Ionic Liquid HCl Storage Medium for Reversible Absorption
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Solution Overview
Problem
Current methods for separating hydrogen chloride (HCl) from industrial process gases are energy-intensive, use precious metal catalysts, and require diaphragms or membranes, making them costly and inefficient.
Innovation Solution
A storage medium comprising an ionic compound with an asymmetrically substituted ammonium cation and a poly(HCl)chloride anion, which allows for reversible absorption and storage of HCl from process gases, and subsequent release of hydrogen and chlorine through electrolysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional methods (gas phase oxidation or electrochemical processes) are used to decompose HCl, then HCl can be converted back into chlorine and hydrogen, but the process is very energy intensive and requires precious metal catalysts and diaphragms or membranes
Solution Approach 1:
The patent introduces an ionic liquid as an intermediary substance that absorbs HCl from the gas phase, forming a complex that can be subsequently decomposed. This intermediary step simplifies the overall process by separating the absorption function from the decomposition function, allowing the use of less expensive catalysts and eliminating the need for diaphragms or membranes in the decomposition step.
Solution Approach 2:
The patent replaces the mechanical/electrochemical decomposition process (which requires precious metal catalysts, diaphragms, and membranes) with a thermal decomposition process of the HCl-ionic liquid complex. This substitution eliminates the need for complex electrochemical equipment and precious metal catalysts, significantly reducing both energy consumption and process complexity.
2Quantity of substance
If symmetrical ammonium salts with long alkyl chains are used for HCl absorption, then HCl can be absorbed, but the alkyl chain can undergo chlorination reactions leading to decomposition or property modification
Solution Approach 1:
The patent employs asymmetrically substituted ammonium cations in the ionic liquid structure. This asymmetry prevents the formation of highly symmetric structures that are more susceptible to chlorination reactions. The asymmetric structure reduces the likelihood of decomposition while maintaining the HCl absorption capability, thus resolving the contradiction between absorption capacity and chemical stability.
3Productivity
If known ionic compounds are used for HCl absorption, then some HCl can be absorbed, but the efficiency is not satisfying
Solution Approach 1:
The patent systematically varies key parameters of the ionic liquid including the type of ammonium cation (methyl, ethyl, propyl, butyl substitutions), the anion composition, temperature, and HCl partial pressure. By optimizing these parameters, the patent achieves both high absorption efficiency and high storage capacity, resolving the contradiction between the two performance metrics.
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 proposed solution enables efficient, cost-effective, and reversible storage of HCl, with simultaneous purification of other impurities, and allows for the release of hydrogen and chlorine at low cell voltage, potentially reducing energy consumption and eliminating the need for precious metal catalysts and membranes.
Implementation Method 1
allows for reversible absorption and storage of HCl from process gas
Implementation Method 2
hydrogen H2 can be released from compound (I) by electrolysis in an electrochemical process
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The present invention relates to a storage medium for storing hydrogen chloride (HCl) comprising at least one ionic compound of the general formulae (I) [NR1 aR2 bR3 c][Cl(HCl)n] (I) Wherein R1, R2, R3 being independent from each other an alkyl moiety selected from the group of methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl and sec-butyl, preferably methyl, ethyl, n-propyl; Wherein at least one of the moieties R1, R2, R3 differs from each of the others moieties R1, R2, R3; Wherein a, b, c are independently from each other 0, 1, 2 or 3, wherein the sum of a+b+c always has to be 4; Wherein n >= 1, preferably n = 1-6, more preferably n = 1, 2, 3, 4, with a viscosity in a range between 5 and 50 mPas, preferably between 10 and 20 mPas (25°C, 1000 hPa).