Montmorillonite formation

Avoid injection of low-salinity solutions in water-sensitive (particularly montmorillonite) formations. Use clay stabilizers. Neutralize before injection. 

Reductive carbonylation of nitro compounds is catalyzed by various Pd catalysts. Phenyl isocyanate (93) is produced by the PdCl2-catalyzed reductive carbonylation (deoxygenation) of nitrobenzene with CO, probably via nitrene formation. Extensive studies have been carried out to develop the phosgene-free commercial process for phenyl isocyanate production from nitroben-zene[76]. Effects of various additives such as phenanthroline have been stu-died[77-79]. The co-catalysts of montmorillonite-bipyridylpalladium acetate and Ru3(CO) 2 are used for the reductive carbonylation oLnitroarenes[80,81]. Extensive studies on the reaction in alcohol to form the A -phenylurethane 94 have also been carried out[82-87]. Reaction of nitrobenzene with CO in the presence of aniline affords diphenylurea (95)[88]. 

In the studies by Skipper et al. the number of water layers (and thus molecules) was fixed on the basis of experimental evidence consequently, the stable states or degrees of swelhng were presumed. Quite differently, Karaborni et al. [44] determined, by means of a combination of GCMC and MD, the number of water molecules directly from a series of simulations in which the distance between montmorillonite planes was varied systematically. They observed that swelling proceeded from the dry state through the formation of one, three, and then five layers of water. This is very different from the usually beheved hydration sequence from one layer to two, then to three layers, and so on, which has been intrinsically assumed by Skipper and coworkers. The authors conclude that the complex swelling behavior accounts for many of the experimental facts. This work demonstrates impressively the power of the grand canonical simulation method. 

As an alternative to lithium enolates. silyl enolates or ketene acetals may be used in a complementary route to pentanedioates. The reaction requires Lewis acid catalysis, for example aluminum trifluoromethanesulfonate (modest diastereoselectivity with unsaturated esters)72 74 antimony(V) chloride/tin(II) trifluoromethanesulfonate (predominant formation of anti-adducts with the more reactive a,/5-unsaturated thioesters)75 montmorillonite clay (modest to good yields but poor diastereoselectivity with unsaturated esters)76 or high pressure77. 

Considering the formation of saturated five-membered heterocycles with two heteroatoms, it is worth to note the possibility to prepare 1,3-dioxolanes, dithiane, oxathianes 148 [93] and dioxolanones 149 [94] by condensation of the corresponding carbonyl compounds under microwave irradiation in acid medium (Scheme 52). The reaction, which is very useful for the protection of carbonyl compounds or for the preparation of useful synthetic intermediates, has also been carried out under batch conditions over Montmorillonite KIO clay in more than 150 g scale, using a 1 L quartz reactor [95]. 

A. Zaitoun and N. Berton. Stabilization of montmorillonite clay in porous media by high-molecular-weight polymers. In Proceedings Volume, pages 155-164. 9th SPE Formation Damage Contr Symp (Lafayette, LA, 2/22-2/23), 1990. 

The severe interaction of the zinc bromide fluid, 19.2 ppg (2.32 g/cc), was unexpected. Severe plugging of the core occurred, caused by precipitation of zinc hydroxide, as the injected solution mixed with and was neutralized by formation brine. Tests in which the zinc bromide fluid was simply titrated with distilled water also produced a precipitate, 0.0036 g/cc. Titration in the presence of the common reservoir clay, montmorillonite, increased both the rate of precipitation, and total quantity to 0.03 g/cc. 

In a closer examination of the formation of oligomers, Ferris and co-workers found that the reaction is favoured by relatively high salt concentrations (e.g. 1M NaCl), while the presence of divalent cations is not necessary. The formation of RNA oligomers was found to be temperature sensitive the yields decrease when the temperature is raised from 4°C to 50° C. The addition of meteorite material (from 3 meteorites) does not catalyse the polymerisation reaction only galena (PbS) can do this. The authors thus assume that RNA oligomers could have been formed on the young Earth in solutions of alkali metal salts in the presence of montmorillonite and a pH value of 7-9 (Miyakawa et al., 2006). Ferris (2006) has provided a short but up-to-date survey of montmorillonite-catalysed RNA oligomerisation. 

The clay mineral montmorillonite, which is often used in different prebiotic syntheses, is probably now the most important mineral for experiments on prebiotic chemistry. It has shown its abilities in the area of simulation experiments on the formation of primitive cellular compartments montmorillonite accelerates the spontaneous conversion of fatty acid micelles to vesicles. Clay particles are often incorporated into the vesicle, just as is RNA, which is adsorbed at such clay particles. If the vesicles have been formed, they can continue to grow if fatty acids are fed to them via micelles. If the vesicles are pressed through 100 nm pore filters, they divide without dilution of their contents. 

The great importance of minerals in prebiotic chemical reactions is undisputed. Interactions between mineral surfaces and organic molecules, and their influence on self-organisation processes, have been the subject of much study. New results from Szostak and co-workers show that the formation of vesicles is not limited to one type of mineral, but can involve various types of surfaces. Different minerals were studied in order to find out how particle size, particle shape, composition and charge can influence vesicle formation. Thus, for example, montmorillonite (Na and K10), kaolinite, talc, aluminium silicates, quartz, perlite, pyrite, hydrotalcite and Teflon particles were studied. Vesicle formation was catalysed best by aluminium solicate, followed by hydrotalcite, kaolinite and talcum (Hanczyc et al., 2007). 

G. Sharma, R. Kumar, and A. K. Chakraborti, A novel environmentally friendly process for carbon-sulfur bond formation catalyzed by montmorillonite clays, J. Mol. Cat. A Chem., 263 (2007) 143-148. 

Yamanaka S, Kanamaru F, Koizumi M. 1974. Role of interlayer cations in the formation of acrylonitrile-montmorillonite complexes. J Phys Chem 78 42-44. 

A solvent-free synthesis of flavones has been achieved that simply involves the MW irradiation of o-hydroxydibenzoylmethanes adsorbed on montmorillonite K 10 clay for 1-1.5 min. A rapid and exclusive formation of cyclized flavones occurs in good yields (Scheme 6.41) [140], The intramolecular Michael addition of o-hydroxy-... 

Wu F, Li J, Peng Z, Deng N (2008) Photochemical formation of hydroxyl radicals catalyzed by montmorillonite. Chemosphere 72 407 113... 

An Iranian group described the synthesis of some [l,3,4]thiadiazolo[2,3-c][l,2,4]triazinones 88 <2002PS2399> and in the course of the synthetic pathway the dihydro derivative 87 was first obtained. These authors found that microwave irradiation of 87 on montmorillonite in the presence of nitrobenzene allowed to accomplish the final oxidative step and yielded the fully conjugated end-product in good yields (50-62%). The reaction as proceeding was interpreted by electron transfer to 89 caused by the microwave irradiation followed by the formation of the intermediate radical 90. 

Reaction of 218 with aromatic aldehydes to give the ring-closed product 220 takes place in boiling ethanol in excellent yield (Scheme 44) <2001PHA376>. The transformation obviously proceeds via formation of a dihydro thiadiazole 219, as also suggested for the transformation of 218 under microwave irradiation in the presence of montmorillonite <2002PS2399>. 

A theoretical model for the adsorption of metals on to clay particles (<0.5 pm) of sodium montmorillonite, has been proposed, and experimental data on the adsorption of nickel and zinc have been discussed in terms of fitting the model and comparison with the Gouy-Chapman theory [10]. In clays, two processes occur. The first is a pH-independent process involving cation exchange in the interlayers and electrostatic interactions. The second is a pH-dependent process involving the formation of surface complexes. The data generally fitted the clay model and were seen as an extension to the Gouy-Chapman model from the surface reactivity to the interior of the hydrated clay particle. 

The effect of mineral and organic soil constituents on the mineralisation of LAS, AE, stearyl trimethylammonium chloride (STAC) and sodium stearate (main soap component) in soils was studied by Knaebel and co-workers [38]. The four 14C-labelled compounds were aseptically adsorbed to montmorillonite, kaolinite, illite, sand and humic acids and subsequently mixed with soil yielding surfactant concentrations of about 50 jig kg-1. The CO2 formation in the serum bottle respirometers was monitored over a period of 2 months indicating that the mineralisation extent was highest for LAS (49-75%). Somewhat lower amounts of produced CO2 were reported for AE and the stearate ranging from 34-58% and 29-47%, respectively. The mineralisation extent of the cationic surfactant did not exceed 21% (kaolinite) and achieved only 7% in the montmorillonite-modified soil. Associating the mineral type with the mineralisation kinetics showed that sand... 

Sorption depends on Sorption Sites. The sorption of alkaline and earth-alkaline cations on expandable three layer clays - smectites (montmorillonites) - can usually be interpreted as stoichiometric exchange of interlayer ions. Heavy metals however are sorbed by surface complex formation to the OH-functional groups of the outer surface (the so-called broken bonds). The non-swellable three-layer silicates, micas such as illite, can usually not exchange their interlayer ions but the outside of these minerals and the weathered crystal edges ("frayed edges") participate in ion exchange reactions. 

The adsorption of transition metal complexes by minerals is often followed by reactions which change the coordination environment around the metal ion. Thus in the adsorption of hexaamminechromium(III) and tris(ethylenediamine) chromium(III) by chlorite, illite and kaolinite, XPS showed that hydrolysis reactions occurred, leading to the formation of aqua complexes (67). In a similar manner, dehydration of hexaaraminecobalt(III) and chloropentaamminecobalt(III) adsorbed on montmorillonite led to the formation of cobalt(II) hydroxide and ammonium ions (68), the reaction being conveniently followed by the IR absorbance of the ammonium ions. Demetallation of complexes can also occur, as in the case of dehydration of tin tetra(4-pyridyl) porphyrin adsorbed on Na hectorite (69). The reaction, which was observed using UV-visible and luminescence spectroscopy, was reversible indicating that the Sn(IV) cation and porphyrin anion remained close to one another after destruction of the complex. 

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