Catalyst history

In addition to this work on charcoal- and silica-supported catalysts and on evaporated platinum films, a number of studies have been made on alumina-supported platinum catalysts (e.g., 111-114, 81,115) in which the aim has been the study of reactions at the platinum alone. In these cases, one cannot automatically dismiss the possibility of participation of the alumina support (i.e., of dual function behavior of the catalyst) because it is known that alumina may have acidic properties, particularly when retained halogen is present. In general terms, there is no immediate answer to this problem because the nature of this sort of catalyst wall be much dependent on the details of catalyst history, preparation, and use. However, there can be little doubt that in many experimental studies using plati-num/alumina, and in which the assumption has been made that the alumina support is inert, this assumption is essentially valid. For instance, one may note the inert alumina used by Davis and Venuto (111) and the justification provided by Gault et al. (116) for the inertness of the alumina used in a substantial body of previous work irrespective of whether the catalyst was... 

At 500°C the reaction rate over the platinum electrode-catalyst appeared to be independent of the e.m.f. of the cell. At 550°C two reaction rate branches were observed, depending on whether the catalyst had been pretreated in oxidising or reducing conditions (see Figure 9). The e.m.f. of the cell also exhibited two branches dependent upon pretreatment (see Figure 9), in a similar manner to other SEP work on oxide catalysts.86,87 It was suggested that the catalyst state (i.e., catalyst oxygen content or 5) was a function of the catalyst history. Different catalyst states corresponded with different catalyst reactivities and the e.m.f. of the cell reflected the catalyst state. 

Catalyst Changeover. Metals Content. The equilibrium sample of a USY octane catalyst, Catalyst A, was withdrawn from an Amoco FCU. Results of metals analyses on the equilibrium catalyst and on its parent are given in Table I. Catalyst A was introduced to the unit during a five-month period over Catalyst B, which was identical to Catalyst A in all respects, except for a low level of contaminant rare earth. Catalyst B had, in turn, been introduced over a rare earth-containing catalyst, Catalyst C, eight months prior to withdrawal of the equilibrium sample. Catalyst history and rare earth contents are summarized in Table II. 

The dramatic increase in irreversible CO adsorption on presulfided supported nickel catalysts at moderate pressures (162) has significant, practical implications in regard to the use of CO chemisorption to measure nickel dispersion. For example, it is often desirable to determine nickel surface areas for catalysts used in a process where sulfur impurities are present in the reactants. Substantial differences in the measurements of nickel surface area by H2 or CO adsorption are possible depending upon the catalyst history and choice of adsorption conditions. In view of the ease with which catalysts may be poisoned by sulfur contaminants at extremely low concentrations in almost any catalytic process, and since large CO uptakes may be observed on supported Ni not necessarily representative of the unpoisoned nickel surface area, the use of CO adsorption to measure nickel surface areas is highly questionable under almost any circumstance. 

Again, as in the case of the static reactor, interpretation is possible only if k is constant throughout the experiment. Since in the flow system the parcels of catalyst in each space element dx are not exposed to identical gas phase conditions with respect to each other at any time, any changes of k which might occur on the basis of its previous exposure history will, in the flow system, bring about a twofold complication in the interpretation of data, since the catalyst histories will not only be functions of time but also of the space coordinate x. 

It is recognized that selectivity in a reaction such as that chosen could be strongly dependent on conversion level, on temperaiuie and perhaps, as noted above, on catalyst history, e.g., steaming. Basic catalyst behavior, in the absence of any hetcrocycle, is reviewed in die following table. Suffice it to say that in no case (steaming, low temperature, low conversion) did these ZSM-5 catalysts produce PET/ET (or OET/ET) ratios approaching those found on injection of helerocycle. 

We can best examine cracking catalyst history by dividing it into two eras the pre-zeolitic era from 1941 to 1964, and the crystalline zeolite era. Catalysts for the various processes had fairly similar properties. They were for the most... 

A different and unexpected behavior was observed for the Pt/C catalyst provided by Johnson Matthey showing that the results obtained by direct adsorption calorimetric measurements provide accurate values of the heats of CO adsorption, and that they are directly related with the catalyst history (carbon used as support, the method of preparation). The calorimetric results obtained for this sample are given in Fig. 12.9 and Table 12.3. 

The polymer is exposed to an extensive heat history in this process. Early work on transesterification technology was troubled by thermal—oxidative limitations of the polymer, especially in the presence of the catalyst. More recent work on catalyst systems, more reactive carbonates, and modified processes have improved the process to the point where color and decomposition can be suppressed. One of the key requirements for the transesterification process is the use of clean starting materials. Methods for purification of both BPA and diphenyl carbonate have been developed. 

Semibatch hydrogenation of edible oils has a long history and a well-estabhshed body of prac tice by manufacturers and catalyst suppliers. Problems of new oils, new specifications, new catalyst poisons,... 

Nonstirred ARC runs may give answers that do not adequately duphcate plant results when there are reactants that may settle out or that require mixing for the reaction to be carried out (DeHaven and Dietsche, The Dow Chemical Company, Pittsburgh, Calif., Catalyst Explosion A Case History, Plant (Operations Progress, April 1990). 

History The histoiy of a plant forms the basis for fault detection. Fault detection is a monitoring activity to identify deteriorating operations, such as deteriorating instrument readings, catalyst usage, and energy performance. The plant data form a database of historical performance that can be used to identify problems as they form. Monitoring of the measurements and estimated model parameters are typic fault-detection activities. 

S cc also Catalysts Combustion Gasoline and Additives Heat and Heating Petroleum Consumption Refineries Refining, History of. 

The FCC process has a long history of innovation and will continue to play a key role in the overall success of the refining industry. The continuing developments will primarily be in the areas of catalyst, process, and hardware technologies. 

---