ÜDS-Fen 2009-1 Soru=69

According to the passage, scientists have, for years, used acid catalysts to ----.

Glucose, nature's most abundant sugar, may soon be
petroleum's fiercest rival. Chemists have long searched
for cheap, renewable, and non-polluting alternatives to the
245 million tonnes of petroleum-based plastics produced
annually. For years, they have been able to convert
sugars into the chemical hydroxymethylfurfural (HMF),
which can be used to make plastic. But the process,
which used acid catalysts to break the sugars down, was
costly and complicated by impurities and low yields.
Researchers at the Pacific Northwest National Laboratory
(PNLL) in Washington replaced the acid catalyst with a
metal catalyst, chromium chloride, and used it to break
down glucose, a sugar found in plant starches and
cellulose. The result: HMF yields increased 10 to 70
percent over the old processes and impurities were
eliminated. The next step to replacing petroleum is to find
a low-impact renewable source for the glucose. Scientists
hope to soon obtain glucose from cellulose rather than
from plant starches. Cellulose is found in straw and
sawdust, two waste products from the agricultural and
wood industries that do not require precious farmland to
be taken away from food crops.