Processes AlphOx

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. 

It was reported independently by three research groups that MFI-type zeolites selectively catalyze the reaction of N20 with benzene to give phenol C6H6 + N20 —> C6H5OH + N2 [93-96]. Fe/ZSM-5 shows remarkable performance in benzene hydroxylation to phenol with N20 as oxidant, which is the first example of a successful gas phase direct phenol synthesis from benzene [97]. No other catalysts show similar high performances to the Fe/ZSM-5 catalyst. At present, iron is the sole element capable of catalyzing the benzene-to-phenol reaction [98]. Direct oxidation of benzene to phenol by N20 has been commercialized in the so-called AlphOx process in Solutia Inc., US A, where N20 is obtained as a by-product in adipic acid production with nitric acid [97, 99, 100] a selectivity >95% to phenol is achieved at >40% conversion at around 4000 C. But the process is cost-effective only if N20 can be obtained cheaply as a by-product in adipic acid production. 

The Fe ion is easily incorporated into zeolites. Ferrosilicates and ferrisilcates are often used as acid catalysts. Direct oxidation of benzene to phenol over Fe-MFI zeolites has been shown to be practical when N20 is used as an oxidant (AlphOx process) [112]. This process is suitable for the abatement ofhighly concentrated N20 (20-40%) gas discharged from adipic acid plants to meet the tightened regulation of emission levels of N20. 

Based on FeZSM-5 zeolites, a new one-step phenol process (the AlphOx) has been developed jointly by Solutia Inc. and the Boreskov Institute of Catalysis [82]. The process was successfully tested with a pilot plant constructed at Solutia facilities in Pensacola (Florida). The process runs in an adiabatic reactor with the parameters shown in Table 7.5. It provides a 97-98% yield of phenol, with 100% N20 conversion per pass and a recycle of benzene. A 1% yield of dihydroxybenzenes (DHB) is also obtained. This valuable by-product is mainly hydroquinone. Periodically, the catalyst is subjected to regeneration by buming-off coke deposits. Its lifetime is 1.5 years. More details on the process are given elsewhere [82, 83],... 

Recently, there have been several process developments that allow for the production of phenol without co-production of acetone. These would tend to compete directly with the need to produce cumene. Developments include the AlphOx process, a joint development of Solutia and the Boreskov Institute of... 

AlphOx A process for oxidizing benzene to phenol, using nitrous oxide as the oxidant and a zeolite catalyst. Developed by the Boreskov Institute of Catalysis and Solutia, and proposed to be commercialized in Pensacola, FL, in 2003 however, this plan was subsequently abandoned. In 2004 the process was relaunched by GTC Technology Inc. and Solutia, following extensive testing by Solutia in Pensacola. 

Figure 1.18 Process flow diagram for the direct hydroxylation of benzene to phenol with modified Fe-ZSM-5 as the catalyst and N2O as the oxidizing agent. N2O is obtained from the waste stream of adipic acid production. This scheme depicts the Solatia Alphox process.

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