Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Inorganic carbon containing
Patent
1981-12-28
1984-03-27
Gantz, Delbert E.
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Inorganic carbon containing
264 291, 423445, 423449, B01J 2118, C01B 3102
Patent
active
044393490
DESCRIPTION:
BRIEF SUMMARY
This invention relates to mesoporous and wider pore carbons which are useful as supports for catalysts or as adsorbants for larger organic molecules, for example aromatic molecules. It also relates to a method for making mesoporous carbons.
Hitherto adsorbant carbons such as activated charcoals have been made by carbonising for example coal, peat, wood or coconut shell to produce a predominantly carbon substrate and then treating the substrate with an oxidising agent to create adsorbant pores in the carbon. Pores created in this way have a wide variety of sizes ranging from micropores (ie having diameters well below 2 nm) through mesopores (ie having diameters of from 2 to 80 nm or more conventionally 2 to 50 nm) to macropores (ie having diameters well above 100 nm). Neither the size of pores created nor the distribution of pore sizes can be pre-determined accurately because a continuing treatment by the oxidising agent not only enlarges existing pores but it also creates new micropores. Accurate pre-determination of pore size and pore size distribution are important because both influence the performance of supported catalysts or adsorbtion reaction.
British patent specification No. 1 536 715 describes an attempt to produce mesoporous carbons having a pre-determinable narrow range of pore sizes. This is done by packing particles of furnace black or channel black in a polymeric binder so that the spaces between adjacent packed particles are of mesoporous size. The binder is then carbonised to render the packed assembly form-stable. However, the pore size and pore size distribution obtained in this way are not accurately pre-determinable partly because the particle sizes of carbon blacks vary over wide ranges even after sieving and partly because GB No. 1 536 715 does not provide means for packing the carbon particles in a regular assembly. A further consequence of irregular packing is that the pathways created by interconnected pores are highly tortuous owing to the irregular location of the adjacent particles which define the pores. High tortuosity inhibits the flow of molecules through the pathways. Also in practice high tortuosity restricts the size of molecules which can flow usefully to below the maximum size of molecule which would theoretically make a clearence fit in a pathway.
An object of this invention is to provide an adsorbant wide pore (especially a mesoporous) carbon comprising a more regular assembly of carbon particles so allowing more accurate pre-determination of the size and size distribution of the pores and creating less tortuous pathways of interconnected pores. A further object is to provide an adsorbant wide pore carbon having a pre-determined degree of regularity. Another object is to provide a method for making such adsorbant wide pore carbons and to provide a method for pre-determining the degree of regularity in the assembly of carbon particles.
Accordingly this invention provides an adsorbant wide pore carbon comprising a form-stable assembly of a family of contiguous spheroidal (preferably spherical or oblate spherical) carbon particles wherein the surfaces of adjacent contiguous particles define interstitial pores characterised in that number of that particles of the family lie in the range 8 to 3000 (preferably 50 to 400) nm, particles of the family is less than 15% (preferably less than 5%) and packed to an extent that the volume of interstitial pores in the zone is from 18 to 30% (preferably 23 to 28%).
Often when such a carbon is provided with a smooth surface it is very lustrous which is indicative of the regularity of the carbon particles in the assembly which in turn implies a low tortuosity of pathways created by interconnected interstitial pores. The size of the pores can be changed in a pre-determinable way by selective variation of the size of the particles.
Close packing of perfect spheres is defined by A. F. Wells in the book "Structural Inorganic Chemistry" fourth edition (pages 130 and 133) published by the Clarendon Press of Oxford in 1975. The contents of th
REFERENCES:
patent: 4029600 (1977-06-01), Schmitt
patent: 4081370 (1978-03-01), Schmitt
patent: 4118341 (1978-10-01), Ishibashi et al.
patent: 4263268 (1981-04-01), Knox et al.
Bligh Stephen G.
Everett Douglas H.
Rojas Fernando
Gantz Delbert E.
McFarlane Anthony
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