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For further resource utilization of solid waste steel slag and the reduction in biodiesel production costs, this study used steel slag as a carrier to synthesize a CaO-CeO2/slag solid base catalyst for the effective transesterification of palm oil into fatty acid methyl esters (FAMEs). The synthesis involved a two-step impregnation of steel slag with nitrate of calcium and cerium and thermal activation at 800 °C for 180 min. Then, the catalysts' textural, chemical, and CO2 temperature-programmed desorption properties were characterized. The catalytic activity depended highly on the ratio of Ca-Ce to steel slag mass; the CaO-CeO2/slag-0.8 catalyst showed outstanding performance. Characterization showed that the surface area and total basicity of the Ca-Ce/slag-0.8 catalyst were 3.66 m2/g and 1.289 mmol/g, respectively. The reactivity results showed that FAMEs obtained using 7 wt.% catalyst, 9:1 of methanol-to-palm-oil molar ratio, 180 min reaction duration, and 70 °C reaction temperature was optimum (i.e., 95.3% yield). In addition, the CaO-CeO2/slag-0.8 catalyst could be reused for at least three cycles, retaining 91.2% of FAMEs yield after n-hexane washing. Hence, the catalyst exhibits an excellent potential for cost-effective and environmentally friendly biodiesel production. [ABSTRACT FROM AUTHOR]

A novel acid-base bifunctional Zn/Ca–Zr catalyst has been synthesized successfully for biodiesel production from palm oil and acidified oil. The influence of synthetic factors on the catalytic activity of resulting Zn/Ca–Zr were discussed. Furthermore, the FAMEs yield was optimized to achieve the maximum value using the Taguchi approach. Results showed that the catalyst synthesized using a metal stoichiometric ratio of 4 : 4: 4, hydrothermal conditions, and activation temperature of 850 °C exhibited the best activity. The highest FAMEs yield was found to be 94.9% under the conditions of 5 wt% catalyst dosage, methanol/palm oil molar ratio of 20, and temperature of 170 °C at 3 h. The contribution percentage indicated that the methanol/oil molar ratio had the most significant effect on the FAMEs yield. Moreover, the Zn/Ca–Zr catalyst can catalyze the simultaneous esterification and transesterification of acidified palm oil with a 95.1% FAMEs yield and 93.3% acid reduction rate. And a 78.2% FAMEs yield can be maintained after four repeated cycles. Molecular simulations indicated the active site of Zn was more easily attacked by FFAs for esterification, while the active site of Ca was retained to adsorb methanol for transesterification, which explained the catalyst's acid-base bifunctional characteristics. [ABSTRACT FROM AUTHOR]

Abstract Thermal degradation properties of stearic acid and its esterification derivants of methyl stearate and ethyl stearate are investigated through thermogravimetric analysis. Based on experiments, which are conducted at the temperature heated rates of 10, 15 and 20 K min−1, the iso-conversional methods of Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa are used to calculate the apparent activation energy. Further, the Avrami theory is used to estimate the apparent reaction order. Apparent thermodynamic parameters of the apparent enthalpy change, apparent Gibbs free energy change and apparent entropy change are calculated. Calculations of apparent kinetic and thermodynamic parameters illustrate that thermal activity of stearic acid is distinctly heightened after esterification and the derived derivants are more easily activated. Meanwhile, influences of alcohol type on esterification products are weak. Conclusions from this study make more comprehensive understanding of the thermal events of biodiesel to be favor for its commercial application. Highlights • Thermogravimetric is practical in evaluating thermal degradation of biodiesel. • Esterification derivants are more easily activated than stearic acid. • Influences of alcohol type on esterification products are weak. • Thermal degradation of biodiesel could be described by more than one model. • Kinetic and thermodynamic calculations manifest thermal degradation profoundly. [ABSTRACT FROM AUTHOR]

A series of carbon catalysts are synthesized through the arylation diazonium salt reduction approach from coal to catalyze esterification of oleic acid with methanol for biodiesel production. Under the activated carbon preparation temperature of 900 °C, mass ratio of 4-aminobenzenesulfonic acid to activated carbon of 6 and arylation temperature of 45 °C, the synthesized carbon catalyst gains the surface area and pore volume of 629.3 m 2  g −1 and 0.29 cm −3  g −1 , respectively. Besides, the carbon catalyst possesses abundant and strong active sites with the 4-sulfophenyl group density of 0.97 mmol g −1 and acid strength of 0.8 < pH < 3.3. Catalytic capability of the carbon catalyst, which is synthesized under the above optimized condition, in esterification is stronger than the commercial Amberlyst-15, where the maximum efficiency achieves 95.04% with the carbon catalyst added mass percentage of 12%, molar ratio of methanol to oleic acid of 10, esterification duration of 4 h and esterification temperature of 65 °C. Due to leaching of the 4-sulfophenyl groups, esterification efficiency declines to 77.63% for the fifth reused cycle of the carbon catalyst. Meanwhile, the regenerated carbon catalyst supplies the esterification efficiency of 86.05%. Chemical composition of the produced biodiesel is identical to pure methyl oleate and its fuel properties are in accordance with ASTM D 6751. [ABSTRACT FROM AUTHOR]

Powder coal is carbonized under nitrogen atmosphere and then treated with concentrate sulfuric acid with the assistance of microwave radiation for heterogeneous acid catalyst synthesis and the capability in catalyzing esterification of oleic acid with methanol for biodiesel production is subsequently studied. The catalysts are characterized by N 2 adsorption-desorption, ultimate analysis, X-ray diffraction, Raman spectra, attenuated total reflectance-Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and acid amount tests to obtain the physicochemical property. Microwave irradiation is a faster and simpler process than the conventional heating, and the sulfonation duration can be shortened to be 5 min. Under the carbonization temperature of 250 °C for 30 min and sulfonation temperature of 75 °C for 5 min, the synthesized catalyst gains the acid amount of 1.73 mmol g −1 and esterification efficiency of 98.1% is achieved with the catalyst dosage mass percentage of 10 wt%, molar ratio of methanol to oleic acid of 12, esterification temperature of 65 °C and esterification duration of 180 min, where the commercial Amberlyst-15 catalyst only presents the efficiency of 71.5% under the same condition. Though the catalytic capability is crippled during the recycling reusage, it can be easily regenerated with its mostly original catalytic activity. [ABSTRACT FROM AUTHOR]

A series of coal-based heterogeneous acid catalysts are prepared by partial carbonization followed by sulfonation approach and the performances in esterification for methyl oleate production are conducted. Characterization methods of XRD, N 2 adsorption-desorption, SEM, TG, FTIR, EDX, acid density tests and Hammett indicator method are carried out to reveal the physical and chemical characteristics of the prepared catalysts. Catalyst with the highest acid density of 1.09 mmol g −1 could be prepared under the condition of carbonization temperature at 350 °C for 2 h and sulfonation with concentrated sulfuric acid at 135 °C for 4 h. Acid value reduction of 97.29% on oleic acid through esterification with methanol, which is catalyzed by this coal-based heterogeneous acid, could be achieved under the optimized condition of 10 wt.% catalyst dosage, molar ratio of methanol/oleic acid of 10, reaction temperature at 67 °C and reaction duration of 4 h. Characterization results demonstrate that carbon in the catalyst, which is composed of aromatic carbon sheets with COOH and SO 3 H groups, is in amorphous structure and its acid strength is 3.3 < p K a < 0.8. Meanwhile, this catalyst could provide favorable thermal stability high to 220 °C and retain satisfactory catalytic activity after five cycles. In addition, catalytic capability could be reactivated with the acid value reduction efficiency of 95.30% after the fifth re-usage. [ABSTRACT FROM AUTHOR]

Thermogravimetric analysis in conjunction with Fourier transform infrared spectroscopy (TG-FTIR) is used to investigate thermal degradation properties of oleic acid and its esterification derivants of methyl ester and ethyl ester. Based on TG experimental results, which are operated under nitrogen atmosphere from 298 to 773 K at the sample temperature heated rates of 5, 10, and 15 K min −1 , respectively, two degradation iso-conversional approaches of Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) are mentioned to calculate the apparent activation energy, based on which the apparent pre-exponential factor is obtained. Meanwhile, Avrami theory is used for the apparent reaction order estimation. Further, thermodynamic parameters of the apparent enthalpy change, apparent Gibbs free energy change and apparent entropy change are calculated to label the thermal degradation process directly. Also, the evolved gaseous products from TG are detected by FTIR online to understand the thermal degradation comprehensively. Information about fatty acid and its methyl ester and ethyl ester derived from TG-FTIR, especially the comparison between esterification derivants and their feedstock, has been rarely reported and is expected to contribute to the commercial application of biodiesel. [ABSTRACT FROM AUTHOR]

The development of heterogeneous base catalyst with acid resistance has become a major topic in the current research on the biodiesel production process. Halloysite nanotubes (HNTs) is supported with bimetallic of calcium and zinc for modification and labeled as HNTs-Ca/Zn to show both the acid and base characteristics. Further, this supported catalyst is used to produce biodiesel from the acidulated palm oil through catalyzing transesterification in one-step in this study. The HNTs-Ca/Zn catalyst, synthesized by the impregnation method, is characterized by TG-DTG, XRD, XPS, TEM, SEM-EDX, nitrogen adsorption-desorption, CO 2 /NH 3 -TPD, FTIR and Raman. The capability of the HNTs-Ca/Zn catalyst in catalyzing transesterification is investigated, where the maximum yield of 95.22% is achieved with the molar ratio of Zn to Ca of 1.5. The advantage of HNTs-Ca/Zn1.5 catalyst is prominent when the transesterification source oil is acidulated, where the biodiesel yield of 92.66% is obtained even at the acid value of 26.02 mg KOH g−1. Besides, reusability of the catalyst is acceptable, where the yield of 77.91% is maintained after the fourth reused cycle. Further, the Genetic Algorithm-Back Propagation (GA-BP) neural network is used to train and predict the transesterification parameters of the reaction temperature, catalyst amount and methanol to oil molar ratio. The prediction of the biodiesel yield is reasonable. At the predicted reaction parameters of 158 °C, catalyst amount of 7.1 wt.% and methanol to oil molar ratio of 15.5, the predicted biodiesel yield is 98.71%, where the experimental verification value is 98.60%. Therefore, the HNTs-Ca/Zn catalyst is considered to demonstrate exceptional catalytic performance and recyclability, offering the potential for biodiesel production. [Display omitted] • HNTs-Ca/Zn acid-base bifunctional catalysts are produced for biodiesel production. • The HNTs-Ca/Zn1.5 catalyst performs excellent acid resistance under 26.02 mg KOH g−1. • Transesterification parameters are optimized by the GA-BP neural network. • The maximum biodiesel yield of 98.60% is obtained under the optimum conditions. [ABSTRACT FROM AUTHOR]

• Biodiesel is produced through transesterification catalyzed La-dolomite catalyst. • La to dolomite molar ratio is optimized as 1 for La-dolomite catalyst preparation. • Biodiesel yield of La-dolomite catalyzed transesterification is up to be 98.7%. • Biodiesel yield is 95.9% for the fifth reused cycle of La-dolomite catalyst. • Activation energy of La-dolomite catalyzed transesterification is 57.68 kJ mol−1. In this study, biodiesel production through transesterification of palm oil using the lanthanum complex dolomite (La-dolomite catalyst) as the heterogeneous base catalyst is investigated. The La-dolomite catalyst preparation is optimized with the La to dolomite molar ratio of 1 and activation temperature of 800 °C. With the catalyst added mass percentage of 7 wt%, molar ratio of methanol to oil of 18, transesterification temperature of 65 °C and transesterification duration of 180 min, the biodiesel yield of 98.7% is achieved and the activation energy of the La-dolomite catalyzed transesterification is calculated to be 57.68 kJ mol−1. The La-dolomite presents satisfying reusability and the biodiesel yield is 95.9% for the fifth reused cycle, where it is 89.1% for the pure calcined dolomite catalyst. Finally, the main physicochemical properties of the transesterification product are measured and compared with GB/T 20828–2015. This study validates the application of the La-dolomite catalyst in catalyzing transesterification for the biodiesel production. [ABSTRACT FROM AUTHOR]

A series of heterogeneous acid catalysts are synthesized from bamboo activated carbon through arylation using sulfanilic acid without reductant. Both the catalyst synthesis conditions and parameters for esterification of oleic acid with ethanol are optimized. The heterogeneous acid catalysts are characterized by XRD, FTIR, N 2 absorption-desorption, EDX and acid-base neutralization titration. At the molar ratio of benzylsulfonic acid group to bamboo activated carbon of 1, sulfonation temperature of 50 °C and sulfonation duration of 10 min, the heterogeneous acid catalyst presents the mesoporous microstructure with surface area of 225.71 m 2  g −1 and pore volume of 0.12 cm −3  g −1 , and total acid density of 1.69 mmol g −1 . With the catalyst added mass percentage of 12% (relative to the oleic acid mass) and molar ratio of ethanol to oleic acid of 7 at 85 °C for 180 min, esterification efficiency of 96% is achieved, which is higher than 91% of esterification with methanol at 65 °C. Microstructure shrinkage is the main reason for catalyst deactivation, and the regenerated heterogeneous acid supplies the catalytic efficiency of 94%. [ABSTRACT FROM AUTHOR]