Morphological Evolution During Synthesis of New AlPO4 Center dot H2O Crystal

A new crystal of aluminophosphate, AIPO(4)(.)H(2)O, is synthesized from two-batch aqueous solution under hydrothermal conditions. Three types of the crystal habits, i.e. the tetragonal double pyramid, the tetragonal prism and the plate-type tetragonal prism, are found from batch-A solution. Two types of the crystal habits, i.e. the hexagonal pyramid and the strip-type tetragonal prism, are found from batch-B solution. The change of crystal morphology is originated from the fluctuation of the synthesis conditions, such as the supersaturation, the temperature and the impurity content. It causes change of the step energies, the defect density and the step roughness, and further, change of the growth rates. Since the crystal morphology is sensitive to the mass transport mechanism, the crystal habits could be changed under the microgravity.

Transformação de metanol em olefinas leves catalisada por zeólitas HZSM-5

A reação de transformação de MeOH em olefinas leves foi investigada sobre zeólitas HZSM-5 com razões SiO2/Al2O3 (SAR) iguais a 30, 80 e 280. As propriedades ácidas e texturais da amostra com SAR 30 foram modificadas por impregnação com ácido fosfórico. A caracterização físico-química das amostras foi realizada empregando-se as técnicas de FRX, fisissorção de N2, DRX, DTP de NH3 e IV com adsorção de piridina. O desempenho catalítico das mesmas foi comparado tanto em condições reacionais similares (mesma T, pressão parcial de MeOH e WHSV) como em condições de isoconversão. Verificou-se, que quanto maior a SAR da zeólita, menor a densidade total e a força dos sítios ácidos presentes, sendo este efeito mais significativo para os sítios de Brönsted. O efeito do aumento da SAR favoreceu a estabilidade catalítica e a formação de olefinas leves, principalmente propeno. No caso das amostras contendo fósforo, foi observada uma redução linear na área específica BET e no volume de microporos com o aumento do teor de fósforo. Estes resultados, aliados aos obtidos por DRX, sugerem que a redução mais significativa na área específica e no volume de microporos pode ser associada à redução na cristalinidade e à formação de espécies amorfas contendo fósforo, que bloqueariam a estrutura porosa da zeólita. Não se observou alteração significativa na força dos sítios fracos, enquanto a força dos sítios fortes diminuiu significativamente. As amostras apresentando menor SAR e menor teor de fósforo foram mais ativas. Por outro lado, em condições de isoconversão de 916%, a amostra mais seletiva à formação de olefinas foi aquela com maior SAR. Dentre as amostras impregnadas, aquela contendo 4% de fósforo foi a mais seletiva a propeno, enquanto a que continha 6% foi mais seletiva a eteno. A amostra com SAR igual a 280 foi investigada variando-se a temperatura de reação (400, 500 e 540C) e a pressão parcial de metanol (0,038; 0,083 e 0,123 atm), através de um planejamento experimental do tipo Box-Benhnken (32). O rendimento otimizado em olefinas leves foi alcançado a 480C e 0,08 atm. O modelo proposto descreveu bem os dados experimentais e evidenciou a existência de uma faixa ótima de temperatura para maximização do rendimento em propeno e eteno, o qual foi também afetado pela pressão parcial de MeOH na faixa estudada. Palavras-chave: ZSM-5, olefinas, propeno, eteno, processo MTO, fósforo.

Novel Bi-doped glasses for broadband optical amplification

Broadband infrared luminescence is observed in various Bi-doped oxide glasses prepared by conventional melting-quenching technique. The absorption spectrum of the Bi-doped germanium oxide glass consists of five broad peaks at below 370, 500, 700, 800 and 1000 nm. The fluorescence spectrum exhibits a broad peak at about 1300 nm with full width at half maximum (FWHM) of more than 300 nm when excited by an 808 nm laser diode. The fluorescence lifetime at room temperature decreases with increasing Bi2O3 concentration. Influence of the glass composition and melting atmosphere on the fluorescence lifetime and luminescent intensity is investigated. The mechanism of the broadband infrared luminescence is suggested. The product of stimulated emission cross-section and lifetime of the Bi-doped aluminophosphate glass is about 5.0 X 10(-24) cm(2) s. The glasses might be promising for applications in broadband optical fiber amplifiers and tunable lasers. (c) 2007 Elsevier B.V. All rights reserved.

Effects of subretinal implant materials on the viability, apoptosis and barrier function of cultured RPE cells

Background: Subretinal microphotodiode array (MPDA) is a type of visual prosthesis used for the implantation in the subretinal space of patients with progressive photoreceptor cell loss. The present study aimed to evaluate the effect of materials for MPDA on the viability, apoptosis and barrier function of cultured pig retinal pigment epithelium (RPE) cells.Methods: Primary culture of pig RPE cells was performed and 24 pig eyes were used to start RPE culture. The third passage of the cultures was plated on different materials for MPDA and MPDAs. The tetrazolium dye-reduction assay (MTT) was used to determine RPE cell viability. Flow cytometry was measured to indicate the apoptosis rates of RPE cells on different materials. RPE cells were also cultured on microporous filters, and the transepithelial resistance and permeability of the experimental molecule were measured to determine the barrier function.Results: The data from all the methods indicated no significant difference between the materials groups and the control group, and the materials tested showed good biocompatibility.Conclusions: The materials for MPDA used in the present study had no direct toxicity to the RPE cells and did not release harmful soluble factors that affected the barrier function of RPE in vitro.

Effect of Ru addition to CO/SiO2/HZSM-5 catalysts on Fischer-Tropsch synthesis of gasoline-range hydrocarbons

Microporous HZSM-5 zeolite and mesoporous SiO2 supported Ru-Co catalysts of various Ru adding amounts were prepared and evaluated for Fischer-Tropsch synthesis (FTS) of gasoline-range hydrocarbons (C-5-C-12). The tailor-made Ru-Co/SiO2/HZSM-5 catalysts possessed both micro- and mesopores, which accelerated hydrocracking/hydroisomerization of long-chain products and provided quick mass transfer channels respectively during FTS. In the same time. Ru increased Cor reduction degree by hydrogen spillover, thus CO conversion of 62.8% and gasoline-range hydrocarbon selectivity of 47%, including more than 14% isoparaffins, were achieved simultaneously when Ru content was optimized at 1 wt% in Ru-Co/SiO2/HZSM-5 catalyst.

Heterogeneous catalysts for biodiesel production

The production of biodiesel is greatly increasing due to its enviromental benefits. However, production costs are still rather high, compared to petroleum-based diesel fuel. The introduction of a solid heterogeneous catalyst in biodiesel production could reduce its price, becoming competitive with diesel also from a financial point of view. Therefore, great research efforts have been underway recently to find the right catalysts. This paper will be concerned with reviewing acid and basic heterogeneous catalyst performances for biodiesel production, examining both scientific and patent literature.

疏水微孔膜的制备及应用

疏水微孔膜主要应用于膜蒸馏、渗透蒸馏以及膜接触器等膜分离过程中。近年来随着这些膜过程应用研究的蓬勃开展，高性能疏水微孔膜的研制逐渐引起人们的广泛关注。在已经开发的疏水性膜材料中，聚四氟乙烯、聚丙烯微孔膜虽然表现出高强度、高疏水性、高抗化学腐蚀性等优异的综合性能，但其复杂的加工工艺，使其难以大规模的推广普及。聚偏氟乙烯是迄今为止唯一可以采用Loeb-Souirajann相转换法这种相对简单的工艺制膜的疏水性材料，但其较差的机械性能有可能成为其工业化应用的瓶颈。因此进一步开发新型高性能的疏水性膜材料，对于拓宽膜材料的来源，加快膜蒸馏等新型膜过程的工业化步伐具有重要的意义。本论文以F26和F24为对象，系统研究了Loeb-Sourirajann相转换制膜过程中各种操作条件对F26和F24微孔膜结构的影响，首次制备出能够应用于膜蒸馏、渗透蒸馏等新型膜过程的F26、F24疏水微孔膜。其次，通过优化各种制膜条件，所制F26、F24微孔膜的渗透性能优于相同条件下的PVDF微孔膜。与国外商品膜的比较表明：自制微孔膜的孔隙率较高，膜蒸馏组件常数与商品膜可比。第三，使用自制的F26微孔膜处理2wt.％的板蓝根溶液，当将其浓度浓缩到20wt．％时，没有检测到有效成分的损失，显示了微孔膜良好的应用前景。第四，自制F26、F24微孔膜的疏水性强于采用相同方法制备的PVDF微孔膜。机械性能的比较也表明F26、F24微孔膜优于相同条件下的PVDF膜。特别是F24微孔膜在拉伸应变和断裂伸长率方面高于PVDF微孔膜8倍之多。第五，使用乙二醇作为添加剂制备F26微孔膜的过程中，在F26微孔膜的上表面首次发现排列规则的大孔现象。利用二甘醇、草酸等作为添加剂时，也发现了同样的现象。这对于丰富微孔膜结构信息，完整地描述多孔皮层的形成机理提供了新的证据。