Effect on product distributions and

The Ru/Rh/Cs/HOAc Catalyst Composition. Table I illustrates the effect, on product distribution and catalytic activity, of the incremental addition of cesium ions to a catalyst precursor composition containing ruthenium and rhodium, in the molar ratio of 10 1, dissolved in glacial acetic acid. The results of control experiments, in which no cesium is present, are also included. 

The magnitude of the rate constants were such that 46e exhibited a U-shaped pH-rate profile with a broad pH-independent region from pH 3.5 to 7.0 in which /Cobs Reaction products isolated within this pH range were consistent with those previously observed for 46a-d, and CU and 1 had effects on product distribution and identity similar to those discussed above for 46a-d. It was concluded that the pH-independent reaction involved N—O bond heterolysis to yield nitrenium ion intermediates as in Scheme 24. ... 

The photochemistry and photophysics of 2-methyl, 2-ethyl, and 2-tert-butylanthracenes on silica gel was examined by Dabestani et al. [38] to assess the substituent effect on product distribution and mechanism. In contrast to anthracene, which forms ground-state pairs at very low surface coverages (1% of a monolayer) [39], substituted anthracenes show no evidence of pairing even at surface coverages as high as 53% of a monolayer. Further-... 

Since biomass pyrolysis product mixtures are very complex and selectivities are low for specific products, considerable effort has been devoted to improving selectivities. Selectivities can sometimes be increased by addition of coreactants or catalysts, or by changing the pyrolysis conditions (cf. Nikitin et al, 1962). For example, the pyrolysis of maplewood impregnated with phosphoric acid increased the yield of methanol to 2.2 wt % of the wood as compared to 1.3 wt % obtained on dry distillation of the untreated wood. Addition of sodium carbonate to oak and maple increased the yield of methanol by 100 and 60%, respectively, compared to pyrolysis yields without sodium carbonate. Other weakly alkaline reagents exhibited a similar effect. Pyrolysis of wood in a stream of benzene, xylene, or kerosine increased the yields of acetic acid, aldehydes, and phenols and reduced the yield of tars. Optimization of pyrolysis conditions will be shown later to have large effects on product distributions and yields. 

Correlations of yields and product quality versus conversion, with conversion varied by changing space velocity (other conditions constant), are normally used as standards of comparison to establish the effects of other operating variables. To this extent, it is usually considered that space velocity has no effect on product distribution and quality except as it affects conversion. 

The NiMo/y-Al203 catalyst used in this work contained 8 wt% Mo and 3 wt% Ni and was prepared by successive incipient wetness impregnation of y-Al203 (CONDEA, pore volume 0.5 cm g, specific area 230 m g-i) with an aqueous solution of (NH4)6Mov024 4H20 (Aldrich) followed by an aqueous solution of Ni(N03)2 6H20 (Aldrich). The catalyst was dried in air at ambient temperature for 4 h, and then dried in an oven at 393 K for 15 h after each impregnation. Finally, the catalyst was calcined at 773 K for 4 h. The catalyst was crushed and sieved to the desired particle size to avoid diffusion effects on product distribution and conversion [9]. 

Pleasantly, this kinetic modeling enables us to extract interesting features of this catalytic system, for example, platinum species distribution over time, catalyst loading or temperature effects on products distribution and reaction rates, and so on, thereby demonstrating its practical usefulness [16,23a]. 

Nickel sulfate associated with porous, inorganic oxide such as alumina is used for catalytic purposes in olefin oligomerization [174]. The ethylene oligomerization activity of Ni-alumina catalyst is approximately proportional to the Ni concentration in the catalytic system. Increasing the Ni concentration resulted in a marked shift to a higher product (comparable at some level of ethylene conversion). The effects on product distribution and catalyst deactivation are due to the Ni being associated with sites of lower basic strength [233,234]. 

There have been three primary motives behind the study of metal carbonyl photochemistry in the gas phase first, to discover the shapes of metal carbonyl fragments in the absence of perturbing solvents or matrices second, to probe the effect of uv photolysis wavelength on product distribution and third, to measure the reaction kinetics of carbonyl fragments. All three areas have already proved fruitful. The photochemistry of two molecules, Fe(CO)5 and Cr(CO)6, has been studied in detail. 

Other authors have studied the effect of the gas space velocity, and their results are in agreement with those reported in this work concerning the effect of space velocity on CO conversion.13 15 In contrast, it is difficult to make a comparison between literature and our GHSV effects on product distribution. As reported by van der Laan and Beenackers,14 in fact, the effect of the space velocity on product distribution is complex and often controversial, so that... 

The adoption of new hypotheses for the reactants adsorption, the removal of all the empiric laws and parameters, and a reevaluation of the temperature effect on product distribution have allowed us to obtain significant improvements with respect to our previous work,10 in terms of both fitting ability and model consistency. 

An approximation of the extent of hydrogen transfer reactions occurring compared to cracking reactions and the net effect on product distribution can be initially seen by a consideration of the zeolite properties of the catalysts tested in the present study ... 

For practical use, combination charts (12 > 20) have been prepared which show the effect of the above process variables on product distribution and also the interrelationships of the yields of the various products. 

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. 

Flash vacuum thermolysis of the formal Diels-Alder adduct (10) of acetyl-methyloxirene to tetramethyl-l,2,4,5-benzenetetracarboxylate to give acetyl-methylketene (15, in Scheme 1) was examined in an attempt to find an example of nonstatistical dynamics effect on product distribution.29 With two carbon-13-labeled starting materials ( and show the labeled carbon in separated experiments), the reaction yielded 15 with different 13C locations. It was originally expected that 10 would give 12, which then via carbene formation would yield 15a and 15b. The ratio of the two products was anticipated to show the occurrence of nonstatistical product distributions. Compound 15c might be formed via 12 and 13, but this route was considered to be minor since 13 was much unstable than 14. 

A concerted mechanism in which the characteristic bond shifts take place through the cyclic transition state has been favored for some time [29,30], The lack of substituent and solvent effects on product distribution [31] and the lack of direct evidence of any intermediates were given as support for the concerted ene mechanism. 

Like thermal reactions, photochemical reactions of 1,2,3-thiadiazoles afford many products (B-79MI42400, 73SST(2)717). Subtle changes, such as ring size, can have a marked effect on product distribution for these reactions (equations 4 and 5) (79JHC1295, 79CB3728). Intermediates proposed for the thermal reaction of 1,2,3-thiadiazoles have also been... 

The NiY zeolite was also shown to be active for the cyclotrimerization of propyne with 1,2,4-trimethylbenzene being the main product. The activities of the above-mentioned transition metal ions for acetylene trimerization are not so surprising since simple salts and complexes of these metals have been known for some time to catalyze this reaction (161, 162). However, the tetramer, cyclooctatetraene, is the principal product in homogeneous catalysis, particularly when simple salts such as nickel formate and acetate are used as catalysts (161). The predominance of the trimer product, benzene, for the zeolite Y catalysts might be indicative of a stereoselective effect on product distribution, possibly due to the spatial restrictions imposed on the reaction transition-state complex inside the zeolite cages. 

The oxidized dimer, [Fe2(TPA)20(0Ac)]3+, 41, was shown to be an efficient catalyst for cyclohexane oxidation using tert-BuOOH as a source of oxygen (69). This catalyst reacts in CH3CN to yield cyclohexanol (9 equiv), cyclohexanone (11 equiv), and (tert-butylperoxy)cyclohexane (16 equiv) in 0.25 h at ambient temperatures and pressures under an inert atmosphere. The catalyst is not degraded during the catalytic reaction as determined by spectroscopic measurements and the fact that it can maintain its turnover efficiency with subsequent additions of oxidant. Solvent effects on product distribution were significant benzo-nitrile favored the hydroxylated products at the expense of (tert-butyl-peroxy)cyclohexane, whereas pyridine had the opposite effect. Addition of the two-electron oxidant trap, dimethyl sulfide, to the catalytic system completely suppressed the formation of cyclohexanol and cyclohexanone, but had no effect on the production of (tert-butylper-oxy)cyclohexane. These and other studies suggested that cyclohexanol and cyclohexanone must arise from an oxidant different from that responsible for the formation of (tert-butylperoxy)cyclohexane. Thus, two modes of tert-BuOOH decomposition were postulated a heterolytic... 

The kinetics of the above-mentioned reaction can frequently be altered by introducing a third substance which may form a complex with either A or B or both and thus alter the energy of activation of the reaction. In the case of oxidations that occur via chain mechanisms, catrdysts may have some influence on product distribution, and yet they frequently have little or no discernible effect on steady-state reaction kinetics. In some instances, additional catalyst may actually retard reaction rates [7-9]. 

The factors controlling the selectivity of cluster formation using E(SiMe3)2 (E = S, Se, Te) at low temperatures are numerous, and small changes in reaction conditions can have a pronounced effect on product distribution. The products obtained are highly variable and are dependent upon the reaction conditions used. Extensive studies of the synthesis of XI-XVI clusters demonstrate that careful... 

In this paper we present our results on a study ofthe deactivation and characterisation of FCC catalysts, together with product yields at realistic coke levels (0.5 to 1.0%), that are typically found on FCC catalysts during industrial operation. In particular, the effect of quinoline and phenanthrene as additives to the n-hexadecane feedstock has been studied at two concentration levels and the relative roles ofthese additives as catalyst poison and coke inducer are discussed. A further aspect investigated is the influence of catalyst formulation. Pure zeolites are seldom used as FCC catalysts instead, catalysts comprise a number of components, which apart from the zeolite, may include matrix, binder and clay. In the present work, catalyst formulations ranging fi"om 100% matrix to 100% zeolite have been examined and the influence ofthe various catalyst compositions on product distribution and coke formation is assessed. 

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