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Synthesis of high quality biodiesel using feedstock and catalyst derived from fish wastes Devarapaga Madhu, Rajan Arora, Shalini Sahani, Veena Singh, and Yogesh Chandra Sharma J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.6b05608 • Publication Date (Web): 23 Feb 2017 Downloaded from http://pubs.acs.org on February 25, 2017
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Synthesis of high quality biodiesel using feedstock and catalyst derived from fish wastes
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Devarapaga Madhu1, Sharma1*
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1
6 7
2
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*Corresponding author
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E mail
[email protected], Tel No. +91 542 6702865, Fax +91 542 6702876
Rajan Arora2, Shalini Sahani1, Veena Singh1,
Yogesh Chandra
Department of Chemistry, Indian Institute of Technology (BHU) Varanasi, Varanasi 221005, India. Department of Chemical Engineering and Technology, Indian Institute of Technology (BHU) Varanasi, Varanasi 221005, India.
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A manuscript submitted for publication in:
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Journal of Agriculture and Food Chemistry
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Synthesis of high quality biodiesel using feedstock and catalyst derived from fish wastes
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Devarapaga Madhu1, Sharma1*
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1
19 20
2
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*Corresponding author
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E mail
[email protected], Tel No. +91 542 6702865, Fax +91 542 6702876
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ABSTRACT
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A low cost and high purity calcium oxide (CaO) was prepared from waste crab shells which
25
were extracted from the dead crabs, used as efficient solid base catalyst in the synthesis of
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biodiesel. Raw fish oil was extracted from waste parts of fish through mechanical expeller
27
followed by solvent extraction. Physical as well as chemical properties of raw fish oil were
28
studied and its free fatty acids (FFA) composition was analysed with GC-MS. Stable and
29
high purity calcium oxide (CaO) was obtained when the material was calcined at 800 °C for
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4 h. Prepared catalyst was characterized by XRD, FT-IR, and TGA/DTA. The
31
structure of the catalyst was analysed with SEM and elemental composition was determined
32
by EDX spectra. Esterification followed by transesterification reactions were conducted for
33
the synthesis of biodiesel. Effect of co-solvent on biodiesel yield was studied in each
34
experiment using different solvents such as toluene, and diethyl ether, hexane,
35
tetrahydrofuran (THF) and acetone. High quality and pure biodiesel was synthesized and
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characterized by 1H NMR and FT-IR. Biodiesel yield was affected by the parameters such
37
as reaction temperature, reaction time, molar ratio (methanol: oil) and catalyst loading.
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Properties of synthesized biodiesel like density, kinematic viscosity, cloud point, etc. were
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determined according to ASTM standards. Reusability of prepared calcium oxide (CaO)
Rajan Arora2, Shalini Sahani1, Veena Singh1,
Yogesh Chandra
Department of Chemistry, Indian Institute of Technology (BHU) Varanasi, Varanasi 221005, India. Department of Chemical Engineering and Technology, Indian Institute of Technology (BHU) Varanasi, Varanasi 221005, India.
surface
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catalyst was checked and the catalyst was found stable up to five runs without significant loss
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of catalytic activity.
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Key words: Fatty acid methyl esters (FAME’s); Free Fatty Acid; Tetrahydrofuran; Waste
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crab shells; Waste fish oil.
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1. INTRODUCTION
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Energy has pivotal role for determination of socioeconomic conditions of any country.
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Energy consumption of any country determines the country’s standard of living1. The excess
47
of energy in the surroundings can be converted, accumulated and amplified for our daily use
48
in a number of ways. The production of energy has always been a concern for researcher and
49
policymakers worldwide. Energy sources are categorized into two main groups, namely
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fossil and renewable energy. Fossil energy can be separated into non-renewable and
51
renewable energy. Non-renewable energy sources comprise petroleum, coal, gas hydrate, gas
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and fissile material and renewable energy sources include solar, hydro, geothermal, biomass
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and wind energy. Recently, the renewable energy sources are contributing more towards the
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total global energy requirement2. Supporting development, indispensable characteristics of
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renewable energy source depend on environmental protection.
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The world energy currently conflicted with the turning point of fossil fuel depletion and
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environmental deterioration. To prevail this problem, renewable energy has currently been
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achieving more attention because of its environmental allowance. The need for energy, the oil
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depletion and its price which are continually increasing, all have inclined the country to
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search alternative new renewable fuels. Green energy is another term for renewable energy
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which is auspicious for alternative, and it is neat and environmentally friendly. As compared
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with fossil energy, green energy produces lower or negligible level of greenhouse gases and
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other pollutants. Emissions like SO2, CO2, and NO2 are lower3,
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renewable energy sources and the production as well as application of green energy plays
4
in comparison to non-
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important role in diminishing the greenhouse impact. Carbon dioxide released from the
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chemical energy obtained from biofuels (via photosynthesis using solar energy) is
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maintaining CO2 levels since green plants are taking the released CO2 from environment.
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Replacing the petroleum fuel, liquid biofuel will be vital in the near future5. Biofuels
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comprise of biodiesel, bio-methanol, bio-ethanol, bio-butanol, vegetable oil, biogas and bio-
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hydrogen. The most important liquid biofuels are biodiesel and bioethanol. Biodiesel is a
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diesel alternative while bioethanol is gasoline substitute. For transportation purpose, liquid
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biofuel have currently drawn attention in number of countries because of their sustainability,
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renewability, bio-degradability and availability, as well as their imminent role in regional
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advancement, inception of rural making job and diminishing the greenhouse gas emissions.
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Oxygen content is the biggest difference between petroleum and biofuel feedstock. Biofuels
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are reliable and are obtained from renewable sources, accessible and sustainable, locally
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available and are non-polluting. Based on their production technology, biofuel can be
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categorized into first-generation biofuels (FGBs), second-generation biofuels (SGBs), third-
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generation biofuels (TGBs)6 and fourth-generation biofuels7.
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Different catalysts are used for synthesis of biodiesel. Most widely used catalysts are
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enzymatic, and acid/base homogeneous and heterogeneous catalysts. Enzymatic catalysts
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have attracted attention as they can withstand free fatty acid and water contents thus assisting
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in purification of biodiesel and glycerol. On the other hand, the enzymztic cztzlysts cannot be
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used commercially as they are costly and show unstable activities with reaction rates much
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lower than homogeneous catalysts8. Common catalysts used for biodiesel synthesis are
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homogenous acid/base catalysts, such as sodium or potassium hydroxide, sodium methoxide,
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sodium ethoxide, sulphuric acid and hydrochloric acid. They have relatively higher kinetic
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rates with high conversion with insignificant side reactions. However, there are numerous
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drawbacks of using them such as corrosive nature, increase in pH of final product9. Removal
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of homogeneous catalysts after transesterification also poses technical problems and large
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amount of wastewater is produced during biodiesel cleaning and separation10. In the
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homogeneous catalytic transesterification, low quality glycerol is produced and thus involves
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meticulous process for purification, catalyst recovery is not possible requiring its
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neutralization at the end of reaction, producing undesired salts which needs to be separated.
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Also, it requires FFA content in feedstock to be less than 3%, so if greater than 3%, it
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necessitates removal of FFAs and moisture. Culminating all these reasons increases the
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processing cost of biodiesel and it’s by products. To settle all these issues, heterogeneous
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catalysts like zeolites, clays, sulfonic ion-exchange resins, pure or mixed oxides,
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heterogenized guanidines, etc.
are being
developed. Heterogeneous catalysts can be
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separated easily and reused, insignificant amount of waste water is produced and separation
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of biodiesel from glycerol is simplified11-12. Reusability of heterogeneous catalysts makes the
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process more economically feasible and also the non-toxic, non-corrosive nature makes the
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process environmentally friendly.
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Previous studies have shown that the fish oil extracted from fish waste13 gave good results for
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the synthesis of biodiesel14. India’s
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9,019,148 tons which includes marine fish production of 3,275,091 tons and inland fish
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production was 5,744,057 tons. During the processing of fish industry, approximately 20-
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80% of fish waste is generated as waste from the total fish weight15. Waste generated from
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fish is used as raw material for the synthesis of biodiesel. In the present work, fish oil has
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been used as raw material for the synthesis of biodiesel since fish market generates huge
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amount of fish waste from which fish oil can be generated16, 17. Fish oil extracted from waste
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not only reduces the amount of waste but also it reduces the amount of total cost of biodiesel
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synthesis. In Indian perspective, it is entirely strenuous to produce biodiesel from the waste
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sources (fish oil extracted from discarded parts of fish and CaO from waste crab shells)
total fish production in the year 2012-2013 was
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because of scarcity of ample feedstock as well as raw material for the catalyst preparation. It
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provides less expensive and more potential option to curtail the overall price of biodiesel
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production. From literature survey, it was clear that very few reports are available on
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transesterification of high acid value feedstocks like fish oil or Millettia pinnata using CaO as
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base heterogeneous catalyst. The present work explores the preparation of waste CaO derived
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from waste crab shells and the efficacy of catalyst in transesterification of fish oil extracted
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from waste parts of fish of Indian origin. The properties of prepared biodiesel were
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considered as per ASTM standards.
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2. EXPERIMENTAL SECTION
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2.1. Material
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The crab shells used for synthesis of the catalyst were collected from Jas Dry Fish
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Merchant-India MART Toothukudi, Tamil Nadu, India. Fish oil was extracted from
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the discarded parts of fish. Methyl alcohol, sulphuric acid, deuterated chloroform
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sodium and sulphate, hexane, toluene, tetrahydrofuran (THF), acetone and diethyl
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ether were of analytical reagent (AR) grade and were purchased from Merck Ltd.,
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Mumbai, India.
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2.2. Fish oil Extraction
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Waste parts of fish such as tails, maw, eyes, viscera, etc. were collected from the local fish
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market (Varanasi), India. The collected discarded parts of fish were washed with hot distilled
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water to eliminate the impurities such as blood and solid particles. Water content of waste
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parts of fish was removed with hot air oven kept at 102 °C for 2 h. Dried waste parts of fish
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were cut into small pieces. Fish oil was extracted from these small pieces through mechanical
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expeller at room temperature. Some amount of oil content still remained in dried matter after
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extraction of fish oil through mechanical expeller. This left amount of oil content was
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extracted through solvent extraction using petroleum ether as solvent. Physical properties of
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waste fish oil such as acid value, density, kinematic victory, boiling point, unsaponifiable
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matter, etc. were determined as shown in Table 1.
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Table 1
144 145
2.3. Catalyst Preparation
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Waste crab shells were dried in a hot air oven at 102 °C for 2 h to remove water content
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present in the waste crab shells. The dried waste crab shells were ground into powder using a
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ball mill. Then the powder was calcined in a muffle furnace at 800 °C for 4 h. The calcined
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material was grounded into fine powder with the help of agate mortar. Catalytic poisoning
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will occur when the catalyst is placed in contact with air because of the presence of moisture
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and carbon dioxide12. Though, the catalytic poisoning was less because of water and carbon
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dioxide, the poisoning was found to be consequential. Therefore, the catalyst was placed in a
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plastic bottle container and then in desiccator to avoid poisoning. The catalyst was
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characterized with various analytical techniques (XRD, FT-IR, TGA/DTA and SEM/EDX)
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and used in the transesterification reactions.
156 157
2.4. Characterization of Biodiesel by Proton NMR Analysis
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The conversion of triglycerides (oil) to fatty acid methyl ester (biodiesel) was analysed using
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proton NMR spectroscopy. The 1H NMR spectrum of biodiesel product is shown in Figure 1.
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A singlet signal at 3.69 ppm represents the methoxy protons of FAME while the triplet at
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2.30 ppm represents α–methylene protons of fatty acid derivatives18-20. The percentage
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conversion of fish oil to biodiesel was calculated by the ratio of integrated signals (area under
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the signal obtained by integration) at 3.69 ppm (AME) and 2.30 ppm (ACH2) in the following
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equation:
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C = 100(2*XACH3)/(3*ACH2)
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(1)
= 100(2*3)/(3*2.07) = 96.61%
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C denotes the conversion (%) of triglycerides to fatty acid methyl esters; the factors 2 and 3
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in numerator and denominator are ascribed to the number of protons on methylene and
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number of protons on methyl ester.
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Figure 1
171 172
2.5. Gas Chromatography–Mass Spectrometry (GC-MS) Analysis
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Fish oil methyl esters were analysed with the Gas Chromatography Mass Spectrometry (GC-
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Mass Spectrometer Perkin Elmer, Mass range: 20 to 620 Daltons (amu)). Samples were
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prepared to analyse when 0.03 mL of fish oil methyl esters were mixed with 2.1 mL of
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hexane. Figure 2 represents the GC-MS chromatogram in which X-axis corresponds to
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retention time and Y-axis corresponds to parentage of relative abundant. Using the known
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compound spectrum from the NIST 2011 library, unknown compound spectrum was
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predicted with the help of Turbo Mass software. The major fish oil methyl esters were
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Myristic acid methyl ester (5.51%), Palmitoleic acid methyl ester (9.70%), Palmitic acid
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methyl ester (14.09%), Arachidonic acid methyl ester (3.21%), Oleic acid methyl ester
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(11.03%), Linolenic acid methyl ester (3.45%), Stearic acid methyl ester (4.05%),
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Eicosapentaenoic acid methyl ester (EPA) (19.96%), Docosahexaenoic acid methyl ester
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(DHA) (13.93%) and Erucic acid methyl ester (1.08%) were shown in Table 2.
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Figure 2
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Table 2
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2.6. FT-IR analysis of biodiesel
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Purified biodiesel was characterized with FT-IR spectroscopy as shown in Figure 3. Sharp
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band was observed at 1742 cm-1 is attributed to C=O stretching frequency and another sharp 8 ACS Paragon Plus Environment
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band observed at 2923 cm-1 is assigned to C-H stretching vibration of methylene groups.
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Sharp absorption band at 1459 cm-1 is due to asymmetric CH2 bending vibrations. The band
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at 1160 cm-1 is due to C-O stretching frequency of fatty acid methyl of ester.
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Figure 3
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2.7. Esterification
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Acid value determination of the feedstock was determined prior to transesterification process.
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Acid value determines whether the esterification step is required or not. The important
197
parameters for determining the viability of the transesterification is free fatty acid content
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present in the raw fish oil21. The FAME conversion is inversely proportional to the acid value
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of the oil in base catalyzed biodiesel synthesis, reason for this is the soap formation with the
200
acid of the base catalyst. In present case, acid value of the feedstock was found to be 11.89
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which is quite high and acid
202
corresponding FAME’s. In acid esterification, fish oil: methanol (1:8) molar ratio was poured
203
in a indigenously fabricated 3 necked round bottom flask and 1% (v/v) of sulphuric acid was
204
added to it and the content was mechanically agitated on a water bath at 60 oC. Esterification
205
reaction was completed in 120 min. After completion of the reaction, the reaction mixture
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was poured in a separating funnel followed by rotavapor separation. After esterification, acid
207
value was reduced to less than 2 ± 0.25 mg KOH/g and it was subjected to transesterification
208
reaction.
209
Acid value of the feedstock and biodiesel was calculated using following equation:
210
Acid Value (mg KOH/g) = VKOH *56.1*CKOH / msample
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FAME’s conversion was calculated using following eq 1.
212
Free Fatty Acid Conversion (%) = (AV1-AV2)/AV1*100
213
Where AV1 (mg KOH g-1) is the acid value of original oil sample, and AV2 (mg KOH
214
g-1) is the acid value of catalysed product.
esterification was performed
to convert FFA’s into
(2)
(3)
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215 216 217
2.8. Transesterification
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After esterification, transesterification reactions were conducted using calcium oxide catalyst
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derived
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transesterification reactor with 250 mL three-neck round bottom flask.
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with an overhead mechanical stirrer and water-cooled reflux condenser. The parameters such
222
as molar ratio of oil: methanol (varied from 1:4 to 1: 14), catalyst loading (varied from 1% to
223
3%), stirrer speed (350 rpm to 850 rpm), reaction temperature (varied from 35 °C to 85 °C)
224
and reaction time (varied from 30 to 130 min) were studied. In each and every experiment,
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co-solvent: methanol (1:1) was added. After completion of each experiment, biodiesel was
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separated using separating funnel followed by rotavapor. Biodiesel was characterized with
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FT-IR, and 1H NMR.
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3. RESULTS AND DISCUSSION
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The prepared catalyst was characterized by Differential Thermal Analysis/Thermo
230
Gravimetric
231
Microscopy/Energy Dispersive X-ray Spectroscopy (SEM/EDX) and Fourier Transform
232
Infrared Spectroscopy (FT-IR).
233
3.1. XRD Analysis
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The powder X-ray diffraction (XRD) analysis was carried out with a Shimadzu
235
diffractometer model XRD 6000. The diffractometer employed Cu-Kα radiation to generate
236
diffraction patterns from the powder crystalline samples at ambient temperature. The Cu-Kα
237
radiation was generated by a Philips glass diffraction X-ray tube (broad focus 2.7 kW type).
238
The XRD diffraction spectra of the calcium oxide derived from white wash as shown in
239
Figure 4. The appearance of calcium oxide peaks derived from waste crab shells in XRD
from
waste
Analysis
crab
shells.
(DTA/TGA),
All
the
X-ray
experiments
Diffraction
were
(XRD),
carried It
Scanning
out
in a
is fitted
Electron
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indicated that the pure calcium oxide was formed when the complete conversion of calcium
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carbonate into calcium oxide by releasing carbon dioxide. The peaks were matched with the
242
Joint Committee on Powder Diffraction Standards (JCPDS) files. The peaks observed at
243
32.2°, 37.3°, 53.8°, 67.3°, and 79.6° (JCPDS 48-1467) of X-ray diffraction tell us the
244
presence of the calcium oxide having the face-centered lattice.
245
Figure 4
246
3.2. SEM analysis
247
The surface morphology of calcium oxide derived from waste crab shells were observed
248
using Scanning Electron Microscope (SEM). Figure 5 represents the scanning electron
249
microscope images showing the surface morphology of the calcium oxide catalyst. The
250
image was taken at various magnifications and at a voltage of 20 kV. The particles are
251
agglomerated due to the precursor's high temperature of calcination. If we plot frequency of
252
the particle vs. size, it reveals that the size of the particles varied between 1.2–2.5 µm but
253
most of them were in 1.6–2 µm range.
254
Figure 5
255
3.3. Energy dispersive X-ray spectroscopy
256
Energy dispersive X-ray spectroscopy is a well-known analytical procedure to determine the
257
elemental or the chemical composition of the calcium oxide derived from waste crab shells.
258
No peaks of carbon were observed in the EDX spectrum. It showed the complete conversion
259
of calcium carbonate present in the crab shells into calcium oxide by releasing carbon dioxide
260
as shown in Figure 6. The percentage weight of Ca inferred from studying EDX spectrum
261
was 53.21 and oxygen was 46.79 as shown in the Table 3. The atomic percentage of Ca was
262
68.78 and oxygen was 31.22.
263
Figure 6
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Table 3 11 ACS Paragon Plus Environment
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3.4. TGA/DTA analysis
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Figure 7 represents the Thermo Gravimetric Analysis (TGA)/ Differential Thermal Analysis
267
(DTA) of un-calcined waste crab shells. 10 mg of sample is taken and kept in a 1 ml
268
aluminum crucible with heating rate of 10 °C/ min at 50 ml/min air flow rate. Pure aluminum
269
powder was taken as reference material. It has been observed that the weight loss of the un-
270
calcined waste crab shells occurred from 27 °C to 770 °C. The total weight loss of un-
271
calcined waste crab shells were found to be 52.7%. Weight loss (5.41%) in TGA curve under
272
0 < T >200 was due to the removal of water content present in the un-calcind waste crab
273
shells and further weight loss (7.2%) observed at 200500 was due to the loss of some
274
amount of organic compounds present in the un-calcined waste crab shells. Sharp weight loss
275
(41.08%) was occurred under 500789 is due to the complete conversion of calcium
276
carbonate into calcium oxide by releasing carbon dioxide, further there was no significance
277
weight loss since stable calcium oxide formation had taken place.
278
Figure 7
279
3.5. FT-IR analysis
280
Figure 8 shows the Fourier transform Infrared (FT-IR) spectra of calcined crab shells 800 °C.
281
FT-IR spectra of calcined crab shells shows major absorption band at band at 506 cm-1 is
282
characteristic of Ca-O bond9. The absorption band at 1083 cm-1 and symmetric stretching
283
vibration band at 1483 cm-1 is corresponding to insignificant amount of carbonate (CO3-2)
284
present in the catalyst derived from the waste crab shells. The FT-IR absorption band at 3646
285
cm-1 indicates the existence of -OH stretching vibration because of water molecule present on
286
the surface of CaO catalyst.
287
Figure 8
288
3.6. Brunauer – Emmett – Teller (BET) surface area of CaO
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Figure 9 represents the Brunauer–Emmett–Teller (BET) surface area of CaO derived from
290
crab shells. BET of CaO was measured with nitrogen gas adsorption–desorption isotherms at
291
– 196 °C. The surface area of CaO derived from crab shells was 16.01 m2/g which was
292
calculated from the isotherm linear plot drawn in between relative pressure (P/Po) vs quantity
293
of nitrogen adsorbed (cm3/g STP). According to previous work, calcium oxide (CaO) derived
294
from pulverized lime stone was found to have a surface area 13.00 m2/g which is slightly
295
lesser than that found in the present work (calcium oxide derived from crab shells). This high
296
surface area of CaO derived from crab shells is its one of the major advantages that facilitated
297
calcium oxide to be a good catalyst in the transesterification. The pore volume and average
298
pore width of catalyst were 0.03013 cm3 /g, 73.6034 Å respectively.
299
Figure 9
300
3.7. Effect of reaction parameters on biodiesel yield
301
To optimise biodiesel production, the effect on biodiesel yield due to various parameters viz.
302
catalyst loading, oil-to-methanol molar ratio, reaction time, reaction temperature and stirrer
303
speed were studied. The effect of co-solvent22 (tetrahydrofuran) on the yield was also
304
investigated. In heterogeneous transesterification process, the reaction mixture constitutes a
305
3-phase system due to presence of solid catalyst, methanol and oil phases, which cause
306
mixing problems. The co-solvent increases the mutual solubility of oil23 and methanol
307
resulting in better mass-transfer. Consequently, we get higher initial reaction rates, shorter
308
reaction time and better yield. The catalyst loading was studied in the range of 1% to 3%.
309
Oil-to-methanol molar ratio was varied from 1:4 to 1:14. Co-solvent was kept proportionate
310
to methanol was (1:1). Reaction time was varied from 30 to 130 minutes; the reaction
311
temperature was varied from 35 °C to 85 °C; and stirrer speed was varied from 350 to 850
312
rpm.
313
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3.8. Effect of catalyst loading on biodiesel yield
315
A series of experiments was carried out at different catalyst loadings and at different oil to
316
methanol ratios keeping other parameters constant. The loading of catalyst was varied from 1
317
to 3 wt% and oil to methanol molar ratio from 1:4 and 1:14. Figure 10 represents the
318
combined effect of catalyst loading and ‘oil: methanol molar ratio’ on biodiesel yield with
319
and without addition of the co-solvent. As the results illustrates, there was a significant and
320
sharp improvement in biodiesel yield by increasing loading of catalyst up to 2.5 wt%.
321
Maximum biodiesel yield (96 %) was obtained at 2.5 wt% with the addition of co-solvent.
322
Oil mixed with methanol forms a well dispersed emulsion and sufficient amount of catalyst
323
provides a proper contact which leads to reactions resulting in high yield of biodiesel24 and
324
beyond 2.5 wt% of catalyst, there was no significant increase in biodiesel yield. This could be
325
attributed to the fact that catalyst makes the reaction mixture more viscous which causing
326
difficulty in mass transfer25. Transesterification of triglycerides is a reversible process, excess
327
quantities of methanol facilitate biodiesel conversion26 since methanol molecules will contact
328
easily with triglycerides. Pure and high yield (96%) occurred at oil to methanol ratio of 1:10
329
beyond which yield starts stagnating or ebbing. The high molar ratio of methanol interferes
330
with the separation of glycerol. The glycerol produced in the reaction diffuses in excess
331
methanol and remains in the solution, driving back the reversible reaction and lowering the
332
yield27. Moreover, in each experiment, it was also observed that addition of co-solvent
333
contributes significantly to an increase in yield.
334
Figure 10
335
3.9. Effect of reaction temperature on biodiesel yield
336
The transesterification of fish oil using 2.5 wt% of CaO catalyst was performed at 35 °C to
337
85 °C temperatures with an oil to methanol ratio of 1:10, reaction time 90 min at a stirrer
338
speed of 650 rpm. Figure 11 represents the effect of temperature on the biodiesel yield with 14 ACS Paragon Plus Environment
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and without addition of the co-solvent. There was a gradual increase in biodiesel yield on
340
increasing the temperature from 35 °C up to 65 °C. The optimum temperature was found to
341
be 65 °C with the addition of co-solvent since high biodiesel yield occurred at this
342
temperature. Due to high viscosity of oils, methanolysis is usually performed near the boiling
343
point of methanol (65 °C) to decrease viscosity, enhance mass transfer and increase reactivity
344
of reactants28. Temperature has a significant effect on the reaction rate but after a threshold
345
temperature (65 °C) the biodiesel yield starts decreasing. On increasing temperature beyond
346
65 °C, no significant effect on biodiesel yield was observed, rather the yield was decreased to
347
some extent. This may be due to vaporisation of methanol which lead to reduced contact with
348
the reactants.
349
Figure 11
350
3.10. Effect of reaction time on biodiesel yield
351
Reaction time required for transesterification depends on the reaction temperature as well as
352
on degree of mixing29. Experiments were conducted by varying the reaction time in the range
353
of 30 to 130 min. at catalyst loading of 2.5 wt%, reaction temperature of 65 °C, oil-to-
354
methanol ratio of 1:10, and a stirrer speed of 650 rpm. Figure 12 represents the effect of
355
reaction time on biodiesel yield with and without addition of co-solvent. The yield showed
356
improvement upon increasing the reaction time up to 90 min. Increasing the time beyond 90
357
min led to a slight decrease in yield. This is because longer reaction time favours reverse
358
reaction of hydrolysis of esters along with soap formation from fatty acids30. Hence,
359
controlling reaction time is critical for enhancing yield. The optimal reaction time for
360
transesterification of fish oil was found to be 90 min at 65 °C and 650 rpm along with the
361
addition of co-solvent. Moreover, the presence of co-solvent was found to increase yield for
362
all of the tested reactions.
15 ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
Page 16 of 44
363
Figure 12
364
3.11. Effect of stirrer speed on biodiesel yield
365
Mixing is important in transesterification reactions since oils and fats are immiscible in solid
366
catalysts and partially soluble in alcohol. Experiments were conducted in which stirrer speed
367
was varied between 350 rpm to 850 rpm while other parameters were kept constant: the
368
catalyst loading was kept at 2.5 wt%, oil-to-methanol ratio at 1:10 and reaction temperature at
369
65 °C for 90 min. Figure 13 represents the effect of stirrer speed on biodiesel yield with and
370
without addition of co-solvent. Initially, there is a significant increase in yield on increasing
371
stirrer speed. This is because the reaction mixture exists in two phases and the agitation helps
372
to intersperse oil and methanol leading to relative homogenisation and greater contact
373
between reactants. High biodiesel yield, 95%, occurred at the optimum stirrer speed 650 ppm.
374
Increasing the stirring beyond the optimum value lead to no significant increase in yield due
375
to vaporisation of methanol reducing its contact with other reactants. In each experiment, it
376
was found that the addition of co-solvent gave a higher yield. The presence of co-solvent
377
accelerates the homogenisation of the two-phase system into a single phase. Consequently, it
378
helps in higher yield of biodiesel at minimum stirrer speed.
379
Figure 13
380
3.12. Effect of co-solvent on biodiesel
381
Effect of co-solvent on biodiesel yield was observed by taking different co-solvents such as
382
toluene, and diethyl ether, hexane, tetrahydrofuran (THF) and acetone as shown in Figure 14.
383
Co-solvent to methanol molar ratio fixed at 1:1 while other factors such as methanol: oil
384
(1:10), reaction temperature (65 °C), stirrer speed (650 rpm) and catalyst loading (2.5%) were
385
kept constant. Reaction mixture exists as two phase system in which methanol exhibited
16 ACS Paragon Plus Environment
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Journal of Agricultural and Food Chemistry
386
hydrophilic nature and fish oil exhibited hydrophobic nature. This immiscibility between
387
alcohol and oil can be reduced by using co-solvents31, 32 to drive the reaction mixture towards
388
the product side. Molar ratio (methanol: oil) of reaction mixture is more important factor for
389
the production of biodiesel since transesterification process is reversible33, to shift the
390
reaction to product side we need to use more amount of methanol in reaction mixture. Instead
391
of using more amount of methanol, co-solvent was added to reaction mixture which not only
392
reduced the amount of methanol but also other factors such as reaction time reaction
393
temperature stirrer speed, etc. Among all the co-solvents, the biodiesel yield (95%) was
394
highest in the case of THF. Tetrahydrofuran (THF) facilitates the reaction mixture (oil phase
395
and alcohol phase) to more homogeneous and also it reduced the energy consumption. So, we
396
selected THF as co-solvent for the synthesis of biodiesel. Optimization of THF determined
397
and was found maximum at 1:1 (co-solvent: alcohol) as shown in Figure 15.
398
Figure 14
399
Figure 15
400
3.13. Separation and purification
401
Reaction mixture was poured into a separating funnel after completion of transesterification
402
reaction to separate biodiesel from its by-products. Biodiesel was taken out from the
403
separating funnel after clear separation through the gravity, and was washed with hot distilled
404
water. Water remained after washing was removed with rotavapour and centrifuged to
405
remove trace amount of solid particles presents in the biodiesel. Thereafter, each and every
406
characterization of biodiesel was done according to ASTM standards. Physical and chemical
407
properties of synthesized biodiesel were provided in Table 4 and found that the density was
408
reduced from 0. 0.899 (waste fish oil) to 0. 869 (biodiesel), flash point was reduced from 270
409
(waste fish oil) to 150 (biodiesel) and pour point was reduced from 13 (waste fish oil) to 17 ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
Page 18 of 44
410
1.02(biodiesel). Kinematic viscosity (at 40 °C) of was reduced 25.51 (waste fish oil) to 4.99
411
(biodiesel) since density is directly proportional to viscosity. Calorific value of synthesized
412
biodiesel was 9650 cal/g and the moisture content was found to be 0.001%. This synthesized
413
biodiesel was checked with copper strip and no corrosion was observed. Calcium oxide
414
derived from waste crab shells delivered good results for the synthesis of biodiesel when
415
compared with other catalysts which were derived from waste materials as shown in Table 5.
416
Table 4
417
Table 5
418
3.14. Reusability and leaching property of catalyst
419
Leaching effect of calcium oxide CaO derived from waste crab shells catalyst was
420
determined in synthesized biodiesel using waste fish oil. It was ratified by elemental analysis
421
using SEM/EDS analysis after completion of the reaction. It was revealed that there was no
422
change in calcium and oxygen amount.
423
conducted34 and no catalyst leaching was observed. After separation of methanol, catalyst
424
was used in transesterification reaction and found that there was no change in its activity35.
425
After washing with methanol, catalyst was reused by two manners. In first process catalyst
426
was calcined at 750˚C and reused up to 5 runs and in second process reused without
427
calcination up to 5 runs as shown in Figure 16. Calcined catalyst gave more conversion than
428
one without calcination. Consequently, it was inferred that calcination provided better
429
activity of the sites of catalyst and hence amended the biodiesel production.
430
Figure 16
431
4. CONCLUSION
432
Biodiesel was synthesized from waste fish oil through esterification and transesterification
433
reactions. A novel heterogeneous solid base catalyst (calcium oxide (CaO)) was derived
434
from waste crab shells and characterized with SEM-EDX, XRD, FTIR, and TGA/DTA.
Further examination of catalyst leaching was
18 ACS Paragon Plus Environment
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Journal of Agricultural and Food Chemistry
435
Synthesized biodiesel was characterized with the proton NMR and FT-IR. Free fatty acid
436
composition of waste fish oil was determined using GC-MS. Effect of various parameters
437
such as stirrer speed, temperature of the reaction, reaction time, and catalyst loading on
438
biodiesel conversion and yield were studied. Effect of co-solvent on biodiesel was further
439
studied by using different solvents such as toluene, and diethyl ether, hexane,
440
tetrahydrofuran (THF) and acetone. High yield 96.6% and pure biodiesel was obtained
441
when 2.5 wt% of synthesized catalyst, 1:12 oil: methanol molar ratio at 65 °C for 90min.
442
Reusability of catalyst up-to five times without loss of activity was observed. No catalyst
443
leachability was observed in transesterification reactions. The qualities of biodiesel were
444
ascertained as per ASTM biodiesel standard and obtained nearly to specification.
445
ACKNOWLEDGMENTS
446
The authors acknowledge the support of Central Instrument Facilities, Indian Institute of
447
Technology (BHU), India and also authors thankful to Institute for supporting financial
448
assistantship through the Institute Fellowship. Authors also acknowledge the financial
449
assistance from DST as DST- IBSA project (GP/LT/Chemistry/15-16-01).
450
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curcas oil into biodiesel using re-crystallized hydrotalcite. Energ. Convers. Manage. 2013, 73, 128.
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532 533
Graphical abstract
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534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551
Table 1. Physical and Chemical Properties of Waste fish oil. 23 ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
Property
Unit -
Color Acid value
ASTM Standards
mg
Page 24 of 44
Value Yellowish red
ASTM D 664
11.89
KOH/g Unsaponifiable matter
% w/w
ASTM D1065
0.78
Density at 15.5 °C
g/cm3
ASTM D 1298
0.899
Boiling point
°C
-
> 356
Cloud point
°C
ASTM D 1510
13
Saponification value
mg
187
KOH/g Pour point
°C
Kinematic viscosity, at 40 mm2/s
ASTM D 97
-1
ASTM D 445
25.51
°C Flash point
°C
ASTM D 93
270
Water content
in%
ASTM D 2709
0.009%
Iodine value
-
ASTM D 2500
110
Copper strip corrosion
-
ASTM D 130
No Corrosion observed
552 553 554 555 556 557 558 559 560 24 ACS Paragon Plus Environment
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Journal of Agricultural and Food Chemistry
561 562
Table 2. Free Fatty Acids and their Composition (%) of Waste fish oil. Sr. Retention
Compound name
Composi Correspondi
Corresponding
tion (%)
ng fatty acid
strucure
Myristic acid
CH3(CH2)12COOH
Palmitoleic
CH₃(CH₂)5CH=CH(CH₂)₇CO
methyl ester
acid
OH
Palmitic acid methyl 14.09
Palmitic acid
CH3(CH2)12COOH
Arachidonic
CH3(CH2)10(CH=CH)4COOH
time 1
17.37
Myristic acid methyl 5.51
fatty
acid
ester 2
3
19.32
19.55
Palmitoleic
acid 9.70
ester 4
21.06
Arachidonic
acid 3.21
methyl ester 5
21.25
Oleic
acid
acid methyl 11.03
Oleic acid
CH3(CH2)14CH=CHCOOH
Linoleic acid
CH3(CH2)10(CH=CH)3COOH
Stearic acid
CH3(CH2)16COOH
Eicosapentaenoic acid 19.96
Eicosapentae
CH3(CH2)8(CH=CH)5COOH
methyl ester (EPA)
noic acid
Docosahexaenoic acid 13.93
Docosahexae
methyl ester (DHA)
noic acid
Erucic
Erucic acid
ester 6
21.29
Linoleic acid methyl 3.45 ester
7
21.46
Stearic
acid
methyl 4.05
ester 8
9
10
22.77
24.33
24.66
acid
methyl 1.08
CH3(CH2)8(CH=CH)6COOH
CH3(CH2)18(CH=CH)COOH
ester 563
25 ACS Paragon Plus Environment
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Page 26 of 44
564 565
Table 3. Elemental Composition of Calcium oxide (weight% and atomic %) by EDS
566
Analysis.
567 568 569 570 571
Element Weight%
Atomic%
O
46.79
68.78
Ca
53.21
31.22
Total
100.00
572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 26 ACS Paragon Plus Environment
Page 27 of 44
Journal of Agricultural and Food Chemistry
591 592
Table 4. Physical and Chemical Properties of Waste fish oil Biodiesel.
Property
Unit
ASTM
Value
Standards -
Color Acid value
mg
Yellowish red ASTM D 664
1.78
KOH/g Density @15.5 °C
g/cm3
ASTM D 1298
0.869
Boiling point
°C
-
356
Cloud point
°C
ASTM D 1510
1.02
Pour point
°C
ASTM D 97
-1
Kinematic viscosit, at 40 °C
mm2/s
ASTM D 445
4.99
Flash point
°C
ASTM D 93
150
ASTM D613
Cetane number Calorific value
cal/g
ASTM D 4809
9650
Water content
in%
ASTM D 2709
0.001%
Copper strip corrosion
-
ASTM D 130
No Corrosion observed
593 594 595 596 597 598 599 600 27 ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
Page 28 of 44
601 602 603 604
Table 5 Represents the Summary of Different Kinds of Waste Catalysts used in the
605
Synthesis of Biodiesel. Cataly st
CaO CaO CaO
CaO CaMg( CO3)2 KAl(S O4)2 K2O βCa3(P O4)2 Hydrox yapatite
Waste material
Reaction conditions
Catalyst amount (wt.%) Crab shells 2.5 Snail Mollusc 2 shells Exoskeleton 4 (Pila globosa) Mollusc shells Chicken egg 3 shells Dolomite 3
Methanol to oil molar ratio 12:1 6:1
Reaction temperat ure (°C) 65 60
10:1
Alum
Conversion (C) or Yield Reaction (Y) time (h) 1.5 8
Y = 96.6 % C = 99.58 %
60
5
C = 97.8 %
9:1
65
3
Y = 95 %
6:1
67.5
3
Y = 91.8 %
7.09
18:1
170
12
Y = 92.5 %
Coal fly ash 15 loaded KNO3 Rohu fish 1.01 (Labeo rohita) bone Sheep bone 20
15:1
70
8
C = 87.5 %
6.27:1
70
5
Y = 97.7 %
18:1
65
4
C = 96.78 %
606 607 608 609 610
28 ACS Paragon Plus Environment
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Journal of Agricultural and Food Chemistry
611 612 613
614 615
Figure 1. NMR Spectrum of Biodiesel synthesized from waste fish oil
616 617 618 619 620 621 622 623 624 625 626
29 ACS Paragon Plus Environment
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Page 30 of 44
627 628 629
630 631 632
Figure 2. GC-MS analysis and identification of fatty acid methyl ester
composition in
waste fish oil
633 634 635 636 637 638
30 ACS Paragon Plus Environment
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Journal of Agricultural and Food Chemistry
639 640 641
642 643
Figure 3. FT-IR Spectrum of synthesized biodiesel from waste fish oil
644 645 646 647 648 649 650 651 652 653 654 655
31 ACS Paragon Plus Environment
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Page 32 of 44
656 657 658
659 660
Figure 4. XRD patterns of calcium oxide derived from waste crab shells
661 662 663 664 665 666 667 668 669 670 671 672
32 ACS Paragon Plus Environment
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Journal of Agricultural and Food Chemistry
673 674 675
676 677
Figure 5. SEM of calcium oxide catalyst derived from waste crab shells
678 679 680 681 682 683 684 685 686 687 688 33 ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
Page 34 of 44
689 690 691 692
693
Figure 6. EDX spectrum of calcium oxide derived from waste crab shells
694 695 696 697 698 699 700 701 702 703 704
34 ACS Paragon Plus Environment
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Journal of Agricultural and Food Chemistry
705 706
707 708
Figure 7. TGA/DTA of uncalcined waste crab shells
709 710 711 712 713 714 715 716 717 718 719 720
35 ACS Paragon Plus Environment
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721 722
723 724
Figure 8. FT-IR Spectrum of calcium oxide derived from crab shells
725 726 727 728 729 730 731 732 733 734 735 736
36 ACS Paragon Plus Environment
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737 738
739 740
Figure 9. BET of calcium oxide (CaO) derived from waste crab shells
741 742 743 744 745 746 747 748 749 750 751 752 753 37 ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
Page 38 of 44
754
755 756
Figure 10. Effect of catalyst loading on biodiesel yield
757 758 759 760 761 762 763 764 765 766 767
38 ACS Paragon Plus Environment
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Journal of Agricultural and Food Chemistry
768 769
Figure 11. Effect of reaction temperature on biodiesel yield
770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 39 ACS Paragon Plus Environment
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Page 40 of 44
786 787 788 789 790 791 792 793 794 795 796 797
Figure 12. Effect of reaction time on biodiesel yield
798 799 800 801 802 803 804 805 806 807 808 809
40 ACS Paragon Plus Environment
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810 811
Figure 13. Effect of agitation speed on biodiesel yield
812 813 814 815 816 817 818 819 820 821 822 823 824
41 ACS Paragon Plus Environment
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825 826
Figure 14. Represents the effect of co-solvents on biodiesel yield
827 828 829 830 831 832 833 834 835 836 837 838 839
42 ACS Paragon Plus Environment
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840 841
Figure 15. Optimization of THF (Co-solvent) with Methanol (Solvent)
842 843 844 845 846 847 848 849 850 851 852 853 854 855 856
43 ACS Paragon Plus Environment
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857 858
Figure 16. Reusability of catalyst with and without calcination
44 ACS Paragon Plus Environment