Biodiesel Production using Synthesized HY Zeolite Catalyst

Biodiesel was produced using oleic acid esterification and transesterification of the sunflower oil methods. Many different factors affecting production procedures were studied such as reaction temperature, the molar ratio of ethanol to oil, reaction time and concentration of HY catalyst. Different techniques such as TGA, FTIR and Mass spectroscopy were used to syntheses biodiesel. Results showed that 78% of oleic acid maximum conversion was obtained at a temperature of 70 o C with molar ratio 12:1 ethanol: oil with 5 wt.% catalysts at 90 min reaction time, while for sunflower oil conversion of 98% at 200oC with 5 weight ratio of ethanol: oil at a time of 3 h was successfully obtained.


Introduction:
Biodiesel is the fuel that attracted much attention and support as more renewable and potential cleaner fuel for diesel engines, producing less air pollution compared with conventional petroleum diesel. Biodiesel can be produced from numerous biological materials, including vegetable oils and waste fats [1]. Transesterification process is the most common way of producing biodiesel where a pure triglyceride is converted into fatty methyl or ethyl ester and glycerol [2].

Triglycerides Alcohol Catalyst Esters Glyceride
Heterogeneous catalysts have been used due to their ease of separation from reaction stream, corrosion reduction and reusability. The objective of the research is firstly to investigate the activity of the synthesized HY catalyst for esterification of oleic acid to produce biodiesel under different reaction conditions (reaction time, temperature, catalytic ratio & alcohol/oil ratio). Secondly, transesterification of treated sunflower oil to produce biodiesel under various reaction conditions (reaction temperature and time). Zeolites have been used as catalysts to convert high free fatty acid oils to FAME. A good conversion of oil into biodiesel was observed at the time between 10 minutes and 50 minutes in the basic and acidic form of zeolites, such as NaY zeolites, while the negative influence of water resulted in low conversion [3]. Zeolite type Y was prepared from Iraqi kaolin with a final Si / Al ratio of 3.1 and used in oleic acid esterification as a catalyst. A variety of parameters such as molar ratio, temperature and mass load catalyst have been tested.
It was observed that 70 ° C, loading 5wt% and 6:1 ethanol to oleic acid ratio fixed as the best reaction conditions. The conversion by zeolite catalyst was 85% after 60 min. Although the highest value was 76% for the commercial sample of HY zeolite.   (1): The conversion of oleic acid can be calculated from each amount of catalyst using the acid value as shown in equation (2): Where, (AVto) is the acid value of the reaction product at a time (0) and (AVt) represents the acid value of the reaction product at a time (t) [4] and [1].

Pre-treatment of sunflower oil
One of the important steps in transesterification reaction was to decrease the acid value to be lower than 2 mg of potassium hydroxide per each gram. Therefore, the sunflower oil was pre-treated to be suitable for the reaction. A glass reactor was loaded with 200 g of the oil and preheated to 70 o C, and different ethanol to oil ratio was used (20,25,30,35) as well as1 wt.% of sulfuric acid was added in the reactor and the reaction continued for 30 min. Then the mixture was transferred to a separating funnel to separate treated oil from alcohol. The top layer was alcohol acid and part of Fatty Acid Ester (FFA) and the bottom layer was the treated oil [6] [2].

trans-esterification reaction
Reactions of the trans-esterification were implemented using a controlled temperature 500 ml glass reactor supplied with a stirring and condensation system.

The Esterification Reactions
Oleic acid esterification with alcohol was carried out using a prepared HY zeolite as a catalyst. This type of reactions is classified to be a reversible reaction, thus an additional amount of ethanol was required for enhancing the reaction conversion.
The esterification reaction is regulated by some factors including reaction temperature, reaction time, ethanol/ oleic acid ratio, and catalyst loading.

Reaction Temperature Effect on the oleic acid conversion
One of the reaction kinetics key factors is the reaction temperature because the rate of reaction is a temperature-dependent function under Arrhenius's law.
Therefore, oleic acid esterification with ethanol takes place in the liquid phase and the targeted reaction was carried out below the boiling point of ethanol. The temperatures 60 and 70oC were investigated at different molar ratios for ethanol to oleic acid of (3/1,6/1, 9/1 and 12/1). There is also a reason for the increased viscosity of the reactant decrease when the temperature increases which means that the molecular diffusion is increased through the internal pores of the catalyst. This leads to a quick reaction for the first 90 minutes at temperature 60 and 70 o C within the vital sites of the catalyst. The conversion of oleic acid was subsequently decreased due to the deactivation of the zeolite HY catalyst which could be resulted from the clustering of water molecules within the catalyst's pore based on the hydrophilic nature of zeolite, thus raising the reverse reaction which led to a decrease in conversion.
Figures (1) & (2) also show the reaction of oleic acid conversion as expected the fractional conversion increases as the reaction time rises with-molar ratio. It was found that the best maximum conversion of 77 % is obtained at a 12/1 molar ratio at 70 o C, which means that reaction reaches equilibrium. All results are compatible with previous results reported in [7][8][9][10].

Impact of catalyst quantity on oleic acid conversion
In the esterification reaction of oleic acid with ethanol, the reality of weight per cent of catalyst to oil was used to test the behavior of prepared HY catalyst.
Reactions were performed at a constant temperature of 70 o C and with a fixed ratio of 12/1 ethanol to oil. The effect of different weight per cent of the catalyst effect is shown in Figure (3). The best results at 5 wt. % of the catalyst.

Fig. (3) Oleic acid conversion as a function of catalyst ratios
As seen in Figure (3) the esterification reaction was directly proportional to the quantity of catalyst loaded, and this issue was expected because the rise in catalyst quantity implies a rise in other active sites where the esterification reaction occurred.
There is a slight increase in conversion between 5wt.% and 10wt.% and this not strong alignment with other researches that stated that an increase in the volume of catalyst above 5 wt. % did not affect the acid value being decreased [11], [12].

Molar ratio of Ethanol / Oil influence on the conversion of oleic Acid
The oleic acid esterification reaction with ethanol is a reversible reaction with an ethanol/oil molar stoichiometry ratio of 1:1. For improved processing, an additional quantity of ethanol is usually required. Unreacted ethanol has to be recovered and a significant amount of energy is required, so the optimum combination of energysaving and effective reaction efficiency should be calculated as effectively as possible. Four ethanol/oil molar ratios were used 3:1, 6:1, 9:1 and 12:1, with a specified 5wt. % catalyst and a steady 70oC reaction temperature. A substantial rise in oleic acid production can be observed, as seen in Figures (4) & (5). It can be concluded that as the molar ratio rises there was a major change in oleic acid production. This excess alcohol moved the equilibrium reaction to the direction of product formation.
Another clarification is the viscosity of the reaction medium, the viscosity of the mixture decrease if the ratio increases since the viscosity of ethanol is being lower than oleic, then at high ratio (low viscosity) the effect of reactant diffusion to catalyst particles was reduced leading to increase in the reaction productivity. It can be observed in different studies and previous work, which the abroad range of the alcohol/oil ratio up to 30/1, also at a higher ratio. But it must be taken into account that at a high ratio there will be higher water and this undesirable since it reduced the final product [3,13,14,15].

Comparison between prepared and commercial HY Zeolite Catalyst
Comparison between prepared and commercial HY catalyst was investigated at 5 wt.% of catalyst and 12/1 Ethanol /oil molar ratio and the conversion was about 77 for synthesized catalyst while for the commercial catalyst is about 80 % as shown in Fig.4. There was a slight increase in conversion between commercial and prepared catalyst due to large pore volume and higher surface area and this delayed the deactivation of the catalyst [16].

Production of Biodiesel
Trans-esterification reaction is carried out using HY synthesized catalyst at be localized on the carbon atom and in the second step, the positive charge will be attacked by an oxygen atom of a hydroxyl group in the alcohol giving a water molecule and ester is formed [17].
So, if there is no sufficient acidity in the catalyst, the reaction in step one and formation of the carbonium ion will be weak and the above mechanism will be disturbed. Sulfonated HY catalyst considered to have good strength acidity, besides its pore volume gives rise to the diffusion of large fatty acid to react inside it producing more biodiesel. [18]. the suggested mechanism is shown in scheme 1 [19].

Characterization of Biodiesel:
The product specifications are very important since from which it can decide the validity of the produced biodiesel. The properties of prepared biodiesel are characterized using different techniques:

GC -Mass, Gas Chromatography Mass Spectroscopy:
GC-Mass spectroscopy was done on specimens of synthesized biodiesel, and the results of mass spectrum for produced was performed to investigate the ethyl ester group. The main characteristics peaks of fatty acid ester appeared by the retention time and the fragmentation pattern data.
These results confirm our selected condition and completeness of the transesterification process of triglycerides in the vegetable oil into biodiesel.

TGA -Thermal Gravimetric analysis:
TGA is an effective way to quantify the produced biodiesel due to the large temperature difference between the weight loss temperature of oil and biodiesel as shown in Figures (7) and (8). It is well known that the biodiesel starts to thermally decompose at approximately 150 o C and continue its thermal decomposition until complete vaporization. However, the vegetable oil begins its thermal degradation at This compatible with transesterification results. These confirm successful biodiesel production. Also, confirm previous GC-MS analysis results.

FTIR Fourier Transform Infrared Spectroscopy
Fatty esters (FAME) are quantified using FTIR.

Biodiesel properties:
Produced biodiesel has different properties that characterized it. These properties are listed below: