The Ninth Visual Object Tracking VOT2021 Challenge Results

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Influences of reaction conditions on methane decomposition over non-supported Ni catalyst

Effects of reaction temperature and methane gas hourly space velocity(GHSV)on methane decomposition over non-supported Ni catalyst have been investigated in this work.Methane molecules activation,Ni particles growth and nano-carbon diffusion were the main factors influencing methane decomposition stability of non-supported Ni.The results of methane decomposition activity test on the non-supported Ni catalyst showed that the prepared non-supported Ni could exhibit a good methane decomposition performance with 273 gC/gNi and 2667 molH2/molNi at 500℃ and 45000 mL/(gcat h).Scanning electron microscope(SEM),X-ray powder diffraction(XRD)and temperature-programmed oxidation(TPO)have been carried out to characterize the used catalysts.The deposited carbon was carbon nanofibers,among which graphitic carbon formation increased with the reaction time of methane decomposition.Ni particle size was not the decisive factor during the carbon growing stage

Recent advances in direct catalytic hydrogenation of carbon dioxide to valuable C2+ hydrocarbons

As one of the most effective methods, CO2 hydrogenation through heterogeneous catalysis is a promising means to mitigating the detrimental effects of anthropogenic CO2 that also accomplishes the effective recycling of carbon element. Considering the inertness of the CO2 molecule as well as the subsequent low chain propagation activity, the products are usually small molecules such as methane, methanol and formic acid. Furthermore, the imprecise regulation of C-C coupling further hinders the acquisition of target products. These problems make CO2 hydrogenation to useful C2+ hydrocarbons more challenging. Therefore, the rational design and fabrication of highly efficient and selective catalysts, including promoter-modified single metal catalysts, composite catalysts and bimetallic catalysts, is an inevitable process to upgrade the end products of CO2 utilization. This review will focus on the recent developments in the highly selective formation of C2+ hydrocarbons, especially the utilization of composite catalysts or multi-functional catalysts, which indicate the great potential derived from the synergistic effect of multi-active sites

Importance of the Initial Oxidation State of Copper for the Catalytic Hydrogenation of Dimethyl Oxalate to Ethylene Glycol

Exposing a Cu-based catalyst to a suitable temperature is of great importance to optimize its hydrogenation performance, as copper is sensitive to temperature. Herein, we investigated the effect of the initial oxidation state of copper, tuned by the reduction temperature, on its catalytic performance in the hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG) through designing a series of catalysts with different reduction temperatures (200-350 degrees C). Among these catalysts, the Cu/SiO2 catalyst prepared by ammonia evaporation with a hydrogen reduction process at 250 degrees C showed the best performance in the hydrogenation of DMO with a conversion of 100 % and a selectivity to EG higher than 95 %. The relationship between the initial oxidation state of copper and catalytic performance was well established by characterizing the physicochemical properties of the Cu/SiO2 catalysts by XRD, TEM, H-2 temperature-programmed reduction, N2O adsorption, and in situ reduction Auger electron spectroscopy. The initial oxidation state of copper determined the conversion of DMO and the distribution of the products, and it could be balanced by reducing the temperature to improve the activity of the catalyst. This work provides a reference for further exploration of the mechanism and guidance for the design of catalysts for the hydrogenation of esters

Effect of Oxide Phase of Promoters on Coke Resistance over Pt/gamma-Al2O3 Catalyst

The effects of different promoters on coke deposition over Pt/Al2O3 catalyst for hydrogen-free cyclohexane dehydrogenation were investigated by catalytic tests and a series of analytical techniques such as X-ray diffraction, CO and H-2 chemisorption, temperature-programmed desorption of NH3, and temperature-programmed reduction. The stability of different promoters modified catalysts is in the order of Zr-Pt/Al2O3 > Ca-Pt/Al2O3 > Ce-Pt/Al2O3 > Zn-Pt/Al2O3 > Ba-Pt/Al2O3. The results clearly show that the addition of promoters to the Pt/Al2O3 catalyst could inhibit coke deposition by increasing Pt dispersion and promoting hydrogen spillover. That is attributed to the high thermodynamic and chemical stability of the metal oxide promoters. They must be highly dispersed and stable without reacting with Al2O3 in calcination or forming alloy with Pt in reduction. The catalytic property of CaLa-Pt/Al2O3 is worse than either Ca-Pt/Al2O3 or La-Pt/Al2O3 because the acidity of catalyst is enhanced and the spillover hydrogen is reduced due to Ca-La strong interaction