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Propylene glycol methyl ether was directly synthesized from propylene and hydrogen peroxide under mild conditions via aluminum modified titanium silicalite-1 as a bifunctional catalyst. It has both active sites capable of epoxidation and active sites capable of ring opening reactions, thus realizing the one-pot preparation of propylene glycol methyl ether by propylene. The synergistic effect of Ti–Al on the catalytic performance and the distribution of propylene glycol methyl ether isomer were investigated in detail, and the synergistic catalysis between the two active sites was characterized. The gradual introduction of aluminum reduced the activation ability for hydrogen peroxide, but gradually increased the selectivity for propylene glycol methyl ether. Under the optimum conditions, the selectivity for propylene glycol methyl ether reached 91.53%. Combined with Density Functional Theory (DFT) calculations, the synergistic catalytic effect of doped Al and framework Ti in titanium silicalite-1 is discussed in detail from a microscopic perspective. Al increases the Lewis acid strength of Ti active sites and promotes the conversion of propylene to propylene oxide (PO), and simultaneously Ti increases the Brønsted acid strength of Al active sites and promotes the conversion of propylene oxide to propylene glycol ether. [ABSTRACT FROM AUTHOR]

Collectively called zooxanthellae, photosynthetic dinoflagellates in the family Symbiodiniaceae are typical endosymbionts that unequivocally mediate coral responses to environmental changes. Symbiodiniaceae are genetically diverse, encompassing at least nine phylogenetically distinct genera (clades A–I). The ribosomal internal transcribed spacer 2 (ITS2) region is commonly utilized for determining Symbiodiniaceae diversity within clades. However, ITS2 is often inadvertently interpreted together with the tailing part of the ribosomal RNA genes (5.8S and 28S or equivalent), leading to unresolved taxonomy and equivocal annotations. To overcome this hurdle, we mined in GenBank and expert reference databases for ITS2 sequences of Symbiodiniaceae having explicit boundaries with adjacent rRNAs. We profiled a Hidden Markov Model of the ITS2‐proximal 5.8S‐28S rRNA interaction, which was shown to facilitate the delimitation of Symbiodiniaceae ITS2 from GenBank, while considerably reducing sequence ambiguity and redundancy in reference databases. The delineation of ITS2 sequences unveiled intra‐clade sequence diversity and inter‐clade secondary structure conservation. We compiled the clean data into a non‐redundant database that archives the largest number of Symbiodiniaceae ITS2 sequences known to date with definite genotype/subclade representations and well‐defined secondary structures. This database provides a fundamental reference catalog for consistent and precise genotyping of Symbiodiniaceae and a tool for automated annotation of user‐supplied sequences. [ABSTRACT FROM AUTHOR]

The adsorption and reactions of CO2 and H2O on both monoclinic and hexagonal crystal K2CO3 were investigated using the density functional theory (DFT) approach. The calculated adsorption energies showed that adsorption of H2O molecules was clearly substantially stronger on the K2CO3 surface than the adsorption of CO2, except on the (001)-1 surface of hexagonal K2CO3, where CO2 is competitively adsorbed with H2O. Carbonation reactions easily occur on pure K2CO3 and involve two parallel paths: one is where adsorbed H2O reacts with molecular CO2 in gas to form the bicarbonate, while the other is where H2O dissociates into OH and H before bicarbonate formation, and then OH reacts with gaseous CO2 to form a bicarbonate. Our results indicate that adding a support or promoter or using a special technique to expose more (001)-1 surfaces in hexagonal K2CO3 may improve the conversion of CO2 to the bicarbonate, which provides a theoretical direction for the experimental preparation of the K2CO3 sorbent to capture CO2. [ABSTRACT FROM AUTHOR]

The adsorption and reactions of CO 2 and H 2 O on both monoclinic and hexagonal crystal K 2 CO 3 were investigated using the density functional theory (DFT) approach. The calculated adsorption energies showed that adsorption of H 2 O molecules was clearly substantially stronger on the K 2 CO 3 surface than the adsorption of CO 2 , except on the (001)-1 surface of hexagonal K 2 CO 3 , where CO 2 is competitively adsorbed with H 2 O. Carbonation reactions easily occur on pure K 2 CO 3 and involve two parallel paths: one is where adsorbed H 2 O reacts with molecular CO 2 in gas to form the bicarbonate, while the other is where H 2 O dissociates into OH and H before bicarbonate formation, and then OH reacts with gaseous CO 2 to form a bicarbonate. Our results indicate that adding a support or promoter or using a special technique to expose more (001)-1 surfaces in hexagonal K 2 CO 3 may improve the conversion of CO 2 to the bicarbonate, which provides a theoretical direction for the experimental preparation of the K 2 CO 3 sorbent to capture CO 2 .