Catalyst loading effect

The reaction sequence of formaldehyde formation and subsequent COad formation can proceed either as sequential reactions of adsorbed species, or it can involve formation and desorption of formaldehyde into the electrol5d e and subsequent re-adsorption and further decomposition of formaldehyde to COad. Considering the significant transport and catalyst loading effects discussed above, it is clear that desorption and subsequent re-adsorption plus dehydrogenation of formaldehyde will play an important role also for COad formation, although a direct reaction of adsorbed RIad species can not be ruled out. 

Biddinger EJ, von Deak D, Singh D, Marsh H, Tan B, Knapke DS, Ozkan US (2011) Examination of catalyst loading effect on the selectivity of CNx and Pl/VC ORR catalysts using RRDE. J Electrochem Soc 158 B402-B409... 

Liquid holdup is made up of a dynamic fraction, 0.03 to 0.25, and a stagnant fraction, 0.01 to 0.05. The high end of the stagnant fraction includes the hquid that partially fills the pores of the catalyst. The effective gas/liquid interface is 20 to 50 percent of the geometric surface of the particles, but it can approach 100 percent at high hquid loads with a consequent increase of reaction rate as the amount of wetted surface changes. 

Research is also being conducted in Japan to aromatize propane in presence of carhon dioxide using a Zn-loaded HZSM-5 catalyst/ The effect of CO2 is thought to improve the equilibrium formation of aromatics by the consumption of product hydrogen (from dehydrogenation of propane) through the reverse water gas shift reaction. 

The comprehensive research program included all facets necessary for the development of these catalysts. Laboratory tests were conducted to determine the necessary catalyst loading, the design operating conditions, the effect of particle size, the effect of various trace constituents on catalyst performance, and finally, resistance of the catalyst to thermal upsets. This paper presents only those findings which have direct sig-... 

The catalysts were reduced with 100% H2 at 371 °C and an inlet space velocity of 1000/hr. Because of the carbon-forming potential of a dry gas recycle composition and the cost of reheating the recycle if the water produced by the methanation reaction is removed, a wet gas recycle composition was used. The catalyst loading, gas composition, and test conditions for these tests are listed in Table II, and the effects of nickel content are compared in Table III. 

Chiral dirhodium(II) carboxamidate catalysts are, by far, the most effective for reactions of allylic diazoacetates [44, 45] and allylic diazoacetamides [46]. Product yields are high, catalyst loading is low (less than 1 mol%), and enan-tioselectivities are exceptional (Scheme 6). The catalysts of choice are the two... 

Figure 11.8. Effect of po2 on the rate (TOF) of C2H4 oxidation on Rh supported on five supports of increasing d>. Catalyst loading 0.5wt%.22,27 Inset Electrochemical promotion of a Rh catalyst film deposited on YSZ Effect of potentiostatically imposed catalyst potential Uwr on the rate and TOF dependence on po2 at fixed Pc2H4-22,33 Reprinted with permission from Elsevier Science (ref. 27) and Academic Press (ref. 33).

Independently, Caddick et al. reported microwave-assisted amination of aryl chlorides using a palladium-N-heterocyclic carbene complex as the catalyst (Scheme 99) [lOlj. Initial experiments in a domestic microwave oven (reflux conditions) revealed that the solvent is crucial for the reaction. The Pd source also proved very important, since Pd(OAc)2 at high power in DMF gave extensive catalyst decomposition and using it at medium and low power gave no reaction at all. Pd(dba)2/imidazohum salt (1 mol% catalyst loading) in DME with the addition of some DMF was found to be suitable. Oil bath experiments indicated that only thermal effects are governing the amination reactions. 

Sigman et al. have optimized their system too [45]. A study of different solvents showed that the best solvent was f-BuOH instead of 1,2-dichloroethane, which increased the conversion and the ee. To ensure that the best conditions were selected, several other reaction variables were evaluated. Reducing the catalyst loading to 2.5 mol % led to a slower conversion, and varying temperature from 50 °C to 70 °C had little effect on the selectivity factor s. Overall, the optimal conditions for this oxidative kinetic resolution were 5 mol % of Pd[(-)-sparteine]Cl2, 20 mol % of (-)-sparteine, 0.25 M alcohol in f-BuOH, molecular sieves (3 A) at 65 °C under a balloon pressure of O2. 

Effects of Catalyst Loading and Oxidant on the Performance of Direct Formic Acid Fuel Cells... 

In this study, we investigated the effects of anode catalyst loading and oxidant on the performance of DFAFC at various temperatures to better understand the significance of anode catalyst in a DFAFC system. 

Fig. 4. Effect of anode catalyst loading on the DFAFC performance.

Fig. 2. Effects of ion dose density on i-V curves. Cathode catalyst loading = 0.2 mg-Pt/cm, H2/air.

Fig. 3. Effects of catalyst loading on i-V curves of the single cells using (a) the untreated and (b) the treated membrane (5 x 10 ions/cm and 1 keV).

GL 21] [no reactor] [P 22] A constant conversion is approached on increasing the reaction rate constant [73]. This shows that liquid transport of hydrogen to the catalyst has a dominant role. In turn, this means that a higher catalyst loading should have not too much effect. 

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