Research On The Mechanism Of Catalytic Reduction Of P-Nitrophenol By Palladium On Alumina ?Pd-Al₂O₃?

p-Nitrophenol?PNP?is a widely used to the dyes,pesticides,pharmaceuticals and other fine chemical products in the production process of important organic synthesis of raw materials.A large amount of p-nitrophenol containing wastewater is increasingly being released into the environment along with the rapid development of the fine chemical industry,resulting in a rapid increase in p-nitrophenol concentration in the surface and groundwater.Because of its nitro and hydroxyl and benzene ring conjugate effect,so p-nitrophenol is difficult to degrade organic matter,is not easy to be degraded by aerobic organisms,while biodegradation of nitroso and hydroxylamine is also carcinogens.PNP can be enriched in aquatic organisms,can stay in the water environment for a long time,and it is not easy to volatilize with the steam,has serious polluting to the environment.It can affect human health through breathing inhalation,food intake,skin contact,etc.,strong inhalation can lead to difficulty breathing,elevated body temperature,headache,nausea,etc.,and even lead to death.Therefore,both China and the US Environmental Protection Agency have classified it as one of the priority control pollutants.PNP is an important organic synthesis of raw materials,but the production process of environmental pollution can not be underestimated.Therefore,how to increase the production of PNP and can reduce its pollution to the environment has become more and more research scholars concerned about the hot spots.At present,at home and abroad on the treatment of PNP containing wastewater are:physical,biological and chemical methods.The catalytic reduction of PNP to p-aminophenol is the main way to treat this type of wastewater.Compared with the traditional PNP removal method,the catalytic hydrogen transfer reduction method has broad application prospects because of the mild reaction conditions,low risk,high chemical selectivity of the reduction products and environmental friendliness.The main contents of this paper are as follows:the effects of rotational speed,pre-reaction,PNP initial concentration,catalyst dosage,sodium formate dosage and reduction system on the catalytic reduction of PNP by Pd-Al₂O₃ are studied under certain conditions.And the reaction mechanism of the catalytic reduction of PNP by Pd-Al₂O₃ was studied by UV spectrophotometer and kinetic analysis.The main conclusions are as follows:?1?Under the isopropanol and sodium formate reduction system,Pd-Al₂O₃ catalyzed the reduction of p-nitrophenol at 160 rpm.?2?In the isopropanol and formate reduction system,there is an obvious"plateau" in the initial reaction.?3?The reaction rate under the different conditions was in accordance with the pseudo-first order kinetic reaction;The reaction rate under the isopropanol and formate reduction system was relatively slow,and the reaction rate under the hydrogen and potassium borohydride reduction system was faster.?4?PNP can only be catalytically reduced to p-hydroxylamine phenol in weakly reducing system?isopropanol and sodium formate,isopropanol and ammonium formate?;In strong reducing systems?H2 and potassium borohydride?,PNP can be reduced to p-aminophenol.