Benzaldehyde Acetals Research Articles

Magnetic chitosan supported copper particles as a heterogeneous catalyst for benzaldehyde glycol acetal reaction

In this work, a series of magnetic chitosan (CS) supported-metal catalysts were successfully prepared for the acetalization of benzaldehyde (BzH) with ethylene glycol (EG). The structural properties of the catalysts were characterized by TEM, FT-IR, XRD, XPS, TGA-DTG, SEM-EDX and VSM. The results showed that Fe3O4-CS-Cu(20 %) catalyst possessed the best catalytic efficiency in all prepared catalysts due to its suitable acidity and excellent stability when they were utilized in the acetalization reaction to generate benzaldehyde glycol acetal. The response surface methodology based on Box-Behnken design was applied to optimize acetalization reaction conditions with the optimal yield of 96.26 % obtained via 3D surface diagram. The attractive feature of prepared catalysts was easy separation from solutions via an external magnetic field application. This work sheds light on the design of novel chitosan-supported metal catalysts which could be widely applied in acetalization industry.

Heterogeneous Acetalization of Benzaldehyde over Lanthanide Oxalate Metal-Organic Frameworks.

Lanthanides (Ln) from the f-blocks of the periodic table have gained significant interest due to their unique characteristics, including magnetism, photoluminescence, and catalysis. In this study, a series of lanthanide metal-organic frameworks [Ln-MOFs, Ln = Eu(III), Tb(III), Nd(III), Er(III), Ho(III), Gd(III), Pr(III), and Dy(III)] were constructed based on oxalic acid and lanthanide metals as the building blocks. These MOFs were comprehensively characterized using various analytical and spectroscopic techniques, including powder X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, energy-dispersive X-ray spectroscopy, nitrogen adsorption-desorption, and Raman spectroscopy. The magnetic properties of the investigated materials were examined, revealing both antiferromagnetic and ferromagnetic interactions within the Ln-Ox MOFs. The catalytic activities of Ln-Ox MOFs were evaluated through the heterogeneous acetalization of benzaldehyde with methanol. Reaction yields by the reported catalysts varied up to 90% depending on the MOF's metal center, and the product was confirmed by gas chromatography-mass spectrometry. Recycling experiments have confirmed the stable regeneration of Ln-Ox MOFs in which the product yields remained the same over four consecutive cycles. The hydrothermal synthesis of these MOFs paves the way for a diverse array of materials showcasing unique lanthanide properties, making them suitable for various applications.

Temperature‐Induced Modifications in Natural Zeolite Clinoptilolite: Effects on Acidity and Catalytic Acetalization

AbstractThis study delves into the acid modification of natural zeolite clinoptilolite, focusing on the identification of acid site types and their catalytic activity in the Brønsted acid‐catalyzed acetalization of benzaldehyde with 1,3‐butanediol. Following calcination, the samples underwent acidification via ammonium‐ion exchange, resulting in approximately 45 % of the clinoptilolite cations being exchanged with ammonium ions. The investigation evaluates the structural, morphological, and textural alterations induced by this modification using XRD, FTIR, and nitrogen adsorption‐desorption measurements. Ammonia‐temperature‐programmed desorption (NH3‐TPD) analysis confirms the presence of medium to strong acidic protons, highlighting the acidity of the modified samples. Employing 27Al and 29Si magic‐angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy elucidated changes in the state and coordination of aluminum post‐sample activation. Specifically, the 27Al MAS NMR spectra indicate a partial dealumination, evidenced by the emergence of 5 and 6‐fold coordinated aluminum. Moreover, 29Si MAS NMR measurements tracked variations in the Si/Al ratio. The study probes the nature of these sites, their influence on catalytic activity, and the synergistic interplay between Brønsted acid sites and 5‐fold coordinated aluminum. The results showcase that the prepared acidic natural clinoptilolite catalysts augment acidity and porosity, fostering promising implications for catalytic applications.

Catalytical advantages of Hf-MOFs in benzaldehyde acetalization

The potential use of acetals as bioadditives based on sustainable feedstocks in the automotive industry is of great interest. If such feedstock is a residual stream, the process would represent a dual environmental challenge, such as the valorization of glycerol obtained as a by-product of biodiesel to produce acetals. There are just scarce works about this synthetic route due to the challenge in finding efficient catalytic converters for glycerol valorization in a single process. Herein four different Metal-Organic Frameworks (MOFs) are evaluated as heterogeneous catalysts for the acetalization reaction of benzaldehyde with methanol, specifically, two structures, MOF-808 and UiO-66, containing two structural metal ions, zirconium and hafnium. The aim of this work is to investigate the influence of the MOF structure, the metallic active sites and the reaction conditions on the catalytic performance of this acetal production-type reaction. Furthermore, the recyclability of the catalyst is evaluated, and a potential reaction mechanism is suggested. As relevant results, Hf-MOFs showed higher benzaldehyde conversion than Zr-based ones, and significant improvements in reaction conditions were achieved, such as a significant reduction in catalyst loading of 99.6 % using UiO-66-Hf, and an optimization of reagent ratios reducing methanol consumption by 50 % for a 92 % of benzaldehyde conversion. The Brønsted character of UiO-66-Hf seems to enhance the reaction rate more than the metal center accessibility and larger pore volumes offered by MOF-808.

Design, Synthesis, and Acid-Responsive Disassembly of Shell-Sheddable Block Copolymer Labeled with Benzaldehyde Acetal Junction.

Smart nanoassemblies degradable through the cleavage of acid-labile linkages have attracted significant attention because of their biological relevance found in tumor tissues. Despite their high potential to achieve controlled/enhanced drug release, a systematic understanding of structural factors that affect their pH sensitivity remains challenging, particulary in the consruction of effective acid-degradable shell-sheddable nanoassemblies. Herein, the authors report the synthesis and acid-responsive degradation through acid-catalyzed hydrolysis of three acetal and ketal diols and identify benzaldehyde acetal (BzAA) exhibiting optimal hydrolysis profiles in targeted pH ranges to be a suitable candidate for junction acid-labile linkage. The authors explore the synthesis and aqueous micellization of well-defined poly(ethylene glycol)-based block copolymer bearing BzAA linkage covalently attached to a polymethacrylate block for the formation of colloidally-stable nanoassemblies with BzAA groups at core/corona interfaces. Promisingly, the investigation on acid-catalyzed hydrolysis and disassembly shows that the formed nanoassemblies meet the criteria for acid-degradable shell-sheddable nanoassemblies: slow degradation at tumoral pH = 6.5 and rapid disassembly at endo/lysosomal pH = 5.0, while colloidal stability at physiological pH = 7.4. This work guides the design principle of acid-degradable shell-sheddable nanoassemblies bearing BzAA at interfaces, thus offering the promise to address the PEG dilemma and improve endocytosis in tumor-targeting drug delivery.

Catalytic evaluation of MOF-808 with metallic centers of Zr(IV), Hf(IV) and Ce(IV) in the acetalization of benzaldehyde with methanol.

In the context of climate change, it is of utmost importance to replace the use of fossil fuels as raw material in areas of industrial interest, for example, in the production of chemical inputs. In this context, a viable option is biomass, since by subjecting it to chemical processes such as pyrolysis, it is possible to obtain platform molecules that are the basis for the generation of value-added chemical products. Acetals are molecules obtained from biomass derivatives, which have various applications in cosmetic chemistry, in the pharmaceutical industry as intermediates or final compounds, food additives, among others. Different catalysts have been used in the acetalization reaction, including MOFs, which have the advantage of being porous materials with high surface area values. The large surface area translates into a greater number of catalytically active sites available for the reaction. Among the MOFs that have been used for this purpose is MOF-808, which is characterized by having a lower number of ligands attached to its metal cluster, therefore, it has a greater exposure of the metals that make up its structure. In this context, the work carried out studied the catalytic performance of MOF-808 when its Zr(IV) metal centers are replaced by Hf(IV) and Ce(IV) atoms in the acetalization reaction of benzaldehyde with methanol. The MOFs obtained by solvothermal synthesis were characterized by powder X-ray diffraction, N2 adsorption and desorption, FT-IR spectroscopy, acid-base potentiometric titration, XPS and thermogravimetric analysis. The results of the catalysis indicate that the MOF with the best performance was MOF-808-Ce, which achieved conversions greater than 80% in a period of ten minutes. MOF-808-Ce exhibits a higher number of defects and therefore a higher availability of catalytic sites for the reaction to occur, which explains the better performance. Finally, the performance of MOF-808 in the acetalization of benzaldehyde with methanol was also supported by density functional theory (DFT) calculations.

Acidic ionic liquid-functionalized ordered mesoporous polymers: Highly efficient solid acid catalysts for water-medium organic reactions

Strong acidic ionic liquid-functionalized mesoporous organic material (MPOM-T-AIL) has been created by quaternary ammonization of mesoporous organic material (MPOM) with 1,3-propane sultone and subsequent strong acid (H2SO4 or HSO3CF3) acidification. The novel supporting material, MPOM, had high nitrogen content and was synthesized by direct high-temperature (400–550 °C) polymerization of an easily prepared and low cost protic salt [pPDA][2HSO4], which was obtained by simple neutralization of p-phenylenediamine with two equivalents of H2SO4. MPOM-T-AIL possesses high BET specific surface area, ordered and uniform mesoporosity, hydrophobic property, and highly active acidic ionic liquid components. Catalytic tests in the water-medium Prins reactions and acetalization of benzaldehyde with ethylene glycol showed that MPOM-T-AIL exhibits much better catalytic activities and reusabilities than commercially available solid acid catalysts Amberlyst 15 and H-ZSM-5, and mineral acid H2SO4. Additionally, MPOM-T-AIL significantly improved the catalytic selectivity of the water-medium Prins reaction, which was strongly related to its hydrophobic property. MPOM-T-AIL with excellent catalytic performance is a promising new solid acid catalyst for various acid-catalyzed reactions.

Acetalization of Alkyl Alcohols with Benzaldehyde over Cesium Phosphomolybdovanadate Salts

In this work, vanadium-substituted cesium phosphomolybdate salts with general formulae Cs3+nPMo12−nVnO40 (n = 0, 1, 2, and 3) were synthesized and evaluated in the acetalization of benzaldehyde with alkyl alcohols. All the catalysts were characterized through Raman, infrared, and ultraviolet–visible spectroscopies, powder X-ray diffraction patterns, isotherms of N2 desorption/adsorption, and measurements of acidity strength. The catalytic activity of cesium phosphomolybdovanadate salts was evaluated in the acetalization reactions of benzaldehyde with alkyl alcohols. Among the salts tested, the Cs4PMo11V1O40 was the most active and selective catalyst in the conversion of benzaldehyde to methyl benzyl acetal and benzoic acid, which was obtained without the use of an oxidant agent. The impact of the main reaction parameters on the conversion and selectivity was evaluated by varying the content of vanadium per heteropolyanion, catalyst load, temperature, and alkyl alcohols. The greatest activity of the Cs4PMo11V1O40 salt was assigned to the highest Brønsted acidity strength, as demonstrated by the acidity measurements and analysis of their surface properties. This solid catalyst has advantages over traditional liquid homogenous catalysts, such as low corrosiveness, a minimum generation of residues and effluents, and easy recovery/reuse. In addition, its synthesis route is easier and quicker than solid-supported catalysts and comprises a potential alternative route to synthesize acetals.

Transition Metal-Promoted Carbon-Silicon Solid Acid Catalysts for the Synthesis and Process Optimization of Benzaldehyde Glycol Acetal.

A series of transition metal (M)-promoted carbon-silicon (C-M-Si; M=Mn, Fe, Co, Ni, Cu, Zn, Zr) solid acid catalysts with designated molar ratio of M/Si=1 : 8 were fabricated and exploited for acetalization of benzaldehyde (BzH) with ethylene glycol (EG). The physical and chemical properties of these C-M-Si catalysts prepared by sol-gel method were characterized by various techniques, namely, SEM, EDS, TGA-DTG, BET, XRD, FTIR, XPS, and NH3 -TPD. Among various examined acidic C-M-Si catalysts, the C-Fe-Si catalyst exhibited the optimal catalytic activity with the benzaldehyde glycol acetal (BEGA) yield of 97.67 %, in excellent agreement with the value (97.88 %) predicted by the response surface methodology (RSM) based on a Box-Behnken design (BBD). C-Fe-Si catalyst with the high catalytic activities and excellent stability and reusability may be ascribed to the suitable acidity and uniform surface distribution of active sites requisite for the acid-catalyzed acetalization reaction.

Solid-phase rapid synthesis of hierarchical UiO-type metal-organic frameworks as excellent solid acid catalysts for acetalization of benzaldehyde with alcohol.

Functionalized metal-organic frameworks (MOFs) have been used in a wide range of applications. Although the development of functionalized MOFs with plentiful open metal sites (defects) provides an avenue for targeted reactions, creating such defects remains challenging. Herein, a UiO-type MOF with hierarchical porosity and plentiful Zr-OH/OH2 sites (capping 35% Zr coordination sites) was synthesized within 40 min by a solid-phase synthesis route without the use of solvent and template. The optimal sample converted 5.7 mmol benzaldehyde to (dimethoxymethyl)benzene within 2 min at 25 °C. The turnover frequency number and activity per unit mass reached 2380 h-1 and 8568 mmol g-1 h-1, respectively, outperforming all previously reported catalysts at room temperature. This excellent catalytic activity was correlated with the defect density in functionalized UiO-66(Zr) and the accessibility of plentiful Zr-OH/OH2 sites as acid sites.

Fast Assembly of Metal Organic Framework UiO-66 in Acid-Base Tunable Deep Eutectic Solvent for the Acetalization of Benzaldehyde and Methanol.

Zirconium-based metal-organic frameworks (MOFs) have attracted extensive attention owing to their robust stability and facile functionalization. However, they are generally prepared in common volatile solvents within a long reaction time. Here, we introduced environmentally friendly, cheap, and acid-based tunable deep eutectic solvents (DESs) formed from 2-methyl imidazole (MIm) and p-toluenesulfonic acid (PTSA) which significantly accelerated the assembly of zirconium-based MOF (UiO-66) without any aggressive additives. PTSA in acidic DES and ZrOCl2 preliminarily formed Zr(IV) oxo organic acid framework, whereas basic DES completely dissolved the ligand of UiO-66. The strong hydrogen bond effect of PTSA and MIm efficiently accelerated the linker exchange between zirconium oxo organic coordination in acidic DES and benzenedicarboxylate linker in weak basic DES within a reaction time of 2 h at 50 °C. Thus, UiO-66 was quickly assembled with small particle sizes and used as an excellent catalyst for the acetalization of benzaldehyde and methanol. Therefore, the developed synthesis approach provides a new green strategy to quickly prepare and design various structures of metal-based compounds under mild reaction conditions.

Magnetically-separable acid-resistant CoFe2O4@Polymer@MIL-100 core-shell catalysts for the acetalization of benzaldehyde and methanol

Novel reusable acid-resistant magnetic polymer nanospheres-immobilized MIL-100 (CoFe2O4@Polymer@MIL-100) catalyst was prepared by a layer-by-layer method to achieve a controllable structure. The obtained core-shell catalyst consisted of modified magnetic nanoparticles as the core, a carboxylic-functionalized polymer as the protective layer, and an MIL-100 shell as the active catalytic layer by chemical bonds on the polymer. The catalysts showed good stability, good magnetic saturation, and acid corrosion resistance. The thickness of the MIL-100 shell could be adjusted by controlling the metal salt concentration and the number of layer-by-layer cycles. Nano-sized MIL-100 showed better mass transfer efficiency and catalytic activity. A conversion of 97.7% after 10 min was observed during acetalization when using CoFe2O4@Polymer@MIL-100 as the catalyst. CoFe2O4@Polymer@MIL-100 could be reused at least five times. The use of a polymer layer on CoFe2O4@Polymer@MIL-100 prevented acidic ligands from corroding the magnetic core. Chemical bonds between MIL-100 and functional magnetic polymer cores improved the catalyst’s stability. CoFe2O4@Polymer@MIL-100 exhibited high activity, excellent stability, and easy magnetic separation.

Practical Synthesis of Variously Substituted 2,3,4-Benzothiadiazepine 2,2-Dioxides

AbstractThe significant pharmacological activity of 2,3-benzodiazepine-4-ones led to an increased interest in this compound family. However, the literature of the closely related 2,3,4-benzothiadiazepine 2,2-dioxides is rather scarce. Earlier we elaborated a synthesis of 5-aryl congeners variously substituted at the aromatic ring. In the present study, a new synthetic route was investigated via highly versatile intermediates, to extend the reaction to a wider aromatic substitution pattern and to the preparation of 5-alkyl and 5-H derivatives. The essence of this approach is, starting from benzaldehyde acetals, acetophenone and benzophenone ketals, to synthesize ortho-formyl- and ortho-acyl-arylmethanesulfonyl chlorides, which are suitable precursors of the target compounds. The synthesis was implemented as follows: ortho-lithiation of the corresponding acetals and ketals and subsequent treatment with paraformaldehyde, or alternatively in two steps, with DMF or ethyl formate, followed by reduction with NaBH4, led to the corresponding hydroxymethyl derivatives. Reaction of these latter with methanesulfonyl chloride gave mesylates that were used to S-alkylate thiourea to afford S-alkylisothiouronium salts. The final steps of the synthesis were carried out in a telescoped reaction. Treatment of the S-alkylisothiouronium salts with N-chlorosuccinimide resulted in the corresponding arylmethanesulfonyl chlorides. Subsequent reaction with hydrazine hydrate followed by an acidic treatment gave 2,3,4-benzothiadiazepine 2,2-dioxides.

Sulfuric Acid Immobilized on Activated Carbon Aminated with Ethylenediamine: An Efficient Reusable Catalyst for the Synthesis of Acetals (Ketals).

Through the amination of oxidized activated carbon with ethylenediamine and then the adsorption of sulfuric acid, a strong carbon-based solid acid catalyst with hydrogen sulfate (denoted as AC-N-SO4H) was prepared, of which the surface acid density was 0.85 mmol/g. The acetalization of benzaldehyde with ethylene glycol catalyzed by AC-N-SO4H was investigated. The optimized catalyst dosage accounted for 5 wt.% of the benzaldehyde mass, and the molar ratio of glycol to benzaldehyde was 1.75. After reacting such mixture at 80 °C for 5 h, the benzaldehyde was almost quantitatively converted into acetal; the conversion yield was up to 99.4%, and no byproduct was detected. It is surprising that the catalyst could be easily recovered and reused ten times without significant deactivation, with the conversion yield remaining above 99%. The catalyst also exhibited good substrate suitability for the acetalization of aliphatic aldehydes and the ketalization of ketones with different 1,2-diols.

Tuning selectivity among acetalization, pinacol coupling, and hydrogenation reactions of benzaldehyde by catalytic and photochemical pathways at room temperature

Benzaldehyde is one of the industrially most useful feedstocks, and its transformation to high-value chemicals is very attractive. Different transformations of benzaldehyde, such as acetalization, pinacol coupling, and hydrogenation, have been achieved herein by adjusting pH, light source, and selection of a catalyst. Consequently, the corresponding products have been obtained with excellent yields (e.g. 92% yield for acetalization, 96% yield for pinacol coupling, and 85% yield for hydrogenation). The mechanisms behind each transformation were studied, and it revealed that pinacol coupling reaction was achieved through a photochemical process under 365 nm irradiation at pH 12, where the introduction of the TiO2 (P25) catalyst would completely shift the selectivity toward benzyl alcohol through a photocatalytic pathway and to benzaldehyde dimethyl acetal via low-temperature thermal catalysis.

Chemical functionalization of chitosan biopolymer and chitosan-magnetite nanocomposite with sulfonic acid for acid-catalyzed reactions

Abstract Chemical functionalization of chitosan biopolymer and chitosan-magnetite nanocomposite was performed with sulfonic acid functional groups to achieve new solid acid materials. The sulfonic acid functional groups were created through the ring opening nucleophilic reaction of amine groups of chitosan with 1,4-butane sultone. Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopies (XPS) verified the successful sulfonic acid functionalization of chitosan. The obtained sulfonic acid functionalized chitosan-magnetite nanocomposite showed superparamagnetic properties according to the vibrating sample magnetometry analysis and exhibited magnetic separation feature from dispersed mixtures. Nitrogen adsorption-desorption analysis indicated the increase in surface area after formation of chitosan-magnetite nanocomposite and functionalization with sulfonic acid. Both of the prepared solid acids exhibited high catalytic activities in the acid-catalyzed acetic acid esterification with n-butanol and benzaldehyde acetalization with ethylene glycol as model reactions. Furthermore, they can be reused several times without considerable loss of their activities.

Incorporation of one or dual Brønsted acidic sites within the mesopores of MCM-41: Synthesis and catalytic activity in acetalization reaction

In recent years, various kinds of heterogeneous acid catalysts have been prepared and utilized for different catalytic applications. Among them, designing the easily recoverable catalysts containing two distinct Brønsted acidic sites with enhanced catalytic properties is promising. In this work, modification of the mesopores of MCM-41 as a siliceous solid support with two suitable nitrogen-containing amino- and piperazine-propylsilyl groups followed by covalent interaction with 1,4-butane sultone introduced sulfonic acid groups to this mesoporous material. The additional electrostatic interaction with phosphotungstic acid groups generated the second acidic sites on ammonium and piperazinium moieties. The successful synthesis of these solid acid catalysts was confirmed by FT-IR, energy dispersive X-ray (EDX), and inductively coupled plasma optical emission (ICP-OES) spectroscopies; CHN elemental analysis; nitrogen sorption; and XRD techniques. The catalytic experiments in benzaldehyde acetalization with ethylene glycol resulted in moderate to high activity from 76% to 97% within 2 h. Moreover, the higher catalytic activity was related to the one possessing two kinds of acidic sites due to the synergistic effect between these acidic sites.

Metal organic frameworks as solid catalyst for flow acetalization of benzaldehyde

MIL-100(Fe) was the first time used in a continuous flow system. Under the continuous flow, higher catalytic efficiency was achieved than in the batch system, which is attributable to a lower inhibition by products. This method provides a new approach to MOFs applied as heterogeneous catalysts for the synthesis of fine chemicals.

Acetalization of glycerol and benzaldehyde to synthesize biofuel additives using SO42-/CeO2–ZrO2 catalyst

Synthesis of 1,3- dioxane and 1,3-dioxolane, using sulfated CeO2–ZrO2 catalyst for acetalization of glycerol with benzaldehyde, is the focus of present work. SO42-/CeO2–ZrO2 catalyst was synthesized using combustion method. Experiments were carried out to analyze the effect of various solvents (n-hexane, toluene, tert-butyl alcohol, pentanol), molar ratios (1:3, 1:5, 1:7), catalyst loadings (3 wt%, 5 wt%, 9 wt %) and temperatures (80 °C, 90 °C, 100 °C) on glycerol conversion and selectivity of the products. Selectivity of 87.20% dioxolane and 12.80% dioxane was obtained at molar ratio of 1:3, 9 wt% catalyst loading and temperature of 100 °C.Strong NH3 desorption peak from NH3-TPD study indicated the high acidic strength of sulphated catalyst. Strong surface acidity and surface porosity (observed from TEM and SEM analysis) contributed to an enhanced activity of the catalyst for glycerol acetalization reaction. The kinetics of the reaction was studied using an elementary kinetic law. A correlation coefficient of 0.98 from the selected kinetic model proved that the rate of acetalization reaction was dependent on glycerol concentration and acetal formation was instantaneous. The study demonstrated the application of an environmentally benign, inexpensive, thermally stable, active SO42-/CeO2–ZrO2 catalyst for glycerol acetalization reaction to synthesize 1,3-dioxolane as the desired product.

New approach for sulfonation of carbonaceous materials: Highly efficient solid acid catalysts for benzaldehyde acetalization with ethylene glycol

Three kinds of carbonaceous solid materials, namely activated carbon (AC), graphene oxide (GO), and graphene oxide–magnetite nanocomposite (GO/SCMNPs), have been utilized as catalyst supports to immobilize active acid sites on their surfaces. In this regard, three solid acid catalysts were prepared by a two-step synthetic approach: (a) surface chemical modification with a suitable nitrogen-containing spacer group and (b) chemical appending of sulfonic acid groups on the immobilized functional groups derived from step (a). Various methods have been exploited for characterization of the synthesized solid acid catalysts, such as FTIR and energy-dispersive X-ray (EDX) spectroscopies, elemental analysis, X-ray diffraction (XRD) analysis, N2 adsorption–desorption, thermogravimetric analysis (TGA), and vibrating sample magnetometry (VSM). The catalytic activities of these carbonaceous acid catalysts have been examined in an acetalization reaction using benzaldehyde and ethylene glycol as starting substrates. An outstanding result was achieved for the acid catalyst based on AC due to a higher concentration of incorporated sulfonic acid groups. Nevertheless, even the good efficiencies of the other two catalysts matched those of previously reported catalyst systems.