Production of Synthetic Fuels and Chemicals from Biomass - Biomass Gasification, Pyrolysis and Torrefaction - page 398

11.5.1.2 Ethanol from Nonfood Sources
The conventional means of producing ethanol from food sources like corn
and sugarcane is commercially highly successful. In contrast, the production
of ethanol from nonfood biomass (lignocellulose), although feasible in prin-
ciple, is not widely used. More processing is required to make the sugar
monomers in lignocellulose feedstock available to the microorganisms that
produce ethanol by fermentation. However, production from food sources,
even though it strains the food supply and is wasteful, is widespread.
Consider that only 50% of the dry kernel mass is transformed into ethanol,
while the remaining kernel and the entire stock of the corn plant, regardless
that it is grown using cultivation energy and incurs expenses, remain unuti-
lized. It is difficult to ferment this part, which contains lignocellulose mass, so
it is discarded as waste. Alternative methods are being developed to convert
the cellulosic components of biomass into ethanol so that they can also be uti-
lized for transport fuel. This option is discussed further in Section 11.5.4 .

11.5.2 Gasoline
Petrogasoline is a mixture of hydrocarbons having a carbon number (i.e., the
number of carbon per hydrocarbon molecules) primarily in the range of
5

11. These hydrocarbons belong to the following groups:

Paraffins or alkanes

Aromatics

Olefins or alkenes

Cycloalkanes or naphthenes

11.5.2.1 Gasoline Production from Methanol
Methanol may be converted into gasoline using several processes. One of
these, Exxon Mobil's MTG process, is well known ( Figure 11.7 ). Methanol
is converted into hydrocarbons consisting of mainly ( 75%) gasoline-grade

.

materials (C 5 C 12 ) with a small amount of liquefied petroleum gas (C 3 C 4 )

and fuel gas (C 1 C 2 ). Mobil uses both fixed beds and fluidized beds of pro-

prietary catalysts for this conversion. The reaction is carried out in two
stages: the first stage is dehydration to produce dimethyl ether intermediate;

Dehydration I

Dehydration II

Storage and
blen ding
Light gasoline
Heavy gasoline
HVP gasoline

Crude
me thanol

MTG Reaction
and cooling
(Z5M-5
catalyst)

Methanol
vaporization

DME Reactor
(Aluminum
catalyst)

Gasoline
distillation

CH 3 OH CH 3 OCH 3 C 2 -C 5

300-320°C

400-420°C

FIGURE 11.7 Production of gasoline from methanol using MTG process.