Product Probing and Microkinetic Modeling of Propane Partial Oxidation over Ni/SiO2 Catalyst

Catalytic partial oxidation (CPO) of hydrocarbons is a key method for producing hydrogen or syngas. To effectively design and optimize catalysts and operating conditions for enhanced hydrogen production while minimizing carbon deposition, it is crucial to understand the mechanisms of surface reactions and the complex interactions between surface and gas-phase reactions at the gas–solid interface. Nickel-based catalysts are particularly promising for industrial applications due to their cost-effectiveness and catalytic activity comparable to that of noble metals. In this study, CPO of propane was conducted over a Ni/SiO₂ catalyst in a packed bed reactor under 0.1 atm pressure, within a temperature range of 573–923 K, and at a C/O ratio of 1.0. Key gas-phase intermediates, including products and reactive intermediates like ethyl and allyl radicals, were detected and quantified using in situ synchrotron vacuum ultraviolet photoionization mass spectrometry coupled with molecular-beam sampling. To further explore the reaction kinetics, microkinetic modeling was employed to investigate both the surface and gas-phase reaction networks involved in propane CPO. A comprehensive surface mechanism was developed and integrated with a detailed gas-phase mechanism to simulate the experimental results. A matrix-based thermodynamic consistency verification method was proposed to ensure the thermodynamic consistency of the developed kinetic model. Rate of production and sensitivity analyses were employed to identify critical reactions and intermediates within the CPO reaction network, demonstrating that propane consumption is predominantly controlled by surface reactions. The study also confirmed the occurrence of both steam reforming and dry reforming during propane CPO, identifying key reaction pathways responsible for forming target products, hydrocarbons, and oxygenated intermediates.