Chemistry Letters 2001
323
A diesel fuel composition has been reported, which is con-
sisted of moderate amounts DMPP and DMET blended into a
conventional diesel fuel. DMET has a very high cetane num-
ber of 105. It is a cetane number promoter when added to diesel
fuel at concentrations above approximately 25 volume %.
Adding DMET to diesel fuel can also increase the oxygen level
of the diesel fuel so that the effect of oxygen level on emissions
could be determined.
It is clear that higher DME conversion accompanies with
more liquid products produced in this DME conversion. More
than 40% of the product is liquid at a gas flow rate of 30
2
–
1
mL·min . This suggests that DBDs could easily convert DME
to liquid chemicals at atmospheric pressure and low tempera-
ture. A more surprising phenomenon with this DBD-DME con-
version is that no carbon deposit has been observed on the
dielectric, while a serious carbon deposit has been formed dur-
8
–10
The gaseous product of such DBD conversion of DME is a
ing plasma conversion of methane or other lower alkanes.
mixture of hydrocarbons, ethers, H and CO. Table 2 shows the
It is interesting to note that the C–O bond breakdown in a
DME molecule does not require a high energy and this leads to
the high DME conversion. The bond strength of C–O in DME
molecule is only 81 kcal/mol at 298 K. [CH ·] and [CH O·] radi-
2
composition of gaseous products observed at 60 °C and differ-
ent gas flow rates. The gaseous products include methane,
ethane, propane, methyl ethyl ether, acetone, methyl isopropyl
ether, diethyl ether, dimethoxymethane and 1,2-dimethoxy-
ethane. The composition of gaseous products changed greatly
with the variation of gas flow rate. Experimental results
3
3
cals can be easily obtained within DME plasmas. Hydrocarbons
and oxygenated hydrocarbons are expected to be formed from
chain reactions initiated by [CH ·] and [CH O·] radicals.
3
3
showed that most of the gaseous products were H , CO and
The potential of plasma conversion of DME has been
demonstrated in this work. Further investigation is being con-
ducted to improve the selectivity of desired product.
2
C –C alkanes. The amount of oxygenates was very little in the
1
3
gaseous phase but large in liquid product. Table 2 also shows
the composition of lower alkanes in the gaseous phase increases
with the decreasing flow rates.
The support from The Research Fund for the Doctoral
Program of Higher Education in China is very appreciated. The
assistance from Mr. Yang Li, Dr. Zhen-hua Li, Dr. Chun-de Yao
and Dr. Ming-fa Yao in Tianjin University is also appreciated.
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