Real-Time Analysis of Cellulose Pyrolysis Using an Open-DIP-APCI Mass Spectrometry Method

Abstract Understanding the molecular pathways governing lignocellulosic biomass pyrolysis is critical for optimizing the production of renewable fuels and platform chemicals. However, conventional analytical approaches such as pyrolysis gas chromatography mass spectrometry (Py–GC/MS) remain largely limited to volatile and low-molecular-weight products providing restricted insights into early-stage pyrolysis chemistry. Here, we present a new device based on a modified direct-insertion probe (DIP) coupled with atmospheric pressure chemical ionization (APCI) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), for real-time molecular-level monitoring of cellulose and glucose fast pyrolysis. This new interface, termed open-DIP, incorporates an open capillary, with a controlled inert gas flow and in situ temperature monitoring. This setup enables the feedstock pyrolysis using the APCI source heater, with an adjusted residence time and consequently allows discrimination between primary and secondary thermal degradation pathways. For cellulose, these processes lead to the formation of anhydro-oligosaccharides, dehydration products, and secondary reaction species. Comparison with a cellulose bio-oil produced in a fluidized-bed pyrolysis reactor confirms that the open-DIP platform selectively captures early-stage pyrolysis products while minimizing secondary reactions. Overall, this approach provides a rapid, low-sample-consumption, and high-resolution analytical tool for probing fast pyrolysis chemistry and offers new opportunities for screening pyrolysis conditions and guiding biomass conversion strategies.