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891.
Cobalt loss from Co-ZrO2 catalyst for Fischer-Tropsch synthesis in continuously stirred tank reactor
Litao Jia Kegong Fang Jiangang Chen Yuhan Sun 《Reaction Kinetics and Catalysis Letters》2008,93(2):351-358
The cobalt loss of the co-precipitated Co-ZrO2 catalyst was investigated during the Fischer-Tropsch synthesis in a continuously stirred tank reactor. The cobalt species
in the produced water originating from the transformation of CoO into Co2+ ions was tested by TPR, XRD and XPS. Furthermore, reduction at a relatively higher temperature resulted in a lower loss of
cobalt. 相似文献
892.
Using a series of silica-supported bases, we demonstrate the synthesis of eight condensation products within an EOF-based flow reactor; in all cases, high yields (>99%) and product purity are obtained. 相似文献
893.
894.
《印度化学会志》2023,100(8):101049
NiCo nanoalloy catalysts were prepared from hydrotalcite precursors and used in CO2 reforming of methane (DRM) under atmospheric and 2 MPa pressure in a fixed-bed reactor at 700-850 °C. The Ni6Co1 catalyst with a molar ratio of Ni/Co to 6 showed the highest stability and activity in DRM under atmospheric pressure. This was due to the homogeneous dispersion of nanoalloy particles (∼14 nm) on the MgAl(O) support, which had a strong metal-support interaction. Nonetheless, a slow and continuous deactivation was spotted under 2 MPa pressure due to the coke deposition. Further modification of Ni6Co1 with optimum amount of Fe (in Ni6Co0.5Fe0.5) formed ternary NiCoFe nanoalloy with improved metal-support interaction and reduced alloy size (∼10 nm). The presence of Fe significantly improved the coke resistance capability and provided high stability under 2 MPa pressure. 相似文献
895.
《Journal of Saudi Chemical Society》2023,27(4):101671
The catalytic oxidation of benzyl alcohol (OBA) is one of the significant methods to produce benzaldehyde, an essential reagent in the chemical and pharmaceutical industries. However, developing an active and efficient catalyst for OBA is a tremendous challenge in commercialization. This research describes a simple, eco-friendly method for producing Fe, Pd, and Fe: Pd bimetallic nanoparticles fabricated by sol immobilization over graphene to conduct OBA. The resulting composite nano-alloys were then characterized using X-ray diffraction (XRD), Fourier transforms infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM). The oxidation state and elemental composition of as-fabricated nanoparticles were analyzed using XPS. The point of zero charges (pHPZC) was analyzed and the PZC value indicated that the proposed adsorbent material tends to have a positive charge. The OBA reaction efficiency (87%) of bimetallic nanocatalysts stabilized in graphene support was increased through surface modification of the ratio of both metals. The experimental error was based on three parallel tests and the carbon balance (99.6%) was analyzed during the experiments A proposed reaction mechanism of OBA validated the β-hydride step's elimination by molecular oxygen converting the metal hydride into a water molecule, forming a peroxide intermediate to form water and oxygen molecules. The Fe on the nanocatalyst’s surface is preferentially responsible for the adsorption of the substrate molecule, resulting in the formation of metal-alkoxide. Since it lacks electrons, Fe is more likely to be oxidized, allowing it to perform better than monometallic catalysts in terms of catalytic activity. The present study has great potential to be applied on an industrial scale and studied for industrialists, researchers, and academicians. 相似文献
896.
《Arabian Journal of Chemistry》2023,16(2):104464
Due to the complexity of the structure–activity relationship of the CuAl2O4 spinel catalyst, optimization of the catalyst structure is a great challenge. In this paper, three different CuAl2O4 spinel catalysts were prepared by the solid-phase method using copper hydroxide, copper nitrate, and copper oxide as the copper source, respectively, to study the difference in the structure of CuAl2O4 spinel catalysts induced by the raw materials and the catalytic behavior for CO hydrogenation. The structure of CuAl2O4 spinel catalyst was characterized by XRD, BET, SEM, TEM, H2-TPR and XPS. The activity of CO hydrogenation over the CuAl2O4 spinel catalyst without pre-reduction was evaluated in the slurry reactor. The results demonstrated that different copper sources had obvious influence on the CuAl2O4 spinel texture properties, surface enrichment degree, as well as decomposition and reduction ability, which further regulated the ratio of Cu+/Cu0 and thus affected the catalytic performance, especially the alcohol distribution. The CuAl2O4 spinel, employing copper hydroxide as the copper source, showed better selectivity of C2+OH, which was assigned to a higher ratio of Cu+/Cu0, along with larger pore size and pore volume. Moreover, the synergistic effect between Cu0 and γ-Al2O3 improved the selectivity of dimethyl ether. 相似文献
897.
An off‐line dynamic optimization procedure is employed to optimize the transition between different grades of linear low density polyethylene in a fluidized bed reactor. This type of reactor is frequently operated under condensed mode, which consists of injecting induced condensing agents (ICA) to absorb part of the reaction heat. However, the presence of ICA affects the solubility of monomers in the polymer, so it is important to account for this effect in a grade transition optimization strategy. A kinetic model is combined with a thermodynamic model based on the Sanchez–Lacombe equation of state to describe the grade transitions. Simplified correlations are then suggested to predict the impact of ICA on ethylene and comonomer solubility in a quaternary system. The results highlight the importance of the thermodynamic model during grade transition. 相似文献
898.
The ring‐opening polymerization of propylene oxide catalyzed by double metal complex (DMC) is carried out in continuous micro‐reactor (C‐MR). It is found that the monomer conversion at the C‐MR outlet is usually 100% within 2 min of average residence time, which means that the polymerization rate in the C‐MR is faster than that in a traditional semi‐continuous tank reactor. However, the induction period still exists in the polymerization in C‐MR, but can be shortened by increasing the reaction temperature or the micro‐reactor length. The mechanism of monomer coordination and ring opening on DMC during the induction period is confirmed by the 1H NMR analysis of the samples obtained under very short average residence time. The molecular weight distribution (MWD) of product from C‐MR is generally narrow, which indicates that the process still maintain the characteristics of the “living” polymerization. That is, there is a very high rate ratio of chain transfer to chain propagation provided by the DMC catalyst. However, with the same average residence time, the MWD of product from the longer C‐MR is broader, which can be attributed to the increase of the chain propagation rate caused by rise of pressure. 相似文献
899.
A nonisothermal two-dimensional lumped kinetic model of reactive liquid chromatography is formulated and applied to simulate the separation of multicomponent mixtures in a fixed-bed cylindrical column operating under nonisothermal condition. The axial and radial variations of concentration and temperature as well as reversibility of the chemical reactions are incorporated in the model equations. The model comprises a system of convection-diffusion-reaction partial differential equations coupled with algebraic and differential equations. Due to the nonlinearity of adsorption and reaction kinetics, it is required to apply an accurate numerical scheme for solving the model equations. In this study, an efficient and accurate high-resolution flux-limiting finite-volume scheme is proposed to solve the model equations. A number of stoichiometrical reactions are numerically simulated to determine the level of coupling between the temperature and concentration profiles. Moreover, the effects of various critical parameters on the process performance are examined. The results obtained are beneficial for understanding reaction and separation processes inside a liquid chromatographic reactor and to improve its performance. 相似文献
900.
The pulp and paper industry is in continuous need for energy-efficient production processes. In the refining process of mechanical pulp, fibrillation is one of the essential unit operations that count for up to 80% of the total energy use. This initial study explores the potential and development of new type of scalable ultrasound reactor for energy efficient mechanical pulping. The developed reactor is of continuous flow type and based on both hydrodynamic and acoustic cavitation in order to modify the mechanical properties of cellulose fibers. A comparison of the prototype tube reactor is made with a batch reactor type where the ultrasonic horn is inserted in the fluid. The pulp samples were sonicated by high-intensity ultrasound, using tuned sonotrodes enhancing the sound pressure and cavitation intensity by a controlled resonance in the contained fluid. The resonant frequency of the batch reactor is 20.8 kHz and for the tube reactor it is 22.8 kHz. The power conversion efficiency for the beaker setup is 25% and 36% in case of the tube reactor in stationary mode. The objective is to verify the benefit of resonance enhanced cavitation intensity when avoiding the effect of Bjerkenes forces. The setup used enables to keep the fibers in the pressure antinodes of the contained fluid. In case of the continuous flow reactor the effect of hydrodynamic cavitation is also induced. The intensity of the ultrasound in both reactors was found to be high enough to produce cavitation in the fluid suspension to enhance the fiber wall treatment. Results show that the mechanical properties of the fibers were changed by the sonification in all tests. The continuous flow type was approximately 50% more efficient than the beaker. The effect of keeping fibers in the antinode of the resonant mode shape of the irradiation frequency was also significant. The effect on fiber properties for the tested mass fraction was determined by a low-intensity ultrasound pulse-echo based measurement method, and by a standard pulp analyzer. 相似文献