https://ogma.newcastle.edu.au/vital/access/ /manager/Index ${session.getAttribute("locale")} 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:33904 Wed 23 Jan 2019 10:40:10 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:33575 Wed 21 Nov 2018 14:49:25 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:19692 Wed 12 Aug 2015 11:16:20 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:19369 2 capture processes. Using software developed in Matlab and existing knowledge of chemical equilibria, investigations into the fundamental properties of formulated amine solvents and their interaction with CO₂ have been carried out. A simple solvent formulation containing equimolar amounts of monoethanolamine (MEA), Amine 1, and a sterically hindered /tertiary amine, Amine 2, has been investigated here. Specifically, the role of Amine 2 in the overall equilibrium behaviour of amine blends is discussed. Systematic variations of the protonation constants and reaction enthalpies of Amine 2 over a range of typical values has revealed that significant improvement can be made in terms of absorption capacity, cyclic capacity, and overall absorption enthalpy in the blends when compared to the standard 5.0 M MEA solvent.]]> Wed 11 Apr 2018 14:03:51 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:18618 Wed 11 Apr 2018 13:02:04 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:12282 Wed 11 Apr 2018 10:49:36 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:46161 2 absorption rates in ammonia-based absorbents via addition of fast reacting primary/secondary amines are of great interest. In this work, a new substituted cyclic amine 4-aminomethyltetrahydropyran (4-AMTHP) was blended with aqueous ammonia to increase its reactivity toward CO₂. Stopped-flow spectrophotometry was employed to investigate the underlying reaction mechanism between dissolved CO₂(aq) and a series of blended NH₃/4-AMTHP solutions under homogeneous conditions. A comprehensive chemical model describing the blended 4-AMTHP–NH₃–CO₂–H₂O system, which involves a total of 11 kinetic reactions and 15 species, has been developed and further evaluated to explore the experimental kinetic and CO₂ mass transfer data measured from a bench-scale wetted-wall column. From the resulting data, it was demonstrated here that the addition of a small quantity of ∼0.3 M 4-AMTHP into the 3 M NH₃/0.9 M CO₂ solution can effectively increase the kinetic reactivity during CO₂ absorption into aqueous ammonia solutions, resulting in a ∼50% increase in mass transfer.]]> Wed 07 Dec 2022 14:17:24 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:49925 9.0 (k7 = 6.99 × 103 M–1·s–1). Below this pH, the formation of protonated monocarbamic acid (DMEDACOOH2) via the pathway involving DMEDAH+ and CO2(aq) becomes active and contributes to the kinetics despite the 107-fold decrease in the rate constant between the two pathways. 1H and 13C NMR spectra as a function of decreasing pH (increasing HCl concentration) at 25.0 °C have been evaluated here to confirm the protonation events in DMEDA. Calculations of the respective DMEDA nitrogen partial charges have also been undertaken to support the NMR protonation study. A comparison of the DMEDA kinetic constants with the corresponding data for piperazine (PZ) reveals that despite the larger basicity of DMEDA, the enhanced and superior kinetic performance of PZ with CO2(aq) above its predicted Bronsted reactivity is not observed in DMEDA.]]> Thu 15 Jun 2023 11:34:48 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:8321 Sat 24 Mar 2018 08:36:59 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:10423 Sat 24 Mar 2018 08:12:37 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:17531 2(aq) and monoethanolamine (MEA) has been investigated using stopped-flow spectrophotometry by following the pH changes during the reactions with colored acid–base indicators. Multivariate global analysis of both the forward and backward kinetic measurements for the reaction of CO₂(aq) with MEA yielded the rate and equilibrium constants, including the protonation constant of MEA carbamate, for the temperature range of 15–45 °C. Analysis of the rate and equilibrium constants in terms of the Arrhenius, Eyring, and van’t Hoff relationships gave the relevant thermodynamic parameters. In addition, the rate and equilibrium constants for the slow, reversible reaction of bicarbonate with MEA are reported at 25.0 °C. At high pH, reactions of the amine with CO₂ and with bicarbonate are significant.]]> Sat 24 Mar 2018 08:03:56 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:19664 Sat 24 Mar 2018 08:01:10 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:20414 G) describing CO₂ absorption and NH₃ vapor loss in 3.0M NH₃ and blended 3.0M NH₃ solutions containing a wide range of K-SAR concentrations from 0.0 to 3.0M were determined using a wetted-wall column contactor at 15–25 °C and CO₂ loadings from 0.0 to 0.5(molCO₂/mol total amine). Additionally, prediction of equilibrium species distribution using fundamental chemical modelling software (ReactLab) in CO₂-loaded NH₃ containing blended solutions were used to explain our experimental results. Addition of K-SAR resulted in significant improvement of K_G of CO₂ absorption in NH₃ solutions, but also increased NH₃ vapor losses. The effect of temperature on K_G of CO₂ absorption in K-SAR solution was greater than in the NH₃/K-SAR blended solution. The improvement in mass transfer upon addition of K-SAR is due to the faster reaction of CO₂ with K-SAR than with NH₃. The greater loss of NH₃ upon addition of K-SAR can be ascribed to the availability of more free NH₃ and the decrease of solubility of CO₂ and NH₃ in the NH₃/K-SAR blended solution. The investigation of K_G of CO₂ and NH₃ vapor losses in NH₃ and other amines (PZ, 1-MPZ, DEA and MEA) blended solutions also proved the competition for CO₂ is one of the reasons for the increasing of NH₃ vapor losses.]]> Sat 24 Mar 2018 08:00:52 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:19609 Sat 24 Mar 2018 07:58:24 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:17954 Sat 24 Mar 2018 07:56:27 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:19716 Sat 24 Mar 2018 07:53:45 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:27126 carb=7600M^-1s^-1 at 35°C and Eₐ=38 kJ mol^-1) and similar carbamate stability but with a ~40% larger enthalpy of protonation. It was also found to be less corrosive and have lower viscosity and heat capacity. Significant performance gains relative to MEA 30wt% were predicted by using BZA in a formulation with either MEA or 2-amino-2-methyl-1-proponal (AMP) with predicted reductions in reboiler duty up to 13%, improvements in mass transfer up to 20% and low corrosion potential.]]> Sat 24 Mar 2018 07:41:34 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:25635 10K_prot) of selected series of primary, secondary and tertiary alkanolamines/amines over the temperature range 288–318 K are reported. Selected series studied involve primary, secondary and tertiary mono-, di- and tri-alkanolamines, secondary amines including heterocyclic species, and both –CH₂OH and –CH₂CH₂OH substituted piperidines. van’t Hoff analyses have resulted in the standard molar enthalpies, ΔH_m^o, and molar entropies, ΔS_m^o, of protonation. Trends in ΔH_m^o are correlated with systematic changes in composition and structure of the selected series of amines/alkanolamines, while ΔH_m^o–ΔS_m^o plots generated linear correlations for the mono-, di-, and tri-alkanolamines, the –CH₂OH and –CH₂CH₂OH substituted piperidines, and the alkylamines. These relationships provide a guide to the selection of an amine(s) solvent for CO₂ capture, based on a greater difference in log₁₀K_prot between the absorber and stripper temperatures.]]> Sat 24 Mar 2018 07:28:09 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:25642 o_m, and entropies, ΔS^o_m of carbamate formation. A ΔH^o_m - ΔS^o_m plot generates a linear correlation for carbamate formation (providing a mean standard molar free energy, ΔG^o_m for carbamate formation of about -7kJ · mol^-1), and this relationship helps provide a guide to the selection of an amine(s) solvent for CO₂ capture, in terms of enthalpy considerations. A linear ΔH^o_m - ΔS^o_m plot also occurs for carbamate protonation. The formation of the carbamates has been correlated with systematic changes in composition and structure, and steric effects have been identified by comparing molecular geometries obtained using density functional B3LYP/6-311++G(d,p) calculations. Trends in steric effects have been identified in the series of compounds monoethanolamine (MEA), 1-amino-2-propanol, 2-amino-1-propanol (AP) and 2-amino-2-methyl-1-propanol (AMP). In the case of 2-piperidinemethanol, 2-piperidineethanol and 3-piperidinemethanol, strong intramolecular hydrogen bonding is shown to be the likely cause for lack of carbamate formation, and in the ring systems of pyrrolidine, morpholine, piperidine and thiomorpho- line trends in carbamate formation (as given by K₉) have been correlated with the internal ring angle at the amine nitrogen, as well as the planarity of the environment around the nitrogen atom.]]> Sat 24 Mar 2018 07:28:08 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:27740 G) describing the absorption of CO₂ into aqueous PZ/NH₃ solutions were determined using a wetted-wall column apparatus at 25°C. The effect of added PZ (from 0 to 0.5M) on the mass transfer of CO₂ into 3.0M NH₃ solutions over a range of pre-loaded CO₂ concentrations of 0.9M at 25°C are reported in this work. The fast kinetic reactions of CO₂(aq) with blended solutions containing PZ/NH₃ were investigated using stopped-flow spectrophotometry at 25.0°C. Analysis of the kinetic measurements using a chemical model which incorporates the complete reaction sets of the individual amines with CO₂ (i.e., NH₃₋CO₂₋H₂O and PZ₋CO₂₋H₂O) resulted in good agreement with the experimental data. The contribution distribution from each reactive species was calculated based on the proposed reaction scheme of the PZ₋NH₃₋CO₂₋H₂O system. Results show that both the PZ/PZH⁺ and PZCO₂̅/PZCO₂H pathways make contributions to the promotion of CO₂ absorption into PZ promoted aqueous NH3 solutions. Importantly, the reactive piperazine mono-carbamate species, PZCO₂̅/PZCO₂H, which is present in the CO₂₋loaded mixtures of PZ/NH₃, plays an important role in the promotion of CO₂ absorption into CO₂₋loaded aqueous NH₃ solutions. The mass transfer simulation results reveal that there are additional reactions occurring in the gas-liquid interface and gas phase due to the volatility of NH₃, which requires further improvement on the simulation model.]]> Sat 24 Mar 2018 07:27:46 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:27485 Sat 24 Mar 2018 07:25:40 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:27484 Sat 24 Mar 2018 07:25:38 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:22247 Sat 24 Mar 2018 07:17:34 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:23052 Sat 24 Mar 2018 07:13:50 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:42598 Fri 26 Aug 2022 12:17:41 AEST ]]>