Non-catalytic biodiesel process with adsorption-based refining

Different feedstocks of varying acidity ranks and water contents were subjected to a series of discontinuous steps that simulated a biodiesel production process. The three steps comprised: (i) the non-catalytic transesterification with supercritical methanol at 280 °C; (ii) the distillation of the unreacted methanol, water and volatile products; and (iii) the adsorption of the impurities with adequate adsorbents. Refined soy oil, chicken oil and waste cooking oil were subjected to the same simple procedure. The process produced biodiesel complying with the water, acid, glycerides and methyl esters content specifications of the EN 14214 standard.Biodiesel production by the reaction of oils in supercritical methanol at 280 °C and methanol-to-oil molar ratios of 15 and 20 produced amounts of glycerol as small as 0.02%. This simplified the subsequent refining of the biodiesel and is considered an advantage over the classic alkali-catalyzed process (that produces 10% of glycerol by-product) because washing steps can be spared.The contents of methyl esters, water and free fatty acids showed a volcano pattern when plotted as a function of the reaction time. In the case of the free fatty acids this was attributed to the initial reaction of water and triglycerides to form acids and glycerol that increased the acidity of the product mixture. At longer reaction times these acids were likely transformed into methyl esters or were decarboxylated to hydrocarbons and CO₂. Water formation was attributed to glycerol decomposition and esterification of free fatty acids.The design of a simple process for biodiesel production using a single reaction step with negligible glycerol production and an adsorption-based refining step was thus studied. A possible scheme integrating reaction, methanol recycling, biodiesel purification and heat recovery was discussed. Advantages and disadvantages of process units were analyzed on terms of operating cost and simplicity.     

Effect of crystallization temperature on the in situ valorization of physic nut (Jatropha curcus L.) wastes using synthetic HZSM-5 catalyst

Physic nut waste is selected as the biomass feedstock for fast pyrolysis as it is available in large amounts from biodiesel production in Thailand. The volatile matter and fixed carbon contents are 73.8% and 13.6% while ash contents are 5.8%. Carbon is the main element with 49.03 wt%. The oxygen content of 39.0 wt% is considerably high which could directly convert to the oxygenated pyrolysis liquid products. To decrease oxygenated compounds, HZSM-5 was used as a catalyst to upgrade pyrolytic products from fast pyrolysis using analytical pyrolysis–GC/MS method. The HZSM-5 catalyst was successfully synthesized by hydrothermal method at 160–180 °C for 24 h. The particle size, surface area, and pore diameter were 11.25–15.52 μm, 567–582 m²/g, and 21.78–26.11 Å, respectively. The pyrolysis was performed at 500 °C with the Jatropha wastes to catalyst ratio of 1:1–1:10. The presence of HZSM-5 contributed to eliminate the undesirable oxygenated compounds such as acids and ketones which could alleviate problem regarding acidity and instability in bio-oil. In addition, it enhanced significantly the yields of desirable hydrocarbon compounds. The increase in catalyst contents had an effect on the enhancement of hydrocarbons yields, and tended to promote deoxygenation and denitrogenation. At moderate biomass to catalyst ratio (1:5), HZSM-5 synthesized at 170 °C contributed to improve the hydrocarbon yields of 95%, including mainly toluene and xylene, which are valuable products because of their high heating value properties.     

Hydrothermal alteration of sedimentary organic matter in the presence and absence of hydrogen to tar then oil

Hydrothermal alteration (hydrous pyrolysis) experiments, in the absence and presence of H₂ (reductive), were conducted on organic matter from marine and lacustrine sediments. The experiments were carried out at discrete temperatures from 150 °C to 350 °C to assess the yields and compositions of the bitumen (tar) formed and subsequently at higher temperatures the oil generated. The yield of bitumen was observed to increase with increasing temperatures. Under hydrous pyrolysis conditions with hydrogen, the yield increases by an order of magnitude and immature lacustrine organic matter shows the highest yield. Bitumen, the extractable organic matter at temperatures below 250-300 °C, contains mainly polar compounds, an unresolved complex mixture (UCM) of branched and cyclic compounds, with low amounts of saturated hydrocarbons. The polar compounds include n-alkanoic acids, n-alkanedioic acids, n-alkanols, isoprenoid ketones and methyl alkanoates. At temperatures above 300 °C, the bitumens transform into petroleum products with saturated hydrocarbons (n-alkanes and biomarkers) and UCM as the major components (>95% of total yield). The degree of maturation of the generated oil increases with increasing temperature under both pyrolysis conditions to full maturity at >350 °C. Although, the bitumen yield is much higher under conditions with added hydrogen, the maturity of the generated oil is lower than with just hydrous pyrolysis.     

Statistical optimization for biodiesel production from waste frying oil through two-step catalyzed process

The aim of this work was to investigate the optimum conditions in biodiesel production from waste frying oil using two-step catalyzed process. In the first step, sulfuric acid was used as a catalyst for the esterification reaction of free fatty acid and methanol in order to reduce the free fatty acid content to be approximate 0.5%. In the second step, the product from the first step was further reacted with methanol using potassium hydroxide as a catalyst. The Box-Behnken design of experiment was carried out using the MINITAB RELEASE 14, and the results were analyzed using response surface methodology. The optimum conditions for biodiesel production were obtained when using methanol to oil molar ratio of 6.1:1, 0.68 wt.% of sulfuric acid, at 51 °C with a reaction time of 60 min in the first step, followed by using molar ratio of methanol to product from the first step of 9.1:1, 1 wt.% KOH, at 55 °C with a reaction time of 60 min in the second step. The percentage of methyl ester in the obtained product was 90.56 ± 0.28%. In addition, the fuel properties of the produced biodiesel were in the acceptable ranges according to Thai standard for community biodiesel.     

Conversion of waste cooking oil to biodiesel using ferric sulfate and supercritical methanol processes

In this comparative study, conversion of waste cooking oil to methyl esters was carried out using the ferric sulfate and the supercritical methanol processes. A two-step transesterification process was used to remove the high free fatty acid contents in the waste cooking oil (WCO). This process resulted in a feedstock to biodiesel conversion yield of about 85-96% using a ferric sulfate catalyst. In the supercritical methanol transesterification method, the yield of biodiesel was about 50-65% in only 15 min of reaction time. The test results revealed that supercritical process method is probably a promising alternative method to the traditional two-step transesterification process using a ferric sulfate catalyst for waste cooking oil conversion. The important variables affecting the methyl ester yield during the transesterification reaction are the molar ratio of alcohol to oil, the catalyst amount and the reaction temperature. The analysis of oil properties, fuel properties and process parameter optimization for the waste cooking oil conversion are also presented.     

Optimization of factors affecting esterification of mixed oil with high percentage of free fatty acid

Increased environmental awareness and depletion of resources are driving industry to develop alternative fuels from renewable sources that are environmentally more acceptable. Biodiesel is a non petroleum based fuel that consists of alkyl esters from transestrification of the refined/edible types of vegetable oils alcohol and alkaline catalysts can be used. These catalysts require anhydrous conditions and feed stocks with low levels of free fatty acids (FFAs). Inexpensive feed stocks are used in biodiesel production to reduce its cost and to get rid of waste oils in environmentally friendly way. These oils may contain high levels of FFAs so it cannot be directly used with the base catalysts currently employed. Acid esterification reduces the FFAs content to the desirable level. The major factors that affect the conversion efficiency of the process are molar ratio of alcohol/oil, amount of catalyst, reaction temperature, catalyst type and stirring speed according to reaction duration. For this study, we used a model acid produced by mixing pure oleic acid with mixed oil (50% sunflower + 50% soybean oil). Methanol was used in the experiments due to its low cost. The best conversion efficiency obtained was 96.6% for a molar ratio of 6:1 at a temperature of 60 °C, 2.5% H₂SO₄ and stirring speed of 300 rpm. Finally, different types of waste cooking oil from home and restaurants were used to study the conversion efficiency compared with optimum conditions calculated for model acid oil to be used in biodiesel production with low cost.     

Improving the cold flow properties of biodiesel from waste cooking oil by surfactants and detergent fractionation

The use of surfactants and detergent fractionation to improve the cold flow properties of biodiesel from waste cooking oil (BWCO) was investigated. The effect of five types of surfactants, including sugar esters (S270 and S1570), silicone oil (TSA 750S), polyglycerol ester (LOP-120DP) and diesel conditioner (DDA) on the reduction of the cold filter plugging point (CFPP) of the BWCO, was evaluated, with the greatest reduction to the CFPP of the BWCO (from −10 °C to −16 °C) being was achieved by the addition of 0.02 wt% of polyglycerol ester (LOP-120P). Detergent fractionation of the BWCO was performed by first mixing partially crystallized biodiesel with a chilled detergent (sodium dodecylsulfate) solution accompanied by an electrolyte (magnesium sulfate), and then separating the mixture by centrifugation to obtain the BWCO liquid. An orthogonal experimental design was utilized to investigate the effects of the various parameters on detergent fractionation. The optimal parameters, as obtained by range analysis, were as follows: detergent loading 0.3 wt%, electrolyte loading 1.0 wt%, and water loading 150 wt%. The CFFP of the liquid biodiesel from waste cooking oil (LBWCO) was −17 °C with a yield of 73.1% when the detergent fractionation was performed under these conditions. A limited number of biodiesel physical and chemical properties were analyzed before and after the addition of surfactants and detergent fractionation.     

Thermal stability of biodiesel in supercritical methanol

Non-catalytic biodiesel production technologies from oils/fats in plants and animals have been developed in our laboratory employing supercritical methanol. Due to conditions in high temperature and high pressure of the supercritical fluid, thermal stability of fatty acid methyl esters and actual biodiesel prepared from various plant oils was studied in supercritical methanol over a range of its condition between 270 °C/17 MPa and 380 °C/56 MPa. In addition, the effect of thermal degradation on cold flow properties was studied. As a result, it was found that all fatty acid methyl esters including poly-unsaturated ones were stable at 270 °C/17 MPa, but at 350 °C/43 MPa, they were partly decomposed to reduce the yield with isomerization from cis-type to trans-type. These behaviors were also observed for actual biodiesel prepared from linseed oil, safflower oil, which are high in poly-unsaturated fatty acids. Cold flow properties of actual biodiesel, however, remained almost unchanged after supercritical methanol exposure at 270 °C/17 MPa and 350 °C/43 MPa. For the latter condition, however, poly-unsaturated fatty acids were sacrificed to be decomposed and reduced in yield. From these results, it was clarified that reaction temperature in supercritical methanol process should be lower than 300 °C, preferably 270 °C with a supercritical pressure higher than 8.09 MPa, in terms of thermal stabilization for high-quality biodiesel production.     

Winterization of biodiesel by micro process engineering

A new method for winterization of biodiesel based on waste cooking oil is demonstrated, using micro heat exchangers with channel diameters of 200 μm. Biodiesel is pumped from a vessel through a micro heat exchanger in such a way, that pure seed crystals of saturated fatty acid methyl esters are produced at the outlet of the micro channels and injected back into the biodiesel vessel. Thus micro process engineering allows the reduction of the sum of saturated fatty acid methyl esters within biodiesel based on waste cooking oil from 21.3% to 9.6%. This corresponds to a reduction in CFPP value of 11 K, which means that this biodiesel can be used at temperatures down to 264 K.     

Transesterification of vegetable oil to biodiesel fuel using alkaline catalyst

Biodiesel is gaining more and more importance as an attractive fuel due to the depleting fossil fuel resources. Chemically biodiesel is monoalkyl esters of long chain fatty acids derived from renewable feed stock like vegetable oils and animal fats. It is produced by transesterification in which, oil or fat is reacted with a monohydric alcohol in presence of a catalyst to give the corresponding monoalkyl esters. This article reports experimental data on the production of fatty acid methyl esters from vegetable oils, soybean and cottonseed oils using sodium hydroxide as alkaline catalyst. The variables affecting the yield and characteristics of the biodiesel produced from these vegetable oils were studied. The variables investigated were reaction time (1-3 h), catalyst concentration (0.5-1.5 w/wt%), and oil-to-methanol molar ratio (1:3-1:9). From the obtained results, the best yield percentage was obtained using a methanol/oil molar ratio of 6:1, sodium hydroxide as catalyst (1%) and 60 ± 1 °C temperature for 1 h. The yield of the fatty acid methyl ester (FAME) was determined according to HPLC. The composition of the FAME was determined according to gas chromatography. The biodiesel samples were physicochemically characterized. From the results it was clear that the produced biodiesel fuel was within the recommended standards of biodiesel fuel.     

Continuous enzymatic production of biodiesel from virgin and waste sunflower oil in supercritical carbon dioxide

A continuous process for biodiesel production in supercritical carbon dioxide was implemented. In the transesterification of virgin sunflower oil with methanol, Lipozyme TL IM led to fatty acid methyl esters yields (FAME) that exceeded 98% at 20 MPa and 40 °C, for a residence time of 20 s and an oil to methanol molar ratio of 1:24. Even for moderate reaction conversions, a fractionation stage based on two separators afforded FAME with >96% purity. Lipozyme TL IM was less efficient with waste cooking sunflower oil. In this case, a combination of Lipozyme TL IM and Novozym 435 afforded FAME yields nearing 99%.     

Production of biodiesel through optimized alkaline-catalyzed transesterification of rapeseed oil

Present work reports an optimized protocol for the production of biodiesel through alkaline-catalyzed transesterification of rapeseed oil. The reaction variables used were methanol/oil molar ratio (3:1-21:1), catalyst concentration (0.25-1.50%), temperature (35-65 °C), mixing intensity (180-600 rpm) and catalyst type. The evaluation of the transesterification process was followed by gas chromatographic analysis of the rapeseed oil fatty acid methyl esters (biodiesel) at different reaction times. The biodiesel with best yield and quality was produced at methanol/oil molar ratio, 6:1; potassium hydroxide catalyst concentration, 1.0%; mixing intensity, 600 rpm and reaction temperature 65 °C. The yield of the biodiesel produced under optimal condition was 95-96%. It was noted that greater or lower the concentration of KOH or methanol than the optimal values, the reaction either did not fully occur or lead to soap formation.The quality of the biodiesel produced was evaluated by the determinations of important properties such as density, specific gravity, kinematic viscosity, higher heating value, acid value, flash point, pour point, cloud point, combustion point, cold filter plugging point, cetane index, ash content, sulphur content, water content, copper strip corrosion value, distillation temperature and fatty acid composition. The produced biodiesel was found to exhibit fuel properties within the limits prescribed by the latest American Standards for Testing Material (ASTM) and European EN standards.     

Fuel properties of biodiesel produced from the crude fish oil from the soapstock of marine fish

The soapstock of a mixture of marine fish was used as the raw material to produce the biodiesel in this study. The soapstock was collected from discarded fish products. Crude fish oil was squeezed from the soapstock of the fish and refined by a series of processes. The refined fish oil was transesterified to produce biodiesel. The fuel properties of the biodiesel were analyzed. The experimental results showed that oleic acid (C18:1) and palmitic acid (C16:0) were the two major components of the marine fish-oil biodiesel. The biodiesel from the mixed marine fish oil contained a significantly greater amount of polyunsaturated fatty acids than did the biodiesel from waste cooking oil. In addition, the marine fish-oil biodiesel contained as high as 37.07 wt.% saturated fatty acids and 37.3 wt.% long chain fatty acids in the range between C20 and C22. Moreover, the marine fish-oil biodiesel appeared to have a larger acid number, a greater increase in the rate of peroxidization with the increase in the time that it was stored, greater kinematic viscosity, higher heating value, higher cetane index, more carbon residue, and a lower peroxide value, flash point, and distillation temperature than those of waste cooking-oil biodiesel.     

Biodiesel production from Croton megalocarpus oil and its process optimization

Production of biodiesel from non-edible feedstocks is attracting more attention than in the past, for the purpose of manufacturing alternative fuels without interfering with the food chain. Biodiesel was produced using Croton megalocarpus oil as a non-edible feedstock. C. megalocarpus oil was obtained from north Tanzania. This study aimed at optimizing the biodiesel production process parameters experimentally. The parameters involved in the optimization process were the amount of the catalyst, of alcohol, temperature, agitation speed and reaction time. The optimum biodiesel conversion efficiency obtained was 88% at the optimal conditions of 1.0 wt.% amount of potassium hydroxide catalyst, 30 wt.% amount of methanol, 60 °C reaction temperature, 400 rpm agitation rate and 60 min reaction time. The properties of croton biodiesel which were determined fell within the recommended biodiesel standards. Croton oil was found with a free fatty acid content of 1.68% which is below the 2% recommended for the application of the one step alkaline transesterification method. The most remarkable feature of croton biodiesel is its cold flow properties. This biodiesel yielded a cloud and pour point of −4 °C and −9 °C, respectively, while its kinematic viscosity lay within the recommended standard value. This points to the viability of using croton biodiesel in cold regions.     

Biodiesel production using supercritical methanol/carbon dioxide mixtures in a continuous reactor

Fatty acid methyl esters (biodiesel) were produced by the transesterification of triglycerides with compressed methanol (critical point at 240 °C and 81 bar) in the presence of solid acids as heterogeneous catalyst (SAC-13). Addition of a co-solvent, supercritical carbon dioxide (critical point at 31 °C and 73 bar), increased the rate of the supercritical alcohols transesterification, making it possible to obtain high biodiesel yields at mild temperature conditions. Experiments were carried out in a fixed bed reactor, and reactions were studied at 150-205 °C, mass flow rate 6-24 ml/min at a pressure of 250 bar. The molar ratio of methanol to oil, and catalyst amount were kept constant (9 g). The reaction temperature and space time were investigated to determine the best way for producing biodiesel. The results obtained show that the observed reaction rate is 20 time faster than conventional biodiesel production processes. The temperature of 200 °C with a reaction time of 2 min were found to be optimal for the maximum (88%) conversion to methyl ester and the free glycerol content was found below the specification limits.     

Biodiesel production from pomace oil and improvement of its properties with synthetic manganese additive

Renewable energy sources are attracting more attention due to lower cost and lower pollution relative to fossil fuels. The aim of this experimental work is the production of renewable and clean methyl ester from pomace oil as an alternative fuel. This oil was obtained from pomace which is the waste of olive oil plants. Optimum producing conditions were determined experimentally. The maximum yield was obtained at 30% of methanol/oil ratio, 60 °C temperature for 60 min with NaOH catalyst. The properties of the biodiesel thus obtained were compared with diesel fuel requirements. An organic based Manganese additive improved the biodiesel properties. Doping the fuel at a ratio of 12 μmol/l oil methyl ester led to a 20.37% decrease in viscosity, 7 °C fall in the flash point and reduced the pour point from 0 °C to −15 °C. This blend of pomace oil methyl ester-diesel fuel with manganese additive was tested in a direct injection diesel engine. The maximum effect of the new fuel blend and diesel fuel on engine performance was obtained at 1400 rpm.     

Biodiesel production from vegetable oil using heterogenous acid and alkali catalyst

Zanthoxylum bungeanum seed oil (ZSO) with high free fatty acids (FFA) can be used for biodiesel production by ferric sulfate-catalyzed esterification followed by transesterification using calcium oxide (CaO) as an alkaline catalyst. Acid value of ZSO with high FFA can be reduced to less than 2 mg KOH/g by one-step esterification with methanol-to-FFA molar ratio 40.91:1, ferric sulfate 9.75% (based on the weight of FFA), reaction temperature 95 °C and reaction time 2 h, which satisfies transesterification using an alkaline catalyst. The response surface methodology (RSM) was used to optimize the conditions for ZSO biodiesel production using CaO as a catalyst. A quadratic polynomial equation was obtained for biodiesel conversion by multiple regression analysis and verification experiments confirmed the validity of the predicted model. The optimum combination for transesterification was methanol-to-oil molar ratio 11.69:1, catalyst amount 2.52%, and reaction time 2.45 h. At this optimum condition, the conversion to biodiesel reached above 96%. This study provided a practical method to biodiesel production from raw feedstocks with high FFA with high reaction rate, less corrosion, less toxicity, and less environmental problems.     

Effect of methanol content on enzymatic production of biodiesel from waste frying oil

The enzymatic production of biodiesel from waste frying oil with methanol has been studied using immobilized lipase Novozym 435 as catalyst. The effects of methanol to oil molar ratio, dosage of enzyme and reaction time were investigated. The optimum reaction conditions were methanol to oil molar ratio of 25:1, 10% of Novozym 435 based on oil weight and reaction period of 4 h at 50 °C obtaining a biodiesel yield of 89.1%. Moreover, the reusability of the lipase over repeated cycles was also investigated under standard conditions.     

Calcium oxide as a solid base catalyst for transesterification of soybean oil and its application to biodiesel production

In order to study solid base catalyst for biodiesel production with environmental benignity, transesterification of edible soybean oil with refluxing methanol was carried out in the presence of calcium oxide (CaO), -hydroxide (Ca(OH)₂), or -carbonate (CaCO₃). At 1 h of reaction time, yield of FAME was 93% for CaO, 12% for Ca(OH)₂, and 0% for CaCO₃. Under the same reacting condition, sodium hydroxide with the homogeneous catalysis brought about the complete conversion into FAME. Also, CaO was used for the further tests transesterifying waste cooking oil (WCO) with acid value of 5.1 mg-KOH/g. The yield of FAME was above 99% at 2 h of reaction time, but a portion of catalyst changed into calcium soap by reacting with free fatty acids included in WCO at initial stage of the transesterification. Owing to the neutralizing reaction of the catalyst, concentration of calcium in FAME increased from 187 ppm to 3065 ppm. By processing WCO at reflux of methanol in the presence of cation-exchange resin, only the free fatty acids could be converted into FAME. The transesterification of the processed WCO with acid value of 0.3 mg-KOH/g resulted in the production of FAME including calcium of 565 ppm.     

Biodiesel production from soybean oil and methanol using hydrotalcites as catalyst

Esters of fatty acids, derived from vegetable oils or animal fats, and known as biodiesel, are a promising alternative diesel fuel regarding the limited resources of fossil fuels and the environmental concerns. In this work, methanolysis of soybean oil was investigated using Mg-Al hydrotalcites as heterogeneous catalyst, evaluating the effect of Mg/Al ratio on the basicity and catalytic activity for biodiesel production. The catalysts were prepared with Al/(Mg + Al) molar ratios of 0.20, 0.25 and 0.33, and characterized by X-ray diffraction (XRD), textural analysis (BET method) and temperature-programmed desorption of CO₂ (CO₂-TPD). When the reaction was carried out at 230 °C with a methanol:soybean oil molar ratio of 13:1, a reaction time of 1 h and a catalyst loading of 5 wt.%, the oil conversion was 90% for the sample with Al/(Mg + Al) ratio of 0.33. This sample was the only one to show basic sites of medium strength. We also investigated the reuse of this catalyst, the effect of calcination temperature and made a comparison between refined and acidic oil.