The slow pyrolysis of cellulose was conducted in a fixed bed reactor at a temperature ranging of 250—550℃. The formation and evolution characteristics of residual char was investigated by elemental composition analysis and two-dimensional infrared correlation spectroscopy. The inter- and intra-molecular hydrogen bonding networks in cellulose were identified and the change of hydrogen bonding patterns during the initial stage of pyrolysis was investigated. The decomposition of cellulose during slow pyrolysis was mainly focused on 250—360℃ with a maximum decomposition rate at about 300℃. The predominant reaction of cellulose carbonization at 250—300℃ was dehydration. Furthermore

the O(3)H…O(5) intra-molecular H-bonds were found to be the most sensitive to temperature

and it changes before that of the methylene groups. However

it changes after that of O(2)H…O(6) intra-molecular and O(6)H…O(3) inter-molecular H-bonds. In the initial stage of carbonization

the cleavage of O(6)H…O(3) intra-molecular H-bonds resulted in the formation of free hydroxyl groups and the tight cellulose structure was loosen up. With temperature rising

the cleavage of intra-molecular H-bonds and the subsequent dehydration generated large amount of carbonyl

double bonds and cyclic ethers in the char. At 300℃

the ring-opening of pyran structure together with the cleavage of glycosidic bond gave rise to the drastic degradation of cellulose. As a result

substantial amount of aliphatic hydrocarbons with double bonds and carbonyl functional groups were generated in the char. These groups were further underwent molecular rearrangement

condensation and aromatization and resulted in the formation of aromatic ring and aryl alkyl ethers. In 300—460℃

the predominant reaction of cellulose carbonization was deoxygenation

such as decarbonylation and decarboxylation. Meanwhile

the content of aliphatic hydrocarbons in char decreased gradually and that of the aromatic structure increased. The predominant carbonization reaction shifted from deoxygenation toward dehydrogenation as temperature exceeded 460℃

such as demethylation and demethylenation. The aromaticity of char increased with temperature and a highly condensed aromatic structures emerged in the char.