Periodic Reporting for period 1 - Pores4Olefins (Engineering Pores for Sustainable Catalytic Olefins Upgrading)
Período documentado: 2021-07-01 hasta 2023-06-30
The research project of this fellowship deals with chemical reactions to upgrade alkenes (hydrocarbons with carbon-carbon double bonds; also known as olefins). Reactions that allow to form new carbon-carbon bonds highlight within those that involve alkenes to obtain value-added chemicals. For instance, metathesis reactions of alkenes enable to create new molecules by breaking and rearranging carbon-carbon double bonds of the initial alkenes, and the dimerization and hydrorylation of alkenes allow carbon-carbon coupling of two molecules to yield one heavier molecule. Currently, all of these reactions are paramount, taking place at industrial scale, for the production of a plethora of chemicals, ranging from small alkenes used in the manufacturing of plastics and polymers to alkylbenzenes used for the synthesis of detergents. These reactions are carried out in the industry in the presence of catalysts (chemical substances other than reactants that make possible, or help, the reaction to happen without entering into the final products). Nevertheless, in most of the cases, although the processes are practical from an industrial point of view, the knowledge about how the reactions occur is still very poor. Increasing the understanding of these reactions is therefore key in order to lead to new catalytic processes that are not only more economically efficient but also environmentally friendly (less energetically demanding, avoiding or forming less side-products and residues, using non-toxic catalysts, etc.). Following this line, this project of fundamental research is focused on gaining new knowledge regarding the heterogeneous catalyzed metathesis, dimerization, and hydroarylation of alkenes. The research is mainly centered in better understanding which are, and how they are formed, the active sites that catalyze these reactions. With the benefit of this knowledge, it will be able to develop new catalysts and processes able to do these types of reactions more efficiently and even to perform more than one of these reactions in one single stage (tandem catalysis). Particularly, in this research the metathesis and dimerization reactions of light alkenes (ethylene, propylene, butylene) are studied in order to lead to a single stage process for the production of propylene from ethylene using catalysts based on molybdenum and nickel. Developing new routes for the production of propylene is very interesting because, with the current demand of propylene, the existing technologies would not meet the market needs in the following decades. The alkene hydroarylation catalyzed by nickel or cobalt is also examined for the production of linear alkylbenzenes that might be used, especially, for the synthesis of more biodegradable surfactants and detergents. Furthermore, the deeper understanding of these reactions is required to develop new efficient processes for the upgrading of platform molecules obtained from biomass feedstock, which are molecules more complex (with carbon-carbon double bonds and oxygen content) than those obtained from fossil resources that are ubiquitously found in the current chemical industry.
The work done on the research project during the outgoing phase of this fellowship was focused on the alkene metathesis reaction, particularly, on the propene metathesis catalyzed by molybdenum-based materials. Different catalysts were used, changing the molybdenum content and the preparation methods for those catalysts. Thermal and chemical pretreatments of the catalysts were done with different molecules, which allow to gain new knowledge on the formation of the active sites for the alkene metathesis reaction. Kinetic measurements enable to understand the reaction network (elementary steps) of the reaction and the distribution of the reaction intermediates on the active sites. A reaction model consistent with the kinetic measurements and elementary steps was developed with the benefit of the understanding of the reaction.
This research has contributed to deepen into the understanding of the nature and formation of the alkene metathesis active sites and the reaction pathways (elementary steps). Following a similar approach for the other two reactions considered in this research (dimerization and hydroarylation of alkenes), it is expected that this work would enable to increase the knowledge of these reactions, ultimately, allowing to develop a strategy for the production of propylene from ethylene in a single stage process through tandem catalysis, and to synthesize selective catalysts for the production of linear alkylbenzenes. The knowledge that will be obtained from this fundamental research could encourage other applied research projects that would allow the improvement of current catalytic processes used in the industry as well as the emergence of new catalytic processes for the production of many chemicals complying with more environmentally friendly practices as demanded by the society.