TRANSESTERIFICATION OF VEGETABLE OILS FOR BIODIESEL SYNTHESIS USING MIXED OXIDES AS CATALYSTS.

Transcription

1 TRANSESTERIFICATION OF VEGETABLE OILS FOR BIODIESEL SYNTHESIS USING MIXED OXIDES AS CATALYSTS. 3.1 INTRODUCTION The increased demand of the diesel fuel has resulted in the scarcity of fossil reserves [1]. Due to various environmental issue like global warming and green-house effect biodiesel synthesis is attaining considerable attention now-a-days from the renewable biological sources like plant based oils- edible, non-edible, animal fats etc. as these biological sources have great potential to substitute petroleum diesel [2]. Biodiesel is the next possible substitute of the conventional diesel as it has many merits over conventional fuel like it is biodegradable, non-toxic, clean burning liquid fuel which reduces emissions of CO, NO2, SO2 etc, particulate matters, unburned hydrocarbons and volatile organic compounds. [3,4,5] Biodiesel can also be called as a future realistic fuel because of its environmental and ecological benefits. Moreover the biodiesel produced from these vegetable oils can be used directly without any requirement of engine modification as its properties are also very close to petroleum diesel like viscosity, flash point, cloud point, cetane no. etc. [6,7] Various edible oils are being used as feedstocks for the production of biodiesel like soyabean oil, sunflower oil, palm oil, rice bran oil etc. Because of higher molecular mass and chemical structure the viscosity of vegetable oil is times higher than that of the mineral diesel. This higher viscosity leads to unfavourable characteristics of pumping and spraying and causes various serious problems in engines like incomplete combustion, poor fuel atomization, and carbon deposition on the injector and valve seats leading to engine fouling. [8-11]. To improve the quality of biodiesel it is mixed with diesel as is possible and recommended. But the quality of the blends i.e biodiesel and diesel should be controlled as their difference in the chemical nature may cause difference in physiochemical properties and simultaneously affect the engine performance and the pollutant emissions. [12] The high visocity of the biodiesel causes highly noxious effect on the 85

2 operation of the injection systems which is relatively and relevantly minimised by the blends of biodiesel and diesel. [13] To reduce the viscosity of vegetable oils various methods are being used like microemultions, thermal cracking, blending with diesel, and trans-esterification. Among them transesterification is the most commonly used. Transesterification is a chemical process in which an ester is reacted with an alcohol in the presence of a catalyst to produce a new ester and a new alcohol i.e a primary alcohol reacts with a triglyceride to produce methyl esters and glycerol as a by-product in the presence of a catalyst as shown below. [11, 13-19] Figure 3.1: General Transesterification Reaction Where, R1, R2, R3 are long fatty acid chains. The catalyst used can be homogeneous or heterogeneous catalyst. As stated above that the transesterification reaction can be catalysed both homogeneously and heterogeneously. Homogenous catalyst includes acids and alkalis. Commonly used acids are Hydrochloric acid, sulphuric acid, sulphonic acid etc and are called acid catalysed transesterification. Commonly used alkalis are sodium and potassium hydroxides and are called base catalysed reactions which proceeds faster and are better in performance than the acid catalysed transesterifications. [13, 20-21] There are advantages of using heterogeneous catalysts over the homogeneous catalysts among 86

3 which product separation, large amounts of waste water produced and reusability of the catalyst predominates, as the heterogeneous catalyst reduces the cost of production. Therefore a variety of heterogeneous catalysts have been investigated developed and used in labs for the synthesis of biodiesel including zeolites, hydrotalcites and mixed oxides. [22] Recently, Singh et.al [23] have reported potassium impregnated mixed oxides of La and Mg prepared by co-ppt method for the transesterification of used cotton seed oil with methanol resulting 96% conversion with a molar ratio of methanol to oil 1:1.54, catalyst amount used 5 wt%, within 20 minutes at 65 0 C. Lee et.al [24] have reported CaO-ZnO and CaO-La2O3 as solid base heterogeneous catalyst for the transesterification of jatropha oil with the highest conversion of 97.03% and 96.27% respectively with a molar ratio of 1:26 and 1:30 oil to methanol, with a catalyst loading amount of 3.65% and 2.02%, in 4 and 3.84 hours at C and C respectively. Istadi et.al [25] have reported K2O/CaO-ZnO as a solid base heterogeneous catalyst prepared by co-ppt method and loading of K2O was done by impregnation method. The synthesised catalyst was used for the transesterification of soybean oil resulting in 81.08% yield with a molar ratio of methanol to oil 15:1, at 6 wt% catalyst loading in 4 hours at 60 0 C. Xie et.al [26] have reported the synthesis of a solid base heterogeneous catalyst loading KNO3 on Al2O3. The best results were 87% yield obtained at 15:1 methanol to oil ratio with a catalyst loading amount of 6.5% in 7 hours. Taufiq-Yap et.al [27] has reported Ca based mixed oxides CaMgO and CaZnO for the transesterification of jatropha oil. The conversion was more than 80% with a methanol to oil ratio of 15:1 with a 4wt% catalyst loading in 6 hours at 338 K. These catalysts were reused 4 times maintaining the conversion rate of more than 80%. In the present chapter we are going to discuss the transesterification reaction i.e the synthesis of biodiesel using mixed oxides as the heterogeneous solid base catalysts. There are various parameters affecting the transesterification reaction like the 87

4 temperature, time, methanol to oil ratio, catalyst type, catalyst amount and stirring speed. [28] The above described factors are also discussed in this chapter as they have a great impact and influence on the reaction. Furthermore, the various physiochemical properties of the vegetable oils and the biodiesel are also discussed according to the ASTM standards. The GC-MS of various biodiesel products here also been discussed in this chapter. In the present investigation we have synthesized the biodiesel products within 2 hours reducing the time of reaction from 6-8 hours with high yields according to the ASTM standards. 3.2 EXPERIMENTAL SECTION Materials: The chemicals used were procured from laboratory and analytical grade chemical suppliers as listed below. The oils were obtained from commercial sources. Chemicals KOH Alumina Iron Oxide Calcium Oxide Magnesium Oxide Zinc Oxide Methanol Company Fisher Scientific Qualigens fine chemicals Fisher Scientific Central Drug House Central Drug House Fisher Scientific Fisher Scientific Oils Used Company Soyabean Fortune Sunflower Palm Rice Bran Groundnut Mustard Kacchi Ghani Jatropha Expelled Oil 88

5 3.2.2 Methods used for the characterization of biodiesel Starting materials and solvents were obtained from Laboratory chemical suppliers and were used without further purification. Products i.e the biodiesel was characterized by GC and the physiochemical properties of the biodiesel were characterized according to the ASTM standards. GC analyses were recorded on Shimadzu GCMS QP 2010 plus (Japan) Column used Rtx-5 sill GC-MS and mass range Scanned 5amu to 350 amu, GC-MS purity is reported by area percentage (%). The various physiochemical properties were also characterized according to the ASTM D6791 standards as it identifies those parameters which a biodiesel (B 100) should meet before being used as a pure fuel or a blended fuel with petroleum based diesel [41]. Some of them are mentioned below: a Flash point and Fire point The flash point is the key property that determines the flammability of the fuel. It measures the tendency of fuel to form a flammable mixture when comes in contact with air. Its value is helpful for safety and shipping regulations in categorizing the flammable and combustible materials. It also indicates the presence of volatile and flammable materials present in a nonflammable material. The flash point predicts the possibility of fire hazards during storage, handling and transportation. The flash point is defined as the minimum temperature at which an ignition source applied causes the vapors of the samples to ignite. The fire point is defined as the minimum temperature at which an ignition source applied causes the vapors of the samples ignite continuously for at least 5 seconds. The fire point is generally C higher than the flash point. The standard method for measuring the Flash Point of biodiesel is D 93 and was measured using Cleveland open cup test unit ACO-7. The flash point is taken using following method: The sample is introduced in the cup of the apparatus till the filling mark and is set and maintained at the specified temperature. The temperature is increased to about C per minute. 89

6 After a specified time, when the temperature increases till 60 0 C a test flame is applied automatically for 2 seconds after every degree rise in temperature and then an observation is made to when the flash occurs. That temperature at which the vapour samples begin to ignite is recorded as flash point of the biodiesel. The sample is further heated at a rate of 1 0 C and the test flame is introduced after every 1 0 C rise in temperature. The temperature at which a clear and distinguishable blue flash is observed is recorded as a fire point b Density and Specific Gravity This is an important factor in the field of petroleum products as they are sold in terms of volume and mass converted via density. Hence, density is defined as mass per unit volume at a specific temperature. Specific Gravity is defined as ratio of the mass of specified volume of certain liquid to the mass of equal volume of pure water at the same temperatures. API Gravity expresses relative masses of biodiesel and was measured using Anton Parr Density meter according to the ASTM D c Kinematic Viscosity This is the most important factor of fuels as it affects the flow of the fuels i.e its fluidity. The kinematic viscosity is defined as the resistance to flow of a fluid against gravity and was measured using Kinematic viscometer according to the ASTM D445. The CGS unit is one Stoke represented as St and its SI unit is one centistoke represented as cst. The fuels having high viscosity leads to poor atomization and less accurate operations of fuel injectors and spray. The viscosity is measured using the following procedure: First fill the bath with water and allow it to heat till 40 0 C. After that fill the viscometer with the fluid whose viscosity is to be measured and place it inside the bath. Now allow the fixed volume of fluid to flow through the calibrated capillary of the viscometer against gravity along with a driving head in a controlled temperature. The time is measured or recorded in seconds by the help of a stop watch. 90

7 Hence, kinematic viscosity is the product of measured time of flow multiplied by the calibration constant of the viscometer and is measured in terms of cst d Cloud Point and Pour Point This is also among one of the important properties of the biodiesel as it describes the fuels operability at lower temperatures showing its implications in cold weather. The cloud point is defined as the temperature at which the cloud of wax crystals appears first in liquids when cooled in controlled temperatures and conditions. At lower temperatures the fuel becomes gel type which is difficult to pump therefore at low temperatures in comparision to petrodiesel biodiesel is less suitable or nonrecommendable. The pour point can be defined as the temperature below which the fuel ceases to flow under controlled conditions and temperatures. Under certain applications these values show the fuel utility at the lowest temperatures. Further operating the fuel below these point results in the fuel filter clogging due to the formation of the wax crystals. They indicate the suitability of the fuel in cold conditions. The cloud point and pour point was measured using Tanaka Hoskins cloud point tester MPC 102 according to the ASTM D The summary of the method of determination is as follows: Firstly the fuel sample is filled inside till the precision mark of the tube in the apparatus at a constant rate. Optical detectors are continuously detecting the fuel samples. Sample is allowed to cool in specified conditions and is examined after every 1 0 C fall of temperature. As the haziness or the cloudiness in the fuel is witnessed simultaneously the temperature recorded is the cloud point. Further cooling is continued and examined after every 3 0 C fall in temperature. When the fuel ceases to flow and shows no movement then that temperature is recorded as pour point e Carbon Residue This property of fuel holds importance as it enumerates the tendency of forming carbonaceous deposits under the degradation conditions. On increasing the temperature 91

8 certain amount of carbon is deposited in a machine which is intolerable. The clogging of the fuel injectors in Internal Combustion Engine and the air compressors due to deposition of carbon residue result in reducing the working efficiency of the machines. The carbon residue is defined as the measure of the quantity of remnants of the residual carbon remaining after combustion. The carbon residue was measured by Rams bottom carbon residue apparatus [42] according to the ASTM D The summary of the procedure is as follows: Firstly the temperature of the apparatus is aggravated to C. The temperature of the furnace is set at C. Now weigh the blank crucible. After weighing the crucibles add to it 4 gms of the fuel sample. Now put it in the furnace for 20 minutes. After that take out the crucible and weigh again. The difference in the weight gives the % reduction or carbon present in the sample. initial final % reduction 100 Initial f Acid Number The acid no is defined as no. of mg of KOH required to neutralize free acids present in 1gm of oil. The acid value of biodiesel according to the ASTM standards should be less than 0.5 mg KOH/gm. The acid values of the oils as well as of biodiesels were calculated using the AOCS official method Ca 5a-40 as discussed by Sarma et.al [42]. The chemicals requires to carry out the acid value test is freshly prepared caustic NaOH with 0.25 N and phenolphthalein indicator. The summary of the procedure is as follows: First of all the sample is weighed (0.5gms) Now, dissolve the weighed sample in 10 ml ethanol and shake it well. To it add 4-5 drops of phenolphthalein. Titrate it with N/10 KOH solution. End point is changes from colourless to light pink. 92

9 Note the readings when the colour changes to pink. Calculations A.V ml of alkali N 28:2 Weight of sample g Iodine Number The iodine value is defined as mass in grams of iodine that can be added to 100 grams of the sample. The iodine value determines the degree of unsaturation i.e. the iodine value indicates the no. of double bonds present in the sample. Higher the value, higher is the no. of double bonds present in it. Iodine value only describes the relative conc. of unsaturation and not the position or distribution of double bonds within the molecule i.e it is independent of the nature of double bonds within the molecule. [43] According to AOCS official method Cd 1-25 as discussed by Sarma et.al [42] the iodine values of the oil and the biodiesel were determined using the freshly prepared Wijs Solution and the starch indicator. The summary of the procedure is as follows: First weigh the sample gms. Now dissolve in 20 ml CHCl3. To it add 20 mil of wiji s solution. Keep the flask for incubation in dark for 30 mins. Add 10 ml of 15% KI solution to it. Now titrate it with the freshly prepared N/10 hypo solution till a pale yellow solution appears. To that solution add 1 ml of starch indicator violet or dark blue colour appears. Again titrate with hypo solution till the blue colour appears to colourless and note down the readings. 93

10 Calculations - The iodine value [(B-S) N 12.69] Weight of sample Where, B = titration of blank, S = the titration of sample, N = normality of sodium thiosulphate solution. 3.3 Transesterification Reaction 3.3. A. General Procedure The transesterification of vegetable with methanol was carried out in a batch reactor consisting of a 500 ml three necked round bottom flask equipped with a refluxing condenser and a temperature controlled magnetic stirrer. The reactor was initially filled with the measured amounts of the catalyst and the methanol was placed on the magnetic stirrer at room temperature and stirred for 10 minutes so that the catalyst was homogeneously mixed in methanol. After this the sunflower oil and the round bottom was equipped with the water cooled condenser and temperature was raised to 65 0 C. The transesterification reaction was performed for 90 minutes under constant stirring. After the reaction was completed the product was transferred in the separating funnel for 24 hours. After 24 hours two different layers were seen in the separating funnel. The lower glycerol layer (by-product of the reaction) was decanted off and further purified and the above biodiesel layer was separated and washed gently with water to remove the residual catalyst or soap traces if any, then dried and sent for the GC Analysis B Transesterification of Jatropha Curcas Oil The transesterification of Jatropha oil is performed in two steps due to its high FFA value which is pretreated to reduce the FFA values. The first step of acid esterification is done by the method used by C.C. Liao [64] The second transesterification step is done according to the above described method General Procedure. All the reaction conditions were similar except the time was 150 minutes and the catalyst loading amount was 3 wt%. 94

11 3.4 C Transesterification of Sunflower Oil using Oxides (CaO, MgO, Al2O3, Fe2O3, ZnO) as a catalyst The transesterification reaction of sunflower oil was carried out with oxides (CaO, MgO, Al2O3, Fe2O3, ZnO) using the general procedure as described above. Table 3.1: Yields of Biodiesel synthesized from Sunflower Oil using Oxides as a catalyst Sl. No. Catalyst Used Reaction Conditions Yield % 1. Al2O CaO Temp = 65 0 C, MgO M:O =15: Fe2O3 Time = 90 minutes ZnO Cat load = 1.5 wt% 24 Disadvantages of using oxides as catalysts: 1. Yields of biodiesel produced are low. 2. Recovery of the catalyst is also low. 3.4 D Transesterification of Sunflower Oil using KOH as a catalyst The Treansesterification of Sunflower oil was carried out with the General Procedure as described above using KOH as a catalyst. The results are given in table below: Table 3.2: Yields of Biodiesel synthesized from Sunflower Oil using KOH as a catalyst Sl. No. Catalyst Used Reaction Conditions Yield % 1. KOH Temp = 65 0 C, M:O =15:1, Time = 90 Minutes, Cat load = 1.5 wt%

12 Disadvantages of using KOH as a catalyst: 1. Separation of the Product is difficult. 2. No recyclability and reusability of the catalyst. 3. Saponification occurs i.e formation of soaps takes place. 4. Low yields of biodiesel are obtained. 5. Use of this catalyst enhances the cost of production. 6. Large amount of water is used for purification of the product. Conclusion: As the yields of biodiesel synthesized using only oxides as catalysts was low ranging from percent and the recovery of the catalyst was also low. Also using KOH as catalyst for biodiesel synthesis gave biodiesel yields of 65.8% but had various disadvantages using KOH as catalyst as described above increased the cost of production of biodiesel. Hence, to overcome all the above disadvantages as well as to obtain better yields of biodiesel we had to load KOH over various oxides to synthesise mixed oxides and use them as heterogeneous basic catalysts for biodiesel preparation. 96

13 Figure 3.2: Reaction Set Up of the Laboratory Figure 3.3: Biodiesel synthesized from 5 types of Oil 97

14 3.4 Transesterification Reaction of Sunflower Oil using KOH/Al2O3 as a catalyst Procedure A The trans-esterification of sunflower oil was carried out in a batch reactor consisting of a 500 ml RB flask two or three necked equipped with a reflux condenser and a magnetic stirrer. To it was added KOH/Al2O3 catalyst and methanol in different ratio s and was stirred for 10 minutes. After 10 minutes when the catalyst was mixed in methanol homogeneously to it was added sunflower oil in different ratios. The reaction was carried out at various temperatures ranging between C, time between 1-5 hours, catalyst loading ratio of 0.5wt% to 5 wt%, stirring between rpm, methanol to oil ratio 3:1 to 24:1, catalytic activity of KOH loading effect on oxides on the transesterification reaction between 5 to 50 %. We studied all the above parameters to discover the optimization condition of the reaction. After the reaction was completed the product was transferred to the separating funnel and kept for 24 hours for separation. After 24 hours two different layers were observed in the separating funnel. The lower layer is glycerol layer which is the by-product of biodiesel was decanted off and purified and the above layer was the biodiesel layer was separated and washed gently with water, dried and sent for the GC analysis. After the detailed study of all the above parameters for the trans-esterification of sunflower oil using KOH/Al2O3 catalyst we concluded that the best yields of 98% were obtained with 35% KOH loading on Al2O3 with a molar ratio of methanol to oil 15:1 at 1.5wt% catalyst loading with 300 stirring speed at 65 0 C in 90 minutes. Results are summarised in table as given below: Table 3.3: Yields of Biodiesel synthesized from Sunflower Oil using KOH/Al2O3 as a catalyst Sl. Catalyst Used Loading % Reaction Conditions Yield % No. of KOH 1. KOH/Al2O Temp = 65 0 C, M:O =15: Time = 90 minutes Cat load = 1.5 wt% StirringSpeed = 300 rpm Refluxing

15 3.4.2 Transesterification Reaction of Sunflower Oil using KOH/CaO as a catalyst. The trans-esterification of Sunflower oil was carried out as described in procedure A with all the varying parameters studied for the optimization of the reaction. After the separation and purifying process the product was sent for GC analysis. After the detailed study of the parameters it was concluded that the best results were carried out with 20% KOH loaded on CaO. The Yields obtained were 99% with methanol to oil ratio of 15:1 at catalyst loading of 1.5wt% with a stirring speed of 300 rpm at 65 0 C in 60 mins. Results are summarised in the following table: Table 3.4: Yields of Biodiesel synthesized from Sunflower Oil using KOH/CaO as a catalyst Sl. Catalyst Used Loading % Reaction Conditions Yield % No. of KOH 1. KOH/CaO Temp = 65 0 C, M:O =15: Time = 60 minutes Cat load = 1.5 wt% StirringSpeed = 300 rpm Refluxing Transesterification Reaction of Sunflower Oil using KOH/MgO as a catalyst. The transesterification of sunflower oil with methanol using KOH/MgO as a catalyst was carried out according to the procedure A with all the varying parameters studied for the optimization of the reaction. After the separation and purifying process the product was sent for GC analysis. After the detailed study of the parameters it was concluded that the best results were carried out with 20% KOH loaded on MgO. The Yields obtained were 99% with methanol to oil ratio of 15:1 at catalyst loading of 1.5wt% with a stirring speed of 300 rpm at 65 0 C in 90 mins. Results are summarised in the following table: 99

16 Table 3.5: Yields of Biodiesel synthesized from Sunflower Oil using KOH/MgO as a catalyst Sl. Catalyst Used Loading % Reaction Conditions Yield % No. of KOH 1. KOH/MgO Temp = 65 0 C, M:O =15: Time = 60 minutes Cat load = 1.5 wt% StirringSpeed = 300 rpm Refluxing Transesterification Reaction of Sunflower Oil using KOH/Fe2O3 as a catalyst. The transesterification of sunflower oil with methanol using KOH/Fe2O3 as a catalyst was carried out according to the procedure A with all the varying parameters studied for the optimization of the reaction. After the separation and purifying process the product was sent for GC analysis. After the detailed study of the parameters it was concluded that the best results were carried out with 15% KOH loaded on Fe2O3. The Yields obtained were 99.5% with methanol to oil ratio of 15:1 at catalyst loading of 1.5wt% with a stirring speed of 300 rpm at 65 0 C in 60 mins. Results are summarised in the following table: Table 3.6: Yields of Biodiesel synthesized from Sunflower Oil using KOH/Fe2O3 as a catalyst Sl. Catalyst Used Loading % Reaction Conditions Yield % No. of KOH 1. KOH/Fe2O Temp = 65 0 C, M:O =15: Time = 60 minutes Cat load = 1.5 wt% StirringSpeed = 300 rpm Refluxing

17 3.4.5 Transesterification Reaction of Sunflower Oil using KOH/ZnO as a catalyst. The transesterification of sunflower oil with methanol using KOH/ZnO as a catalyst was carried out according to the procedure A with all the varying parameters studied for the optimization of the reaction. After the separation and purifying process the product was sent for GC analysis. After the detailed study of the parameters it was concluded that the best results were carried out with 15% KOH loaded on ZnO. The Yields obtained were 98.5% with methanol to oil ratio of 15:1 at catalyst loading of 1.5wt% with a stirring speed of 300 rpm at 65 0 C in 60 mins. Results are summarised in the following table: Table 3.7: Yields of Biodiesel synthesized from Sunflower Oil using KOH/ZnO as a catalyst Sl. No. Catalyst Used Loading % of KOH Reaction Conditions Yield % 1. KOH/ZnO Temp = 65 0 C, M:O =15: Time = 60 minutes Cat load = 1.5 wt% StirringSpeed = 300 rpm Refluxing After studying the various parameters of all the catalysts with the sunflower oil, all the optimizations of the reaction conditions were discovered. Different oils with methanol and KOH loaded on Oxides (with best loading %) as catalysts were reacted under optimized conditions. The biodiesel samples maintained their fuel properties according to the ASTM standards. The detailed results are given below in table: 101

18 Table 3.8: Comparative Yields of Biodiesel synthesized from various oils using best ratios of different mixed oxides. Sl. No Catalyst Used Loadin g % of KOH SBO a Y (%) PO b Y (%) RBO c Y (%) GDO d Y (%) MO e Y (%) JCO f Y (%) 1. KOH/ Al2O KOH/CaO KOH/MgO KOH/Fe2O KOH/ZnO Reaction Conditions: Temp 65 0 C, Methanol to Oil ratio- 15:1, Stirring speed 300 rpm, Catalyst Loading wt%, Time 90 minutes with KOH/Al 2O 3 60 minutes with KOH/CaO, KOH/MgO, KOH/Fe 2O 3, KOH/ZnO. Jatropha Oil Time 2.5 hours, Catalyst loading 3 wt%. Where, Y (%) Yield %, a Soyabean Oil, b Palm Oil, c Rice Bran Oil, d Groundnut Oil, e Mustard Oil, f Jatropha curcas Oil. 3.5 Recyclability of the Catalyst The catalysts were recycled using the filtration process. The recycled catalysts were again sent for XRD analysis to determine the change in the structure of the surface of the catalyst if any. After the XRD analysis it was clear that the Catalysts were stable and maintained their structure as well as yields even after 4-5 runs. The discussion is as follows: KOH/Al2O3 The Fresh KOH/Al2O3 loading of 35% shows diffraction peaks at 2 angles 39.4 and 50.6 which confirmed the presence and increase in K2O phase. Along with the K2O phase a new phase was also observed at 30,31,34,36,40,44 and 52 positions which were ascribed to compound containing potassium and aluminium elements i.e. Al-O-K these results agree with reported values. The XRD of the catalyst used 4 times showed K2O diffraction peaks indicating the catalyst to be stable. Only the intensities of the peaks ascribed to K2O got slightly decreased as shown in figure below. 102

19 Figure 3.4: XRD Spectra of Reused 35% KOH/Al2O KOH/CaO The fresh KOH/CaO with KOH loading of 20% exhibited 2 angles at 38.6, 51.5 and 55.6 which were ascribed to K2O crystal phase which was the main active site of the catalyst. The five times reused KOH/CaO 20% catalyst exhibited the diffraction peaks 2 angles at 39.1,51 and 55.9 indicating the stability and sustained activity of the catalyst even after 5 cycles as shown in figure 3.5 below. Figure 3.5: XRD Spectra of reused 20% KOH/CaO KOH/Fe2O3 This 15 % KOH/Fe2O3 exhibited the diffraction peaks at 2 angles at 31.6, 39.6, 58.0, 62.8 which can be ascribed to K2O as the surface of the catalyst increases along with the 103

20 crystallinity of the structure. The five times re-used 15 % KOH/Fe2O3 exhibited the peaks of K2O at 31.6, 39.6, 57, 58 maintaining the stability of the catalyst and its catalytic activity. The XRD spectra as shown in figure 3.7 below. Fig 3.6: XRD Spectra of Reused 15% KOH/Fe2O3 KOH/ZnO As the loading % of KOH was increased from 10 to 15 % an increase in the order of the structure and the crystallinity was observed as the diffraction peaks became intense exhibiting the 2 angles at 30.8, 37.3, 38.5, 39.5, 51.8, 53.3, 55 and 57.3 which can be ascribed to the peaks of K2O. The XRD peaks of the 5 times reused catalyst exhibited the diffraction peaks 2 angles at 39.8, 41.1, 56.8 and 63.1 can be ascribed to the K2O peaks indicating the stability of the catalyst except that the intensities of the catalyst decreased slightly. The XRD spectra as shown in figure 3.7 below. Fig 3.7: XRD Spectra of Reused 15% KOH/ZnO 104

21 3.6 Result and Discussions Transesterification Parameters Optimization There are various reaction variables which influence the transesterification reaction i.e the conversion of Oils to Biodiesel. Hence all such reaction variables were examined, among them the important ones are the effect of molar ratio of methanol to oil, effect of reaction temperature, time, catalyst loading %, stirring effect, and recyclability of the catalyst. So, all these optimization parameters are investigated in detail and their effects on biodiesel yields are as follows: a. Effect of Temperature The effect of reaction temperature is an important optimization parameter as it influences the reaction rate as well as biodiesel yield as intrinsic rate constants are the strong functions of temperature [29]. Generally, the reaction is conducted at atmospheric pressure close to the boiling temperature of methanol [30]. The effect of temperature on the yield of methyl esters is shown in the figure given below. The fig. states that there is a gradual increase in the yield of biodiesel as the temperature is increased from 50 to 65 0 C. The maximum yield of 98% with KOH/Al2O3, 99% with KOH/CaO and KOH/MgO, 99.5 with KOH/Fe2O3 and 98.5 with KOH/ZnO were seen. As the transesterification reaction is endothermic in nature therefore large amount of heat is required for the synthesis of biodiesel. The rate of reaction increases with increase in temperature. On further increasing the temperature from 65 0 C the yield of biodiesel starts decreasing. The reason behind it is that methanol vaporises and hence lack of sufficient quantity of methanol reduces the biodiesel yield and secondly the polarity of the methanol decreases with the increase in temperature [31] It states that at lower temperatures the yields of methyl esters is lower and increase in the temperature influences the yields of methyl esters in a positive direction. [10] Several researchers agree to this view. [32-34] On further increasing the temperature from 65 0 C the methyl ester yields starts decreasing and then becomes almost constant as the evaporative loss of methanol is more than its enhancement of miscibility or its contact probabilities in oils. [35] Thus the optimal temperature for the transesterification of various oils was found to be 65 0 C. 105

22 Figure 3.8: Effect of temperature on yields of biodiesel 106

23 b. Effect of Time- This optimization parameter has direct effect on the yields of biodiesel [35]. The dependence of FAME yields on reaction time was investigated. To study the effect of time on the yields of methyl esters the reactions were conducted between 1 hour to 5 hours. The biodiesel yields were increased with increase in the reaction time. [35] As seen in the fig. below that the biodiesel yields increases as reaction time increases from 1 to 1.5 hour. On further increasing the reaction time the biodiesel yields first remains almost constant because of near equilibrium conversion then gradually starts decreasing. The best FAME yields obtained were at 1.5 hours. For 1 hour the yield was low and after 1.5 hours of the reaction the yields obtained were almost constant and finally decrease till 5 hours. The results are depicted in figure below states that the transestrification reaction is strongly dependent on this Optimization parameter, as in beginning of the reaction it was slow which may be due to the miscibility and dispersion in between the two phases of methanol and oil. In the time range of 1 hour to 1.5 hour the FAME yields increased rapidly. On further increasing the time from 1.5 hour resulted to reduction in FAME yields because of the transesterification reaction going in backward direction as a result the formation of esters decreases thus enhancing more fatty acids to form soaps. [36-38] So, the optimum reaction time obtained was 1.5 hour. Figure 3.9: Effect of Time on Biodiesel Yield 107

24 c. Influence of wt% of KOH loading on biodiesel yield- The influence of KOH loading on Oxides and their effect on biodiesel yields was also investigated. The study of effect of loading % of KOH on oxides a series of catalysts were prepared by varying the loading % of KOH from 15, 20,25,30,35,40 and 50% as shown in figure 3.10 given as below. When the loading % of KOH was 5 and 10% then the KOH got dispersed from the support and hence the yields of biodiesel were low. As the loading % of KOH was increased from 10 to 15 % the yield in the biodiesel production was also increased. The biodiesel yields of 15% KOH/Iron Oxide and 15% KOH/ZnO gave highest yields of 99.5 and 98.5% respectively. On further increasing the KOH loading % from 15 to 20 % the highest yield of biodiesel obtained were 99% with 20% KOH/MgO and 20% KOH/CaO and the best results obtained from alumina support was of 35% loading of KOH which yielded 98% biodiesel. The reason behind the high catalytic activity and basicity was that on loading the KOH% on the support a new phase of K2O was observed and simultaneously the yield of biodiesel was increased. On further increasing the loading % of KOH a new phase of X-O-K is observed (where X is Metal oxide). On further increasing the loading % of KOH on support, decrease in the yields of biodiesel was observed. This may be due to the agglomeration of excess KOH phase which covered the active basic sites of the catalyst due to which the surface area of the catalyst was decreased simultaneously lowering its catalytic activity. [7] Figure 3.10: Effect of KOH loading on various oxides 108

25 d. Influence of molar ratio of Methanol to Oil The molar ratio of methanol to oil is one of the important parameter which affects the yield of FAMEs and simultaneously the cost of biodiesel. The stoichiometric ratio of the methanolysis is three moles of methanol to one mole of oil. But practically more stoichiometric ratio of methanol to oil is required to promote the reaction towards the completion and synthesize more FAMEs and drive the reaction in the positive direction. [26] The reason behind it is that by adding or introducing excess amount of methanol the equilibrium shifts towards the right hand side improving the yield of biodiesel. The effect of the influence of molar ratio of methanol to oil was studied and as depicted in fig. below, the biodiesel yield increased considerably with the increase in the loading methanol molar ratio. The maximum biodiesel yields were obtained with a molar ratio of 15:1. The biodiesel yield increased with the increasing molar ratio from 6:1 to 15:1. Beyond this molar ratio of 15:1 on further addition of excess methanol had no significant effect on the yields or production of biodiesel. The reason to this is that as the methanol content is increased the catalyst content is decreased. Secondly, excess methanol enhances the solubility of methanol in glycerol which creates the separation issues of glycerol. It also promotes emulsification of the product because of the polar hydroxyl group present in methanol. [44-46] So on further increasing the molar ratio from 15:1 to 24:1 had no significant effect on the biodiesel production yield. Hence, we can conclude from the figure 3.11 as given below that an excess methanol feed is effective to elevate the FAME yields to a certain extent after that it shows no significant changes and hence the optimum molar ratio found through our experimental investigations of methanol to oil was 15:1. Many researchers support to this view. [26, 38-39] Figure 3.11: Influence of molar ratio of Methanol to Oil 109

26 e. Influence of catalyst loading ratio on biodiesel yield- The catalyst loading % in the reaction plays an important role as its high and low quantities directly affect the reaction and simultaneously the biodiesel yields. If the catalyst loading amount is high than the required amount than the slurry becomes viscous and faces the mixing problems as a result demands a high power consumption to overcome the mixing problems. And if the amount of catalyst loading is low than the required amount then the desired biodiesel yield was not produced. Hence, to avoid the above two problems the optimum catalyst loading amount was to be studied. Therefore the amount of catalyst was investigated in the transesterification reaction with oils varied in the range of 0.5 wt% to 4 wt%. The results depicted that the reaction is strongly depended on the catalyst applied as shown in figure 3.12 as given below. When the doses were increased from 0.5 to 1.5% the yield of biodiesel also increased above 98% indicating no. of active sites at 1.5 % are much more than that of 0.5 and 1%. On further increasing the amount of the catalyst from 1.5 wt% to 2, 2.5, and further the yield of biodiesel decreased. Therefore, the biodiesel yields below 1.5% loading was low and after increasing the amount of catalyst loading from 1.5% to 2%, 2.5% no significant changes in the yields were observed. This may be due to viscous slurry which may have possibly caused mixing problems among the reactants. The highest biodiesel yields were obtained at the optimum catalyst loading of 1.5 wt% which may associated with high surface area and high basicity of the catalyst. [38,40] Figure 3.12: Effect of catalyst loading percentage on Biodiesel Yield 110

27 f. Effect of Stirring- The effects of stirring on biodiesel yield were also investigated as they also plays an important role in the transesterification reaction. Since, oil and methanol are immiscible with each other hence they need a platform to react as the reaction takes place at the interfacial region of the phases. So initially the reactants form a three phase system i.e oil-methanol-catalyst. As the three reactants are initially involved in the transesterification reaction so it is a diffusion controlled reaction. Therefore to increase the area of contact between the phases vigourous stirring is needed to obtain better biodiesel yield. Hence if the stirring speed of the reaction is low then because of the poor diffusion there will be a slow reaction rate. Generally high stirring speed is used to give a better contact platform between the catalyst and the reactants which increases the rate of reaction. Hence the transesterification reactions were carried out at various stirring speeds as illustrated in figure 3.13 as given below. As we increased the stirring speed from 100 rpm to 600 rpm the yields of biodiesel increased from 49-51% to above 98% in 1.5 hours. At lower stirring speeds due to improper mixing the yields of biodiesel obtained were low. On increasing the stirring speed the reaction rate was faster because of proper diffusion and efficient mixing as a result the yields of biodiesel were maximum. [26,38] The results are depicted in figure 3.13 below showing stirring speed. Figure 3.13: Effect of Stirring on Biodiesel Yield 111

28 g. Effect of stirring and heating- The effect of stirring and heating on the FAME yields was also studied. The results are depicted in figure The reactions were performed in three conditions as illustrated in figure 3.14 that in the first reaction only temperature was raised without stirring. In the second reaction only stirring was performed without any heat and in the third reaction both heat as well as stirring were performed simultaneously. The results obtained in form of biodiesel yields were that when only heat or temperature was used then the yields obtained were about 30-35%. when only stirring was done without any heat the biodiesel yields obtained were approx. 5-10%. When temperature and stirring both were performed simultaneously then the biodiesel yields were above 98%. The effect of stirring in combination with temperature is also studied that only on heating or only on stirring the FAME yields were low but on both stirring at high rate and heating then the FAME yields were more than 98%. Figure 3.14: Effect of Stirring and Heat on the yields of biodiesel h. Reusability of the catalyst- The most important factor in the economics and process of the use of heterogeneous catalysts is its recovery or recyclability or reusability in biodiesel production as it directly affects its cost of production. [2] This factor and its recyclability, reproducibility activities were investigated carefully as it is economically important on commercial scale. The best possible way to recycle the catalyst and reduce its cost of production is filtration. The catalyst was consecutively recovered and reused up to five times. The fresh catalyst yields were above 98%, after 1 st use the yield was about 91%, after 2 nd use its yield was about 90% after 3 rd use its 112

29 yield was above 86%, after 4 th use its yield was above 78%, after 5 th use its yield were above 75% respectively as shown in figure The XRD Spectra of catalyst used 5 times shows the pattern similar to starting samples. Figure 3.15: Reusability of the catalyst 3.7 COMPARISION OF BIODIESEL YIELDS AND REACTION CONDITIONS WITH OTHER SYSTEMS AS REPORTED IN LITERATURE: The catalysts synthesized in our labs are more facile, versatile and magnificent which gives fruitful results and better yields than others as can be seen as follows: KOH/Al2O3 Chen et.al [48] have reported the use of K/ Al2O3 as a catalyst in the transesterification of rice bran oil with a molar ratio of 24:1 with a catalyst loading of 7.05% with a stirring speed of 900 rpm in 1.5 hours at 60 0 C with the yields above 90 %. Liu et.al [49] have reported the transesterification of rapeseed oil with K2CO3/Al2O3 yielding 98.85% with a molar ratio of methanol to oil 15:1, catalyst loading of 4 wt % with a stirring speed of 150 rpm in 3 hours at 50 0 C. Bo et.al [50] have reported the transesterification of palm oil with KF/Al2O3 yielding 90% with a molar ratio of methanol to oil 12:1, catalyst loading of 4 wt % in 3 hours at 65 0 C. Verziu et.al [51] have reported the transesterification of sunflower oil with KF/Al2O3 yielding above 90% with a molar ratio of methanol to oil 15:1, catalyst loading of 4 wt % in 2 hours at 75 0 C. Benjapornkulahong et.al [52] have 113

30 reported the transesterification of palm kernal oil with KNO3/Al2O3 yielding over 94.7% with a molar ratio of methanol to oil 65:1, catalyst loading of 4 wt % in 3 hours at 60 0 C. Niroj et.al [47] have reported the transesterification of palm oil with KOH/Al2O3 yielding 91.07% with a molar ratio of methanol to oil 15:1, catalyst loading of 3 wt % with a stirring speed of 300 rpm in 3 hours at 60 0 C. The catalyst synthesized in the present work yielded better results in the transesterification reactions. The yields obtained in the present work is more than 98% with 7 types of oils like soybean, sunflower, palm, rice bran, mustard, groundnut, jatropha oil with KOH/Al2O3 with 35 wt% loading as a catalyst with 15:1 molar ratio of oil to methanol, at 1.5 wt% loading of the catalyst with 300 rpm stirring in just 1.5 hours at 65 0 C KOH/CaO Liao et.al [53] have reported the transesterification of Jatropha Carcus oil with KOH/CaO yielding over 97% with a molar ratio of methanol to oil 8.42:1 at catalyst loading of 3.17 wt % in 67.9 minutes at 60 0 C Wang et.al [54] have reported the transesterification of chinese tallow seed oil with KF/CaO yielding over 96 % with a molar ratio of methanol to oil 9:1, catalyst loading of 3 wt % in 2 hours at 65 0 C Mahesh et.al [55] have reported the transesterification of waste cooking oil with KBr/CaO yielding 80% with a molar ratio of methanol to oil 12:1, catalyst loading of 4 wt % with the stirring speed of 500 rpm in 2 hours at 65 0 C Liang et.al [56] have reported the transesterification of soybean oil with K2CO3/CaO yielding 98% with a molar ratio of oil to methanol 6:1 and catalyst loading of 50 mg in 2 hours at 70 0 C. The yields obtained in the present work is more than 98% with 7 types of oils like soybean, sunflower, palm, rice bran, mustard, groundnut, jatropha oil with KOH/CaO with 20 wt% loading as a catalyst with 15:1 molar ratio of oil to methanol, at 1.5 wt% loading of the catalyst with 300 rpm stirring in just 1.5 hours at 65 0 C KOH/MgO Tao Wan et.al [57] have reported the transesterification of rapeseed oil with 30% KF/MgO yielding 79.82% with a molar ratio of methanol to oil 15:1, catalyst loading of 3 wt % in 5 hours. Liang et.al [56] have reported the transesterification of soybean oil with K2CO3/MgO yielding 99% with a molar ratio of oil to methanol 6:1 and catalyst 114

31 loading of 50 mg in 2 hours at 70 0 C Illgen et.al [30] have reported the transesterification of Canola Oil with 20% KOH/MgO yielding 95.05% with a molar ratio of methanol to oil 12:1, catalyst loading of 3 wt % with the stirring speed of 1000 rpm in 9 hours at 333 K. Ramirez et.al [58] have reported the transesterification of waste cooking oil with KOH/MgO yielding 100% with a molar ratio of methanol to oil 4:1, catalyst loading of 4 wt % in 1 hours at 60 0 C. The yields obtained in the present work is more than 98% with 7 types of oils like soybean, sunflower, palm, rice bran, mustard, groundnut, jatropha oil with KOH/MgO with 20 wt% loading as a catalyst with 15:1 molar ratio of oil to methanol, at 1.5 wt% loading of the catalyst with 300 rpm stirring in 1 hours at 65 0 C KOH/Fe2O3 Hirano et.al [59] have reported the transesterification of soybean and rapeseed oil with 20% KOH/Fe2O3 yielding 40% with a molar ratio of 13:100 of methanol to oil ratio at 60 0 C in normal atmospheric pressure. Xu et.al [60] have reported the transesterification of soybean oil with KOH/Fe2O3 yielding 10% with a molar ratio of methanol to oil 6:1 at 3 wt% catalysts loading at 65 0 C. He also reported the transesterification of soybean oil with KF/Fe2O3 yielding 83% with a molar ratio of methanol to oil 6:1 at 3 wt% catalysts loading at 65 0 C. The yields obtained in the present work is more than 98% with 7 types of oils like soybean, sunflower, palm, rice bran, mustard, groundnut, jatropha oil with KOH/Fe2O3 with 15 wt% loading as a catalyst with 15:1 molar ratio of oil to methanol, at 1.5 wt% loading of the catalyst with 300 rpm stirring in 1 hours at 65 0 C KOH/ZnO Huang et.al [61] Have reported the transesterification of Soybean Oil with 15 wt% KOH/ZnO yielding 84% with a molar ratio of Oil to methanol of 10:1 and the catalyst loading of 3 wt % in 9 hours at refluxing. Liang et.al [56] have reported the transesterification of soybean oil with K2CO3/ZnO yielding 93% with a molar ratio of oil to methanol 6:1 and catalyst loading of 50 mg in 2 hours at 70 0 C. Xie et.al [39] have reported the transesterification of Soybean Oil with KI/ZnO yielding 72.6% with a molar ratio of Oil to methanol of 15:1 and the catalyst loading of 2 wt % in 8 hours at refluxing. Huang et.al [61] have reported the transesterification of Soybean Oil with 15 wt% KF/ZnO yielding 87% with a molar ratio of Oil to methanol 10:1 and the catalyst 115

32 loading of 3 wt % in 9 hours at refluxing. Karavalakis et.al [62] have reported the transesterification of Soybean Oil with 20 wt% KNO3/ZnO yielding 87% with a molar ratio of Oil to methanol of 6:1 and the catalyst loading of 3 wt % in 90 minutes at 65 0 C. Huang et.al [61] have reported the transesterification of Soybean Oil with 15 wt% K2CO3/ZnO yielding 72% with a molar ratio of Oil to methanol of 10:1 and the catalyst loading of 3 wt % in 9 hours at refluxing. The yields obtained in the present work is more than 98% with 7 types of oils like soybean, sunflower, palm, rice bran, mustard, groundnut, jatropha oil with KOH/ZnO with 15 wt% loading as a catalyst with 15:1 molar ratio of oil to methanol, at 1.5 wt% loading of the catalyst with 300 rpm stirring in 1 hours at 65 0 C. 116

33 3.8 BIODIESEL CHARACTERIZATIONS FAME analysis by GC of Sunflower oil Biodiesel Fifteen fatty acids have been reported in the refined sunflower oil purchased from the commercial sources comprising palmitic, oleic, linoleic, linolenic stearic acids. The linoleic acid was found to be the major fatty acid in sunflower oil followed by oleic acid then palmitic acid comprising of approximately 9.18% saturated fatty acid, of monosaturated fatty acid, poly unsaturated fatty acids. The % yield of sunflower oil to Fatty Acid Methyl Esters after the reaction was found to be 98% after the separation of the glycerol layer. The Fatty Acid Methyl Esters obtained as a result and characterized by GC consists of methyl palmitate 8.43%, methyl stearate- 0.75%, methyl oleate-30.19%, methyl linolenate %, methyl eicoseonate-0.44%, methyl lignocerate-0.38%. Figure 3.16: GC analysis of Biodiesel synthesised from sunflower oil 117