Catalytic maximum yield

Catalytic upgrading of bio-oil was carried out over Ga modified ZSM-5 for the pyrolysis of sawdust in a bubbling fluidized bed reactor. Effect of gas velocity (Uo/U ,f) on the yield of pyrolysis products was investigated. The maximum yield of oil products was found to be about 60% at the Uo/Umf of 4.0. The yield of gas was increased as catalyst added. HZSM-5 shows the larger gas yield than Ga/HZSM-5. When bio-oil was upgraded with HZSM-5 or Ga/HZSM-5, the amount of aromatics in product increased. Product yields over Ga/HZSM-5 shows higher amount of aromatic components such as benzene, toluene, xylene (BTX) than HZSM-5. 

There has been a very brief report on the use of [Ni(ii -C5Hj)Cl(NHC)]/NaQPr for the hydrodebromination of p-bromotoluene. As expected, the catalytic efficiency was carbene dependant (decreasing in the order IMes > SIMes > SIPr > IPr) although only a maximum yield of 40% was achieved. Interestingly, very similar catalytic efficiency was observed irrespective of whether the reaction was performed in refluxing THF at 65°C or in refluxing dioxane at 105°C [13]. 

The process is operated at a platinum electrode and a reduced efficiency due to side reactions is observed. A maximum yield of 55% is reported. The use of in situ generated NBS and bromine for the synthesis of nucleosides from silylated pyrimidines has been studied. Nokami etal. [125] suggest the use of only catalytic amounts of NBS or bromine and regeneration of the catalyst by anodic electrolysis in an undivided cell system. 

Reactions of substituted a-ketoalkynes (RC=CCOR ) with 6-amino-l,3-dimethyluracil and a water-soluble nickel catalytic system [Ni(CN)2-CO-KCN-NaOH] afforded 2,4-dioxopyrido[2,3- pyrimidine derivatives 532 under very mild conditions (room temperature and atmospheric pressure). The mechanism involved a nucleophilic attack by Ni(0), formed in situ, onto the triple bond of the substrate. The reaction terminates within 30 min, giving 98% of 532, while in the absence of this catalytic system the reaction took a longer time (lOh) to reach a maximum yield of 30% <2001J(P1)2341>. A regioselective interaction of 6-aminouracil derivatives with GF3COCH2COR in boiling AcOH afforded the cyclized 5-trifluoromethylpyrido[2,3-, pyrimidines 533 <200381531 >. 

To produce the maximum yield of finished gasoline in a hydrocracker-reformer combination, the hydrocracker should be operated to give maximum liquid yields, followed by a modem low pressure catalytic reformer to give the desired octane improvement (6). More severe hydrocracker operation produces higher octane naphtha but leads to an increase in the production of butanes with reduced yields of finished... 

The reactions involved in the glycal synthesis have been studied in considerable detail, especially in the conversion of arabinose into 2-des-oxyribose. For this particular conversion the overall yield has been doubled by recently introduced improvements but it is still very low.112 The reduction of the acetobromoaldose to the acetylated glycal by zinc dust and acetic acid was found to proceed in better yield if a few drops of chloroplatinic acid were added at intervals to maintain a vigorous reaction.112 120 127 Moreover, the reaction could then be conducted at lower temperatures (i. e., — 5° to —10°). This was particularly the case in the pentose series, and the simultaneous formation of the pentose tetraacetate by replacement of the bromo group by an acetyl residue, was much reduced.60 112 Hughes148 demonstrated that the maximum yield of triacetylglucal from acetobromoglucose was obtained when the addition of zinc dust and catalytic amounts of chloroplatinic acid was spread over several hours and the reaction mixture was maintained at 0°. 

Figure 4.7 shows that after reaching the maximum yield the consumption rate of vinylethylbenzenes decreases only slightly. This indicates deficient H202 concentration at the stage of divinylbenzene synthesis. The S-shape of the kinetic curves obtained testifies to the auto-catalytic type of the process with the autoacceleration period from the beginning of these curves to inflection points. 

Ray et al.29 used V205/Cr2 03 catalysts supported on A1203 for the ammoxidation of xylenes. The maximum yields increased from 40% for o-xylene to 70% for m-xylene and, using a catalyst with boria addition, to 89% for p-xylene. From t.p.r. and e.s.r. measurements the authors conclude that a new compound VCr04 is present which is responsible for the catalytic activity. 

Anyway, it is doubtful whether Letts and Collie thought about zinc as the catalyst of the reaction of tin with alkyl halides (in spite of their demonstration) since this fact was established considerably later. The authors also found that the reaction of EtI with a Sn—Zn alloy (33-50%) containing 5% of Cu gave a maximum yield of E Sn. Thus, long before Rochows s finding the catalytic influence of copper in the direct synthesis of organometallic compounds was observed636. 

Sant and Varma (183) found that low concentrations of zirconium lowered the temperature required to reach the maximum yield. Various interpretations of this observation have been put forward either the increase in surface area or the increase in oxygen transport rates can be sufficiently altered by the zirconium to result in high yields of MA at lower temperatures. The studies generally agree that aroimd 1.5% zirconium has the most beneficial effect on the activity, and good catalytic performance could be achieved at lower temperatures (172). One of the reasons for this that has been proposed is that zirconium and titanium both create acidic surface sites on the vanadium phosphate surface. These sites prevent the desorption of reaction intermediates (butene, butadiene, and furan) while facilitating the desorption of the acidic MA. 

Obtained data show that, the mixtures of the different types of the natural and synthetic organic polymers can be successfully converted with a high yield to light distillate fraction by pyrolysis under inert atmosphere and catalytic hydtopyrolysis in the autoclave conditions. The optimum tenqreiature of biomass / plastic mixtures conveision which coiresponds to the maximum yield of liquids is 390 - 400 C. In the CO liquefaction processes the interaction between products of natural and synthetic polymers thermal deconqwsition takes place. 

However, approximate treatment is possible. Ikeda and Tashiro (19) report an optimization of catalytic reactions in fluid beds. They And that the maximum yield of the intermediate product decreases, and that the optimum contact time increases for first-order consecutive and parallel reaction systems if contact efficiency in the reactor decreases. They also showed the most economical equilibrium activity and the optimal size distribution of catalyst. 

The first process of this type utilized gases as raw materials and produced carbon blacks for rubber with only moderate reinforcement properties at a maximum yield of 30%. The changeover to liquid and melting raw materials increased the yield of carbon black for rubber to 40 to 70% and enabled a much broader range of raw of products to be produced, so that this type of raw material is now almost exclusively used e.g. aromatic compound-rich viscous residues from oil refineries, coking plants, catalytic crackers and steam crackers for the production of ethene and from the catalytic synthesis of petrol. 

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