Self-Defense Effects of Ti-Modified Attapulgite for Alkali-Resistant NOx Catalytic Reduction.

Nowadays, the serious deactivation of deNOx catalysts caused by alkali metal poisoning was still a huge bottleneck in the practical application of selective catalytic reduction of NOx with NH3. Herein, alkali-resistant NOx catalytic reduction over metal oxide catalysts using Ti-modified attapulgite (ATP) as supports has been originally demonstrated. The self-defense effects of Ti-modified ATP for alkali-resistant NOx catalytic reduction have been clarified. Ti-modified ATP with self-defense ability was obtained by removing alkaline metal cation impurities in the natural ATP materials without destroying its initial layered-chain structure through the ion-exchange procedure, accompanied with an obvious enrichment of Brønsted acid and Lewis acid sites. The self-defense effects embodied that both ion-exchanged Ti octahedral centers and abundant Si-OH sites in the Ti-ion-exchange-modified ATP could effectively anchor alkali metals via coordinate bonding or ion-exchange process, which induced alkali metals to be immobilized by the Ti-ion-exchange-modified ATP carrier rather than impair active species. Under this special protection of self-defense effects, Ti-ion-exchange-modified ATP supported catalysts still retained plentiful acidic sites and superior redox ability even after alkali metal poisoning, giving rise to the maintenance of sufficient NHx and NOx adsorption and the subsequent efficient reaction, which in turn resulted in high NOx catalytic reduction capacity of the catalyst. The strategy provided new inspiration for the development of novel and efficient selective catalytic reduction of NOx with NH3 (NH3-SCR) catalysts with high alkali resistance.

Efficient NOx Abatement over Alkali-Resistant Catalysts via Constructing Durable Dimeric VOx Species.

The presence of alkali metals in flue gas is still an obstacle to the practical application of catalysts for selective catalytic reduction (SCR) of NOx by NH3. Polymeric vanadyl species play an essential role in ensuring the effective NOx abatement for NH3-SCR. However, polymeric vanadyl would be conventionally deactivated by the poison of alkali metals such as potassium, and it still remains a great challenge to construct robust and stable vanadyl species. Here, it was demonstrated that a more durable dimeric VOx active site could be constructed with the assistance of triethylamine, thereby achieving alkali-resistant NOx abatement. Due to the rational construction of polymerization structures, the obtained TiO2-supported cerium vanadate catalyst featured more stable dimeric VOx species and the active sites could survive even after the poisoning of alkali metal. Moreover, the depolymerization of VOx was suppressed endowing the catalysts with more Brønsted and Lewis acid sites after the poisoning of alkali metal, which ensured the efficient NOx reduction. This work unraveled the effects of alkali metal on the polymerization state of active species and opens up a way to develop low-temperature alkali-resistant catalysts for NOx abatement.

Involvement of UDP-glucose pyrophosphorylase from Verticillium dahliae in cell morphogenesis, stress responses, and host infection.

UDP-glucose pyrophosphorylase (UGP, EC 2.7.7.9) is an essential enzyme involved in carbohydrate metabolism. In Saccharomyces cerevisiae and other fungi, the UGP gene is indispensable for normal cell development, polysaccharide synthesis, and stress response. However, the function of the UGP homolog in plant pathogenic fungi has been rarely explored during pathogenesis. In this study, we characterize a UGP homolog named VdUGP from Verticillium dahliae, a soil-borne fungus that causes plant vascular wilt. In comparison with wild-type strain V07DF2 and complementation strains, the VdUGP knocked down mutant 24C9 exhibited sensitivity to sodium dodecyl sulfate (perturbing membrane integrity) and high sodium chloride concentration (high osmotic pressure stress). More than 25 % of the conidia of the mutant developed into short and swollen hypha and formed hyperbranching and compact colonies. The mutant exhibited decreased virulence on cotton and tobacco seedlings. Further investigation determined that the germination of the mutant spores was significantly delayed compared with the wild-type strain on the host roots. RNA-seq analysis revealed that a considerable number of genes encoding secreted proteins and carbohydrate-active enzymes were significantly downregulated in the mutant at an early stage of infection compared with those of the wild-type strain. RNA-seq data indicated that mutation affected many Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways both in the pathogen and in the inoculated plants at the infection stage. These alterations of the mutant in cultural phenotypes, virulence, and gene expression profiles clearly indicated that VdUGP played important roles in fungal cell morphogenesis, stress responses, and host infection.