CO₂ conversion into valuable fuels using chromium based supports

AbstractCO2 utilization by direct catalytic conversion of CO2 driven by solar energy is an attractive approach for producing alternative value added products suitable for end-use infrastructure. In order to fully harness the solar spectrum and increase photocatalytic activity and selectivity, Cr-TiO2 based films were deposited on ceramic honeycomb monoliths with varying concentrations synthesized by sol-gel technique and dip coating route. The improved photocatalytic activity of the Cr-TiO2 monoliths in the visible light region compared to pure TiO2 can be attributed to increased visible light absorption and accessible active metal sites arising from the appropriate metal dispersion and loading amount

Effects of titania based catalysts on in-situ pyrolysis of <i>Pavlova</i> microalgae

Pavlova microalga was pyrolysed in presence of titania based catalysts in a fixed bed reactor at various temperatures. The effects of catalysts on Pavlova microalga pyrolysis were investigated. A large fraction of the starting energy (∼ 63–74% daf) was recovered in the bio-oils when the catalysts were used. The bio-oil yield was 20% higher in presence of Ni/TiO2 (22.55 wt%) at 500 °C. The High Heating Values of the produced bio-oils were in the range of ∼ 35–37 MJ/kg and suffered strong deoxygenation, with O content (% daf) diminished from 51 wt% to ∼ 9–12 wt%. The 1H Nuclear Magnetic Resounance and Gas Chromatography Mass Spectrometry suggested that the titania catalysts enlarged the aliphatics and aromatic compounds and decreased oxygenates in the bio-oils. Ni/TiO2 had the greatest activity in increasing aliphatic protons (60%) and decreasing coke formation. Its enhanced cracking activity was due to its higher availability on the catalyst surface, compared to Co and Ce, and to strong interaction between Ni and TiO2 support. Despite the fact that the bio-oils were partially de-nitrogenated, the N-content still represent a major limitation for their use as bio-fuels without further upgrading

Photocatalytic reduction of CO2 by CO co-feed combined with photocatalytic water splitting in a novel twin reactor

As a promising way to control greenhouse gas emission and alleviate global energy shortage, photocatalytic reduction of carbon dioxide attracts more attentions in recent years since it can produce fuels efficiently with the combination of H2 through water splitting. In this work, a computational model which characterizes the photocatalytic reduction of carbon dioxide by CO co-feed in a novel twin reactor is developed with three subsidiaries of chemical reaction kinetics, gas–liquid mass transfer, and transient sun light intensity distribution. Thanks to previous experimental work as the reliable verification for the numerical simulation, the variations of the CH3OH concentration with the CO/CO2 ratio of gas mixture, pressure and temperature are obtained and analyzed. The results show that the carbon in CO can form CH3OH directly, however the excessive CO will react with HCOOCH3 to form CH3CHO, which results in a reduced CH3OH concentration. Besides, the CH3OH concentration subsequently increases as the temperature and pressure increase, and the CH3OH product and reaction rate vary widely with time due to the changing sun light intensity during the day

Role of catalyst carriers in CO₂photoreduction over nanocrystalline nickel loaded TiO₂-based photocatalysts

Nickel-based TiO2 photocatalysts were immobilized onto carriers (quartz plates and monoliths) in a unique reactor configuration to provide a high ratio of illuminated surface area of catalyst for the reduction in CO2 to fuels under UV and visible light. The incorporation of Ni2+ in the TiO2 matrix inhibits the grain growth of anatase crystallites and suppresses phase transformation. The Ni2+ atom is also found to be replacing some of the Ti atoms in the crystal lattice of TiO2 during the sol–gel method, thus causing a change in optical absorption. Using water as a reductant, vapour-phase CO2 was reduced to fuels with the monolith threaded with optical fibres and quartz plate photoreactor system following 4 h of light irradiation. More importantly, the improved conversion efficiency is ascribed to the presence of Ni2+ species which served as electrons traps that suppressed recombination, resulting in effective charge separation and CO2 reduction