Bentonite clay catalyst

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 ]. 

Cationic polymerization of cyclosiloxanes is well known but used much less frequently than anionic reactions. The most widely used catalysts include sulfuric acid and its derivatives, alkyl and aryl sulfonic acids and trifluoroacetic acid1 2,1221. Due to their ease of removal, in industrial applications acid catalysts are generally employed on supports such as bentonite clay or Fuller s earth. 

Cracking catalysts include synthetic and natural sihca-alumina, treated bentonite clay, fuller s earth, aluminum hydrosUicates, and bauxite. These catalysts are in the form of beads, pellets, and powder, and are used in a fixed, moving, or fluidized bed. The catalyst is usually heated and hfted into the reactor area by the incoming oil feed which, in mrn, is immediately vaporized upon contact. Vapors from the reactors pass upward through a cyclone separator which removes most of the entrained catalyst. The vapors then enter the fractionator, where the desired products are removed and heavier fractions are recycled to the reactor. 

The other iron-containing clay catalyst prepared by reacting a Texas bentonite with an ACH-Fe(N02)3 solution gave an (Fe.ACH)-bentonite sample containing 9.7% Fe2 3 after drying in air at 120 C/10h had d(OOl) = 17.8A and BET surface area of 296 m /g. Calcination reduced pillar s height after heating in air at 400 C/10h, the d(OOl) value decreased to about 15.7A probably as a result of some iron removal from the pillars. 

At MAT conditions, montmorilIonites pillared with alumina clusters, and having similar surface area, generate (at a given conversion level) similar amounts of coke (when used to crack gas oil) irrespective of the iron content of the parent bentonite. Thus, the presence of iron cannot be used to explain the high tendency for coke (and light gas) make of pillared clay catalysts. 

Both the natural clay and the synthetic types of catalyst undergo normal aging. Abnormal aging, due to sulfur compounds, has been found only with natural clay catalyst the synthetic types are stable under similar conditions. Natural clay catalysts can be protected against abnormal aging from sulfur compounds by hydrating with steam after regeneration. Certain types of iron-free clays and bentonitic clays treated to remove iron do not show sulfur deactivation. 

Nagy, N. M., and J. Kdnya. 2008. Palladium-bentonites as catalysts, 4th Mid-European Clay Conference, Zakopane, 22-28. September 2008 119. 

The first successful catalytic cracking process was the Houdry process, announced in 1933 (132) and commercialized in 1936 (172). This was a fixed-bed process employing, at first, an activated bentonite clay as catalyst. It had been known previously that certain types of decolorizing clays catalyzed the decomposition of hydrocarbon oils (165,188), but a carbonaceous deposit rapidly accumulated on the clay and seriously impaired its activity. During his early work in France, between 1927 and 1930, Houdry found that catalyst activity could be maintained at a satisfactory level by carefully burning off the carbonaceous deposit, or coke, at frequent intervals before the concentration became high enough to interfere seriously with the desired catalytic reactions. 

Butylamine has been oxidized quantitatively to buty-ronitrile by 3-chloroperbenzoic acid using a ruthenium tetramesitylporphyrin catalyst.277 Dialkylsulfides can be oxidized to the corresponding sulfoxides in 90% yield by magnesium monoperoxyphthalate on moist bentonite clay in acetonitrile.278 The inorganic support promotes the reagent and allows for an easy workup. p-Toluenepersul-fonic acid has been used to oxidize amines to their amine oxides in 40-95% yields.279... 

The first industrial siliceous cracking catalyst was an acid-leached bentonite clay to which about 1 % of manganese dioxide was added for the purpose of increasing the rate of burning of carbonaceous deposits during regeneration. Essentially the same type of catalyst, without the added manganese dioxide, is in wide use today. 

Preferred bentonite clays are those whose chief constituent is mont-morillonite, a mineral of the composition corresponding to the empirical formula, 4Si02-Al203 H20. The principal sources of raw clay for the manufacture of the presently most widely used natural catalyst (Filtrol Corporation) are deposits in Arizona and Mississippi. The clay from these deposits contains appreciable amounts of impurities, principally CaO, MgO, and Fe203, which replace part of the A1203 in the ideal montmorillonite structure. The catalyst is prepared by leaching the raw clay with dilute sulfuric acid until about half of the alumina and associated impurities is removed. The resulting product is then washed, partially dried, and extruded into pellets, after which it is activated by calcination. A typical analysis of the finished catalyst is as follows (Mills, 12). 

Clays have found an application. For exampie, a mixture of phenol, diisobutylene and 2% of an activated Montmoriilonite clay catalyst, when held at 158-161 C, resulted in a 98% yield of 4-octylphenol as a white crystalline solid (ref. 8). Poiyaikylphenols and phenol with an active ciay at 160-170 C afford the monoalkylphenoi (ref. 9). The pretreatment of a bentonite ciay with an organic solvent and a strong acid (72% sulphuric acid) at 77°C has been described which results in a catalyst thirty times more active than an untreated one (ref. 10). 

When Ae bentonite clays are treated with acids, up to 80% of the aluminum can be extracted from the montmorillonite lattice together with most of the magnesium and iron. No silica is dissolved during the extraction process, but it is probable that some may be peptized to form an active amorphous phase with alumina. This increases the surface area and pore volume of the catalyst. Typical analyses of commercial catalysts shown in Table 5.4 indicate that sulfuric acid was a common activating agent. ... 

The first part of this article specifically deals with representative laboratoiy applications to fine chemistry of clearly identified, unaltered KIO, excluding its modified forms (cation-exchanged, doped by salt deposition, pillared, etc.) and industrial uses in bulk. This illustrative medley shows the prowess of KIO as a strong Brpnsted acidic catalyst. The second part deals with cation-exchanged (mainly Fe ") montmorillonite. Clayfen and claycop, versatile stoichiometric reagents obtained by metal nitrate deposition on KIO, are used in oxidation and nitration reactions. They are treated under Iron(III) Nitrate-KlO Montrrufrillonite Clay and Copperfll) Nitrate-KlO Bentonite Clay. 

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