Maximum yield of intermediate

Fig. 5-6 Maximum yield of intermediate product X) for consecutive reactions...

The method, as suggested by Westerterp et al. [1] and by Van Gelder et al. [12], to obtain the maximal yield of an intermediate product without hydrogen recycle has been experimentally evaluated. The packed bubble column reactor can be run with a correct amount of hydrogen supplied to achieve the maximum yield of intermediate product at a certain feed rate of reactant in the liquid phase. A small amount of the inert gas - in our case nitrogen - must be added to the reactor to assure a stable performance of the reactor in case almost all supplied hydrogen is consumed. The reactor pressure... 

Sj> 1, the effectiveness factor for A is less than that for B, assuming equal diffusiv-ities, so that both point and overall selectivities for production of intermediate are adversely affected. In both illustrations of Figure 7.11, the loss in point selectivity or in maximum yield of intermediate is in the order of 50%, so these selectivity problems are not trivial. 

The optimal residence time for reaching the maximum yield of intermediate is... 

Figure 3.25 Maximum yield of intermediate product referred to maximum yield in PFR as function of axial dispersion (cell model).

Table 14.2 Hydrogenation of cyclooctadiene (COD) on a Ni catalyst coated with different ILs partition coefficients (in n-dodecane), maximum yield of intermediate cyclooctene (COE), and rate of COD-conversion for X -Qp = 50% (p(Hj) = 50bar, 50°C, e = 0.06, a = 0.15, =...

Table 14.4 Maximum yield of intermediate(s) during hydrogenation of COD, octine,...

Figure 4.5.30 Influence ofthe ratio icA,i// on the maximum yield of intermediate B for a series reaction on a non-porous catalyst (A B- C) in a batch or plug flow reactor for two values of k i/kAj = jgj = jS dashed line no external mass transfer resistance).

The maximum yield of a primary intermediate, as well as the efficiency (and conversion) at maximum yield, can also be calculated (22). Maximum yield plots are shown in Eigure 3. 

The influence of dispersion on the yield of an intermediate produced in a series reaction has also been studied. When 3 JuL is less than 0.05, Tichacek s results (22) indicate that the fractional decrease in the maximum amount of intermediate formed relative to plug flow conditions is approximated by l/uL itself. Results obtained at higher dispersion numbers are given in the original article. 

Figure 12.13 contains a plot of the yield of the intermediate V as a function of the fraction A reacted for a value of kjk2 equal to 5. In this case, we see that the maximum yield of V based on the initial concentration of A is equal to 66.9%. 

SRE (Fig. 7) and POE (Fig. 10) reactions, a maximum yield of H2 could be attained in the OSRE reaction above 600 °C because CH4, if formed as an intermediate by ethanol decomposition could be completely converted into syngas above this temperature.7,8,10,109 The participation of reverse WGS reaction at high temperature leads to an increase in CO composition above 400 °C with a concomitant decrease in the composition of C02. Thus, at higher operating temperatures of above 600 °C, the system would produce mainly syngas rather than a mixture of H2 and C02. A comparison of equilibrium compositions of POE and OSRE reactions indicates that the presence of steam in this system increases the maximum yield of H2 from about 50% in the POE reaction (Fig. 10) to about 65% in the OSRE, and this is very close to that observed in the SRE reaction (around 70%) due to the participation of steam... 

As expected, the CSTR requires a longer residence time for maximum yield of B. It also gives lower maximum selectivity and yield to the intermediate product than aPFTR. 

The PFTR will always give a higher maximum yield of an intermediate if aU reactions obey positive-order kinetics. 

Maximum yield of epoxides can be expected with molecules, first 1,1-dimethy-lalkenes, which prefer addition to abstraction (allyl hydrogen removal).11,259,260 These oxidations are not steroselective mixtures of the isomeric oxiranes are formed in the reaction of isomeric n-octenes.261 This was interpreted as additional evidence of the formation of radical intermediate 28 allowing the rotation about the carbon—carbon bond. 

Phthalic anhydride is the most important product in the oxidation of o-xylene, which has become competitive with naphthalene as a feedstock for the industrial production of this component. This process is carried out at 350— 400°C and the industrial catalysts consist of doped V2Os or V2Os—Ti02 mixtures, pure or supported. Maximum yields of 70—75 mol. % (95—105 wt. %) are reported. Carbon oxides are the main by-products, besides minor amounts of tolualdehyde and maleic anhydride. Tolualde-hyde is the main product at low conversion and an essential intermediate in the phthalic anhydride formation, while maleic anhydride is mainly formed as a side-product directly from o-xlyene. 

The allylic hydroperoxide, 2,3-dimethyl-3-hydroperoxy-l-butene, III, was detected during the oxidation of TME in the presence of [MCl(CO)-(Ph3P)2] (M = Rh, Ir) and reached a maximum yield of 11% after 3.5 hours when the rhodium complex was used (Figure 1). James and Ochiai (13) have cited spectral evidence for hydroperoxide intermediates, and Fusi et ah (14) obtained evidence which supports the intermediacy of an allylic hydroperoxide during cyclohexene oxidation in the presence of metal complexes. The allylic hydroperoxide (III) which is formed during the oxidation of TME in the presence of [MCl(CO) (Ph3P)2]... 

Lawesson s reagent (LR) is a very effective thionating agent of carbonyl compounds. However, attempted thionation with LR of iV-alkylhydroxamic acids gave maximum yields of 55-60%. Previous work had established that the thionation products, the thiohydroxamic acids (THA), were accompanied by the corresponding amides (A) formed by reduction and the thioamides (TA), the products of thionation of the amides (A) (Scheme 16). Now the reaction of (V-isopropylhydroxamic acid (HA R = IV) with LR has been followed by 31P NMR spectroscopy and several P-containing intermediates have been identified. This has permitted the delineation of a rational, but complex, pathway to each of the products of the reaction.45... 

FIGURE 42 Comparison of mean initial activities per unit silica volume (ry jio ) for the selective hydrogenation of 3-methyl-l-pentyn-3-ol (A) and mean maximum yields of the desired intermediate product 3-methyl-l-penten-3-ol in the hydrogenation of 3-methyl-l-pentyn-3-ol (B) averaged over several runs for the conversion catalyzed by acicular mullite with large pores, acicular mullite with small pores, and cordierite. Conditions hydrogen pressure 2.3 bar alkyne concentration 20 mol/m solvent, ethanol and temperature, 297.4 K. 

Photocycloaddition of ethoxyethene to the enone (81) at 254 nm in methanol affords the adduct (82). Addition of the same alkene to the enone (83) also proceeds via a cyclobutane intermediate but this is unstable and ring opens to afford the cyclo-octane derivative (84). A study of the addition of the optically active alkene (85) to the enone (86) affords four cyclobutane adducts two from head-to-head addition and two from head-to-tail addition. These cycloadditions load to a double induction giving either increased or decreased diastereoselectivity.The intermolecular cycloaddition of ethylene to the enone (87) yields the two adducts (88) and (89). The photoadducts are apparently susceptible to secondary irradiation and the maximum yields of the adducts was obtained at 50% consumption of the starting material (87). Under these conditions (88) and (89) were obtained in 71 and 23% respectively. The isomer (88) was taken on through several steps to afford ultimately racemic starpuric acid a... 

However, approximate treatment is possible. Ikeda and Tashiro (19) report an optimization of catalytic reactions in fluid beds. They And that the maximum yield of the intermediate product decreases, and that the optimum contact time increases for first-order consecutive and parallel reaction systems if contact efficiency in the reactor decreases. They also showed the most economical equilibrium activity and the optimal size distribution of catalyst. 

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