Ordered Porous Solids

Recent Advances and Prospects

Valentin Valtchev, Svetlana Mintova, Michael Tsapatsis, Valentin Valtchev, Svetlana Mintova, Michael Tsapatsis

• Editore: Elsevier Science
• Anno: 2011
• ISBN:
  9780080932453
• Argomento: Scienze fisiche
• Categoria: Mineralogia

The developments in the area of ordered nanoporous solids have moved beyond the traditional catalytic and separation uses and given rise to a wide variety of new applications in different branches of chemistry, physics, material science, etc. The activity in this area is due to the outstanding properties of nanoporous materials that have attracted the attention of researchers from different communities. However, recent achievements in a specific field often remain out of the focus of collaborating communities. This work summarizes the latest developments and prospects in the area of ordered porous solids, including synthetic layered materials (clays), microporous zeolite-type materials, ordered mesoporous solids, metal-organic-framework compounds (MOFs), carbon, etc. All aspects, from synthesis via comprehensive characterization to the advanced applications of ordered porous materials, are presented. The chapters are written by leading experts in their respective fields with an emphasis on recent progress and the state of the art.

• Summarizes the latest developments in the field of ordered nanoporous solids
• Presents state-of-the-art coverage of applications related to porous solids
• Incorporates 28 contributions from experts across the disciplines

Chapter 1. A New Family of Mesoporous Oxides—Synthesis, Characterisation and Applications of TUD-1

Contents

1. Introduction 4
2. MCM-41 and FSM-16 5
3. TUD-1 6
4. Redox Metal Incorporation into Siliceous TUD-1 Framework 10
   1. Ti-TUD-1 10
   2. Fe-TUD-1 11
   3. Co- and Cr-TUD-1 14
   4. Ce-TUD-1 17
   5. Zr-TUD-1 18
5. Al² O³ -TUD-1 and Al-TUD-1 19
6. TUD-1 as Potential Drug Carriers 21
7. Particle Incorporation 22
   1. Zeolite Beta 22
   2. ITQ-2—Delaminated zeolite 26
8. Conclusion 28
9. References 29

Keywords

Mesoporous oxides

Nanoparticles

Composite materials

Synthesis

Catalysis

Abbreviations

CTMA

Cetyltrimethylammonium

FTIR

Fourier Transform Infrared

MPV

Meerwein-Ponndorf-Verley

NMR

Nuclear Magnetic Resonance

SMPO

Styrene Monomer Propylene Oxide

TBHP

tert-Butylhydroperoxide

TEA

Triethanolamine

TEAOH

Tetraethylammonium hydroxide

TEOS

Tetraethoxysilane

TOF

Turnover frequency

(HR) TEM

(High Resolution) Transmission Electron Microscopy

UV-vis

Ultraviolet-Visible Spectroscopy

XRD

X-ray Diffraction

Abstract

There exists much work regarding the synthesis of mesoporous materials. TUD-1 is one recent development whereby a non-surfactant organic compound (triethanolamine) templates the formation of mesoporous oxides. Transition metals varying from atomically dispersed isolated centres to nanoparticulate oxides are incorporated easily and controllably in a one-pot synthesis mixture, and have shown considerable catalytic performance when evaluated in various reaction types. Furthermore, composite micro-/mesoporous systems have been synthesised and applied successfully in a range of acid-catalysed reactions. This chapter aims to provide an up to date review of TUD-1 and its derivatives, their synthesis, characterisation and application.

1. Introduction

Porous materials of varying chemical characteristics (basic, acidic, redox-active, inert, conducting, semi-conducting, etc.) are of fundamental importance in the areas of science and technology.^[1,2] This is due to the presence of voids of controllable dimensions at the atomic, molecular and nanometre scale.^[3] Their use in industry is extensive ranging from areas such as petroleum refining,^[4] detergents,^[5] medicinal applications^[6] and separations.^[7] The International Union of Pure and Applied Chemistry (IUPAC) divides porous materials into three classes based on their pore diameter (d): microporous d < 2.0 nm, mesoporous 2.0 ≤ d ≤ 50 nm and macroporous d > 50nm.^[8] Pore architectures (size, shape, connectivity) and the nature of the pore distribution, in combination with the chemical characteristics of the pore walls, determine the properties (and hence applications) of such materials.

Arguably, the most important group of porous materials so far is the microporous one, in particular zeolites. Although these crystalline aluminosilicates are used extensively in industry, they do suffer from significant drawbacks as a result of their small pore sizes. Zeolites can experience problems in mass transfer, affecting diffusivities of the reactants and products to and from the active sites. In addition, in some reactions, like catalytic cracking, this might lead to coke formation, degrading the catalytic activity of a zeolite. The inability of bulky substituents to make use of the extensive internal surface area restricts their use in important chemical processes. Much work has been carried out in the literature to address the limitations of zeolites, one of the methods being the synthesis of materials with larger sized pores. One of the most significant contributions has sprung from work involving mesoporous material synthesis, initiated by the groups led by Beck^[9] and Kuroda.^[10]

2. MCM-41 and FSM-16

The best-known family of mesoporous materials is MS41, and from that group, MCM-41, first reported in 1992.^[9] The material was synthesised in an effort to form an improved alternative to zeolites. MCM-41 material exhibits a regular, hexagonal arrangement of pores (P6mm symmetry) with one-dimensional parallel channels, formed as a result of liquid crystal templating. This mechanism is thought to be a result of either the silicate synthesis gel condensing around the pre-arranged micelles formed from the cetyltrimethylammonium (CTMA⁺) template or by the silicate influencing the formation of the liquid crystal phase (Fig. 1.1),^[11] depending on the concentrations used. Pore sizes obtained for this material can range from 1.5 to 10 nm.

Figure 1.1. Possible mechanistic pathways for the formation of MCM-41: (1) liquid crystal phase initiated and (2) silicate anion initiated.

Reprinted with permission from Beck et al. ^[11] Copyright (1992) TheAmericanChemical Society.

FSM-16, a material with a ...