Catalytic converter additive

On 06/20/2011 12:06 PM, Tegger wrote:
> jim > wrote in
> t:
>
>> On 06/19/2011 07:46 AM, Tegger wrote:
>>> jim > wrote in
>>> t:
>>>
>>>
>>>>
>>>> when run too hot because of raw fuel dump, the catalytic metal wash
>>>> diffuses too deep into the ceramic matrix for it to work.
>>>
>>>
>>>
>>> The surface of the cat's element is wispy, like cotton candy.
>>
>> yes it's porous, but cotton candy, it ain't. imagine you had a bucket
>> of pebbles, and you stuck them all together with a wash of pva glue.
>> there would be holes between the pebbles that you could pass liquids
>> and gasses through, but they're stuck together at their contact points
>> to give them the function of a larger contiguous solid on the macro
>> scale.
>> no "wisps", just lots of very tiny pebbles.
>
>
>
> OK, porous pebbles, then. I guess "cotton candy" was too wispy an analogy.
>
> <http://openlearn.open.ac.uk/mod/oucontent/view.php?id=398548&section=1.5.2>
>
>
>
>>
>>
>>> That gives it
>>> a tremendous amount of surface-area for the physical volume of the
>>> element.
>>
>> indeed.
>>
>>
>>> Remember that cats work on adsorption principles, not absorption.
>>
>> well, adsorption is certainly part of the catalytic process, but
>> catalysis is not simply adsorption - the glass in your windows are
>> exposed to air for instance, and they have an adsorbed layer of air
>> molecules as a result [and lots of other stuff] - but there is no
>> catalysis going on.
>
>
>
> The reactions occur on the surface of the washcoat, so "adsorption"
> is correct.

no, catalysis is /not/ adsorption! adsorption is all about us all the
time and nothing happens. catalysis is catalysis and that's very
special because stuff /does/ happen!


>
>
>
>>
>> http://www.thenakedscientists.com/HT.../interview/569
>> /
>
>
>
>
> That page tells you nothing about the ceramic substrate, which is the
> "wispy" part.
>
> <http://openlearn.open.ac.uk/mod/oucontent/view.php?id=398548&section=1.5.2>

are hard cookies "whispy too? because sintered ceramics are just like them.

i did actually explain the wash and the diffusion mechanism that binds
the ceramic particles, but you snipped it. the composition of the
ceramic substrate isn't particularly relevant provided it meets physical
requirements and doesn't react with the catalytic agents.


--
nomina rutrum rutrum

jim beam > wrote in
:

> On 06/20/2011 12:06 PM, Tegger wrote:

>>
>>
>>
>> The reactions occur on the surface of the washcoat, so "adsorption"
>> is correct.
>
> no, catalysis is /not/ adsorption!



I didn't say it was. I said the reactions happen on the surface of the cat.



<snip>


>
> i did actually explain the wash and the diffusion mechanism that binds
> the ceramic particles, but you snipped it. the composition of the
> ceramic substrate isn't particularly relevant provided it meets
> physical requirements and doesn't react with the catalytic agents.
>
>


But the reactive portion does sinter when overheated, just like I said.
Reduced surface area=reduced effectiveness.


--
Tegger

On 06/20/2011 04:53 PM, Tegger wrote:
> jim > wrote in
> :
>
>> On 06/20/2011 12:06 PM, Tegger wrote:
>
>>>
>>>
>>>
>>> The reactions occur on the surface of the washcoat, so "adsorption"
>>> is correct.
>>
>> no, catalysis is /not/ adsorption!
>
>
>
> I didn't say it was.

then i was confused when you said "cats work on adsorption principles".


> I said the reactions happen on the surface of the cat.
>
>
>
> <snip>
>
>
>>
>> i did actually explain the wash and the diffusion mechanism that binds
>> the ceramic particles, but you snipped it. the composition of the
>> ceramic substrate isn't particularly relevant provided it meets
>> physical requirements and doesn't react with the catalytic agents.
>>
>>
>
>
> But the reactive portion does sinter when overheated, just like I said.

no, the substrate sinters, and the reactive portion diffuses.


> Reduced surface area=reduced effectiveness.

yup. in part.


--
nomina rutrum rutrum

jim beam > wrote:
>
>are hard cookies "whispy too? because sintered ceramics are just like them.

They are like hard merangue cookies.

For that matter, so are many sleeve bearings.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

In article >,
Scott Dorsey > wrote:
>jim beam > wrote:
>>
>>are hard cookies "whispy too? because sintered ceramics are just like them.
>
>They are like hard merangue cookies.

No, actually, they are more like a honey cake. There are big grains, but
the space between the grains is filled up with liquid.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On 06/21/2011 05:03 AM, Scott Dorsey wrote:
> In >,
> Scott > wrote:
>> jim > wrote:
>>>
>>> are hard cookies "whispy too? because sintered ceramics are just like them.
>>
>> They are like hard merangue cookies.
>
> No, actually, they are more like a honey cake. There are big grains, but
> the space between the grains is filled up with liquid.
> --scott
>

that's not a representative example - solid state with a considerable
void percentage is by far the norm. there are some sinters that have a
liquidus phase, but they're usually the applications where they don't
get much high temperature use.


--
nomina rutrum rutrum

In article > ,
jim beam > wrote:
>On 06/21/2011 05:03 AM, Scott Dorsey wrote:
>> In >,
>> Scott > wrote:
>>> jim > wrote:
>>>>
>>>> are hard cookies "whispy too? because sintered ceramics are just like them.
>>>
>>> They are like hard merangue cookies.
>>
>> No, actually, they are more like a honey cake. There are big grains, but
>> the space between the grains is filled up with liquid.
>
>that's not a representative example - solid state with a considerable
>void percentage is by far the norm. there are some sinters that have a
>liquidus phase, but they're usually the applications where they don't
>get much high temperature use.

In the case of the bearings, the liquid is lubricating oil.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On 06/21/2011 08:47 AM, Scott Dorsey wrote:
> In article<JMCdnbLbEr0wOp3TnZ2dnUVZ_vSdnZ2d@speakeasy .net>,
> jim > wrote:
>> On 06/21/2011 05:03 AM, Scott Dorsey wrote:
>>> In >,
>>> Scott > wrote:
>>>> jim > wrote:
>>>>>
>>>>> are hard cookies "whispy too? because sintered ceramics are just like them.
>>>>
>>>> They are like hard merangue cookies.
>>>
>>> No, actually, they are more like a honey cake. There are big grains, but
>>> the space between the grains is filled up with liquid.
>>
>> that's not a representative example - solid state with a considerable
>> void percentage is by far the norm. there are some sinters that have a
>> liquidus phase, but they're usually the applications where they don't
>> get much high temperature use.
>
> In the case of the bearings, the liquid is lubricating oil.
> --scott
>

that's introduced /after/ the sinter - completely irrelevant.


--
nomina rutrum rutrum