ML／Y分子筛复合材料的制备,表征及其催化性能研究

采用沸石合成法制备了ＭＬ／Ｙ（Ｍ＝ Ｆｅ,Ｃｏ,Ｃｒ;Ｌ＝ ８－ ｑｕｉｎｏｌｉｎｏｌａｎｄ ｓａｌｉｃｙｌｉｃ ａｃｉｄ （ｄｅｎｏｔｅｄ ａｓＱｘ ａｎｄ ＳＡｒｅｓｐｅｃｔｉｖｅｌｙ）） 复合材料,并通过ＸＲＤ、ＦＴＩＲ、ＩＣＰ、ＵＶ－ ｖｉｓ 及催化反应等手段对其进行了表征。ＦＴＩＲ和ＵＶ－ ｖｉｓ 测试结果表明： 合成体系中含有的金属配合物经过水热晶化后封装或固定在分子筛的空腔中。通过Ｘ射线衍射原位跟踪Ｙ型分子筛的晶化过程,发现合成体系中含有金属配合物的性质及其量的多少不仅对Ｙ型分子筛的晶化有很大影响,而且使其封装或固定在分子筛中的量也有所差异。另外,以环己烷氧化为探针反应考察了ＭＬ／Ｙ的催化性能,结果表明ＭＬ／Ｙ的氧化能力来自于所封装或固定的金属配合物,其氧化能力主要取决于配合物中心离子的性质     

Heat capacity and thermodynamic properties of 1-hexadecanol

Three different nitrocellulose (NC) samples produced from linters were investigated. DSC studies on the NC+sym-diethyldiphenylurea (C1) mixtures were carried out. The influence of storage time on their pore structures was examined using thermoporometry. The results led to conclusion that large pores are multiples of small ones. The parameter n was used to characterize the number of C1 molecules equivalent to NC ring. Its value for short storage time was about 9 but for longer time reached the value of 3. The influence of thermal history on the phase transition and porosity of the different nitrocellulose samples was different.     

Selective carboxylation of substituted phenols with engineered Escherichia coli whole-cells

Selective carboxylation of substituted phenols is realized in the presence of bicarbonate under ambient pressure by engineered Escherichia coli whole-cells expressing various hydroxybenzoate decarboxylases, leading to their corresponding ortho-hydroxybenzoates. This process may be further developed as an efficient route to upgrade lignin-derived phenolic compounds as valuable building blocks.     

Numerical and Experimental Investigation of the Conjugate Heat Transfer for a High-Pressure Pneumatic Control Valve Assembly

This paper uses heat transfer experiments and computational fluid dynamics (CFD) simulations to investigate the conjugate heat transfer (CHT) in a high-pressure pneumatic control valve assembly. A heat transfer test rig was constructed, and time–temperature histories of five test points placed on the valve assembly’s outer surface were recorded for study validation. The Unsteady Reynolds-Averaged Navier–Stokes (URANS) CFD methods with the standard k-ε turbulence closure equations were adopted in the numerical computations. Polyhedral grids were used; time step and mesh convergence studies were conducted. Simulated and measured temperatures profile comparisons revealed a good agreement. The CHT results obtained from CFD showed huge velocity fields downstream of the valve throat and the vent hole. The airflow through the valve was icy, mainly in the supersonic flow areas. Low temperatures below 273.15 K were recorded on the internal and external walls of the valve assembly. The consistency of the measured data with the numerical results demonstrates the effectiveness of polyhedral grids in exploring the CHT using CFD methods. The local entropy production rate analysis revealed that irreversibility is mainly due to viscous dissipation. The current CHT investigation provides a potential basis for thermostress analysis and optimization.     

Deep learning-based symbol detection algorithm in IMDD-OOFDM system

In the current research on intensity-modulation and direct-detection optical orthogonal frequency division multiplexing(IMDD-OOFDM) system, effective channel compensation is a key factor to improve system performance. In order to improve the efficiency of channel compensation, a deep learning-based symbol detection algorithm is proposed in this paper for IMDD-OOFDM system. Firstly, a high-speed data streams symbol synchronization algorithm based on a training sequence is used to ensure accurate ...     

Artificial intelligence for optical transport networks: architecture,application and challenges

Optical network plays an important role in telecommunication networks, which supports high-capacity and long-distance transmission of Internet traffic. However, as the scaling and evolving of optical networks, it faces great challenges in terms of network operation, optimization and maintenance. Artificial intelligence(AI) has been proved to have superiority on addressing complex problems, by mimicking cognitive skills similar with human mind. In this paper, we provide a comprehensive investigat...     

Recent Advances on Metal-Organic Frameworks in the Conversion of Carbon Dioxide

With the development of modern industry,global warming is becoming a challenging issue due to the emissions of large quantities of greenhouse gases,mainly carbon dioxide(CO₂).The conversion of CO₂to useful compounds is considered as an effective and economic way to solve such a climate problem.Metal-organic frameworks(MOFs)are an emerging class of porous crystalline materials that have shown great potential in the conversion of CO₂.The advantages of MOFs in CO 2 conversion lie in their high surface areas,adjustable pore size,and high porosity.More importantly,desirable functional sites can be easily designed and precisely installed to the pore wall of target MOFs by pre-assembly and/or post-synthetic modification(PSM)ways.This review summarizes the recent advances in constructing MOF catalysts for the application in CO₂conversion.We believe that the design and synthesis of MOF catalysts for CO₂conversion can be a promising way to solve the“greenhouse effect”.     

Electrochemically driven C–N bond formation from CO2 and ammonia at the triple-phase boundary

Electrosynthetic techniques are gaining prominence across the fields of chemistry, engineering and energy science. However, most works within the direction of synthetic heterogeneous electrocatalysis focus on water electrolysis and CO₂ reduction. In this work, we moved to expand the scope of small molecule electrosynthesis by developing a synthetic scheme which couples CO₂ and NH₃ at a gas–liquid–solid boundary to produce species with C–N bonds. Specifically, by bringing in CO₂ from the gas phase and NH₃ from the liquid phase together over solid copper catalysts, we have succeeded in forming formamide and acetamide products for the first time from these reactants. In a subsequent complementary step, we have combined electrochemical analysis and a newly developed operando spectroelectrochemical method, capable of probing the aforementioned gas–liquid–solid boundary, to extract an initial level of mechanistic analysis regarding the reaction pathways of these reactions and the current system''s limitations. We believe that the development and understanding of this set of reaction pathways will play significant role in expanding the community''s understanding of on-surface electrosynthetic reactions as well as push this set of inherently sustainable technologies towards widespread applicability.

Electrocatalytic formation of C–N bonds was achieved through the electrolysis of CO₂ and NH₃ over Cu catalysts. A combined analytical and spectroscopic approach gave insights into the reaction mechanism leading to formamide and acetamide products.