PO-only Routes Several Approaches for Sustainable Alternatives

In the hydroperoxidation route, either a-methylbenzyl alcohol or t-butanol are the reaction coproducts both molecules are dehydrated to yield either a styrene monomer (2.5 ton per ton ofPO) or isobutene (2.1 ton per ton of PO), respectively. t-Butanol may also be the direct feed for MTBE production. Balancing the markets for PO and the coproducts has proven difficult with these routes, thus leading to a volatile economic performance over time. Furthermore, the hydroperoxidation routes require relatively large capital investments. Existing hydroperoxidation plants continue to operate and are incrementally improved however, future investments in these technologies will decline. 

PO-only Routes Several Approaches for Sustainable Alternatives 

Alternative routes that do not produce sizeable quantities of coproducts and that do not use chlorine-based chemistry have already been, or will be, implemented at the commercial level. In April 2003, Sumitomo Chemical commercialized the first PO-only plant in Japan, which produces PO by oxidation of propene with cumyl hydroperoxide (the latter being obtained by hydroperoxidation of cumene) without a significant formation of coproducts. Nowadays, the plant located at the Chiba factory, a joint venture between Nihon Oxirane Co and Lyondell, produces around 200 000 tons of PO/year. A second plant was started in May 2009 in Saudi Arabia, a joint project with Saudi Arabian Oil Co. 

This process is a variant of the PO/SM process that uses cumene instead of ethylbenzene and recycles the coproduct cumyl alcohol via dehydration to a-methyl-styrene and hydrogenation back to cumene (the latter two steps can be combined into a single hydrogenolysis step). Cumene hydroperoxidation technology is well-known for its use in phenol and acetone production. 

New approaches under investigation include the direct oxidation of propene with molecular oxygen, eventually in the presence ofhydrogen  

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PO-only Routes Several Approaches for Sustainable Alternatives 325 Table 6.1 S umma7 of newly developing PO production processes. 

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