Preparation Of Solid Catalytic CPS-NHPI And Investigating Catalytic Property In Oxidation Reaction

The oxidation of Alkanes and alcohols into the corresponding oxidation products is oneof the most important functional group transformations in organic synthesis，which plays animportant role in production of fine chemicals. But the traditional oxidation processcommonly used inorganic strong oxidant stoichiometry, which brings serious environmentalproblems. According to the view of green and sustainable chemistry, oxidation reaction withoxygen or air which is a clean and economical way of organic synthesis, in recent years hasbeen the strong research and development. N-hydroxyphthalimide (NHPI) using molecularoxygen as the oxygen source, has attracted much attention for which it can efficiently catalyzea variety of organic compounds under mild conditions to obtain the target product. Theheterogeneous NHPI catalyst is one of the most important subjects in the study of catalyticoxidation. In our present investigation, a new preparation method of crosslinked CrosslinkedPolystyrene Microspheres (CPS) as the carrier to manufacturer immobilized NHPI catalysthas been designed. On this basis, different transition metal salts was constituted with thepolymer-supported catalyst as catalyst systems was used to realize the catalytic oxidation oftoluene and benzyl alcohol with molecular oxygen, and their catalytic performance wereexamined and investigated.First of all, The chloromethylated crosslinked polystyrene microspheres (CMCPS) wasprepared with crosslinked polystyrene microspheres (CPS microspheres) as matrix and1,4-dichloro methoxy butane(BCMB) as chloromethylation reagent; Then phthalic anhydridewas bonded onto polymeric microspheres through the esterification reaction between thechloromethyl groups on CMCPS microspheres and the carboxyl group of trimellitic anhydride(TMA), obtaining the microspheres CPS-PA; Finally, like as the synthesis of small moleculeNHPI, the bonded phthalic anhydride (PA) reacted with hydroxylamine hydrochloride,resulting in the microspheres CPS-NHPI. NHPI-immobilized microspheres (CPS-NHPI) wereobtained and were characterized by several methods. The effects of the main factors in theesterification reaction were examined so that the reaction conditions were optimized. Theexperimental results show that the reaction of CMCPS microspheres with TMA is a key step. This reaction can smoothly be carried out with triethylamine as acid-binding agent and usingthe polar solvent N,N-dimethylacetamide at110℃, the conversion of chloromethyl ofCMCPS microspheres can reaches73％.After obtaining the the microspheres CPS-NHPI, The compositional catalyst systemconstituted by microspheres CPS-NHPI and a little of Co(OAc)2was used in the oxidationreaction of toluene by molecular oxygen. The catalytic activity of the catalyst catalystsystem and the effects of the main factors were examined. The experimental results show thatthe compositional catalyst constituted by CPS-NHPI and Co(OAc)2can effectively catalyzethe oxidation process of toluene by molecular oxygen under the mild conditions (at thetemperature of80℃and using dioxygen under ordinary pressure), and make toluene to bedeeply oxidized into benzoic acid, exhibiting high catalytic activity (the conversion of tolueneis57％). Furthermore, the compositional catalyst has excellent catalytic selectivity, and theselectivity of benzoic acid reaches84％. The catalytic oxidation reaction follows themechanism of free radical chain reaction. Among several transition metal salts, the co-catalysteffect of Co(OAc)2is the best. The suitable molar ratio of the immobilized NHPI onCPS-NHPI microspheres to Co(OAc)2is14:1, the appropriate used amount of the catalyst forthe catalytic oxidation system is that the NHPI contained in the primary catalyst CPS-NHPI is12mol％of the substrate, and the appropriate reaction temperature is80℃. The solidcatalyst CPS-NHPI microspheres possess excellent reusing and cycling property.At last, The compositional catalyst system constituted by microspheres CPS-NHPI and alittle of Co(OAc)2was used in the oxidation reaction of benzyl alcohol by molecular oxygen.The catalytic activity of the catalyst catalyst system and the effects of the main factors wereexamined. The experimental results show that the compositional catalyst constituted byCPS-NHPI and Co(OAc)2can effectively catalyze the oxidation process of benzyl alcohol bymolecular oxygen under the mild conditions (at the temperature of65℃and using dioxygenunder ordinary pressure), and make benzyl alcohol to be deeply oxidized into benzoic acid,exhibiting high catalytic activity (the conversion of benzyl alcohol is15.2％). Furthermore,the compositional catalyst has excellent catalytic selectivity, and the selectivity of benzoicacid reaches94.8％. The catalytic oxidation reaction follows the mechanism of free radicalchain reaction. Among several transition metal salts, the co-catalyst effect of Co(OAc)2is the best. The suitable molar ratio of the immobilized NHPI on CPS-NHPI microspheres toCo(OAc)2is14:1, the appropriate used amount of the catalyst for the catalytic oxidationsystem is that the NHPI contained in the primary catalyst CPS-NHPI is12mol％of thesubstrate, and the appropriate reaction temperature is65℃. The solid catalyst CPS-NHPImicrospheres possess excellent reusing and cycling property.