Solution to the sorption hysteresis by novel compact composite multi-salt sorbents

Abstract

Two novel types of consolidated composite sorbents of NH 4 Cl/CaCl 2 /MnCl 2 and NH 4 Cl/CaCl 2 are developed by the matrix of expanded natural graphite treated with sulfuric acid (ENG-TSA). The Clapeyron curves and sorption / desorption properties of different sorbents are tested and compared under non-equilibrium conditions. Compared with single-salt sorbent, the multi-salt / ENG-TSA sorbents show the combining properties of each kind of metal chloride they contain. One novel phenomenon is discovered in the study is that the sorption hysteresis of single salts, which is regarded as one common phenomenon for chemisorption, can be changed by the composite sorbents of multi-salt. For the composite bi-salt sorbent of NH 4 Cl/CaCl 2 the sorption hysteresis is much less significant than the single metal chlorides of NH 4 Cl and CaCl 2 . For the tri-salt composite sorbent of NH 4 Cl/CaCl 2 /MnCl 2 the sorption hysteresis disappears. The reason is analyzed and it may be related to the resorption between the metal chlorides they contain, which leads to a reduction of reaction heat that is believed to be a typical reason for sorption hysteresis.

Performance analysis on a novel self-adaptive sorption system to reduce nitrogen oxides emission of diesel engine

“…Chemical reaction processes of these salts with ammonia could be according to equations 3-9 without considering sorption hysteresis. [26]. ENG-TSA is first dried in an oven with a controlled temperature of 120 o C. Then ENG-TSA will be mixed with metal halide water solution.…”

Mechanism of hysteresis for composite multi-halide and its superior performance for low grade energy recovery

“…For such type of sorbents the obvious sorption hysteresis commonly exists 29,30 and could not be neglected. Recently it was found that compact composite multi-halide sorbents (NH 4 Cl/CaCl 2 /MnCl 2 -NH 3 ) 31 could reduce the sorption hysteresis significantly. The preliminary prediction thought that it might be caused by the resorption among different halides, but it was not investigated with detailed analysis and experiments.…”