November 2014
Methanol Gasoline Blends Require Good Water
Monitoring Practices
Phase Stability
Good phase stability for methanol gasoline blends can be achieved with sufficient water tolerance
(water solubility limits) and by implementing good water monitoring practices in the gasoline product
distribution system. Like other alcohol gasoline blends, the methanol blend will separate into two
phases when exposed to amounts of water that exceed its water tolerance properties. The bottom
phase will generally contain most of the alcohol and water along with some of the aromatics from the
gasoline. This two-phase situation needs to be avoided, since the bottom phase can cause poor vehicle
operation as well as contribute to corrosion of the metals in the fuel system.
Typical Water Tolerances for Methanol in Gasoline
Methanol V%
21 ºC
0.15% Vol water
0 ºC
Experience suggests that the methanol blend at point of
production should have a minimum water tolerance of
0.15 volume percent in the gasoline blend at room
temperature (21C) to provide adequate protection from
potential water exposure in the gasoline distribution
system.
The nearby chart shows higher methanol
concentrations provide increased water tolerance at 21C,
but M15 (15% methanol) blends still fall short of the
preferred water tolerance target. The water tolerance
target for the M15 blend can usually be achieved by
adding one to two volume percent of higher alcohols
such as ethanol, propanol or butanol that act as cosolvents for the methanol in the gasoline.
As the chart illustrates, the lower methanol blends will
produce lower water tolerances which will then require
greater additions of co-solvent alcohols to achieve the targeted water tolerance property for the
finished gasoline blend supplied to the retail market.
Good Water Monitoring Practices
In addition to achieving targeted water tolerance properties in the methanol blend at point of blending,
good water monitoring practices also need to be established in the gasoline distribution system from
the point where methanol is first blended into the gasoline product. As Chart 1 illustrates, the gasoline
distribution system from point of production at the oil refinery until it reaches the consumers’ vehicle
tanks at the retail market can potentially be complex, depending on the distance and terrain between
the refinery and the retail gasoline market.
Washington: 124 South West Street, Suite 203, Alexandria, VA 22314 USA +01 703 248 3636
Singapore: 10 Anson Road, #32-10 International Plaza, Singapore 079903 +65 6325 6300
Brussels: Avenue Jules Bordet, 1421140 Brussels, Belgium +32 276 116 59
Beijing: 11/F 1177 Gateway Plaza, No 18 Xiaguangli, Beijing 10027, China +86 10 5923 1107
www.methanol.org
www.methanol.org.cn
www.methanolfuels.org
methanol.org 1
For quality control, there are generally two potential points for methanol to be blended in the gasoline.
The preferred point is at the refinery gasoline operations, where the refinery can take full advantage of
methanol’s high octane and where there is also an on-site laboratory to ensure that the blend meets all
gasoline specifications.
However, if the risk of water exposure cannot be controlled in the gasoline distribution system between
the refinery and market terminals, then the methanol blending will have to be conducted at the market
terminal and blended at the targeted volume concentration in the tank truck that delivers the finished
gasoline to the retail stations. In this case, the refinery will have to produce a sub-octane and sub-RVP
gasoline basefuel that is designed to meet the finished gasoline specification when the targeted
concentration of methanol is blended into the delivery tank truck.
Because of lower quality control in terminal blending, some excess quality in terms of higher octane and
lower RVP may need to be allowed in the finished gasoline blend.
Methanol Can Be Potentially Blended at Two Points
In Gasoline Distribution System
Blending at Terminal Requires Special Basefuel with sub-RVP and sub-Octane
Terminal Blending
into Delivery Truck
Refinery Blending
Retail
Outlets
Bulk Plants
Tanker
and
barges
Pipeline
and
marketing
terminal
Pipeline
and
marketing
terminal
Refinery
Terminals
Trucking
Firms
Oil Refinery
Product Pipelines
Product Pipelines
Farms
Typical Gasoline Distribution System
Retail Outlets
other large users
Commercial,
Industrial, and
utility consumers
Tanker Trucks
CHART 1
Water Monitoring Practices at Retail Gasoline Stations
Since retail gasoline stations have the highest potential for exposing gasoline to excess water, particular
attention needs to be applied to the water monitoring practices at the retail gasoline stations. The
diagram in Chart 2 illustrates the various points for water to enter the gasoline storage system at the
retail stations. Procedures need to be established to minimize the water entering the storage system so
Washington: 124 South West Street, Suite 203, Alexandria, VA 22314 USA +01 703 248 3636
Singapore: 10 Anson Road, #32-10 International Plaza, Singapore 079903 +65 6325 6300
Brussels: Avenue Jules Bordet, 1421140 Brussels, Belgium +32 276 116 59
Beijing: 11/F 1177 Gateway Plaza, No 18 Xiaguangli, Beijing 10027, China +86 10 5923 1107
www.methanol.org
www.methanol.org.cn
www.methanolfuels.org
methanol.org 2
as to prevent the water tolerance of the methanol blend
being exceeded before it is sold to the gasoline consumers.
Possible Water Entry Points Into a Gasoline Storage System
Gasoline Tanker
Truck Delivery
Gasoline
Water is
delivered
with fuel
Water or rain enters
fill container
Gasoline
Methanol
Blend
Source: Steel Tank Institute
Fill Pipe
Underground
Gasoline
Storage Tank
Pump
Water is
discharged
from fill
containment
into tank
Loose
fittings allow
groundwater
to enter
During the daily inventory check for gasoline supplies in
the underground storage tank at the retail station, the
operator will also check to see if there is any ‘free’ water at
the bottom of the underground tank, by applying a water
detection white paste to the bottom length of the
inventory measuring stick so as to detect any free water as
illustrated in Chart 3. The white paste will normally turn
red up to the point where the water is in contact with the
paste on the measuring stick. When water is detected in
the underground tank, the station operator will contact a
pump out service for removal of the water, and will also locate the source of the water so as to correct
the situation.
CHART 2
In the case of alcohols blends, the water bottom phase is mostly alcohol, and will not cause the
conventional white paste to turn red which thereby produces a false indication of having no free water.
Therefore, when alcohol blends are being sold, it is necessary to switch to specially formulated water
detection paste like that shown in Chart 3.
CHART 3
Methanol Blends Require Regular Checking for Water in Underground Tanks
Special paste required for detecting
water bottoms in gasoline tanks
The use of a co-solvent alcohol is critical
to any gasoline / methanol blend. The
co-solvent alcohol prevents water from
separating out of the tank gasoline in
service station storage tanks.
Sar-Gel water/alcohol-indicating paste
Was developed for use by gasoline stations
to test for ‘free water’ in bottom of tanks
Washington: 124 South West Street, Suite 203, Alexandria, VA 22314 USA +01 703 248 3636
Singapore: 10 Anson Road, #32-10 International Plaza, Singapore 079903 +65 6325 6300
Brussels: Avenue Jules Bordet, 1421140 Brussels, Belgium +32 276 116 59
Beijing: 11/F 1177 Gateway Plaza, No 18 Xiaguangli, Beijing 10027, China +86 10 5923 1107
www.methanol.org
www.methanol.org.cn
www.methanolfuels.org
methanol.org 3