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51.
Large-scale strongly nonlinear and nonconvex mixed-integer nonlinear programming (MINLP) models frequently appear in optimization-based process synthesis, integration, intensification, and process control. However, they are usually difficult to solve by existing algorithms within acceptable time. In this study, we propose two robust homotopy continuation enhanced branch and bound (HCBB) algorithms (denoted as HCBB-FP and HCBB-RB) where the homotopy continuation method is employed to gradually approach the optimum of the NLP subproblem at a node from the solution at its parent node. A variable step length is adapted to effectively balance feasibility and computational efficiency. The computational results from solving four existing process synthesis problems demonstrate that the proposed HCBB algorithms can find the same optimal solution from different initial points, while the existing MINLP algorithms fail or find much worse solutions. In addition, HCBB-RB is superior to HCBB-FP due to much lower computational effort required for the same locally optimal solution. 相似文献
52.
Biyun Fang Chuanfeng Zhang Zeliang Qi Chunyan Li Jun Ni Xiuyun Wang Jianxin Lin Chak-Tong Au Bingyu Lin Lilong Jiang 《American Institute of Chemical Engineers》2022,68(11):e17849
The design of an efficient non-noble metal catalyst is of burgeoning interest for ammonia synthesis. Herein, we report a Mo2C/CeO2 catalyst that is superior in ammonia synthesis activity. In this catalyst, molybdenum carbide coexisted with the ceria overlayers which is from the ceria support as the strong metal–support interaction. There is a high proportion of low-valent Mo species, as well as high concentration of Ce3+ and surface oxygen species. The presence of Mo2C and CeO2 overlayers not only leads to enhancement of hydrogen and nitrogen adsorption, but also facilitates the desorption and exchange of adsorbed species with the gaseous reagents. Compared with the Mo/CeO2 catalyst prepared without carbonization, the Mo2C/CeO2 catalyst is more than sevenfold higher in ammonia synthesis rate. This work not only presents an explicit example of designing Mo-based catalyst that is highly efficient for ammonia synthesis by tuning the adsorption and desorption properties of the reactant gases, but opens a perspective for other elements in ammonia synthesis. 相似文献
53.
Polyoxymethylene dimethyl ethers are recognized as the prospective diesel additive to decrease the pollutant emission from the light-duty vehicles, which can be polymerize form the monomer of dimethoxymethane (DMM). The industrial synthesis of DMM is mainly involved two-step process: methanol is oxidized to form the formaldehyde in fixed bed reactor and then reacted with the generated formaldehyde through acetalization in continuous stirred-tank reactor. Due to huge energy consumption, this typical synthesis route of DMM needs to be upgraded and more green routes should be determined. In this review, four state-of-the-art one-step direct synthetic routes, including two upgrading routes (methanol direct oxidation and direct dehydrogenation) and two green routes (methanol diethyl ether direct oxidation and carbon oxides direct hydrogenation), have been summarized and compared. Combination with the reaction mechanism and catalytic performance on the different catalysts, the challenges and opportunities for every synthetic route are proposed. The relationships between catalyst structure and property in different synthesis strategy are also investigated and then the suggestions of the design of catalyst are given about future research directions that efforts should be made in. Hopefully, this review can bridge the gap between newly developed catalysts and synthesis technology to realize their commercial applications in the near future. 相似文献
54.
《International Journal of Hydrogen Energy》2021,46(63):32069-32080
In this work, Ni foam supported hierarchical NiCo2O4 nanomaterials are successfully prepared through a hydrothermal process and subsequent calcination process, then the hierarchical NiCo2O4 is converted to hierarchical NiCo2S4 through a hydrothermal anion exchange process. The hierarchical nanomaterials are constructed by a nanorod core and nanoribbons shell. The morphology evolution mechanism of the hierarchical NiCo2O4 is studied by exploratory experiments, the results show that the morphology evolution from nanorod to hierarchical nanostructure undergo a solid–solid process, and the calcination temperature is crucial for the formation of the hierarchical nanostructure. The hierarchical NiCo2O4 and NiCo2S4 nanomaterials are both used as electrocatalysts for methanol oxidation reaction in alkaline electrolyte, and the electrocatalytic activity of the NiCo2S4 is higher than that of the NiCo2O4. Cycling test shows the good stability of the NiCo2S4, and the slight loss of activity during cycling is caused by the surface oxidation of NiCo2S4 in alkaline electrolyte. This work indicate that the hierarchical NiCo2S4 is a promising non-noble metal electrocatalyst for direct methanol fuel cells. 相似文献
55.
Seyed Mohammad Mostashari Rahebeh Amiri Dehkharghani Faramarz Afshar-Taromi Majid Farsadrooh 《International Journal of Hydrogen Energy》2021,46(14):9406-9416
Direct Ethanol Fuel Cells (DEFCs) have fascinated remarkable attention on account of their high current density and being environmentally friendly. Developing efficient and durable catalysts with a simple and fast method is a great challenge in the practical applications of DEFCs. To this end, the bimetallic Pd–Ag with adjustable Pd:Ag ratios were synthesized via a simple and one-pot strategy on activated carbon as a support in this study. The Pd–Ag/C catalysts with different molar ratios were synthesized by simultaneous reduction of Pd and Ag ions in the presence of the ethanolic sodium hydroxide as a green reducing agent for the first time. Several different methods, including FE-SEM, HR-TEM, XRD, XPS EDX, ICP-OES, and BET were used to confirm the structure and morphology of the catalysts. The performance of catalysts was also examined in ethanol oxidation. Obtained results of electrochemical experiments revealed that the Pd3–Ag1/C catalyst had superior catalytic activity (2911.98 mAmg?1Pd), durability, and long-stability compared to the other catalysts. The excellent catalytic characteristic can be attributed to the synergistic effect between Pd and Ag. We presume that our simple method have the chance to be utilized as a proper method for the synthesis of fuel cell catalysts. 相似文献
56.
Dinabandhu Patra Ramakrishnan Ganesan Balaji Gopalan 《International Journal of Hydrogen Energy》2021,46(50):25486-25499
We report the catalytic enhancement of hydrogen generation by 1) in situ Fe (0) formed and 2) nitroarenes substrates during Fe3O4@Pd core-shell nanoparticles catalyzed tandem reaction. The active hydrogen species are generated in Pd shell, which either combine to form H2 gas or take part in relatively faster nitroarene reduction reaction. The rate of hydrogen generation from ammonia borane is dependent on the nitroarene substrate and is higher when 4-nitrophenol is used. This is due to the difference in ammonia borane adsorption on the surface of the catalyst. During recyclability, the H2 generation rate of 2 wt% Pd loaded samples is higher than other compositions. Such an enhancement has been attributed to the formation of Fe (0) via γ-FeOOH mediated by Pd species, presumably through Pd(OH)2. The electronic connection between Fe and Pd interface is thus shown to play an important role in the catalytic enhancement of the tandem reaction. 相似文献
57.
Ehsan Akbari Seyed Mehdi Alavi Mehran Rezaei Afsanehsadat Larimi 《International Journal of Hydrogen Energy》2021,46(7):5181-5196
In this study, a series of BaO-MnOx mixed oxide catalysts were synthesized by the mechanochemical method and employed in lean methane catalytic combustion (MCC) at low temperatures. The synthesized catalysts were characterized by XRD, BET, TGA, FT-IR, H2-TPR, O2-TPD, and FESEM analyses. The results indicated that the 10 wt% BaO-MnOx catalyst with a BET surface area of 25 m2 g?1 possessed the best catalytic performance. The higher activity of the 10 wt% BaO-MnOx catalyst was due to the higher ability to supply oxygen through the components during the MCC process. The light-off temperature corresponding to 50% of the methane conversion was about 330 °C, which was about 50 °C lower than the pure MnOx. Moreover, for the BaO(10)-MnOx catalyst, the 10 and 90% of methane conversion temperatures were about 305 and 427 °C, respectively. Also, the 10 wt% BaO-MnOx catalyst exhibited high catalytic stability under dry feed condition at 450 °C for 50 h. Furthermore, the influence of various parameters such as calcination temperature, feed ratio, GHSV, pretreatment condition, and presence of water vapor in the feedstock was studied on the catalytic performance. 相似文献
58.
《International Journal of Hydrogen Energy》2021,46(79):39011-39022
The main object of this research is the development of a mathematical framework to simulate a commercial ammonia plant and obtaining the optimal operating conditions of process at steady state condition. The considered ammonia plant consists of steam and autothermal reforming reactors, low and high temperature shift converters, hydrogen purification section, methanation, and ammonia synthesis reactors. The catalytic reactors are heterogeneously modeled based on the mass and energy balance equations considering heat and mass transfer resistances in the gas and catalyst phases. In addition, an equilibrium model is applied to simulate the absorption column. Then, the accuracy of developed framework is investigated against plant data. The results show that the internal mass transfer resistance in the commercial catalyst limits the syngas production in the reforming section. In the second step, an optimization problem is formulated to enhance the ammonia production considering safety and operating limitations. The formulated optimization problem is handled employing the genetic algorithm. The results show that more syngas production in the optimized hydrogen unit is one of the main reasons for higher ammonia synthesis in the considered plant. Applying optimal conditions on the process increases ammonia production potential from 1890 to 2179 mol s−1. 相似文献
59.
Sylvain Grosjean Mirella Wawryszyn Hatice Mutlu Stefan Brse Joerg Lahann Patrick Theato 《Advanced materials (Deerfield Beach, Fla.)》2019,31(26)
Bioinspiration has emerged as an important design principle in the rapidly growing field of materials science and especially its subarea, soft matter science. For example, biological cells form hierarchically organized tissues that not only are optimized and designed for durability, but also have to adapt to their external environment, undergo self‐repair, and perform many highly complex functions. Being able to create artificial soft materials that mimic those highly complex functions will enable future materials applications. Herein, soft matter technologies that are used to realize bioinspired material structures are described, and potential pathways to integrate these into a comprehensive soft matter research environment are addressed. Solutions become available because soft matter technologies are benefitting from the synergies between organic synthesis, polymer chemistry, and materials science. 相似文献
60.