Product selectivity feed ratio effect

Figures 1 shows the catalytic performance of the Fe-BEA catalysts in the temperature range of 250-550 °C. It is clear from the figure that propylene yield depends on particle size of the parent BEA zeolite. Effect of the N20 concentration has been analyzed under reaction regimes RS-1 and RS-2. Increase in N20 concentration resulted in the same propene yields but increased the N20 conversion and decreased the selectivity toward propylene. At higher temperature has been obtained increases in the formation of the molecular oxygen which further accelerates production of the undesired carbon oxides. Thus, at lower feed concentration of N20, i.e. at 1 1 feed ratio of reactants (RS-1), formation of carbon oxides is suppressed and the selectivity of ODHP reaction is...

On its face value, the cumene conversion and benzene selectivity seem to be better at Cp = 50 than 5. This is only because more catalyst has been used. In fact, it is 10 times more. The normalized benzene selectivities given in columns 3 and 5 with respect to Cp = 5 and 50 provide clearer indication. The physical structures of the catalyst pores and zeolites obtmned from electronic scanning microscope analysis are also important. However, they are not reported here since this is out of the scope of the present contribution and can be found elsewhere[ 15]. To achieve the optimal catalyst effectiveness and obtain the maximum product selectivity, the preferable operation conditions, in the present case, are at a catalyst to feed ratio of 5 while the conversion level is at 60%. 

Thus, an increase in total pressure ratio P1/P2 will improve purity for a given a. The various effects of pressure ratio and membrane selectivity are shown in Figure 10.5.33 It will be observed that under certain conditions the pressure ratio is of even greater importance than intrinsic selectivity. Thus, with a feed gas relatively poor in the more permeable component, and an a of about 40, further increase in selectivity has little effect on product purity, whereas an increase in... 

Figure 4. The effect of co-feeding methanol with wood. Selected product ratios for wood alone, methanol alone, and wood co-fed with methanol with the methanol products subtracted. The ratios are light aromatics/ H2O + CO + COo, (arom/inorg) COo/water and trimethylbenzene/toluene (TMB/TOO. Temperature = 500 C wood WHSV= 2.9 methanol WHSV= 2.8.

In single-end control structures, only one composition or one temperature is controlled. The remaining control degree of freedom is selected to provide the least amount of product quality variability. For example, a constant reflux ratio RR can be maintained or the reflux-to-feed ratio R/F can be fixed. The control engineer must find out whether this more simple approach will provide effective control of the compositions of both product streams. One approach to this problem is to use steady-state simulations to see how much the reflux ratio and the reflux flow rate must change to maintain the specified impurity levels in both product streams (heavy-key impurity in the distillate X/>(hk) and light-key impurity in the bottoms Xb(lk)) when changes in feed composition occur. The procedure is call feed composition sensitivity analysis. ... 

The yield of products from catalytic pyrolysis depends on catalyst type and catalyst to feed ratios besides pyrolysis temperature and residence time (Ojha and Vinu, 2015). Different types of catalysts have different properties such as surface acidity, specific surface area, pore size, and pore size distributions which also determine the yield and selectivity of various products. The range of different functionalities of the catalysts should be matched to the various pyrolysis feedstocks as each feedstock may have a preferred pyrolysis catalyst. Therefore research has been precise in developing particular catalysts for specific raw material (depending on pyrolysis reactor). The section below describes the properties and effect specific catalysts have on pyrolysis vapor upgrading. 

Toluene alkylation with isopropyl alcohol was chosen as the test reaction as we can follow in a detail the effect of zeolite structural parameters on the toluene conversion, selectivity to cymenes, selectivity to para-cymene, and isopropyl/n-propyl ratio. It should be stressed that toluene/isopropyl alcohol molar ratio used in the feed was 9.6, which indicates the theoretical toluene conversion around 10.4 %. As you can see from Fig. 2 conversion of toluene over SSZ-33 after 15 min of T-O-S is 21 %, which is almost two times higher than the theoretical toluene conversion for alkylation reaction. The value of toluene conversion over SSZ-33 is influenced by a high rate of toluene disproportionation. About 50 % of toluene converted is transformed into benzene and xylenes. Toluene conversion over zeolites Beta and SSZ-35 is around 12 %, which is due to a much smaller contribution of toluene disproportionation to the overall toluene conversion. A slight increase in toluene conversion over ZSM-5 zeolite is connected with the fact that desorption and transport of products in toluene alkylation with isopropyl alcohol is the rate controlling step of this reaction [9]... 

However, (Ph3P)2Rh(CO)Cl on alumina or activated carbon were effective hydroformylation catalysts under more severe conditions 108). At 148°C and a pressure of 49 atm (CO 37.5 mol%, H2 37.5, propylene 25), good activity was found. The propylene conversion was 30% at a contact time of 0.92 cm3 of reactor void space/cm3 of feed per minute. Isomer ratios of 1.3 to 1.9 1 n iso were realized. By-product formation was low, with <1% conversion to alcohols plus alkanes and 2.2% high-boiling materials. This system was stable for a 300 hour operating time, with no detectable loss of activity or selectivity. 

Table I shows the effects of Mel/DME and CO/DME ratios in the feed gas on product yields. With increasing Mel/DME ratio both methyl acetate yield and selectivity increased. The yield of methyl acetate increased with an increase in the CO/DME ratio whereas its selectivity decreased. In the case of methanol carbonylation on Ni/A.C. catalyst, the product yield and selectivity were strongly affected by CO/MeOH ratio but not by Mel/MeOH ratio (14-16). The promoting effect of methyl iodide on the methanol carbonylation reached a maximum at a very low partial pressure, that is 0.1 atm or lower. However, both CO/DME and Mel/DME ratios were important for regulating the product yield and selectivity of the dimethyl ether carbonylation. This suggests that the two steps, namely, the dissociative adsorption of methyl iodide on nickel (Equation 4) and the insertion of CO (Equation 5) are slow in the case of dimethyl ether reaction.

Figure 4 shows the effect of operational pressure on the reaction. The yield of acetic anhydride increased with an increase in the pressure. The selectivity to acetic anhydride was low at 30 atm because of a fairly high selectivity to AcOH. Figure 5 shows the effect of CO/AcOMe ratio in the feed at an operational pressure of 15 atm. When the ratio was 1, little acetic anhydride was formed. However, acetic anhydride comprised one of the main products when the CO/AcOMe ratio was raised up to 10. Thus, high operational pressure and high CO partial pressure were found to be advantageous for the synthesis of acetic anhydride. 

Figure 8.15 The effect of stage-cut on the separation of a 50/50 feed gas mixture (pressure ratio, 20 membrane selectivity, 20). At low stage-cuts a concentrated permeate product, but only modest removal from the residue, can be obtained. At high stage-cuts almost complete removal is obtained, but the permeate product is only slightly more enriched than the original feed...

Table IV shows the effect of benzene-to-propylene ratio in the feed on selectivity at two space velocities. It Is very apparent that when the ratio Is Increased, the selectivity becomes higher. The reasons for this are three-fold. Kinetics of the two alkylation reactions favor production of cumene if the benzene-to-propylene Is higher. The equilibrium concentration of cumene Is higher, because of higher benzene concentration.

The product distribution between nitrile and imide depends upon the reaction conditions and the nature of the catalyst used [105]. The influence of various reaction parameters such as (i) reaction temperature (ii) water vapor addition in the feed gas (iii) NH3/o-xylene mole ratio and (iv) space velocity, were studied [105]. The removal of water vapor from the feed gas has a highly pronounced promotional effect on the selectivity of phthalonitrile. The nitrile selectivity increased from 2.1 to 34% at the expense of phthalimide (which decreased from 53 to 9%) with the complete removal of water vapor in the reactant feed mixture. This observation gives an indication that phthalonitrile being formed in the reaction is further hydrolyzed to phthalimide via the amide intermediate in presence of water... 

---