Catalyst For Aldol Condensation Research Articles

Bifunctional Hybrid Organosiliceous Catalysts for Aldol Condensation – Hydrogenation Tandem Reactions of Furfural in Continuous-Flow Reactor

Bifunctional Hybrid Organosiliceous Catalysts for Aldol Condensation – Hydrogenation Tandem Reactions of Furfural in Continuous-Flow Reactor

Vanillin conversion by aldol condensation using hydrotalcite Mg-Al and modified-Y zeolite as heterogeneous catalysts

Mg-Alhydrotalcite, MgO-Al2O3 mixed oxides and modified-Y zeolite (sulfated Y zeolite and copper ion-exchanged Y zeolite) were prepared and characterized by XRD, EDX and XRF techniques. These materials were used as heterogeneous catalysts in aldol condensation of vanillin and acetone.The obtained results showed that the heterogeneous acid catalysts as modified-Y zeolites were more effective than the heterogeneous base catalysts as hydrotalcite Mg-Al and MgO-Al2O3 mixed oxides in aldol condensation reaction of vanillin. The highest conversion of vanillin was 95.5% when the reaction was carried out at 120oC in 5 hours, using sulfated Y zeolite.

BiPO4 decorated with Ni–Fe layered double hydroxide as a highly efficient and reusable heterogeneous catalyst for aldol condensation in green solvent

BiPO4 decorated with Ni–Fe Layered double hydroxide (BiPO4@Ni–Fe LDH) was synthesized and applied as a catalyst for aldol condensation of carbonyl compounds and aldehydes with good yield in glycerin as a green solvent. The catalytic performance of BiPO4@Ni–Fe LDH compared with BiPO4 and Ni–Fe LDH as a catalyst for aldol condensation. Also, the BiPO4@Ni–Fe LDH was recovered and reutilized for at least five runs without significant loss of catalytic activity.

On the influence of acidic admixtures in furfural on the performance of MgAl mixed oxide catalysts in aldol condensation of furfural and acetone

Aldol condensation of furfural and acetone is often used as a model reaction to test acid-base properties of solid catalysts. The present study describes the effect of furfural acidity on the catalytic performance of MgAl mixed oxides. Three furfural sources differing in their acidity were used and compared in aldol condensation at T = 55 °C and acetone to furfural molar ratio of 10. The furfural conversion over MgAl mixed oxides depended on the acidity of the furfural source, and the catalysts were partially consumed for neutralization of acid admixtures present in furfural. Only for some furfurals could the furfural conversion be improved by distilling the as-received furfural prior to the aldol condensation experiments. Moreover, the storage of the freshly distilled furfural during a few days, even in a closed flask and at a dark place, resulted in a substantial decrease in furfural conversion in aldol condensation. The results indicate that the distillation of the as-received furfural is an effective method to control the performance of basic catalysts at comparable reaction conditions only for some furfurals. Furthermore, the storage of the freshly distilled furfural has to be performed with care to avoid its re-oxidation.

MgRuAl-layered Double Hydroxides (LDH): An Efficient Multifunctional Catalyst for Aldol Condensation and Transfer Hydrogenation Reactions

Background: Layered double hydroxides (LDH) are drawing much attention as solid catalysts in recent years and have applications in various organic transformations as they possess a variety of basic sites which could be obtained by exchange of metal ions or by intercalation of suitable anions into their interlayer space. Ru based complexes have widespread catalytic applications in many organic reactions. Herein, novel ruthenium containing ternary LDH has been synthesized and used as a multifunctional catalyst for Aldol condensation and transfer hydrogenation reactions. Methods: Ternary LDH multifunctional catalyst containing Mg, Ru and Al was prepared by coprecipitation and hydrothermal treatment. The catalyst was characterized by elemental analysis, Powder XRD, FT-IR, BET, TGA, DRS, SEM, EDX, XPS and TEM. The products of the reactions were characterized by 1H NMR and GC-MS. Results: The analysis of catalyst revealed incorporation of Ru in the brucite layers of the LDH and showed the mosaic single crystal with BET surface area of 84.25 m2 g-1. This catalyst yielded 85–98% products for Aldol condensation reactions within 4 h reaction time, and 82–98% products for transfer hydrogenation reactions within 16 h reaction time. Conclusion: The resultant MgRuAl-LDH with acid and base sites was found to be highly active and selective for one-step synthesis of nitrile compounds. The catalyst works more efficiently for Aldol condensation reactions in shorter reaction times compared to transfer hydrogenation reactions.

Виробництво акрилової кислоти: порівняння промислового та нових перспективних методів її одержання

Виконано порівняльний огляд основних перспективних методів одержання акрилової кислоти. Показано, що значного розвитку з огляду на доступність сировинної бази набув метод одержання акрилової кислоти з гліцерину (побічного продукту виробництва біодизелю), а також способом ферментації біомаси. Окрім цього, показано, що вдосконалення каталізаторів альдольної конденсації оцтової кислоти з формальдегідом в акрилову кислоту робить цей метод її синтезу одним із найбільш конкурентних. Встановлено, що модифікація поруватої структури B–P–W–V–Oх/SiO2 каталізаторів процесу альдольної конденсації є дієвим способом впливу на їхні каталітичні властивості. Оптимальним розміром пор B–P–W–V–Oх/SiO2 каталізаторів є 11–16 нм. В оптимальних умовах (температура 380 °С, час контакту 8 с) вихід акрилової кислоти в процесі альдольної конденсації оцтової кислоти з формальдегідом становить 68 % за селективності її утворення 91 %. Розроблений каталізатор також є ефективним у процесі окиснювальної конденсації метанолу з оцтовою кислотою. Особливістю цього методу є те, що в процесі утворюються одночасно два цінні продукти – акрилова кислота та метилакрилат. Сумарний вихід акрилатів становить 54,7 % за селективності їх утворення 80,1 % (температура 400 °С, час контакту 8 с). Розглянуто перспективи використання новітніх Se-вмісних каталітичних систем на мікрогелевій основі для низькотемпературного синтезу акрилової кислоти та метилакрилату з акролеїну.

Marine solids/NaNO3: As Natural and Efficient Catalysts for Aldol condensation

A new and efficient method have been developed for the synthesis of α,β-unsaturated carbonyl compounds from various aldehydes and ketones, using marine calcinated coral/NaNO3 and cuttlebone/NaNO3, as natural and efficient catalysts for cross aldol condensation. The aim of present study was to study the marine solids/NaNO3: as natural and efficient catalyst for Aldol condensation. The materials were purchased from Merck and Aldrich Companies. The IR spectra were recorded on a Perkin-Elmer RXI infrared spectrometer. H NMR spectra were recorded on a 400 MHz Brucker FT-NMR spectrometer. The SEM image was recorded on 1455 VP LEO-Germany. TLC accomplished the purity of substrates and reactions monitored on silica gel (Merck, Germany) Polygram SIGL/UV254 plates. The melting points are uncorrected. Results showed that, the marine solid are efficient catalysts for aldol condensation, but cuttlebone/NaNO3 catalyze this reaction in shorter time (1 hr) than calcinated coral/NaNO3 (6 hr). However, these marine solids have several advantages such as small amount of the catalyst, good absorbent natural solid, easy to handle, and products in good-to-high yields. In conclusion we found marine catalysts, Calcinated Cuttlebone/NaNO3 or Coral/NaNO3 to be an effective catalyst for aldol condensation from ketones having α-hydrogens and aldehydes in 50 % ethanol at reflux conditions. The α,β-unsaturated carbonyl products were obtained in good to high yields. This method offered marked improvement compared to previously reported ones.

Characterization of potassium-modified FAU zeolites and their performance in aldol condensation of furfural and acetone

The effects of both Si/Al ratio and preparation method (ion exchange vs. impregnation) on the physico-chemical properties of potassium modified Y zeolites were studied in detail. The samples were used as basic catalysts for aldol condensation of furfural and acetone. A relationship between physico-chemical properties and catalytic performance of potassium-containing Y zeolites was established using XRD, N2 physisorption, IR spectroscopy of adsorbed CO2‎ and CO2-TPD. Neither ion-exchange nor impregnation with KNO3 removed completely all acid sites in Y (Si/Al=2.5). Moreover, K2O clusters were not formed under thermal activation of the samples prepared from the parent H-Y(2.5). As a consequence, both ion-exchanged and impregnated K-Y(2.5) possessed low activity in aldol condensation, but they had high ability to dehydrate reaction products. In contrast, thermal activation of USY zeolites (Si/Al=15 and 40) impregnated with potassium resulted in the formation of K2O species which, according to CO2-IR spectroscopy and CO2-TPD, were strong basic sites. It was concluded that the lower amount of proton sites available for an ion-exchange together with the ‎larger mesopore volume and more defective crystalline framework promoted the accumulation of KNO3 in the USY zeolites during the impregnation step. Subsequently, K2O species were formed by thermal treatment. Impregnated and calcined USY zeolites possessed a superior catalytic activity in comparison with HY (Si/Al=2.5). The presence of K2O species as strong basic sites in K-impregnated USY zeolites was favorable for both the high activity of the catalysts in aldol condensation and the occurrence of the second condensation step.

The occurrence of Cannizzaro reaction over Mg-Al hydrotalcites

Mg-Al mixed oxides and reconstructed hydrotalcites prepared from mixed oxides by rehydration attract much attention as solid basic catalysts for organic reactions, such as aldol condensation. Therefore, the understanding of parameters that govern their catalytic performance is of great importance. Cannizzaro reaction in the presence of mixed oxide and reconstructed HTC as basic catalysts was used as a model reaction to characterize both catalytic systems and to understand their behavior in aldol condensation. The performance of the samples was investigated in the conversion of aqueous furfural mixture using stirred batch reactor operating at T=50°C. The properties of both initial samples and catalysts after reaction were studied by different physico-chemical methods, such as XRD, DRIFT and TGA. It was shown that both mixed oxide and reconstructed HTC possessed poor activity in the conversion of dried furfural proving the importance of water presence for the reaction to take place. Addition of water to the reaction mixture resulted in growth of the yield of both furfuryl alcohol and furoyl furoate as reaction products. Furoic acid was not identified by GC analysis, but the interaction of the acid with the basic sites of catalysts was confirmed by DRIFT and TGA analyses indicating that at optimum reaction conditions, most of the basic sites were involved in the formation of furoate species. The formation of the surface furoate species influenced the behavior of the basic catalysts in aldol condensation of furfural and acetone. It allows concluding that the occurrence of Cannizzaro reaction should be taken into account when considering the behavior of basic catalysts in organic reactions with furfural as a reactant.

Catalytic applications of alkali-functionalized carbon nanospheres and their supported Pd nanoparticles

Carbon nanospheres (CNSs) prepared by hydrothermal approach and post-functionalization with alkali solutions were employed as solid base catalysts in aldol condensation. The negative charge and alkalinity of CNS surfaces were controlled by the concentration of alkali solutions, leading to the high selectivity superior to aqueous NaOH as the traditional catalyst. Furthermore, CNSs with varying surface alkalinity can be adopted as proper supports for highly dispersed Pd nanoparticles with well-controlled size distribution. The optimized alkaline CNS-supported Pd catalysts demonstrated enhanced reactivities in the solvent-free selective oxidation of benzyl alcohol and the aerobic oxidation of glycerol. In-depth characterizations of their structural and electronic properties by transmission electron microscope (TEM), field emission scanning electron microscope (FESEM), Fourier transform infrared spectroscope (FTIR) and X-ray photoelectron spectroscopy (XPS) were performed to elucidate the nature of the active sites and the mechanism. The effect of electron density, size of Pd nanoparticles as well as the surface alkalinity of supports on the catalytic performance has been unveiled.

ChemInform Abstract: Modified Calcium Oxide as Stable Solid Base Catalyst for Aldol Condensation Reaction.

A highly efficient and stable solid-base catalyst for Aldol condensation was prepared by modifying commercial CaO with benzyl bromide in a simple way. It was found that modified CaO can effectively catalyse the Aldol condensation of cyclohexanone and benzaldehyde, as well as various benzaldehydes, to produce 2-benzylidenecyclohexanone with a good selectivity and high yield. Higher yield of 95.8% was obtained over modified CaO after 3 h, which is short compared with the yield of 92.1% after 12 h over commercial CaO. The influence of several reaction parameters, such as temperature, catalyst loading, was investigated. The humidity test over modified CaO reveals that the basic centres of modified CaO are stable for CO2 and moisture. From the results of Fourier transform-infrared (FT-IR) and Thermogravity analysis (TG) characterization, the modifier was bonded on surface of CaO chemically and almost no Ca(OH)2 formed during the modification process. The type of aldehyde has great influence on the yield of aldol condensation.

Two-Step Preparation of Benzylacetone

Two-step preparation of benzylacetone has been investigated using layered double hydroxides (LDHs) as catalysts for aldol condensation of benzaldehyde and acetone and Ni supported catalysts for consecutive hydrogenation of benzylideneacetone. Activity and selectivity of LDHs of various Mg/Al ratios to desired product, benzylideneacetone, have been compared in the liquid phase at 333 K. An aldol condensation yield at 100 % conversion of benzaldehyde was 78 % using catalyst HT-2.0. In the following, optimal hydrogenation conditions—temperature of 353 K, hydrogen pressure of 5 MPa and 5 wt% of catalyst NiSAT® 320 were found. At 95 % conversion of benzylideneacetone the selectivity to desired product was 99 %.

Flame retardancy effects of halogenated phosphates on poly(ethylene terephthalate) fabric

AbstractA Chemical research on the flame retardancy effect of halogenated phosphates on poly(ethylene terephathalate) fabric was carried out by thermogravimetry, infrared spectral analysis, and mass spectrometry. The following conclusions were drawn: (1) The flame retardancy effect of halogenated phosphates such as tris(2,3‐dibromopropyl) phosphate is due to altering the pyrolysis reaction of polyester by aldol condensation. (2) The probability that liberated halogen compounds from the phosphates act as radical acceptors in a flame zone may be low. (3) Incorporation of halogen elements into phosphates appear to depress evaporation of phosphates, which act as acidic catalysts in aldol condensation from the condensed phase.