Invited review
Synthetic organo- and polymer–clays: preparation, characterization, and materials applications

https://doi.org/10.1016/S0169-1317(00)00005-3Get rights and content

Abstract

We have over the years developed and patented a general technique for the hydrothermal synthesis of clay minerals in the presence of organic, organometallic, and polymeric intercalants. This review will summarize the details for crystallization of modified hectorites along with their characterization and materials applications. Among the several potential uses of these synthetic materials, there are two important applications concerning catalysis and composites. The fate of the template dictates which of these applications is pertinent. First, if the organic molecule or polymer is used with the intention of acting as templates of pore structure, then the organic template is removed after the modified clay has been crystallized. Upon template removal, the now porous materials are examined for their use as potential catalysts and catalyst supports. We have recently proven a correlation between catalyst pore size in the mesoporous range and the size and concentration of a polymeric template that is used. Preliminary hydrodesulfurization catalytic results have been obtained using these materials. If, on the other hand, intercalants are allowed to remain as a part of the structure, then a distinctive class of organic–inorganic composites becomes possible. When polymeric intercalants are used, especially at high concentrations, the materials have relevance to nanocomposite applications. Work in this area has focused on incorporating polymers at higher than 85 wt.% of the nanocomposite.

Section snippets

Background

The most common question asked in regards to this work is “Why bother to make organo-clays synthetically when natural clays are so abundant and so easily modified with organics?” One aim of this review is to address this question, whose answer lies mainly in designed materials applications. Variables such as purity, composition, reproducibility, and specifically designed features can be often controlled better this way than by using natural clay specimens, which, among other certain drawbacks,

General synthetic details

Precursor clay gels are of the composition:0.32R,1.0LiF,5.3Mg(OH)2,8SiO2,nH2Oto correlate with the ideal hectorite composition (Grim, 1968):Ex0.66[Li0.66Mg5.34Si8O20(OH,F)4]where R=monovalent organic salt and Ex=exchangeable cation (Ex=Li,R from this gel). Syntheses were not successful when the cited amount of R=LiF=0.66 mol was used (Barrer and Dicks, 1967). A typical (scaled-down) reaction begins by dissolving 0.72 mmol of organic (monovalent) in water and adding 4.8 mmol LiF with stirring.

Materials applications

At least two quite different applications arise depending upon the fate of the template in the synthetic organo-clay. First, if the organic molecule or polymer is used with the intention of acting as templates of pore structure, then the organic template is removed after the modified clay has been crystallized. Upon template removal, the now porous materials are examined for their use as potential catalysts and catalyst supports. If, on the other hand, the templates are allowed to remain as a

Summary

Let us once again address the question posed at the very beginning of this article: Why bother to create synthetic polymer–clay materials? In addition to the variables already discussed (purity, compositional variety, reproducibility) are those of tunability and other designer properties, such as pore size, aspect ratio, and layer charge. The tunability of the MSCs with respect to pore size, for example, has an advantage over the similar M41S class of materials in that the synthetic procedure

Acknowledgements

Several collaborators have contributed greatly to the progress of this overall project, including Langqiu Xu, P. Thiyagarajan, Christopher L. Marshall, Kang Song, James R. Brenner, Di Wei, Delwin L. Elder, Gerry W. Zajac (BP-Amoco), Randall E. Winans, Sönke Seifert, Roseanne Csencsits, David Gregory, and Robert E. Botto (all of ANL unless otherwise stated). The helpful comments of R. Vaia regarding the manuscript are appreciated. This work was performed under the auspices of the U.S. Department

References (79)

  • P. Aranda et al.

    Microwave assisted blending-intercalation of ion–conductor polymers into layered silicates

    Mater. Res. Soc. Symp. Proc.

    (1998)
  • A.C. Balazs et al.

    Modeling the interactions between polymers and clay surfaces through self-consistent field theory

    Macromolecules

    (1998)
  • R.M. Barrer et al.

    Chemistry of soil minerals: Part IV. Synthetic alkyl-ammonium montmorillonites and hectorites

    J. Chem. Soc. A

    (1967)
  • Beall, G.W., Tsipursky, S., Sorokin, A., Goldman, A., 1996. Intercalates; exfoliates; process for manufacturing...
  • Beall, G.W., Tsipursky, S., Sorokin, A., Goldman, A., 1999a. Intercalates and exfoliates formed with monomeric amines...
  • Beall, G.W., Tsipursky, S., Sorokin, A., Goldman, A., 1999b. Intercalates and exfoliates formed with oligomers and...
  • W.I. Beaton et al.

    Resid hydroprocessing at Amoco

    Catal. Rev. Sci. Eng.

    (1991)
  • S.L. Burkett et al.

    Synthesis of hybrid inorganic–organic mesoporous silica by co-condensation of siloxane and organosiloxane precursors

    Chem. Commun.

    (1996)
  • S.D. Burnside et al.

    Synthesis and properties of new poly(dimethylsiloxane) nanocomoposites

    Chem. Mater.

    (1995)
  • K.A. Carrado

    Preparation of hectorite clays utilizing organic and organometallic complexes during hydrothermal crystallization

    Ind. Eng. Chem. Res.

    (1992)
  • K.A. Carrado et al.

    The direct synthesis of organic and organometallic-containing mica-type aluminosilicates

    Prepr. Pap. — Am. Chem. Soc., Div. Petrol. Chem.

    (1993)
  • K.A. Carrado et al.

    In situ synthesis of polymer–clay nanocomposites from silicate gels

    Chem. Mater.

    (1998)
  • K.A. Carrado et al.

    Hydrothermal crystallization of porphyrin-containing layer silicates

    Inorg. Chem.

    (1991)
  • K.A. Carrado et al.

    Incorporation of phthalocyanines by cationic and anionic clays via ion-exchange and direct synthesis

    Chem. Mater.

    (1993)
  • K.A. Carrado et al.

    Polyvinyl alcohol–clay complexes formed by direct synthesis

    Clays Clay Miner.

    (1996)
  • K.A. Carrado et al.

    A study of organo-hectorite clay crystallization

    Clay Miner.

    (1997)
  • K.A. Carrado et al.

    Crystal growth of organo-hectorite clay as revealed by atomic force microscopy

    Langmuir

    (1997)
  • K.A. Carrado et al.

    Porous networks derived from synthetic polymer–clay complexes

  • K.A. Carrado et al.

    Mesoporous synthetic clays: synthesis, characterization, and use as HDS catalyst supports

  • K.A. Carrado et al.

    The crystallization of hectorite clay as monitored by small angle X-ray scattering and NMR

    Prepr. Pap. — Am. Chem. Soc., Fuel Chem. Div.

    (2000)
  • K.A. Carrado et al.

    Polymer–clay nanocomposites from synthetic polymer-silicate gels

    (2000)
  • Carrado-Gregar, K., Winans, R.E., Botto, R.E., 1994. Organic or organometallic template mediated clay synthesis.U.S....
  • Y. Chen et al.

    Synthesis and characterization of polyimide silica hybrid composites

    Chem. Mater.

    (1999)
  • R. Dagani

    Putting the ‘nano’ into composites

    Chem. Eng. News

    (1999)
  • B. Delmon

    New technical challenges and recent advances in hydrotreatment catalysis. A critical updating review

    Catal. Lett.

    (1993)
  • J.G. Doh et al.

    Synthesis and properties of polystyrene–organoammonium montmorillonite hybrid

    Polym. Bull.

    (1998)
  • H.R. Fischer et al.

    Nanocomposites from polymers and layered minerals

    Acta Polym.

    (1999)
  • Y. Fukushima et al.

    Swelling behaviour of montmorilloinite by poly-6-amide

    Clay Miner.

    (1988)
  • P.H. Gamlen et al.

    Structure and dynamics of microcrystalline graphite, graphon, by neutron scattering

    J. Chem. Soc., Faraday Trans. 2

    (1976)
  • Cited by (0)

    View full text