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In this work, the beads and powder potassium hydroxide (KOH) and potassium carbonate (K2CO3) supported on alumina oxide (Al2O3) were successfully prepared via incipient wetness impregnation technique. Herein, the perforated hydrophilic materials (PHM) made from low-density polyethylene (LDPE) was used as the catalyst reactor bed. The prepared catalysts were investigated using TGA, XRD, BET, SEM-EDX, TPD, FTIR while spent catalysts were analyzed using XRF and ICP-AES to study its deactivation mechanism. The catalytic performance of beads and powder KOH/Al2O3 and K2CO3/Al2O3 catalysts were evaluated via transesterification of waste cooking oil (WCO) to biodiesel. It was found that the optimum conditions for transesterification reaction were 1:12 of oil-to-methanol molar ratio and 5 wt.% of catalyst at 65 °C. As a result, the mesoporous size of beads KOH/Al2O3 and K2CO3/Al2O3 catalysts yielded 86.8% and 77.3% at 2 h' reaction time of fatty acids methyl ester (FAME), respectively. It was revealed that the utilization of PHM for beads K2CO3/Al2O3 increase the reusability of the catalyst up to 7 cycles. Furthermore, the FAME produced was confirmed by the gas chromatography-mass spectroscopic technique. From this finding, beads KOH/Al2O3 and K2CO3/Al2O3 catalysts showed a promising performance to convert WCO to FAME or known as biodiesel. [ABSTRACT FROM AUTHOR]

• Highly active Na 2 O impregnated-CNTs nanocatalyst was prepared and synthesized. • Positive metal cations possess Lewis acidity that increases the catalytic activity. • Na 2 O impregnated-CNTs nanocatalyst gave above 97% of FAME yield. • Leaching of Na+ lower than 5 mg L−1 as required by EN14214 international standard. The present work demonstrated the preparation of sodium oxide impregnated on carbon nanotubes (CNTs) and its application as a heterogeneous catalyst for transesterification of waste cooking oil. The catalyst was prepared by impregnation of metal oxide such as sodium oxide, Na 2 O on the CNTs by calcination at 500 °C for 3 h. It was assumed that the positive metal ion which is Na+ (cations) possess Lewis acidity, whereby, high negativity of oxygen ions can acts as the Brønsted bases, which could enhance the activity of the catalyst. The characterization of synthesized Na 2 O impregnated-CNTs nanocatalyst was performed using Temperature-programmed desorption of carbon dioxide (TPD-CO 2), X-ray diffraction (XRD), infrared spectroscopy and Field emission scanning electron microscope (FESEM). Herein, the mechanism of the transesterification process assisted by the Lewis acidic metal oxide on carbon support was proposed and explained. Series of reactions were carried out to determine the performance of the catalyst. It was found that the prepared Na 2 O (20 wt%) /CNTs catalysts yielded above 97% of FAME yield at 65 °C assisted by 3 wt% of catalyst amount and 20:1 of methanol-to-oil molar ratio in 3 h of reaction time. Moreover, the results on catalyst's reusability indicated that the catalyst could last for 3 subsequent reaction cycles due to deactivation of the catalyst caused by leaching of metal oxides and poisioning effect on the active sites. It can be concluded that the prepared Lewis acidic carbon catalyst has a potential to catalyse the production of biodiesel from waste cooking oil (WCO). [ABSTRACT FROM AUTHOR]

The present work investigated the biodiesel production from used cooking oil catalyzed by nano-bifunctional supermagnetic heterogeneous catalysts (RHC/K2O/Fe) derived from rice husk doped with K2O and Fe synthesized by the wet impregnation method. The synthesized catalysts (RHC/K2O/Fe) were characterized for crystallinity by X-ray diffraction spectroscopy (XRD), total acidity and basicity using CO2/NH3-TPD, textural properties through Brunauer-Emmett-Teller (BET), thermal stability via thermogravimetric analyzer (TGA), functional group determination by Fourier-transform infrared spectroscopy (FTIR), surface morphology through field emission scanning electron microscopy (FESEM), and magnetic properties by vibrating sample magnetometer (VSM). The VSM result demonstrated that the super-paramagnetic catalyst (RHC/K2O-20%/Fe-5%) could be simply separated and regained after the reaction using an external magnetic field. The operating conditions such as catalyst loading, methanol/oil molar ratio, temperature, and reaction duration were studied. The screened RHC/K2O-20%/Fe-5% catalyst was selected for further optimization and the optimum reaction parameters found were 4 wt % of catalyst, a molar ratio of methanol/oil of 12:1, 4 h reaction duration, and 75 °C reaction temperature with a maximal yield of 98.6%. The reusability study and reactivation results revealed that the nano-bifunctional magnetic catalyst (RHC/K2O-20%/Fe-5%) could be preserved by high catalytic activity even after being reused five times. [ABSTRACT FROM AUTHOR]

[Display omitted] The hydrothermal carbonization (HTC) technique is known for its advantages in producing hydrochar from biomass samples with high water content compared to conventional pyrolysis techniques. This study utilized HTC to produce an activated carbon catalyst from renewable mesocarp fiber derived from palm oil processing. The introduction of K 2 CO 3 and Cu(NO 3) 2 produced a bifunctional catalyst suitable for conversion of used cooking oil to biodiesel. The catalyst possessed a mesoporous structure with a BET surface area of 3909.33 m2/g. An optimum treatment ratio of 4:1 (K 2 CO 3 : Cu(NO 3) 2) provided elevated basic (5.52 mmol/g) and acidic (1.68 mmol/g) concentrations on the catalytic surface, which promoted esterification and transesterification reactions. Maximum yield (96.4%) of biodiesel was obtained at 70 °C for 2 h with 5 wt% catalyst and a 12:1 molar ratio of methanol to oil. The catalyst endured up to 5 reaction cycles while maintaining biodiesel yields of more than 80%. These findings indicated that HTC pretreatment yielded a high-quality bifunctional catalyst for conversion of low-quality used cooking oil for production of biodiesel. [ABSTRACT FROM AUTHOR]

Biodiesel is one of the ideal options, considering it is a renewable, biodegradable, non-toxic, environmentally friendly fuel with low pollutant emission. However, biodiesel encounters challenges, mostly connected to its high manufacturing costs, that hinder its continued development and advancement. Focusing on more affordable and environmentally friendly inputs, such as suitable and abundant feedstock and efficient catalysts, is crucial. This paper aims to summarize the literature on biodiesel production and life cycle assessment (LCA) studies, critically review the catalyst and oil feedstock employed, and the findings of the LCAs, focusing on spotting prospective low-cost feedstock sources. Furthermore, an overview of recent LCA-related works applied in various biodiesel processes incorporating various catalysts and oil feedstock was evaluated. The application of LCA and its environmental impacts in biodiesel production was discussed and summarised in table form. The importance of using a sustainable and favorable approach could result in cost-efficient biodiesel production. Additionally, the advantages and limitations of the LCA in biodiesel production have been discussed. Last, the status and challenges of LCA in biodiesel production are covered. The findings of using cheaper feedstock are expected to inspire future studies and help industry professionals develop sustainable biodiesel production. • A comprehensive review of LCA framework and biodiesel process technologies were covered. • LCA of biodiesel production using various catalysts and oil feedstock was reviewed. • Challenges and status were discussed for sustainable biodiesel production. [ABSTRACT FROM AUTHOR]

A highly mesoporous activated carbon derived from palm kernel shell was successfully prepared by hydrothermal-assisted carbonization (HTC) by improving the degradation of lignocellulosic composition and increase the porous texture of carbon structure. Additional NaOH treatment increased the surface area of the catalyst which enhanced the loading of the active site. Further impregnation of HTC based activated carbon with K 2 CO 3 and CuO via wet impregnation provided bifunctional characteristics suitable for simultaneous esterification and transesterification processes. The physicochemical properties of the prepared catalysts were conducted through the state-of-the-art techniques including N 2 adsorption-desorption analysis, functional group determination, surface morphology study, electron dispersive x-ray mapping, elemental distribution analysis, amount of basicity and acidity strength and thermal degradation behavior analysis. The investigation found that the chemical treatment with NaOH significantly increased the surface area from 3.57 to 3368.60 m2/g and impregnation with K 2 CO 3 and CuO offered higher amount of basicity of 5.73 mmol/g and acidity of 1.48 mmol/g, respectively. These properties enhanced the simultaneous esterification-transesterification of waste cooking oil to biodiesel. The catalytic study produced 95.36 ± 1.4% of biodiesel over 4 wt% of PKSHAC-K 2 CO 3(20%) CuO (5%) catalyst, 12:1 of methanol to oil molar ratio, reaction temperature of 70 °C for duration of 2 h. Meanwhile, the catalyst can be employed for five subsequent reaction cycles with FAME yield of 82.5 ± 2.5%. Thus, the synthesized bifunctional nanocatalyst supported on the HTC based activated carbon has been validated as an efficient catalyst for biodiesel production. Image 1 • Hydrothermal-assisted carbonization creates high surface area of 3368 m2/g. • Large surface area provides high surface for metal impregnation. • Amount of basicity and acidity was improved with high loading of active sites. • Reaction over PKSHAC-K 2 CO 3(20%) CuO (5%) produced 95.36 ± 1.4% biodiesel from WCO. • Catalyst can be reutilized for 5 cycles with <80% biodiesel. [ABSTRACT FROM AUTHOR]

The use of carbon-based catalysts has drawn so much interest in biodiesel production due to improved reaction performance. However, there was lack of comprehensive studies in term of its kinetic and thermodynamic perspective. Therefore, a methodical study is essential to uncover the influence of the carbon catalyst with respect to reaction rate and yield. This study represents kinetic and thermodynamic of heterogeneously K 3 PO 4 /AC-catalysed transesterification. It was done correspondingly via pseudo-first order mechanism and Eyring-Polanyi equation, whereby, under the optimal reaction temperature of 333.15 K, all data have fitted satisfactorily in both models with resulted R 2 of 0.99, respectively. Activation energy (E a ) and Gibbs free energy (ΔG) were calculated as 34.2 kJ mol −1 and −33.68 kJ mol −1 , indicating the reaction was exergonic and spontaneous at high temperature. [ABSTRACT FROM AUTHOR]

Hydrothermal carbonization (HTC) provides alternatives technique to produce a nanosize activated carbon from biomass with a high surface area. Herein, this study we prepared empty fruit bunch-based activated carbon (EFBHAC) using HTC technique. The activated carbon was then functionalized with K 2 CO 3 and Cu(NO 3) 2 to produce bifunctional nano-catalyst for simultaneous esterification-transesterification of waste cooking oil (WCO). The physicochemical properties were performed i.e. N 2 sorptions analysis, TPD-CO 2 /NH 3 , FESEM, EDX, FTIR and XRD analysis. The results revealed that produced EFBHAC possessed a BET surface area of 4056.17 m2 g−1, with pore volume of 0.827 cm3 g−1 and 5.42 nm of pore diameter resulting from hydrolysis, dehydration decarboxylation, aromatization and re-condensation during HTC process. Impregnation of EFBHAC with K 2 CO 3 and Cu(NO 3) 2 granted a high amount of basicity and acidity of 9.21 mmol g−1 and 31.41 mmol g−1, respectively, accountable to high biodiesel yield of 97.1%, produced at the optimum condition of 5 wt% of catalyst loading, 12:1 of methanol to oil molar ratio at 70 °C for 2 h. More than 80% of biodiesel was produced after the 5th cycle depicted the good reusability. The transformations from WCO to biodiesel was confirmed via 1H NMR, FTIR and TGA analysis. Fuel properties revealed kinematic viscosity of 3.3 mm2 s−1, cetane number of 51, flash point of 160.5 °C, cloud and pour point of 11 °C and −3 °C, respectively. These results show the excellent potential of waste materials to prepare bifunctional nano-catalysts to produce higher biodiesel yield which has potential to be commercialized. [Display omitted] • Empty fruit bunch was transformed into high quality activated carbon via HTC process. • Catalyst support help to reduce costs as the reaction occurs on the catalyst surface. • Bifunctional nano-catalyst overcome saponification problem through one-pot reaction. • Produced biodiesel is proven to have quality equivalent to international standards. [ABSTRACT FROM AUTHOR]