High-performance ring-opening catalysts based on iridium-containing zeolite Beta in the hydroconversion of decalin

Decalin was converted in a flow-type reactor under a hydrogen pressure of 5.2 MPa on Ir/H,A-Beta zeolite catalysts, where A stands for an alkali metal cation. In one series of catalysts, the Ir content was 3 wt.%, and the nature of A was varied from lithium to cesium. In a second series, the iridium content in Ir/H,Cs-Beta was varied from 1 to 5 wt.%. On some of these catalysts, open-chain decanes (OCDs) were formed with unprecedented selectivities and yields of up to 47 and 44%, respectively. The term “High-Performance Ring-Opening Catalysts” (HIPEROCs) was defined. Evidence is presented for hydrogenolysis on the metal being the main ring-opening mechanism on HIPEROCs. The main function of the Brønsted-acid sites is a mild isomerization of six-membered into five-membered naphthenic rings which are much easier to open by hydrogenolysis. Valuable mechanistic information can be deduced from the carbon-number distributions and the naphthenes vs. alkanes content of the hydrocracked products (C9-).

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► Open-chain decanes were made from decalin with unprecedented yields up to 44%.
► The acid strength of the Ir/Beta catalyst was tuned by exchange with alkali cations.
► The term high-performance ring-opening catalysts (HIPEROCs) was introduced.
► The main mechanism of ring opening on HIPEROCs is hydrogenolysis on the metal.
► A detailed reaction scheme was advanced for selective ring opening on HIPEROCs.