Toxic leachability during land treatment and reuse feasibility of spent hydroprocessing catalysts

• Main Authors: Lai Jung Ta, 賴勇達
• Other Authors: Liu Jhy Chern
• Format: Others
• Language: zh-TW
• Published: 1995
• Online Access: http://ndltd.ncl.edu.tw/handle/42170180582093200406

碩士 === 國立臺灣科技大學 === 化學工程研究所 === 83 === A study was conducted on the leaching toxicity and the reuse feasibility of the residual oil cracking(ROC) spent catalysts. In assessing the leaching behavior of nickel and vanadium, an automatic pH/ORP control system was utilized. At pH=5, the equilibrium nickel solubility did not change with the redox potential. Compared with result from sequential extraction, the amount of nickel dissolved was equal to the exchangeable fraction of spent catalyst. At pH=8, the dissolved nickel concentration increased with decreasing ORP, and is portional to the dissolved iron concentration. The dissolved concentration of vanadium increased with decreasing ORP at both pH=5 and pH=8. Thisbehavior could be explained by the reducing reaction of vanadium. Second, we used batch reactor to study the effect of pH, surface loading and temperature on the adsorption of fluoride by spent catalysts. Both equilibrium and kinetics of adsorption were investigated. Result show that the ROC spent catalyst is a good adsorbent. The adsorption of fluoride could be modeled with the linear adsorption isotherm. The adsorption capacity increased with temperature and surface loading. The adsorption reactionas a first order reaction. At low pH, the fluoride adsorptionuld be attributed to the silica portion in spent catalysts; whereas, fluoride adsorption could be attributed to the alumina portion under acidic to slightly basic conditions. Judging from the activated energy, the adsorption reaction is proposed to be a physical adsorption, and is mainly driven by the electrostatic force.