Benzenes selective

Toluene/benzene selectivity decreases in the order X = CH3 > H Cl > NO2, in agreement with the expectation that the least stable (and most reactive) carbocation would be least selective. The reactions also show low position selectivity. 

LHSV Temp.,°F % Conversion Selectivity to Benzene Selectivity to Isohexane... 

The reaction is performed either noncatalytically at temperatures of 600-800°C and at pressures of 30-100 bar, or catalytically on a CoO contact at 550-650°C and at the same pressure of 30-100 bar. A problem of the catalytic process is the poisoning of the catalyst by deposition of coke-like material, but the conversion, yield, and purity of the benzene are better (>99%) in the catalytic than in the noncatalytic process. In the noncatalytic process the benzene selectivity is about 95%, if the conversion of the toluene is kept at 60-80%. 

Catalysts were prepared with 0.5, 1.0, 2.0 and 5.0 wt% of iron loaded on activated carbon. Benzene hydroxylation with hydrogen peroxide as oxidant was carried out. The conversion of benzene, selectivity and yield of phenol for these catalysts are shown in Fig. 4. As the weight of loaded metal increased the benzene conversion increased by about 33% but the selectivity to phenol decreased. The yield of phenol that was obtained with S.OFe/AC was about 16%. 

As a consequence of the lower coke selectivity of the Cs-exchanged catalyst, the selectivity to the desired benzene product was largely increased by about 35% and remained more stable with TOS with respect to the untreated catalyst (Fig. 5). As expected from their high coke formation, the steamed catalysts displayed the lowest benzene selectivity. 

Figure 5 Benzene selectivity as a function Figure 6. Benzene-to-naphthalene weight of TOS. Same symbols as in Fig. 3. ratio at TOS 7 h.

Zeolite S1O2/ AI2O3 ratio Metal (wt%) Feed SV Temp Pressure Conversion Aromatics Selectivity Benzene Selectivity Notes Reference... 

Kinetically controlled conditions favor the formation of mixed fluorinated compounds if per-halo derivatives are fluorinated with hydrogen fluoride. Therefore, catalysts or coreagents are used to overcome this problem. Thus, selective fluorination of l,3-bis(trichloromethyl)benzene cannot be achieved by hydrogen fluoride using variations in temperature, pressure or time.247 However, if antimony(V) fluoride is added to hydrogen fluoride the reaction produces l-(tri-chloromethyl)-3-(trifluoromethyl)benzene. Selective fluorination can also be performed in compounds with different substitution patterns.247,251 253... 

PMMA-PS-PMMA M = 316 Butanone, toluene (neutral) Acetone (selective for PMMA) Triethyl benzene (selective for PS)... 

Benzene (selective for PS) THF, dioxane, chloroform, cyclohexane (neutral)... 

Therefore, at 70% benzene selectivity, the selectivity of N20 is only 12-13%, which makes the process unfeasible. 

The molecular structure of arsabenzene,49) 4-methylarsabenzene 50) and 4-methyl-stibabenzene 50) have been determined from an NMR study of liquids oriented in a liquid crystal phase. Unfortunately, no structural data are yet available for bisma-benzene. Selected bond lengths and angles of the complete family of group 5 heterobenzenes are illustrated in Fig. 1. 

Cyclohexane Selectivity, 100 um -Benzene Selectivity, 100 um Cyclohexane Selectivity, 5 um Benzene Selectivity, 5 um... 

Table ID. Terminal Cracking Index and Benzene Selectivity Parameter at 733 K...

Calculate the benzene selectivity from toluene. Let Pb be the production rate of benzene. Then,... 

Determine the benzene selectivity from toluene. First, find the relevant stoichiometric factor, namely, the stoichiometeric moles of toluene required per mole of benzene produced. From the reaction to produce benzene from toluene, this stoichiometric factor is seen to equal 1. 

Determine the benzene selectivity from hydrogen. As in step 2, the stoichiometric factor with respect to hydrogen and benzene is, likewise, 1, from the first reaction in this section. 

It is possible to replace all three hydrogen atoms of the methyl group of toluene sequentially by chlorine leading to (chloromethyl)benzene (4), (dichloromethyl)benzene (5) and (trichloromethyl)benzene (6). Introduction of the first chlorine atom proceeds at a much faster rate than the second and so it is possible to prepare (chloromethyl)benzene selectively. In order to achieve the required degree of chlorination, chlorine gas is passed into the reaction mixture until the mass gain corresponds to the appropriate level of substitution. 

The benzene selectivity in /i-hexane conversion over Pt/KL catalysts increases with conversion, but the selectivity for methylcyclopentane decreases (21). Lane et al. show that the MCP yield passes through a maximum between 40 and 60% conversion, 2-methylpentane and 3-methylpentane peak around 80% conversion, and hydrogenolysis products and benzene increases with -hexane conversion (29). The same reaction product distribution was found for a variety of supports, e.g., AI2O3, Si02, KL, and KY. On Pt/KY, Pt/NaY, and Pt/ALOj the 2MP/3MP ratios... 

Catalyst Conversion (wt%) Benzene Selectivity (%) Benzene Yield (wt%)... 

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