Research paper Kinetics of biomass catalytic pyrolysis Changbo Lu, Wenli Song, Weigang Lin ⁎ Institute of Process Engineering, Chinese Academy of Sciences, Beijing, 100190, China abstract article info Available online 22 April 2009 Keywords: Biomass Catalytic pyrolysis Kinetic mechanism Kinetic parameters The Coats–Redfern method was used to analyze the kinetic characteristics of biomass catalytic pyrolysis, indicating that it can be described by multi-step reactions, rather than as a simple first-order reaction. Friedman model-free calculations were used to describe the starting reaction types and the corresponding initial kinetic parameters. Finally, nonlinear regression of biomass catalytic pyrolysis showed that the reaction mechanism of the whole process could be kinetically characterized by three successive reactions: a one-dimensional diffusion reaction, followed by an apparent first-order reaction, and then by a two- dimensional diffusion reaction. The kinetic parameters and equations were also calculated. © 2009 Elsevier Inc. All rights reserved. 1. Introduction The pyrolysis of biomass is a complicated process involving numerous intermediate products and overlapping reactions. The kinetic parameters of biomass pyrolysis depend on the feedstock composition and also on the pyrolytic conditions, such as decomposition tempera- ture, heating rate, particle size and the presence or absence of catalysts. Failure to account for any of these factors would render the calculations of the pyrolytic parameters and prediction of its mechanisms invalid. In recent years, many studies have focused on the effects of biomass composition and thermal cracking conditions on the pyrolytic kinetic characters, and have proposed different hypothetical reaction routes and steps using individual kinetic models to describe and simulate the biomass pyrolysis process as closely as possible (Koufopanos et al., 1991; Babu and Chaurasia, 2002, 2003; Fisher et al., 2002). Previous studies have tended to concentrate on characterizing the biomass pyrolytic process as a whole, rather than analyzing and characterizing the individual steps and their reaction types. Kinetic parameters have been calculated using conventional differential or integral methods, which have limited abilities to solve the kinetic parameters of such complicated reaction systems as biomass pyrolysis or biomass catalytic pyrolysis. In this study, we aimed to simulate biomass catalytic pyrolysis using non-linear regression, and to simulta- neously describe the kinetic parameters and reaction mechanism. 2. Experimental A NETZSCH 449 C (manufactured by Netzsch in Germany ) thermo- gravimetry differential scanning calorimetry (TG-DSC) system was used to give the TG and differential TG (DTG) experimental points for biomass pyrolysis and catalytic pyrolysis at different heating rates. The experi- ments were carried out in an atmosphere of N 2 and Ar, with a carrier flow rate of 60 ml/min, using 10-mg samples. The heating rates were programmed at 10 °C, 20 °C, 30 °C and 40 °C/min. The biomass samples used in this study were wheat straws grinded and collected from the suburban areas of Beijing and had diameters b 0.15 nm. The catalysts for pyrolysis were classified into three groups: solid acid catalysts (HUSY/γ-Al 2 O 3 : Hydrogen exchanged ultra-stable Y zeolite loaded on γ-Al 2 O 3 ; REY/γ-Al 2 O 3 : rare-earth Y zeolite loaded on γ-Al 2 O 3 ; HZSM-5/γ-Al 2 O 3 : Hydrogen exchanged ZSM-5 zeolite loaded on γ-Al 2 O 3 ), bifunctional catalysts (Ni–Mo–HUSY/γ-Al 2 O 3 , Ni–Mo–REY/γ-Al 2 O 3 , and Ni–Mo–HZSM-5/ γ-Al 2 O 3 : the corresponding acid catalyst additionally impregnated with nickel and molybdenum according to an atom ration of 1:4) and two industrial catalysts CIP and MLC used for heavy oil cracking (from China Petroleum and Chemical Corporation, CIP and MLC are products models). 3. Results and discussion The TG and DTG curves of biomass pyrolysis and catalytic pyrolysis using different catalysts showed that the primary decomposition reactions occurred between 150 and 500 °C and the maximum weight loss rate was reached at 340–360 °C (Fig. 1). 3.1. General characteristics of biomass catalytic pyrolysis Assuming that the catalytic pyrolysis of biomass follows apparent first-order reaction kinetics (though this assumption is later shown not to be completely valid), the Coats–Redfern integral method was used to analyze the pyrolytic characters of this complicated process. Biotechnology Advances 27 (2009) 583–587 ⁎ Corresponding author. Institute of Process Engineering, Chinese Academy of Sciences, Beijing, 100190, China. Tel.: +86 10 82627078. E-mail address: wglin@home.ipe.ac.cn (W. Lin). 0734-9750/$ – see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.biotechadv.2009.04.014 Contents lists available at ScienceDirect Biotechnology Advances journal homepage: www.elsevier.com/locate/biotechadv