Propene process integration

The integration of propene oxide and hydrogen peroxide processes appears, from a short-term perspective, a more realistic approach than in situ generation. It is also favored by the location of both facilities at the same chemical site. Basically, process integration envisages a simplification of H2O2 recovery that can even... 

Since the early 1980s, EniChem has been a pioneer in the development of the process, holding a portfolio of patents [10c,dj. The integration of HP synthesis by means of alkylanthraquinone/alkylanthrahydroquinone (RAQ/RAHQ) cycle technology, with PO production, by means of propene epoxidation with H P, is possible because of the peculiar properties of the TS-1 catalyst (Scheme 6.5). TS-1 can selectively epoxidize propene using diluted HP [12]. A water- methanol mixture is the solvent for the epoxidation the alcohol is necessary to obtain a sufficient reaction rate. Therefore, a cost-saving feature in this process is the fact that the crude H P produced can be used directly in the epoxidation of propene. Moreover, integration of the two processes is also allowed by the easily accomplished separation of propene and PO from the water-methanol mixture. Methanol, after separation and purification, can be recycled to the epoxidation step. 

Conlin and co-workers have also studied the fragmentation of a siletane (silacyclobutane). In this case, both the E- and Z-isomers of 1,1,2,3-tetra-methylsilane 45 were prepared and thermolyzed (Scheme 8).144 Both E-and Z-isomers of 45 led to the same products in slightly different ratios the major products were propene with silene 46, and E- and Z-2-butenes with silene 47. Silene formation was inferred from detection of the disila-cyclobutane products. During these processes, the stereochemical integrity of the compounds was largely preserved. 

Figure 18.3 Integrated process scheme for the production of propene oxide.

Scheme 6.5 RAQ/RAHQ process for the generation of HP, and integration with propene epoxidation.

Figure 6.4 Simplified flow-sheet ofthe integrated insitu HPPO (a) and H PPO (b) processes for propene epoxidation with generation of HP, developed by EniChem.

Figure 6.8 Block diagram of the ARCO integrated process for propene epoxidation with in situ generation of HP [21].

According to another process, ethene and butadiene are economically obtained through a propene metathesis reaction integrated into the cracking and fractionation units of the petroleum plant [15]. Thus, ethene resulting from the disproportionation step enriches the ethene content of the C2 fraction from the cracking unit, whereas butadiene is formed by subsequent dehydrogenation of the butene fraction. 

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