Biodiesel production from non-edible Silybum marianum oil using heterogeneous solid base catalyst under ultrasonication

The aim of this study is to investigate modified TiO₂ doped with C₄H₄O₆HK as heterogeneous solid base catalyst for transesterification of non-edible, Silybum marianum oil to biodiesel using methanol under ultrasonication. Upon screening the catalytic performance of modified TiO₂ doped with different K-compounds, 0.7 C₄H₄O₆HK doped on TiO₂ was selected. The preparation of the catalyst was done using incipient wetness impregnation method. Having doped modified TiO₂ with C₄H₄O₆HK, followed by impregnation, drying and calcination at 600 °C for 6 h, the catalyst was characterized by XRD, FTIR, SEM, BET, TGA, UV and the Hammett indicators. The yield of the biodiesel was proportional to the catalyst basicity. The catalyst had granular and porous structures with high basicity and superior performance. Combined conditions of 16:1 molar ratio of methanol to oil, 5 wt.% catalyst amount, 60 °C reaction temperature and 30 min reaction time was enough for maximum yield of 90.1%. The catalyst maintained sustained activity after five cycles of use. The oxidative stability which was the main problem of the biodiesel was improved from 2.0 h to 3.2 h after 30 days using ascorbic acid as antioxidant. The other properties including the flash point, cetane number and the cold flow ones were however, comparable to international standards. The study indicated that Ti-0.7-600-6 is an efficient, economical and environmentally, friendly catalyst under ultrasonication for producing biodiesel from S. marianum oil with a substantial yield.     

Two-stage continuous production process for fatty acid methyl ester from high FFA crude palm oil using rotor-stator hydrocavitation

Two-stage continuous production process for fatty acid methyl ester (FAME) from crude palm oil was performed using the rotor–stator hydrocavitation reactor. The novel ABS filament printed rotor having spherical holes on the surface of the rotor which is an efficient, fast and cost-effective procedure, was installed in the stainless steel stator of hydrosonic reactor. The 3D printed hydrosonic reactor was used to treat the FFA-rich in MCPO by esterification and followed by transesterification to produce the methyl ester. The optimum conditions of both esterification and transesterification processes were determined using the response surface methodology (RSM). For the 1st step esterification, the conditions of methanol 17.7 vol%, sulfuric acid 2.9 vol%, 3000 rpm rotor speed, hole’s diameter and depth 4 and 6 mm, and 25 L/h MCPO, were used for decreasing the FFA from 11.456 to 1.028 wt%. For the 2nd step, transesterification was employed with the optimal condition of 28.6 vol% methanol, 6.2 g/L of potassium hydroxide, 3000 rpm rotor speed, the dimension of the spherical holes on the rotor’s surface having diameter of 6.4 mm and 6.2 mm in depth, and esterified oil flow rate 25 L/h, for producing the methyl ester to over 99.163 wt%. Moreover, the purified biodiesel yields and the average energy consumption for the entire two-stage continuous process between hydrosonic and ultrasonic clamp reactors were compared. The results of purified methyl ester clearly indicate that the methyl esters of 99.163 wt% and 97.814 wt% were achieved from hydrosonic and ultrasonic clamp reactors, respectively, under the same optimized conditions. The maximum yields of purified biodiesel were 97.51 vol% and 88.69 vol% using hydrosonic and ultrasonic clamp reactors, respectively. The average energy consumption for the entire continuous two-stage process for both hydrosonic and ultrasonic clamp reactors were 0.049 and 0.056 kW h/L, respectively. For practical industrial processes, stainless steel rotors inside the stator was manufactured by CNC machine, which was also verified under the optimum conditions. The results showed that 1.07 wt% FFA and 99.221 wt% methyl ester of were obtained from first step and second step, respectively.     

Modeling of process intensification of biodiesel production from Aegle Marmelos Correa seed oil using microreactor assisted with ultrasonic mixing

Conventionally, the batch type reactors were used for the production of biodiesel. However, in recent years, the usage of microreactors has started emerging as a significant substitute for biodiesel production due to its higher conversion rate at a short duration. These microreactors have a significantly high surface to volume ratio and high heat-mass transfer rate. The disadvantage of this type of reactors is its low mixing rate of the reagents. This can be overcome with the assistance of ultrasonic mixing. The main objective of this paper is to study the interlaced effect of a continuous flow microreactor and ultrasonic mixing on trans-esterification of Aegle Marmelos Correa seed oil using sodium methoxide catalyst. Results of microreactors with 0.3 mm and 0.8 mm diameter were compared. The effects of process parameters namely, flow rate (2–10 mL/min), reaction temperature (45–65 °C), catalyst amount (0.5–2.5 wt%), oil to methanol molar ratio (1:6–1:18) and ultrasonic mixing time (30–150 s) were studied using response surface methodology (RSM). The biodiesel yield of 98% and 91.8% were obtained for 0.3 mm and 0.8 mm microreactors, respectively. The maximum biodiesel yield observed in 0.3 mm reactor under following optimum conditions: 6.8 mL/min flow rate, 48 °C reaction temperature, 1.3 wt% catalyst, 1:9 oil to methanol molar ratio and 83 s ultrasonic mixing time. The predictive and generalization abilities of RSM and artificial neural network (ANN) models were evaluated and compared. The study showed that ANN and RSM models could predict the yield with an R² value of 0.9955 and 0.9900 respectively. However, the ANN model predicted the yield with the least mean square error value of 0.00001294, which is much lower than RSM.     

Intensification of biodiesel production from soybean oil and waste cooking oil in the presence of heterogeneous catalyst using high speed homogenizer

In the present work, high speed homogenizer has been used for the intensification of biodiesel synthesis from soybean oil and waste cooking oil (WCO) used as a sustainable feedstock. High acid value waste cooking oil (27 mg of KOH/g of oil) was first esterified with methanol using sulphuric acid as catalyst in two stages to bring the acid value to desired value of 1.5 mg of KOH/g of oil. Transesterification of soybean oil (directly due to lower acid value) and esterified waste cooking oil was performed in the presence of heterogeneous catalyst (CaO) for the production of biodiesel. Various experiments were performed for understanding the effect of operating parameters viz. molar ratio, catalyst loading, reaction temperature and speed of rotation of the homogenizer. For soybean oil, the maximum biodiesel yield as 84% was obtained with catalyst loading of 3 wt% and molar ratio of oil to methanol of 1:10 at 50 °C with 12,000 rpm as the speed of rotation in 30 min. Similarly biodiesel yield of 88% was obtained from waste cooking oil under identical operating conditions except for the catalyst loading which was 1 wt%. Significant increase in the rate of biodiesel production with yields from soybean oil as 84% (in 30 min) and from WCO as 88% (30 min) was established due to the use of high speed homogenizer as compared to the conventional stirring method (requiring 2–3 h for obtaining similar biodiesel yield). The observed intensification was attributed to the turbulence caused at microscale and generation of fine emulsions due to the cavitational effects. Overall it can be concluded from this study that high speed homogenizer can be used as an alternate cavitating device to efficiently produce biodiesel in the presence of heterogeneous catalysts.     

Role of H2O2 in the fluctuating patterns of COD (chemical oxygen demand) during the treatment of palm oil mill effluent (POME) using pilot scale triple frequency ultrasound cavitation reactor

Palm oil mill effluent (POME) is a highly contaminating wastewater due to its high chemical oxygen demand (COD) and biochemical oxygen demand (BOD). Conventional treatment methods require longer residence time (10–15 days) and higher operating cost. Owing to this, finding a suitable and efficient method for the treatment of POME is crucial. In this investigation, ultrasound cavitation technology has been used as an alternative technique to treat POME. Cavitation is the phenomenon of formation, growth and collapse of bubbles in a liquid. The end process of collapse leads to intense conditions of temperature and pressure and shock waves which assist various physical and chemical transformations. Two different ultrasound systems i.e. ultrasonic bath (37 kHz) and a hexagonal triple frequency ultrasonic reactor (28, 40 and 70 kHz) of 15 L have been used. The results showed a fluctuating COD pattern (in between 45,000 and 60,000 mg/L) while using ultrasound bath alone, whereas a non-fluctuating COD pattern with a final COD of 27,000 mg/L was achieved when hydrogen peroxide was introduced. Similarly for the triple frequency ultrasound reactor, coupling all the three frequencies resulted into a final COD of 41,300 mg/L compared to any other individual or combination of two frequencies. With the possibility of larger and continuous ultrasonic cavitational reactors, it is believed that this could be a promising and a fruitful green process engineering technique for the treatment of POME.     

Experimental and theoretical study of crude oil pretreatment using low-frequency ultrasonic waves

In this work, an ultrasound experimental setup was designed to investigate the feasibility of using low-frequency ultrasonic waves as a substitute to reduce the consumption of chemical demulsifiers in the pretreatment of crude oil. The experiments were planned to study the effects of irradiation time, ultrasonic field intensity and initial water content on the efficiency of separation. The results of experiments showed that by selecting a proper irradiation time and field intensity, it is possible to decrease the usage of demulsifiers by 50%. Moreover, a population balance model was proposed to explicate the experimental data. A hybrid coalescence model was developed to determine the frequency of aggregation. The parameters of the model were estimated by linear regression. The parameter estimation was performed using a parallel execution of the particle swarm optimization algorithm. The results of the model showed a decent agreement with the experimental data.