Feature ArticleDeactivation study of the hydrodeoxygenation of p-methylguaiacol over silica supported rhodium and platinum catalysts

- No direct link between carbon deposit and catalyst deactivation.
- Deactivation affected catalyst reactive site in different way changing the products selectivity.
- Steady state condition was achieved on the catalyst showing the highest carbon deposit.

Hydrodeoxygenation of para-methylguaiacol using silica supported Rh or Pt catalysts was investigated using a fixed-bed reactor at 300 °C, under 4 barg hydrogen and a WHSV of 2.5 h−1. The activity, selectivity and deactivation of the catalysts were examined in relation to time on stream. Three catalysts were tested: 2.5% Rh/silica supplied by Johnson Matthey (JM), 2.5% Rh/silica and 1.55% Pt/silica both prepared in-house. The Rh/silica (JM) showed the best stability with steady-state reached after 6 h on stream and a constant activity over 3 days of reaction. In contrast the other two catalysts did not reach steady state within the timeframe of the tests, with continuous deactivation over the time on stream. Nevertheless higher coking was observed on the Rh/silica (JM) catalyst, while all three catalysts showed evidence of sintering. The Pt catalyst (A) showed higher selectivity for the production of 4-methylcatechol while the Rh catalysts were more selective toward the cresols. In all cases, complete hydrodeoxygenation of the methylguaiacol to methylcyclohexane was not observed.

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