Using the zeolite ZSM-5, new technology has been developed for catalytically oligomerizing light olefins (C, to C, ) to gasoline (C, to C,,,) and diesel (C,o to C2J range product. This reaction produces product constrained by both the shape selectivity of the zeolite catalyst and the thermodynamics governing the oligomerization reaction.
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SCOPEMany refinery and synthetic fuel processes produce effect shape selectivity has on product chemistry and large amounts of light C,/C, olefins which can then b e to determine what effects thermodynamics have on catalytically oligomerized to gasoline-or diesel-range constraining molecular weight. The relationship of products. A new development in this area is the use of these effects to commercial oligomerization technolshape-selective zeolite catalysts. This reaction has ogy is also discussed. been studied over ZSM-5 catalyst to determine what
CONCLUSIONS AND SIGNIFICANCEThe reaction of light olefins over ZSM-5 catalyst was product molecular weight is shown up to -625 K to be found to proceed sequentially by reaction to discrete governed by the kinetics of the reaction, dependent on oligomers, followed by cracking and copolymerization. temperature, pressure, and space velocity. Above The shape of the product molecules is governed pri--625 K equilibrium constraints become important and marily by the pore structure of zeolite catalyst. The limit the molecular weight of the product.
ExperimentalIn general, all experiments were conducted in high-pressure pilot-plant reactors capable of operating up to approximately 18,000 kPa. The reactors used were enclosed in either a three-or four-zone furnace with an isothermal zone, holding from 10 to 100 cm' of catalyst. Reactor pressure was maintained by a gas phase backpressure control valve, while liquid depressurization was by liquid level control on a high-pressure phase separator. Product analysis was by both gas chromatography and mass spectrometry.
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