Aromatics, increase

Table 7 also indicates that the rate enhancements for a 3- and 5-methyl group vary significantly among 1,2-azoles. The difference between the increments in log units for a 3-and 5-methyl group, which should vary directly with bond fixation in the ground state, is larger for isoxazole (1.4) than for pyrazole (0.7) and for isothiazole (0.2). This indicates that the aromaticity increases in the same order and contributes the first quantitative evidence that the 1,2-azoles follow the same aromaticity order as furan < pyrrole < thiophene. 

As feedstocks progress from ethane to heavier fractions with lower H/C ratios, the yield of ethylene decreases, and the feed per pound ethylene product ratio increases markedly. Table 3-15 shows yields from steam cracking of different feedstocks, and how the liquid by-products and BTX aromatics increase dramatically with heavier feeds. 

Aniline Point is the minimum temperature for complete miscibility of equal volumes of aniline and the hydrocarbon sample. In cat cracking, aniline solution is used to determine aromaticity of FCC feedstocks. Aromaticity increases with reducing aniline point. 

On the contrary, for oil E the quantity of asphaltenes decreases from 8.1 for the initial crude oil to 4-1 for the sample produced at the end of the test (Fig. 12). Moreover, the amounts of resins + asphaltenes decreases whereas the amounts of saturates and aromatics increase (51 4 in the initial oil, 72.4 for a sample recovered at t = 24 h). The analysis by GC shows that each oil fraction is enriched in components with molecular chains ranging from 15 to 30 carbons which don t exist in the initial oil (n-alkanes, aromatics O q-CLq which are less complex than the initial ones, thiophenic compounds C -C ). The elemental... 

Increasing the residence time also has beneficial and detrimental features. On the positive side the heteroatom content is reduced while on the negative side the aromaticity increases. 

Clearly, the hardnesses of thermoplastic polymers are not intrinsic. They depend on various extrinsic factors. Only trends can be cited. For example, as the molecular weight in polyethylene materials increases, they become harder. And, as the molecular aromaticity increases, a polymeric material becomes harder. Thus, higher molecular weight anthracene is harder than napthalene and more aromatic Kevlar is harder than polymethacrylate. 

Sulfur compounds are most commonly removed or converted to a harmless form by chemical treatment with lye. Doctor solution, copper chloride, or similar treating agents (Speight, 1999). Hydrorefining processes (Speight, 1999) are also often used in place of chemical treatments. When used as a solvent, naphtha is selected for its low sulfur content and the usual treatment processes remove only sulfur compounds. Naphtha, with its small aromatic content, has a slight odor, but the aromatics increase the solvent power of the naphtha and there is no need to remove aromatics unless odor-free naphtha is specified. 

Expansion of Sorbex technology to the production of m-xylene shows how the process concept can be used for multiple applications in separations that cannot be performed by other means. One can expect that, as demand for new, difficult to separate aromatics increases, the simulated moving bed liquid adsorption processes can provide a means for production. 

A typical catalytic hydrodealkylation scheme is shown in Figure 3 (49). The most common feedstock is toluene, but xylenes can also be used. Recent studies have demonstrated that C9 and heavier monoaromatics produce benzene in a conventional hydrodealkylation unit in yields comparable to that of toluene (51). The use of feeds containing up to 100% of C9 1Cu aromatics increases the flexibility of the hydrodealkylation procedure which is sensitive to the price differential of benzene and toluene. When toluene is in demand, benzene supplies can be maintained from dealkylation of heavy feedstocks. 

A volatile, paraffin fuel will deposit the least amount of coke. Decreasing volatility increases coke deposition but has little effect on smoke. Increasing aromaticity increases both coke and smoke. Minor components have no effect within the maximum permitted by fuel specifications. 

Pt-Sn Pt-Pb Sn and Pb have similar effects. Reaction conditions determine effectiveness of Sn or Pb additions reactions inhibited under mild conditions while aromatization increased and hydrogenolysis decreased under more severe conditions.97 ... 

Magnetic susceptibility anisotropy has been used to estimate relative aromaticities of some azines <1977JOC897>. If the extent of -electron delocalization for benzene is taken as 1.0, the corresponding values for azines are pyridine 0.7, pyridazine 0.7, pyrimidine 0.5, and 1,3,5-triazine 0.3. Another quantitative magnetic index is the exaltation of the total magnetic susceptibility (A). All aromatic systems reveal large A values, whereas for nonaromatic compounds A is close to zero and it is assumed that aromaticity increases with A. For six-membered monocycles the following values of A have been reported (in units of cm3 mol-1 x —106) benzene (17.9), pyridine (18.3), pyridazine (8.7), pyrimidine (18.2), pyrazine (12.7), l-ethyl-2-pyridone (13.0), and 1,3,5-triazine (19.0). 

Successive introduction of nitrogen atoms into benzene causes a gradual reduction in aromatic stabilization. The diazines still show typical aromatic behavior in that in most of their reactions they revert to type. However, with the triazines and tetrazines, decreasing aromaticity increases the ease of both thermal and photochemical fragmentations and rearrangements, and of cyclic transition state reactions with other reagents. 

With the exception of experiments at [29] 605°C, the gas fraction is the main product (58-71%), having a maximum yield at a temperature of about 700°C. BTX-aromatics increase from 1.6% at 605°C up to 16% at 805°C. Distillation residue is higher at lower temperature (at which heavier hydrocarbons are produced) and at the highest (since more condensed aromatics are present). Chlorine is present in the water and in the solids... 

Ava-Henrfs Law Constant, Josien and Fuson have made extensive studies of solvent effects on IR frequencies (1055, 1059), contributing much interesting and accurate data on H bonding systems. They note a systematic correlation between Av for either methanol or pyrrole and the Henry s Law constant of HCl in a series of aromatic solvents (1060). As the basicity of the aromatic increases, the constant decreases-and Ava rises. The data they compile are shown in Table 3-IV. For... 

When a sample is heated, hydrogen aromaticity increases owing to the decrease of hydrogen in the species other than aromatics. If this change can be expressed as a first-order irreversible reaction, the rate of change in a batch system is written as... 

Each series of LC-GPC subfractions was investigated previously by and C NMR methods and was found to have approximately mono-, di-, and tri- and/or tetraaromatic derivatives for Fr-M, D, and T, respectively, as the average structural units (9). It was confirmed also that values of aromaticity increase gradually with the increasing GPC fraction number from 1 to 7 within each subfraction the value is largest for the T series and smallest for the M series at equivalent elution volumes. From the results described above, the separations by LC and GPC according to... 

The initial rate of hydrogenation of fused polycyclic aromatics increases with the number of rings present phenanthrene > naphthalene > benzene. Only one ring is generally saturated at a time. This partial hydrogenation is accomplished because... 

The transformation of n-butane over H-ZSM-5 resulted in the formation of aromatic hydrocarbons benzene, toluene and isomers of xylenes. The gaseous products obtained were methane, ethane, ethene, propane, propene, butenes (cis-, trans- and iso- butenes) and hydrogen. The n-butane conversion and selectivity to aromatics increased with increasing temperature. More cracking products than aromatics were formed over this catalyst. 

Apart from the prevailing fragmentation, different C0 products were important at the two nH pressures. The initial higher selectivity of methylcyclopentane at p(nH)=10 Torr (Fig. la) points to a metallic activity [9, 12]. These centres seem to deactivate rapidly as the reaction proceeded. Higher nH pressures suppressed this initial Cg-cychzation. More isomers were formed at p(nH)=40 Torr (Fig. lb). Whereas the selectivity of both saturated Cc products decreased, that of aromatics increased exceemng linearity at hi er total conversion values. A fourfold increase of p(nH) caused about a tenfold increase in aromatization selectivity (Kgs la and b). 

The conversion of butane on Zn-Sil, Zn(Imp) and Zn(A-P) was studied. As shown in Figure 1, on all catalysts, the conversion of butane increased with W/F at 823K, while the selectivity to aromatics increased only slightly with W/F. The catalytic activity and the selectivity of Zn(Imp) were the highest in these catalysts. These results, suggest that the dehydrogenation activity of Zn loaded on ZSM-5 surface is higher than that of Zn loaded in the zeolite framework of ZSM-5. 

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