无粘结剂ZSM-11催化剂上异丁烯直接胺化生成叔丁胺

叔丁胺是一种重要的化工原料和中间体,广泛应用于制备橡胶促进剂、医药、农药和着色剂等下游产品.异丁烯在分子筛催化剂上直接胺化生产叔丁胺是一个经济环保过程,其中ZSM-5和BEA分子筛的催化性能优于其它系列分子筛.ZSM-11与ZSM-5分子筛具有相似的孔道结构,我们以前的实验结果表明,与ZSM-5相比,ZSM-11表现出更优越的芳构化反应性能,在干气中乙烯低温芳构化方面也有明显优势.在此基础上,我们进行无粘结剂ZSM-11分子筛催化剂合成,并应用于异丁烯直接胺化生产叔丁胺反应.传统水热技术合成的分子筛通常为粉末,机械强度不能达到实际应用的要求,在工业化过程中分子筛粉末一般需要加入粘结剂成型使其具备一定的机械强度和形状,但是粘结剂会降低分子筛催化剂的活性和选择性,有可能会引发一些副反应,因此无粘结剂分子筛催化剂引起人们广泛关注.无粘结剂分子筛是指分子筛颗粒中不含惰性粘结剂或只含有少量粘结剂,主要依靠分子筛晶粒间的相互作用支撑存在,具有一定形状、尺寸和机械强度的催化材料.无粘结剂分子筛催化剂中分子筛含量较高,可利用的有效表面积较大,在离子交换及工业催化等方面具有明显优势.本文采用水热合成的ZSM-11分子筛原粉与二氧化硅机械混合(ZSM-11/SiO2=70/30)挤条后,通过气固相合成法制备了无粘结剂ZSM-11分子筛催化剂(Cat-C).作为对比,还分别制备了ZSM-11和SiO2机械混合(ZSM-11/SiO2=70/30)样品HZSM-11+SiO2及ZSM-11和氧化铝机械混合(ZSM-11/Al2O3=70/30)样品HZSM-11+Al2O3.利用X射线衍射、透射电镜、NH3程序升温脱附和吸附吡啶红外光谱等对分子筛催化剂的物理化学性能进行了表征.同时,以这些分子筛样品为催化剂,在固定床反应装置上进行了异丁烯胺化反应评价,反应条件为270℃,5.0 MPa,氨烯比为4和异丁烯空速0.5 h?1.结果表明,与HZSM-11+SiO2和HZSM-11+Al2O3相比,Cat-C上叔丁胺生成速率最高.关联催化剂物化性能和反应性能发现,催化剂孔道结构与叔丁胺生成并不存在明显的关联性,而较多的Br?nsted酸和较少的Lewis酸才是Cat-C具有良好反应性能的主要原因.具有一定机械强度的无粘结剂ZSM-11分子筛催化剂制备简单,在异丁烯直接胺化过程中叔丁胺生成速率高,具有很好的工业化应用前景.     

Mechanistic study of Ce-modified MnO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>/TiO<Subscript>2</Subscript> catalysts with high NH<Subscript>3</Subscript>-SCR performance and SO<Subscript>2</Subscript> resistance at low temperatures

A series of Ce–MnO _x /TiO₂ catalysts were prepared using a novel sol–gel template method and investigated for low-temperature selective catalytic reduction (SCR) of NO with NH₃ at temperatures ranging from 353 to 473 K. The 0.07Ce–MnO _x /TiO₂ catalyst showed the highest activity and best resistance to SO₂ poisoning. The structure and properties of the catalysts were characterized using X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), thermogravimetry (TG)–differential scanning calorimetry (DSC)–mass spectroscopy (MS), high-resolution transmission electron microscopy (HRTEM), Brunauer–Emmett–Teller (BET) measurements, H₂-temperature-programmed reduction (TPR), and NH₃-temperature-programmed desorption (TPD). The superior catalytic activity of the 0.07Ce–MnO _x /TiO₂ catalyst was probably due to a change in the active components, an increase in surface active oxygen and surface acid sites, and lower crystallinity and larger surface area with Ce doping. Furthermore, the reduction ability also became stronger. The SO₂ poisoning resistance of the 0.07Ce–MnO _x /TiO₂ catalyst improved because doping with Ce can effectively decrease the formation of ammonium salt on the catalyst surface and the sulfation of MnO _x . In situ diffuse-reflectance infrared Fourier-transform (DRIFT) spectroscopy experiments indicated that addition of Ce could promote adsorption of NH₃ and inhibit generation of some nitryl species. The SCR reactions over the catalysts mainly followed the Eley–Rideal mechanism accompanied with a partial Langmuir–Hinshelwood mechanism.     

Red-emitting salicylaldehyde Schiff base with AIE behaviour and large Stokes shift

Three salicylaldehyde Schiff base (SSB) with AIE behavior were designed and facilely synthesized through a condensation reaction. In solid and aggregation states, these SSB dyes exhibited yellow to red emission with large Stokes shift. One of SSB dyes could specifically stain lipid droplets in living cells.     

Electrophoretic Determination of Formaldehyde in Human Urine: Application to Alzheimer’s Disease

The primary clinical diagnosis of Alzheimer’s disease is mainly based on medical history and neuropsychiatric inventory. It is urgent to seek biological indicators with better sensitivity and higher specificity to clinically diagnose and evaluate Alzheimer’s disease. In this work, an electrophoretic method based on 2-thiobarbituric acid derivatization and amperometric detection was developed to determine formaldehyde as a urinary biomarker of Alzheimer’s disease. Under the optimum conditions, the formaldehyde derivative was well separated from the coexisting interferences in urine sample. The limit of detection for formaldehyde was 80.0?nM (2.4?ng/?mL) based on an electrophoretic stacking technology. The average recovery values were in the range of 91.7–110%, and the relative standard deviation values were less than 4.1%. This method has been applied to analyze human urine samples from healthy volunteers and patients with different degrees of Alzheimer’s disease. The assay results showed that the content of urinary formaldehyde in patients suffering Alzheimer’s disease was significantly higher than that in healthy subjects (P?相似文献   

Zirconium–Porphyrin‐Based Metal–Organic Framework Hollow Nanotubes for Immobilization of Noble‐Metal Single Atoms

Single atoms immobilized on metal–organic frameworks (MOFs) with unique nanostructures have drawn tremendous attention in the application of catalysis but remain a great challenge. Various single noble‐metal atoms have now been successfully anchored on the well‐defined anchoring sites of the zirconium porphyrin MOF hollow nanotubes, which are probed by aberration‐corrected scanning transmission electron microscopy and synchrotron‐radiation‐based X‐ray absorption fine‐structure spectroscopy. Owing to the hollow structure and excellent photoelectrochemical performance, the HNTM‐Ir/Pt exhibits outstanding catalytic activity in the visible‐light photocatalytic H₂ evolution via water splitting. The single atom immobilized on MOFs with hollow structures are expected to pave the way to expand the potential applications of MOFs.     

硫酸铈铵对三角褐指藻岩藻黄素含量的影响及转录差异研究

利用血球计数法测定藻密度,研究不同浓度硫酸铈铵诱导子对三角褐指藻细胞生长的影响。采用高效液相色谱(HPLC)测定经不同浓度诱导子处理后三角褐指藻岩藻黄素的含量。通过荧光定量PCR研究岩藻黄素生物合成途径中相关基因转录差异,并利用SAS9.0统计软件对荧光定量PCR结果做主成分分析。结果显示:在一定浓度范围内硫酸铈铵(0.2~1.6 mg·L-1)抑制三角褐指藻细胞的生长。HPLC结果表明:随着硫酸铈铵浓度的增加,岩藻黄素含量呈先上升后下降的趋势,当硫酸铈铵浓度为0.2 mg·L-1时,岩藻黄素含量最高,达1.28 mg·g-1DW,比对照组提高了60%。定量PCR分析结果表明,硫酸铈铵浓度在0.2 mg·L-1时,岩藻黄素生物合成相关基因玉米黄素环氧酶基因(zep)、八氢番茄红素合成酶基因(pys)、ζ-胡萝卜素脱氢酶基因(zds)、番茄红素β-环化酶基因(lcyb)、胡萝卜素异构酶基因(rtiso)和八氢番茄红素脱氢酶基因(pds)转录水平与对照组相比极显著提高(P<0.01),与岩藻黄素含量变化相一致。主成分分析(PCA)结果表明:这些基因与岩藻黄素生物合成显著相关,其中,lcyb基因和pds基因对岩藻黄素生物合成贡献率最大。     

常用玻璃量器检定注意事项

总结了常用玻璃量器检定过程中的注意事项,讨论了外观检查、清洁度、涂抹油脂、温度控制、液面观察方法对常用玻璃量器检定结果的影响,其中定容时是否使用黑色遮光带造成的影响最大。     

骨架环肽的化学合成研究进展

骨架环肽是线性肽的C端和N端通过酰胺键进行首尾环合而形成的环状分子.研究者从细菌、真菌、植物和动物中发现了大量的骨架环肽.这种首尾环合的结构,使得骨架环肽具有很好的酶稳定性、热稳定性和化学稳定性,部分骨架环肽具有细胞膜通透性.骨架环肽分子异常的稳定性和高效的生物活性,使得其成为目前药物领域的研究热点.为了更深入地研究它们的结构和功能,骨架环肽的制备成为一个重要问题.概述了化学合成骨架环肽的一些方法,包括:(1)固相环合策略;(2)液相环合策略;(3)分子内自然化学连接策略,并对这些方法的特点和效率进行了讨论比较.     

Fluorescent Coumarin–Artemisinin Conjugates as Mitochondria‐Targeting Theranostic Probes for Enhanced Anticancer Activities

Mitochondria‐targeting theranostic probes that enable the simultaneously reporting of and triggering of mitochondrial dysfunctions in cancer cells are highly attractive for cancer diagnosis and therapy. Three fluorescent mitochondria‐targeting theranostic probes have been developed by linking a mitochondrial dye, coumarin‐3‐carboximide, with a widely used traditional Chinese medicine, artemisinin, to kill cancer cells. Fluorescence images showed that the designed coumarin–artemisinin conjugates localized mainly in mitochondria, leading to enhanced anticancer activities over artemisinin. High cytotoxicity against cancer cells correlated with the strong ability to accumulate in mitochondria, which could efficiently increase the intracellular reactive oxygen species level and induce cell apoptosis. This study highlights the potential of using mitochondria‐targeting fluorophores to selectively trigger and directly visualize subcellular drug delivery in living cells.