC = AC+ + e-
And, in the illustrative theoretical presence of H2O2, for example, to understand the underlying chemistry (NOT to be added to alcohol), a possible
one electron reduction chain:
H2O2 ⇌ H+ + HO2-
e- + H+ ⇌ .H
.H + HO2- = OH- + .OH
Net: H2O2 + e- = OH- + .OH
Or, as AC = AC+ + e- , we equivalently have:
H2O2 + AC = AC+ + OH- + .OH
This precise relation was originally proposed by Kurniawan et al., 2009 and Bach et al., 2011 and appears in this thesis https://tspace.library.utoronto.ca/bitstream/1807/68525/1/Si... , to quote:
“GAC has been known to act as a catalyst in the decomposition of H2O2 (Khalil et al., 2001) and has been used in a number of drinking water
treatment plants due to its ability to quench H2O2 (Cotton et al.., 2010). Two major theories have been put forward for quenching mechanism of
hydrogen peroxide by GAC (Kurniawan et al., 2009 and Bach et al., 2011). The hypothesis by Kurniawan et al. (2009) is given as follows:
AC + H2O2 → AC+ + OH− + .OH Equation 1. 11
AC+ → AC + H+ + .OOH Equation 1. 2 ”
Other theoretically related works include https://www.researchgate.net/publication/276120744_Enhanced_... to quote:
“... literature has reported that carbon materials have reducing power. Activated carbon is known to serve as a redox mediator, possibly by
reactions involving carbonyl/quinone groups on the surface, and a portion of these functional groups have very low redox potentials…”
Also, https://www.nap.edu/read/12646/chapter/6?term=%22samples+of+... , which notes that ‘samples of new unused carbon added to water give a pH
reading around 10’ .
All of the foregoing implies to me a possible role for activated carbon (AC) in an aluminum, ROH and some water (I may try adding a small amount of
MgCl2 as an electrolyte given the galvanic corrosion of aluminum in the presence of noble carbon in seawater, see https://www.corrosionpedia.com/galvanic-corrosion-of-metals-... ) mix in the following proposed reaction scheme:
3 x [ AC = AC+ + e- ]
3 x [ H2O ⇌ H+ + OH- ]
3 x [ H+ + e- = .H ]
Al --> Al3+ + 3 e-
Al + 3 OH- -->Al(OH)3 + 3 e-
3 x [ AC+ + e- = AC ]
3 x [ .H + ROH = .RO + H2 (g) ]
3 x [ .RO + e- = RO- ]
Net:
2 Al + 3 ROH + 3 H2O --AC--> Al(RO)3 + Al(OH)3 + 3 H2 (g)
As a side comment that may impact reactivity, note that hydrogen is chemisorbed on carbon surfaces (see https://www.sciencedirect.com/topics/materials-science/carbo...) and in the presence of UV or solar light, a likely beneficial added presence of
the hydrogen atom radical (.H).
To prepare a form of activated carbon, I am thinking of working with very fine carbon or perhaps graphite, soak it in a select alcohol of interest,
ignite the mix to heat the carbon and imbue it with organic groups, quench the fire and let it aerate. Repeat the soaking in alcohol, ignition,
quenching and aeration. The idea is to introduce oxygen containing groups which are known to impact the polarity on carbon surface (see https://www.nap.edu/read/12646/chapter/6#34 ).
[Edited on 5-11-2018 by AJKOER] |