See discussions, stats, and author profiles for this publication at: http://www.researchgate.net/publication/251574141 Conversion of carbohydrates biomass into levulinate esters using heterogeneous catalysts ARTICLE in APPLIED ENERGY · DECEMBER 2011 Impact Factor: 5.61 · DOI: 10.1016/j.apenergy.2011.05.049 CITATIONS READS 47 87 4 AUTHORS: Lincai Peng Lu Lin Kunming University of Science and Technol… Dalian University of Technology 23 PUBLICATIONS 287 CITATIONS 100 PUBLICATIONS 1,261 CITATIONS SEE PROFILE SEE PROFILE Hui Li Qiulin Yang Kunming University of Science and Technol… Tianjin University of Science and Technology 17 PUBLICATIONS 153 CITATIONS 12 PUBLICATIONS 91 CITATIONS SEE PROFILE SEE PROFILE All in-text references underlined in blue are linked to publications on ResearchGate, Available from: Lincai Peng letting you access and read them immediately. Retrieved on: 24 November 2015 Applied Energy 88 (2011) 4590–4596 Contents lists available at ScienceDirect Applied Energy journal homepage: www.elsevier.com/locate/apenergy Conversion of carbohydrates biomass into levulinate esters using heterogeneous catalysts ⇑ Lincai Peng, Lu Lin , Hui Li, Qiulin Yang State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou 510640, Guangdong, China article info abstract Article history: The catalytic performances of common solid acids (ZSM-5(25), ZSM-5(36), NaY, H-mordenite, Zr3(PO4)4, Received 20 February 2011 2À 2À SO4 /ZrO2,SO4 /TiO2, and TiO2) for the conversion of carbohydrates such as glucose to methyl levulinate Received in revised form 22 May 2011 in near-critical methanol were investigated to develop an environmentally benign catalyst with high Accepted 26 May 2011 activity. Among these catalysts employed, sulfated metal oxides (especially SO2À/TiO ) were found to Available online 21 June 2011 4 2 be a type of potential catalysts for prospective utilization, which showed remarkably high selectivity and yield of methyl levulinate and had negligible undesired dimethyl ether formation from the dehydra- Keywords: tion of methanol. With SO2À/TiO as the catalyst, methyl levulinate in ca. 43, 33 and 59 mol% yields could Carbohydrates 4 2 be obtained from sucrose, glucose and fructose, respectively, at 473 K for 2 h reaction time with a catalyst Catalysis 2À Methyl levulinate loading of 2.5 wt.%. The heterogeneous catalyst (SO4 /TiO2) was easily recovered by filtration and exhib- Heterogeneous catalyst ited good catalytic activities after calcination in five cycles of reusing. The surface structure and acidity 2À 2À SO4 /TiO2 variations of the fresh and recycled SO4 /TiO2 catalysts after calcination were characterized by XRD and NH3-TPD techniques. The results indicate that the catalyst crystallization structure was preserved after multiple cycles, the acid amount and acid strength of the catalyst reduced gradually as the increas- ing of recycling times. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Industrially, levulinate esters were mainly obtained through esterification of levulinic acid with alkyl alcohols in the presence Due to gradual diminishment of fossil fuel reserves and progres- of sulfuric acid that leads to a high yield of products [9]. Immobi- sive depravation of environmental quality, the development of lized lipases as the biocatalyst for this process can also be equally renewable biomass energy invites more and more concerns [1]. effective under milder reaction conditions [5,10]. However, levu- In recent decades, extensive research is being carried out world- linic acid as raw material for this purpose is of high cost with its wide to convert cellulosic biomass into liquid fuels and high- present production from the acid hydrolysis of cellulose and sug- quality chemicals and to develop economically feasible processes ars. Recently, Mascal and Nikitin [11] had developed a new and on an industrial scale [2–4], among which the preparation of levu- efficient procedure for the conversion of cellulosic biomass into linate esters have been one of the focuses under study. Levulinate levulinate esters in overall yields exceeding 80% through two reac- esters, like methyl levulinate, ethyl levulinate, and butyl levulinate, tion steps: biomass reacted with hydrochloric acid into 5-(chloro- are a kind of short chain fatty esters with their properties similar to methyl)furfural followed by the alcoholysis of resulting product the biodiesel fatty acid methyl esters (FAME) [5,6]. These esters are with alcohols. However, the intermediates obtained from biomass suitable to be used as additives for gasoline and diesel of transpor- must be isolated before the subsequent process for all above tation fuels, which have manifold excellent performances, such as routes, the isolation procedure which requires the use of some non-toxic, high lubricity, flashpoint stability and better flow prop- energy consuming technique (distillation) or of environmentally erties under cold condition [7]. On the other hand, levulinate esters non-friendly solvents. Direct production of levulinate esters from also can either be used in the flavoring and fragrance industries or biomass or biomass-based sugars is also possible by the acid-cata- as substrates for various kinds of condensation and addition reac- lyzed reaction with alcohols, which is economically more attrac- tions at the ester and keto groups in organic chemistry [8]. tive, has yet to be developed. The generally accepted reaction pathway for the direct conversion of cellulose to levulinate esters is schematically given in Fig. 1 [8,12]. Compared with the numerous reactions studied in aqueous ⇑ Corresponding author. Tel./fax: +86 20 22236719. solvent for the making of chemicals [13], the reaction system in E-mail address: [email protected] (L. Lin). alcohols media has some advantages, for example, minimized 0306-2619/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.apenergy.2011.05.049 L. Peng et al. / Applied Energy 88 (2011) 4590–4596 4591 OH OH OH OH +ROH O OH O O HO HO O HO OH H2O HO HO O HO O HO OR OH O OH O H+ OH OH OH n Cellulose Alkyl glucoside + H 3H2O O O +ROH +H O OHC O 2 OR H3C R + HCOOR O H+ Levulinate ester Formate ester 5-alkoxymethylfurfural Fig. 1. Reaction pathway for the acid-catalyzed conversion of cellulose to levulinate esters. wastewater discharged and higher-grade products easily isolated 2. Experimental by fractionation. Process development for conversion of biomass into biofuels and high-value chemicals in sub- and supercritical 2.1. Catalysts preparation alcohols has been largely studied in recent years [14,15]. There 2À 2À have also been several reports about the production of levulinate SO4 /ZrO2 and SO4 /TiO2 were prepared by precipitation and esters in near-critical alcohols from carbohydrates biomass, such impregnation method, and the detailed procedure was presented as sucrose, glucose, fructose and biomass feedstocks including elsewhere [32]. Other solid acid catalysts were obtained commer- wood, bagasse, wheat meal and agricultural wastes [8,12,16,17]. cially. As for zeolites, ZSM-5, H-mordenite and NaY were from the For example, Le Van Mao et al. [18] most recently developed a Catalyst Plant of Nankai University. TiO2 was obtained from one-pot system for the direct catalytic conversion of cellulosic Aladdin Reagent. Zr3(PO4)4 was purchased from Xiamen Xindakang biomass into alkyl levulinates and other esters, and the product Inorganic Materials Co. Ltd. All catalysts were calcined at 773 K for extraction. In these studies, a homogeneous acid (H2SO4) was most 3 h in static air prior to use. commonly employed as the catalyst, since it is relatively cheap and also very active. However it suffers from several obvious draw- 2.2. Catalytic reaction procedure backs, such as equipment corrosion, side reaction for the inter- molecular dehydration of the massive alcohols to ether and the The experiments were carried out in a cylindrical stainless steel requirement of special processing for the neutralization of spent pressurized reactor with inner diameter 33 mm, depth 117 mm H SO [19,20]. Owing to the existence of these problems, it is ex- 2 4 and 100 mL total volume made by PARR instrument company, tremely important and necessary to develop an environmentally USA. The reactor was heated in an adjustable electric stove. The benign catalyst with high activity for the direct production of lev- temperature of the reactor contents was monitored by a thermo- ulinate esters. couple connected to the reactor. For each experiment, carbohy- In recent years, solid acid catalysts have attracted considerable drate (2.5 g), methanol (50 mL), and a given amount of solid acid interests as heterogeneous catalysts, which can overcome the above catalyst were mixed to form a suspension and were poured into mentioned some disadvantages of the inorganic acid in acid cataly- the reactor. The reactor was then brought to the desired tempera- sis and have been broadly applied to catalyze dehydration, alkyl- ture by external heating and shaken at 500 rpm. After certain reac- ation, cracking, isomerization, esterification, acylation, and so on tion time, the reactor was taken from the stove and quenched in an [21–26]. The conversion of cellulose in supercritical methanol ice cool water bath to terminate the reaction. The liquid substance (573 K/10 MPa) in the presence of solid acid catalysts has been re- and solid acid catalyst were separated by filtration, and then ana- ported, giving a 20% yield of methyl levulinate over Cs H PW O x 3Àx 12 40 lyzed. To test the catalyst stability, SO2À/TiO catalyst was recov- and sulfated zirconia [27]. However, minimal attention has been gi- 4 2 ered and reused without any treatment in a new reaction cycle ven to the use of solid acid catalysts to replace conventional H SO 2 4 under the same reaction conditions described above. In another for the direct synthesis of levulinate esters in near-critical methanol. run, prior to each reuse, the recovered catalyst was calcined at Presently, commercially available heterogeneous acid catalysts 773 K for 3 h in static air.