Proceedings of International Forum for Green Asia 2017
Special issue of Evergreen - Joint Journal of Novel Carbon Resource Sciences & Green Asia StrategyP-17

Char-free and Flash Pyrolytic Gasification of Cellulose
Ni’mah Ayu Lestari,1,2 Shinji Kudo,3 and Jun-ichiro Hayashi1,31Interdisciplinary Graduate School of Engineering, Kyushu University, Kasuga-koen, Kasuga, 8168580, Japan, 2Green Asia Education Center, Kyushu University, 3Institute for Material Chemistry andEngineering, Kyushu University
Abstract
Highly crystalline cellulose, microcrystalline cellulose (MCC) was pyrolyzed by heating to thetemperature of 445-764 °C at a rate > 103 °C /s. Curie-point pyrolyzer, employed for the flash
pyrolysis, allowed to investigate the primary pyrolysis of MCC, minimizing the extent of thesecondary pyrolysis of volatiles in the gas phase. The primary volatile products were analyzed byusing gas chromatography and gas chromatography/mass spectroscopy. The flash pyrolysis withpeak temperature over 500 °C gave the yield of char (carbonized residual solid) lower than 3 wt%.
The char yield with 764°C was even below 1 wt%. It was thus demonstrated that MCC can beconverted into volatiles near completely. Effect of crystallinity of cellulose was examined. MCC
was subjected to ball milling to reduce the crystallinity of MCC. It is known that reduced crystallinity
enhances the crosslinking of hydrogen-bonded hydroxyls in amorphous moiety, resulting in highchar yield. However, the flash pyrolysis of the ball-milled MCC, regardless of the peak temperature,
gave product yields very similar to those from MCC, indicating that the flash pyrolysis was also
applicable to near-char-less conversion of amorphous cellulose. Some details of the productcomposition are also reported.
Key words: Cellulose, pyrolysis, gasification

1. Introduction
Bioethanol is attracting attention worldwide asenvironmentally friendly fuel. It is generally
produced by fermentation of sugarcane orsaccharified starch from corn, followed bypurification. Because of availability of thefeedstock and technical easiness in the production,
it is one of the major vehicle fuels in Brazil. An
emerging application of bioethanol is production ofethylene, an important chemical in petrochemistry.
Braskem, a leading petrochemical company inBrazil, produces 200,000 tons of polyethylene per
year from sugar cane-derived ethylene.[1] However,for countries like Japan, large scale production ofsugarcane and corn is geographically difficult.
Another potential feedstock for the ethanol andethylene is cellulose in lignocellulosic biomass,
such as wood and cellulosic wastes from paperindustry, but saccharification of cellulose needs
costly enzymes and long reaction time due to its
robust chemical structure.
We here propose an alternative approach to
produce bioethanol and bioethylene from cellulose,
which is consisted of cellulose conversion to47

syngas by gasification, catalytic synthesis ofethylene from syngas, and hydration of ethylene toform ethanol. Since gasification of carbonaceous
resources generally requires high temperature andthus much energy, it is important for this approachto develop a method to gasify cellulose under
milder conditions, following the stoichiometry(C6H10O5 + H2O → 6H2 + 6CO). However,pyrolysis, occurring in gasification as primary
reaction, generally produces substantial amount ofchar, which is hard to be gasified at low
temperatures. It is therefore necessary to suppress
the char formation in pyrolysis as much as possible.
In this study, we employed curie point
pyrolyzer (CPP) to investigate characteristics ofcellulose pyrolysis with very rapid heating (flashpyrolysis). The rapid heating was considered to beeffective to suppress the char formation if it isfaster than the reaction rate of crosslinking ofhydrogen-bonded hydroxyls in cellulose. Twotypes of cellulose with different crystallinity weretested to know the influence of cellulose chemicalstructure on the product.

Proceedings of International Forum for Green Asia 2017
Special issue of Evergreen - Joint Journal of Novel Carbon Resource Sciences & Green Asia Strategy

P-17
enough, the intermediate liquid instantly evaporates
as volatiles. If this is not the case, it re-polymerizes
to form secondary char.

2. Experimental Setup

Microcrystalline cellulose (MCC, SigmaAldrich) was used as cellulose sample with highcrystallinity. Amorphous cellulose was obtainedby ball-milling of MCC for 60 h (BM-MCC).
Flash pyrolysis was carried out using CPP (JHP22). 2 mg of the sample was pyrolyzed at>1000 °C/s with some maximum temperatures(445, 500, 590, 670 and 764 °C). The yield ofchar was obtained from the mass after pyrolysis,
and that of compounds in volatiles were analyzedwith GCs.

Yield, wt%-dry cellulose

15

Relative mass, wt%

200

400
Temperature, °C

600

800Fig. 2 shows formation of substantial amountof water and gaseous products (H2, CO, CO2, andCH4) in the flash pyrolysis. The highest water
yield was observed at 445 °C, which wasprobably caused by incomplete pyrolysis during
heating-up and occurrence of slow pyrolysis inholding time at that temperature (10 s). The yieldof gaseous product increased with pyrolysis
temperature up to 6.1 wt%. According to areport,[3] gaseous products are hardly produced in
the primary pyrolysis (< 1 wt%). The formationof these products (water and gaseous product)
attributes to the unavoidable secondary reactionof volatiles in gas phase in the device of CPP usedin this study. Ideal pyrolysis for realizing
cellulose
gasification
following
thestoichiometry above produces only levoglucosan(LGA, C6H10O5), which is a type of anhydrosugar.
GC/MS analysis of condensed volatiles frompyrolysis revealed that the main component wasLGA, but formations of other compounds such asother anhydrosugars and furanic compounds
were also observed, indicating the occurrence ofside reactions in pyrolysis as well as gas phase.

806040MCCBM-MCC

0400
600
Temperature, °C

Gas BM-MCC

5Fig. 2. Yields of H2O and gaseous products (H2, CO,CO2, and CH4) in flash pyrolysis at variousmaximum temperatures.

100200Gas MCC

0The crystallinity index of cellulose wasdetermined from FT-IR spectrum. Ball-millingfor 60 h effectively increased amorphous portionand decreased the crystallinity degree from theinitial value of 0.68 (MCC) to 0.2.

0H2O BM-MCC

03. Results and Discussion

20H2O MCC
10800

Fig. 1. Char yield in flash pyrolysis at various
maximum temperatures.
Fig. 1 shows mass decreasing curves for MCC
and BM-MCC in pyrolysis. It was clearly seen thathigher content of amorphous portion did not
influence the mass decreasing curves. More
importantly, for both MCC and BM-MCC, the charyields were very low above 590 °C, less than 3 wt%,
and decreased as low as 0.8 wt% at 764 °C. Thus,
the purpose of this study, near-char-free pyrolytic
conversion of cellulose, was achieved by theemployment of flash pyrolysis, regardless of thecrystallinity of the feedstock cellulose. These
results indicate availability of cellulosic wastes,
which generally have amorphous nature, asfeedstock. There are two potential explanations onthese effects of heating rate. The one is, asmentioned above, the effect to suppress
crosslinking of hydrogen-bonded hydroxyl groups
in cellulose. Another explanation is based on anintermediate liquid mechanism,[2] where, in thecourse of heating, “intermediate liquid” forms overcellulose surface. When the heating rate is high

5. Conclusion
Near-char-free pyrolysis of MCC and BM-MCC
was demonstrated using CPP.

References[1] http://www.braskem.com/site.aspx/Im-green.
[2] Lédé, J. J. Anal. Appl. Pyrolysis, 94, 17-32(2012).
[3] Westerhod, R. J. M. et al. React. Chem. Eng., 1,555-566 (2016)48