Photo splitting of bio-polyols and sugars to methanol and syngas.

Methanol is a clean liquid energy carrier of sunshine and a key platform chemical for the synthesis of olefins and aromatics. Herein, we report the conversion of biomass-derived polyols and sugars into methanol and syngas (CO+H2) via UV light irradiation under room temperature, and the bio-syngas can be further used for the synthesis of methanol. The cellulose and even raw wood sawdust could be converted into methanol or syngas after hydrogenolysis or hydrolysis pretreatment. We find Cu dispersed on titanium oxide nanorod (TNR) rich in defects is effective for the selective C-C bond cleavage to methanol. Methanol is obtained from glycerol with a co-production of H2. A syngas with CO selectivity up to 90% in the gas phase is obtained via controlling the energy band structure of Cu/TNR.

Site-specific X-ray induced dynamics in liquid methanol.

Complex chemical and biochemical systems are susceptible to damage from ionising radiation. However, questions remain over the extent to which such damage is influenced by the nature of the surrounding chemical environment, which can consist of both hydrophobic and hydrophilic domains. To gain fundamental insight into the first crucial mechanistic steps of radiation damage in such systems, we need to understand the initial radiation response, i.e. dynamics occurring on the same timescale as electronic relaxation, which occur in these different environments. Amphiphilic molecules contain both hydrophobic and hydrophilic domains, but the propensity for charge delocalisation and proton dynamics to occur in these different domains has been largely unexplored so far. Here, we present carbon and oxygen 1s Auger spectra for liquid methanol, one of the simplest amphiphilic molecules, as well as its fully deuterated equivalent d4-methanol, in order to explore X-ray induced charge delocalisation and proton dynamics occurring on the few femtosecond timescale. Unexpectedly, we find a similar propensity for proton dynamics to occur at both the carbon and oxygen site within the lifetime of the core hole. Our results could serve as a model for decay processes that are likely to occur in other more complex amphiphilic systems.

Enhanced photo-catalytic activity of ordered mesoporous indium oxide nanocrystals in the conversion of CO2 into methanol.

Ordered mesoporous indium oxide nanocrystal (m-In2O3) was synthesized by nanocasting technique, in which highly ordered mesoporous silca (SBA-15) was used as structural matrix. X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM) Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halanda (BJH) studies were carried out on m-In2O3 and the results revealed that this material has a highly ordered mesoporous surface with reduced grain size, increased surface area and surface volume compared to the non porous indium oxide. The diffuse reluctance spectrum exhibited substantially improved light absorption efficiency in m-In2O3 compared to normal indium oxide, however, no considerable change in the band gap energies of these materials was observed. When m-In2O3 was used as a photo-catalyst in the photo-catalytic process of converting carbon dioxide (CO2) into methanol under the pulsed laser radiation of 266-nm wavelengths, an enhanced photo-catalytic activity with the quantum efficiency of 4.5% and conversion efficiency of 46.3% were observed. It was found that the methanol production yield in this chemical process is as high as 485 µlg-1 h-1 after 150 min of irradiation, which is substantially higher than the yields reported in the literature. It is quite clear from the results that the introduction of mesoporosity in indium oxide, and the consequent enhancement of positive attributes required for a photo-catalyst, transformed photo-catalytically weak indium oxide into an effective photo-catalyst for the conversion of CO2 into methanol.

Removal of isopropyl alcohol and methanol in ultrapure water production system using a 185 nm ultraviolet and ion exchange system.

The oxidation of low-molecular-weight (LMW) compounds, including isopropyl alcohol (IPA) and methanol in ultrapure water (UPW) production system was evaluated using the continuously operating 185 nm total organic carbon (TOC) reduction UV and ion exchange system. The initial concentration of compounds was in the range of tens of ppb which was the general feed condition of UV system located after 2 pass reverse osmosis (RO) in the UPW production system. UV irradiation transformed the compounds to less oxidative products that were ultimately converted to CO2. The ion exchange system then removed carboxyl-containing organic acids generated by UV oxidation. It means that the oxidation efficiency of organic compounds by UV irradiation can be accurately measured by the summation of the final product (CO2) and the by-product containing carboxyl functional group. The removal efficiency of LMW compounds decreased when either the initial TOC concentration increased or the UV intensity was reduced. Finally, the insertion of a baffle into the UV oxidation system was found to enhance solution turbulence and improve the oxidation efficiency.

Photochemical degradation of the UV filter octyl methoxycinnamate in solution and in aggregates.

The photodegradation of the ultraviolet (UV) filter octyl methoxycinnamate (OMC) is investigated in both dilute solution and in aggregated form. In dilute solution, the ratio of trans and cis isomers achieved at the photostationary state is solvent-dependent because of variations in the isomerization quantum yield. The two isomeric forms at the photostationary state are highly resistant to further photodegradation and no other UVA-absorbing species are formed. Aggregation of OMC, either in a neat film or in aqueous colloidal suspensions, leads to irreversible photodegradation of the molecule and the formation of multiple photoproducts. In addition to previously identified photoproducts like the UVB-absorbing cis and trans isomers and photodimers, we find photoproduct species whose absorption extends into the UVA. Characterization of the photophysical properties of these species indicates that they have long-lived excited-states (τf > 1 ns, 400 nm), unlike the isomeric forms of OMC (τf < 30 ps, 266 nm), and that excitation at 405 nm can sensitize the formation of singlet oxygen. These results show that the environment of OMC affects the photochemistry of the molecule and that the environmental conditions must be taken into account when considering the molecule's stability. In particular, aggregation of OMC molecules results in complex photochemistry that can produce species whose absorption extends into UVA and are capable of generating reactive oxygen species.

Sonocatalytic and sonophotocatalytic degradation of Rhodamine 6G containing wastewaters.

The present work deals with degradation of aqueous solution of Rhodamine 6G (Rh 6G) using sonocatalytic and sonophotocatalytic treatment schemes based on the use of cupric oxide (CuO) and titanium dioxide (TiO2) as the solid catalysts. Experiments have been carried out at the operating capacity of 2 L and constant initial pH of 12.5. The effect of catalyst loading on the sonochemical degradation has been investigated by varying the loading over the range of 1.5-4.5 g/L. It has been observed that the maximum degradation of 52.2% was obtained at an optimum concentration of CuO as 1.5 g/L whereas for TiO2 maximum degradation was observed as 51.2% at a loading of 4 g/L over similar treatment period. Studies with presence of radical scavengers such as methanol (CH3OH) and n-butanol (C4H9OH) indicated lower extents of degradation confirming the dominance of radical mechanism. The combined approach of ultrasound, solid catalyst and scavengers has also been investigated at optimum loadings to simulate real conditions. The optimal solid loading was used for studies involving oxidation using UV irradiations where 26.4% and 28.9% of degradation was achieved at optimal loading of CuO and TiO2, respectively. Studies using combination of UV and US irradiations have also been carried out using the optimal concentration of the catalysts. It has been observed that maximum degradation of 63.3% is achieved using combined US and UV with TiO2 (4 g/L) as the photocatalyst. Overall it can be said that the combined processes give higher extent of degradation as compared to the individual processes based on US or UV irradiations.

Ultrasound-assisted synthesis of aliphatic acid esters at room temperature.

This work describes the ultrasound-assisted synthesis of saturated aliphatic esters from synthetic aliphatic acids and either methanol or ethanol. The products were isolated in good yields after short reaction times under mild conditions.

Photodegradation of malachite green and malachite green carbinol under irradiation with different wavelength ranges.

The dye malachite green (MG) is used worldwide as a fungicide in aquaculture. It is a toxic substance which in aqueous solutions is partly converted into its non-ionic colorless form (leucocarbinol). The equilibrium between these two forms is pH-dependent (pK=6.9). To assess the photodegradation of MG under sunlight conditions, both species were irradiated separately in aqueous solutions with different pH values (4.0 and 12.0) using various ultraviolet and visible wavelength ranges (UV/VIS). A 700 W high-pressure mercury lamp with special filters was used. No artificial photooxidizers such as H2O2 or TiO2 were added. MG leucocarbinol proved to be much more sensitive to irradiation than the dye form. Quantum yields Φ were calculated for some wavelength ranges as follows: MG carbinol: Φ((280-312 nm)) is 4.3 × 10⁻³, Φ((313 - 410 nm)) is 5.8 × 10⁻³, and MG dye: Φ((280 - 312 nm)) is 4.8 × 10(-5), Φ((313-365nm)) is 1.1×10⁻5, and Φ((> 365nm)) is 0, respectively. Therefore, the solar photolysis of MG is an important sink and primarily depends on the photodegradation of the colorless leucocarbinol. During the irradiation of MG leucocarbinol with wavelengths > 365 nm, an intermediate was formed which has photocatalytical properties.

Photolytical transformation rates of individual polybrominated diphenyl ethers in technical octabromo diphenyl ether (DE-79).

Polybrominated diphenyl ethers (PBDEs) are of environmental concern due to their persistence, potential to bioaccumulate, and possible toxic effects, especially for the lower brominated homologues. Reductive debromination under UV light has been identified as the main abiotic pathway for PBDE transformation. Although the kinetics and transformation products have been determined for individual PBDE congeners in different matrices, no effort has been made to determine the kinetics of these congeners when technical mixtures are exposed to UV light. We irradiated technical octabromodiphenyl ether (DE-79) in a perdeuterated solvent to determine the photolytic transformation kinetics of native PBDE congeners. Each deuterium that replaced bromine resulted in a shift to higher masses compared to the native congener, which was measured by gas chromatography with electron ionization mass spectrometry in the selected ion monitoring mode (GC/EI-MS-SIM). Tri-, tetra-, and pentabromodiphenyl ether products (BDE 28, BDE 47, BDE 49, BDE 99, BDE 100) could be proportioned to higher brominated precursors as a function of irradiation time. The kinetics of UV-irradiated single PBDE congeners matched well with results of previous studies of single congeners. However, when the same congeners were irradiated in the technical DE-79 mixture, their half-lives were longer by 20-160%. This study indicates that individually irradiated PBDE congeners behave differently than if present as a mixture. This result should be taken into account in models predicting the environmental fate of PBDEs and most likely also the mixtures of other contaminant groups.

Photodegradation of methanol under UV-visible irradiation by titania dispersed on polyester cloth.

Titania supported on polyester fabric (TiO(2)-PY) with varying titania loadings (2-7 wt%) were prepared via the dip-coating method at room temperature using an aqueous slurry of anatase titania. Structural and morphological characterizations by X-ray diffraction and scanning electron microscopy revealed that the titanium dioxide crystallites deposited on the surface of the polyester fabric were in the micrometer range while their phase remained to be anatase. Photocatalytic activity of TiO(2)-PY fabric catalysts was evaluated for vapor-phase oxidation of methanol in air as a test reaction in the presence of UV as well as solar radiation under ambient conditions. These catalysts were found to be quite active in both UV and solar irradiation with activity being higher in the former case. CO(2) yield from photo-oxidation of methanol depended on titania content and also on its dispersion over polyester fabric support.

Singlet oxygen photosensitisation by the fluorescent probe Singlet Oxygen Sensor Green.

The fluorescent probe Singlet Oxygen Sensor Green is able to produce singlet oxygen under exposure to UV or visible radiation.

Mineralization of CCl4 by the UVC-photolysis of hydrogen peroxide in the presence of methanol.

A method for a photochemically induced mineralization of CCl4 is described in which use is made of reductive radicals. The UVC-photolysis (254 nm) of H2O2 added to aqueous solutions of CCl4 is leading to the homolysis of the oxidant yielding hydroxyl radicals (HO) that subsequently react with added methanol to generate hydroxymethyl radicals (CH2OH). The latter radicals initiate mineralization of CCl4 by reductive C-Cl bond splitting. CHCl3, C2Cl4 and C2Cl6 were found as reaction intermediates, but are quantitatively depleted in a parallel oxidative reaction manifold leading to mineralization. Carbon dioxide radical anion, CO2(-), an intermediate in the mineralization pathway of methanol, is also shown to initiate the mineralization of CCl4 by reductive dechlorination. A reaction mechanism is proposed and validated with computer simulations of all the experimental results.

Enhanced hydrogen generation by particles during sonochemical decomposition of water.

A novel effect of any oxide particle/intermetallics enhancing hydrogen generation from water as compared to water alone when subjected to ultrasonic irradiation is reported here. Addition of methanol to water or decrease in particle size also improved the hydrogen yield. Hydrogen generation from water was further enhanced by the presence of both methanol and particles in water.

Reactivity of chalcones with 1-hydroxymethyl radicals.

Reactivity of chalcones with reactive species issued from methanol radiolysis was investigated in the absence or presence of dioxygen. Chalcones are natural antioxidants that are present in fruit and vegetables. Their degradation in the radiolysed solutions was followed by HPLC, NMR, FAB-LSIMS mass spectroscopy and analytical TLC in deaerated solution. Among the 18 identified radiolytic compounds, 16 were new. The formation of the radiolytic products was not influenced by A- and B-ring substitutions. To explain the degradation process, we thus suggested that the primary step was an attack of the alpha,beta-double bond by the 1-hydroxymethyl radical, either at C(alpha) or at C(beta). This step was followed by addition, cyclization or bond dissociations. Different chemical pathways were discussed that implicate the reactive species issued from methanol radiolysis. This paper highlights the relative importance of the different radical species, especially the carbon-centered radical, 1-hydroxymethyl (HMR) and the corresponding oxygen-centered isomer. In addition, an interesting unusual role of dioxygen should be noted; indeed, in the presence of dioxygen, degradation of chalcones was inhibited.

Kinetics of photocatalytic VOCs abatement in a standardized reactor.

A standardized micro-pilot scale continuous flow apparatus has been built up, using two types of differential photoreactors, and equipped with a refined control of the working conditions in order to study the photocatalytic degradation as a way to abate VOCs in air. Kinetic measurements have been carried out on trichloroethylene (TCE), methanol and benzene as model pollutants. The absence of diffusional limitation and of reaction product effect on the kinetics have both been demonstrated under our working conditions. The influences of concentration, light flux and temperature on the initial degradation rate have been studied. A simple Langmuir-Hinshelwood kinetic model has been verified for TCE and methanol, whereas benzene degradation was more complex and did not follow this simple mechanism. The determined experimental data aim at being useful in the scaling-up of photocatalytic reactors.

Removal of methanol from pulp and paper mills using combined activated carbon adsorption and photocatalytic regeneration.

Methanol is one of the major hazardous air pollutants emitted from chemical pulp mills. Its collection and treatment is required by the Maximum Achievable Control Technology portion of the 1998 Cluster Rule. The objective of this study is to investigate the technical feasibility of combined adsorption and photocatalytic regeneration for the removal and destruction of methanol. To facilitate the regeneration, activated carbon (AC) was coated with commercially available photocatalyst by a spray desiccation method. Laboratory-scale experiments were conducted in a fixed-bed reactor equipped with an 8 W black light UV lamp (peak wavelength at 365 nm) at the center. The photocatalyst loaded onto AC had no significant impact on the adsorption capacity of the carbon. High humidity was found to greatly reduce the material's capacity in the adsorption and simultaneous adsorption and photocatalytic oxidation of methanol. The photocatalytic regeneration process is limited by the desorption of the adsorbate. Increasing desorption rate by using purge air greatly increased the regeneration capacity. When the desorption rate was greater than the photocatalytic oxidation rate, however, part of the methanol was directly desorbed without degradation.

A comparative study and development of an improved method for the reduction of nitroarenes into arylamines by Al/NH4X (X=Cl, Br, I) in methanol under ultrasonic conditions.

Nitroarenes were shown by us earlier to undergo reduction when treated with Al/NH4Cl in methanol under sonic conditions to give anilines in high yields [D. Nagaraja, M.A. Pasha, Tetrahedron Lett. 40 (1999) 7855]. Now, a comparative study has been carried out and an efficient and improved procedure for this reduction by using Al/NH4X (X=Cl, Br, I) is reported. A plausible mechanism of the reaction is envisaged.

Structure of copper(II) dithiocarbamate mixed-ligand complexes and their photoreactivities in alcohols.

The composition of the co-ordination sphere of Cu(II) dithiocarbamate mixed-ligand complexes Cu(Et2)dtc)X (X = Cl-, Br-) and Cu(Et2)dtc)(+)...Y- (Y- = ClO4-, NO3-) is studied from the combined analysis of spectrophotometric and EPR data. The results obtained about CT-photolysis of the complexes in EtOH and i-PrOH are compared with our previous data of photolysis in chloromethane/ROH solutions. Reaction mechanism and the role of alcohol are discussed on the ground of electronic and EPR spectra and quantum yield results.

Organics produced by ion irradiation of ices: some recent results.

Some results, recently obtained from laboratory experiments of ion irradiation of ice mixtures containing H, C, N, and O, are here summarized. They are relevant to the formation and evolution of complex organics on interstellar dust, comets and other small bodies in the external Solar System. In particular the formation of CN-bearing species is discussed. Interstellar dust incorporated into primitive Solar System bodies and subsequently delivered to the early Earth, may have contributed to the origin of life. The delivery of CN-bearing species seems to have been necessary because molecules containing the cyanogen bond are difficult to be produced in an environment that is not strongly reducing as that of the early Earth probably was. Moreover we report on an ongoing research program concerning the interaction between refractory materials produced by ion irradiation of simple ices and biological materials (amino acids, proteins, cells).

Radiation chemistry of ices of planetological interest at low temperature.

We present the results of recent experiments on some physico-chemical effects induced by fast ion colliding with solids of relevance for the physics of planetary objects. The production of molecular solids, polymer-like materials and amorphous carbon by irradiation of frozen hydrocarbons and pentacene is discussed. We also report on a set of experimental results obtained irradiating methanol and water-methanol mixtures. Because of bombardment different species form. The techniques used for the analysis are "in situ" infrared (IR) and Raman spectroscopy. The experimental results are finally discussed in the light of their relevance for planetary physics.