Tail Gas Selective Hydrogenation with Dissolved Hydrogen Feed
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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
1Ease of operation
If hydrogen gas is directly fed at the reactor inlet, then the hydrogenation reaction can proceed, but the distribution of hydrogen gas is uneven due to equipment and pipeline layout, reducing selectivity and causing temperature hotspots
Solution Approach 1:
The patent applies preliminary action by dissolving hydrogen gas in the C4 liquid phase before it enters the reactor. The C4 stream is pressurized and contacted with hydrogen gas in advance, allowing hydrogen to dissolve and distribute uniformly throughout the liquid phase. This pre-dissolution prevents the uneven distribution and temperature hotspots that occur when hydrogen is fed directly as gas at the reactor inlet.
Solution Approach 2:
The patent uses the C4 liquid phase as an intermediary carrier to transport hydrogen gas to the catalyst. Instead of introducing hydrogen gas directly to the catalyst surface, it first dissolves in the C4 liquid, which then carries the hydrogen through the liquid membrane to the catalyst. This intermediary approach ensures uniform distribution and controlled release of hydrogen at the reaction site.
2Reliability
If excess hydrogen gas is provided to ensure complete alkyne hydrogenation, then alkyne removal efficiency improves, but diolefins and butenes undergo further hydrogenation to form alkanes, reducing selectivity
Solution Approach 1:
The patent applies parameter changes by controlling the hydrogen-to-C4 liquid ratio and dissolving hydrogen in the liquid phase before reaction. This changes the physical state and delivery mechanism of hydrogen, allowing precise control of hydrogen availability at the catalyst surface. The dissolved hydrogen provides sufficient hydrogenation driving force while preventing excess hydrogen from causing over-hydrogenation of diolefins and butenes to alkanes.
Solution Approach 2:
The patent ensures continuous and uniform supply of dissolved hydrogen to the catalyst throughout the reaction zone. The hydrogen-dissolved C4 liquid flows continuously through the reactor, providing steady hydrogen availability that maintains high alkyne conversion without creating localized excess hydrogen conditions that would lead to non-selective over-hydrogenation.
3Manufacturing precision
If hydrogen gas is limited in the reaction system, then selectivity is improved, but hydrogenation reaction rate decreases and alkynes cannot be completely removed
Solution Approach 1:
The patent changes the physical parameter of hydrogen delivery from gaseous phase to dissolved liquid phase. This parameter change increases the effective concentration and uniformity of hydrogen distribution in the reaction zone, enabling complete alkyne removal while maintaining selectivity. The dissolved hydrogen provides sufficient reaction rate without the need for excess hydrogen gas that would compromise selectivity.
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 optimized raw material preparation, resulting in higher yields of 1,3-butadiene and butene-1.
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
selective hydrogenation reaction of C4 components is a three-phase reaction of gas, liquid and solid
Implementation Method 4
undergoes selective hydrogenation to obtain a product rich in 1-butene and having the content of butadiene and alkyne of less than 10 ppm
Data Source
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.