Selection and Testing of Catalysts in Practice

To summarize a suitable catalyst was found by means of mechanistic reasoning, and it was shown that planned research can lead to a satisfactory solution within a relatively short time and with minimum effort. 

To shorten the laborious process of purely empirical catalyst selection, which sometimes involves hundreds of tests, today use is made of the various catalyst concepts 

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Selection and Testing of Catalysts in Practice 361 b) With POLYMATH the rate law can be determined as follows ... 

Hie objective of MAT testing in many labs is to compare both activity and selectivity differences between catalysts. Given that a variety of testing approaches are in practice, what effects do these methods have on ranking of catalysts To answer this question the three catalysts summarized in Table 1 were evaluated using seven different steaming/MAT approaches. Table 4 summarizes the seven methods evaluated. The definitions for cut points in this study are C5-421°F (gasoline), 421-602°F (LOO) and 602°F-plus (bottoms). Dry gas includes H2, H2S and C1-C2 hydrocarbons. LFG are the C3-C4... 

There are many examples of laboratory catalysts very successful as to activity and selectivity, but unsuitable to industrial development due to lack of mechanical strength, whose measurement is a key part of every quality control for any industrial catalyst. In practice, no catalyst should be loaded in an industrial reactor without having tested its mechanical properties. 

Raw materials and auxiliary products used in a process as well as materials of construction for equipment items can be the eause of scale-up effects . Pure raw and auxiliary materials must be used in laboratory studies to eliminate the influence of impurities on the ehoice of the process route, catalyst selection, and search for satisfactory process conditions. However, pure chemicals are usually too expensive to use for manufacture on a commercial scale. It is common practice to use raw materials of technical grade in a full-scale plant. These materials contain impurities, which can act as catalysts or inhibitors. They can react with reactants or intermediates, thereby decreasing yields and selectivities of desired produets. Therefore, raw materials of technical grade, even from different suppliers must first be tested on laboratory scale. 

The study of pyridine-piperidine reactions under high pressure conditions has given much information concerning the kinetics of HDN, but these results are however complicated by alkyl transfer (disproportionation) reactions, and thus the possibility of using such reactions as an easy test for determination of mechanism and as a catalyst probe is partly excluded. The study of polycyclic amines (quinoline, etc.) for the same purpose is limited by the complexity and the number of different possible routes, but is a very interesting test reaction for an overall study of catalytic activity or selectivity toward HDN in industrial conditions. Because no disproportionation occurs and the numbers of products and routes are reasonable, the studies of pyridine-piperidine and alkylpyridine-alkylpiperidine HDN under normal H2 pressure and low amine pressure (< lOTorr) are very powerful test reactions both for mechanism determination and catalyst study, although these conditions are far removed from those of industrial practice. 

In another brief examination [ 15] of the impact of monolith supports for mcthanation catalysts, a comparison between nickel and ruthenium catalysts was made utilizing a metal (Fecralloy) support. The conversion tests were run at 673 K, 5400 kPa, 3.47 sec", and with a gas composition of 62% hydrogen, 18% carbon monoxide, and 20% water vapor. A ruthenium pellet catalyst that was run in comparison was approximately twice as active as ruthenium on the monolith. However, the difference in product (methane) selectivity was 97% for the metal monolith catalyst and 83% for the pellet bed. In the comparison between nickel and ruthenium, shown in Fig. 14, the ruthenium was more active and selective. The lack of impact on activity or selectivity as a result of steam addition to the reactant mixture provided useful practical data as well. No further details regarding the catalyst characteristics were provided. 

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