Phosphorus Dosing during Catalytic n -Butane Oxidation in a μ-Reactor: A Proof of Concept

The selectiveoxidationofn-butaneto maleicanhydrideover vanadium−phosphorusoxide catalystsis subjectto a dynamicchangein the catalystactivity.This phenomenoniscalled phosphorusdynamicsand plays a vital role in the predictionof catalyticreactionrates, but to date, no modelsmeasuredundertransportlimitationfree conditionshave been published.Thisstudy presentsthe first investigationof the phosphorusdynamicsover extendedperiodsof time (multipledays on stream)undertransportlimitationfree conditionsin aμ-fixed-bedreactor.Initially,temperaturevariationexperimentsare conductedtoinvestigatewhetherphosphorusdynamicstakes place in aμ-reactorand to determinethe onset of phosphorusloss. Then,asetup for dosingof liquid organophosphorousspecieson the scaleof nL min−1is proposed,and functionalityis demonstratedvia step test experiments.Resultsof the temperaturevariationshowedthat phosphorusloss occursin theμ-reactorbut starts at temperaturesexceedingthose of industrialscale reactorsby 30−80K. It wasfurtherobservedthat additionof steamto the feed increasesthe intensityof the phosphorusdynamicsand lowersthe onsettemperature.Step test resultsdemonstratedthe functionalityof the dosingsetup if a suitableinert materialis chosenand the metalsurfacesdownstreamthe dosingare treatedaccordingto a passivationprocedureproposedin this study.The additionof steamappearsto be requiredfor appropriatedistributionof the dosedorganophosphorousspeciesover the catalystbed.