Sohds recycle rate

With a reaction-limited deposition process, the film should have uniform thickness as long as the partial pressures ofreactants do not vary with position. In a tubular reactor, the conversion of reactants must be kept small or the film thickness will depend on the location of the sohd in the reactor, with upstream regions having a greater deposition rate. It is therefore common to use a gas recirculation reactor (a recycle PFTR) so that the composition of the reactants is independent of position in the reactor to assure uniform film thickness. 

Fig. 3.6. Effect of the recycling reaction on birhythmicity. A series of bifurcation diagrams are represented for increasing values of the maximum rate of product recycling, o- (in s ) (a) 0 (b) 0.5 (c) 0.6 (d) 1.2 (e) 1.3 (f) 1.4 (g) 1.5 (h) 2. Each diagram shows the steady-state concentration of substrate, o, and the mtiximum concentration of substrate in the course of oscillations, < m> s a function of parameter (qvlk ) equal to the steady-state concentration of product. The curve yielding the steady-state level of substrate is therefore identical with the product nullcline. The sohd and dashed lines denote, respectively, stable and unstable branches of periodic or steady-state solutions. Parameter values are <7=10s, L = 5xl0, /iC=10, m = 4, q = l, k = 0.06s. Periodic re mes were obtained by numerical integration of eqns (3.1). The stability properties of the steady state were determined by Unear stabUity analysis. Birhythmicity is apparent in (d)-(f), while in (h) two distinct instabiUty domains appear as a function of parameter v (Moran Goldbeter, 1984).

Given is a typical connection of a mixing element M with an evaporative crystallizer C as illustrated in Fig. 4.2-9, showing also a filter F for liquid/sohd separation and a splitter S. The sphtter S is provided to limit the enrichment of contaminant in the system. In the mixer M the feed is mixed with the recycle from the splitter S. The flows are numbered consecutively by J = 0-7. The flows J = 1-7 ate unknown and shall be resolved with respect to rate and compositioa... 

A solution of compound 49 (66 mg, 0.066 mmol) in CCI4 (65 mL) in a Pyrex flask was irradiated with a high-pressure mercury lamp (500 W) from the distance of 20 cm for 6 h under air. The resulting brown solution was evaporated and the residual black sohd was dissolved in ODCB (3 mL), which was subjected to preparative HPLC using a Cosmosil 5PBB column (10 mm id x 250 mm) eluted with ODCB (flow rate, 2 mL min ) to afford open-cage fidlerene derivatives 54 (40 mg, 0.038 mmol, 60%) and 55 (21 mg, 0.020 mmol, 31%) after nine recycles, both as brown powders. 

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