Speciation Detection Deciphering C₂H₂/Cl-Driven Mercury Escape Mechanisms in PVC Production

Area of Science:

• Environmental Chemistry
• Chemical Engineering
• Materials Science

Background:

• Mercury emissions from polyvinyl chloride (PVC) production present significant environmental concerns.
• Existing methods struggle to quantify mercury speciation in reactive C2H2/HCl atmospheres.

Purpose of the Study:

• To develop and validate an advanced operando mercury speciation platform for PVC production.
• To mechanistically investigate mercury emission pathways and quantify mercury loss.

Main Methods:

• Optimization of the Ontario Hydro method (OHM) to create the PVC-OHM platform.
• Simultaneous real-time detection of elemental mercury (Hg0) and divalent mercury (Hg2+) with high sensitivity.
• Mechanistic investigation of mercury escape pathways under industrially relevant conditions.

Main Results:

• The PVC-OHM platform achieved high sensitivity (0.12 μg/m3) for Hg0 and Hg2+ detection.
• Identified three dominant mercury escape pathways: thermal desorption (80% of total Hg loss), C2H2-driven reductive decomposition, and chlorine adsorption-induced desorption.
• Quantified significant mercury loss (3.08 mg Hg0 and 9.01 mg Hg2+ per gram of catalyst) linked to thermal gradients (250-300 °C).

Conclusions:

• Established the first experimentally validated framework for mercury fate prediction in carbide-based PVC synthesis.
• Highlighted the critical role of localized thermal gradients in mercury emissions.
• Proposed actionable strategies for emission control, including hotspot mitigation and coordination environment optimization.