Solubility and Heat of Absorption of CO₂ into Diisopropylamine and N,N-Diethylethanolamine Mixed with Organic Solvents

Abstract

We have evaluated the vapor–liquid equilibrium and heat of absorption of CO2 over water-lean mixtures of the amines diisopropylamine and N,N-diethylethanolamine (DEEA). This extends our previous research on water-lean solvents containing ethanolamine. The organic diluents N-methyl-2-pyrrolidone (NMP) and ethylene glycol (MEG) have been employed for solvent formulation. Since both diisopropylamine (a hindered amine) and N,N-diethylethanolamine (a tertiary amine) react with CO2 to form mainly bicarbonate in aqueous solutions, their behavior in nonaqueous mixtures is quite different from that of monoethanolamine. While MEG seems to maintain the reactivity of both diisopropylamine and DEEA even in nonaqueous mixtures, nonaqueous solvents with NMP act essentially as physical absorbents. This is an important indication that MEG is able to take part in the reaction mechanism between these amines and CO2, perhaps through alkylcarbonate formation, a fact that can be traced back to its relatively low autoprotolysis constant (pK S). This study represents a departure from our previous treatment on loss of CO2 solubility in water-lean solvents with monoethanolamine based on solvation phenomena alone, as it has become clear that the shift in equilibria in solvents with hindered and tertiary amines must account for Le Chatelier’s principle.

Capture of CO2 Using Mixed Amines and Solvent Regeneration in a Lab-Scale Continuous Bubble-Column Scrubber

“…They can be determined when thermal data are available [32,[50][51][52][53][54]. Thermal data used here include those of heat capacity [50], the heat of absorption [32,[52][53][54], and latent heat [51].…”

“…They can be determined when thermal data are available [32,[50][51][52][53][54]. Thermal data used here include those of heat capacity [50], the heat of absorption [32,[52][53][54], and latent heat [51]. In Equation ( 31), C p is the heat capacity of scrubbed solutions, ∆H ad the heat of absorption, ∆T the temperature difference, m sol the mass of regeneration solution, ∆m CO 2 [kg] the mass loss of CO 2 after stripping, ∆H vap the heat of evaporation, and ∆m 1 the scrubbed solution loss during stripping.…”

“…Due to this, several solvents have adopted, such as amines [11][12][13][14][15], amino salts [16,17], ammonia water [18,19], so hydroxide [20], potassium carbonate [21], piperazines [22], ionic liquids, and ph solvents [10], with amines being the most popular solvents in these capture proc The drawbacks of a single solvent, such as loading, corrosion rate, degradation rat regeneration energy, were improved by adopting new solvents, including mixed a and non-aqueous solvents [23][24][25][26][27][28]. There are four kinds of amines, basically classi primary amines (such as monoethanolamine, MEA) [29,30], secondary amines (s diisopropanolamine, DIPA) [31][32][33], tertiary amines (such as triethanolamine, TEA 36], and steric amine (such as 2-amino-2-methyl-1-propanol, AMP) [37][38][39]. Struct these amines have at least one hydroxyl group and one amino group, as shown in 1.…”

Optimization of novel nonaqueous hexanol‐based monoethanolamine/methyl diethanolamine solvent forCO2absorption

“…25,26 Such cosolvents can increase CO 2 solubility in tertiary amines as well as increase the absorption capacity. 27,28 These solvents are described as nonaqueous, water-free, or water-lean solvents, and they have been increasingly studied. 29,30 Alkanolamine-alcohol blends are characterized by their high boiling point, low specific heat capacity, and low vaporization enthalpy.…”

“…Water could be supplemented or even replaced with organic cosolvents 25,26 . Such cosolvents can increase CO 2 solubility in tertiary amines as well as increase the absorption capacity 27,28 . These solvents are described as nonaqueous, water‐free, or water‐lean solvents, and they have been increasingly studied 29,30 …”