Catalytic Reforming of Volatiles from Biomass Pyrolysis for Hydrogen

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Catalytic reforming of volatiles from biomass pyrolysis for hydrogen-rich gas production over limonite ore Xiao-Yan Zhao, Jie Ren, Jing-Pei Cao, Fu Wei, Chen Zhu, Xing Fan, Yun-Peng Zhao, and Xian-Yong Wei Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.7b00005 • Publication Date (Web): 08 Mar 2017 Downloaded from http://pubs.acs.org on March 14, 2017

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Energy & Fuels

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Catalytic reforming of volatiles from biomass pyrolysis for hydrogen-rich gas production over

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limonite ore

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Xiao-Yan Zhao, Jie Ren, Jing-Pei Cao*, Fu Wei, Chen Zhu, Xing Fan, Yun-Peng Zhao, Xian-Yong

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Wei

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Key Laboratory of Coal Processing and Efﬁcient Utilization (Ministry of Education), China

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University of Mining & Technology, Xuzhou 221116, Jiangsu, China

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Abstract

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The feasibility of using natural limonite ore for catalytic cracking of biomass pyrolysis volatiles

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was investigated to study the effects of catalyst treated method, temperature, space velocity, and

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atmosphere on carbon conversion and gas yields. Limonite ore has a certain catalytic activity in the

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cracking of tarry material and the activity could be significantly enhanced after reduction with H2.

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When the reduced limonite was used, the gas yield increased to the maximum value of 41.6 mmol/g

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and the yield of carbon in water soluble tar decreased to a negligible value (0.7%) by increasing the

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reforming temperature from 400 to 650 oC. The reforming activity of the reduced limonite is

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comparable with the commercial Ni/Al2O3 catalyst. Steam can inhibit carbon deposition on limonite

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and give a H2-rich gas (H2 content 70.4 vol.%) in a high yield of 74.1 mmol/g at 700 oC. Lower

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space velocity improve carbon conversion and gas production. The study revealed the possibility of

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using limonite as an alternative and attractive catalyst to the commercial precious metal catalysts for

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catalytic gasification of biomass in low temperature.

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Keywords: Biomass; Catalytic reforming; Gasification; Limonite; Volatiles

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1. Introduction

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With the depletion of fossil fuels and increasing concern over pollution and its effects on

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climate change, biomass has attracted more attention as a valuable energy source.1 Biomass

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utilization is recognized as one of the most promising solutions for current energy and * Corresponding author. Tel./fax: +86 516 83591059. E-mail address: [email protected]; [email protected]; [email protected] (J. P. Cao)

ACS Paragon Plus Environment

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environmental problems.2 Thermochemical conversion of biomass, such as combustion, gasification

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and pyrolysis, have been developed.3-5 Among that, gasification of biomass for combustible gas and

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H2-rich gas production was regarded to be the most promising process due to its high conversion

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efficiency.6 The gaseous products can be widely used as fuel for power generation or feedstock for

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chemical synthesis and fuel cells.7

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However, biomass gasification is still in the developing stage due to some challenges. The most

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severe problem is dealing with the tar formed during gasification.8-11 As a sticky material, biomass

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tar usually condenses in the low-temperature zone of the downstream applications and blocks the

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narrow pipeline, which makes troubles for either gasification process or the subsequent utilization

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of gasous product.12 Among the approaches for tar reduction, catalytic gasification is one of the

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most effective methods of tar elimination even at moderate conditions.13-16 Catalyst can efficiently

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promote the tar cracking, and improve the gas production, such as CaO/Al2O3,17 zeolite catalyst

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and transition metal based catalysts, especially for nickel ones,19-21 which were proven to be active

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for tar decomposition even at a relatively low temperature.22,23 Nevertheless, Ni is a noble metal,

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using the expensive commercial Ni catalysts for biomass gasificaiton is economically infeasible.

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Iron oxide was employed as a catalyst for tar cracking. Uddin et al.24 found that iron oxide

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(Fe2O3) was transformed to Fe3O4 during the gasification reaction, and exhibited a certain catalytic

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activity for gasification of biomass tar. The iron oxide caused the cracking of the tar and affected

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the composition and yield of the gaseous products. Specific surface area (SSA) of the iron oxide

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was the main contributors to the tar cracking. Li et al.25 studied the catalytic behavior of Indonesian

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natural limonite ore for decomposition of coal volatile. The low cost and high activity limonite ore

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showed a fine surface structure and a high SSA and was active for hydropyrolysis of coal volatiles

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between 600 and 800 oC. Matsumura et al.26 tested Australian natural limonite, which contains

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about 30% mud and 57% iron brown spots, for the decomposition of the asphaltenes and found that

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the limonite was more active for asphaltenes cracking than Ni/Mo at the same temperature.


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Nordgreen et al.27 studied the hematite as catalyst for gasification of birch in fluidized bed and

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found that the tar cracked completely when the temperature reached 900 oC. He et al.28 investigated

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the catalytic cracking of pyrolytic vapors of low-rank coal over limonite ore and found that limonite

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was active for tar cracking. Limonite with abundant resource, low price and easy disposal is thought

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to be an attractive alternative to the commercial metal catalysts.25,26

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In this study, the physical and chemical properties of limonite samples treated under different

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conditions were studied. The feasibility of using limonite ore for reforming of biomass volatile at

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low temperature was carried out in a two-stage fixed-bed reactor. The effects of catalyst, space

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velocity (SV), temperature, atmosphere of the carbon conversion and gas yield were significantly

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investigated.

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2. Materials and Methods

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2.1. Materials

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The corncob was used as the biomass sample, and the sample preparation and main

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characteristics were described in detail previously.29 The proximate and ultimate analyses of the

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corncob was listed in Table S1 (as shown in the Supporting Information). The catalyst used is an

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Indonesian limonite, which is provided by Kobe Steel, Ltd. A commercial Ni/Al2O3, which was

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proven to be active for tar cracking, and sand were used for catalytic and non-catalytic comparison.

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All the catalysts were prepared to be 1-2 mm particle size before use. The limonite was

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characterized by X-Ray Fluorite Spectroscopy, X-ray diffraction (XRD), transmission electron

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microscope (TEM), thermogravimetric (TG) analyzer and adsorption apparatus. The preparation

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and characterization of materials in detail was presented in Supporting Information.

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2.2. Catalytic reforming and products analysis

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The catalytic volatiles reforming experiment was performed in a two-stage fixed-bed quartz

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reactor as reported previously.29 The reforming temperature was set at a temperature range of

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400-750 oC and the SV was set as 2400, 3600 and 7200 h-1 by packed catalyst heights of 3, 2 and 1


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cm. About 1 g corncob was put on the first stage and prescribed amount of catalyst was put on the

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second stage. Before the temperature of the first stage was raised from 30 oC to 900 oC, the second

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stage of the quartz reactor was firstly heated to 650 oC for catalyst reduction by H2 for 1 h and then

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set prescribed temperature of 400-750 oC and switched to Ar atmosphere for the reaction. For steam

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catalytic reforming, steam was injected through a single-channel pump as reported.30 The total flow

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rate and the steam partial pressure were controlled at 120 mL/min and 30 kPa, respectively.

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Catalytic reforming test under the calcined limonite without H2 reduction was also conducted.

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The reforming product was cooled in two traps with deionized water at -10 oC. The gaseous

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products were collected for 1 h in a valved gas sampling bag and analyzed by Shimadzu GC-2014

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GC/FID and GC/TCD. The gas yield was calculated by Eq. (1). n(x)=(V(total)×y(x))/22.4

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(1)

y(x): The volume content of x in gas bag (vol.%); V(x): Total volume of gas in bag (mL); n(x): The yield for x (mmol).

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A Shimadzu TOC-L analyzer was used to determine the total soluble carbon in deionized water.

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Tar and carbon deposited (Cdep) on the reactor wall and catalysts were burned out at 800 oC under

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O2 for 1 h. The gaseous product was collected and the concentration of CO2 was detected by GC to

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calculate the content of the Cdep. An Elementar vario MACRO cube CHNS elemental determinator

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was used to analyze the carbon content in char collected in the first stage (Cchar).

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3. Results and discussion

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3.1. Characterization of limonite

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3.1.1. XRD analysis

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Figure 1a shows the XRD spectra of the limonite raw material (L-RA), the limonite calcined at

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650 oC for 1 h (L-CA) and the limonite reduced at 650 oC for 1 h (L-RE). It can be found that the

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main crystalline species detected in raw limonite ore is goethite (FeOOH). For the calcined limonite,

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the diffraction signal of goethite (FeOOH) was almost diminished completely with increased


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hematite (Fe2O3) signals, suggesting the conversion of goethite (FeOOH) to hematite (Fe2O3)

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during the calcined process (Eq. (2)). González et al.31 and Mochizuki et al.32 also reported the

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conversion of goethite (FeOOH) to hematite (Fe2O3). 2FeOOH → Fe2O3 + H2O

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(2)

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XRD analysis showed that the crystalline phase of goethite (FeOOH) transformed into metallic

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iron rather than hematite (Fe2O3) when the limonite was reduced under H2 atmosphere at 650 oC for

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1 h, which indicated the catalyst reduction temperature at 650 oC is suitable enough. Figure 1b

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shows the typical XRD spectra of the raw limonite sample and the thermally treated ones at

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200-700 oC for 3 h, and it can be concluded that goethite (FeOOH) peaks at 21.3°, 33.3°, 36.7°,

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53.3° and 59.9° have no change in phase. When the calcination temperature reached to 300 oC, the

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goethite diffraction peak almost entirely disappeared. At the same time, some new hematite

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diffraction peaks appeared.33,34 It also can be concluded that the diffraction peak of hematite

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gradually strengthened with the increase of temperature. The reactivity of natural limonite for tar

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reforming could further be increased by reduction with H2.35 Therefore, 650 oC was selected as the

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catalyst reduction temperature in this experiment.

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3.1.2. TEM analysis

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TEM images about limonite were recorded after treated at different temperatures of 25, 300,

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500 and 700 oC. As shown in Figure 2, the acicular should be goethite, the main ingredient in

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natural limonite, which can be calculated to 10-30 nm diameter of goethite (FeOOH) crystals. There

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is no significant change in acicular shape after calcination at 300 oC, except for the formation of

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nanometer pore goethite with diameter of 0.5-3 nm due to water removal and dihydroxylation

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process at 300 oC. Combined with XRD analysis, it can be concluded that the acicular product is

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hematite (Fe2O3). The trend is well consistent with previous report.36 After calcination at 500 oC, the

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nanometer pore became larger in comparison with that treated at 300 oC. The bulk of the hematite

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was sintered when the calcination temperature increased to 700 oC.


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3.1.3. TG analysis

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As shown in Figure 3, it can be observed the total mass loss with average value of 15.21 wt.%.

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The derivative TG (DTG) curve can be resolved into three stages associated to the main weight loss

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peaks. The first stage occurred below 150 oC interval representing the 2.31 wt.% of weight-loss,

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which corresponded to the loss of absorbed water of limonite. The second stage of decomposition at

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150-400 oC, with a weight loss of 10.58 wt.%, was associated to dehydroxylation.37 However,

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according to the Eq. (2), the conversion of goethite to hematite should have the theoretical weight

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loss of 10.1%. The phenomenon should be due to the existence of considerable strong interactions

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between broken bonds and desorption of hydroxylation on goethite surface. This conclusion is in

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good agreement with the studies of Parfitt et al.,37 Russel et al.,38 and Rochester et al.39 which

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proved two types of surface hydroxyl group exist in limonite. Above 700 oC, a sharp peak accounts

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for 2.3% of the total weight loss occurred. This stage can be contributed to desorption of the

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remanent hydroxyl.

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3.1.4. SSA and pore size analysis

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As shown in Figure 4, an obvious change can be found for SSA below 200 oC. When the

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temperature was increased to 350 oC, the SSA significantly increased to the maximum value of

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183.1 m2/g, which should be due to the dehydroxylation of goethite and the formation of slit-shaped

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micropores. The SSA decreased to 72.6 m2/g at 700 oC due to the internal and interparticles

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sintering, which can be found in XRD and TEM analyses. The presence and change of slit-shaped

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micropores is in agreement with that mentioned in 3.1.3. As Figure 5 shows, the pore mainly

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distributed 0.3-20 nm. The peak at 2.9 nm for the raw limonite should be attributed to the

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micropores arising from the interparticles clearance. After treated at 300 and 400 oC, a strong peak

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appeared below 1.3 nm for the two samples, which is well analogous to the results reported.34,35 The

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peak shifts to 3.5 nm when treated the limonite at 400 oC and the intensity becomes weak with the

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increased temperature. The dramatic increase of SSA should be ascribed to slit-shaped micropores


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from goethite dehydroxylation. The micropore in the limonite disappeared at 600-700 oC. The

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uniform mesopores, mainly around 4.5 nm, can provide an excellent environment for volatile

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reforming. Thus, with the increase of treated temperature, newly formed micropores are easily

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transformed to mesoporous and macropores, as a result causes the decrease of SSA and increase of

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pore size.

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3.2. Catalytic reforming of volatiles over limonite

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3.2.1. Effect of catalyst

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The gaseous composition and the H2/CO and CO/CO2 molar ratios are important index for

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syngas production. As shown in Figures 6 and 7, the gas yield was quite low (13.7 mmol/g) when

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sand was used at 650 oC, and the H2/CO molar ratio of the gas was 0.85. When the L-CA was used,

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about 49.8% and 6.1% of carbon were converted to carbon in gas (Cgas) and Cdep, respectively,

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indicating that the L-CA can promote volatiles reforming and giving a gaseous product with a

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H2/CO molar ratio of 2.93. L-CA showed a certain activity for tar cracking. These results were well

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consistent with the reports from Hurley et al.40 However, there was still 1.6% of carbon left in water

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soluble oil (CWSO) over L-CA during reforming under inert atmosphere. At the same temperature,

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the gas yield was 41.16 mmol/g (daf) when L-RE was used. Ni/Al2O3 was reported being quite

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active for tar cracking at 650 oC.16 L-RE has a comparable activity with the commercial Ni/Al2O3.

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Compared with Ni/Al2O3, L-RE gives a relative lower H2/CO ratio of 1.72 but a higher CO/CO2

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ratio of 3.31. Compared with Ni/Al2O3, L-RE gives a higher carbon balance of 97.8% and lower

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CWSO yield, but a higher Cdep yield partly due to the high SSA of limonite shown in Figure 4. Thus,

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it can be concluded that the L-RE was efficient for corncob volatiles reforming, and the activity is

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comparable with the commercial Ni/Al2O3. In addition, as listed in Table 1, the limonite ore also

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contains quite low content of Ni, Cr, Co, CaO and MgO, all these impurities have been reported

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active for biomass volatiles reforming.16-20 Understanding of the catalytic effects of the impurities in

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limonite is challenging work and deserves further investigation.


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3.2.2. Effect of SV

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Generally, the low SV is in favor of catalytic reaction.30 As Figures 6 and 7 display, about 46.3%

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of carbon was found in Cgas, and the yield of gas reached to 36.22 mmol/g. 9.4% of carbon was

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converted to Cdep at a SV of 7200 h-1. In addition, 4.6% of carbon was found in WSO. From Figures

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6 and 7 it can be seen that the gas yield reached to 41.61 mmol/g, and the H2 and CO production

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reached to 21.65 mmol/g and 12.61 mmol/g, when the SV was decreased to 3600 h−1. It can be

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found that gasification efficiency was enhanced and Cdep was decreased. No obvious change can be

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found of the Cgas (42.28 mmol/g) and CWSO when the SV was further decreased to 2400 h-1. Lower

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SV was in favor of volatiles reforming and gas products formation because of the relatively long

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residence time, which is well consistent with the report of Uddin et al.24

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3.2.3. Effect of reforming temperature

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Catalytic temperature was reported to be the most important factor affecting the activity for

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volatiles reforming.14 As illustrated in Figures 8 and 9, L-RE gives a gas yield of 1.3 times higher

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than non-catalytic test at 400 oC. However, the CWSO yield (8.1%) was quite high at 400 oC. The gas

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yield increased to the maximum value of 41.6 mmol/g when the temperature was ramped to 650 oC.

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On the other hand, the CWSO yield decreased significantly to a negligible amount of 0.7%. The

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yields of CH4 and CO2 decreased with increasing temperature and attained to a yield 3.6 and 3.8

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mmol/g, respectively. On the contrary, the H2 and CO yields increased rapidly. The results indicated

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that the L-RE is active for reforming of CH4 with CO2 (Eq. (3)). Further raising the temperature to

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750 oC lead to a slight decrease in the yield of H2 and CO. As mentioned in Figure 4, the SSA of

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limonite decreased with the increasing temperature, which might cause the decline of the activity.

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The lower heating value (LHV) of the gaseous products was calculated following previous

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literature,5 and the result showed that the LHV decreased from 14.6 to 12.8 MJ/m-3 with the

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temperature rising from 400 to 750 oC. In general, CH4 has the highest heating value in the gaseous

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products. The decrease of CH4 content leads to a decrease in the LHV of the gaseous products.


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Moreover, the H2/CO ratio gets a value range around 1.7-1.8 between 650 and 750 oC, which is

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comparable with the molar ratio of 1.87 over Ni/Al2O3. The trend suggests that the gaseous product

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from biomass gasification over limonite can be potential candidate for FT synthesis. CH4 + CO2 ↔ 2CO + H2

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(3)

3.2.4. Effect of temperature on catalytic steam reforming

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Steam as the gasification agent is effective atmosphere for the increase of H2 production.41

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Figure 10 shows the reaction mechanism of steam reforming. The volatiles will oligomerize and

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generate Cdep, while steam can dissociate hydroxyl radicals produced at catalyst surface, then react

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with the volatiles to generate COx and H2. Steam reforming is considered as an efficient method for

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H2-rich gas production via the reaction of volatiles with steam at temperatures of 650-700 oC. Thus,

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steam reforming test was investigated over L-RE under a SV of 3600 h-1 and a steam partial

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pressure of 30 kPa at 400-750 oC.

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As displayed in Figure 11 and Table 2, steam reforming decomposed most of the tarry materials

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and gave a high H2 yield via the steam reforming reactions. The H2 content was 59.2 vol.% at 400

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o

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Compared with catalytic reforming, steam reforming mainly promotes the decomposition of tarry

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materials to H2, CO, and small amounts of CO2 below 500 oC. The CWSO yield decreased from 6.9%,

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a value quite lower than that of catalytic reforming, to a negligible value of 0.3% when the

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temperature was increased from 400 to 700 oC. In this temperature range, the water-gas shift

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reactions will produce additional H2 and CO2. The yield of gas significantly increased to a high

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value of 74.1 mmol/g at 700 oC. There is no obvious change when the temperature further ramped

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to 750 oC, besides a slightly decrease in CH4 yield to produce H2 and CO2 (Eq. (4)).

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C and increased to a level of 70.4-71.0 vol.% when the temperature raised to 650-750 oC.

CH4 + 2H2O ↔ 4H2+ CO2

(4)

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Steam reforming of biomass and waste over Ni/Al2O3 also gave a higher H2 content.30 The

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temperature range of 650-750 oC is suitable for catalytic steam reforming, which gives a high gas


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yield of 71.35-74.38 mmol/g. Similar with that obtained over Ni/Al2O3, the H2/CO molar ratio over

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L-RE is about 3.64-3.82 at 650-750 oC. In addition, the highest molar ratio of CO/CO2 reached to

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2.46 at this temperature range. A higher molar ratio of CO/CO2 will have a stronger influence on the

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calorific content of the gaseous product. Therefore, limonite can be used as an economical and

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alternative catalyst for steam gasification of biomass to produce hydrogen-rich gas at relatively low

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temperature.

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As Figures 9 and 12 show, no obvious change can be found of the Cdep yield below 600 oC

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between catalytic reforming and steam reforming. In general, carbon and water were almost

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non-reactive below 800 oC without catalyst.42 The Cdep yield decreased significantly to 8.0% at 600

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o

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can promote this reaction at 600 oC.30 In this study, Steam reforming of Cdep above 600 oC was

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ascribed to the presence of metal Fe catalyst. In summary, steam reforming of biomass volatiles

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over limonite is favorable for not only producing tar-free H2-rich gas, but also avoiding Cdep on

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catalyst, at a relatively low temperature range of 650-750 oC.

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4. Conclusions

C and further decreased below 3% when raising the temperature to 700-750 oC. Ni-based catalyst

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The natural limonite ore can be converted to a porous Fe-based catalyst after reduction at 650 oC

241

and significantly promotes biomass volatiles reforming and produces a tar-free synthetic gas in a

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high yield of 41.6 mmol/g of 650 oC. Steam introduction significantly promotes the gasification of

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Cdep and gives a H2-rich gas (up to 70.4 vol.%) in a high yield of 74.1 mmol/g. Catalytic reforming

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and steam reforming of biomass volatiles significantly depends on temperature, SV and atmosphere.

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With abundant resource, low price and easy disposal of spent catalyst, limonite is thought to be an

246

attractive and alternative to the commercial metal catalysts. Further work will focus on other impact

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parameters, such as steam partial pressure and feedstock type, along with assessment of the lifetime.

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Supporting Information

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Material suppliers and properties, proximate and ultimate analyses of the samples (Table S1),


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and preparation and characterization of the catalyst.

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Acknowledgements

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This work was subsidized by the Fundamental Research Funds for the Central Universities

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(China University of Mining & Technology, 2015XKQY05), National Natural Science Foundation

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of China (Grant 21676292), Natural Science Foundation of Jiangsu Province (Grant BK20151141)

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and the Priority Academic Program Development of Jiangsu Higher Education Institutions.

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References

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(2) Chan, F. L.; Tanksale, A. Renew. Sust. Energ. Rev. 2014, 38, 428-438.

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(3) Wang, Y.; Li, X.; Mourant, D.; Gunawan, R.; Zhang, S.; Li, C. Z. Energy Fuels 2012, 26, 241–

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Figure captions

318

Table 1 Chemical composition of the Indonesian limonite (expressed as wt.% of metal oxides).

319

Table 2 The gas yields (mmol/g) under Ar and steam atmosphere at different temperatures.

320

Figure 1 XRD patterns of L-RA, L-CA and L-RE (a) and thermally treated limonite (b).

321

Figure 2 TEM images of natural limonite and thermally treated limonite.

322

Figure 3 TG and DTG curves of limonite.

323

Figure 4 SSA of raw limonite and thermally treated limonite.


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

324

Figure 5 Pore size distribution of raw limonite and thermally treated limonite.

325

Figure 6 Effects of catalyst and SV on gas yield.

326

Figure 7 Effects of catalyst and SV on carbon balance.

327

Figure 8 Effect of temperature on gas yield during catalytic reforming.

328

Figure 9 Effect of temperature on carbon balance during catalytic reforming.

329

Figure 10 Catalytic steam reforming mechanism of volatiles.

330

Figure 11 Effect of temperature on gas yield during steam reforming.

331

Figure 12 Effect of temperature on carbon balance during steam reforming.


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

332

Energy & Fuels

Table 1. Chemical composition of the Indonesian limonite (expressed as wt.% of metal oxides). Sample

Fe2O3

SiO2

Al2O3

NiO

Co2O3

Cr2O3

CaO

MgO

Limonite

65.00

1.67

11.24

1.69

0.13

1.70

0.07

0.25

333


Energy & Fuels

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334

Page 16 of 28

Table 2. The gas yields (mmol/g) under Ar and steam atmosphere at different temperatures.

Catalyst

Temperature (oC)

Ar

Steam

H2

CO

CO2

CH4

H2

CO

CO2

CH4

L-RE

400

6.7

2.2

4.5

4.5

18.1

3.1

6.6

2.8

L-RE

500

9.1

3.8

5.4

4.3

31.4

6.1

7.1

2.3

L-RE

600

15.5

9.8

4.1

4.0

41.2

9.6

7.0

2.3

L-RE

650

21.7

12.6

3.8

3.6

50.2

13.1

5.9

2.1

L-RE

700

21.5

12.4

3.0

3.8

52.2

14.3

5.8

1.8

L-RE

750

21.7

12.5

2.9

3.7

52.8

14.5

5.9

1.2

Ni/Al2O3

650

25.4

13.5

5.2

2.8

51.0

13.2

6.1

1.8

335


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

336

a

∆ : Fe × : Fe 2 O 3

∆

∗ ∗

b ∗

∗

∗

∆ FeOOH * Fe2O3

∗

o

700 C

∗∗

+ : FeOOH

o

600 C ∆ ∆

o

500 C

L-RE

o

400 C

× × ×

×

×

×

××

o

300 C

L-CA

+

∆

∆ ∆∆

+ +

+

++

∆

∆

o

∆

200 C

+ +

o

25 C

L-RA 20

337 338

30

40

50

60

2 θ ( o)

70

80

90 10

20

30

40

o

50

2θ ( )

60

70

80

Figure 1. XRD patterns of L-RA, L-CA and L-RE (a) and thermally treated limonite (b).


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

339

340 341

Figure 2. TEM images of natural limonite and thermally treated limonite.


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100

0.00 -0.02 -0.04 -0.06 -0.08

90 -0.10 -0.12 85

-0.14 -0.16

80 100

342 343

200

300

400 500 600 o Temperature ( C)

700

800

-0.18 900

Figure 3. TG and DTG curves of limonite.

344


o

Weight loss (%)

95

DTG (%/ C)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Energy & Fuels

190 170 150 2

SSA(m /g)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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130 110 90 70 50 0

345 346

100

200

300 400 500 o Temperature( C)

600

700

Figure 4. SSA of raw limonite and thermally treated limonite.


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Energy & Fuels

o

700 C o 600 C

o

500 C

o

400 C

o

300 C o

200 C Raw

0

2

4

6

8

10

12

14

16

18

20

347

Pore size (nm)

348

Figure 5. Pore size distribution of raw limonite and thermally treated limonite.


Energy & Fuels

50

o

-1

650 C SV: 3600 h

o

650 C

40 Gas yield (mmol/g, daf)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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20

CO2

10

0

349 350

H2

30

CO CH4

sand

L-CA Ni/Al2O3 L-RE Catalyst

7200

2400 -1 SV (h )

Figure 6. Effect of catalyst and SV on gas yield.


Page 23 of 28

o

-1

o

650 C SV: 3600 h

100

Carbon balance (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

650 C Cwso Cdep

80 Cgas

60

40

20 Cchar

0

351 352

Sand

L-CA Ni/Al2O3 L-RE Catalyst

7200 2400 -1 SV (h )

Figure 7. Effect of catalyst and SV on carbon balance.


Energy & Fuels

40 Gas yield (mmol/g, daf)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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30

H2

20 CO2

10

CO CH4

0 400

353 354

500

700 750 650 600 o Reforming temperature ( C)

Figure 8. Effect of temperature on gas yield during catalytic reforming.


Page 25 of 28

100

CWSO Cdep

80

Carbon balance (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

40

20

0

355 356

Cgas

60

Cchar

400

500 650 700 600 o Reforming temperature ( C)

750

Figure 9. Effect of temperature on carbon balance during catalytic reforming.


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

357 358

Figure 10. Catalytic steam reforming mechanism of volatiles.


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80

Gas yield (mmol/g, daf)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

60 H2

40

20

0

CO CO2 CH4

400

500

600 650 L-RE

700

750

650 NiAl2O3

o

359 360

Reforming temperature ( C)

Figure 11. Effect of temperature on gas yield during steam reforming.


Energy & Fuels

100

CWSO Cdep

80 Carbon balance (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 28

Cgas

60

40

20

0

361 362

Cchar

400

500

600 650 700 750 L-RE o Reforming temperature ( C)

650 NiAl2O3

Figure 12. Effect of temperature on carbon balance during steam reforming.


Catalytic Reforming of Volatiles from Biomass Pyrolysis for Hydrogen

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