Use Of Homogeneous Catalysts Research Articles

Hydrogenation with Dissolved Pt‐Complexes Homogenously Distributed in the Ionic Liquid or Enriched at the Gas/Ionic Liquid Interface

AbstractThe use of homogeneous catalysts dissolved in ionic liquids (ILs) is an established field of research. Thin IL films containing dissolved catalyst complexes can be immobilized on solid porous supports, thereby creating a heterogenized catalyst material. Aiming at the deliberate positioning of such supported ionic liquid phase (SILP) catalyst, we carried out investigations of two very similar Pt‐complexes: depending on the ligand periphery, the first one is homogeneously dissolved in the IL while the second one strongly enriches at the gas/IL interface. To study these different locations within thick IL films of approximately 1 mm thickness, we investigated the hydrogenation of ethene in a continuous pool‐reactor setup. The two complexes dissolved in the IL [C4C1Im][PF6] showed different activity which can be attributed to their different locations. At 313 K and 0.62 MPa total pressure, the surface‐enriched complex was approximately two times more active. However, under these conditions the formation of Pt particles could be observed, with the surface‐enriched complex exhibiting a stronger tendency for particle formation compared to the one homogeneously distributed in the IL, as derived from XPS and light‐scattering measurements.

Hydrothermal Valorization via Liquid Hot Water and Hydrothermal Carbonization of Pea Pod Waste: Characterization of the Biochar and Quantification of Platform Molecules

Pea pod cultivation spans various regions and climates, with a global production of around 20 million tons. The pea peel wastes, which make up 30–40% of the total weight of the peas, are freely available in large quantities. The biomass used was characterized via ultimate, proximate, and structural analysis, obtaining 20.2%w of cellulose and 17.4%w of hemicellulose, which, via valorization processes, can be transformed into platform chemicals. Hydrothermal valorization presents itself as a clean form of treatment for these wastes, ranging from 120 to 180 °C (LHW) and from 180 to 260 °C (HTC). The use of LHW can lead to the production of sugars (up to 70%w yield) and levulinic acid (4%w yield), while the use of HTC leads to formic acid (40%w yield) and levulinic acid (4%w yield). The use of LHW for longer periods favors the production of HMF and furfural. The use of homogeneous catalysts (H2SO4, CH3COOH, KOH, and NaHCO3) was implemented, and their selectivity was described. Solid fractions of LHW and HTC were characterized via FTIR and elemental analysis, and the change in their structure was described as they shifted from biomass to biochar. Optimal conditions for each platform chemical were reported to best utilize the pea pod waste.

Biodiesel production from waste cooking oil using KOH/HY-type nano-catalyst derived from silica sand

The present study aimed to synthesize a Y-nanozeolite catalyst using the hydrothermal method and Iraqi sand-derived silica as a low-cost and readily available raw material. The catalyst was tested before and after loading with potassium hydroxide (KOH). The experiments were conducted in a batch reactor under different temperatures (40, 50, and 60 °C) and a 3-h reaction time, using the prepared Y-catalyst with three different particle sizes (75, 600, and 1000 μm). The results showed that increasing the temperature and/or reaction time generally resulted in increased conversion and yield when the catalyst was unpromoted with KOH, reaching a range of 55.56% and 33.33%, respectively. However, a significant increase in the conversion and yield was observed after promoting the catalyst with 10% KOH molecules. The optimal conditions for achieving the highest conversion and yield of biodiesel were determined to be 86.67% and 82.22%, respectively. These conditions involved a temperature of 60 °C, a reaction time of 2 h, and the use of a catalyst with a particle size of 75 μm loaded with 10% KOH. The use of a heterogeneous catalyst loaded with the base in a low percentage helps to dispense with the use of homogeneous catalysts with a high percentage of bases.

Advancements of Biochar-Based Catalyst for Improved Production of Biodiesel: A Comprehensive Review

Despite being a limited and scarce resource, the necessity and exploitation of fossil fuels are unstoppable in serving human demands. In order to supply energy demand without causing environmental damage, it is crucial to utilize a variety of renewable feedstock resources. Biochar, made up mostly of carbon, oxygen, and hydrogen, is the product of the thermochemical processes of pyrolysis, hydrothermal carbonization, torrefaction, and hydrothermal liquefaction. Biochar, once activated, has the potential to act as a catalyst in a variety of energy generation processes, including transesterification and fermentation. Transesterification is the process that is used to produce biodiesel from a variety of oils, both edible and non-edible, as well as animal fats in the presence of either a homogeneous or a heterogeneous catalyst. When selecting a catalyst, the amount of free fatty acid (FFA) content in the oil is considered. Homogeneous catalysts are superior to heterogeneous catalysts because they are unaffected by the concentration of free fatty acids in the oil. Homogeneous catalysts are extremely hazardous, as they are poisonous, combustible, and corrosive. In addition, the production of soaps as a byproduct and a large volume of wastewater from the use of homogeneous catalysts necessitates additional pretreatment procedures and costs for adequate disposal. This article examines the biochar-based fuel-generation catalyst in detail. At first, a wide variety of thermochemical methods were provided for manufacturing biochar and its production. Biochar’s chemical nature was analyzed, and the case for using it as a catalyst in the production of biofuels was also scrutinized. An explanation of how the biochar catalyst can improve fuel synthesis is provided for readers. Biodiesel’s transesterification and esterification processes, biomass hydrolysis, and biohydrogen generation with the help of a biochar catalyst are all reviewed in detail.

Advances in production & activation of marine macroalgae-derived biochar catalyst for sustainable biodiesel production

Biodiesel is considered as a promising sustainable biofuel from renewable resources with lower pollutant emissions. However, high production cost, difficulty in recovering catalyst, and an expensive separation process associated with the use of homogeneous catalysts are still critical challenges. Heterogeneous catalysts derived from biomass are considered as viable options. Marine macroalgae-derived biochar owing to its vast surface area, diverse functional groups, presence of inorganics, and high porosity, could be considered as a suitable heterogeneous catalyst or as a supported catalyst for biodiesel synthesis. Thermochemical conversion processes, such as hydrothermal carbonization and pyrolysis, convert marine macroalgae biomass into biochar, which primarily composed of carbon, oxygen, and inorganics (Ca, K, Mg, Fe, etc.). The activation of macroalgae-derived biochar either physically or chemically played a vital role towards biofuel production. The catalytic activity and the performance of the macroalgae-derived biochar catalyst are influenced by its physicochemical properties (–SO3H group density, porosity, overall surface area, functional groups, and so on). Biodiesel production over marine macroalgae-derived biochar catalyst represents a more sustainable solution to current energy demands and develops economically beneficial biodiesel technology. This article provides a critical assessment of the marine macroalgae-derived biochar catalysts for the production of biodiesel. Initially, macroalgal biochar is produced through different thermochemical conversion technologies, including hydrothermal carbonization and pyrolysis, and its yield and physicochemical characteristics are discussed. After that, various techniques for the activation of macroalgae-derived biochar are discussed.

Boosting the Transesterification Reaction by Adding a Single Na Atom into g-C3N4 Catalyst for Biodiesel Production: A First-Principles Study

Increasing environmental problems and the energy crisis have led to interest in the development of alternative energy. One of the most promising sustainable alternatives to fossil fuel is biodiesel which is typically produced from the transesterification of refined vegetable oils using a homogeneous base catalyst. However, the current process limitations and steep production costs associated with the use of homogeneous catalysts have limited the global-wide acceptance of biodiesel. Heterogeneous catalysts have been considered suitable alternatives, but they still suffer from low catalytic activity. In this study, by using density functional theory (DFT) calculations, we examined the electronic and catalytic activity of the single Na-doped graphitic carbon nitrides (indicated by Na-doped g-C3N4) toward the efficient biodiesel (acetic acid methyl ester) production via the transesterification of triglyceride (triacetin). Our DFT calculation on reaction energetics and barriers revealed the enhancement of biodiesel productivity in the Na-doped catalyst compared to the pristine g-C3N4 catalyst. This was related to the large reduction of the barrier in the rate-limiting step. In addition, we investigated the acidity/basicity and electron distribution and density of state for the Na-doped and pristine g-C3N4 catalysts to better understand the role of the Na atom in determining the transesterification reaction. This study highlights the importance of the dopant in a g-C3N4 catalyst in determining the transesterification reaction, which may open new routes to improve biodiesel production.

Toward a Hydrogen Economy: Development of Heterogeneous Catalysts for Chemical Hydrogen Storage and Release Reactions

Chemical hydrogen storage and release processes are essential steps for the implementation of new energy vectors. In general, the individual reactions involved in such technologies need catalysts to allow discharging and recharging hydrogen in a stable and efficient manner. In recent years, the development of hydrogen storage materials and their use in renewable energy systems have experienced rapid growth. While many academic works in this area make use of homogeneous catalysts, there is the practical need for heterogeneous catalytic systems, which often can be more easily applied on a larger industrial scale. In this Review we highlight the present status of using heterogeneous materials as catalysts for both chemical hydrogen storage and release systems, providing detailed reaction parameters for practical demonstration. The pros and cons of the currently known systems and their differences relative to homogeneous catalysts are also explained and critically discussed.

Kariya Pod-husks: A Novel Biocatalyst in Biodiesel Production

Diverse challenges faced with the use of homogeneous catalysts in biodiesel production coupled with the interest in converting waste resources to useful products in solving occurring climatic and environmental challenges around the world have triggered research into the use of various heterogeneous catalysts. In this study, the catalytic properties of kariya pod-husks were investigated to examine their suitability in biodiesel production. Kariya pod-husks were ash and calcined at 600oC for 4 h. In the morphological structure examination, the scanning electron image of calcined kariya pod-husks shows that it has a more compact microstructure with a cluster of big crystals but irregular pores which is an attribute of high catalytic potentials. The elemental composition of the calcined kariya pod-husks reveals that it contains a higher percentage weight of calcium (42%) and potassium (31%) which makes it a more suitable catalyst for biodiesel production. The developed catalyst was further used in the production of kariya biodiesel. A biodiesel yield of 94% was obtained. This study shows that calcined kariya pod-husks could catalyze biodiesel production. It also helps in proving suitable biocatalyst to solve the challenges associated with the separation of catalyst from the product stream which consequently aids in the creation of continuous chemical processes.

Kariya Pod-Husks: A Novel Biocatalyst in Biodiesel Production

Diverse challenges faced with the use of homogeneous catalysts in biodiesel production coupled with the interest in converting waste resources to useful products in solving occurring climatic and environmental challenges around the world have triggered research into the use of various heterogeneous catalysts. In this study, the catalytic properties of kariya pod-husks were investigated to examine their suitability in biodiesel production. Kariya podhusks were ash and calcined at 600°C for 4 h. In the morphological structure examination, the scanning electron image of calcined kariya pod-husks shows that it has a more compact microstructure with a cluster of big crystals but irregular pores which is an attribute of high catalytic potentials. The elemental composition of the calcined kariya pod-husks reveals that it contains a higher percentage weight of calcium (42%) and potassium (31%) which makes it a more suitable catalyst for biodiesel production. The developed catalyst was further used in the production of kariya biodiesel. A biodiesel yield of 94% was obtained. This study shows that calcined kariya pod-husks could catalyze biodiesel production. It also helps in proving suitable biocatalyst to solve the challenges associated with the separation of catalyst from the product stream which consequently aids in the creation of continuous chemical processes.

Clay-Supported Metal Oxide Nanoparticles in Catalytic Advanced Oxidation Processes: A Review.

Advanced oxidation processes (AOPs) utilizing heterogeneous catalysts have attracted great attention in the last decade. The use of solid catalysts, including metal and metal oxide nanoparticle support materials, exhibited better performance compared with the use of homogeneous catalysts, which is mainly related to their stability in hostile environments and recyclability and reusability. Various solid supports have been reported to enhance the performance of metal and metal oxide catalysts for AOPs; undoubtedly, the utilization of clay as a support is the priority under consideration and has received intensive interest. This review provides up-to-date progress on the synthesis, features, and future perspectives of clay-supported metal and metal oxide for AOPs. The methods and characteristics of metal and metal oxide incorporated into the clay structure are strongly influenced by various factors in the synthesis, including the kind of clay mineral. In addition, the benefits of nanomaterials from a green chemistry perspective are key aspects for their further considerations in various applications. Special emphasis is given to the basic schemes for clay modifications and role of clay supports for the enhanced mechanism of AOPs. The scaling-up issue is suggested for being studied to further applications at industrial scale.

Nickel-phenanthroline Complex Supported on Mesoporous Carbon as a Catalyst for Carboxylation under CO2 Atmosphere

Carbon dioxide is a highly potential renewable C1 source for synthesis of fine chemicals. Utilization of CO2 in carboxylation reactions requires catalysts, such as: nickel complex for CO2 activation. However, the use of homogeneous catalysts in the reaction is still less efficient due to the difficulty of separating the product and catalyst from reaction mixture. Therefore, it is necessary to heterogenize the nickel complex in a solid support such as mesoporous carbon. In this report, mesoporous carbon (MC) prepared from phloroglucinol and formaldehyde through soft template method was used as a solid support for Ni-phenanthroline complex (Ni-phen). The catalyst was characterized by Fourier Transform Infra Red (FT-IR), X-Ray Diffraction (XRD), Scanning Electron Microscope - Energy Dispersive X-Ray (SEM-EDX), and Surface Area Analyzer (SAA). The result of SAA characterization showed that the pore diameter of MC was 6.7 nm and Ni-phen/MC was 5.1 nm which indicates that the materials have meso-size pores. Ni-phen/MC material was then used as a heterogeneous catalyst in the carboxylation reaction of phenylacetylene under an ambient CO2 pressure. The reactions were carried out in several variations of conditions such as temperature, time and catalyst types. Based on the results of the reaction, the best conditions were obtained at 25 °C for 8 h of reaction time using Ni-phen/MC catalyst. 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).

Front Cover: Magnesium Oxide‐Catalyzed Conversion of Chitin to Lactic Acid (ChemistryOpen 3/2021)

The Front Cover shows the conversion of chitin, which is generated by food processing, into lactic acid with catalysis by magnesium oxides. Although chitin, a main component of the shells of crustaceans, can be converted to valuable products by means of homogeneous catalysis, most of the chitin is treated as industrial waste because use of homogeneous catalysts is compromised by difficulties associated with product separation from the catalysts and the recyclability of the catalysts. Thus, a method for converting chitin to useful chemicals, such as lactic acid, by using solid catalysts would be beneficial. Magnesium oxide catalysts can be reused twice without loss of activity. More information can be found in the Full Paper by Kodchakon Kun‐asa et al.

Unexpected coordination behavior of ruthenium to a polymeric α-diimine containing the poly[bis(arylimino)acenaphthene] fragment

Use of homogeneous catalysts poses the problem of their recovery at the end of the reaction. A possible strategy to circumvent this problem is to make the ligand part of a polymer with limited solubility. In this work, we investigated the immobilization of complexes of Ar-BIAN ligands (Ar-BIAN = bis(arylimido)acenaphthene). We employed 4,4′-methylene-bis(aniline) as an amine able to bridge two acenaphthene moieties. However, the obtained product was a mixture of short-chain oligomers. A ruthenium complex of this mixture (Oligo-BIAN) was indeed catalytically active in the model hydrogenation of nitrobenzene to aniline by CO/H2O but the complexes were too soluble in the reaction mixture to allow for an easy recovery. We thus further extended the molecular weight of Oligo-BIAN by polymerizing it with terephthaloyl chloride obtaining a polyamide (Poly-BIAN). The latter was insoluble in all solvents but its ruthenium complex was catalytically inactive in the model reaction. An deeper investigation, showed that coordination mode of monomeric Ar-BIAN ligands and Oligo-BIAN to [Ru(CO)3Cl2(THF)] is differs from that of Poly-BIAN. This result was completely unexpected and constitutes a general warning not to give for granted the coordination mode of a complex to a functionalized polymer.

Study of Esterification Reaction Between Ethanol and Acetic Acid Using Homogeneous and Heterogeneous Catalyst

The Ethyl acetate is the final product of esterification reaction between ethanol and acetate acid which usually used as a solvent. Catalysts are used to boost the esterification reaction rate, mostly the homogenous catalyst (acid liquid catalyst) is used. The use of homogeneous catalyst needs quite long process to separate, that is the reason why using the heterogeneous catalyst is the alternate way. The purpose of this research is to compare the performance of homogeneous catalyst (sulphuric acid) and heteregenous catalyst (natural zeolite from Bayah) by variating the factors that has an impact on reaction. The reaction was happened in batch reactor by variating the speed of agitation speed in range 500-700 rpm and the catalyst molecules size 60 mesh and 100 mesh for the solid catalysts. The goal of the variation is to maximize the reactant mass transfer to the active site of the catalyst. The result of this research shows that on the agitation speed of 700 rpm and 100 mesh Bayah natural zeolite is able to yield bigger conversion of acetate acid compared to using the sulphuric acid catalyst, which are 45.03% and 15.19% .

Microwave‐heated γ‐Alumina Applied to the Reduction of Aldehydes to Alcohols

AbstractThe development of cheap and robust heterogeneous catalysts for the Meerwein‐Ponndorf‐Verley (MPV) reduction is desirable due to the difficulties in product isolation and catalyst recovery associated with the traditional use of homogeneous catalysts for MPV. Herein, we show that microwave heated γ‐Al2O3 can be used for the reduction of aldehydes to alcohols. The reaction is efficient and has a broad substrates scope (19 entries). The products can be isolated by simple filtration, and the catalyst can be regenerated. With the use of microwave heating, we can direct the heating to the catalyst rather than to the whole reaction medium. Furthermore, DFT was used to study the reaction mechanism, and we can conclude that a dual‐site mechanism is operative where the aldehyde and 2‐propoxide are situated on two adjacent Al sites during the reduction. Additionally, volcano plots were used to rationalize the reactivity of Al2O3 in comparison to other metal oxides.

A review on the waste biomass derived catalysts for biodiesel production

Biodiesel is produced through the process of transesterification of different edible and non-edible oils and animal fats. The process takes place either in the presence of a homogeneous or heterogeneous catalyst. A suitable catalyst is selected based on the amount of free fatty acid (FFA) content present in the oil. The major difference between homogeneous and heterogeneous catalysts is that the homogeneous catalysts are insensitive to the amount of free fatty acids present in the oil. Also, homogeneous catalysts are toxic, highly flammable, and corrosive. Besides, the use of homogeneous catalysts produces soaps as a by-product and a bulk of wastewater which requires additional pretreatment methods and expenses for proper disposal. The research on the biodiesel synthesis in the presence of heterogeneous catalysts (carbon-based catalysts) is continuously studied to achieve a suitable process to produce biodiesel and to improve fuel quality on an industrial scale. Heterogeneous catalysts have great significance in the biodiesel production because of their simple and less expensive manufacturing process, ease of separation, and high reusability. They can be prepared easily by functionalizing the carbon surface with acid or base. Carbon-based catalysts have a high surface area and porosity that can enhance the rate of the esterification/transesterification process. Also, solid acid catalysts can convert the low-quality feedstocks to biodiesel in the presence of active acidic sites. Besides, carbon-based catalysts can be produced through waste e.g. sugarcane bagasse and their use make the production of biodiesel “Greener” one. This review paper is mainly based on the utilization of different catalysts derived from waste biomass in the biodiesel. Under optimum conditions biodiesel (FAME) yields 90%–99% were reported in the literature. • Biodiesel synthesis using waste cooking oil is reviewed. • Issues with the currently employed catalysts are reported. • Application of sugar bagasse for renewable catalyst has been discussed. • Carbon and CaO based functionalized catalysts for biodiesel synthesis are discussed.

Production of long alkyl ethers in homogeneous systems: A study of glyceryl monododecyl ethers

In this study, the etherification of glycerol was executed with dodecanol through use of homogeneous catalysts. First, a univariate study of direct condensation was executed to determine the effects of the variables reaction time, catalyst type and glycerol:dodecanol molar ratio on the dodecyl ether (DOE) and glyceryl monododecyl ether (GMDE) production. A full 23 factorial design was used to evaluate the effect of glycerol:dodecanol molar ratio, catalyst loading and temperature on the production of dodecyl ether (DOE), glyceryl monododecyl ether (GMDE) substituted on carbon 1 (C1) or carbon 2 (C2). The GMDE yield was 35% in 3 h. The experimental results indicated that rising temperature positively affected GMDE content and higher catalyst loading increased DOE production. In the case of traditional routes, Williamson synthesis produced just 5% GMDE while when applying solketal synthesis, high yield and purity of this compound were obtained, demonstrating the viability of GMDE production.

Graphitic carbon nitrides: Efficient heterogeneous catalysts for biodiesel production

Abstract Biodiesel remains one of the most promising sustainable alternatives to fossil fuel-derived energy; however, current process limitations and steep production costs associated with the use of homogeneous catalysts have limited global-wide acceptance and adoption. While heterogeneous catalysts have been put forth as suitable alternatives, they suffer from numerous drawbacks including high metal content and cost. As such, the search for novel and inexpensive alternatives is currently underway. Graphitic carbon nitride macrostructures have been widely investigated for photocatalytic applications yet their role in driving chemically-catalyzed reactions remains relatively unexplored. Herein, we synthesized and investigated the use of bulk, fiber, acid- and thermal-treated carbon nitrides as heterogeneous catalysts for the transesterification of canola oil to biodiesel. A conversion of 96% was achieved using 1 wt% catalyst loading, a low oil to methanol ratio of 1:24 and a reaction temperature and time of 150 °C and 3 h, respectively. Carbon nitrides offer a high thermal stability, cost effective and metal-free alternative to the many proposed metal-containing heterogeneous catalysts for biodiesel production, while maintaining high biodiesel conversions of >90%.

Synthesis of heterogeneous catalysts by the hydrolytic Sol-Gel method for the biodiesel production

The biodiesel is important as a renewable fuel, but some parameters of the industrial production, such as the use of homogeneous catalysts and the large quantities of residues (wastewater and glycerin) are a problem. In this work, four heterogeneous catalysts were synthesized by the hydrolytic Sol-Gel method for the biodiesel production and to possible reduce the production costs because the catalyst can be reused. The catalyst can also reduce the wastewater and glycerin contaminations. The catalysts were characterized by X-ray diffraction, basicity determination, and infrared spectroscopy. According to the National Agency of Petroleum, Natural Gas and Biofuels, the biodiesel samples were characterized by specific gravity, copper corrosivity, kinematic viscosity, acidity, Karl Fischer coulometry, and gas chromatography. The wastewaters were characterized by ultraviolet and visible spectroscopy, pH, dissolved oxygen, ashes, and solids (total, volatile, and non-volatile). The wastewater from heterogeneous catalysis was less harmful to the environment and can be easily treated, with reduction of 78.58% of organic residues to be converted by the wastewater treatment. In conclusion, the new catalyst produced biodiesel successfully and showed high catalytic activity (97.58% of ester content and 92.94% of yield), and produced wastewater and glycerin with lower amount of residues (eco-friendly).

The Contribution Of Heterogeneous And Homogeneous Catalysts Towards Biodiesel Quality

Homogeneous catalysts and heterogeneous catalysts are two types of catalysts used in the transesterification reaction process to produce biodiesel. Homogeneous catalysts that are commonly used are NaOH and KOH, while heterogeneous catalysts are CaO, super base CaO and Zeolite. This research was conducted to determine the contribution of catalysts NaOH, CaO, super base CaO, and zeolite to the quality of biodiesel produced from bulk palm oil, The reaction process is carried out in a Stirred Tank Flow Reactor equipped with a condenser. The results showed that the use of homogeneous catalysts could increase the acquisition of biodiesel but generally triggered high acid levels in the reaction products. Whereas heterogeneous catalysts can reduce biodiesel acid numbers, although the acquisition of biodiesel is lower than homogeneous catalysts.