Effect of Zinc Dialkyl Dithiophosphate Replenishment on Tribological Performance of Heavy-Duty Diesel Engine Oil

Soot is the main contamination that affects oil performance and increases oil drain intervals in heavyduty engine oil. It is also believed that additive concentration in engine oil can be influenced due to additive depletion over time and additive adsorption on soot particles. To extend oil drain intervals and improve oil performance, filter manufactures explore removing the soot to a certain level and replenishing the consumed additives. Zinc Dialkyl Dithiophosphate (ZDDP) is one of the most favoured anti-wear additives that reacts very rapidly with rubbing surfaces to form tribofilm that reduce wear. In this study, the experimental work aims to investigate the effect of ZDDP replenishment on tribological performance in the existence of soot and after removing soot from heavy-duty used oil. The study reveals that reclaiming the used oil can be achieved by removing the soot to a certain level. The results demonstrate that the reclaimed oil after removing soot is still not as good as the fresh oil. This study proves that additive depletion, additive adsorption on soot and the decomposition of antiwear additive adversely influence the reclaimed oil performance. However, replenishing the consumed additive by adding a small amount of ZDDP helps to improve the reclaimed oil performance compared to a large amount of ZDDP which is required to re-gain the oil performance in the existence of soot.

Hydro-liquefaction of asphaltene catalyzed by molybdenum-nickel bimetallic catalysts in slurry bed

The aim of this study is to achieve the hydro-liquefaction of asphaltene for the production of liquid fuel. The oil soluble molybdenum catalysts, molybdenum dialkyl dithiophosphate, and nickel carboxylate precursor with different carbon chains, were synthesized. The catalysts were characterized by ICP-OES, TEM and XPS. Their catalytic performance for the hydro-liquefaction of asphaltene to liquid fuels was investigated in a slurry bed reactor by using decalin as hydrogen donor and dispersant. The results show that the bimetal catalytic system composed of molybdenum dialkyl dithiophosphate and caproic acid nickel produces more MoS2 and NiS x active species. The metal contents of which accounts for 81.8 and 81.0 wt% of the total amount of Mo and Ni, respectively, and thus exhibits the best catalytic performance among the catalysts studied. The liquid yield of the asphaltene hydrogenation over the bimetal catalyst is 84.6 wt%, which is much higher than that over other catalysts, and the coke content is only 8.6 wt% under the conditions of 1000 μg/g of total metal addition, 1:1 Mo/Ni metal mass ratio and 1:1 asphaltene/naphthalene mass ratio. The content of saturated and aromatic components in the liquid products of asphaltene hydrogenation of the bimetal catalyst system is 78.9 wt%, which is a high-quality liquid fuel component.

Tribological interaction of plasma functionalized CaCO3 nanoparticles with zinc and ashless dithiophosphate additives

Surface-modified CaCO3 nanoparticles, synthesized through plasma-enhanced chemical vapor deposition (PECVD), were employed to improve lubricant additive technology for internal combustion engines via reduction and/or replacement of additives, such as zinc dialkyl dithiophosphate (ZDDP), in engine oil. Various oil formulations were prepared with functionalized CaCO3 nanoparticles, in combination with ashless dialkyl dithiophosphate (DDP) and ZDDP at low concentrations of phosphorus. Tribological test results indicate synergistic interaction of functionalized CaCO3 nanoparticles with ZDDP and DDP, providing enhanced friction and wear performance under boundary lubrication. A comparative study of the tribo-surfaces morphology and chemistry was assessed via atomic force microscopy and X-ray absorption near-edge spectroscopy. Improved wear protection by functionalized CaCO3BM (borate and methacrylate coated) nanoparticles under boundary lubrication was attributed to the formation of calcium and boron-rich 50–80 nm thick tribofilms on the worn surfaces. XANES results revealed that plasma functionalized CaCO3 nanoparticles interact with ZDDP and DDP and participate in tribofilm formation through tribo-chemical reactions and metal cation supply to form stable and wear-resistant tribofilms. These results provide strong support for the potential application of plasma functionalized CaCO3 nano-additives to reduce the concentration of harmful P-based additives in automotive lubricants.

Avocado oil mixed with an antiwear additive as a potential lubricant – Measurement of antiwear and extreme pressure properties

The paper aims to study the antiwear (AW) and extreme pressure (EP) properties of avocado oil mixed with zinc dialkyl dithiophosphate (ZDDP) in concentrations of 1% to 3% by weight for lubrication purposes. The AW and EP tests are conducted as per ASTM-4172 and ASTM-2783 standards respectively. Further, the rheological behavior of avocado oil mixed with ZDDP is determined for varying shear rates of 50 – 2000 s−1. The maximum improvement in the wear properties for avocado oil is equal to 39.8% at 1 wt.%. The load wear index of pure avocado oil increases from 32.6 to 80.3 at 3 wt.% ZDDP whereas, the weld point increases to 252 kgf at 3 wt.% ZDDP. The improvement in the antiwear and extreme pressure properties are attributed to the protective film formation on the tribopairs as characterized by SEM and EDX analysis. Also, the addition of ZDDP increases the viscosity of the oil at all concentrations and maintains the Newtonian behavior of oil.

Modifications Required for Palm Oil to be Qualified as a Mechanical Lubricant

Adaptation of apt chemical modifications and incorporation of suitable additives, especially, nano-additives, could improve the properties of bio-lubricants derived from palm oil. This makes it one of the best alternatives to mineral oil lubricants. Possible chemical modifications are hydrogenation, esterification/ transesterification, epoxidation and metathesis. Feasible additives and nano-additives available in the market for minimizing the drawbacks of palm oil as a lubricant are ionic liquids, phosphorus, sulphur, zinc dialkyl dithiophosphate, metal, metal oxides, metal sulphides, carbonates, borates, carbon materials, organic materials, hexagonal boron nitride, alumina, CaO, CuO, ZnO, TiO2 and lanthanum borates. Few of them may not be environmental friendly. In line with market potentials and demand, it could be predicted that ROI of funding for the research and development of palm oil as a bio-lubricant may be significantly high. The study addresses tribological performance and properties, chemical modifications and formulation with additives of palm oil as a bio-lubricant.