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Vanadium phosphate oxide (VPO) catalysts derived from VOHPO 4 Á0.5H 2 O and VO(H 2 PO 4 ) 2 precursors showed improved rates in the catalysed liquid phase oxidation of p-cymene. Both catalysts showed high performance with conversions of up to 30% achieved within 3 h with a selectivity towards the tertiary cymene hydroperoxide (TCHP) of 75-80% when compared to lower conversions and poorer TCHP selectivity in the non-catalysed industrial oxidation processes that takes about 8-12 h reaction time. The temperature dependent structural changes during activation within the catalysts were studied by in situ XRD and TGA-MS. The in situ XRD showed that the VO(H 2 PO 4 ) 2 form mainly an amorphous phase at temperature up to 600°C while above 650-750°C a stable VO(PO 3 ) 2 phase was obtained. The in situ XRD studies of the (VO) 2 P 2 O 7 phase derived from VOHPO 4 Á0.5H 2 O showed to became more crystalline with increasing temperature from 400 to 750°C. No formation of VOPO 4 phases were observed in the activated (VO) 2 P 2 O 7 catalyst even at high temperature under the in situ XRD conditions.

Mechanistic proposals and predictions made in a preceding paper (Part A) were evaluated by carrying out the catalytic air oxidation of p-cresol in an alternative solvent system, comprising either a mixture of ethylene glycol and acetic acid (for oxidations under acidic conditions) or ethylene glycol and water (for oxidations under basic conditions). The results obtained in these experiments confirmed that ethylene glycol acts as a nucleophile in these solvent systems, thereby stabilizing the quinomethide intermediate and resulting in highly efficient oxidations in both alkaline and acidic media. 4-Hydroxybenzaldehyde, the desired product, was thus obtained in isolated yields of up to 98% and purities >99%. The inherent drawbacks associated with alkaline methanol and aqueous acetic acid solutions were thus circumvented, and the result is a highly efficient process for the production of 4-hydroxybenzaldehyde.

Trialkoxysilanes were synthesized in a packed bed flow tubular reactor by the reaction of silicon and alcohol in the presence of a variety of copper catalysts. The effect of key parameters, which affect the silicon conversion rates and selectivity for the desired trialkoxysilanes, were investigated and optimized using ethanol as the model reagent. The study was extended to the other alcohols namely methanol, n-propanol, and n-butanol. Copper catalysts which were tested in the alkoxylation reaction included CuCl, Cu(OH) 2 , CuO, and CuSO 4 ; with CuCl showing the most activity while the uncatalysed reaction resulted in negligible reaction rates. High temperature catalyst preheating (>500 °C) resulted in a lower rate of reaction than when lower temperatures were used (<350 °C). The optimum reaction temperature range and alcohol flow rate were 230−240 °C and 0.1 mL/min, respectively. The reaction was deduced to be best described by the first-order kinetic model. The effect of alcohol (C1− C4) on the reaction revealed that conversion and selectivity generally decrease with an increase in carbon chain length. Ethanol showed the highest selectivity (97%) and conversion (64%) as compared to other alcohols studied, showing that it was the most efficient and stable alkoxylation alcohol for this reaction.