Selective oxidation catalysis over manganese and tungsten based oxide catalysts
File(s)
Author(s)
Peng, Senpei
Type
Thesis
Abstract
Catalytic oxidation plays a vital role in the industrial synthesis of organic chemical products. The imperative for a transition to more sustainable and economical manufacturing has prompted extensive research in heterogeneous catalysis for selective oxidation. Selective oxidation of cyclohexane is a key reaction in the polymer industry for the manufacture of the intermediates for some Nylon fibres. Metal oxide based catalysts have displayed great potential in catalysing this reaction. However, the effects of syntheses and catalyst surface properties on the catalyst activity were not sufficiently discussed in the literature. This study investigates the effects of initial synthesis pH on the catalytic activity and surface site properties of nanostructured MnWO4. Surface sites with varying acidic and redox properties are probed by 2-propanol TPD, potentially associated with Mn and W species. The relative abundance of the sites and surface defects are found to be correlated with catalyst initial synthesis pH. Different types sites are found to exhibit distinct activity in contributing steps of the reaction, suggesting that metal oxides with a combination of acidic and redox sites could exhibit robust catalytic activity in similar reactions. Based on these, other related metal oxide catalysts and their promotion are studied, of which the Ce-Mn-W based mixed oxides showed considerable catalytic performance. The activity of the MnWO4 and related single oxides is also studied in cyclooctene epoxidation and continuous gas phase oxidation reactions. In the epoxidation of cyclooctene, the catalysts exhibited activity predominantly in the initiation stage of the reaction. In the continuous gas phase reactions, the catalysts did not exhibit the expected activity in the oxidation of cyclohexane, whereas catalytic activity and selectivity showed systematic variations in the oxidation of cyclohexanol.
Version
Open Access
Date Issued
2024-01-15
Date Awarded
2024-06-01
Copyright Statement
Attribution-NonCommercial 4.0 International Licence (CC BY-NC)
License URL
Advisor
Chadwick, David
Publisher Department
Chemical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)