Ethylene from propylene

Disproportionation of Olefins. Disproportionation or the metathesis reaction offers an opportunity to convert surplus olefins to other desirable olefins. Phillips Petroleum and Institut Fransais du Petrc le have pioneered this technology for the dimerization of light olefins. The original metathesis reaction of Phillips Petroleum was intended to convert propylene to 2-butene and ethylene (58). The reverse reaction that converts 2-butene in the presence of excess ethylene to propylene has also been demonstrated (59). A commercial unit with a capacity of about 136,000 t/yr of propylene from ethylene via 2-butene has been in operation in the Gulf Coast since 1985 (60,61). In this process, ethylene is first dimerized to 2-butene foUowed by metathesis to yield propylene. Since this is a two-stage process, 2-butene can be produced from the first stage, if needed. In the dimerization step, about 95% purity of 2-butene is achieved at 90% ethylene conversion. 

Figure 9-3. A flow diagram showing the metathesis process for producing polymer grade propylene from ethylene and 2-butene.

Technologies for the reverse process to produce propylene from ethylene and 2-butenes were also developed.138 139 The Arco process139 dimerizes ethylene to 2-butenes, which, in turn, are metathesized with ethylene to yield propylene. The process is not practiced at present, but it is a potential technology in case of a propylene shortage. 

Applications of the olefin metathesis reversible chemical reaction, discovered by Phillips Petroleum in the 1960s, were also developed in the subsequent years. By this reaction, Arco produces propylene from ethylene and butene-2 Hercules prepares its plastic, Metton, from dicyclopentadiene and Shell synthesizes its C12-C14 SHOP (Shell Higher Olefin Process) alcohols used for detergents. 

Butene-2. Most butene-2 in the United States goes into production of gasoline alkylate. Some butene-2 is used in solvent applications, and it is also the intermediate in the disproportionation process for producing propylene from ethylene. 

Application To produce propylene from ethylene and butenes using Lummus olefin conversion technology (OCT). Other OCT process configurations involve interconversion of light olefins and production of C2— C5 mono-olefins. 

The latest industrial application of metathesis was developed by Phillips who started up a plant in late 1985 at Cbannelview, Texas, on the L ondell Petrochemical Complex with a production capacity of 135,000 t/year of propylene from ethylene. This facility carries out the disproportionation of ethylene and 2-butenes, in the vapor phase, around 300 to 350°C, at about 0.5.10 Pa absolute, with a VHSV of 50 to 200 and a once-througb conversion of about 15 per cent 2-butenes are themselves obtained by the dimerization of ethylene in a homogeneous phase, which may be followed by a hydroisomerization step to convert the 1-butene formed (see Sections 13.3.2. A and B). IFP is also developing a liquid phase process in this area. 

The process layout for production of propylene from ethylene and butene is shown in Figure 10.7. ... 

Olefin metathesis is a useful reaction for the production of propylene from ethylene and butenes using certain transition-metal compound catalysts. The two main equilibrium reactions that take place simultaneously are metathesis and isomerization. Metathesis transforms the carbon-carbon double bond, a functional group that is unreactive toward many reagents that react with many other functional groups. New carbon-carbon double bonds are formed at or near room temperature even in aqueous media from starting materials. Because olefin metathesis is a reversible reaction, propylene can be produced from ethylene and butene-2. Metathesis can be added to steam crackers to enhance the production of propylene by the transformation of ethylene and the cracking of mixed butenes. Fig. 3 shows a schematic flow diagram of a typical metathesis process. Examples of metathesis... 

Rh/alumina propylene from ethylene 50 regenerate every 10 days... 

Another example is synthesis of propylene from ethylene which comprises dimerization of ethylene (on metal sites of Ni-AlSBA-15), isomerization of butene-1 into... 

Fig. 8.15 One-pot synthesis of propylene from ethylene. (From D. Andrei, M. I. Popa, F. Fajula, C. Cammarano, A. A. Khudhair, K. Bouchmella, P. FI. Mutin, V. Flulea, Ethylene to propylene by one-pot catalytic cascade reactions, ACS Catal. 5 (2015) 2774—2777. Copyright 2015 American Chemical Society).

---