An analysis of lignin removal in a fixed bed reactor by reaction of cereal straws with ozone

Ozonolysis

“…The same 50% delignification of wheat straw was achieved in a fixed-bed column with 40% (w/w) moisture, 60 L/h flow, and an ozone concentration of 2.7% (w/w) with 2 h reaction time. The percentage of ozone consumed was 100% after 60 min reaction and about 97% after 120 min reaction, which corresponded to 0.09 g O 3 by gram of dry wheat straw [3].…”

“…In addition to moisture, many other factors were identified as responsible for changes in the ozonolysis pretreatment effect, such as the reactor design [23,27,30,41], feed configuration [13,17], particle size [2,23,24,39], pH [11,24,34], ozone concentration [12,13,23], ozone/air flow rate [23,24] and time of ozonolysis [3]. No data were found regarding the influence of temperature on ozonolysis pretreatment; the only article mentioning ozonolysis experiments at 40 C and 0 C provided only ozone consumption results and no pretreatment efficiency data [54].…”

“…In types (i) and (ii), the reactor flow model approximated an ideal mixing model in which the ozone concentration in the reaction medium was the same as that in the reactor outlet flow, whereas in type (iii), the model approximated a plug flow reactor and the ozone concentration decreased through the reactor, from the inlet to the outlet. From these fundamental types of reactor, a variety of design alternatives have been employed in ozonolysis experiments, such as rotatory glass [31,33,37,38], semi batch tank reactor [11,30,34,35,37,55], stirred bed reactor [23], bubble column [41], layer fixed bed [5,16,26,27,39], rotating horizontal cylinder [23], and fixed bed column [3,12,13,17,24,30].…”

“…García-Cubero et al [3] studied ozonolysis reactions in a fixed-bed column (50 cm in height and 2.7 cm in diameter) with rye and wheat straw. The ozonated straw was divided into four parts to study the evolution of lignin degradation and enzymatic hydrolysis yield, not only over time, but also over the length of the bed.…”

“…The pretreatment stage is required to alter and open the structure of the lignocellulosic biomass and to facilitate the enzymes' access during the hydrolysis stage, enhancing the rate and yield of sugar release. Moreover, pretreatment, which is a necessary step to reduce the natural recalcitrance of lignocellulosic materials, is estimated to be responsible for up to 20% of the total production cost [1,3]. The development of suitable, efficient, economic and sustainable pretreatments is probably the most important challenge in the development of the biorefinery concept.…”