Catalyst testing procedure

In a discussion of catalyst testing procedures, Dowden and Bridger Adv. Catalysis, 9 (669), 1957] have reported the effect of particle size and mass velocity on the rate of oxidation of S02 to S03. They studied this reaction at 400 and at 470 °C using commercial catalyst pellets (5.88 mm diameter) and two sizes of crushed pellets (2.36 and 1.14 mm diameter). In all runs the feedstream composition was kept constant. 

In this study, performance comparisons of various catalytic materials were performed. In order to compare the performances, data from different sources were modeled, their kinetic parameters were extracted, and for comparison, all of the data used for this study were brought to a single space time and the results were compared. Some drastic changes in the catalyst performances were observed when the space time corrections were properly done. The results of this study clearly demonstrated that, it is imperative to reach a consensus about the catalyst testing procedures in order to be able to compare the performances of the catalysts tested in different laboratories. 

In the development phase of catalyst research, testing of the catalyst s chemical and physical properties and evaluation of the catalyst s performance ate two essential tasks. In the manufacturing process, many of the same analyses and evaluations are used for quaHty assurance. A number of the testing procedures outlined eadier for catalyst supports can also be appHed to catalysts (32). 

Propylene + NH3 The results of propylene and ammonia coadsorption experiments are summarized in Fig. 3. Two series of tests were made. In the first series of tests (procedure A) propylene is put in contact at r.t. with the catalyst for 5 min, then removed by evacuation at r.t. later ammonia 1800 1600 1400 1200 cm is put in contact for 2 min at r.t. and then... 

The catalyst concentration can be varied in a wide range for the above-mentioned parameter set, without changing the reaction kinetics [9]. Since gas/liquid micro reactors span a broad range of residence times, typically much shorter than for conventional apparatus, this allows a flexible adaptation of the test procedure to the needs of micro flow characterization. 

The extension of this work to include catalyst particles with internal voids is more complex, as there are regions of catalytic activity adjacent to the internal holes, complicating the testing procedure. A comparison of several different catalyst configurations of internal voids has recently been completed, and a description of the method, its verification, and the results obtained will be the subject of a future publication. 

Unknown new catalysts have to be treated in the same way as the reference catalyst and this is always an uncertainty factor in the test procedure, but this must be accepted if it should be possible to investigate new catalysts. 

Reactions were carried out in liquid phase in a well-stirred (1000 rpm) high-pressure reactor (Parr Instruments, 300 mL) at 30 bar and 150°C. The reaction mixture consisted of 61 g of ADPA (Acros Chemicals), 53 g MIBK (Acros Chemicals) and 370 mg of catalyst. The test procedures used here is similar to that described earlier by Bartels et al. (7). The reactor was operated at a constant pressure with the liquid phase in batch mode and the hydrogen fed in at a rate proportional to its consumption. The reaction was monitored by hydrogen uptake and the product yield was determined from gas chromatographic (Agilent Technologies, 6890N) analysis. 

Catalyst Testing. The hexane isomerization activity was measured for several catalysts containing about 0.2 wt % Pt. Appreciable differences in activity were evident which depended upon the method of preparation (Table VI). None of the catalysts is particularly active (c/. equilibrium values in Table VI). The surface areas of the catalysts (Table VI) are somewhat less than expected, and thus one can speculate that better activation procedures will lead to some improvement in performance. 

A similar flow approach but in the area of solid transport was reported by Ajmera et al. [39], They also used suction for the fast exchange of catalyst powder in a single-channel reactor applied for catalyst testing (Figure 3.3). For this purpose, they applied below atmospheric pressure at the reactor exit to draw in a defined amount of catalyst powder in a flat fixed bed. Over-pressure was applied in order to reverse this procedure after testing was finished. 

The value of catalyst testing is enhanced by reporting the results in a professional way. It is important to describe the following procedures Was a batch mode of operation or continuous, steady-state operation used What was the reactor configuration How were the catalysts prepared Was activation or pretreatment required ... 

In an effort to understand hew the petroleum industry addresses the problem of fresh FOC catalyst evaluation, a survey of testing philosophies from 15 companies was conducted. The objective was to identify the merits of various steaming procedures as well as catalyst testing. The results of the survey shew that each laboratory has a unique testing program, with wide differences being practiced in both steam deactivation and Micro Activity (MAT)... 

While ASTM procedures for both steaming and MAT testing have been established (ASTM D-4463 and D-3907, respectively), a general survey of the petroleum industry indicates that neither of these methods are specifically practiced. Instead, each laboratory has developed individualized steaming and MAT testing procedures that best suit their needs. While many laboratories perform complete chemical and physical analyses on fresh FOC catalysts, the vast majority do not perform such analyses on the steamed catalysts. The latter actually represent the catalysts evaluated vhile the former are in essence a "precursor". While it may be argued that fresh properties can be used as an indicator of steamed properties, a thorough evaluation of catalysts should include an examination of the steamed chemical and physical properties. 

Setting reasonable specifications depends on the development of reliable test procedures and well-characterized reference materials for method development. Statistical control processes can be used to eliminate variations to reduce off-specification catalysts and contractual disputes. 

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