The Effect Of Strong Interaction Between NiO And ZrO₂,Al₂O₃ Supports On The Dehydrogenation Properties Of Ethylene And Propane Was Studied

Ethylene and propylene are important basic chemical raw materials,and their downstream products and derivatives are widely used in fields such as construction,automotive parts,and textiles.The traditional routes for producing ethylene and propylene using petroleum steam cracking and catalytic cracking technologies can no longer meet the needs of the current market.Direct dehydrogenation of ethane and propane from natural gas to olefins has important economic value.Oxide catalysts with defective sites can efficiently catalyze the dehydrogenation of low-carbon alkanes.In this paper,nano NiO/ZrO₂ and NiO-Al₂O₃ oxide catalysts were designed and prepared,and they were used to catalyze the oxygen-lean dehydrogenation of propane and the oxidative dehydrogenation of ethane,respectively.Strong interactions between NiO and ZrO₂ or Al₂O₃ supports control the redox activity of surface oxygen species and the formation of defective structural active sites.The main research results of this article are as follows:1.Recently,the ZrO₂-based catalysts for PDH exhibited high activity owing to the formation of oxygen vacancy and coordinatively unsaturated Zr(Zr_cu)sites.However,industrial C₃H₈ raw gases typically contain trace amounts of oxygen at 10-1000 ppm,which can significantly decrease the propane dehydrogenation（PDH）activity of nano-sized ZrO₂ catalyst,because that oxygen vacancy can be filled by theO₂ molecules rapidly,while the rate of lattice oxygen consumption is relatively slow.Here,highly dispersed NiO_x species loading on ZrO₂ significantly increased C₃H₆formation rate（up to 6.6 times）and decreased the activation energy.The strong interaction between NiO_x species and ZrO₂ enhances the ability of ZrO₂ to release its lattice oxygen,and increases the concentration of oxygen vacancy and unsaturated Zr-O acid-base pairs for PDH.This strategy can expand to other metal oxides interacted with ZrO₂ to eliminate the inhibiting effect of trace oxygen,such as GaO_x,CoO_x,CrO_x,LaO_x,and InO_x.2.Plasma treated metal oxide materials typically generated defective oxygen species,which are consider as the active sites in the oxidative dehydrogenation（ODH）of ethane to ethane.Here,Ar,O₂,and H₂ plasma pretreated Ni-Al（NA）composite oxide were used as ODH catalyst.Plasma treatment not only dispersed the aggregated NiO particles in space,but also promote the growth of small nanograins or reduction.Ar andO₂ plasma pretreatment increased catalytic performance of NA catalyst,while H₂ plasma decreased the catalytic performance.O₂-plasma-treated NA exhibited 37.4%ethane conversion and 76.7%ethene selectivity at 475 ^oC and excellent stability without deactivation within 40 h.The ratio of defective oxygen and lattice oxygen（O_V/O_L）can be calculated according to XPS characterization.C₂H₆ conversion increased and C₂H₄ selectivity decreased linearly with theO_V/O_L value,respectively.Thus,the concentration of surface defective oxygen species can be regulated by different plasma treatment and is crucial for oxidative dehydrogenation of ethane.