Acid base catalyzed transesterification kinetics of waste cooking oil

The present study reports the results of kinetics study of acid base catalyzed two step transesterification process of waste cooking oil, carried out at pre-determined optimum temperature of 65 °C and 50 °C for esterification and transesterification process respectively under the optimum condition of methanol to oil ratio of 3:7 (v/v), catalyst concentration 1%(w/w) for H₂SO₄ and NaOH and 400 rpm of stirring. The optimum temperature was determined based on the yield of ME at different temperature. Simply, the optimum concentration of H₂SO₄ and NaOH was determined with respect to ME Yield. The results indicated that both esterification and transesterification reaction are of first order rate reaction with reaction rate constant of 0.0031 min^− 1 and 0.0078 min^− 1 respectively showing that the former is a slower process than the later. The maximum yield of 21.50% of ME during esterification and 90.6% from transesterification of pretreated WCO has been obtained. This is the first study of its kind which deals with simplified kinetics of two step acid-base catalyzed transesterification process carried under the above optimum conditions and took about 6 h for complete conversion of TG to ME with least amount of activation energy. Also various parameters related to experiments are optimized with respect to ME yield.     

Biodiesel synthesis combining pre-esterification with alkali catalyzed process from rapeseed oil deodorizer distillate

A two-step technique combining pre-esterification catalyzed by cation exchange resin with transesterification catalyzed by base alkali was developed to produce biodiesel from rapeseed oil deodorizer distillate (RDOD). The free fatty acids (FFAs) in the feedstock were converted to methyl esters in the pre-esterification step using a column reactor packed with cation exchange resin. The acid value of oil was reduced from the initial 97.60 mg-KOH g^? 1 oil to 1.12 mg-KOH g^? 1 oil under the conditions of cation exchange resin D002 catalyst packed dosage 18 wt.% (based on oil weight), oil to methanol molar ratio 1:9, reaction temperature 60 °C, and reaction time 4 h. The biodiesel yield by transesterification was 97.4% in 1.5 h using 0.8 wt.% KOH as catalyst and a molar ratio of oil to methanol 1:4 at 60 °C. The properties of RDOD biodiesel production in a packed column reactor followed by KOH catalyzed transesterification were measured up the standards of EN14214 and ASTM6751-03.     

Comprehensive utilization of the mixture of oil sediments and soapstocks for producing FAME and phosphatides

Comprehensive utilization of the mixture of oil sediments (OS) and soapstock (SS) for producing FAME and phosphatides was investigated. A process consisting of three steps was employed for obtaining high conversion and by-product. In the first step, the OS–SS mixture was extracted with ethyl ether and the mixture was divided into three phases. The organic top phase contained triglycerides and phosphatides was extracted with cooled acetone and the acetone insoluble (phosphatides) was obtained. At the same time, triglycerides were separated also. In the second step, soap phase was then acidified with sulfuric acid to yield fatty acid. This “high-acid” acid oil was efficiently converted to methyl esters by acid-catalyzed esterification. The esterification reaction has been carried out with 5:1 methanol/oil (mol/mol) in the presence 3% H₂S0₄ (wt.%) as an acid catalyst at 85 °C for 5 h. FAME recovery under these conditions was 92.1% of theoretical. In the third step, alkaline catalyzed transesterification process converts the triglycerides to its mono-esters and glycerol. The optimized variables, 6:1 methanol/oil (mol/mol) with 1% NaOH (wt.%) reacted at 65 °C for 1 h, giving a maximum ester yield of 94%. Five important fuel properties of FAME from the OS–SS mixture were found to be comparable to those of No. 2 diesel fuel and conforming to both the American and German standards for biodiesel.     

High yield of monoacylglycerols production through low‐temperature chemical and enzymatic glycerolysis

The present study aimed to produce MAG through low‐temperature chemical glycerolysis. Over 80% MAG yield with 97% TAG conversion was obtained within short reaction times at temperature of 35–55°C, when tert‐butanol (TB) or tert‐pentanol (TP) was used as reaction medium and sodium hydroxide (NaOH) as catalyst. TB gave a faster reaction rate than TP. Catalysts were important for the low‐temperature chemical glycerolysis reaction. Of the eight common base catalysts evaluated, only NaOH and potassium hydroxide (KOH) were effective, and NaOH was better than KOH. Reaction parameters were studied and optimized. The optimum conditions were TB dosage 3:1 (TB to oil in weight ratio), NaOH concentration 0.45 wt% based on oil, molar ratio of glycerol to oil 5:1. Under these conditions, similar MAG yield and TAG conversion was also observed by Novozym 435 catalyzed glycerolysis, however, a 4 h reaction was required. Practical applications: The process of NaOH catalyzed chemical glycerolysis for MAG production in TB solvent system described in this study provides several advantages including short reaction time and high product yield, which is potential for industrial considerations.     

A Novel Method for the Production of Biodiesel from the Whole Stillage-Extracted Corn Oil

The extraction of corn oil from whole stillage and condensed distillers’ solubles (CDS) with hexane and its conversion to biodiesel were investigated. The analysis of the extracted oil showed 6–8 wt.% free fatty acid (FFA) in this oil. Acid, base, acid–base, and acid–base catalyzed transesterifications with intermediate neutralization with anion exchange resin were investigated. Experiments were performed with model corn oil substrates which contained 1.0–6.0 wt.% FFA. The effect of catalyst at 0.50–1.25 wt.% was studied at a 1:8 oil/methanol molar ratio. At 6.0 wt.% FFA concentration, the acid-catalyzed scheme was slow and resulted in less than 20% yield after 4 h, while the base-catalyzed was mostly consumed by the FFA and very little conversion was achieved. The acid–base catalyzed scheme succeeded in reducing the FFA content of the oil through the acid-catalyzed stage, and yields in excess of 85% were achieved after the second stage of the reaction with a base catalyst. However, formation of water and soap prevented the separation of product phases. An alternative acid–base catalyzed scheme was examined which made use of a strong anion exchange resin to neutralize the substrate after the initial acid-catalyzed stage. This scheme resulted in the effective removal of the acid catalyst as well as the residual FFA prior to the base-catalyzed stage. The subsequent base-catalyzed stage resulted in yields in excess of 98% for a 7.0 wt.% FFA corn oil and for the corn oil extracted from CDS.     

Single‐step ultrasonic synthesis of biodiesel from crude Jatropha curcas oil

A novel single‐step process with chlorosulfonic acid catalyst for ultrasonic biodiesel synthesis using feedstock with high free fatty acid content is investigated.Jatropha curcas oil has been used as the model feedstock with methanol as alcohol. The distinct merit of chlorosulfonic acid is that it catalyzes both esterification and transesterification reactions. Moreover, chlorosulfonic acid also counteracts inhibition caused by water formed during esterification, which is the cause for very slow kinetics of acid catalyzed transesterification. In addition, sonication of the reaction mixture also causes strong micromixing and emulsification that enhances the transesterification kinetics. Statistical optimization of the process shows 93% yield for 8.5 wt % catalyst, 20:1 alcohol to oil molar ratio and temperature of 333 K. Peculiar feature of this process is that high yield is seen at moderate temperature and molar ratio, which are much smaller than that for conventional sulfuric acid catalyzed processes. The activation energy for the process (57 kJ/mol) is at least 3× lower than the energy for sulfuric acid catalyzed transesterification. The thermodynamic analysis reveals that the net Gibbs energy change for the single‐step process is almost same as that for sulfuric acid catalyzed process. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1572–1581, 2014     

Two-step biodiesel production from Jatropha curcas crude oil using SiO2·HF solid catalyst for FFA esterification step

A high quality biodiesel was produced from Mexican Jatropha curcas crude oil (JCCO) by a two step catalyzed process. The free fatty acids (FFA) were first esterified with methanol, catalyzed by a solid catalyst: SiO₂ pretreated with HF. The catalyst showed a high number of Lewis acid surface sites, and no CO₂ or H₂O adsorption activity. This catalyst showed a high FFA esterification activity and high stability. After 30 esterification runs, the catalyst activity remained unchanged. During the second step, the triglycerides present in the JCCO were transesterified with methanol catalyzed by NaOH. The chromatographic analysis of the biodiesel obtained, revealed that the process proposed in this investigation led to a very high quality biodiesel, meeting the international requirements for its utilization as a fuel. The combustion gas emissions of the JCCO biodiesel were studied by FTIR spectroscopy using a laboratory combustor. These preliminary results showed low amounts of aromatic and sulfur containing compounds. However, halogenated compounds and dicyclopentadiene were also detected at the combustor exhaust.     

Tri-potassium phosphate as a solid catalyst for biodiesel production from waste cooking oil

Transesterification of waste cooking oil with methanol, using tri-potassium phosphate as a solid catalyst, was investigated. Tri-potassium phosphate shows high catalytic properties for the transesterification reaction, compared to CaO and tri-sodium phosphate. Transesterification of waste cooking oil required approximately two times more solid catalyst than transesterification of sunflower oil. The fatty acid methyl ester (FAME) yield reached 97.3% when the transesterification was performed with a catalyst concentration of 4 wt.% at 60 °C for 120 min. After regeneration of the used catalyst with aqueous KOH solution, the FAME yield recovered to 88%. Addition of a co-solvent changed the reaction state from three-phase to two-phase, but reduced the FAME yield, contrary to the results with homogeneous catalysts. The catalyst particles were easily agglomerated by the glycerol drops derived from the homogeneous liquid in the presence of co-solvents, reducing the catalytic activity.     

Glycerolysis of Soybean Oil with Crude Glycerol Containing Residual Alkaline Catalysts from Biodiesel Production

The glycerolysis reaction of soybean oil was evaluated using crude glycerol obtained from the transesterification of soybean oil with methanol, catalyzed by sodium methoxide and sodium hydroxide, without any purification step other than the methanol removal. Crude glycerol with the lower content of remaining inorganic catalyst produced the highest concentration of monoglycerides (about 42%). The effect of the addition of water on the glycerolysis reaction was analyzed, evidencing a low formation rate of products in the first stages of the reaction due to the transformation of the inorganic catalyst to soaps, which are weaker bases. The sample of crude glycerol that led to the best results was evaluated at several temperatures. It was observed that the reaction with crude glycerol exhibits a lower formation rate of monoglycerides at low temperatures (160 and 180 °C) compared with the reaction with pure glycerol and catalyzed with NaOH. This behavior was explained by the lower activity of the soaps present in the crude glycerol respect to the inorganic base. Above 200 °C the reaction is very fast and the monoglycerides formed are consumed to produce diglycerides.     

The use of a modified TDSP for biodiesel production from soybean, linseed and waste cooking oil

In this study, the Transesterification Double Step Process (TDSP) for the production of biodiesel from vegetable oil was modified to yield a shorter reaction time and products with improved quality. TDSP consists in a two step transesterification procedure which starts with a basic catalysis, followed by an acidic catalysis. The process modifications included a reduction in the concentration of catalysts, a reduction in the reaction time of the first step and the direct mixing of methanol/acid solution, without cooling the system between the first and second step. A comparison between washed and unwashed biodiesel demonstrates that the final washing and drying procedure is necessary for satisfactory results. The products were analyzed by ¹H-NMR and nineteen different biodiesel analyses specific for international quality certification. The modified procedure resulted in a high conversion index (97% for waste cooking oil and soybean oil and 98% for linseed oil) and high yield (87 ± 5% for waste cooking oil, 92 ± 3% for soybean and 93 ± 3% for linseed oil). The biodiesel produced by the modified TDSP met ASTM, EN ISO and ABNT standards before the addition of stabilizer.     

Production of Isopropyl and Methyl Esters from Yellow Mustard Oil/IPA Miscellas

Using an isopropyl alcohol (IPA):flour [volume:weight (ml:g)] ratio of 1.5:1 per stage of extraction resulted in an oil yield of 86.3%. The combined miscella (IPA + oil), which contained 90.6 wt% IPA, 9.8 wt% oil, and 2.1 wt% water, was used as a feedstock for biodiesel production by transesterification. Transesterification of the IPA/oil miscella dehydrated using adsorption on 4Å molecular sieves with 1.2 wt% (based on oil) potassium hydroxide for 2 h at 72 °C converted only 29% of the feed to esters. The addition of methanol (MeOH) resulted in an ester yield of 87%, consisting of 79% methyl ester and 7% isopropyl ester when starting with an IPA:oil:MeOH molar ratio of 146:1:30. By increasing the KOH catalyst to 3 wt%, the ester yield increased to 94%. To increase the ester yield, the miscella was pretreated with sulfuric acid. This resulted in a reduction of the IPA content, the removal of other impurities such as phospholipids, and reduction of the water mass fraction to less than 1%. When IPA was used as a cosolvent with methanol in the transesterification process, a very high ester conversion (>99%) was achieved. The biodiesel produced was compliant with ASTM standards, showing that IPA can be used as a solvent for oil extraction from yellow mustard flour.     

Methylation of wood fatty and resin acids for production of biodiesel

The purpose of the present paper is to evaluate the potentiality of the wood oil of Oriental spruce (Spruce orientalis) for biodiesel production. Two methods have been applied for obtained wood oil with and without solvent such as separation of crude tall oil from sulfate soaps by Kraft pulping process. Production of biodiesel from wood oil follows two steps, first extraction of oil using a solvent (acetone) and then base catalyzed (KOH) or non-catalytic supercritical methanol transesterification. This paper studied the effect of temperature on transesterification of wood oil to find the optimum temperature of maximum biodiesel yield. Transesterification of the wood oils were performed in a 100-mL cylindrical autoclave using supercritical methanol. In a typical run, the autoclave was charged with a given amount of the wood oil (20-25 g) and alcohol (20-50 g) with changed molar ratios at 500, 525, 550 and 575 K. The yield of the biodiesel produced under optimal condition is 96-98%.     

Palm fatty acid biodiesel: process optimization and study of reaction kinetics

The relatively high cost of refined oils render the resulting fuels unable to compete with petroleum derived fuel. In this study, biodiesel is prepared from palm fatty acid (PFA) which is a by-product of palm oil refinery. The process conditions were optimized for production of palm fatty acid methyl esters. A maximum conversion of 94.4% was obtained using two step trans-esterification with 1:10 molar ratio of oil to methanol at 65°C. Sulfuric acid and Sodium hydroxide were used as acid and base catalyst respectively. The composition of fatty acid methyl esters (FAME) obtained was similar to that of palm oil. The biodiesel produced met the established specifications of biodiesel of American Society for Testing and Materials (ASTM). The kinetics of the trans-esterification reaction was also studied and the data reveals that the reaction is of first order in fatty acid and methanol (MeOH) and over all the reaction is of second order.     

Two step sol-gel processing of TEOS based hydrophobic silica aerogels using trimethylethoxysilane as a co-precursor

The experimental results on the surface modification of tetraethoxysilane (TEOS) based silica aerogels using trimethylethoxysilane (TMES) as a co-precursor by two step sol-gel process are reported. The molar ratio of MeOH/TEOS was fixed at 17 and TMES/TEOS ratio was varied from 0.38 to 1.14. The concentration and quantity of acidic water (oxalic acid) added in the first step and base water (ammonium hydroxide) in the second step were also varied. The best quality superhydrophobic aerogels could be obtained with only distilled water (without any acid catalyst) in the first stage and the basic water in the second step of the sol-gel process. The molar ratio of TEOS: TMES: MeOH: distilled water: basic water was optimized at 1:0.86:17:4.9:4.9, respectively. The surface modification has been confirmed from the Fourier transform infrared spectroscopy measurements while the hydrophobicity was quantified in terms of the contact angle measurements. The TMES/TEOS based aerogel powder could be used to transport micro-liters of water in the form of water marbles. The aerogels have been characterized by the bulk density, porosity, thermal conductivity, contact angle measurements and the transmission electron microscopy (TEM).      

Process optimization for methyl ester production from waste cooking oil using activated carbon supported potassium fluoride

This paper presents the transesterification of waste cooking palm oil (WCO) using activated carbon supported potassium fluoride catalyst. A central composite rotatable design was used to optimize the effect of molar ratio of methanol to oil, reaction period, catalyst loading and reaction temperature on the transesterification process. The reactor was pressurized up to 10 bar using nitrogen gas. All the variables were found to affect significantly the methyl ester yield where the most effective factors being the amount of catalyst and reaction temperature, followed by methanol to oil ratio. A quadratic polynomial equation was obtained for methyl ester yield by multiple regression analysis using response surface methodology (RSM). The optimum condition for transesterification of WCO to methyl ester was obtained at 3 wt.% amount of catalyst, 175 °C temperature, 8.85 methanol to oil molar ratio and 1 h reaction time. At the optimum condition, the predicted methyl ester yield was 83.00 wt.%. The experimental value was well within the estimated value of the model. The catalyst showed good performance with a high yield of methyl ester and the separation of the catalyst from the liquid mixture is easy.     

Biodiesel production from waste cooking oil in a microtube reactor

Waste cooking oil (WCO) was used to produce biodiesel in a microtube reactor. First, the acid value of the WCO was reduced from 3.96 mg KOH/g to less than 1 mg KOH/g via acid catalyzed esterification. The effects of the methanol-to-WCO molar ratio (4.5:1–18:1), the H₂SO₄ concentration (0.5–2 wt.%), reaction temperature (55–70 °C), and reaction time (5–20 s) were studied. The optimal conditions were 9:1 methanol-to-WCO molar ratio, 1 wt.% H₂SO₄, 65 °C and 5 s of reaction time. Triglycerides in the product from the first step were transesterified with methanol and alkaline catalyst. Methyl ester content of the biodiesel was 91.76%.     

An integrated process of catalytic hydrolysis and membrane separation for fatty acids production from lard oil

An integrated process of catalytic hydrolysis and membrane separation was developed for fatty acids (FAs) production from lard oil. Both sulphonated cation exchange resin (SCER) and 0.98 g/g H₂SO₄ as catalysts were used to produce fatty acids (FAs) from lard oil by three‐step hydrolysis, respectively. Simultaneously, polyethersulphone (PES) ultrafiltration membrane was employed to separate glycerol and water from the products. The hydrophilicity and morphology of the pristine and used PES membranes were characterized by contact angle measurement and field‐emission scanning electronic microscopy, respectively. The final optimal yields of FAs obtained by SCER and H₂SO₄ catalysis at 100 °C and atmospheric pressure were 85.6 % at 16.0 h of operation and 94.5 % at 18.0 h of operation, respectively. Furthermore, the yield of FAs obtained from an integrated process of SCER‐catalyzed hydrolysis and membrane separation achieved up to 99.9 % at 10.0 h, 90 °C, and operating pressure of 100 kPa.

     

Study of variables affecting the synthesis of biodiesel from Madhuca Indica oil

Biodiesel derived from non‐edible Madhuca Indica oil (MIO) seems to be a better alternative to diesel oil in India. In the present work, effects of reaction variables such as mass ratio of methanol to oil, catalyst concentration, reaction time and reaction temperature on biodiesel yield were studied. The acid value of the commercially available MIO is high, and hence a two‐step process was used to produce biodiesel from MIO. In the first step, the acid value of the MIO was reduced to less than 1 mg KOH/g, using acid‐catalyzed transesterification. In the second step, the pretreated MIO was converted to biodiesel using alkaline‐catalyzed transesterification. From the experimental results, it is observed that the optimized conditions for biodiesel production are a 1 : 4 mass ratio of methanol to oil, 55 °C reaction temperature, 120 min of reaction time, and 1% sodium hydroxide catalyst. The properties of the MIO biodiesel were found to be within the biodiesel limits of the European Union. Hence, the MIO biodiesel can be used as a substitute for diesel for the sustainable development of rural areas and as a renewable fuel.     

Production of lubricating base oil from slop wax by different subsequent refining techniques

Different subsequent refining techniques including solvent dewaxing and solvent extraction have been used to produce lubricating base oil from slop wax waste by-product. The solvent dewaxing technique was performed using two different solvent mixtures of methyl ethyl ketone and toluene with and without benzene at different dilution solvent ratios and at different dewaxing temperatures. The solvent extraction technique was carried out using N-methyl-2-pyrrolidone solvent at 90 °C and at constant dilution solvent ratio of 3:1 by weight. The resulting data revealed that the highest yield of lubricating base oil having the lowest pour point (−6 °C) and the highest iso- and cyclo-paraffins to n-paraffins ratio (5.11) is obtained by solvent dewaxing process only. While the lowest yield of lubricating base oil having the highest pour point (−1 °C) and the lowest iso- and cyclo-paraffins to n-paraffins ratio (4.08) is obtained using solvent dewaxing followed by solvent extraction process. These lubricating base oil products, especially the one that having the lowest pour point (−6 °C) matches the principal characteristics of AX 973853 type of premium low viscosity textile machinery oils obtained by Mobile Velocite Oil Company.     

Biodiesel production from mixtures of canola oil and used cooking oil

Used cooking oil (UCO) was mixed with canola oil at various ratios in order to make use of used cooking oil for production of biodiesel and also lower the cost of biodiesel production. Methyl and ethyl esters were prepared by means of KOH-catalyzed transesterification from the mixtures of both the oils. Water content, acid value and viscosity of most esters met ASTM standard except for ethyl esters prepared from used cooking oil. Canola oil content of at least 60% in the used cooking oil/canola oil feedstock is required in order to produce ethyl ester satisfying ASTM specifications. Although ethanolysis was proved to be more challenging, ethyl esters showed reduced crystallization temperature (−45.0 to −54.4 °C) as compared to methyl esters (−35.3 to −43.0 °C). A somewhat better low-temperature property of ester was observed at higher used cooking oil to canola oil ratio in spite of similar fatty acid compositions of both oils.