Supporting Information
Tribological study of oil-miscible quaternary ammonium
phosphites ionic liquids as lubricant additives in PAO
Xisheng Fu1, Lingguo Sun1, Xuguang Zhou1, Zhipeng Li1,2 and Tianhui Ren2,†
1Lubricating Oil Key Laboratory of Petrochina, Lanzhou Lubricating Oil R&DInstitute of
Petrochina, Lanzhou 730060, China
2School of Chemistry and Chemical Engineering, Key Laboratory for
Thin Film
andMicrofabrication, Shanghai Jiao Tong University, Shanghai 200240, China
Synthesis of quaternary ammonium carbonate (QAC): 395.7 g (1.0 mol) of
tri(octyl-decyl)amine, 300 mL absolute methanol and 45.0 g (0.5 mol) of dimethylcarbonate were
introduced into a 1000 mL high pressure autoclave. Then the autoclave was filled with argon to 5
MPa and heated with stirring. The reaction was conducted at 180ºCfor 8 h. The final mixture was
collected and recrystallized from ethyl acetate to obtain the product in a yield of 83.8%. The
structure of the compound was confirmed by IR, 1H NMR and Elemental analysis (EA).
QAC: IR (KBr, cm-1) 2956, 2856 (-CH3); 2926 (-CH2-); 1650 (C=O); 1465, 1380 (-CH3).1H NMR
(400 MHz, CDCl3) δ (ppm) 3.26-3.25 (t, 12H), 3.18-3.15 (d, 6H), 1.62 (s, 12H), 1.31-1.23 (d,
72H), 0.85 (s, 18H). EA (% calculated) C57H120N2O3: C 77.85 (77.66), H 13.86 (13.72), N 3.12
(3.18).
It
should be noted that the band observed at around 3400 cm-1 are referred to the residual alcohol in the dialkyl
phosphite.
Fig S11H NMR spectrum of QAC
Table S1
Physical characteristics of the dialkyl phosphite esters.
Items
Appearance(25ºC)
Phosphorus, wt. %
Kinematic viscosity (100 ºC, mm2/s)
Open flash point (ºC)
Dioctyl phosphite ester
Didodecyl phosphite ester
Bright &clear
9.45
3.17
143
Bright &clear
6.83
3.81
167
Water (wt. %)
Mechanical impurities (wt. %)
Total acid number (mg KOH/g)
<0.03
0.015
48.3
<0.03
0.012
21.4
Dioctyl phosphite ester: 1H NMR (400 MHz, CDCl3) δ (ppm) 5.91-7.65 (d, 1H), 4.08-3.62 (m,
4H), 1.68-1.57 (d, 4H), 1.28 (s, 20H), 0.89-0.87 (t, 6H).31P NMR (400 MHz, CDCl3) δ (ppm):
8.89 (s).
Didodecyl phosphite ester: 1H NMR (400 MHz, CDCl3) δ (ppm) 5.91-7.66 (d, 1H), 4.07-3.65 (m,
4H), 1.72-1.57 (m, 4H), 1.27 (s, 36H), 0.89-0.87 (t, 6H). 31P NMR (400 MHz, CDCl3) δ (ppm):
8.91 (s).
Fig S21H NMR spectrum of dioctyl phosphite ester
Fig S331P NMR spectrum of dioctyl phosphite ester
Fig S41H NMR spectrum of didodecyl phosphite ester
Fig S531P NMR spectrum of didodecyl phosphite ester
Table S2
Physical characteristics of the Zinc primary-secondary dialkyl dithiophosphate.
Items
Appearance(25ºC)
Phosphorus, wt. %
Sulfur, wt. %
Zinc, wt. %
Flash point (COC, ºC)
Water (wt. %)
Density(15.6 ºC, Kg/m3)
Total acid number (mg KOH/g)
Zinc primary-secondary dialkyl dithiophosphate
Light yellow
≥6.5
13.5~16.0
≥8.0
180
<0.09
1050-1150
5.5
POPA: IR (KBr, cm-1) 2956, 2856 (-CH3); 2926 (-CH2-); 1467, 1378 (-CH3); 1214 (C-N), 1065
(P-O). 1H NMR (400 MHz, CDCl3) δ (ppm) 3.83-3.55 (m, 4H), 3.27-3.23 (m, 6H), 3.21-3.17 (d,
3H), 1.64-1.50 (m, 10H), 1.32-1.24 (d, 56H), 0.87-0.84 (t, 15H). 31P NMR (400 MHz, CDCl3) δ
(ppm): 4.34 (s). EA (% calculated) C44H94NO3P: C 73.81 (73.79), H 13.16 (13.23), N 1.89 (1.96),
P 4.25 (4.32).
PTPA: IR (KBr, cm-1) 2956, 2854 (-CH3); 2924 (-CH2-); 1467, 1378 (-CH3); 1212 (C-N), 1065
(P-O). 1H NMR (400 MHz, CDCl3) δ (ppm) 3.78-3.54 (m, 4H), 3.31-3.29 (m, 6H), 3.22-3.20 (d,
3H), 1.63-1.52 (m, 10H), 1.33-1.23 (d, 72H), 0.87-0.84 (t, 15H). 31P NMR (400 MHz, CDCl3) δ
(ppm): 4.13-4.06 (d). EA (% calculated) C52H110NO3P: C 75.46 (75.39), H 13.26 (13.38), N 1.64
(1.69), P 3.75 (3.74).

It should be noted that the peaks at around 5.9-7.6 ppm with large J-coupling constant for P-H, clearly decrease in
POPA and PTPA, also indicating that the proposed reaction is reliable. These peaks are ascribed to the trace
unreacted phosphite ester.
Fig S61H NMR spectrum of POPA
Fig S731P NMR spectrum of POPA
Fig S81H NMR spectrum of PTPA
Fig S931P NMR spectrum of PTPA
Fig. S10 Ionic liquid samples of POPA and PTPA