Sonia Zulfiqar

Polymeric ionic liquids for CO2 capture and separation: potential, progress and challenges

The increasing level of carbon dioxide (CO2) in the atmosphere is a big threat to the environment and plays a key role towards global warming and climate change. In this context to combat such issues, polymeric ionic liquids (PILs) serve as potential substitutes that offer an extremely versatile and tunable platform to fabricate a wide variety of sorbents for CO2 capture, in particular, for flue gas separation (CO2/N2) and natural gas purification (CO2/CH4). Formerly, there have been several reports on exploitation of ionic liquids for CO2 sorption with promising results. However, just a few have focused on polymeric ionic liquids which significantly over-performed the sorption efficiency of the molecular ionic liquids. This review is first ever of its kind which showcases the potential of PILs as a new member of the CO2 adsorbent family. The most dynamic aspect of PILs research at present is the curiosity to explore their potential as solid sorbents for CO2 capture and separation. This review not only highlights the recent advances in the area of PILs as sorbents for CO2 uptake but also portrays the forthcoming challenges in improving their efficiency. The effect of various cations, anions, polymer backbones, alkyl substituents, porosity, cross-linking, molecular weight and moisture on the CO2 sorption capacity and separating efficiency is scrutinized in detail. Moreover, future strategies to increase the CO2 capture performance of PILs are also discussed.

Amidoximes: promising candidates for CO2 capture

Monoethanolamine (MEA) dominates power plant carbon dioxide (CO2) scrubbing processes, though with major disadvantages such as a 8–35% energy penalty. Here we report that structurally comparable amidoximes are promising CO2 capture agents based on RIMP2 electronic structure calculations. This was experimentally verified by the synthesis and testing of representative amidoximes for capture efficiencies at pressures as high as 180 bar. Acetamidoxime, which has the highest percent amidoxime functionality showed the highest CO2 capacity (2.71 mmol g−1) when compared to terephthalamidoxime (two amidoximes per molecule) and tetraquinoamidoxime (four amidoximes per molecule). Polyamidoxime surpassed activated charcoal Norit RB3 for CO2 capture per unit surface area. Adsorption isotherms exhibit Type IV behavior and acetamidoxime found to increase CO2 capture with temperature, a less observed anomaly. Porous amidoximes are proposed as valuable alternatives to MEA.

CO2 Adsorption Studies on Hydroxy Metal Carbonates M(CO3)x(OH)y (M = Zn, Zn–Mg, Mg, Mg–Cu, Cu, Ni, and Pb) at High Pressures up to 175 bar

Carbon dioxide (CO(2)) adsorption capacities of several hydroxy metal carbonates have been studied using the state-of-the-art Rubotherm sorption apparatus to obtain adsorption and desorption isotherms of these compounds up to 175 bar. The carbonate compounds were prepared by simply reacting a carbonate (CO(3)(2-)) solution with solutions of Zn(2+), Zn(2+)/Mg(2+), Mg(2+), Cu(2+)/Mg(2+), Cu(2+), Pb(2+), and Ni(2+) metal ions, resulting in hydroxyzincite, hydromagnesite, mcguinnessite, malachite, nullaginite, and hydrocerussite, respectively. Mineral compositions are calculated by using a combination of powder XRD, TGA, FTIR, and ICP-OES analysis. Adsorption capacities of hydroxy nickel carbonate compound observed from Rubotherm magnetic suspension sorption apparatus has shown highest performance among the other components that were investigated in this work (1.72 mmol CO(2)/g adsorbent at 175 bar and 316 K).

Soluble Aromatic Polyamide Bearing Sulfone Linkages: Synthesis and Characterization

New soluble and linear aromatic polyamide chains were produced by condensing 4-aminophenylsulfone with isophthaloyl chloride in dimethylacetamide as a solvent under an inert atmosphere. HCl produced as a byproduct was removed from the reaction mixture by precipitating with a stoichiometric amount of triethylamine. A clear polyamide solution was obtained after isolation of the precipitates. Thin and transparent film was cast from the solution by baking out the solvent and after drying, the film was employed for various analyses. It was found to be soluble in various organic solvents. The structure elucidation of the resulting polyamide was carried out using infrared and nuclear magnetic resonance spectroscopy. The molecular weight distribution was determined by gel permeation chromatography. These results confirmed the formation of the aromatic polyamide. Thermogravimetry, differential scanning calorimetry, water absorption and mechanical measurements were also performed to further verify the physical properties of the aromatic polyamide.

Recent Developments in Sulfur-Containing Polymers

Currently, a lot of research efforts have been directed toward exploiting the special high-performance characteristics of polymers with sulfur in the backbone. Sulfur-containing polymers fall under various classes and cover an extremely broad property range. The impetus to their development resulted from the unique properties and success in their applications, depending upon the type of linkage introduced. This review basically sets out to explain the design, synthesis, properties, and applications of various sulfur-containing polymers especially polyamides, polyimides, poly(amide-imide)s, polybenzimidazoles, polyurethanes, polyesters, etc. Outstanding performance of these polymers came up from their structures having sulfur-based groups such as thiophene, sulfide, sulfone, thiazol, and thiourea. Thus these linkages endow special features to such functional polymers. The sulfur-containing polymers are also described here with reference to their relevance as optically active, liquid crystalline, flame retardant, and fuel cell materials. Several endeavors are underway to take advantage of incorporated sulfur moiety in the polymer backbone, as a consequence to ascertain their validity on the forefront of scientific investigations.

Amidoxime porous polymers for CO2 capture

CO2 capture from fossil fuel based electricity generation remains costly since new power plants with monoethanol amine (MEA) as the scrubbing agent are under construction. Amidoximes are known to mimic MEA, and porous polymers with amidoximes could offer a sustainable solution to carbon capture. Here we report the first amidoxime porous polymers (APPs) where aromatic polyamides (aramids) having amidoxime pendant groups were synthesized through low temperature condensation of 4,4′-oxydianiline (ODA) and p-phenylene diamine (p-PDA) with a new type of nitrile-bearing aromatic diacid chloride. The nitrile pendant groups of the polyamides were converted to an amidoxime functionality by a rapid hydroxylamine addition (APP-1 and APP-2). The CO2 adsorption capacities of these polyamides were measured at low pressure (1 bar) and two different temperatures (273 and 298 K) and high pressure (up to 225 bar – the highest measuring pressure to date) at 318 K. The low pressure CO2 uptake of APP-1 was found to be 0.32 mmol g−1 compared with APP-2 (0.07 mmol g−1) at 273 K, whereas at high pressure they showed a substantial increase in CO2 adsorption capacity exhibiting 24.69 and 11.67 mmol g−1 for APP-1 and APP-2 respectively. Both aramids were found to be solution processable, enabling membrane applications.

Nanoporous amide networks based on tetraphenyladamantane for selective CO2 capture

Reduction of anthropogenic CO2 emissions and CO2 separation from post-combustion flue gases are among the imperative issues in the spotlight at present. Hence, it is highly desirable to develop efficient adsorbents for mitigating climate change with possible energy savings. Here, we report the design of a facile one pot catalyst-free synthetic protocol for the generation of three different nitrogen rich nanoporous amide networks (NANs) based on tetraphenyladamantane. Besides the porous architecture, CO2 capturing potential and high thermal stability, these NANs possess notable CO2/N2 selectivity with reasonable retention while increasing the temperature from 273 K to 298 K. The quantum chemical calculations also suggest that CO2 interacts mainly in the region of polar amide groups (–CONH–) present in NANs and this interaction is much stronger than that with N2 thus leading to better selectivity and affirming them as promising contenders for efficient gas separation.

Synthesis, morphology, and properties of self-assembled nanostructured aramid and polystyrene blends.

Aramid (Ar), produced from the reaction of aromatic diamines and diacid chloride, was reactively compatibilized with amino-functionalized polystyrene (APS) to explore blend morphology and interfacial cohesion. Two blend systems, Ar/PS and Ar/APS, were investigated over a range of pristine polystyrene (PS) or modified APS ratios. Morphology and thermal and mechanical properties were probed to evaluate the effect of amine units of APS on the compatibility with Ar. π-π stacking interactions in tandem with the random distribution of graft attachment locations and polydispersity of graft length in Ar-g-APS copolymer, aided merger of unreacted chains to drive molecular self-assembly process thus fortifying the nanostructured blends. Considerable augmentation of the blend morphology and thermal stability was achieved by incorporation of reactivity into Ar/APS system. A 20 wt % APS-containing blend was found to demonstrate optimum mechanical reinforcement, complemented by the optimal, thermal, and morphological profiles of the same blend. Future prospects are envisaged.

Synthesis and Characterization of Aromatic–Aliphatic Polyamide Nanocomposite Films Incorporating a Thermally Stable Organoclay

Nanocomposites were synthesized from reactive thermally stable montmorillonite and aromatic–aliphatic polyamide obtained from 4-aminophenyl sulfone and sebacoyl chloride. Carbonyl chloride terminal chain ends were generated using 1% extra sebacoyl chloride that could interact chemically with the organoclay. The distribution of clay in the nanocomposites was investigated by XRD, SEM, and TEM. Mechanical and thermal properties of these materials were monitored using tensile testing, TGA, and DSC. The results revealed delaminated and intercalated nanostructures leading to improved tensile strength and modulus up to 6 wt% addition of organoclay. The elongation at break and toughness of the nanocomposites decreased with increasing clay contents. The nanocomposites were thermally stable in the range 400–450 °C. The glass transition temperature increased relative to the neat polyamide due to the interfacial interactions between the two phases. Water uptake of the hybrids decreased upon the addition of organoclay depicting reduced permeability.

Probing the potential of polyester for CO2 capture

Global warming, the major environmental issue confronted by humanity today, is caused by rising level of green house gases. Carbon capture and storage technologies offer potential for tapering CO₂ emission in the atmosphere. Adsorption is believed to be a promising technology for CO₂ capture. For this purpose, a polyester was synthesized by polycondensation of 1,3,5-benzenetricarbonyl trichloride and cyanuric acid in pyridine and dichloromethane mixture. The polymer was then characterized using FT-IR, TGA, BET surface area and pore size analysis, FESEM and CO₂ adsorption measurements. The CO₂ adsorption capacities of the polyester were evaluated at a pressure of 1bar and two different temperatures (273 and 298K). The performance of these materials to adsorb CO₂ at atmospheric pressure was measured by optimum CO₂ uptake of 0.244 mmol/g at 273K. The synthesized polyester, therefore, has the potential to be exploited as CO₂ adsorbent in pre-combustion capture process.