Papers by Keyword: Catalyst

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Authors: Xiang Cheng Li, Bo Quan Zhu, Fei Zhao
Abstract: SiC whiskers are the common reinforced phases in alumina carbon refractories. In this paper, the effect of transition metal catalyst on the evolution of matrix phase and the formation of β-Si3Al3O3N5 whiskers were studied. It was found that the whiskers of both SiC and β-Si3Al3O3N5 in alumina carbon materials with the catalyst in reducing atmosphere were generated. The existence of catalyst can promote the nitriding process of Si metal and facilitate the formation of β-Si3Al3O3N5 whiskers. The growth mechanism of both SiC and β-Si3Al3O3N5 whiskers agrees with the vapor-liquid-solid model.
Authors: Ai Isohashi, Yasuhisa Sano, Shun Sadakuni, Kazuto Yamauchi
Abstract: A novel abrasive-free polishing method called catalyst-referred etching (CARE) has been developed. CARE can be used to chemically planarize a silicon carbide (SiC) surface with an etching agent activated by a catalyst. Platinum (Pt) and hydrofluoric (HF) acid are used as the catalyst and etchant, respectively. CARE can produce an atomically flat and crystallographically highly ordered surface of 4HSiC (0001) with a root-mean-square roughness of less than 0.1 nm regardless of the cut-off angle. However, industrial use of CARE is difficult because of HF acid usage. In this study, pure water was investigated as an alternative etchant to HF acid. We examined CARE using pure water by applying it to the planarization of a 4HSiC substrate and observed a feasible performance. The removal mechanism is considered to be the dissociative adsorption of water molecules to the SiC bonds of the topmost Si atom, namely the hydrolysis of the back bond, and the catalysis of Pt is considered to enhance the reaction. CARE with pure water is expected to represent a breakthrough method for surface processing of SiC, and will be widely applied in industrial processes such as planarization after high temperature processing in device fabrication.
Authors: Wei Jun Zhang, Xiao Kun He, Li Shen, Jin Hu, You Dong Cao, Lin Su
Abstract: This paper verified the relationship between the cell density of three types of substrates with different cell densities (400cpsi, 600cpsi, 900cpsi) and light-off factor (LOF). The results tested on engine bench demonstrated that, higher cell density of substrate could improve the light-off performance characteristics of catalysts. The effect of increasing cell density of substrate on air-fuel ratio characteristic of catalyst. It was effective measurement that higher cell density enlarged the operating window of catalyst.
Authors: Manish Srivastava, Ashok Kumar Das, Partha Khanra, Nam Hoon Kim, Joong Hee Lee
Abstract: Graphene/CeO2 nanocomposite has been successfully prepared by directly growing CeO2 nanoparticles on graphene sheets via in-situ reduction of graphene oxide containing the metal precursor. The presence of cetyltrimethyl ammonium bromide (CTAB) results the formation of CeO2 nanoparticles with a narrow size distribution. The structural, morphological, particles size and optical properties of the synthesized products were investigated through X-ray diffraction (XRD), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FT-IR) and UVvis absorbance spectroscopy, respectively. The XRD pattern shows that graphene/CeO2 nanocomposite is highly crystalline in nature. Growth of CeO2 nanoparticles with size in range of 5-18 nm on the graphene sheet were observed by TEM measurement. Optical energy band gap was calculated to be ~3.30 eV corresponding to direct transition. The catalytic activity of the synthesized nanocomposite was investigated taking hydrazine hydrate as a model system. Significant enhancement in the peak current with respect to CeO2 was observed on graphene/CeO2 nanocomposite-based electrode demonstrating the higher catalytic activity of graphene/CeO2 nanocomposite-based electrode.
Authors: Xiao Ming Yue, Zhi Min Zong, Bing Sun, Ying Hua Wang, Yu Qing, Fang Jing Liu, Xian Yong Wei
Abstract: A new catalyst with two active constituents interacting with activated carbon was prepared. As a model reaction for coal liquefaction, the hydrocracking of di(1-naphthyl)methane (DNM) was investigated under different reaction conditions over the catalyst. The results show that the catalyst converts DNM hydrocraking into 1-methylnaphthalene and naphthalene with high selectively, without any hydrogenation product. Kinetic analysis indicates that DNM hydrocracking in the temperature range of 170-300 °C could be considered as a first order reaction. The activation energy E and pre-exponential factor A for DNM hydrocracking for different reaction times were calculated.
Authors: Xiao Qing Niu
Abstract: In poly ferric sulfate production process with pyrite cinder as the main raw material, the sodium nitrite as catalyst is too toxic to be used largely. By orthogonal experiment and single factor experiments, the best reaction conditions were studied for the sodium nitrite as the catalyst, the amount of catalyst is 0.8%, the reaction temperature is 50°C and the reaction time is 60 minutes. According these conditions, the catalyst (CH-2) was used to promote the oxidation-polymerization reaction. Results showed that the use of this non-sodium nitrite catalyst could not eliminate the product toxicity that would be caused by using sodium nitrite catalyst but also make the toxicity of PFS was eliminated and the performance was better.
Authors: Kazushige Ohno
Abstract: The long time of twenty years has passed since Diesel Particulate Filter (DPF) was proposed before the practical use. The main factors that DPF has been put to practical use in this time, are the same time proposal of the evaluation method of SiC porous materials linked to the performance on the vehicle, and that the nature of thermal shock required for the soot regeneration (combustion of soot) in the DPF is different from the conventional requirement for the rather rapid thermal shock. For the requirements, these include demonstrating utmost the characteristic of SiC’s high thermal conductivity, and overcoming the difficulty of thermal expansion of SiC-DPF by dividing the filter into segments binding with the cement of lower Young’s modulus, and the innovation of technology around the diesel exhaust system such as Common-Rail system. As the results of these, the cumulative shipments of SiC-DPF have reached about 5 million, and it goes at no claim in the market.
Authors: Chun Ping Li, Hui Jie Duan, Jie Bai, Tong Xu
Abstract: In this paper, we reported an approach to fabricate PAN/β-cyclodextrin (β-CD) composite nanofibre with copper nanoparticles (NPs) grown on the surface by the simple electrospinning process. In the experiment, electrospinning method, soaking and adsorption method, together with reduction method were used to achieve the aim of coating. The final product was characterized using scanning electronic microscope (SEM), and fourier transform infrared spectroscopy (FTIR).
Authors: Jian Qiang Li, Wei Pan, Rui Gang Wang, Jian Chen
Authors: Mohammad Ebrahim Zeynali
Abstract: The dehydrogenation of diethylbenzene to divinylbenzene is a catalytic reaction. The catalyst for the dehydrogenation was prepared by co-precipitation of iron and chromium hydroxide from nitrate solution, followed by doping with potassium carbonate and drying. To make available the internal surface area of the catalyst for the reactant, the pores must be of the proper sizes to allow the reactant to diffuse and penetrate inside the catalyst pellets. The prepared catalyst was considered as a model for investigating the role of diffusion in catalyst design. In this study, different mechanisms of diffusion, such as Knudsen and bulk, were investigated for the case of diethylbenzene diffusion into the catalyst and it was concluded that the pore sizes should be in a range that permits transitional diffusion (both Knudsen and bulk diffusion). The catalyst grain size can be controlled and varied by acting on parameters such as the speed and time of mixing, type of alkali, temperature and pH. Particle size distribution experiments were conducted for different types of alkali and speeds of mixing in order to characterize the catalyst. The effects of the grain size, formed during co-precipitation, upon the pore size distribution of the catalyst pellet which affects the effective diffusivity were discussed. The pore size distribution of the model catalyst was obtained and the effective diffusivities were calculated by numerical integration of the Johanson-Stewart equation.
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