Fields of harmony: trade standards and China’s value-added exports in global value chains

This study uses a gravity model to analyse the effects of different trade standards on China’s value-added and total exports in global value chains (G.V.C.s). The results indicate that harmonisation with international standards promotes both types of exports in China. Hence, the country should not neglect the implementation of standards. Mandatory standards have a greater impact on exports than voluntary standards. In addition, mandatory internationally harmonised standards have a greater trade promotion effect on total exports than on value-added exports. Voluntary country-specific standards have a greater trade inhibiting effect on value-added exports than on total exports. Voluntary internationally harmonised standards do not show statistically significant impacts on either export type. Therefore, emerging economies should optimise the scale and structure of standards, ensure their implementation, and improve their international harmonisation to promote exports and reap the benefits of joining G.V.C.s

Coherent photo-produced J/ψ/\psi and dielectron yields in isobaric collisions

Recently, significant enhancements of J/$\psi$ and $e^{+} e^{-}$ pair production at very low transverse momenta were observed by the STAR and ALICE collaboration in peripheral hadronic A+A collisions. The anomaly excesses point to evidence of coherent photon-nucleus and photon-photon interactions in violent hadronic heavy-ion collisions, which were conventionally studied only in ultra-peripheral collisions. The isobaric collisions performed at RHIC provides a unique opportunity to test the existence of coherent photon products in hadronic heavy-ion collisions. The idea is that the possible production of coherent photon products is significantly different in different collision systems due to the variations in their charge and nuclear density distributions. In this letter, we focus on the peripheral collisions and provide theoretical predictions for coherent production of J/$\psi$ and dielectron in isobaric collisions. We show that the expected yields differ significantly to perform the experimental test

Compartmentalization of incompatible reagents within Pickering emulsion droplets for one-pot cascade reactions

It is a dream that future synthetic chemistry can mimic living systems to process multistep cascade reactions in a one-pot fashion. One of the key challenges is the mutual destruction of incompatible or opposing reagents, for example, acid and base, oxidants and reductants. A conceptually novel strategy is developed here to address this challenge. This strategy is based on a layered Pickering emulsion system, which is obtained through lamination of Pickering emulsions. In this working Pickering emulsion, the dispersed phase can separately compartmentalize the incompatible reagents to avoid their mutual destruction, while the continuous phase allows other reagent molecules to diffuse freely to access the compartmentalized reagents for chemical reactions. The compartmentalization effects and molecular transport ability of the Pickering emulsion were investigated. The deacetalization–reduction, deacetalization–Knoevenagel, deacetalization–Henry and diazotization–iodization cascade reactions demonstrate well the versatility and flexibility of our strategy in processing the one-pot cascade reactions involving mutually destructive reagents

Supercritical Fluid Assisted Recovery of Organometallic Catalysts from Polymers

The recovery of organometallic catalysts from polymer matrices is of great importance in promoting the application of homogeneous catalysts in industry. Such a green recovery technique will not only popularize the techniques of green catalytic hydrogenation of polymers by Rempel’s group, but also consummates the technique of heterogenization of organometallic catalysts. The high value product of hydrogenated nitrile butadiene rubber (HNBR) with dissolution of Wilkinson’s catalyst [RhCl(TPP)3] was selected as the model polymer matrix for developing a green separation technique. The supercritical carbon dioxide (scCO2) soluble fluorous Wilkinson’s catalyst [RhCl(P(p-CF3C6H4)3)3] was synthesized and shown exhibit a very limited activity in the catalytic hydrogenation of bulk HNBR. Its recovery from a HNBR matrix using scCO2 however failed. In spite of the assistance of the scCO2 dissolvable chelating ligand thenoyltrifluoroacetone (TTA), the weak compatibility of scCO2 with rhodium complexes failed again as an extraction solvent for the HNBR matrix. Inspired by the merits of CO2-expanded liquids (CXLs) and the versatility of CO2 in changing the physical properties of polymer melts, CXLs were tested as extracting solvents for separation of Wilkinson’s catalyst from bulk HNBR. CO2-expanded water (CXW) and CO2-expanded alcohols including methanol and ethanol (CXM and CXE) were examined with the assistance of a variety of chelating agents. The investigated chelating agents include ethylenediaminetetraacetic acid (EDTA), ethylenediaminetetraacetic acid disodium salt (EDTA-Na2), diethylenetriamine (DETA), N,N,N',N',N"-pentamethyldiethylenetriamine (PMDETA), and N,N,N’,N’-tetramethylethylenediamine (TMEDA). CXM and PMDETA were recognized as the optimal combination of extracting solvent and chelating agent for recovery of Wilkinson’s catalyst from HNBR. An extraction system consisting of CXM and PMDETA was carefully investigated with respect to the effects of temperature and pressure on the extraction performance over the temperature range of 40 to 100 °C and the pressure range of 20 to 200 bar. Increasing temperature effectively increased the extraction rate and became less influential when the temperature was above 80 °C. Increasing pressure at a fixed temperature was found to improve the extraction rate followed by suppressing it. Nevertheless, further increasing the pressure to an extreme high value above the respective critical point was able to promote the extraction rate again. The complex effects of pressure were thoroughly investigated by the means of analyzing the dissolution behavior of CO2 in HNBR and the variation of the extraction phase composition at different operational conditions. 0.14 g/mL was determined as the CO2 density by which the optimal pressure at a fixed temperature can be estimated. Based on a careful interpretation of the experimental results, an extraction mechanism was illustrated for interpreting the present extraction system. Additionally, the reactions involved in the extraction process were illustrated to reveal the principal challenges present in the extraction process and pointed out the potential solution for eliminating the obstacles. Two special operations-sequential operation and pressure varying procedure were tested for their effectiveness in enhancing the extraction ratio. A pressure varying procedure was found to be beneficial in further improving the extraction ratio, while sequential operation did not show any promise in enhancing the recovery. At last, the developed technique was shown to be highly efficient in applying it to HNBR particles coagulated from the HNBR latex. A residue of 59 ppm rhodium was obtained after 9 hours of operation. This study establishes a technology platform for separating the expensive catalyst from the polymer matrix, using “green” CO2-expanded liquids