Catalyst characterization test

By following this multistep procedure, the kinetics were evaluated on a wide range of data (both conditions and feedstock) not used in the parameter estimation. The start-of-cycle kinetics were extended to other catalysts and catalyst states by defining an appropriate catalyst state vector (a = aD, al5 a , ac), which is different from 1 at the start of cycle. A catalyst characterization test was developed to estimate parameters for new catalysts. 

Translation of Laboratory Fluid Cracking Catalyst Characterization Tests to Riser Reactors... 

A theory has been developed which translates observed coke-conversion selectivity, or dynamic activity, from widely-used MAT or fixed fluidized bed laboratory catalyst characterization tests to steady state risers. The analysis accounts for nonsteady state reactor operation and poor gas-phase hydrodynamics typical of small fluid bed reactors as well as the nonisothermal nature of the MAT test. Variations in catalyst type (e.g. REY versus USY) are accounted for by postulating different coke deactivation rates, activation energies and heats of reaction. For accurate translation, these parameters must be determined from independent experiments. 

This work provides conclusive evidence that transient catalyst characterization tests can result in erroneous catalyst ranking. For example, USY catalysts show higher activity than REY catalysts in the laboratory tests but lower activity in a steady state riser. Although emphasis in this paper is placed mainly on the coke-conversion selectivity, the analysis is also extended to yields of other FCC products. 

The effect of time averaging on yields in transient tests can be minimized by shortening the duration of the test. Also, a fixed bed test is superior to an FFB activity test in that backmixing is minimized. Furthermore, an isothermal fixed bed test would be easier to interpret than the adiabatic MAT test. This work shows that from the point of view of a catalyst characterization test, a small steady state riser will give the most direct information for catalyst performance in a commercial riser. 

Figure 7 Predicted product selectivities as a function of conversion for three different laboratory catalyst characterization test units.

Catalyst characterization tests include measurement of surface areas, chemisorption, pore-size distributions, crystal structure as determined by X-ray crystallography, reaction mechanisms as revealed by kinetics, and isotopic tracers and diagnostic catalytic reactions to test functional capabilities. These have been interpreted in terms of variation of catalyst preparation-structure-performance relationships. 

To make 1, [CpRu(CH3CN)3]3 F6 in acetone was allowed to react with 4, forming a mixture of 3d and chelate 1 (10). This mixture could be used but for purposes of catalyst characterization and further testing was converted to > 90% pure 1 by repeated coevaporation of added acetone with the acetonitrile liberated. Complex 1 showed diagnostie NMR data consistent with a chiral stracture and foin unique, diastereotopic methyl groups. 

The results of the unsteady-state reactivity tests and of the catalysts characterization allow us to propose a model for the active layer of VPP under reaction conditions, illustrated in Figure 55.5. In this model, the surface is in dynamic equilibrium with the gas phase, and its nature is a function of both reaction... 

Highly mesoporous carbon supported Pd catalysts were prepared using sodium formate and hydrogen for the reduction of the catalyst precursors. These catalysts were tested in the enantioselective hydrogenation of isophorone and of 2-benzylidene-l-benzosuberone. The support and the catalysts were characterized by different methods such as nitrogen adsorption, hydrogen chemisorption, SEM, XPS and TPD. 

In this chapter, two carbon-supported PtSn catalysts with core-shell nanostructure were designed and prepared to explore the effect of the nanostructure of PtSn nanoparticles on the performance of ethanol electro-oxidation. The physical (XRD, TEM, EDX, XPS) characterization was carried out to clarify the microstructure, the composition, and the chemical environment of nanoparticles. The electrochemical characterization, including cyclic voltammetry, chronoamperometry, of the two PtSn/C catalysts was conducted to characterize the electrochemical activities to ethanol oxidation. Finally, the performances of DEFCs with PtSn/C anode catalysts were tested. The microstmc-ture and composition of PtSn catalysts were correlated with their performance for ethanol electrooxidation. 

The object of this review is threefold (1) to discuss the various characterization techniques which have been applied to this catalyst system, (2) to relate what each technique reveals about the nature of the catalyst, and (3) to present an overall picture of the state of the catalyst as it now appears. We will not discuss the vast literature on catalyst activity testing, kinetics, or mechanisms here. These are subjects for review themselves. However, we will mention some selective catalyst activity tests which were designed to give some fundamental insight into the catalyst state or active sites present. Also, we will not discuss in detail the considerable work reported on pure compounds (unsupported) of molybdenum, cobalt, and/or aluminum but we will have occasion to compare some of their properties to our catalyst systems to assess to what degree they may be present in the catalyst. 

HT technology for catalysts-automated synthesis and testing appears to be reasonably adapted to date, but further improvements are expected for HT catalysts characterization, which is still restricted to costly and in general ex-situ spectroscopic techniques. These tools would provide the new catalyst descriptors needed to improve the ability to predict catalytic performances without testing. 

While most catalyst vendors rely on fixed bed microactivity (MAT) tests, fixed fluid bed (FFB) reactor experiments are widely used within Mobil to characterize FCC catalysts. The amount of catalyst used is constant for each test, and products are collected for a known period of time. In MAT experiments, catalyst bed is fixed while in FFB test the catalyst bed is fluidized. As products are collected over the decay cycle of the catalyst, the resulting conversion and coke yields are strongly influenced by catalyst deactivation. Systematic differences exist between the measured conversion or catalyst activity and coke yields for the MAT and FFB tests. The magnitude of these differences varies depending on the type of catalyst being tested (REY or USY). Experimental data in Figure 1 clearly show that FFB conversion is higher than MAT conversion for USY catalysts. On the other hand, FFB conversion is lower than MAT conversion for REY catalysts. Furthermore, the quantitative... 

Potential pitfalls exist in ranking catalysts based solely on correlations of laboratory tests (MAT or FFB) to riser performance when catalysts decay at significantly different rates. Weekman first pointed out the erroneous conversion ranking of decaying catalysts in fixed bed and moving bed isothermal reactors (1-3). Phenomena such as axial dispersion in the FFB reactor, the nonisothermal nature of the MAT test, and feedstock differences further complicate the catalyst characterization. In addition, differences between REY, USY and RE-USY catalyst types exist due to differences in coke deactivation rates, heats of reaction, activation energies and intrinsic activities. 

The liquids require a hydrorefining step to stabilize their reactive properties, to reduce the asphaltenes and preasphaltenes, to reduce sulfur, nitrogen, and oxygen, and to make the liquids more distillable. The extent of hydrorefining depends on the end use of liquids—fuel oil or chemical feedstocks. The objective of this work is to evaluate the hydrorefining processibility of ORC flash pyrolysis coal tar as a part of the tar characterization task. Results of the initial phase of catalyst screening tests are reported in this chapter. 

As can be seen, the field of catalyst characterization makes extensive use of most available chemical testing methodologies, and requires the cooperation and collaboration of many different people to be successful. Due to the complexity of catalyst preparation and use, it is not surprising that different laboratories have developed different methods and procedures to measure the same property. 

When a catalyst with practical potential is identified, further experimentation usually includes characterization of the reaction mechanism and kinetic measurements. More careful experimentation and higher accuracy are increasingly important. Subsequentiy, catalyst life tests may be required, preferably in a simulated industrial environment, to determine the long-term catalyst behavior. This may necessitate optimization of reaction conditions and further catalyst improvements. 

The X-ray diffraction (XRD) patterns were collected on a RIGAKU diffractometer, operated at 30kV and 20 mA and using CuK radiation (A,=0.15405nm). The specific surface areas of the catalysts were tested on a home-made analyzer, following the BET method from air isotherms determined at liquid nitrogen temperature. The structure properties of the catalysts were characterized by IR spectroscopy using a PE-783 IR spectrometer. The amount of samples were mixed with KBr in form of disks, and the spectra were taken at room temperature. 

The implementation of combinatorial chemistry and automated methods for rapid synthesis, testing, and characterization of catalysts, has opened a wide range of new opportunities in catalysis. However, so far, Mossbauer spectroscopy has not been introduced into this methodology. Two hurdles must be overcome for Mossbauer spectroscopy to become important in high-throughput catalyst characterization the system for recording spectra must be scaled down, and the data acquisition and exploitation systems must be adapted. 

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