S P L a b a A R R A A K C H S 1 l e V c f ( l ( c S o d w d n o C P t t c i 0 h Carbohydrate Polymers 89 (2012) 992– 996 Contents lists available at SciVerse ScienceDirect Carbohydrate Polymers j ourna l ho me pag e: www.elsev ier .com/ locate /carbpol hort communication reparation and characterization of cellulose/hydrous niobium oxide hybrid eandro José Maschioa,∗, Paulo Henrique Fernandes Pereirab, Maria Lucia Caetano Pinto da Silvaa Chemistry Department – DEQUI/EEL/USP. Rod. Itajubá-Lorena, Km 74,5 – Lorena – Cep: 12600 000 – SP – Brazil Fatigue and Aeronautical Materials Research Group – DMT/FEG/UNESP. Av. Ariberto Pereira da Cunha, 333 – Guaratinguetá – Cep: 12516 410 – SP – Brazil r t i c l e i n f o rticle history: eceived 28 September 2011 eceived in revised form 13 February 2012 a b s t r a c t A composite of cellulose extracted from bagasse with Nb2O5·nH2O in three different proportions (16.67, 37.5 and 50.0 wt%) was prepared using the co-precipitation method. The materials were characterized by X-ray diffractometry (XRD), Fourier transform infra-red spectroscopy (FTIR), thermogravimetric anal- ccepted 4 April 2012 vailable online 22 April 2012 eywords: ellulose ydrous niobium oxide ysis (TG/DTG), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). TG data obtained show that the presence of inorganic material influenced slightly the stability of the hybrid mate- rial. The precipitation of 16.67 wt.% of oxide was sufficient to inhibit the combustion peaks present in the DSC curve of cellulose. This work will help find new applications for these materials. Published by Elsevier Ltd. ugarcane bagasse . Introduction Sugarcane bagasse is a fibrous material mainly composed of cel- ulose, hemicelluloses, and lignin (Miretzky & Cirelli, 2010; Viera t al., 2007; Wang, Li, Xiao, & Wu, 2009). According to Mulinari, oorwald, Cioffi, Silva, and Luz (2009), this agro-industrial residue ontains cellulose (46.0%), hemicellulose (24.5%), lignin (19.95%), at and waxes (3.5%), ash (2.4%), silica (2.0%) and other elements 1.7%). World production of sugarcane bagasse is between 320 mil- ion to 380 million tons per year according to Abbasi and Abbasi 2010). The use of waste as raw material for various chemical pro- esses already occurs, but a large amount is still not reused (Pantoja, ader, Damianovic, Foresti, & Silva, 2010). Due to the large amount f bagasse produced, there has been a growing trend towards the evelopment and optimization of processes using this industrial aste as raw material. More recently, particular attention has been directed to the evelopment of nanocomposites based on cellulose and inorganic anoparticles, such as SiO2, TiO2, CaCO3, NbOPO4·nH2O, among thers (Maliyekkal, Lisha, & Pradeep, 2010; Pereira, Voorwald, ioffi, & Silva, 2010a; Pinto, Marques, Barros-Timmons, Trindade, & ascoal Neto, 2008; Vilela et al., 2010; Xie, Yu, & Shi, 2009), because hese materials normally have improved mechanical, optical and hermal properties due to the combination of inorganic and organic omponents. Organic–inorganic hybrid materials are of more than academic nterest, since their inherent properties frequently lead to the ∗ Corresponding author. E-mail address: ljmaschio@gmail.com (L.J. Maschio). 144-8617/$ – see front matter. Published by Elsevier Ltd. ttp://dx.doi.org/10.1016/j.carbpol.2012.04.043 development of innovative industrial applications. Such fields as optics, electronics, ionics, mechanics, energy, environment, biol- ogy, medicine, smart coatings, fuel and solar cells, catalysts, sensors, fire retardant, production of composites or membranes are some examples of promising applications areas where these types of materials have been successfully applied (Pereira, Voorwald, Cioffi, & Silva, 2011). The world’s 5th largest country in terms of its area, and rich in natural resources, Brazil’s economy is based on the exploration of both renewable and non-renewable resources. It is the world’s leading producer of niobium (Tanimoto, Durany, Villalba, & Pires, 2010; Vilela et al., 2010). Its niobium reserves totaled 842.46 million tons and are concentrated in the states of Minas Gerais (75.08%), Amazonas (21.34%) and Goiás (3.58%) (DNPM, 2009). Thus, hydrous niobium oxide has shown to be an attractive alternative to the inorganic portion in the preparation of organic–inorganic hybrids. In this work, the objective of this paper is to prepare and charac- terize cellulose/Nb2O5·nH2O hybrids by X-ray diffratometry (XRD), Fourier transform infra-red spectroscopy (FTIR), thermogravimet- ric analysis (TG/DTG), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The proposed application of the materials prepared in this study is their use as additives in polymer matrices and inorganic membranes. 2. Experimental 2.1. Preparation of the bleached cellulose The bagasse was pretreated with a 10% sulfuric acid solution in 350 L stainless reactor for 10 min, with solid/liquid of 1:20 (w/v). Therefore, we obtained cellulose and lignin free of hemicellulose. dx.doi.org/10.1016/j.carbpol.2012.04.043 http://www.sciencedirect.com/science/journal/01448617 http://www.elsevier.com/locate/carbpol mailto:ljmaschio@gmail.com dx.doi.org/10.1016/j.carbpol.2012.04.043 rate Polymers 89 (2012) 992– 996 993 T w a w c r R 2 e p l h 1 o t s f w i 2 C ( g ( t c e c t w r m a S 5 a c t w 3 t d f t f a t a p I r 70605040302010 e d c b in te ns ity ( cp s) 2 (degree)θ a I max I min first is attributed to desorption of water from the polysaccharide structure (Bertoti, Luporini, & Esperidião, 2009). The second step (182–404 ◦C) can be assigned to the decomposition of the cellu- lose and lignin portion. The third step (404–736 ◦C) corresponds Table 1 Crystallinity index for the cellulose and Cell/Nb2O5·nH2O hybrids. Material Degree crystallinity (%) L.J. Maschio et al. / Carbohyd he cellulignin was submitted in alkaline in a 350 L stainless reactor ith 150 L of destilled water, 10 kg pretreatead sugarcane bagasse nd 30 L of aqueous solution containning 3 kg NaOH. The reaction as performed at 100 ◦C for 1 h under stirring at 100 rpm. The final oncentration of the mixture was 1.5 wt% NaOH and solid/liquid atio of 1:20 (w/v), obtained a crude pulp (Pereira et al., 2010a; ocha, 2000). .2. Preparation of the cellulose/hydrous niobium oxide hybrids Cellulose/Nb2O5·nH2O hybrids were prepared in three differ- nt proportions 16.67, 37.5 and 50.0 wt.%. These materials were repared by a co-precipitation method. The dissolution of metal- ic niobium was held in a polyethylene becker with nitric and ydrofluoric acid, both concentrated, with a molar relation of HF:3HNO3. Then, to this solution was added cellulose with 140 mL f deionized water. Then excess of ammonium hydroxide solu- ion (1:3 molar) was added dropwise to the solution with constant tirring at room temperature until a crystalline precipitation was ormed into cellulose. After the precipitation, the materials were ashed several times until pH ∼7 with deionized water and dried n oven at 50 ◦C until a constant weight was achieved. .3. Characterization of the materials The hydrous niobium oxide, the cellulose and the hybrids ellulose/Nb2O5·nH2O were characterized by X-ray diffratometry XRD), Fourier transform infra-red spectroscopy (FTIR), thermo- ravimetric analysis (TG/DTG), differential scanning calorimetry DSC) and scanning electron microscopy (SEM). X-ray diffractograms were obtained with a Rich Seifert diffrac- ometer model XRD6000 with radiation CuK�, tension of 30 kV, urrent of 40 mA, and 0.05 (2�/5 s) scanning from values of 2� it nters 10–70◦ (2�). FTIR spectra of hydrous niobium oxide, cellulose and ellulose/Nb2O5·nH2O hybrids were obtained in a FTIR spec- rophotometer Perkin Elmer. The powered samples were mixed ith KBr to produce tablets. The scan was performed in the spectral ange of 4000–400 cm−1. Thermogravimetric analyses (TG/DTG) were carried with a Shi- adzu TGA-50 thermal analyzer from room temperature to 900 ◦C t a heating of 20 ◦C min−1 in N2 atmosphere. DSC analysis was performed using a calorimetric instrument eiko Instruments model Exstar 6000, by the heat of the sample mg in temperatures between 25 and 550 ◦C, rates under oxygen tmosphere at a range 10 ◦C min−1. Surface materials were examined by Scanning Electron Micro- opy (SEM) a JEOL JSM5310 model. Samples to be observed under he SEM were mounted on conductive adhesive tape, sputter coated ith gold and observed in the SEM using a voltage of 15 kV. . Results and discussion X-Ray diffraction (XRD) patterns were used to investigate he crystallinity of the materials. In Fig. 1 presented the X-ray iffractograms of cellulose, Nb2O5·nH2O and hybrids materials. Dif- erences between cellulose and hybrid material can be observed in he X-ray diffractograms shown in Fig. 1. It is possible to observe a change in the intensity of the peaks ound between diffraction at the following 2� angles: 16.3◦, 22.8◦ nd 28◦. The strongest cellulose peak, at 2� = 22.8◦, originates from he cellulose crystalline plane 0 0 2 (Zhao et al., 2007) and the peak t 2� = 16.3◦ corresponds to the cellulose (1 0 1) crystallographic lanes. The diffractograms, probably representing typical cellulose diffractograms, show a peak at 22 < 2� < 23◦ and a shoulder in the egion 2� = 14–17◦ (Elanthikkal, Gopalakrishnapanicker, Varghese, Fig. 1. X-ray diffractogram of Nb2O5·nH2O (a), cellulose (b), hybrid 16.67 wt.% (c), hybrid 37.5 wt.% (d), hybrid 50 wt.% (e). & Guthrie, 2010), and common crystal formation was observed in native cellulose (Zhang et al., 2010). Fig. 1 shows the changes as the amount of deposited oxides increases. Through DRX curves was calculated the crystallinity index (Icr) of the materials. Icr was calculated as the ratio of the intensity dif- ferences in the peak positions at 18◦ and 22◦ according to Eq. (1) (Ass, Belgacem, & Frollini, 2006; Guimarães, Frollini, Silva, Wypych, & Satyanarayana, 2009; Pereira et al., 2010a). Icr = 1 − Imin Imax (1) where Imin is the intensity at minimum of the crystalline peak (18◦ < 2� < 19◦) and Imax is the intensity at its maximum (22◦ < 2� < 23◦). According to this method, the degree of crystallinity was calculated (Table 1). With the increased Nb2O5·nH2O into cellulose surface loading occurred a decreased in the intensity of peaks corresponding to cellulose, when compared with the peak related to metallic oxide, resulting in a diminution of the relationship between amorphous and crystalline phase of the fiber, which caused a decrease in the crystallinity index materials. The Fig. 2 shows the consequences arising from the heating and subsequent thermal degradation of the materials studied. TG curve in Fig. 2a of the hydrous niobium oxide shows a weight loss occurring in two distinct stages within the tempera- ture range of 25–800 ◦C. In the first one, between the temperature of 40 ◦C and 170 ◦C, was caused by desorption of physically adsorbed water (Rodrigues & Silva, 2009). The weight loss on the second step was caused by the hydroxyl groups’ condensation. TG curve in Fig. 2b for the cellulose shows three weight loss steps. The Cellulose 71.30 Cell/Nb2O5·nH2O 16.67 wt.% 70.89 Cell/Nb2O5·nH2O 37.50 wt.% 58.92 Cell/Nb2O5·nH2O 50.00 wt.% 53.11 994 L.J. Maschio et al. / Carbohydrate Polymers 89 (2012) 992– 996 10008006004002000 0 20 40 60 80 100 W ei gh t l os s % Temperature (°C) a b c d e F 3 t Y c t m p F i t d c p 4 t d o t t e T R m i 5004003002001000 -10 0 10 20 30 40 H ea t F lo w ( m W ) Temperature (°C) Cellulose Hybrid 16.67 wt.% Hybrid 37.50 wt.% Hybrid 50.00 wt.% 1385, 1643, and 650 cm−1. The position 3400 cm−1 corresponds to O–H stretching vibration. This increase absorption in 3400 cm−1 showed an increase hydrophilic character of the fiber with the ig. 2. TG curves of Nb2O5·nH2O (a), cellulose (b), hybrid 16.67 wt.% (c), hybrid 7.5 wt.% (d) and hybrid 50 wt.% (e). o the residual lignin decomposition reactions degradation (Yang, an, Chen, Lee, & Zheng, 2007). From Table 2, it may be observed a progressive increase in per- entage of the residue with an increase of Nb2O5·nH2O in respect o the pureness cellulose that indicated the presence of inorganic aterial. This higher amount of remaining residue confirmed the resence of hydrous niobium oxide on the cellulose surface. In ig. 2, it is shown that the presence of inorganic material slightly nfluenced the stability of hybrid material. TG curves shows that he hybrid 50.00 wt.% is the best of them because present the minor m in the second step. This case is attributed the more interaction ellulose–hydrous niobium oxide. DSC analysis in oxygen showed that active combustion took lace at 275 ◦C and ended at 475 ◦C with two major peaks at 331 and 46 ◦C. During the thermal degradation of cellulose, depolymeriza- ion occurs and formation of 1.6 anhydro-glucose takes place and its ecomposition involves the formation of volatiles. The formation f volatile products during the degradation cellulose is indicated by he exothermic peak at 35 ◦C and 275 ◦C in DSC curve of cellulose. The first exothermic event refers to the steps that can be related o flaming combustion of the volatiles. In this peak the value of nthalpy is higher for the cellulose. Enthalpy values for the hybrids able 2 esults of TG curves with the corresponding temperatures to the maximum rate of ass loss in (dm) in the respective intervals of temperature (�T) with losses of mass n TG (�m) and residue (R). Material �m (%) �T (◦C) dm (◦C) R (%) 10.87 36–254 107 79.66 Nb2O5·nH2O 9.47 254–850 367 Crude pulp 8.42 35–182 64 3.62 72.18 182–404 358 15.78 404–736 438 Hybrid 16.67 wt.% 4.45 39–144 65 16.95 65.21 144–407 341 13.39 407–681 485 Hybrid 37.50 wt.% 7.58 33–176 62 37.42 5.14 176–283 271 42.15 283–418 340 7.71 418–665 494 Hybrid 50.00 wt.% 6.23 35–170 65 45.86 8.65 170–294 267 32.16 294–427 342 7.10 427–665 497 Fig. 3. DSC curves of Nb2O5·nH2O, cellulose, hybrid 16.67 wt.%, hybrid 37.5 wt.% and hybrid 50 wt.%. show that the deposition of Nb2O5·nH2O significantly reduced the enthalpy in relation to cellulose. The second exothermic peak was attributed to char oxidation. In hybrids cell/Nb2O5·nH2O (Lee, Chen, & Rowell, 2004), this second event is not present, which may be explained by the presence of hydrous niobium oxide on the fiber surface, which inhibited the same and acted as a flame retardant. In Fig. 3, it may be noted that the increase Nb2O5·nH2O loading does not cause significant changes in the DSC curves. Therefore, the precipitation of 16.67 wt.% of oxide was sufficient to inhibit the combustion peaks present in the DSC curve of cellulose. The FTIR spectra for the samples are shown in Fig. 4. Many dif- ferences between cellulose and hybrids materials can be observed in the FTIR spectra of the studied materials. It is possible to observe a major absorption of peaks of 3400, 5001000150020002500300035004000 Hybrid 50.00 wt.% Hybrid 37.5 wt.% Hybrid 16.67 wt.% Cellulose A bs or ba nc e Wavenumber (cm-1) Fig. 4. FTIR spectra of Nb2O5·nH2O (a), cellulose (b), hybrid 16.67% (c), hybrid 37.5 wt.% (d), hybrid 50 wt.% (e). L.J. Maschio et al. / Carbohydrate Polymers 89 (2012) 992– 996 995 Fig. 5. SEM cellulose fibers with 200× (a), 1000× (b). Fig. 6. SEM, hybrid 16.67 wt.% (a–c), hybrid 37.5 wt.% (d–f) and hybrid 50 wt.% (g–i). 9 rate P i a s e 1 ( p t T o r ( l b e a c a c n d r t 5 c m c n a d 4 d o o w s o D N o S o p R A A Interactions between cellulose and N-methylmorpholine-N-oxide. Carbohy- 96 L.J. Maschio et al. / Carbohyd ncreasing incorporation of Nb2O5·nH2O onto the fibers. The peak t 2900 cm−1 indicates the absorption region of the symmetrical tretching C–H of polysaccharides. Increasing oxide loading gen- rates a reduction in the absorption of this peak. The peak at 640 cm−1 is attributable to a vibration of OH groups from water Mulinari et al., 2009; Pereira et al., 2010b). The intensity of this eak is higher for the hybrid 50.00%, which can be explained by he fact that the amount of hydration water present is higher. he peak at 1385 cm−1 indicated the presence of surface hydroxyl n the metal oxide surface. The characteristic absorption in the ange of 900–500 cm−1 is attributable to vibration Nb–O vibration Rodrigues & Silva, 2010). According to Reddy and Yang (2005), in general all natural cel- ulose fibers are multi-cellular, where a bundle of individual cells ound by natural polymers such as lignin and pectin. The scanning lectron micrographs presented in Fig. 5 shows cellulose fibers that re packed together. The Fig. 5b shows photomicrographs of the ellulose fibers and the presence of “pits” longitudinally arranged long the entire cell wall, the inside and outside the parenchyma ells of fibers that are responsible for transportation water and utrients throughout various cells to the roots and leaves. For oxide eposition on the fibers, it is interesting to observe a large area and oughness on the surface. The micrographs in Fig. 6 shows of different magnification of he hybrids materials prepared (hybrid 16.67 wt.%, 37.50 wt.% and 0.00 wt.%). Observed hydrous niobium oxide was dispersed on the ellulose surface. Fig. 6h clearly shows that deposition of inorganic aterial. The deposition was on a no-homogenous surface of the ellulose fiber. From EDS analyses the presence of the elements iobium and oxygen was confirmed. EDS analysis indicate which ll the sulfur acid utilized in the treatment of the fiber was removed uring the washing with deionized water. . Conclusions With the increased Nb2O5·nH2O in cellulose surface loading, a ecrease in the crystallinity index materials occurred. The presence f the metallic oxide influences significantly the thermal stability f hybrid materials. According to the results of TG, the hybrid one hich contains 50.00% Nb2O5·nH2O presents advantages on others tudied proportions. The lower quantity of oxides was enough in rder to inhibit the combustion peaks of cellulose present in the SC graphics, but the results show that the deposition of 50.00% b2O5·nH2O provides to total inhibition of these peaks. Through the FTIR spectra, a specific absorption region could be bserved between 900–500 cm−1 atributed to the Nb–O vibration. EM images show a non-homogenous deposition of Nb2O5·nH2O n the surface of the cellulose matrix. SEM and EDS confirm the resence of Nb2O5·nH2O on the surfaces of the fibers. eferences bbasi, T., & Abbasi, S. A. (2010). Biomass energy and the environmental impacts associated with its production and utilization. Renewable and Sustainable Energy Reviews, 14, 919–937. ss, B. A. P., Belgacem, M. N., & Frollini, E. (2006). Mercerized linters cellulose: characterization and acetylation in N-N-dimethylacetamide/lithium chloride. Carbohydrate Polymers, 63, 19–29. olymers 89 (2012) 992– 996 Bertoti, A. R., Luporini, S., & Esperidião, M. C. A. (2009). Effects of acetylation in vapor phase and mercerization on the properties of sugarcane fibers. Carbohydrate Polymers, 77, 20–24. DNPM Economia Mineral do Brasil 2009, DNPM, Brasília (2009). Internet file, URL http://www.dnpm.gov.br. Elanthikkal, S., Gopalakrishnapanicker, U., Varghese, S., & Guthrie, J. T. (2010). Cellulose microfibres produced from banana plant wastes: isolation and char- acterization. Carbohydrate Polymers, 80, 852–859. Guimarães, J. L., Frollini, E., Silva, C. G., Wypych, F., & Satyanarayana, K. G. (2009). Characterization of banana, sugarcane bagasse and sponge gourd fibers of Brazil. Industrial Crops and Products, 30, 407–415. Lee, H. L., Chen, G. C., & Rowell, R. M. (2004). Thermal properties of wood reacted with a phosphorous pentoxide–amine system. Journal of Applied Polymer Science, 91, 2465–2481. Maliyekkal, S. M., Lisha, K. P., & Pradeep, T. (2010). A novel cellulose–manganese oxide hybrid material by in situ soft chemical synthesis and its application for the removal of Pb(II) from water. Journal of Hazardous Materials, 181, 986–995. Miretzky, P., & Cirelli, A. F. (2010). Cr(VI) and Cr(III) removal from aqueous solution by raw and modified lignocellulosic materials: a review. Journal of Hazardous Materials, 180, 1–19. Mulinari, R. M., Voorwald, H. C. J., Cioffi, M. O. H., Silva, M. C. P., & Luz, S. M. (2009). Preparation and properties of HDPE/sugarcane bagasse cellulose composites obtained for thermokinetic mixer. Carbohydrate Polymers, 75, 317–321. Pantoja, J. L. R., Sader, L. T., Damianovic, M. H. R. Z., Foresti, E., & Silva, E. L. (2010). Per- formance evaluation of packing materials in the removal of hydrogen sulphide in gas-phase biofilters: polyurethane foam, sugarcane bagasse, and coconut fibre. Chemical Engineering Journal, 158, 441–450. Pereira, P. H. F., Voorwald, H. C. J., Cioffi, M. O. H., & Silva, M. L. C. P. (2010). Prepa- ration and characterization of cellulose/hydrous niobium phosphate hybrid. BioResources, 5(2), 1010–1021. Pereira, P. H. F., Voorwald, H. C. J., Cioffi, M. O. H., Mulinari, D. R., Luz, S. M., & Silva, M. L. C. P. (2010). Sugarcane bagasse pulping and bleaching: thermal and chemical characterization. BioResources, 6(3), 2471–2482. Pereira, P. H. F., Voorwald, H. C. J., Cioffi, M. O. H., & Silva, M. L. C. P. (2011). Novel cellulose/NbOPO4·nH2O hybrid material from sugarcane bagasse. BioResources, 6(1), 867–878. Pinto, R. J. B., Marques, P. A. A. P., Barros-Timmons, A. M., Trindade, T., & Pascoal Neto, C. (2008). Novel SiO2/cellulose nanocomposites obtained by in situ syn- thesis and via polyelectrolytes assembly. Composites Science and Technology, 68, 1088–1093. Reddy, N., & Yang, Y. (2005). Biofibers from agricultural byproducts for industrial applications. TRENDS in Biotechnology, 23(1), 22–27. Rocha, G. J. M. (2000). Deslignificaç ão de bagaç o de cana de aç úcar assistida por oxigênio. Doctoral thesis. São Carlos, USP, p. 136. Rodrigues, L. A., & Silva, M. L. C. P. (2009). An investigation of phosphate adsorption from aqueous solution onto hydrous niobium oxide prepared by co-precipitation method. Colloids and Surfaces A: Physicochemical Engineering Aspects, 334, 191–196. Rodrigues, L. A., & Silva, M. L. C. P. (2010). Synthesis of Nb2O5·nH2O nanoparticles by water-in-oil microemulsion. Journal of Non-Crystalline Solids, 356, 125–128. Tanimoto, A. H., Durany, X. G., Villalba, G., & Pires, A. C. (2010). Material flow account- ing of the copper cycle in Brazil. Resources, Conservation and Recycling, 55, 20–28. Viera, R. G. P., Rodrigues Filho, G., Assunç ão, R. M. N., Meireles, C. S., Vieira, J. G., & Oliveira, G. S. (2007). Synthesis and characterization of methylcellulose from sugar cane bagasse cellulose. Carbohydrate Polymers, 67, 182–189. Vilela, C., Freire, C. S. R., Marques, P. A. A. P., Trindade, T., Pascoal Neto, C., & Fardim, P. (2010). Synthesis and characterization of new CaCO3/Cellulose nanocomposites prepared by controlled hydrolysis of dimethylcarbonate. Carbohydrate Polymers, 79, 1150–1156. Wang, Z. M., Li, L., Xiao, K. J., & Wu, J. W. (2009). Homogeneous sulfation of bagasse cellulose in an ionic liquid and anticoagulation activity. Bioresource Technology, 100, 1687–1690. Xie, K., Yu, Y., & Shi, Y. (2009). Synthesis and characterization of cellulose/silica hybrid materials with chemical crosslinking. Carbohydrate Polymers, 78, 799–805. Yang, H., Yan, R., Chen, H., Lee, D. H., & Zheng, C. (2007). Characteristics of hemicel- lulose, cellulose and lignin pyrolysis. Fuel, 86, 1781–1788. Zhao, H., Kwak, J. H., Wang, Y., Franz, J. A., White, J. M., & Holladay, J. E. (2007). drate Polymers, 67, 97–103. Zhang, J., Luo, J., Tong, D., Zhu, L., Dong, L., & Hu, C. (2010). The dependence of pyrolysis behavior on the crystal state of cellulose. Carbohydrate Polymers, 79, 164–169. http://www.dnpm.gov.br/ Preparation and characterization of cellulose/hydrous niobium oxide hybrid 1 Introduction 2 Experimental 2.1 Preparation of the bleached cellulose 2.2 Preparation of the cellulose/hydrous niobium oxide hybrids 2.3 Characterization of the materials 3 Results and discussion 4 Conclusions References