Preparation And Characterization Of Cu-ZSM-5 Zeolite Catalyst Coated On Paper-like Stainless Steel Fibers By Ion-Exchanged Method For Catalytic Wet Peroxide Oxidation Of Phenol

Phenol-containing wastewater is one of the industrial pollution with toxicity and degradation resisitant characteristics.Therefore,it is so important to develop a high efficiency degradation technology to ensure the human's health and water security.Catalytic wet peroxide oxidation method is favored because of mild reaction condition,high reaction rate and relatively low cost.In this technology,the catalyst plays an key role in improving the efficiency and selectivity.Thus,a microfiber composite molecular zeolite membrane catalyst was prepared and applied to the catalytic wet peroxide oxidation of phenol in order to improve catalytic activity,enhance mass and heat transfer and reduce bed resistance.In this work,Cu-ZSM-5 zeolite membrane catalysts coating on paper-like sintered stainless fibers were prepared by ion-exchanged method for the catalytic wet peroxide oxidation of phenol in a structured fixed bed reactor.Firstly,Cu-ZSM-5 zeolite membrane catalysts coating on paper-like sintered stainless fibers?PSSF?were prepared by ion-exchanged method for the catalytic wet peroxide oxidation?CWPO?of phenol in a structured fixed bed reactor.Firstly,two types of Cu-ZSM-5/PSSF catalysts were synthesized by ion-exchanged and impregnation methods.Then,the structures and properties of the catalysts were characterized by SEM,EDS mapping,BET,FT-IR,UV-vis,H₂-TPR and XPS,respectively.The experimental results showed that the continuous and compact ZSM-5 membrane?about 5?m in average thickness?was coated well over the PSSF surface.The catalyst prepared by ion exchanged method had more amount of Cu⁺species and more lattice oxygen than that of the catalyst prepared by impregnation.In addition,the CWPO performance of phenol was independently conducted in the structured fixed bed composed of the two Cu-ZSM-5/PSSF catalysts.The experimental results showed that the phenol was entirely eliminated,and high TOC conversion?80%?,CO₂selectivity?around 80%?as well as low total copper leaching rate?about 23%?were obtained over the catalyst prepared by ion-exchanged method,while TOC conversion of 51%,CO₂selectivity of 52%and high total copper leaching rate?about 60%?were achieved over the catalyst prepared by impregnation method.Finally,good durability with low Cu leaching concentration?only about 17 ppm?and complete phenol conversion were obtained after continuously operating 11 h.Meanwhile,the loss of Cu⁺active component and hard coke formations over the catalysts prepared by ion-exchanged method were primary reason for the deactivation.Meanwhile,Cu-ZSM-5 zeolite membrane catalysts prepared by ion exchange method were synthesized on paper-like sintered stainless fibers?PSSFs?with three-dimensional net structure for the catalytic wet peroxide oxidation?CWPO?of phenol in structured fixed bed reactor.The experimental results exhibited that the BET of optimal catalyst was 165 m²/g with the ion exchange concentration of 0.1 mol/L and time of 24 h,respectively,at temperature of 40 ^oC and one time ion exchange.The FT-IR results illustrated that band intensity was the lowest,and original Cu⁺species and lattice oxygen were predominant in optimal catalyst according to the XPS results.Then,the effects of ion exchange concentration,time,temperature and times on catalytic performance of phenol were also investigated in structured fixed bed.It was found that the phenol was completely removed,TOC conversion?around 76.6%?,high CO₂selectivity?about 78%?and low copper leaching rate?about 30%?were achieved with only 1.91 wt%copper loading over the optimal catalyst.Finally,the catalytic performance of Cu and Fe bimetallic catalysts was explored by changing the ion exchange sequence.And it could be found that the better catalytic activity was obtained over the Fe/Cu-ZSM-5/PSSF membrane catalyst,the TOC conversion rate was higher over Fe/Cu-ZSM-5/PSSF membrane catalyst than that of the Cu-ZSM-5/PSSF membrane catalyst,the value was improved by 3%.The introduction of Fe in the bimetallic metal catalyst not only increased the activity of the catalyst,but also inhibited the loss of Cu active components.In the bimetallic catalyst,there is an interaction between Fe and Cu metal.The reason could be that Cu transferred some electrons to Fe,leading to the valence of Cu became higher,which was more positive to catalytic reduction.