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Silica alumina catalysts stability

In 1940, Houdry Process Corporation initiated commercial manufacture of a synthetic silica-alumina catalyst at Paulsboro, New Jersey (133). The synthetic catalyst is produced in pellet form (51,265) and contains 12 to 13% alumina (221,276). It has the advantages of controlled chemical composition, higher purity, and greater heat stability, but is more expensive than the activated-clay catalyst. [Pg.366]

A ceramic monolith catalyst support, cordierite, consisting of silica, alumina and magnesium oxide. The purpose of this is to provide support, strength and stability over a wide temperature range. [Pg.107]

The catalyst must also have acidity in the matrix in order to reduce the molecular weight of molecules too large to enter the zeolite and in order to also convert heavy-cycle oil to light-cycle oil. Our studies have established that good balance in acidity between the matrix and the zeolite tends to enhance selectivity. A stable matrix acidity is also required, and here a high alumina silica-alumina cogel was selected due to its demonstrated stability in the pre-zeolite era. Certainly many other acidic matrices could probably be substituted. [Pg.338]

At about 250° C a catalyst consisting of a low sodium zeolite and a noble metal is used in a recently developed process (3). It is claimed that no extensive feed pretreatment is required and that the stability of the catalyst is not impaired by common feed impurities. An older process using a catalyst consisting of platinum supported on amorphous silica-alumina (4) operates at 400° C. Naturally the higher the operation... [Pg.527]

The stability of MCM-41 is of great interest because, from the practical point of view, it is important to evaluate its potential application as a catalyst or adsorbent. It is known that purely-siliceous MCM-41 (designated here as PSM) has a high thermal stability in air and in oxygen containing low concentration (2.3 kPa) of water vapor at 700 °C for 2 h [1], However, the uniform mesoporous structure of PSM was found to be collapsed in hot water and aqueous solution due to silicate hydrolysis [2], limiting its applications associated with aqueous solutions. After MCM-41 samples were steamed in 100% water vapor at 750°C for 5 h. their surface areas were found to be lower than amorphous silica-alumina and no mesoporous structure could be identified by XRD measurement [3]. In addition, PSM showed poor stability in basic solution [4]. [Pg.227]

Alumina will also bind Cr03 and stabilize it to 900°C, and it can polymerize ethylene when reduced to Cr(II). High surface area y alumina can be made having the porosity necesssary for good activity. Besides the electronic differences between Si—O—Cr and A1—O—Cr bonds, such alumina catalysts typically have 50-100% more hydroxyl groups than silica at normal calcining temperatures. This is clear in Fig. 21, which shows the hydroxyl populations of three different supports. The hydroxyl concentration was measured by reaction with methylmagnesium iodide. [Pg.88]

The polymerization behavior of Cr/alumina seems to reflect the higher hydroxyl population. More surface hydroxyls also means more sites available to support chromium, and alumina does stabilize about twice as much Cr(Vl) as silica. However, the higher chromium levels do not yield a more active catalyst. Cr/alumina is typically only one tenth as active as Cr/silica. Termination rates are also extremely depressed on Cr/alumina. Both effects could be attributed to the extra hydroxyls, which are thought to interfere with polymerization. [Pg.88]

Reaction of the sandwich-type POM [(Fc(0H2)2)j(A-a-PW9034)2 9 with a colloidal suspension of silica/alumina nanopartides ((Si/A102)Cl) resulted in the production of a novel supported POM catalyst [146-148]. In this case, about 58 POM molecules per cationic silica/alumina nanoparticle were electrostatically stabilized on the surface. The aerobic oxidation of 2-chloroethyl ethyl sulfide (mustard simulant) to the corresponding harmless sulfoxide proceeded efficiently in the presence of the heterogeneous catalyst and the catalytic activity of the heterogeneous catalyst was much higher than that of the parent POM. In addition, this catalytic activity was much enhanced when binary cupric triflate and nitrate [Cu(OTf)2/Cu(N03)2 = 1.5] were also present [148],... [Pg.206]

Heterogeneous catalysts are solid materials that sometimes consist of the bulk material itself, for example, acid zeolite catalysts [10] or fused catalysts [11], Or in other cases of an active component or components deposited, as a rule, on a highly developed area support, for example, silica, alumina, carbon or in some cases a zeolite. The function of the support is to enhance the catalyst properties, for example, the stability of the active component or components, or in some cases to be even included in the catalytic reaction, for example, by providing acidic sites in bifunctional zeolite catalysts [10],... [Pg.422]

The introduction of zeolites in cracking catalysts combined with various non-zeolite matrix types (a.o. higher stability silica-alumina types) certainly complicates the picture of FCC hydrothermal deactivation. Letzsch et al [7] have shown that like amorphous catalysts the zeolite is more strongly deactivated hydrothermally than purely thermally. [Pg.130]

Many catalysts consist of an active component or components (see Section B) deposited on a support (such as silica, alumina, carbon). The role of the support may be to improve the properties (e.g. stability) of the active componcnt(s), or to participate directly in the catalytic reaction (e.g. by providing acidic sites). The following terms define general preparation methods. [Pg.532]


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See also in sourсe #XX -- [ Pg.6 , Pg.7 ]




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