Glossary - Biomass Gasification, Pyrolysis and Torrefaction - page 493

Glossary

Carbohydrates Organic compounds of carbon, hydrogen, and oxygen, with the general
formula C m (H 2 O) n . The carbon and hydrogen are in the 2:1 atom ratio. Carbohydrates
can be viewed as hydrates of carbon. They include sugars, starches, cellulose, and
other cellular products.
Cellulose The main constituent of cell walls with the generic formula (C 6 H 10 O 5 ).
Cracking The breaking up of large complex organic molecules into smaller molecules
using pressure and temperature with or without a catalyst. The product of cracking
depends on temperature, pressure, and catalyst used. No single unique reaction takes
place in the cracker. The hydrocarbon molecules are broken up in a fairly random way
to produce mixtures of smaller hydrocarbons.
Depolymerization The decomposition of a polymer into smaller fragments, or the break-
down of macromolecular compounds into relatively simple compounds.
Esterification The chemical process for making esters, which are compounds of the
chemical structure R

COOR 0 in which R and R 0 are either alkyl or aryl groups. The
most common method for preparing esters is to heat a carboxylic acid, R

a

a CO a OH,

OH, and remove the water that is formed.
Esters Any chemical compounds derived by reacting an oxoacid (it contains an oxo
group, X

with an alcohol, R' a

O) with a hydroxyl compound such as an alcohol or a phenol.
Ethanol A popular alcohol (C 2 H 5 OH) used in spark-ignition engines, either alone or
blended with petroleum-derived gasoline.
Gasoline In the United States and Canada, the petroleum-derived oil that runs normal
spark-ignition car engines is called gasoline. In many other places it is called petrol.
Gasoline is a mixture of a large number of hydrocarbons containing 4 12 carbon atoms
per molecule in proportions that can vary depending on the crude oil and the user's
specification. In the United States, gasoline is usually a blend of straight-run gasoline,
reformate, alkylate, and some butane. The approximate composition is 15% C4 C8
straight-chain alkanes, 25 40% C4 C10 branched alkanes, 10% cycloalkanes, , 25%
aromatics ( , 1.0% benzene), and 10% straight-chain and cyclic alkenes (ACS, 2005).
The average heating value of gasoline is 44.4 MJ kg and its specific gravity is
0.67

5

108 (Ritter, 2005).
Hemicellulose An important component of plant cell walls that can be any of several
heteropolymers present in almost all plant cell walls along with cellulose.
Hydrocracking A cracking process that uses a catalyst and occurs at high hydrogen
partial pressure to “crack” the fractions into smaller molecules, to produce high-octane
gasoline and other good quality, stable distillates.
Hydrolysis The breaking of hydrogen bonds in long-chained organic molecules.
Hydrotreating A process used in a refinery in which the feedstock is treated with hydro-
gen at elevated temperature and pressure in the presence of appropriate catalysts to
remove contaminants such as sulfur, nitrogen, metals, and condensed-ring aromatics or
metals.

0.77. Its average molecular weight is

B