Sterically Hindered Di-(hydroxyalkyl)amines for Selective H2S Capture
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Solution Overview
Problem
Current deacidification processes for industrial and natural gases face challenges such as insufficient selectivity of H2S absorption relative to CO2, slow CO2 or COS capture kinetics, and high energy consumption for solvent regeneration, leading to increased operational costs and investment in equipment.
Innovation Solution
The use of tertiary or secondary monoamines with severe steric hindrance, specifically di-(hydroxyalkyl)-monoamines, as absorbent solutions in aqueous form, which enhance H2S absorption capacity and selectivity while improving CO2 and COS capture kinetics, and reducing energy consumption during regeneration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If tertiary amines or hindered amines are used to achieve selective H2S absorption, then H2S selectivity is improved, but H2S absorption capacity decreases at high loading rates
Solution Approach 1:
The invention changes the chemical structure parameters of the amine by introducing severe steric encumbrance around the nitrogen atom with specific hydroxyalkyl groups. This structural modification creates a unique reaction environment where H2S can still access the nitrogen atom through a different mechanism than CO2, achieving both high selectivity and high capacity by altering the molecular parameters rather than simply choosing between different amine classes
Solution Approach 2:
The invention creates a composite chemical structure by combining the amine functional group with specific hydroxyalkyl substituents having severe steric encumbrance. This composite molecular structure exhibits properties that neither simple tertiary amines nor simple secondary amines possess alone, achieving simultaneous high H2S selectivity and high absorption capacity through the synergistic effect of the composite structure
2Quantity of substance
If conventional amines are used for total deacidification, then CO2 and COS capture capacity is achieved, but reaction kinetics are too slow
Solution Approach 1:
The invention modifies the reaction kinetics parameter by changing the steric environment around the nitrogen atom. The severe encumbrance created by the hydroxyalkyl groups with multiple alkyl substituents alters the activation energy and reaction pathway, resulting in dramatically accelerated CO2 and COS capture kinetics while preserving the capacity to achieve total deacidification
3Productivity
If conventional absorbent solutions are used, then deacidification is achieved, but cyclic capacity is limited
Solution Approach 1:
The invention changes the thermodynamic parameters of the absorbent system by introducing the novel di-(hydroxyalkyl)amines with severe steric encumbrance. This structural modification alters the equilibrium constants and heat of reaction, resulting in enhanced cyclic capacity that allows more acid gases to be absorbed and desorbed per unit of absorbent, thereby increasing overall productivity
4Quantity of substance
If conventional amine solutions are used for CO2 capture in post-combustion, then CO2 absorption is achieved, but regeneration energy consumption is too high
Solution Approach 1:
The invention changes the thermodynamic parameters of the amine-CO2 system by introducing the novel molecular structure with severe steric encumbrance. This structural modification alters the heat of reaction and equilibrium characteristics, resulting in a system that achieves the same CO2 absorption capacity but requires significantly less energy for thermal regeneration, thereby reducing operating costs
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
These di-(hydroxyalkyl)-monoamines achieve higher absorption capacities and selectivity for H2S, faster reaction kinetics for CO2 and COS, and lower energy consumption for solvent regeneration, thereby reducing operational costs and equipment size.
Implementation Method 1
Absorption processes using an aqueous solution of amines are commonly used to remove the acidic compounds (in particular CO2, H2S, COS, CS2, SO2 and mercaptans) present in a gas. The gas is deacidified by bringing it into contact with the absorbent solution
Implementation Method 2
the absorbent solution is thermally regenerated
Data Source
Figure 1
AI summary
The method for eliminating acidic compounds contained in a gaseous effluent consists of placing into contact, in column C1, a gaseous effluent 1 with an absorbent solution 4 comprising an aqueous solution of one or a plurality of dihydroxyalkylamines having one of the formulas (I) and (II).