Ni/Al2O3催化甲烷裂解

分别通过浸渍法和共沉淀法制备了不同Ni负载量的Ni/Al2O3催化剂。考察了Ni负载量、制备方法以及反应温度对Ni/Al2O3催化甲烷裂解性能的影响。结果表明,在550℃,浸渍法制备的Ni/Al2O3催化剂,当Ni负载量为20%(质量分数)、Ni金属平均粒径为11.25 nm时,具有最佳的甲烷催化裂解效果,其每摩尔Ni的氢气产量和每克Ni碳产量分别为164 mol和15.30 g。催化剂制备方法对Ni/Al2O3甲烷催化裂解反应有显著影响,相同Ni负载量共沉淀法制备的Ni/Al2O3甲烷催化裂解总体效果要好于浸渍法制备的Ni/Al2O3,而且反应过程中生成的碳纤维较长,管径也较均一。550℃时,共沉淀法制备的Ni负载量为41.2%(质量分数)的Ni/Al2O3催化剂在反应至350 min时,仍保持着30%以上的转化率。     

COMPLEX SALTS [Pd(NH3)4][Pd(NH3)3NO2] [CrOx3]·H2O AND [Pd(NH3)4][Pd(NH3)3NO2] [CoOx3]·H2O AND SOLID SOLUTIONS [Pd(NH3)4] [Pd(NH3)3NO2][CoOx3]x[RhOx3]1–x·H2O : PROMISING PRECURSORS FOR POROUS NANOALLOYS

Journal of Structural Chemistry - New complex salts [Pd(NH3)4][Pd(NH3)3NO2][CrOx3]·H2O I, [Pd(NH3)4][Pd(NH3)3NO2][CoOx3]·H2O II, and a series of solid solutions...     

燃烧法合成铝酸盐发光粉的研究

利用金属硝酸盐和尿素发生的氧化还原反应，制备了发绿光的铝酸盐发光粉Ｃｅ０．６７Ｔｂ０．３３ＭｇＡｌ１２Ｏ２０．５．反应在６００℃下完成．对产物的性质进行了表征和研究．考察了尿素用量，炉温及其它制备条件对发光粉的性质，特别是亮度的影响     

On the asymptotic behaviour of solution for the generalized double dispersion equation

In this article, we investigate the Cauchy problem for the generalized double dispersion equation in n-dimensional space. We establish the decay estimates of solution to the corresponding linear equation. Under smallness condition on the initial data, we prove the global existence and asymptotic behaviour of the small amplitude solution in the time-weighted Sobolev space by the contraction mapping principle.     

The relationship between properties of fluorinated graphite intercalates and matrix composition

Inclusion compounds (intercalates) of fluorinated graphite matrix with methylene dichloride (C₂F _x Br _z ·yCH₂Cl₂, x = 0.49, 0.69, 0.87, 0.92, z ≈ 0.01) were synthesized by guest substitution from acetonitrile to methylene dichloride. The kinetics of the thermal decomposition (the first stage of filling → the second stage of filling) was studied under isothermal conditions at 291–303 K. The relationship between the structure of host matrices with thermal properties and kinetic parameters of inclusion compounds is discussed.     

Density functional study of hypophosphite adsorption on Ni (1 1 1) and Cu (1 1 1) surfaces

Surface structures and electronic properties of hypophosphite, H₂PO₂⁻, molecularly adsorbed on Ni(1 1 1) and Cu(1 1 1) surfaces are investigated in this work by density functional theory at B3LYP/6-31++g(d, p) level. We employ a four-metal-atom cluster as the simplified model for the surface and have fully optimized the geometry and orientation of H₂PO₂⁻ on the metal cluster. Six stable orientations have been discovered on both Ni (1 1 1) and Cu (1 1 1) surfaces. The most stable orientation of H₂PO₂⁻ was found to have its two oxygen atoms interact the surface with two PO bonds pointing downward. Results of the Mulliken population analysis showed that the back donation from 3d orbitals of the transition metal substrate to the unfilled 3d orbital of the phosphorus atom in H₂PO₂⁻ and 4s orbital's acceptance of electron donation from one lone pair of the oxygen atom in H₂PO₂⁻ play very important roles in the H₂PO₂⁻ adsorption on the transition metals. The averaged electron configuration of Ni in Ni₄ cluster is 4s^0.634p^0.023d^9.35 and that of Cu in Cu₄ cluster is 4s^1.004p^0.033d^9.97. Because of this subtle difference of electron configuration, the adsorption energy is larger on the Ni surface than on the Cu surface. The amount of charge transfers due to above two donations is larger from H₂PO₂⁻ to the Ni surface than to the Cu surface, leading to a more positively charged P atom in Ni_nH₂PO₂⁻ than in Cu_nH₂PO₂⁻. These results indicate that the phosphorus atom in Ni_nH₂PO₂⁻ complex is easier to be attacked by a nucleophile such as OH⁻ and subsequent oxidation of H₂PO₂⁻ can take place more favorably on Ni substrate than on Cu substrate.     

Fractional Parts of Noninteger Powers of Primes

Mathematical Notes - Let $$\alpha > 0$$ be any fixed noninteger. In the paper, we prove an analogue of the Bombieri–Vinogradov theorem for the set of primes $$p$$ satisfying the...     

Bounded Gaps between Primes of Special Form

Doklady Mathematics - Let 0 < α, σ < 1 be arbitrary fixed constants, let $${{q}_{1}} < {{q}_{2}} < \ldots < {{q}_{n}} < {{q}_{{n + 1}}}$$...     

Thermodynamic calculations of the interaction of scandium halides with aluminum

The fundamental characteristics of the reduction of scandium trifluoride and trichloride with aluminum were studied by thermodynamic modeling over wide temperature and pressure ranges (1100–1400 K and 1–10⁶ Pa for ScF₃ and 800–1200 K and 1–10⁵ Pa for ScCl₃). Calculations of the equilibrium compositions of the systems were performed to draw conclusions about the contents of condensed and gaseous components and determine the temperatures of the complete reduction of trihalides with the formation of a two-phase alloy containing a saturated solution of scandium in aluminum and the Al₃Sc intermetallic compound. The results of modeling were in agreement with the available experimental data.