Study on aromatics production via the catalytic pyrolysis vapor upgrading of biomass using metal-loaded modified H-ZSM-5

Accepted Manuscript Title: Study on Aromatics Production via the Catalytic Pyrolysis Vapor Upgrading of Biomass Using Metal-loaded Modified H-ZSM-5 Authors: Yunwu Zheng, Fei Wang, Xiaoqin Yang, Yuanbo Huang, Can Liu, Zhifeng Zheng, Jiyou Gu PII: DOI: Reference:

S0165-2370(17)30083-9 http://dx.doi.org/doi:10.1016/j.jaap.2017.06.011 JAAP 4061

To appear in:

J. Anal. Appl. Pyrolysis

Received date: Revised date: Accepted date:

19-1-2017 16-5-2017 11-6-2017

Please cite this article as: Yunwu Zheng, Fei Wang, Xiaoqin Yang, Yuanbo Huang, Can Liu, Zhifeng Zheng, Jiyou Gu, Study on Aromatics Production via the Catalytic Pyrolysis Vapor Upgrading of Biomass Using Metal-loaded Modified H-ZSM-5, Journal of Analytical and Applied Pyrolysishttp://dx.doi.org/10.1016/j.jaap.2017.06.011 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Study on Aromatics Production via the Catalytic Pyrolysis Vapor Upgrading of Biomass Using Metal-loaded Modified H-ZSM-5

Yunwu Zheng1, 2, Fei Wang2, Xiaoqin Yang 2, Yuanbo Huang2, Can Liu2,Zhifeng Zheng2, Jiyou Gu1

1

Key Laboratory of Bio-based Material Science & Technology, Ministry of Education; College of Materials

Science and Engineering, Northeast Forestry University, Harbin 150040, China; 2

University Key Laboratory of Biomass Chemical Refinery & Synthesis, Yunnan Province; College of Materials

Engineering, Southwest Forestry University, Kunming 650224,China

*Corresponding Author: Jiyou Gu, Zhifeng Zheng, Email: [email protected],[email protected] Tel.: +86-13708707976

Graphical abstract

Metal-Modified ZSM-5 can effectively improve the aromatic hydrocarbon selectivity over catalytic pyrolysis upgrading.

Highlights 

Effects of transition metals on mass balance of pyrolysis products were investigated.



Higher selectivity of BTXE is obtained from catalytic pyrolysis upgrading of biomass using M-ZSM-5 catalyst



High amounts of toluene and benzene isomers were produced with Zn-ZSM-5.



Yield of pyrolytic oil varied with metal type and its amount of loading.

ABSTRACT The main objective of this work was to study aromatics production via the catalytic pyrolysis upgrading of biomass using metal-loaded modified H-ZSM-5. M-ZSM-5 catalysts were prepared through the impregnation method with Zn, Ga, Ni, Co, Mg and Cu. The prepared M-ZSM-5 catalysts were evaluated by x-ray diffraction, thermal desorption spectroscopy and scanning electron microscopy. The properties, composition and product distribution of bio-oil were also analysed. Results showed that the M-ZSM-5 catalysts yielded a higher amount of non-condensable gas at the expense of the liquid yields. The Ga-ZSM-5 catalysts produced the highest yields of bio-oil (25.76 wt %), but the lowest amount of coke (22.08 wt%) compared with the unmodified ZSM-5 catalyst (33.38 wt%). The content of the single-ring aromatics prepared by using the Zn-ZSM-5 catalysts was the highest at 90.28 wt%, whereas that of the polycyclic aromatic hydrocarbon prepared by the Ni-ZSM-5 catalysts was the highest at 31.36 wt%. Moreover, the selectivity of the single-ring aromatic hydrocarbons, such as C7 and C8, were significantly affected by the use of the M-ZSM-5 catalysts. The Zn-ZSM-5 catalysts were the most selective for toluene and xylenes with contents of 36.52wt% and 35.32 wt%, respectively, whereas the Co-based catalysts were the most selective for indene. The Ni-based catalysts can obviously improve the selectivities of benzene production and C10+ polycyclic aromatic hydrocarbons. Zn-ZSM-5 was the most effective catalyst that can be used in the production of aromatic hydrocarbons.

Keywords：Aromatic, Catalytic upgrading, De-oxygenation, Metal-loaded ZSM-5 zeolites, Pyrolysis

1. Introduction Energy depletion and the excessive consumption of fossil fuel resources have caused increasingly serious environmental pollution; thus, searching for new alternative forms of energy had become a major problem as the survival and development of human society depend on these. In relation to these, the use of biomass energy as a renewable and clean form of energy had received increasing attention [1]. Meanwhile, catalytic pyrolysis is an important energy-efficient approach in utilising biomass. Catalytic pyrolysis is an improved fast pyrolysis method that is used for the preparation of benzene, toluene, xylene and other aromatic compounds via the pyrolysis of biomass under catalytic reaction. The catalyst is the soul of a catalytic conversion and studies must find ways to ensure better selectivity, high catalytic activity and long service life. At present, molecular sieve catalysts are the main catalysts used for the catalytic conversion of biomass in the preparation of aromatics. Previous studies had reported that the HZSM-5 molecular sieve has a better acidity and heat resistance as well as excellent selective cracking and catalysis, isomerisation and catalytic properties, thus making the most effective catalysts for the preparation of aromatic compounds through the catalytic conversion of biomass [2-3]. However, the coking rate is relatively higher and the deactivation phenomenon is more serious because of the relatively low aromatics yield. In order to solve these problems, the catalyst must be further modified and improved. At present, the improvement of the HZSM-5 catalyst has mainly focused on the modification of the impregnated metal-load, which is deemed advantageous because of the simple preparation process, easier industrial application, as well as the abilities to adjust the acidity of ZSM-5 and promote desirable reactions during pyrolysis, all of which can potentially increase the yields of beneficial compounds and reduce coke formation. The metals that have been proposed for this purpose include Ni [4]; Co [5]; Mo, Pd, Fe, Ir [4]; Ce [6]; Ga [7-8]; Zn [9] and Al, Cu, Na, Bi, Ag, La [10],et al. Improvements in the aromatic yield and selectivity through the catalytic conversion of biomass feedstocks and model compounds over the metal-modified zeolite are shown in Table 1. In the impregnation modification method, impregnated metals, such as Ni, Co, Zn and Ga, modified M/HZSM-5 to reduce the concentration of oxygen-containing compounds more effectively, increase the yield and selectivity of aromatic compounds and effectively reduce the yields of coke and heavy oil. Iliopoulou [5] and colleagues used Ni- and Co-modified ZSM-5 catalysts via in-situ catalytic pyrolysis-upgrading biomass. They found that Ni loading can effectively reduce the oxygen content of bio-oil, while increasing the content of aromatic hydrocarbons. They reported that the effect of Co was weaker than that of Ni, and that the addition of metal oxide reduced the surface acid sites of the zeolite to some extent, thereby increasing the stability of the

catalysts [5]. Wang et al. [17] used microwave-assisted catalytic pyrolysis of fir biomass to prepare aromatic compounds. The effects of Zn loadings (0,0.5%, 1%, 2%, 5%) on the yield and selectivity of aromatics are obtained via Py/GC-MS. In the presence of Zn, the yield of bio-oil is decreased, the water and synthetic gas contents are increased, and the yield of the aromatic hydrocarbon also increased. When the load amount is 0.5 wt%, the aromatics yield reached 50.7%. Furthermore, the load of Zn changes the distribution of HZSM-5 acid sites, and the partial B acid is converted into L acid, which hinders the alkylation of benzene and decreases toluene content. The dual function Ga/ZSM-5 molecular sieve catalyst can effectively improve yield and selectivity of aromatic hydrocarbon. Park [25] studied the Ga/ZSM-5 molecular sieve catalyst on the catalytic gasification of pine powder pyrolysis at 400℃ and found that it could effectively improve the yields and selectivities of bio-oil and aromatics as well as improved the yields of benzene, toluene and xylene (BTX). The author reported that the yields were twice that of the unmodified one. The effect of Ga-modified HZSM-5 on the yield of aromatics had been further demonstrated by Cheng et al. [8]. They found that via the ion exchange and impregnation method, the Ga/ZSM-5 molecular sieve catalyst had the highest selectivity among aromatics; furthermore, the addition of Ga increased the rates of alkene decarbonylation and aromatisation in the oligomerisation and cracking reaction. Though numerous studies have been reported on the aromatic hydrocarbon from pyrolysis of biomass over various metal promoted ZSM-5 catalyst, there is no clear picture of the comparative performance of these catalysts, and pyrolysis methods without the ex situ catalytic pyrolysis vapour upgrading, moreover, the metal was still very expensive, so in this work, some cheap metal-loaded (Zn, Ni, Co, Mg, Cu and Ga) ZSM-5 catalysts were synthesized for catalytic pyrolysis upgrading of biomass. Ga-ZSM-5 was synthesized for comparision. And loading amounts (1%, 5% and 10%) as well as cooperative load on yields and aromatic selectivity were also investigated. It is anticipated that the results presented here complement those of parallel contributors and provide vital guidance for the rational selection of highly active catalysts for conversion of biomass to BTXE.

2. Materials and methods 2.1 Materials The Yunnan pine particle used in this study was collected from Pu’er City in Yunnan Province, China. Prior to the experiments, the Yunnan pine particle was sieved to a particle size within the range of 0.250 to 0.420 mm. The feedstock was dried at 105 ± 2°C until it reached constant weight, after which the samples were sealed in bags. The main characteristics of Yunnan pine are listed in Table 2. The proximate analysis of Yunnan pine was

conducted on a TG 209 F3 Tarsus. By using ASTM standards E-871, E-1755 and E-872, the moisture, ash and volatility were identified, respectively. The fixed carbon content was calculated by the difference. EA 1108 Elemental Analyser was used to conduct the ultimate analysis of Yunnan pine. The cellulose, hemicelluloses and lignin contents were determined according to the method of the determination of structural carbohydrates and lignin in biomass outlined by the National Renewable Energy Laboratory[26]. Tetrahydrofuran, AR, was provided by Tianjin Zhiyuan Chemical Reagent Company. High-purity nitrogen was provided by Kunming Messer Company. Ni(NO3)2.6H2O (99.999% metals basis, Aladdin); Zn(NiO3)2.6H2O (99.99% metals basis, Aladdin), Ga(NO3)3·xH2O (99.99% metals basis, Aladdin), Co(NO3)2.6H2O (99.999% metals basis, Aladdin), Mg(NO3)2.6H2O (99.99% AR, Aladdin), Cu(NO3)2 · xH2O (99.999% metals basis, Aladdin). The HZSM-5 molecular sieve catalyst with white bar structure was obtained from the Catalyst Plant of Nankai University. The Si/Al ratio of ZSM-5 was about 25. The chemical composition of the catalysts was as follows: Al2O3, 5 wt%–5.5 wt%; SiO2, 80 wt%–85 wt%. The absorption capacities of hexane, cyclohexane and water were 9.5 wt%–10.5 wt%, 2.0 wt%––2.5 wt% and 11.0 wt%–12.0 wt%, respectively. Before the experiment, the bare HZSM-5 was ground manually in a mortar and allowed to pass through a 0.185–0.250-mm sieve. To obtain H-form, the power was ion-exchanged with 0.5 mol/mL NH4NO3 solution at 80℃for 2h. the samples were washed with deionized water, dried at 105℃ overnight and then calcined at 500℃ for 4h in nitrogen atmosphere.

2.2 Methods The 1, 5 and 10 wt% (metal ion mass accounts for catalyst mass) metal-ZSM-5catalysts were prepared by conventional wet impregnation method. First, certain amounts of calcined ZSM-5 catalyst and nitrate metal ion compound were taken. Distilled water was added to dissolve the suspension; the quantity of water to catalyst ratio was 1.5 mL/1 g. The suspension was stirred at 30℃ for 3 h, after which it was filtered and washed with deionised water to eliminate the remaining salts. After drying at 105℃ for 12 h, the M-ZSM-5 powders were heated for 4 h at 5℃/min to 550℃./min for calcination under an ambient atmosphere. Zn-Ni-ZSM-5, Zn-Ga-ZSM-5 and Zn-Co-ZSM-5 were also prepared from the calcined ZSM-5 catalyst by wet impregnation method using a mixed solution. The amounts of Zn, Ga, Ni and Co used in the suspension were selected so as to obtain 5 wt% with the same procedure.

2.3 Pyrolysis process of biomass The fixed-bed reactor for the pyrolysis of Yunnan pine was designed especially for this research. The furnace was heated electrically, and the temperature inside was measured using a thermocouple. The schematic diagram of the fixed-bed reactor is shown in Fig. 1. The pyrolysis reaction was conducted in the reactor, which had a steel pipe through the hole of the furnace. The top of the reactor was connected to a straight condenser, which was kept at about 5℃ using ice-water. The distance between the top of the furnace and condenser was about 30 cm. First, the dry glass fibre was inserted into the vertically installed reactor to be used for loading the feedstock. Then, 1.20 g of Yunnan pine was placed into the reactor. The bottom of the reactor was linked to the high-purity nitrogen, whereas the top of the reactor was connected to the condenser. The reactor was purged with high-purity nitrogen for 5 min before the experiment was initiated. Then, the heat was applied rapidly at a heating rate of 250°C/min and then held for 30 min. Nitrogen flow was maintained at 150 mL/min throughout the process; the catalytic temperature was 500℃, the pyrolysis temperature was 450℃ and the biomass to catalyst ratio was 1:2. Next, the obtained bio-oil was dissolved using tetrahydrofuran (THF) and then quantified. THF was used as a decent solvent to dissolve and dilute the bio-oil. The yield of bio-char was obtained by weighing. The yields of the gaseous products were calculated from the difference using Eqs. (1), (2) and (3) YL 

M

1

M

0

 100%

(1)

Y S -e x -s itu 

M

2

M

0

 100%

(2)

Y G  1-Y L -Y S

(3)

where Y L is the yield of bio-oil, Y S - ex - situ is the yield of solid residue with ex-situ catalytic pyrolysis upgrading, YG

is the yield of non-condensable gas, M

and M

2

0

is the weight of biomass feedstock, M

1

is the weight of liquid

is the weight of solid residue.

2.4 Catalyst characterisation 2.4.1 NH3-TPD The acidities of the catalysts were determined by temperature programmed desorption (TPD; Chemisorption analyser, Quantachrome Instruments, Boynton Beach, FL). Catalysts (about 50 mg–150 mg) were degassed by

heating to 150℃ (2.5℃ /min heating rate) with He flowing for 30 min and then cooled to 50℃ within 60 min. The sample was allowed to absorb NH3 gas with 10% concentration at 50℃ for 60 min; it was subsequently heated to 500℃ at a heating rate of 5℃ /min with He flowing for 120 min to determine its acidity. A blank run for catalysts that did not absorb NH3 was carried out as background. Three different volumes (0.5, 1 and 1.5 mL) of a standard NH3 gas (10% NH3 and 90% He) were used to calibrate acidity. 2.4.2 XRD XRD (TTR III) was also used to analyse the structure of the catalysts with different SiO2-Al2O3 ratios. An accelerating voltage of 40 kV was used at 40 mA. The X-ray diffraction (XRD) grams were obtained at the scanning rate of 2.0°/min within the range 2θ = 5.0°–60.0°. 2.4.3 SEM The microstructures of the M-ZSM-5 catalysts were characterised by scanning electron microscope (SEM; JSM-6301). The maximum acceleration voltage was set at 15 kV, and the sample was uniformly dispersed in the copper with a double-sided adhesive. 2.4.4 N2 physisorption Surface areas were measured using ASAP2020 (Micrometrics) surface area and pore size analyser. Prior to the measurement, the samples were out-gassed at 250℃ for 12 h under vacuum. For analysis, samples were cooled to–196℃ in a liquid nitrogen bath and liquid nitrogen was used as adsorption gas. The BET surface area was calculated from the linear portion of the BET plot. The micropore volume and external surface areas were calculated by the t-plot method, whereas the pore size distribution was determined by the BJH model. 2.4.5 Element analysis The C, H, N and O contents of Yunnan pine and its products were quantified by EA 1108 Elemental Analyser. Those of C, N and H were determined first, and the mass fraction of O was calculated by subtracting the ash contents of C, N and H from the total mass of the sample. Next, the water content of bio-oil was analysed by the Karl–Fischer titration. A mixture of methanol and chloroform with the mass ratio of 3:1 was used as the titration solvent. The higher heating values (HHV) of bio-char and bio-oil were calculated by using the equation given by [27] HHV(MJ/kg)

= 0.3491

× C  1.1783

× H  0.1005

× S - 0.1034

× O - 0.0151

× N - 0.0211

× A

, (4)

where C, H, S, O and N represent the weight percentages of carbon, hydrogen, sulphur, oxygen and nitrogen, respectively, and A represents the weight percent of ash. 2.4.6 X-ray photoelectron spectroscopy XPS measurements were performed at room temperature with monochromatic Al-K radiation (1486.6 eV) using a K-Alpha X-ray photoelectron spectrometer (supplied by Thermo Fisher Scientific Co., Massachusetts, USA). The X-ray beam was 100 W, 200 mm in diameter and laster scanned over a 2 mm by 0.4 mm area on the sample. High-energy photoemission spectra were collected using pass energy of 50 eV and a resolution of 0.1 eV. For the Ag3d5/2 line, these conditions produced a FWHM of 0.80 eV. 2.5 Chemical analysis of bio-oil The gas chromatography-mass spectrometer (GC-MS) analysis of bio-oil was performed on an ITQ 900 (Thermo Fisher Scientific, USA), using capillary chromatographic column HP-5MS (30 m×0.25 mm×0.25 μm). The temperature of the injector was 280℃, and the split ratio of the carrier gas was 1:10 using high-purity helium. Oven temperature was initially held at 50℃ for 5 min. The temperature was ramped from 50℃ to 280℃ at 5℃/min−1, and held for 5 min. For the MS condition, the ionisation method used was EI, ionisation energy was set at 70 eV, the scan per second over range electron (m/z) was within 30 amu–500 amu, and ion source temperature

was 230℃.

3. Results and discussion 3.1 Catalyst characteristics The XRD patterns of the metal-loaded ZSM-5 catalysts are shown in Fig. 2. As can be seen, the main peaks of modified catalysts are presented at the 2θ of 8°, 8.8°, 23.1°, 23.9° and 24.4°, respectively, which are in the range of typical specific peaks of ZSM-5 (2θ = 7°–9° and 23°–25°). The sharp reflections also correspond to the MFI structure. The XRD spectra of the M-ZSM-5 catalysts are very similar, although the characteristic diffraction peaks of metal oxides are not detected by XRD. Given that the intensities of the diffraction peaks of different molecular sieves have not changed too much. These results showed that the structure of ZSM-5 molecular sieve was not destroyed. Moreover, the metal oxide is highly dispersed on the surface of the molecular sieve after the modification of the metal impregnation. As shown in Fig. 2, the low-angle diffraction-peak intensity of the Cu-HZSM-5 molecular sieve was the lowest, indicating that the Cu element easily passed through the inner part of the molecular sieve pore [28].

NH3-TPD was used to characterise the strength of accessible acid sites in the catalysts (Fig. 3). In all cases, two characteristic contributions centred at 200℃ and 450℃, respectively, are observed. The peak of the high-temperature area is the largest, indicating that its acidity is the strongest. The desorption peak of the higher temperature zone decreased obviously after metal impregnation; however, no significant change in the desorption peak at the lower temperature, suggesting that the introduction of metal can effectively change the surface acidity of the molecular sieve catalyst and reduce the number of surface acid sites, especially the number of strong acid sites. In addition, metal ions react with the Brønsted acid centre, resulting in the decrease of the Brønsted acid site. In the Cu and Mg load systems, the total acids decreased to 0.16 and 0.21 mmol/g respectively, indicating that Cu2+and Mg2+ may be poured into the internal pore of the ZSM-5 molecular sieve. Table 3 shows the specific surface areas and pore structures of different catalyst samples. As shown in Table 3, H-ZSM-5 has a high specific surface area (338.44 m2.g−1), and the specific surface area of the modified catalyst is decreased within the range of 285 m2.g−1–295 m2.g−1. Pore volume decreased and the average pore size increased, but the difference was not obvious possibly because of the accumulation of transition metal species on the molecular sieve orifice or deep into the channel interior, which blocked the molecular sieve channel interior, resulting in smaller pore volume [29]. Moreover, blockage in the most micro pore size of microporous and mesoporous pore sizes, after average, the total pore size increased, suggesting that the metal ions are dispersed throughout the ZSM-5 surface. The results were similar to the Schultz E L results [30]. The Cu-ZSM-5 molecular sieve pore volume shows the most decrease, which may be a result of excessive Cu species entering the channel and causing obstruction. These results are similar to those obtained by XRD. The SEM micrographs of the metal-loaded ZSM-5 catalysts, which were synthesized through the impregnation method, are shown in Fig. 5. As can be seen, the surface grain morphology of modified HZSM-5 molecular sieve was similar to that of the ZSM-5 catalyst. Grain size with a larger surface Gibbs free energy and catalyst power appeared in the agglomeration due to interconnection with each other, which covers the surface of the catalyst. Thus, the catalyst surface was more compact, the gap was smaller and most crystalline grains tended to grow into cubic shape(with sizes ranging from 2 um–5 um). These can be attributed to the fact that the crystalline grain size was smaller and the size distribution was not uniform; therefore, the catalyst surface did not have a fixed shape. At the same time, it can be seen from the Fig.6, the dispersion of Zn and Cu were better, the grain size was relatively smaller, but the grain size of Mg-ZSM-5 catalyst was larger and agglomerated into a whole, and the apparent morphology of other metals were not different.

3.2 Analysis of bio-oil product yield and performance The bio-oil, non-condensable gas and char obtained by the catalytic pyrolysis upgrading of biomass with different metal-loaded catalysts are shown in Fig. 6. As can be seen, the addition of catalyst can significantly increase the gas yield, but the liquid yield decreased from 36.82 wt% to 14.88 wt %. Higher liquid yields were achieved with the Ga-ZSM-5 and Zn-ZSM-5 catalysts at 25.76 and 22.69 wt%, respectively. Cu-ZSM-5 produced the lowest bio-oil yield compared with the unmodified ZSM-5, which decreased by 38.38 wt%. This is because of the remarkable dehydrogenation and deoxygenation effects of Ga, Zn and Ni, which are advantageous to the pyrolysis reaction of biomass, and put direct degradation of the large molecular substances into small molecules. Meanwhile, the metal-loaded catalysts can effectively decrease the coke deposit, because the primary product of biomass pyrolysis mainly contains aldehyde, ketone, acid, phenol and other kinds of oxygen-containing compounds; such oxygen compounds are prone to dehydration reaction in the catalyst acidic centre, allowing for the easy aggregate formation of carbon deposition [31]. Meanwhile, when the catalyst was modified, the Brønsted acid calculation also decreases (see Fig. 3). Thus, the dehydration reaction of the primary product was weakened, and the inhibition of coke deposition was achieved. Among all the metal-loaded catalysts, the effects of Ga, Ni and Zn are most significant, decreasing the amount of coke deposition from 31.76 wt% to 23.82, 22.08 and 26.06 wt%, respectively, However, for the Cu-supported catalyst, the excessive decrease in pore volume hindered the diffusion of molecules, resulting in an increase in the amount of carbon deposition. The performances of the ZSM-5 material as a catalyst for bio-oil upgrading are presented in Table 4, which indicates that the addition of the catalyst can significantly improve the performances of bio-oil, increase the C and H contents as well as decrease oxygen content. The increase in calorific value shows that the transition metal with better C-O bond-breaking ability can have a significant catalytic effect. In addition, the large number of oxygen functional groups taking off in the forms of H2O, CO and CO2 increased the amount of aromatic hydrocarbons. Different loading metals have varying catalytic effects, with the Zn-supported ZSM-5 catalyst having the most significant effect on the improvement of bio-oil yield and performances. Meanwhile, the total content of C and H and the H/C molar ratio in the Zn-ZSM-5 catalyst are the highest at 82.96 wt % and 1.58, respectively, thus enhancing the dehydration of bio-oil. Meanwhile, the content of O is only 17.04 wt%, which accounts for 53.31 wt% of the crude oil. The calorific value is increased by 43.04 wt%; and water content was decreased because of seriously deoxygenation reaction[32]. Thus, the reduction of oxygen content is sufficient to diminish the stability problems associated with polymerization reactions during its storage and transportation. The order of the deoxygenating effects of different loading metals is as follows: Ga-ZSM-5＞Zn-ZSM-5＞Ni-ZSM-5＞Co-ZSM-5

＞Mg-ZSM-5＞Cu-ZSM-5＞H-ZSM-5. Moreover, the calorific value is slightly lower than those of diesel oil (45.50) and heavy oil (40).

3.3 Effects of metals on the aromatic selectivity in the catalytic pyrolysis upgrading of biomass Fig. 7 shows the effects of the supported metal catalysts on the yield and aromatic selectivity of the catalytic pyrolysis upgrading of biomass. As shown in Fig. 7(a), the M-ZSM-5 catalyst obviously improved the contents of the single-ring and double-ring aromatic hydrocarbons (napthalenes); however, it has less influence on the effects of the tri-ring aromatics, such as phenantrene, anthracene and fluorene, which are all lower than 1 wt%. Zn-ZSM-5, Ga-ZSM-5and H-ZSM-5 can produce the highest single-ring aromatic contents of 90.28 wt%, 75.58 wt%and 74.58 wt%, respectively. The content of the single-ring aromatics prepared by Ni-ZSM-5 catalyst was the lowest (67.51 wt%), whereas that of the prepared polycyclic aromatic hydrocarbon was the highest (31.36 wt%). These findings may be attributed to the transition metal element modification, which strengthened the hydrogen transfer reaction in the pyrolysis reaction. At the same time, the introduction of metal elements reduces the acidity of the molecular sieve; thus, the hydrogen transfer reaction of the type I product (the product of the single-ring aromatics) is strengthened. Meanwhile, the hydrogen transfer reaction of the type II product (the product of the polycyclic aromatic hydrocarbons) is inhibited [35]. Thus, the selectivity of hydrogen transfer reaction can be optimised by the transition metal-modified HZSM-5 catalyst. Compared with the unmodified ZSM-5 catalyst, when the loading amount of Zn is 5 wt%, the yield of the single-ring aromatic hydrocarbon is improved, whereas that of PAHs is decreased. This is because promoting the formation and transformation of carbon positive ions as well as the hydrogen atom transfer are the key factors in the catalytic pyrolysis of biomass [36]. The Lewis acid on the surface of ZSM-5 can promote the hydrogen transfer, and the Brønsted acid can promote the formation and transformation of the carbon positive ion. The Lewis acid on the surface of HZSM-5 zeolite increases with the increase of Zn loading, whereas the Bronsted acid decreases with the increase of Zn loading [37]. When Zn metals are added to the HZSM-5 catalyst, the Zn ion and hydroxyl group on the Brønsted acid site can lead to substitution reaction, which, in turn, can reduce the Bronsted acid strength as well as the catalytic pyrolysis performance, although this does not lead to excessive pyrolysis. In addition, after the modification of Zn, the Lewis acid increased and promoted the reaction process. The metal Zn has better dehydrogenation and aromatisation abilities, which can reduce the production of coke and promote the intermediate product of the pyrolysis to form aromatic hydrocarbons. The introduction of Ga in the Ga-ZSM-5 catalyst improves total acidity and reduces the content of the Brønsted acid while increasing the Lewis acid content significantly [38]; so, enhancing the aromatisation activity

of the molecular sieves catalysts. This finding can be attributed to the introduction of Ga by the impregnation method, in the form of gallium oxide dispersed in the outer surface or channel of the molecular sieve. These Ga species located in a non-skeletal site, providing an active aromatisation centre. As part of the carrier molecular sieve framework, Al can produce the strong acid centre. The metal centre and the acid centre functions constitute the dual-function catalyst and together, they promote aromatisation. Moreover, Ga species as a dehydrogenation activity centre can have a synergistic effect with the acid site of the molecular sieve, that is, the addition of Ga can promote the decarboxylation reaction and the cyclic reaction of olefins. To reduce the carbon deposition rate, the cleavage of the intermediate products must be inhibited to increase the likelihood of aromatisation [39]. Owing to the lower acidity of the Cu-ZSM-5 catalyst (as seen in TPD in Fig. 3), most copper cations are located in the ion exchange positions. The decarbonylation reactions are possibly promoted by the metal sites rather than by the acidity site [40]; thus, the yield of aromatics was lower, the coke deposition was higher, and the likelihood of PAH formation were also higher. Significant differences are observed between the Mg-ZSM-5 and other metal-loaded catalysts; the former catalyst exhibits lower aromatic yield and higher formation of both coke and PAHs compared with the latter. These features are in agreement with the remarkable decrease of the strong acidity site in the NH3-TPD spectra, which decreases the role of cracking and esterification reactions in the upgrading process. Hence, the formation of aromatic compounds is related to the occurrence of the decarboxylation and dehydration reactions. When the reaction degrees are reduced, the oxygen-containing compounds increase. At the same time, the excessive deposition of coke on the surface of the catalyst hinders the accessibility to the active sites. Therefore, catalytic efficiency is reduced, and the aromatic content is decreased. Although the Ni-ZSM-5 catalyst has high acidity, because Ni elements are enriched at the channel mouth of the molecular sieve, the steric effect is increased, thus blocking the shape selectivity of the catalytic pyrolysis gas. At the same time, after the excessive Ni-modified ZSM-5, the Lewis acid also becomes excessive after the formation of aromatic hydrocarbons; this facilitates the continued occurrence of the dehydrogenation reaction. The depth of dehydrogenation which results in a large number of carbon deposition species blocked the molecular sieve pore, deactivating the catalyst and reducing the yield of aromatics. Therefore, because of the total acidity of metal-loaded catalysts, the special Brønsted acid site is reduced and the acid content, specific surface area, pore volume and pore size are all changed. The ability to generate large molecular compounds in the inner or outer surface of the aperture of the molecular sieve is also hindered, thus reducing the production of coke. Furthermore, the conversion of oxide to aromatics increases along with the content of aromatic hydrocarbons. The H-ZSM-5 catalyst has been shown to be very active in the catalytic pyrolysis upgrading of biomass and

in enhancing the selectivity of aromatics in pyrolysis bio-oil. The aromatic selectivity of ex situ catalytic pyrolysis upgrading of biomass for different loading metal catalysts are shown in Fig. 7 (b–d). Compared with the non-catalyst experiments, all the M-ZSM-5 catalysts have a major influence on the selectivity of light aromatics, such as the C7 and C8 compounds, among others (the yields ranged from 20 wt%-36.52 wt% and 23 wt%-35.23wt%, respectively). However, the content of C6 compounds is lower (only 5 wt%-10 wt %) because of the alkylation of benzene and its reaction with oxygenated compounds [41]. Zn-ZSM-5 can obviously increase the content of toluene compared with unmodified HZSM-5; the yield reaches 36.52 wt% (representing an increase of 8.25 wt%). This is followed by Ga-ZSM-5 (27.52 wt%). Meanwhile, H-ZSM-5 and Ni-ZSM-5 can also significantly improve the content of benzene. The order of the toluene selectivity of the M-ZSM-5 cation catalyst is Zn＞H＞Ga＞Cu＞Ni＞Mg＞Co, that of benzene selectivity is H＞Ni~Zn＞Ga and that of xylene is Zn＞Mg ＞Ga＞H, Co, Cu＞N. Benzene, toluene and xylene (BTX) are the major compounds of biomass pyrolysis and petrochemical compounds for enhancing octane values. In the polycyclic aromatic hydrocarbons, the pore size of the Ni-ZSM-5 catalyst is similar to those of naphthalene and naphthalene. This similarity is advantageous to the generation and diffusion of large molecules, such as naphthalene series, because the content is the highest (see Fig. 7(d)) in C10 and C11 but lowest in di-methyl naphthalene (C12). Meanwhile, the contents of the two methyl naphthalenes are relatively low (C12); therefore, Ni-ZSM-5 is better for more than C10 of polycyclic aromatic hydrocarbon selectivity, whereas Co is better for the selectivity of indene (C9). The lowest selectivity for polycyclic aromatic hydrocarbons is found in the Zn cation, whereas others show almost no difference. These findings are related to the pore size and acidity of the catalyst. For the Ni-ZSM-5 catalyst, this may be due to the hydrodealkylation (action) of xylene and toluene. For other alkylated benzene to benzene upon their formation, the content of benzene is enhanced, while those of toluene and xylene are decreased [30]. Meanwhile, the demethylation of dimethyl benzene mainly undergoes two processes: xylene to toluene and toluene to benzene [42]. For the Zn, H and Ga-ZSM-5 catalysts, the reaction path is the same as that of the Ni-ZSM-5 catalyst; however, because its hydrogenolysis is relatively weaker, the reaction path of toluene to benzene is more difficult; thus, the content of toluene is relatively higher. In addition, Ga and Zn species are highly dispersed in the pores of the molecular sieve, which makes the intermediate product of pyrolysis come into full contact with the Zn and Ga species; further reaction leads to the significant improvement in the selectivity of the aromatics [43]. For the polycyclic aromatic hydrocarbons, the single-ring aromatic and polycyclic aromatic hydrocarbons result in a competitive reaction; the presence of metal ions increases the content of the former,

which prevents the further polymerisation of light aromatic hydrocarbons and oxygenated compounds as well as hinders the preparation of the latter [44]. When the Ni-ZSM-5 catalyst is used, the pore size of the catalyst is decreased owing to the excessive aggregation of the catalyst; hence, the acidity is decreased, the amount of coke is increased and the naphthalene content is also increased. A simplified summary of the reaction pathways for the observed relativities is presented in Scheme 1.

3.4 Effect of metal loading amount on the yield and selectivity of bio-oil Table 5 shows the effects of the loading amount on aromatic selectivity at Zn, Ga and Co loadings of 1, 5 and 10 wt%, respectively. As seen in Table 5, aromatic yields increased from 69wt% to 86.49wt% with the Zn loading amount ranging from 0 wt%-5 wt%. As the loadings increase, the content of aromatics decreases. The Zn component has better dehydrogenation ability, and the existence of Zn reduces the occurrence of hydrogen transfer, reducing hydrocarbon generation and increasing aromatic selectivity at the same time. However, with the increase of Zn loading, the effect of dehydrogenation was enhanced, thus leading to the increase of low-carbon olefins and non-condensable gases, such as CO and CO2 [45]. Moreover, aromatisation is a synergistic, catalytic process with the reaction of the Brønsted acid and Lewis acid; the loading of Zn can increase the Lewis acid site, reducing the Brønsted acid at the same time. The higher or the lower ratios of B/L are unfavourable for increasing aromatic yield [46]. Therefore, the maximum load is 5 wt% Zn. For the Co- and Ga-modified ZSM-5, because of the similar radius of the Ni and Co atoms. With the increasing amount of Co, a large number of particles enter the pores of the catalyst, thereby blocking the channel and reducing the content of aromatics. In the Ga-ZSM-5 catalyst, the introduction of the Ga atom can improve total acidity, simultaneously reducing and increasing the Brønsted acid and the Lewis acid contents, respectively. The addition of Ga can also simultaneously promote the decarboxylic reaction and the cyclic reaction of olefins. To reduce the carbon deposition rate, the cleavage of the intermediate products must be inhibited, and aromatisation must be promoted. Therefore, with the increase of Ga, the content of aromatics also continued to increase; however, the increase is not larger than that of the unmodified H-ZSM-5 catalyst.

3.5 Effect of synergistic loading on the selectivity of aromatic hydrocarbons To elucidate the effect of cooperative load on the production distribution of biomass pyrolysis (as shown in Table 6), the metal contents on HZSM-5 catalyst detected by XPS, spectroscope was in the range of initial metal content 5wt%. It was noticed that the actual loading of the supported metal by XPS were less than 5wt%, lower

than the calculated value. And the content of BTXE in bio-oil is decreased by the composite load and the Zn-Ni load. The content of aromatics shows the greatest decrease (26.19%). The Zn-Co co-modified ZSM-5 catalyst has higher aromatic selectivity than that of the unmodified H-ZSM-5 catalyst, and the aromatic content increased by 10.08%. The results show that Co plays a catalytic role in the Zn-Co-ZSM-5 catalyst, that is, Co and Zn produce a kind of synergy and jointly promote the catalytic activity of biomass. Meanwhile, the Ni- and Ga-modified ZSM-5 catalysts do not show significant change compared with the unmodified ZSM-5 catalyst. This finding may be due to the change in the impregnation process and the unstable load of the Zn metal, resulting in the loss of Zn. Moreover, when the second metal is loaded, it is attached to the surface of the Zn, thus covering the Zn. Therefore, the actual participation in the catalytic reaction is still achieved by a separate metal, whereas the Zn element modification results in relatively significant changes in the B/L acid ratio, leading to the destruction of synergy.

4. Conclusion 1) The M-ZSM-5 catalysts yielded a higher amount of non-condensable gas at the expense of the liquid yields, from 36.82 wt% down to 14.88 wt%. The Ga-ZSM-5 and Zn-ZSM-5 catalysts produced the highest yields of bio-oil (25.76 and 22.69wt%, respectively). The yield of Cu-ZSM-5 is the lowest (38.38%). The addition of the catalyst can significantly inhibit the accumulation of carbon. In particular, the effect of Ga is the most significant, with the amount of carbon deposition decreasing from 31.76 wt% to 22.08 wt%. The addition of catalyst can also significantly improve the performance of bio-oil; the contents of C and H is increased, the content of oxygen decreased and the calorific value increased. The order of deoxygenation is as follows: Ga-ZSM-5＞Zn-ZSM-5＞ Ni-ZSM-5＞Co-ZSM-5＞Mg-ZSM-5＞Cu-ZSM-5＞H-ZSM-5. 2) The M-ZSM-5 catalyst can significantly improve the contents of the single- and double-ring aromatics, but it has less influence on the effect of the tri-ring aromatics, such as phenantrene, anthracene and fluorine. The highest content of the single-ring aromatics prepared by Zn-ZSM-5 is 90.28 wt%, whereas the content of the polycyclic aromatic hydrocarbon prepared by using the Ni-ZSM-5 catalyst is only 31.36 wt%. 3) The selectivities of the single-ring aromatic hydrocarbons, such as C7 and C8, are significantly affected by the use of all the M-ZSM-5 catalysts (20 wt%–36.52 wt% and 23 wt%–35.32 wt% respectively). The Zn-ZSM-5 catalysts are the most selective for toluene and xylene (36.52 and 35.32 wt%, respectively), whereas the Co-based catalysts are identified to be the most selective for indene. The Ni-based catalysts can obviously improve the selectivity of benzene production and C10+ polycyclic aromatic hydrocarbon. Hence, the Zn-ZSM-5 catalysts are the most effective catalyst to be used in aromatic hydrocarbons. The order of the preparation of toluene with

different supported metal catalysts is Zn＞H＞Ga＞Cu＞Ni＞Mg＞Co, that of benzene is H＞Ni~Zn＞Ga and that for xylene is Zn＞Mg＞Ga＞H, Co, Cu＞Ni.

Acknowledgments This work was supported by the National Natural Science Foundation of China (31670599), the 948 project (Grant No. 2013-4-08) in the State Forestry Administration, the Special Fund for Renewable Energy Development in Yunnan Province (Yunnan Finance Industry No. [2015]86), the Yunnan Provincial Department of Education Major Project of Scientific Research Foundation (Grant No. ZD2014012), and the Key Laboratory of Bio-based Material Science & Technology (Northeast Forestry University), Ministry of Education.

References [1] Klass D L． Biomass for renewable energy，fuels and chemicals[J]. Bio Renew Energy Fuels Chem,29 (1998) 1028-1037． [2] Stefanidis S D, Kalogiannis K G, Iliopoulou E F, et al. In-situ upgrading of biomass pyrolysis vapors: catalyst screening on a fixed bed reactor[J]. Bioresour. Technol., 102(2011) 8261-8267. [3] Jae J, Tompsett G A, Foster A J, et al. Investigation into the shape selectivity of zeolite catalysts for biomass conversion [J]. J. Catal., 279(2011) 257-268. [4] French R, Czernik S. Catalytic pyrolysis of biomass for biofuels production[J]. Fuel Process. Technol., 91(2010) 25-32. [5] Iliopoulou E F, Stefanidis S D, Kalogiannis K G, et al. Catalytic upgrading of biomass pyrolysis vapors using transition metal-modified ZSM-5 zeolite[J]. Appl. Catal., B: Environ, 127(2012) 281-290. [6] Varzaneh A Z, Kootenaei A H S, Towfighi J, et al. Optimization and deactivation study of Fe–Ce/HZSM-5 catalyst in steam catalytic cracking of mixed ethanol/naphtha feed[J]. J. Anal. Appl. Pyrolysis, 102(2013) 144-153. [7] Park H J, Dong J I, Jeon J K, et al. Conversion of the pyrolytic vapor of radiata pine over zeolites[J]. J Ind Eng Chem, 13(2007) 182-189. [8] Cheng Y T, Jae J, Shi J, et al. Production of Renewable Aromatic Compounds by Catalytic Fast Pyrolysis of Lignocellulosic Biomass with Bifunctional Ga/ZSM‐5 Catalysts[J]. Angew. Chem. Int. Ed., 124(2012) 1416-1419. [9] Fanchiang W L, Lin Y C. Catalytic fast pyrolysis of furfural over H-ZSM-5 and Zn/H-ZSM-5 catalysts[J]. Appl. Catal., A: Gen, 419(2012)102-110. [10] French R, Czernik S. Catalytic pyrolysis of biomass for biofuels production[J]. Fuel Process. Technol., 91(2010) 25-32. [11] Thangalazhy-Gopakumar S, Adhikari S, Gupta R B. Catalytic pyrolysis of biomass over H+ ZSM-5 under hydrogen pressure[J]. Energ fuel, 26(2012) 5300-5306. [12] Vichaphund S, Aht-ong D, Sricharoenchaikul V, et al. Production of aromatic compounds from catalytic fast pyrolysis of Jatropha residues using metal/HZSM-5 prepared by ion-exchange and impregnation methods[J]. Renew Energ, 79(2015) 28-37.

[13] Huang W, Gong F, Fan M, et al. Production of light olefins by catalytic conversion of lignocellulosic biomass with HZSM-5 zeolite impregnated with 6wt.% lanthanum[J]. Bioresour. Technol., 121(2012) 248-255. [14] Cheng Y T, Wang Z, Gilbert C J, et al. Production of p-Xylene from Biomass by Catalytic Fast Pyrolysis Using ZSM‐5 Catalysts with Reduced Pore Openings[J]. Angew. Chem. Int. Ed., 51(2012) 11097-11100. [15] Choi S J, Park S H, Jeon J K, et al. Catalytic conversion of particle board over microporous catalysts[J]. Renew energ, 54(2013): 105-110. [16] Valle B, Gayubo A G, Alonso A, et al. Hydrothermally stable HZSM-5 zeolite catalysts for the transformation of crude bio-oil into hydrocarbons[J]. Appl. Catal., B: Environ, 100(2010) 318-327. [17] Wang L, Lei H, Bu Q, et al. Aromatic hydrocarbons production from ex situ catalysis of pyrolysis vapor over Zinc modified ZSM-5 in a packed-bed catalysis coupled with microwave pyrolysis reactor[J]. Fuel, 129(2014) 78-85. [18] Zhu X, Lu Q, Li W, et al. Fast and catalytic pyrolysis of xylan: Effects of temperature and M/HZSM-5 (M= Fe, Zn) catalysts on pyrolytic products[J]. Front. Energy Power Eng. China, 4(2010) 424-429. [19] Ni Y, Sun A, Wu X, et al. The preparation of nano-sized H [Zn, Al] ZSM-5 zeolite and its application in the aromatization of methanol[J]. Microporous Mesoporous Mater., 143(2011) 435-442. [20] Youming N I, Aiming S U N, Xiaoling W U, et al. Aromatization of methanol over La/Zn/HZSM-5 catalysts[J]. Chin. J. Chem. Eng., 19(2011) 439-445. [21] Zaidi H A, Pant K K. Catalytic conversion of methanol to gasoline range hydrocarbons[J]. Catal. Today, 96(2004) 155-160. [22] Inoue Y, Nakashiro K, Ono Y. Selective conversion of methanol into aromatic hydrocarbons over silver-exchanged ZSM-5 zeolites[J]. Microporous Mater., 4(1995) 379-383. [23] Fan M, Deng S, Wang T, et al. Production of BTX through Catalytic Depolymerization of Lignin [J]. Chinese J Chem Phys, 27(2014) 221-226. [24] Neumann G T, Hicks J C. Effects of cerium and aluminum in cerium-containing hierarchical HZSM-5 catalysts for biomass upgrading[J]. Top. Catal., 55(2012) 196-208. [25] Park H J, Park Y K, Kim J S, et al. Bio-oil upgrading over Ga modified zeolites in a bubbling fluidized bed reactor[J]. Stud. Surf. Sci. Catal., 159(2006) 553-556. [26] Sluiter, A., Hames, B., Ruiz, R., Scarlata, C., Sluiter, J., Templeton, D., and Crocker, D. Determination of Structural Carbohydrates and Lignin in Biomass (NREL/TP-510-42618), National Renewable Energy Laboratory, Golden, CO, USA, 2008.

[27] Channiwala S A, Parikh P P. A unified correlation for estimating HHV of solid, liquid and gaseous fuels[J]. Fuel, 81(2002) 1051-1063. [28] Zhang L, Gao J, Hu J, et al. Lanthanum oxides-improved catalytic performance of ZSM-5 in toluene alkylation with methanol[J]. Catal. Lett., 130(2009) 355-361. [29] Long X, Zhang Q, Liu Z T, et al. Magnesia modified H-ZSM-5 as an efficient acidic catalyst for steam reforming of dimethyl ether[J]. Appl. Catal., B: Environ, 134(2013) 381-388. [30] Schultz E L, Mullen C A, Boateng A A. Aromatic Hydrocarbon Production from Eucalyptus urophylla Pyrolysis over Several Metal‐Modified ZSM‐5 Catalysts [J]. Energy Technol, 2017, 5(1): 196-204. [31] Zhang H, Carlson T R, Xiao R, et al. Catalytic fast pyrolysis of wood and alcohol mixtures in a fluidized bed reactor[J]. Green Chem., 14(2012) 98-110. [32] Peng J, Chen P, Lou H, et al. Catalytic upgrading of bio-oil by HZSM-5 in sub-and super-critical ethanol[J]. Bioresour. Technol., 2009, 100(13): 3415-3418. [33] http://www.icis.com/v2/magazine/home.aspx/ [34] Czernik S, Bridgwater A V. Overview of applications of biomass fast pyrolysis oil[J]. Energ Fuel, 18(2004) 590-598. [35] Wu C, Yin X, Liu H. Status and prospects for biomass gasification[J]. J. Fuel Chem. Technol, 41(2013) 798-804. [36] Nguyen T S, Zabeti M, Lefferts L, et al. Catalytic upgrading of biomass pyrolysis vapours using faujasite zeolite catalysts[J]. Biomass Bioenerg, 48(2013) 100-110. [37] Yin S, Lin J, Yu Z. Effect of zinc content on properties of Zn/HZSM-5 zeolite catalyst[J]. Chinese J Catal, 22(2001) 57-61.. [38] Miao Q, Dong M, Niu X J, et al. Synthesis of gallium-containing ZSM-5 molecular sieves and their catalytic performance in methanol aromatization[J]. J.Fuel Chem.Tech., 40(2012) 1230-1239. [39] Cheng Y T, Jae J, Shi J, et al. Production of Renewable Aromatic Compounds by Catalytic Fast Pyrolysis of Lignocellulosic Biomass with Bifunctional Ga/ZSM-5 Catalysts[J]. Angew. Chem. Int. Ed., 124(2012) 1416-1419. [40] Veses A, Puértolas B, Callén M S, et al. Catalytic upgrading of biomass derived pyrolysis vapors over metal-loaded ZSM-5 zeolites: Effect of different metal cations on the bio-oil final properties [J]. Microporous Mesoporous Mater., 209(2015) 189-196. [41] Thangalazhy-Gopakumar S, Adhikari S, Gupta R B. Catalytic pyrolysis of biomass over H+ ZSM-5 under

hydrogen pressure[J]. Energ fuel, 26(2012) 5300-5306. [42] Weiss A H, Doelp L C. Kinetics of catalytic xylene hydrodealkylation[J]. Ind. Eng. Chem. Proc. Des. Dev., 3(1964) 73-78. [43] Liu R, Zhu H, Wu Z, et al. Aromatization of propane over Ga-modified ZSM-5 catalysts[J]. J.Fuel Chem.Tech., 43(2015) 961-969. [44] Carlson T R, Cheng Y T, Jae J, et al. Production of green aromatics and olefins by catalytic fast pyrolysis of wood sawdust[J]. Energ Environ Sci 4(2011) 145-161. [45] Zhang J X, Guan N J. Aromatization of propane over Zn/HZSM-5 modified by non-metal and second metal components[J]. Acta Petr Sin, 15(2000) 7-11. [46] Bhan A, Nicholas Delgass W. Propane aromatization over HZSM-5 and Ga/HZSM-5 catalysts[J]. Cat. Rev., 50(008) 19-151.

Fig.1 The schematic diagram of fixed-bed

1400 a

Mg-ZSM-5 Zn-ZSM-5 Ni-ZSM-5 H-ZSM-5

1200 1000

Cu-ZSM-5 Ga-ZSM-5 Co-ZSM-5

Intensity(a.u)

800 600 400 200 0 -200 10

20

1400

30

40

2θ(degrees)

Mg-ZSM-5 Zn-ZSM-5 Ni-ZSM-5 H-ZSM-5

b 1200 1000

50

Cu-ZSM-5 Ga-ZSM-5 Co-ZSM-5

Intensity(a.u)

800 600 400 200 0 -200 22

23

2θ(degrees)

24

25

Fig. 2 XRD patterns of parent and metal cation-loaded ZSM-5 zeolites

TCD Signal(mV)

Total acid density (mmol/g): (Ni) 0.57, (Co) 0.36, (Ga) 0.39 (Zn) 0.44, (H) 0.67, (Cu) 0.16 (Mg) 0.21. Ni-ZSM-5 Co-ZSM-5 Ga-ZSM-5 Zn-ZSM-5 H-ZSM-5 Cu-ZSM-5 Mg-ZSM-5

100

200

300

400

500

Temperature(℃)

Fig.3 Ammonia TPD profiles of the parent and metal cation-loaded ZSM-5 zeolites

H-ZSM-5 Ni-ZSM-5 Co-ZSM-5 Cu-ZSM-5

250

0.03

Zn-ZSM-5 Ga-ZSM-5 Mg-ZSM-5

H-ZSM-5 Ni-ZSM-5 Co-ZSM-5

0.02

Pore Volume (cm3g-1nm-1)

Amount pf Adsorbed (cm3g-1)

300

200 150 100 50 0

Zn-ZSM-5 Ga-ZSM-5 Mg-ZSM-5 Cu-ZSM-5

0.01

0.00

-0.01

-0.02

0.0

0.2

0.4 0.6 Relative Pressure(P/P0)

0.8

Fig.4. Pore structure parameters of catalysts

1.0

2

4

8

16

Pore Size(nm)

32

64

Fig.5. SEM micrographs of H-ZSM-5 catalytic：A（H-ZSM-5），B（Zn-ZSM-5），C（Ni-ZSM-5），D （Co-ZSM-5） ，E（Cu-ZSM-5） ，F （Ga-ZSM-5） ，G（Mg-ZSM-5）

60

solid yield (wt%) gas yield （ wt%）

liquid yield （ wt%）

Production yield(wt %)

50

40

30

20

10

-5 gZS M -5 Cu -Z SM -5 Zn -Z SM -5 G aZS M -5 Ni -Z SM -5 Co -Z SM -5 M

H -Z SM

Bl an k

0

Fig. 6 product yields of pine catalytic pyrolysis with different metal-loaded catalysts

H-ZSM-5 Ga-ZSM-5 Ni-ZSM-5 Mg-ZSM-5 Co-ZSM-5 Zn-ZSM-5 Cu-ZSM-5

Product yield(%)

60

40

20

H-ZSM-5 Ga-ZSM-5 Ni-ZSM-5 Mg-ZSM-5 Co-ZSM-5 Zn-ZSM-5 Cu-ZSM-5

b

35

Aromatic selectivity(%)

a 80

30 25 20 15 10 5 0 Benzene

0

Aromatic selectivity(%)

12

2-ring AH

H-ZSM-5 Ga-ZSM-5 Ni-ZSM-5 Mg-ZSM-5 Co-ZSM-5 Zn-ZSM-5 Cu-ZSM-5

c

10 8 6 4

o-Xylene

p-Xylene Ethylbenzene

Aromatic compounds

d

H-ZSM-5 Ga-ZSM-5 Ni-ZSM-5 Mg-ZSM-5 Co-ZSM-5 Zn-ZSM-5 Cu-ZSM-5

40

30

20

10

2 0

Toluene

3-ring AH

Product selectivity(%)

1-ring AH

lene lene lene lene Naphtha Methylnaphtha imethylnaphtha Ethylnaphtha D

Polycyclic aromatic compounds

0 C6

C7

C8

C9 C10 C11 C12 C13 C14 C15 AC+

Carbon number

Fig.7. production yields and aromatic selectivity for the biomass catalytic pyrolysis using M-ZSM-5 catalyst （ a:production yields, b:single-ring aromatic selectivity, c:polycyclic aromatic selectivity, d:carbon number）

O OH O OH OH O O O

OH

O OH

O OH OH Dehydration Decarbonylation

Hydrocarbon Pool

OH OH OMe

OMe CO CO2 H2O Aromatization Zn＞ H, Ga＞Mg＞Cu＞Ni, Co

Oxygenated Pyrolysis Vapor

Hydrodealkylation

H＞Ni， Zn＞Ga

CH4

Hydrodealkylation Zn＞H＞Ga＞Ni

BTXE / Alkylated Benzenes

CH4

Ring Growth Ni＞Cu＞H＞Mg＞Ga＞Co＞Zn

Polymerization

Polycyclic aromatic hydrocarbon and Coke

Naphthalene and its derivatives

Scheme.1. Reaction pathways for the aromatic productions from biomass pyrolysis upgrading with metal-loaded modified H-ZSM-5 catalyst

Table 1 Aromatic yield and selectivity by catalytic conversion of biomass feedstocks and model compounds over metal-modified zeolite Ratio of biomass

Aromatic

Production selectivity /%

compounds

to catalyst

yield /%

Benzene

Toluene

Xylene

Feedstock No

and

model

Catalysts

Ref

1

Co/HZSM-5

Pine wood

0.11

39.8

8

11.1

9.6

11

2

Ni-HZSM-5

Pine wood

0.11

41.3

7.4

10.6

10

11

3

Mo/HZSM-5

Pine wood

0.11

42.5

6.4

11.5

11

11

4

Pd/HZSM-5

Pine wood

0.11

46.4

6.7

12

11.9

11

5

Ga/HZSM-5

Pine wood

10

23.2

19.6

34.3

18.9

12

6

Co/HZSM-5

Remnant of leprosy

1

20.4

4.9

49.1

28.7

12

7

Ni-HZSM-5

Remnant of leprosy

1

30.6

40

36.4

22.2

12

8

Mo/HZSM-5

Remnant of leprosy

1

26.9

---

48.7

21.4

12

9

Pd/HZSM-5

Remnant of leprosy

1

39.3

9.3

36.8

20.7

12

10

Ga/HZSM-5

Remnant of leprosy

1

29.4

11

40.4

23.9

12

11

La/HZSM-5

Lignin

0.33

---

0.58

1.65

1.29

13

12

Ga/HZSM-5

Furan

10.4

39.7

33.7

15.1

1.5

14

13

Ga/HZSM-5

Pinewood sawdust

0.35

21.6

---

---

---

15

14

Ga/HZSM-5

Montery pine sawdust

4

23.4

---

---

---

8

15

Ni/HZSM-5

40%biooil+60%methanol

2.7

42

---

---

---

16

16

Zn/HZSM-5

Douglas fir

GHSV h-1 0.048h

50.7

---

---

---

17

17

Zn/HZSM-5

Furan

GHSV h-1 2412

26.3

71.6

25

---

9

18

Fe/HZSM-5

Xylitol

0.5

---

2.4

12

14.8

18

19

Zn/HZSM-5

Xylitol

0.5

---

2.0

10.8

12.1

18

20

Zn/HZSM-5

Methanol

WHSV h-1 3.2h

45.6

3.9

18.3

23.4

19

21

Zn,Al/HZSM-5

Methanol

WHSV h-1 3.2h

46.7

4.5

19.6

22.6

19

22

Zn,La/HZSM-5

Methanol

WHSV h-1 0.8h

56.6

4.7

22.9

29.0

20

23

La/HZSM-5

Methanol

WHSV h-1 0.8h

30.5

5.6

14.5

10.4

20

24

Zn/HZSM-5

Methanol

WHSV h-1 0.8h

47.9

4.6

20.1

23.2

20

25

CuO/HZSM-5

Methanol

4.138

76.5

0.1

3.34

12.2

21

26

ZnO/HZSM-5

Methanol

4.138

66.9

0.19

0.73

7.0

21

27

CuO/ZnO/ZSM-5

Methanol

4.138

69.4

0.13

1.91

12.58

21

28

Ag/HZSM-5

Methanol

9.0

80.3

---

---

---

22

29

Na/HZSM-5

Wood

2.0

46.3

3.8

9.0

6.2

23

30

Ce/HZSM-5

Glucose

9.0

8.9

6.0

18.4

15.8

24

Table 2. Proximate, Ultimate, and Component Analysis of Yunnan pine Proximate analysis (wt-%) a

Moisure

2.12 a Air-dry

a

Volatile

83.22

a

Fixed Carbon

13.45

basis; b By difference

Ultimate analysis (wt-%) a

Component analysis (wt-%)

Ash

C

H

N

S

Ob

Cellulose

Hemicellulose

Lignin

1.21

49.66

8.23

0.21

0.13

41.77

44.39

24.16

31.45

Table 3. Properties of metal-loaded ZSM-5catalyst SBET

Smicro

Sext

Vtotal

Vmeso

Vmicro

Dpore size

(m2/g)a

(m2/g)b

(m2/g) b

(mL/g)c

(mL/g)d

(mL/g) b

(nm)e

H-ZSM-5

338.44

195.64

142.80

0.2861

0.1845

0.1016

3.38

Ga-ZSM-5

293.48

163.55

129.93

0.2467

0.1617

0.08499

3.39

Ni-ZSM-5

291.37

162.93

128.44

0.2488

0.1641

0.08472

3.45

Mg-ZSM-5

282.09

167.72

114.37

0.2448

0.1585

0.08626

3.42

Co-ZSM-5

288.94

161.02

127.92

0.2460

0.1622

0.08376

3.44

Zn-ZSM-5

288.15

167.60

120.55

0.2483

0.1609

0.08738

3.38

Cu-ZSM-5

287.54

165.99

121.55

0.2387

0.1516

0.08708

3.41

Sample

a、e

From N2 absorption measurement (BET method). b P/P0=0.95, from BJH analysis c From N2 absorption measurement (t-plot

method). d By difference method

Table 4. Element Analysis of the different upgraded bio-oil Catalysts

C

H

N

Oa

H/C mole ratio

O/C mole ratio

HHV（MJ/Kg）b

Water content (%)

Blank

55.58

7.64

0.28

36.50

1.65

0.49

24.63

20.15

H-ZSM-5

68.97

8.26

0.12

22.65

1.44

0.25

31.47

6.75

Mg-ZSM-5

72.94

8.83

0.00

18.23

1.45

0.19

33.98

6.52

Cu-ZSM-5

70.59

8.92

0.07

20.42

1.52

0.22

33.04

5.88

Zn-ZSM-5

73.28

9.68

0.00

17.04

1.58

0.17

35.23

3.60

Ga-ZSM-5

73.80

9.22

0.03

16.95

1.50

0.17

34.87

3.68

Ni-ZSM-5

73.69

9.16

0.00

17.15

1.49

0.17

34.75

3.65

Co-ZSM-5

73.09

9.17

0.00

17.74

1.46

0.18

34.13

5.91

Diesel oil [33]

86.58

13.29

65ppm

0.01

1.842

0

45.50

---

Heavy oil [34]

85.00

11.00

0.30

1.00

1.553

0.009

40.00

---

a:Calculated by difference

Table 5. Aromatic selectivity (%) producted during catalytic pyrolysis upgraded of biomass Mononuclear aromatic production (%)

Naphthalene

and

SBTXE

Catalysts

Other Benzene

Toluene

o-Xylene

p-Xylene

Ethyl benzene

its derivatives

(%)

H-ZSM-5

10.83

28.27

1.30

24.05

4.55

17.99

69.00

13.01

1 Ga-ZSM-5

4.37

22.03

14.62

18.16

4.94

15.89

64.12

19.99

5 Ga-ZSM-5

7.22

27.52

15.16

13.56

4.96

16.95

68.42

14.63

10 Ga-ZSM-5

8.01

25.62

18.04

12.69

5.12

15.17

69.48

15.35

1 Co-ZSM-5

6.17

22.53

19.53

8.58

7.50

18.46

64.31

17.23

5 Co-ZSM-5

5.84

19.77

14.12

10.58

5.04

15.32

55.35

29.33

10 Co-ZSM-5

4.16

18.64

12.89

14.37

3.68

20.38

53.74

25.88

1 Zn-ZSM-5

5.58

23.25

23.25

18.58

10.28

5.38

80.94

13.68

5 Zn-ZSM-5

7.83

36.52

21.85

13.47

6.82

7.87

86.49

5.64

10 Zn-ZSM-5

8.16

35.68

17.12

12.91

4.78

12.09

78.65

9.26

Table 6. Effect of cooperative loaded on the selectivity of aromatic production Element (%)

Mononuclear aromatic production（%）

SBTXE

Catalysts

Nap

Other （%）

Zn

Ni

Ga

Co

Benzene

Toluene

o-Xylene

p-Xylene

EB

H-ZSM-5

-

-

-

-

10.83

28.27

1.3

24.05

4.55

17.99

13.01

69

Zn-Ni-ZSM-5

4.02

4.39

-

-

10.79

26.04

17.31

10.93

3.46

13.65

17.81

68.54

Zn-Ga-ZSM-5

4.38

-

4.13

-

8.84

30.85

13.78

15.86

0

13.6

17.08

69.32

Zn-Co-ZSM-5

4.17

-

-

5.28

14.98

40.79

10.01

10.36

2.94

13.68

7.24

79.08

a: Ethyl benzene;b: Naphthalene and its derivatives