Catalyst For Esterification Research Articles

Supercritical methanol-induced esterification of microalgal lipids employing biomineralized cell walls as the catalyst

The methyl esterification of lipids employing supercritical methanol is an environmentally benign method since it does not produce alkaline wastewater, as is the case with conventional methods employing sodium hydroxide. Previous studies have shown that solid base catalysts are effective in decreasing reaction temperatures in the supercritical methanol methyl esterification. We focused on the coccolithophore Pleurochrysis carterae, which exhibits coccolith, i.e., CaCO3 cell walls, and confirmed that the coccoliths acted as a catalyst in the methyl esterification of lipids in P. carterae employing supercritical methanol. To confirm the catalytic effect of the coccolith, the results of the supercritical methanol reaction of extracted lipids from P. carterae without coccolith were compared. The results showed that significant differences occurred, confirming that coccolith of P. carterae acts as a catalyst. To confirm the catalytic effect of CaCO3, the main component of coccolith, the green alga Chlorella vulgaris with cellulose cell walls was used to compare non-catalyst, addition of CaCO3and addition of CaSO4–0.5H2O, which is reported to be effective. The results revealed that the amount of the product obtained from the methyl esterification of fatty acids in C. vulgaris employing CaCO3 was more significant than those obtained without any catalyst or with CaSO4–0.5H2O, indicating the effectiveness of CaCO3 as a catalyst for methyl esterification by supercritical methanol. Coccolithophores, which exhibit CaCO3 cell walls, are desirable raw materials for biofuels because they can function as catalysts.

Sodium doped zirconia drenched SBA-15 as a reusable solid catalyst for concurrent esterification and transesterification of low-quality oils

Sodium doped zirconia impregnated SBA-15 has been prepared without using hydrothermal treatment trailing the wet impregnation route. The prepared catalyst has been characterized by employing various techniques viz., BET for surface area analysis, SEM for morphological study, XPS for element oxidation state determination. It was found that catalyst seized both acidic and basic sites therefore, successfully employed for one-pot or concurrent esterification and transesterification of virgin cottonseed oil and high FFA containing vegetable oils. Under optimum reaction conditions of catalyst concentration of 10 wt% with respect to weight of oil, MeOH/oil molar ratio of 30:1 and at 65 °C reaction temperature, the catalyst could confer > 98 % fatty acid methyl ester yield within 3 h of reaction duration. Regeneration study advocated that the catalyst may well be recycled for 5 successive cycles without any significant trouncing of activity and even yielded 86% fatty acid methyl esters during 6th cycle. Keywords: Heterogeneous catalysts, mesoporous, basicity, acidity, transesterification, thermodynamic parameters

Insight into the noble-metal-free NiCoAl catalyst boosting the reductive esterification of furancarboxylic acid to methyl 2-tetrahydrofuroate

Reduction of high oxidation level furancarboxylic acid (FA) with the retention of the carboxyl group is particularly important for the utilization, however, it has been rarely explored over non-precious catalysts and is challenging. Here, we demonstrate an excellent noble-metal-free trimetallic NiCoAl catalyst for the reductive esterification of FA to methyl 2-tetrahydrofuroate (MeTHFC), which delivers the complete conversion of FA and MeTHFC yield of up to 99%. More importantly, Ni0.5Co0.5Al could offer YMeTHFC > 90% over five reusability cycles. Detailed investigations suggest that the high activity originates from the synergistic of Ni-Co alloys sites and acid sites in Ni0.5Co0.5Al. The Ni-Co alloy sites were mainly responsible for the adsorption and dissociation of H2, which in turn improved hydrogenation activity, while the acid sites facilitated the esterification of FA and the adsorption and further activation of the furan ring. This work provides an eco-friendly noble-metal-free catalyst to enrich the strategies for the reductive esterification process.

Stability of novel eco-friendly sulfated metal oxide solid acid catalyst for esterification and condensation reaction

<h2>Abstract</h2> In this paper, the metal oxide supports and active component precursors of SO₄²⁻/M_xO_y solid acid were screened, and S₂O₈²‐⁻/Cr₂O₃-Fe₂O₃ (S₂-CrFe) was prepared. The NH₃-TPD results showed that the solid acids loaded with S₂O₈²⁻ had stronger acidity than those loaded with SO₄²⁻, and the mixture of the two metal oxides could adjust the acidity of the solid acids. The optimum conditions for the preparation of S₂-CrFe were as follows: the mass ratio of Cr₂O₃ to Fe₂O₃ was 1:1, the concentration of ammonium persulfate solution was 1 mol/L, and the calcination temperature was 550 °C. The yield of esterification catalyzed by the solid acid obtained under these conditions was 91.2%. The stability of the new solid acid was investigated, and it was found that S₂-CrFe was easy to be deactivated, so it was considered to be modified by organosilane and lanthanum oxide. The experimental results showed that after the modified solid acid was recycled for four times, the yield of ethyl acetate was more than 60%.

Protonic ionic liquids as efficient phase-separation catalysts for esterification of trimethylolpropane and acrylic acid

The H 2 SO 4 -based imidazole ionic liquids performed as phase-separation catalysts for the esterification of trimethylolpropane and acrylic acids, exhibiting the best trimethylolpropane conversion (100%) and trimethylolpropane acrylate selectivity (86.4%). • H 2 SO 4 -based ionic liquids were applied as catalysts for esterification of trimethylolpropane and acrylic acid. • A novel phase-separation catalytic process was observed during the reaction. • 100% of trimethylolpropane conversion and 86.4% of trimethylolpropane acrylate selectivity were achieved. • The phase-separated ionic liquids can be steadily reused. Trimethylolpropane acrylate (TMPTA) is becoming an important organic chemistry intermediate, but it’s synthesis through the acid-catalyzed esterification of trimethylolpropane and acrylic acid is a challenge due to the poor activity and catalyst separation problems. In this work, a series of 1,3-propanesultone (PS)-functionalized imidazole ionic liquids (ILs) are prepared and evaluated as the acid catalysts for this reaction, including the catalytic performance comparison, optimization of reaction conditions, and the catalytic reusability. The obtained H 2 SO 4 -based IL ([IMPSH]HSO 4 ) caused a phase-separation catalytic process (reacted as a homogeneous catalyst, but precipitated at the end of reaction like a heterogeneous catalyst), presenting the best trimethylolpropane conversion (100%) and TMPTA selectivity (86.4%). Such catalytic performance is even better than that of homogeneous H 2 SO 4 . Moreover, the catalyst can be steadily reused at least four times without obvious change in activity and its structure. The highly efficient and environmentally benign performance of [IMPSH]HSO 4 -catalyzed esterification of trimethylolpropane and acrylic acid make it possible to achieve industrial applications.

Sulfonic acid-functionalized silica with controlled hydrophobicity as an effective catalyst for esterification of levulinic acid

As one of the essential additives in biodiesel and flavoring agents, solvents, and plasticizers in industry, ethyl levulinate (EL) has gained attention in the last two decades, and the global production of the compound is rapidly increased over the years. So far, esterification of biomass-derived levulinic acid (LA) with ethanol (EtOH) in the presence of highly corrosive mineral acid catalysts is the most common technique for the reaction. To avoid the harsh environment during the reaction and to ease the separation of the catalyst, the research has been recently focused on developing highly active solid acid catalysts. In this research, we have systematically investigated the catalytic activity of sulfonic acid-functionalized silica (SiO2-SO3H) with different hydrophobicity for esterification of LA with EtOH. The hydrophobicity of SiO2-SO3H was tuned by incorporating three different alkylsilanes, e.g., methyl (Me), octyl (Oct), and hexadecyl (HD) silanes on the surface of the material. We found that the longer the alkyl group, the lower the acidity and thus resulted in the lower the catalytic activity. On the other hand, the particle size and hydrophobicity increase with the length in the alkyl group. SiO2-SO3H modified with the methyl group (SiO2-SO3H/Me) showed the highest acidity (0.76 mmol g–1) and the highest catalytic performance (70.6% conversion). Moreover, while all alkyl-modified catalysts followed pseudo-first-order, the pseudo-first-order rate constant (k1p) for the reaction over SiO2-SO3H/Me was 5.4 × 10–3 min–1. The kinetic results of this study could be useful for reactor modeling and simulation in the future.

2-Hydroxyethylammonium Bisulfate (2-HEAS) as a Brønsted Acidic Ionic Liquid Catalyst for Esterification

Brønsted acidic ionic liquids (BAILs) with great variety as effective catalysts for the synthesis of valuable chemicals such as esters have attracted particular attention. In this work, an ionic acid 2-hydroxyethylammonium bisulfate (2-HEAS) was successfully synthesized and used to catalyze esterification reactions. The powerful FTIR and NMR techniques were used to determine the ionic liquid properties. All results and data showed that the ionic liquid has been synthesized successfully. The catalytic activity of IL during esterification of acetic acid in the presence of various alcohols was investigated. The impacts of a few imperative parameters such as reaction time and temperature, molar ratio of acid to alcohol, and catalyst dosage were investigated. The results showed that the 2-HEAS catalyst is suitable for esterification of methanol, ethanol, and butanol. Furthermore, the esterification efficiencies of methyl acetate, ethyl acetate, and butyl acetate produced were high and quantitative. Moreover, a homogeneous catalyst was employed to separate esters from the reaction medium. Additionally, the catalyst was easily removed from products and was reusable six times.

Metal-exchanged phosphotungstate nanoparticles with improved acidity as the catalyst for esterification of glycerol with acetic acid

Abstract A series of metal-exchanged phosphotungstate salts, Fe-TPA, Cr-TPA, Cu-TPA, and Ni-TPA were synthesized by sonication and tested for glycerol esterification with acetic acid to obtain biofuel additives. A systematic, chemical, structural, and morphological characterization and determination of acidity were used by various analytical techniques. XRD and FT-IR studies confirmed the Keggin structure of all metal exchanged phosphotungstate salts with no impurities coming from metal nitrate salts. The incorporation of metal cations in phosphotungstic acid leads to decreased crystallite size as seen from XRD diffractograms. N2 adsorption-desorption analysis showed that the Type II isotherms were obtained for all metal exchanged phophostungstate salts, characteristic of non-porous or macroporous materials. SEM images of metal exchanged phosphotungstate salts displayed well-shaped crystalline particles. SEM-EDX analysis showed that the calculated tungsten metal ratios are in good agreement with the theoretical ratios of those for all the metal exchanged salts, verified by XRF results. The exchange of protons by the metal cations improved the thermal stability observed in the TGA analysis. The acidity strengths, from NH3-TPD analysis, were found in the following order; TPA &gt; Fe-TPA &gt; Cr-TPA &gt; Cu-TPA. Additionally, pyridine-FTIR gives that the exchanging of transition metal into the phosphotungstic acid decreased the Brønsted acidity while increasing the Lewis acidity and this mostly affects the efficiency of the esterification reaction. The activity of metal exchanged salts was in the given order; Fe-TPA &gt; Cr-TPA &gt; Cu-TPA &gt; Ni-TPA. Among these Fe-TPA salt, having a good ratio of Brønsted and Lewis acidity, have the selectivity for di- and triacetin (68 and 10%), with the highest conversion (96%). The iron phosphotungstate salts are a promising catalyst with sustainable Bronsted acidity during the reaction, high desired product selectivity at low temperature, easy synthesizability, inexpensive, and environmentally friendly.

Gold Nanoparticles Supported on Poly(2,6‐dimethyl‐1,4‐phenylene oxide) as Robust, Selective and Cost‐Effective Catalyst for Aerobic Oxidation and Direct Oxidative Esterification of Alcohols

AbstractA new catalytic system based on gold nanoparticles (AuNPs) incarcerated in poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) matrix has been synthesized and successfully tested in aerobic oxidation of alkyl alcohols. PPO is a cheap and commercially available polymer, showing nanoporous morphology, high glass transition temperature (Tg =220 °C), semi‐crystallinity, excellent thermal stability, and interesting chemo‐physical properties. The synthesis of the AuNPs‐PPO catalyst is simple, cost‐effective and allows a fine control of the gold concentration, as well as an optimal dispersion of 7–8 nm sized AuNPs in the polymer matrix. AuNPs‐PPO is an efficient, robust and selective catalyst active in the aerobic oxidation and oxidative esterification of alcohols in water under mild reaction conditions (35 °C, atmospheric pressure of oxygen). The testing of AuNPs‐PPO in aerobic oxidation of 1‐phenylethanol to acetophenone, as a benchmark reaction, highlighted that this gold catalyst exhibits activity values among the highest so far reported for polymer‐supported AuNPs under mild reaction conditions. The oxidation of primary alcohols, such as benzyl and cinnamyl alcohols, could be addressed to the corresponding aldehyde or carboxylate derivatives. Alkyl cinnamates were obtained with efficiency in the one‐pot aerobic oxidation of cinnamyl alcohol in the presence of alkyl alcohols, such as n‐butanol or n‐hexanol. The role of the polymer matrix and the reaction conditions on both activity and selectivity of the AuNPs‐PPO catalyst were also investigated and discussed.

Synthesis of sulfonated carbon-based catalysts from organosolv lignin and methanesulfonic acid: Its activity toward esterification of stearic acid

This work aims to offer a new acid type, methanesulfonic acid, to produce environmentally benign sulfonated carbon-based catalysts for esterification. The sulfonated catalysts were synthesized using two types of lignin sources, commercial lignin (CL) and lignin extracted from sugarcane bagasse (EL) through solvothermal carbonization and followed by sulfonation step. Overall, lignin sources and types of sulfonic acids were the factors affecting the catalyst performance. The results indicated that the high oxygenated functional groups on surface of chars prepared from EL gave the materials with better catalytic performance than prepared from CL. Moreover, the catalysts functionalized with methanesulfonic acid presented the higher catalytic activity than with sulfuric acid due to their higher surface area and better thermal stability. The highest methyl stearate yield (89.2%) from esterification of stearic acid with methanol were achieved at 240 °C with the reaction time of 10 min using the molar ratio of stearic acid to methanol of 1:9 and catalyst loading of 5 wt% in case of using EL char as a carbon source and methanesulfonic acid as a sulfonating agent. The catalyst could also be reused up to seven cycles with a yield higher than 80%.

Hydrolytic vs. Nonhydrolytic Sol-Gel in Preparation of Mixed Oxide Silica–Alumina Catalysts for Esterification

The development of green and sustainable materials for use as heterogeneous catalysts is a growing area of research in chemistry. In this paper, mesoporous SiO2-Al2O3 mixed oxide catalysts with different Si/Al ratios were prepared via hydrolytic (HSG) and nonhydrolytic sol-gel (NHSG) processes. The HSG route was explored in acidic and basic media, while NHSG was investigated in the presence of diisopropylether as an oxygen donor. The obtained materials were characterized using EDX, N2-physisorption, powder XRD, 29Si, 27Al MAS-NMR, and NH3-TPD. This approach offered good control of composition and the Si/Al ratio was found to influence both the texture and the acidity of the mesoporous materials. According to 27Al and 29Si MAS NMR analyses, silicon and aluminum were more regularly distributed in NHSG samples that were also more acidic. Silica–alumina catalysts prepared via NHSG were more active in esterification of acetic acid with n-BuOH.

Chemical insights into flexizyme-mediated tRNA acylation

A critical step in repurposing the cellular translation machinery for the synthesis of polymeric products istheacylation of transfer RNA (tRNA) with unnatural monomers. Toward this goal, flexizymes, ribozymescapable of aminoacylation, have emerged as a uniquely adept tool for charging tRNA with everincreasingly diverse substrates. In this review, we present a library of monomer substrates that have been tested for tRNA acylation with the flexizyme system. From this mile-high view, we provide insights for understanding the chemical factors that influence flexizyme-mediated tRNA acylation. We conclude that flexizymes are primitive esterification catalysts that display a modest binding affinity to the monomer's aromatic recognition element. Together, these robust, yet flexible, flexizyme systems provide researchers with unprecedented access for preparing unnatural acyl-tRNA and the opportunity to repurpose the translation machinery for the synthesis of novel biologically derived structures beyond native proteins and peptides.

Solvent-free oxidative esterification of furfural to 2-methyl furoate using novel copper-exchanged tungstophosphoric acid supported on montmorillonite K-10 catalyst

The valorization of bio-based chemicals using green processes plays a vital role in the up-gradation of biofuels that are useful to reduce the demand for fossil feedstock. Furfural is a promising renewable biomass-based platform chemical, which can be catalyically transformed into many value-added chemicals. Oxidative esterification of furfural produces 2-methyl furoate, which is used as flavour and fragrance in fine chemical industries. There lies a challenge to find a cheaper and efficient catalyst for one-pot oxidative esterification of furfural. Supported heteropolyacids (HPAs) are useful for many biomass transformation reactions owing to their strong Bronsted acidity as well as high surface area, which both help promote catalytic surface reaction. In the present work, we have synthesized Cu exchanged tungstophosphoric acid (TPA) with different supports, viz. SiO2, ZrO2, and montmorillonite K-10 clay (K10) which were prepared by incipient wetness impregnation. Oxidative esterification of furfural with methyl alcohol was investigated using the aforesaid catalysts and tert-butyl hydroperoxide (TBHP) as an oxidant. 20% w/w Cu substituted TPA (abbreviated as Cu-TK10) catalyst is green, stable, active, selective, reusable, and cheaper. It was observed that the higher acidic strength and good surface area are responsible for oxidative esterification of furfural and methyl alcohol with higher selectivity. In this work, 91% conversion with 100% selectivity was achieved in 5 h at 120 °C using 1:3 molar ratio of furfural and TBHP with a catalyst loading of 0.01 g/cm3. The synthesized catalysts were analyzed by various characterization techniques such as SEM, XRD, FT-IR, BET surface area analyser, and NH3-TPD, before and after use. This is an interesting example of valorization of furfural.

Sulfonated Mesoporous Silica-Carbon Composite Derived from a Silicate-Polyethylene Glycol Gel and Its Application as Solid Acid Catalysts

Solid acid catalyst is a promising alternative to the counterpart homogeneous acid for esterification reaction from the viewpoint of reusability and environmental concerns. This work aims to develop sulfonated mesoporous silica-carbon composite as solid acid catalyst for the esterification. The catalyst was synthesized from sodium silicate as the silica precursor and polyethylene glycol (PEG) as both carbon precursor and template via a sol-gel route in an aqueous system. Then, it was carbonized to produce mesoporous silica-carbon composite. Using the proposed method, the surface area of the silica-carbon composite could reach as high as 1074.21 m2/g. Although the surface area decreased to 614.02 m²/g when it was functionalized with sulfonate groups, the composite had a high ionic capacity of 5.3 mEq/g and exhibited high catalytic activity for esterification reaction of acetic acid with ethanol. At a reaction temperature of 80 °C, the acetic acid conversion reached 76.55% in 4 h. In addition, the catalyst had good reusability, which can be comparable with the commercial catalyst Foltrol F-007. It appears that the sulfonated silica-carbon composite prepared from sodium silicate using PEG as the carbon source a promising candidate as catalyst for esterification and the related area. Copyright © 2021 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).

Synthesis and characterization of novel chlorinated SnO2 nanomaterials for biodiesel production via stearic acid esterification with methanol

Up to now the chlorinated SnO2 (xClSnOAmmonia) as solid acid catalysts for stearic acid esterification have not been reported in the literature. Non-chlorinated SnO2 catalysts were prepared by precipitation method using different precipitating agents (ammonium hydroxide, SnOAmmonia, sodium carbonate, SnOCarbonate, and urea, SnOUrea). The impact of different precipitation agents and chloride ion (Cl¯) doping on physicochemical properties of SnO2 were studied by XRD, HR-TEM, BET and NH3-TPD analyses. The surface parameters of SnO2 catalyst were varied with changing the precipitant agent and Cl¯ ion doping. The total acidity of SnOAmmonia was about 32 % and 64 % larger than SnOCarbonate and SnOUrea, respectively. Furthermore, the chlorinated SnO2 with the highest Cl¯ ion loading (0.30ClSnOAmmonia) exhibited a noteworthy increase in total acidity as compared to non-chlorinated SnO2.The catalytic activity of the non-chlorinated catalysts increased gradually as a following order SnOUrea < SnOCarbonate < SnOAmmonia. Noteworthy, the chlorinated catalysts demonstrated progressively enhancements in the activity as increasing Cl¯ ion loadings.

Synergic effect between gold and vanadate substituted hydroxyapatite support for synthesis of methyl methacrylate by one-step oxidative esterification

• Au/HVP catalyst displays excellent performance for oxidative esterification. • The high selectivity derives from the good capacity of activation of oxygen. • O 2 was adsorbed and activated with the synergic effect of gold with the support. • The active sites are located at the interfacial sites between gold and the support. Synthesis of methyl methacrylate (MMA) via direct oxidative esterification from methacrolein (MAL) and methanol (MeOH) is of great significance in chemical industry. Supported gold catalysts are considered as one of the most potential candidates for this reaction but suffer from low activity and deactivation issue. Herein, by modulating the phase structure of hydroxyapatite (HAP) with different cations and anions, a synergic effect between gold and vanadate substituted hydroxyapatite (HVP) support for the synthesis of MMA was discovered. In direct oxidative esterification, among the evaluated catalyst/support systems, Au/HVP catalyst displays the best performance and unprecedented stability, which acts as one of the best-performing gold catalysts for oxidative esterification. Various characterizations such as X-ray diffraction (XRD), Raman spectra, scanning electron microscopy (SEM), transmission electron microscope (TEM) and in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) of CO were conducted to disclose the structural and electronic property of the catalysts. Through in-situ FT-IR spectra of MAL and MeOH, the substrate was proved to be easily transformed on Au/HVP catalyst to ester. Besides, the presence of O 2 was found to facilitate the adsorption of MAL. The results of temperature programmed desorption (TPD) of O 2 implied that gold particles together with HVP support is promotional for activation and dissociation of oxygen, leading to good activity and high selectivity.

Effect of water on the organofunctionalization of SAPO-5 to form an efficient oleic acid esterification catalyst

In this study, SAPO-5 having a high silicon content was synthesized and further modified by functionalization with sulfonic acid groups using 3-mercaptopropyltrimethoxysilane (MTPS) as a precursor. In particular, we focused on the effect of water on the organofunctionalization process using SAPO-5 either dehydrated under vacuum (S5–SO3H/Vac) or without any thermal pretreatment (S5–SO3H). Using X-ray diffractometry, inductively coupled plasma–optical emission spectroscopy, elemental analysis of carbon, nitrogen, hydrogen and sulfur, thermogravimetric analysis, Fourier transform infrared spectroscopy, and 29Si, 27Al, 31P, and 13C NMR spectroscopy, it was possible to identify important structural differences in the obtained hybrid materials. The results showed that S5–SO3H has a Si:S molar ratio five times larger than that of S5–SO3H/Vac. The presence of Tm sites (organic-modified silica sites, Si–C bonds), as revealed by 29Si MAS-NMR measurements, suggests that the organic pending groups are bonded covalently to the Si–OH groups in the SAPO-5 network during silanization. Further differences between the material obtained under dry conditions and that prepared from hydrated SAPO-5 were revealed by measuring the acidity via potentiometric titration: S5–SO3H was 40% more acidic than S5–SO3H/Vac. Both materials were also tested for their catalytic oleic acid esterification ability. Although the turnover frequency of S5–SO3H/Vac was four times higher than that of S5–SO3H, its conversion after five sequential cycles dropped from 97.4 to 28.3%. In contrast, S5–SO3H yielded a conversion of 84.4%, starting from 99.4%, after the same number of cycles; thus, microporous SAPO-5 is a promising catalyst support for reactions involving bulky molecules such as oleic acid.

Free Fatty Acid Reduction of Palm Oil Mill Effluent (POME) Using Heterogeneous Acid Catalyst for Esterification

In this study, Amberlyst-15 as heterogeneous catalyst was used for the reduction of free fatty acid (FFA) from the palm oil mill effluent (POME) for biodiesel production with acid-catalyzed esterification process. The objective of this study was to decrease a high FFA in POME to less than 2 wt.% FFA, for used as a raw material to produce biodiesel in the second-step transesterification process. Amberlyst-15 as an eco-friendly catalyst with non-toxic wastes after reactions, when compared to homogeneous catalysts such as sulfuric acid. Therefore, an esterification reaction with a heterogeneous acid catalyst was carried out to examine the FFA conversions. The conditions of two parameters of Amberlyst-15 catalyst (10–40 wt.%), and 1–8 h reaction time were varied, whereas the methanol to oil molar ratio and the speed of the stirrer were fixed at 5:1 and 300 rpm, respectively. As a result, the FFA sharply decreased from 89.16 wt.% to 1.75 wt.% under the conditions of 40 wt.% of Amberlyst-15, 5 h reaction time, 5:1 molar ratio methanol to oil, speed of the 300 rpm stirrer. The Amberlyst-15 had the potential to reduce high FFA in POME using the esterification reaction.

Application of acidic ionic liquids for the treatment of acidic low grade palm oil for biodiesel production

Employing low quality feedstocks for biodiesel production can present cost reduction opportunities due to its wide availability and cost effectiveness. However, most low quality feedstocks have high free fatty acid (FFA) content which is not feasible for biodiesel production through direct transesterification due to soap formation. Thus, a pre-treatment step through FFA esterification could reduce the FFA content while simultaneously yielding fatty acid methyl esters (FAME). In this study, the catalytic activity of ten ionic liquids (ILs) were screened for the esterification of FFA in acidic crude palm oil (ACPO). 1‑butyl‑3-methylimidazolium hydrogen sulfate as IL exhibited the highest catalytic activity and was further investigated to determine the optimum operating parameters such as IL dosage, molar ratio, reaction temperature and time. Single factor optimization was employed for the laboratory scale batch esterification reaction. The FFA content was reduced from 10.77% to less than 1% using the following optimum conditions: 4% IL to oil, molar ratio of 10:1 (methanol to oil), 120 min reaction time and 60 °C reaction temperature. Under optimum conditions, the IL can be recycled five times with minimal loss in catalytic activity, highlighting its feasibility as an industrial catalyst for esterification of acidic oils and fats.

Mineral acid-activated sugarcane bagasse ash as solid acid catalyst for the liquid phase esterification of acetic acid with n-amyl, benzyl, and n-butyl alcohols

Liquid phase esterification of carboxylic acids with alcohols is an important organic synthesis process in the petrochemical and fine chemical industries. These reactions required mineral acid catalysts, which are corrosive and difficult to be separated from the reaction mixture. Therefore, the use of solid acid catalysts is economically viable, reusable, and environmentally amicable. In this study, sugarcane bagasse ash (SCBA) was impregnated with 1–10 wt% of sulfuric acid (H2SO4) or perchloric acid (HClO4) for the liquid-phase esterification of acetic acid with n-amyl, benzyl, and n-butyl alcohols under various reaction conditions. The catalysts were characterized using X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier-transform infrared (FTIR), N2 sorption, and scanning electron microscopy (SEM). Their acidities were measured through the dehydration of isopropyl alcohol and pyridine adsorption FTIR. The effects of the acid activation of SCBA on its texture properties (such as surface area and the nature of the surface functional groups), acidity, and catalytic activity were studied in detail. FTIR of the pre-saturated catalysts with pyridine reflected the presence of Brønsted and Lewis acid sites. The concentrations of the acid sites were improved by increasing the percentages of acid loading. All the catalysts showed high catalytic activity with 100% selectivity to ester formation. The catalyst pretreated with H2SO4 showed the higher ester yields compared to that of treated with HClO4. The optimum reaction conditions were a reaction time of 2 h, an alcohol-to-acid molar ratio of 1:3, and catalyst loading of 0.5 g. The highest yields of n-amyl acetate, benzyl acetate, and n-butyl acetate of 98, 90.8, and 70.5%, respectively, were achieved over the SCBA pretreated with 10 wt% H2SO4 catalyst. The high catalytic performance of this catalyst is due to the high surface acidity generated by the inductive effect of the SO bond.