Shell epoxide production

There are several alternatives to the polluting chlorohydrin route. One is the styrene monomer propene oxide (SMPO) process, used by Shell and Lyondell (Figure 1.6a) [14]. It is less polluting, but couples the epoxide production to that of styrene, a huge-volume product. Thus, this route depends heavily on the styrene market price. Another alternative, the ARCO/Oxirane process, uses a molybdenum... 

Olefin epoxidation is an important industrial domain. The general approach of SOMC in this large area was to understand better the elementary steps of this reaction catalyzed by silica-supported titanium complexes, to identify precisely reaction intermediates and to explain catalyst deachvahon and titanium lixiviation that take place in the industrial Shell SMPO (styrene monomer propylene oxide) process [73]. (=SiO) Ti(OCap)4 (OCap=OR, OSiRs, OR R = hydrocarbyl) supported on MCM-41 have been evaluated as catalysts for 1-octene epoxidation by tert-butyl hydroperoxide (TBHP). Initial activity, selechvity and chemical evolution have been followed. In all cases the major product is 1,2-epoxyoctane, the diol corresponding to hydrolysis never being detected. 

The activity of titanium based catalysts for the oxidation of organic compounds is well known. Wulff et al. in 1971 [1] patented for Shell Oil a process for the selective epoxidation of propylene with hydroperoxides like ethylbenzene hydroperoxide (EBH) or tertiary-butyl hydroperoxide (TBH) with the use of a catalyst made of Ti02 deposited on high surface area Si02. A Shell Oil plant for the production of 130,000 tons/y of propylene oxide at Moerdijk, Holland, is based on this technology. 

I to 5. 0 mol per mol of hydroperoxide. The presence of sodium naphtheoate, by prevenling side reaction, helps to reduce the excess propylene required (from lO/l to 2/1 in moles). In the Shell technology, epoxidation is catalyzed by metallic oxides (molybdenum, vanadium, titanium, etc.) supported on sih cau The liighiy exothe c reaction takes place around 100 to 130 at 3.5.10 Pa absolute. Hydroperoxide conver> sion is very hi (> 97 per cent). Propylene oxide molar selectivity exceeds 70 per cent and that of the styrene precursors 93 per cent As for propylene, its once-through conversion is about 15 per cent, for a oxide molar selectivity greater than 90 per cent, and the main by-products are dimers and heavier hydrocarbons. 

Early attempts to epoxidize simple a,)8-unsaturated aldehydes with hydrogen peroxide in the presence of alkali alforded only acidic products. Payne (Shell Development Co.) found, however, that highly alkali-sensitive aldehydes such as acrolein and methacrolein can be epoxidized successfully by controlling the pH to 8-8.5. Thus acrolein is added to a dilute solution of hydrogen peroxide maintained... 

The results of the oxidation of C2—C5 olefins over copper(i) oxide, silver, and gold catalysts are summarized in Table 1. We have excluded data from studies where additives have been deliberately included in the catalyst, or process gas stream, in order to improve the performance. Where several studies have been carried out we have quoted the best selectively obtained. While copper(i) oxide and gold give unsaturated aldehydes as the major product of partial oxidation, silver gives the epoxide. Copperfii) oxide is not a selective catalyst for olefin oxidation. The difference in behaviour between copper(i) and copper(ii) oxides is in line with the general trend in oxide catalysis. The selective catalysts tend to be those with either a full or an empty tZ-shell, i.e. the oxides of Groups IVA, VA, and VIA, and IB, IIB, IVB, VB, and VIB. ... 

Shell subsequently developed a heterogeneous, silica-supported titania catalyst [11,12] which forms the basis of the commercial process for the epoxidation of propylene with ethylbenzene hydroperoxide. The co-product alcohol is dehydrated, in a separate step, to styrene. Ti(IV)Si02 was the first truly heterogeneous epoxidation catalyst useful for continuous operation in the liquid phase. 

The bottoms product from the isobutane separation is a mixture of tertiary butyl alcohol and tertiary butyl hydroperoxide. This mixture enters the epoxidation reactor where it reacts with propylene to form propylene oxide. The catalyst is either molybdenum based as in the process developed by Halcon and practiced by ARCO or TiOj on silica in the Shell process. 

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