Base Catalyst Research Articles

Formulation of Body Lotion with Sucrose Ester Emulsifier

Abstract Sucrose ester is synthesized from palm fatty acid methyl ester and sucrose using a base catalyst. Emulsifiers that replace palm oil with sucrose esters are biodegradable and potentially non-toxic to the skin. The efficiency of sucrose ester production was obtained by using water as a solvent for sucrose, with a mass ratio of 3:5 for water and sucrose. Dilution of sucrose with water reduces caramelization during reaction. Based on laboratory research, sucrose ester has good emulsion stability from sucrose myristate ester, sucrose palmitate ester, and sucrose laurate ester. The design used a random block design with three levels of variation in sucrose ester concentration, namely 2%, 6%, and 10%. Based on ANOVA, there is a very significant effect between variations in concentration on specific gravity, pH, viscosity and surface tension. Verification tests were carried out on consumer references in the form of organoleptic tests on 35 respondents. Then, microbial tests are carried out based on Indonesian National Standards, namely the maximum number of total plates (10−2 colonies), negative tests for fungi, Staphylococcus aureus, Pseudomonas aeruginosa, and Coliform (maximum 3). Determining the best combination uses the Composite Performance Index (CPI) and Analytical Hierarchy Process (AHP). Based on organoleptic tests, the best sample is 10% myristate. The analysis of organoleptic results is consistent with the analysis of laboratory results which states that the lotion sample made from 10% sucrose myristate ester is the best sample. The best lotion samples have good emulsion stability and are not contaminated by microbes.

Cyclopropenium Sulfide as Lewis Base Catalyst for Chemoselective and Regioselective Electrophilic Selenylation of Phenols

Cyclopropenium Sulfide as Lewis Base Catalyst for Chemoselective and Regioselective Electrophilic Selenylation of Phenols

Transesterification of DMC with ethanol over K2CO3/Al2O3: The structure-performance relationship and catalytic mechanism

The transesterification of dimethyl carbonate (DMC) with ethanol to ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) has attracted increasing attention, which could be greatly promoted by heterogeneous solid base catalysts. The K2CO3/Al2O3 solid base catalysts with different active sites such as K2CO3, KAl(OH)2CO3, and KAlO2 were prepared for the transesterification reaction. The active sites of K2CO3 and KAl(OH)2CO3 mainly exist on the surface of KA-200 and KA-300, while K2CO3 and KAlO2 were mainly present on KA-400 and KA-500. The effects of active sites and the phase of support were studied systematically. KAl(OH)2CO3 showed higher activity than K2CO3 and KAlO2. In contrast, K2CO3 and KAlO2 displayed higher stability, with the activity of KA-400 kept stable over 2000 h. The excessive OH group of γ-AlOOH and water in the reaction system have a negative effect on the activity of the K2CO3/Al2O3 catalysts. The catalytic characterizations, transesterification reactions, and DFT calculations suggested that K+ in the KAl(OH)2CO3 species, with higher electron cloud density than that in K2CO3/γ-Al2O3, could efficiently promote the dissociation of ethanol and subsequent replacement of methoxy with ethoxy. The rate-determining step for the transesterification reaction was suggested to be the dissociation of ethanol.

Water modulates the chemiexcitation efficiency of the peroxyoxalate reaction: Enhancement at low and decrease at higher concentrations

Chemiluminescence transformations are widely utilized in analytical and bioanalytical applications. Specifically, the peroxyoxalate system can be employed for sensitive quantification of a wide variety of analytes. Under anhydrous conditions, the peroxyoxalate reaction shows extremely high emission quantum yields, comparable to highly efficient bioluminescence systems. However, in aqueous media, important for bioanalytical applications, the emission efficiency suffers a significant decrease of several orders of magnitudes, although the reason for this loss in efficiency is unknown up to now.In the present work, we show the results of a detailed photophysical study on the effect of water on the chemiexcitation efficiency of the peroxyoxalate reaction using bis(2,4-dinitrophenyl) oxalate as reagent and imidazole as base catalyst in the presence of different chemiluminescence activators. It is shown that in 1,2-dimethoxyethane/water mixtures (DME:H2O), singlet quantum yields increase with increasing the water concentrations up to 0.7 mol/L, followed by a steady decrease at higher water concentrations. The decrease in quantum yields is not predominantly due to concurrent ester hydrolysis, as quantum yields could be corrected for this side reaction. This indicates that the quantum yield decrease is due to the diminished chemiexcitation efficiency in the presence of water. Using different activators, it is shown that chemiexcitation occurs via electron transfer and electron back-transfer steps between a high-energy intermediate and the activator. Additionally, its efficiency is governed by the energetics of the electron back-transfer step, in agreement with the Chemically Initiated Electron Exchange Luminescence (CIEEL) mechanism, also in partially aqueous environment. Lower excitation efficiency in aqueous media may be due to formation of solvent-separated radical ion pairs, inhibiting chemiexcitation.

Recent advances in co-immobilization of organic acids and bases for cooperative and tandem catalysis

Acid–base bifunctional catalysts have been extensively used for a series of CC bond formation reactions. Among these catalysts, organic acid–base catalysts have attracted wide attention due to their structural variety, conformational dynamics, and enantioselectivity. To prevent mutual deactivation, a simple, effective, and versatile strategy is the attachment of both acid and base onto the surfaces of supports. In particular, the co-immobilization of organic acids and bases not only enhances synergistic effects in cooperative catalysis but also improves yields to desired products by controlling the diffusion of intermediates in tandem catalysis, leading to significant improvements in energy and atom efficiency. In this review, we highlight recent works addressing the broad topic of the co-immobilization of organic acids and bases for cooperative and tandem catalysis. We mainly focus on the synthetic strategies for silica-supported organic acid–base catalysts and polymer-supported organic acid–base catalysts. Furthermore, we summarize and discuss the structure–activity relationships of these catalysts. Last, the remaining issues and prospects will be discussed to advance the rational design and engineering of co-immobilized acid–base bifunctional catalysts.

Determination of concentration of basic sites on oxides by IR spectroscopy

As it is commonly known, CO2 reacts simultaneously with basic O2− and basic OH sites on oxides forming carbonates and bicarbonates, which can be followed by infrared spectroscopy (IR). However, here, we succeeded to elaborate experimental conditions under which CO2 reacted solely with O2− forming CO32− for ZrO2 and CeO2, and calculated the extinction coefficients of diagnostic bands of carbonate and bicarbonate species. For the first time, the developed IR method enabled the concentrations of O2− and basic OH for ZrO2, CeO2, Al2O3 and CuO to be measured separately. Moreover, in the case of all IR studied oxides, the sum of concentrations of O−2 and basic OH basic sites was comparable with the concentration determined by pulse adsorption of CO2. Thus, the presented extinction coefficients can be applied for IR basicity studies of various basic catalysts. We also followed the effect of thermal treatment on basicity of oxides.

Synthesis of biofuel from Luffas cylindrical-Dennettia tripetala oil blend (BT40) using catalytic sweet corn stock acidified with iron (III) sulfate (Fe2(SO4)3)

In an attempt to model and optimize the biodiesel production from the binary oil blends, a BTO40 obtained from the mixture of Dennettia tripetala (DTO) and Luffas cylindrical (LCO) oilseeds was employed in a double-stage microwave-assisted batch process (DSMABP). The DTO40 was esterified with iron (III) sulfate (Fe2(SO4)3) and then transesterified with catalyst selectivity between calcined fermented sweet corn stock (CFCS) and calcined non-fermented sweet corn stock (CNFCS). Catalyst characterization was carried out using analyzers, while process modeling and optimization were carried out using statistical tools. The produced biodiesel qualities were evaluated, and the catalyst potential was tested by a catalyst reusability test. Results show that a BTO40 was suitable for maximum biodiesel yield of 98.92% (wt./wt.) with HHV of 43.84 MJ/kg, CN of 79.73, flash point of 120 °C, cloud point of -3 °C, pour point of -6 °C, cold filter plugging point of +2 °C, oxidative stability of 4.6 h, and carbon residue of 0.02% nm. The statistical modeling and optimization by RSMI-Optimal predicted a mean value of biodiesel to be 99.28% (wt./wt.), the ANNGA predicted a mean biodiesel yield of 99.78% (wt./wt.), and γGCFW predicted 99.82% (wt./wt.), respectively, at different variable conditions. These values were validated in triplicate, and the average means were obtained as 98.57% (wt./wt.), 99.69% (wt./wt.), and 99.71% (wt./wt.), respectively. Catalyst usability tests show DFSCS has high alkali potential as a base catalyst. The produced biodiesel properties are in total agreement with the recommended biodiesel standard. The study concluded that BTO40 treated with a 0.1 M Fe2(SO4)3 solution in a base-catalyzed calcined fermented sweet corn stock for biodiesel synthesis can be used as an alternative fuel.

Tuning the cross-linked structure of basic poly(ionic liquid) to develop an efficient catalyst for the conversion of vinyl carbonate to dimethyl carbonate

Dimethyl carbonate (DMC) is a crucial chemical raw material widely used in organic synthesis, lithium-ion battery electrolytes, and various other fields. The current primary industrial process employs a conventional sodium methoxide basic catalyst to produce DMC through the transesterification reaction between vinyl carbonate and methanol. However, the utilization of this catalyst presents several challenges during the process, including equipment corrosion, generation of solid waste, susceptibility to deactivation, and complexities in separation and recovery. To address these limitations, a series of alkaline poly(ionic liquid)s, i.e., [DVBPIL][PHO], [DVCPIL][PHO], [TBVPIL][PHO], with different cross-linking degrees and structures were synthesized through the construction of cross-linked polymeric monomers and functionalization. These poly(ionic liquid)s exhibit cross-linked structures and controllable cationic and anionic characteristics. Research was conducted to investigate the effect of the cross-linking degree and structure on the catalytic performance of transesterification in synthesizing DMC. It was discovered that the appropriate cross-linking degree and structure of the [DVCPIL][PHO] catalyst resulted in a DMC yield of up to 80.6%. Furthermore, this catalyst material exhibited good stability, maintaining its catalytic activity after repeated use five times without significant changes. The results of this study demonstrate the potential for using alkaline poly(ionic liquid)s as a highly efficient and sustainable alternative to traditional catalysts for the transesterification synthesis of DMC.

Enhanced Biodiesel Production from Waste Cooking Oil Using Potash-Enriched Natural Base Catalyst

The transesterification reaction of waste cooking oil with methanol using a sugar apple peel ash catalyst has been reported. Under optimized conditions, the reaction of the oil with methanol in a molar ratio of 1:10, in the presence of a catalyst (2 g) at 60 °C temperature offered a 94.5% yield of biodiesel within 120 min. The heterogeneous catalyst was developed via a straightforward calcination process using fruit processing industry waste peels of sugar apples. The characterization of the catalyst by FTIR, EDS, SEM, XRD, N2 sorption, and XRF analysis revealed a higher concentration of potassium species which is possibly responsible for the promotion of the transesterification reaction more efficiently. This approach offers cost competitiveness, reusability of the catalyst, simplicity of operation, and high biodiesel yields. This study underscores the potential of utilizing waste materials for sustainable biodiesel production, contributing to environmental preservation and economic viability.

Choline hydroxide, an efficient, green, and recyclable base catalyst, promoted the synthesis of 3-aroylflavones via Baker–Venkataraman rearrangement

ABSTRACT 3-Aroylflavones, a new synthesized group of flavones, have been recently studied via Baker–Venkataraman rearrangement under ‘one-pot’ or sequential ‘one-pot’ reaction conditions. Choline hydroxide, an inexpensive, easily prepared, and green homogeneous catalyst has been found to be the most efficient catalyst among several base catalysts such as KOH/pyridine, KOH/triethylamine, and CaO-ES/triethylamine in the sequential ‘one-pot’ synthesis of 3-aroylflavones. Moreover, the catalyst’s efficiency, and high recyclability to six times without considerable loss of 3-aroylflavones have enhanced the importance of the procedure. Furthermore, 1D-NMR, 2D-NMR, and HRMS have also been used to elucidate the structures of synthesized compounds.

The Affects of Ce Doping Cr\(_2\)O\(_3\) Based Catalysts Supported on Activated Carbon for 1,2-Dichloroethane Abatement

Hydrothermal method is used to prepare activated carbon (AC) supported chromium-based catalysts for the catalytic combustion of 1,2-dichloroethane (DCE). The physicochemical properties relating catalysts are evaluated by several characterization techniques such as XRD, SEM, XPS, N2 adsorption-desorption isotherms, H2-TPR and NH3-TPR. The outcomes demonstrated that the Cr2O3 is the perfect targeted base catalyst adding to the facts that the hydrothermal approach is an appropriate way to create catalysts with superior properties. The textural characteristics, reducibility, and acidity of the Cr-based catalysts were all enhanced by the addition of cerium (Ce) and AC. Nevertheless, the research shows how crucial the Ce doping amount is for adjusting the physicochemical characteristics and catalytic efficacy of Cr-based catalysts. The catalyst 20Ce-Cr/AC has the maximum catalytic activity when it came to DCE combustion, where its T50 and T90 attaining of 247°C and 269.5°C, correspondingly. This is explained by the ideal Ce doping level, which improves the redox characteristics and revealed more active sites.

Ring-opening polymerization of six-membered cyclic hybrid dimers composed of an oxoester and thioester

Three cyclic oxoester-thioester hybrid monomers, 1 (3-methyl-1,4-oxathiane-2,5-dione), 2 (6-methyl-1,4-oxathiane-2,5-dione), and 3 (3,6-dimethyl-1,4-oxathiane-2,5-dione), were studied for anionic and cationic ring-opening polymerizations. These monomers are six-membered cyclic cross-dimers corresponding to combinations of glycolic and lactic acids with their thiol analogs. Anionic polymerizations using thiol as the initiator and 2,6-lutidine as the base catalyst were successful for the chemoselective cleavage of the thioester with the thiol propagating end. The polymerizability increased in the order of 3 < 1 < 2, which was in good agreement with the increasing ring strain order evaluated by Density Functional Theory calculations. The living character, to some extent, was suggested by the postpolymerization reactions, which involved a two-stage feed of the monomers and a thiol-ene terminal coupling reaction to form a block copolymer with PEG. Additionally, it was found that the polymerization took place in 2,6-lutidine without a thiol initiator and produced macrocyclic polymers. The cationic polymerizations took place with the aid of CF3SO3H and benzyl alcohol but involved side reactions with low chemoselective ring cleavage. The thioester unit caused the polymers to exhibit a lower Tg with greater thermal and photo degradability.

Catalytic hydrothermal conversion of polypropylene

This work reports preliminary-stage studies demonstrating the highly selective conversion of polypropylene to short-chained olefins via hydrothermal catalytic processing. The production of such monomer species from waste polymers is highly desirable and has the potential to play a key role in plastics recycling and in the circular economy more broadly. Addition polymers such as polypropylene are, however, known to be particularly challenging to recycle into propene or other short-chained alkenes. Herein, we have compared and contrasted acid- and base-catalysed hydrothermal processing at a temperature of 360 °C, analysing the products of reaction by gas chromatography – mass spectrometry (GC-MS) and Fourier transform infrared (FTIR) spectroscopy. Employing the basic catalyst K2CO3, results in a 95 % yield of gas-phase products of which 52 % are propene and 9 % butenes on a mole basis. The solid acid catalyst HZSM-5 also selectively yields gaseous products, 21 % of which are propene and 22 % are butenes, the reaction proceeding via β-scission of the starting oligomers. These results represent a potential step-change in the production of monomer units from addition polymers, highlighting the potential value of catalytic hydrothermal processing in the field of polymer recycling.

Exploring the dual dynamic synergy of transesterification and siloxane exchange in vitrimers

Despite the benefits of dynamic polymer networks with multiple dynamic bonds, identifying compatible combinations of dynamic chemistries that work synergistically to achieve desirable properties, remains a significant challenge. This work focuses on the potential of utilizing both siloxane and ester dynamic bonds in epoxy-acid cured vitrimers to finetune chemical exchange reactions. We identified to what extent a common basic catalyst (TBD) can simultaneously activate siloxane and ester exchange in the corresponding epoxy-based vitrimers. Our results showed that TBD is not only able to facilitate network formation but also improved the dynamic behavior of the resulting networks dramatically, with an overall exchange rate faster than the sum of the individual exchange chemistries, as shown by stress-relaxation studies. It has been demonstrated that the siloxane and ester dynamic bonds work together in a synergistic way to facilitate topology rearrangement. The relative increase or decrease in mobility of neighboring chains, located around a specific dynamic bond within the polymer network, was investigated in detail by adjusting the concentration of dynamic bonds and catalyst. The herein reported strategy allows the production of dual dynamic polymer networks that exhibit much shorter relaxation times and thus improved (re)processability in comparison to vitrimers with one type of dynamic bond.

Merging of Palladium and Organocatalysis Enabled Asymmetric Decarboxylative (2+1) Cycloadditions toward Cyclopropanes.

A cascade reaction enabling enantio- and diastereoselective construction of strained cyclopropanes is described. This asymmetric (2+1) annulation process uses vinyl methylene carbonate and 2-cyanoacrylate as reaction partners in the presence of Pd(PPh3)4 as a precatalyst and an enantioenriched phosphoramidite ligand featuring a morpholine functionality. Mechanistic investigations unveil that the PPh3 derived from the Pd(PPh3)4 and the morpholine-containing phosphoramidite work as cooperative phosphorus and Brønsted base catalysts to promote the reaction.

An improved microwave‐assisted facile one‐pot synthesis of novel pyrazolylphosphonates via Knoevenagel‐phospha‐Michael protocol

AbstractIn this study, a highly effective microwave‐assisted method employing a multicomponent domino Knoevenagel/phospha‐Michael reaction has been established. This approach facilitates the synthesis of a novel set of pyrazolylphosphonate derivatives in good yields by combining aryl aldehydes with pyrazolones and trialkylphosphites, utilizing piperidine as a Bronsted base catalyst. All pyrazolylphosphonates have been characterized by means of IR, 1H‐NMR, 13C‐NMR, and HRMS analyses and physical methods. This protocol can be characterized by its eco‐friendly nature, exceptional efficiency in terms of product yields, and short reaction times.

Investigation for flavanone synthesis in subcritical water with La-ZrO2, Mg-ZrO2, and Ca-ZrO2 as solid base catalysts

In this study, flavanone was synthesized via a two-step process, Claisen–Schmidt condensation between 2’-hydroxyactophenone and benzaldehyde followed by isomerization, in subcritical water with ZrO2 based catalysts. Kinetic analysis was conducted to quantitatively show the catalytic activity of different modified ZrO2. The activity of ZrO2 was improved upon incorporating with active metal species. Compared with La-ZrO2 and Mg-ZrO2, Ca-ZrO2 showed the highest activity attributed to strong basicity, but substantial formation of side product and loss of product were observed. La-ZrO2 showed weaker activity than Mg-ZrO2, though La-ZrO2 had higher basicity. One explanation was the dissociation of water to provide OH− on the catalyst surface was more challenging since containing significantly more active sites with strong water affinity. Moreover, such active sites contributed less to reaction due to dense water surrounding the catalyst surface. The reaction catalyzed by Mg-ZrO2 reached flavanone selectivity of 72.2 % in 3 hours at 150 °C.

Enantiospecific Analysis of Carboxylic Acids Using Cinchona Alkaloid Dimers as Chiral Solvating Agents.

Cinchona alkaloid derivatives as Brønsted base catalysts have attracted considerable attention in the field of asymmetric catalysis. However, their potential application as chiral solvating agents has not been described. In this research, we investigated the use of the Cinchona alkaloid dimer, namely, (DHQ)2PHAL, as a chiral solvating agent for discerning various mandelic acid derivatives through 1H NMR spectroscopy. The addition of catalytic amounts of DMAP facilitated this process. Our experimental results demonstrate that dimeric (DHQ)2PHAL exhibits remarkable chiral discrimination properties regarding the diagnostic split protons of 1H NMR signals (including 24 examples, up to 0.321 ppm). Furthermore, it serves as an excellent chiral discriminating agent and provides good resolution for racemic chiral phosphoric acid as determined by 31P NMR spectroscopy. The quality of enantiodifferentiation has also been evaluated by means of the parameter "resolution (Rs)". Significantly, this class of CSAs based on (alkaloid)2linker systems with an azaaromatic linker can be directly employed, which is commercially available in an enantiopure form at very low cost and exhibits promising potential in determining the enantiopurity of α-hydroxy acids by chemoselective and biocatalytic reactions.

Novel hybrid thiazoles, bis-thiazoles linked to azo-sulfamethoxazole: Synthesis, docking, and antimicrobial activity

The reaction of sulfamethoxazolehydrazonoyl chloride with thiosemicarbazones, bis-thiosemicarbazones, or 4-amino-3-mercapto-1,2,4-triazole in dioxane in the presence of triethylamine as a basic catalyst at reflux resulted in the regioselective synthesis of thiazoles and bis-thiazoles linked to azo-sulfamethoxazole as novel hybrid molecules. The structures of the new compounds were confirmed using a range of spectra. Each compound's antibacterial properties were evaluated using the agar well-diffusion technique, and most of them demonstrated significant potency. In silico investigations revealed that the described compounds had strong interactions with the binding sites of MurE ligase, tyrosyl-tRNA synthetase, and dihydropteroate synthase, demonstrating inhibitory activity.

Enhancing the crystallinity of covalent organic frameworks to achieve improved photocatalytic hydrogen peroxide production under ambient conditions

Photocatalytic production of hydrogen peroxide (H2O2) presents a promising strategy for environmental remediation and energy production. However, achieving clean and efficient H2O2 production under ambient conditions without organic sacrificial agents remains challenging. Enhancing the low crystallinity of covalent organic frameworks (COFs) can promote the separation and transmission of photo-generated carriers, thereby boosting their photocatalytic performance. Herein, we introduce a novel synthetic approach by substituting traditional acetic acid catalysts with organic base catalysts to enhance the crystallinity of β-ketoenamine-linked COF, TpBD-COF. Compared to TpBD-COF-A synthesized using acetic acid catalysts, TpBD-COF-B, synthesized with organic base catalysts, exhibited advancements including increased absorption intensity in the visible spectrum, reduced photoluminescence intensity, enhanced photo-generated carrier separation performance, and a 2.1-fold increase in photocatalytic H2O2 production. Under visible light irradiation, TpBD-COF-B achieved a photocatalytic H2O2 production rate of 533 µmol h−1 g−1 using only air and water, without the need for organic sacrificial agents. Furthermore, TpBD-COF-B also exhibited good performance in long-term catalytic production experiments, tests with actual water bodies, and cyclic usage experiments. This study offers a strategy for enhancing the crystallinity of COFs to improve their photocatalytic activity, with promising applications in clean energy production and environmental remediation.