Low-quality Oil Research Articles

Synergistic effect of La2O3-Al2O3 based catalysts for efficient biodiesel production

Comprehensive synergistic effect of La2O3-Al2O3 on the catalytic performance of transesterification reaction of palm oil with methanol for biodiesel production was studied. The prepared catalyst possessed bifunctional acid-base properties. The well-balanced of acido-basic sites amounts over the catalyst at the La2O3 loading of 40 % and the calcined temperature of 600 °C gave the maximum fatty acid methyl ester (FAME) content of 93.12 %, under the optimum conditions of 1:30 molar ratio of oil to methanol, 200 °C reaction temperature, 39 bar reaction pressure, 5 wt% catalyst loading and 5 h reaction time. The catalyst exhibited reasonable stability. The partial leaching of La3+ ions and deposition of organics resulted in the loss of activity. The results showed that the catalyst generated new weak basic sites and more effective in the transesterification compared to strong basic sites as reported previously. The different strengths of new acid sites were also formed. The balancing of acid-base sites amount was a key to control the catalytic activity and the formation of side reactions. This gives critical guidance in further catalyst development for biodiesel production of waste oils or low-quality oils via simultaneous esterification and transesterification, which helps the biodiesel system being economical and scalable.

Usefulness of the 1H NMR Multisuppression Approach for the Global Characterization of Monovarietal Extra-Virgin Olive Oils.

Extra-virgin olive oil (EVOO) is one of the most appreciated vegetable oils worldwide, but its high price makes it prone to suffer adulteration with lower quality oils. Therefore, it is important to have methodologies able to study EVOO composition as a whole in a simple and fast way, in order to guarantee its quality and safety. For this purpose, in this study, commercial samples of five Spanish olive cultivars (Arbequina, Arroniz, Cornicabra, Hojiblanca, Picual) were studied by Proton Nuclear Magnetic Resonance (1H NMR) spectroscopy, using standard and multisuppression pulses. The aim was to explore the possibility of 1H NMR use to characterize in a single run and in a global way the composition of these monocultivar oils, regarding not only their main components (fatty acids supported on triglycerides) but also minor ones (squalene, sterols, diterpenic wax esters of phytol and geranylgeraniol, phenolic and secoiridoid derivatives, like tyrosol, hydroxytyrosol, oleacein, oleocanthal, and lignans, among others, and aldehydes). The use of univariate and multivariate statistical analyses confirmed the presence of compositional features that were specific to some olive varieties. The Arbequina and Arroniz oils showed the most characteristic features that allowed for clearly differentiating them from the others. In contrast, the discrimination between the Cornicabra, Hojiblanca and Picual oils was not so easily achieved.

RSM and ANN methodologies in modeling the enhanced biodiesel production using novel protic ionic liquid anchored on g-C3N4@Fe3O4 nanohybrid

Herin, a new nanohybrid acid catalyst was fabricated for the efficient biodiesel production. At the first, magnetic porous nanosheets of graphitic carbon nitride (g-C3N4@Fe3O4) was prepared and then functionalized with sulfonic acid. Next, the preparation of the catalyst was completed by mixing this surface modified support with n-methyl imidazolium butyl sulfonate zwitterion to achieve non-covalent immobilized acidic ionic liquid on g-C3N4@Fe3O4 support. The catalyst underwent characterization through various techniques such as 1H and 13C NMR, FTIR, SEM, TEM, TGA, EDX and BET which revealing that the magnetic support loaded acidic ionic liquids via a robust charge interaction effect enabling the one-pot production of biodiesel from low-quality oils. Furthermore, the catalyst could be simply recovered using a permanent magnet and reused multiple times without a significant decline in catalytic activity. Consequently, the solid catalyst based on ionic liquids holds promise for the sustainable and eco-friendly production of biodiesel from low-quality oils. Furthermore, Response Surface Methodology (RSM) and Artificial Neural Networks (ANN) were used to model the yield and various process parameters. The findings underscore the enhanced predictive capabilities of ANN in comparison to RSM.

RSM optimization and kinetics study of α-Fe2O3/g-C3N4@H photocatalyst with S-type heterojunction for esterifying crude castor oil to reduce acidity and synthesize biodiesel

The preparation of biodiesel from low-quality oil conforms to the concept of sustainable development. In this study, low-quality castor oil was used as raw material, and α-Fe2O3/g-C3N4@halloysite photocatalyst prepared by two-step calcination method was used to pre-esterify the raw material to reduce the acid value, so that the quality of the raw material met the requirements of a homogeneous alkali catalyst, and then biodiesel was prepared by transesterification catalyzed by NaOH. The results show that the doped g-C3N4 has a larger specific surface area and better photoelectric properties, and the photocatalyst loaded with 10 wt% α-Fe2O3 has stronger light absorption characteristics and electron-hole separation ability. Response surface method was used to optimize the experiment: the molar ratio of ethanol to oil was 11.74:1, the amount of catalyst was 3.44 wt%, and the reaction time was 2.72 h. The reaction temperature was 74.57 ℃, and the conversion rate of FFAs (free fatty acids) was 97.62 %. The catalyst was recycled 5 times, and the conversion rate of FFAs still exceeded 80 %. The photocatalytic esterification reaction in this study conformed to the reversible second-order kinetic model. The physicochemical properties of castor oil-based biodiesel prepared by adding additives or preparing B20 biodiesel meet ASTM D6751 and EN 14214 standards.

The influences of street food vendor frying equipment on the quality of frying oil

This study was initiated to determine the quality of fresh and used oil for street vendor fried food products in Harar City, Ethiopia. Using a purposive sample technique, 12 respondents were selected for the study. The study obtained a total of 12 oil samples, categorized as fresh, in-use, and discarded, from two distinct groups of respondents. Specifically, six samples were collected from vendors utilizing an electric fryer constructed from stainless steel, while the remaining six samples were acquired from vendors employing a pan heated by wood or charcoal.The moisture content of fresh, in-use, and discarded oil samples, among other physical characteristics of the samples obtained from two types of vendors, was examined and found to vary between 0.14 and 0.44%, 0.19 and 0.52%, and 0.25 and 0.75%, respectively. Comparably, the refractive indices of oil samples that were fresh, in use, and discarded were 1.4595–1.4686, 1.4670–1.4885, and 1.4810–1.4960, in that order. Furthermore, the ranges of viscosities for fresh oil, oil samples in use, and oil samples that were discarded were 57.15–76.94, 100–196.50, and 210.22–288.50 mPa, respectively. Chemical properties, including % free fatty acid for similar samples, range from 0.22 to 1.30, 1.12 2.54, and 1.38–3.66%, respectively. Peroxide values of fresh, in-use, and discarded oil samples, have a maximum value of 11.19 meq/kg, 42.90, and 57.60 meq/kg, respectively. The iodine value showed the highest value for the fresh oil sample, while the minimum was obtained under discarded oil sample. The result indicated that they used low-quality oil. The values obtained after frying for samples collected from vendors who used a pan fryer heated with charcoal or wood fire deviated significantly from the requirements, indicating that the palm oil used by those street vendors was unsafe to consume because it could endanger the consumers' health.

Application of Phosphonium- and Choline Chloride Based Deep Eutectic Solvents as Catalyst for Emulsifier Production from Low Quality Oil Assisted by Microwave Irradiation

Monoglycerides (MAG) and Diglycerides (DAG) have wide applications in the food, pharmaceutical and cosmetic industries. Despite the economic competitiveness of producing this type of emulsifier from vegetable oils, the increasing demand for products with high nutritional value makes certain types of healthy oils such as rice bran oil (RBO) a potential raw material for high quality fats to serve this growing market. However, the high free fatty acids (FFA) and RBO content which is insoluble in acetone make it difficult to process and is categorized as a low-quality oil, causing RBO to be only used as biodiesel feedstock. Enzymatic catalytic route for glycerolysis of vegetable oil offers milder operating conditions and higher product selectivity (MAG) but it has high production costs and long processing time. In this study, biodegradable catalysts were used, namely deep eutectic solvents (DES) based on phosponium and choline chloride for glycerolysis of dewaxed/degummed RBO (DDRBO) assisted with microwave irradiation. Effects of different types of DES catalysts (phosphonium and choline chloride based DES) on DES-catalyzed glycerolysis of low quality oil will be evaluated using 5%wt of DES, 300 W(150°C) for about 15 minutes. Out of the four DESs used, DES [TBAB][PTSAM] and DES [ChCl][AcAd] both showed outstanding catalytic performance. Especially [ChCl][AcAd] as a reaction catalyst for DDRBO glycerolysis showed the best catalytic activity, and high selectivity for the formation of monoglycerides (MG). Meanwhile [TBAB][PTSAM] showed high selectivity (92.57%) for diglyceride (DG) formation.

Production of biodiesel from low-quality vegetable oils with a high content of free fatty acids by alkaline transesterification

The extraction of natural fats as well as the production of derived products based on them are renewable processes that play a major role in the modern energy industry. An example in this regard is the so-called biodiesel fuel which is Fatty Acid Methyl Esters (FAME), the production of which in recent years has reached enormous scales. Its main advantage is that it is an ecological product (methyl ester of higher fatty acids), which before and after use does not pollute the environment. Quality biodiesel fuel, in turn, is obtained from quality raw materials, which invariably limits its production. On the other hand, every year as a result of improper storage or processing, as well as obtained as waste products huge amounts of low-quality oils remain unutilized and they in turn, represent a valuable raw material and source of energy after their conversion into biodiesel fuel. The present work investigates the possibility of obtaining methyl esters of fatty acids (biodiesel) from low-quality (bad-quality) vegetable oils with high acid values by transesterification with an alkaline catalyst, which includes the selection of suitable catalysts and conditions for the optimal course of the process.

Exploring the quality and safety issues in the coconut oil processing industry in Sri Lanka: A Review

Coconut oil is a significant dietary component in Sri Lanka and serves as the primary source of fat for Sri Lankans, primarily used for culinary purposes. This review focuses on the quality and safety concerns within the coconut oil processing industry of Sri Lanka. The study collected data through interviews with industry personnel, conducted field visits to both small-scale and large-scale operations, and analyzed existing research. Several factors impact the quality and safety of coconut oil products. Key issues include the increase in free fatty acid content, the production of aflatoxin in copra, phthalate contamination from packaging, and the contamination of coconut oil with polyaromatic hydrocarbons (PAH). These quality and safety concerns result from cross-contamination with metals and other chemicals during equipment use, a shortage of trained personnel, insufficient laboratory testing of oil quality parameters before market distribution, and inadequate surveillance of small and medium-sized oil mills by regulatory bodies. Additionally, the local market faces high levels of adulteration, where coconut oil is mixed with lower-quality oils, stored improperly, or is of overall poor quality. Issues related to coconut cultivation include a decline in yields due to inefficient land usage, reduced productivity, climate change impacts, pest infestations, diseases, and increased production costs. The adulteration problem arises from the supply-demand gap for coconut oil in Sri Lanka and the high cost of producing one litre of good-quality coconut oil. The Sri Lankan government and the Sri Lanka Standards Institution have introduced a product standard for coconut oil production, outlining key parameters for the final product. Nevertheless, the absence of a comprehensive process standard affects quality control throughout production. Small and medium-scale producers lack awareness of SLSI standards, leading to non-compliance, along with an absence of regular quality and safety checks. Consequently, stringent enforcement is necessary to address these challenges. While improvements have been made, unresolved issues remain; therefore, a quality assurance system for the coconut oil processing industry is an urgent requirement, especially for small and medium-scale oil production facilities, which are key suppliers to the local market.

Rapid Authentication and Detection of Olive Oil Adulteration Using Laser-Induced Breakdown Spectroscopy.

The adulteration of olive oil is a crucial matter for food safety authorities, global organizations, and consumers. To guarantee olive oil authenticity, the European Union (EU) has promoted the labeling of olive oils with the indices of Protected Designation of Origin (PDO) and Protected Geographical Identification (PGI), while food security agencies are also interested in newly emerging technologies capable of operating reliably, fast, and in real-time, either in situ or remotely, for quality control. Among the proposed methods, photonic technologies appear to be suitable and promising for dealing with this issue. In this regard, a laser-based technique, namely, Laser-Induced Breakdown Spectroscopy (LIBS), assisted via machine learning tools, is proposed for the real-time detection of olive oil adulteration with lower-quality oils (i.e., pomace, soybean, sunflower, and corn oils). The results of the present work demonstrate the high efficiency and potential of the LIBS technique for the rapid detection of olive oil adulteration and the detection of adulterants.

Aperture Design Optimization of Wire-Wrapped Screens for SAGD Production Wells

Wire-wrapped screens have been established as one of the primary sand control devices in Steam-Assisted Gravity Drainage (SAGD) wells due to the high open-to-flow area and superior plugging attributes. However, their design is still a point of interest for thermal operations. Generally, existing approaches rely on one or more particular points of reservoir sands’ particle size distribution (PSD) and rules of thumb inferred from other devices like the slotted liners. This study used Sand Retention Testing (SRT) to analyze the performance of WWS under various testing conditions, which were neglected in the current design criteria. The experimental investigation leads to a set of graphical design criteria that provide an optimum aperture size window. The results show that the sand retention performance of WWS is highly dependent on the flow velocities of the wetting phase. Moreover, the testing showed satisfactory plugging performance of WWS even with narrow aperture sizes, proving a superior performance for low-quality oil sands.

Quality Assessment of Fried Oils from Different Street Food Vendors and Restaurants in Different Areas of Gilgit, Pakistan

The study was designed to estimate the quality of the frying oils used in northern areas of Pakistan. A cross-sectional analysis was performed to investigate the behavior and common practices of street food vendors (SFVs) regarding oil selection, food preparation, and awareness of rancid oil on human health. Seventy-Eight (78) commercial fried oil samples were evaluated based on the free fatty acid (FFAs), peroxide value (PV), moisture contents (MC), total polar matter (TPM), color, and iodine value (IV). The analysis showed that FFAs, PV, TPM, color, and IV significantly deviated from standard values provided by Pakistan Standard Quality Control Authority, (PSQCA) Pakistan. The SFVs used low-quality oil because of low price and ease of availability over quality, frying oil was changed infrequently and blended with new oil. Furthermore, the majority of SFVs were unaware of the hazards of rancid oil to human health, food handling practices were unsanitary, and cleaning methods were ineffective. Quality control, legislation, and SFVs safety and hygiene training are the most critical requirements to improve the overall quality of fried street foods in Gilgit, Pakistan.

Phytomediated Selenium Nanoparticles Improved Physio-morphological, Antioxidant, and Oil Bioactive Compounds of Sesame under Induced Biotic Stress.

Vegetable oil consumption is expected to reach almost 200 billion kilograms by 2030 in the world and almost 2.97 million tons in Pakistan. A large quantity of edible oil is imported annually from other countries to fill the gap between local production and consumption. Compared to other edible oil crops such as soybean, rapeseed, peanut and olive, sesame has innately higher (55%) oil content, which makes it an excellent candidate to be considered to meet local edible oil production. Oil seed crops, especially sesame, are affected by various pathogens, which results in decreased oil production with low quality oil. Selenium nanoparticles (SeNPs) work synergistically, as it has antifungal activity along with improving plant growth. Different concentrations of SeNPs were used, on three different varieties of sesame (TS-5, TH-6, and Till-18). Plant growth and development were accelerated by SeNPs, which ultimately led to an increase in crop yield. Morphological parameters revealed that SeNPs resulted in a growth increase of 55.7% in root length, 48% increase in leaf number/plant, and 38% in stem diameter. Out of three sesame varieties, TS-5 seedlings treated with 40 mg/L SeNPs showed 96.7% germination and 53% SVI at 40 mg/L. Sesame varieties dramatically increased antioxidant capability using SeNPs, resulting in 147% increase in SOD and 140% increase in POD enzyme units in TH-6 and 76% elevation in CAT enzymes in TS-5 (mean ± S.E). GCMS analysis revealed that bioactive compound I, sesamin, sesamol, and tocopherol contents were increased along with enhanced production of different unsaturated fatty acids. Kegg pathway analysis and MSEA revealed that these compounds were mainly involved in biosynthesis of unsaturated fatty acids, suggesting that SeNPs have elicited the biosynthesis of unsaturated fatty acids such as oleic acid, linoleic acid, and α-linoleic acid. This study concluded that SeNPs (40 mg/L) have an excellent capability to be used for crop improvement along with better oil quality.

Adsorptive pretreatment of waste cooking oil using quicklime for fatty acid methyl esters synthesis

Synthesis of biodiesel from various plant oils is realized by the transesterification of triglycerides with methanol or by a reaction usually defined as methanolysis. The usage of low-quality oils, such as waste cooking oil (WCO), is followed by undesirable side reactions as a result of the increased content of free fatty acids (FFA), and water. The presence of FFA in WCO usually requires a pretreatment stage before subjecting it to methanolysis. In the present work, heterogeneously catalyzed methanolysis of WCO with and without pretreatment was investigated. Removal of FFA from WCO was conducted by using only quicklime or with the addition of a small amount of methanol (FFA to methanol = 1:3 molar ratio). The obtained results showed that pretreatment of WCO with quicklime at 30 ?C after 1 h reduces the FFA content by 72 %, while the adsorption capacity was determined to be 910 mg g-1. The adsorptive pretreatment, as a simple operation, using low-cost quicklime under mild conditions, had a positive effect on the transesterification rate with CaO?ZnO as a catalyst, enabling the achievement of over 96 % of biodiesel yield in only 15 min, compared to 1 h without the pretreatment. Furthermore, pretreated WCO allows an increase in repeated catalyst use and overall savings in the necessary amount of catalyst. The present study showed that quicklime is an economic, environmental-friendly, and sustainable material for FFA removal from WCO.

State-of-the-art catalysts for clean fuel (methyl esters) production—a comprehensive review

There has been growing and recent interest in using non-edible feedstocks, such as waste animal fats, as an alternative to vegetable oils in biodiesel production to address the food versus fuel debate. Waste animal fats are cost effective and yield good quality biodiesel. Therefore, waste animal fats are appealing and excellent feedstocks to produce biodiesel. Commercially, the biodiesel is obtained by transesterification reaction of triglycerides present in oil/fat with alcohol in the presence of homogeneous base catalysts. However, free fatty acids found in low-quality oil feedstocks are particularly sensitive to homogeneous base catalysts, necessitating extra acid pretreatment and neutralization procedures that not only raise the overall expense of producing biodiesel but also create environmental contamination. Optimistically, the use of solid catalysts can offer an environmentally friendly, cost-effective and practical route for the manufacture of biodiesel from inexpensive oil feedstocks, including waste animal fat. The present review article covers catalyzed transesterification/esterification using various catalysts with particular focus on the use of heterogeneous catalysts when using waste animal fat as feedstock for biodiesel production. In particular, the properties of biodiesel obtained from waste animal fats are also compared to the biodiesel properties of standard organizations, such as the European Committee for Standardization (ISO) and the American Society for Testing and Materials (ASTM). Moreover, this paper also offers future research directions that can direct researchers to fill in knowledge gaps impeding the creation of efficient heterogeneous catalysts for long-term biodiesel generation. To the best of our knowledge, the valorization of waste animal fats from slaughterhouses is not feasible and has some techno-economic concerns. However, this technology is more desirable considering the environmental point of view to address the pollution problems caused by these wastes.

Continuous extraction of naphthenic acid from low-grade oil using 1,6-hexanediol in an ammonia solution

The efficient use of low-quality crude oil is one short-term solution to overcoming the imminent energy crisis due to the depletion of fossil resources. Several methods have been developed to upgrade low-quality oil, the most important part of which is the removal of acidic components. High-acid crudes can be converted to lower-acid crudes using various methods based on physical and chemical principles. In this contribution, we suggest an efficient and economical method based on liquid–liquid extraction. The candidate solvent was screened from a thermodynamic analysis in a previous study, and the additives and process conditions were adjusted according to experimental results. As the final solvent choice, 1,6-hexanediol in an aqueous ammonia solution showed the best performance with the minimal amount of solvent (weight fraction of 0.6). Experiments showed that the proposed solvent can be used to treat real crude oil used in the industry. A continuous operation scheme was suggested with solvent regeneration and recycling combined with separation of the acidic residue. The results showed that the proposed extraction process can reduce 85% of the acidic component in high-acid crudes and that repeated use of the solvent is possible.

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

Enzymatic method for obtaining fatty acid concentrate from fish oil

Fish oil, depending on the quality, is used for various industries. High-quality oils are used in the pharmaceutical and food industries. Changing the quality of fish oils are associated with the processes of hydrolysis and oxidation. Lower quality oils are used for fodder and technical purposes. One of the areas of fish oils technical use is the production of free fatty acids. Acids are obtained by oil hydrolysis. The enzymatic method of hydrolysis is considered to be promising. The method does not require high energy costs. The enzyme should be immobilized. This ensures the reusability of the enzyme in the technological process. Fish oil acids are distinguished by a high degree of unsaturation of their fatty acid composition. Therefore, these compounds can be used to obtain surface-active, film-forming and antifriction technical products.

A Comparative Study of Different Quality Oil Shales Developed in the Middle Jurassic Shimengou Formation, Yuqia Area, Northern Qaidam Basin, China

Oil shales are developed in the Shale Member of the Middle Jurassic Shimengou Formation in the Qaidam Basin, China. The oil shales can be classified into three quality groups (low-, medium-, and high-quality oil shales) through a comprehensive analysis protocol that includes Rock-Eval pyrolysis, total organic carbon (TOC) content, proximate analysis, gas chromatography-mass spectrometry (GC-MS), X-ray diffraction (XRD), major and trace element analyses, and maceral analysis. The low-quality oil shales mainly contain type II1 kerogen, the medium-quality oil shales mainly contain type I-II1 kerogen, and the high-quality oil shales mainly contain type I kerogen. All are immature to early thermally mature. The oil yield of the oil shales is directly related to their quality and are positively correlated with TOC content and calorific value. All studied samples were deposited under anaerobic conditions but in different paleoenvironments. The low-quality oil shales were mainly deposited in fresh-water environments, whereas the high-quality oil shales were usually developed in highly saline and reducing environments. Salinity stratification and evidence of algal blooms that are conducive to organic matter enrichment were identified in both medium- and high-quality oil shales, the latter having the highest paleoproductivity and the best preservation conditions. In summary, shale quality is controlled by a combination of factors, including algal abundance, preservation conditions, the existence of algal blooms and salinity stratification, and paleoproductivity. This study reveals how these different factors affect the quality of oil shales, which might provide an in-depth explanation for the formation process of lacustrine oil shales.

Molybdenum and zirconium oxides supported on KIT-6 silica: A recyclable composite catalyst for one–pot biodiesel production from simulated low-quality oils

The development of feasible ecofriendly processes for biodiesel production is highly desirable to meet the requirement of green chemistry and sustainable development. To reach this goal, the molybdenum and zirconium oxides were incorporated into commercial available KIT-6, mesoporous silica nanoparticle, by a solvothermal method, to form MoO3/ZrO2/KIT-6 catalyst. The targeted solid composite catalysts were structurally characterized using XRD, TEM, SEM, XPS, EDS, TG, and nitrogen porosimetry measurement. The characterization results showed that the ordered porous structure of the support was well persevered with high surface area, and the molybdenum and zirconium oxides could be highly dispersed on the mesoporous support. The acidic nature of the solid catalyst was evaluated in detail by means of NH3-TPD and infrared spectra of adsorbed pyridine techniques. It was indicated that the acidities of the solid catalysts, with both Brønsted and Lewis acid sites, could greatly affected their catalytic activity. This catalyst displayed high activities to the transesterification of triglycerides and esterification of free fatty acids (FFAs) simultaneously owing to the synergistic effect of Brønsted and Lewis acid sites, thus achieving one-pot heterogeneous production of biodiesel as the low-quality oil was used as feedstocks. The influence of reaction parameters and the catalyst reusability were also investigated, and the best oil conversion of 92.7% was obtained under the optimized reaction conditions. The targeted catalyst exhibited a better FFAs and water tolerant for the reaction, advantageously with no noticeable decline in the catalytic performance even after five reaction cycles.

Heterogeneous H6PV3MoW8O40/AC-Ag catalyst for biodiesel production: Preparation, characterization and catalytic performance

The heterogenization of Keggin-structure heteropoly acids (HPAs) has been proposed as a strategy to improve their application in biodiesel production in an attempt to comply the green and clean production demand. Herein, the commercial activated carbon (AC) was firstly modified with different metal ions (Cs+, K+ and Ag+), and then the H6PV3MoW8O40 acid was incorporated into as-modified AC supports, so as to prepare HPAs-based solid catalysts. By screening tests, the 35%H6PV3MoW8O40/AC-Ag hybrid solid catalyst showed highly catalytic performance for transesterification of soybean oil. The best oil conversion of 91.3% was achieved under optimized conditions: methanol/oil molar ratio of 30:1, reaction time of 10 h, reaction temperature of 140 °C and catalyst dosage of 8 wt.%. Characterization results of XRD, IR, ICP and TG indicated that H6PV3MoW8O40 was highly dispersed on the AC-Ag support as the loading was less than 35%. Proton exchange with Ag may contribute to the highly dispersion of H6PV3MoW8O40 on the support and thus enhance the interaction of the heteropoly acids with the support, thereof leading to the increased catalytic stability. The as-prepared 35%H6PV3MoW8O40/AC-Ag catalyst was easily recycled and had good resistance to free fatty acid (FFA) and water, which were usually included in the low-quality oils. Moreover, as a bifunctional catalyst, the solid acid catalyst could simultaneously catalyze the transesterification of soybean oil and esterification of FFAs, and a probable mechanism of the catalytic process was also proposed. All the features of this novel solid catalyst are more advantageous than the homogenous H6PV3MoW8O40 catalyst, successfully creating an efficient and sustainable approach of biodiesel production especially from the low-quality oils.