Piperazine/N-methylpiperazine/N,N’-dimethylpiperazine as an Aqueous Solvent for Carbon Dioxide Capture

Stephanie A Freeman,Thu Nguyen,Humera Rafique,Qing Xu,Gary T Rochelle,Xi Chen

doi:10.2516/ogst/2012089

Abstract

A blend of piperazine (PZ), N-methylpiperazine (MPZ) and N,N’-dimethylpiperazine (DMPZ) is described as a novel CO2 capture solvent for aqueous absorption-stripping. This blend provides improved solid solubility and heat of absorption compared to concentrated PZ. No insolubility was observed for regions of high CO2 loading, unlike PZ solvents. The blend performed like concentrated PZ in terms of CO2 capacity and CO2 absorption rate, both of which were more than double that of a traditional 7 molal (30 wt%) MonoEthanolAmine (MEA). Thermal equilibrium was established between the three constituent amines that increases the thermal stability compared to traditional blended solvents. The primary drawback of this novel solvent system is enhanced amine volatility at absorber conditions compared with both concentrated PZ and MEA.

Highlights

Amine-based absorption-stripping is the most promising solution for post-combustion carbon dioxide (CO2) capture from coal-fired power plant flue gas
A new solvent concept proposed here is the use of amines that demonstrate noticeable levels of overall thermal degradation but degrade to useful products that can react with CO2 and maintain alkalinity of the solution
Total alkalinity was verified through acid titration and CO2 concentration was verified through Total Inorganic Carbon (TIC) analysis as described previously [13, 18]

Summary

Introduction

Amine-based absorption-stripping is the most promising solution for post-combustion carbon dioxide (CO2) capture from coal-fired power plant flue gas Advanced amine solvents such as concentrated, aqueous piperazine (PZ) are being proposed to replace traditional alkanolamines such as MonoEthanolAmine (MEA) due to advantageous CO2 absorption rates and overall energy performance [1, 2]. A new solvent concept proposed here is the use of amines that demonstrate noticeable levels of overall thermal degradation but degrade to useful products that can react with CO2 and maintain alkalinity of the solution One example of this solvent concept presented here is the use of a blend of PZ, N-methylpiperazine (MPZ), and N,N’-dimethylpiperazine (DMPZ) [3]. The same has been seen for N-methyldiethanolamine (MDEA)/PZ which degrades to diethanolamine (DEA) and substituted PZ molecules (1-methylpiperazine, N-(2-hydroxyethyl) piperazine and others) which can react and carry CO2 during absorption-stripping [14, 15]

Methods

Results

Conclusion