Photooxidation of cyclohexene in the presence of SO₂: SOA yield and chemical composition

Secondary organic aerosol (SOA) formation from a cyclohexene ∕ NOx system with various SO2 concentrations under UV light was investigated to study the effects of cyclic alkenes on the atmospheric environment in polluted urban areas. A clear decrease at first and then an increase in the SOA yield was found with increasing SO2 concentrations. The lowest SOA yield was obtained when the initial SO2 concentration was in the range of 30–40 ppb, while higher SOA yield compared to that without SO2 could not be obtained until the initial SO2 concentration was higher than 85 ppb. The decreasing SOA yield might be due to the fact that the promoting effect of acid-catalysed reactions on SOA formation was less important than the inhibiting effect of decreasing OH concentration at low initial SO2 concentrations, caused by the competition reactions of OH with SO2 and cyclohexene. The competitive reaction was an important factor for SOA yield and it should not be neglected in photooxidation reactions. The composition of organic compounds in SOA was measured using several complementary techniques including Fourier transform infrared (FTIR) spectroscopy, ion chromatography (IC), and Exactive Plus Orbitrap mass spectrometer equipped with electrospray interface (ESI). We present new evidence that organosulfates were produced from the photooxidation of cyclohexene in the presence of SO2.

Zeolites for Fine Chemical Production State of Art and Perspectives

The paper analyses the role of catalysis and that of renewable resources in the frame of a sustainable development. The possible uses of natural feedstocks for chemical production and the application of catalytic<br />methods to their transformations are reviewed, with emphasis on carbohydrates and vegetable oils and on zeolite catalysts, respectively. The problems arising from the embedment of active sites on the catalyst<br />surface are discussed, with the aid of specific examples taken from oxidation and acid catalysed reactions.

Methanal Extrusion in ipso-Substitution Reactions of Hydroxymethylindoles

A range of 3-hydroxymethylindoles undergo acid-catalysed reactions involving ipso-electrophilic substitution with the extrusion of methanal and the formation of diindolylmethane moieties. Both inter- and intramolecular processes lead to macrocyclic compounds 10 and 14.

Non-covalent immobilisation of p-toluenesulfonic acid in a porous molecular crystal for size-specific acid-catalysed reactions

A porous molecular crystal non-covalently immobilising p-toluenesulfonic acid in the nanochannels serves as a size-specific heterogeneous acid catalyst.

Acid-catalysed carboxymethylation, methylation and dehydration of alcohols and phenols with dimethyl carbonate under mild conditions

Dimethyl carbonate (DMC) chemistry has been extended to include acid-catalysed reactions of different aliphatic alcohols and phenols.

Oxidomolybdenum complexes for acid catalysis using alcohols as solvents and reactants

With ethanol as solvent and reactant, a molybdenum (pre)catalyst promotes selective acid-catalysed reactions. Depending on the conditions, the MoVIcomplex is converted to MoVIoxidoalkoxido, MoVoxido-bridged dinuclear, and MoVIoctanuclear complexes.