Application of Atomic Layer Deposition on Industrial Catalyst
Improved Catalyst Selectivity and Longevity for Propane Dehydrogenation Using Atomic Layer Deposition
Propylene is regarded as a crucial chemical building block in the chemical industry and currently is produced primarily through either steam or fluidized catalytic cracking. However, these two commercial approaches do not meet the current or future global demands for propylene. With the price of propane at historic lows due to the availability of propane from shale gas, propane dehydrogenation (PDH) processes such as OleflexTM from UOP which utilizes a highly active and selective supported platinum catalyst have become economically attractive. However, at the high temperatures of PDH, the stability of platinum catalysts can be limited by sintering of the platinum nanoparticles. Pt sintering results in lower propane activity and selectivity. The goal of this project is to overcome catalyst degradation issues via atomic layer deposition (ALD) overcoating technology, which deposits protective layers over and around the active metal, preserving catalyst integrity under reaction conditions.
In this project, industrial 1/16″ alumina extrudates were used as catalyst support. To investigate the optimal extrudates surface area and porosity for catalyst performance and ALD overcoating efficiency, the extrudates were calcined at several temperatures. TiO2 ALD was utilized as probe material to show that the ALD precursor is able to penetrate the internal pores of the extrudates equally. The gradual decrease of chemisorbed H2 amount on Pt nanoparticles with addition of the Al2O3 ALD cycles shows a very good control of layer-by-layer deposition. The similarity of the propane conversion for each catalyst after ALD overcoating shows the Al2O3 preferentially deposited on less active Pt sites for PDH reaction. The ALD overcoated catalyst shows improved performance in terms of resistance to sintering and appears to be optimized after five to ten ALD cycles. The selectivity to propylene is also increased as the number of ALD cycles.