The nature of active acid sites of zeolite H-BEA with different Si/Al ratios (15-407) in liquid phase etherification of isobutylene with ethanol in a continuous flow reactor in the temperature range 80-180 °C has been explored. We describe and discuss data concerning the strength and concentration of acid sites of H-BEA obtained by techniques of stepwise (quasi-equilibrium) thermal desorption of ammonia, X-ray diffraction, low-temperature adsorption of nitrogen, FTIR spectroscopy of adsorbed pyridine and solid-state Al MAS NMR. The average values of the adsorption energy of NH on H-BEA were experimentally determined as 63.7; 91.3 and 121.9 mmol g (weak, medium, and strong, respectively). In agreement with this, a correlation between the rate of ethyl--butyl ether synthesis and the concentration of weak acid sites ( = 61.6-68.9 kJ mol) has been observed. It was concluded that the active sites of H-BEA for this reaction are Brønsted hydroxyls representing internal silanol groups associated with octahedrally coordinated aluminum in the second coordination sphere.
Download full-text PDF |
Source |
|---|---|
| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9074949 | PMC |
| http://dx.doi.org/10.1039/c9ra07721a | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Lysine succinylome analysis of MRSA reveals critical roles in energy metabolism and virulence.
Lett Appl Microbiol
January 2025
Clinical Laboratory, Huzhou Central Hospital, Affiliated Central Hospital of Huzhou University, Fifth School of Clinical Medicine of Zhejiang Chinese Medical University.
MRSA's resistance poses a global health challenge. This study investigates lysine succinylation in MRSA using proteomics and bioinformatics approaches to uncover metabolic and virulence mechanisms, with the goal of identifying novel therapeutic targets. Mass spectrometry and bioinformatics analyses mapped the MRSA succinylome, identifying 8 048 succinylation sites on 1 210 proteins.
View Article and Find Full Text PDFFrom Natural Product Derivative to Hexagonal Prism Supermolecule: Potent Biofilm Disintegration, Enhanced Foliar Affinity, and Effective Management of Tomato Bacterial Canker.
Angew Chem Int Ed Engl
January 2025
Guizhou University, State Key Laboratory of Green Pesticide, Center for Research and Development of Fine Chemicals, Huaxi, 550025, Guiyang, CHINA.
Clavibacter michiganensis (Cmm), designated as an A2 quarantine pest by the European and Mediterranean Plant Protection Organization (EPPO), incites bacterial canker of tomato, which presently eludes rapid and effective control methodologies. Dense biofilms formed by Cmm shield internal bacteria from host immune defenses and obstruct the ingress of agrochemicals. Even when agrochemicals disintegrate biofilms, splashing and bouncing during application disperse active ingredients away from target sites.
View Article and Find Full Text PDFRecombinant Expression of a New Antimicrobial Peptide Composed of hBD-3 and hBD-4 in Escherichia coli and Investigation of Its Activity Against Multidrug-Resistant Bacteria.
Probiotics Antimicrob Proteins
January 2025
State Key Laboratory of Pathogen and Biosecurity, Academy of Military Medical Sciences, No. 20 Dongda Street, Beijing, 100071, Fengtai District, China.
Human β-defensin (HBD) has been recognized as a promising antimicrobial agent due to its broad-spectrum antimicrobial activity against various pathogens. In our previous work, we engineered a chimeric human β-defensin, designated H4, by fusing human β-defensin 3 and human β-defensin 4, resulting in enhanced antimicrobial activity and salt stability. However, the high cost of chemical synthesis due to the relatively large number of amino acids in H4 has limited its applications.
View Article and Find Full Text PDFSAMHD1 shapes deoxynucleotide triphosphate homeostasis by interconnecting the depletion and biosynthesis of different dNTPs.
Nat Commun
January 2025
Department of Biochemistry and Structural Biology, UT Health San Antonio, San Antonio, TX, USA.
SAMHD1 is a dNTPase that impedes replication of HIV-1 in myeloid cells and resting T lymphocytes. Here we elucidate the substrate activation mechanism of SAMHD1, which involves dNTP binding at allosteric sites and transient tetramerization. Our findings reveal that tetramerization alone is insufficient to promote dNTP hydrolysis; instead, the activation mechanism requires an inactive tetrameric intermediate with partially occupied allosteric sites.
View Article and Find Full Text PDFTandem Reaction on Ru/Cu-CHA Catalysts for Ammonia Elimination with Enhanced Activity and Selectivity.
Environ Sci Technol
January 2025
State Key Joint Laboratory of Environment Simulation and Pollution Control, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
Ammonia emissions from vehicles and power plants cause severe environmental issues, including haze pollution and nitrogen deposition. Selective catalytic oxidation (SCO) is a promising technology for ammonia abatement, but current catalysts often struggle with insufficient activity and poor nitrogen selectivity, leading to the formation of secondary pollutants. In this study, we developed a bifunctional Ru/Cu-CHA zeolite catalyst for ammonia oxidation, incorporating both SCO sites (Ru) and selective catalytic reduction sites (SCR, Cu).
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!