Acid Catalyst Research Articles

An overview of the potential utilization of solid acid catalysts for enhanced biodiesel production through hydrodynamic cavitation assistance: A mini‐review

AbstractUtilizing a catalytic approach for producing biodiesel from non‐edible oils holds promise as a solution for the next generation of fuels. Therefore, the emerging research on replacing conventional catalysts and developing new waste‐derived heterogeneous catalysts with acid–base properties in the intensified biodiesel production process aims to achieve significant scientific outcomes including developing a low‐cost biorefinery and mitigating the increasing energy demand. Hence, a prospective replacement of green renewable solid acid catalysts over conventional or regularly used catalysts in the production of biodiesel using hydrodynamic cavitation‐assisted reactors has been discussed in this review. The synthesis and importance of different solid acid catalysts zeolite‐based and heteropolyacids is also discussed in this review. It is concluded that, to date, these catalysts are well used in biomass pyrolysis and very minimal in the pretreatment of lignocellulosic biomass, but there is no proper report on their application in the biodiesel synthesis from various non‐commercial feedstocks. In this study, it is also reported that the hydrodynamic cavitation‐assisted synthesis of biodiesel represents a novel approach with the potential to significantly boost yield and serve as a breakthrough method for industrial applications. The economic survey, circular economy, and life‐cycle assessment studies concerning the proposed study are also presented in this study, from which it is concluded that the complete replacement of these green catalysts in the production of biodiesel will aid in the development of a clean and green sustainable environment.

MBene Brønsted Acid Catalyst for Hydrogen Evolution Reaction in Alkaline Electrolyte

MBene Brønsted Acid Catalyst for Hydrogen Evolution Reaction in Alkaline Electrolyte

Towards quantifying catalytic activity of homogeneous Brønsted acid catalysts

Towards quantifying catalytic activity of homogeneous Brønsted acid catalysts

Pretreatment of corn straw using biomass-derived organic solvents for enzymatic saccharification: Specificity between acid catalyst and solvent

Pretreatment of corn straw using biomass-derived organic solvents for enzymatic saccharification: Specificity between acid catalyst and solvent

Rod-shaped silica promotes cellulose hydrolysis by inducing interior structural breakage via penetrated breaking.

Solid acid catalysts have attracted much attention in cellulose hydrolysis due to their high product selectivity, easy preparation and reusability. However, most current researches only focus on modifying their surface functional groups but overlook the impact of carrier shape on hydrolytic performance. Herein, we synthesize a series of rod-shaped silica with varying sizes for cellulose hydrolysis to analyze the shape mode to enhance the breaking of cellulose structure during solid-solid reaction. Experimental results show rod-shaped silica produces particular penetrating mode to enter into the interior of cellulose and thus causing strong disruption. This mode quickly disrupts the aggregated structure of cellulose, fragmenting it in a short time. The cellulose fragments are rapidly converted to glucose in a 0.02 M H+ solution. This process achieves an 83.92 % cellulose conversion rate and a 52.98 % glucose yield. The discovery suggests a new strategy to design one-dimensional solid catalyst for the efficient hydrolysis of cellulose to sugar.

A Theoretical Study on the Mechanism of Bifunctional Brønsted Acid/Base-Catalyzed CO2-Fixation Reaction with Homoallylic Amine.

The reaction mechanism and the enantioselectivity of the Brønsted acid/base (trans-stilbene diamine, simplified by BAM)-catalyzed CO2 fixation with homoallylic amine have been investigated using density functional theory (DFT) calculations. The proposed mechanism involves the initial activation of the amine by the Brønsted acid, followed by the nucleophilic attack of the amine on CO2 to form a carbamate intermediate. The Brønsted base subsequently deprotonates the carbamate intermediate to form the cyclic carbamate product, regenerating the Brønsted acid catalyst. The C-O cyclization is the enantio-determining step. The hydrogen bond network formed by the catalyst and substrate, similar to an enzyme pocket, plays a key role in stereoselectivity. In addition, the energy decomposition analysis (EDA) confirms that hydrogen bonding is driven by orbital and electrostatic attractions. The more Brønsted basic BAM catalyst (OMe at the quinoline 7-position) exhibits enhanced enantioselectivity.

Effect of Acid Catalyst on Epoxydation Reaction of Nyamplung Seed Oil

Epoxy is a cyclic ether compound that contains an oxirane group and has been widely applied as a stabilizer, plasticizer in polyvinyl chloride (PVC), surfactant, pesticide raw material, and as a polymer resin coating. The raw materials in epoxy synthesis come from petroleum derivatives, which are non-renewable natural resources. Therefore, there is a need for alternative raw materials that can be renewed, such as vegetable oil. In this study, nyamplung seed oil was used. Epoxy synthesis is usually carried out using carboxylic acid epoxidation with the help of an acid catalyst. This research aims to determine the effect of the type of acid catalyst and its concentration on the epoxidation reaction of nyamplung seed oil and the characterization of the epoxy produced. The research results show that using an acid catalyst can increase the formation of oxirane groups at a certain concentration, where the highest oxirane number value was obtained when using the H2SO4 catalyst, namely 3.15%. The resulting epoxy is pale yellow, has a typical absorption area (COC) at a wave number of 825 cm-1, an iodine value of 13.96 g iod/100 g, a viscosity of 20.80 cP, and a relative per cent conversion to oxirane of 73.4 %

Oxygen Atom Migration of Allylic Esters via an Organocatalyzed Claisen‐type Rearrangement

AbstractDirect transforming molecular skeleton to the other useful one is highly desirable for synthetic chemists. Oxygen atom migration of allylic esters is a powerful avenue for skeleton editing, and various methodologies involving palladium, Lewis acid and cobalt hydride catalysts have been reported. However, these protocols commonly suffer from inferior functional group tolerance and limited preparative application due to the harsh conditions and metal residues. Herein, we report a practical approach for the transformation by using an organocatalyst 4‐dimethylaminopyridine (DMAP). We test this protocol generality and practicality with uniform gram‐scale reactions, and it tolerates with a broad range of functional groups including boric ester, nitrile, ester and others (42 examples). Moreover, corresponding products exhibit versatile reactivity with a series of nucleophiles to open up a platform for bioactive molecules synthesis. A plausible reaction mechanism is proposed to rationalize the experimental observations.

Silanol-Enhanced Dehydrogenation of Ammonia Borane with Silicic Acid Catalyst

Silanol-Enhanced Dehydrogenation of Ammonia Borane with Silicic Acid Catalyst

Facile one-pot green synthesis, antioxidant and antimicrobial activities of 7-(substituted phenyl)-7,11-dihydro-6H,8H-chromeno[3′,4′:5,6]pyrano[2,3-d]pyrimidine-6,8,10(9H)-trione derivatives

The work aims to develop a simple and efficient protocol for one-pot three-component synthesis to produce a series of poly functionalized 7-(substituted phenyl)-7,11-dihydro-6H,8H-chromeno[3′,4′:5,6]pyrano[2,3-d]pyrimidine-6,8,10(9H)-trione derivatives using Sulfonated reduced graphene oxide (rGO-SO3H) as an efficient catalyst via one-pot multicomponent reaction of 4-hydroxycoumarin, aromatic aldehydes and barbituric acid under microwave irradiation and solvent-free conditions in good to excellent yields. The reported protocol is metal-free, highly atom-economic, better yielding in quick reaction time, simple to operate and eco-friendly with reaction conditions comparatively milder. Use of low-cost acidic catalyst under neat conditions makes the reaction an environmentally benign protocol. Additionally, the compounds were screened for their free radical scavenging, antibacterial and antifungal activities which showed good activities when compared than that of standard drugs.

Computational Insights into the Mechanism of Lewis Acid-Catalyzed Alkene-Aldehyde Coupling.

The Lewis acid-catalyzed coupling of alkenes and aldehydes presents a modern, versatile synthetic alternative to classical carbonyl addition chemistry, offering exceptional regio- and stereoselectivity. In this work, we present a comprehensive computational investigation into the reaction mechanism of this transformation. Our findings confirm the occurrence of an enantioselective trans-annular [1,5]-hydride shift step and demonstrate that the enantioselectivity of the reaction arises predominantly from steric clashes between functional groups in the cyclization step. Combining computational and experimental results, we establish that the Lewis acid catalyst facilitates the initial C-O coupling step between the alkene and the activated aldehyde. Investigations into systems with longer alkyl chains reveal that while they follow a similar mechanistic pathway, cyclization becomes kinetically hindered, preventing the reaction from proceeding. These insights illuminate the factors governing reaction outcomes and limitations, paving the way for future developments in this area.

Confined Growth by Self-Combustion of a Cu-Based Nanophase into Mesostructured Acid Supports for DME Production from CO2.

This work deals with the design of nanocomposite hydrogenation-dehydration bifunctional catalysts for the one-pot conversion of CO2 to dimethyl ether (DME), focusing on obtaining a high and homogeneous dispersion of a Cu-based CO2 hydrogenation phase into the pores of mesostructured supports. Particularly, three aluminosilicate mesostructured acid catalysts with catalytic activity towards methanol dehydration and featuring different porous structures (Al-MCM-41, Al-SBA-15, Al-SBA-16) were synthesized and used as supports to host a CuO/ZnO/ZrO2 (CZZ) CO2 hydrogenation catalyst for methanol synthesis. The use of a mesostructured support allows to maximize the exposed surface of the CO2 reduction function by nanostructuring it through its confinement within the mesochannels, thus obtaining nanocomposite bifunctional catalysts with an ultra-small hydrogenation nanophase. The nanocomposites were obtained using an impregnation strategy combined with a self-combustion reaction, allowing to incorporate the CO2 reduction phase inside the mesopores. In all cases, the characterization shows that the hydrogenation phase species are highly and homogeneously dispersed into the supports as either small nanoparticles or as a nanolayer. The as-obtained nanocomposites were tested for their catalytic activity and the results discussed taking into account the structural, textural, and acidic properties of the supports and nanocomposites.

Design of an efficient magnetic brush solid acid and its catalytic use in organic reactions

In this research, with the Green Chemistry approach, to load more sulfonic acid active sites on catalyst surfaces, a nanocomposite material based on core-shell magnetite coated with vinyl silane and a sulfonated polymeric brush-like structure is designed and synthesized as a new class of efficient solid acid catalysts, referred to as Fe3O4@VS-APS brush solid acid. The synthesized catalyst was comprehensively characterized by a range of instrumental techniques, including XRD, SEM, TEM, FT-IR, EDX, TGA, and VSM. The activity of the catalyst was evaluated in Biginelli, Strecker, and esterification reactions. The Fe3O4@VS-APS brush solid acid has special features, such as easy reusability when a simple magnet is used for four reaction runs, an appropriate balance between hydrophobic and hydrophilic properties on the catalyst surface, and effective catalytic performance in the production of 3,4-dihydropyrimidin-2-one(thione) derivatives, 2-phenyl-2-(phenylamino)acetonitrile and octyl acetate.

Anhydrous HCl gas-induced alcoholysis of cotton linter fibers

Abstract Abstract Alcoholysis has attracted attention because of its potential to isolate platform chemicals and biofuel precursors from cellulosic biomass. We investigated the degradation of native cellulose fibers via alcoholysis using various alcohols (ethanol, 2–propanol, t–butanol, and ethylene glycol) and anhydrous HCl gas as an acid catalyst. We explored the impact of these different systems on the leveling-off degree of polymerization (LODP). Fibers soaked in ethylene glycol and t–butanol reached LODP under the default conditions, i.e., 50 wt.% alcohol content. When subjected to a post-hydrolysis step, the fibers previously alcoholyzed in ethanol and 2–propanol attained the LODP level as well. However, the production of monosaccharides during post–hydrolysis was 20 times higher from the fibers that had been alcoholyzed previously by ethanol than with 2–propanol. Graphical abstract

Bifunctional mixed-valence ruthenium heterostructure for robust electrocatalytic water splitting in acid media

The incorporation of non-metal dopants can significantly enhance catalytic activity and improve stability. Furthermore, the creation of heterostructures is particularly advantageous to facilitate charge transfer and optimize electronic properties. This study presents an effective bifunctional mixed-valence Ruthenium heterostructure synthesized through a cascading process involving grinding with carbon nitride and subsequent thermal treatment. The catalyst exhibits outstanding electrocatalytic performance with remarkably low overpotentials of 197 mV for the oxygen evolution reaction (OER) and 24.8 mV for the hydrogen evolution reaction (HER), respectively, with the stability exceeding 24 h at a current density of 10 mA cm⁻2 in acidic media. Additionally, when employed in an acidic oxygen water splitting (OWS) electrolyzer, the bifunctional catalyst demonstrates excellent activity, achieving an ultralow cell voltage of 1.53 V to sustain 10 mA cm⁻2. Enhanced performance is attributed to efficient charge transfer and increased exposure of active sites, providing valuable insights for the development of effective acidic water-electrolysis catalysts for sustainable hydrogen production.

Green one-pot synthesis of quinoxaline derivatives using sulfo-anthranilic acid functionalized alginate-MCFe2O4 nanostructures: a novel superparamagnetic catalyst with antiproliferative potential.

This study reports a green, multi-component synthesis of 2-aminoimidazole-linked quinoxaline Schiff bases using a novel superparamagnetic acid catalyst. The catalyst consists of sulfo-anthranilic acid (SAA) immobilized on MnCoFe2O4@alginate magnetic nanorods (MNRs), achieving high SAA loading (1.8 mmol g-1) and product yields (91-97%). Characterization of the MCFe2O4@Alginate@SAA MNR catalyst revealed an inverse spinel structure (XRD), a saturation magnetization of 31 emu g-1 (VSM), 17.5% organic content (TGA), and a rod-like morphology with diameters of 30-60 nm and lengths of 150-250 nm (SEM). Elemental composition confirmed by EDX analysis indicated successful SAA immobilization and high catalyst purity. The synthesized quinoxaline derivatives were evaluated for antiproliferative activity against SKOV3 and HCT-116 cancer cell lines using the MTT assay. Several compounds, notably 4a, 4s, 4t, 4w, and 4x, exhibited potent activity, inhibiting HCT-116 proliferation by >50% at 50 μg mL-1. Compound 4a demonstrated the most significant inhibition, with 82.3% against SKOV3 cells after 48 h and 69.0% against HCT-116 cells after 24 h, both at 50 μg mL-1. These results suggest the potential of 2-aminoimidazole-linked quinoxaline Schiff bases, particularly 4a, as promising multi-target chemotherapy agents.

Lemon Juice as a Natural Biodegradable Catalyst for an Ecofriendly One-Pot Pseudo-Three-Component Synthesis of N,1-Dimethyl-6-(methylsulfanyl)-3,5-dinitro-1,4-dihydropyridine-2-amines

AbstractA one-pot pseudo-three-component reaction strategy has been designed for synthesizing all-carbon-functionalized hexasubstituted N,1-dimethyl-6-(methylsulfanyl)-3,5-dinitro-1,4-dihydropyridine-2-amines under neat conditions using inexpensive, readily available, natural, biodegradable lemon juice as a catalyst. The acidic reaction environment induced by lemon juice provided a superior catalytic performance, with a high reaction rate and high product yields, to those of a pool of Lewis and Brønsted acid catalysts. The wide substrate scope and functional-group tolerance permitted diversity creation with electronic and structural variations in a robust and operationally simple manner. The recoverability/reusability of the lemon juice catalyst and the easy purification of the end products by precipitation/filtration avoid the need for column chromatography or hazardous organic solvents and confirm that this is an environmentally benign sustainable technology. Moreover, a gram-scale operation and chemical modifications of the final products demonstrated some promising advantages.

An Unexpected Activity of a Minor Cannabinoid: Cannabicyclol (CBL) Is a Potent Positive Allosteric Modulator of Serotonin 5-HT1A Receptor.

Cannabicyclol ((±)-CBL), a minor phytocannabinoid, is largely unexplored, with its biological activity previously undocumented. We studied its conversion from cannabichromene (CBC) using various acidic catalysts. Montmorillonite (K30) in chloroform at room temperature had the highest yield (60%) with minimal byproducts. Key reaction conditions, such as solvent, temperature, and time, significantly impacted the yield. The structure of (±)-CBL was confirmed via X-ray crystallography. Stability studies showed that (±)-CBL and its MCT oil dilution remain stable at 25-40 °C for three months. Radioligand binding assays revealed high affinity of CBL for the 5-HT1A receptor but weak interaction with CB1 and CB2 receptors. At 10 μM and 1 μM, (±)-CBL inhibited [3H]-8-hydroxy-DPAT binding to 5-HT1A by 75% and 20%, respectively. Functional assays showed that (±)-CBL acts as a weak agonist at high concentrations but a potent positive allosteric modulator of serotonin-induced activation at low concentrations. At 4 μM, (±)-CBL increased serotonin-induced β-arrestin recruitment from 20% to 80%. This unique modulatory profile highlights the potential of (±)-CBL in drug discovery targeting serotonin receptors.

Low-temperature catalytic oxidation of ethanol over doped nickel phosphates.

This work is focused on the synthesis and performance of Ni3(PO4)2-based catalysts doped with Cu, Co, Mn, Ce, Zr, and Mg for the complete oxidation of ethanol, aiming at reducing emissions from ethanol-blended gasoline. Nickel phosphate was prepared via the co-precipitation method, followed by impregnation with the specified dopants. The catalysts were thoroughly characterized by XRD, N2-physisorption, XRF, FTIR and Raman spectroscopy, FESEM, NH3-TPD, CO2-TPD, and H2-TPR to explain their performance. All catalysts achieved complete ethanol conversion (100%) at a temperature below 320°C. The performance of the catalysts was strongly influenced by the dopant type of which Co, Ce, Mn, and Mg showed high CO2 selectivity (selectivity > 90% at 95% ethanol conversion temperature (T95)). The mechanism of oxidation is affected by the acido-basicity of the catalysts and the redox properties leading to a reaction through ethylene formation over the acid catalysts and acetaldehyde over the basic catalysts. The redox properties of the doped catalysts play a crucial role in enhancing the catalytic activity and selectivity toward CO₂, as the redox-active dopants facilitate the activation of oxygen species, which are essential for the complete oxidation of ethanol. In particular, Co and Ce demonstrated superior redox characteristics, facilitating the conversion of intermediate species and leading to higher CO2 selectivity while minimizing undesirable by-products.

Photoinduced Catalytic Alkylation of Active Methine Compounds with Nonactivated Alkenes Using Yttrium Triflate as a Lewis Acid Catalyst

Photoinduced catalytic alkylation reactions of active methine compounds with nonactivated alkenes have been developed using an organophotocatalyst, a metal Lewis acid, an arylthiol, and an amine base catalyst system. The alkylation reactions proceeded smoothly under ambient conditions with blue light irradiation, affording the desired products bearing quaternary carbon centers in high yields. Furthermore, enantioselective alkylation with an nonactivated alkene was achieved using a chiral Lewis acid.