Benzene oxidation nitrous oxide

Another example of heterogeneous catalysis by oxo-ions is the one-step oxidation of benzene to phenol with nitrous oxide, N2O. Fe/MFI catalysts have, again been found to be very active. This catalysis was discovered by Iwamoto and has been extensively studied by the group of G. Panov in Novosibirsk. " Preparations of Fe/MFI which appear highly active for this reaction display poor activity for NOj reduction and those which are optimum for that process, are poor for benzene oxidation. This shows that different sites are used. Work by Jia et al. revealed that the active sites for benzene oxidation appear to be Fe-oxo-ions containing only one Fe ion. This does not necessarily mean that the sites are mononuclear. A recent work by Zhu et al. has rather suggested that the site consists of one Fe and one Al + ion, the latter ion having left the zeolite framework. ... 

A specificity of N20 oxidant compared to 02 is one of the most interesting points arising from benzene oxidation over FeZSM-5 zeolites. The specificity is clearly seen from the results presented in Table 7.6 [ 118]. With nitrous oxide, benzene conversion is 27% at 623 K, whereas with dioxygen it is only 0.3% at 773 K. Moreover, the reaction route changes totally N20 leads to selective formation of phenol, while 02 leads only to the products of complete oxidation. 

The H-ZSM-5 coatings were tested for the one-step oxidation of benzene by nitrous oxide to phenol. The grids had a total area of 9 cm2, a wire diameter of 250 pm and a mesh size of 800 pm. Fifteen grids formed a stack separated by steel rings. By acid pretreatment of the grids, defects were generated which are known to become crystallization centers during the synthesis of the zeolite. 

For many simple compounds having no more than one double bond, the modern picture may be quite adequately represented by the Lewis structures (although the Lewis rules are noncommittal about the shapes of molecules). For compounds such as butadiene, benzene, and nitrous oxide, where there is extensive delocalization of electron density, the Lewis structures are not as suitable as the x-electron structures or, better still, as the streamer structures. Both of the latter type, however, are more difficult to draw and, for more complex molecules, more difficult to visualize they become extremely unwieldy when one attempts to use them to represent the progress of a chemical reaction. 

Figure 13.3 shows a plant layout. Recycled benzene along with makeup benzene and nitrous oxide are preheated and continuously fed to a moving bed reactor utilizing the zeolite catalyst. The latter flows vertically down the reactor by gravity, while the reaction gas flows across the annular catalyst beds. The predominant reactions are exothermic about 250 kj are released per mole of phenol produced. In addition, significantly more heat can be generated by the deep oxidation of benzene to... 

Except for a few points, the parity plot of benzene and nitrous oxide mole fractions displays a satisfactory agreement with a maximum deviation of 10% (Fig. 6 left). The higher deviation between calculated and measured phenol values (Fig. 6 right) stems from the simplicity of the model for the description of more complex consecutive reactions of phenol. 

The successful commercialization of the overall process concept depended on the viability of the first step which is a breakthrou technology. The data reported in the literature showed high selectivity of benzene conversion to phenol and good productivity. However, the catalyst coked quickly - in most reported cases the catalyst lost its activity in a matter of a few hours. Another problem of the reported chemistry is the low N20-to-phenol selectivity. In fact, the stoichiometry of benzene oxidation to CO2 by N2O implies that 1% of benzene selectivity loss to deep oxidation is accompanied by 15% selectivity loss in N2O conversion. Considering that the supply of nitrous oxide is limited, the efiBciency of its utilization is very important for the commercial operation. 

U. Hiemer, E. Klemm, F. Scheffler, T. Selvam, W. Schwieger, G. Emig, Microreaction engineering studies of the hydroxylation of benzene with nitrous oxide, Chem. Eng. J. 101 (2004) 17. 

Hiemer et al. [50] studied the hydroxylation of benzene with nitrous oxide. This highly endothermic reaction proceeded with higher selectivities at significantly higher space time yields than was possible in the conventional tubular reactor. 

A special case is the hydroxylation of benzene with nitrous oxide as oxidant, for which commercialization has been announced [55]. The reaction occurs on Fe-silicalite-1, in the gas phase, at temperatures close to 400 °C, producing molecular nitrogen as by-product. Other zeolites and supported metals and metal oxides are less satisfactory catalysts. Toluene, chlorobenzene, and fluorobenzene are similarly hydroxylated, yielding all three possible isomers. Phenol produces catechol and hydroquinone. 

In the recent past, the focus of new developments was on alternative phenol processes that overcome the disadvantage of the coupled product acetone in the cumene oxidation process. These processes are based on the oxidation of benzene with nitrous oxide or hydrogen peroxide [7]. The main research on the cumene oxidation process is process intensification by improving the oxidation reaction and improved process and reactor design. 

In the commercially relevant reports of benzene oxidation catalyzed by framework metal-containing zeotype materials hydrogen peroxide or nitrous oxide (N2O) are used as oxidants. Thus phenol is produced without major by-product formation. 

Solutia (USA), in joint work with the Boreskov Institute of Catalysis, Russia, developed a one-step process to manufacture phenol from benzene using nitrous oxide as the oxidant (see Fig. 3.12). Nitrous oxide (a greenhouse gas) is a waste product from Solutia s adipic acid process. The preferred catalysts are acidified ZSM-5 and ZSM-11 zeolites containing iron or a silica/alumina ratio of 100 1 containing 0.45 wt% iron(III) oxide. The catalyst s half-life is 3 to 4 days, and it can be restored by passing air through the bed at high temperatures. 

A first success in the direct of benzene oxidation was provided by the Solatia process, discovered by Panov and co-workers at the Boreskov Institute of Catalysis in Novosibirsk, Russia and developed in close cooperation with Monsanto. In this process, the oxidant is nitrous oxide (N2O) and an iron-containing zeolite is the catalyst. Nevertheless, despite its brilliant results, it is unlikely that the Solatia process can become a major source of phenol since nitrous oxide availability is quite limited and its deliberate production would be expensive. 

In a polluted or urban atmosphere, O formation by the CH oxidation mechanism is overshadowed by the oxidation of other VOCs. Seed OH can be produced from reactions 4 and 5, but the photodisassociation of carbonyls and nitrous acid [7782-77-6] HNO2, (formed from the reaction of OH + NO and other reactions) are also important sources of OH ia polluted environments. An imperfect, but useful, measure of the rate of O formation by VOC oxidation is the rate of the initial OH-VOC reaction, shown ia Table 4 relative to the OH-CH rate for some commonly occurring VOCs. Also given are the median VOC concentrations. Shown for comparison are the relative reaction rates for two VOC species that are emitted by vegetation isoprene and a-piuene. In general, internally bonded olefins are the most reactive, followed ia decreasiag order by terminally bonded olefins, multi alkyl aromatics, monoalkyl aromatics, C and higher paraffins, C2—C paraffins, benzene, acetylene, and ethane. 

Direct hydroxylation of benzene to phenol could be achieved using zeolite catalysts containing rhodium, platinum, palladium, or irridium. The oxidizing agent is nitrous oxide, which is unavoidable a byproduct from the oxidation of KA oil (see KA oil, this chapter) to adipic acid using nitric acid as the oxidant. 

Efforts to identify the specific compounds responsible for the psychotropic effects of volatile solvents are complicated by the fact that many of these products contain more than one potentially psychoactive ingredient. Another factor obscuring the identity of the psychoactive ingredients of these agents is that patients addicted to these compounds frequendy seek the effects not of the product s primary ingredient but of a secondary ingredient such as the propellant gas (e.g., nitrous oxide). To date, the best-studied psychoactive compounds identified in volatile solvents include toluene, 1,1,1-trichloroethane, and trichloroethylene. However, other less well studied compounds, such as benzene, acetone, and methanol, also appear to have significant psychoactive effects. 

Nitrous oxide as an efficient oxygen donor was noticed when used in such a delicate reaction as the direct oxidation of benzene to phenol ... 

Hensen EJM, Zhu Q, van Santen RA. 2005. Selective oxidation of benzene to phenol with nitrous oxide over MFI zeolites. 2. On the effect of the iron and aluminum content and the preparation route. J Catal 233 136-146. 

Organic solvents inhaled by abusers include gasoline, glue, aerosols, amyl nitrite, butyl nitrite, typewriter correction fluid, lighter fluid, cleaning fluids, paint products, nail polish remover, waxes, and varnishes. Chemicals in these products include nitrous oxide, toluene, benzene, methanol, methylene chloride, acetone, methyl ethyl ketone, methyl butyl ketone, trichloroethylene, and trichloroethane. 

J. Jia, K. S. Pillai, and W. M. H. Sachtler, One-step oxidation of benzene to phenol with nitrous... 

Q. Zhu, R. M. van Teeffelen, R. A van Santen, and E. J. M. Hensen, Effect of high-temperature treatment on Fe/ZSM-5 prepared by chemical vapor deposition of FeCls 11. Nitrous oxide decomposition, selective oxidation of benzene to phenol, selective reduction of nitrous oxide by MO-butane, J. Catal. 221, 575—583 (2004)... 

Notte, P.P. (2000) The AlphOx process or the one-step hydroxylation of benzene into phenol by nitrous oxide. Understanding and tuning the ZSM-5 catalyst activities. Top. Catal., 13, 387-394. 

Most models of gas uptake in the respiratory tract have been concerned with carbon dioxide, carbon monoxide, oxygen, and anesthetic gases like chloroform, ether, nitrous oxide, benzene, and carbon disulfide (e.g., see Lin and Gumming and Papper and Kitz ). Unfortunately, there are only a few preliminary models of pollutant-gas transport and uptake in the respiratory tract. 

Aromatic radical-cations are generated by pulse-radiolysis of benzene derivatives in aqueous solution. Radiolysis generates solvated electrons, protons and hydroxyl radicals. The electrons are converted by reaction with peroxydisulpbate ion to form sulphate radical-anion, which is an oxidising species, and sulphate. In another proceedure, electrons and protons react with dissolved nitrous oxide to form hydroxyl radicals and water, Hydroxyl radicals are then made to react with either thallium(i) or silver(i) to generate thallium(ii) or silver(ll) which are powerfully... 

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