Pier and others,

SOFNOCAT catalytically oxidises CO - oxygen required!
 From our experience and as far as I remember from the SOFNOCAT
description, it is poisoned by SO2 and other sulphur-bearing gases. I am
not sure whether one can re-activate it.
Sergey



Paul Eby wrote:

> As I understand the catalyst, it requires oxygen in the gas stream to
> work.
> We are stripping CO out of air samples, so the oxygen is supplied in that
> manner.
>
> I'm wondering if reducing the catalyst under H2 might not improve things.
> Perhaps I'll just have to try it, but was hoping someone had beaten me to
> it....
>
> Paul
>
>
> At 08:11 AM 16/06/2005, you wrote:
>
>> Dear Paul and others,
>>
>> I looked to find the composition of the catalyst, but the only
>> description
>> given on internet (found the provider/manufacturer of SOFNOCAT easily by
>> Google) is a precious metal material, and nothing else. Suppose it is
>> impossible to get more info on the composition for manufaiurers reasons.
>>
>> There are two ways to convert CO into CO2:
>> 2CO + O2 = 2CO2 [1]
>> 2CO = CO2 + C [2]
>>
>> Since no oxygen is part of the catalyst material, as I understood,
>> conversion of CO into CO2 only can occur by reaction [2], meaning a
>> carbon
>> stays behind at the surface of the catalyst for each molecule of CO2
>> formed.
>> This also can be an explanation for becoming less effective in time -
>> there
>> is simply less surface of catalyst at which the reaction is taking
>> place.
>> Restoring, eventually can be done by oxydising gently the carbon on the
>> catalysts surface, if not leading to oxidation of the catalyst itself or
>> sintering of the catalyst grains and thus reducing the catalytic surface
>> where the reaction can take place. And sintering may be another
>> reason of
>> decrease in catalyst active surface during the conversion process, if
>> occuring at the applied temperature at all. Further, I am wondering if
>> traces of halogens in your sample gas might effect (pollute) the
>> catalyst,
>> but that is just a suggestion and probably, if happening at all, just a
>> minor effect compared by the first.
>>
>> Another point for this conversion [2] is to consider the effect on the
>> C-isotopic composition? Ideally all oxygen is recovered but C is lost
>> and
>> certainly will introduce isotopic fractionation (how large depends on
>> the
>> conversion temperature; you did not mention that, but I guess a
>> couple of
>> hundred degrees). So, if only oxygen is your interest it will not
>> introduce
>> fractionation, but if also the carbon is of interest you will have a
>> problem.
>>
>> Hope this helps,
>> Best wishes,
>> Pier.
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>>
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>>
>>