Process Optimisation of In Situ H2 Generation From Ammonia Using Ni on Alumina Coated Cordierite Monoliths

A catalyst of Ni supported on alumina coated monolith has been prepared, characterized and tested in NH₃ decomposition. The characterization of the catalyst by XPS and TPR showed that there is no formation of aluminates after catalyst use. It is studied the effect of the space velocity, by varying the feed flow rate and the catalyst??s length. Some evidences are shown about the reaction inhibition by produced H₂ and about the reasons for the better performance of the monolith than packed bed catalyst.     

Cordierite Honeycomb Monoliths Coated with Zirconia and Its Modified Forms for Biodiesel Synthesis from Pongamia glabra

This study investigates the use of cordierite honeycomb monoliths coated with solid acids such as zirconia, Mo(VI)/ZrO₂ and Pt‐SO₄^2?/ZrO₂ and solid bases like zirconia–calcia, zirconia–magnesia mixed oxides in the synthesis of biodiesel from oil (PG‐oil). Solid acids were used for the esterification of free fatty acids in PG‐oil with methanol to reduce the percentage of free fatty acids in the oil followed by transesterification of PG‐oil over solid bases to synthesize biodiesel. The oxide catalysts were coated on honeycombs by an impregnation technique and characterized for their surface acidity/basicity, crystallinity and morphology. The effect of the molar ratio of PG‐oil/methanol in esterification and transesterification was studied. Reactivation and reusability of both solid acid and solid base catalysts was investigated. The catalysts were also prepared in their powder forms and their activity was compared with that of honeycomb coated forms. A twofold increase in the yield of biodiesel was obtained when the catalysts were used in honeycomb coated forms. The results revealed that the honeycombs coated with mixed oxides such as zirconia–calcia and zirconia–magnesia were economical, efficient and eco‐friendly (3e concept) for biodiesel production with ~95 % yield.     

不同铁源对制备堇青石蜂窝陶瓷的影响

以SiO2粉、Al2 O3粉、MgO粉为原料,Fe2 O3、FeCl3和Fe2(NO3)3为外加剂,在空气气氛下经1400℃3 h烧成制备堇青石蜂窝陶瓷,研究以不同铁源做外加剂对堇青石蜂窝陶瓷的物相组成、显微结构和孔径分布的影响.采用XRD和SEM对烧成后试样进行物相组成分析和显微结构检测.结果表明:Fe2 O3作为外加剂时,堇青石晶粒呈短柱状且排布方向一致,并且显微结构中有少量的微裂纹,孔径在5μm处出现分布峰值;而FeCl3和Fe2(NO3)3为外加剂时,显微结构中熔融相较多,堇青石颗粒部分呈短柱状,且部分晶粒排布方向不一致.     

Adsorption of Carbon Dioxide on High-Silica Zeolites with Different Framework Topology

Adsorption isotherms of carbon dioxide were measured on six high-silica zeolites TNU-9, IM-5, SSZ-74, ferrierite, ZSM-5 and ZSM-11 comprising three-dimensional 10-ring (8-ring for ferrierite) at 273, 293, 313 and 333 K. Based on the known temperature dependence of CO₂ adsorption, isosteric heats of adsorption were calculated. The obtained adsorption capacities and isosteric adsorption heats related to the amount of CO₂ adsorbed have provided detailed insight into the carbon dioxide interaction with zeolites of different framework topology. The zeolites TNU-9 and ferrierite are characterized by pronounced energetic heterogeneity whereas due to the location of Na⁺ cations in the same positions the isosteric adsorption heats of CO₂ adsorption on IM-5, ZSM-5 and ZSM-11 zeolites are rather constant for molecular ratio CO₂/Na⁺ < 1. As IM-5 zeolite has a maximum adsorption capacity, it appears to have optimum properties for carbon dioxide separation.     

Nano-Scale Cordierite Glass-Ceramic from Natural Raw Materials with Different Fluoride Additions

Silicon - Stable cordierite glass-ceramics were prepared from natural kaolin, silica sand and magnesite as raw materials. Furthermore the effect of fluorine additions was tested by addingAlF3 or...     

合成温度对堇青石—莫来石复相材料中堇青石、莫来石生成量的影响

以MgO-Al2O3-SiO2三元相图为依据,在M2A2S5－A2S3连线上进行了堇青石－莫来石复相材料组成点的设计,并在高温下合成了堇青石与莫来石比例为1：1的复相材料,重点讨论了烧成温度对堇青石－莫来石复相材料中堇青石,莫来石生成量的影响,XRD定量分析结果表明,当合成温度范围约在1380－1420℃之间时,可在复相材料中得到接近理论的相组成。     

添加剂对合成堇青石的影响

本文研究了锆英砂、碳酸钡、硅线石、氟化钙四种添加剂及其含量对合成堇青石晶相组成的影响。结果表明:四种添加剂的加入均提高了堇青石的含量,且加入量都有一最佳值,分别为锆英砂2wt%、碳酸钡3wt%、硅线石2wt%、氟化钙2wt%。     

Fractal Dimension of Different Structural-Type Zeolites and of the Active Sites

Fragments of faujasite, ZSM-11, ZSM-5, mordenite, sodalite, and beta-A zeolites show different fractal dimensions. The fractal dimension averaged for non-buried atoms produces mental pictures of zeolites that change from a slightly to a rather porous material. The 2–12-rings of –SiH₂–OH–AlH₂– units model Brønsted acids. The SURMO2/GEPOL comparison characterizes cavities. The 6-ring model shows maximal fractal dimension and is expected to be the most reactive.     

Monoliths in Heterogeneous Catalysis

The use of structured catalysts in the chemical industry has been considered for years. Conventional fixed-bed reactors have some obvious disadvantages such as maldistributions of various kinds (including a nonuniform access of reactants to the catalytic surface), high pressure drop in the bed, etc. Structured catalysts are promising as far as elimination of these setbacks is concerned. Two basic kinds of structured catalysts can be distinguished:

1. Structural packings covered with catalytically active material, similar in design to those used in distillation and absorption columns and/or static mixers. Good examples of catalysts of this kind are those offered by Sulzer, clearly developed by Sulzer column packings and static mixers. As in packed beds, there is an intensive radial convective mass transport over the entire cross-section of these packings. Structural packing catalysts and the reactors containing them are, however, not within the scope of this review.
2. Monolithic catalysts are continuous unitary structures which contain many small, mostly parallel passages. A ceramic or metallic support is coated with a layer of material in which active ingredients are dispersed. An interaction between these passages can occur if walls are permeable. The catalytically active material is present on or inside the walls of these passages. Radial mass transport can occur only by diffusion through the pores of the permeable walls.

     

不同铝源对SiC/堇青石复相多孔陶瓷的制备及性能影响

以碳化硅、氮化铝、层析氧化铝、氢氧化铝、氟化铝、滑石为主要原料,石墨为造孔剂通过原位反应烧结技术制备碳化硅/堇青石复相多孔陶瓷.研究了含铝化合物种类、烧结温度、石墨含量对SiC/堇青石复相多孔陶瓷相组成、微观结构、气孔率和抗折强度的影响,同时对S0组在1200℃烧结温度下制得的SiC/堇青石复合多孔陶瓷的孔径分布进行了测试分析.结果表明:以AlN为铝源在1200℃下烧结,石墨含量在15％时,堇青石结合SiC多孔陶瓷的抗弯强度和气孔率两项综合性能达到最优,气孔率为31.99％,相应的弯曲强度86.20 MPa.S0组的平均孔径大小在3.0191 μm.     

堇青石红外特性的研究

参考国内外资料,结合红外辐射产生的条件、发射率的基本概念综述了堇青石具有高红外发射率的机理,从合成原料、合成方法和添加剂的加入等方面分析了对堇青石红外发射率产生影响的因素。对堇青石红外陶瓷材料的发展方向进行了展望。     

沸石的改性技术

本文以大量文献为基础,总结了重质原料流化催化裂化催化剂所用Y型沸石分子筛的改性技术。改性技术包括水热改性法,用EDTA、SiCl₄、（NH₄)₂SiF₆、光气或草酸等化学脱铝改性法,以及使用酸、碱、盐式络合剂的水热与化学脱铝相结合的改性方法。     

堇青石棚板的试制

叙述了利用镁质粘土和高岭土原料人工合成堇青石 ,再与其它原料配合制成的堇青石棚板 ,取代了高价外购的堇青石棚板 ,进一步降低了生产成本 ,提高了企业的经济效益     

Washcoating method for Pd/γ-Al2O3 deposition on metallic foams

A method for coating open celled metal foams with a thin layer of Pd–Al₂O₃ was developed. The method makes use of a sol–gel of pseudobohemite as a precursor of γ-Al₂O₃ to fill the porous structure by percolation whilst the excess of material is flushed away with an air jet. The influence of solid content, acid content and ageing on the sol–gel rheological behaviour was studied to find a sol–gel dispersion with an appropriate viscosity whose deposition resulted in a 20 μm thick coating layer. Foam samples of different nominal porosities (10, 20 and 40 PPI) were coated with this method and activated with palladium using a wet impregnation procedure with loadings of 3% (w/w) palladium on the alumina.As an alternative approach, dry impregnation of γ-Al₂O₃ with palladium was performed and a slurry was prepared adding water and nitric acid. The slurry was deposited by percolation through the foam structure. The coating quality was evaluated with adhesion tests and the activity of coated foams was measured by performing catalytic oxidation of CO in a 9 mm i.d. tubular reactor. Both methods produced highly active foams, resulting in light off temperatures between 175 and 250 °C depending on CO concentration. Moreover, the mass transfer controlled regime was achieved in all runs independently of the coating method. Nevertheless, conversions reached when the sol–gel dispersion was deposited and activated via wet impregnation were higher than the ones obtained with the coating method based on slurry deposition of active powders, indicating that the sol–gel deposition resulted in more uniform coating.     

低温合成堇青石

本研究采用废玻璃纤维和高纯Ａｌ_２Ｏ_３、ＳｉＯ_２、ＭｇＯ，在常压下于＜１２００℃，４～８ｈ人工合成高纯堇青石。废玻璃纤维中的ＣａＯ、Ｆｅ_２Ｏ_３、Ｒ_２Ｏ能溶入堇青石的晶体结构，并可有效地扩大烧结范围，降低热膨胀系数。讨论了试样的配方组成、合成温度、保温时间和冷却条件等对堇青石的合成量和晶粒大小的影响。