Methanol to olefin (ethylene and propylene) is one of the most important reactions connecting coal based products and petrochemicals, which provides a chance to produce basic chemicals for non-oil resources, such as coal or natural gas.
The reaction takes place in an FCC-type, dense-phase, circulating, fluidized-bed reaction system with continuous catalyst regeneration. The catalyst is a molecular sieve acid catalyst and its high selectivity to light olefins is the result of both the activity of the acid sites and the favorable pore diameter of the molecular sieve framework structure. Methanol and water are preheated and fed to the fluidized-bed reactor and exposed to catalyst in the reaction zone at temperatures between 400 and 550°C.Part of the fluidized catalyst from the reaction zone continuously circulates in a closed loop between the reaction system and the catalyst regeneration system, where coke is removed from the catalyst. The reacted gas is cooled by interchange with the feed gas and by direct-contact with circulating water. Water formed during the reaction is condensed. Both reaction and catalyst regeneration are strongly exothermic. Heat integration is applied to improve energy efficiency.
63 patents were authorized. Since 2010, the world’s first methanol-based coal-to-olefin industrial plant with the production capacity of 600 kt olefin annually has started its successful operation until now. The technical specifications and trial scale of the technology proved it the most advanced methanol to olefin technology around the world.
So far 19 DMTO units with a total light olefin production capacity of 10.59 Mt/a have been licensed, and totally 7 plants have been successfully started up and on operation.
The success of DMTO technology is a cornerstone for China to produce olefins via a non-petrochemical route using its own DMTO technologies and facilities. It is also a big step in China’s Strategy for coal replace oil.