Propylene epoxidation with EBHP

Experimental results were plotted according to Eq. (14.4), and straight lines passing through zero fit the experimental points quite well, as illustrated in Eig. 14.9. Therefore, propylene epoxidation with EBHP can be treated as pseudo-first order with respect to EBHP concentration (Ca)- The rate equation can therefore be written as... 

FIGURE 14.9 Test of pseudo-first-order kinetic model for propylene epoxidation with ethylbenzene hydroperoxide (EBHP) over Ti/MCM-41. 

Molybdenum complexes are the most effective catalysts known for the selective epoxidation of olefins with alkyl hydroperoxides (210-212). Commonly known is the Arco or Halcon process for the large-scale manufacture of propylene oxide from propylene. This process uses t-BuOOH or ethyl benzene hydroperoxide (EBHP) as an oxidant and Mo(CO)6, for example, as a source of Mo. The Mo(CO)6 acts as a catalyst precursor, which is converted into a soluble active form by complexation with diols (3). Chemists have designed several supported versions of the catalysts for this epoxidation chemistry. A clear classification can be made on the basis of the nature of the support. 

The subsequent step, the epoxidation of propylene by EBHP, is carried out in the liquid phase over a proprietary heterogeneous catalyst, to produce crude PO and MPC. The feed to the reactors consists of make-up and recycle propylene and EBHP in EB. The reaction train consists of a number of adiabatic fixed bed reactors with interstage cooling. Deactivated catalyst is replaced, incinerated to remove residual hydrocarbons, and dispersed in a landfill. 

Chemical vapor deposition (CVD) using TiC was used to prepare Ti/Si02, Ti/MCM-41, and Ti/MCM-48 catalysts. These catalysts were characterized by inductively coupled plasma-atomic emission spectroscopy (ICP-AES), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, nitrogen adsorption, and were used to catalyze the epoxidation of propylene to propylene oxide (PO) with in situ prepared ethylbenzene hydroperoxide (EBHP). CVD time and CVD temperature affected the catalyst performance significantly. The optimum temperature range was 800-900 °C, and the optimum deposition time was 2.5-3 h. The maximum PO yields obtained in a batch reactor were 87.2, 94.3, and 88.8% for Ti/Si02, Ti/ MCM-41, and Ti/MCM-48, respectively. Ti/MCM-41 had higher titanium... 

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