MgO–SBA-15 Supported Pd–Pb Catalysts for Oxidative Esterification of Methacrolein with Methanol to Methyl Methacrylate

Novel MgO–SBA-15 supported catalysts were prepared for oxidative esterification of methacrolein (MAL) with methanol to methyl methacrylate (MMA). The MgO–SBA-15 supports were synthesized with different magnesia loadings from different magnesium precursors and hydrochloric acid molar concentrations. The MgO–SBA-15 supports and Pd–Pb 3 Pb particles on magnesia-modified Pd–Pb 3 Pb particle sizes and then resulted in the different number of active sites. Besides magnesia loadings, other factors, such as hydrochloric acid molar concentration and magnesium precursors, had considerable influences on the catalytic activity

Chin. J. Chem. Eng.

Novel MgO-SBA-15 supported catalysts were prepared for oxidative esterification of methacrolein (MAL) with methanol to methyl methacrylate (MMA). The MgO-SBA-15 supports were synthesized with different magnesia loadings from different magnesium precursors and hydrochloric acid molar concentrations. The MgO-SBA-15 supports and Pd-Pb/MgO-SBA-15 catalysts were characterized by several analysis methods. The results revealed that the addition of MgO improved the ordered structure of SBA-15 supports and provided surface alkalinity of SBA-15 supports. The average size of the Pd3Pb particles on magnesia-modified Pd-Pb/MgO-SBA-15 catalysts was smaller than that on the pure silica-based Pd-Pb/SBA-15 catalysts. The experiments on catalyst performance showed that the magnesia-modified Pd-Pb/MgO-SBA-15 catalysts had higher activity than pure silica-based Pd-Pb/SBA-15 catalysts, showing the strong dependence of catalytic activity on the average size of active particles. The difference of activity between Pd-Pb/SBA-15 catalysts and Pd-Pb/MgO-SBA-15 catalysts was due to the discrepant structural properties and surface alkalinity provided by MgO, which led to the different Pd3Pb particle sizes and then resulted in the different number of active sites. Besides magnesia loadings, other factors, such as hydrochloric acid molar concentration and magnesium precursors, had considerable influences on the catalytic activity. (C) 2014 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.Novel MgO-SBA-15 supported catalysts were prepared for oxidative esterification of methacrolein (MAL) with methanol to methyl methacrylate (MMA). The MgO-SBA-15 supports were synthesized with different magnesia loadings from different magnesium precursors and hydrochloric acid molar concentrations. The MgO-SBA-15 supports and Pd-Pb/MgO-SBA-15 catalysts were characterized by several analysis methods. The results revealed that the addition of MgO improved the ordered structure of SBA-15 supports and provided surface alkalinity of SBA-15 supports. The average size of the Pd3Pb particles on magnesia-modified Pd-Pb/MgO-SBA-15 catalysts was smaller than that on the pure silica-based Pd-Pb/SBA-15 catalysts. The experiments on catalyst performance showed that the magnesia-modified Pd-Pb/MgO-SBA-15 catalysts had higher activity than pure silica-based Pd-Pb/SBA-15 catalysts, showing the strong dependence of catalytic activity on the average size of active particles. The difference of activity between Pd-Pb/SBA-15 catalysts and Pd-Pb/MgO-SBA-15 catalysts was due to the discrepant structural properties and surface alkalinity provided by MgO, which led to the different Pd3Pb particle sizes and then resulted in the different number of active sites. Besides magnesia loadings, other factors, such as hydrochloric acid molar concentration and magnesium precursors, had considerable influences on the catalytic activity. (C) 2014 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved

Ethylene hydroformylation in imidazolium-based ionic liquids catalyzed by rhodium-phosphine complexes

In this research, the catalytic activity of a rhodium-based (Rh) catalyst with imidazolium-based ionic liquids (IBILs) as solvents for ethylene hydroformylation was studied. The structures of IBILs had an important influence on the activity and stability of the Rh catalyst. The IBILs with longer cation side chains, which were the strong steric hindrances around the Rh catalyst, were more unfavorable for the catalytic activity. The turnover frequency (TOF) of the Rh catalyst was 10627 h(-1) when [Bmim][BF4] was used as solvent. The activity of the Rh complexes in the ionic liquid is better than they do in toluene. We used electrospray ionization mass spectrometry to characterize the catalyst after the reaction and found that [Bmim](+) acts as a ligand of the Rh catalyst to form a new active catalytic site [Rh(CO)(PPh3)(2)(Bmim)(BF4)](+) through the coordination of the Rh atom with the imidazole-2-C group of [Bmim][BF4], and it was essential for the stabilization of the Rh catalyst and prevented the formation of low-active Rh clusters. In addition, the catalyst recycling test showed that the Rh catalyst could be reused with [Bmim][BF4] as solvent without obvious loss of catalytic activity. (c) 2012 Elsevier B.V. All rights reserved

Deactivation and regeneration of the supported bimetallic Pd-Pb catalyst in direct oxidative esterification of methacrolein with methanol

The deactivation of the supported bimetallic Pd-Pb catalyst in the repeated runs of direct oxidative esterification of methacrolein with methanol in the atmosphere was investigated. The catalysts before and after stability tests were characterized by X-ray diffraction, transmission electron microscopy, X-ray photo-electron spectroscopy, inductively coupled plasma mass spectrometry, Brunauer-Emmett-Teller method and thermogravimetric analysis. The results indicated that the major factor affecting the deactivation of the catalyst was the deposition of organic substances on the surface active sites of the catalyst during batch reaction. Washing the deactivated catalyst with either MeOH or an aqueous hydrazine solution at 80 degrees C could completely recover the initial activity of the catalyst, and calcining the deactivated catalyst in air at 500 degrees C and then reducing in an aqueous hydrazine solution could partly recover its activity. The deactivation and regeneration of the catalyst in the direct oxidative esterification at gas-liquid-solid phase are important and meaningful. (c) 2013 Elsevier B.V. All rights reserved

Effects of Enclosure Succession on the Morphological Characteristics and Nutrient Content of a Bamboo Whip System in a Moso Bamboo (<i>Phyllostachys edulis</i>) Forest on Wuyi Mountain, China

To investigate the morphological characteristics and nutrient content of bamboo whip systems in the Wuyi Mountain Moso bamboo (Phyllostachys edulis) forest in response to enclosure succession. The mixed Moso bamboo forests in the Wuyi Mountain Nature Reserve with 0, 4, 6, 11, 16, and 41 enclosure years were taken as the object of investigation. All the bamboo whips in the 2 m × 2 m sample plots were excavated layer-by-layer according to the soil layers of 0–20 cm, 20–40 cm, and 40–60 cm, and a total of 54 plots were dug. The morphological characteristics and nutrient contents of the Moso bamboo whips in the different soil layers were analyzed and evaluated. Enclosure management measures can not only effectively improve vegetation coverage, biodiversity, and biomass, but also improve soil moisture and nutrient status, indirectly affecting the vegetation, which is of great significance for preventing soil erosion. The results showed that the whip number, whip diameter, flagella number, whip length, and whip weight in the 0–20 cm soil layer were significantly increased by 169.2%, 11.0%, 197.5%, 113.7%, and 109.0% (p p p p p p p p p p < 0.05). In summary, enclosure measures were implemented for Moso bamboo forests in the Wuyi Mountain Nature Reserve, which promote the growth of Moso bamboo whips and optimize the structure of bamboo whips

Reduced smooth muscle-fibroblasts transformation potentially decreases intestinal wound healing and colitis-associated cancer in ageing mice

Abstract Cancer and impaired tissue wound healing with ageing are closely related to the quality of life of the elderly population. Given the increased incidence of cancer and the population ageing trend globally, it is very important to explore how ageing impairs tissue wound healing and spontaneous cancer. In a murine model of DSS-induced acute colitis and AOM/DSS-induced colitis-associated cancer (CAC), we found ageing significantly decreases intestinal wound healing and simultaneous CAC initiation, although ageing does not affect the incidence of AOM-induced, sporadic non-inflammatory CRC. Mechanistically, reduced fibroblasts were observed in the colitis microenvironment of ageing mice. Through conditional lineage tracing, an important source of fibroblasts potentially derived from intestinal smooth muscle cells (ISMCs) was identified orchestrating intestinal wound healing and CAC initiation in young mice. However, the number of transformed fibroblasts from ISMCs significantly decreased in ageing mice, accompanied by decreased intestinal wound healing and decreased CAC initiation. ISMCs-fibroblasts transformation in young mice and reduction of this transformation in ageing mice were also confirmed by ex-vivo intestinal muscular layer culture experiments. We further found that activation of YAP/TAZ in ISMCs is required for the transformation of ISMCs into fibroblasts. Meanwhile, the reduction of YAP/TAZ activation in ISMCs during intestinal wound healing was observed in ageing mice. Conditional knockdown of YAP/TAZ in ISMCs of young mice results in reduced fibroblasts in the colitis microenvironment, decreased intestinal wound healing and decreased CAC initiation, similar to the phenotype of ageing mice. In addition, the data from intestine samples derived from inflammatory bowel disease (IBD) patients show that activation of YAP/TAZ also occurs in ISMCs from these patients. Collectively, our work reveals an important role of the ageing stromal microenvironment in intestinal wound healing and CAC initiation. Furthermore, our work also identified a potential source of fibroblasts involved in colitis and CAC