Selective decomposition of cumene hydroperoxide into phenol and acetone over nanocrystalline ZSM-5

Abstract

Phenol is an industrially important chemical, generally produced via sulphuric acid catalysed decomposition of cumene hydroperoxide (CHP). The effluent containing the acid used as catalyst has to be neutralised and extracted to avoid corrosion and environmental problems. In the current work, a simple process was developed based on the use of nanocrystalline ZSM-5 (Si/Al = 100) catalyst. The catalyst was characterised by XRD, SEM, TEM, DLS and FT-IR analyses. The activity of this catalyst was tested for the liquid-phase decomposition of cumene hydroperoxide. The effects of various parameters such as, catalyst weight, catalyst particle size, concentration of CHP, reaction temperature and reusability of catalyst were studied. It was observed that the nanocrystalline ZSM-5 with smaller particle size showed superior activity. In addition, these catalysts have excellent reusability and can be used instead of sulphuric acid for selective decomposition of CHP into phenol and acetone with 100% conversion.

Solid Acid Catalysts for the Hock Cleavage of Hydroperoxides

“…Zeolites are shape-selective, often improving the processes yield and selectivity, and consequentially products quality. For the cleavage of CHP in the cumene process, several types of zeolites have been tested, including X-, USY-, Beta-, and ZSM-5type zeolites [51,[60][61][62][63][64][65][66]. Zeolites are mostly used in a fixed bed reactor and the reaction parameters strongly depend on the used zeolite.…”

“…The selectivity is only slightly inferior to ZSM-5 and Beta zeolites. KUMAR showed that lowering the particle size of ZSM-5 crystals from 90 nm to nanocrystals with a particle size of 18.3 nm results in a rise in CHP conversion from 60.1% to 94% [66] due to lower diffusion restrictions and therefore an enhanced accessibility to the acid sites. Besides good accessibility of the catalytic active sites of the catalyst, the conversion of CHP strongly depends on the number and strength of Brønsted acid sites of the zeolites [51,65].…”

“…Over HUSY with Si/Al ratios of 15-40 CHP converts up to 100% with good selectivity (0.1% w/w HUSY, 60 • C, 20 min reaction time). The high hydrophilicity of the HUSY zeolite require to be activated at 500 • C. That pre-activation diminishes poisoning by water, preventing loss of activity over several runs [66,[72][73][74].…”

Zeolite-Based Catalysis for Phenol Production

“…It could be argued that the morphology of the catalysts plays an important role, considering the good performances reported for nanocrystalline ZSM-5. 126 The narrow pore size of ZSM-5 imposes diffusion limitations on CHP and, therefore, it can be hypothesized that samples with a high external surface area can favor the reaction thanks to the greater quantity of acid sites accessible to the reagents.…”

“…The poor catalytic activity of ZSM-5 evidenced in this work is in contrast with the results reported by Sasidharan and Kumar and the lack of characterization data in the two papers does not help the understanding of the different behavior of the catalysts employed. It could be argued that the morphology of the catalysts plays an important role, considering the good performances reported for nanocrystalline ZSM-5 . The narrow pore size of ZSM-5 imposes diffusion limitations on CHP and, therefore, it can be hypothesized that samples with a high external surface area can favor the reaction thanks to the greater quantity of acid sites accessible to the reagents.…”