Scholarly article on topic 'Esterification of Palm Fatty Acid Distillate with High Amount of Free Fatty Acids Using Coconut Shell Char Based Catalyst'

Esterification of Palm Fatty Acid Distillate with High Amount of Free Fatty Acids Using Coconut Shell Char Based Catalyst Academic research paper on "Chemical sciences"

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{biodiesel / "esterification palm fatty acid disttillate" / "coconut shell" / "free fatty acid"}

Abstract of research paper on Chemical sciences, author of scientific article — Arif Hidayat, Rochmadi, Karna Wijaya, Annisa Nurdiawati, Winarto Kurniawan, et al.

Abstract Indonesia, as the biggest palm oil producers and exporters in the world, is producing large amounts of low-grade oil wastessuch as palm fatty acid distillate (PFAD) from palm oil industries. Production of fatty acid methyl ester (FAME) from PFAD that having high amount of free fatty acids (FFA) was studied in this work. Low cost feedstocks such as PFADneed to be utilized to replace edible oils in order to improve the economical feasibility of biodiesel. The esterification of FFAin PFAD with methanol using a coconut shell biochar (CSB) catalyst is a promising method to convert FFA into biodiesel. In this study, the CSBcatalysts were synthesized by sulfonating the coconut shell biochar using concentrated H2SO4. The physico-characteristics and acid site densities were analyzed by Nitrogen gas adsorption, FT-IR, X-ray fluorescent (XRF), and acid-base back titration methods. The effects of the mass ratio of catalyst to oil (1-7%), the molar ratio of methanol to oil (6:1 to 12:1), and the reaction temperature (40, 50 and 60oC) were studied for the conversion of FFA to optimize the reaction conditions. The optimal conditions were an methanol/PFAD molar ratio of 12:1, the amount of catalyst of 7%wt, and reaction temperature of 60oC.

Academic research paper on topic "Esterification of Palm Fatty Acid Distillate with High Amount of Free Fatty Acids Using Coconut Shell Char Based Catalyst"

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Energy Procedia 75 (2015) 969 - 974

The 7th International Conference on Applied Energy - ICAE2015

Esterification of palm fatty acid distillate with high amount of free fatty acids using coconut shell char based catalyst

Arif Hidayata *, Rochmadib, Karna Wijayac, Annisa Nurdiawatid, Winarto Kurniawand, Hirofumi Hinodee, Kunio Yoshikawad, Arief Budimanb

aChemical Engineering Department, Indonesia Islamic University, Jalan Kaliurang km 14,5 Yogyakarta 55584, Indonesia bChemical Engineering Department, Gadjah Mada University Jalan Grafika 2 Yogyakarta 55281, Indonesia cChemistry Department, Gadjah Mada University Sekip Utara Bulaksumur Yogyakarta 55281, Indonesia dInternational Development Engineering, Tokyo Institute of Technology 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan eDepartment of Environmental Science and Technology, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama _226-8502, Japan_

Abstract

Indonesia, as the biggest palm oil producers and exporters in the world, is producing large amounts of low-grade oil wastes such as palm fatty acid distillate (PFAD) from palm oil industries. Production of fatty acid methyl ester (FAME) from PFAD that having high amount of free fatty acids (FFA) was studied in this work. Low cost feedstocks such as PFAD need to be utilized to replace edible oils in order to improve the economical feasibility of biodiesel. The esterification of FFA in PFAD with methanol using a coconut shell biochar (CSB) catalyst is a promising method to convert FFA into biodiesel. In this study, the CSB catalysts were synthesized by sulfonating the coconut shell biochar using concentrated H2SO4. The physico-characteristics and acid site densities were analyzed by Nitrogen gas adsorption, FT-IR, X-ray fluorescent (XRF), and acid-base back titration methods. The effects of the mass ratio of catalyst to oil (1-7%), the molar ratio of methanol to oil (6:1 to 12:1), and the reaction temperature (40, 50 and 60oC) were studied for the conversion of FFA to optimize the reaction conditions. The optimal conditions were an methanol/PFAD molar ratio of 12:1, the amount of catalyst of 7%wt, and reaction temperature of 60oC.

© 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-reviewunderresponsibilityofAppliedEnergy Innovationlnstitute

Keywords: biodiesel, esterification palm fatty acid disttillate, coconut shell, free fatty acid

1. Introduction

* Corresponding author. Tel.: +62-274-895287; fax: +62-274-895007. E-mail address: arif.hidayat@uii.ac.id.

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 Applied Energy Innovation Institute

doi: 10.1016/j.egypro.2015.07.301

Biodiesel, an alternative fuel for diesel engines, is biodegradable, nontoxic and renewable. Generally, biodiesel is produced via the transesterification of vegetable oils or animal fats with short chain alcohols (e.g., methanol), which is carried out by acid or base catalysis, to form alkyl esters that have properties similar to those of fossil-derived diesel. Biodiesel can also be prepared by the esterification of free fatty acid present in animal fats (e.g. Lard or tallow), with methanol over acid catalysts [1].

Recently, low cost feedstocks such as waste cooking oil and animal fats have been utilized to replace vegetable oils [2] in order to improve the economical feasibility of biodiesel. The use of low cost feedstocks for biodiesel production has advantages: (i) do not compete with the food market; (ii) recycles waste; and (iii) reduces production costs therefore increasing biodiesel economic competitiveness [3]. Examples of these feedstocks are recycled vegetable oils, chicken fat, animal fat, jathropa oil, cottonseed oil, fatty acid recovered from degumming residues, residues from several industries, etc. The low cost feedstocks have large amounts of FFA. The presence of high FFA lead to saponification and subsequent reduction in the methyl esters produced. These feedstocks can be converted to biodiesel with high yields using acid-catalyzed esterification as a first reaction step. One of the promising low cost feedstock is PFAD. PFAD is a by-product of the palm oil milling process and is considered as low grade oil with high free fatty acids.

Traditionally, esterification reactions are carried out using homogeneous catalysts, such as sulfuric acid. However, in order to become a "green process", the homogenous catalysts need to replace by heterogeneous catalysts. Compared with conventional homogeneous acids, heterogeneous catalysts have many significant advantages such as less corrosion, less toxicity and less environmental problems [4]. Esterification with solid acid catalyst, including acid zeolites [5], ion-exchange resins [6], sulfonic acid-modified mesostructured silica [7], tungsten oxide zirconia [8], sulfonated polymers (Amberlyst-15) [9], lanthanum (La3+) and HZSM-5 [10] and sulfated zirconia [11] has been carried out. However, most of the catalysts reported so far utilized complex and expensive synthesis routes, demonstrated poor reusability and were non-biodegradable. Carbon materials are relatively cheap, widely available and can be easily functionalized with -SO3H groups through simple treatment with concentrated sulfuric acid [12].

Carbon materials is widely used as a catalyst support in a variety of industrial and environmental applications for its chemical stability, high specific surface area, and low cost [13]. Toda et al. (2005) reported the use of such a sulfonated AC as an effective catalyst for biodiesel production by the esterification of vegetable oils. According to Zong et al. (14), the activity of sulfonated carbon-based catalyst (D-glucose based) for the production of methyl ester is much higher than that of sulfonated zirconia which is one of the commonly used solid acid catalysts for biodiesel production. The main difference is attributed to fewer acid sites of sulfated zirconia compared to those of sulfonated carbon-catalysts [15]. Functionalized carbon (e.g., attached SO3H groups) has been generated from refined sugars (pure cellulose, glucose and starch) and was demonstrated to catalyze the transesterification of oleic and stearic acid with ethanol [15]. Guo et al. (2012) used lignin-derived from nutshells of Xanthoceras sorbifolia (an oil plant in China) to prepare similar sulfonated carbon catalyst in a one-step method involving simultaneous carbonisation and sulfonation. The prepared catalyst was evaluated for biodiesel production from acidified soybean soapstock containing high FFA [15]. A study of sulfonated activated carbon prepared by sulfonating biochar and wood based activated carbon was conducted recently by Kastner et al. (2012). The catalysts were prepared by sulfonating the biochar and wood derived activated carbon using concentrated H2SO4 and gaseous SO3. The sulfonated carbons were tested for their ability to esterfy free fatty acids with methanol in blends with vegetable oil and animal fat [16].

In this study, the carbon based catalyst were synthesized by sulfonating the coconut shell char using concentrated H2SO4. The physico-characteristics and acid site densities were analyzed by Nitrogen gas adsorption, FT-IR, X-ray fluorescent (XRF), and acid-base back titration methods. The catalytic performances of the carbon based catalyst were conducted through esterification of PFAD with methanol.

Several factors which may influence the esterification of PFAD were investigated, including the reaction time, wt% of the catalyst, molar ratio of methanol to oil, amount of catalyst, and stirrer speed.

2. Methodology

2.1. Preparation of catalyst

Coconut shell biochar (CSB) based catalyst samples were prepared via concentrated sulfuric acid. The biochar were sulfonated according to the method of Toda et al. [2005]. 100 mL of concentrated sulfuric acid was added to 5 g of biochar in a 500 mL round bottom flask. The mixture was heated to 150oC for 12 hours. After heating, the slurry was placed in cool distilled water and filtered. The biochar catalyst was washed with 80oC distilled water until the wash water was neutral and free from sulfate ions. Then, the biochar was dried in an oven at 70oC for approximately 1 h. BET surface area, average pore diameter and total pore volume of the catalysts were determined by nitrogen adsorption-desorption isotherm at 77.35 K using the BET method. FT-IR spectra of various samples were employed to identify the functional groups in the catalysts. The total acid site density was measured via back titration method. The elements composition were analyzed by XRF.

2.2. Activity test

Esterification of PFAD using the CSB catalysts was conducted in a 250 mL three-neck flask equipped with reflux condenser and temperature indicator on a hot plate with a magnetic stirrer. The reaction procedure is as follows: mixture of catalyst and methanol was heated to 60oC under continuous stirring at 500 rpm. Subsequently, PFAD was added into the mixture under vigorous stirring (500 rpm). Experiment was carried out at 40-60oC for 4 h. The molar ratio of methanol to PFAD ranged from 6:1 to 12:1 while the amount of CSB catalyst varied from 1 to 7 wt.% of the PFAD. The samples were regularly collected for analysis every 30 min.

The samples were analyzed by titration procedure for the evaluation of free residual acidity. Once the sample was taken from the reactor, it was washed with water in order to stop the reaction and separates the catalyst and the alcohol from the oil phase. To improve the separation of the phases, the sample was centrifuged for 20 min. A weighted amount of the sample was dissolved in ethanol in order to be able to make the titration analyses, and some drops of phenolphthalein as indicator were added to the system to be able to measure the conversion. The titration was done with a 0.02 N alkaline solution of KOH. The amount of KOH consumed was register and the acidity can be calculated using the following equation:

where is the acid value of the mixture, is volume of solution employed for titration, weight of the solution, is concentration measured by titration and is weight of sample

The conversion of free fatty acid was calculated using this equation:

a,i — at

XFFA =

where is the initial acidity of the mixture and is the acidity at "t" time.

3. Results and Discussion 3.1. Catalyst Characterization

is molecular

The porosity of the prepared coconut shell biochar based catalyst was analyzed using the BET method. The BET surface area of the catalyst was found to be 244.236 m2.g-1 and average pore size radius of 2.43 nm. It is interesting to note that sulfonation using H2SO4 significantly increased surface area and pore structure formed in the biochars. Sulfonation clearly increased the acid density as measured by base titration and the sulfur content of the carbon (Table 1). The acid density that measured by back titration method, was significantly larger than that indicated by the sulfur content, suggesting that sulfonation using H2SO4 not only created sulfonic acid groups, but created additional weak acid groups (e.g., COOH). According to Table 1, the ratio of O and S against C are high in the catalyst suggested that the catalyst consist of carbon sheets that are high in SO3H, COOH, and OH functional groups.

Table 1. Surface area and acid properties of the samples.

Sample Surface area (m2/g) Average pore size radius (nm) Elemental composition (wt%) Acid density (mmol/g)

C O S Total SO3H

Coconut shell 161.29 2.48 54.85 45.14 - 0.14 -

biochar

CSB catalyst 244.236 2.43 74.51 20.94 4.55 2.21 1.93

The FT-IR spectra of coconut shell biochar and CSB catalysts are shown in Fig. 1. Compared to sample coconut shell biochar, the distinguished features of CSB catalysts were the presence of new absorption bands at 1037 and 1150 cm-1, which are attributed to SO3H groups. This indicates that the SO3H groups were successfully incorporated into the carbon framework by a sulfonation using H2SO4. On the other hand, the bands due to -OH stretching at 3440 cm-1, C=O stretching at 1715 cm-1, and C=C bonds stretching at 1610 cm"1 were observed for both samples independent of the sulfonation.

1000 1500 2000 2500 3000 3500

Wavemimbers (cm"1)

Fig. 1.The FT-IR spectra of coconut shell biochar and CSB catalysts

3.2. Activity test

The effect of CSB catalyst loading on esterification of PFAD with methanol was studied at 60oC. The results are shown in Fig. 2. It was observed that the increase in catalyst loading from 1 to 7 wt% of PFAD showed an increase on the FFA conversion. These results can be attributed to an increase in the availability and number of catalytically active sites. It was observed that the conversion was increased firstly with the increase of catalyst amount (75% at 1 wt% of catalyst to 87% at 7 wt% of catalyst, after 4 h of reaction). However, the conversion was increased slowly, with further increase in the catalyst amount. This behaviour was attributed to the increase in the number of catalytically active site.

Catalyst loading (wt%)

Fig. 2. Effect of molar ratio on conversion of FFA (Reaction conditions: 4 h, 60oC, molar ratio of methanol to PFAD=12:1).

Three reaction temperatures such as 40, 50 and 60oC have been selected to investigate the influence of reaction temperatures on the esterification of PFAD with methanol. The FFA conversion via esterification has noticeable dependency on the reaction temperatures as seen in Fig. 3. Fig. 3 shows that the FFA conversion increases from 64 to 84% as the temperature increases from 40 to 60oC. The increased of FFA conversion might be not only due to the effect of increase of the reaction rate by increasing temperatures but also some improvement of the mass transfer limitation between reactant and catalyst.

Reaction temperature (oC)

Fig. 3. Effect of reaction temperatures on conversion of FFA(Reaction conditions: 4 h, molar ratio of methanol to PFAD=12:1, 7

wt% of catalyst).

The esterification of PFAD with methanol is a reversible reaction. High conversion can only be obtained if the backward reaction is minimized. There are two ways to reduce the rate of backward reaction: (1) to remove the product water simultaneously or (2) to use excess of one of the reactants (methanol). In this system, it is not easy to remove water, as the boiling point of methanol (65°C) is lower than the boiling point of water (100°C). Thus, the second option was applied in the present work. However, the excess of methanol used in the reaction can be collected and reused. In this study the molar ratio of methanol to PFAD was varied from 6:1 to 12:1. Fig. 4 describes the effect of the molar ratio on the conversion of FFA. It has been seen that yield of the process increases with increase in molar ratio. With further increase in molar ratio the conversion efficiency more or less remains the same. However it can be concluded that the molar ratio increased from 8:1 to 12:1 there is no significant change observed with a higher molar ratio in the reduction of FFA.

6 : 1 8 : 1 10 : 1 12 : 1 molar ratio methanol to PAFD

Fig. 4. Effect of molar ratio methanol to PFAD on conversion of FFA(Reaction conditions: 4 h, 60oC, 7 wt% of catalyst).

4. Conclusions

The effects of the mass ratio of catalyst to oil (1-7%), the molar ratio of methanol to oil (6:1 to 12:1), and the reaction temperature (40, 50 and 60oC) were studied for the conversion of PFAD to optimize the reaction conditions. The optimal conditions were an methanol/PFAD molar ratio of 12:1, the amount of catalyst of 7%wt, and reaction temperature of 60oC.

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