Alumina-silicate catalyst

Faujasite is a naturally occurring mineral, having a specific crystalline, alumina-silicate structure, used in the manufacturing of the FCC catalyst. Zeolite faujasite is a synthetic form of the mineral. 

Zeolite is a synthetic crystalline alumina-silicate material used in the manufacturing of FCC catalyst. 

Partial oxidation reactions are usually carried out over transition metal oxides capable of changing their valent state during their interaction with reacting molecules. Naturally, zeolites with their alumina-silicate composition did not prove themselves as good oxidation catalysts. They failed also to serve as efScient catalyst supporters, since transition metals being introduced into the zeolite matrix lose their ability to activate dioxygen [3,4],... 

The Mobility of Silica in Steam. The reactivity of silica and silica-containing materials to steam has been assumed in the literature to explain several phenomena, a few of which are the sintering of silica (35), the aging of amorphous silica alumina cracking catalysts (36) and the formation of ultrastable molecular sieves (37). The basis of all these explanations is the interaction of siliceous materials with water to form mobile, low molecular weight silicon compounds by hydrolysis (38) such as ... 

The rates of hydrolysis of siliceous materials will be affected by several factors. For instance, the rate will be directly related to surface area, explaining the low rates observed for silica deposition from the Vycor apparatus. Also, the composition of the siliceous material will Influence the rate of hydrolysis, explaining the differing amounts of silica transferred from pure silica, silica alumina, zeolite, and the high alumina cracking catalyst. 

The way in which the proton is associated with the alumina-silica catalyst is a matter of some doubt. Thomas (78) assumes the aluminium to be tetrahedral when linked with tetrahedral silicon, the extra valence electron being supplied by hydrogen from water contained in the catalyst (Fig. 21a). Both aluminium hydroxide and silicic acid are very weak acids because of the affinity of oxygen for the hydrogen (83), and a coordination of aluminium with the hydroxyl oxygen contained in the catalysts... 

Oborin (270,271) examined the suitability of alumina-containing catalysts including silica-alumina for the reactions involved in cracking of hydrocarbons and found that the activity of the catalyst could be explained on the basis of structure analysis evidence obtained by him which supported the view that a mixture of silica and alumina rather than an aluminum silicate was present. He also found that the distance between two aluminum atoms was approximately 2.56 A., which is close to the distance between alternate carbon atoms in a hydrocarbon, thus... 

Tlie reaction is generally carried out at atmospheric pressure and at 350—400°C. A variety of catalysts, eg, bases and metal salts and oxides on silica or alumina—silicates, have been patented (86—91). Conversions are in the 30—70% range and selectivities in the 60—90% range, depending on the catalyst and the ratio of formaldehyde to acetate. 

There are many examples of the alkylation of aromatics with olefins to produce alkylbenzene In textbooks, the open literature, and In numerous patents. This reaction Is catalyzed by both proton and Lewis acids In a homogeneous phase and In heterogeneous phases. The latter systems are characterized by both proton (H FO ) and Lewis acids (BF ) on supports and the amorphous and crystalline alumina silicates. And, the reaction has been studied extensively. However, up until the start of this Investigation (1969) there had not been a systematic investigation of the kinetic parameters nor an adequate catalyst aging study on the alkylation of benzene with propylene over a crystalline alumina silicate. 

The second catalytic method involves reaction of pyridine with alkyl alcohols at both atmospheric (65) and elevated pressures (66-68) over alumina or alumino-silicate catalysts. The atmospheric pressure reaction afforded a mixture of all three picoline Isomers in approximately equal amounts with multi-substitution also reported. At elevated pressures, the substitution is claimed to be primarily in the 3- position with low conversions. 

Zeolites, crystalline alumina silicates with open regular structure, oiFer unusual opportunities for carrying out catal3rtic studies. Their well-defined crystalline structure and their regular pore distribution permit a better description of the surface than that offered by alumina-silica gel catalysts. Consequently, in recent years they have been the object of many scientific investigations. In addition, zeolites of a variety of types have shown highly desirable properties in industrial catalysis (1.2). This chapter is a review of the work on zeolites carried out at Princeton University and is not intended to be an exhaustive review of the topic. 

Platinum (metal)- and acid (oxide)-catalyzed processes were developed to convert petroleum to high-octane fuels. Hydrodesulfurization catalysis removed sulfur from the crude to prevent catalyst deactivation. The discovery of microporous crystalline alumina silicates (zeolites) provided more selective and active catalysts for many reactions, including cracking, hydrocracking, alkylation, isomerization, and oligomerization. Catalysts that polymerize ethylene, propylene, and other molecules were discovered. A new generation of bimetallic catalysts that were dispersed on high-surface-area (100-400 m /g) oxides was synthesized. 

Microporous, crystalline oxides (alumina, silicates, phosphates, etc.) are used as catalyst is in the petroleum and in the chemical technologies in large volume to carry out cracking, isomerization, alkylation, and many other important hydrocarbon conversion reactions [198, 199, 203]. Discuss the structure of these so-called zeolites that have one-dimensional and two-dimensional micropores. How can the acidity of the catalysts be altered How do their acid strengths compare with concentration H2SO4 and HF ... 

Silicates which have been calcined may show an acid reaction when placed in an aqueous medium. Gayer (14) reported, many years ago, that his silica-alumina polymerization catalyst, when tested with an indicator in an aqueous medium, was acid in reaction. He reported no connection between this observation and catalyst activity. Such a catalyst if placed in water can be titrated with a base. Long periods (18 hours) may be allowed for reaction with a base, and the results can... 

Catalytic cracking Eugene J. Houdry finds a catalyst, alumina silicate, that... 

Commonly used porous supports are as follows Alumina, silica oxide, activated carbon, molecular sieve, alumina silicate, diatomite, pumice, asbestos, pottery clay, magnesium oxide, activated clay and so on. The shape and size of supports can be chosen according to the requirement of catalysts. 

Many catalysts have been used but the standard catalysts are generally mixtures of silica and alumina or natural or synthetic aluminium silicate zeolites. 

To accelerate the polymerization process, some water-soluble salts of heavy metals (Fe, Co, Ni, Pb) are added to the reaction system (0.01-1% with respect to the monomer mass). These additions facilitate the reaction heat removal and allow the reaction to be carried out at lower temperatures. To reduce the coagulate formation and deposits of polymers on the reactor walls, the additions of water-soluble salts (borates, phosphates, and silicates of alkali metals) are introduced into the reaction mixture. The residual monomer content in the emulsion can be decreased by hydrogenizing the double bond in the presence of catalysts (Raney Ni, and salts of Ru, Co, Fe, Pd, Pt, Ir, Ro, and Co on alumina). The same purpose can be achieved by adding amidase to the emulsion. 

The temperature profiles for each catalyst at two different space velocities are plotted in Figure 1. The catalysts with lower nickel content had reasonable activity, but the activity obviously decreased with nickel content. At 25,000/hr space velocity, the 30% nickel-on-alumina catalyst used 50% of the bed to obtain the maximum temperature whereas with 50% nickel the reaction used only 30% or the bed. The method used to prepare the C150-3-02 catalyst resulted in a non-reduceable nickel silicate... 

In the catalytic cracking method, a suitable catalyst such as aluminum silicate or alumina is used. This provision produces an improved quality and yield of gasoline. This method has several advantages over the thermal cracking method. Among these, special mention... 

Some non-silica sol-gel materials have also been developed to immobilize bioactive molecules for the construction of biosensors and to synthesize new catalysts for the functional devices. Liu et al. [33] proved that alumina sol-gel was a suitable matrix to improve the immobilization of tyrosinase for detection of trace phenols. Titania is another kind of non-silica material easily obtained from the sol-gel process [34, 35], Luckarift et al. [36] introduced a new method for enzyme immobilization in a bio-mimetic silica support. In this biosilicification process precipitation was catalyzed by the R5 peptide, the repeat unit of the silaffin, which was identified from the diatom Cylindrotheca fusiformis. During the enzyme immobilization in biosilicification the reaction mixture consisted of silicic acid (hydrolyzed tetramethyl orthosilicate) and R5 peptide and enzyme. In the process of precipitation the reaction enzyme was entrapped and nm-sized biosilica-immobilized spheres were formed. Carturan et al. [11] developed a biosil method for the encapsulation of plant and animal cells. 

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