Comprehensive characterization of engine deposits from fuel containing MMT

Area of Science:

• Materials Science
• Analytical Chemistry
• Combustion Engineering

Background:

• Organometallic additives are used in fuels to prevent engine knocking.
• Understanding the composition of combustion chamber deposits is crucial for engine performance and longevity.
• Methylcyclopentadienyl manganese tricarbonyl (MMT) is a common organometallic antiknock additive.

Purpose of the Study:

• To characterize the morphology and chemical composition of combustion chamber deposits.
• To investigate the impact of methylcyclopentadienyl manganese tricarbonyl (MMT) on deposit formation.
• To identify specific manganese-containing compounds within the deposits.

Main Methods:

• Scanning Electron Microscopy (SEM) for morphology.
• Energy Dispersive X-ray Spectroscopy (EDX) for bulk chemical composition.
• Glow-Discharge Mass Spectrometry (GDMS) for bulk composition.
• X-ray Diffraction (XRD) for crystalline structure.
• X-ray Photoemission Spectroscopy (XPS) and X-ray Photoabsorption Spectroscopy (XAS) for surface analysis and speciation.

Main Results:

• Deposits contained a mixture of calcium sulfate, manganese phosphate, and manganese oxide in the bulk.
• The surface of the deposits showed a composition of manganese sulfate, manganese phosphate, and manganese oxide.
• SEM and EDX provided insights into the physical structure and elemental makeup of the deposits.

Conclusions:

• The organometallic additive methylcyclopentadienyl manganese tricarbonyl (MMT) contributes manganese compounds to combustion chamber deposits.
• Both bulk and surface analyses reveal the presence of various manganese species, indicating complex deposit chemistry.
• The findings aid in understanding the behavior of MMT in engines and its contribution to deposit formation.