No. 16

April 16, 2021

DECOMPOSITION OF OILS BY ACTION OF DISCHARGE PLASMA (3)-OXYGEN CONTAINING HYDROCARBON COMPOUNDS-

In the last issue, various hydrocarbon compounds were tested using a newly invented needle-plate electrodes discharge plasma
generator and we found that they were decomposed by discharge plasma action to produce hydrogen. This report summarizes ourfindings of how hydrogen production is affected by the structure of oxygenated hydrocarbon compounds.
Table 1 shows the oil species, structural formula, hydrogenproduction caused by discharge plasma action and volume
resistivity of the oxygenated hydrocarbon compounds tested,
where the amount of hydrogen production indicates thepercentage when that of n-hexadecane is 100. In the ester
compounds, the volume resistivity and hydrogen production
volume is increased with increasing in the alkyl chain length.
This trend does not depend on the posiotion of the alkyl chain,neither at the center or at the ends. On the other hand, in theether compounds, the volume resistivity and the amount ofhydrogen are decreased with increasing in the number ofoxygen atoms in the molecule. Glycol compounds showed
lower volume resistivity than other oxygenated hydrocarbon
compounds and no hydrogen production.

Figure 1 shows the amount of evolved hydrogen as afunction of volume resistivity of the ester, ether and glycol
compounds tested. No hydrogen is produced at and below thevolume resistivity of 1.1×109 Ω･cm. However at and above
3.5×109 Ω･cm, hydrogen is clearly produced, the volume ofwhich increases steeply with the volume resistivity,
approaching to an almost constant maximum value. Thismeans that there exists a critical volume resistivity to causehydrogen production, which is 109Ω・cm. It should be notedthat for all types of oxygenated hydrocarbon compound tested,
the relation between hydrogen production and volume
resistivity lies on a single curved line.
Electric Conduction

Electric Discharge

Glycol80●：Ester▲：Ether■：GlycolVolume resistivity
Ω・cm

Dimethyl
Malonate

02.2×107

DibutylMalonate

04.1×108

DihexylMalonate

14.4×109

Dimethyl
Succinate02.7×107

01.E+06
106 1.E+07
107 1.E+08
108 1.E+09
109 1.E+101010 1.E+111011 1.E+121012 1.E+131013 1.E+141014

Dimethyl
Glutarate

06.0×107

Volume resistivity, Ω・cm

DimethylAdipate

01.1×109

DimethylSebacate

173.5×109

DiethylSebacate67

1.3×1010

DibutylSebacate93

6.1×1010

DihexylSebacate

952.2×1011

Dihexyl Ether103

6.3×1012

Dioctyl Ether91

2.2×1013

Diethylene Glycol
Dibutyl Ether88

1.4×1010

Tetraethylene Glycol
Dimethyl Ether0

3.5×107

Tripropylene
Glycol02.0×107

Tetraethylene
Glycol06.8×106

EtherGlycol
Ether

100

H2, %

Oil Species

DiEster

Amount of hydrogen, %120

Table 1 Oxygenated hydrocarbon compound samples– molecular structure, hydrogen production
and volume resistivity

Kyodo Yushi Co., Ltd.

Structural formula60
4020Fig. 1 Dependence of hydrogen production on volume resistivity

These results suggest that oils having volume resistivity ofless than 109 Ω･cm can be a promising lubricating oil to be
developed for avoiding the shortened (fatigue) service life ofrolling bearing through white structure flaking.
Noyama, S., Iijima, M., Dong, D., Nakayama, K.: JAST Tribology Conference, 2018
Autumn Ise, A34
Noyama, S., Iijima, M., Dong, D., Nakayama, K.: JAST Tribology Conference, 2019
Spring Tokyo, A2

2-2-30 Tsujido Kandai, Fujisawa, 251-8588 Japan

http://www.kyodoyushi.co.jp