Butadiene Tail Gas Hydrogenation with Uniform Hydrogen Distribution
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Solution Overview
Problem
Existing methods for selective hydrogenation of butadiene extraction tail gas face challenges in achieving uniform hydrogen distribution, leading to reduced selectivity and catalyst degradation due to uneven reactor temperature and side reactions, particularly in industrial-scale operations.
Innovation Solution
A method and apparatus that optimize hydrogen gas allocation and feeding modes, using dissolution and partial introduction to ensure even distribution, combined with catalysts like palladium-containing and palladium-free catalysts, and a two-stage hydrogenation process to improve selectivity and extend catalyst life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hydrogen gas is directly fed at the reactor inlet, then the hydrogenation reaction can proceed, but the distribution of hydrogen is uneven affecting selectivity of the catalyst
Solution Approach 1:
The patent divides the hydrogen feeding process into multiple stages: pre-dissolution in liquid C4 stream, then controlled introduction into the reactor. This segmentation ensures uniform distribution of hydrogen throughout the reaction zone, preventing localized excess or deficiency that would compromise catalyst selectivity.
Solution Approach 2:
The patent uses liquid C4 stream as an intermediary medium to dissolve and transport hydrogen gas to the reactor. This intermediary approach allows for more controlled and uniform hydrogen distribution compared to direct gas-phase feeding, improving both productivity and manufacturing precision.
2Reliability
If hydrogen gas is excess to ensure complete alkyne hydrogenation, then alkynes can be completely removed, but diolefins and butenes undergo further hydrogenation decreasing selectivity
Solution Approach 1:
The patent applies partial action by providing just enough hydrogen for complete alkyne hydrogenation through controlled feeding. The hydrogen is introduced gradually and uniformly, ensuring complete removal of alkynes while preventing excess hydrogen from causing unwanted hydrogenation of diolefins and butenes, thus maintaining high selectivity.
Solution Approach 2:
The patent implements feedback control by monitoring the hydrogenation reaction progress and adjusting hydrogen feeding rate accordingly. This ensures that hydrogen is supplied at the optimal rate to achieve complete alkyne removal without exceeding the amount needed, thereby preventing loss of selectivity.
3Ease of operation
If hydrogen gas is limited to dissolve in C4 components, then mass transfer occurs through liquid membrane, but hydrogenation reaction is limited by insufficient hydrogen gas on catalyst surface
Solution Approach 1:
The patent applies preliminary action by pre-dissolving hydrogen gas in the liquid C4 stream before it enters the reactor. This pre-saturation ensures that when the liquid reaches the catalyst surface, sufficient hydrogen is already available, eliminating the limitation of hydrogen supply and maintaining high reaction productivity.
Solution Approach 2:
The patent changes the physical state parameters by controlling the dissolution of hydrogen gas in the liquid C4 stream at specific temperatures and pressures. By optimizing these parameters, the patent achieves both adequate hydrogen solubility for mass transfer and sufficient hydrogen availability on the catalyst surface for high reaction rate.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances the selectivity of the hydrogenation reaction, reduces side reactions, and prolongs catalyst life by ensuring uniform hydrogen distribution and optimizing raw material dilution, thereby improving product yield and reducing impurity impacts.
Implementation Method 1
hydrogen gas is limited to dissolve in C4 components, and then reacts with reactants such as alkynes and dienes in C4 components by mass transfer through the liquid membrane to the surface of catalyst
Implementation Method 2
reacts with reactants such as alkynes and dienes in C4 components by mass transfer through the liquid membrane to the surface of catalyst
Implementation Method 3
the inventors have found that hydrogenation reaction is limited by hydrogen gas, that is, on the surface of a catalyst, where hydrogen gas is insufficient, the alkynes cannot undergo the hydrogenation reaction
Implementation Method 4
separated through a stabilization tower to recover a C4 hydrogenation product
Data Source
Figure 1~3
AI summary
The present invention belongs to the field of petrochemical industry, and discloses a method for selective hydrogenation of butadiene extraction tail gas and a selective hydrogenation apparatus thereof. The method for selective hydrogenation of butadiene extraction tail gas comprises: (1) an alkyne-containing tail gas from a butadiene extraction unit is fed into a raw material tank, optionally impurities entrained in the alkyne-containing tail gas are removed before being fed into the raw material tank; (2) a C4 raw material in the raw material tank is pressurized by a feed pump to a pressure required for reaction, then merged with a circulated C4 stream from a first-stage reactor outlet buffer tank and fed into a first-stage mixer, wherein it is mixed with hydrogen gas, and fed into the first-stage reactor to undergo a first-stage hydrogenation reaction, and a first-stage reaction stream obtained by the reaction is fed into the first-stage reactor outlet buffer tank; the hydrogen gas required for the reaction in the first-stage reactor is fed through a first feeding mode or a second feeding mode: the first feeding mode comprises: all the hydrogen gas required for the reaction is fed through the first-stage reactor outlet buffer tank, and then fed into the first-stage reactor through a first route at an outlet of the first-stage reactor outlet buffer tank; the second feeding mode comprises: a part of the hydrogen gas required for the reaction is fed through the first-stage reactor outlet buffer tank, and then fed into the first-stage reactor through the first route at an outlet of the first-stage reactor outlet buffer tank; and the other part of the hydrogen gas is fed through the first-stage mixer, and then fed into the first-stage reactor; (3) there is no gas-phase discharge from the first-stage reactor outlet buffer tank, and a liquid-phase product is divided into at least two streams, the first stream is returned to the first-stage reactor as the circulated C4 stream, and the second stream is used as a feed to a stabilization tower or subjected to further hydrotreatment prior to being fed into the stabilization tower; (4) a C4 hydrogenation product is recovered after separation in the stabilization tower.