Temperature reaction conditions

Thermal cracking takes place without a catalyst at temperatures up to 900 °C. The exact processes are complex, although they undoubtedly involve radical reactions. The high-temperature reaction conditions cause spontaneous homolytic breaking of C-C and C-H bonds, with resultant formation of smaller fragments. We might imagine, for instance, that a molecule of butane... 

Mobility and Flexibility of Catalyst Surfaces at High-Pressure High-Temperature Reaction Conditions... 

A chiral diphosphite based on binaphthol, coordinated with rhodium (I) forming a nine-member ed ring, led to an efficient hydroformylation of vinylarenes, although moderate ees were obtained (up to 46%) at mild pressure and temperature reaction conditions.364 Chiral diphosphites and phosphinite-phosphites derived from spiro[4.4]nonane-l,6-diol were synthesized. Using these catalysts in the asymmetric hydroformylation of styrene, high regioselectivity (97%) and... 

Esterification of stearic acid and acetic acid with propanol and butanol in the presence of Fe2(S04)3/KSF montmorillonite [37]. The rate enhancement observed (1.5-2.5 times) was ascribed to the higher temperature of the catalyst bed (calculated to be 9-18 K above the bulk temperature). Reaction conditions batch (no stirring) and a stirred single-mode tank reactor, catalyst particle size 5 mm, 10-fold excess of alcohol. 

Fig. 5 Activity of Rh-3-SILP catalyst at different syngas compositions (pH2 Pco ratios) and temperatures (Reaction conditions T = 100°C, ptotai = 10bar) [32]...

The Chevron/Gulf process also uses triethylaluminum but in a catalytic reaction at higher temperature. Reaction conditions exert a strong effect on product distribution. Under the proper conditions (200-250°C, 140-270 atm) the rates of insertion and chain transfer (displacement) are comparable, ensuring frequent p-hydrogen elimination. A broader product distribution compared with that of the two-step ethyl process is obtained. 

The application of SCF as reaction media for enzymatic synthesis has several advantages, such as the higher initial reaction rates, higher conversion, possible separation of products from unreacted substrates, over solvent-free, or solvent systems (where either water or organic solvents are used). Owing to the lower mass-transfer limitations and mild (temperature) reaction conditions, at first the reactions which were performed in non-aqueous systems will be transposed to supercritical media. An additional benefit of using SCFs as... 

On completion of the reaction, the material may be carefully degassed to remove any entrapped gasses and unreacted diisocyanate. Care must be taken to prevent foaming. Applying vacuum to the glassware does create the potential for it to implode. Suitable safety precautions must be taken. Table 3.2 indicates some typical time/temperature reaction conditions for some simple prepolymers. 

We have done a lot of work with unhydrogenated solvents on this and found that incorporation is a major problem. We, too, have been looking at lower temperature reaction conditions as part of our work. We think that is an objective that would have a profound impact on economics. We just haven t gotten there yet for sure. 

Finally, we note that the two steps for isobutane activation are kineti-cally significant under the high-temperature reaction conditions. The kinetic model was used to calculate the predicted surface coverage under reaction conditions. Approximately 96% of the surface sites are free under the low-temperature reaction conditions, whereas more than 99% of the sites are free at the higher temperatures. The most abundant surface species are predicted to be adsorbed C3—C. The most abundant heavy species are predicted to be Cg—Cq. The fractional surface coverage by adsorbed Q0—CJ2 is very low (e.g., 10-8), consistent with our decision to neglect surface species heavier than C 2. 

Radical reactions with acyl radicals sometimes involve decarbonylation as side-reactions, especially when stabilized secondary or tertiary radicals can be formed. These side-reactions can be suppressed using low-temperature reaction conditions together with different reducing agents such as tris(trimethylsilyl)silane.254... 

Under high-temperature reaction conditions, metal surfaces are dynamic systems in which metal atoms or metal oxide species are highly mobile high rates of diffusion lead to changes in surface structure to minimize overall surface energy. 

The simple experimental and product isolation procedures combined with ease of recovery and reuse of this novel reaction media contribute to the development of green strategy for the preparation of isoxazolidines. Furthermore, the use of [bmim] [PFg] solvent system for this transformation avoids the use of toxic or corrosive reagents and high temperature reaction conditions, and thus, it provides convenient procedure to carry out the reactions at ambient temperature. 

Fig.7 Current generated as a function of temperature (reaction conditions are the same as Fig.6)...

Under the low pressure and moderate temperature reaction conditions, the lack of higher hydrocarbons in the product stream is not surprising since these products are thermodynamically unfavourable. Although the pore structures show no dramatic steric influence on the product distributions, they are sufficient... 

For room-temperature reaction conditions without the addition of extra base, an appropriate metal salt (often the acetate) is chosen to drive the reaction and concentrated solutions are used. Terephthalic acid (254 mg, 1.53 mmol, Aldrich) is dissolved in 20 mL of DMF in a 50-mL Erlenmeyer flask, and zinc acetate dihydrate (718 mg, 3.27 mmol, Alfa Aesar) is dissolved in a separate container in 20 mL of DMF via vigorous shaking and sonication. The zinc salt solution is added dropwise to the terephthalic acid solution flask over 15 min while stirring with a Teflon-coated magnetic stirring bar. A white precipitate is formed almost immediately, and the solution is stirred for 45 min. Powder X-ray diffraction is used to confirm phase pure MOF-5. This procedure has successfully been scaled up to 3.37 g. 

Wash as in step 6 however, labeled cells should be resuspended with 0.65 mL of room temperature competition buffer containing 0.1-1 pM of non-biotinylated competitor antigen. Room temperature reaction conditions will allow normal kinetics of scFv-Ag interaction. The competition mixture will prevent clones that dissociate bound antigen from rebinding Bt-Ag. 

Figure 4 The rate of reaction as a function of temperature. Reaction conditions 1 g 5% Ir/graphite, P 20 bar H2.

Product equilibration is not likely under room temperature reaction conditions, but there are some cases where it has been deliberately used to enhance the ( )-enoate selectivity of reactions that otherwise afford mixtures. Entries 47-49 in Table 19 demonstrate that catalytic amounts of p-dimethyl-aminopyridine (DMAP) will induce the Z E equilibration of a, -unsaturated thiol esters at room temperature (chloroform solution), resulting in enhanced ( )-enoate selectivity (101b). This procedure is not effective with the corresponding oxygen esters, however. 

Fig. 4. Variation in the selectivity to carbon dioxide as a function of reaction temperature (Reaction conditions 0.4% CH4, 20% O2 in N2 sample volume -147 cm, space velocity -10000 hr7)...

Investigation of the sol-gel derived bismuih-molybdcnum-titanium xerogel and aerogel mixed oxide as catalyst for the oxidation of butadiene to furan l 14J 15] indicated activities and selectivities comparable to other suitable catalysts. The unique microstructure and good catalytic performance of the bismuth molybdenum oxide particles are attributed to lilania matrix. How ever, these favorable properties are limited to low temperature reaction conditions since both xerogels and aerogels are prone to rapid restructuring at elevated temperatures, which result in the loss of their unique redox properties. 

Fig. 4. Hydrocracking (HC) conversions obtained for the different catalysts as a function of the reaction temperature. Reaction conditions 3.0 MPa. 2 h WHSV and 1000 H2 (stp)/feed ratio ( ) NiMo/ITQ-2. ( ) NiMo/USY. (A) NiMo/ASA. (t) NiMo/y-Al203.

Reaction conditions CH3CN, room temperature. Reaction conditions CH3CN, room temperature. 

Figure 4. Relationship between total carbon conversion and reaction temperature. Reaction conditions P (total) = 55 bar, Cu/ZnO (B) = 0.5 g, W/Fsy gas = 10 g.h.moT, A Psyngas = 40 bar, B Psyngas = 18 bar, C Psyngas 10 bar. Balance pressure 2-butanol...

The previous synthesis involves use of corrosive chemicals such as thionyl chloride/phosphoryl chloride, costly reagents such as platinum oxide, and flammable gas such as hydrogen at high-temperature reaction conditions. To overcome these issues, an easily scalable, convergent, and versatile process for the preparation of erlotinib was reported in 56% overall yield. Nitro reduction using sodium dithionite in aqueous medium gave aniline... 

Solvent CsXlO Reaction temperature Reaction conditions... 

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