As the raw material of lithium-ion batteries, lithium carbonate plays an important role in the development of new energy field. Due to the extremely uneven distribution of lithium resources in the world, the security of supply in countries with less say would be greatly threatened if trade restrictions or other accidents occurred in large-scale exporting countries. It is of great significance to help these countries find new partners based on the existing trade topology. This study uses the link prediction method, based on the perspective of the topological structure of trade networks in various countries and trade rules, and eliminates the influence of large-scale lithium carbonate exporting countries on the lithium carbonate trade of other countries, to find potential lithium carbonate trade links among importing and small-scale exporting countries, and summarizes three trade rules: (1) in potential relationships involving two net importers, a relationship involving either China or the Netherlands is more likely to occur; (2) for all potential relationships, a relationship that actually occurred for more than two years in the period in 2009–2018 is more likely to occur in the future; and (3) potential relationships pairing a net exporter with a net importer are more likely to occur than other country combinations. The results show that over the next five to six years, Denmark and Italy, Netherlands and South Africa, Turkey and USA are most likely to have a lithium carbonate trading relationship, while Slovenia and USA, and Belgium and Thailand are the least likely to trade lithium carbonate. Through this study, we can strengthen the supply security of lithium carbonate resources in international trade, and provide international trade policy recommendations for the governments of importing countries and small-scale exporting countries.
Introduction:
L-proline is an efficient chiral small-molecule organocatalyst for the direct asymmetric aldol reaction between unmodified acetone and a variety of aldehydes.
background:
The direct asymmetric aldol reaction is an effective method to construct C-C bonds in an enantioselective fashion. L-proline, as an efficient chiral small-molecule organocatalyst for the direct asymmetric aldol reaction between unmodified ketone and a variety of aldehydes, is widely used in the synthesis of natural products and drug molecules. However, it is difficult to separate and recover from the reaction medium.
Method:
However, it is difficult to separate from the reaction medium for reuse. In this work, polyacrylic acid (PAA) supported The acylation reaction between L-hydroxyproline and PAA prepared l-proline (P(AA-co-PA)) catalysts with various catalyst loadings. Fourier characterized them transforms infrared spectroscopy, nuclear magnetic resonance spectrum, gel permeation chromatography and thermogravimetry analysis.
objective:
The introduction of some hydrophilic groups into the macromolecular chains is to make the supported L-proline catalyst not only insoluble in the organic phase but also capable of enhancing the hydrogen bonding, thus improving the activity and selectivity.
Result:
These macromolecular catalysts were used to catalyze acetone and benzaldehydes' direct asymmetric aldol reaction. The influence of the catalyst structure on the catalytic performance was studied, and the reaction conditions were optimized.
method:
Polyacrylic acid (PAA) supported L-proline (P(AA-co-PA)) catalysts with 20% - 80% loadings were prepared by the acylation reaction between L-hydroxyproline and PAA. They were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectrum and gel permeation chromatography. These macromolecular catalysts were used to catalyze the direct asymmetric aldol reaction of acetone and p-nitrobenzaldehyde.
Conclusion:
The results showed that P(AA-co-PA) with 50 mol% catalyst loading had excellent catalytic performance, much higher than that of L-proline and L-hydroxyproline. Its recovery was achieved by simple filtration. After being reused 7 times, its catalytic performance was still higher than that of L-proline.
result:
The results showed that P(AA-co-PA) with 50% loading had excellent catalytic performance. At 25 ℃, the yield of β-hydroxyketone reached 88% with high enantiomeric excess value (84%), much higher than that of L-proline and L-hydroxyproline. Moreover, the recovery of the macromolecular catalyst was achieved by simple filtration. After being reused for 7 times, its catalytic performance was still higher than that of L-proline.
other:
None
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.