Method for selective hydrogenation and separation for pyrolysis gas

Abstract

The invention discloses a method for selective hydrogenation and separation for pyrolysis gas, and belongs to the technical field of selective hydrogenation of unsaturated hydrocarbon. In order to solve the problems existing in the prior art that the liquid flow of a mixed phase hydrogenation reactor contains a large number of C3 and C4 components, cannot fully play a role in flushing in the reactor and repeatedly enters a front-end deethanization tower to cause high energy consumption, large equipment size, high operation cost and disadvantage to improve C3 selectivity and the like, the invention provides the method for selective hydrogenation for C2-C10 high unsaturated hydrocarbon (alkyne and diolefin) by using material flow at the bottom of the deethanization tower as liquid flow at the upstream side of the front-end deethanization tower of an olefin production device. The method enables the liquid flow of the mixed phase hydrogenation reactor to fully come into play, reduces the charging amount entering the front-end deethanization tower and energy consumption and equipment investment, and is favorable for improving the selectivity.

Description

technical field [0001] The present invention relates to a method for the selective hydrogenation of alkynes and dienes, more specifically, the present invention relates to a method for the selective hydrogenation of alkynes and dienes in cracked gas from an olefin production unit. Background technique [0002] Unless otherwise specified, the highly unsaturated hydrocarbons mentioned in the present invention refer to hydrocarbons containing triple bonds or two double bonds. [0003] Processes for the conversion of hydrocarbons at high temperatures, such as steam thermal cracking or catalytic cracking, can provide unsaturated hydrocarbons, such as ethylene, acetylene, propylene, butadiene, butene; saturated alkanes, such as ethane, propane, butane; There are also light components such as methane, hydrogen and carbon monoxide and hydrocarbons with a boiling point in the gasoline range. The gas-phase monoolefins with more than two carbon atoms obtained by these processes also c...

AI Technical Summary

Problems solved by technology

The shortcoming of this patent is: 1, because this patent application places the mixed-phase hydrogenation reactor on the downstream side of the front depropanizer, what enters the mixed-phase hydrogenation reactor is cooled and partially condensed rich in C 3 and lighter component streams, so this patented technology can only hydrogenate low-carbon alkynes in the mixed-phase hydrogenation reactor, and cannot hydrogenate high-carbon unsaturated hydrocarbons such as butyne and butadiene. Therefore, the amount of hydrogen consumed is limited, and a large amount of remaining hydrogen enters the cryogenic part of the cracked gas, resulting in high energy consumption

2. If the remaining high-carbon alkynes and dienes enter the polymerization process, the activity of the polymerization catalyst will be reduced, and the physical properties of the polymer will be deteriorated

3. Since the patent application does not carry out hydrotreating on the stream entering the front depropanizer, the alkynes and diolefins in the stream are likely to cause coking in the tower and increase energy consumption

4. Due to the use of this patent application technology, a series of additional equipment is required to separate the C 3 and C 3 The above components are additionally treated to remove alkynes and diolefins, thereby increasing equipment investment and production energy consumption as a whole

In the mixed-phase hydrogenation reactor, the carbon three components are in the gas phase, and the carbon four components are mostly in the gas phase. They cannot fully play the role of flushing the catalyst bed, and at the same time they repeatedly enter the front depropanizer or the front ethane tower, Undoubtedly this increases the energy consumption, equipment size and operating cost of the pre-depropanizer or pre-ethanizer

In the case of using the front ethane column, the liquid phase stream recycled back to the mixed-phase hydrogenation reactor contains propylene, which is very detrimental to the selectivity of the mixed-phase hydrogenation, resulting in loss of propylene

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