Hydrogen peroxide, synthesis

When solid NaOH or KOH was introduced into the space between the electrodes in a 5 mm lumps and a discharge in ammonia was operated at 5 torr and 5 mA the hydrazine content increased by a factor of about seven (Fig. 24). However, the continuous operation of the discharge caused the catalyst to melt. With intermittent operation of the discharge the catalyst did not melt and the degree of conversion into hydrazine reached 15%, double that obtained with a continuous discharge (Fig. 24). The effect was explain l by assuming that the formation of hydrazine 

Dependence of the degree of conversion y of ammonia into hydrazine on specific energy (i = S mA, Pnhj = 5 torr) for (a) intermittent and (b) continuous discharges with NaOH as catalyst. Curve (c) is for continuous discharge in the absence of a catalyst  

Surely the mean surface coverage of the catalyst with NH3 molecules is higher during an experiment with an intermittent discharge than with a continuous discharge under similar conditions. 

Spectroscopic investigations also showed that the introduction of the solid alkali did not lead to an anomalous population of rotational levels in NH but raised the vibrational temperature from = 3(XK) K to c= 4000 K. It was sugg ted that the recombination of ions, presumably N, on the catalyst surface leads to an increase in the number of nitrogen molecules at high levels of vibrational excitation. However, the location of NaOH catalyst at the cathode or anode does not influence significantly either the decomposition of ammonia or the synthesis of hydrazine (Fig. 25) 

This suggested that ions do not play a significant role in the synthesis of hydrazine on the surface of soUd alkali. 

The initial goal is to achieve the production of a 1% solution at laboratory scale and to transfer this to an on-site production scale within 5 years. 

Recently, a new microreactor for the direct synthesis of hydrogen peroxide has been designed at the AIST, Tsukuba, and Mitsubishi Gas Chemical Inc., Tokyo. It operates at room temperature and IMPa. The reactor is made of glass and the catalyst is palladium on titania. The yield of 40% was reached, based on hydrogen, and the concentration was 10% [56]. 

As the potential of this technology is tremendous, companies are putting their effort in investigating the reaction kinetics and stability of hydrogen peroxide formation in a microreactor. Some such studies are performed at BASF Catalyst [57] and give a promising input for optimizing the reaction for more efficient 

Clariant GmbH in Frankfurt, Germany, performed the synthesis of phenylboronic add from phenylmagnesium bromide and boronic acid trimethyl ester on a pilot- 

This reaction suffers, as many organometallic reactions, from insufficient mixing, since its reaction speed (at room temperature and below) is faster than the mixing times of many conventional mixer equipments. Thus, the reaction proceeds under nonstochiometric conditions with timely and spatially changing concentration profiles, which promotes consecutive reactions. In addition, too long processing times, quite typical for batch reactions, favor side reactions such as oxidations and 

---

A few fundamental studies have also been reported on the topic of hydrogen peroxide synthesis by direct combination of H2 and 02 in a microreactor. A recent contribution ofVoloshin et al. [86] from the Stevens Institute ofTechnology shows the first results on the role of reaction conditions. A maximum concentration of 1.3 wt% H202 was achieved. Further studies are necessary, but this interesting direction warrants further investigation. 

UOP then carried out pilot-scale tests at still higher pressures in a fully automated explosion cell to reproduce vendor work and to study conditions and kinetics. Design was based on direct hydrogen peroxide synthesis using a mini-trickle bed reactor with a micro mixer. 

Figure 5.9 Hydrogen peroxide synthesis pilot microprocess plant by courtesy of FMC Corporation in Princeton, USA, and Niyi Lawal/Stevens Institute) [41].

Fig. 15. Two-compartment trickle-bed cell used for hydrogen peroxide synthesis. (Adapted from [73]).

G. Perez de Lema, I. Arribas, A. Prieto, T. Parra, G. de Arriba, D. Rodriguez-Puyol, et al.. Cyclosporin a-lnduced Hydrogen Peroxide Synthesis by Cultured Human Mesangial Cells Is Blocked by Exogenous Antioxidants, Life Sci 62 (1998) 1745-53. 

Neutral catalysts or catalyst precursors based on fluorinated ligand systems have been applied in compressed CO2 to a broad range of transformations such as Zn- and Cr-catalyzed copolymerization of epoxides and CO2 [53, 54], Mo-catalyzed olefin metathesis [9], Pd-catalyzed coupling reactions [43, 55, 56] and Pd-catalyzed hydrogen peroxide synthesis [57]. Rhodium complexes with perfluoroalkyl-substituted P ligands proved successful in hydroformylation of terminal alkenes [28, 42, 44, 58], enantioselective hydroformylation [18, 59, 60], hydrogenation [61], hydroboration [62], and polymerization of phenylacetylene... 

Results showed that Au/ZnO and Au/Pd/ZnO catalysts exhibit some hydrogen peroxide synthesis at 308 K, although at a low rate. This is an improvement on use of the Pd catalyst that only generated water as a product (see Fig. 6.21). 

Oliveira, P.P., Patrito, E.M., and Sellers, H. 1994. Hydrogen peroxide synthesis over metallic catalysts. Surface Science 313, 25 0. 

P. P. Olivera, E. M. Patrito, H. Sellers, Hydrogen peroxide synthesis over metallic catalysts, Sutf. Sci. 313 (1994) 25. 

Voloshin Y, Haider R, Lawal A (2007) Kinetics of hydrogen peroxide synthesis by direct combination of H2 and 02 in a microreactor. Catal Today 125(l-2) 40 7... 

Quinones in Hydrogen Peroxide Synthesis and Cataiytic Aerobic Oxidation Reactions... 

---