Maximum conversion

Figure 9.13. Conversion of various concentrations of NO to N02 in a humid feed on Pt/Si02 as a function of temperature [42]. Feed 10% 02, 5% H20, and 100-1500 ppm NO in N2. ( ) 100ppm, (A) 500ppm, ( ) lOOOppm, and ( ) 1500ppm NO. Sample weight = 0.8g. V = 150 LN/h. At intermediate temperatures a conversion maximum is found, because the increasing oxidation activity of the catalyst is limited by the (—) thermodynamic equilibrium between NO and N02.

Dividing by the rate at which fuel energy AH is added to the system in a steady state situation maintaining the current one obtains the actual efficiency for the conversion maximum. 

Generalizing, the effect of water in the feed is twofold. Water in the feed causes a shift of the conversion maximum to higher temperatures (clearly visible in Figs. 2 and 3). This temperature shift is noticeable already at low temperatures. The shift is caused by a reversible inhibition of active sites by water. Water in the feed can also cause irreversible deactivation by dealumination (CeNa-MOR) which only occurs at high temperatures and results in a decreased deNOx activity mainly in the low temperature region. 

Experimentally, catalysts have been found which show considerable differences regarding this property (see Fig. 2). A more or less pronounced conversion maximum for NO as function of temperature is found with all three-way catalysts. 

BCMO can be polymerized in the solid state under the influence of ionizing radiation 23 25>. This is a handy method of preparing polymer directly from monomer, in the absence of solvent and initiators. Polymerizations proceed to limited conversions (maximum 15-20% was observed at temperatures just below the melting point Tm = 18.5 °C). The rate increases with increasing temperatures (up to the melting point), irradiation time, dose rate and the size of the monomer crystals. Molecular weights are relatively high, fn] = 0.5 dl/g (in cyclohexanone at 40 °C). 

Figure 4a shows the variation in the conversion of propane on new catalyst and on catalyst aged at 900°C as a function of the O2 concentration. It is found that inhibition by O2 in an overall oxidizing gas mixture exists both for new catalyst and for aged catalyst. The conversion maximum is situated in a sliglitly reducing gas mixture. 

Figure 2.11. Schematic representation of optimal operating point for a process based on different economic criteria. Productivity may be obtained from the tangent to the curve. Reaction times t j, maximum productivity in a continuous process t2, maximum productivity in a discontinuous process with tg = deadtime maximum profit t4, minimum cost t, maximum conversion—maximum product concentration as S -> 0.

Figure 12.13 Influence of the catalyst loading (a) and of the reactor length (b) on methanol conversion, maximum reactor temperature, and CO and H2 mole fractions [63].

---