Aged catalyst

In the synthesis of AGE with an acid as the catalyst, aHyl alcohol is added to the epoxy group of epichlorohydrin, yielding 3-aHyloxy-l-chloro-2-propanol [4638-03-3], which then undergoes cyclization with alkaU to yield AGE. Catalysts such as H2SO4, SnCl, BE (C2H )20 (33), heteropolyacids, HQO, andy -CH CgH SO H (34) are used. 

E. Jobson and co-workers. Deterioration of Three-Way Automotive Catalysts, Parti—Steady State and Transient Emission of Aged Catalyst, SAE 930937, Society of Automotive Engineers, Warrendale, Pa., 1993. 

The CF and GF represent the coke- and gas-forming tendencies of an E-cat compared to a standard steam-aged catalyst sample at the same conversion. The CF and GF are influenced by the type of fresh catalyst and the level of metals deposited on the E-cat. Both the coke and gas factors can be indicative of the dehydrogenation activity of the metals on the catalyst. The addition of amorphous alumina to the catalyst will tend to increase the nonselective cracking, which forms coke and gas. 

Conversion efficiencies of the dynamometer-aged catalysts were measured in a standard A/F sweep test on an engine dynamometer [6]. The sweep experiments were carried out at 450 and 85,000 h space velocity (volumetric basis standard conditions). The sweep ranged from 0.5 A/F lean of stoichiometry to 0.5 A/F rich of stoichiometry with imposed A/F perturbations of+.0.5 A/F at 1 Hz. After sweep evaluation, small samples of catalyst were renrroved from the front region of the brick for chemisorption and flow reactor experiments. 

CO/NOx cross-over efficiencies of aged catalysts in dynamometer sweep experiments do not correlate with either noble me dispersion or noble metal surface area. 

Rates of oxygen uptake in the dynamometer-aged catalysts are consistent with published oxidation kinetics of l- m-thick Pd films. 

We thank K. S. Patel and D. M. DiCicco for providing the dynamometer-aged catalysts and sweep evaluation data. E. Gulari and C. Sze (U. of Michigan) assisted with the design of the pulsed reactor system. 

Figure 7. Comparison between initial and aged catalysts in terms of (A) size distribution and (B) morphological distribution.

Et4N]2[Fe2lr2(CO)i2] cluster precursor, which exhibit a high activity in the synthesis of methanol from CO and H2, were studied by Ir and Fe Mossbauer spectroscopy. The study extends from the precursors via the fresh to the aged catalysts. The presence of iridium in the metallic state as well as the presence of trivalent, divalent and alloyed iron is detected. Representative Ir and Fe Mossbauer spectra are shown in Fig. 7.69. Information about the adsorption on the surface of MgO... 

Table 4.1 lists the ions observed from a 121,000 km vehicle-aged catalyst, and the poisons to which they can be attributed. 

Figure 10.14. Comparison between theoretical and experimental XRD patterns recorded on prereduced Pt/CoOx/La203 (a) and after ageing in the reaction conditions (b) Theoretical XRD patterns of LajOj is reported in Figure 10.14a and of La(OH)3 on aged catalyst in Figure 10.14b.

Mowery, D.L., Graboski, M.S., Ohno, T.R. et al. (1999) Deactivation of Pd0-Al203 oxidation catalyst in lean-burn natural gas engine exhaust aged catalyst characterization and studies of poisoning by H20 and S02, Appl. Catal. B 21, 157. 

The conditions that lead to the formation of the first C-C bond during MTO, the mechanism for making ethylene and propylene from methanol, the critical catalyst parameters that are responsible for the wide variation in light alkene selectivities observed among different framework types and between fresh versus aged catalysts are some of the most intriguing questions of the catalysis field today [100-105]. 

Light-off Temperature of Aged Catalysts Catalyst A Contained 1.5g/dm3 Pt, 0.35g/dm3 Rh with CZ and Catalyst Contained the Same Amount of Precious Metals with ACZ... 

The local structure around a target element is revealed by EXAFS analysis. The Fourier transforms (FTs) of the aged catalysts and reference samples... 

K/Pt/Ti02 K/Pt/ZT70 K/Pt/Zr02 Fig. 33. The state of potassium over the sulfur-aged catalysts. 

The real-time observation of sintered Pt on CZ materials by in situ time-resolved Turbo-XAS demonstrates the re-dispersion of Pt particles. The Pt particle size of the aged catalyst decrease from 7 to 5 nm after 60 s and then to 3nm after 1,000 s under the alternating flow of reducing and oxidizing gases at 600°C. 

BaO within a few nanometers around the Pt can work as NOx storage material in the reaction containing S02. Also, the smaller the sulfate particle size in the aged catalyst is, the easier its decomposition. 

For the fresh and the specifically aged catalyst materials, the dependence of the normalized NOx storage capacity on temperature could be kept the same (Giithenke et al, 2007b). This minimized the number of parameters to be re-adapted for two catalysts with different ageing level. Thus, only the maximum NOx storage capacity and the pre-exponential factors for the reactions R1-R22 had to be re-evaluated, cf. Table III and Eq. (36). 

Fig. 3E Validation of the NSRC model for passenger car application—comparison of measured (meas) and calculated (calc) cumulative NOx emissions for the NEDC driving cycle aged catalyst (Giithenke et al., 2007b). The covered fraction of the NOx storage capacity (spatially averaged i/fNO ) is calculated by the model. Reprinted with permission from SAE Paper 2007-01-1117 2007 SAE International. Integral NOx conversions X evaluated from experiment and simulation data Aexp = 42.0%, = 44.3%.

The major problem of the application of zeolites in alkane-alkene alkylation is their rapid deactivation by carbonaceous deposits. These either strongly adsorb on acidic sites or block the pores preventing the access of the reactants to the active sites. A further problem is that in addition to activity loss, the selectivity of the zeolite-catalyzed alkylation also decreases severely. Specifically, alkene formation through oligomerization becomes the dominant reaction. This is explained by decreasing ability of the aging catalyst to promote intermolecular hydride transfer. These are the main reasons why the developments of several commercial processes reached only the pilot plant stage.356 New observations with Y zeolites reconfirm the problems found in earlier studies.358,359... 

---