共查询到20条相似文献,搜索用时 156 毫秒
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流化床煤气化炉内脱硫的研究 Ⅱ.脱硫剂焙烧反应动力学与脱硫反应动力学初步研究 总被引:1,自引:0,他引:1
钙质脱硫剂的焙烧反应是炉内脱硫的关键过程,本文研究了影响石灰石和白云石焙烧速率的因素。操作温度750℃以上时,焙烧速率很快。CO_2分压显著地影响焙烧过程,P_(CO)2高于平衡分压时,石灰几乎不分解。在本实验的粒度范围内,脱硫剂粒度对焙烧速率影响不大。采用未反应核收缩模型模拟焙烧过程的结果和实验结果基本一致。脱硫反应速率对气相H_2S浓度呈一级反应,操作温度特别在600~700℃的低温时显著地影响反应速率。 相似文献
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杂环化合物广泛存在于天然产物和药物分子中,许多杂环化合物还具有潜在生物活性和药理作用。因此,如何快速高效地构建小分子杂环化合物库成为当今有机合成和药物化学领域的研究热点。Ugi反应在多样性导向合成方面具有得天独厚的优势,能够解决待合成化合物数量庞大、结构复杂的难题;同时,Diels-Alder [4+2]环加成反应能够高效构建碳-碳键,以较高的立体选择性和区域选择性合成六元环系。目前,集二者于一身的Ugi/Diels-Alder串联反应在构建杂环化合物方面展现出了巨大优势和无穷潜能。本文以不同类型的DA反应分类:按照呋喃作为双烯体、吡咯作为双烯体、噻吩为双烯体、口恶唑作为双烯体、 1,2,4-三嗪作为双烯体、苯作为双烯体、不饱和键和芳环共同作为双烯体等对UDA串联反应的研究进行了综述。 相似文献
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介绍Friedel和Crafts在进行Gustavson反应的实验过程中如何发现了Zincke反应的本质,从而创立了以无水三氯化铝等金属卤化物为催化剂的烷基化和酰基化反应。 相似文献
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低浓度三分子双曲型反应-扩散方程的非线性理论 总被引:2,自引:0,他引:2
建立了低浓度三分子模型双曲型反应-扩散的波动方程,研究了定态的稳定性,重点研究了Turing不稳定问题,指出双曲型方程的Turing不稳定不受扩散系数不相等(Dx≠Dy)这一条件的约束,进而对方程作近似的分支分析,讨论了出现极限环的条件,最后对极限环和定态不稳定作了数值研究. 相似文献
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A constructive application of Frisch method for deriving permeation time lags for different transport equations is shown. Two main classes, i.e. parabolic and hyperbolic diffusional mass transport equations, are presented and compared. An influence of drift and chemical reaction terms on the time lag is discussed. 相似文献
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Davis MJ 《The journal of physical chemistry. A》2006,110(16):5235-5256
The approach to equilibrium for systems of reaction-diffusion equations on bounded domains is studied geometrically. It is shown that equilibrium is approached via low-dimensional manifolds in the infinite-dimensional function space for these dissipative, parabolic systems. The fundamental aspects of this process are mapped out in some detail for single species cases and for two-species cases where there is an exact solution. It is shown how the manifolds reduce the dimensionality of the system from infinite dimensions to only a few dimensions. 相似文献
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An effective medium theory is employed to derive a simple qualitative model of a pattern forming chemical reaction in a microemulsion. This spatially heterogeneous system is composed of water nanodroplets randomly distributed in oil. While some steps of the reaction are performed only inside the droplets, the transport through the extended medium occurs by diffusion of intermediate chemical reactants as well as by collisions of the droplets. We start to model the system with heterogeneous reaction-diffusion equations and then derive an equivalent effective spatially homogeneous reaction-diffusion model by using earlier results on homogenization in heterogeneous reaction-diffusion systems [S.Alonso, M.Ba?r, and R.Kapral, J. Chem. Phys. 134, 214102 (2009)]. We study the linear stability of the spatially homogeneous state in the resulting effective model and obtain a phase diagram of pattern formation, that is qualitatively similar to earlier experimental results for the Belousov-Zhabotinsky reaction in an aerosol OT (AOT)-water-in-oil microemulsion [V.K.Vanag and I.R.Epstein, Phys. Rev. Lett. 87, 228301 (2001)]. Moreover, we reproduce many patterns that have been observed in experiments with the Belousov-Zhabotinsky reaction in an AOT oil-in-water microemulsion by direct numerical simulations. 相似文献
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Desiderio A. Vasquez 《Journal of computational chemistry》1992,13(5):570-578
The Tyson-Fife reaction-diffusion equations are solved numerically using a locally implicit approach. Since the variables evolve at very different time scales, the resulting system of equations is stiff. The reaction term is responsible for the stiffness and the time step is increased by using an implicit method. The diffusion operator is evaluated explicitly and the system of implicit nonlinear equations is decoupled. The method is particularly useful for parameter values in which the equations are very stiff, such as the values obtained directly from the experimental reaction rate constants. Previous efforts modified the parameters on the equations to avoid stiffness. The equations then become a simplified model of excitable media and, for those cases, the locally implicit method gives a faster although less accurate solution. Nevertheless, since the modified equations no longer represent a particular chemical system an accurate solution is not as important. The algorithm is applied to observe the transition from simple motion to compound motion of a spiral tip. 相似文献
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Ackerman DM Wang J Wendel JH Liu DJ Pruski M Evans JW 《The Journal of chemical physics》2011,134(11):114107
We analyze the spatiotemporal behavior of species concentrations in a diffusion-mediated conversion reaction which occurs at catalytic sites within linear pores of nanometer diameter. Diffusion within the pores is subject to a strict single-file (no passing) constraint. Both transient and steady-state behavior is precisely characterized by kinetic Monte Carlo simulations of a spatially discrete lattice-gas model for this reaction-diffusion process considering various distributions of catalytic sites. Exact hierarchical master equations can also be developed for this model. Their analysis, after application of mean-field type truncation approximations, produces discrete reaction-diffusion type equations (mf-RDE). For slowly varying concentrations, we further develop coarse-grained continuum hydrodynamic reaction-diffusion equations (h-RDE) incorporating a precise treatment of single-file diffusion in this multispecies system. The h-RDE successfully describe nontrivial aspects of transient behavior, in contrast to the mf-RDE, and also correctly capture unreactive steady-state behavior in the pore interior. However, steady-state reactivity, which is localized near the pore ends when those regions are catalytic, is controlled by fluctuations not incorporated into the hydrodynamic treatment. The mf-RDE partly capture these fluctuation effects, but cannot describe scaling behavior of the reactivity. 相似文献
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Mahara H Suematsu NJ Yamaguchi T Ohgane K Nishiura Y Shimomura M 《The Journal of chemical physics》2004,121(18):8968-8972
Even though the field of nonequilibrium thermodynamics has been popular and its importance has been suggested by Demirel and Sandler [J. Phys. Chem. B 108, 31 (2004)], there are only a few investigations of reaction-diffusion systems from the aspect of thermodynamics. A possible reason is that model equations are complicated and difficult to analyze because the corresponding chemical reactions need to be reversible for thermodynamical calculations. Here, we introduce a simple model for calculation of entropy production rate: a three-variable reversible Gray-Scott model. The rate of entropy production in self-replicating pattern formation is calculated, and the results are compared with those reported based on the Brusselator model in the context of biological cell division. 相似文献