Catalytic Degradation Of Phenol-Containing Wastewater With Hydrogen Production

The effluents from pesticides,herbicides and its intermediate products always contain high concentration of phenolics,which is high toxic and biorefractory.Thus, biological treatment of such a wastewater is extremely difficult.Removal of phenolics by chemical methods,however,needs expensive oxidant or carried out under rigour conditions such as high temperature and pressure.Moreover,most of the existent methods convert organics(phenolics)into H₂O and CO₂ without resource recovering.In the present thesis,a novel method for the degradation of phenol-containing wastewater for hydrogen production has been proposed.In this process,aqueous phase reforming of phenolics into H₂,CO₂ and etc.is carried out under the mild reaction conditions of temperature and pressure over the Raney Ni or Sn modified Raney Ni catalysts.Therefore,it provides an economical route for the treatment of phenolics wastewater with resources recovering for hydrogen production.The experimental result for the treatment of phenolics wastewater with hydrogen production is showed in the following:Two different treatments of aqueous and steam phase reforming over Raney Ni catalyst have been compared.The results indicate that 100%degradation of phenol could be realized under certain conditions.Raney Ni is effective for those recovering resource processes.As for aqueous phase reforming ways,it can not only prevents energy consumption that is always occurred during gasification but also gets low CO content H₂,however,the content of by-product CH₄ is relatively high.The effects of temperature,phenol concentration and LHSV on the degradation of phenol have been investigated.The results indicate that higher temperature and lower LHSV can enhance the degradation rate of phenol,but the selectivity to hydrogen is decreased.The effect of Sn-modified Raney Ni(Sn-Raney Ni)catalysts on those recovering resource processes have been investigated.The results indicate that high selectivity to hydrogen could be realized after introducing Sn.The degradation of phenol and selectivity to hydrogen are 100%and 98.6%,respectively over Sn-modified Raney Ni catalyst(Sn:Ni=0.6)under the optimized conditions.We further research for the physical and chemical properties of the Sn-Raney Ni catalyst by using methods such as XRD,BET and reveals that with the blending of Sn,the specific surface area of Raney Ni is greatly reduced.XRD shows that Ni-Sn alloy is formed because of catalyst's phase transformation,which account for the main factor to prevent methane formation.In additional,the thermodynamics and reaction mechanisms for the phenol degradation process have also been investigated in this thesis,through which the intrinsic requirements of catalyst for the phenol-containing wastewater degradation reaction process were obtained.