Stabilizing copper species using zeolite for ethanol catalytic dehydrogenation to acetaldehyde

The selective dehydrogenation of ethanol to acetaldehyde is a promising route for acetaldehyde production.Although Cu-based catalysts exhibit high activity in ethanol dehydrogenation,a rapid deactivation due to Cu sintering always occurs.In this study,highly dispersed Cu species were stabilized using the silanol defects in Beta zeolite(denoted as Beta)resulting from dealumination,and applied as robust catalysts for ethanol-to-acetaldehyde conversion.Typically,a long catalyst lifetime of 100 h with an acetaldehyde yield of^70%could be achieved over 5%Cu/Beta.The presence of Cu^+and Cu0 species and the agglomeration of Cu particles after a long-term reaction for 180 h were revealed by transmission electron microscopy,thermogravimetric analysis,and CO-diffuse-reflectance infrared Fourier transform spectroscopy,and were responsible for the deactivation of the Cu/Beta catalyst in the ethanol-to-acetaldehyde conversion.

Defect‐rich BN‐supported Cu with superior dispersion for ethanol conversion to aldehyde and hydrogen

Copper‐based heterogeneous catalysts commonly exhibit uncontrolled growth of copper species under reaction conditions because of the low Hüttig temperature(surface mobility of atoms)and Tamman temperature(bulk mobility)for copper at just 134 and 405°C,respectively.Herein,we report the use of defect‐enriched hexagonal boron nitride nanosheets(BNSs)as a support to anchor the Cu species,which resulted in superior dispersion of the Cu species.The obtained Cu/BNS catalyst was highly stable for ethanol dehydrogenation,with a high selectivity of 98%for producing acetaldehyde and an exceptionally high acetaldehyde productivity of 7.33 g_(AcH) g_(cat)^(‒1) h^(‒1) under a weight hourly space velocity of 9.6 g_(EtOH) g_(cat)^(‒1) h^(‒1).The overall performance of our designed catalyst far exceeded that of most reported heterogeneous catalysts in terms of the stability of the Cu species and the yield of acetaldehyde in this reaction.The hydroxyl groups at the defect edges of BNS were responsible for the stabilization of the copper species,and the metal‐support interaction was reinforced through charge transfer,as evidenced by coupling atomic resolution images with probe molecule infrared spectroscopy and X‐ray photoelectron spectroscopy.A designed in situ diffuse reflectance infrared Fourier transform spectroscopy study of ethanol/acetaldehyde adsorption further revealed that Cu/BNS favored ethanol adsorption while suppressing acetaldehyde adsorption and further side reactions.This study demonstrates a new method for designing highly dispersed Cu‐based catalysts with high durability.

Supported metal catalysts at the single-atom limit – A viewpoint

An account of recent work on supported single‐atom catalyst design is given here for reactions as diverse as the low‐temperature water‐gas shift,methanol steam reforming,selective ethanol dehydrogenation,and selective hydrogenation of alkynes and dienes.It is of fundamental interest to investigate the intrinsic activity and selectivity of the active metal atom site and compare them to the properties of the corresponding metal nanoparticles and sub‐nm clusters.It is also important to understand what constitutes a stable active metal atom site in the various reaction environments,and maximize their loadings to allow us to design robust catalysts for industrial applications.Combined activity and stability studies,ideally following the evolution of the active site as a function of catalyst treatment in real time are recommended.Advanced characterization methods with atomic resolution will play a key role here and will be used to guide the design of new catalysts.