The Nature of Zeolite Catalytic Sites

<p>The nature of zeolite catalytic sites was studied by observing their interactions with sorbants. In situ FTIR studies of a range of sorbants on H+ZSM-5, H+mordenite and H+Y showed that the zeolite Bronsted proton was transferred towards the sorbant. Sorbants could be placed in three classes depending on the type of hydrogen bond formed. "Class A" sorbants were alcohols, alkanes, ammonia, amines and carboxylic acids and showed a single v0-H band shifted from the vO-H of the zeolite. The shift in vO-H increased with increasing proton affinity of the sorbant. "Class B" sorbants were alkenes and aromatics and showed a resultant broad, flat vO-H due to bonding through the t electrons of the double bond or aromatic ring. "Class C" sorbants included water, ethers, ketenes, aldehydes, nitriles and carboxylic acids (also Class A). They showed extremely broad hydroxyl bands from -3700 to -1200 cm-1 with several maxima. Bonding was through oxygen or nitrogen lone electron pairs. A novel, low temperature (-400 [degrees] C), reaction of acetic acid to ketene was observed over alkali-exchanged zeolites. Thermal desorption/mass spectrometry, mini-reactor mass spectrometry and in situ FTIR techniques were used to investigate the products obtained by varying the carboxylic acid and the catalyst, and the reaction mechanism.</p>

The Nature of Zeolite Catalytic Sites

<p>The nature of zeolite catalytic sites was studied by observing their interactions with sorbants. In situ FTIR studies of a range of sorbants on H+ZSM-5, H+mordenite and H+Y showed that the zeolite Bronsted proton was transferred towards the sorbant. Sorbants could be placed in three classes depending on the type of hydrogen bond formed. "Class A" sorbants were alcohols, alkanes, ammonia, amines and carboxylic acids and showed a single v0-H band shifted from the vO-H of the zeolite. The shift in vO-H increased with increasing proton affinity of the sorbant. "Class B" sorbants were alkenes and aromatics and showed a resultant broad, flat vO-H due to bonding through the t electrons of the double bond or aromatic ring. "Class C" sorbants included water, ethers, ketenes, aldehydes, nitriles and carboxylic acids (also Class A). They showed extremely broad hydroxyl bands from -3700 to -1200 cm-1 with several maxima. Bonding was through oxygen or nitrogen lone electron pairs. A novel, low temperature (-400 [degrees] C), reaction of acetic acid to ketene was observed over alkali-exchanged zeolites. Thermal desorption/mass spectrometry, mini-reactor mass spectrometry and in situ FTIR techniques were used to investigate the products obtained by varying the carboxylic acid and the catalyst, and the reaction mechanism.</p>

PREPARATION AND CHARACTERISATION OF NEW BIOMATERIALS BASED ON CHITOSAN IODIDE WITH BIOLOGICALLY ACTIVE DYES

New composite materials were obtained based on chitosan iodide and organic dyes – methylene blue and fuchsine in fucorcin (Castellani liquid) – by using a simple synthetic procedure. The materials were characterised by scanning electron microscopy, X-ray diffraction, temperature-programmed desorption mass spectrometry, infrared spectroscopy and visible and ultraviolet light spectroscopy. The dyes in the composites were distributed uniformly and did not form separate phases. These composites could form structured porous sponges and films and therefore be used in various fields of application. The materials displayed antibacterial activity against antibiotic resistant gram-positive and gram-negative bacteria.

Probing the Formation of Isolated Cyclo-FF Peptide Clusters by Far-Infrared Action Spectroscopy

Small cyclic peptides containing phenylalanine residues are prone to aggregate in the gas phase into highly hydrophobic chains. A combination of laser desorption, mass spectrometry and conformational selective IR-UV action...

Plasma-desorption mass spectrometry as an express diagnostic test for bovine leukaemia

Plasma-desorption mass spectrometry with ionization of 252Californium fission fragments (252Cf-PD MS) was used to develop an express diagnostic test for bovine leukaemia. The test is based on the mass spectrometric parameters of artificial lipid membranes formed on the gold substrate from the lipid fraction of blood cells (mainly lymphocytes), by the self-assembly technique according to the biomimetic principle. Mass spectrometric analysis of artificial lipid membranes obtained from blood plasma of control and leukemic cattle gave a reliable diagnosis of leukaemia. The basis for the diagnosis were the ionization parameters of the fragmentation of lipid molecules from normal and leukemic cell membranes. In leukemic cell membranes, separate dense areas (rafts) 200 – 300 nm in diameter, saturated with cholesterol and phospholipids, are formed. The number of rafts per unit of cell membrane of leukemic cells significantly exceeded the permitted parameters of normal cell membranes. The increased number of rafts in artificial membranes formed in the membranes of leukemic cells was reliably reflected in mass spectra, due to the 180 – 250% increase in intensity of peaks of cholesterol fragment ions in comparison to control cells.