A high-throughput reactor array applied to the parameter exploration of copper-exchanged zeolites for dilute methane oxidation

Abstract

Methane abatement through thermocatalysis could be a powerful tool to reduce sub-flammable methane emissions. Copper-doped zeolites are cost-effective, earth-abundant alternatives to platinum group metal catalysts that have demonstrated oxidation of dilute methane (i.e., less than 1% CH₄). Optimization of these copper catalysts necessitates high-throughput experimentation to efficiently explore the complex parameter space governing catalyst activity and catalyst kinetics. Here, we designed, built, and demonstrated the use of a high-throughput reactor for heterogeneous catalysis (catalytic array for screening and high-throughput discovery (CASHD)). CASHD consists of eight reactors with individual temperature, flow, and effluent valve control. The system was used to screen 16 catalysts consisting of different zeolite frameworks (BEA, FER, MFI, and MOR) and copper loadings (1.8–5.0 wt%). The best performing zeolite catalyst tested, as measured by a light-off curve, was 4.3 wt% Cu MFI with a T₅₀ of 366 °C. The catalysts' kinetics were subsequently evaluated through an Arrhenius experiment. BEA catalysts, generally had higher activation energies, averaging to 119 ± 16 kJ mol⁻¹, than FER, MFI, and MOR which had average activation energies of 87 ± 4, 85 ± 7, and 94 ± 7 kJ mol⁻¹, respectively. Two in situ characterization techniques complemented these kinetic analyses: diffuse reflectance ultraviolet-visible spectroscopy to probe the catalyst surface and isotopic-abundance analysis to quantify the effluent gas. Such high-throughput experimentation as demonstrated on the CASHD system will enable better integration of computationally enhanced materials discovery with experimental validation, accelerating catalyst discovery for low-temperature methane abatement catalysts.