A new approach for the aerobic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid without using transition metal catalysts

The organic compound 2,5-furandicarboxylic acid（FDCA） has been identified by the US Department of Energy（DOE） as a valuable platform chemical for a wide range of industrial applications. Currently, the most popular route for FDCA synthesis is reported to be the oxidation of 5-hydroxymethylfurfural（HMF）by O_2 over the catalysis of noble metals（e.g., Au, Pt, Ru, and Pd）. However, the high costs of noble metal catalysts remain a major barrier for producing FDCA at an industrial scale. Herein, we report a transition metal-free synthesis strategy for the oxidation of HMF to FDCA under O_2 or ambient air. A simple but unprecedented process for the aerobic oxidation of HMF was carried out in organic solvents using only bases as the promoters. According to the high performance liquid chromatography（HPLC） analysis, excellent product yield（91%） was obtained in the presence of NaOH in dimethylformamide（DMF） at room temperature（25 ℃）. A plausible mechanism for the NaOH-promoted aerobic oxidation of HMF in DMF is also outlined in this paper. After the reaction, the sodium salt of FDCA particles were dispersed in the reaction mixture, making it possible for product separation and solvent reuse. The new HMF oxidation approach is expected to be a practical alternative to current ones, which depend on the use of noble metal catalysts.

Laser measurement system for acrylic transmittance of JUNO central detector

Background During the research phase of acrylic panel for the Jiangmen Underground Neutrino Observatory(JUNO)central detector(CD),the darkroom transmittance measurement system(DTMS)was designed and built,and a massive amount of measurements were carried out to help determine the composition and processing techniques of the acrylic panel.Motivation The mass production of acrylic panels was started after the pilot production.The requirement of transmittance measurement put forward new demands on operation,and a new measurement system was considered to support removable and non-destructive measurement on site.Result After the accomplishment of design,development and verification were completed,the laser measurement system came into use in the acrylic workshop of Taixing Donchamp Acrylic Ltd,and the transmittance results of acrylic spherical panels met the requirement of JUNO.The optical design,tooling design,data processing interface and uncertainty analyses of the laser measurement system are discussed in detail,and the measured transmittance results are also introduced in this article.

Thermal reliability analysis of the central detector of JUNO

Introduction The Jiangmen Underground Neutrino Observatory(JUNO)is a multipurpose neutrino experiment designed to determine neutrino mass hierarchy,precisely measure oscillation parameters and study solar neutrinos,supernova neutrinos and geo-neutrinos,etc.The central detector(CD)of JUNO has 20,000 tons liquid scintillator as target mass,which contains inside a huge acrylic sphere with inner diameter of 35.4 m,supported by a stainless steel structure.The whole structure of CD will be installed inside a cylindrical water pool,and the acrylic sphere will be submerged in the center of water pool.The operating temperature of CD is designed to be 21℃ as long as over 20 years,which is determined by the mechanical requirement of the structure and physics consideration.Methods For this operating temperature,a special cooling system will be used to maintain the temperature inside the water pool.The main structure of CD is composed of acrylic and stainless steel,and they have much different thermal expansion coefficients,strengths and life times.Change in temperature may affect the safety of CD.As part of reliability analysis,the effect of cooling system failure on the CD is considered,and finite element method is used in our thermal calculation.In this article,the temperature fields before and after cooling system failure are calculated and analyzed,and the temperatures of different locations of water pool after cooling system failure are compared and discussed in detail.

The design of the small prototype for the central detector of JUNO

Background The Jiangmen Underground Neutrino Observatory(JUNO)is a multipurpose neutrino experiment designed to determine neutrino mass hierarchy,precisely measure oscillation parameters and study solar neutrinos,supernova neutrinos and geo-neutrinos.The JUNO Central Detector 20 kton liquid scintillator target mass is contained by a huge acrylic sphere with a 35.4 m inner diameter,supported by a stainless steel structure,and the sphere is eventually submerged in pure water.Motivation Before the JUNO Central Detector is built,a small prototype has been designed and static loading experiments will be carried out to verify the consistency of the finite-element calculations and static loading experiments and test the subsystems performances,such as the monitoring system and liquid scintillator filling system.Methods The small prototype is composed of an acrylic sphere with a 3 m inner diameter and an aluminum alloy support structure.In this article,the structure of the small prototype is briefly described.A detailed simulation study using finite element analysis is conducted to account for liquid-filled condition,temperature variation and existence of high load(due to vacuum pumping)and demonstrate a satisfying mechanical performance of the small prototype.The experimental plan about the prototype on the basis of the simulation will also be mentioned.

Study of MRPC technology for BESIII endcap-TOF upgrade

Purpose In order to improve the charged particle identi-fication capability,end-cap time-of-flight(ETOF)detector of the Beijing Spectrometer(BESIII)has been upgraded with multi-gap resistive plate chamber(MRPC)technology,aiming at an overall time resolution of 80 ps for minimum-ionization particles to extend the K/πseparation(2σ)momentum range to 1.4 GeV/c.Methods The previous version of ETOF in BESIII consisted of plastic scintillators.The multi-hit events distort both shape and amplitude of the output signals.MRPC technique was chosen for the BESIII ETOF upgrade as it provides high time resolution and high detection efficiency,is of relatively low cost and is insensitive to neutral particles.Most importantly,the fine segmentation of the MRPC readout stripes can suppress multi-hit events effectively.Results The final design of MRPC module for ETOF is characterized by double-stack(2×6)structure,dual-end readout mode and precision electronics.To batch-produce and test these MRPC modules,a series of tools and production procedures as well as related performance simulation and test methods were developed.Results showed that each MRPC module’s intrinsic time resolution(including the electronics contribution)is around 50 ps and the efficiency is better than 97%.The overall performance of the upgraded ETOF is better than the designed index.The new ETOF has been successfully installed at BESIII and run in 2016.