The catalytic cracking of n‐alkenes on ZSM‐5 zeolite at 405°C can occur both by a monomolecular mechanism and a bimolecular process. In the latter, cracking is preceeded by dimerization. We show that pentenes are cracked exclusively by the bimolecular process. The dominant cracking mechanism for n‐hexenes also requires initial dimerization, although a small proportion (<19%) of the total cracking may proceed by a monomolecular process. Cracking of n‐heptenes is predominantly monomolecular, with only 13% of the total occurring via an initial dimer formation. The cracking of n‐octenes and n‐nonenes can be interpreted by assuming a monomolecular mechanism only. Thus it appears that at 405°C olefins smaller than C6 are stable with respect to direct cracking and must dimerize before a species is formed which is unstable enough to crack. No molecular hydrogen was produced in any of the cracking reactions reported here in the range of conversions studied.

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The reaction of cyclopentane has been studied on HY zeolite at 500°C. Initial reaction processes included ring cleavage to acyclic C5 species, and cracking to produce fragments in the range C1 ‐ C4. Hydrogen transfer accompanied those processes, so that paraffins as well as olefins were observed as initial products. Cyclopentene was formed as an unstable initial product by the dehydrogenation of the feed, although molecular hydrogen was not found as a primary product. Other dehydrogenated species initially formed included coke and aromatics in the range C6 ‐ C10.

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An examination of previously reported kinetic expressions describing peroxide bleaching of wood pulp under alkaline conditions reveals that the overall process can be considered as a combination of two parallel reaction routes. The first route corresponds to a reaction involving direct participation of the perhydroxyl anion in chromophore elimination. This mechanism can be identified with the classical explanation for peroxide bleaching. The second route can be associated with reactions in which chromophores are eliminated through the action of free radical intermediate species. New experimental evidence is presented to show that processes catalysed by transition metal ions can lead to enhancement of bleaching.A two stage peroxide bleaching sequence, initially under acidic conditions in the presence of chromium, followed by alkaline conditions produces an acceleration in bleaching rate, without significant additional consumption of peroxide.

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