Ultrasound assisted two-stage biodiesel synthesis from non-edible Schleichera triguga oil using heterogeneous catalyst: Kinetics and thermodynamic analysis

A review on recent biodiesel intensification process through cavitation and microwave reactors: Yield, energy, and economic analysis

The use of biodiesel as a reliable and green energy source has grown over the past few years. Biodiesel is sustainable and biodegradable because it is only made from vegetable contents and waste cooking oil. Although biodiesel has many advantages over conventional fuels, there are still a lot of technological issues that need to be addressed during the production process. The yield of biodiesel produced using conventional methods is poor and the process is time-consuming. Process enhancements like cavitation and microwave have thus been developed to address this problem. Starting with a comparison to the conventional biodiesel process, this paper has reviewed the most recent developments in the increase of mixture and transfer of heat in these two reactors. This paper examined biodiesel improvement using microwave and cavitation reactors, including biodiesel yield, by meticulously reviewing and analyzing previous works. The production of biodiesel from various raw materials using a range of catalysts, energy requirements, as well as operating factors, activation energy, and constraints also have been discussed. Additionally, the economic analysis discusses the feasibility and cost-effectiveness of implementing these technologies on a commercial scale. Overall, this review provides valuable insights into the intensification of biodiesel production using cavitation and microwave reactors while considering both the technical and economic aspects.

Continuous Double-Step Esterification Production of Palm Fatty Acid Distillate Methyl Ester Using Ultrasonic Tubular Reactor

Double-step esterification to produce biodiesel from palm fatty acid distillate (PFAD) was performed by utilizing an ultrasound clamp reactor. Six pairs of ultrasonic clamps were attached to the left and right sides of the stainless-steel tube, and each pair was separated 100 mm apart from each other. Therefore, a total of 12 units of ultrasound clamps distributed 4800 W maximum power (12 × 400 W) throughout the continuous reactor by an ultrasonic generator. To optimize each step of the continuous esterification process for producing methyl ester from PFAD, a response surface methodology was used. The final 93.32 wt % methyl ester purity was attained under a double-step esterification process. For the first step, a 3.75:1 molar ratio of methanol to PFAD (46.4 vol % methanol), 6.6 vol % sulfuric acid, and 400 mm length of ultrasound clamp at 25 L/h PFAD flow rate for converting the PFAD to 60.24 wt % methyl ester were recommended. For the second step, the esterification was repeated under a molar ratio of methanol to the first esterified oil of 2.87:1 (61.6 vol % methanol), 5.6 vol % of sulfuric acid, and 400 mm length of ultrasound clamp at 25 L/h esterified oil flow rate. The ultrasonic clamp reactor achieved high yields of esterified oil and the crude biodiesel in a relatively short residence period of 32 s. To determine the product yields of a double-step esterification process, the maximum yields were 103.9 wt % first esterified oil, 107.6% crude biodiesel, and 98 wt % purified biodiesel when calculated on the basis of 100 vol % initial PFAD. The average energy consumed in the production of double-step esterification biodiesel was 0.05796 kWh/L. Therefore, this current approach has a high potential for producing biodiesel with less energy and requires less time to convert the PFAD to a high purity of methyl ester.

Transesterification Using Ultrasonic Spray of Triolein Containing CaO Particles into Methanol Vapor in a 3-Phase Reactor

Ultrasonic spraying was used in a three-phase reactor to produce small droplets of triolein mixed with CaO as a solid catalyst at temperatures above the boiling point of methanol for enhancement of the transesterification of triolein. Droplets fell in the methanol countercurrent flow and were collected at the bottom of the reactor, followed by circulation to the ultrasonic spray system. The experimental parameters included triolein flow rates of 2.5–9.0 mL/min, reaction temperatures of 70–100 °C, and catalyst contents of 1.0–7.0 wt%. The methanol feed rate was set to be constant. The results suggested that the enhancement was successful after using the three-phase reactor by generating a high contact surface area for the droplets, which was a key factor for determining the performance. Comparing the results with conventional transesterification in the liquid phase using the same CaO at 60 °C, the three-phase reactor produced a methyl ester yield 2–5% higher during the 60 min trial period. However, the yield became lower after 60 min because the mass transfer of methanol to the droplets was limited. The transesterification kinetics were estimated based on the experimental data—assuming a first-order reaction—and the results indicated a range of the rate constant, an apparent activation energy, and a pre-exponential factor of 1.21–3.70 × 10−2 min−1, 36.1 kJ mol−1, and 64.9 min−1, respectively, suggesting that the three-phase reactor was effective for fast transesterification at the initial stage.

Experimental investigation of biodiesel production from Madhuca longifolia seed through in situ transesterification and its kinetics and thermodynamic studies

The present investigation aims to develop simultaneous extraction and conversion of inedible Madhuca longifolia seed oil into biodiesel by one-step acid-catalyzed in situ transesterification/reactive extraction process. Six different types of pretreatment were used to assess maximum yield of biodiesel. The maximum yield of 96% biodiesel was acquired with ultrasonic pretreatment at 1% moisture content, 0.61 mm seed grain size, 55 °C temperature, 400 rpm stirring speed, 15 wt% catalyst (H₂SO₄) concentration, and with 1:35 seed oil to methanol ratio in a time period of 180 min. This reaction kinetics precedes first order also the finest value of rate constant and activation energy were calculated as 0.003 min^-1 and 14.840 kJ mol^-1. The thermodynamic energy properties ΔG, ΔH, and ΔS are computed as 96457.172 J/mol, 12121.812 J/mol K, and - 257.12 J/mol K correspondingly. The enumerated outcome illustrates a heat absorb non-spontaneous/endergonic and endothermal reaction. The result of proposed work unveils ultrasonic pretreatment escalates the biodiesel efficiency and reactive extraction exemplifies the clean, cost-effective single-step approach for production of biodiesel from non-edible sources.

Kinetics and Thermodynamics Study of Ultrasound-Assisted Depolymerization of k-Carrageenan in Acidic Solution

K-carrageenan is a natural polymer with high molecular weight ranging from 100 to 1000 kDa. The oligocarrageenan with low molecular weight is widely used in biomedical application. The aim of this work was to depolymerize k-carrageenan in an acidic solution with the assistance of ultrasound irradiation. The ultrasonication was conducted at various pH (3 and 6), temperatures (30-60 °C), and depolymerization time (0-24 minutes). The results show that the depolymerization reaction follows pseudo-first-order kinetic model with reaction rate constant of 1.856×10-7 to 2.138×10-6 s-1. The reaction rate constant increases at higher temperature and lower pH. The Q10-temperature coefficients of the depolymerization are 1.25 and 1.51 for pH 6 and 3, respectively. The enthalpy of activation (ΔH‡) and the Gibbs energy of activation (ΔG‡) are positive, while the entropy of activation (ΔS‡) is negative, indicating that the activation step of the ultrasound-assisted depolymerization of k-carrageenan is endothermic, non-spontaneous, and the molecules at the transition state is more ordered than at the ground state. The ΔH‡ and the ΔS‡ are not affected by temperature, while the ΔG‡ is a weak function of temperature. The ΔH‡ and ΔS‡ become smaller at higher pH, while the ΔG‡ increases with the increase of pH. The kinetics and thermodynamics analysis show that the ultrasound-assisted depolymerization of k-carrageenan in acidic solution is possibly through three mechanisms, i.e. bond cleavage due to cavitational effect of microbubbles, hydroxyl radical and hydrogen peroxide, as well as proton. Copyright © 2020 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Optimization of an Ultrasonic-Assisted Biodiesel Production Process from One Genotype of Rapeseed (TERI (OE) R-983) as a Novel Feedstock Using Response Surface Methodology

In recent years, due to the favorable climate conditions of Iran, the cultivation of rapeseed has increased significantly. The aim of this study was to investigate the possibility of biodiesel production from one genotype of rapeseed (TERI (OE) R-983). An ultrasonic approach was used in order to intensify the reaction. Response surface methodology (RSM) was applied to identify the optimum conditions of the process. The results of this research showed that the conversion of biodiesel was found to be 87.175% under the optimized conditions of a 4.63:1 molar ratio (methanol to oil), 56.50% amplitude, and 0.4 s pulses for a reaction time of 5.22 min. Increasing the operating conditions, such as the molar ratio from 4:1 to 5.5:1, amplitude from 50% to 72.5%, reaction time from 3 min to 7 min, and pulse from 0.4 s to 1 s, increased the FAME (fatty acid methyl esters) yield by approximately 4.5%, 2.3%, 1.2%, and 0.5%, respectively. The properties of the TERI (OE) R-983 methyl ester met the requirements of the biodiesel standard (ASTM D6751), indicating the potential of the produced biodiesel as an alternative fuel.

Effect of high-intensity ultrasound irradiation on the stability and structural features of coconut-grain milk composite systems utilizing maize kernels and starch with different amylose contents

In this paper, a coconut milk composite system (glycerin monostearate as an emulsifier) with different maize additives (e.g., maize kernels and starch with different amylose contents) was treated with high-intensity ultrasound irradiation (HIUS, frequency 20 kHz). The stability and structural features of the added coconut milk emulsion were studied. Comparing the mechanical emulsifications, coconut milk with maize kernels was similar to coconut milk with high-amylose maize starch. However, coconut milk with a high proportion of amylopectin had the best stability. After ultrasonic treatment, the particle sizes were found to be smaller than those in the nonultrasound-treated coconut milk, and the particles demonstrated a monomodal size distribution. The electronegativity of the compound system was significantly improved. The electronegativity of the maize kernel and high-amylose maize starch-coconut milk systems was significantly decreased, and this change was beneficial to the stability of the systems. However, ultrasonic treatment did not change the fluid type of the coconut milk compound system (which showed pseudoplastic fluid characteristics). The proportion of amylose in maize had an important influence on the stability of the compound system. The apparent viscosity and crystallization order of the high-amylose maize starch-coconut milk system were high. However, the waxy maize starch system showed high complex viscosity and tended to be liquid with ultrasonic treatment. Ultrasound treatment reduced the particle size of coconut milk and homogenized the distribution of the system. Additionally, the amylase of the system contained amylose encapsulated in the interfacial layer after ultrasound treatment. The tiny gel beads formed by waxy maize starch had a good fusion effect on coconut milk fat/protein droplets. The results indicated that the stability of coconut-grain milk composite systems can be enhanced with the use of maize additives and ultrasound irradiation through space effects, electrostatic effects and continuous phase viscosity.

A novel acid catalyst based on super/subcritical CO2-enriched water for the efficient esterification of rosin

Rosin esters are widely applied as masticatory substances and beverage stabilizers, while classical acid-catalysed processes will lead to metal residue or environmental issues. Super/subcritical CO₂-enriched high temperature liquid water (HTLW) as a green acid catalyst in the esterification reaction of rosin with glycerol was investigated. The pH of CO₂-H₂O binary system, as calculated based on gas-liquid equilibrium, charge balance and chemical equilibrium equations, ranged from 3.49 to 3.70 depending on the reaction conditions, indicating effective acid catalysis. Response surface methodology experiments showed the optimum conditions were 3.5 h, 3.9 MPa CO₂ pressure, a rosin-to-glycerol molar ratio of 1.32 and 269°C, and an enhanced esterification yield of 94.74% was achieved, which was superior to that obtained using a ZnO catalyst. It was found that the esterification kinetics was a pseudo first-order reaction, and the enthalpy and entropy of activation were calculated using the Arrhenius-Polanyi equation. The presence of super/subcritical CO₂-enriched HTLW catalyst can decrease the activation energy and significantly accelerate the reaction rate.

Intensification of heterogeneously catalyzed Suzuki-Miyaura cross-coupling reaction using ultrasound: Understanding effect of operating parameters

Palladium-catalyzed Suzuki-Miyaura cross-coupling reaction is a significant reaction for obtaining industrially important products. The current research work deals with intensification of reaction of 4-bromoanisole and phenylboronic acid catalyzed with 5wt% Pd/C (5% by weight Pd supported on C available as commercial catalyst) using ultrasound and more importantly, without use of any additional phase transfer catalyst. Heterogeneous catalyst has been selected in the present work so as to harness the benefits of easy separation and the possible limitations of heterogeneous operation are minimized by introducing ultrasonic irradiations. The effect of operating parameters such as ultrasound power, temperature, catalyst loading and molar ratio on the progress of reaction has been investigated. It has been observed that an optimum power, temperature and catalyst loading exist for maximum benefits whereas higher molar ratio was found to be favourable for the progress of the reaction. Also, the use of ultrasound reduced the reaction time from 70min required in conventional approach to only 35min under conditions of frequency of 22kHz, power dissipation of 40W and catalyst loading as 1.5mol% (refers to total quantum of catalyst used in the work) in ethanol-water system under ambient conditions. The work also demonstrated successful results at ten times higher volume as compared to the normally used volumes in the case of simple ultrasonic horn. Overall, the work has successfully demonstrated process intensification benefits obtained due to the use of ultrasound for heterogeneously catalyzed Suzuki-Miyaura cross-coupling reaction.

Ultrasound assisted selective catalytic transfer hydrogenation of soybean oil using 5% Pd/C as catalyst under ambient conditions in water

Catalytic transfer hydrogenation (CTH) is an alternative approach that does not require the use of potentially dangerous hydrogen gas. Pd/C is the most favoured catalyst for the selective hydrogenation of soybean oil yielding lower extent of formation of stearic acid and trans-isomer, which have adverse health effects. The present work deals with intensification of catalytic transfer hydrogenation of soybean oil in the presence of 5wt.% Pd/C using ultrasound under ambient reaction conditions. The effect of important operating parameters such as ultrasound power, temperature, type of hydrogen donor, catalyst loading and donor concentration on the progress of reaction has been investigated. It was established that the maximum extent of hydrogenation as indicated by reduction in iodine value from 135 to 95 was observed under optimized conditions of irradiation power as 100W, 22kHz frequency, 90% duty cycle, ammonium formate concentration of 0.32mol/50ml water and 2% (w/w) Pd/C loading at ambient temperature and pressure in the presence of water as solvent. The approach also offered excellent selectivity with much lower trans-isomer formation as compared to the conventional approach of high pressure hydrogenation. Overall, the work has successfully demonstrated process intensification benefits due to the use of ultrasound for the Pd/C catalyzed transfer hydrogenation of soybean oil.

Chemical/Structural Modification of Canola Oil and Canola Biodiesel: Kinetic Studies and Biodegradability of the Alkoxides

Canola oil and canola biodiesel derived alkoxides are prepared in the present investigation through a series of structural modifications. Epoxidation of canola oil and canola biodiesel were carried out by hydrogen peroxide using IR-120 as an acidic catalyst. The alkoxylation of epoxidized feedstocks was promoted using 2-propanol and tert-Butyl alcohol in the presence of montmorillonite catalyst and optimum reaction conditions were obtained for complete epoxide conversion to alkoxylated products as follows: reaction temperature of 90 °C, epoxide to alcohol molar ratio of 1:6, and reaction time between 6 and 8 h. The products were identified with one- and two-dimensional Nuclear Magnetic Resonance (NMR) techniques, and the kinetic and thermodynamic parameters of the alkoxylation reactions were also investigated. The thermo-oxidative stability, rheology, biodegradability and lubricity properties of the prepared alkoxides were determined using American Society for Testing and Materials (ASTM) and American Oil Chemists Society (AOCS) standard methods. Structural modification of the feedstocks enhanced the significant properties for lubrication and exhibited their potential application as gear and engine oils.

Sono-sulfated zirconia nanocatalyst supported on MCM-41 for biodiesel production from sunflower oil: Influence of ultrasound irradiation power on catalytic properties and performance

Sono-sulfated zirconia nanocatalyst supported on MCM-41 was prepared by an ultrasound-assisted impregnation/hydrothermal hybrid method. The effect of irradiation power was studied by changing power of the sonication (30, 60 and 90W) during the synthesis which led to different physiochemical properties of the nanocatalyst. XRD, FESEM, EDX, FTIR and BET analyses exhibited smaller particles with higher surface area and less population of particle aggregates at highly irradiated nanocatalysts. The nanocatalyst irradiated at 90W for 30min showed a very narrow particle size distribution. About 59% of nanocatalyst particles were in the range of 1-30nm. The performance of investigated nanocatalysts in biodiesel production from sunflower oil showed ultrasound-assisted synthesized nanocatalysts had higher conversion in comparison to non-sonicated catalyst. Biodiesel conversion in catalyst with 90W and 30min ultrasonic irradiation exceeded 96.9% under constant condition at 60°C reaction temperature, methanol/oil molar ratio of 9:1 and 5% catalyst concentration. After five cycles, biodiesel conversion of non-sonicated catalyst was well maintained in a high extend (71.4%) while biodiesel conversion of non-sonicated catalyst barely reached to 43.5%. Among sonicated nanocatalysts, with increasing power of irradiation, the nanocatalyst represented higher conversion and reusability.