A synthesis of solid acid catalysts for using in hydrolysis of cellulose from rice straw into glucose - T–Que Phuong Phan

Journal of Science and Technology 55 (1B) (2017) 145–151 A SYNTHESIS OF SOLID ACID CATALYSTS FOR USING IN HYDROLYSIS OF CELLULOSE FROM RICE STRAW INTO GLUCOSE T–Que Phuong Phan1, *, Sy–Nguyen Pham1, H–Khoi Nguyen Nguyen2, T–Ngoc Phuong Lieu2, Huu–Thien Pham1, Van–Qui Nguyen1, Dinh–Thanh Nguyen1 1Institute of Applied Material Science, Viet Nam Academy of Science and Technology 1 Mac Dinh Chi street, Ben Nghe Ward , District 1, Ho Chi Minh City, Vietnam 2Department of Inorganic Chemical Engineering, Faculty of Chemical Engineering, HCMUT–VNUHCM, 268 Ly Thuong Kiet Street, District 10, Ho Chi Minh City, Vietnam *Email: ptqp2106@gmail.com Received: 30 December 2016; Accepted for publication: 3 March 2017 ABSTRACT In this study, a carbon–based solid acid catalyst was prepared via hydrothermal carbonization method (HTC) using glucose and pyrolysed waste tyre as carbon precursors and aqueous solution of H2SO4 as sulfonation agent. Prepared catalysts were characterized by X–ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared FT–IR and Brunauer–Emmett–Teller (BET). As the result, catalysts were manufactured with the appropriate physical and chemical characteristics and high acidity. Keywords: glucose, cellulose, catalysis, hydrothermal carbonization (HTC). 1. INTRODUCTION Biomass is one of the most promising renewable and sustainable alternative for energy and chemical production. As an energy source, biomass can be utilized without depleting the existing reserves. Current research interest is, therefore, to convert biomass to fuels and chemicals [1]. In recent years, many researchers have found alternative source material for the production of biofuel to replace fossil fuels urgently. The use of materials derived from biomass to produce biofuels and chemicals for plastics as well as pharmaceuticals not only enhances the value of the agricultural production but also contributes to solving environmental pollution issues and ensuring ecological balance. From the time being, efficient use of biomass is only 10% compared with that generated biomass energy. Meanwhile, resource-products are regarded as one of the potential sources of raw materials for energy production [2, 3]. For the effective consumption of cellulose, the primary and essential step is the hydrolysis of cellulose into glucose [1, 4]. Many studies have been concentrated on homogeneous acids and celluloses in a long period of time. With homogeneous acids, although they exhibit reasonable prices and good catalytic activities but practical applications are difficult due to a lot of problems A synthesis of solid acid catalysts using for hydrolysis of cellulose from rice straw into glucose 146 including reactor corrosion, waste treatment and poor recyclability [5–7]. In contrast to homogeneous acids, celluloses that can be derived from aspergillus niger, trichoderma reesei are more selective and competitive to hydrolyze cellulose into glucose at lower reaction temperature [8]. However, enzymatic hydrolyses of cellulose is a slow process, which will spend a long time to achieve a satisfactory yield of glucose [9]. In addition, prior to enzymatic hydrolysis of cellulose into glucose, an energy and cost–intensive pretreatment is necessary to remove the recalcitrance to celluloses. At this moment, celluloses are still very expensive [10]. From the viewpoint of green chemistry and industrialization, solid acid catalysts such as metal oxides, H–form zeolites, heteropoly acids, functionalized carbonaceous acids and magnetic functionalized carbon acids, which are separable, recoverable and reusable, should be the excellent choices for the hydrolysis of cellulose into glucose, because they have tremendous potentials to overcome the above–mentioned limitation [11]. In other words, solid acids catalysts case opens up opportunity to explore more efficient, economical, simple and greener processes for the hydrolysis of cellulose into glucose. In this study, the solid acid catalysts (CS, CS1, CS2 and CP) were synthesized by hydrothermal carbonization (HTC) and characterized using analytical techniques such as XRD, SEM, EDS, FT–IR. Finally, their catalysts were high acidity and used for hydrolysis of cellulose from rice straw into glucose. 2. MATERIALS AND METHODS 2.1. Materials Glucose (> 99.5 % – Xilong, China), Ethanol (96 % – Xilong, China), H2SO4 (98 % – Xilong, China) and carbon from pyrolysed waste tyre. All the chemicals were used without further purification. 2.2. Synthesis of carbonaceous material from glucose (CS) The glucose–derived carbonaceous material without in–situ functionalization was prepared by hydrothermal carbonization of glucose in the absence of any additive. Typically, 20 g of glucose was dissolved in 60 mL of water, and the mixture was then loaded into a 100 mL stainless steel autoclave. After that, it was heated up to 180 °C and kept for 10 h at the autogenous pressure. The resulting solid product was isolated by centrifugation, washed repeatedly with ethanol and water for several times, and oven–dried at 80 °C for 12 h. The obtained carbonaceous solid material is denoted as glucose–derived carbonaceous material 2.3. The synthesis of functional groups attached carbon catalyst To realize in–situ functionalization of the carbonaceous material bearing with –SO3H groups on surface, H2SO4 solution was used in the sulfonation processes. The as–synthesized 10 g CS was dispersed in a sulfuric acid solution under stirring. The suspension was placed in a 100 mL stainless steel auto clave and maintained at 180 °C for 4 h. The black products were filtered, washed and then dried following the same procedures in CS preparation. Sulfuric acid solutions with different concentrations were employed in the sulfonation processes. The sulfonated CS solid acid catalysts were labeled as CS1, CS2 according to the sulfuric acid and water volumetric ratios of 1:1 and 2:1, respectively. The sulfonation of CP (carbon from pyrolysed waste tyre) was prepared following the same procedures in CS2 sulfonation. 2.4 SIE 0.1 Ele (B aft 10 As (G con Ac Ch 2.5 det aci aci In ba sam att . Physical c In this w MENS–D5 5418 nm) a ctron Micro ET) specific er degassing 00e. Sulfur h Corp, US ermany). Th taining the Methods ademy of S i Minh City . The proce Acid dens ermining th dic sites: on d sites, incl general, the sed solid aci Figure 1 ples, broad ributed to su haracteriza ork, X–ray d 000 diffract t the scannin scope (SEM surface are the sample content of t A), and ele e FTIR spe prepared bio of analyses cience and T , Vietnam. ss of determ ity of solid e catalytic a e is the stron uding –COO –SO3H gro d prepared in Figure 1. X illustrates th diffraction ccessful hy tion iffraction (X ometer usin g rate of 0.0 ) was condu a was obtain at 300 °C he catalyst w mental ana ctrum for th mass carbon were conduc echnology, ining the ac acid catalyst ctivity. In ter g acid sites H and –OH ups are the this study w 3. RESU RD patterns e XRD pat peaks at lo drothernal c RD) patter g monochr 3°/s and in cted using J ed by nitro for 2 h unde as measure lysis was c e carbon m powder. ted at Instit 1 Mac Dinh id sites den s as well as ms of sulfo (the introdu from incom active sites as calculate LTS AND of catalysts (a terns of the w diffractio arbonization ns of C–SO omatic high the scanning SM–6500F, gen adsorpti r nitrogen g d with EDX arried out u aterials was ute of Appl Chi Street sities of cat carbon back nated carbon ced –SO3H g plete carbo . Therefore d by cation DISCUSSIO ) CS; (b) CS1 as–prepare n angles (2 from gluco T–Que 3H catalysts intensity C range from JEOL. Brun on–desorptio as, using Q (Model–90 sing Eleme obtained by ied Material , Ben Nghe alyst ground are e materials, t roups); and nization of t , the –SO3H exchange an N ; (c) CP; (d) C d CS, CS1, θ) of 10–30 se precusor Phuong Ph were recor uKα radiat 20 to 70°. auer–Emme n isotherms uantachrom 00, Thermo ntar Vario using a K s Science, V Ward, Distr ssential elem here are two the other is he carbon p amount of alysis [12]. S2. CP and CS ° are observ and carbon an, et al. 147 ded with ion (λ = Scanning tt–Teller at 77 K e NOVA Jarrell– EL cube Br pellet iet Nam ict 1, Ho ents for types of the weak recursor. carbon– 2. In all ed [12], derived A s 14 fro bet sum gro gro Th ban ynthesis of 8 m tyre pyro ter carbon s Figure 2 marized as ups. The b ups, while e bands at 1 ds at 1118 solid acid ca lysis. Comp tructure of th Fig Figure is the FTIR follows. Th ands at abo the C=C for 750 and 170 and 1038 cm talysts using ared to CS1 ose is. ure 2. FTIR 3. SEM imag image of e bands at a ut 3000 and condense a 0 cm–1 are co –1 [13] are for hydrolys , the higher (a) CS, (b) CS e of (a) CS, (b CS, CS1, round 3500 2800 cm–1 romatic app rresponding ascribed to t is of cellulo the intensit 1, (c) CP and ) CS1, (c) CS CP and CS and 3400 c are assigned ears at app to C=O gro he S=O, imp se from rice y of peak of (d) CS2. 2 and (d) CP 2. The repr m–1are attrib to –OH of roximately 1 ups (acid ca licating the straw into gl CS2 and C . esentative b uted to phen carboxylic 650 and 16 rboxylic); ad appearance ucose P is, the ands are olic OH –COOH 00 cm–1; sorption of SO3H in C– CO CS are the att pre sul sul ass all samples O groups ar OH group [ SEM mic 2, and CP a based on ca size of part ributable to p Figure 4 sent at as–p fur in SO3H fonated mat igned to mit (Figure 2). P e located at 14]. rographs of t 180 °C wa rbon source icle trend to retty high p and Table 1 repared carb groups were erial are con igating acid Ta Eleme C O S Anoth Tota Fig eaks at 161 1707 and 1 solid produ s separately s and the in decrease fro yrolysis tem show EDX on material observed in tained in SO sites of cata ble 1. The ED nt CS 96.6 3.3 er 0 l 10 ure 4. The E 8 and 1382 203 cm–1, re cts are show spherical. T crease in aci m 0.67 μm perature and results of C s and corres all sulfonat 3H groups. T lyst, which l X results of CS 1 93 9 5. 1.0 0 0 10 DX results of cm–1 are ind spectively, n in Figure he morpho d concentrat to 68.6 nm w long pyroly S, CS1, CS ponding sul ed samples, he decrease ed to low ca CS, CS1, CS2 1 CS2 .8 86.0 2 8.27 0 5.68 0 0 100 CS, CS1, CS T–Que icative of C demonstratin 3, the morp logy and siz ion from 49 hen the aci sis time (18 2 and CP. C fonated cata suggesting t in S conten talytic activi and CP. CP 5 84.23 6.86 4.69 4.22 100 2 and CP. Phuong Ph =C group. g the existe hology of C e of carbon % to 65%. H d concentrat 0 °C, 4 h). and O elem lysts. S peak hat all S ato t of CS1 cat ty. an, et al. 149 C=O and nce of – S, CS1, particles owever, ion rises, ents are s due to ms in the alyst was A synthesis of solid acid catalysts using for hydrolysis of cellulose from rice straw into glucose 150 Table 2. Specific surface area and acid density. Samples SBET (m2/g) Acid density (mmol/g) CS 38.55 0.24 CS1 43.95 0.42 CS2 55.37 1.08 CP 45.16 0.58 The acid site densities of catalysts were determined by EDX analytic method (Table 2) and acid–base back–titration. The acid titration experiments demonstrated that much higher acid site densities than the estimations based on sulfur elemental analysis. The higher estimated acid densities from titration are due to phenolic –OH and –COOH groups originating from incomplete carbonization of glucose. The strong sulfonation also may oxidize aliphatic CH3/CH2 groups to carboxylic acid groups, which may further explain the significant increase in total acid densit after sulfonation. The strength and density of acid sites of carbon–based solid acid is a vital factor closely related to the catalytic activity. The sulfonated CS have both strong and weak acid sites on the surfaces. As shown in Table 2, the total acid density on the surface increase from CS, CS1 and CS2 with increasing the concentration of the sulfuric acid solutions. The preparation of catalysts includes two stages. Firstly, glucose is thermally treated by hydrothermal carbonization at 180 °C for 10 h to obtain a solid carbon material. Then, the obtained carbon material is sulfonated with different concentrations of sulfuric acid to introduce –SO3H groups at 180 °C for 4 h. Specific surface area of CS2, CS1 and CP are 55.372 m2/g, 43.949 m2/g and 45.162 m2/g, respectively. High acid density of CS1; CS2, CP are 0.417 mmol/g, 1.083 mmol/g, 0.58 mmol/g in turn. This indicated that catalytic activity mainly depends on total acid density regardless of its specific surface area. The carbon catalyst exhibits high catalytic performance in the presence of hydrophilic molecules despite its relatively low specific area, attributable to the incorporation of high densities of hydrophilic molecules into the carbon bulk binding with the flexible carbon sheets [15]. 4. CONCLUSIONS Rice straw treated with the two–stage process composed of separating hemicellulose with acid sulfuric and lignin by the aid of sulfomethylation agent for 7 h may be used as raw material for hydrolysis reaction of cellulose into glucose in support of the catalyst. Successful synthesized carbon catalyst containing –SO3H functional groups via hydrothermal carbon chemistry (HTC) method from glucose precursors and pyrolysed tire. 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