Preparation Of Boron-Based Monolithic Catalysts And Their Application For Oxidative Dehydrogenation Of Propane

The oxidative dehydrogenation of propane?ODHP?is a promising route for propylene production with lower energy consumption,anti-carbon deposition and equilibrium limit broken in propane conversion.Recently,boron-based catalysts are burgeoning with impressed activity and selectivity compared with the traditional metal-based catalysts.To promote the industrialization of boron-based catalysts,it is of great significance to develop a catalyst optimize mass transfer processes during the ODHP reaction.Monolithic catalysts have attracted great interests in recent years due to their significant advantages such as better mass and heat transfer,lower pressure drop and narrow residence time distribution.Based on what mentioned above,boron oxide wash-coated cordierite monolithic catalysts were prepared for ODHP.The synthesis conditions and the reaction conditions were also investigated in this paper,to achieve a desirable monolithic catalyst that could operate effectively under the high space velocity?GHSV?.First,we prepared a series of cordierite supported boron oxide catalysts?CHC@B₂O₃?and tested their catalytic activity in ODHP reaction.The CHC@B₂O₃ catalyst showed 22.2%propane conversion and 81.8%propylene selectivity at 505oC.Furthermore,catalytic stability test of CHC@B₂O₃ at 500oC showed that the propane conversion and olefin selectivity were constant,however after a 20 h reaction,the active component of boron oxide on the substrate lose 10%weight.This may attribute to the low melting point of B₂O₃ and weak interaction between B₂O₃ and the cordierite substrate.Second,to enhance the anchor of B₂O₃,SiO₂ was wash-coated on the cordierite followed by wash-coating B₂O₃?CHC@SiO₂-B₂O₃?.We found that the CHC@SiO₂-B₂O₃ catalyst remained good catalytic activity,and the stability test showed that the catalytic activity remained stable with the propane conversion of 16%for 20 h without weight lost.Next,we investigated the catalytic performance under high space velocity,the results showed that the catalyst achieved propane conversion of 16.9%and olefin selectivity of 97.2%at 535oC under GHSV of 345,600 mLg^-1_B2O3h^-1,and the CO₂ selectivity decrease to 0.1%.These results suggest that the large opening frontal area with a shorter contact time enlarged the overall throughput and promoted the heat and mass transfer of the catalyst,and the higher gas-to-surface ratio provide enough space for gas phase radical reaction to maintain a good activity and olefin selectivity under high GHSV.