Preparation Of Pd Based Catalysts Supported On MOFs And Application In Hydrodechlorination Of Chlorophenol

The pollution of water resources is becoming more and more serious in the modern society,and the chlorophenol is the common pollutant.The common methods for removing chlorophenol pollutants in water include the physical adsorption,biological,chemical reduction,etc.,but they generally have some disadvantages,such as the high cost,cumbersome operation,and high environmental conditions.While the catalytic hydrodechlorination has attracted more and more attentions due to its clean,high efficiency,controllable cost,and mild conditions in the field of chlorophenol removal.Efficient catalyst is the core of the hydrodechlorination reaction,and the Pd-based catalysts are the most used hydrodechlorination catalysts.The key affecting in the performance of the catalyst are the carrier of Pd-based catalysts and the activity of Pd in the guest center.Metal organic frameworks(MOFs)is a new type of porous material,which was widely used in gas storage,heterogeneous catalysis and other fields,due to its stable structure and high mechanical strength,and the field of catalysis is the earliest and fastest growing field.The new supported catalyst formed by combining MOFs as the carrier of the hydrodechlorination catalyst with Pd in the guest center was studied in this paper.UiO-66 is used as a metal-supported carrier,and its strong acid site(Lewis acid site)is an important factor affecting the catalytic effect.However,there are few studies focus on the strong acid site of UiO-66,which limits its application as a catalyst carrier.In addition,the proportion of Pd0 in the guest center,the degree of dispersion,and the density of the outer electron cloud are not high,which is not conducive to mass transfer and diffusion,and prevents the reactant molecules from contacting it.Base on the above problems,the following work has been carried out:(1)Enhance the Lewis acid position of UIO-66 by defect regulation.UiO-66 was selected as the catalyst support,and the defect controllable properties of UiO-66 were fully utilized.Different regulators were selected for defect adjustment,and the defect adjusted catalyst supports UiO-66-x AA,UiO-66-TFA and UiO-66-BA were synthesized.Supported catalyst Pd / UiO-66 was synthesized by prepared UiO-66 supports with different defects and nano metal Pd particles(PD MNPs),and its hydrochlorination activity of chlorophenol was evaluated.The results showed that the selectivity of hydrochlorination of p-chlorophenol was 100%,the conversion of cyclohexanone was 99.50%.It shows that the activity of the catalyst can be effectively improved by using the modified UiO-66 support.(2)By adjusting the co-catalyst of Cu,to change the proportion of active center pd0,dispersion and outer electron cloud density.The co-catalyst Cu can affect the ability of Pd to absorb H2 and activate Cl-C and C=O bonds.In this study,co-catalyst Cu was loaded on Pd / UiO-66 catalyst to obtain Pd-Cu / UiO-66 composite catalyst containing co-catalyst.The co-catalysts with different contents of Cu were regulated,the selectivity of p-chlorophenol,cyclohexanone and reaction frequency reached 100%.The results showed that the co-catalyst regulation can significantly improve the activity of the catalyst.