Basic Research On Microwave Pretreatment Process Of Waste Aluminum-based Hydrogenation Catalys

Petrochemical industry uses kinds of catalysts in hydrotreating processes.Commonly,these catalysts consist of several environmentally critical and economyically valuable metals such as Mo,Ni and V.Thus it is imperative to develop an effective,low cost and environment friendly way to recycle the rare metals from spent hydrotreatingcatalysts.To overcome the disadvantages of traditional oxidation pretreatment,our research focuses on the fundamentals for microwave-oxidizing pre-treatment of spent Al-based hydrogenation catalyst.The main research contents and results are listed as follows:(1)TGA-DSC analyses of waste Al-based hydrotreating catalyst were carried out under air atmosphere.The pyrolysis process consisted of the three stages:a fast devolatilization of organics,an oxidation process of metal sulfide,and a slow degradation stage of residue during which the main reaction is occurred in the temperature from 350～850℃.The oil removal process and the oxidation of metal sulfide all follow one dimensional diffusion of Parabolic model and first-order reaction of Coats-Redfern model.(2)Oil removal experiments of spent Al-based hydrotreating catalyst with ethanol combing ultrasonic were performed.The influence of temperature,time,and solid-liquid ratio of catalyst and ethanol on oil removal efficiency were investigated.When oil removal time is 2h,the temperature is 55℃,and the solid-liquid ratio were 1:5,the deoiling rate is over 99%.(3)The spent Al-based hydrotreating catalyst were pretreated by Microwave heating under air atmosphere.The effects of pretreating temperature,pretreating time,microwave power,and granularity on desulfurization rate and decarburization rate were investigated.When pretreatment temperature is 650℃,the pretreatment time is 45 min,microwave power is 960W and grain size is 200-mesh,the desulfurization rate and decarburization rate are 96.73%and 99.76%,respectively.The structure and morphology of exhausted catalyst before and after microwave radiation-pretreatment were characterized by XRD,SEM,XPS and nitrogen adsorption techniques,which indicated that all the metals sulphides converted into metal oxides,and no impurity CoMoO4 generated.(4)The leaching experiments of Mo from the spent catalyst were carried out.Under the optimum pretreatment conditions,over 96.42%Mo can be leached with 1.6 M sodium carbonate solution,which is two precent high than that pretreated via tranditional electric furnace heating.(5)Dielectric properties of spent Al-based catalyst during the pre-treating at different temperature were measured by using the resonance cavity perturbation technique at 915 MHz.The effects on temperature rise characteristics with different sample mass and different microwave power were investigated.On this basis,the effect of temperature on the dielectric properties of the spent catalyst and the pure components in the spent catalyst were investigated.The results indicate that the spent catalyst has a strong microwave absorbing properties,and the temperature has a pivotal effect on the dielectric constant.When the temperature is 650℃,the spent catalyst exhibited the strongest ability of converting microwave energy to heat.