MICROWAVE SWING ADSORPTION FOR VOCS ELIMINATION WITH FAU TYPE ZEOLITES AS ADSORBENTS H. Nigar, N. Navascués, O. de la Iglesia, José L. Hueso*, R. Mallada, J. Santamaría Department Of Chemical Engineering And Environmental Technologies, Zaragoza University, Zaragoza, Spain Emails: [email protected]; [email protected] INTRODUCTION EFFECT SOURCE VOCS VOCs ? SOLUTION Desorption: Microwave heating Adsorption • • • • • Allows to collect for reusing VOCs • Preconcentration of VOCs for catalytic oxidation Volatile Organic Compounds (VOCs), organic compounds which easily evaporate and enter the atmosphere Industries Vehicles Health ABSORB MICROWAVE RADIATION GOOD ADSORBENT • Carcinogens • Chronic health threats • Harm to Liver, kidney, Immune, nervous, and reproductive systems. • Destruction of the ozone layer Household Products Perfumes Environmental Selective heating Avoid heat transfer problems Fast heating and cooling Energy saving FAU type Zeolite • Narrow pore size distribution • Catalytic activity • High specific area=Adsorption Capacity • Ion exchange ability • High thermal and chemical stability. EXPERIMENTAL ADSORPTION – DESORPTION EXPERIMENTS MATERIALS PRETREATMENT Na2O Zeolite Si/Al CBV100 CBV400 CBV780 2.5 2.5 40 ADSORPTION BASELINE N2 100ml/min Hexane N2 100 ml/min 100ml/min 100ml/min N2 100ml/min 100ml/min T T MS *MS: Mass spectrometer MW: Microwave Heating CH:Conventional Heating T DESORPTION Hexane N2 Cation Weight [%] Na+ 13.0 H+ 2.8 H+ 0.03 SWEEPING MS MS Vent T MS MS T CH/MW CH/MW CHARACTERIZATION MICROWAVE HEATING ARGON ADSORPTION 200 CBV780 CBV400 CBV780 175 TGA 100 CBV100 160W 240 150 50 25 90 85 CBV400 80 0,002 0,004 0,006 0,008 P/P0 0,010 0,012 0,014 Pore TGA Surface dp Volume Weight Zeolite Area [Å] [cm3/g] [m²/g] loss (%) 24.3 CBV100 758 6.9 0.341 14.7 CBV400 738 7.1 0.256 12.6 CBV780 711 7.3 0.217 250 CBV400 40,7°C/min 200 180 120 CBV780 25,6°C/min 150 CBV780 120 90 Water Intensity 100 26,5°C/min 60 60 CBV100 75 0 0,000 Temperature [°C] 75 Temperature 5°C/min 180 95 Weigth Loss [%] 3 cm /gSTP 100 300 300 150 125 MICROWAVE HEATING VS CONVENTIONAL HEATING AND COOLING Temperature [°C] CHARACTERIZATION 50 300 30 100 200 300 400 500 Temperature [°C] 600 700 Conventional Cooling 3°C/min Microwave Cooling 160°C/min 0 2400 800 3200 Time [s] 4000 4800 TEM 120 60 10 20 30 Time [min] 40 50 30 Runaway could take place in zeolites that highly absorb MW, could lead to remove the structural water. Water Intensity 0 20 Faster cooling Faster heating MW 180 Higher heating ramp is reached by CBV100 Zeolite, which has more water uptake. Higher temperature could be reached in zeolites that contain mobile Na+ Time [min] 200W Temperature 70°C/min 240 10 60 RESULTS HEXANE ADSORPTION AND DESORPTION Hexane Adsorption Capacities 180 CBV100 160W Microwave vs. Conventional 180 CBV100 160W CBV400 CBV780 60 CBV100 100W CBV780 160W 60 CBV400 160W Hexane Intensity [a.u.] 120 CBV100 120 Hexane Intensity [a.u.] Hexane intensity [a.u.] Hexane Desorption in MW Hexane Desorption in Conventional Heating Temperature [°C] *7 different batches Hexane Desorption in Microwave Heating Temperature [°C] Adsorption Capacities* Zeolite [mg hexane/g zeolite] CBV100 107.3 ± 3.33 CBV400 57.6 ± 3.30 CBV780 48.9 ± 1.91 Hexane Desorption in Conventional Heating CBV100 100W 0 530 Lower adsorption capacity is reached by CBV 780, which has lower micropore volume 535 540 Time (min) 545 550 Faster desorption is obtained by CBV 780, which has higher porous size 0 10 20 Time [min] 30 40 At the same power, desorption of CBV100 and CBV780 are at the same time. At the same temperature, desorption kinetic is similar to conventional desorption 420 425 430 435 Time [min] 440 445 450 Faster desorption in microwave heating !!! CONCLUSIONS • Microwave heating process in zeolites depends on the amount of water physisorbed and the type of cations in zeolite structure. Increasing the degree of hydration and mobility of cation, increase the temperature, which favors the desorption. • Zeolites could be instable under MW radiation. • Adsorption capacities and kinetics for FAU type zeolites have been obtained and correlated with adsorbent properties i.e. pore size and pore volume and hydrophilicity. • Microwave desorption provide a faster desorption than conventional desorption. • Differences in desorption kinetics between microwave and conventional is due to different temperature reached by zeolites at the same power. ACKNOWLEDGEMENTS This research is supported by EU Commission ERC Advanced grant (I-2011/004 – Hector Project) The author gratefully acknowledge financial support from the Spanish Ministry of Education for the Training of University Professors (Formación del Profesorado Universitario – Hakan Nigar FPU12/06864)
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