Mica montmorillonite clay

Recently, interest in clays as acidic catalysts has been quickened by the reported high catalytic activity of a synthetic mica-montmorillonite clay and its nickel-containing analogs. Wright et al. (247) have described the structure, thermal modification and surface acidity of the clay, which they designated SMM for synthetic mica-montmorillonite. 

From pyridine poisoning experiments and FT/IR measurements it can be concluded that this increased activity stems from the increased acidity of the resulting NiSMM (Ni-synthetic mica montmorillonite) clay, due to reduction of Ni. 

VAN SANTEN ET AL. Nickel-Substituted Mica Montmorillonite Clay... 

HAMILTON (J.D.), 1967. Partially-ordered, mixed-layer mica-montmorillonite from Maitland, New South Wales. Clay Min. ], 63-78. 

K is obtained from associated K-feldspars and micas. The layer charge is increased by the reduction of iron in the octahedral sheet and incorporation of Al, entering through the ditrigonal holes in the basal oxygen plane, into the tetrahedral sheets (Weaver and Beck, 1971a Pollard, 1971). Weaver and Beck have presented evidence that indicates mixed-layer clays formed in this manner contain 20—30% chloritic layers and are actually mixed-layer illite-chlorite-montmorillonite clays. 

The reactions of several other minerals which thermally decompose to form mullite have been studied by Si and Al NMR. These include the mica mineral muscovite, which also contained sufficient iron to permit a complementary Fe Mossbauer study (MacKenzie et al. 1987), the hydroxyfluoride mineral topaz (Day et al. 1995) and the semi-amorphous aluminosilicate minerals allophane (MacKenzie et al. 1991) and imogolite (MacKenzie et al. 1989). The same combination of NMR nuclei has been used to study the thermal decomposition of other aluminosilicates including an illite-rich clay (Roch et al. 1998), montmorillonite (Brown et al. 1987), and a related mineral, Fuller s Earth (Drachman et al. 1997). NMR has also been used to study the effect of water vapour on the thermal decomposition of montmorillonite clay compacts (Temuujin et al. 2000a). 

Z. Liu, D. Jiang, H. Cai, and E. Min, The Hydroisomerization Nature of Ni-substituted Mica Montmorillonite and its Silica Oligomers Pillared Clay in Hexane Reaction. Chem. J. Chin. Univ., 1991, 12, 397-399. 

There has been renewed interest in catalytically active clays since the report by Swift and Black ( 1) to the effect that replacement of octahedrally coordinated aluminium ions by nickel or cobalt in synthetic smectite clays, as done by Granquist ( ), results in a new type of catalyst, called nickel- (or cobalt-) substituted mica montmorillonite (Ni(Co)SMM), which is very active in the isomerization and cracking of hydrocarbons. 

A typical reaction mixture used for the preparation of SMM consisted of 88 g SiO2/Al2O3 (25 % AI2O3), 67.2 g Al(isoprop)3, 9.1 g NH4F, and some water. About 120 g of white product was obtained after hydrothermal treatment (16 h at 300 C) and XRD confirmed that the product thus formed was pure synthetic beidellite. Since beidellite is NiSMM without Ni, it can also be described as synthetic mica montmorillonite (SMM). The composition of the clay was ... 

Rectorite is one of an almost infinite number of randomly mixed layer clays (411. collectively called illites, which include several other ordered interstratified varieties, including chlorite, corrensite and allevardite. Rectorite has the advantages of a mica and a smectite, in that alternate interlayers are expanding and non-expanding. It may be viewed as an ordered synthetic mica-montmorillonite (SMM) in the nomenclature familiar to catalytic... 

Other early MAS-NMR studies avoided the paramagnetic issue by synthesizing clays hydrothermally (16-18). Their conclusions were similar to previous conclusions Si is a powerful means of studying short-range order around Si in the lattice, while Al NMR is somewhat useful, but plagued by broadening and thus quantitation problems. Samples studied were synthetic beidellite (16], synthetic mica montmorillonites 117], and a series of synthetic 2 1 trioctahedral clays (18]. 

The probe molecule pyridine has often been used more recently in the study of clay surface acidity by IR methods. Figure 7 shows data of pyridine chemisorption on a synthetic mica-montmorillonite catalyst as an example (62,63) of the types of bands of interest. The spectra are interpreted as showing chemisorption of pyridine at both protic and aprotic sites. The clay was first heated for 15 h at 650°C under vacuum and then cooled and spectrum A taken. Note that there are no bands in the 1400-1700 cm region, the residual hydroxyl near 3450 cm S and edge silanol hydroxyl at 3747 cm . Pyridine vapor was then chemisorbed and spectrum B taken. The bands at 1456 cm and 1547 cm are assigned to Lewis and Bronsted sites, respectively. Since the 3747 cm edge silanol band decreases, it is assumed that these protons are involved in the mechanism. Lewis sites predominated under these particular conditions. 

Additives used in final products Fillers barium and strontium ferrites, boron carbide, calcinated clays, calcium carbonate, carbon black, carbon-silica dual phase filler, clays, dolomite, fumed silica, iron oxide, magnesium aluminum silicate, magnesium carbonate, mica, montmorillonite, nickel zinc ferrite, nylon fibers, pulverized polyurethane foam, quartz, silica carbide, soapstone, talc, zinc oxide Plasticizers naphthenic oil, polybutene, aromatic oil, esters of dicarboxylic acid Plasticizers adipates, aromatic mineral oil, paraffin oil, phosphates, phthalates, polyethylene glycol, processing oil, sebacates Antistatics dIhydrogen phosphate of 8-amlnocaprolc add. Iodine doping Antistatics carbon black, quaternary ammonium salt, zinc oxide whisker Antiblocking diatomaceous earth Release propylene wax Slip erucamide+stearamide ... 

Interstratified or mixed-layer minerals represent a special case of intergrowths. The simplest case is that in which there exist layers that are more or less hydrated, and this is a case that occurs frequently in clay minerals [Figure 1(a)]. Montmorillonites and vermiculites are, for example, essentially units of hydrated mica that is to say, they contain between their lamellae water molecules. For this reason, it may be supposed a priori that the most frequent type of interstratification will be that of mica-montmorillonite and mica-vermiculite. 

Several attempts have been made to reproduce artificially the formation in nature of interstratified minerals. It is possible for instance, to start with a given mineral such as a montmorillonite and try, by adding potassium, to make it into an interstratified mica-montmorillonite. The contrary process may also be tried. Jones and Thomas [1959] have found that on exchanging montmorillonite with potassium, the clay goes through the stages... 

Several studies of the synthesis of mixed-layer minerals have been made. Tomita and SuDO [1968] have used HCl and H2SO4 treatment on a preheated 2M sericite and obtained a regularly interstratified allevarditelike structure, which on MgCl treatment, gives mica-montmorillonite. Ross and Kodoma [1970] have studied the release of K " from interstratified mica clays treated with tetraphenyl boron and 0.1 N BaCl2, finding that the rate was lower when the Si/AF ratio of the layer approached that of mucsovite. 

Silicates with layer. structures include some of the most familiar and important minerals known to man, partieularly the clay minerals [such as kaolinite (china clay), montmorillonite (bentonite, fuller s earth), and vermiculite], the micas (e.g. muscovite, phlogopite, and biotite), and others such as chrysotile (white asbestos). 

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