Screening results, catalyst

Figure 11.21 Results of high-throughput screening of catalysts in a 384-parallel single-bead reactor in a partial oxidation reaction, (a) Arrangement of inactive and total oxidation catalysts in the reactor, (b) screening results for the conversion of a hydrocarbon at 400°C, 1 mL/min per bead.

The reaction of hydrazonoester 6 with allenyl pinacol boronate 7 was set as a model, and several metal hydroxides (20 mol%) were screened as catalysts in H20-DMF (1 3) at room temperature [104]. It was found that allenyl adduct 8 was produced with high selectivity in the presence of bismuth(III) hydroxide, Bi(OH)3 (Scheme 3). Interestingly, copper(II) hydroxide, Cu(OH)2, preferentially gave propargyl adduct 9. On the basis of these promising results, we further optimized the reaction conditions using Bi(OH)3 and Cu(OH)2 (Table 5). 

Figure 6.40 (Thio)urea catalysts derived from dihydroquinine and dihydroquinidine screening results obtained from the asymmetric Michael addition of dimethyl malonate to frans-p-nitrostyrene.

Figure 6.51 Biflinctional (thio)urea-phoshine catalysts 166-168 prepared from (R)-2 -diphenylphosphanyl- [1,1 ]binaphthalenyl-2-ylamine and the corresponding iso(thio) cyanate the yield of the catalysts is given in parentheses. Catalyst screening results ofthe...

Consequently, Dehmlow and coworkers modified the cinchona alkaloid structure to elucidate the role of each ofthe structural motifs of cinchona alkaloid-derived chiral phase-transfer catalysts in asymmetric reactions. Thus, the quinoline nucleus of cinchona alkaloid was replaced with various simple or sterically bulky substituents, and the resulting catalysts were screened in asymmetric reactions (Scheme 7.2). The initial results using catalysts 8-11 in the asymmetric borohydride reduction of pivalophenone, the hydroxylation of 2-ethyl-l-tetralone and the alkylation of SchifF s base each exhibited lower enantiomeric excesses than the corresponding cinchona alkaloid-derived chiral phase-transfer catalysts [14]. 

Fig. 11.17 Chronoamperometric screening results from the ternary catalyst library described in Figs. 11.15 and 11.16. Surface-area-normalized activity values of each individual composition are plotted as a function of composition. Color-coding indicates activity red = high, blue = low. The pt-Ru binary compositions are connected by a solid line to underscore the activity trends observed in this binary system. Conditions 1 M methanol, 0.5 M H2S04, 550 mV/RHE, 5 min.

The testing of a 7.5 x 106 membered octapeptide library with fixed N-terminal 7i-(CH3)-histidine (Pmh) and C-terminal alanine resulted in identification of catalysts with higher activity than DMAP for the acetylation of sec-phenylethanol [17]. The identified catalyst Boc-Pmh-L-Asn(Trt)-D-Val-L-His(Trt)-D-Phe-D-Val-D-Val-L-Ala-resin 10 then served as a parent compound for a second-generation library. This screening yielded catalysts with yet greater activity and specificity. Interestingly, all... 

Another version of the Conia-ene reaction is the focus of this research. Here the reaction of y-alkynic (3-ketoesters was tested.48 The screening resulted in a copper / silver cocatalysis system. It remains unclear why the authors did not at least run some reactions with gold catalysts, too, especially since they even cite the work on the gold-catalyzed Conia-ene reaction in the introduction (Section 12.1). 

A variety of different metal complexes have been screened as catalysts for allylic amination using phenyl hydroxylamine 108 as the nitrogen fragment donor, and it was found that iron-complexes have better redox capacity compared to molybdenum [64]. With the iron compounds, higher yields and a lower amount of hydroxylamine-derived byproducts are obtained. These byproducts constitute one of the problems in this type of allylic amination reactions in general, as their formation is difficult to suppress. The allylic amination reaction of a-methyl styrene 112 with 108 can, e.g., be catalyzed by the molybdenum dioxo complex 107, iron phthalocyanine 114, or by the combination of the iron chlorides 115 [64,65]. It appears from the results in... 

Catalyst Screening Results. A comparison of the catalysts performance is given in Table VIII. Shell 214, (nickel-molybdenum (Ni-Mo)) on alumina, is the best among the five types of catalysts tested with Shell 244, Co-Mo on alumina being nearly as good. It achieved high removal of heteroatoms with the least hydrogen consumption. The... 

The PFR is efficient for screening solid catalyst in a single fluid phase. It can also be used in later research stages to assess commercial criteria. Consider the evaluation of the ultimate commercial performance of a newly developed fixed-bed catalyst. The theory of similarity teaches that for the laboratory and the industrial reactor, the Damkohler number (NDa), the Sherwood number (Nsh), and the Thiele modulus (<)>) need to be kept constant (Figure 2). As a result, the laboratory reactor must have the same length as the envisioned commercial reactor (7). In this case, scale up is done by increasing the diameter of the reactor. This example further illustrates that laboratory reactors are not necessarily small in size. 

Screening results for L8 in the 02-promoted oxidation showed the expected Rh > Pd > Pt activity plus a temperature dependence for the most active alloy catalysts. Eighty percent to 85% of Rh was preferred in the alloys below 350 °C, while at higher temperatures the most active library individuals contained just 70-80% Rh. The NO-promoted oxidation could also lead to production of N2O via an undesired secondary process that should preferably be minimized. The screening results (measured as N2 and N2O production) were often comparable in terms of metal reactivity, but N2O formation at different temperatures was indeed observed and could be minimized, selecting Rh-rich alloys at 600 °C as the best catalysts from L8. 

The pressure drop for flow through the gas passages resulting from momentum transfer from the flowing gas to the stationary screen-enclosed catalyst slabs follows from the general Fanning equation... 

The laboratory experiments were designed for preliminary work and for screening of catalysts to be used in our current catalytic gasification research program. Results from these studies are intended to identify those catalysts which best promote synthesis gas production (H /CO) and maximize reduction of char and liquid yields. 

Table 1. Screening test results. Catalysts are tested with 15 wt% soot...

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