Catalytic
conversion of cellulose to ethylene glycol (EG) or 1,2-propylene
glycol (1,2-PG) represents an attractive approach in the valorization
of biomass, due to the high atom economy of the reaction process and
large market demand of the diol products. The one-pot catalytic conversion
of cellulose is a complex reaction network, comprising hydrolysis,
retro-aldol condensation, hydrogenation, isomerization, dehydrogenation,
thermal side reactions, etc. In addition to EG and 1,2-PG, a variety
of byproducts such as sorbitol, mannitol, erythritol, 1,2-butanediol,
and glycerol may be coproduced. The key point for obtaining high selectivity
for EG or 1,2-PG lies in effective control of the major reaction steps
in the reaction network proceeding at matching rates. In this Perspective,
we depict the general reaction route for glycol production from cellulose
and summarize the active elements for the retro-aldol condensation
reaction, which is the determinant step for the formation of C2 and C3 intermediates. In situ or operando methods
for the catalyst characterization are discussed. Then the reaction
kinetics for one representative example, i.e. the tungstenic catalyst,
is summarized briefly and approaches to control the product selectivity
are suggested. After an overview of the progress and challenges in
catalytic conversion of lignocellulose for applications, we present
an outlook for cellulose conversion to diols from the aspects of catalyst
development, reaction mechanism study, and practical applications.
