Catalysts catalyst types

Metal Catalyst Catalyst type Preparation method Temp. (°Q Carbon source Ref. 

Figure 9 Time on stream pattern of the gas phase hydrogenation of crotonaldehyde over Sn-PtlSi02 catalyst (catalyst type (H-3), Sna ctJP s — Reaction temperature 80 °C, amount of catalyst 100 mg, flow rate 90-ml/min. Reaction products O - crotylalcohol, - butyraldehyde, O - hydrocarbons, x - butylal-cohol.

Molecular Weight Distribution. In industry, the MWD of PE resins is often represented by the value of the melt flow ratio (MER) as defined in Table 2. The MER value of PE is primarilly a function of catalyst type. Phillips catalysts produce PE resins with a broad MWD and their MER usually exceeds 100 Ziegler catalysts provide resins with a MWD of a medium width (MFR = 25-50) and metallocene catalysts produce PE resins with a narrow MWD (MFR = 15-25). IfPE resins with especially broad molecular weight distributions are needed, they can be produced either by using special mixed catalysts or in a series of coimected polymerization reactors operating under different reaction conditions. 

Metallocene Catalysts. Three types of metallocene catalysts are presentiy used ia industry Kaminsky, combination, and Dow catalysts. 

MAO is a relatively expensive chemical its price in 1994 was about 450/kg of 30 wt % MAO solution, but projected to decrease to about 200/kg (28). Continuous efforts to replace MAO have resulted in the development of co-catalysts containing mixtures of MAO and trimethyl aluminum (29) as well as new co-catalyst types (30,31). Another approach is to prepare MAO directiy in a polymeriza tion reactor by co-feeding into it trimethyl aluminum and water (32). 

Miscellaneous. Chloroplatinic acid is used in the production of automobile catalysts. Platino-type prints based on reduction of Pt(II) to Pt(0) by a photosensitive reducing agent such as iron(III) oxalate are used in art photography (261,262). Infrared imaging devices based on a platinum siLicide detector have been developed (263). 

Producer Location Trade name Catalyst type... 

The cure rate of a sihcone sealant is dependent on the reactivity of the cross-linker, catalyst type, catalyst level, the diffusion of moisture into the sealant, and the diffusion of the leaving group out of the sealant. For one-part sealants, moisture diffusion is the controlling step and causes a cured skin to form on the exposed sealant surface and progress inward. The diffusion of moisture is highly dependent on the temperature and relative humidity conditions. 

There is an enormous volume of Hterature available on the appHcations for supported catalysts. Examples are compiled here based on important synthesis methods and industrial uses. The organization is according to specific reactions and appHcations rather than according to catalyst type. 

Silicone reliners are supplied as either a one-component system that cures in the presence of moisture or heat, or a two-component system containing base and catalyst. Both types adhere poody to denture base and carmot be polished satisfactorily. Some silicones support propagation of bacteria such as Candida albicans. Acrylic-based sifloxane monomers and resins have been proposed for overcoming these deficiencies (211). 

Primary Variables. The most obvious variables are those whose effects on performance are to be evaluated directiy these ate the variables that, most likely, created the need for the investigation in the first place. Such variables may be quantitative, such as catalyst concentration, temperature, or pressure, or they may be quaUtative, such as method of preparation, catalyst type, or batch of material. 

Quahtative variables can be broken down into two categories. The first consists of those variables whose specific effects ate to be compared directiy eg, comparison of the effect on performance of two proposed preparation methods or of three catalyst types. The requited number of conditions for such variables is generally evident. Such variables are sometimes referred to as fixed effects or Type I variables. 

Polymer Structure. Isopiene can undergo 1,4-, 1,2-, oi 3,4-addition polymerisation depending on the catalyst type and conditions, lesultiag ia several structures ... 

Operating Temperature. The operating temperature needed to achieve a particular VOC destmction efficiency depends primarily on the species of pollutants contained in the waste stream, the concentration of the pollutants, and the catalyst type (14). One of the most important factors is the hydrocarbon species. Each has a catalytic initiation temperature which is also dependent on the type of catalyst used (14). 

NO removals of 90% are achievable. The primary variable is temperature, which depends on catalyst type (38). The principal components of an SCR... 

Variables It is possible to identify a large number of variables that influence the design and performance of a chemical reactor with heat transfer, from the vessel size and type catalyst distribution among the beds catalyst type, size, and porosity to the geometry of the heat-transfer surface, such as tube diameter, length, pitch, and so on. Experience has shown, however, that the reactor temperature, and often also the pressure, are the primary variables feed compositions and velocities are of secondary importance and the geometric characteristics of the catalyst and heat-exchange provisions are tertiary factors. Tertiary factors are usually set by standard plant practice. Many of the major optimization studies cited by Westerterp et al. (1984), for instance, are devoted to reactor temperature as a means of optimization. 

Oxidants commonly used include ozone, permanganate, chlorine, chlorine dioxide, and ferrate, often in combination with catalysts. Standard-type mixed reactors are used with contact times of several minutes to an hour. Special reactors for use with ultraviolet light have been developed. 

Catalyst type Coal minerals Coal minerals Coal minerals Supported aKZO-aO-60 aKZO-aO-60... 

The Fischer-Tropsch reaction is highly exothermic. Therefore, adequate heat removal is critical. High temperatures residt in high yields of methane, as well as coking and sintering of the catalyst. Three types of reac tors (tubular fixed bed, fluidized bed, and slurry) provide good temperature control, and all three types are being used for synthesis gas conversion. The first plants used tubular or plate-type fixed-bed reactors. Later, SASOL, in South Africa, used fluidized-bed reactors, and most recently, slurry reactors have come into use. 

Correlations have been used as a tool for catalyst selection studies. Predictions of the product yields and qualities possible with various catalysts can provide the necessary information for a refiner to study the economics of switching catalysts, for instance. With a good idea of the profitability of changing catalyst types, the refinery can justify such a change in his cat crackings operation. 

Troublesome amounts of C and Q acetylenes are also produced in cracking. In the butadiene and isoprene recovery processes, the acetylenes in the feed are either hydrogenated, polymerized, or extracted and burned. Acetylene hydrogenation catalyst types include palladium on alumina, and some non-noble metals. 

When potassium fluoride is combined with a variety of quaternary ammonium salts its reaction rate is accelerated and the overall yields of a vanety of halogen displacements are improved [57, p 112ff. Variables like catalyst type and moisture content of the alkali metal fluoride need to be optimized. In addition, the maximum yield is a function of two parallel reactions direct fluorination and catalyst decomposition due to its low thermal stability in the presence of fluoride ion [5,8, 59, 60] One example is trimethylsilyl fluoride, which can be prepared from the chloride by using either 18-crown-6 (Procedure 3, p 192) or Aliquot 336 in wet chlorobenzene, as illustrated in equation 35 [61],... 

Because the anioas of nitroalkanes are stable, retro-acyladoc smoothly In the presence of a base catalyst. This type of reacdo organic synthesis." Nucleophilic attack of water or alcohol to ct-the ring cleavage v/ith the formadon of Oj-nitro acids and Oj-niti... 

The reaction occurs at approximately 80-130°C using the proper catalyst. Many catalysts have been tried for this reaction, and there is an indication that the best catalyst types are those of the tertiary amine and quaternary ammonium functionalized resins. This route produces ethylene glycol of a high purity and avoids selectivity problems associated with the hydrolysis of ethylene oxide. 

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