Electrochemically mediated amine regeneration is a new post-combustion capture technology with the potential to exploit the excellent removal efficiencies of thermal amine scrubbers while reducing parasitic energy losses and capital costs. The improvements result from the use of an electrochemical stripping cycle, in lieu of the traditional thermal swing, to facilitate CO 2 desorption and amine regeneration; metal cations generated at an anode react with the amines, displacing the CO 2 , which is then flashed off, and the amines are regenerated by subsequent reduction of the metal cations in a cathode cell. The advantages of such a process include higher CO 2 desorption pressures, smaller absorbers, and lower energy demands. Several example chemistries using different polyamines and copper are presented. Experimental results indicate an open-circuit efficiency of 54% (15 kJ per mole CO 2) is achievable at the tested conditions and models predict that 69% efficiency is possible at higher temperatures and pressures. A bench scale system produced 1.6 mL min À1 CO 2 while operating at 0.4 volts and 42% Faradaic efficiency; this corresponds to a work of less than 100 kJ per mole. Broader context For the next several decades, coal will remain one of the most utilized sources of electricity in the world. While coal is cheap and abundant, it is also the dirtiest form of fossil fuel. Just one coal-red power plant emits 100's of metric tons per hour of carbon dioxide (CO 2); enough to ll the Empire State Building ve times per day. Carbon capture and sequestration is the only way to satisfy the world's growing energy demands while addressing climate change. Many technologies exist to capture the CO 2 from the ue gas leaving a powerplant. Thermal amine scrubbing is the most developed of these technologies, but is inefficient, capitally expensive, and inapplicable to existing power plants. Electrochemically Mediated Amine Regeneration (EMAR) is new a technology, developed at MIT, which addresses many of the shortcomings of thermal scrubbing while remaining similar enough that the process could be rapidly deployed by industry. We show through modeling and experiments that the EMAR system should be capable at of separating CO 2 for less than 15 kJ per mole with low current densities at 70 C. Our bench-scale system, running at room temperature, operates at 100 kJ per mole.

The complexation and decomplexation of CO2 with a series of quinones of different basicity during electrochemical cycling in dimethylformamide solutions were studied systematically by cyclic voltammetry. In the absence of CO2, all quinones exhibited two well-separated reduction waves. For weakly complexing quinones, a positive shift in the second reduction wave was observed in the presence of CO2, corresponding to the dianion quinone-CO2 complex formation. The peak position and peak height of the first reduction wave was unchanged, indicating no formation of complexes between the semiquinones and CO2. The relative heights of both reduction waves remained constant. In the case of strongly complexing quinones, the second reduction wave disappeared while the peak height of the first reduction wave approximately doubled, indicating that the two electrons transferred simultaneously at this potential. The observed voltammograms were rationalized through several equilibrium arguments. Both weakly and strongly complexing quinones underwent either stepwise or concerted mechanisms of oxidation and CO2 dissociation depending on the sweep rate in the cyclic voltammetric experiments. Relative to stepwise oxidation, the concerted process requires a more positive electrode potential to remove the electron from the carbonate complexes to release CO2 and regenerate the quinone. For weakly complexing quinones, the stepwise process corresponds to oxidation of the uncomplexed dianion and accompanying equilibrium shift, while for strongly complexing quinones the stepwise process would correspond to the oxidation of mono(carbonate) dianion to the complexed semiquinone and accompanying equilibrium shift. This study provides a mechanistic interpretation of the interactions that lead to the formation of quinone-CO2 complexes required for the potential development of an energy efficient electrochemical separation process and discusses important considerations for practical implementation of CO2 capture in the presence of oxygen with lower vapor pressure solvents.

A series of tri- and bimetallic titanium-gold, titanium-palladium and titanium-platinum derivatives of general formulas [Ti{η5-C5H4(CH2)nPPh2(AuCl)}2].2THF n = 0 (1); n = 2 (2); n = 3 (3) and [TiCl2{η5-C5H4κ-(CH2)nPPh2}2(PtCl2)].2THF (M = Pd, n = 0 (4); n = 2 (5); n = 3 (6); M = Pt, n = 0 (7); n = 2 (8); n = 3 (9)) have been synthesized and characterized by different spectroscopic techniques and mass spectrometry. The molecular structures of compounds 1–9 have been investigated by means of density-functional calculations. The calculated IR spectra of the optimized structures fit well with the experimental IR data obtained for 1–9. The stability of the heterometallic compounds in deuterated solvents (CDCl3, d6-dmso, mixtures 50:50 d6-dmso/D2O, 1:99 d6-dmso/D2O at acidic pH and at neutral pH) has been evaluated by 31P and 1H NMR spectroscopy showing a higher stability for these compounds than for Cp2TiCl2 or precursors [Ti{η5-C5H4(CH2)nPPh2}2]. The new compounds display a lower acidity (1 to 2 units) than Cp2TiCl2. The decomposition products have been identified over time. Complexes 1–9 have been tested as potential anticancer agents and their cytotoxicity properties were evaluated in vitro against HeLa human cervical carcinoma and DU-145 human prostate cancer cells. TiAu2 and TiPd compounds were highly cytotoxic for these two cell lines. The interactions of the compounds with Calf Thymus DNA have been evaluated by Thermal Denaturation (1–9) and by Circular Dichroism (1, 3, 4, 7) spectroscopic methods. All these complexes show a stronger interaction with DNA than that displayed by Cp2TiCl2 at neutral pH. The data is consistent with electrostatic interactions with DNA for TiAu2 compounds and for a covalent binding mode for TiM (M = Pd, Pt) complexes.