Author's personal copy L.Zhang et al.Renewable and Sustainable Energy Reviews 24 (2013)66-72 71 4.2.Recommendations for future work [7]Liu RH.Shen CJ.Wu H.Deng CJ.Liu SY.Characterisation of bio-oil from fast pyrolysis of rice husk in fluidised bed reactor.Journal of the Energy Institute 2011:842:73-9. The components of bio-oil are very complex.On one hand,the [Chen Tianju.Wu Ceng.Liu Ronghou.Fei Wenting.Liu Shiyu.Effect of hot vapor pyrolysis bio-oil has many advantages in properties,such as less filtration on the characterization of bio-oil from rice husks with fast pyrolysis toxic,good lubricity and stronger biodegradation and so on.On the in a fluidized-bed reactor.Bioresource Technology 2011:102:6178-85. other hand,it also has lots of disadvantages in characteristics,that [9]Zheng Ji-lu.Bio-oil from fast pyrolysis of rice husk:yields and related properties and improvem ent the pyrolysis system.Journal of Analytical is,high contents of water,oxygen,ash and solids,low pH value, and Applied Pyrolysis 2007:1(80):30-5. high viscosity,chemical and thermal instability,low heating value, [10]Zhang Q,Chang J.Wang T.Xu Y.Review of biomass pyrolysis oil properties and and poor ignition and combustion properties.Although the upgrading research.Energy Conversion and Management 2007:48:87-92. upgraded bio-oil could be used as alternative fuel of boiler and [11]Oasmaa A.Czernik S.Fuel oil quality of biomass pyrolysis oils-state of the art for the end users.Energy Fuels 1999:13(4):914-21. internal combustion engine,now it still cannot replace the fossil [12]Qiang Lu,Wen-Zhi Li.Xi-Feng Zhu.Overview of fuel properties of biomass fast fuels completely due to the restriction in technologies and costing. pyrolysis oils.Energy Com version and Management 2009:50(5):1376-83. [13]Zhang Huiyan,Xiao Rui.Huang He.Xiao Gang.Comparison of non-catalytic How to develop and use the upgrading technologies to realize the and catalytic fast pyrolysis of corncob in a fluidized bed reactor.Bioresource industrial application of bio-oil from biomass pyrolysis is a big Technology2009:100(3y1428-34. matter.In order to facilitate this issue,great efforts should be paid [14]Xu Ying.Wang Tiejun.Ma Longlong.Zhang Qi.Wang Lu.Upgrading of liquid fuel from the vacuum pyrolysis of biomass over the Mo-Ni/y-Al2O catalysts. in the following aspects in the future Biomass and Bioenerey 2009:3308):1030-6. [15]Ying Xu,Tiejun Wang.Longlong Ma.Guanyi Chen.Upgrading of fast pyrolysis (1)more appropriate catalysts (e.g.,bifunctional catalysts or liquid fuel from biomass over Ru/y-Al2O3 catalyst.Energy Conversion and multifunctional catalysts)and dependable,steady and fully Management 2012:55:172-7. [16]Xu Ying.Wang Tiejun,Ma Longlong.Zhang Qi,Wang Lu.Upgrading of liquid developed reactor systems need to be developed in the future. fuel from the vacuum pyrolysis of bior nas over the Mo-Ni/t-AlO catalysts (2)During the upgrading of bio-oil using various catalysts,the Biomass and Bioenergy 2009:33(8):1030-6. mechanism on catalyst deactivation needed to be further [17]Guo Jianhua,Ruan Renxiang.Zhang Ying.Hydrotreating of phenolic com- explained,and the catalysts with high durability.strong cndustral and E ch2012:51:6599-604 renewable ability and high efficiency need to be developed [18]Xiong Wan-Ming.Fu Yao,Zeng Fan-Xin.Guo Qing-Xiang.An in situ reduction urgently. approach for bio-oil hydroprocessing.Fuel Processing Technology 2011:92 (3)During the researches on emulsification,seeking for more 81599-605. [19]Yang Tang.Wanjin Yu,Liuye Mo.Hui Lou.Xiaoming Zheng.One-step economic and abundant surfactants as substitutes for the high- hydrogenation-esterification of aldehyde and acid to ester over bifunctional priced surfactants remains an interesting topic to investigate. Pt catalysts:a model reaction as novel route for catalytic upgrading of fast (4)The researches on how to combine pyrolysis reactors with ergy Fuels 008:22(53484-8. 1201 Yu Waniin.Tang Yang.Mo Liuve.Chen Ping.Lou Hui.Zheng xi reaction conditions organically and how to efficiently use Bifunctional Pd/Al-SBA-15 catalyzed one-step hydrogenation-esterification upgrading technologies of other oils for reference need to be of furfural and acetic acid:a model reaction for catalytic upgrading of bio- oil.Catalysis Communications 2011:13(1):35-9. done in the future so that new ideas would be found. [21]Yu Wanjin,Tang Yang.Mo Liuye,Chen Ping.Lou Hui,Zheng Xiaoming.One-step (5)In order to promote the industrialization of upgrading of bio- hydrogenation-esterification of furfural and acetic acid over bifunctional Pd oil,more efforts should be paid to develop more experimental catalysts for bio-oil upgrading.Bioresource Technology 2011:102(17):8241-6. facilities with larger scale and high efficiency. [22]Tang Yang.Miao Shaojun,Shanks Brent H.Zheng Xiaoming.Bifunctional mesoporous organic-inorganic hybrid silica for combined one-step hydro- genation/esterification.Applied Catalysis A 2010:375(2):310-7. 123 Tang Yang.Miao Shaojun,Pham Hien N.Datye Abhaya,Zheng Xiaoming. Shanks Brent H.Enhancement of Pt catalytic activity in the hydrogenation of aldehydes.Applied Catalysis A 2011:406(1-2):81-8. 124]Wang Yuxin,Fang Yunming.He Tao.Hu Haoquan,Wu Jinhu.Hydrodeoxy- Acknowledgments gena tion of dibenzofuran over noble metal supported on mesoporous zeolite Catalysis Communications 2011:12(13):1201-5. [25]Wang Yuxin,He Tao,Liu Kaituo.Wu Jinhu,Fang Yunming.From biomass to Financial support from National Natural Science Foundation of advanced bio-fuel by catalytic pyroly is/hydro-processing:hydrodeoxygena- China through contract(Grant no.51176121)and financial support tion of bio-oil derived from biomass catalytic pyrolysis.Bioresource Technol- from The National Science and Technology Supporting Plan 0gy2012:108:280-4. [26]Su-Ping Zhang.Yong-Jie Yan.Zher gwei Ren,Tingchen Li.Study of hydrodeox- through contract(Grant no.2011BAD22B07)are greatly acknowl- on of bio-oil from the fast pyrolysis of biomass.Energy Source edged.In addition,Daniel Lycett-Brown from the University of 2003:25(1):57-65. Southampton,UK is greatly acknowledged for his valuable sugges- [27]Wang Weiyan,Yang Yunquan.Luo Hean.Peng Huizuo,He Bing.Liu Wenying. tion and correction of the manuscript. Preparation of Ni(Co)-W-B amorphous catalysts for cyclopentanone hydro- deoxygenation.Catalysis Communications 2011:12(14):1275-9. [28]Wang Weiyan,Yang Yunquan,Luo Hean.Hu Tao,Liu Wenying.Amorphous Co-Mo-B catalvst with high activity for the hvdrodeoxvgenation of bio-oil References Catalysis Communications 2011:12(6):436-40. [29]Weiyan Wang.Yunquan Yang.Hean Luo.Tao Hu,Wenying Liu.Preparation and hydrodeoxygenation properties of Co-Mo-0-B amorphous catalyst. [1]Xu Junming.Jiang Jianchun.Chen Jie,Sun Yunjuan.Biofuel production from Reaction Kinetics,Mechanisms,and Catalysis 2011:102(1):207-17. catalytic cracking of woody oils.Bioresource Technology 2010:101(14):5586-91. 30]Shurong Wang.Qian Liu,Kaige Wang.Xiujuan Guo,Zhongyang Luo.Kefa Cen [2]Xiu Shu angning.Shahbaz Abolghase m and upgra et al.Study on catalytic pyrolysis of manchurian ash for production of bio-oil. research:a review.Renewable and Sustainable Energy Reviews 2012:16 International Journal of Green Energy 2010:7(3):300-9. (7):4406-14. [31]Pan Pan,Changwei Hu,Wenyan Yang.Yuesong Li,Linlin Dong.Liangfang Zhu. [3]Dang Qi.Luo Zhongyang.Zhang Jixiang.Wang Jun. Chen Wen.Yang Yi et al.The direct pyrolysis and catalytic pyrolysis of Nannochloropsis sp Experimental study on bio-oil upgrading over Pt/SO4/ZrOz/SBA-15 catalyst residue for renewable bio-oils.Bioresource Technology 2010:101(12):4593-9. in supercritical ethanol.Fuel 2012:103:683-92. [32]Wang Pan,Zhan Sihui,Yu Hongbing.Xue Xufang.Hong Nan.The effects of 14]Zhang Qi.Chang Jie,Wang Tiejun.Xu Ying.Review of biomass pyrolysis oil temperature and catalysts on the pyrolysis of industrial wastes(herb residue) prop rties and upgrading research.Energy Conversion and Management Bioresource Technology 2010:101(9):3236-41. 2007:48(1):87-92. [33]Wu-Jun Liu.Ke Tian,Hong Jiang.Xue-Song Zhang.Hong-Sheng Ding.Han- [5]Yao Lu.Xian-Yong Wei.Jing-Pei Cao,Peng Li,Fang-Jing Liu.Yun-Peng Zhao. Qing Yu.Selectively roving the bio-oil quality by catalytic fast et al.Characterization of a bio-oil from pyrolysis of rice husk by detailed heavy-metal-pollu ed b omass: take copper Environ compositional analysi and structural investigation of lignin.Bioresource mental Science and Technology 2012:46(14):7849-56. 1 echnology2012.116114-9. [34]Huiyan Zhang.Rui Xiao,Denghui Wang.Zhaoping Zhong.Min Song.Qiwen [6]Rui Lu,Guo-Ping Sheng.Yan-Yun Hu,Ping Zheng.Hong Jiang.Yong Tang.et al. Pan.et al Catalytic fast pyrolysis of biomass in a fluidized bed with freshand Fractional characterization of a bio-oil derived from rice husk.Biomass and spent fluidized catalytic cracking (FCC)catalysts.Energy Fuels 009:23 Bioenergy2011:35(1):671-8. (12y6199-206.Author's personal copy 4.2. Recommendations for future work The components of bio-oil are very complex. On one hand, the pyrolysis bio-oil has many advantages in properties, such as less toxic, good lubricity and stronger biodegradation and so on. On the other hand, it also has lots of disadvantages in characteristics, that is, high contents of water, oxygen, ash and solids, low pH value, high viscosity, chemical and thermal instability, low heating value, and poor ignition and combustion properties. Although the upgraded bio-oil could be used as alternative fuel of boiler and internal combustion engine, now it still cannot replace the fossil fuels completely due to the restriction in technologies and costing. How to develop and use the upgrading technologies to realize the industrial application of bio-oil from biomass pyrolysis is a big matter. In order to facilitate this issue, great efforts should be paid in the following aspects in the future: (1) more appropriate catalysts (e.g., bifunctional catalysts or multifunctional catalysts) and dependable, steady and fully developed reactor systems need to be developed in the future. (2) During the upgrading of bio-oil using various catalysts, the mechanism on catalyst deactivation needed to be further explained, and the catalysts with high durability, strong renewable ability and high efficiency need to be developed urgently. (3) During the researches on emulsification, seeking for more economic and abundant surfactants as substitutes for the high￾priced surfactants remains an interesting topic to investigate. (4) The researches on how to combine pyrolysis reactors with reaction conditions organically and how to efficiently use upgrading technologies of other oils for reference need to be done in the future so that new ideas would be found. (5) In order to promote the industrialization of upgrading of bio￾oil, more efforts should be paid to develop more experimental facilities with larger scale and high efficiency. Acknowledgments Financial support from National Natural Science Foundation of China through contract (Grant no. 51176121) and financial support from The National Science and Technology Supporting Plan through contract (Grant no. 2011BAD22B07) are greatly acknowl￾edged. In addition, Daniel Lycett-Brown from the University of Southampton, UK is greatly acknowledged for his valuable sugges￾tion and correction of the manuscript. References [1] Xu Junming, Jiang Jianchun, Chen Jie, Sun Yunjuan. Biofuel production from catalytic cracking of woody oils. Bioresource Technology 2010;101(14):5586–91. [2] Xiu Shuangning, Shahbaz Abolghasem. Bio-oil production and upgrading research: a review. Renewable and Sustainable Energy Reviews 2012;16 (7):4406–14. [3] Dang Qi, Luo Zhongyang, Zhang Jixiang, Wang Jun, Chen Wen, Yang Yi. Experimental study on bio-oil upgrading over Pt/SO4 2−/ZrO2/SBA-15 catalyst in supercritical ethanol. Fuel 2012;103:683–92. [4] Zhang Qi, Chang Jie, Wang Tiejun, Xu Ying. Review of biomass pyrolysis oil properties and upgrading research. Energy Conversion and Management 2007;48(1):87–92. [5] Yao Lu, Xian-Yong Wei, Jing-Pei Cao, Peng Li, Fang-Jing Liu, Yun-Peng Zhao, et al. Characterization of a bio-oil from pyrolysis of rice husk by detailed compositional analysis and structural investigation of lignin. Bioresource Technology 2012;116:114–9. [6] Rui Lu, Guo-Ping Sheng, Yan-Yun Hu, Ping Zheng, Hong Jiang, Yong Tang, et al. Fractional characterization of a bio-oil derived from rice husk. Biomass and Bioenergy 2011;35(1):671–8. [7] Liu RH, Shen CJ, Wu HJ, Deng CJ, Liu SY. Characterisation of bio-oil from fast pyrolysis of rice husk in fluidised bed reactor. Journal of the Energy Institute 2011;84(2):73–9. [8] Chen Tianju, Wu Ceng, Liu Ronghou, Fei Wenting, Liu Shiyu. Effect of hot vapor filtration on the characterization of bio-oil from rice husks with fast pyrolysis in a fluidized-bed reactor. Bioresource Technology 2011;102:6178–85. [9] Zheng Ji-lu. Bio-oil from fast pyrolysis of rice husk: yields and related properties and improvement of the pyrolysis system. Journal of Analytical and Applied Pyrolysis 2007;1(80):30–5. [10] Zhang Q, Chang J, Wang T, Xu Y. Review of biomass pyrolysis oil properties and upgrading research. Energy Conversion and Management 2007;48:87–92. [11] Oasmaa A, Czernik S. Fuel oil quality of biomass pyrolysis oils—state of the art for the end users. Energy Fuels 1999;13(4):914–21. [12] Qiang Lu, Wen-Zhi Li, Xi-Feng Zhu. Overview of fuel properties of biomass fast pyrolysis oils. Energy Conversion and Management 2009;50(5):1376–83. [13] Zhang Huiyan, Xiao Rui, Huang He, Xiao Gang. Comparison of non-catalytic and catalytic fast pyrolysis of corncob in a fluidized bed reactor. Bioresource Technology 2009;100(3):1428–34. [14] Xu Ying, Wang Tiejun, Ma Longlong, Zhang Qi, Wang Lu. Upgrading of liquid fuel from the vacuum pyrolysis of biomass over the Mo–Ni/γ-Al2O3 catalysts. Biomass and Bioenergy 2009;33(8):1030–6. [15] Ying Xu, Tiejun Wang, Longlong Ma, Guanyi Chen. Upgrading of fast pyrolysis liquid fuel from biomass over Ru/γ-Al2O3 catalyst. Energy Conversion and Management 2012;55:172–7. [16] Xu Ying, Wang Tiejun, Ma Longlong, Zhang Qi, Wang Lu. Upgrading of liquid fuel from the vacuum pyrolysis of biomass over the Mo–Ni/γ-Al2O3 catalysts. Biomass and Bioenergy 2009;33(8):1030–6. [17] Guo Jianhua, Ruan Renxiang, Zhang Ying. Hydrotreating of phenolic com￾pounds separated from bio-oil to alcohols. Industrial and Engineering Chem￾istry Research 2012;51:6599–604. [18] Xiong Wan-Ming, Fu Yao, Zeng Fan-Xin, Guo Qing-Xiang. An in situ reduction approach for bio-oil hydroprocessing. Fuel Processing Technology 2011;92 (8):1599–605. [19] Yang Tang, Wanjin Yu, Liuye Mo, Hui Lou, Xiaoming Zheng. One-step hydrogenation–esterification of aldehyde and acid to ester over bifunctional Pt catalysts: a model reaction as novel route for catalytic upgrading of fast pyrolysis bio-oil. Energy Fuels 2008;22(5):3484–8. [20] Yu Wanjin, Tang Yang, Mo Liuye, Chen Ping, Lou Hui, Zheng Xiaoming. Bifunctional Pd/Al-SBA-15 catalyzed one-step hydrogenation–esterification of furfural and acetic acid: a model reaction for catalytic upgrading of bio￾oil. Catalysis Communications 2011;13(1):35–9. [21] Yu Wanjin, Tang Yang, Mo Liuye, Chen Ping, Lou Hui, Zheng Xiaoming. One-step hydrogenation–esterification of furfural and acetic acid over bifunctional Pd catalysts for bio-oil upgrading. 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Study of hydrodeox￾ygenation of bio-oil from the fast pyrolysis of biomass. Energy Sources 2003;25(1):57–65. [27] Wang Weiyan, Yang Yunquan, Luo Hean, Peng Huizuo, He Bing, Liu Wenying. Preparation of Ni(Co)–W–B amorphous catalysts for cyclopentanone hydro￾deoxygenation. Catalysis Communications 2011;12(14):1275–9. [28] Wang Weiyan, Yang Yunquan, Luo Hean, Hu Tao, Liu Wenying. Amorphous Co–Mo–B catalyst with high activity for the hydrodeoxygenation of bio-oil. Catalysis Communications 2011;12(6):436–40. [29] Weiyan Wang, Yunquan Yang, Hean Luo, Tao Hu, Wenying Liu. Preparation and hydrodeoxygenation properties of Co–Mo–O–B amorphous catalyst. Reaction Kinetics, Mechanisms, and Catalysis 2011;102(1):207–17. [30] Shurong Wang, Qian Liu, Kaige Wang, Xiujuan Guo, Zhongyang Luo, Kefa Cen, et al. Study on catalytic pyrolysis of manchurian ash for production of bio-oil. International Journal of Green Energy 2010;7(3):300–9. [31] Pan Pan, Changwei Hu, Wenyan Yang, Yuesong Li, Linlin Dong, Liangfang Zhu, et al. The direct pyrolysis and catalytic pyrolysis of Nannochloropsis sp. residue for renewable bio-oils. Bioresource Technology 2010;101(12):4593–9. [32] Wang Pan, Zhan Sihui, Yu Hongbing, Xue Xufang, Hong Nan. The effects of temperature and catalysts on the pyrolysis of industrial wastes (herb residue). Bioresource Technology 2010;101(9):3236–41. [33] Wu-Jun Liu, Ke Tian, Hong Jiang, Xue-Song Zhang, Hong-Sheng Ding, Han￾Qing Yu. Selectively improving the bio-oil quality by catalytic fast pyrolysis of heavy-metal-polluted biomass: take copper (Cu) as an example. Environ￾mental Science and Technology 2012;46(14):7849–56. [34] Huiyan Zhang, Rui Xiao, Denghui Wang, Zhaoping Zhong, Min Song, Qiwen Pan, et al. Catalytic fast pyrolysis of biomass in a fluidized bed with fresh and spent fluidized catalytic cracking (FCC) catalysts. Energy Fuels 2009;23 (12):6199–206. L. 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