Improved olefin plant recovery system employing a combination of catalytic distillation and fixed bed catalytic steps

A catalytic distillation tower, fixed bed reactor technology, applied in cracking gas effluent, olefin production, catalytic distillation field, can solve difficult industrial scale, limited methods of catalyst deactivation, hydrogen flow changes of alkynes and dienes, etc. question

Inactive Publication Date: 2007-05-09
ABB LUMMUS GLOBAL INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Second, it is difficult to maintain the process during CO flow (which affects catalyst activity) and/or changes in the diene/alkyne concentration in the feed and to implement it on an industrial scale
Third, there are very limited options for dealing with eventual catalyst deactivation
If this change occurs in a one-step process, it can lead to a loss of de-alkyne efficiency and su

Method used

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  • Improved olefin plant recovery system employing a combination of catalytic distillation and fixed bed catalytic steps
  • Improved olefin plant recovery system employing a combination of catalytic distillation and fixed bed catalytic steps
  • Improved olefin plant recovery system employing a combination of catalytic distillation and fixed bed catalytic steps

Examples

Experimental program
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Effect test

Embodiment 1

[0064] This example represents the prior art outlined in prior US Patent No. 5,679,241 (Fig. 1), based on a one-step catalytic distillation column operated at a reflux ratio of 4.4. Typical pre-alkyne hydrogenation catalysts contain less than 2000 ppm palladium, operated at a pressure of 195 psig and an average catalyst temperature of 230°F, C 2 Alkyne conversion reached 84% with 0% ethylene loss / gain. At the reactor outlet C 2Alkynes are 370 ppm and dienes and alkynes together are 19070 ppm. The overall alkyne / diene conversion was 79.5%. This example represents a single column run with no ethylene loss. It can be seen that: C 2 Large excess of alkynes. This would result in an off-spec ethylene product.

Embodiment 2

[0066] This example also represents the prior art, based on the single catalytic distillation column of Example 1 (using a higher catalyst temperature and a slightly lower reflux ratio of 4.1). The hydrogenation intensity of a single column can be increased to achieve low C 2 Alkyne levels. This can be accomplished by increasing the temperature or increasing the activity of the catalyst. Higher temperature operation will reduce the alkyne content, so as to obtain qualified ethylene products. Compared to Example 1, the conversion of all dienes and alkynes is higher in this case, however there is also a loss of 0.6% of ethylene. At the reactor outlet, C 2 Alkynes are 240 ppm and dienes and alkynes together are 12340 ppm. The overall alkyne / diene conversion was 86.7%. It can be seen that: C 2 Increased conversion of alkynes leads to increased loss of ethylene. This is uneconomical. In addition, ethylene products still cannot meet the specification limit of 1-2ppm.

Embodiment 3

[0068] This example represents the prior art and is based on the single catalytic distillation column of Example 1 (higher carbon monoxide level in the feed). Carbon monoxide is a catalyst poison, so the conversion of dienes and alkynes is significantly reduced. When the CO level in the feed is 0.1 mole %, the C in the product 2 460 ppm for alkynes and 33860 ppm for dienes and alkynes combined. The CO-induced reduction in catalyst activity resulted in loss of catalyst yield (0.12–0.09 lbmol / hr-ft catalyst structure) and lower overall alkyne / diene conversion (63.6% versus 79.5% in the baseline case).

[0069] The measure taken against the reduction in activity is to increase the temperature of the catalyst in the catalytic distillation column. This would require a pressure increase beyond what the operating unit would actually operate at. The options to compensate for the increase in CO are therefore limited with respect to the prior art.

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PUM

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Abstract

Presented is an improvement to a previous invention involving the catalytic hydrogenation of the C2 to C5 and heavier acetylenes and dienes in a thermally cracked feed stream without significantly hydrogenating the C2 and C3 olefins. The improvement involves the use of a fixed bed hydrogenation reactor system in combination with a modified version of the catalytic distillation unit used in the prior art. The modification to the catalytic distillation unit involves improvement of the liquid recycle scheme. The fixed bed reactors combined with the modified catalytic distillation allows for 100% conversion of acetylene and helps to maintain high conversion of the other dienes and acetylenes with no ethylene or propylene conversion under a variety of conditions. These condition variations include but are not limited to the feed diene and acetylene composition, the mol% carbon monoxide in the feed, and catalyst deactivation. With catalytic distillation alone, complete conversion of the acetylene as stated above can not be achieved without ethylene loss, nor would satisfactory operation and control be possible under the variety of conditions experienced during a commercial operation.

Description

Background of the invention [0001] The present invention relates to a process for the production of olefins, and in particular to the treatment of cracking furnace effluents for more efficient product recovery and by-product treatment. [0002] During the pyrolysis of various feedstocks to produce ethylene and propylene, several by-products and unsaturated dienes and alkynes are produced. The pure effluent from the pyrolysis furnace (commonly referred to as cracked gas) requires processing to separate by-products from the original olefinic product and to remove dienes and alkynes. Removal of C from cracked gas 2 And heavy diene and alkyne species are carried out by a combination of distillation separation and hydrogenation reaction. For alkynes in particular, separation alone would result in excessive loss of ethylene product due to the very similar relative volatilities of acetylene and ethylene. Currently, distillation and hydrogenation are carried out in several separate...

Claims

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Application Information

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IPC IPC(8): C10G7/00C10G7/12C10G45/32C10G45/36C10G65/06C10G70/02C10G45/40C10G49/00
CPCC10G49/002C10G45/36C10G45/40C10G65/06
Inventor R·J·加特赛德R·I·海恩斯T·斯库尔利斯C·苏姆纳
Owner ABB LUMMUS GLOBAL INC
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