Liquid P31 Studies - NMR Testing Laboratory

Phosphorus NMR Investigations of Zinc Dithiophosphate Anti-Wear Agents

Liquid-state ³¹P NMR can be used to determine the chemistry changes in Zinc dithiophosphate (ZnDTP) additives present in lubricant oils as anti-wear agents. These studies allow the determination of exact phosphorus chemistry quantification allowing observation of dimerized and monmer ZnDTP, the effects of alkyl group substitution as well as presence of overbasing and glycolization can readily be observed. Breakdown/oxidation products such as phosphate or partially oxidized DTP can be readily observed. This type of analysis is useful in assessing the state of anti-wear agent technology after exposure to different operational conditions in engines or industrial application.

These types of analyses can also be applied to molybdenum based anti-wear agents such as MoDTC and MoDTP.
Liquid-state NMR of phosphorus species is extremely applicable to many homogeneous catalysis applications and yields valuable information on active component availability.

Below is some information on the chemical shift ranges of interest as well as some example spectra of the degradation of a ZnDTP over time at 185C

Chemical Shift Ranges for ³¹P NMR Studies of ZnDTP’s

Shift (ppm)	Phosphorus Species
105 – 120	ZnDTP Dimer
95 – 105	ZnDTP Monomer
90 – 95	DTP
70 – 50	O₃P=S
50 – 20	O₂SP=O
20 to – 120	PO₄