High-pressure photoreactors

Rossetti 1, Villa A, Pirola C, Prati L, Ramis G (2014) A novel high-pressure photoreactor for CO2 photoconversion to fuels. RSC Adv 4 28883-28885... 

In the vapor phase experiments, the photograftings are carried out in specially designed photoreactor constructed and built in our laboratory (Figure 1). The reactor is equipped with a 1 kW high pressure mercury UV lamp (HPM-15 from Philips) which can be moved to vary the distance to the substrate. The grafting takes place in an atmosphere of nitrogen in a thermostated chamber closed with a clear quartz window. Sensitizer and monomer evaporates from a solution of a volatile solvent in an open bucket which is shielded from the UV-irradiation with aluminium foil. 

Photolytic. Fukuda et al. (1988) studied the photodegradation of acenaphthene and alkylated naphthalenes in distilled water and artificial seawater using a high-pressure mercury lamp. Based upon a rate constant of 0.23/h, the photolytic half-life of acenaphthene in water is 3 h. Behymer and Hites (1985) determined the effect of different substrates on the rate of photooxidation of acenaphthene using a rotary photoreactor equipped with a 450-W medium pressure mercury lamp (X = 300-410 nm). The photolytic half-lives of acenaphthene absorbed onto silica gel, alumina, and fly ash were 2.0, 2.2, and 44 h, respectively. The estimated photooxidation half-life of acenaphthene in the atmosphere via OH radicals is 0.879 to 8.79 h (Atkinson, 1987). 

A solution of alkene (50 mmol) in CHjClj (600 mL) and 0.25 M aq NuaSOj (200 mL) was rapidly stirred in a photoreactor with an immersion lamp (Heraeus TQ 718 Z3, high-pressure Hg radiator with cadmium iodide admixture 700-W power input), and cooled to 8-10°C. Over 3h, CHIj (19.7 g, 50 mmol or 39.4 g, 100 mmol for the dienes) was added in small portions (new quantities were always introduced when the color of the formed iodine has just disappeared). When the addition was complete, the irradiation was continued for another 10 min. The phases were separated, the aqueous layer was washed with a little extra... 

For some experiments the gas exiting from the photoreactor was continuously bubbled in hquid acetomtrile. The resulting solution was analyzed by high pressure liquid chromatography (HPLC) (Varian 9050) in order to detect... 

Figure 2 Emission properties of a) mercury low-pressure lamp (strong 254 line), b) mercury high-pressure lamp and c) RPR-3(XX)A lamp for Rayonet photoreactors (3(X) nm line).

In an atmosphere of argon, a solution of 13.5 g (88%, 94 mmol) of S.6b and 300 mg (11 mmol) of copper (I) trifluoromethanesulfonate benzene complex (CuOTf) in 120 mL of dry diethyl ether is irradiated in a Pyrex photoreactor with a water cooled quartz immersion well by a high-pressure mercury lamp (HPK 125 W, Fa. Philips). After the reaction is complete (monitored by GLC), the mixture is concentrated in vacuo and purified by column chromatography (cyclohexane/ethyl acetate 2 3) to give 10.5 g (64% from... 

Squires, Venier, and Aida (1983) describe an experimental technique they use to study the effect of solvent viscosity on the cisitrans ratio of stilbene irradiated in supercritical CO2. They use a dynamic flow technique similar to that described in chapter 4. In their system trau5-stilbene is coated onto glass beads, which are then packed into a high-pressure column. Supercritical CO2 flows through the column and solubilizes some of the trans-stilbene. The C02-stilbene phase is continuously irradiated with ultraviolet light as it flows through a quartz photoreactor at a fixed temperature and pressure. As the solvent viscosity increases, the photoisomerization of the cis isomer is inhibited while that of the trans isomer is facilitated. We should expect to see the cisitrans ratio of stilbene vary as the density of CO2 varies. This viscosity effect is clearly shown in figure 11.11. While there is a small effect of pressure on the... 

A solution of 3.48 g (0.03 mol) of ethyl pyruvate and 3.48 g (0.03 mol) of 1,1-diethoxyethene in 100 mL of benzene is irradiated under N2 using a high-pressure mercury lamp (Philips UPK 125 W) and a Pyrex photoreactor. After evaporating the solvent the oxetane is obtained as a colorless oil yield 79%. 

The solution of 5.08 g 2-methyl-4-nitroimidazole in 200 mL 42% tetrafluoroboric acid was cooled to -10°C to this cooled solution was added 5.08 g zinc dust (78 mmol) in portions of 0.1 g with rapid stirring. Each addition was made only after the prior portion had dissolved and the temperature had fallen to at least -5°C. The addition took about 1 h. Small aliquots were removed, diluted with water, and examined by UV. Total loss of the chromophore at 310 nm indicated the completion of reduction. Then a solution 2.04 g sodium nitrite (44 mmol) in 10 mL water was added dropwise. The resulting solution of the diazonium salt was diluted to 380 mL with cold 42% tetrafluoroboric acid and was irradiated under argon in a Pyrex immersion-well photoreactor using a 400-W high-pressure mercury lamp (Riko 400-HA). After 90 min, the diazonium chromophore at 280 nm had disappeared. The solution was cooled to - 10°C with dry ice, neutralized slowly with 25% aqueous sodium hydroxide to pH 5-6, and extracted with EtOAc (5 x 200 mL). The combined extracts were dried over Na2S04 and evaporated. The residual material was purified on 100 mL silica gel with EtOAc as an eluent to give 1.06 g 4-fluoro-2-methylimidazole, in a yield of 27%, m.p. 142-144°C. 

Photolytic. When MCPA in dilute aqueous solution was exposed to summer sunlight or an indoor photoreactor (k >290 nm), 2-methyl-4-chlorophenol formed as the major product as well as o-cresol and 4-chloro-2-formylphenol (Soderquist and Crosby, 1975). Clapes et al. (1986) studied the photodecomposition of aqueous solution of MCPA (120 ppm, pH 5.4, 25°C) in a photoreactor equipped with a high pressure mercury lamp. After... 

For the photocatalytic reduction of CO2, in 1979, Inoue et al. introduced a slurry reactor in which catalysts were suspended in water [143]. Until 2000, slurry-type reactors were widely considered for reduction of CO2 under UV or visible irradiation. On the other hand, Tahir and Amin suggested that this type of reactor is not efficient for enhancing the photocatalytic activity due to the low surface area and complicated separation process required to isolate the miniature catalyst grains [144]. Furthermore, one of the UmitatirHis for CO2 photoreduction in the liquid phase is due to its low solubility in water. Therefore, Rossetti et al. developed an innovative cmicept of photoreactor, allowing to operate under high pressure (up to... 

Shen et al. (1995) investigated the effect of light absorbance on the decomposition of aqueous chlorophenols (CPs) by UV/H202. The photoreaction system was batch annular photoreactors with 254-nm, low-pressure UV lamps at 25°C. The light absorbance and photolytic properties of chlorophenols and H202 were found to be highly dependent on the solution pH and can be adequately described with the linear summation of the light absorbance of undissociated and dissociated species of chlorophenols ... 

Similarly, as in case of the MCs described above, the mass transfer in the presented PMR was achieved without any transmembrane pressure. This allowed avoidance of membrane fouling, even in the case of highly turbid water. Moreover, due to keeping the bentonite away from the photoreactor, it was possible to avoid the loss of radiation due to screening by bentonite particles. 

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