Catalyst manufacturing

Shaped products used for adsorbent purposes are generally less sophisticated and therefore less expensive than catalytic products. In 1985, it was reported that 10,000 t/yr of activated alumina adsorbents were produced in the United States. North American producers of Bayer process-based activated aluminas include Alcoa, La Roche (formerly Kaiser Chemicals), Discovery, and Alcan. Gel-based activated aluminas are produced by La Roche, Vista, and several of the major catalyst manufacturers. In Europe, principal sources of supply are Rhc ne-Poulenc and Condea. 

Bayerite is a commercially available technical product that is produced in small quantities mainly for alumina catalyst manufacture. High purity aluminum [7429-90-5j metal has been converted to bayerite to produce very high purity aluminum oxides. 

Recent commercialization efforts have focused on improved activity synthesis catalysts, which allow ammonia synthesis to be conducted at significantly lower pressures and temperatures. Catalyst manufacturers have focused on enhancing the activity of the iron-based catalyst through the use of promoters (23). 

Many, but not all, reactor configurations are discussed. Process design, catalyst manufacture, thermodynamics, design of experiments (qv), and process economics, as well as separations, the technologies of which often are appHcable to reactor technology, are discussed elsewhere in the Eniyclopedia (see Catalysis Separation Thermodynamics). 

Polymerization and depolymerization of sihcate anions and their interactions with other ions and complexing agents are of great interest in sol—gel and catalyst manufacture, detergency, oil and gas production, waste management, and limnology (45—50). The complex silanol condensation process may be represented empirically by... 

The choice of parameter used in the determination of size distribution should include consideration of the information needed in the interpretation of the data. For example, in the case of a manufacturer of paint pigment, the size parameter that best describes the hiding power (performance of the pigment) is the projected area of particles. A powdered catalyst manufacturer is primarily concerned with surface-area equivalence. 

Almost all industrial catalysts are developed by researchers who are motivated to improve processes or create new ones. Thus the organization that first uses a new catalyst is usually the one that has discovered it. This organization, however, only rarely becomes the manufacturer of the catalyst used on a large scale. Catalysts are for the most part highly complex specialty chemicals, and catalyst manufacturers tend to be more efficient than others in producing them. Catalyst manufacturing is a competitive industry. Catalyst users often develop close relations with catalyst manufacturers, and the two may work together to develop and improve proprietary catalysts. 

A catalyst manufactured using a shaped support assumes the same general size and shape of the support, and this is an important consideration in the process design, since these properties determine packing density and the pressure drop across the reactor. Depending on the nature of the main reaction and any side reactions, the contact time of the reactants and products with the catalyst must be optimized for maximum overall efficiency. Since this is frequendy accompHshed by altering dow rates, described in terms of space velocity, the size and shape of the catalyst must be selected carehiUy to allow operation within the capabiUties of the hardware. 

Porosity and Pore Size. The support porosity is the volume of the support occupied by void space and usually is described in units of cm /g. This value represents the maximum amount of Hquid that may be absorbed into the pore stmcture, which is an especially important consideration for deposition of metal salts or other active materials on the support surface by Hquid impregnation techniques. The concentration of active material to be used in the impregnating solution is deterrnined by the support porosity and the desired level of active material loading on the catalyst. If the porosity is too low, inefficient use of the support material and reactor volume may result. If the porosity is too high, the support body may not contain sufficient soHd material to provide the strength necessary to survive catalyst manufacture and handling. 

In addition to developiag satisfactory catalysts, the designer also may have to develop a catalyst support or work with a support manufacturer to achieve this. In iadustry, catalyst manufacturers either form symbiotic relationships with support manufacturers or become experts ia support design and manufacture themselves. There have been a number of iadustrial acquisitions and joiat ventures formed to exploit just such a relationship. 

The performance of a catalyst often depends as much on the care and method of preparation as on the identity of the active components. This fact has been learned by many who have failed to obtain reproducibiUty among catalyst preparations ia the laboratory or have been responsible for quaUty assurance ia catalyst manufacture. Also, there are many examples of strong effects of trace impurities ia raw material or catalyst support on catalyst performance. 

Two or more soHd catalyst components can be mixed to produce a composite that functions as a supported catalyst. The ingredients may be mixed as wet or dry powders and pressed into tablets, roUed into spheres, or pelletized, and then activated. The promoted potassium ferrite catalysts used to dehydrogenate ethylbenzene in the manufacture of styrene or to dehydrogenate butanes in the manufacture of butenes are examples of catalysts manufactured by pelletization and calcination of physically mixed soHd components. In this case a potassium salt, iron oxide, and other ingredients are mixed, extmded, and calcined to produce the iron oxide-supported potassium ferrite catalyst. 

The data most frequentiy collected and reported in catalyst performance evaluations are activity or turnover number, selectivity to the desired product(s), overall yield, catalyst life, and the identities and yields of by-products produced. These data are used to further catalyst or process development research efforts, to monitor catalyst manufacture, and to provide quaUty assurance information to catalyst users. 

Much effort has been made by catalyst manufacturers to improve catalyst atttition resistance and thus reduce the formation of fines (see Catalysts, supported). In the 10-year petiod from 1980 to 1990, most catalyst manufacturers improved the atttition resistance of their catalyst by a factor of at least 3—4. This improvement was achieved even though the catalyst zeoHte content duting this petiod was continually increasing, a factor that makes achieving catalyst hardness more difficult. As an example of the type of atttition improvement that has been achieved, the catalyst atttition index, which is directiy related to catalyst loss rate in a laboratory attrition test, decreased from 1.0 to 0.35 for one constant catalyst grade during 1989—1990 (37). 

Other apphcations for monochlorobenzene include production of diphenyl-ether, ortho- and i ra-phenylphenol, 4,4 -dichlorodiphenylsulfone, which is a primary raw material for the manufacture of polysulfones, diphenyldichlorosilane, which is an intermediate for specialty siUcones, Grignard reagents, and in dinitrochlorobenzene and catalyst manufacture. 

Stiles, A. B. 1983, Catalyst Manufacture, Laboratory and Commercial Preparations. Marcel Dekker, Inc., New York. 

The proper method to remove the catalyst involves stabilization. The method for this is usually recommended by the catalyst manufacturer. With the reactor still closed, cold and flushed with nitrogen, admit nitrogen with less than 1 % oxygen in it, while the impeller is running. This oxidizes the organics and the metallic surface of the catalyst under well-controlled conditions after which the catalyst can be exposed to air without danger of overheating. 

Only catalysts that are completely inactive within reasonable condition should be rejected. Finding better conditions for a catalyst that shows some promise is best left for the catalyst manufacturer or the investigator. Those most familiar with process chemistry and recycle reactors will be best able to find the optimum condition for a promising catalyst. 

The Chemistry and Technology of Coal, James G. Speight Pneumatic and Hydraulic Conveying of Solids, O. A. Williams Catalyst Manufacture Laboratory and Commercial Preparations, Alvin B. Stiles... 

Catalyst Manufacture, Alvin B. Stiles and Theodore A. Koch Handbook of Grignard Reagents, edited by Gary S. Silverman and Philip E. Rakita... 

Eventually all catalysts become spent. At this stage they can be discarded, itself sometimes a problem, or returned to a refiner for recovery of metal values. In commercial use, noble-metal catalysts are always returned to a refiner. At the refinery, the catalyst is destroyed and the noble metals are recovered and converted to high-purity metal. In a loop system, the pure metal is converted to a suitable salt and again used for catalyst manufacture. In the entire loop, some metal will be lost and must be replaced with fresh metal. Refining is nowadays very efficient, and most metal loss will occur in the process itself, The total cost of a catalyst used in a loop is accordingly given by ... 

In general, platinum, with or without modifiers, makes the best catalyst for minimizing dehalogenalion, combined with a fast rate of reduction of the nilro function. Excellent results have been obtained by use of supported noble-metal sulfides (4/). These catalysts [manufactured by Engelhard Industries, Newark, New Jersey (5/)] have a high intrinsic selectivity for this type of reduction and have given excellent results under a wide range of conditions. Elevated temperatures and pressures are necessary to achieve reasonable rates (33,34). 

The filler is a clay incorporated into the catalyst to dilute its activity. Kaoline [A. 2(OH)2, Si205] is the most common clay used in the FCC catalyst. One FCC catalyst manufacturer uses kaoline clay as a skeleton to grow the zeolite in situ. 

The catalyst manufacturers control PSD of the fresh catalyst, mainly through the spray-drying cycle. In the spray dryer, the catalyst slurry must be effectively atomized to achieve proper distribution. As illustrated in Figure 3-10, the PSD does not have a normal distribution shape. The average particle size (APS) is not actually the average of the catalyst particles, but rather the median value. 

Refiners send E-cat samples to catalyst manufacturers on a regular basis. As a service to the refiners, the catalyst suppliers provide analyses of the samples in a form similar to the one shown in Figure 3-12. Although the absolute E-cat results may differ from one vendor to another, the results are most useful as a trend indicator. 

Improved crystallinity by producing more uniform zeolite crystals, FCC catalyst manufacturers have greater control over the zeolite acid site distribution. In addition, there is an upward trend in the quantity of zeolite being included in the catalyst. 

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