Solutia process

The selective insertion of an oxygen atom into a benzene carbon-hydrogen bond to yield phenol is not a classical organic chemistry reaction. The first process for such a reactions was the Solutia process, based on discoveries by Panov and coworkers at the Boreskov Institute of Catalysis in Novosibirsk and then developed in close cooperation with Monsanto. In this process, the oxidant is nitrous oxide, N2O, while an iron-containing zeolite is used as the catalyst (Equation 13.4)  

The reaction is run in the gas phase at 350 °C and, at 27% of benzene conversion, selectivity for phenol is claimed to be 98% [5]. The main by-products are dihydrox-ybenzenes (about 1%) and carbon oxides (0.2-0.3%). Selectivity is of paramount importance for this process, since 15 molecules of nitrous oxide are consumed for the total oxidation of just one molecule of benzene (Equation 13.5)  

The catalyst is an iron-containing ZSM-5 zeolite. Its half-life is three to four days so that, periodically, catalytic activity must be restored by passing air through the deactivated catalyst at high temperature no performance deterioration has been reported after more than 100 regeneration cycles. 

There is signiflcant debate about the mechanism of this reaction and, in particular, about the nature of the iron sites responsible for the unique reactivity. It is generally 

Material Metric tonne per metric tonne of phenol 

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Yields of adipic acid range around 92%. Typically for each mole of adipic acid produced, 2 moles of nitric acid are converted to N2O which could, in principle, be used for other processes, such as the Solutia process for the direct oxidation of benzene to phenol (Section 2.14). 

In the BIC/Solutia process, using a zeolite that contains only small amounts of iron, benzene can be oxidized to phenol with a selectivity of over 95% at around 300 °C, but N2O selectivity is lower than 95% [He]. 

Despite the remarkable performance of this innovative process, which was scaled up to the pilot unit, the BIC/Solutia process has not yet been put into commercial operation. This may be due to rapid catalyst deactivation caused by tar deposition, to low efficiency with respect to N2O and to the poor economics of such small-sized phenol plants, suited to balance the AA process unit, as compared to bigger, traditional plants for phenol production. An alternative option would be to build large phenol plants and produce N2O separately. For instance, a patent belonging to Solutia [llg] discusses the use of a Bi/Mn/Al/0 catalyst for the oxidation of ammonia to nitrous oxide. N2O selectivity is reported to be about 92% at 99.2% conversion. The cost of N2O is projected to be about 25% that of H2O2 [llh]. 

Table 13.4 gives the material balance of the Solutia process. 

Despite its brilliant results, it seems unlikely that the Solutia process can become a major source of phenol. Nitrous oxide availability is quite limited and its production on-purpose (by the conventional ammonium nitrate decomposition, which enables nitrous oxide of high purity to be produced for medical anesthetic applications, or even by selective oxidation of ammonia) would result too expensive. Therefore, the only reasonable scenario to exploit the Solutia process is its implementation close to adipic acid plants, where nitrous oxide is co-produced by the nitric oxidation of cyclohexanol-cyclohexanone mixtures and where it could be used to produce phenol instead of being disposed of However, the stoichiometry of the process is such that a relatively small phenol plant would require a world-scale adipic acid plant for its nitrous oxide supply. In fact, a pilot plant has been operated using this technology, but its commercialization has been postponed. 

Figure 1.17 Reaction steps, reaction conditions, and typical results for the direct hydroxylation of benzene to phenol with modified Fe-ZSM-5 as the catalyst and NjO as the oxidizing agent according to the Solutia process. Adapted from Chemical Engineering, September 2004, p. i, with permission from Chemical Engineering.

Panov s group in collaboration with Monsanto researchers contributed significantly to the development and implementation of this process in a pilot scale (nowadays, the Solutia process) [59, 85]. The reaction is performed in the gas phase at 350°C. The selectivity toward phenol attains 97-98% at 27% benzene conversion and 100% N O conversion. Dihydroxy benzenes (ca. 1%, mainly hydroquinone (HQ)) and carbon monoxide (0.2-0.3%) are main by-products. The catalyst half-life is restricted by a few days, but catalytic activity can be easily restored by buming-off coke deposits. The catalyst can thus sustain more than 100 regeneration cycles. The manufacture of adipic acid provides a cheap technical access to N O. More information about the Solutia process can be found in the two book chapters [58, 59]. Unfortunately, its commercialization has been postponed on the score of economics [9b]. 

Solutia has been producing hexamethylenediamine via low pressure slurry hydrogenation of adiponitrile since 1973. This process can also been adapted for the production of other amines such as DMAPA. The catalyst employed for... 

Figure 1 Solutia low pressure amine synthesis process.

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. 

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],... 

Describe the mechanistic, almost military, but very people-centric process followed for the post-merger integration of UCB Chemical and UCB Films with Solutia s resins, additives, and adhesives business ... 

It would be dishonest to say that these managers had an easy life and that the whole process of integration between a company that considered itself entrepreneurial and pragmatic and one that saw itself as having better structure and processes was an easy one. However, two years after the acquisition of the business from Solutia, at the time when the sale to Cytec was concluded, the company was clearly a very different one - having combined the best of both originating entities - and ready for the next big step. Thanks to the hard work of the joint workforce, UCB received several unsolicited bids for the business and eventually decided to divest to Cytec to create a EUR two billion focused specialty chemicals player at better conditions and faster than expected by the financial markets. 

L. Shannon Davis is the director of Industrial Products Technology at Solutia, Inc., a specialty chemicals company. She received her B.S. from Georgia Southern College and her Ph.D. in inorganic chemistry from the University of Florida. She began her career in 1988 at Monsanto s Pensacola, Florida, site as a senior chemist in the nylon intermediates business unit, where she worked on processes for the... 

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. 

An interesting aspect is the utilization in the process of the N2O co-produced in the oxidation of KA oil to adipic acid (Section 2.2). This allows a waste product of the integrated production cycle to be reused in the first stage of the cycle also saving on disposal costs. Solutia has recently announced, but has not yet implemented, the commercialization of an integrated adipic acid process based on this concept. 

The Kraft process is used for production of pulp for high-quality paper. Improvements to the Kraft process are described in U.S. 5,507,912 (to H. A. Simons Ltd.) and U.S. 7,097,739 (to Solutia Inc.). Estimate the annual savings gained by each of these processes relative to conventional Kraft pulping. 

Santicizer 148 [Solutia]. (alkyl diaryl phosphate ester). TM for a flexible, processable, and compatible flame-retardant plasticizer. 

In terms of sustainability, the process starting from propene would be preferable, since it avoids the risks connected with the use of HCN in the butadiene route, even if produced on demand. However, the butadiene route to produce adiponitrile (ADN) is more cost-effective, owing to the need to use an electrochemical reaction for acrylonitrile dimerization. The problem of cost, however, is highly dependent on several factors, including sensitivity to natural gas prices (which influences butadiene cost), the market for acrylonitrile, and soon. The acrylonitrile route is used by Solutia, BASF and Asahi Kasei. New plants to make caprolactam, using ADN as intermediate, are under construction in Asia. 

The hydrogenation of phenol has been adopted by Solutia and Radici. This process has some advantages, particularly for smaller scale manufacturers and for companies... 

Nowadays, Asahi, BASF, Bayer, Invista, Rhodia, Radici and Solutia use catalytic or thermal processes to destroy N2O. Recovery of waste heat from the exothermic abatement reactions is more effective with thermal systems due to their higher... 

As an alternative, N2O can be recovered from the off-gas in pure form, either for selling or for use as an oxidant in some downstream processes. Within this context, an innovative solution has been developed by Solutia, together with the Boreskov Institute of Catalysis, in which N2O is the oxidant used for the hydroxylation of benzene to phenol in the presence ofaZSM-5 catalyst exchanged with Fe(III) [11]. Phenol can then be hydrogenated to yield cyclohexanol, hence completing the N2O cycle (Scheme 7.3). 

Recycling the recovery of scrap metal and solvents and the use of distil lation residues as a fuel for cement are all recycling initiatives. However, the report does not suggest that Solutia UK is actively seeking to reuse waste streams from either its own or from other companies processes in order to reduce raw material and energy usage. 

Therefore, the balance is only assured in the case of 100% selectivity. Indeed, Solatia (formerly the chemical division of Monsanto) (293) has claimed a new process for the production of adipic acid without formation of acetone (which is normally obtained as a coproduct during cleavage of cumene hydroperoxide to phenol). Solutia patents (293,294) claim that the benzene-to-phenol selectivity is high while the N2O selectivity is lower than 90%. These numbers seem to indicate that some N2O has to be added, and the possibihty for successfijl industrial appHcation will depend on the amount of extra N2O required. 

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