Abstract
V2O5/NaY-SiO2 adsorbents were prepared by soaking up vanadium oxalate precursors into pellet NaY-SiO2. The NaY-SiO2 supports were prepared from NaY-SiO2 dough followed by extrusion and calcination at 450 °C. Ethanol was used as a model adsorbate to test the performance of the adsorbents. The regeneration efficacy, defined as the ratio of the adsorption capacity of a regenerated adsorbent to that of the fresh adsorbent, was investigated through the dynamics of fixed-bed adsorption (breakthrough curve). TPO, DSC, and FT-IR were used to characterize carbonaceous species on the adsorbents; meanwhile, synchrotron XRPD, XAS, and the N2 isotherm were used to characterize the zeolite, vanadia structure, and surface area, respectively. The results indicated that in low temperature (300 °C) regeneration, adsorption sites covered by alkylated aromatic coke formed during regeneration, causing adsorbent deactivation. In contrast, during regeneration at a high temperature (450 °C), the deactivation was caused by the destruction of the NaY framework concomitant with channel blockage, as suggested by the BET surface area combined with Rietvelt XRPD refinement results. In addition, the appearance of V-O-V contribution in the EXAFS spectra indicated the aggregation of isolated VO4, which led to a decrease in the combustion rate of the carbonaceous species deposited on the adsorbents. For regeneration at 350 and 400 °C, only trace coke formation and minor structural destruction were observed. Long-term life tests indicated that regeneration at 400 °C presents a higher maintenance of stability.
Highlights
The waste gas streams from chemical processes, electro-optical industries, and semiconductor manufacturing plants often involve volatile organic compounds (VOCs) [1,2]
In the first step, VOCcontaining air is passed through a cooler, where the VOCs are removed by adsorption at a low temperature
Since shrinking a unit cell is associated with removing aluminum atoms from NaY frameworks, the results suggest dealumination occurs in regeneration at 450 ◦ C
Summary
The waste gas streams from chemical processes, electro-optical industries, and semiconductor manufacturing plants often involve volatile organic compounds (VOCs) [1,2]. For. VOC abatement, either the capture or the destruction of the pollutants can be used. VOC abatement, either the capture or the destruction of the pollutants can be used When these compounds need to be recovered, condensation, absorption, or adsorption/desorption should be chosen [3,4]. Since a certain amount of energy is required to overcome the oxidation activation energy when treating low VOC concentration streams using a concentrator/incinerator, the system involves three steps to reduce the required energy [8]. In the first step, VOCcontaining air is passed through a cooler, where the VOCs are removed by adsorption at a low temperature. The heat generated during oxidation is used to preheat the incoming gas stream for the desorption of VOCs, thereby reducing the auxiliary fuel and the fuel cost
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