Surfactant Classes Syntheses

Surfactant-based synthesis of mesoporous metal oxides and metal sulfides emerged about four years after the initial report of MCM-41 [21-36]. High surface area and thermally robust mesoporous metal oxides and sulfides represent a new class of materials with diverse opportunities for the development of improved fuel and solar cells, batteries, membranes, chemical delivery vehicles, heavy metal sponges, sensors, magnetic devices and new catalysts. All of these applications could benefit from tailorable Bronsted and Lewis acidity and basicity, flexible oxidation states, and tunable electronic, optical and magnetic properties. 

Carboxyamphoteric surfactants based on fatty alkyl imidazolines ( imidazolinium surfactants) make up a large part of the amphoteric surfactants. The very divergent interpretation of their chemical structure is partly attributable to little-developed analytical procedures in the past, but is also a consequence of special processing methods by different manufacturers. Materials of this surfactant class are based on the imidazolines obtained by the condensation of fatty acids, or their esters, with AEEA. In Figures 12.4 and 12.5, a summary of the synthesis of amphoteric surfactants based on imidazolines [4,8] is presented. 

Based on petrochemicals, linear alkyl benzene sulfonates (LAS) are the most important surfactants. First description can be found in patents from the mid-1930s [2] using Fischer-Tropsch synthesis and Friedel-Crafts reactions. With the beginning of the 1950s the importance of the class of surfactants rose. The main use is in household and cleaning products. 

A new class of heterogeneous catalyst has emerged from the incorporation of mono- and bimetallic nanocolloids in the mesopores of MCM-41 or via the entrapment of pro-prepared colloidal metal in sol-gel materials [170-172], Noble metal nanoparticles containing Mex-MCM-41 were synthesized using surfactant stabilized palladium, iridium, and rhodium nanoparticles in the synthesis gel. The materials were characterized by a number of physical methods, showed that the nanoparticles were present inside the pores of MCM-41. They were found to be active catalysts in the hydrogenation of cyclic olefins such as cyclohexene, cyclooctene, cyclododecene, and... 

Another large class of chemicals produced starting from ethanol are ethyl-amines. When heated to 150-220 °C over a silica- or alumina-supported nickel catalyst, ethanol and ammonia react to produce ethylamine. Further reaction leads to diethylamine and triethylamine. The ethylamines find use in the synthesis of pharmaceuticals, agricultural chemicals, and surfactants. 

During the past ten years, there have been numerous reports on the synthesis and the application of crown ethers of specific character to various fields. There have been also a few studies of the surface and micellar properties of crown ethers with hydrophobic groups (J - 17). The author has called them surface active crown ethers as a new class of surfactant possessing a promising function (11). 

Design and synthesis of polycyclic molecules with unusual shape, symmetry, and chemically distinct surfaces resulted in a novel class of heterobowls such as 10 (see Section 14.09.2). Although no utilitarian applications of these compounds have been reported yet, this is perhaps because of their recent discovery, the heterobowls might display many interesting properties, such as selective activity for metal ions, face-selective chemical reactivity, surfactant chemistry, and enzyme mimicry <1997TL4173, 2001JOC6905>. 

It is in this class of compounds that the practice of semi-synthesis particularly in the industrial sphere of single or two-step operations is pre-eminent and traditional. The preparation of soap, monoglycerides, or their sulphates, the fatty alcohols, amides and numerous other functional compounds many of which are examples of nucleophilic substitution almost entirely devolve on the reactions of glycerides many of which are examples of nucleophilic substitution. The range of these tranformations particularly with reference to recent developments in surfactant chemistry has been summarised (ref. 100) and discussed with regard to edible applications (ref.101). 

Synthesis of Fluorinated Sulfonamides. All compounds presented in this paper were prepared and provided by 3M Company. The general class of compound has been knewn for many years as surfactants (26,27). The general synthetic scheme is as follows ... 

The templates used in the synthesis of mesostructured and mesoporous materials can be classified into two categories The first class of templates includes soft templates, which are ordered arrays of self-assembled surfactant micelles, similar to the ones used by the researchers at Mobil. Alternately, mesoporous materials can themselves be used as templates to synthesize new mesostructured materials, and such templates can be termed as rigid templates. In the following sections, we focus on the use of supramolecular assemblies of surfactants as well as on the use of rigid templates as the templates for the synthesis of mesostructured materials. 

Many of the non-silica compositions showed problems with the stability and quality of the structure. Efforts to address these issues have been on going and quite successful in some cases such as all-alumina compositions (see below). Silica-based materials remain dominant as the most versatile and best quality molecular sieves (structure and stability) available by a facile synthesis. These attributes, especially the convenient synthesis made mesoporous silicate attractive for post-synthesis functionalization with other elements as well as organic moieties with active groups/ccnters. Recently the compositional diversity has been extended further to include both silica and organic moieties within the framework. The new class is referred to as periodic mesoporous organosilicas (PMOs). The synthesis involves surfactant-assisted assembly by hydrolysis of organo-silicon compounds. Additional discussion of the PMOs is presented below. 

The surfactant tcmplated mesoporous materials were treated as an extension of microporous solids and have been adopted by the scientific community as part of the zeolite endeavor. On the other hand there are fundamental differences between the two classes and this has had a significant impact and consequences in the areas of synthesis, characterization, and practical applications, especially catalysis. 

Chapter 1 gives a systematic view of different classes of surface active substances non-ionic, anionic, cationic, amphoteric and zwitter-ionic surfactants. For each class, the synthesis of a surfactant from different initial substances (including the reaction mechanisms, main production routes, conditions for the best performance etc.), and the chemical analysis of the product properties are summarised. Reference information about manufacturers, nomenclature... 

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