Biomedical Engineering Reference
In-Depth Information
pure cellulose. The traditional process of biomass hydrolysis to glucose and then
the conversion is long, conversion efficiency is low, and environment pollution is
a result. However, gasification, pyrolysis, and liquefaction tend to provide whole
transformation of raw materials. In this process, all the sugars in the raw materials
are reduced to the corresponding sugar alcohol, resulting in separation difficulties
of the target product.
Therefore, future research will primarily focus on the following aspects:
①
In cellulose, there are a large number of hydroxyl groups and strong hydrogen
bonds, easily generating a supramolecular structure and resulting in difficult
solubility of raw materials in most solvents. How to effectively destroy or weaken
the hydrogen bonds in the reaction system is a common problem in the biomass-
based conversion process.
②
The catalysts of cellulose to prepare sugar alcohols are mainly inorganic acids,
but the pollution by such catalysts is large scale and has a dramatic effect
on the environment. There is also a precious metal catalyst, but it increases
raw material costs. Therefore, based on the C-O-C bond catalytic breaking
mechanism, comparing the reactivity of the glycosidic bond in neutral medium
and acidic medium and designing and preparing highly efficient, highly selec-
tive, nonpolluting catalytic system may achieve the rapid depolymerization of
cellulose under mild conditions.
③
Selective breakage of the C-C bond and the C-O bond. The process of cellulose
conversion to ethylene glycol and propylene glycol includes a hydrocracking
process of the C-C bond and C-O bond. These bond energies are large, and
the requirements for product formation for the cracking type and location of
bonds are high; thus, a highly active catalyst system must be designed and
prepared. However, the high catalytic activity will generate methane, methanol,
and other by-products, resulting in decreasing selectivity. Therefore, the design
and development of a catalyst system to make the C-C bond and C-O bond
effectively crack, with selectivity of region and location, are the core and keys
for this direction of research.
4.5.3
Development Tendency of Selectively Structural
Fractionation Technology
China is a major importer and consumer of fossil resources, but it is also a big
country of biomass resources. Exploiting the theory and technology of conversion
of biomass resources and developing the next-generation refining process for the
biological and chemical industries with lignocellulosic biomass resources as the raw
materials are the important tasks of the biorefining industry in China. These also are
the forefront and focus of international academia and industry concerns.
Creating a new industrial model based on biomass as the common raw material
must break through the key scientific problems that constrain biomass from
