Sulfated Zirconia Catalyst for Hydrolysis of Palm Oil Lignocellulosic Wastes

Available online at www.sciencedirect.com

ScienceDirect Energy Procedia 65 (2015) 8 – 13

Conference and Exhibition Indonesia - New, Renewable Energy and Energy Conservation (The 3rd Indo-EBTKE ConEx 2014)

Sulfated Zirconia Catalyst for Hydrolysis of Palm Oil Lignocellulosic Wastes Anis Kristiania*, Kiky Corneliasari Sembiringa, Fauzan Auliaa, Haznan Abimanyua a

Research Centre for Chemistry – Indonesian Institute of Sciences, Kawasan PUSPIPTEK, Serpong, Tangerang Selatan, 15314, Indonesia

Abstract The waste plant materials remaining from palm oil extraction consist of cellulose, hemicellulose and lignin. They are potential sources of cellulose, which can be used as raw material for production of fermentable sugar. In this study, a single stage of heterogeneous acid catalyst hydrolysis were carried out in ionic liquid solution over sulfated zirconia catalysts prepared by modified sol gel method. Among the sulfated zirconia catalysts tested, sulfated zirconia prepared by SFE showed the highest hydrolysis catalytic activity up to 37.20 % in EFB treated and 53.95 % in frond treated. In addition, the process variable of reaction time hydrolysis was also investigated over both sulfated zirconia catalyst. The objective of this research is to do catalytic hydrolysis of lignocellulosic waste by using sulfated zirconia catalyst prepared by sol gel method.

© 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license © 2015 A. Kristiani, K.C. Sembiring, F. Aulia, H. Abimanyu. Published by Elsevier Ltd. (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the Scientific Committee of EBTKE ConEx 2014. Peer-review under responsibility of the Scientific Committee of EBTKE ConEx 2014 Keywords: Cellulose; empty fruit bunches; frond; hydrolysis; palm oil; sulfated zirconia catalysts.

Nomenclature BMIMCl CTAC DNS EFB

1-butyl-3-methylimidazolium chloride cetyltrimethylammonium chloride dinitrosalicylic acid empty fruit bunches

h min 1 psi TRS

hour minute 6,894.76 Pascals total reducing sugar

* Corresponding author. Tel.: +62 812 1950 0131; fax: +62 21 756 0549 E-mail address: [email protected]

1876-6102 © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the Scientific Committee of EBTKE ConEx 2014 doi:10.1016/j.egypro.2015.01.022

Anis Kristiani et al. / Energy Procedia 65 (2015) 8 – 13

SFE SZ SZ SFE SZ immersing

supercritical fluid extraction sulfated zirconia sulfated zirconia catalyst dried by SFE sulfated zirconia catalyst dried by immersing

1. Introduction Lignocelluloses biomass is one of the most abundant biomass and non-food bio-feedstock used in bioethanol production. Comparing with other biomass, lignocelluloses biomass is more efficient and environmentally friendly. Lignocelluloses biomass as an organic residue consists of mainly cellulose, lignin and hemicelluloses, whose basic units are sugars that can be fermented into ethanol or other chemicals. The carbohydrate polymers (cellulose and hemicelluloses) are tightly bound to the lignin. Up to 80 % of the lignocelluloses are polysaccharide [1]. Lignocelluloses plant structures also contain a variety of plant-specific chemicals in the matrix, called extractives (resins, phenolics, and other chemicals), and minerals (calcium, magnesium, potassium, and others). Palm oil production is on a steeply rising path. The EFB are waste by-products of palm oil industries that are being investigated for further uses. Currently, palm oil mills typically use the shell and the drier part of the fibre product stream, rather than EFB, to fuel their boilers, as the raw EFB contain nearly 60 % water [2]. As the most abundant source of biomass and because of its non-edible nature, cellulose is a promising alternative for the sustainable production of chemicals and fuels [3]. Hydrolysis of cellulose to glucose is a key technology for effective use of lignocellulose because glucose can be efficiently converted into various chemicals, biofuels, foods and medicines [4-7]. Cellulose hydrolysis can be achieved with enzymes [8], dilute acids [9] and sub- or supercritical water [7,10-12] however, these processes have significant drawbacks such as high cost of enzymes, difficulty in separation of catalysts, corrosion of reactors, waste effluents and severe reaction conditions. Some of these problems can potentially be overcome with the application of solid acid/base catalysts. Onda et al. [13] showed highly selective hydrolysis of cellulose into glucose under hydrothermal conditions at 423 K in the presence of sulfonated activated carbon (AC-SO3H) and demonstrated that this catalyst was superior to zeolite, mixed-oxide TiO2-ZrO2 [14] and ionic liquids [15]. Many studies have been contributed to the hydrolysis of cellulose catalyzed by mineral acids at relatively lower temperatures (523 K). Although high yields of glucose can be achieved using concentrated H 2SO4 (30 % to 70 %), the hydrolysis of cellulose with dilute acids (1 %), which is more feasible at a commercial scale, affords lower glucose yields [16]. Solid acids such as carbon materials bearing SO 3H groups and layered transition metal oxides (e.g., HNbMoO6) have also been examined for the hydrolysis of cellulose, but the yield of glucose is low [17]. Higher glucose yield (40 % to 60 %) could only be attained in the conversion of the cellulose with a decreased crystallinity after a pretreatment with trifluoroacetic acid or ball milling [16,18]. The use of ionic liquids as reaction media could also enhance the efficiency for cellulose conversions in the presence of an acid catalyst [19]. The conversion of cellulose into glucose and the simultaneous hydrogenation of glucose into sugar alcohols, such as sorbitol and mannitol on Ru/C [20], polymer stabilized Ru nanoclusters [21], and Pt and Ru supported by H-USY and c-Al2O3 [22] has been reported. In order to replace the mineral acids in the acid hydrolysis of cellulose, solid acid catalysts such as sulfonated activated carbon (AC-SO3H) [23], sulfonic acid mesoporous materials [24,25], and Brønsted acidic zeolites [21,22] were used. Higher glucose yields were reported for sulfate modified catalysts than for acidic zeolites. The research was aimed to implement hydrolysis process of lignocellulosic materials over sulfated zirconia catalysts. The prepared catalysts were prepared by using modified sol gel method then dried by different method, i.e. immersed by CTAC surfactant and SFE and characterized their physical and chemical properties before tested their catalytic activity. 2. Experimental method 2.1. Catalyst preparation The precursor employed in the preparation of the sol-gel catalyst was zirconia butoxide in n-butanol. The

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sulfated zirconia was prepared as follow: 16.778 mol of zirconium (IV) butoxide and 16.516 n-butanol was introduced in a glass system at low temperature (0 oC) under constant stirring. Then, 6.718 mL of n-butanol; 0.496 mL of distilled water and 0.684 mL of HNO3 were drop-wise added to the solution and continue stirred constantly. After that, 0.489 mL of H2SO4 was added to the reaction system and the resulting suspension was maintained and stirred constantly until gelling was achieved. The wet gel was treated through two methods to compare the result. First method was surfactant immersion, the wet gel was immersed overnight at room temperature (25 oC) in an n-butanol solution of CTAC surfactant, decanted and then dried under vacuum for 24 h at 70 oC. The second method was SFE which conducted at 60 oC, extractor pressure of 2 000 psi, CO2 flow of (5 to 6) mL· min-1, separator pressure of 500 psi. Finally, all samples calcined for 2 h at 500 oC. 2.2. Catalytic activity test 0.2 g of raw material, 3.8 g of ionic liquid, [bmim]Cl as solvent, 0.25 mL of aquadest as anti solvent and 0.1 g of catalyst were placed into batch reactor. The hydrolysis reaction was carried out at 160 °C for 3 h. After reaction finished, 10 mL of aquadest was added into reactor then filtered. The TRS in liquid product was analyzed by using DNS method. 2.3. Liquid hydrolysis product analysis 0.25 mL of DNS reagent and 0.25 mL of liquid hydrolysis product were mixed and boiled in water bath at 5 °C to 100 °C for 5 min then cooled in room temperature. The solution was diluted by adding 2 mL of water then measured by using UV-Vis Spektrofotometer at 540 nm. TRS concentration was measured by using standard curve of glucose. 3. Results and discussion 3.1. Catalysts properties The properties of catalysts prepared were characterized, in term of specific surface area, pore volume, pore size, total acidity and surface acidity. Table 1 shows that SZSFE resulted in higher specific surface area, pore volume, pore size and acidity than SZimmersing. Table 1. Catalytic properties of zirconia sulfated catalyst Catalysts

Spesific surface area 2

(m

·g ) -1

Pore volume

·g )

3

(cm

-1

Pore size

Total acidity

Surface acidity

(nm)

(mmol· g )

(mmol· g-1)

-1

SZ immersing

81.79

0.063

15.32

5.85

0.61

SZ SFE

119.90

0.39

64.53

13.41

2.33

3.2. Catalytic activity test Sulfated zirconia catalysts prepared were tested their catalytic activity for hydrolysis process to produce TRS. Table 2 shows that pre-treatment by using NaOH can remove 14.5 % of lignin in EFB and 3.1 % of lignin in frond. Then, these raw materials will be used for hydrolysis by using SZ catalyst.

Anis Kristiani et al. / Energy Procedia 65 (2015) 8 – 13 Table 2. Compositional analysis of palm oil lignocellulosic waste Lignin

Cellulose

Hemicellulose

(%)

(%)

(%)

EFB untreated

36.40

30.85

13.94

EFB treated

21.97

52.30

21.32

Frond untreated

29.50

40.01

30.78

Frond treated

26.36

47.84

8.23

Raw material

Variation of raw material used was investigated to see their catalytic activity in hydrolysis of lignocellulose. Palm oil lignocellulosic wastes used are frond and EFB, both untreated and treated by using NaOH. Table 3. Catalytic activity of SZ catalyst in lignocellulosic hydrolysis SZ immersing TRS yield

SZ SFE TRS yield

(%)

(%)

Cellulose

17.85

23.13

EFB untreated

8.61

16.77

EFB treated

17.51

37.20

Frond untreated

9.37

19.75

Frond treated

16.57

28.16

Raw material

(Raw material 0.2 g; catalyst 0.1 g; Ionic Liquid BMIMCl 3.8 g; 160 oC; 3h)

Table 3 shows that pretreatment by using NaOH in EFB increased the TRS yield, from 8.61 % to 17.51 % and in frond, from 9.37 % to 16.57 % by using SZimmersing and 16.77 % to 37.20 % and in frond, from 19.75 % to 28.16 % by using SZSFE. Increasing of TRS yield correlated with decreasing of lignin content and increasing of cellulose content after pretreatment. Optimation of hydrolysis process was done by variation of hydrolysis time by using EFB and frond treated by NaOH.

Fig. 1. Hydrolysis of EFB treated by NaOH

Figure 1 and Figure 2 elucidated that SZ SFE catalyst gave higher % TRS yield than SZimmersing both for hydrolysis of EFB treated and frond treated. Hydrolysis for 3 h gave the highest % TRS yield up to 37.20 % in EFB treated by

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using SZSFE. While, hydrolysis for 4 h gave the highest % TRS yield up to 53.95 % in frond treated by using SZSFE.

Fig. 2. Hydrolysis of frond treated by NaOH

4. Conclusion SZ catalyst have successfully been synthesized by sol gel method, SZimmersing and SZSFE. Characterization resulted that SZSFE has higher specific surface area, pore size, pore volume and acidity than SZimmersing. The hydrolysis of both in cellulose and lignocellulose in BMIMCl ionic liquid, SZSFE showed superior catalytic activity than SZimmersing. SZ SFE catalyst showed the highest hydrolysis catalytic activity up to 37.20 % in EFB treated and 53.95 % in frond treated. Therefore, sulfated zirconia catalyst may have potential application in the hydrolysis reaction of lignocellulosic biomass in order to get fermentable sugar as intermediate product for ethanol production. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]

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