Catalyst – solid sorbent – or support therefor: product or process – Solid sorbent – Free carbon containing
Patent
1992-01-13
1994-02-01
Konopka, Paul E.
Catalyst, solid sorbent, or support therefor: product or process
Solid sorbent
Free carbon containing
165905, 165 1, 252378R, 423448, 502406, 502416, B01J 2020, B01J 802, C04B 3554, F25B 1708
Patent
active
052832198
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an active composite comprising a compressed support and an agent which is reactive towards a gas. The present invention also relates to a method for implementation of gas/solid or gas/liquid physicochemical processes using such an active composite as reaction medium
In some sectors, such as, for example, that of chemical heat pumps based on the thermicity of the reaction between a solid and a gas, or of the adsorption of a gas on a solid, a mixture of a finely divided material, such as expanded graphite, and a solid reactant, for example a salt or an adsorbent such as a zeolite, is used. The mixture of expanded graphite and this solid, which is the seat of a chemical reaction or of a physical adsorption, has numerous advantages during a chemical reaction or a physical adsorption between the solid and a gas. The expanded graphite is in the form of platelets or platelet particles having a very large specific surface area and permits the diffusion of the gas even in a confined medium.
The substantial improvement observed in the kinetics of reversible solid/gas reactions, as resulting from the mixture of the active solid with natural graphite expanded by a thermal route, in the given proportions by mass and compacted in a fixed volume, results from an excellent permeability of the fixed bed prepared in this way to the reactive gas and in a thermal conductivity accompanied by a good heat exchange coefficient at the walls. Conventionally, the preparation of such a reagent leads to a homogeneous isotropic bed, the isotropic conductivity of which lies at values of 0.5 to 2 Wm.sup.-1 K.sup.-1 depending on the conditions of preparation (proportion and compacting), and the exchange coefficient of which at the walls is between 50 and 150 Wm.sup.-2 K.sup.-1.
Despite these advantages, the use of such mixtures in the granular state has drawbacks because of the difficulty in obtaining truly homogeneous mixtures, the difficulty in handling these and the large volume which they occupy. Moreover, the reactant, which is frequently hygroscopic, has a tendency to absorb moisture if the mixing operation is prolonged; a subsequent dehydration is lengthy and even costly and may influence the quality of the final product even after dehydration.
The aim of the present invention is, therefore, an active composite which is in the form of a block which can be handled easily and which, while preserving excellent permeability in one direction, has heat transfer properties in a preferred direction.
To this end, the invention proposes an active composite comprising a compressed support and an agent which is reactive towards a gas, characterised in that the compressed support comprises recompressed expanded graphite having a density of between 0.02 and 1.5. Unless stated otherwise, all values of density are expressed by conventional units (g/cm.sup.3 or g cm.sup.-3).
According to a preferred embodiment, the active composite contains from 1 to 95% by weight of recompressed expanded graphite and from 99 to 5% by weight of active agent.
The invention also provides a method for the implementation of solid/gas or solid/liquid [sic] physicochemical processes, characterised in that it uses, as reaction medium, an active composite comprising a compress support and an agent which is reactive towards a gas, the compressed support comprising recompressed expanded graphite having a density of between 0.02 and 1.5.
Such a block of active composite is intended to be used to carry out either a reaction of the solid/gas type, or an adsorption between a gas and a solid, or the absorption of a gas in a liquid, for example a saturated or unsaturated solution of a solid, or a reaction between a gas and a liquid catalysed by a solid, or the seat of a condensation/evaporation of a gas, or, finally, a gas conversion reaction catalysed by a solid. Thus, the present invention provides a method for carrying out either reactions of the gas/solid type, or gas/solid adsorption, or absorption of a gas in a liquid or, finally, catalytic c
REFERENCES:
patent: 3404061 (1968-10-01), Shane et al.
patent: 4432408 (1984-02-01), Caines
patent: 4595774 (1986-06-01), Coste et al.
Drapier Claude
Lebrun Michel
Mauran Sylvain
Moreau Michel
Prades Philippe
Konopka Paul E.
Le Carbone Lorraine
Societe Nationale Elf Aquitaine
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