Base Catalyst Research Articles

Development of Catalytic Enantioselective Mannich Reactions Using Esters.

Catalytic enantioselective Mannich reactions of simple nonactivated esters proceeded using a chiral potassium strong base catalyst prepared from a chiral bisoxazoline and potassium hexamethyldisilazide. Alkyl acetates, alkyl propionates, and an alkyl butyrate were employed as the simple esters, and the desired reactions proceeded smoothly to afford Mannich products in good to high yields with high enantioselectivities. One of the products was successfully employed in the asymmetric total synthesis of Maraviroc.

Heterogeneous Base Catalyst from Hybrid Banana-and-Plantain Peels in papaya Seed Oil (Carica papaya) Methyl-Ester Synthesis

Heterogeneous Base Catalyst from Hybrid Banana-and-Plantain Peels in papaya Seed Oil (Carica papaya) Methyl-Ester Synthesis

Biodiesel Synthesis from the Waste Biomass

In this work, physicochemical properties of the waste used oil (WUO) were carried out for its aptness for biodiesel production. Burnt Animal Bone was used as a precursor for the biodiesel production. The produced biodiesel was characterized and the optimum biodiesel produced was determined via statistical analysis. This was with a view to add value to WUO and finding environmentally friendly alternative to fossil fuel. WUO was obtained from eatery in Yenegoa, Bayelsa State, Nigeria. The foreign materials and dirt in the oil was removed by filtration after preheating. The physiochemical and other parameters (cetane number, API, aniline point among others) properties of WUO were determined using standard methods. The BAB was burnt to ash in a furnace, sieved into fine powder, and then characterized using FTIR, SEM, XRF, BET adsorption, and qualitative analysis. Biodiesel production was done via base catalyst transesterification while statistical analysis was done using Microsoft Excel 8.0. In order to ascertain the quality of the biodiesel, the physicochemical properties were determined. Results showed that the refined WUO properties were in line with oil property requirement for biodiesel production. The physicochemical characteristics of the WUO showed physical state of the oil to be liquid/dark brownish at 28 oC, viscosity 6.58 cP at 28 oC, acid value, 0.96 (mg KOH/g oil), FFA (% oleic acid), 0.48, iodine value, 152.00 (g I2/100g oil), peroxide value, 5.1 milli-equivalent of peroxide/kg of oil among others. The derived catalyst showed high basic strength with Calcium oxide (87.63 wt. %) as the dominant element in the catalyst. Optimum biodiesel yield was obtained at run 5 with 98.52 (%wt. /wt.) at reaction time of 30 min, catalyst amount of 2.0 (%wt.), reaction temperature of 100 oC, and ethanol-oil molar ratio of 4:1. The produced biodiesel properties conformed to the recommended standard ASTM D6751 and EN 14214. The study concluded that WUO could serve as feedstock for biodiesel production that is environmentally friendly and the derived catalyst could be used as a bio-base in Industries.

Interrogating l-fuconate dehydratase with tartronate and 3-hydroxypyruvate reveals subtle differences within the mandelate racemase-subgroup of the enolase superfamily

Enzymes of the enolase superfamily share a conserved structure and a common partial reaction (i.e., metal-assisted, Brønsted base-catalyzed enol(ate) formation). The architectures of the enolization apparatus at the active sites of the mandelate racemase (MR)-subgroup members MR and l-fuconate dehydratase (FucD) are almost indistinguishable at the structural level. Tartronate and 3-hydroxypyruvate (3-HP) recognize the enolization apparatus and can be used to interrogate the active sites for differences that may not be apparent from structural data. We report a circular dichroism-based assay of FucD activity that monitors the change in ellipticity at 216 nm (Δ[Θ]S–P = 8985 ± 87 deg cm2 mol−1) accompanying the conversion of l-fuconate to 2-keto-3-deoxy-l-fuconate. Tartronate was a linear mixed-type inhibitor of FucD (Ki = 8.4 ± 0.7 mM, αKi = 63 ± 11 mM), binding 18-fold weaker than l-fuconate, compared with 2-fold weaker binding of tartronate by MR relative to mandelate. 3-HP irreversibly inactivated FucD (kinact/KI = 0.018 ± 0.002 M−1s−1) with an efficiency that was ∼4.6 × 103-fold less than that observed with MR. The inactivation arose predominantly from modifications at multiple sites and Tris-HCl, but not l-fuconate, afforded protection against inactivation. Similar to the reaction of 3-HP with MR, 3-HP modified the Brønsted base catalyst (Lys 220) at the active site of FucD, which was facilitated by the Brønsted acid catalyst His 351. Thus, the interactions of tartronate and 3-HP with MR and FucD revealed differences in binding affinity and reactivity that differentiated between the enzymes’ enolization apparatuses.

Control of composition and surface area of aluminosilicates by tuning base catalyst concentration

Abstract Amorphous aluminosilicate nanosheets (a-ASns) consisting of small homogeneous nanoplates were synthesized in a bottom-up approach using the “hydrophilic two-dimensional reactor in amphiphilic phases” (TRAP) method. We found the appropriate operation variable to control the composition of a-ASns: the concentration of base catalysts.

Enantioselective Synthesis of Planar-Chiral Sulfur-Containing Cyclophanes by Chiral Sulfide Catalyzed Electrophilic Sulfenylation of Arenes.

An efficient catalytic asymmetric electrophilic sulfenylation reaction for the synthesis of planar-chiral sulfur-containing cyclophanes has been developed for the first time. This was achieved by using a new Lewis base catalyst and a new ortho-trifluoromethyl-substituted sulfenylating reagent. Using the substrates with low rotational energy barrier, the transformation proceeded through a dynamic kinetic resolution, and the high rotational energy barrier of the substrates allowed the reaction to undergo a kinetic resolution process. Meanwhile, this transformation was compatible with a desymmetrization process when the symmetric substrates were used. Various planar-chiral sulfur-containing cyclophanes were readily obtained in moderate to excellent yields with moderate to excellent enantioselectivities (up to 97 % yield and 95 % ee). This approach was used to synthesize pharmaceutically relevant planar-chiral sulfur-containing molecules. Density functional theory calculations showed that π-π interactions between the sulfenyl group and the aromatic ring in the substrate play a crucial role in enantioinduction in this sulfenylation reaction.

Enantioselective Synthesis of Planar‐Chiral Sulfur‐Containing Cyclophanes by Chiral Sulfide Catalyzed Electrophilic Sulfenylation of Arenes

AbstractAn efficient catalytic asymmetric electrophilic sulfenylation reaction for the synthesis of planar‐chiral sulfur‐containing cyclophanes has been developed for the first time. This was achieved by using a new Lewis base catalyst and a new ortho‐trifluoromethyl‐substituted sulfenylating reagent. Using the substrates with low rotational energy barrier, the transformation proceeded through a dynamic kinetic resolution, and the high rotational energy barrier of the substrates allowed the reaction to undergo a kinetic resolution process. Meanwhile, this transformation was compatible with a desymmetrization process when the symmetric substrates were used. Various planar‐chiral sulfur‐containing cyclophanes were readily obtained in moderate to excellent yields with moderate to excellent enantioselectivities (up to 97 % yield and 95 % ee). This approach was used to synthesize pharmaceutically relevant planar‐chiral sulfur‐containing molecules. Density functional theory calculations showed that π‐π interactions between the sulfenyl group and the aromatic ring in the substrate play a crucial role in enantioinduction in this sulfenylation reaction.

Thiourea as Bifunctional Hydrogen Bond Donor and Brønsted Base Catalyst for Green One-Pot Synthesis of 2-Aryl/Heteroaryl/Styryl Benzothiazoles in the Aqueous Medium under Ultrasound Irradiation.

A green organocatalysis cascade strategy using thiourea in catalytic amounts as both a hydrogen bond donor and a Brønsted base bifunctional catalyst was utilized to synthesize a series of 2-aryl/heteroaryl/styryl benzothiazole derivatives. This strategy involved an ultrasound-irradiated one-pot two-component reaction between substituted aldehydes and 2-amino thiophenols in an aqueous medium at 60 °C, using air as an oxidant. At the gram-scale, this protocol yielded 87% of the desired product, making it suitable for production at a larger scale. This green and mild protocol offers excellent yields, cost-effectiveness, atom economy, step economy, and a simple operation that does not require extra purification steps. Furthermore, the catalyst is easily recoverable and can be used for up to five cycles without a significant loss of any activity.

Analysis of Silica-Hexadecyltrimethoxysilane Nanosol Hybrids through optimization of Silica Nanosol Concentration and determining fabric types on Hydrophobicity

An analysis of the silica nanosol-hexadecyltrimethoxysilane hybrid has been carried out through optimizing the concentration of silica nanosol and determining the type of fabric regarding hydrophobicity. This research began with the synthesis of silica nanosol via the sol-gel method, where TEOS as a precursor was dissolved in a mixture of ethanol-distilled water with a base catalyst with a contact time of 2 hours. The concentration of silica nanosol was varied by 0.025, 0.05, and 0.075 mol. The dip-coating method was used to coat the fabric with nanosol, with a tensile rate of 3 cm per second. Then the fabric was re-coated with silica nanosol in HDTMS solution (4% wt/wt ethanol) and dried in a 120°C oven for 10 minutes. This research tested calico, cotton and mori fabrics. A Canon DSLR camera with a Thamron 100mm lens was used to measure the contact angle of the fabric surface. ImageJ software processes images to obtain contact angle values on the fabric surface. The fabric was then characterized using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM) and the silica nanosol was characterized using a Transmission Electron Microscope (TEM). The optimum concentration of silica-hdtms nanosol was obtained at a concentration of 0.075 mol with surface contact angles of cotton, mori and calico fabrics of 134, 132 and 135°. The flow speed of water with a slope of 100 on cotton, mori, and calico fabric produces flow speeds of 3.3, 6, and 5 m/s.

Produksi Biodiesel Dari Minyak Goreng Bekas Menggunakan Katalis Abu Tandan Kosong Sawit

Biodiesel is an alternative diesel fuel made from renewable materials such as vegetable and animal sources. Used cooking oil is waste cooking oil that is often found in households, very easy to obtain and always available all the time. Used cooking oil can be used as raw material for making biodiesel because it contains triglycerides through a transesterification process with the addition of a base catalyst, one of which is the ash of empty palm fruit bunches. This research aims to determine the effect of adding ash from empty palm fruit bunches on making biodiesel from used cooking oil. The method used in this research is transesterification with the addition of a catalyst of empty palm fruit bunch ash varied at concentrations of 1%, 2%, 3%, 4%, 5% with a mole ratio of 1: 6 (oil: methanol). The tests on the biodiesel produced consist of acid number, viscosity and density.

Base‐Catalyzed Synthesis of N‐Aryl Thioacetamides from Multicomponent Reaction of Phenylacetylenes, Sulfur and Anilines

AbstractIn the presence of a base catalyst (20 mol %) such as DBU, DABCO or Na2S ⋅ 3H2O/N‐methylpyrrolidone, phenylacetylenes were found to efficiently undergo sulfurative amination with elemental sulfur and anilines under neat conditions, leading to N‐aryl thioamides with complete atom efficiency.

Selective synthesis of methyl ethyl carbonate intensified by reactive distillation from consecutive transesterification of methyl carbonate and ethanol

Reactive distillation (RD) can be effectively used to improve the selectivity of the intermediate product for complex multi-reaction schemes, which involves using distillation to manipulate the column profiles in the RD column (RDC) to attribute the desired reaction and the manipulating reactions to facilitate separation. As the demand for ethyl methyl carbonate (EMC) has increased significantly due to its structural characteristics, the selective synthesis of EMC from the consecutive transesterification of dimethyl carbonate (DMC) and ethanol (EtOH) in the presence of azeotropes between reactants and products was studied as featured reaction schemes. The basic resin catalyst KC161 is utilized to build the kinetic reaction model and supplement the primary data for the process design. The pilot-scale RD experiments are explored to verify the feasibility and the reliability of the model. The impact of critical operation and structure parameters on the conversion and selectivity of the reaction and the azeotropes formed in the system were analyzed. A hybrid distillation process containing an RDC, pressure-swing distillation columns, and a regular distillation column, was designed and optimized based on minimized total annual cost (TAC) using a sequential iterative algorithm. 0. 9997 (mole purity) EMC and 0. 9999 (mole purity) diethyl carbonate (DEC) were obtained with EMC selectivity up to 0.863%.

Catalytic Conversion of Cyclopentanone into Dimethyl Adipate over Solid Basic Catalysts with Dimethyl Carbonate

The synthesis of dimethyl adipate (DAP), a stable configuration of adipic acid, from biomass-derived cyclopentanone (CPO) and dimethyl carbonate (DMC) constitutes an attractive greener route than petroleum-based industrial processes. Solid basic catalysts such as MgO, Mg5(CO3)4(OH)2·4H2O, KOCH3 and Ca(OCH3)2 have been used achieving a DAP yield up to 30% at 533 K. In addition to the type of catalyst, other operating conditions such as the substrate, reaction time, temperature and CPO concentration have been studied. The methylation of DAP and CPO and the self-aldol condensation of CPO to form dimers and oligomers are reactions that occur in parallel with the production of DAP. It has been established that the main challenge is the self-aldol condensation of CPO. It has been identified that at short reaction times, to prevent methylation, and at dilute concentrations, to avoid CPO self-condensation, the DAP formation rate is much higher than these other competitive reactions. Finally, it should be noted that a DAP productivity up to 3.45 g·gcat−1·h−1 has been achieved under mild conditions.

Valorization of durian peel as a carbon feedstock for a sustainable production of heterogeneous base catalyst, single cell oil and yeast-based biodiesel

The present study reports a successful attempt to produce single cell oil (SCO), heterogeneous base catalyst and yeast-based biodiesel from durian peel as a promising carbon feedstock by means of the waste-to-energy concept. For this purpose, first, durian peel (DP) was hydrolyzed by dilute sulfuric acid to obtain xylose-rich DP hydrolysate (XDPH) and post-hydrolysis DP solid residue (DPS). Candida viswanathii PSY8, a newly isolated oleaginous yeast, showed high SCO accumulation (5.1 ± 0.1 g/L) and SCO content (35.3 ± 0.13 %) on undetoxified XDPH medium. A novel heterogeneous base catalyst (DPS-K) prepared from DPS by wet impregnation technique with KOH, exhibited considerable catalytic activity to convert SCO-rich wet yeast of C. viswanathii PSY8 into yeast-based biodiesel (FAME) via direct transesterification with a maximum FAME yield of 94.3 % under optimal conditions (6 wt% catalyst, 10:1 methanol to wet yeast ratio, 75 °C, and 2 h). Moreover, most of the yeast-based biodiesel properties obtained from the FAME profiles were correlated well with the biodiesel standards limit of Thai, ASTMD6751 and EN 14214. Additionally, the energy output of FAME produced about 37.5 MJ/kg was estimated. Thus, this present finding demonstrated the favorable strategy for sustainable and eco-friendly production of new generation biodiesel.

Construction of stable heterogeneous catalysts with alkali metals loaded on weakly alkaline carbon-nitrogen materials for transesterification

It is important to enhance the basicity of solid catalysts for the application of heterogeneous catalysts in the synthesis of dimethyl carbonate. Notably, the role of the carrier in the supported solid base catalyst cannot be ignored. Herein, the catalyst (named 1.0Ca/g-C3N4 (M)), prepared by one-step thermal polymerization, achieved a yield of 68.4 % and a selectivity of 96.8 % for DMC and maintained its performance after four consecutive cycles at 130 °C. It could be seen from the characterization that the amino group on the surface of the carrier, as an electron pushing group, endowed the Ca connected at its end with more abundant valence electrons, so that the catalyst exhibited a higher alkalinity. This study provides a new reference for the development of multiphase catalysts in transesterification reactions.

Transesterification of acidic palm oil using solid waste/CaO as a bifunctional catalyst

Conventional solid base catalysts are difficult to adapt to the low-grade oil used in the industrial production of biodiesel due to the high acidity. In this paper, an acid-base bifunctional catalyst loaded with CaO from the solid waste of blast furnace dust was prepared to produce biodiesel by transesterification. Meanwhile, palm oil with oleic acid was used to simulate acid oil. The catalysts were characterized by XRD, XPS, BET, SEM-EDX, CO2-TPD and NH3-TPD. The biodiesel produced was tested and found to be compliant with ASTM D 6751. the response surface method based on the Central composite design (RSM-CCD) is used to optimize key parameters for the production of biodiesel. Under the optimal experimental conditions (i.e., methanol to oil ratio of 15.24, catalyst dosage of 7.96%, reaction temperature of 148.95 °C and reaction duration of 2 h, even with the oleic acid addition of 4%) the yield of biodiesel prepared by SW-CaO catalyst was 87.67%.

Stable Mg Single-Atom Solid Base Catalysts Anchored on Metal-Organic Framework-Derived Nitrogen-Doped Carbon.

Solid base catalysts are widely used in the chemical industry owing to their advantages of environmental friendliness and easy separation. However, their application is limited by basic site aggregation and poor stability. In this study, we report the preparation of magnesium (Mg) single-atom catalysts with high activity and stability by a sublimation-trapping strategy. The Mg net was sublimated as Mg vapor at 620 °C, subsequently transported through argon, and finally trapped on the defects of nitrogen-doped carbon derived from metal-organic framework ZIF-8, producing Mg1/NC. Because of the atomically dispersed Mg sites, the obtained Mg1/NC exhibits high catalytic activity and stability for Knoevenagel condensation of benzaldehyde with malononitrile, which is a typical base-catalyzed reaction. The Mg1/NC catalyst achieves a high efficiency with a turnover frequency of 49.6 h-1, which is much better than that of the traditional counterpart MgO/NC (7.7 h-1). In particular, the activity of Mg1/NC shows no decrease after five catalytic cycles, while that of MgO/NC declines due to the instability of basic sites.

Mono- and Co- solvency based transesterification of Caryota urens seed oil

This study aims to comprehensively evaluate the reaction parameters and fuel properties of biodiesel derived from underutilized waste Caryota urens seed oil (CUO) using mono- and co-solvency-based transesterification. The CUO was extracted through both solvent extraction at the laboratory scale and mechanical screw press for large-scale purposes, with a maximum oil content of 7.76 ± 1.52% (wt%) reported. Transesterification of CUO was carried out using methyl, ethyl, and methyl-ethyl-based reaction systems employing KOH as a base catalyst and ethanol as a co-solvent. The highest yields were achieved under optimized reaction conditions: molar ratio of 1:9, catalyst concentration of 0.75, 0.6, and 0.6 wt%, reaction temperatures of 60, 75, and 70 °C, reaction times of 135, 90, and 40 min, and methanol to ethanol ratio of 4.5/4.5. Notably, the addition of ethanol in an equivalent ratio to methanol altered the reaction kinetics and product distributions, encouraged reactions at higher temperatures without any loss of solvent loss, reduced the overall reaction time, enhanced the overall ester yield, and exhibited the most favourable fuel properties. In fact, fuel properties of both CUO ethyl and methyl-ethyl esters, evaluated as per ASTM D6751 standards, reported enhanced calorific value (40.14 and 39.67 MJ/kg), cetane number (69.29 and 68.27), kinematic viscosity (5.27 and 5.03 mm2/s), and reduced density (870.76 and 871.41 kg/m3) than compared to CUO methyl esters. The findings of this research indicate that CUO esters, regardless of their form, hold significant potential as a promising source of biodiesel fuel.

Catalytic fast pyrolysis of waste pine sawdust over solid base, acid and base-acid tandem catalysts

Catalytic pyrolysis is an effective means for high-value utilization of biomass. This study investigated the effect of solid base catalysts (CaO, calcium aluminate catalysts CaAl-1, CaAl-2, CaAl-3), acid zeolite catalysts (ZSM-5, Fe/ZSM-5, Co/ZSM-5, Ni/ZSM-5, Cu/ZSM-5, Zn/ZSM-5) and base-acid tandem catalysts on pine sawdust pyrolysis using Py-GC/MS. Acid zeolite catalysts exhibited robust deoxidation and aromatization capabilities, favoring aromatics, while solid base catalysts yielded more phenols and ketones. Among the solid base catalysts, CaAl-3 (CaO-Ca12Al14O33) showed comparable deoxygenation activity to CaO and optimal aromatic selectivity with structural stability. Zn/ZSM-5 excelled in deoxygenation and aromatic selectivity (70.42%) among metal-modified ZSM-5 catalysts. Base-acid tandem catalysis promoted the formation of aliphatics and BTX (benzene, toluene, xylene) while suppressing polycyclic aromatics. The highest BTX content (44.35%) was achieved with CaO-Ca12Al14O33&Zn/ZSM-5 tandem catalysts in a 1:3 ratio. This work demonstrates base-acid tandem catalysis as a promising approach for converting pine sawdust into valuable chemicals.

Enhancing carbon dioxide conversion in methane dry reforming multistep reactions through transformation of active species on catalyst surface

This study employed a novel one-pot method to encapsulate cerium species on the Ni–Al heterogeneous interface, aiming to achieve the capture and efficient utilization of greenhouse gas (CO2). Characterization results revealed that nickel species experienced various forms such as oxides and carbon-nickel compounds at the heterogeneous interface. The presence of cerium groups within the catalytic system induces the precipitation of nickel grain monomers on the support, decomposing the CH4–CO2 reforming process into a multistep reaction that breaks the thermodynamic barrier and kinetic limitation of the multicarbon coupling phenomenon, and greatly reduces the energy consumption of the reaction. Results showed that at a temperature of 800 °C and a Ni/Ce molar ratio of 0.2 in the catalyst, the activity was stable and the CO2 conversion reached 81.69 %, which was a 15.33 % enhancement compared to the base catalyst. Additionally, the mutual conversion of Ce3+/Ce4+ promoted the internal electron interaction process in the catalytic system, increasing the number of oxygen vacancies and reducing acidic sites, which facilitated reactant activation and carbon elimination. This work provides insights for the efficient utilization of greenhouse gases.