Catalyst operating conditions

Catalyst life must be predictable to avoid unexpected shut down and lost production. It is necessary therefore to establish good operating procedures that achieve 

Adiabatic beds One or more packed beds in series or parallel—gas or gas/liquid feed. Adiabatic temperature increase with interbed cooling to control selectivity. 

Tube-cooled isothermal Catalyst loaded into or around tubes. Temperature rise controlled by suitable cooling medium not perfectly isothermal. 

Fluid beds Very fine catalyst particles are fluidized in the reacting gas. Used for exothermic reactions to give uniform bed temperature. 

Batoh/autoolave Sufficient catalyst of appropriate size for batch of feed. Heat of reaction controlled by heating or cooling coils. 

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Methanol Synthesis. AH commercial methanol processes employ a synthesis loop, and Figure 6 shows a typical example as part of the overall process flow sheet. This configuration overcomes equiUbtium conversion limitations at typical catalyst operating conditions as shown in Figure 1. A recycle system that gives high overall conversions is feasible because product methanol and water can be removed from the loop by condensation. 

Pilot Studies. AppHcations requiring the reduction of VOC emissions have increased dramatically. On-site pilot tests are beneficial in providing useful information regarding VOC emission reduction appHcations. Information that can be obtained includes optimum catalyst operating conditions, the presence of contaminants in the gas stream, and the effects of these contaminants (see Pilotplants and microplants). 

As with troubleshooting, a proper debottlenecking exercise must consider the effects of feedstock, catalyst, operating conditions, mechanical hardware, environmental issues, and the ability of the rest of the refinery to handle the additional feed/product rates and quality. 

Fig. 15. (a) Novel atomic resolution-ETEM (87) and (b) schematic of various components for imaging, chemical analysis and diffraction under catalyst operating conditions. 

Exploration for an acceptable or optimum design for a new reactor may require consideration of several feed and product specifications, reactor types, catalysts, operating conditions, and economic evaluations. Modifications to an existing process likewise may need to consider many cases. Commercial software may be used to facilitate examination of options. A typical package can handle a number of reactions in various ideal reactors under isothermal, adiabatic, or heat-transfer conditions in one or two phases. Outputs can provide profiles of composition, pressure, and temperature as well as vessel size. 

A relevant characteristic of the technology should be the ability to remove the water selectively and continuously in order to shift the chemical equilibrium to full conversion. Because the presence of a liquid water phase will lead to rapid deactivation of the solid catalyst, operating conditions for water-free organic liquid should be found. In addition, the thermodynamic behavior of the reaction mixture is nonideal, particularly with respect to the couple alcohol-water. 

Figure 6. TPR/D profile for treatment A- B- C- D over a Cr203/Si02 catalyst. Operation conditions H2(10)/Ar(90), 10 K/min...

This work, on the other hand, is directed at understanding the kinetics of carbon formation and the species responsible for deactivation. In order to understand what is happening during deactivation, it is first necessary to have an understanding of the reaction kinetics. While reaction kinetics have been reported for iron Fischer-Tropsch catalysts, operating conditions were not sufficiently general and the catalysts were different from those used in this work. Hence, it was necessary to obtain reaction parameters over a wide range of conditions to meet the needs of this study. These parameters were obtained under conditions of little or no deactivation as well as under conditions for which deactivation plays a major role so that effects due to reaction and deactivation could be separated. 

By now this basic formulation has had many interpretations. For example (Activity) has been used to refer to coke-on-catalyst, amine index of the material, reference to conversion in some specific chemical test who knows what else. The value of n, reported in various studies as ranging from 0 to 12, has been represented to indicate diffusion control (0.5) up to essentially "... we don t know what is going on here. .. (12). .. ". The factor is a proportionality constant specific to catalyst, operating conditions and chemical reaction. Voorhies model, based on time-on-stream observations, is obviously not general, but it is a good place to start. 

Depending upon the catalyst operating conditions, a number of reactions may... 

The extent to which each of the main reactions contributes to the removal of carbon monoxide, hydrocarbons and nitrogen oxides depends on the catalyst formulation and the catalyst operating conditions. Detailed kinetic data for these reactions are rarely found in the literature. Some fundamental data do exist for the oxidation of carbon monoxide, reaction 11, and some overall kinetic data exist for the other reactions [15-19],... 

The washcoat components support the catalytic function of the precious metals and even take part in the catalytic reaction. Furthermore, they guarantee the resistance of the precious metal components against deactivation processes occurring at high temperature catalyst operation conditions. As shown in Fig. 37, the washcoat layer typically has a thickness of about 10-30 pm on the walls of the support and of about 100-150 pm in the corners of the support. These values are valid for ceramic supports with square shaped channels. 

The main task of the cerium oxide washcoat component is oxygen storage, because the cerium ion is easily reduced and oxidized under typical catalyst operating conditions, formally according to the reaction... 

Figure 40 shows the conversion of CO, HC and NO e at typical automotive catalyst operation conditions for a precious metal based catalyst on a ceramic monolith with an extremely low precious metal loading, and for a precious metal free catalyst in which the same ceramic monolith support was used but with a washcoat consisting of a typical base metal catalyst formulation. The extremely poor con-... 

Until 1995, most of the monolithic three-way catalysts contained platinum and rhodium, in mass ratios of about 5-20 1 Pt Rh. The total precious metal loading is typically 0.9-2.2gU catalyst volume. These are only typical values, as the amount of precious metals and the mass ratio of platinum to rhodium depends on the specific application of the catalyst and is governed by factors such as the composition of engine-out emissions, the emissions targets to be reached, the catalyst operating conditions and the properties of the fuels used. 

Because of the wide range of catalyst operation conditions, it is to be expected that a variety of kinetic regimes will occur during the use of the catalyst. This is exemplified in the Arrhenius diagram for the eqs 13 and 11 measured in a Berty reactor with a monolithic catalyst (Figs. 46 and 47) [36]. 

In the application of catalytic converters to vehicles, an extremely broad range of different converter designs are used. The reasons for this are that each vehicle has different raw emissions, different catalyst operation conditions and different - in most cases limited - space available in the vehicle underbody to accommodate the catalyst. 

The influence of the total amount of precious metals on the conversion also depends upon the catalyst operation conditions (Fig. 72). After engine aging, the HC light-off under lean conditions is improved by about 40 K upon increasing the Pd loading from 3.5gl to 40gl , whereas the improvement is only about 20K under stoichiometric conditions. 

Each of the precious metals will interact in a different way with the major wash-coat constituents, AI2O3 and CeOa- The extent of these interactions is controlled by the catalyst operation conditions, especially the temperature and the net oxidizing... 

Fig. 2 Single cell Performances of DMFCs with different cathode catalyst. Operation conditions temperature 50, MeOH IM and O.lcc/min, Air flow 52.5cc/min...

Type of catalyst Operating condition PCM emission Rrference... 

The present volume contains the text of the lectures followed by those of the communications, the latter being classified under three main topics Hydrogenation, Oxidation and Acid Catalysis. All the communications were read by two referees, who obliged authors in many cases to present revised versions. In most of the papers the emphasis is placed on the selectivity of the reactions, taking into consideration all its aspects chemo-, regio- and stereoselectivity (including enantioselectivity). If the comprehension of the parameters (physicochemical characteristics of the catalysts, operating conditions, etc.) which determine this selectivity sometimes imposes the choice of simple reactions, various syntheses of complex products of industrial interest are also reported. 

General Introduction. Three processes, the Oxo, Synol, and Isosynthesis, are related to the Fischer-Tropsch process in that hydrocarbons or oxygenated chemicals are produced from mixtures of hydrogen and carbon monoxide. The principal catalysts, operating conditions, and products pf these syntheses and similar data on the Fischer-Tropsch process and some of its variations are compared in Table 11-8. 

Different kinds of transient experiment aimed either at the elucidation of reaction mechanistic features or at the estimation of kinetic parameters were performed over the powdered catalyst. Operating conditions as similar as possible... 

Catalyst compositions Source of precursor Cost of catalysts Operating conditions Energy Consumption/ (GJ/t)... 

Reaction Membrane/ configuration Catalyst Operating conditions Ref. 

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