Silica alumina catalyst, fluorination

Catalyst Fluorination. The adsorption and desorption record and calculated data for a silica-alumina catalyst of low alumina content and a median pore radius of 78 A. were obtained. This indicated a fairly wide distribution of pore sizes in this material. 

Zeolites, by being in a half way between amorphous silica-alumina and fluorinated alumina, were early recognized as potential components of bifunctional isomerization catalysts. The earliest report of zeolites being used in this application deal on Pt containing X and Y structures (3). They found that the activity increased from the Na to the Ca to the decationized forms. The residual sodium content, and therefore the final acidity of the Pt or Pd HY zeolite catalysts was critical for these type of catalysts (2,4-6). However, to make a successful commercial catalyst the following characteristic have to be accomplished by the zeolitic component ... 

An alkene mixture of industrial source (equal amounts of C9-C13 alkenes and alkanes) was used in the alkylation of benzene on three Nafion-silica catalysts with 5%, 13%, and 20% loadings.195 20% Nafion-silica showed high and stable activity and its performance exceeded that of a Y-zeolite-based material. The selectivity to 2-phenylalkanes (25%) was higher than in the Detal process using fluorinated silica-alumina but decreased somewhat with increasing Nafion content. 

Linear alkylbenzenes are made from linear terminal olefins and benzene and are important precursors of biodegradable anionic surfactants (LAS, linear alkylbenzenesulfonates). The conventional catalyst is HF, first to be replaced by a fluorinated silica-alumina in the DETAL process. The DETAL process is safer than the HF process and also more cost-effective because no special metallurgy is required and no calcium fluoride waste stream exists.52 Zeolites such as Beta may come to the fore here because they display a higher selectivity to the desired 2-phenyl isomers.55... 

These catalysts are silica-aluminas whose cracking and disproportionation power has been altered by steam treatment, the use of an inhibitor, or of aluminas containing a halogenated compound or fluorine. They are very rugged, are employed without hydrogen and hence cannot isomerize ethylbenzene, which is therefore cracked or transformed by a disproportionation reaction into benzene and C10 aromatics. Consequently, they can only be used with feeds poor in ethylbenzene. However, no naphthenic hydrocarbons are formed. 

Hydrocracking catalysts designed for a maximum production of jet fiiel or gas oil utilize a moderate acidic function, made of modified zeolite or amorphous silica-alumina. Doped alumina, essentially by fluorine, can also be used for these applications. 

A similar type of catalyst including a supported noble metal for regeneration was described extensively in a series of patents assigned to UOP (209-214). The catalysts were prepared by the sublimation of metal halides, especially aluminum chloride and boron trifluoride, onto an alumina carrier modified with alkali or rare earth-alkali metal ions. The noble metal was preferably deposited in an eggshell concentration profile. An earlier patent assigned to Texaco (215) describes the use of chlorinated alumina in the isobutane alkylation with higher alkenes, especially hexenes. TMPs were supposed to form via self-alkylation. Fluorinated alumina and silica samples were also tested in isobutane alkylation,... 

Parallel to the development of catalysts for olefin metathesis, the first alkyne metathesis catalysts were W and Mo metal oxides or carbonyls suspended on alumina or silica.65 The first homogeneous catalysts were developed by Mortreux and consisted of a mixture of Mo(CO)6 and substituted phenols.66 It was not until the work of Schrock and his collaborators, however, that a well-defined, isolable alkylidyne catalyst (38) was synthesized, characterized, and shown to catalyze alkyne metathesis.67 Later modifications on 38 included substituting the alkoxy groups with fluorinated analogs, and for the corresponding Mo alkylidynes (39), the fluorinated alkoxy groups are essential for catalytic activity.68... 

Fluorinated silica and alumina have also been used for isobutane alkylation with olefins in a batch reactor at 0°C. The fluorinated alumina was active only when mixed with BF3 H2O, but the fluorinated silica was active by itself The selectivity to trimethylpentanes obtained with these catalysts is much lower than that obtained with H2SO4 as a catalyst (48). At 80°C, however, F/AI2O3 catalysts are active for isobutane/2-butene alkylation, though relatively low butene conversions (27% for the most active catalyst containing 1.3% F) are obtained (49). As expected, octenes are the predominant hydrocarbons in the Cg fraction at such a low conversions. The F/AI2O3 catalysts contained both Bronsted and Lewis acid sites in a proportion that depends on the F loading. A good correlation between... 

The choice of an appropriate support is of no less importance than that of active phase of a catalyst. We have focused our attention on the application of hydrophobic supports to prepare effective platinum catalysts for hydrosilylation since our preliminary experiments have shown that in a number of hydrosilylation reactions hydrophobic material-supported catalysts appeared to be superior to those based on hydrophilic supports such as alumina and silica. We have also aimed at selecting such supports which, in addition to their hydrophobicity, do not have acid centers on their surfaces, and due to this, they do not catalyze undesirable side reactions of isomerization. The supports selected for our study were styrene-divinylbenzene copolymer (SDB) and fluorinated carbon (FC), because nonfunctionalized SDB is free of acid sites and surface acidity of FC is extremely weak (H 9). The performance of SDB- and FC-supported platinum catalysts was studied in several reactions of hydrosilylation. 

Increasing the attrition lesistance of the few fluid-bed catalysts brings to an appreciable reduction of catalyst costs due to a decreased consumption. High surface area alumina in its various forms (boehmite, bayerite, gamma, delta) and silica-alnmina are the preferred supports for fluid bed catalysts. However in mai cases their attrition resistance is not satisfactory, like, for instance, in the case of pure and silica containing boehmites. A remarkable improvement of the attrition resistance of these supports can be obtained by fluorination withHF (Table 1). 

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