FR2758551A1 - Method for augmenting the porosity of clay supports such as sepiolite - Google Patents

Abstract

A method is claimed for a treatment designed to augment the porosity of clay supports essentially incorporating in their structures some metallic atoms and its particular application for sepiolite. It consists of submitting these supports to a sensitisation acid washing then to a centrifugation and a drying of the treated active material by ultra-sonic waves in order to allow pressurising of the molecular linkage between the silica and magnesium of the open structure of the porosity of the supports and realising a shearing effect to liberate the heavy magnesium atoms from the silica structure. Such a treatment of the sepiolite augments the cross section of the intercrystalline channels of the porosity and sensitises the internal exchange surfaces. The apparatus for carrying the above method is also claimed.

Description

The present invention relates to a device for processing the supports of the

  CLAY type essentially comprising in their molecular structures metal atoms in general and its particular application for sepiolite which can serve as a support and basic constituent for the constitution of materials and products absorbing volatile compounds from the atmosphere These clay supports have particular structures characterizing a large porosity which is interesting for the surfaces of exchange with gases from the atmosphere. The characterization for the circulation of gases in these porosities is determined by

  the opening of these intercrystalline canals.

  In the particular case of sepiolite, the constitution of the longitudinal porosities is defined by a distribution in sheets of units of tetrahedral silicas linked by means of oxygen atoms to an octahedral sheet comprising magnesium atoms for supports of the magnesian type. . This particular structure characterizes the cylindrical porosities whose opening is conditioned by the positioning of the metallic atoms including the magnesium atoms for magnesium sepiolite in particular This distribution is represented schematically in a single plane for the correct

  functional understanding of the device in Figure 2.

  FIG. 2 represents the channels of the unit porosities comprising in the tetrahedral section the silica atoms (21) the oxygen atoms (22) and the magnesium atoms (23) which are positioned in octahedral connection on the end of the channels cylindrical. This distribution consolidates the cylindrical channels (20) of the porosities and the channels (30) characterize the opening

octahedral porosity.

  To promote the circulation of volatile compounds from the atmosphere in these channels, the device which is the subject of the invention consists in opening these porosities and in lightening them from heavy metallic atoms which by their weight have the natural tendency of bonds to close and cause thus a more or less obstruction

  important octahedral openings.

  To favor the capacity of physico-chemical reactions, to transform the volatile compounds circulating in these channels, it is useful to ensure a pretreatment of these active centers of absorption to sensitize and increase the capacities of interactions of the silica hydroxyl groups with the external molecules by forming covalent bonds with certain organic reagents. The device which is the subject of the invention particularly performs this sensitization treatment by acid washing and the opening of the porosities is increased by a significant value by the centrifugation of the sepiolite to remove the heavy atoms from

  magnesium at the opening of the porosities.

  Figure i shows the treatment equipment to condition the opening of the pores and to sensitize the

internal exchange surfaces.

  The device comprises a pretreatment washing capacity (1) a centrifugation machine (7) with its multiplier (8) and its heating jacket (6). The material to be treated, the clay and the magnesium sepiolite in particular is injected under pressure and atomized at the top of the tank (1). The arrivals of acidic liquid under pressure on the spray nozzles (3) and (4) of the capacity (1) makes it possible to carry out an energetic mechanical washing of the material introduced (2) under a very fine particle size at the top of the capacity (1). This energetic acid treatment in a fluidized environment significantly increases the cross section of the intercrystalline channels of the porosities of the

material thus treated.

  This constituent, mixed and fluidized with an acidic liquid, is introduced into the upper part of the centrifuge (7). The mixture is centrifuged at a speed greater than 10,000 revolutions per minute and in an envelope maintained at a temperature between 150 and 200 degrees centigrade by canes

  heating (6) for heating the casing of the centrifuge (7).

  The temperature treatment of the material, the sepiolite in an acid medium increases the cross section of the porosity channels. The high speed centrifugation of the mixture allows, by the shear effect, the stressing of the molecular bond silica and magnesium of the open structure of the porosities as shown in Figure 2. The external stress forces of heavy metal atoms including magnesium for the particular structure of sepiolite, induced by centrifugation, are characterized by the establishment of a tensile stress field (24) on the magnesium atoms (23) to operate the shear effect (26) of the bond silica (21). The sheared bond (26) freed from the weight of the metal atoms leads to an opening (30) more

  large porosity of the treated material.

  At the lower outlet of the centrifugation stages, the heavy residues comprising inter alia the metallic atoms are extracted at the periphery (9), the liquid is discharged at (10) and the treated material leaves the central part to enter the capacity for

drying (11).

  The drying of the granules of treated material is ensured by ultrasonic waves at adjustable frequency and power emitted by the bases (12) positioned at the periphery of the drying capacity (11) The dried granules exit through the nozzle (13) to be sprayed into a buffer tank (16). The reservoir (16) comprises a heating drum (17) which makes it possible to maintain the temperature and perfect the drying of the material thus treated. The clay or sepiolite material in particular thus treated can be directed

  towards processing facilities (19).

  Process liquid can be directed directly into the

  bioreactors of link processing (18).

  The capacities (11) and (16) are ventilated and put under vacuum by a fan (14) and a filter (15) This energizing depression of the capacities (11) and (16) essentially promotes the flow and drying of the treated material which circulates in

fluidized bed.

Claims (5)

  1) Treatment method intended to increase the porosity of supports of the CLAY type essentially comprising in their structures metal atoms in general and its particular application for sepiolite, characterized in that it consists in subjecting these supports to an acidic sensitization washing then to a centrifugation and a drying of the active material treated by ultrasonic waves in order to allow the stressing of the molecular bond silica (21) and magnesium (23) of the open structure of the porosities (30) of said supports and achieve the shear effect (26) to release the heavy magnesium atoms (23) from the silica structure, such treatment of sepiolite increases the cross section of the intercrystalline channels of the porosities and sensitizes the internal exchange surfaces 2) Method according to claim 1 characterized in that the treatment includes washing the material to be treated in very fine particle size injected in ato'nized form into the upper part (2) of a capacity (1) is carried out by an acidic liquid introduced under pressure to ensure a vigorous mechanical pretreatment of sensitization and furthermore comprises a high speed centrifugation this material which is then directed into a tank (11) disposed at the outlet of the centrifuge to be dried by waves ultra sound.   3) Device for implementing the method according to the   Claims 1 and 2 characterized in that it comprises a   washing capacity (1) into which the material to be treated is injected in atomized form at the top (2) and mixed with an acidic liquid introduced under pressure by nozzles (3) and (4), a centrifuge (7) comprising a multiplier (8) allowing a speed of rotation greater than 10,000 revolutions per minute and said centrifuge is provided at the lower outlet of the high-speed centrifugation stages with an outlet (9) for extracting heavy residues at the periphery, an outlet (10) for the treatment liquid and an outlet in the central part directing the treated material into a drying capacity (11) with ultrasonic waves to be recovered at the outlet in a storage buffer tank (16) 4) Device according to claim 3 characterized in that the outer casing of the centrifuge (7) is provided with heating rods (6) intended to maintain the whole of the centrifugation at a temperature comprised between e 150 and 200 degrees centigrade) Device according to claim 3 and claim 4 characterized in that the ultra sonar waves emitted by bases (12) are of variable frequencies and powers and positioned at the periphery of the drying capacity (11)   6) Device according to claims 3, 4 and 5 characterized in that   that the capacity (11) comprises a nozzle (13) on the outlet of the dried granules of said capacity for spraying the granules in a buffer tank (16) maintained at temperature by a heating drum (17) to complete the drying of the matter processed.   7) Device according to any one of claims 3 to 6   characterized in that the capacities (11) and (16) are ventilated and placed under vacuum by a fan (14) comprising a filter (15) to promote the drying of the treated material which circulates in a bed fluidized.   8) Application of the supports treated from the process according to the   Claims 1 and 2 to the production of absorbents for the compounds atmospheric volatiles