Method of creating a pillared layered clay (PILC)

Catalyst – solid sorbent – or support therefor: product or process – Irradiation by – or application of – electrical – magnetic or...

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502 62, 502 84, B01J 2012, B01J 2116

Patent

active

053842952

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

PILCs may have application in the manufacture of electrically-conductive papers. A synthetic hectorite smectite clay (LAPONITE, from Laporte Industries Ltd) is mildly conductive and is used commercially in the manufacture of certain papers, both to pigment the paper and give it conductivity. It is an object of the present invention to increase the electrical conductivity of such clays as LAPONITE, while not losing any of their other properties which give them suitability for their use in papermaking.
In Inorg. Chim. Acta. 1987, 134, at page 99 Mandair and co-workers describe an attempt to increase the conductivity of LAPONITE and a natural montmorillonite by the intercalation of organic molecules. Increase of an order of magnitude in D.C. conductivity were measured.
A method of creating a PILC is disclosed in Inorg. Chem. 1989, 28, 2439-2443 by Petridis, D, and his co-workers. The method involves hydrolysing dimethyltin (IV) chloride and intercalating between the molecular layers of the clay the resulting dimethyltin (IV) cation. Thereafter, tin oxide pillars in the clay are created by heating the intercalated clay with glycerol to more than 200.degree. C.


DESCRIPTION OF THE INVENTION

It is one object of the present invention to devise a route for PILC production which avoids the cation exchange step or the heating step utilised in the Petridis method, so as to preserve to a greater extent the original properties of the clay, and provide enhanced prospects for improvement of electrical conductivity. According to the invention, this object is achieved by selecting as the pillaring precursor an electrically neutral organometallic molecule with a carbon-metal bond which is susceptible to proton attack whereby protons donated from sites of Bronsted acidity in the clay cleave the carbon-metal bond to yield an organic fragment of the precursor and a metal-containing pillaring fragment.
The precursor is preferably aryl, most preferably phenyl. The metal constituent up to now preferred is tin. Suitable molecules are:
The precursor is conviently presented in a liquid alcohol carrier, conveniently ethanol. Energy to bring about the intercalation of the precursor into the clay can be provided by mechanical shaking, but the thermal energy delivered by an ordinary domestic microwave oven has proved extremely effective with laboratory experimental samples, yielding in 5 minutes a very substantial part of the maximum intercalation achievable with any particular sample.
As mentioned above, the clay can be a montmorillonite but is preferably a synthetic hectorite such as sodium or potassium LAPONITE.


BRIEF DESCRIPTION OF THE DRAWING

The invention will now be further described with reference to the following Example and the attached accompanying drawing which shows conductivity plotted against frequency for materials 10, 11, 12 and 13.


EXAMPLE

LAPONITE clay material in its RD form, that is, free from fluoride and tetron) was obtained from Laporte Industries Ltd. Ph.sub.3 SnCl and Ph.sub.2 SnCl.sub.2 were obtained from Aldrich Chemical Co. Ltd. Triphenyltin oxide was prepared by hydrolysis of Ph.sub.3 SnCl.
To 10 cm.sup.3 of dry ethanol was added 0.3 g of the triphenyl tin oxide and 1.0 g of the LAPONITE clay. In a 700 W microwave oven the mixture was subjected to 5 one minute bursts of microwave radiation. Afterwards, 0.2 g of the oxide were recovered from ethanol washings. Further experiments using irradiation times from 1 to 30 minutes established an optimum time of 5 minutes.
The experiment was repeated with the other two pillaring precursors. The results are given in Table 1 below:


TABLE 1 ______________________________________ % Material (W/W) Intercalated Mechanical Microwave COMPOUND Shaking Irradiation ______________________________________ (Ph.sub.3 Sn).sub.2 O 10 33 Ph.sub.3 SnCl 45 75 Ph.sub.2 SnCl.sub.2 38 44 ______________________________________
To assess conductivity, pressed discs of clay (0.25 g) were used. Copper wires attached to the discs

REFERENCES:
patent: 4510257 (1985-04-01), Lewis et al.
patent: 4515901 (1985-05-01), Elattar
patent: 5264404 (1993-11-01), Takahama et al.

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