Morpholine-Based Hindered Amine Absorbent for Selective H2S Removal
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Solution Overview
Problem
Current processes for removing acid gases from fluid streams, particularly hydrogen sulfide, face challenges such as decreased selectivity at higher pressures, foaming issues, and volatility of absorbents, which affect the efficiency and cost of regeneration and recompression in natural gas systems.
Innovation Solution
A process using an absorbent solution comprising compounds of the general formula (I) with specific alkyl and amino group configurations, which includes both secondary and tertiary amino groups for enhanced steric hindrance, reduces foaming and volatility while maintaining high cyclic capacity, specifically designed for selective hydrogen sulfide removal from gas mixtures containing carbon dioxide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If hydroxyl-substituted amines (alkanolamines) are used to improve solubility of reaction products, then solubility and circulation capability are improved, but selectivity for H2S removal decreases due to direct reaction with CO2 and physisorption at higher pressures
Solution Approach 1:
The invention extracts the problematic hydroxyl groups from the amine structure and replaces them with carboxylate groups. This extraction removes the source of non-selective CO2 reaction while preserving the desired H2S selectivity. The carboxylate groups provide sufficient solubility without the harmful direct reaction with CO2 that characterizes hydroxyl-substituted amines.
Solution Approach 2:
The invention changes the chemical parameter of the amine functional group from hydroxyl (-OH) to carboxylate (-COO-). This parameter change fundamentally alters the reaction behavior: carboxylate groups do not directly react with CO2 like hydroxyl groups do, thereby maintaining H2S selectivity while still providing good solubility for the reaction products in the aqueous solvent system.
2Productivity
If alkanolamines are used to effectively remove acid gases at high pressures, then acid gas removal efficiency is improved, but selectivity for H2S removal decreases due to stabilization of bicarbonate/carbonate products at hydroxyl sites
Solution Approach 1:
The invention extracts the hydroxyl groups responsible for non-selective CO2 reaction and replaces them with carboxylate groups. This removal eliminates the stabilization of bicarbonate/carbonate products at hydroxyl sites, preventing the loss of H2S selectivity that occurs at high pressures with conventional alkanolamines.
Solution Approach 2:
The invention creates a composite amine structure combining a sterically hindered amine core with carboxylate substituents. This composite structure maintains the kinetic selectivity of the hindered amine for H2S while the carboxylate groups provide alternative functionality that does not compete with H2S reaction, unlike hydroxyl groups which stabilize CO2 reaction products.
3Manufacturing precision
If sterically hindered secondary and tertiary amines are used for selective H2S removal, then kinetic selectivity for H2S over CO2 is improved, but foaming and volatility issues arise
Solution Approach 1:
The invention creates a composite amine structure with sterically hindered secondary and tertiary amino groups combined with carboxylate groups. This composite structure maintains the kinetic selectivity benefits of hindered amines while the carboxylate groups reduce surface activity, thereby minimizing foaming tendencies and improving operational stability.
Solution Approach 2:
The invention changes the substituent parameter from hydroxyl to carboxylate groups on the sterically hindered amine structure. This parameter change reduces the surfactant properties and foaming tendency while preserving the kinetic selectivity for H2S. The carboxylate groups are less surface-active than hydroxyl groups, reducing foaming issues.
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
The process achieves high selectivity for hydrogen sulfide removal with reduced CO2 absorption, minimizing foaming and absorbent loss, and offers improved cyclic capacity and operational stability, thereby enhancing the efficiency and cost-effectiveness of acid gas treatment.
Implementation Method 1
The reaction kinetics allow H2S to react more rapidly with the amine groups of the sorbent to form a hydrosulfide salt in aqueous solution
Implementation Method 2
H2S to react more rapidly with the amine groups of the sorbent to form a hydrosulfide salt
Implementation Method 3
CO2 is reacted in a slow reaction with the amine and with water to give bicarbonate
Data Source
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AI summary
A process for removing acid gases from a fluid stream, wherein the fluid stream is contacted with an absorbent comprising a compound of the general formula (I), wherein R1 and R2 are independently C1-C4-alkyl; R3 is selected from hydrogen and C1-C4-alkyl, R4, R5 and R6 are independently selected from hydrogen and C1-C4-alkyl; x and y are integers from 2 to 4 and z is an integer from 1 to 3, to obtain a treated fluid stream and a laden absorbent. The process allows for a high cyclic capacity while the compounds of the absorbent have a reduced tendency to foaming and low volatility.