The role of Ni2+ diffusion on the reducibility of NiO/MgO system: A combined TRP-XPS study

The progressive dissolution of nickel ions in the lattice of MgO matrix, promoted by the calcination temperature, has been monitored using XPS. The reducibility of Ni/MgO catalysts is affected by the modification of the surface chemical composition. TPR peaks have been correlated with several NiO forms. Both XPS and TPR results indicate a different behaviour pattern for the supported and physically mixed NiO/MgO systems, and this has been attributed to the different available contact area between NiO and MgO. The formation of both NiO rich and MgO rich NiO-MgO solid solutions, with the tendency to evolve towards the bulk solid solution, has been invoked to explain the substantial changes in the TPR pattern of the different air calcined systems.     

On the reducibility of a nonlinear periodic system with degenerate equilibrium

In this paper, we prove the reducibility of a class of nonlinear periodic differential equation with degenerate equilibrium point under small perturbations, and obtain a periodic solution near the equilibrium point. The result is new and more general, including that of the paper [X. Lu and J. Xu, On small perturbations of a nonlinear periodic system with degenerate equilibrium, Nonlinear Differ. Equ. Appl. 21 (2014), pp. 361–370 ].     

Controllability discrepancy and irreducibility/reducibility of Floquet factorisations in linear continuous-time periodic systems

The paper reports interesting but unnoticed facts about irreducibility (resp., reducibility) of Flouqet factorisations and their harmonic implication in term of controllability in finite-dimensional linear continuous-time periodic (FDLCP) systems. Reducibility and irreducibility are attributed to matrix logarithm algorithms during computing Floquet factorisations in FDLCP systems, which are a pair of essential features but remain unnoticed in the Floquet theory so far. The study reveals that reducible Floquet factorisations may bring in harmonic waves variance into the Fourier analysis of FDLCP systems that in turn may alter our interpretation of controllability when the Floquet factors are used separately during controllability testing; namely, controllability interpretation discrepancy (or simply, controllability discrepancy) may occur and must be examined whenever reducible Floquet factorisations are involved. On the contrary, when irreducible Floquet factorisations are employed, controllability interpretation discrepancy can be avoided. Examples are included to illustrate such observations.     

Study of W/HZSM-5-Based Catalysts for Dehydro-aromatization of CH4 in Absence of O2. II. Action of Promoters Zn and Li

By correlating the results of the NH₃-TPD characteristic study and the catalyst activity assay of the W/HZSM-5-based catalysts, we confirmed that the intensity and concentration of the surface B-acid sites have pronounced effects on the catalyst performance for dehydro-aromatization of methane (DHAM). It was found experimentally that, by addition of a proper amount of Mg²⁺, the strong B-acid sites at the catalyst surface could be effectively eliminated, whereas the addition of a proper amount of Zn²⁺ or Li⁺ resulted not only in eliminating most of the strong surface B-acid sites but also in generating a kind of new medium-strong acid sites, mostly B-acid sites, simultaneously. The latter could serve as the catalytically active sites for dehydro-aromatization of methane; on such medium-strong surface B-acid sites, the formation of coke would be also alleviated to a greater extent. By simultaneous addition of Mg²⁺ and Zn²⁺, optimized adjustment in surface acidity of the catalyst could be realized. On the other hand, the doping of the Zn²⁺ or Li⁺ component to the tungsten oxide matrix would facilitate inhibiting aggregation of the W-containing active species and improving dispersion of the W component at the surface of the catalyst, thus leading to a pronounced decrease in the reduction temperature for the hard-to-be-reduced W⁶⁺ species and an increase in quantity of the reducible W⁶⁺ species at the reaction temperature for DHAM, as has been evidenced by the results of a H₂-TPR study on the reducibility of the Zn²⁺ (or La³⁺, Li⁺, Mn²⁺)-promoted W/HZSM-5 system. The above two roles that Zn²⁺ and Li⁺ as promoters played both contributed to the persistence of high methane conversion and benzene selectivity, and the alleviation of coke deposition, as well as the prolongation of the catalyst lifetime.     

Influence of platinum on ceria sulfation

The influence of platinum on ceria sulfation has been studied using thermogravimetry and infrared spectroscopy. The same types of sulfate species — surface and bulk-like species — are evidenced with or without Pt. Pt does not modify the thermal stability of both types of sulfate. It favors sulfate formation on low-surface-area CeO₂ samples. The reducibility of sulfate by H₂ is promoted by Pt irrespective of the types of sulfate formed on ceria. H₂S, which is formed by H₂ reduction of sulfate, partly remains on the catalyst. It is adsorbed not only on the oxide but also on Pt. Sulfur poisoning of Pt has been shown by IR study of CO adsorption.     

MgCl2溶液对烧结矿低温还原粉化率的影响

试验测定了 Mg Cl2 溶液不同浓度和喷洒量对济钢现有原料条件下烧结矿低温还原粉化率 (RDI)和还原度 (RI)的影响。结果表明 :每 5 0 0 g烧结矿喷洒 10～ 2 0 m L浓度为 1.0 %～ 3 .5 %的 Mg Cl2 溶液 ,能显著降低烧结矿的 RDI,且还原度不受影响 ,以 5 0 0 g烧结矿喷洒浓度为 2 .5 %的 Mg Cl2 溶液 10 m L综合效果最佳 ,可使烧结矿的 RDI从 3 6%降至 4.4%。     

基于正则FI代数的MT理想及其应用

 本文基于经典代数的角度对正则FI代数进行了再研究.首先,在正则FI代数中通过蕴涵算子提出了MT理想的概念,讨论了正则FI代数中MT理想与同余关系的联系;其次,在正则FI代数中引入素MT理想的概念,并以素MT理想为工具给出了正则FI代数的条件嵌入定理;最后,通过以蕴涵算子表示的隐式余三角模对MT理想的特征进行了描述,并通过特征定理给出了正则FI代数中MT理想的生成方法.     

翼钢高炉原料对烧结矿冶金性能的影响

通过系统的烧结实验,对翼钢进口富矿粉（PB粉）的烧结成矿规律、工艺参数进行了深入系统的研究。结果表明：在目前翼钢原料条件下,配加适量的PB粉（30%-40%）可以明显提高烧结矿的强度、成品率、还原度及低温还原粉化性能。     

Electrospun nanofibrous Ni/LaAlO3 catalysts for syngas production by high temperature methane partial oxidation

Ni/Al₂O₃ catalysts have been widely used for methane reforming while the formation of NiAl₂O₄ with low reducibility reduces catalyst efficiency. La₂O₃ was used to promote the catalytic activity of Ni/Al₂O₃ catalysts through improving Ni dispersion. LaAlO₃ perovskite showed catalytic activity in methane coupling and also used as a catalyst support for methane reforming. This study systematically investigated the effect of La₂O₃ addition into Ni/Al₂O₃ catalysts and found the formation of LaAlO₃ perovskite played an important role, which requires high crystallization temperatures. The thermally-stable structure of nanofibrous catalysts was employed to develop high-performance Ni/LaAlO₃ catalysts. High calcination temperature resulted in the enhanced crystallinity of LaAlO₃ perovskite, improved Ni reducibility and strengthened catalyst/support interaction, which contributed to high catalytic performance during methane partial oxidation. The Ni/LaAlO₃ catalyst calcined at 1100 °C generated a CH₄ conversion of 91.2% during methane partial oxidation with H₂ and CO selectivities of 95.5% and 92.4%, respectively. It is because La₂O₃ addition into Ni/Al₂O₃ promoted Ni reduction via forming LaAlO₃. Therefore, an efficient and thermally-stable fibrous Ni/LaAlO₃ catalyst has been developed for high temperature methane partial oxidation.