Synthesis of glycerol carbonate from biodiesel by-product glycerol over calcined dolomite

Hybrid carbonaceous adsorbents based on clay and cellulose for cadmium recovery from aqueous solution

The current work describes the synthesis of carbonaceous composites via pyrolysis, based on CMF, extracted from Alfa fibers, and Moroccan clay ghassoul (Gh), for potential use in heavy metal removal from wastewater. Following synthesis, the carbonaceous ghassoul (ca-Gh) material was characterized using X-ray fluorescence (XRF), Scanning Electron Microscopy coupled with Energy Dispersive X-ray (SEM-EDX), zeta-potential and Brunauer-Emmett-Teller (BET). The material was then used as an adsorbent for the removal of cadmium (Cd2+) from aqueous solutions. Studies were conducted into the effect of adsorbent dosage, kinetic time, initial concentration of Cd2+, temperature and also pH effect. Thermodynamic and kinetic tests demonstrated that the adsorption equilibrium was attained within 60 min allowing the determination of the adsorption capacity of the studied materials. The investigation of the adsorption kinetics also reveals that all the data could be fit by the pseudo-second-order model. The Langmuir isotherm model might fully describe the adsorption isotherms. The experimental maximum adsorption capacity was found to be 20.6 mg g-1 and 261.9 mg g-1 for Gh and ca-Gh, respectively. The thermodynamic parameters show that the adsorption of Cd2+ onto the investigated material is spontaneous and endothermic.

Ni modified distillation waste derived heterogeneous catalyst utilized for the production of glycerol carbonate from a biodiesel by-product glycerol: Optimization and green metric studies

Biodiesel prices could be made competitive with petrol-diesel prices by valorizing its by-product glycerol. Glycerol carbonate can be derived from glycerol and is one of the widely needed chemical having high price and its extensive application in different industrial purposes. Glycerol carbonate can be synthesized via many routes; among them catalytic route gives promising activity and selectivity towards glycerol carbonate. For the first time, Ni modified distillation waste (CaO) derived heterogeneous catalyst Ni/CaO (NDW) was synthesized and utilized for the conversion of glycerol (Gl) to glycerol carbonate (GC). The catalyst's physicochemical properties were studied by performing TGA-DSC, XRD, FT-IR, SEM- EDAX, HRTEM, and basicity through Hammet indicator. Through NDW, solvent-free synthesis of glycerol carbonate was achieved using glycerol and dimethyl carbonate (DMC) as reactants upon conventional heating (90 °C). The validation of the synthesized product was performed through proton and carbon NMR analysis. In addition to this, HR-MS was performed to check the composition of the product formed. A plausible mechanism for the transesterification of glycerol (Gl) to glycerol carbonate (GC) was also designed. Higher conversion (99.2%) and selectivity (95%) towards glycerol carbonate (GC) were achieved at mild reaction conditions, viz., 1:3 M ratio of glycerol to DMC, reaction temperature 90 °C, reaction duration of 90 min with catalyst dose of 300 mg. The green metric parameters were also calculated to show that the overall process is sustainable and the environment benign.

Glycerol and Catalysis by Waste/Low-Cost Materials—A Review

The growing global demand for renewable energy sources can be reached using biofuels such as biodiesel, for example. The most used route to produce biodiesel is the transesterification reaction of oils or fats with short-chain alcohols, generating fatty acid esters (biodiesel) and a very important by-product, glycerol (Gly). Gly is widely used in different sectors of the industry, and in order to add value to this by-product, heterogeneous catalysis becomes a relevant tool, whether to transform glycerol into other chemical products of interest or even use it in the production of catalysts. Among the several studies found in the literature, the use of low-cost materials and/or wastes from the most diverse activities to prepare active catalytic materials for the transformation of Gly has been increasingly reported due to its valuable advantages, especially related to the cost of raw materials and environmental aspects. Thus, this brief review article presents the relationship between catalysis, low-cost materials, waste, and glycerol, through different studies that show glycerol being transformed through reactions catalyzed by materials produced from low-cost sources/waste or with the glycerol itself used as a catalyst.

Biodiesel Is Dead: Long Life to Advanced Biofuels—A Comprehensive Critical Review

Many countries are immersed in several strategies to reduce the carbon dioxide (CO2) emissions of internal combustion engines. One option is the substitution of these engines by electric and/or hydrogen engines. However, apart from the strategic and logistical difficulties associated with this change, the application of electric or hydrogen engines in heavy transport, e.g., trucks, shipping, and aircrafts, also presents technological difficulties in the short-medium term. In addition, the replacement of the current car fleet will take decades. This is why the use of biofuels is presented as the only viable alternative to diminishing CO2 emissions in the very near future. Nowadays, it is assumed that vegetable oils will be the main raw material for replacing fossil fuels in diesel engines. In this context, it has also been assumed that the reduction in the viscosity of straight vegetable oils (SVO) must be performed through a transesterification reaction with methanol in order to obtain the mixture of fatty acid methyl esters (FAMEs) that constitute biodiesel. Nevertheless, the complexity in the industrial production of this biofuel, mainly due to the costs of eliminating the glycerol produced, has caused a significant delay in the energy transition. For this reason, several advanced biofuels that avoid the glycerol production and exhibit similar properties to fossil diesel have been developed. In this way, “green diesels” have emerged as products of different processes, such as the cracking or pyrolysis of vegetable oil, as well as catalytic (hydro)cracking. In addition, some biodiesel-like biofuels, such as Gliperol (DMC-Biod) or Ecodiesel, as well as straight vegetable oils, in blends with plant-based sources with low viscosity have been described as renewable biofuels capable of performing in combustion ignition engines. After evaluating the research carried out in the last decades, it can be concluded that green diesel and biodiesel-like biofuels could constitute the main alternative to addressing the energy transition, although green diesel will be the principal option in aviation fuel.

Embedded ionic liquid modified ZIF-8 in CaMgAl hydrotalcites for bio-glycerol transesterification

Novel modified MOF intercalated hydrotalcites was synthesized for catalyzing the conversion of glycerol into high value-added glycerol carbonate in this paper. [APmim]OH/ZIF-8 was prepared by encapsulating aminopropyl hydroxide imidazole ionic liquid in ZIF-8 and inserted in Ca-Mg-Al hydrotalcites with layered structures to prepare [APmim]OH/ZIF-8/LDH with strong basicity and high specific surface area. ZIF-8, [APmim]OH/ZIF-8 and [APmim]OH/ZIF-8/LDH were characterized by XRD, FT-IR, SEM and nitrogen adsorption-desorption. The results showed that the conversion rate of glycerol can reach 98.6% and the glycerol carbonate yield was 96.5% in the transesterification of glycerol with dimethyl carbonate catalyzed by [APmim]OH/ZIF-8/LDH when the molar ratio of DMC and glycerol was 3 : 1, the catalyst dosage was 3 wt%, the reaction temperature was 75 °C and the reaction time was 80 minutes. The glycerol conversion rate can still reach more than 90% after five reaction cycles.

An Overview of the Latest Advances in the Catalytic Synthesis of Glycerol Carbonate

In recent years, the development of renewable energy alternatives to traditional fossil fuels has become one of the major challenges all over the world, due to the decline of fossil fuel reserves and their effect on global warming. Biodiesel has become a popular alternative energy source to reduce gas emissions compared to traditional fossil fuels. According to statistics, a nine-fold increase in global biofuel production between 2000 and 2020 was observed. However, its production generates a large amount of glycerol as a by-product, posing an environmental problem when disposed directly in landfills or by incineration. Therefore, low-value glycerol should be converted into high value-added derivatives. As glycerol carbonate is one of the most important derivatives of glycerol, this review aims to discuss the studies over the last ten years about glycerol carbonate synthetic methods, including the typical routes such as phosgene, esterification reaction, urea, oxidative and direct carbonylation as well as several rare synthetic procedures. At the same time, it summarizes the different catalytic reaction systems of each route comparing the advantages and disadvantages of various catalysts and evaluating their catalytic activity. Finally, the future development of glycerol carbonate synthesis is prospected from the point of view of development, technology research and industrialization.

Process and Energy Intensification of Glycerol Carbonate Production from Glycerol and Dimethyl Carbonate in the Presence of Eggshell-Derived CaO Heterogeneous Catalyst

The process and energy intensifications for the synthesis of glycerol carbonate (GC) from glycerol and dimethyl carbonate (DMC) using an eggshell-derived CaO heterogeneous catalyst were investigated. The transesterification reaction between glycerol and DMC was typically limited by mass transfer because of the immiscible nature of the reactants. By varying the stirring speed, it was observed that the mass transfer limitation could be neglected at 800 rpm. The presence of the CaO solid catalyst made the mass transport-limited reaction process more prominent. Mass transfer intensification using a simple kitchen countertop blender as an alternative to overcome the external mass transfer limitation of a typical magnetic stirrer was demonstrated. A lower amount of the catalyst and a shorter reaction time were required to achieve 93% glycerol conversion or 91% GC yield, and the turnover frequency (TOF) increased almost 5 times from 1.5 to 7.2 min−1 when using a conventional magnetic stirrer and countertop blender, respectively. In addition, using a simple kitchen countertop blender with 7200 rpm, the reaction temperature of 60 °C could be reached within approximately 3 min without the need of a heating unit. This was the result of the self-frictional heat generated by the high-shear blender. This was considered to be heat transfer intensification, as heat was generated locally (in situ), offering a higher homogeneity distribution. Meanwhile, the trend toward energy intensification was promising as the yield efficiency increased from 0.064 to 2.391 g/kJ. A comparison among other process intensification techniques, e.g., microwave reactor, ultrasonic reactor, and reactive distillation was also rationalized.

Combined first-principles calculations and experimental study on the photocatalytic mechanism of natural dolomite

Mineral-based photocatalysts have received great attention due to their low cost. In this study, the photocatalytic activity of natural dolomite and its mechanism were investigated based on designed experiments and first-principles calculations. The kinetic study showed that natural dolomite showed notable photocatalytic activity for the degradation of target compounds including methylene blue, diphenhydramine, and tetracycline. The EPR analysis demonstrated that O₂⁻˙, ˙OH, and ¹O₂ were produced in the dolomite system under simulated sunlight irradiation. The first-principles calculations indicated that the isomorphous substitution of Fe²⁺ for Mg²⁺ in the dolomite lattice led to the impurity levels appearing in the forbidden band, which caused a significant decrease of the band gap from 5.02 to 1.63 eV. As a result, natural dolomite could act as a semiconductor photocatalyst in photochemical reactions due to the substitution of Mg²⁺ by Fe²⁺. Under simulated sunlight irradiation, photogenerated electron–hole pairs in the natural dolomite were separated and transferred to the surface, and then formed reactive radicals through further reactions, thereby enhancing the degradation of target compounds. This research may contribute to the understanding of the photocatalytic activity of natural minerals.

Natural dolomite exhibits notable photocatalytic activity due to the isomorphous substitution of Fe²⁺ for Mg²⁺ in the lattice, implying that it can be used as a low-cost photocatalyst.

Synthesis of Hydrotalcites from Waste Steel Slag with [Bmim]OH Intercalated for the Transesterification of Glycerol Carbonate

Ca-Mg-Al hydrotalcites were prepared by coprecipitation from Type S95 steel slag of Shanghai Baosteel Group as supports of ionic liquid in this paper. Five basic ionic liquids [Bmim][CH₃COO], [Bmim][HCOO], [Bmim]OH, [Bmim]Br and ChOH were prepared and their catalytic performance on the synthesis of glycerol carbonate by transesterification between dimethyl carbonate and glycerol was investigated. The characterization results indicated that [Bmim]OH is the best ionic liquid (IL) for the transesterification reaction of glycerol carbonate. The hydrotalcites before and after intercalation by ionic liquid were characterized by XRD, FTIR, SEM, EDS and the IL were characterized by FT-IR, ¹³C-NMR and basicity determination via the Hammett method. The analysis results implied that the dispersion of [Bmim]OH in hydrotalcites reduced the alkali density appropriately and facilitated the generation of glycerol carbonate. The yield of glycerol carbonate and the conversion rate of glycerol reached 95.0% and 96.1%, respectively, when the molar ratio of dimethyl carbonate and glycerol was 3:1, the catalyst dosage was 3 wt%, the reaction temperature was 75 °C and the reaction time was 120 min. The layered structure of hydrotalcites increased the stability of ionic liquid intercalated in carriers, thus the glycerol conversion and the GC yield still remained 91.9% and 90.5% in the fifth reaction cycle.

Synthesis of hydrotalcite-type mixed oxide catalysts from waste steel slag for transesterification of glycerol and dimethyl carbonate

The mixed metal oxides S-CaMgAl MO prepared by acidolysis, coprecipitation and calcination under different temperatures from S95 steel slag of Shanghai Baosteel Co., Ltd. were used to catalyze the transesterification of dimethyl carbonate (DMC) and glycerol for synthesizing glycerol carbonate (GC). The catalysts were characterized by EDS, XRD, FT-IR, SEM, CO₂-TPD and nitrogen adsorption–desorption isotherms. S-CaMgAl MO calcined at 600 °C had excellent catalytic performance due to the large pore size and proper alkalinity. The effects of reaction temperature, reaction time and the amount of catalyst on transesterification were investigated to obtain the optimal reaction conditions. The glycerol carbonate yield reached 96.2% and the glycerol conversion was 98.3% under the condition of 3 wt% catalyst, 1:3 molar ratio of glycerol and DMC, 75 °C reaction temperature and 90 min reaction time. In addition, the GC yield and glycerol conversion still achieved above 90% after five cycles of S-CaMgAl MO.

A review on recent trends in reactor systems and azeotrope separation strategies for catalytic conversion of biodiesel-derived glycerol

The increasing demand for biodiesel (BD) as a renewable and sustainable energy source has impelled the generation of abundant and low-cost byproduct glycerol, which accounts for 10 wt% of total BD production and requires urgent utilization. The transesterification reaction, which utilizes glycerol and dimethyl carbonate (DMC) to synthesize valuable glycerol carbonate (GC) is an established reaction pathway to valorize oversupplied glycerol. Commercialization of inexpensive GC is constrained by the nature, stability, and basicity of applied catalyst, reaction conditions, types of the reactor system and separation methods of reaction products. This study presents a review and diversity of recent reports on reactor systems and DMC-methanol azeotrope separation strategies explored in GC synthesis from biodiesel-derived glycerol. Also, recent trends on heterogeneous catalysts, their performance, and the effects of reaction conditions were presented. Conducted studies revealed that the choice for reactor systems is constrained by factors such as energy consumption and operational safety and a significant mild reaction conditions could be realized using a microwave reactor. Furthermore, the reactive-extractive distillation and pervaporation processes showed high energy-efficiency and appreciable separation of DMC-methanol azeotrope. Thus, the development of stable catalyst and process intensification to fabricate an integrated reactor-separation system with high energy efficiency are fundamental and must be explored. This study portrays the recent research effort made in this direction and the limitations that require urgent attention.

A Facile Approach to Develop Rice Husk Derived Green Catalyst for One-pot Synthesis of Glycerol Carbonate from Glycerol

The profitability margin of biodiesel production hampering due to surplus amount of glycerol with the low market price. Thus, developing an alternative route highly demanded for the conversion of glycerol into value-added chemicals. In the present manuscript, green synthesis route was explored by utilizing rice husk derived catalyst. The catalytic properties of the prepared catalyst were investigated by using various characterization techniques. The basic strength of the catalyst was influenced by varying the calcination temperature (200 °C to 500 °C) as well as active metal (cerium) loading (5 wt. % to 20 wt. %). The present investigation revealed that 10 wt. % Ce on Na2SiO3 catalyst calcined at 400 °C exhibited the moderate basic sites of 13.89 mmol/g, which showed potential catalytic activity for the transesterification of glycerol to glycerol carbonate under optimum condition: 92 % glycerol carbonate yield and 98 % glycerol conversion. The catalyst stability study revealed that the catalyst could be reused up to four consecutive cycles without an appreciable drop in catalytic activity. The kinetics of the reaction was also studied, and the activation energy was calculated as 23.80 kJ/mol.

Biodiesel at the Crossroads: A Critical Review

The delay in the energy transition, focused in the replacement of fossil diesel with biodiesel, is mainly caused by the need of reducing the costs associated to the transesterification reaction of vegetable oils with methanol. This reaction, on an industrial scale, presents several problems associated with the glycerol generated during the process. The costs to eliminate this glycerol have to be added to the implicit cost of using seed oil as raw material. Recently, several alternative methods to convert vegetable oils into high quality diesel fuels, which avoid the glycerol generation, are being under development, such as Gliperol, DMC-Biod, or Ecodiesel. Besides, there are renewable diesel fuels known as “green diesel”, obtained by several catalytic processes (cracking or pyrolysis, hydrodeoxygenation and hydrotreating) of vegetable oils and which exhibit a lot of similarities with fossil fuels. Likewise, it has also been addressed as a novel strategy, the use of straight vegetable oils in blends with various plant-based sources such as alcohols, vegetable oils, and several organic compounds that are renewable and biodegradable. These plant-based sources are capable of achieving the effective reduction of the viscosity of the blends, allowing their use in combustion ignition engines. The aim of this review is to evaluate the real possibilities that conventional biodiesel has in order to success as the main biofuel for the energy transition, as well as the use of alternative biofuels that can take part in the energy transition in a successful way.

Recent Development of Heterogeneous Catalysis in the Transesterification of Glycerol to Glycerol Carbonate

Glycerol is one of the most crucial by-products in the production of biodiesel, and owing to its oversaturation in the market, several synthetic strategies have been developed to transform it into other higher value-added products such as glycerol carbonate, epichlorohydrin, 1,3-propanediol, etc. Amongst them, glycerol carbonate is considered to be the most valuable product. Considering the facile separation and reusability of catalyst, heterogeneous base catalysts have attracted considerable attention due to the obvious advantages over Brϕnsted acid and homogeneous base catalysts in the transesterification of glycerol. Herein, we will give a short overview on the recent development of the heterogeneous catalysis in the transesterification of glycerol with dialkyl carbonate. Focus will be concentrated on the heterogeneous base catalysts including alkaline-earth metal oxides (MgO, CaO, and mixed oxides), hydrotalcites, zeolites, clinoptilolites, organic bases, etc. Their catalytic mechanisms during the heterogeneous process will be elucidated in detail.

Production of Glycerol Carbonate from Glycerol over Templated-Sodium-Aluminate Catalysts Prepared Using a Spray-Drying Method

Glycerol carbonate (GLC) was synthesized from glycerol and dimethyl carbonate (DMC) over sodium aluminate (NaAlO₂) catalysts. The catalysts were prepared using a spray-drying method and compared with those prepared using the conventional hot-air drying method. Polyvinylpyrrolidone and glycerol were used as a catalyst template to increase the surface area and porosity of the catalysts. Additionally, different operating conditions were investigated such as the catalyst concentration, glycerol-to-DMC ratio, reaction temperature, reaction time, and catalyst reusability. The NaAlO₂ catalyst prepared using the spray-drying method with 30 wt % glycerol as the template yielded the maximum GLC (85%) with 100% GLC selectivity.

Efficient synthesis of epoxybutane from butanediol via a two-step process

A novel approach for the synthesis of epoxybutane via decarboxylation of butenyl carbonate derived from butanediol was developed for the first time. For the carbonylation of butanediol with dimethyl carbonate, NaAlO₂ has exhibited excellent catalytic activity under mild reaction conditions. The yield of butenyl carbonate reached as high as 96.2%. NaAlO₂ provides suitable acid-base active sites to promote the transesterification reaction of butanediol and dimethyl carbonate. For the following step of decarboxylation of butenyl carbonate, ionic liquid 1-butyl-3-methylimidazolium bromide could effectively catalyze the decarboxylation process both in batch or continuous processes. Moreover, the catalytic mechanism for the crucial step of decarboxylation of butenyl carbonate over 1-butyl-3-methylimidazolium bromide was explored using DFT calculations. The results showed that the electrostatic and hydrogen-bond effects of 1-butyl-3-methylimidazolium bromide played a crucial role for the generation of epoxybutane. Briefly, the Br anion of the ionic liquid attacks the methylene of the ring and the H of the ionic liquid cation attacks the carbonyl oxygen, which facilitated the five-ring opening and subsequent decarboxylation to form BO. This study not only provided a new and green synthetic route for producing epoxybutane, but also contributed to the effective utilization of butanediol, which is inevitably produced as by-product in the process of coal to ethylene glycol, suggesting a promising application in the clean manufacture of epoxybutane with inexpensive cost.

Enzymatic Synthesis of Glycerol Carbonate Using a Lipase Immobilized on Magnetic Organosilica Nanoflowers as a Catalyst

For synthesizing glycerol carbonate (GC) by a reaction between glycerol (GL) and dimethyl carbonate (DMC), a lipase immobilized on magnetic organosilica nanoflowers was prepared and utilized as a biocatalyst. Candida antarctica lipase B (CALB) was chosen as a model enzyme for preparing an immobilized biocatalyst (CALB@nanoflowers). The obtained CALB@nanoflowers was characterized using scanning electron microscopy, transmission electron microscopy, and confocal laser scanning microscopy. Effects of GL/DMC molar ratio, biocatalyst amount, temperature, surfactant and molecular sieve addition, and reaction time on the conversion of GL and the selectivity of CALB@nanoflowers were investigated. The optimal catalytic performance (yield of GC: 88.66% and conversion of GL: 94.24%) was achieved under the condition of 1:20 molar ratio of GL to DMC with 0.2 g of molecular sieves added at 50 °C for 24 h. After recycling seven times, the CALB@nanoflowers maintained over 79% of its initial activity and the yield of GC was 70.31%.