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Investigation of the Effects of Controlled Periodic Illumination on the Oxidation of Gaseous Trichloroethylene Using a Thin Film of TiO2 Karen J. Buechler,† Richard D. Noble,*,† Carl A. Koval,‡ and William A. Jacoby§,| Departments of Chemical Engineering and Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, and National Renewable Energy Laboratory, Golden, Colorado 80401
Enhancement of gas-phase photocatalytic oxidation by controlled periodic illumination (CPI) was investigated. The oxidation of trichloroethylene (TCE) was studied in a versatile reactor designed to provide periodic illumination of the TiO2 films. The reactor was operated in two different geometric configurations, tubular and annular. Multiple flow regimes were investigated: kinetic- and diffusion-limited. No enhancement on the rate or the selectivity of TCE oxidation was observed at any of the CPI conditions investigated in the kinetically limited flow regime. The ratio of TCE oxidized to dichloroacetyl chloride (DCAC) produced was 0.59 at all light and dark times investigated for kinetically limited operation. In diffusion-limited regimes, CPI increased the rate of oxidation and decreased the relative amount of DCAC in the product stream. In the kinetic-limited regimes the apparent quantum yield was constant at around 150%; however, in the diffusion-limited regimes the apparent quantum yield almost doubled with CPI. Background The photocatalytic oxidation of compounds on TiO2 has been extensively studied as a possible method for the destruction of aqueous and gaseous pollutants.1-3 There are several drawbacks to this method that include low quantum yields and high levels of partial oxidation products. Various researchers have proposed mechanisms for the low quantum yields that all involve electron-hole pair recombination.4,5 Sczechowski et al.6-9 have investigated a method for improving the quantum yield. They suggested that the rate-limiting step must not require photons since the quantum yields were low. They periodically illuminated the catalyst to allow more time for the rate-limiting step to occur before putting more photons into the system. In an aqueous slurry of TiO2 they demonstrated a 500% increase in the apparent quantum yield of formate oxidation to CO2 and H2O. In their well-mixed slurry reactor, the diffusional mass-transfer limitations were assumed to be negligible because of the small particle sizes. Stewart and Fox10 suggest that a dark recovery time improves the apparent quantum yield for photooxidations. Upadhya and Ollis11 have proposed a model that qualitatively fit Sczechowski’s data. This model assumes that the dark rate-limiting step is the adsorption of O2 onto the surface and/or the transfer of the conduction band electron to the adsorbed O2. The current study has attempted to expand the work by Sczechowski et al. by looking at several things: gasphase oxidations on thin films of catalyst and more complicated chemical systems so that the effect of periodic illumination on the production of partial oxidation products can be investigated. The compound chosen * To whom correspondence should be addressed. † Department of Chemical Engineering, University of Colorado. ‡ Department of Chemistry and Biochemistry, University of Colorado. § National Renewable Energy Laboratory. | Currently at Department of Chemical Engineering, University of Missouri-Columbia, Columbia, MO 65211.
for this study is trichloroethylene (TCE). The photocatalytic oxidation of TCE is a fast reaction studied extensively.12-21 The identified gas-phase photocatalytic products are dichloroacetyl chloride (DCAC), phosgene (COCl2), carbon monoxide (CO), carbon dioxide (CO2), hydrochloric acid (HCl), and water. The mechanism for TCE oxidation by TiO2 photocatalysis is still under investigation. It has been suggested that two different reaction pathways exist:16 direct oxidation of TCE to products (COCl2, CO, CO2, and HCl) and oxidation through DCAC as the primary intermediate to products. One unresolved aspect is the identity of the oxidation initiation species. Nimlos et al.15 proposed that the initiation species are chlorine radicals. These chlorine radicals could be produced by the reaction of TCE with the hydroxyl radicals on the illuminated TiO2 surface. It has also been suggested12 that the initiation species are hydroxyl radicals on the surface of TiO2. A recent study by Fan et al. has not found any evidence of hydroxyl radicals on the illuminated TiO2 surface or the gases above the surface in the presence of TCE, O2, and N2. They do suggest the presence of surface O2- formed from electron transfer from the illuminated catalyst to molecularly absorbed oxygen. The presence of the DCAC as the primary intermediate is also supported in their study. Experimental Section We have developed a novel reactor system to study the steady-state products from the oxidation of TCE on a thin film of TiO2. A diagram of the experimental setup is shown in Figure 1. The basic operation procedure is to adjust the gas flow to set the initial concentration of TCE and total volumetric flow rate. The reaction mixture flows from the bottom to the top in the reactor. The effluent from the photocatalytic reactor then flows directly into the Nicolet 8220 FTIR analytical cell. This cell is 2.3 L in volume and has an IR path length of 10 m. Multiple cell volumes of reactor effluent are allowed to pass into the cell before spectra are taken. This ensures that the reaction is at steady state and that the
10.1021/ie9804374 CCC: $18.00 © 1999 American Chemical Society Published on Web 01/26/1999
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Figure 1. Overall system diagram.
gases filling the FTIR cell have been completely exchanged with the steady-state reaction products. The cell and reactor are both operated at ambient temperature and pressures. The photocatalytic reactor is composed of two parts: a quartz tube and a Pyrex insert. The quartz tube has an internal diameter of 4.8 cm. The insert is a Pyrex tube closed off on both ends. This insert has an external diameter of 4.2 cm. The reactor vessel is either a small annular region or a large tubular region. These two different geometries were used to demonstrate differences in mass-transfer characteristics. Most of these experiments were performed in the 3 mm annular region created with the insert inside the quartz tube. The total length of the annular space is 50 cm. The total length of the catalyst coating is 17.2 cm. The catalyst bed is approximately centered on the length of the annulus. Titanium dioxide coatings were deposited by successively drying an aqueous Degussa P-25 slurry, annealing the TiO2 at 100 °C for 30 min, and rinsing off loose and excess TiO2 powders. Degussa P-25 has been reported to have particle sizes of 20 nm, a specific surface area of 45 m2/g, and a fraction of anatase:rutile of 80:20.22 The coatings used in all of these contained 200-500 mg of TiO2 deposited on the outside of the Pyrex insert or the inside of the quartz tube. The light source for this photocatalytic reactor consists of an evenly spaced circular array of eight black lamps. These lamps provide UV illumination with the peak intensity at 360 nm. The reactor does not have enough internal reflectance to allow the light intensity to be constant in the angular direction. The light intensity varies from 0.2 to 1.3 mW/cm2 with an average intensity of 0.8 mW/cm2 as the intensity is measured at the catalyst surface in the angular direction. These measurements were taken with a UVP radiometer equipped with a UVX-36 sensor. This sensor has a response factor of approximately 1 at 360 nm. Positioned between the lamps and the annulus is an aluminum cylinder, as seen in Figure 2. This cylinder is connected to a variable speed motor that rotates the cylinder around the annular reactor. The aluminum cylinder has slits cut along its length to create small arcs of light, which sweep across the stationary reactor. By controlling the width of the slit, we control the width of the arc of photons. By controlling the speed of rotation, we can vary the time it takes this arc of photons to sweep across the entire reactor. It is important to note that at any given moment the same number of photons irrespective of sleeve rotation illuminates the same area of catalyst. The light time (tl), dark time (td), and ratio of the light to dark time (tl/td) were varied by setting the width and number of slits and by varying the rotation speed of the cylinder. As the cylinder rotated, it was assumed that the light intensity at the
Figure 2. Expanded view of photocatalytic reactor capable of providing periodic illumination of TiO2 film. Table 1. Annular Experimental Slit Configurations and Light and Dark Time Data (the Given Light and Dark Times Are for a Sleeve Rotation of 12 rpm) configuration number × width
tl (s)
td (s)
tl/td
3×1 1×3 2 length 6 × 1 1/ length 1 × 6 2 6×1 1×6
0.083 0.250 0.083 0.500 0.083 0.500
1.58 4.75 0.75 4.50 0.75 4.50
0.053 0.053 0.111 0.111 0.111 0.111
1/
total slit photon rate area (cm2) (µmol of photons/s) 11.3 11.3 11.3 11.3 22.7 22.7
0.046 0.046 0.046 0.046 0.091 0.091
catalyst surface was the measured average of 0.8 mW/ cm2. During the continuous illumination experiments, the cylinder was carefully positioned so that the average light intensity from each of the exposed slits was at this average of 0.8 mW/cm2. The IR spectra are analyzed for TCE, DCAC, phosgene, CO2, CO, HCl, and H2O. The area under the peaks was evaluated by the Nicolet Omnic IR software. The wavenumbers (cm-1) used for quantification are TCE (890-965), DCAC (1040-1150), phosgene (824-872), CO2 (2283-2385), CO (2021-2233), HCl (2645-3049), and H2O (3200-4000). Calibrations for each species were generated using standard methods. This method allowed a carbon balance to be closed to within 5%. The current series of experiments studied the effects of bulk flow rate (Q), tl, td, ratio of tl/td, and total photon flux on the rate of TCE decomposition and the product distribution. DCAC was chosen as the intermediate to use for comparison between settings because of its initial formation in one reaction sequence. The tubular experiments were conducted with different numbers (2-6) of six degree arc lengths exposed. These experiments were all conducted at the 0.8 mW/cm2 light intensity and at a bulk flow rate of 8.5 L/min. Tubular experiments will be compared to annular experiments to demonstrate the effects of very different mass-transfer characteristics. The tubular experiments will have much lower rates of mass transfer than the annular experiments. In the annular experiments, six different slit patterns (see Table 1) with two different total areas illuminated were used. For instance the “6 × 1” configuration was six evenly spaced slits of 17.2 cm length and 6° of width. While the “1/2 length 1 × 6” was one slit of 8.6 cm length and 36° of width. The cylinder was rotated at various speeds (0-12 rev/min) to generate the different light and dark times. Table 1 shows what the light and dark times were for all of the configurations at 12 rev/min. The light time was calculated by
t1 )
ws ω 360 60
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Figure 3. Observed TCE reaction rate vs bulk flow rate in reactor. Annular reactor, sleeve rotation at 0 rpm. The data are shown for all slit configurations.
Figure 4. Apparent quantum yield of TCE disappearance vs bulk flow rate at various sleeve rotation rates. Annular reactor has a 1 × 6 slit configuration.
where ws was the width of one slit in degrees and ω was the sleeve rotation rate in rev/min. Similarly, the dark time is calculated by
td )
360/n - ws ω 360 60
where n is the number of slits. The bulk flow rate was varied from 0.5 up to 5 L/min and the steady-state product stream was analyzed at each set of conditions. Results The reaction kinetics versus mass-transport characteristics of the reactor were established. The TCE oxidation rate was measured as a function of the bulk flow rate in the annular reactor at a constant concentration of TCE. Figure 3 shows the TCE oxidation rate as a function of the bulk flow rate. The behavior of the rate with the flow rate is as expected. At lower flow rates the reaction rate increased with the flow rate. By increasing the flow rate, we are increasing the flux of reactants (O2 and TCE) to the surface of the catalyst. At higher flow rates, the increase in the flow rate no longer has any effect on the oxidation rate of TCE. This indicates that the reactor is now limited by the surface reaction since the rate is no longer affected by an increase in TCE or O2 flux. It is also evident that the sleeve does block out the relative amount of light that it should. Looking at Figure 3 and Table 1, one can see that the slit configurations 6 × 1 and 1 × 6 which should produce twice the illuminated area of the other configurations have observed reaction rates which are twice the observed reaction rates for the other slit configurations. Experiments were performed in the annular reactor at the same initial concentration of 80 ppm TCE and at flow rates, which would be both diffusionally and kinetically limited. The experiments at the various flow rates showed a flow rate dependence of the rotational effect. Figure 4 shows the TCE oxidation rate versus flow rate at various rotation speeds in the 6 × 1 slit configuration. It is clear that, at low flow rates, the sleeve rotation did affect the rate of TCE oxidation. At higher flow rates the rotation did not appear to affect the TCE oxidation rate. All the other configurations investigated had similar results. The data on the products for the oxidation of TCE show an interesting trend. Figure 5 shows the amount of DCAC in the product spectrum as a function of TCE oxidation. These data are for the 3.8 and 5.0 L/min bulk
Figure 5. Apparent quantum yield of DCAC formation rate vs apparent quantum yield of TCE disappearance at all slit configurations, sleeve rotations, and flow rates of 3.8 and 5.0 L/min in the annular configuration. The data for the different sleeve rotations and bulk flow rates are not differentiated. The straight line in a linear fit to all of the data with a slope ) 0.59 and adjusted R2 ) 0.74.
Figure 6. Apparent quantum yield of DCAC formation rate vs apparent quantum yield of TCE disappearance. Annular reactor at 0.5 and 2.5 L/min and all sleeve rotation rates. The solid line represents the fraction of TCE which proceeds through the DCAC intermediate from the higher flow rate annular data.
flow rates and all of the slit configurations investigated. It is interesting to note that the amount of DCAC produced per TCE oxidized is constant for all slit configurations, rotation speeds, and non-mass-transferlimited bulk flow rates. Figure 6 shows similar data for the lower flow rates in the annulus. These show that the selectivity toward DCAC is lower. Figure 7 shows a similar plot for the data taken in the tubular reactor geometry. There does not appear to be any definite trend in these data, although they do appear to be lower fractions of DCAC to TCE.
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Figure 7. Apparent quantum yield of DCAC formation rate vs apparent quantum yield of TCE disappearance in the tubular geometry. The slit configurations denoted “ns” mean that all the slits were not symmetrically spaced. The solid line represents the fraction of TCE which proceeds through the DCAC intermediate from the higher flow rate annular data.
Discussion The effect of controlled periodic illumination on the apparent quantum yield is measured indirectly in this study. By comparing the stationary sleeve experiments to the rotating sleeve experiments with all other factors being constant, we can see if the observed rate of reaction is changed. It is important to note that the area of catalyst illuminated at any moment is constant. Also, the rotation does not change the number of photons being put into the system. However, during rotation, the light is distributed over the entire area of the TiO2 film as opposed to the small portion of the area illuminated during the continuous experiments with the cylinder stationary. This causes any individual TiO2 particle to see a short period of light and then a longer period of dark. If CPI does enhance the photocatalytic reaction, we would expect the observed reaction rate and the conversion to increase when the sleeve is rotating. An increase in the observed reaction rate can be correlated to an increase in the apparent quantum yield. At the lower two flow rates (0.5 and 2.5 L/min) there was an effect of the sleeve rotation on the observed rate of TCE oxidation. There was not an effect of the sleeve rotation at high flow rates in the annular reactor. This indicates that the effect seen at low flow rates disappears as the flux of reactants to the surface is increased. Thus, at the lower flow rates, there is a benefit to spreading the reaction out over the whole surface area of the catalyst. Since this effect disappears at higher fluxes of reactants, we must presume that the enhancement is due to the time that the rotation gives each catalytic site to desorb the products and intermediates and adsorb TCE and O2 before the light sweeps back to that site. With higher effective concentrations of reactants at the surface, the instantaneous rate of the surface reaction will be higher. The failure of CPI to enhance the rate of reaction in the kinetically limited regime is an interesting result. Taking a closer look at the literature surrounding the proposed mechanisms for the gas-solid photocatalytic oxidation of TCE, we found that the only proposed steps that require photons are the formation of the oxidation initiation species. Phillips and Raupp13 propose that oxidation is initiated by the reaction of OH• with TCE and continues through a free radical chain reaction mechanism. Fan and Yates20 suggest that the oxidation is initiated by photoexcited adsorbed O2. They further suggest that the excitation of O2(ads) is the rate-limiting
Figure 8. Electron removed from TCE per incident photon at all of the rotation rates vs the bulk flow rate in the reactor. The reactor was in the annular geometry with a 1 × 6 slit configuration.
step. Nimols et al.15 suggest that this species is atomic Cl. The reaction of TCE with OH•, the reaction of the O atom with TCE, or the oxidation of Cl- by illuminated TiO2 may form Cl atoms. Each of these possible mechanisms for initial Cl atom formation requires photons. In any of these proposed mechanism schemes for the photocatalytic oxidation of TCE, the formation of the radical initiation species is rate-limiting and requires photons. Assuming that this formation is nonreversible and nonequilibrating, this would be consistent with periodic illumination not having an effect. Another requirement for CPI to not affect the observed rate would be recombination processes being slower than the formation of products. The non-diffusion-limited annular results (Figure 5) show a constant ratio of DCAC formed in the product spectrum to the amount of TCE oxidized. By performing a linear regression of these data, the ratio of DCAC formed to TCE oxidized is 0.59 (model DCAC). This is approximately the same as the 55% fitted by Jacoby16 during kinetic modeling of results from a continuously illuminated reactor. This would indicate that at least 59% of TCE oxidizes through DCAC as opposed to direct oxidation to phosgene, CO2, and CO. The constant ratio of DCAC/TCE would imply that the light and dark times do not effect the pathway of oxidation in any detectable fashion. This is not unexpected since there was not an effect of controlled periodic illumination on the observed rate of reaction. By looking at Figures 6 and 7 it is seen that the experiments which did show some controlled periodic illumination effect on the observed rate also showed lower amounts of DCAC in the product stream. In the low flow rate annular experiments, this could be due to the much higher conversion of TCE (60-100%) which was seen in these experiments. At the higher conversions of TCE, the DCAC will more likely be oxidized to products at the end of the reactor bed than at lower conversions. In the tubular experiments where the difference from the 0.59 line is especially large, the TCE conversion was the same or less than those of the annular experiments at 3.8 and 5.0 L/min. The lower amounts of DCAC in the product stream indicate that the oxidation of each TCE molecule proceeded to a greater degree. This is also consistent with the diffusion limitations seen in this reactor. The DCAC is likely to readsorb to the TiO2 and react to products than to escape the boundary layer into the bulk reactant stream. To evaluate the efficiency of the photons to produce oxidized products, the number of electrons removed from
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the products was estimated from the oxidation states of the carbon atoms in the products. For instance, the reaction of TCE to form DCAC removes one electron per carbon atom. The oxidation of TCE to form phosgene transfers two electrons per carbon. Figure 8 shows the electrons removed from TCE per photon for the annular experiments at all flow rates and rotation rates for the 1/ length 1 × 6 slit configuration. As with the selectivity 2 and rate data, the only effect of the rotation rate is at the low flow rate. It is clear that at 0.5 L/min the periodic illumination almost doubles this apparent quantum yield from 90% to 160%. It is important to point out that the number of photons used in these calculations is based upon the light entering the reactor. No attempt was made to account for reflection or scattering effects. If these losses were accounted for, these efficiencies would be even higher. This lends support for some mechanism by which multiple oxidation steps are initiated with a single photon. Conclusions During the operation of the reactor in a diffusionlimited regime, controlled periodic illumination did enhance the apparent quantum yield of TCE oxidation from 90% to 160%. Dark times allow the concentration of reactants at the catalyst surface to increase before photons initiate reaction. This would cause higher instantaneous reaction rates as compared to continuous illumination at the same light intensity. The kinetically limited gas-phase oxidation of TCE in air is not significantly affected by controlled periodic illumination. The dark time in the kinetically limited CPI experiments did not enhance the reaction. As soon as the photons are absorbed by the catalyst, all necessary reagents and surface sites are present for reaction to proceed. An apparent quantum yield of 150% was measured in this kinetically limited regime. At least 59% of TCE oxidized through DCAC as a stable gas-phase intermediate. Acknowledgment The authors would like to acknowledge funding from the National Renewable Energy Laboratory, a National Science Foundation Minority Graduate Fellowship, and the Association of Western Universities. Literature Cited (1) Ollis, D. F., Al-Ekabi, H., Eds. Photocatalytic Purification and Treatment of Water; Elseiver: Amsterdam, The Netherlands, 1993. (2) Hoffman, M. R.; Martin, M. T.; Choi, W.; Bahnemann, D. W. Environmental Applications of Semiconductor Photocatalysis. Chem. Rev. 1995, 95, 69. (3) Linsebigler, A. L.; Guangquan, L.; Yates, J. T. Photocatalysis on TiO2 Surfaces: Principal, Mechanisms, and Selected Results. Chem. Rev. 1995, 95 (3), 735. (4) Grela, M. A.; Colussi, A. J. Kinetics of Stochastic Charge Transfer and Recombination Events in Semiconductor Colloids. Relevance to Photocatalysis Efficiency. J. Phys. Chem. 1996, 100, 18214-18221. (5) Kesselman, J. M.; Shreve, G. A.; Hoffmann, M. R.; Lewis, N. S. Flux-Matching Conditions at TiO2 Photoelectrodes: Is
Interfacial Electron Transfer to O2 Rate-Limiting in the TiO2Catalyzed Photochemical Degradation of Organics? J. Phys. Chem. 1994, 98, 13385-13395. (6) Sczechowski, J. G.; Koval, C. A.; Noble, R. D. Evidence of Critical Illumination and Dark Recovery Times for Increasing the Photoefficiency of Aqueous Heterogeneous Photocatalysis. J. Photochem. Photobiol. A 1993, 74, 273. (7) Sczechowski, J. G.; Koval, C. A.; Noble, R. D. A Taylor Vortex Reactor for Heterogeneous Photocatalysis. Chem. Eng. Sci. 1995, 50, 3163. (8) Sczechowski, J. G.; Koval, C. A.; Noble, R. D. In Photocatalytic Purification and Treatment of Water and Air; Ollis, D. F., Al-Ekabi, H., Eds.; Elsevier: Amsterdam, The Netherlands, 1993; pp 121-138. (9) Sczechowski, J. G. Increasing the Photoefficiency in Heterogeneous Photocatalysis through Controlled Periodic Illumination. Ph.D. Dissertation, University of Colorado, Boulder, CO, 1993. (10) Stewart, G.; Fox, M. A. The Effect of Dark Recovery Time on the Photoefficiency of Heterogeneous Photocatalysis by TiO2 Suspended in Non-Aqueous Media. Res. Chem. Intermed. 1995, 21 (8/9), 933-938. (11) Upadhya, S.; Ollis, D. F. Simple Photocatalysis Model for Photoefficiency Enhancement via Controlled Periodic Illumination. J. Phys. Chem. B 1997, 101 (14), 2625-2631. (12) Dibble, L. A.; Raupp, G. B. Kinetics of the Gas-Solid Heterogeneous Photocatalytic Oxidation of Thichloroethylene by Near UV Illuminated Titanium Dioxide. Catal. Lett. 1990, 4, 345354. (13) Phillips, L. A.; Raupp, G. B. Infrared Spectroscopic Investigation of Gas-Solid Heterogeneous Photocatalytic Oxidation of Trichloroethylene. J. Mol. Catal. 1992, 77, 297-311. (14) Dibble, L. A.; Raupp, G. B. Fluidized-Bed Photocatalytic Oxidation of Trichloroethylene in Contaminated Aristreams. Environ. Sci. Technol. 1992, 26, 492-495. (15) Nimlos, M. R.; Jacoby, W. A.; Blake, D. M.; Milne, T. A. Direct Mass Spectrometric Studies of the Destruction of Hazardous Wastes. 2. Gas-Phase Photocatalytic Oxidation of Trichloroethylene over TiO2: Products and Mechanisms. Environ. Sci. Technol. 1993, 27, 732-740. (16) Jacoby, W. A.; Blake, D. M.; Noble, R. D.; Koval, C. A. Kinetics of the Oxidation of Trichloroethylene in Air via Heterogeneous Photocatalysis. J. Catal. 1995, 157, 87-96. (17) Jacoby, W. A. Destruction of Trichloroethylene in Air via Semiconductor Mediated Gas-Solid Heterogeneous Photocatalysis. Ph.D. Dissertation, University of Colorado, Boulder, CO, 1993. (18) Kleindienst, T. E.; Shepson, P. B.; Nero, C. M.; Bufalini, J. J. The Production of Chlorine Atoms from the Reaction of OH with Chlorinated Hydrocarbons. Int. J. Chem. Kinet. 1989, 21, 863-884. (19) Lu, G.; Linsebigler, A.; Yates, J. T. Photooxidation of CH3Cl on TiO2(110): A Mechanism Not Involving H2O. J. Phys. Chem. 1995, 99, 7627-7631. (20) Fan, J.; Yates, J. T. Mechanism of Photooxidation of Trichloroethylene on TiO2: Detection of Intermediates by Infrared Spectroscopy. J. Am. Chem. Soc. 1996, 118, 4686-4692. (21) Larson, S. A.; Falconer, J. L. Characterization of TiO2 Photocatalysts Used in Trichloroethene Oxidation. Appl. Catal. B 1994, 4, 325-342. (22) Bickley, R. I.; Gonzalez-Carreno, T.; Lees, J. S.; Palmisano, L.; Tilley, R. J. D. A Structural Investigation of Titanium Dioxide Photocatalysts. J. Solid State Chem. 1991, 92, 178-190.
Received for review July 8, 1998 Revised manuscript received October 12, 1998 Accepted November 30, 1998 IE9804374
