Sn对V2O5/Al2O3催化剂在异丁烷脱氢反应中的影响

以Al₂O₃为载体,采用等体积浸渍法制备了负载型高分散氧化钒催化剂（12%V₂O₅/Al₂O₃）,并选择Sn作为助剂对12%V₂O₅/Al₂O₃催化剂的表面性质进行调控,采用XRD、N₂等温吸脱附、NH₃-TPD、H₂-TPR、XPS、TEM和Raman光谱等方法对催化剂进行表征,结合活性评价实验,研究了催化剂表面物种分散状态、酸性和活性物种价态的变化与异丁烷脱氢活性和稳定性之间的关系。表征结果显示,Sn对V₂O₅/Al₂O₃表面的酸性和V物种在催化剂表面的分布和价态具有一定的调节作用,当Sn质量分数为1%时,氧化锡在催化剂表面分散均匀,对表面积和孔结构影响较小,同时,表面酸性变化较小,表面低价态的钒物种增多。活性评价结果表明,该催化剂在临氢反应条件下保持了最佳的脱氢活性及稳定性,异丁烷脱氢反应480min后,异丁烷转化率为46.8%,异丁烯收率为39.8%。     

A V-Nitrogenase Variant Containing a Citrate-Substituted Cofactor

Nitrogenases catalyze the ambient reduction of N₂ and CO at its cofactor site. Herein we present a biochemical and spectroscopic characterization of an Azotobacter vinelandii V nitrogenase variant expressing a citrate-substituted cofactor. Designated VnfDGK^Cit, the catalytic component of this V nitrogenase variant has an αβ₂(δ) subunit composition and carries an 8Fe P* cluster and a citrate-substituted V cluster analogue in the αβ dimer, as well as a 4Fe cluster in the “orphaned” β-subunit. Interestingly, when normalized based on the amount of cofactor, VnfDGK^Cit shows a shift of N₂ reduction from H₂ evolution toward NH₃ formation and an opposite shift of CO reduction from hydrocarbon formation toward H₂ evolution. These observations point to a role of the organic ligand in proton delivery during catalysis and imply the use of different reaction sites/mechanisms by nitrogenase for different substrate reductions. Moreover, the increased NH₃/H₂ ratio upon citrate substitution suggests the possibility to modify the organic ligand for improved ammonia synthesis in the future.     

Coextraction of vanadium and manganese from high-manganese containing vanadium wastewater by a solvent extraction-precipitation process

High-manganese containing vanadium wastewater (HMVW) is commonly produced during the vanadium extraction process from vanadium titano-magnetite. HMVW cannot be reused and discharged directly, and is harmful to the environment and affect product quality due to heavy metals in the wastewater. The wastewater is usually treated by lime neutralization, but valuable metals (especially V and Mn) cannot be recovered. In this study, an efficient and environmentally friendly method was developed to recover valuable metals by using a solvent extraction-precipitation process. In the solvent extraction process, 98.15% of vanadium was recovered, and the V₂O₅ product, with a purity of 98.60%, was obtained under optimal conditions. For the precipitation process, 91.05% of manganese was recovered as MnCO₃ which meets the III grade standard of HG/T 2836-2011. Thermodynamic simulation analysis indicated that MnCO₃ was selectively precipitated at pH 6.5 while Mg and Ca could hardly be precipitated. The results of X-ray diffraction and scanning electron microscopy demonstrated that the obtained V₂O₅ and MnCO₃ displayed a good degree of crystallinity. The treated wastewater can be returned for leaching, and resources (V and Mn) in the wastewater were utilized efficiently in an environmentally friendly way. Therefore, this study provides a novel method for the coextraction of V and Mn from HMVW.     

含钒石煤无盐焙烧酸浸生产五氧化二钒工艺的研究

系统地研究了石煤无盐焙烧酸浸生产五氧化二钒的工艺技术 ,提出了各工序的工艺条件。焙烧转化率 57% ,锻烧回收率 98% ,总收率 47%～ 50 % ,具有较好的经济效益和有效地改进了环境污染。     

用复相光催化剂WO_3/CdS/W深度处理印染废水的研究

用复相光催化剂WO3 /CdS/W对印染废水的深度处理进行了研究。探讨了光催化反应机理 ,讨论了复相光催化剂的组成、用量、试液pH值、光照时间与COD、色度去除率的关系。实验结果表明 :以WO3 /CdS/W为复相光催化剂 ,其组成为m(WO3 ) /m(CdS) /m(W ) =6 0∶39∶1(质量比 )、用量为 0 .30 0 g、试液pH为 6 .5、光照 10h ,印染废水的COD、色度去除率分别达到 6 9.8%、71.0 %     

碱度对含铬型钒钛磁铁矿烧结性能的影响

以承德建龙特殊钢有限公司现场条件为依据,通过烧结杯实验模拟碱度(R)对含铬型钒钛磁铁矿烧结性能的影响,分析了其显微结构.结果表明,随碱度提高,烧结速度先增大后减小,R=2.5时最大,为19.70 mm/min,烧损增大;R=2.7时转鼓强度最高,为63.53%;碱度提高改善含铬型钒钛烧结矿的低温还原粉化指数(RDI),R=2.7时大于3.15mm的颗粒的RDI最高,为75.09%;碱度增大生产率先增大后减小,R=2.5时最高,为1.35 t/(m2·h).R=2.1~2.5时燃耗比上升,R=2.1时最低,为43.21 kg/t.碱度提高有利于提高软化开始和软化终了温度,改善含铬型钒钛烧结矿的软化性能、矿物组成及结构,是其性能改善的内因.该矿适宜的生产碱度为2.5.     

Oxidative Dehydrogenation of Propane over Mesoporous HMS Silica Supported Vanadia

Vanadium-containing mesoporous HMS catalysts have been prepared and characterized for the oxidative dehydrogenation (ODH) of propane. It is demonstrated that the vanadium supported HMS catalysts exhibit a much higher catalytic activity than the literature results obtained over the vanadium supported MCM-41 catalysts in the ODH of propane. The improved catalytic activity of the V-HMS catalysts has been attributed to the presence of high concentration of well-dispersed vanadium species on the surface of the mesoporous HMS materials.     

天然气代替重油在铬酸酐生产中的应用

在铬酸酐生产中,天然气与重油相比,具有无污染,热利用率高,成本低,操作简便等优点。     

Preparation of polyethylene oxide/LixV2‐δO4‐δ nanocomposites

Polyethylene oxide (PEO)/LixV_2‐δO_4‐δ nanocomposites were prepared in aqueous solution. Characterization of the nanocomposites using thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), powder X‐ray diffraction (XRD), and Fourier transform infrared spectrum (FTIR) shows that polymer chains intercalate inorganic host lamella and exhibit lattice expansion along the stacking direction of 4.2 Å. A possible model for the structure of the nanocomposite is also provided. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2162–2166, 2001     

Production of p‐toluenesulfonic acid by sulfonating toluene with gaseous sulfur trioxide

Toluene was sulfonated by gaseous sulfur trioxide to prepare p‐toluenesulfonic acid. The effects of reaction temperature and toluene conversion on the isomer selectivities and the dynamic viscosity of the reaction mixture in a well‐stirred tubular glass reactor of 4 cm diameter and 16 cm height were investigated. Lower selectivity to the m‐isomer was obtained at lower reaction temperature and lower conversion of toluene, whereas the selectivity to the p‐isomer seemed to be less affected by these parameters. With the increase in toluene conversion a sharp increase in viscosity of the reaction mixture was observed, which was attributed to the saturation of the toluenesulfonic acids dissolved in toluene. A pilot‐scale stainless steel jet loop reactor (JLR) of 0.3 m diameter and 4 m height with an external cooler was constructed and used for the continuous sulfonation of toluene. It was found that the JLR was very effective for the fast removal of the large amount of reaction heat, and selectivities to the p‐isomer around 85% and to the m‐isomer below 1.2% were obtained. © 2001 Society of Chemical Industry