Effectiveness of catalyst

The relative effectiveness of nucleating agents in a polymer can be determined by measuring recrystallization exotherms of samples molded at different temperatures (105). The effect of catalyst concentration and filler content has been determined on unsaturated polyesters by using dynamic thermal techniques (124). Effects of formulation change on the heat of mbber vulcanization can be determined by dsc pressurized cells may be needed to reduce volatilization during the cure process (125). 

SolubiHty of carbon dioxide in ethanolamines is affected by temperature, amine solution strength, and carbon dioxide partial pressure. Information on the performance of amines is available in the Hterature and from amine manufacturers. Values for the solubiHty of carbon dioxide and hydrogen sulfide mixtures in monoethanolamine and for the solubiHty of carbon dioxide in diethanolamine are given (36,37). SolubiHty of carbon dioxide in monoethanolamine is provided (38). The effects of catalysts have been studied to improve the activity of amines and provide absorption data for carbon dioxide in both mono- and diethanolamine solutions with and without sodium arsenite as a catalyst (39). Absorption kinetics over a range of contact times for carbon dioxide in monoethanolamine have also been investigated (40). 

Saturation of the oil with hydrogen is maintained by agitation. The rate of reaction depends on agitation and catalyst concentration. Beyond a certain agitation rate, resistance to mass transfer is eliminated and the rate oecomes independent of pressure. The effect of catalyst concentration also reaches hmiting values. The effects of pressure and temperature on the rate are indicated by Fig. 23-34 and of catalyst concentration by Fig. 23-35. Reaction time is related to temperature, catalyst concentration, and IV in Table 23-13. 

FIG. 23-35 Effect of catalyst concentration and stirring rate on hydrogenation of soybean oil. (Swern, ed., Baileys Industrial Fat and Oil Products, vol. 2, Wiley, 1979.)... 

What are the effects of catalyst behaviour, e.g. aging, poisoning, disintegration, activation, regeneration ... 

Effect of Catalyst The catalysts used in hydrotreating are molybdena on alumina, cobalt molybdate on alumina, nickel molybdate on alumina or nickel tungstate. Which catalyst is used depends on the particular application. Cobalt molybdate catalyst is generally used when sulfur removal is the primary interest. The nickel catalysts find application in the treating of cracked stocks for olefin or aromatic saturation. One preferred application for molybdena catalyst is sweetening, (removal of mercaptans). The molybdena on alumina catalyst is also preferred for reducing the carbon residue of heating oils. 

Kinetic investigation of the reaction of cotarnine and a few aromatic aldehydes (iV-methylcotarnine, m-nitrobenzaldehyde) with hydrogen eyanide in anhydrous tetrahydrofuran showed such differences in the kinetic and thermodynamic parameters for cotarnine compared to those for the aldehydes, and also in the effect of catalysts, so that the possibility that cotarnine was reacting in the hypothetical amino-aldehyde form could be completely eliminated. Even if the amino-aldehyde form is present in concentrations under the limit of spectroscopic detection, then it still certainly plays no pfi,rt in the chemical reactions. This is also expected by Kabachnik s conclusions for the reactions of tautomeric systems where the equilibrium is very predominantly on one side. 

Equilibrium (continued) calculations, 192 constant, 151, table, 154 crystallization and, 144 dynamic nature of, 144, 165 effect of catalyst, 148 effect of concentration, 148 of energy, 167 of randomness, 166 of temperature, 67. 148, 167 factors determining, 155, 158 law of chemical, 152, 173 liquid-gas, 66 qualitative aspects of, 142 quantitative aspects of, 151 recognizing, 143 slate of, 142, 147 sugars, 425 thermal, 56... 

Finally, one must know the effect of catalyst particle size on Kw. For a pore diffusion-controlled reaction, activity should be inversely proportional to catalyst particle diameter, that is directly proportional to external catalyst surface area. 

Typical Effects of Catalyst Invention on Cost Sheet... 

A discussion with 14 refs on expls and proplnts considering the thermodynamic characteristics of expl substances, the kinetics of combustion of powders and the effects of catalysts, corrosion, and instability on the kinetics, the occurrence of deflagration on detonation, and forms of solid mixts in view of the augmentation of their performance and the extension of conditions used in their mixts. The importance of modern methods of calcn is stressed... 

Kinetic studies of the effects of catalysts on hydrogen exchange... 

It was appropriate to consider some of the experimental data relating to the effects of catalysts upon hydrogen exchange, previously and in another context (p. 207). Further data are now discussed. 

Can one further enhance the performance of this classically promoted Rh catalyst by using electrochemical promotion The promoted Rh catalyst, is, after all, already deposited on YSZ and one can directly examine what additional effect may have the application of an external voltage UWR ( 1 V) and the concomitant supply (+1 V) or removal (-1 V) of O2 to or from the promoted Rh surface. The result is shown in Fig. 2.3 with the curves labeled electrochemical promotion of a promoted catalyst . It is clear that positive potentials, i.e. supply of O2 to the catalyst surface, further enhances its performance. The light-off temperature is further decreased and the selectivity is further enhanced. Why This we will see in subsequent chapters when we examine the effect of catalyst potential UWR on the chemisorptive bond strength of various adsorbates, such as NO, N, CO and O. But the fact is that positive potentials (+1V) can further significantly enhance the performance of an already promoted catalyst. So one can electrochemically promote an already classically promoted catalyst. 

Figure 4.16, Effect of catalyst potential, dimensionless catalyst potential n(=FUWR/RT), corresponding linearized51 Na coverage 0ns and pCo on the rate of CO oxidation on Pt/(T-A1203. T=350°C, po2=6 kPa.51 Reprinted with permission from Academic Press.

Figure 4.18. NO reduction by H2 on Pt/p"-Al2Oj. Effect of catalyst potential on the rates of formation of N2 and N20 and on the selectivity to N2.52 Reprinted with permission from Academic Press.

Figure 4.2J. Effect of catalyst-electrode potential Uwr on the work function of the gas exposed catalyst-electrode surface. Open symbols open circuit operation varying gas composition. Closed symbols closed circuit operation C2H4,02, He and NH3, 02, He mixtures.54,55 Reprinted from ref. 55 with permission from Elsevier Science.

Figure 4.28. Electrophobic behaviour Effect of catalyst work function on the activation energy E and catalytic rate enhancement ratio r/r0 for C2H4 oxidation on Pt p02 4.8 kPa, Pc2H4 0.4 kPa (a) and CH4 oxidation on Pt p02 =2.0 kPa, Pch4 =2.0 kPa (b)."4 Reprinted with permission from Elsevier Science.

Figure 4.29. Electrophilic behaviour Effect of catalyst potential and work function change AO on the rate of C2H4 oxidation on a Pt film deposited on CaZr0 9Ino 03.a which is a H+ conductor.104 Reprinted with permission from the Institute for Ionics.

Figure 4.30. Volcano-type behaviour Effect of catalyst potential on the rate of ethylene oxidation on a Pt film deposited on NASICON (Na3Zr2Si2PO 2), a Na+ conductor T=430°C, P02 =7.2 kPa, Pc2H4= kPa.102 Reproduced by permission of The Electrochemical Society.

Figure 4.33. Inverted volcano behaviour. Effect of catalyst potential and work function on the rate of C2H6 oxidation on Pt/YSZ. po2=107 kPa, pc2H6 65 kPa T=500°C , T=460°C , T=420°C.24 Reprinted with permission from Academic Press.

Figure 4.35. Effect of catalyst work function on the activation energy EA, preexponential factor k° and catalytic rate enhancement ratio r/r0 for C2H4 oxidation on Pt/YSZ 4 p02=4.8 kPa, Pc2H4=0-4 kPa,4,54 kg is the open-circuit preexponential factor, T is the mean temperature of the kinetic investigation, 375°C.4 T0 is the (experimentally inaccessible) isokinetic temperature, 886°C.4 25,50...

Figure 4.36. Effect of catalyst potential UWR and work function on the activation energy E (squares) and preexponential factor r° (circles) of C2H4 oxidation on Rh/YSZ. open symbols open-circuit conditions. Te is the isokinetic temperature 372°C and r is the open-circuit preexponential factor. Conditions po2=l.3 kPa, pc2n =7.4 kPa.50 Reprinted with permission from Academic Press.

Figure 4.42. Ethylene epoxidation on Ag/p"-Al203.101 Steady-state effect of catalyst potential on the selectivity to ethylene oxide at various levels of gas-phase dichloroethane (a) and 3-dimensional representation of the effect of dichloroethane concentration, catalyst potential and corresponding Na coverage on the selectivity to ethylene oxide (b).101 Reprinted with permission from Academic Press.

Figure 5.8. Effect of catalyst-electrode potential UWR on the work function O of the gas exposed catalyst-electrode surface (a) Pt/YSZ, T = 300°C (squares), Pt/p"-Al203, T = 240°C (circles), filled symbols closed-circuit operation, open symbols open-circuit operation, 02, C2H4/02 and NH3/02 mixtures.2-26 (b) Ag/YSZ, T - 547°C,24 (c) Pt/p"-Al203, T = 200°C,25 (d) Ir02/YSZ, T = 330°C, air,27 (e) Ir02/YSZ, T = 380°C, po2 = 15 kPa, pC2H4 = 5 10 2 kPa,27 (f) Ir02/ p"-Al203, T = 330°C, air.27...

Figure 5.13. Effect of catalyst overpotential, AUWR, on catalytic rate and on catalyst work function changes, AO, during ethylene oxidation on Pt/YSZ at 400°C.34Reprinted with permission from Elsevier Science.

Figure 5.24. Effect of catalyst potential, Uwr, on oxygen peak desorption temperature, Tp during 02 TPD from Pt/YSZ.4,5 The exact definition of Uwr has been given in Figure 4.45. It is the UWr value at the beginning of the TPD run and differs little (<0.1 V) from the UWR value at Tp.4,7 Reprinted with permission from the American Chemical Society.

Figure 5.26. Effect of catalyst potential on the oxygen desorption activation energy, Ed, calculated from the modified Redhead analysis for Pt, Ag and Au electrodes deposited on YSZ.44,46 Reprinted from ref. 44 with permission from the Institute for Ionics.

Figure 6.3. Examples for the four types of global electrochemical promotion behaviour (a) electrophobic, (b) electrophilic, (c) volcano-type, (d) inverted volcano-type, (a) Effect of catalyst potential and work function change (vs I = 0) for high (20 1) and (40 1) CH4 to 02 feed ratios, Pt/YSZH (b) Effect of catalyst potential on the rate enhancement ratio for the rate of NO reduction by C2H4 consumption on Pt/YSZ15 (c) NEMCA generated volcano plots during CO oxidation on Pt/YSZ16 (d) Effect of dimensionless catalyst potential on the rate constant of H2CO formation, Pt/YSZ.17 n=FUWR/RT (=A(D/kbT).

Figure 7.Effect of catalyst overpotential r on the rate and reaction order of C2H4 oxidation on two Pt catalyst films, labeled R1 and R2. For Rb p02=4.8 kPa and Pc2H4=0-4 kPa. For R2, Po2=6.4 kPa and Pc2H4=0 4 kPa.1...

Figure 8.3. Effect of catalyst overpotential AUWR and work function

---