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... The etherification of glycerol to polyglycerol is either homogeneously or heterogeneously catalyzed. Homogenously catalyzed etherification of glycerol to polyglycerol is aimed to be preferential to short-chain lowmolecular-weight oligomers of [10][11][12]. One of its downsides is it allows secondary reactions where 90% of glycerol is consumed but the main oligomers only account for 20% of the product with the balance consisting of undesired products which is a mixture of cyclic and unsaturated acyclic alkenes, aldehydes, and ketones [10,12]. ...
... Homogenously catalyzed etherification of glycerol to polyglycerol is aimed to be preferential to short-chain lowmolecular-weight oligomers of [10][11][12]. One of its downsides is it allows secondary reactions where 90% of glycerol is consumed but the main oligomers only account for 20% of the product with the balance consisting of undesired products which is a mixture of cyclic and unsaturated acyclic alkenes, aldehydes, and ketones [10,12]. Additionally, the homogeneously catalyzed-etherification reaction is sometimes performed at reduced pressure with an inert atmosphere [11,12]. ...
The production of biodiesel generates glycerol as a by-product that needs valorization. Glycerol, when converted to polyglycerol, is a potential polyol for bio-based thermoplastic polyurethane (TPU) production. In this study, a novel polyglycerol polyester polyol (PPP) was developed from refined glycerol and coconut oil-based polyester polyol. Glycerol was first converted to glycerol acetate and then polymerized with coconut oil-based polyester polyol (CPP) as secondary polyol and phthalic anhydride. The resulting PPP polymerized at 220 °C and OH:COOH molar ratio of 2.5 exhibited an OH number of <100 mg KOH·g sample-1, an acid number of <10 mg KOH·g sample-1, and a molecular weight (MW) of 3697 g mol-1 meeting the polyol requirement properties for TPU (Handlin et al., 2001; Parcheta et al., 2020) [1-2]. Fourier-transform infrared (FTIR) spectroscopic characterization determined that higher reaction temperatures increase the polymerization rate and decrease the OH and acid numbers. Further, higher OH:COOH molar ratios decrease the polymerization rate and acid number, and increase the OH number. Gel permeation chromatography determined the molecular weight of PPP and suggested two distinct molecular structures which differ only in the number of moles of CPP in the structure. A differential scanning calorimetric (DSC) experiment on a sample of PPP-based polyurethane revealed that it was able to melt and remelt after 3 heating cycles which demonstrates its thermoplastic ability. The novel PPP derived from the glycerol by-product of biodiesel industries can potentially replace petroleum-derived polyols for TPU production.
... Etherification is defined as a transformation of glycerol molecules to form polyglycerols. For instance, condensation of two glycerol molecules leads to the formation of diglycerol with linear, branched, or cyclic isomers [120]. Etherification is associated with development of mono-, di-, and tri-tert-butylglycerol ether mixtrures [121] as shown in Figure 3. ...
Utilization of biofuels generated from renewable sources has attracted broad attention due to their benefits such as reducing consumption of fossil fuels, sustainability, and consequently prevention of global warming. The production of biodiesel causes a huge amount of by-product, crude glycerol, to accumulate. Glycerol, because of its unique structure having three hydroxyl groups, can be converted to a variety of industrially valuable products. In recent decades, increasing studies have been carried out on different catalytic pathways to selectively produce a wide range of glycerol derivatives. In the current review, the main routes including carboxylation, oxidation, etherification, hydrogenolysis, esterification, and dehydration to convert glycerol to value-added products are investigated. In order to achieve more glycerol conversion and higher desired product selectivity, acquisition of knowledge on the catalysts, the type of acidic or basic, the supports, and studying various reaction pathways and operating parameters are necessary. This review attempts to summarize the knowledge of catalytic reactions and mechanisms leading to value-added derivatives of glycerol. Additionally, the application of main products from glycerol are discussed. In addition, an overview on the market of glycerol, its properties, applications, and prospects is presented.
... such molecules has been encountered in heterogeneous catalysis. The dimerization reaction usually occurs in the presence of acid/base catalysts in solvent-free conditions [46,47]. The diglycerol molecules can be formed either in cyclic, linear, or branched form depending on the catalyst type, temperature, and reaction time [48]. ...
... It is important to note that the formation of such molecules has been encountered in heterogeneous catalysis. The dimerization reaction usually occurs in the presence of acid/base catalysts in solvent-free conditions [46,47]. The diglycerol molecules can be formed either in cyclic, linear, or branched form depending on the catalyst type, temperature, and reaction time [48]. ...
... The diglycerol molecules can be formed either in cyclic, linear, or branched form depending on the catalyst type, temperature, and reaction time [48]. The demand for the linear diglycerol formed in this work has increased by more than 50% from 2012 to 2022 [47]. The formation of two products in one pot renders the La-and Sn-perovskites versatile catalysts. ...
Catalytic transfer hydrogenation reactions (CTHs) produce value-added chemicals in the most economical, safe, green, and sustainable way. However, understanding the reaction mechanism and developing stable, selective, and cheap catalysts has been a significant challenge. Herein, we report on the hydrogenation of cinnamaldehyde utilizing glycerol as a hydrogen donor and metal-oxides (SnO2, LaFeO3, and LaSnO3) as heterogeneous catalysts. The perovskite types were used because they are easy to synthesize, the metal components are readily available, and they are good alternatives to noble metals. The catalysts were synthesized through the nanocasting (hard-template) method with SiO2 (KIT-6) as a template. The template was synthesized using the soft-template (sol-gel) method resulting in a high surface area of 624 m2/g. Furthermore, catalytic evaluations gave high cinnamaldehyde percentage conversions of up to 99%. Interestingly, these catalysts were also found to catalyze the etherification of glycerol in one pot. Therefore, we propose competitive surface catalytic reactions driven by the transition metal cations as the binding sites for the cinnamaldehyde and the sacrificial glycerol.
... Lignocellulosic biomass residues are gained much attention as an alternative resource because of their availability in large amounts, low in price, and can contribute to 10%-15% total world primary energy supply [10][11][12]. Lignocellulose possesses a higher amount of cellulose, hemicellulose, and then lignin compounds that are responsible to produce a variety of fuels and chemicals upon degradation of their polymeric structure [13,14]. In a similar pattern, plants and nonedible seeds gained special consideration to produce clean biofuel [15,16]. ...
Biomass pyrolysis produces valuable solid, liquid, and gas products. However, the liquid products observed low heating value due to low hydrocarbon contents with the presence of high oxygenated species. To upgrade the bio-oil, appropriate solid acid catalysts are incorporated in the biomass pyrolysis process to deoxygenate the species to enhance the heating value of the bio-oil called catalytic upgrading process. The study presents the progress of catalytic pyrolysis process using shape-selective zeolites for improving hydrocarbon in the bio-oil. To compare the performance, commercial and synthesis microporous zeolites are tested in the in situ catalytic pyrolysis process. ZSM-5, ferrite, and mordenite were the commercial zeolites at the Si/Al ratio of 23, 20, and 20, respectively, are employed. On the other hand, layered MCM-22 (20) and its counterpart ITQ-2 (20) were synthesized using established protocol and tested in catalytic biomass pyrolysis process in drop-type pyrolyzer. These zeolites are categorized as various pore sizes, shapes, and acidity which impacts on deoxygenation performance. Among synthesized zeolites, ITQ-2 showed higher deoxygenation which results in increased aromatics production. Overall, ZSM-5 appeared as the most suitable catalyst for higher deoxygenation with higher aromatics production in comparison to other shape-selective zeolites.
... The introduction of bioethanol would help the smooth burning of gasoline in Compression ignition (CI) engines as it generates less black smoke with fewer NOx and hydrocarbons emissions [15].Biodiesel and biobutanol are blended with commercial gasoline without any difficulty and engine modification. Normally, the blends of B-10 and B-20 are commercially opted [16][17][18]. The synthesis of ethanol as a gasoline alternative using lignocelluloses displays a promising alternative for the biofuel manufacturing industry. ...
... Another study identified a 90% removal of hemicellulose and lignin from sugarcane bagasse with the application of a 100 W ultrasound and 2 h of sonication time in distilled water maintained at a temperature of 55 • C wherein the ultrasound attacked the veracity of cell walls, slashing the linkages of ether, and enhancing extractability of hemicellulose [50]. [17]. ...
Lignocelluloses' pretreatment is targeted for the improvement of hydrolysis of their carbohydrates, i.e., cellulose and hemicelluloses. Modification of the hardheaded structure of lignocelluloses is a fundamental stair in biofuels and biochemicals production. The high crystalline configurations of cellulose embed with hemicelluloses and lignin, give rise to recalcitrance structure. Second-generation biofuel production processes, using lignocellulosic biomass as a feedstock, is based on a three-stage process, including pretreatment, enzymatic hydrolysis, and fermentation. The pretreatment stage is the most critical, influencing, costly stage. The perfect pretreatment process is designated to provide minimum cellulosic crystallinity with remarkable low lignin content as well as inhibitory compounds through a sustainable economical process. In the present review, advances in lignocel-lulosic pretreatment technologies for biofuels production are reviewed and critically discussed. The article further discusses the pros and cons of the various pretreatment methodologies as well as addresses the role and impact of different process parameters associated with the pretreatment process.
This work describes the conversion of the waste glycerol (as generated in the biodiesel industry, supplied by Petrobras) to valuable chemicals (such as formic acid, diglycerol, and dioxanes). The reactions were evaluated in batch and continuous-flow fixed-bed reactors (PBR) on a pilot scale using high porosity mesoporous silica (≈ 1500 m² g⁻¹) and Al-modified silica catalysts (Si/Al = 15/1 and 5/1). The Al addition increased the acidity of the catalysts and reduced their surface areas (698 m² g⁻¹ in Si/Al = 5). High glycerol conversion (80%) was reached for 15 Si/Al and 5 Si/Al whereas SiO2 tends to deactivate in a continuous-flow fixed-bed reactor (PBR). Furthermore, the catalysts exhibited different selectivity: SiO2 produced mainly formic acid (≈ 65% average) in the liquid phase whereas the Al-modified catalysts generated a large amount of diglycerol, possibly due to the different acidity of the catalysts. This study indicates the potential industrial use of the catalysts and contributes to increasing the sustainability of the biodiesel industry.
Lignocellulosic biomass is a vital resource for providing clean future energy with a sustainable environment. Besides lignocellulosic residues, nonlignocellulosic residues such as sewage sludge from industrial and municipal wastes are gained much attention due to its large quantities and ability to produce cheap and clean energy to potentially replace fossil fuels. These cheap and abundantly resources can reduce global warming owing to their less polluting nature. The low-quality biomass and high ash content of sewage sludge-based thermal conversion processes face several disadvantages towards its commercialization. Therefore, it is necessary to utilize these residues in combination with coal for improvement in energy conversion processes. As per author information, no concrete study is available to discuss the synergy and decomposition mechanism of residues blending. The objective of this study is to present the state-of-the-art review based on the thermal coconversion of biomass/sewage sludge, coal/biomass, and coal/sewage sludge blends through thermogravimetric analysis (TGA) to explore the synergistic effects of the composition, thermal conversion, and blending for bioenergy production. This paper will also contribute to detailing the operating conditions (heating rate, temperature, and residence time) of copyrolysis and cocombustion processes, properties, and chemical composition that may affect these processes and will provide a basis to improve the yield of biofuels from biomass/sewage sludge, coal/sewage sludge, and coal/biomass blends in thermal coconversion through thermogravimetric technique. Furthermore, the influencing factors and the possible decomposition mechanism are elaborated and discussed in detail. This study will provide recent development and future prospects for cothermal conversion of biomass, sewage, coal, and their blends.
