Photocatalytic reduction of carbon dioxide

Carbon dioxide reforming happens all the time in nature by photosynthesis of plants. It thus provides a great challenge to equal or surpass this photosynthesis in an artificial system. This paper presents a literature review of using semi-conductor to assist photocatalytic reduction of carbon dioxide under UV irradiation. It analyses some key factors influencing the reaction rates which have been studied worldwide in respective areas. Special interest is taken in recommending possible improvements for the heterogeneous photocatalysis involving gas-solid interfaces, particularly in relation to the influencing factors affecting product concentrations and the reduction rate.

Photocatalytic production of methane and hydrogen through reduction of carbon dioxide with water using titania pellets

This paper presents an experimental study on employing a pellet form of catalyst in photo-reduction of carbon dioxide with water. Water was first absorbed into titania pellets. Highly purified carbon dioxide gas was then discharged into a reactor containing the wet pellets, which were then illuminated continuously for 65 hours using UVC lamps. Analysing the products accumulated in the reactor confirmed that methane and hydrogen were produced through photo-reduction of carbon dioxide with water. No other hydrocarbons were detected. Increasing the temperature in the reactor has showed little change on the amount of methane produced.

Photocatalytic reduction of carbon dioxide into gaseous hydrocarbon using TiO2 pellets

It has been shown that CO₂ could be transformed into hydrocarbons when it is in contact with water vapour and catalysts under UV irradiation. This paper presents an experimental set-up to study the process employing a new approach of heterogeneous photocatalysis using pellet form of catalyst instead of immobilized catalysts on solid substrates. In the experiment, CO₂ mixed with water vapour in saturation state was discharged into a quartz reactor containing porous TiO₂ pellets and illuminated by various UV lamps of different wavelengths for 48 h continuously. The gaseous products extracted were identified using gas chromatography. The results confirmed that CO₂ could be reformed in the presence of water vapour and TiO₂ pellets into CH₄ under continuous UV irradiation at room conditions. It showed that when UVC (253.7 nm) light was used, total yield of methane was approximately 200 ppm which was a fairly good reduction yield as compared to those obtained from the processes using immobilized catalysts through thin-film technique and anchoring method. CO and H₂ were also detected. Switching from UVC to UVA (365 nm) resulted in significant decrease in the product yields. The pellet form of catalyst has been found to be attractive for use in further research on photocatalytic reduction of CO₂.

Carbon dioxide levels and ventilation strategies in 'green' office buildings

Energy efficient office buildings are intended to provide a comfortable and healthy environment for their occupants as well as reducing the energy consumption of the building. They are often designed as "showcase" buildings illustrating the potential for savings through some innovative design technology. But do such buildings actually deliver the desired energy savings and satisfactory comfort conditions for occupants? Measurements of a "green" University campus building in Victoria, Australia, designed with an innovative fabric energy storage system, demonstrate that the ventilation system is not providing acceptable indoor air quality conditions. The design strategies used to reduce energy consumption have had negative consequences on the air quality of the building. Insufficient fresh air is being drawn into the building leading to an excessive build up of carbon dioxide. It is recommended that monitoring systems need to use a wider range of measurements than temperature alone to guarantee good quality indoor air and working conditions and that commissioning of buildings should include adequate monitoring of the operational performance of the building. Designers need to be made aware of the potential consequences of their decisions when attempting innovative energy-efficient designs.

Gas chromatography-chemical ionization-mass spectrometric fatty acid analysis of a commercial supercritical carbon dioxide lipid extract from New Zealand green-lipped mussel (Perna canaliculus)

Supercritical fluid extracts of New Zealand green-lipped mussels (NZGLM) have been suggested to have therapeutic properties related to their oil components. The large number of minor FA in NZGLM extract was characterized by a GC-CIMS/MS method that excels at identification of double-bond positions in FAME. The extract contained five major lipid classes: sterol esters, TAG, FFA, sterols, and polar lipids. The total FA content of the lipid extract was 0.664 g/mL. Fifty-three unsaturated FA (UFA) were fully identified, of which 37 were PUFA, and a further 21 UFA were detected for which concentrations were too low for assignment of double-bond positions. There were 17 saturated FA, with 14∶0, 16∶0, and 18∶0 present in the greatest concentration. The 10 n−3 PUFA detected included 20∶5n−3 and 22∶6n−3, the two main n−3 FA; n−3 PUFA at low concentrations were 18∶3, 18∶4, 20∶3, 20∶4, 21∶5, 22∶5, 24∶6, and 28∶8. There were 43 UFA from the n−4, n−5, n−6, n−7, n−8, n−9, n−10, n−11 families, with 16∶2n−4, 16∶1n−5, 18∶1n−5, 18∶2n−6, 20∶4n−6, 16∶1n−7, 20∶1n−7, 16∶1n−9, 18∶1n−9, and 20∶1n−9 being the most abundant. In general, we estimated that FAME concentrations greater than 0.05% (w/w) were sufficient to assign double-bond positions. In total, 91 FA were detected in an extract of the NZGLM, whereas previous studies of fresh flesh from the NZGLM had reported identification of 42 FA. These data demonstrate a remarkable diversity of NZGLM FA.

Kinetic modelling for photosynthesis of hydrogen and Methane through catalytic reduction of carbon dioxide with water vapour

In a photocatalytic reduction process when products formed are not effectively desorbed, they could hinder the diffusion of intermediates on the surface of the catalyst, as well as increase the chance of collisions among the products, resulting photo-oxidation in a reserve reaction on the surface. This paper analyses a simple kinetic model incorporating the coupled effect of the adsorptive photocatalytic reduction and oxidation. The development is based on Langmuir–Hinshelwood mechanism to model the formation rates of hydrogen and methane through photocatalytic reduction of carbon dioxide with water vapour. Experimental data obtained from literatures have achieved a very good fit. Such model could aid as a tool for related areas of studies. A comparative study using the model developed, showed that product concentration in term of ppm would be an effective measurement of product yields through photocatalytic reduction of carbon dioxide with water vapour.

Re-cycling carbon dioxide into fuel-like hydrocarbons by photocatalytic process

A new approach of heterogenous photocatalysis using titanium dioxide pellets was explored. It was found to be attractive for use in photocatalytic reduction of carbon dioxide with wavelength and temperature being crucial factors. The study also proposes a kinetic modelling for the process to simulate the product-yield profile.

Carbon dioxide emissions and economic growth : panel data evidence from developing countries

In this paper we test the Environment Kuznet's Curve (EKC) hypothesis for 43 developing countries. We suggest examining the EKC hypothesis based on the short- and long-run income elasticities; that is, if the long-run income elasticity is smaller than the short-run income elasticity then it is evident that a country has reduced carbon dioxide emissions as its income has increased. Our empirical analysis based on individual countries suggests that Jordan, Iraq, Kuwait, Yemen, Qatar, the UAE, Argentina, Mexico, Venezuela, Algeria, Kenya, Nigeria, Congo, Ghana, and South Africa—approximately 35 per cent of the sample—carbon dioxide emissions have fallen over the long run; that is, as these economies have grown emissions have fallen since the long-run income elasticity is smaller than the short-run elasticity. We also examine the EKC hypothesis for panels of countries constructed on the basis of regional location using the panel cointegration and the panel long-run estimation techniques. We find that only for the Middle Eastern and South Asian panels, the income elasticity in the long run is smaller than the short run, implying that carbon dioxide emission has fallen with a rise in income.

Concomitant reactivity of the m-Terphenylindium dihydroxide [2,6-Mes2C6H3In(OH)2]4 toward carbon dioxide and ethylene glycol

The stepwise reaction of [2,6-Mes₂C₆H₃In(OH)₂]₄ with carbon dioxide and ethylene glycol proceeded with the formation of (2,6-Mes₂C₆H₃In)₄(CO₃)₂(OH)₄(H₂O)₂ (1) and (2,6-Mes₂C₆H₃In)₄(OCH₂CH₂O)₂(OH)₄ (2), respectively, and eventually produced (2,6-Mes₂C₆H₃In)₄(CO₃)₂(OCH₂CH₂OH)₂(OH)₂ (3). Attempts to liberate ethylene carbonate upon heating of 3 were unsuccessful.