Lamps immersion type

Figure 24. Scheme of multilamp immersion-type photochemical installation for the photocatalyzed oxidative degradation of industrial waste water [12]. A Bypass circuit. B Reactor circuit. 1 Gas-liquid mixture and injection. 2 Reservoir. 3 Pump (ceramics). 4 Water pump. 5 Heating circuit. 6 Cooling circuit, hv Medium pressure mercury lamps (Pyrex). T Thermometers. 

Based on the experimental data of Jacob and Dranoff [111], Cerda et al. [113] evaluated the LSSE and ESVE models and found for the latter a much better agreement between experimental and calculated data. However, Tournier et al. state that none of the above mentioned models could be used to interpret all the experimental results obtained from radiant power measurements in an immersion-type photochemical reactor using a lamp jacket equipped with a compartment for filter solutions [78]. 

The recrystallized a-oxoamide 1 (100-300 mg) was sandwiched between a pair of Pyrex plates (diickness 2 mm) and put into a polyethylene envelope. The envelope was sealed and placed in a cold medium (water, ice-water, or dry ice-methanol) and irradiated with a high-pressure mercury lamp (100 W) for 1-10 h. The lamp was used with a vessel for immersion type irradiation which contained dry air. The products were isolated by column chromatography on silica gel. 

UV irradiation of a dry benzene soln (120 mL) containing 1,1-diarylethene (0.40-0.05 mol) and diphenyldiazomethane (0.15-0.076 mol) was carried out in an immersion-type irradiation vessel equipped with a mercury high-pressure lamp (Philips, HP 125 W) surrounded by a quartz water jacket. The solution was purged with Oj-free Nj for 15 min prior to the photochemical reaction, which was run under dry Nj. Irradiation, performed at 13 °C, lasted for about 15-30 h. The workup procedure consisted of removal of benzene followed in some cases by column chromatography (50 cm) of the oily product on acidic alumina with various solvents and recrystallization of the colorless crystals from EtOH. 

Benzaldehyde in methanol containing a catalytic amount of HCl irradiated 5 hrs. at 5° with a 100 w. immersion-type high-pressure Hg-lamp under a stream of oxygen methyl benzoate. Y 90% conversion 25%. F. e. s. H. Sakuragi and K. Tokumaru, Chem. Lett. 1974y 475. 

The simplest photochemical reactors are certainly those of the immersion type, where the lamps are immersed in the reaction medium that they irradiate directly, the gases being injected through perforated tubings at the bottom of the reactor. However, these reactors rapidly get dirty because of by-product deposits and they are difficult to cool and favor the production of chloroalkanes due to higher absorption of chlorine. Residence times range between 2 and 10 h. For example, with a residence time of 2 h and a 34% sulfochlorination rate, the production of sulfochlorides containing ca. 12% di- and polysulfochlorides can reach 80 kg/h m [37]. 

The experiments were carried out in a glass-jacketed reactor vessel filled with 60 cm (or, in some cases 180 cm ) of reaction mixture and wrapped with aluminium foil. A 125-W immersion-type medium-pressure mercury lamp was applied as a radiation source. The light intensity was determined by ferrioxalate actinometry [20] (7a 1.5x10 mol photons dm" s" at 366 nm). A GBC UV-vis 911A spectrophotometer was used for the analysis. 

Photocatalytical experiments were made in a 400-ml thermo-stated batch reactor (25 0.1 °C) equipped with an immersion-type UV lamp (high-pressure mercury lamp, 150 W, 240-580 nm). In our experiments the surrounding of the lamp with a glass filter allowed a considerable proportion of the high-energy photons (A < 310 nm) to be filtered out. 

Irradiation Studies. Irradiation of l,3-diphenoxy-2-propanol (3), 0.01 M in acetonitrile, was conducted at 254 nm, utilizing a 2.5-W low pressure Hg immersion lamp (PCQ9G-1, Ultraviolet Products), and at wavelengths longer than 280vnm, utilizing a Hanovia 450-W high-pressure Hg immersion lamp (Type L) and 9700 Corex filter sleeve. Irradiation of 1,3-diphenoxy-2-methyl-2-propanol (5), 0.01 M in acetonitrile, was also conducted at 254 nm. 

Early accelerated weathering apparatus utilized carbon arc lamps with various filters to generate a spectrum that reproduced some of the harmful effects of sunlight. Improved versions of these are still in use and are specified for certain applications. However, many users and specifiers have turned to xenon arc lamp-based machines as these produce a spectrum that more closely matches that of sunlight (Fig. 6.1). Additionally, they are generally less expensive to purchase and to run than the carbon arc machines. Both types nowadays have facilities for the provision of controlled humidity, water spray, periodic water immersion and/or variable temperature cycles. 

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