# Inhibition Effect and Mechanism of Phenolic Antioxidants on Coal Spontaneous Combustion

## TL;DR

This study shows that phenolic antioxidants, especially PG, can effectively prevent coal spontaneous combustion by delaying reactions and blocking oxygen.

## Contribution

A novel evaluation system and multiscale analysis reveal the superior performance of PG due to its three phenolic hydroxyl groups.

## Key findings

- PG increased the initial exothermic temperature by 21.7°C, the most among the tested antioxidants.
- PG treatment reduced coal's specific surface area and pore volume, enhancing its microstructural density.
- Quantum calculations confirmed that antioxidant-radical reactions are spontaneous and exothermic, with ·OH being the most reactive.

## Abstract

Coal spontaneous combustion is a major safety and environmental
concern in mining operations. This study systematically evaluated
three phenolic antioxidants (BHA, BHT, and PG) as promising inhibitors
through multiscale experiments and quantum chemical calculations.
Results showed that all antioxidants delayed the coal–oxygen
reaction by increasing characteristic temperatures and reducing heat
release. For instance, the initial exothermic temperature T2 was increased by 21.7 °C, 13.71 °C, and 5.02 °C for
PG, BHT, and BHA, respectively. A novel comprehensive evaluation system,
based on the coal spontaneous combustion risk coefficient (Cr) and destructive coefficient (Cd), identified PG as the
most effective inhibitor overall. Analyses via SEM and LTNA showed
that PG treatment reduced the coal’s specific surface area
and pore volume, leading to a densification of its microstructure.
This physical alteration contributes an additional oxygen-blocking
effect. EPR and in situ FTIR confirmed that these antioxidants act
as hydrogen donors, effectively quenching active free radicals (e.g.,
·OH, CH3·) and suppressing the conversion of
carbon-centered to oxygen-centered radicals, thereby terminating chain
reactions. Quantum chemical calculations corroborated that the reactions
between the antioxidants and key radicals are spontaneous and exothermic.
The reactivity order was determined as ·OH > CH3·
> Ar–CH2· > Ar–CH2–O·
> Ar–CH2–OO. These results elucidated
the
underlying structure–activity relationship: PG’s superior
performance is directly attributable to its three phenolic hydroxyl
groups, which provide a greater total radical scavenging capacity
compared to the single group in BHA or BHT. This study confirms that
PG is an efficient, low-cost, and environmentally friendly inhibitor
with strong potential to prevent coal spontaneous combustion, providing
a theoretical basis for its industrial application.