Batch process and system for the production of olefins (Lummus Technology)

PATENT
Batch process and system for the production of olefins (Lummus Technology)
PCT number PCT/US2009/002076
Publication date Jun 3, 2014
Also published as CA2718763A1
Inventors Robert J. Gartside, Shaun M. McGovern, Thulasidas Chellppannair
Original Assignee Lummus Technology Inc.
Abstract
Described herein is a process for producing an alpha olefin by obtaining a feed stream of internal olefins having a first carbon number and alpha olefins having a first carbon number. The olefins are isomerized to increase the quantity of the alpha olefins. The olefins are then fractionated, subjecting the overhead material to catalytic metathesis to produce a mixed olefin effluent of internal olefins having a second carbon number and other hydrocarbons. The first isomerization reactor and fractionator are prepared to receive the olefins having a second carbon number, where the internal olefin intermediate is isomerized in the prepared first isomerization reactor. The second isomerization effluent is fractionated in the prepared first fractionator to separate the alpha olefins having the second carbon number from the internal olefins having the second carbon number. A corresponding system is also described, along with a heat pump that may be incorporated into the process.
BACKGROUND
The disclosed embodiments generally relate to processes and systems for producing alpha olefins and more particularly to a batch process for the production of alpha olefins.
A conventional process for production of comonomer grade hexene-1 from C4 raffinate feed streams is a continuous process that has three stages. First butene-1 is separated from the feed stream in a C4 fractionator. The butene-2 in the fractionator bottoms stream is isomerized to butene-1 and recycled to the fractionator. Second, the butene-1 is sent to an autometathesis reactor to form ethylene and hexene-3. The reactor effluent is sent to a depentanizer to separate hexenes. The products are lights that go overhead, the hexene-3 is a liquid bottoms product, and the C4/C5 products are recycled. Third, the hexene-3 feed is isomerized and the hexene-1 product is separated in a C6 fractionator.
U.S. Pat. No. 6,727,396 (Gartside, April 2004) describes a continuous process for production of hexene-1, combining the isomerization and metathesis steps. Typical metathesis reactions are described in U.S. Pat. No. 3,595,920 (Ellis et al, July 1971). U.S. Pat. No. 4,709,115 (Jung et al, November, 1987) discusses improving the selectivity and conversion of butene-1 and butene-2 to hexene-3 by using catalytic distillation. The removal of the lighter components pushes the reaction equilibrium toward the heavy products. U.S. Pat. No. 5,057,638 (Sweeney, October 1991) discusses a method for production of hexene-1 from butene-1 in which the butene-1 is metathesized to hexene-3. Subsequently, a hydration/dehydration procedure is applied to produce a mixture of n-hexenes containing hexene-1.
Various other processes are known for the processing of C4 olefins. U.S. Pat. No. 6,875,901 (Gartside et al, April 2005) describes olefin isomerization technology used for production of terminal olefins. The process is applied to the production of butene-1 from butene-2. U.S. Pat. No. 6,777,582 (Gartside et al, August 2004), describes butene-1 autometathesis technology, including differences from the conventional metathesis reaction of butene-2 and ethylene to produce propylene.
Closed-loop heat pumps are used in various processes. U.S. Pat. No. 6,589,395 describes a process in which a closed-loop heat pump is included on a general distillation tower. This document describes the use of a heat source and heat sink that can be substituted for the heat pump should the compressor fail. U.S. Pat. No. 5,386,075 (Keil et al, January 1995) and U.S. Pat. No. 4,615,769 (Horigome et al, October 1986) discuss the use of an open-loop heat pump in an ethylbenzene/styrene distillation.
It would be useful to develop a process for producing alpha olefins that has improved efficiency when operated on a small scale.
SUMMARY
One embodiment is a process for producing an alpha olefin comprising obtaining a feed stream comprising an internal olefin having a first carbon number and an alpha olefin having a first carbon number, isomerizing the feed stream in a first isomerization reactor to increase the quantity of the alpha olefin having the first carbon number, forming a first isomerization effluent, fractionating the first isomerization effluent in a first fractionator to obtain a bottoms stream comprising the internal olefin having the first carbon number and an overhead stream comprising the alpha olefin having the first carbon number, subjecting the overhead stream to catalytic metathesis in a metathesis reactor under conditions and in the presence of a first metathesis catalyst to produce a mixed olefin effluent comprising an internal olefin having a second carbon number and other hydrocarbons, fractionating the mixed olefin effluent in a second fractionator to remove at least a portion of the other hydrocarbons and obtain an internal olefin intermediate, preparing the first isomerization reactor to receive the internal olefin intermediate, isomerizing the internal olefin intermediate in the prepared first isomerization reactor to form a second isomerization effluent comprising an increased quantity of alpha olefins having the second carbon number, preparing the first fractionator to receive the second isomerization effluent, and fractionating the second isomerization effluent in the prepared first fractionator to separate the alpha olefin having the second carbon number from the internal olefin having the second carbon number. In some embodiments, a portion of the butene-1 is removed from the first fractionator as butene-1 product.
Another embodiment is a process for producing hexene-1 comprising obtaining a C4 feed containing butene-1 and butene-2, isomerizing butene-2 to butene-1 in a first isomerization reactor, forming a first isomerization reactor effluent, fractionating the first isomerization reactor effluent in a first fractionator to form an overhead stream comprising butene-1 and a bottoms stream comprising butene-2, subjecting at least a portion of the overhead product to catalytic metathesis in a first metathesis reactor under conditions and in the presence of a first metathesis catalyst to produce a mixed olefin effluent comprising ethylene and hexene-3, fractionating the mixed olefin effluent in a second fractionator to form a hexene stream comprising hexene-3 and an overhead product stream comprising ethylene, preparing the first isomerization reactor to receive the hexene stream, isomerizing the hexene stream to form a second isomerization effluent comprising hexene-1 and hexene-2 and the remaining hexene-3, preparing the first fractionator to receive the second isomerization effluent, and fractionating the second isomerization effluent in the prepared fractionator to obtain a hexene-1 stream.
Yet another embodiment is a system for producing an alpha olefin, comprising a first isomerization reactor configured to isomerize a first batch of an olefin having a first carbon number to form a first isomerization reactor effluent and subsequently process a second batch of an olefin having a second carbon number to form a second isomerization reactor effluent, a metathesis reactor positioned downstream from the first isomerization reactor, the metathesis reactor being configured to disproportionate the first isomerization reactor effluent to form a metathesis reaction product, a first fractionator positioned downstream from the isomerization reactor and being configured to separately fractionate the first and second isomerization reactor effluents, a second fractionator positioned downstream from the metathesis reactor to remove light hydrocarbons from the metathesis reaction product, a storage tank disposed downstream from the first or second fractionator, and a storage tank outlet line connecting the storage tank to an inlet of the first isomerization reactor and/or to the inlet of the metathesis reactor.
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