Compositional and Mechanistic Studies of Cu-zeolites for the Direct Activation of Lower Alkanes

Abstract

Due to poor access and energy-intensive conversion reactions, large reservoirs of natural gas are underutilized. Natural gas and biogas mainly contain small and stable hydrocarbons (light alkanes) and could be a more sustainable resource in the nearest future for the chemical industry, compared to coal and oil. However, due to the stability of alkanes, it is notoriously difficult to make specific products, because, in a reaction, the products are usually more reactive, and unwanted by-products are formed. With the help of activity testing and multiple characterization techniques, we have obtained insight into a direct, but stepwise pathway to convert alkanes to functionalized products for the industry that is potentially less energy-demanding than the existing ones. The stepwise pathway proceeds over oxidized Cu ions anchored to porous materials (zeolites) that hinder the reactants and products from interacting. With this approach, there is almost no over-oxidation, although, the product yield per time from this reaction is low. Accordingly, our focus has been on exploring different parts of the reaction to understand the individual steps and how they can be improved. We have obtained more insight into the Cu speciation and found important activity relationships with both zeolite structure and Cu ion reducibility.