Investigating the kinetics of liquid-free,OSDA-free ZSM-5 zeolite synthesis from iron ore tailings

In this study, ZSM-5, which is a Mobil-type five-type zeolite with well-defined crystal morphology, is successfully synthesized via a seed-assisted, liquid-free method that uses iron ore tailings as a silica source. The ZSM-5 crystallization kinetics at 423, 433, and 443 K and different synthesis times are investigated to identify the nucleation and crystallization mechanisms of the synthesized ZSM-5 zeolites, and results suggest that the crystallization kinetics follow a Kolmogorov-Johnson-Mehl-Avrami-type behavior. The activation energies for the induction and transition periods are 112.38 and 58.35 kJ mol⁻¹, respectively. Furthermore, the Avrami exponent indicates three-dimensional crystal growth from both sporadic and instantaneous nucleation mechanisms. A comparison of our results with previous reports of the ZSM-5 crystallization mechanism demonstrates that the seed crystals play a significant role in nucleation and crystal growth. Finally, seed surface crystallization and new nuclei crystallization dual mechanism has been proposed to describe the crystallization process of ZSM-5.     

Design and synthesis of the honeycomb PtSnNa/ZSM-5 monolithic catalyst for propane dehydrogenation

A novel PtSnNa/ZSM-5 monolithic catalyst was designed and synthesized for the propane dehydrogenation reaction, which was a significant transformation in industry. Experimental results showed that although the propane conversion and the propylene selectivity gradually fell down along with the reaction time, the descent speed of the PtSnNa/ZSM-5 monolithic catalyst was slower than that of the granule catalyst and the propane conversion and propylene selectivity of the reaction with monolithic catalyst still remained at a high level after 12 hr. The monolithic catalyst had regular pore structure that facilitated the separation of the product from the catalyst and reduced the limitation on internal and external diffusion and mass transfer, and led to the high catalytic activity and stability. The catalyst could be easily fabricated and was of highly industrial application potential.     

Embedding Banach spaces into the space of bounded functions with countable support

We prove that a WLD subspace of the space consisting of all bounded, countably supported functions on a set Γ embeds isomorphically into if and only if it does not contain isometric copies of . Moreover, a subspace of is constructed that has an unconditional basis, does not embed into , and whose every weakly compact subset is separable (in particular, it cannot contain any isomorphic copies of ).     

Properties of G-martingales with finite variation and the application to G-Sobolev spaces

As is known, if $B={\left(B_t\right)}_{t\in [0,T]}$ is a $G$-Brownian motion, a process of form ${\int }_0^t{\eta }_{s}d{〈B〉}_s?{\int }_0^{t}2G\left({\eta }_s\right)ds$, $\eta \in M_G^1(0,T)$, is a non-increasing $G$-martingale. In this paper, we shall show that a non-increasing $G$-martingale cannot be form of ${\int }_0^t{\eta }_{s}ds$ or ${\int }_0^t{\gamma }_{s}d{〈B〉}_s$, $\eta ,\gamma \in M_G^1(0,T)$, which implies that the decomposition for generalized $G$-Itô processes is unique: For arbitrary $\zeta \in H_G^1(0,T)$, $\eta \in M_G^1(0,T)$ and non-increasing $G$-martingales $K,L$, if ${\int }_0^t{\zeta }_{s}d{B}_s+{\int }_0^t{\eta }_{s}ds+K_t=L_t,t\in [0,T],$then we have $\eta \equiv 0$, $\zeta \equiv 0$ and$K_t=L_t$. As an application, we give a characterization to the $G$-Sobolev spaces introduced in Peng and Song (2015).     

Organic-Free Interzeolite Transformation in the Absence of Common Building Units

Zeolite crystals can be used as seeds or aluminosilicate sources in syntheses to control polymorphs and/or reduce the quantity of organics used as structure-directing agents. A frequently invoked hypothesis for interzeolite transformations is that zeolites share some underlying similarity in structure, most notably in cases pertaining to organic-free syntheses. Herein, we show for the first time that ZSM-5 (MFI) can be directly obtained from USY (FAU) through an interzeolite transformation between parent–daughter structures lacking common building units in the absence of a structure-directing agent and seeds. We show that interzeolite transformation leads to a crystalline product with fewer defects. Our findings also reveal that ZSM-5 is a metastable intermediate that undergoes further transformation to mordenite (MOR) and quartz. The MFI-to-MOR transition is counter to reported trends for which transformations lead to structures with reduced molar volume. Herein, we propose mechanistic arguments that suggest the driving force for interzeolite transformation is more complex than guidelines posited in the literature.     

IM-5分子筛在Ni-Cu催化剂甲烷热裂解制氢反应中的作用研究

甲烷热裂解制氢并生成高附加值的纳米碳材料,被认为是极具发展前景的氢气生产途径,但高性能催化剂的研发仍存在诸多挑战.我们选择多种载体(TS-1、 IM-5、 Y、介孔SiO₂、 γ-Al₂O₃、 CNTs),采用浸渍法制备Ni-Cu负载催化剂,通过低温N2吸附-脱附、 XRD、 SEM和H₂-TPR等系列表征方法对样品进行分析,考察不同载体对催化剂甲烷裂解制氢和纳米碳材料的影响.实验结果发现,分子筛载体独特的孔道结构有利于金属颗粒的分散,能有效避免反应中界面效应导致的催化剂失活,可提高催化剂反应活性并延长反应寿命,也显著提高了其碳产率.其中以IM-5分子筛为载体的催化剂表现最佳,在反应温度为700℃时, NiCu/IM-5催化剂甲烷转化率高达80%,氢气选择性达100%,反应400 min后活性未见明显降低. NiCu/IM-5催化剂碳产率高达1 446 g_C/g_cat,是NiCu/SiO₂催化剂的5.7倍, NiCu/γ-Al     

Alcohol-Assisted Synthesis of Sheet-Like ZSM-5 Zeolites with Controllable Aspect Ratios

Sheet-like ZSM-5 has been regarded as a promising material for catalytic applications due to its diffusion superiority. However, it still remains a challenge to obtain a desirable sheet-like morphology because of the complex synthesis process of zeolites. Here, a facile strategy for synthesizing sheet-like ZSM-5 is developed by only adding ethanol as zeolite growth modifier in the synthesis gel. It is thought that ethanol might be preferentially absorbed on the {010} surface of zeolite crystals, interact with the exposed silicon hydroxyl groups on the crystal {010} facet, and suppress the growth of b axis, resulting in the sheet-like shape. Through finely tunning synthesis parameters, sheet-like ZSM-5 crystals with thin b-axis thickness of 90 nm and different aspect ratios could be obtained. Owing to its shorter diffusion path and optimized acidity, sheet-like ZSM-5 exhibits better catalytic performance than conventional ZSM-5 in the alkylation of benzene with ethanol.     

Comparative study of Co3O4-ZSM-5 catalysts synthesized by different hydrothermal methods for the catalytic oxidation of dichloromethane

In this work, various Co₃O₄-ZSM-5 catalysts were prepared by the microwave hydrothermal method (MH-Co₃O₄@ZSM-5), dynamic hydrothermal method (DH-Co₃O₄@ZSM-5), and conventional hydrothermal method (CH-Co₃O₄/ZSM-5). Their catalytic oxidation of dichloromethane (DCM) was analyzed. Detailed characterizations such as X-ray diffractometer (XRD), scanning microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), H₂ temperature-programmed reduction (H₂-TPR), temperature-programmed desorption of O₂ (O₂-TPD), temperature-programmed desorption of NH₃ (NH₃-TPD), diffuse reflectance infrared Fourier-transform spectra with NH₃ molecules (NH₃-DRIFT), and temperature-programmed surface reaction (TPSR) were performed. Results showed that with the assistance of microwave, MH-Co₃O₄@ZSM-5 formed a uniform core-shell structure, while the other two samples did not. MH-Co₃O₄@ZSM-5 possessed rich surface adsorbed oxygen species, higher ratio of Co³⁺/Co²⁺, strong acidity, high reducibility, and oxygen mobility among the three Co₃O₄-ZSM-5 catalysts, which was beneficial for the improvement of DCM oxidation. In the oxidation of dichloromethane, MH-Co₃O₄@ZSM-5 presented the best activity and mineralization, which was consistent with the characterizations results. Meanwhile, according to the TPSR test, HCl or Cl₂ removal from the catalyst surface was also promoted in MH-Co₃O₄@ZSM-5 by their abundant Brønsted acid sites and the promotion of Deacon reaction by Co₃O₄ or the synergistic effect of Co₃O₄ and ZSM-5. According to the results of in situ DRIFT studies, a possible reaction pathway of DCM oxidation was proposed over the MH-Co₃O₄@ZSM-5 catalysts.     

ZSM-5分子筛酸位分布及其甲醇制烯烃催化性能的定向管理与调控

ZSM-5分子筛在甲醇制烯烃(MTO)过程中的催化性能和反应机理与其孔道中酸位点分布位置紧密相关. 本文证明在水热合成过程中加入适量的钠离子(Na⁺)可以增加ZSM-5分子筛交叉腔酸位点比例; 从而促进高级甲基苯的生成并加速芳烃循环, 有利于乙烯生成. 相反, 在合成过程中不添加钠离子, 所制备的ZSM-5分子筛直孔道和正弦孔道酸位点比例明显提高, 有利于促进烯烃循环并提高丙烯和C₃₊烯烃选择性.     

Curcumin Analogue L48H37 Suppresses Human Osteosarcoma U2OS and MG-63 Cells’ Migration and Invasion in Culture by Inhibition of uPA via the JAK/STAT Signaling Pathway

Osteosarcoma, the most prevalent malignant bone tumor in the pediatric age group, is responsible for the great majority of cancer-associated deaths owing to its highly metastatic potential. The anti-metastatic effects of the new curcumin analogue L48H37 in human osteosarcoma are still unknown; hence, we investigated whether L48H37 represses human osteosarcoma cells’ biological behavior of migratory potential and invasive activities and attempted to delve into its underlying mechanisms. L48H37 up to 5 μM inhibited, without cytotoxicity, the motility, migration, and invasion of human osteosarcoma U2OS and MG-63 cells. In U2OS cells, the human protease array revealed an obvious decrease in urokinase plasminogen activator (uPA) expression after L48H37 treatment, and L48H37 actually reduced the level, protein and mRNA expression, and promoter activity of uPA dose-dependently. L48H37 decreased the phosphorylation of STAT3, JAK1, JAK2, and JAK3 in U2OS cells, but did not affect the phosphorylation of ERK, JNK, p38, and Akt. Using colivelin, an activator of STAT3, the L48H37-induced decrease in uPA and migratory potential could be countered as expected. Collectively, L48H37 represses the invasion and migration capabilities of U2OS and MG-63 cells by the suppression of uPA expression and the inhibition of JAK/STAT signaling. These results suggest that L48H37 may be a potential candidate for anti-metastatic treatment of human osteosarcoma.