Piperazine Solvent Research Articles

CO2 solubility and physicochemical properties of 2-amino 2-methyl-1-propanol based solvents for post-combustion CO2 capture. Predictive modeling using machine learning

Global warming, caused by Carbon Dioxide (CO2) emissions from hard-to-abate industries, necessitates CO2 capture as one of the promising alternatives. Post-combustion CO2 capture (PCC) can be retrofitted for industries where chemical absorption using an amine-based solvent is an efficient method for CO2 capture. An essential factor for CO2 absorption in an amine mixture is the study of CO2 solubility and CO2 + Amine physicochemical properties to identify the more efficient solvents. Often experimental data are available in the literature, but precisemodeling is necessary to use such data for further utilization in a process-plant model. In this work, a blended solvent aqueous 2-amine-2methyl-1-Propanal (AMP) with Piperazine (PZ) and 1-(2-aminoethyl) piperazine (AEP) have been identified as a potential candidate for PCC application. The fundamental properties such as the density, viscosity and CO2 solubility in AMP + PZ and AMP + AEP blended solutions have been predicted by employing machine learning to get an exceptionally efficient model. This data-mining technique efficiently calculates solubility, density, and viscosity by using 691, 559, and 559 experimental data sets respectively, from the literature of AMP + PZ. Similarly, 120 data sets of solubility have been collected from the literature for AMP + AEP. Random Forest regression, Artificial Neural Network (ANN), and XGBoost regression algorithms are adapted to predict CO2 solubility in aqueous AMP blended solution. The effectiveness of these models has been confirmed through statistical analysis, leading to the conclusion that XGBoost outperforms the other two approaches. Moreover, an identical approach has been employed to develop a predictive model for the density and viscosity of AMP + PZ solvent. The outcomes imply that the machine learning algorithm performs better with experimental data and may be utilised as an effective simulation tool.

Proposal and investigation of CO2 capture from fired heater flue gases to increase methanol production: A case study

In a petrochemical complex in Iran, for production of 209575 kg of MeOH/h, 154,712 kg/h of flue gas with a CO2 concentration of 10.74 mol% enter the atmosphere through a fired heater. The target of this study is to investigate the effect of using post-combustion CO2 capture technology to reduce carbon dioxide emissions and use it to increase methanol production. In order to, the proposed process was simulated and effect of three different solvents, including piperazine (PZ) 30 wt%, monoethanolamine (MEA) 30 wt%, and a blend of MEA 20 wt %+ PZ 10 wt % were investigated. This study investigated solvent regeneration energy, CO2 absorption rate, energy efficiency, and exergy efficiency of stripper column. Simulation results showed PZ with 93% energy efficiency, 55.45% exergy efficiency of stripper column, CO2 emission intensity equal to 0.01 tCO2/tMeOH and lowest solvent regeneration energy equal to 2.6 GJreb/tCO2 has better performance than the other two solvents. Also, the simulation results showed that blending CO2 output from PZ solvent with syngas increases methanol production by 7.8%. The techno-economic analysis also indicated proposed process is more profitable than original process.

Dynamic analysis of carbon dioxide desorption with 2‐amino‐2‐methyl‐1‐propanol and piperazine blends

AbstractIn this study, the dynamic behavior of CO2 desorption in an aqueous blend of 2‐amino‐2‐methyl‐1‐propanol (AMP) and piperazine (PZ) was investigated. Solvent desorption, an important method used to capture CO2 by absorption into amines, was carried out in a laboratory column with a film promoter and monitored online by infrared spectroscopy. A PLS model was used to quantify the free amines, carbonated species, and total absorbed CO2 in all its chemical forms present in the liquid phase. The desorption was performed at atmospheric pressure and temperatures of 323, 333, and 343 K with blend solutions of 30/0, 25/5, 20/10, and 0/15 wt.% AMP/PZ. The liquid mass transfer coefficient (kL) decreased with higher CO2 loadings and was not significantly affected by temperature. AMP enhanced the liquid mass transfer coefficient of the PZ solvents, and the highest kL occurred at the higher PZ blend concentrations. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd.

Density, viscosity, physical CO2 diffusivity, and CO2 absorption capacity of novel blended N-methyl-4-piperidinol and piperazine solvent

In the present work, novel blended piperazine (PZ) and N-methyl-4-piperidinol (MPDL) solvent was investigated in terms of density, viscosity, physical diffusivity of CO2, and CO2 absorption capacity. Density and viscosity were measured over PZ/MPDL concentration ratios of 5/25, 10/20, and 15/15 %wt. and temperatures of 313, 323, and 333 K. Physical diffusivity of CO2 was calculated based on viscosity data by the modified Stokes–Einstein equation. Lastly, CO2 absorption capacity (mol CO2/mol amine) was experimentally determined in a temperature-controlled absorption reactor at 313 K and 10% v/v CO2. The results showed that density and viscosity of novel blended PZ-MPDL solvent increased as PZ concentration ratio increased and decreased as temperature increased. On another hand, physical diffusivity of CO2 decreased as PZ concentration ratio increased and increased as temperature increased. Based on the physical properties data (i.e., density, viscosity, and physical diffusivity of CO2), it can be summarized that the studied physical properties of PZ-MPDL were in the same ranges with those of conventional amine solvents. Additionally, it was found that CO2 absorption capacity of PZ-MPDL can be improved by increasing PZ concentration ratio. As a result, 15/15 %wt. PZ-MPDL showed the highest CO2 absorption capacity (0.741 mol CO2/mol amine) among the three studied concentrations. It also possessed 49% higher CO2 absorption capacity than the conventional benchmarking 30 %wt. monoethanolamine (MEA).

Technical and economic performance assessment of post-combustion carbon capture using piperazine for large scale natural gas combined cycle power plants through process simulation

The main challenges to the commercial deployment of the solvent-based post-combustion carbon capture technology include high energy consumption and high capital and operating costs. New solvents and alternative process configurations are being pursued to reduce the energy consumption and costs of the process. This paper investigates the technical and economic performance of the process using piperazine (PZ) solvent for a 250 MWe natural gas combined cycle power plant. Three different configurations of the process using PZ were evaluated and compared to the standard process using 30 wt% monoethanolamine (MEA) solvent. The technical performance of the process was evaluated using the rate-based model developed in Aspen Plus® V8.4 and the economic evaluation was carried out in Aspen Process Economic Analyzer®V8.4. The technical results showed that the total energy demand of the process reduces from 5.34 GJ/tCO2 using 30 wt% MEA to 3.56 GJ/tCO2 using 30 wt% PZ. The lowest energy demand of 2.76 GJ/tCO2 was achieved with the advanced flash stripper using 40 wt% PZ. The economic results show that the lowest total annual cost of M$26.58 per year and CO2 capture cost of $34.65 per tonneCO2 were obtained using the advanced flash stripper (AFS) with 40 wt% PZ. It was concluded that the 40 wt% PZ solvent would bring practical technical and economic benefits to the large-scale applications of the capture process compared to the current 30 wt% MEA solution. Therefore, this study will inspire policymakers and researchers towards the large-scale deployment of solvent-based PCC process.

Pilot plant demonstration of piperazine with the advanced flash stripper

Amine scrubbing is an important alternative for CO2 capture from coal- and gas-fired power plants. 5 m piperazine (PZ) with the Advanced Flash Stripper (AFS) has all the attributes of a benchmark system for the second-generation amine scrubbing process for CO2 capture. This process has been demonstrated with more than 2000 h of operation on 0.6 MWe of coal-fired flue gas at the National Carbon Capture Center. In the first 600 h, the AFS configuration was used, and the stripper sump level was kept high at 80%. From 600 to 850 h, the system switched to simple stripper configuration and from 850 to 1100 h, switched back to AFS. After 1100 h, the mitigation methods for oxidation were tested with the AFS, including nitrogen sparging, applying the SO2 prescrubber to remove NO2, and lowering the stripper sump level to 15%. The energy required per tonne CO2 removed was less than 2.1 GJ steam and less than 232 kW h total equivalent work. The stripper operated at 150 °C, producing CO2 up to 6 bara. The 5 m PZ solvent was used reliably with little solids precipitation. CO2 removal from 90 to 99% was achieved with less than 12 m of packing. PZ oxidation was less than 0.1 kg PZ/tonne CO2 with the AFS and the absence of NO2. As estimated from NH3 production, the mitigation methods reduced the PZ oxidation rate by 13%. The trends in dissolved iron correlated with the PZ oxidation rate rather than the extent of oxidation. PZ emissions were managed to less than 1 ppm with water wash and an elevated lean solvent temperature. With aqueous PZ, carbon steel was frequently protected by deposition of FeCO3, making it an attractive alternative to stainless steel.

Fe2+ Solubility and Siderite Formation in Monoethanolamine and Piperazine Solvents

Fe2+ Solubility and Siderite Formation in Monoethanolamine and Piperazine Solvents

Dynamic modeling and control of an intercooled absorber for post-combustion CO2 capture

A medium-order dynamic model was developed in gPROMS® for an intercooled CO2 absorber column with piperazine solvent. This model represents an improvement from previously published rate-based dynamic models because it uses a regressed eNRTL thermodynamic package and a liquid film mass transfer coefficient with an experimentally measured CO2 loading dependence. Off-design simulation results were validated against a high-order steady state model, and the maximum predicted column temperature differed by less than 1.2°C for 100–85% flue gas load. Operating the absorber at a constant liquid to gas (L/G) ratio results in favorable dynamic behavior with disturbances in flue gas load, but a commercial system will not have a reliable flue gas flow measurement. The medium-order model was used to identify a liquid phase temperature within the top bed of absorber packing as a control variable that is sensitive to changes in L/G ratio. As the flue gas load was ramped from 100% to 80%, a maximum L/G ratio deviation of 0.9% was observed when controlling the column temperature with the solvent flowrate. Feedforward control may be necessary to account for other process disturbances that influence the temperature profile and was shown to be effective at counteracting a step change in intercooling temperature.

Control Relevant Model of Amine Scrubbing for CO2 Capture from Power Plants

A low-order amine scrubbing model was developed for an intercooled absorber and advanced flash stripper configuration with piperazine solvent. The low-order lumped parameter model uses semi-empirical thermodynamics and rate-based mass transfer and embeds reaction kinetics in a constant overall transfer coefficient. The predicted off-design steady state of this model is compared to a high-order Aspen Plus simulation for 100–85% power plant load. The difference in CO2 removal rate between the two models is less than 1% when power plant load is greater than 94%. The removal rate is systematically overpredicted in the low-order model because a constant CO2 mass transfer coefficient in the absorber leads to an overprediction of absorber performance at part-load operation. Compared to pilot plant data, the low-order model captures the dynamic response of a step change in the stripper pressure control valve. The characteristic time of the total CO2 inventory is found to be 77 min, compared to a total liquid resi...

Dynamic simulation and analysis of a pilot-scale CO2 post-combustion capture unit using piperazine and MEA

Post-combustion capture is a promising technology for developing CO2 neutral power plants. However, to make it economically and technically feasible, capture plants must follow the fast and large load changes of the power plants without decreasing the overall performance of the plant. Dynamic modeling and simulation is therefore needed to evaluate the performance of this plant under critical operation.In this work, we evaluate the transient response of an absorber and a desorber for step changes of key process parameters, e.g. flue gas flow and composition, lean and rich CO2 loading, etc. We show the results for the baseline 30 wt% MEA and the low energy piperazine (PZ) solutions. This analysis reveals that the absorber reaches steady-state faster using MEA compared to PZ. This is related to the shift of the mass transfer zone due to changes in temperature. The transient operation in the regeneration unit is somewhat similar while using both solvents: an initial fast decrease of the lean loading is followed by a slow transient period as the system approaches steady-state conditions. We show the presence of inverse response in the stripper column when the rich loading decreases or the feed’s temperature reduces using PZ solvent. Thus, we demonstrate that the dynamics of the MEA system cannot be extrapolated to other solvents.

Photodegradation in natural waters of nitrosamines and nitramines derived from CO2 capture plant operation

Amine solvents used in post combustion CO2 capture (PCCC) plants react with NOx, forming carcinogenic nitrosamine and nitramine compounds. These can be emitted to the atmosphere, undergoing deposition to aquatic and terrestrial environments. In the current study, the hydrolytic and photolytic degradation of nine nitramines and nitrosamines identified as possible degradation products of 2-monoethanolamine and piperazine solvents are studied. Nitrosamines and nitramines are generally resistant to hydrolysis, although nitrosopiperazine and piperazine nitramine both undergo up to 50% degradation at 50°C and pH 7, but not at lower temperatures or other pH values. Owing to absorbance at ∼340nm, the nitrosamines degrade rapidly in aqueous solution when exposed to sunlight (half-lives in the range 6–11min), whilst nitramines are photolytically stable. Light screening by natural organic matter (1–100mg/L) lead to an ∼3-fold decrease in nitrosodiethanolamine (NDELA; 1mg/L) degradation rate. A theoretical study indicates environmentally relevant concentrations of NDELA may be persistent due to competition with NOM for photons. The main photodegradation products are identified for each nitrosamine, and degradation mechanisms suggested.

Pilot‐scale parametric evaluation of concentrated piperazine for CO2 capture at an Australian coal‐fired power station

AbstractConcentrated piperazine (PZ) is a promising new solvent under consideration for post‐combustion capture (PCC) of CO2. A solution of 8 molal PZ was recently evaluated at the Tarong CO2 capture pilot plant in Australia. Initial operation involved evaluation of different operating conditions at the plant to determine the minimum energy conditions for this solvent. Comparison was made to results achieved previously at the same pilot plant with 30 wt% monoethanolamine (MEA). Regeneration energy requirements achieved with concentrated PZ were consistently lower than those achieved with MEA. The lowest regeneration energy for PZ at the pilot plant (2.9 MJ/kgCO2) was roughly 15% lower than the best result predicted for MEA. Inter‐cooling located at the center of the absorber column was also evaluated for the concentrated PZ solvent. The benefit of inter‐cooling was found to depend on the operating conditions of the plant, with operation at higher liquid‐to‐gas (L/G) ratios showing a more pronounced effect. For an L/G ratio of 3.3 kg/kg, inter‐cooling was found to lower the regeneration energy required for PZ by approximately 10%.

Oxidative degradation of aqueous PZ solution and AMP/PZ blends for post-combustion carbon dioxide capture

Aqueous blends of 2-amino-2-methyl-1-propanol (AMP) and piperazine (PZ) appear to be commercially attractive solvents for post-combustion CO2 capture by absorption/stripping. An experimental study on the oxidative degradation of aqueous PZ solutions and AMP/PZ blends was carried out. The oxidative degradation experiments were performed in a 200mL glass batch reactor with an oxygen partial pressure of 250kPa, and at the temperatures of 80–120°C. The amine loss was determined by cation ion chromatography (IC) while the degradation compounds were identified and quantified by gas chromatography–mass spectrometry (GC–MS), cation IC and anion IC. Possible chemical pathways of PZ oxidative degradation are proposed to account for the observed degradation products. As compared to oxidative degradation of single AMP and PZ solvents, no new product was observed in partially degraded AMP/PZ blends. However, PZ degraded faster in the blends than it degraded individually at identical degradation conditions.

Absorption of Nitrogen Oxides in Aqueous Amines

Abstract Nitric oxide (NO) and nitrogen dioxide (NO2) were absorbed into aqueous amine to determine the absorbing species, the absorption kinetics, and the aqueous products at the ppm-level NOx concentrations typical of flue gas from fossil fuel power plants. At flue gas conditions of 0.5-5 ppm of NO2, absorption is dominated by free radical absorption of NO2 as nitrite. NO2 absorption kinetics are first order in NO2 partial pressure, half order in free amine concentration, and fastest in methyldiethanolamine (MDEA). The reaction-enhanced liquid mass transfer coefficient for NO2 absorption in 8 m piperazine (PZ) at absorber conditions is 9.7*10-7 mol/s·m2·Pa, yielding 92% NO2 absorption at a typical A/G of 3.3*106 s·Pa·m2/mol. Similarly, a 9 m monoethanolamine (MEA) solvent will absorb roughly 70% of the inlet NO2 while a 7 m MDEA/2 m PZ solvent will absorb over 99% of the NO2. Nitrite and nitrate are the main NOx absorption products in MDEA with nitrite dominating at low NO2 partial pressures. In PZ, the amine free radical formed during NO2 absorption will react with NO to directly form n-nitrosopiperazine (MNPZ) or react with itself to form 2-piperazinol (2-PZOH). Typical nitrosamine yields in 5 m PZ are around 15% of total absorbed NOx and can be halved with the addition of 200 mM Inhibitor A, a free radical scavenger. Nitrate and nitramine are minor products of NOx absorption, accounting for less than 5% of total absorbed NOx.

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

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.

Piperazine Degradation in Pilot Plants

Concentrated, aqueous piperazine (PZ) has shown promise as a solvent for use in amine scrubbing of post - combustion flue gas to reduce CO2 emissions. Compared with 1-ethanolamine (MEA), PZ has a greater CO2 absorption rate, capacity, and thermal stability. These properties should reduce the overall energy requirements of a CO2 capture facility operating with PZ solvent compared to one operating with MEA.Between 2009 and 2011, 4 campaigns were run at the pilot plant at the Separations Research Program (SRP) of the University of Texas using an inventory of 8 m PZ. Synthetic flue gas consisting of CO2 mixed with air was used at a flow rate equivalent to a 0.1 MW coal-fired power plant. Due to the high oxygen content of the synthetic flue gas, substantial oxidative degradation was anticipated in this campaign. Another campaign was run at “Pilot Plant 2” (PP2) using PZ. This pilot plant used a slipstream of real flue gas drawn from a coal-fired power plant. Solvent samples were collected during campaigns at both SRP and PP2.The operating CO2 capacity of the SRP PZ solvent decreased approximately 10% compared to fresh, undegraded 8 m PZ. The heat of CO2 absorption and the CO2 absorption rate at 40°C (absorber operating conditions) did not change significantly, but greater temperature dependence was observed at higher temperature. These property changes indicate that changes in the solvent have occurred, but that the resulting solvent is not significantly worse than clean piperazine.It is known from bench-scale studies that PZ can degrade into a variety of products, including ethylenediamine (EDA), formate, N-formylpiperazine (FPZ), acetate, and 1-(2-aminoethyl)-piperazine (AEP). These products were observed in the degraded solvents of both pilot plants, in small concentrations compared to bench-scale results.As a secondary amine, PZ could potentially react with nitrite to form the known carcinogens N-nitrosopiperazine (MNPZ). Nitrite could accumulate in the solvent either through absorption of NO2 from the flue gas or degradation of the amine solvent. The synthetic SRP flue gas contained only ambient atmospheric levels of NOx. MNPZ was observed in the SRP solvent at a low concentration of 0.09 mmol/kg. The flue gas used in PP2 was drawn from a coal boiler and was treated by selective catalytic reduction to reduce NOx concentration. Samples collected at regular intervals from PP2 show that after an initial spike up to 2.87 mmol/kg early in the campaign, MNPZ settled at a steady state concentration of around 0.9 1.2 mmol/kg. It is hypothesized that thermal degradation of the MNPZ in the stripper prevented further accumulation beyond these levels.

Two-Stage Flash for CO2 Regeneration: Dynamic Modeling and Pilot Plant Validation

High operating cost and significant decrease in net power generation are major barriers to the implementation of post- combustion amine scrubbing for CO2 capture from coal-fired power plants. To improve efficiency and make the process more attractive economically, alternative process configurations and second generation solvents are being investigated. Dynamic modeling can be a useful tool in understanding the optimal operating conditions and control strategies for a proposed modified process; however, there are limited examples of dynamic model development for amine scrubbing. The Separations Research Program (SRP) at the University of Texas at Austin has completed a pilot plant campaign using a two-stage flash for CO2 regeneration as an alternative to a simple stripper, and piperazine solvent as an alternative to the baseline standard of monoethanolamine. This work develops a dynamic model for the alternative SRP configuration using first principles material and energy balances assuming an equilibrium stage process, and the model is validated with steady state SRP data. The model output was reasonably well matched to pilot plant measurements, with average temperature deviations of ≤1.7°C and average pressure errors of ≤ 3.4%.

Measurement of Nitrosamine and Nitramine Formation from NOx Reactions with Amines during Amine-Based Carbon Dioxide Capture for Postcombustion Carbon Sequestration

With years of full-scale experience for precombustion CO(2) capture, amine-based technologies are emerging as the prime contender for postcombustion CO(2) capture. However, concerns for postcombustion applications have focused on the possible contamination of air or drinking water supplies downwind by potentially carcinogenic N-nitrosamines and N-nitramines released following their formation by NO(x) reactions with amines within the capture unit. Analytical methods for N-nitrosamines in drinking waters were adapted to measure specific N-nitrosamines and N-nitramines and total N-nitrosamines in solvent and washwater samples. The high levels of amines, aldehydes, and nitrite in these samples presented a risk for the artifactual formation of N-nitrosamines during sample storage or analysis. Application of a 30-fold molar excess of sulfamic acid to nitrite at pH 2 destroyed nitrite with no significant risk of artifactual nitrosation of amines. Analysis of aqueous morpholine solutions purged with different gas-phase NO and NO(2) concentrations indicated that N-nitrosamine formation generally exceeds N-nitramine formation. The total N-nitrosamine formation rate was at least an order of magnitude higher for the secondary amine piperazine (PZ) than for the primary amines 2-amino-2-methyl-1-propanol (AMP) and monoethanolamine (MEA) and the tertiary amine methyldiethanolamine (MDEA). Analysis of pilot washwater samples indicated a 59 μM total N-nitrosamine concentration for a system operated with a 25% AMP/15% PZ solvent, but only 0.73 μM for a 35% MEA solvent. Unfortunately, a greater fraction of the total N-nitrosamine signal was uncharacterized for the MEA-associated washwater. At a 0.73 μM total N-nitrosamine concentration, a ~25000-fold reduction in concentration is needed between washwater units and downwind drinking water supplies to meet proposed permit limits.

Aqueous Solubility of Piperazine and 2-Amino-2-methyl-1-propanol plus Their Mixtures Using an Improved Freezing-Point Depression Method

In this work the solid–liquid equilibrium (SLE) and freezing-point depression (FPD) in the electrolytic binary aqueous systems piperazine (PZ, CAS No. 110-85-0) and aqueous 2-amino-2-methyl-1-propanol (AMP, CAS No. 124-68-5) were measured. The FPD and solubility were also determined in the ternary AMP–PZ–H2O system. A method was developed by which solubility can be determined at higher temperatures using the FPD setup. A total of 86 data points are listed in the full concentration range from (−35 to 90) °C. The solid phases piperazine hexahydrate (PZ·6H2O), piperazine hemihydrate (PZ·1/2H2O), and anhydrous PZ precipitated during the experiments. The data can be used in the formulation, prevention, or intentional formation of slurries in piperazine solvents for promoting CO2 capture using absorption and desorption.

Aqueous piperazine as the new standard for CO 2 capture technology

Amine scrubbing will be the technology of choice for CO 2 capture from coal-fired power plants. 7 m monoethanolamine (30 wt% MEA) has been the standard solvent to represent the capability of this technology. This paper presents a new standard process that uses 8 m piperazine (40 wt% PZ) with regeneration at 150 °C by a two-stage flash. The performance data for the piperazine system is non-proprietary and available for standard comparisons. The expected energy requirement for a piperazine or other advanced amine scrubbing processes will approach 220 kWh/tonnes CO 2 removed. The minimum work for this separation is 113 kWh/tonnes. The major exergy losses (kWh/tonnes CO 2) in the piperazine process are: condenser, 34; exchanger, 25; compressor, 22; absorber, 14. Because mechanical adiabatic compression has an overall thermodynamic efficiency of 55–60%, amine scrubbing with thermal swing regeneration provides better energy performance with greater heat of CO 2 absorption and maximum regeneration temperature. Piperazine can be used up to 150 °C without significant thermal degradation. This allows better energy performance and minimizes the impacts of degradation products. The piperazine solvent is resistant to oxidative degradation, has less volatility than MEA, and is not corrosive to stainless steel. It is also suitable for reclaiming by distillation and other methods already commercialized by the gas treating industry.