Catalyst scale

To understand heterogeneous catalysis it is necessary to characterize the surface of the catalyst, where reactants bond and chemical transformations subsequently take place. The activity of a solid catalyst scales directly with the number of exposed active sites on the surface, and the activity is optimized by dispersing the active material as nanometer-sized particles onto highly porous supports with surface areas often in excess of 500m /g. When the dimensions of the catalytic material become sufficiently small, the properties become size-dependent, and it is often insufficient to model a catalytically active material from its macroscopic properties. The structural complexity of the materials, combined with the high temperatures and pressures of catalysis, may limit the possibilities for detailed structural characterization of real catalysts. 

Holena, M., Baerns, M., Feedforward neural networks in catalysis, a tool for the approximation of the dependency of yield on catalyst composition, and for knowledge extraction, Catal. Today 2003, 81, 485-494. Serra, J. M., Corma, A., Argente, E., Valero, S., Botti, V., Neuronal networks for modeling of kinetic reaction data applicable to catalyst scale up and process control and optimization in the frame of combinatorial catalysis, Appl. Catal. A 2003, 254, 133-145. 

Catalyst scale-up is a process in which a catalyst previously made in small quantities in a laboratory is manufactured in quantities of more than 100 lb with equipment that performs the same operations as larger commercial equipment. If possible, this should involve equipment that simulates the series of unit operations that will be used in commercial catalyst preparation. 

Figure 6 (a) SEM image of SWNTs produced by arc-discharge method using Ni Y (4.2 1 at.%) catalyst (scale bar 1 pm). (Reprinted with permission from Ref. 20. 1997 Macmillan Magazines Ltd.) (h) Electron diffraction pattern of carbon nanotubes produced by arc-discharge method. (Reprinted with permission from Y. Saito, T. Yoshikawa, S. Bandow, M. Tomita, and T. Hayashi, Phys. Rev. B., 1993, 48, 1907. 1993 by the American Physical Society)... 

E.F. Sanders and E.J. Schlossmacher, "Catalyst Scale-up-Pitfall or Payoff " (1983) in Applied Industrial Catalysis, Vol. 1, Academic Press. 

Uses Epoxy curing agent chelating agent for oil field, textile, water treatment, detergent fields herbicide intermediate polyamide resins for adhesives, films, plastics, inks PU for extenders catalysts scale/cor-rosion inhibitors coatings... 

Properties Misc. with water m.w. 114.19 sp.gr. 0.94 b.p. 183 C (760 mm) flash pt. 167 F Toxicology LDLo (oral, rat) 1 g/kg LCLo (inh., rat, 4 h) 3200 mg/m si. toxic by ing. and inh. primary skin irritant TSCA listed Precaution Corrosive liq. combustible Hazardous Decomp. Prods. Heated to decomp., emits toxic fumes of NOx Uses Epoxy curing agent chelating agent for oil field, textile, water treatment, detergent fields herbicide intermediate polyamide resins for adhesives, films, plastics, inks PU for extenders catalysts scale/corrosion inhibitors coatings... 

The observed kinetics of heterogeneously catalyzed reactions are affected by various phenomena at different scales. For a detailed investigation of a reaction mechanism the effects of mass and heat transfer limitations at the catalyst scale should be negligible. Also no deviations from the ideal plug flow or perfectly mixed flow pattern should occur at the reactor scale. 

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