Catalytic Pyrolysis of Tar Model Compound with Various Bio-Char Catalysts to Recycle Char from Biomass Pyrolysis

Abstract

a Tar and char can be regarded as unwanted byproducts during the gasification process. In this study, three types of catalyst, i.e., biomass char (bio-char), nickel supported on biomass (Ni+bio-char), and nickel supported on bio-char (bio-char+Ni), were studied to compare the catalytic effects of different preparation methods on tar model compound removal. The structural characteristics of the three catalysts were also investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) methods. The results revealed that Ni+bio-char catalyst showed much higher activity for the reformation of toluene (C7H8) as a tar model compound than the other two catalysts. Toluene could be completely converted to small gas molecules at a conversion rate of 99.92% at 800 °C, and the maximum yield of gas was 432 mL/(mL C7H8). In particular, the H2 and CH4 yields were 339 and 85 mL/(mL C7H8) at 850 °C, respectively. An N2 absorption-desorption experiment demonstrated that the specific surface area of Ni+bio-char was 32.87 times that of bio-char and 8.39 times that of bio-char+Ni. Moreover, metallic nickel (Ni 0 ) particles could be generated in the carbon matrix of Ni+bio-char catalyst. SEM analysis confirmed that the Ni+bio-char catalyst had a more porous structure. Nickel supported on biomass might be a promising catalyst for tar reformation because of its excellent catalytic activities.

Sustainable Hydrogen Production from Waste Wood and CO2

“…45 Moreover, the high specific surface area of the char also enhances the cracking/reforming of high molecular weight compounds (tar) in the later stages of processing by adsorbing them along the pores distributed at the surface of the char. 53,54 When 100% CO 2 is used as a carrier gas in the pyrolysis process, the outlet gas mixture contains mainly CO (55. 4 + ↔ + in the process, leading to an increase of H 2 and CO concentration in the gas stream.…”

“…The high porosity of the char will promote the mass transfer among the gas gasifying agent and char particles, accelerating the heterogeneous solid–gas reactions, occurring in the gasification step, i.e., the Boudouard reaction (C + CO 2 → 2CO) and the water gas reaction (C + H 2 O → 2CO + H 2 ), leading to the formation of H 2 and CO with minimum unburnt carbon in the ash residues . Moreover, the high specific surface area of the char also enhances the cracking/reforming of high molecular weight compounds (tar) in the later stages of processing by adsorbing them along the pores distributed at the surface of the char. , When 100% CO 2 is used as a carrier gas in the pyrolysis process, the outlet gas mixture contains mainly CO (55.4 mol %) and H 2 (27.8 mol %) compared to 47.6 mol % CO and 22.3 mol % H 2 obtained in the N 2 environment (Table ). This is because CO 2 promotes char reactions (C + CO 2 → 2CO) and CO 2 reforming reactions in the process, leading to an increase of H 2 and CO concentration in the gas stream.…”

“…39 Moreover, an enhancement in char properties (high porosity; 618 m 2 /g) results from the presence of CO 2 during pyrolysis compared to 98.4 m 2 /g in a N 2 atmosphere (Table 4) and also promotes the tar cracking/reforming process by adsorbing along the pores distributed at the surface of the char. 53,68 At a fixed S/C molar ratio of 3.4, the tar gradually decreased with the increasing CO 2 percentage in the carrier gas, i.e., from 18.3 g/Nm 3 at a CO 2 /N 2 ratio of 1:5 to 12.6 g/Nm 3 at a CO 2 /N 2 ratio of 1:1 and 11.9 g/Nm 3 at a CO 2 /N 2 ratio of 5:1, respectively (Table 8), which is similar to what is reported in the literature. 69,70 As shown in Table 8, a lower CO 2 concentration than 1:1 in the carrier gas had no significant effect on the tar composition compared to N 2 /steam gasification at a fixed S/C molar ratio of 3.4.…”

Recent Progress in the Steam Reforming of Bio-Oil for Hydrogen Production: A Review of Operating Parameters, Catalytic Systems and Technological Innovations

“…Lignocellulosic biomass, such as agricultural residues and dedicated energy crops, has a vast unused potential for continuous energy supply at a low price and with neutral carbon dioxide (CO 2 ) environmental impact [8][9][10]. The utilization of lignocelluloses can open a renewable carbon-neutral roadmap [11,12] for the production of heat, electrical power and biofuels.…”

Thermogravimetric mass spectrometry of lignin pyrolysis under the co-action of CaO and K2HPO4·3H2O

“…The catalytic pyrolysis of biomass is the selective conversion of biomass into high-value chemicals or high-quality bio-oil under the action of catalysts (Wang 2010;Ren et al 2013;Liu et al 2016;Yang et al 2019). It is an important way to utilize biomass and has attracted the attention of researchers (Luo et al 2017;Wang et al 2018).…”