Integrated Production of Aromatic Amines and N-Doped Carbon from

Mar 3, 2017 - iChEM, CAS Key Laboratory of Urban Pollutant Conversion, Anhui Province Key Laboratory of Biomass Clean Energy, Department of ...
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Integrated Production of Aromatic Amines and N‑Doped Carbon from Lignin via ex Situ Catalytic Fast Pyrolysis in the Presence of Ammonia over Zeolites Lujiang Xu, Qian Yao, Ying Zhang,* and Yao Fu* iChEM, CAS Key Laboratory of Urban Pollutant Conversion, Anhui Province Key Laboratory of Biomass Clean Energy, Department of Chemistry, University of Science and Technology of China, Hefei 230026, China

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ABSTRACT: Due to the irregular polymeric structure and carbon based inactive property, lignin valorization is very difficult. In this study we proposed a new route for lignin valorization by which aromatic amines can be directly produced from lignin by ex situ catalytic fast pyrolysis with ammonia over zeolite catalysts. Meanwhile, the obtained pyrolytic biochar can be activated to produce high surface area N-doped carbon for electrochemical application. Wheat straw lignin served as feed to optimize the pyrolysis conditions. MCM-41, β-zeolite, HZSM-5, HY, ZnO/HZSM-5, and ZnO/HY were screened, and ZnO/HZSM-5 (2 wt % Zn, Si/Al = 50) showed the optimal reactivity for producing aromatic amines due to the desired pore structure and acidity. Temperature, residence time, and ammonia content in the carrier gas displayed significant effects on the product distribution. The maximum yield of aromatic amines was obtained at moderate temperatures around 600 °C, 0.57 s, and 75% ammonia in the carrier gas. Under the optimized conditions, the total carbon yields of pyrolytic bio-oil and aromatic amines were 9.8% and 5.6%, respectively. The selectivity of aniline in the aromatic amines was up to 87.3%. Moreover, the pyrolysis byproduct, biochar, was further activated by KOH at 800 °C under ammonia atmosphere for producing N-doped carbon with high surface area. The pyrolytic biochar and N-doped carbon were characterized by elemental analysis, SEM, XRD, nitrogen adsorption−desorption, and XPS. Cyclic voltammetry (CV) and galvanostatic charge−discharge were employed to investigate the electrochemical performance of pyrolytic biochar and N-doped carbon. The specific capacitance of N-doped carbon reached about 128.4 F g−1. KEYWORDS: Aromatic amines, N-Doped carbon, Lignin, Ex situ catalytic fast pyrolysis, Ammonia

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INTRODUCTION Lignin is the second most common component of biomass, and it accounts for 10−40 wt % of lignocellulosic biomass.1,2 It is composed of three phenylpropenyl units: p-coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol.3,4 Thus, lignin is also regarded as a potential raw material for producing biosourced bulk aromatic chemicals. However, due to its highly irregular polymeric structure and the carbon based inactive property, lignin valorization is very difficult. Lignin is usually viewed as a waste byproduct in the current biorefinery processes. About 70 million tons of lignin are produced in the pulp and paper industry every year.5 Most of the lignin is used to supply heat and power for the biorefinery processes. Only about 5% of lignin is used as low value products, such as low grade-fuel and concrete additive.6,7 © 2017 American Chemical Society

Fast pyrolysis a promising technology that can convert lignin into gases, biochar, and bio-oil.8 Monomeric phenols are the main products in the bio-oil. However, due to the high content of oxygen and complex compounds, the bio-oil cannot be used as a fuel directly.9 Ex situ catalytic fast pyrolysis (CFP) can selectively convert lignin and lignin pyrolysis vapors into chemicals or fuels, such as phenols and aromatic hydrocarbons, and the pyrolytic biochar could be easily separated and collected for further application.10 For examples, Zhou et al. reported that lignin pyrolysis vapor could be upgraded over HZSM-5 catalysts via ex situ CFP under N2 atmosphere.11 They Received: October 21, 2016 Revised: February 28, 2017 Published: March 3, 2017 2960

DOI: 10.1021/acssuschemeng.6b02542 ACS Sustainable Chem. Eng. 2017, 5, 2960−2969

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ACS Sustainable Chemistry & Engineering

interconnected hierarchical porous N-doped carbon via hydrothermal treatment and KOH activation, and the obtained Ndoped carbon also exhibited favorable features for supercapacitor application.36 In this study, we demonstrated a new route for lignin valorization that aromatic amines and N-doped carbon could be produced by ex situ catalytic fast pyrolysis of lignin over zeolite with ammonia as both carrier gas and reactant. In order to further understand the major factors which may affect the aromatic amines production in the ex situ CFP of wheat straw lignin process, the effects of catalyst, reaction temperature, catalyst usage, carrier gas (NH3 to N2 ratio), and residence time were investigated systematically. Moreover, the pyrolysis byproduct, biochar, was further activated by KOH under ammonia atmosphere for producing N-doped carbon with high surface area. Furthermore, N-doped carbon underwent an electrochemical test for application of supercapacitor.

found that the content of oxygen free aromatics (mainly benzene and toluene) in the obtained organic liquid product was about 70 wt % at 600 °C, and the carbon yield of bio-oil was about 10.9%. Olcese et al. used Fe/SiO2 and Fe/activated carbon for ex situ CFP of lignin under atmospheric H2 pressure and found both of the catalysts showed good reactivity for upgrading of lignin pyrolytic vapors to produce aromatic hydrocarbons and simple phenols.12 The carbon yield of bio-oil was about 10%. Besides, Rezaei et al. also synthesized ironbased catalyst (Fe/HBeta) and investigated the effect of ligninderived phenolics on zeolite deactivation during the ex situ CFP of palm kernel shell under an H2 atmosphere process.13 The carbon yield of aromatic hydrocarbons was only 5.13%. Although ex situ CFP could effectively convert lignin to fuels and chemicals via a deoxygenation/hydrodeoxygenation process, due to the polymeric structure and carbon based inactive property, the yield of products in the lignin pyrolysis process is very low, and the main products in the ex situ CFP were pyrolytic biochar and coke, which were viewed as waste byproducts without efficient utilization. Therefore, it is necessary to develop a new route for lignin valorization. Aromatic amines are the major building blocks and key intermediates for producing dyes, agrochemicals, rubber chemicals, and pharmaceuticals.14−16 Industrial aromatic amines production involves two steps.17−19 First, aromatic hydrocarbons are nitrated with a concentrated mixture of nitric acid and sulfuric acid to get nitrobenzene and substituted nitrobenzenes. Then, nitrobenzenes are hydrogenated in the presence of metal catalysts under H2 atmosphere. In this process, a large amount of sulfuric acid and nitric acid as a nitrification agent of aromatic compounds is consumed. In addition, nitrogen oxides are generate when the nitrocompounds are formed, which results in air pollution.20 Therefore, it is necessary to develop an efficient method for producing aromatic amines directly from renewable resources. Tanabe et al. reported that high acidity of silica−titania could catalyze amination of phenol with ammonia to produce aniline.21 Katada et al. reported that aniline could be produced from phenol over β-zeolite under ammonia.22 In addition, we also found that N-heterocycles (pyrroles, pyridines, and indoles) could be produced from biomass and bioderived chemicals via modified CFP, that is a thermocatalytic conversion and ammonization (TCC-A) process.23−25 Besides the bio-oil and gases, biochar is also produced as byproduct in the CFP process, especially the CFP of lignin process. However, it is always treated as waste without effective utilization. Recently, because of the good electronic conductivity, adjustable porosity, and stability, the carbon materials, especially N-doped carbon, from biomass have attracted intensive interest as adsorbents, as catalyst supports, and in energy conversion/storage applications.26−31 Qiao et al. studied and characterized the N-containing biochar from chitin biomass.32 Wang et al. synthesized unusual sheets-like activated carbon from willow catkins and used it as high performance supercapacitors.33 Ren et al. also developed three-dimensional N-doped carbonaceous aerogels from sugars and polypyrrole with an outstanding specific capacitance.34 In addition, lignin also served as raw material to prepare N-doped carbon with superior performance for capacitors. Navarro-Suárez et al. synthesized nanoporous carbon with narrow and tunable pore size distribution and good specific capacitance by activation with potassium hydroxide (KOH).35 Zhang et al. used ligninderived byproducts as carbon precursors to synthesize

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EXPERIMENTAL SECTION

Chemicals. Wheat straw lignin (brown and low grade sulfur lignin from wheat straw) was purchased from Hefei Lanxu Biotechnology Co. Ltd. In this study, it was used as the model lignin to investigate the reaction conditions. Aniline, 2-methylaniline, phenol, m-cresol, guaiacol, eugenol, bicyclohexane, 4-ethyl phenol, and 4-propenyl guaiacol were received from Shanghai Aladdin Chemical Reagent Co., Ltd. Zn(NO3)2·6H2O, benzene, toluene, o-xylene, p-xylene, m-xylene, vinylbenzene, and naphthalene were received from Sinopharm Chemical Reagent Co., Ltd. All these chemicals were AR level and used without further purification. The reagent and carrier gas (such as NH3, N2, Ar, He) and standard gases (such as H2, CH4, C2H4, C2H6, C3H6, and C3H8) for reaction and quantification were received from Nanjing special gases factory. Catalyst Preparation. The commercial zeolites, such as HZSM-5, β-zeolite, MCM-41, and HY, used in this study were purchased from the Catalyst Plant of Nankai University. The modified catalysts (ZnO/HZSM-5 and ZnO/HY) used in this study were prepared using incipient wetness impregnation with a 0.1 M Zn(NO3)2 solution.37 The metal loading of zinc (Zn) was about 2 wt %. After the impregnation, the samples were dried in an oven at 100 °C overnight and then calcined in the muffle furnace at 500 °C for 3 h. The particle size of all the above catalysts was about 40 meshes. The detailed information for these catalysts is shown in Table 1.

Table 1. Physical−Chemical Properties of Catalysts

a

Catalyst

Si/Al ratioa

BET Surface area (m2/g)

Pore diameter (nm)a

Total acid (μmol/g)

MCM-41 β-Zeolite HZSM-5 HY ZnO/HZSM-5 ZnO/HY

∞ 50 50 7.5 50 7.5

1000 640 350 620 354.2 478.3

3.8 0.7 0.5 0.7 0.5 0.7

260.0 683.3 293.6 2206.3 198.8 1465.0

The data were provided by the manufactures.

Bench-Top Pyrolysis Set. The diagram of the benchtop pyrolysis set in this study is shown in Figure S1. The pyrolysis set consists of a gravity feed type feeder, a quartz tube reaction reactor, a condensation tube, and a heating furnace. The catalyst was fixed in the reactor as catalyst bed. The solid lignin was fed into the reactor manually with a certain rate. The pyrolysis reaction occurred in the heating zone of the heating furnace. The pyrolytic products were collected by the condensation tube, which was bathed in liquid nitrogen. The incondensable volatile products were collected with a gasbag. In this study, each pyrolysis experiment was repeated three times, and the average variations on the measured variables were less than 10%. 2961

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ACS Sustainable Chemistry & Engineering Table 2. CFP of Lignin with Ammonia over Different Catalystsa Entry

1

2

3

4

5

6

7

Catalyst Metal loading (wt %) Identified carbon (C%) Biochar Gases Carbon detected in the organic bio-oil

None

HZSM-5

HY

β-zeolite

MCM-41

78.1 50.3 17.5 10.3

87.1 65.4 17.2 4.5

ZnO/HZSM-5 2.0 86.0 55.8 21.1 9.8

ZnO/HY 2.0 85.7 61.1 19.4 5.2

Phenolic compounds Aromatic hydrocarbons Aromatic amines

10.3 N.D. N.D.

0.1 1.1 3.3

2.3 1.9 5.6

0.4 0.3 4.5

Phenolic compoundsb Aromatic hydrocarbonsc Aromatic aminesd

100 N.D. N.D.

2.2 24.4 73.3

25.3 13.2 57.1

7.7 5.8 86.5

Aniline Methylanilines Naphthylamines

N.D. N.D. N.D.

91.3 6.3 2.4

87.3 10.5 2.2

88.7 9.8 1.5

85.2 87.8 86.4 59.5 64.3 67.1 18.7 19.1 16.2 7.0 4.4 3.1 Detected products in the organic bio-oil (C%) 1.0 0.3 0.1 1.7 0.2 0.8 4.3 3.9 2.2 Detected products Selectivity (%) 14.3 6.8 3.2 24.3 4.5 25.8 61.4 88.6 71.0 Aromatic amines selectivity 85.1 93.4 98.1 12.6 6.6 1.9 2.3 0 0

Reaction conditions: mass of lignin: 0.5 g, pyrolysis temperature: 600 °C catalyst usage: 1 g, ammonia flow rate: 60 mL/min, residence time: 0.57s. Phenolic compounds: phenol, m-cresol, guaiacol, etc. cAromatic hydrocarbons: benzene, toluene, xylenes, ethylbenzene, naphthalene, etc. d Aromatic amines: aniline, 2-methylaniline, 3-methylaniline, naphthylamine, etc. a b

Method for Preparing N-Doped Carbon. Before the activation, pyrolytic biochar and KOH (weight ratio: 1:4) were physically mixed and grounded. Then, the mixed sample was set on a ceramic boat and inserted into a stainless steel tube for further activation. The activation conditions of pyrolytic biochar under ammonia are as follows: heating rate 3 °C/min, 800 °C for 1 h. At the end of activation, the sample was cooled down with ammonia. After the activation, the sample was thoroughly washed with a 10 vol % HCl solution several times to remove the inorganic impurities. Then, the sample was also washed with purified water until the pH of the sample became neutral, and dried at 110 °C in air for 10 h. The final obtained product was Ndoped carbon. Characterization of Catalysts and Carbon Materials. The elemental content of pyrolytic biochar and N-doped carbon was measured with an elemental analyzer (VarioELIII, Germany). Powder X-ray diffraction (XRD) analyses of pyrolytic biochar, N-doped carbon, and the catalysts were characterized on a theta rotating anode X-ray diffractometer (TTR-III, Rigaku, Japan). X-ray photoelectron spectroscopy (XPS) analyses of pyrolytic biochar and N-doped carbon were conducted on an ESCALAB250 instrument (Thermo-VG Scientific, UK). The N2-adsorption/desorption isotherms of catalysts, pyrolytic biochar, and N-doped carbon were characterized with the ASAP 2020M+C analyzer at −196 °C (Micromeritics, USA). Scanning electron micrographs (SEM) of pyrolytic biochar and N-doped carbon were taken using a scanning electron microscope (SEM, Sirion 200, FEI Electron Optics Company, USA). For the NH3-TPD tests, the detailed method was reported in our previous work.23 Energy Storage Performance of the N-Doped Carbon. The electrochemical properties of pyrolytic biochar and N-doped carbon were tested on a CHI 660C electrochemical workstation (Shanghai Shenhua Instrument Co., Ltd.) at room temperature in a threeelectrode system. In this system, the electrolyte was 0.1 mol KOH solution, the reference electrode was an Ag/AgCl electrode, and the counter electrode was platinum wire. The work electrode was prepared by loading a slurry which consisted of 80 wt % active material (e.g., pyrolytic biochar, or N-doped carbon), 10 wt % carbon black, and 10 wt % PTFE (polytetra fluoroethylene) on a nickel foam and drying at 353 K for 30 min. The specific capacitance of pyrolytic biochar and Ndoped carbon was evaluated by the galvanostatic charge−discharge (GCD) curves and using the following equation (eq 1): I × Δt C= m × ΔV

In this equation, C is the specific capacitance, I is the discharge constant current, Δt (s) is the discharging time, ΔV is the voltage difference, and m is the weight of active materials in the electrode. Method for Analysis and Quantitation. The carbon yield and selectivity of biochar, gases, aromatic amines, phenolic compounds, and aromatic hydrocarbons were calculated from eqs 2−8. The detailed methods for analysis and quantitation were reported in our previous work.23−25

Residence time =

Catalyst volume Volume flow rate of carrier gas

(2)

Bio‐char yield (C mol%) Moles of carbon in the solid residue = × 100% Moles of carbon in feedstocks

(3)

Gases yield (C mol%) Moles of carbon in gases identified = × 100% Moles of carbon in feedstocks

(4)

Aromatic amines yield (C mol%) Moles of carbon in aromatic amines identified = × 100% Moles of carbon in feedstocks (5)

Aromatic hydrocarbons yield (C mol%) Moles of carbon in aromatics identified = × 100% Moles of carbon in feedstocks

(6)

Phenols yield (C mol%) Moles of carbon in phenols identified = × 100% Moles of carbon in feedstocks

(7)

Selectivity (%) = (1) 2962

Moles of carbon in target compound × 100% Moles of carbon in organic bio‐oil (8) DOI: 10.1021/acssuschemeng.6b02542 ACS Sustainable Chem. Eng. 2017, 5, 2960−2969

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Figure 1. Possible reaction pathway from lignin to aromatic amines during ex situ CFP in the presence of ammonia.

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RESULTS AND DISCUSSION Effect of Catalysts. The pyrolysis behavior of wheat straw lignin with ammonia in the absence of catalyst in the range 500−750 °C was investigated first. The detailed product distributions (Peak area %) are shown in Table S1. When the pyrolysis temperature was below 650 °C, phenolic compounds, such as phenol, m-cresol, guaiacol, etc., were the main compounds in the lignin pyrolytic bio-oil. With the pyrolysis temperature increasing to 700 and 750 °C, the content of phenolic compounds in the bio-oil decreased, while the content of aromatic hydrocarbons increased. As shown in Figure S2, the product distribution changed significantly with the introduction of HZSM-5 catalyst. Phenolic compounds were not the main products in the lignin pyrolytic bio-oil, while aromatic amines (such as aniline, 2-methylaniline, 3-methylaniline) and aromatic hydrocarbons (benzene, toluene, naphthalene) became the main products in the lignin pyrolytic bio-oil. Aniline was the main compound in the aromatic amines. The desired catalyst was essential to selectively produce aromatic amines. In order to further optimize and investigate the effect of catalyst on the production of aromatic amines, six kinds of catalyst (HZSM-5, HY, β-zeolite, MCM-41, ZnO/ HZSM-5,and ZnO/HY) were tested in this study. The pyrolysis temperature condition was at 600 °C, under pure ammonia atmosphere, and the residence time of pyrolysis vapor over the lyst bed was about 0.57 s. The physical−hemical properties of the catalysts are shown in Table 1. The NH3-TPD curves and XRD patterns of these catalysts are shown in Figure S3 and Figure S4. Table 2 summarizes the detailed product distribution of CFP of lignin with ammonia over different catalysts. It can be seen that the products from CFP of lignin with ammonia over different catalysts were biochar, gases, and organic bio-oil. The organic bio-oil was composed of aromatic hydrocarbons, phenolic compounds,and aromatic amines. The selectivity of aromatic amines in the organic bio-oil was above 55%. In addition, the main product in the aromatic amines was aniline, and the selectivity of aniline in the aromatic amines was above 85%. As shown in entries 2−5 of Table 2, four kinds of zeolites (HZSM-5, HY, β-zeolite, and MCM-41) with different pore structures were screened first, and the product distributions are different. Compared with HZSM-5, HY, β-zeolite, and MCM41 are prior to production of biochar, but not organic bio-oil. The carbon yields of biochar over HY, β-zeolite, and MCM-41 were 64.3%, 67.1%, and 65.4, respectively, which were more than that of HZSM-5 (59.5%). Meanwhile, the carbon yields of organic bio-oil over HY, β-zeolite, and MCM-41 were 4.4%, 3.1%, and 4.5%, which was also much lower than that of HZSM-5 (7.0%). The kinetic diameter of aniline is 0.579 nm, similar to the pore diameter of HZSM-5.38 HZSM-5 consists of two perpendicularly intersecting channels (0.54 × 0.56 nm2 for the larger one and 0.51 × 0.54 nm2 for the smaller one).39 The

intersection of these channels, which contains the proposed active site, is approximately a 0.9 nm cavity. Although β-zeolite has intersecting channels similar to ZSM-5, it is a mixture of three polymorphs which are different from ZSM-5, and has pore diameters about 0.7 nm.40 MCM-41 possesses hexagonally packed arrays of channels with pore diameter around 3.8 nm, which has no suitable pore structure for producing aromatic amines.41 Therefore, more coke was produced catalyzed by βzeolite and MCM-41. Y-zeolite has a three-dimensional faujasite structure. The diameter of the supercages is 1.2−1.3 nm while the diameter of the channels connecting the supercages is 0.8−0.9 nm.42 Furthermore, the total acid amounts of Y zeolite (shown in Table 1) were much more than that of HZSM-5. Thus, more coke was produced during the CFP of lignin over HY in the presence of ammonia. The organic bio-oil is composed of aromatic hydrocarbons, phenolic compounds, and aromatic amines. For aromatic amines production, HZSM-5 and HY showed better catalytic performance than β-zeolite and MCM-41 did. When HZSM-5 and HY served as the catalyst, the carbon yields of aromatic amines were 4.3%, and 3.9%, respectively. Meanwhile, the selectivity of aromatic amines in the organic bio-oil over HZSM-5 and HY was 61.4% and 88.6%, respectively. When HY served as the catalysts, the selectivity of aniline in aromatic amines was up to 93.4%, and higher than that of HZSM-5 (85.1%). Although the carbon yield of aromatic amines over HZSM-5 was higher than that of HY, the selectivity of aromatic amines over HZSM-5 was lower than that of HY. Therefore, compared to β-zeolite and MCM-41, HZSM-5 and HY were optimal for producing aromatics amines. Fanchiang et al. noticed that doping Zn to HZSM-5 could enhance the production of aromatics in the CFP of the furfural process due to the change of acid site concentration and the creation of acid sites by anchored Zn ca tions.37 HZSM-5 and HY were also modified by Zn metal and tested for CFP of lignin with ammonia. As shown in entries 6 and 7 of Table 2, the doping of Zn to HZSM-5 and HY could inhibit the production of biochar and enhance the production of organic bio-oil and aromatic amines. When ZnO/HZSM-5 served as the catalyst, the carbon yield of organic bio-oil and aromatic amines was up to 9.8% and 5.6%, which were much higher than that of HZSM-5. When ZnO/HY served as the catalyst, the carbon yields of organic bio-oil and aromatic amines reached 5.2% and 4.5%. The improvement was not so significant as ZnO/HZSM-5. Therefore, ZnO/HZSM-5 was selected as the optimal catalyst for producing aromatic amines in the following CFP of lignin with ammonia tests. In addition, the chemical mechanism of ammonization over ZnO/HZSM-5 was also investigated viaex situ CFP of ligninderived phenols (phenol, methylphenol, guaiacol) over ZnO/ HZSM-5 in the presence of ammonia. Thilakaratne and coworkers have studied the mechanism of aromatic hydrocarbons 2963

DOI: 10.1021/acssuschemeng.6b02542 ACS Sustainable Chem. Eng. 2017, 5, 2960−2969

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ACS Sustainable Chemistry & Engineering formation during ex situ CFP of lignin-derived phenols over HZSM-5.43 Herein, the formation of aromatic hydrocarbons was not studied. Lignin-derived phenols are dissolved with cyclohexane to avoid lignin-derived phenols clotting in this study. As shown in Table S2, the conversion of lignin-derived phenols is 100%, and aromatic amines could be effectively produced from lignin-derived phenols. The carbon yield of aromatic amines from phenols is more than 30%. Figure 1 shows the possible reaction pathway from lignin to aromatic amines during the ex situ CFP in the presence of ammonia. First, lignin pyrolyzed to form pyrolysis vapors (mainly phenol, guaiacol, methylphenol), and then pyrolysis vapors catalyzed by ZnO/HZSM-5 to form aromatic amines via ammonization reaction. Effect of Pyrolysis Temperature. The pyrolysis temperature is an important factor that could affect the product distribution in the pryolysis process. In this study, the effect of pyrolysis temperature on the CFP of lignin with ammonia over ZnO/HZSM-5 was investigated in the temperature range 500− 700 °C. Figure 2 shows the overall yield of biochar, gases, and organic bio-oil (a); organic bio-oil selectivity (b); and gases selectivity (c) of CFP of lignin with ammonia at different pyrolysis temperatures. The detailed product distributions are shown in Table S3. According to Figure 2a, the overall yield, and the selectivity of organic bio-oil and gases were sensitive to the pyrolysis temperature. Low temperature was favored to produce biochar, and high temperature was favored to form gases. When the temperature increased from 500 to 700 °C, the carbon yield of biochar decreased from 64.5% to 46.9%. Meanwhile, the carbon yield of gases increased from 10.7% to 30.5%. In addition, too high or low pyrolysis temperature is not conducive to the production of bio-oil. The highest carbon yield of organic bio-oil was obtained at 600 °C. Figure 2b shows that the product distribution in the organic bio-oil changed dramatically with the pyrolysis temperature changing. The selectivity of phenolic compounds decreased from 48.6% to 4.2% with the pyrolysis temperature increasing. For the selectivity of aromatic hydrocarbons, when the pyrolysis temperature was below 600 °C, it was around 15%, and it decreased slightly with the pyrolysis temperature increasing. However, if the pyrolysis temperature further increased to 650 and 700 °C, the selectivity of aromatic hydrocarbons increased rapidly. When the pyrolysis temperature was at 700 °C, the selectivity of aromatic hydrocarbons was up to 44.4%. For the selectivity of aromatic amines in the organic bio-oil, the maximum (61.2%) was obtained at 600 °C. The selectivity of aromatic amines increased with the pyrolysis temperature increasing until 600 °C and then decreased. By contrast, when the pyrolysis temperature was above 600 °C, as the pyrolysis temperature increased, the selectivity of aromatic amines decreased. Figure2c shows the effect of pyrolysis temperature on the gas product distribution. CO, CH4, C2 hydrocarbons (C2H4 and C2H6), and C3 hydrocarbons (C3H6 and C3H8) were the main products detected in the gases. The selectivity of CO and C3 hydrocarbons decreased, but CH4 and C2 hydrocarbons selectivity increased with the pyrolysis temperature increasing. When the pyrolysis temperature was at 500 °C, the selectivity of CH4, C2, and C3 was 4.3%, 12.3%, and 28.5%, respectively. However, when the pyrolysis temperature increased to 700 °C, the selectivity of CH4 and C2 hydrocarbons increased to 16.7% and 35.3%, while the selectivity of C3 hydrocarbons decreased to 6.2%. This indicated that the side reaction (such as cracking) became

Figure 2. Effect of pyrolysis temperature on the overall yield (a), the organic bio-oil selectivity (b), and the gas selectivity (c) obtained by catalytic fast pyrolysis of lignin with ammonia over ZnO/HZSM-5. Pyrolysis conditions: catalyst: ZnO/HZSM-5 Si/Al = 50; catalyst usage: 1 g; pure ammonia, 60 mL/min; residence time: 0.57 s.

more significant at a higher temperature. Combined with the carbon yield of organic bio-oil in Figure 2a and the selectivity of aromatic amines in Figure 2b, the optimal pyrolysis temperature for catalytic fast pyrolysis of lignin with ammonia could be around 600 °C. Effect of Residence Time. To further optimize the pyrolysis condition for producing aromatic amines, the effect of the residence time of pyrolysis vapor through the catalyst bed was investigated. Herein, the residence time was in the range 0.34−1.71 s via changing the flow rate of ammonia from 2964

DOI: 10.1021/acssuschemeng.6b02542 ACS Sustainable Chem. Eng. 2017, 5, 2960−2969

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ACS Sustainable Chemistry & Engineering 100 mL/min to 20 mL/min via fixing the pyrolysis temperature and catalyst usage at 600 °C and 1 g. Figure 3 shows the carbon

gas = 60 mL/min). Table 3 shows the detailed carbon yield and selectivity of products in the organic bio-oil. Accordingly, the Table 3. Effect of Ammonia Content in the Carrier Gasa Entry Ammonia contentb Organic bio-oil (C%) Phenolic compounds Aromatic hydrocarbons Aromatic amines

1

2

25% 50% 8.5 9.4 2.4 2.2 3.2 2.8 2.9 4.4 Products selectivity (%) Phenolic compounds 28.2 23.4 Aromatic hydrocarbons 37.6 29.8 Aromatic amines 34.1 46.8

3

4

75% 10.1 2.4 2.2 5.5

100%c 9.8 2.3 1.9 5.6

23.8 21.8 54.5

23.5 19.4 57.1

a

Reaction conditions: mass of lignin: 0.5 g, pyrolysis temperature, 600 °C; catalyst: ZnO/HZSM-5; catalyst usage, 1 g, residence time, 0.57 s, total flow rate of carrier gas, 60 mL/min. bThe diluted carrier gas is composed of ammonia (NH3) and nitrogen (N2), ammonia content: volume contents. cPure ammonia.

carbon yield and selectivity of phenolic compounds were not sensitive to ammonia content in the carrier gas. With the ammonia content in the carrier gas increasing from 25% to 100%, the carbon yield and selectivity of phenolic compounds were around 2.2% and 25%, respectively. However, the carbon yield and selectivity of aromatic hydrocarbons and aromatic amines were affected by ammonia content significantly. With the ammonia content increasing, the carbon yield and selectivity of aromatic hydrocarbons decreased. By contrast, aromatic amines increased with the ammonia content increasing from 25% to 75%. When the ammonia content was 75%, the carbon yield and selectivity of aromatic amines were 5.5% and 54.5%, which were a bit lower than the results obtained under the pure ammonia. However, the total carbon yield of organic bio-oil was 10.1%, a bit higher than that under pure ammonia. Therefore, the optimal ammonia content for producing aromatic amines via catalytic fast pyrolysis of lignin under ammonia was between 75% and 100%, and the ammonia content at 75% was selected as the carrier gas in the following pyrolysis process. Through systematically investigating the parameters in the CFP of lignin with the ammonia process and using wheat straw lignin as model feed, the suitable pyrolysis conditions for producing aromatic amines were at 600 °C and using ZnO/ HZSM-5 as catalyst under 75% ammonia/25% nitrogen combination gas. The residence time was 0.57 s, and the total flow rate of carrier gas was 60 mL/min. In addition, ZnO/HZSM-5 after reaction was also characterized by elemental analysis, N2-adsorption/desorption, and NH3-TPD. As shown in Table S5, the elemental content of carbon and nitrogen in ZnO/HZSM-5 after reaction is 1.95% and 0.65%, indicating that coke formed on the catalyst after the reaction. Through the N2-adsorption/desorption, the BET surface area of catalyst after reaction decreased from 354.2 m2/ g to 154.8 m2/g. Figure S5 shows the NH3-TPD spectra of catalyst after reaction, and the acid amounts decreased a lot after reaction. When the desorption temperature was above 550 °C, a new peak emerged for the catalyst after reaction which should come from the decomposition of coke formed on the catalyst. The catalyst could be regenerated in air at elevated temperature.

Figure 3. Effect of residence time of pyrolysis vapors through the catalyst bed on the carbon yield (a) and organic bio-oil selectivity (b). Pyrolysis conditions: pyrolysis temperature: 600 °C; catalyst: ZnO/ HZSM-5 Si/Al = 50, Zn: 2 wt %; catalyst usage: 1 g; pure ammonia.

yield and selectivity of organic bio-oil production at different residence times. The detailed product distributions are shown in Table S4. Figure 3 shows that the carbon yield and selectivity of organic bio-oil were affected by the residence time significantly. With the residence time increasing from 0.34 s to 1.71 s, the carbon yield and selectivity of phenolic compounds decreased from 3.4% and 35.4% to 0.6% and 8.0%, while the carbon yield and selectivity of aromatic hydrocarbons increased from 1.6% and 16.7% to 4.3% and 57.3%, respectively. For aromatic amines, the highest carbon yield and selectivity were 5.6% and 57.1%, which were obtained at 0.57 s. Therefore, the optimal residence time for producing aromatic amines was about 0.57 s, and the carrier flow rate of ammonia was 60 mL/min. Effect of Dilution of Ammonia with N2. Ammonia served as both the reagent and the carrier gas in this process. Carrier gas is important for the CFP process. Moreover, the price of pure ammonia is much more expensive than N2 in the fast pyrolysis process. Herein, the ammonia diluted with N2 was also investigated via changing the volume contents of ammonia and fixing the pyrolysis temperature (600 °C), catalyst (ZnO/ HZSM-5), and residence time (0.57 s, total flow rate of carrier 2965

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Table 4. Elemental Contents and Physical Properties of Pyrolytic Bio-char and N-Doped Carbon after Activationa Elemental contents

Biochar N-doped carbon a

C

H

O

N

Ash

H/C mole ratio

78.8 89.9

3.2 3.8

12.1 3.5

3.2 2.8

2.7 N.D

1:2.1 1:1.9

N/C mole ratio

BET surface area(m2/g)

External surface area (m2/g)

Micropore area(m2/g)

Pore size (nm)

Total pore Volume(cm3/g)

1:28.7 1:37.5

18.1 1614.3

17.8 356.3

0.3 1258.0

5.3 2.4

0.024 0.975

N.D: Not detected.

Figure 4. XRD pattern of pyrolytic biochar and N-doped carbon (a); scanning electron microscopy (SEM) of pyrolytic biochar (b); SEM of Ndoped carbon (c); nitrogen adsorption−desorption isotherm of pyrolytic biochar and N-doped carbon (d).

N-Doped Carbon Preparation and Electrochemical Test. In the above study, we focused on optimizing the suitable pyrolysis conditions for producing aromatic amines directly from lignin. Due to the special property of lignin, the carbon yield of biochar was more than 45%. Instead of treating it as waste without efficient utilization as usual, the biochar obtained from CFP of wheat straw lignin was activated by KOH under ammonia atmosphere for producing N-doped carbon with high surface area. Table 4 shows the elemental contents and physical properties of pyrolytic biochar and N-doped carbon. The elemental content of C, H, O, N, and ash in biochar before activation was 78.8%, 3.2%, 9.1%, 6.2%, and 2.7%, respectively. After the activation with KOH and acid wash, no ash was detected in the N-doped carbon. The elemental content of C, H, O, and N was 89.9%, 3.8%, 3.5%, and 2.8%, respectively. In addition, the samples were also characterized by X-ray diffraction analysis and shown in Figure 4a. Some impure peaks were shown in the pattern of pyrolytic biochar, indicating impurities in the pyrolytic biochar, such as ash. No impure peak existed in the XRD pattern of N-doped carbon, which indicates

the ash and KOH have been removed thoroughly through the etching with HCl solution process. The morphology of pyrolytic biochar and N-doped carbon was also characterized by SEM. The SEM image of pyrolytic biochar (Figure 4b) shows irregular particles and monolithic morphology without macropores. In contrast, the SEM image of N-doped carbon (Figure 4c) shows randomly opened macropores with different sizes distributed on the surface of Ndoped carbon. The porosity of the pyrolytic biochar and N-doped carbon was determined by N2-adsorption/desorption measurements and summarized in Table 4. The surface area and total pore volume of pyrolytic biochar were 18.1 m2/g and 0.024 cm3/g. Meanwhile, the external surface area was 17.8 m2/g, and the micropore area was only 0.3 m2/g. This also indicated that there were no macropores on the surface of pyrolytic biochar. After the KOH activation under ammonia, the surface area and total pore volume of pyrolytic biochar increased to 1614.3 m2/g and 0.975 cm3/g. Meanwhile, the external surface area and micropore area were 356.3 m2/g and 1258.0 m2/g. This was consistent with the result of the SEM image that many 2966

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of pyrolytic biochar were 19.2% and 80.8%, respectively. After the KOH activation, more pyridinic-N and quaternary-N were produced from pyrrolinic-N. In addition, for C 1s and O 1s in Figure S6, amorphous C−C (284.7 eV), CN (286.3 eV), and C−N (288.2 eV) were observed in the C 1s XPS spectra of pyrolytic biochar. No C−N (288.2 eV) was observed in the Ndoped carbon after activation. There is no significant difference between the O 1s of pyrolytic biochar and N-doped carbon. Cyclic voltammetry (CV) and galvanostatic charge and discharge were used to investigate the electrochemical performance of pyrolytic biochar and N-doped carbon within the potential voltage in the range of 0 and 0.8 V. The electrochemical performances of pyrolytic biochar and Ndoped carbon are comparatively shown in Figure 6. After the

macropores existed in the N-doped carbon. As shown in Figure 4d, the isotherm of N-doped carbon exhibited a typical-IV curve with an obvious type-H4 hysteresis loop at P/Po = 0.45. The existence of a type-H4 hysteresis loop is indicative of micro-, meso, and macropores coexisting in the N-doped carbon, and it also indicated that the N-doped carbon could be a desired material for energy storage and conversion.44−46 As shown in Figure 5, the chemical species in the pyrolytic biochar and N-doped carbon was also characterized by XPS

Figure 5. XPS curves of pyrolytic biochar and N-doped carbon. Survey of C 1s, N 1s, and O 1s (a); spectra of N 1s (b). Figure 6. Cyclic voltammetry (CV) curves of pyrolytic biochar and Ndoped carbon at 100 mV·S1− scan rate (a); charge and discharge curves of pyrolytic biochar and N-doped carbon electrodes, constant current densities: 1 A·g−1 (b).

measurement. The surface atomic concentrations of C, O, and N calculated from the peak areas of corresponding XPS spectra are shown in Table S6 in the Supporting Information. In Figure 5a, remarkable C 1s, N 1s, and O 1s peaks were observed in the XPS survey spectra. N species were introduced into the pyrolytic biochar and N-doped carbon. In addition, an impurity peak at about 500 eV was observed from the pyrolytic biochar ssample, which may be caused by the ash. As listed in Table 4, the atom concentration of C on the surface increased to 89.2% after the KOH activation treatment, while the atom concentration of O on the surface decreased to 6.3%. The atom concentration of N remained approximately 4.5%. From N 1s in Figure 5b, pyridinic-N (398.6 eV), pyrrolinic-N (400.4 eV), and quaternary-N (401.2 eV) were observed in the N 1s XPS spectra of N-doped carbon. No quaternary-N (401.2 eV) was observed in the pyrolytic biochar.47,48 The atom percent of pyridinic-N, pyrrolinic-N, and quaternary-N in the total N 1s of N-doped carbon were 36.9%, 54.0%, and 9.1%, respectively (Table S6). The pyridinic-N and pyrrolinic-N in the total N 1s

KOH activation under ammonia, the CV curve of N-doped carbon significantly enlarged and possessed a high capacitance (Figure 6a). Figure 6b compared the charge and discharge behaviors of the pyrolytic biochar and N-doped carbon. The discharging time of N-doped carbon was significantly longer than that of pyrolytic biochar, also indicating that N-doped carbon had a much larger capacitance after the KOH activation. In addition, all the curves in Figure 6b exhibited symmetric triangles with gradual changes of slope in the potential range from 0 to 0.8 V, which also suggests good electric double-layer capacitance performance.49,50 From the discharge curve, the specific capacitance of N-doped carbon was calculated to be 128.4 F·g−1, while the specific capacitance of pyrolytic biochar was 8.3 F·g−1. These results verified that, after treatment with 2967

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KOH, the obtained N-doped carbon has outstanding electrochemical performance.

Ying Zhang: 0000-0003-2519-7359 Yao Fu: 0000-0003-2282-4839

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CONCLUSIONS In this study we proposed a new route for lignin valorization. Aromatic amines and N-doped carbon can be produced by ex situ catalytic fast pyrolysis of lignin with ammonia over zeolite catalysts. Among MCM-41, β-zeolite, HZSM-5, HY, ZnO/ HZSM-5, and ZnO/HY, ZnO/HZSM-5 (2 wt % Zn, Si/Al = 50) catalyst showed the optimal reactivity for producing aromatic amines due to the desired pore structure and acidity. Temperature influenced the product distribution significantly. The optimal temperature for producing aromatic amines was around 600 °C. The residence time of pyrolytic vapors through catalyst bed investigation indicated that a higher residence time could cause the overreaction of pyrolytic vapors over the catalyst to produce more aromatic hydrocarbons, and less aromatic amines and phenolic compounds. The desired residence time was about 0.57 s, and the flow rate of carrier gas was 60 mL/min. The desired ammonia content in the carrier gas for aromatic amines production was in the range 75% to 100%. Under the optimized conditions, the highest carbon yield of aromatic amines and their selectivity in the Ncontaining chemicals were 5.6% and 57.1%, respectively. The selectivity of aniline in the aromatic amines was up to 87.3%. The pyrolysis byproduct biochar which was mostly treated as waste can be activated by KOH under ammonia atmosphere to produce N-doped carbon with high surface area. After the activation, no ash was detected and randomly opened macropores with different sizes are distributed on the surface of N-doped carbon. The surface area and total pore volume of N-doped carbon reached 1614.3 m2/g and 0.975 cm3/g. Cyclic voltammetry (CV) and galvanostatic charge−discharge tests verified that, after treatment with KOH, the obtained N-doped carbon has outstanding electrochemical performance. The specific capacitance of N-doped carbon reached about 128.4 F·g−1.

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Notes

The authors declare no competing financial interest.

ACKNOWLEDGMENTS

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REFERENCES

The authors are grateful to NSFC (21572213), the National Basic Research Program of China (2013CB228103), Anhui Provincial Natural Science Foundation (1408085MKL04), and the Fundamental Research Funds for the Central Universities for financial support.

(1) Zakzeski, J.; Bruijnincx, P. C. A.; Jongerius, A. L.; Weckhuysen, B. M. The catalytic valorization of lignin for the production of renewable chemicals. Chem. Rev. 2010, 110, 3552−3599. (2) Perlack, R. D.; Wright, L. L.; Turhollow, A. F.; Graham, R. L.; Stokes, B. J.; Erbach, D. C. Biomass as feedstock for a bioenergy and bioproducts industry: the technical feasibility of a billion-ton annual supply. U. S. Department of Energy: Oak Ridge, 2005. (3) Calvo-Flores, F. G.; Dobado, J. A. Lignin as renewable raw material. ChemSusChem 2010, 3, 1227−1235. (4) Li, C.; Zhao, X.; Wang, A.; Huber, G. W.; Zhang, T. Catalytic transformation of lignin for the production of chemicals and fuels. Chem. Rev. 2015, 115, 11559−11624. (5) Liu, W. J.; Jiang, H.; Yu, H. Q. Thermochemical conversion of lignin to functional materials: a review and future directions. Green Chem. 2015, 17, 4888−4907. (6) Hu, L.; Pan, H.; Zhou, Y.; Zhang, M. Methods to improve lignin’s reactivity as a phenol substitute and as replacement for other phenolic compounds: A brief review. Bioresources 2011, 6, 3515−3525. (7) Berlin, A.; Balakshin, M. In Bioenergy Research: advances and applications: Gupta, V. K., Kubicek, M. G. T. P., Xu, J. S., Eds.; Elsevier: Amsterdam, 2014. (8) Bridgwater, A. V.; Peacocke, G. V. C. Fast pyrolysis processes for biomass. Renewable Sustainable Energy Rev. 2000, 4, 1−73. (9) Liu, C.; Wang, H.; Karim, A. M.; Sun, J.; Wang, Y. Catalytic fast pyrolysis of lignocellulosic biomass. Chem. Soc. Rev. 2014, 43, 7594− 7623. (10) Xu, L. J.; Zhang, Y.; Fu, Y. Advances in upgrading lignin pyrolysis vapors by ex situ catalytic fast pyrolysis. Energy Technol. 2017, 5, 30−51. (11) Zhou, G. F.; Jensen, P. A.; Le, D. M.; Knudsen, N. O.; Jensen, A. D. Direct upgrading of fast pyrolysis lignin vapor over the HZSM-5 catalyst. Green Chem. 2016, 18, 1965−1975. (12) Olcese, R. N.; Lardier, G.; Bettahar, M.; Ghanbaja, J.; Fontana, S. V.; Carré; Aubriet, F.; Petitjean, D.; Dufour, A. Aromatic chemicals by iron-catalyzed hydrotreatment of lignin pyrolysis vapor. ChemSusChem 2013, 6, 1490−1499. (13) Rezaei, P. S.; Shafaghat, H.; Wan Daud, W. M. A. Aromatic hydrocarbon production by catalytic pyrolysis of palm kernel shell waste using a bifunctional Fe/HBeta catalyst: effect of lignin-derived phenolics on zeolite deactivation. Green Chem. 2016, 18, 1684−1693. (14) Downing, R. S.; Kunkeler, P. J.; van Bekkum, H. Catalytic syntheses of aromatic amines. Catal. Today 1997, 37, 121−136. (15) Ono, N. The nitro group in organic synthesis; Wiley-VCH: New York, 2001. (16) Li, J.; Shi, X. Y.; Bi, Y. Y.; Wei, J. F.; Chen, Z. G. Pd nanoparticles in ionic liquid brush: A highly active and reusable heterogeneous catalytic assembly for solvent-free or on-water hydrogenation of nitroarene under mild conditions. ACS Catal. 2011, 1, 657−664. (17) Blaser, H. U.; Siegrist, U.; Steiner, H.; Studer, M. In Fine chemicals through heterogeneous catalysis; Sheldon, R. A., van Bekkum, H., Eds.; Wiley-VCH: Weinheim, 2001.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acssuschemeng.6b02542. The effect of pyrolysis temperature on the product distributions (peak area %) of pyrolysis of lignin with ammonia; detailed product distribution of effect of pyrolysis temperature and residence time; elemental contents and physical properties of ZnO/HZSM-5 before and after reaction; surface atomic concentrations and functional groups on the surface of carbon materials; benchtop pyrolysis set; GC/MS spectra of products via CFP and non-CFP of lignin with ammonia; NH3-TPD spectra and XRD patterns of different catalysts; NH3TPD spectra of ZnO/HZSM-5 before and after reaction (PDF)

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AUTHOR INFORMATION

Corresponding Authors

*Tel.: +86 551 63603463; fax: +8655163606689; e-mail: [email protected] (Ying Zhang). *Tel.: +86 551 63603463; fax: +8655163606689; e-mail: [email protected] (Yao Fu). 2968

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ACS Sustainable Chemistry & Engineering (18) Blaser, H. U.; Steiner, H.; Studer, M. Selective catalytic hydrogenation of functionalized nitroarenes: an update. ChemCatChem 2009, 1, 210−221. (19) Saha, A.; Ranu, B. Highly chemoselective reduction of aromatic nitro compounds by copper nanoparticles/ammonium formate. J. Org. Chem. 2008, 73, 6867−6870. (20) Jagadeesh, R. V.; Banerjee, D.; Arockiam, P. B.; Junge, H.; Junge, K.; Pohl, M. M.; Radnik, J.; Brückner, A.; Beller, M. Highly selective transfer hydrogenation of functionalised nitroarenes using cobalt-based nanocatalysts. Green Chem. 2015, 17, 898−902. (21) Tanabe, K.; Ito, M.; Sato, M. High acidity of silica−titania and its high catalytic activity for amination of phenol with ammonia. J. Chem. Soc., Chem. Commun. 1973, 18, 676−677. (22) Katada, N.; Iijima, S.; Igi, H.; Niwa, M. Synthesis of aniline from phenol and ammonia over zeolite beta. Stud. Surf. Sci. Catal. 1997, 105, 1227−1234. (23) Xu, L. J.; Jiang, Y. Y.; Yao, Q.; Han, Z.; Zhang, Y.; Fu, Y.; Guo, Q. X.; Huber, G. W. Direct production of indoles via thermo-catalytic conversion of bio-derived furans with ammonia over zeolites. Green Chem. 2015, 17, 1281−1290. (24) Xu, L. J.; Han, Z.; Yao, Q.; Deng, J.; Zhang, Y.; Fu, Y.; Guo, Q. X. Towards the sustainable production of pyridines via thermocatalytic conversion of glycerol with ammonia over zeolite catalysts. Green Chem. 2015, 17, 2426−2435. (25) Xu, L. J.; Yao, Q.; Deng, J.; Han, Z.; Zhang, Y.; Fu, Y.; Huber, G. W.; Guo, Q. X. Renewable N-heterocycles production by thermocatalytic conversion and ammonization of biomass over ZSM-5. ACS Sustainable Chem. Eng. 2015, 3, 2890−2899. (26) Estevez, L.; Dua, R.; Bhandari, N.; Ramanujapuram, A.; Wang, P.; Giannelis, E. P. A facile approach for the synthesis of monolithic hierarchical porous carbons-high performance materials for amine based CO2 capture and supercapacitor. Energy Environ. Sci. 2013, 6, 1785−1790. (27) Parlett, C. M. A.; Wilson, K.; Lee, A. F. Hierarchical porous materials: catalytic applications. Chem. Soc. Rev. 2013, 42, 3876−3893. (28) Wang, C.; Wang, Y.; Graser, J.; Zhao, R.; Gao, F.; O’Connell, M. J. Solution-based carbohydrate synthesis of individual solid, hollow, and porous carbon nanospheres using spray pyrolysis. ACS Nano 2013, 7, 11156−11165. (29) Guo, D. C.; Mi, J.; Hao, G. P.; Dong, W.; Xiong, G.; Li, W. C.; Lu, A. H. Ionic liquid C16mimBF4 assisted synthesis of poly (benzoxazine-co-resol)-based hierarchically porous carbons with superior performance in supercapacitors. Energy Environ. Sci. 2013, 6, 652−659. (30) Zhang, L. L.; Zhao, X. S. Carbon-based materials as supercapacitor electrodes. Chem. Soc. Rev. 2009, 38, 2520−2531. (31) Reza, M. T.; Yang, X. K.; Coronella, C. J.; Lin, H. F.; Hathwaik, U.; Shintani, D.; Bishnu, P.; Neupane, B. P.; Miller, G. C. Hydrothermal carbonization (HTC) and pelletization of two arid land plants bagasse for energy densification. ACS Sustainable Chem. Eng. 2016, 4, 1106−1114. (32) Qiao, Y.; Shuai Chen, S.; Liu, Y.; Sun, H. Z.; Jia, S. Y.; Shi, J. Y.; Pedersen, C. M.; Wang, Y. X.; Hou, X. L. Pyrolysis of chitin biomass: TG−MS analysis and solid char residue characterization. Carbohydr. Polym. 2015, 133, 163−170. (33) Wang, K.; Zhao, N.; Lei, S. W.; Yan, R.; Tian, X. D.; Wang, J. Z.; Song, Y.; Xu, D. F.; Guo, Q. G.; Liu, L. Promising biomass-based activated carbons derived from willow catkins for high performance supercapacitors. Electrochim. Acta 2015, 166, 1−11. (34) Ren, Y. M.; Zhang, J. M.; Xu, Q.; Chen, Z. M.; Yang, D. Y.; Wang, B.; Jiang, Z. Biomass-derived three-dimensional porous Ndoped carbonaceous aerogel for efficient supercapacitor electrodes. RSC Adv. 2014, 4, 23412−23419. (35) Navarro-Suárez, A. M.; Carretero-González, J.; Roddatis, V.; Goikolea, E.; Ségalini, J.; Redondo, E.; Rojo, T.; Mysyk, R. Nanoporous carbons from natural lignin: study of structural−textural properties and application to organic-based supercapacitors. RSC Adv. 2014, 4, 48336−48343.

(36) Zhang, L. M.; You, T. T.; Zhou, T.; Zhou, X.; Xu, F. Interconnected hierarchical porous carbon from lignin-derived byproducts of bioethanol production for ultra-high performance supercapacitors. ACS Appl. Mater. Interfaces 2016, 8, 13918−13925. (37) Fanchiang, W. L.; Lin, Y. C. Catalytic fast pyrolysis of furfural over HZSM-5 and Zn/H-ZSM-5 catalysts. Appl. Catal., A 2012, 419− 420, 102−110. (38) Titus, E.; Kalkar, A. K.; Gaikar, V. G. Adsorption of anilines and cresols on NaX and different cation exchanged zeolites (equilibrium,kinetic, and IR investigations). Sep. Sci. Technol. 2002, 37, 105− 125. (39) Carlson, T. R.; Tompsett, G. A.; Conner, W. C.; Huber, G. W. Aromatic production from catalytic fast pyrolysis of biomass-derived feedstocks. Top. Catal. 2009, 52, 241−252. (40) Kresge, C. T.; Leonowicz, M. E.; Roth, W. J. Ordered mesoporous molecular sieves synthesized by a liquid-crystal template mechanism. Nature 1992, 359, 710−712. (41) Xia, Q. H.; Shen, S. C.; Song, J. Structure, morphology, and catalytic activity of β zeolite synthesized in a fluoride medium for asymmetric hydrogenation. J. Catal. 2003, 219, 74−84. (42) Lim, M. H.; Blanford, C. F.; Stein, A. Synthesis and characterization of a reactive vinyl-functionalized MCM-41: Probing the internal pore structure by a bromination reaction. J. Am. Chem. Soc. 1997, 119, 4090−4091. (43) Thilakaratne, R.; Tessonnier, J.; Brown, R. C. Conversion of methoxy and hydroxyl functionalities of phenolic monomers over zeolites. Green Chem. 2016, 18, 2231−2239. (44) Wei, J.; Zhou, D. D.; Sun, Z. K.; Deng, Y. H.; Xia, Y. Y.; Zhao, D. Y. A controllable synthesis of rich nitrogen-doped ordered mesoporous carbon for CO2 capture and supercapacitors. Adv. Funct. Mater. 2013, 23, 2322−2328. (45) Zhang, Y. W.; Ge, J.; Wang, L.; Wang, D. H.; Ding, F.; Tao, X. M.; Chen, W. Manageable N-doped graphene for high performance oxygen reduction reaction. Sci. Rep. 2013, 3, 2771−2778. (46) Li, Z.; Xu, Z. W.; Tan, X. H.; Wang, H. L.; Holt, C. M. B.; Stephenson, T.; Olsen, B. C.; Mitlin, D. Mesoporous nitrogen-rich carbons derived from protein for ultra-high capacity battery anodes and supercapacitors. Energy Environ. Sci. 2013, 6, 871−878. (47) Kim, W.; Joo, J. B.; Kim, N.; Oh, S.; Kim, P.; Yi, J. Preparation of nitrogen-doped mesoporous carbon nanopipes for the electrochemical double layer capacitor. Carbon 2009, 47, 1407−1411. (48) Luo, W.; Wang, B.; Heron, C. G.; Allen, M. J.; Morre, J.; Maier, C. S.; Stickle, W. F.; Ji, X. Pyrolysis of cellulose under ammonia leads to nitrogen-doped nanoporous carbon generated through methane formation. Nano Lett. 2014, 14, 2225−2229. (49) Chen, X. Y.; Chen, C.; Zhang, Z. J.; Xie, D. H.; Deng, X. Nitrogen-doped porous carbon prepared from urea formaldehyde resins by template carbonization method for supercapacitors. Ind. Eng. Chem. Res. 2013, 52, 10181−10188. (50) Qie, L.; Chen, W. M.; Xu, H. H.; Xiong, X. Q.; Jiang, Y.; Zou, F.; Hu, X. L.; Xin, Y.; Zhang, Z. L.; Huang, Y. H. Synthesis of functionalized 3D hierarchical porous carbon for high-performance supercapacitors. Energy Environ. Sci. 2013, 6, 2497−2504.

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