Montmorillonite clays catalyst

Bolognini, M., Cavani, F, Cimini, M., Dal Pozzo, L., Maselli, L., Venerito, D., Pizzoli, F, and Veronesi, G. 2004. An environmentally friendly s)mthesis of 2,4-dihydroxybenzophenone by the single-step O-mono-benzoylation of 1,3-dihydroxybenzene (resorcinol) and Fries rearrangement of intermediate resorcinol monobenzoate the activity of acid-treated montmorillonite clay catalysts. C. R. Chim. 7 143-150. 

Dimerization of fatty acids occurs in the presence of radical sources, on heating, and under the influence of clay catalysts, this last being employed on a commercial basis to meet the demand for dimer acids. Typical manufacturing conditions use 4% montmorillonite clay catalyst at 230 °C for 6-8 hours. Fractionation of the product into monomer, dimer and trimer involves some form of molecular distillation. 

Dehydration of 1-pentanol or 2-pentanol to the corresponding olefins has been accompHshed, in high purity and yields, by vapor-phase heterogeneous catalyzed processes using a variety of catalysts including neutral gamma —Al Og catalyst doped with an alkah metal (23), zinc aluminate (24,25), hthiated clays (26), Ca2(P0 2 montmorillonite clays (28). Dehydration of 2-methyl-1-butanol occurs over zinc aluminate catalyst at... 

Bentonite is a rock rich in montmorillonite that has usually resulted from the alteration of volcanic dust (ash) of the intermediate (latitic) siliceous types. In general, reUcts of partially unaltered feldspar, quartz, or volcanic glass shards offer evidence of the parent rock. Most adsorbent clays, bleaching clays, and many clay catalysts are smectites, although some are palygorskite [1337-76 ]. 

Newer catalysts for the PK synthesis include montmorillonite clays,... 

Bakke et al. (1982) have shown how montmorillonite catalyses chlorination and nitration of toluene nitration leads to 56 % para and 41 % ortho derivative compared to approximately 40 % para and 60 % ortho derivatives in the absence of the catalyst. Montmorillonite clays have an acidity comparable to nitric acid / sulphuric acid mixtures and the use of iron-exchanged material (Clayfen) gives a remarkable improvement in the para, ortho ratio in the nitration of phenols. The nitration of estrones, which is relevant in making various estrogenic drugs, can be improved in a remarkable way by using molecular engineered layer structures (MELS), while a reduction in the cost by a factor of six has been indicated. With a Clayfen type catalyst, it seems possible to manipulate the para, ortho ratio drastically for a variety of substrates and this should be useful in the manufacture of fine chemicals. In principle, such catalysts may approach biomimetic chemistry our ability to predict selectivity is very limited. 

Zinc chloride exchanged clay catalysts have been reported to be highly active for the Friedel-Crafts alkylation and acylation reactions these are commercially sold by Contract Catalysts under the name Envirocats. These are montmorillonite catalysts modified by ZnCU and FeCli. Some of the reported examples of Friedel-Crafts reactions are given below there are claims that some of the processes are commercially practised. 

The first indication of a possible connection between geological processes occurring at the boundaries between tectonic plates of the mid-oceanic ridges and the biogenesis problem was provided by J. B. Corliss (1981). He considered the hydrothermal conditions to be ideal reactors for abiotic synthesis these ideal conditions were the water temperature gradients, the pH, and the concentrations of solutes in the hot springs. The presence of certain minerals which could act as catalysts, such as montmorillonite, clay minerals, iron oxide, sulphides etc., was also very important. The initial model presented for the hydrothermal synthesis of biomolecules (Corliss, 1981) was modified, particularly by Russell (1989) and Wachtershauser (see Sect. 7.3). 

In this chapter, we demonstrate the potential of such agents as catalysts/promoters in key steps for the derivatization of sugars. The most significant catalytic approaches in carbohydrate chemistry that use aluminosilicate porous materials, namely zeolites and montmorillonite clays, are reviewed and discussed. Silica gel is a porous solid silicate that has also been used for heterogeneous catalysis of organic reactions in general. We include here its usefulness as promoter and reagent support for the reactions under consideration. 

Glycals can be transformed into 1,6-anhydro sugar derivatives by intramolecular cyclization in the presence of Lewis and Brpnsted acids, a reaction that has been termed the intramolecular Ferrier glycosylation.168 Sharma el al.169 showed that a montmorillonite clay-supported silver reagent can be an efficient catalyst for this transformation. The 1,6-anhydro-2,3-dehydro sugars obtained were then selectively dihydroxylated to furnish 1,6-anhydro saccharides. 

Imidazole has been condensed with ethyl acrylate by using two basic clays (Li+ and Cs+ montmorillonites) as catalysts in a microwave oven [70]. The role of alkali promoters (Li+ and Cs+) was studied and it was found that the greater the basicity and the irradiation time and power, the higher were the conversions. The yield of N-sub-stituted imidazole is maximum for 0.1 g Cs+ montmorillonite at 850 W after irradiation for 5 min (Scheme 8.48). 

The use of heterogeneous catalysts in this reaction has also been achieved palladium-montmorillonite clays [93] or palladium/activated carbon [94] in the presence of dppb transformed 2-allylphenols into lactones, the regiose-lectivity of the reaction being largely dependant on the nature of the support. Very recently, palladium complexes immobilized onto silica-supported (polyaminoamido)dendrimers were used as catalysts in the presence of dppb for the cyclocarbonylation of 2-allylphenols, 2-allylanilines, 2-vinylphenols, and 2-vinylanilines affording five-, six-, or seven-membered lactones and lactams. Good conversions are realized and the catalyst can be recycled 3-5 times [95]. 

Yet more improvements in the synthesis of chlorocyclophosphazenes have appeared. Yields in the PC15-NH4C1 reaction are increased by the use of heavy-metal salts as catalysts,93 but similar results may also be achieved by the use of acid-treated montmorillonite clay.94 The use of surfactants can also improve yields of cyclic products.95... 

The first cracking catalysts were acid-leached montmorillonite clays. The acid leach was to remove various metal impurities, principally iron, copper, and nickel, that could exert adverse effects on the cracking performance of a catalyst. The catalysts were first used in fixed- and moving-bed reactor systems in the form of shaped pellets. Later, with the development of the fluid catalytic cracking process, clay catalysts were made in the form of a ground, sized powder. Clay catalysts are relatively inexpensive and have been used extensively for many years. 

Rare-earth exchanged [Ce ", La ", Sm"" and RE (RE = La/Ce/Pr/Nd)] Na-Y zeolites, K-10 montmorillonite clay and amorphous silica-alumina have also been employed as solid acid catalysts for the vapour-phase Beckmann rearrangement of salicylaldoxime 245 to benzoxazole 248 (equation 74) and of cinnamaldoxime to isoquinoline . Under appropriate reaction conditions on zeolites, salicyl aldoxime 245 undergoes E-Z isomerization followed by Beckmann rearrangement and leads to the formation of benzoxazole 248 as the major product. Fragmentation product 247 and primary amide 246 are formed as minor compounds. When catalysts with both Br0nsted and Lewis acidity were used, a correlation between the amount of Br0nsted acid sites and benzoxazole 248 yields was observed. 

There has been an enormous technological interest in tertfa/j-butanol (tBA) dehydration during the past thirty years, first as a primary route to methyl te/f-butyl ether (MTBE) (1) and more recently for the production of isooctane and polyisobutylene (2). A number of commercializable processes have been developed for isobutylene manufacture (eq 1) in both the USA and Japan (3,4). These processes typically involve either vapor-phase tBA dehydration over a silica-alumina catalyst at 260-370°C, or liquid-phase processing utilizing either homogenous (sulfonic acid), or solid acid catalysis (e.g. acidic cationic resins). More recently, tBA dehydration has been examined using silica-supported heteropoly acids (5), montmorillonite clays (6), titanosilicates (7), as well as the use of compressed liquid water (8). 

The Beta-zeolite catalyst samples were purchased from PQ Corporation and from UOP. The HF-treated p-zeolite and montmorillonite clay samples were prepared as described previously (9,12). 

Montmorillonite clays are layered silicates montmorillonite K-10 is a specially manufactured acidic catalyst (Montmorillonite K10, [1318-93-0] A. Comelis, P. Laszlo, M. W. Zettler in eEROS Encyclopedia of Reagents for Organic Synthesis, L. A. Paquette, Ed., John Wiley and Sons, Inc., online reference available at http //www.intersciene.wiley.com)... 

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