Molecular spectroscopic studies of the effect of base oils on additive—additive interactions

Abstract

The effect of different types of base oil of API Groups I to V, such as mineral based (solvent refined, hydrofinished, hydro‐cracked/ wax isomerised) and synthetic based (polyalphaolefin and ester), on the interaction of zinc dialkyldithiophosphate (ZDDP) with polyisobutylene succinimide (PIBS) has been studied by variable‐temperature (VT) IR and 31P NMR spectro‐scopic techniques. Since ZDDPs are known to exist in monomeric and polymeric forms and as neutral and basic salts, and their functioning is temperature dependent, the structural changes observed in the NMR and IR spectra of the ZDDP—PIBS system in different base oils have been addressed with this in mind. The strength and composition of ZDDP—PIBS complexes has been explained in terms of the degree of solvation provided by the medium (base oil) in which they are present, and thermodynamic parameters ΔH and ΔS estimated from the VT IR spectra. The results indicate that the complexes are stronger and stable in polar base oils, such as from Groups I and V. The equilibrium shifts towards the neutral form of ZDDP in polar base oils. The results have been substantiated by correlating the variation in the shift and width of IR and 31P NMR signals to the stability of the complexes and low values of ΔH and ΔS. Polar solvents, such as methanol and tetrahydro‐furan, also favour the formation of the neutral form of ZDDP and stronger complexes between PIBS and ZDDP, in a manner similar to that observed for polar base oils.

Estimation of Total Aromatic Content of Vacuum Gas Oil (VGO) Fractions (370−560 °C) by 1H NMR Spectroscopy

“…2D HSQC (Edited) (Heteronuclear Single Quantum Coherence) Experiments and DEPT-135 Spectra Recording. The DEPT spectral recordings were conducted, in accordance with the procedure given in the work of Sarpal and co-workers. − The 2D HSQC (edited) spectra were obtained by the pulse sequence and program reported by Davis…”

“…As a part of long drawn program in our laboratory, in regard to the development of analytical methods based on NMR spectroscopic technique for various petroleum fractions, − ,− a new 1 H NMR based method has been proposed for the hydrocarbon-type analysis of VGO fractions (370−560 °C). The refiners for process optimization and catalyst selection, and for assessing the quality of the end product, require the hydrocarbon group-type composition of VGOs.…”

Formulating lubricating oils

“…The stability of the additive package is quite different from that of the additives on their own. ZDDP is well known to interact with most other additives employed in engine oil formulations, such as detergents (metal sulphonates/phenates) [43,80,82], AW/EP ashless dialkyldithiophosphate or its amine salts [83], succinimide-based dispersants (PIBS) [83] and MoDTC [81]. In particular, ZDDPs, once used extensively as anti-wear additives and antioxidants in automotive lubricants, strongly inhibit iron-catalysed oxidations, but their activity is greatly reduced in the presence of basic additives (e.g.…”

“…With the introduction of better quality and environmentally friendly base oils (API Groups II to IV), the study of additive-additive interactions has gained in practical importance due to the entirely different types of behaviour shown by formulations prepared using these base oils [43,82,83]. More systematic studies on the effect of base oils on interaction behaviour is important in relation to the development of additives that will have better compatibility and show improved performance, in particular in the more polar vegetable based oils.…”