Absorption Separation And Photocatalytic Conversion Research Of Carbon Dioxide

CO₂is a major component of greenhouse gases （GHG） which can potentially causethe global warming. Capture and utilization of CO₂is not noly ease the greenhouseeffect, but also store source of carbon. Adsorption is an efficient way which can be usedto reduce CO₂emissions, especially zeolite modified by organic amine is suitable forseparation of CO₂from gas mixture，with its low energy requirement for sorbentregeneration and high capture capacity. To further reduce the cost, promote theindustrialization process and establish efficient carbon dioxide capture system,developing a sorbent with high capture capacity and high stability and a goodperformance reactor with favorable heat and mass transfer is urgently needed. Aftercapture, CO₂can be converted to liquid fuel by solar energy, it is very meaningful fromthe perspective of carbon and energy balance. For efficient use of solar energy andeffective reduction of carbon dioxide, a photocatalyst responsing to visible light andhigh selectivity needs to be designed.In order to realize efficient adsorption of carbon dioxide, monolithic absorptivematerials were prepared for the first time by coating method usingtetraethylenepentamine （TEPA） modified mesoporous molecular sieve （SBA-15（P））adsorbent as active component, and honeycomb ceramic as inert support. Differentmonolithic absorptive materials was achieved according to the different of activecomponents and post-processing. The test of CO₂adsorption/desorption measurementshows that the monolithic absorptive material of amine solution-removal process has thebest absorbent adsorption capacities and cycle stability. The materials werecharacterized using X-ray diffraction （XRD）, N2-adsorption, elemental analysis, fouriertransform infrared spectroscopy （FTIR） and scanning electron microscope （SEM）techniques, the results proved that the distribution state and bonding forms withSBA-15（P） of amine molecular on the monolithic adsorbent could be further regulated,is equivalent to the "second dipping" function, so as to ascertain the high adsorptivecapacity and recycle stability of monolithic absorptive material.In order to explore thephotoreduction of carbon dioxide under visible lightconditions, a kind of copper-loaded and sulfur-doped TiO₂photocatalyst was preparedby electroless plating method, and the physical structure and electronic properties of theprepared Cu/S-TiO₂were characterized by UV-Vis, XRD, XPS, EXAFS, TEM and STEM techniques. It was illustrated that copper species loaded by electroless copperplating was Cu2O/CuO. The Cu/S-TiO₂prepared by electroless plating method showedexcellent visible light absorption ability. Moreover, the electroless plated copper werehighly dispersed on the surface of S-TiO₂, which could facilitate the photogeneratedcharges capture, transfer and separation. Thus, the catalyst exhibited a higherphotocatalytic activity for CO₂reduction, and the liquid production was mainlymethanol. The in-situ IR spectra indicate that the OH radical acted as an intermediateparticipating in the photocatalytic reaction. The formation of low omic reticulatedcircuit structure prepared by electroless copper plating method, facilitates the transferand separation, which would enhance photocatalytic hydrogen evolution can effectivelycapture photogenerated charges and transferring them to active copper site, whichwould enhance photoreduce CO₂. Based on this, a possible mechanism of photoreducedCO₂by Cu/S-TiO₂prepared by electroless copper plating method was proposed.