Kinetics of One-Pot Regioselective Cohydrogenation of Styrene Oxide and Aryl Alkenes: A Step toward Sustainable Development of a Novel Integrated Process for 2-Phenylethanol Production

Abstract

A strategy of one-pot regioselective cohydrogenation of styrene oxide (STOX) and aryl alkenes (styrene and alpha-methylstyrene) in the presence of aralkyl alcohols (1-phenylethanol and 2-phenyl-2-propanol) is proposed. It would help reduce capital and operational expenditure in the aralkyl hydroperoxide-based 2-phenylethanol (2PEA) manufacturing process. Reactions are performed in a stirred tank reactor in the presence of a 5% Pd/C catalyst. A range of operating conditions are proposed wherein STOX is converted to 2PEA, whereas the aryl alkenes are converted to their corresponding alkylbenzenes. Interestingly, the rate of hydrogenation of STOX is much slower than the rapid hydrogenation of the aryl alkenes. The kinetic model for the reaction is proposed based on the experimental data, and the associated parameters are estimated by nonlinear regression. The apparent activation energy for STOX hydrogenation over the range of operating conditions is calculated as 47.65 kJ mol–1. The estimated kinetic parameters are apposite for the technocommercial feasibility study and subsequent scaling-up issues of the aralkyl hydroperoxide-based novel scheme of 2PEA production. Based on the observations, conceptual flowsheets for 2PEA manufacturing using cumene hydroperoxide and ethylbenzene hydroperoxide are also proposed.

One‐pot synthesis of phenylacetaldehyde from styrene via metal oxide catalysed oxidation in presence of cumene hydroperoxide

“…Industrial applicability of CHP-induced catalytic styrene oxidation for selective production of STOX has been elucidated in previous works. [1][2][3] In the perfumery market, 50% (w/w) PhA in 2-phenylethanol (2PEA) is generally sold as the fragrant building block. 36 Our previ- | 179…”

“…In the perfumery market, 50% (w/w) PhA in 2‐phenylethanol (2PEA) is generally sold as the fragrant building block 36 . Our previous work 2 have revealed that under considerably mild operating conditions (~333 K, <15 atm) a mixture of STOX, PhA and AcP can be hydrogenized in such a way so that the keto compounds (PhA and AcP) remain as they were while STOX almost stoichiometrically get converted into 2PEA in presence of commercial Pd/C catalyst. Under similar operating conditions, hydrogenation of CHP yields ACA quasi‐stoichiometrically, along with traces of AMS 37,38 .…”

“…To further intensify the whole scheme, a reactor ( R0 ) can be put at the upstream to R1 wherein aerobic oxidation of cumene can take place for the generation of CHP. Out of three reactions shown in Figure 9, aerobic oxidation of cumene for selective production of CHP and catalytic hydrogenation of CHP and STOX are industrially practiced process 2 . Separation schemes SS0 is used to recycle unconverted cumene and thereby concentrate (upto ~50% w/w) the CHP rich stream going into R1 to match the feed optimum condition required for catalytic oxidation.…”

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Heterogeneously catalysed styrene oxidation can produce valorized styrene derivatives (VSD) like styrene oxide (STOX), benzaldehyde (BzA), phenyl acetaldehyde (PhA), benzoic acid (BzAc), acetophenone (AcP) and phenylacetic acid (PhAc). [1][2][3] Figure 1 illustrates possible product profile of styrene oxidation along with the applications of the individual VSD and its approximated current market price. 4,5 It is also evident that the there exists a vivid spectrum of application of these VSDs the cost of which are folds higher than that of styrene.

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“…Figure 9, aerobic oxidation of cumene for selective production of CHP and catalytic hydrogenation of CHP and STOX are industrially practiced process 2. Separation schemes SS0 is used to recycle unconverted cumene and thereby concentrate (upto ~50% w/w) the CHP rich stream going into R1 to match the feed optimum condition required for catalytic oxidation.…”