Authors:

Isabel C St

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Bronsted acidic catalysts such as zeolites are used in industry to produce transportation range fuels and feedstock compounds using light olefins. However, rapid deactivation, occlusion of micropores, dealumination, and changing active site concentrations are major challenges of zeolites needing to be addressed. Coordinatively unsaturated Lewis acidic Aluminum ions can oligomerize olefins like other Lewis acidic catalysts such as Gallium, Zinc, and Nickel with higher turnover rates. Crabtree et al. postulated that Aluminum's higher positive charge density allows electron rich carbon-carbon double bonds of olefins to easily coordinate onto active sites. Currently, the reactions rate for Aluminum based catalysts plateau in activity around weight loadings of 0.3wt% due to the formation of inert clusters of Aluminum on the surface of the commercial silica, indicating that commercial silica supports a small number of active sites. Synthesizing the Aluminum catalyst using tetraethyl orthosilicate (TEOS) and aqueous Aluminum creates more active sites from higher dispersion of metal on the surface of the silica. This synthesis method consists of combining Aluminum nitrate into acidic solution, adding TEOS while mixing and polymerizing the solution overnight. The catalyst is then calcined at high temperatures to eliminate residual compounds. Propylene oligomerization is performed using a fixed bed reactor and product gas stream is analyzed using a gas chromatograph. We hypothesize that increased acid concentration during synthesis will create more silanol sites for Aluminum bonding. Reaction rates are expected to increase with weight loading of Aluminum, predicted conversion will correlate linearly with trend line established from lower weight percentages. Keywords: Aluminum; Heterogeneous Catalysts; Silica Synthesis; High Dispersion; Propylene Oligomerization

Source:

Purdue University / 2025

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Co-authors:

Isabel C St