Anyone have an e-copy of Siller and Bhaduri?
Still unclear how catalysts are a panacea for CO2 air capture. There still
needs to be a chemical driving force that transfers gas into solution and keeps
it there. Adding CA, nano particles, etc to water doesn't magically consume
CO2. You've got to remove acid or add base to the solution to drive the
reaction. If you are talking about mitigating point sources, then obviously
pCO2 flue gas pCO2 water is the driving force. Then keeping it in solution
requires some additional chemistry like adding a base. If minerals are added as
the base, carbonates would be must preferred over silicates because of CO2
reaction kinetics. I can't imagine CO2 hydration being the rate limiting step
in most silicate weathering, so unclear how a hydration catalyst helps here,
but i should read the paper.
-Greg
From: geoengineering@googlegroups.com [geoengineering@googlegroups.com] on
behalf of David Lewis [jrandomwin...@gmail.com]
Sent: Thursday, March 07, 2013 3:38 PM
To: geoengineering@googlegroups.com
Subject: [geo] Re: Nickel nanoparticles catalyse reversible hydration of carbon
dioxide for mineralization carbon capture and storage OR Sea Urchins May Save
the World
I was interested that Siller and Bhaduri, authors of this nickel nanoparticle
paper, compared what they think nickel nanoparticles can do favorably to what
carbonic anhydrase can do.
A discussion of the properties and significance of carbonic anhydrase is
located on the Stanford website, i.e. at the Global Climate and Energy Project,
i.e. in this Jennifer Wilcox Carbon Capture 101
Tutorialhttp://vimeo.com/30557085.
Wilcox devotes most of the tutorial discussing the best CO2 capture chemistry
presently commercially available, i.e. amine chemistry.
As an aside, she brought up carbonic anhydrase at minute 34:30. A transcript:
There is a special case called carbonic anhydrase. This is an enzyme. This
is how we filter out CO2 in our own bodies. So this is present in the red
blood cells of mammals. And essentially carbonic anhydrase is a zinc based
enzyme and you can see here there are three histadine groups surrounding the
zinc. And you have water associated with it. In solution, the proton will go
into solution and so you have this hydroxyl group directly bound to the zinc
and so what ends up happening is that OH will hydrate CO2. So [garbled] its
carbonate interaction with the OH of the zinc, and the interesting aspect about
this is that it occurs about ten orders of magnitude faster. So CO2 to
bicarbonate formation is up to ten orders of magnitude faster than CO2 in
aqueous solution without anything added. That's just in water.It can be
anywhere from four to six orders of magnitude greater than amine chemistry -
for forming carbonate from CO2. So it's a pretty significant enzyme.
Currently though the source is questionable, where we can get this, since it is
only available in red blood cells. And, you know, that's limited. So there
are a lot of groups - there's a group at Columbia, there's a group at Lawrence
Livermore National Labs, working on synthetically making carbonic anhydrase as
additives for the absorption process for separation.
I asked Siller for a description of the speed she and Bhaduri observed nickel
could catalyse CO2 to carbonic acid, in the terms Wilcox uses, i.e. compared to
CO2 in water, and/or compared to amine chemistry, i.e. CO2 and amines in water.
Her reply:
We have tried to determine the rates of conversion of CO2 to acid by nickel
nanoparticles with stop-flow technique to compare them with carbonic anhydrase
from the literature - however we have problems since nobody before us did not
work (sic) on this system and if we just copy literature and try to use
reagents which are used for CO2 capture by carbonic anhydrase... the measured
rates are unreliable So we are trying to find the right reagents for
kinetic measurements.
I asked Klaus Lackner for his reaction about the importance of this discovery
that nickel acts similarly to carbonic anhydrase. He commented on the
Siller/Bhaduri plan to remove carbonic acid as it forms so the nickel can
continually produce more, by using olivine:
Keep in mind that other people have used bicarbonate brines to digest olivine
and they were rate limited too. These processes which start with bicarbonate
ions in the water end up being severely rate limited even though they simply
ignored the question of how to get the CO2 in the water.
I asked Siller what she thought of what Lackner brought up. Siller: we have
some ideas we are exploring currently.
Lackner also thought having a magnetic catalyst wasn't necessarily going to be
a game changer. With regard to the ability to recover the catalyst. Yes it
is easy to pick up nickel magnetically, but the same will happen to the iron
that one invariably finds in the olivine rock. So magnetic
