Rich Solvents Research Articles

Linking Multicomponent Interactions of Catalyst Ink and Catalyst Layer Fabrication with Electrochemical CO2 Reduction Performance

The controllable fabrication of catalyst layers (CL) by tuning the multiscale structure formation is complex but vital to achieving optimum CO2 reduction (CO2R) performance. The CL formation is deeply influenced by catalyst ink. An in-depth understanding on the role of each catalyst ink component and how multicomponent interactions affect ink status, catalyst layer structure, and CO2R performance is crucial.In this work, the roles of various ingredients of catalyst ink were systematically investigated from simple binary inks to complete catalyst inks. Our results showed Ag agglomerates can be broken down more efficiently in water than in alcohols due to stronger inter-particle repulsive forces induced by water disassociation. Ag particles-Nafion networks were found to play a decisive role in stabilizing catalyst ink, mitigating agglomeration and particle sintering. The catalyst ink was comprehensively characterized and reported by static multiple light scattering (SMLS) for the first time in this study. The evolution of catalyst ink was identified in three stages: stable, flocculation and sedimentation. Isopropanol (IPA)-rich solvents were demonstrated to be more effective in stabilizing catalyst ink due to better dispersed Nafion aggregates and further enhanced Ag particle-Nafion interactions.Subsequently, catalyst layer structure and CO2R performance were correlated with multi-component interactions in catalyst ink. Strong Ag particle-Nafion interactions were proven to promote not only ink stability, but also catalyst layer homogeneity and reaction site distribution. Water-rich inks helped improve the porosity and durability of GDEs. The cathodic potential of GDEs made by 70%-water inks (-0.75 V vs. NHE) was 30% lower than zero-water inks (-1.1 V vs. NHE), and the highest CO selectivity was boosted to 97% at an industrial meaningful current density of 200 mA/cm2 by enhancing Ag particle-Nafion interactions through rational design of ink formulation, dispersing and fabrication processes.Simultaneously, a scalable manufacturing methodology of robust GDE was developed and validated to achieve optimal CO2R performance. It will not only provide a meaningful reference for lab applications (fast and reproducible GDE fabrication aiming at new catalysts, ionomers, membranes or operation conditions development), but also provide a steppingstone to industrial applications (GDE fabrication aiming at large scale, good durability and quality of conformance). Figure 1

Correlating catalyst ink design and catalyst layer fabrication with electrochemical CO2 reduction performance

The controllable fabrication of catalyst layers (CL) by tuning the multiscale structure formation is complex but vital to achieving optimum carbon dioxide reduction (CO2R) performance. An in-depth understanding on the role of each catalyst ink component and how multi-component interactions affect ink status, catalyst layer structure, and CO2R performance is crucial. In this work, the roles of different ingredients of catalyst ink were systematically investigated from simple binary inks to complete catalyst inks. Silver (Ag) particles-Nafion interactions were found to play a decisive role in stabilizing catalyst ink, mitigating agglomeration and particle sintering. The catalyst ink was comprehensively characterized and reported by static multiple light scattering (SMLS) for the first time in this paper. The evolution of catalyst ink was identified in three stages: stable, flocculation and sedimentation. Isopropanol (IPA)-rich solvents were found to be more effective in stabilizing catalyst ink due to better dispersed Nafion aggregates and further enhanced Ag particle-Nafion interactions. Subsequently, catalyst layer structure and CO2R performance were correlated with multi-component interactions in catalyst ink. Strong Ag particle-Nafion interactions were proven to promote not only ink stability, but also catalyst layer homogeneity and reaction site distribution. The carbon monoxide (CO) selectivity was boosted from 80.5 % to 94 % at an industrial meaningful current density of 200 mA/cm2 using commercial Ag nanoparticles by rational design of ink formulation, dispersing and fabrication processes. Simultaneously, a scalable manufacturing methodology of robust gas diffusion electrodes (GDEs) to achieve optimal CO2R performance was developed and validated.

Optimization of Methods for Purification of Gas Mixtures to Remove Carbon Dioxide (A Review)

This review provides an analysis of modern process technologies for carbon dioxide removal from various gas mixtures (such as natural gas or hydrocarbon conversion gases in ammonia and syngas production facilities), as well as from flue gases generated during the combustion of carbon-containing feedstocks in power plants. The review also discusses various approaches to improve absorption/desorption processes, both in terms of extending the range of practicable amine solvents and the prospects for the implementation of a new equipment type, namely membrane contactors based on hollow fiber membranes or ceramic tubular elements. Finally, the paper describes a process configuration for the decarbonation of rich amine solvents at ≤90°C using 12% monoethanolamine (MEA) solutions to prevent the solvent from thermo-oxidative degradation.

Monitoring of the blend monoethanolamine/methyldiethanolamine/water for post-combustion CO2 capture

The blend MEA/MDEA (5/25%wt.) was studied on the LEMEDES-CO2 lab-scale pilot plant, with representative conditions of post-combustion CO2 capture for power generation during 900 h. CO2 loadings were determined and showed average values of 0.12 and 0.40 respectively for the lean and rich solvents. Stability of the two amines, namely MEA and MDEA, was monitored using ionic chromatography; results did not show any significant degradation of MDEA during the campaign, in contrary to MEA which showed a significant degradation in the range of 0.03 points per day. Analytical methods involving GC–MS and IC were developed in order to identify potential degradation products in the liquid phase of the solvent. Study of the gaseous emissions’ composition was also realized using sampling on different solid sorbents followed by thermal desorption and GC–MS analysis. A total of 22 compounds were listed including amines, organic acids, and pyrazines derivatives. 12 degradation products were found in the solvent itself and 11 in the treated flue gas among which MDEA, the constituent amine of the blend. A quantitative monitoring was carried out for formic and oxalic acids. Results showed concentrations reaching 500 mg/L for oxalic acid and 1400 mg/L for formic acid.

Complexation reactions in pyridine and 2,6-dimethylpyridine-water system: The quantum-chemical description and the path to liquid phase separation.

Phase separation in substituted pyridines in water is usually described as an interplay between temperature-driven breakage of hydrogen bonds and the associating interaction of the van der Waals force. In previous quantum-chemical studies, the strength of hydrogen bonding between one water and one pyridine molecules (the 1:1 complex) was assigned a pivotal role. It was accepted that the disassembly of the 1:1 complex at a critical temperature leads to phase separation and formation of the miscibility gap. Yet, for over two decades, notable empirical data and theoretical arguments were presented against that view, thus revealing the need in a revised quantum-mechanical description. In the present study, pyridine-water and 2,6-dimethylpyridine-water systems at different complexation stages are calculated using high level Kohn-Sham theory. The hydrophobic-hydrophilic properties are accounted for by the polarizable continuum solvation model. Inclusion of solvation in free energy of formation calculations reveals that 1:1 complexes are abundant in the organically rich solvents but higher level oligomers (i.e., 2:1 dimers with two pyridines and one water molecule) are the only feasible stable products in the more polar media. At the critical temperature, the dissolution of the external hydrogen bonds between the 2:1 dimer and the surrounding water molecules induces the demixing process. The 1:1 complex acts as a precursor in the formation of the dimers but is not directly involved in the demixing mechanism. The existence of the miscibility gap in one pyridine-water system and the lack of it in another is explained by the ability of the former to maintain stable dimerization. Free energy of formation of several reaction paths producing the 2:1 dimers is calculated and critically analyzed.

Visualization of Surface Acoustic Waves in Thin Liquid Films.

We demonstrate that the propagation path of a surface acoustic wave (SAW), excited with an interdigitated transducer (IDT), can be visualized using a thin liquid film dispensed onto a lithium niobate (LiNbO3) substrate. The practical advantages of this visualization method are its rapid and simple implementation, with many potential applications including in characterising acoustic pumping within microfluidic channels. It also enables low-cost characterisation of IDT designs thereby allowing the determination of anisotropy and orientation of the piezoelectric substrate without the requirement for sophisticated and expensive equipment. Here, we show that the optical visibility of the sound path critically depends on the physical properties of the liquid film and identify heptane and methanol as most contrast rich solvents for visualization of SAW. We also provide a detailed theoretical description of this effect.

Charge-transfer complexation between naphthalene diimides and aromatic solvents.

Naphthalene diimides (NDIs) form emissive ground-state charge-transfer (CT) complexes with various electron rich aromatic solvents like benzene, o-xylene and mesitylene. TD-DFT calculation of the complexes suggests CT interaction and accounts for the observed ground-state changes.

Solvent switchable CuII complexes

Dinuclear/tetranuclear interconversion of a magnetically coupled copper(ii) Schiff base complex driven by water rich solvents.

Effect of addition of weak acids on CO2 desorption from rich amine solvents

Experiments were conducted to study the effect of addition of four weak acids (adipic, suberic, phthalic and sebacic acids) on the regeneration of three types of CO2-loaded rich solvents (Monoethanolamine (MEA), Diethanolamine (DEA) and Methyldiethanolamine (MDEA)). It was found that CO2 could be released faster and in a larger quantity when the amount of acid added to the solvent was increased while other desorption conditions were maintained unchanged. Adipic acid appeared to be more effective than phthalic, suberic and sebacic acids in enhancing solvent regeneration rate. Among the three amines investigated, MEA had the highest CO2 desorption rate, while DEA saved the most energy. The effect of adipic acid residue in the MEA solvent on CO2 absorption was also investigated. The residue acid reduced the absorption capacity of the MEA solvent significantly when the solvent concentration was low and slightly when the concentration was high.

Correlation of the Rates of Solvolysis of Neopentyl Chloroformate—A Recommended Protecting Agent

The specific rates of solvolysis of neopentyl chloroformate (1) have been determined in 21 pure and binary solvents at 45.0 °C. In most solvents the values are essentially identical to those for ethyl and n-propyl chloroformates. However, in aqueous-1,1,1,3,3,3-hexafluoro-2-propanol mixtures (HFIP) rich in fluoroalcohol, 1 solvolyses appreciably faster than the other two substrates. Linear free energy relationship (LFER) comparison of the specific rates of solvolysis of 1 with those for phenyl chloroformate and those for n-propyl chloroformate are helpful in the mechanistic considerations, as is also the treatment in terms of the Extended Grunwald-Winstein equation. It is proposed that the faster reaction for 1 in HFIP rich solvents is due to the influence of a 1,2-methyl shift, leading to a tertiary alkyl cation, outweighing the only weak nucleophilic solvation of the cation possible in these low nucleophilicity solvents.

Reduction of Energy Requirement of CO2Desorption by Adding Acid into CO2-Loaded Solvent†

The effect of the addition of weak acids into CO2-loaded solvents or rich solvents on the energy requirement of CO2 desorption was investigated experimentally. The commercially available CO2 solvent monoethanolamine (MEA) was used to absorb different amounts of CO2. Subsequently, a few weak acids such as suberic acid, phthalic acid, and oxalic acid were added into the solvents to study the effect of acid amount on the rate of CO2 release. It was found that CO2 could be released much faster and in much larger quantity with the addition of weak acids while the other desorption conditions were maintained the same. The amount of CO2 released was found to be proportional to the amount of acid added. Acid addition could be potentially used to reduce the energy requirement for CO2 desorption from solvent.

Calorimetric determination of enthalpy changes for the proton ionization of N-tris(hydroxymethyl)methyl-4-aminobutanesulfonic acid (TABS), N-tris(hydroxymethyl)methyl-3-aminopropanesulfonic acid (TAPS) and 3-[ N-tris(hydroxymethyl)methylamino]-2-hyroxypropane sulfonic acid (TAPSO) in water–methanol mixtures

Enthalpies for the two proton ionizations of the biochemical buffers N-tris(hydroxymethyl)methyl-4-aminobutanesulfonic acid (TABS), N-tris(hydroxymethyl)methyl-3-aminopropanesulfonic acid (TAPS) and 3-[ N-tris(hydroxymethyl)methylamino]-2-hyroxypropane sulfonic acid (TAPSO) were obtained in water–methanol mixtures with methanol mole fraction ( X m) from 0 to 0.360. The ionization enthalpy for the first proton (Δ H 1) of all three buffers was small and exhibited slight changes upon methanol addition. The ionization enthalpy of the second proton (Δ H 2) of TABS increased from 39.6 to 49.8 kJ mol −1 and for TAPS from 40.1 to 43.2 kJ mol −1, with a minimum of 38.2 kJ mol −1 at X m = 0.059. For TAPSO the increase was from 33.1 to 35.6 kJ mol −1 at X m = 0.194, with measurements at higher X m precluded by low solubility of TAPSO in methanol rich solvents. The solvent composition was selected so as to include the region of maximum structure enhancement of water by methanol. The results were interpreted in terms of solvent–solvent and solvent–solute interactions.

The Structure of Gas-Phase Bradykinin Fragment 1-5 (RPPGF) Ions: An Ion Mobility Spectrometry and H/D Exchange Ion-Molecule Reaction Chemistry Study

Ion mobility-mass spectrometry (IM-MS) data is interpreted as evidence that gas-phase bradykinin fragment 1-5 (BK1-5, RPPGF) [M + H](+) ions exist as three distinct structural forms, and the relative abundances of the structural forms depend on the solvent used to prepare the matrix-assisted laser desorption ionization (MALDI) samples. Samples prepared from organic rich solvents (90% methanol/10% water) yield ions having an ion mobility arrival-time distribution (ATD) that is dominated by a single peak; conversely, samples prepared using mostly aqueous solvents (10% methanol/90% water) yield an ATD composed of three distinct peaks. The BK1-5 [M + H](+) ions were also studied by gas-phase hydrogen/deuterium (H/D) exchange ion-molecule reactions and this data supports our interpretation of the IM-MS data. Plausible structures for BK1-5 ions were generated by molecular dynamics (MD). Candidate MD-generated structures correlated to measured cross-sections suggest a compact conformer containing a beta-turn whereas a more extended, open form does not contain such an interaction. This study illustrates the importance of intra-molecular interactions in the stabilization of the gas-phase ions, and these results clearly illustrate that solution-phase parameters (i.e., MALDI sample preparation) greatly influence the structures of gas-phase ions.

An investigation of influence of solvent on the degradation kinetics of carotenoids in oil extracts of Calendula officinalis

The stability of carotenoids was studied in marigold oil extracts prepared with following solvents: Myritol 312?, paraffin oil, almond oil, olive oil, sunflower oil, grape seed oil, and soybean oil. The concentration of the carotenoids was determined by spectroscopic measurement at 450 nm. Degradation rate showed a first order dependence on the concentration of carotenoids with a faster first stage (which lasted 35-50 days, depending on the solvent) and a slower second stage. The highest degradation rates were observed in extracts prepared with linoleic acid rich solvents (sunflower oil, soybean oil and grape seed oil), while the lowest were found in oil with saturated fatty acids (Myritol 312?) and paraffin oil. These results confirm the connection between the degradation of carotenoids and lipid autoxidation, and suggest that the influence of the oil solvents on the stability of oil extracts of Calendula officinalis is a factor that must be considered when selecting a solvent for the production of marigold oil extracts.

Dissociation Constants of p-Nitroaniline in Mixed Solvents and a Critical Assessment of the Solvent-Sorting Equilibrium Method for the Determination of the Single Ion Gibbs Energy of Transfer of H+ Ion from Aqueous to Aquo Rich Organic Solvents

Abstract The dissociation constants of p-nitroaniline (B) (BH+ ⇔ B + H+ ) in methanol + water and propan-1-ol + water mixtures have been determined. Due to the presence of -NH2 and -NO2 groups in complimentary para positions, the dissociation constants for p-nitroaniline decrease with increase in percentage of organic co-solvents contrary to those observed in case of aniline, metanitroaniline etc. A critical assessment of the solvent-sorting equilibrium method using p-nitroaniline as indicator has been made. The method is not suitable to determine the Gibbs energy of transfer of H+ from aqueous to aquo-rich organic solvents.

A comprehensive investigation of variations in melting ranges and NMR data of 2,4-dinitrophenylhydrazine derivatives

The well-known characterization method of aldehydes and ketones utilizing their 2,4-dinitrophenylhydrazones (DNPs) often gives variable melting ranges and conflicting results for a single derivative. We have found that the DNPs melting point discrepancies and the irreproducibility of the method are mainly due to syn–anti (E–Z) isomerization caused by traces of acids which remain in the products when prepared by the conventional methods. A bicarbonate washing of the DNPs removes the acid, stabilizes the melting range and reproducibly gives higher-melting derivatives. In the DNP preparations of aldehydes and some unsymmetrical ketones only the kinetically favored (and also thermodynamically more stable) syn (E) isomer is formed. The six different melting ranges of acetaldehyde DNP (AA-DNP) previously reported by other investigators are correlated with the amounts of acid present in their DNP crystals. Derivatives with higher concentrations of acid(s) give lower melting ranges. In the presence of small amounts of acid, E–Z isomerization occurs in most solvents but not in methanol or dimethyl sulfoxide (DMSO). Larger amounts of acid cause the isomerization in all solvents, but the process is much slower in the aforementioned solvents. Alcohols, but not chlorinated solvents, are suitable for the DNPs recrystallization. E–Z isomerization of AA-DNP also occurs thermally by first order kinetics when its pure E isomer is heated at its melted state. An equilibrium ratio of 2∶1 (E∶Z) is reached after 10 minutes. A substantial decrease (up to 2.05 ppm) is observed for the NMR chemical shifts of the AA-DNPs protons in benzene and electron rich aromatic solvents compared to those obtained in chloroform, acetonitrile, acetone, methanol, DMSO or even cyclohexane and electron deficient nitrobenzene. An explanation is given for the drastic chemical shift changes.

Effect of solvent and pH on the spectral characteristics of meso-tetrakis( p-hydroxyphenyl) porphyrin in dimethylformamide and dimethylformamide + water mixed solvents

The spectral changes in meso-tetrakis( p-hydroxyphenyl) porphyrin free base p-OHTPPH 2 are studied in DMF + H 2O mixed solvents and DMF alone from pH 2.0 to greater than 12. Drastic changes in spectral characteristics appear at high pH values > 12. Besides the modification of Soret and Q-bands, a new CT-band develops on the red-side of the Q-bands in water rich solvents. In a graded mixture of H 2O and DMF, as solvent, mole fraction x DMF varying from 0.04 to 0.7, the Q-band as well as the CT-band red shift and increase in intensity with increasing mole fraction of DMF. At x DMF > 0.7, i.e. x = 1, the spectrum changes dramatically into a single banded broad spectrum of acid type at pH 12 with concomitant disappearance of the CT-band. For p-OMeTPPH 2, the spectrum transforms to metalloporphyrin type at high pH, but for o-OHTPPH 2, the spectral characteristics of both p-OHTPPH 2 and p-OMeTPPH 2 are observed in DMF as solvent.

Solvation of Ions in Acetonitrile‐Methanol Solutions of Sodium Iodide

AbstractThe self‐diffusion coefficients of acetonitrile, methanol and ions in salt free acetonitrile‐methanol mixtures and in solutions of NaI have been measured at 25°C for the whole composition range of the binary solvent, for the salt molarity ranging from 1 · 10−4 to 1 · 10−2. The limiting self‐diffusion coefficients of sodium and iodide ions increase monotonously with increasing concentration of acetonitrile. The composition dependences of the ionic radii allow to postulate a preferential solvation of iodide ions by acetonitrile. That phenomenon has been found for those compositions of the mixed solvent, for which a microheterogeneity of the system has been observed. In methanol rich solvents (xAN < 0.5) the observed microheterogeneity results from the self‐association of methanol. The preferential solvation of iodide ions causes an enlargement of acetonitrile aggregates resulting in enhancement of microheterogeneity of the system. These results confirm a hypothesis that if interactions between ions and components of the mixed solvent are similar the preferential solvation of ions is promoted by the structure of solvent.

Design Of Miscible Solvents For A Rich Gas Drive-Comparison Of Slim Tube And Rising Bubble Tests

Abstract This study addresses miscible solvent design for the planned hydrocarbon flood in the Virginia Hills Beaverhill Lake Unit in north central Alberta. The development a/miscibility between reservoir fluid and a series of increasingly rich solvents was studied in a rising bubble apparatus. In order to establish the validity of this relatively new technique of solvent design, the rising bubble test observations were compared to results of conventional slim tube tests previously conducted with the same soh1ents. A very good correlation was found between the minimum solvent enrichment/or miscibility determined by the two techniques. The rising bubble method is shown to be not only much faster but also superior in some respects to slim tube testing. Introduction The Virginia Hills Beaverhill Lake reservoir, a carbonate reef formation in north central Alberta, was discovered in 1957 and has been under water flood since 1963. Of the original estimated 60 × 106 m3 oil in place, about one-third has been recovered to date. Current plans are for implementation of a miscible enriched gas flood, with solvent injection targeted for 1990(1). The relatively high reservoir temperature (100 °C) and intermediate pressure (20 MPa to 27 MPa) are common to several Alberta pools where miscible gas injection is currently underway. The Virginia Hills development is a joint venture project with Shell Canada as the operator. The annual cost of the solvent (a blend of dry gas and natural gas liquids streams) required by the project is estimated to exceed $30 million. It is thus important to design the solvent containing the minimum amount of expensive natural gas liquids (NGL) yet be miscible so as to maximize the oil recovery. As the composition of the NGL stream available from the pipeline is expected to vary throughout the miscible flood project life, solvent enrichment levels have to be determined for a variety of NGL stream compositions. Given the time consuming and costly nature of the slim tube tests (and our unwillingness to rely entirely on minimum solvent enrichment predicted with the equation of state), the rising bubble apparatus (RBA) tests present an attractive alternative. However, while the slim tube test is universally accepted by the industry, the validity of this more recently emerged method of solvent design has to be established. A systematic comparison of the two techniques was therefore undertaken, the results of which are presented in this paper. Equation of state (EOS) calculations were used throughout the study to interpret, in qualitative terms, the oil-solvent phase behaviour and its trends. Background - Mass Transfer Mechanism in Virginia Hills Miscible Rich Gas Drive Table 1 shows the composition of the Virginia Hills recombined reservoir fluid (VH fluid). This is a light but somewhat waxy crude containing about 3070 (wt) asphaltenes. The compositions of typical dry gas and NGL streams available for blending the solvent are also shown in Table 1. Throughout this paper, the solvents are referred to by their NGL to dry gas molar ratio; 75/25 solvent thus contains 750/0 NGL and 250/0 dry gas.

Effects of Impurities on Minimum Miscibility Pressures and Minimum Enrichment Levels for CO2 and Rich-Gas Displacements

Abstract Multicontact miscible displacement processes are becoming increasingly popular as a means of recovering secondary and tertiary oil reserves in the U.S. and Canada. Economics of multicontact miscible flooding are governed to some extent by the availability of large sources of high purity CO2 or suitable liquefied petroleum gas (LPG) streams. This is because achievement of miscibility depends on the solvent composition as well as the system temperature and pressure. Atypical components in a CO2 or solvent stream therefore may increase the required pressure or enrichment levels for achievement of miscibility. Several papers have been published discussing the pressure (for CO2) and composition (for rich gas) levels required for miscible displacement. The potential CO2 supply could be increased if complicated cleanup procedures for injected and produced fluids were not required. For engineering studies it is important that CO2 streams containing H2S and hydrocarbons be evaluated for their miscible flooding potential. It is also important to evaluate the effects of CO2 and C5 + components in rich gas mixtures to determine whether they can be used to reduce calculated enrichment levels for solvent systems. This paper presents results of studies using mixtures of CO2, H2S, and C1, CO2-LPG, and rich gas solvents containing CO2 or C5 to displace oil miscibly in slim-tube experiments. The purpose of this work is to show the effects of various components on pressure and compositions required for miscibility. As expected, the changes in CO2 miscibility pressure are direct functions of temperature. It is reported that the addition of H2S and C2+ hydrocarbons lowers the miscibility pressure for CO2, whereas the presence of C1 in a CO2 solvent increases it. More important, the results give a quantitative titative measure of the degree of reduction/elevation in miscibility pressure to be expected with impure CO2 streams. The paper also presents similar results from displacements with typical rich gas solvents mixed with CO2 and/or C5. It is reported that CO2 increases the minimum enrichment required, while a heavier hydrocarbon component actually can reduce anticipated enrichment levels.