Acid-treated clays

Clay, acid-treated 60 18 Cage-mill type... 

Clays (acid-treated and Treatment of edible oils pillared) removal of organic pigments ... 

Houdry Fixed bed Clay Acid treated Granulated... 

TCC, Houdry flow Moving bed Clay Acid treated Pellets... 

Matrix Kaolin Kaolin Alumina (major), sili-ca/alumina, cerium-pillared clays, acid treated meta kaolin. 

Petroleum Waxes. Waxes derived from petroleum are hydrocarbons of three types paraffin [64742-43-4] (clay-treated) sernimicrocrystaUine or intermediate and microcrystalHne [64742-42-3] (clay-treated). SernimicrocrystaUine waxes are not generally marketed as such (7). Others include acid-treated, chemically neutrali2ed, and hydrotreated and paraffin and hydrocarbon waxes, untreated. The quaHty and quantity of the wax separated from the cmde oil depends on the source of the cmde oil and the degree of refining to which it has been subjected prior to wax separation. Petroleum waxes are produced in massive quantities throughout the world. Subject to the wax content in the cmde, paraffin and, to a substantially lesser degree, microcrystalHne wax are produced in almost all countries of the world that refine cmde oil. Production capacity in the United States and imports for the years 1990 to 1995 are Hsted in Table 2. Canada suppHes over 50% of the petroleum wax imported into the United States (3). 

Acid-treated clays were the first catalysts used in catalytic cracking processes, but have been replaced by synthetic amorphous silica-alumina, which is more active and stable. Incorporating zeolites (crystalline alumina-silica) with the silica/alumina catalyst improves selectivity towards aromatics. These catalysts have both Fewis and Bronsted acid sites that promote carbonium ion formation. An important structural feature of zeolites is the presence of holes in the crystal lattice, which are formed by the silica-alumina tetrahedra. Each tetrahedron is made of four oxygen anions with either an aluminum or a silicon cation in the center. Each oxygen anion with a -2 oxidation state is shared between either two silicon, two aluminum, or an aluminum and a silicon cation. 

The first commercial fluidized cracking catalyst was acid-treated natural clay. Later, synthetic. silica-alumina materials containing 10 lo... 

Chitnis and Sharma (1997) have given an exhaustive account of industrial applications of acid-treated clays. Table 4.3 gives some examples of industrial importance. 

Acid-treated clay catalyst Engelhard F-24 was found to be very effective for the alkylation of diphenylamine (DPA) with an olefin such as a-methyl styrene (AMS) to obtain a mixture of mono and dialkylated diphenylamines (Chitnis and Sharma, 1995). For example, alkylation of DPA with AMS produced a mixture of 4-(a,a-dimethyl benzyl) diphenylamine, i.e. monocumyl-diphenylamine (MCDPA) and 4,4 -bis(a,a-dimethylbenzyl) diphenylamine, i.e. dicumyldiphenylamine (DCDPA) (Eqn.(l 1)). The dialkylated diphenylamine, i.e. DCDPA, is indu.strially important as an antioxidant and heat stabilizer. DCDPA is reported to be an ideal antioxidant for many materials like polyethylene, polypropylene, polyether polyol, polyacetals, nylon 6, synthetic lubricants, hot melt adhesives, etc. 

The various other grades of acid-treated clay catalysts like Engelhard F-25, F-34, F-44,F-54, F-124, F-224, G-62, Tonsil K 306, etc. were also found to be useful catalysts for the alkylation of DPA with AMS. This alkylation reaction was unsuccessful with macroporous... 

Shah et al. (1994) have studied the preparation of a class of compounds called Indans, by cross-dimerization of AMS with amylenes, using an ion-exchange resin and acid-treated clay catalysts (Eqns. (12) and (13)). Indans can be subsequently converted, e.g. by acetylation, into perfumric compounds having mu.sk odour. For example, 1,1,2,3,3-pentamethylindan, the product obtained by cross-dimerization of AMS and wo-amylene (Eqn. (12)), can be reacted with propylene oxide and /7 ra-formaldehyde to give an indan type isochroman musk compound, 6-oxa-l,l,2,3,3,8-hexamethyl-2,3,5,6,7,8-hexahydro-lH-benz(f)-indene, sold as Galaxolide commercially. 

The selectivity for cross-dimerization relative to the dimerization of AMS, was found to be better with the acid-treated clay catalyst Engelhard F-24 than with the ion-exchange resin catalyst Amberlyst-15. Also, the formation of undesired side products, i.e. diisoamylenes, was lower in the case of Engelhard F-24 than for Amberlyst-15. 

Dimerization of unsaturated fatty acids, to. so-called dimer acids, is widely practised in industry, where acid-treated clays are invariably used as a catalyst. In the case of oleic acid the major products are dimers, trimers, and isosteric acid. Koster et al. (1998) have investigated the relative importance of the various acid sites as well as structural and textural parameters of montmorrilonite. The interlamellar space dominates the oleic acid dimerization and the active site is the tetrahedrol substitution site. 

The hydroamination of alkenes has been performed in the presence of heterogeneous acidic catalysts such as zeolites, amorphous aluminosilicates, phosphates, mesoporous oxides, pillared interlayered clays (PILCs), amorphous oxides, acid-treated sheet silicates or NafioN-H resins. They can be used either under batch conditions or in continuous operation at high temperature (above 200°C) under high pressure (above 100 bar). 

A clay mineral and/or its acid-treated products109,110 are used as color developers. A diphenylmethane derivative of structure 82 has been micro-... 

Catalytic cracking is a process that is currently performed exclusively over fluidized catalyst beds. The fluid catalytic cracking (FCC) process was introduced in 1942 and at that time replaced the conventional moving bed processes. These early processes were based on acid-treated clays as acidic catalysts. The replacement of the amorphous aluminosilicate catalysts by Faujasite-type zeolites in the early-1960s is regarded as a major improvement in FCC performance. The new acidic catalysts had a remarkable activity and produced substantially higher yields than the old ones. 

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... 

Prior to 1938, gasoline was obtained from thermal-cracking plants then the Houdry fixed-bed catalytic cracking process led to the development of a fluidized-bed process by Standard Oil for the catalytic production of motor fuels (4-8). Acid-treated clays of the montmorilIonite type were the first fluid-cracking catalysts widely employed by the industry. However, the ever greater demand for aviation fuels during the 1939-1945 period prompted the search for more active and selective catalysts. Research on novel catalyst... 

Acid-treated clays Alcylation reactions (e.g. of benzene with benzyl chloride) Dimerization reactions (e.g. of a-methylstyrene) Etherification reactions (e.g. of ferf-butanol with methanol) Condensation reactions (e.g. of cyclohexanone) Separation of close boiling aromatic amines Separation of isomers of xylene... 

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