Ethyl ester production by homogeneous alkaline transesterification: influence of the catalyst

In this work, the process for ethyl ester production is studied using refined sunflower oil, and NaOH, KOH, CH₃ONa, and CH₃OK, as catalysts. In all cases, the reaction is carried out in a single reaction step. The best conversion is obtained when the catalyst is either sodium methoxide or potassium methoxide. We found that during the transesterification with ethanol, soap formation is more important than in the case of methanol. The saponification reaction consumes an important fraction of the catalyst. The amount of catalyst consumed by this reaction is 100% in the case of using hydroxides as catalyst (KOH or NaOH), and 25%, and 28% when using CH₃ONa and CH₃OK as catalysts, respectively. Ethanol increases the catalyst solubility in the oil-ethyl ester phase, thus accelerating the saponification reaction.It is possible to obtain high conversions in a one-step reaction, with a total glycerine concentration close to 0.25%.     

Transesterification of soybean oil using combusted oyster shell waste as a catalyst

Transesterification of soybean oil catalyzed by combusted oyster shell, which is waste material from shellfish farms, was examined. Powdered oyster shell combusted at a temperature above 700 degrees C, at which point the calcium carbonate of oyster shell transformed to calcium oxide, acted as a catalyst in the transesterification of soybean oil. On the basis of factorial design, the reaction conditions of catalyst concentration and reaction time were optimized in terms of the fatty acid methyl ester concentration expressed as biodiesel purity. Under the optimized reaction conditions of a catalyst concentration and reaction time of 25wt.%. and 5h, respectively, the biodiesel yield, expressed relative to the amount of soybean oil poured into the reaction vial, was more than 70% with high biodiesel purity. These results indicate oyster shell waste combusted at high temperature can be reused in biodiesel production as a catalyst.     

Mass-transfer effects on the rate of isomerization of D-glucose into D-fructose, catalyzed by whole-cell immobilized glucose isomerase.

The investigated catalyst system consists of immobilized Arthrobacter cells containing the enzyme glucose isomerase, which catalyzes the isomerization of glucose into fructose. The internal structure of the catalyst was determined from electrom microscope photographs of replicas of freeze-etched catalyst. On the basis of the photographs a model for the internal structure of the catalyst was proposed. This structure was subsequently used to describe the reaction including mass-transfer effects. It appeared that under normal operating conditions the external mass-transfer rate does not influence the overall rate of reaction. The effect of internal mass-transfer resistances on the overall reaction rate can well be accounted for by the so-called porous sphere model. The intrinsic kinetics of the isomerization catalyzed by the present catalyst system can be represented by a modified Michaelis-Menten equation for a reversible one-substrate reaction.     

Catalytic Packed-Bed Reactor Configuration for Biodiesel Production Using Waste Oil as Feedstock

Pumice, a natural porous silica material, exchanged with potassium is an efficient heterogeneous particulate catalytic material for triglycerides and free fatty acids transesterification reaction from sunflower oil and waste frying oil at low temperature. In this work, a packed-bed catalytic configuration reactor using this catalytic material was developed for biodiesel fuel production from sunflower oil and frying oil feedstock. Reactor operation variables as methanol/oil molar ratio, catalyst amount, reaction time, and reaction temperature were studied. Results were compared with those obtained from the same transesterification reaction proceeding in a slurry batch reactor. The packed-bed catalytic reactor configuration can be useful in order to minimize catalyst mechanical damage occurring in the slurry reactor due to continuous stirring. The possibility of using a packed-bed reactor shows some advantages because the catalyst stays confined in the reactor bed and the reaction products can be easily separated, besides the mechanical stability of the catalyst particles is achieved.     

The dehydration of fermentative 2,3-butanediol into methyl ethyl ketone

A solid acid catalyst consisted of sulfonic groups covalently bound to an inorganic matrice was developed to dehydrate 2,3-butanediol into methyl ethyl ketone. Rate constant and apparent activation energy of the dehydration reaction were determined. The decay course of the catalyst was a two-stage curve. The catalyst was deactivated more rapidly in the first stage than in the second stage. The strategy of maintaining constant degree of dehydration was employed to lengthen the lifetime of catalyst. Treatment of the 2,3-butanediol containing fermentation broth with activated carbon greatly facilitated the subsequent dehydration reaction.     

Synthesis of methyl esters from palm (Elaeis guineensis) oil using cobalt doped MgO as solid oxide catalyst

The potential of Mg(x)Co(2-)(x)O(2) as heterogeneous reusable catalyst in transesterification of palm oil to methyl ester was investigated. The catalyst was prepared via co-precipitation of the metal hydroxides at different Mg-Co ratios. Mg(1.7)Co(0.3)O(2) catalyst was more active than Mg(0.3)Co(1.7)O(2) in the transesterification of palm oil with methanol. The catalysts calcined at temperature 300 °C for 4 h resulted in highly active oxides and the highest transesterification of 90% was achieved at methanol/oil molar ratio of 9:1, catalyst loading of 5.00 wt.%, reaction temperature of 150 °C and reaction time of 2 h. The catalyst could easily be removed from reaction mixture, but showed 50% decrease in activity when reused due to leaching of active sites.     

Labeling study of avidin by modular method for affinity labeling (MoAL)

We studied the specific labeling of avidin with biotinylated modular ligand catalysts via MoAL, which we recently established. The labeling yield was found to depend on the linker length connecting the catalytic site to biotin in the modular ligand catalyst 1, and the maximum yield was obtained with 1d possessing octamethylene linker. The labeling reaction reached a maximum rate with only 4 equiv of the ligand catalyst. Presumably, all the subunits of avidin with homotetrameric structure formed a stable complex with 4 equiv of the catalyst because of the extremely high affinity. The ligand catalyst bound to avidin first catalyzed N-triazinylation of the ε-amino group of Lys111, and the resulting regenerated catalyst then catalyzed the reaction of Asp108 and CDMT.     

Aldol reaction catalyzed by a hydrophilic catalyst in aqueous micelle as an enzyme mimic system

Chitosan-supported L-proline complex was synthesized and applied as a catalyst for the direct asymmetric aldol reaction in various organic solvents and water as well. It was found that the novel synthesized catalyst was able to efficiently catalyze the aldol reaction in various media. The catalytic capacity and stereoselectivity of the catalyst were obviously improved with the introduction of aqueous micelle, possibly because the micelle functioned as a hydrophobic pocket, like the hydrophobic portion in enzymes. Moreover, the present synthetic catalyst showed performance similar to that of enzymes and could be used as a model of enzyme catalysis to help better understand the mystic mechanism of enzymes.     

Photophosphorylation Associated with Photosystem II: IV. KINETIC ANALYSES OF PHOTOSYSTEM II CYCLIC PHOTOPHOSPHORYLATION ACTIVITY: EVIDENCE FOR TWO CYCLIC REACTIONS

Photosystem II-dependent cyclic photophosphorylation activity produced by addition of p-phenylenediamines to KCN-Hg-NH₂OH-inhibited chloroplasts is the product of two separate reactions when a proton/electron donor is the catalyst. The activity observed with an electron donor as catalyst consists of a single reaction. One of the cyclic reactions, evoked by low (≤40 micromolar) concentrations of a proton/electron donor is sensitive to dibromothymoquinone and to perturbation of membrane organization by sonication. The second reaction, requiring higher catalyst concentrations, is less sensitive to either dibromothymoquinone or membrane perturbation. These results indicate that at low concentrations, proton/electron or electron donor catalysts act to produce a photosystem II cyclic reaction which is dependent on membrane-bound electron carriers. High concentrations of proton/electron donors, on the other hand, can produce a phosphorylation reaction in which the catalyst itself is largely responsible for cyclic activity.     

Ion exchange resins as catalyst for the isomerization of alpha-pinene to camphene

Camphene is an industrial intermediate compound for commercial chemicals such as isoborneol, isobornyl acetate and camphor. Industrially, the conventional process for camphene production consists of the isomerization of alpha-pinene using acidic TiO2 as catalyst. The use of this catalyst presents problems such as considerable time for preparation, reproducibility and recovery of catalyst from products after the alpha-pinene isomerization. For the first time, a commercial exchange resin was used as catalyst for this reaction. Based on the concentration of product as a function of the reaction time, the path of the alpha-pinene transformation to camphene and byproducts is proposed. Temperature and alpha-pinene/catalyst ratio were studied in order to optimize the yield to camphene production. The obtained results were comparable with those reported for acidic TiO2.     

A facile Er(OTf)3-catalyzed synthesis of 2,3-unsaturated O- and S-glycosides

Er(OTf)(3) is a useful catalyst for the Ferrier rearrangement furnishing high yields of O- and S-glycosides. The transformation has wide applicability, cleaner reaction profiles, mild reaction conditions, and high stereoselectivity and the catalyst, which is also commercially available, can be recovered and reused.     

Anchoring of palladium(II) in chemically modified mesoporous silica: An efficient heterogeneous catalyst for Suzuki cross-coupling reaction

The synthesis and characterization of a highly efficient and reusable catalyst, Pd(II) immobilized in mesoporous silica MCM-41, are described. Pd(II) Schiff-base moiety has been anchored onto mesoporous silica surface via silicon alkoxide chemistry. The catalyst has been characterized by small-angle X-ray diffraction (SAX), FTIR and electronic spectroscopy as well as elemental analysis. The catalyst is used in Suzuki cross-coupling reaction of various aryl halides, including less reactive chlorobenzene, and phenylboronic acid to give biaryls in excellent yields without any additive or ligand. High selectivity for the bi-aryl products containing both electron-donating and electron-withdrawing substituents, mild reaction conditions and possibility of easy recycle makes the catalyst highly desirable to address the industrial needs and environmental concerns.     

Acetylation of glycerol to biofuel additives over sulfated activated carbon catalyst

Oxygenated fuel additives can be produced by acetylation of glycerol. A 91% glycerol conversion with a selectivity of 38%, 28% and 34% for mono-, di- and triacetyl glyceride, respectively, was achieved at 120 °C and 3 h of reaction time in the presence of a catalyst derived from activated carbon (AC) treated with sulfuric acid at 85 °C for 4h to introduce acidic functionalities to its surface. The unique catalytic activity of the catalyst, AC-SA5, was attributed to the presence of sulfur containing functional groups on the AC surface, which enhanced the surface interaction between the glycerol molecule and acyl group of the acetic acid. The catalyst was reused in up to four consecutive batch runs and no significant decline of its initial activity was observed. The conversion and selectivity variation during the acetylation is attributed to the reaction time, reaction temperature, catalyst loading and glycerol to acetic acid molar ratio.     

海滨锦葵油制备生物柴油工艺条件优化

以海滨锦葵油为原料制备生物柴油。通过单因素试验及正交试验研究了反应温度、催化剂用量、醇油摩尔比、反应时间、搅拌强度等因素对酯交换率的影响。结果表明,在试验范围内各影响因素对酯交换率作用的大小依次为：搅拌强度＞催化剂用量＞醇油摩尔比＞反应时间＞反应温度。海滨锦葵油制备生物柴油的最佳工艺参数为：搅拌强度为1800r.min-1,催化剂KOH用量为海滨锦葵油质量的1%,醇油摩尔比6/1,反应时间60min,反应温度65℃,在该工艺条件下,酯交换反应三次,酯交换率达到97.8%。     

Production of biodiesel and lactic acid from rapeseed oil using sodium silicate as catalyst

Biodiesel and lactic acid from rapeseed oil was produced using sodium silicate as catalyst. The transesterification in the presence of the catalyst proceeded with a maximum yield of 99.6% under optimized conditions [3% (w/w) sodium silicate, methanol/oil molar ratio 9/1, reaction time 60 min, reaction temperature 60 °C, and stirring rate 250 rpm]. After six consecutive transesterification reactions, the catalyst was collected and used for catalysis of the conversion of glycerol to lactic acid. A maximum yield of 80.5% was achieved when the reaction was carried out at a temperature of 300 °C for 90 min. Thus, sodium silicate is an effective catalyst for transesterification and lactic acid production from the biodiesel by-product, glycerol.     

Earthworm extract as a biocatalyst for asymmetric Mannich addition of cyclic ketimine 3-aryl-2H-1,4-benzoxazines

The asymmetric Mannich reaction of 3-substituted-2H-1,4-benzoxazines and acetone catalysed by a crude extract from earthworms is reported. The influence of solvents, water contents, catalyst loading, amounts of substrates and temperature on the reaction was investigated. Yields of up to 51% with enantioselectivities of up to 87% ee were achieved under the optimized conditions. This research promotes the development of earthworm extract as a catalyst in Mannich reaction.     

Natural catalyst for luminol chemiluminescence: application to validate peroxide levels in commercial hair dyes

Here, we report a hydrothermally treated green leaves (Moringa oleifera) extract exploited as an efficient and highly sensitive catalyst to catalyze the chemiluminescence (CL) reaction of luminol. In the absence of enhancer, this green and hydrothermally treated catalyst was found to significantly enhance the CL intensity ~3.5-fold compared with the traditionally used K₃Fe(CN)₆ catalyst. The structure and surface morphology of the catalyst was elucidated using X-ray photoelectron spectroscopy, scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. The synergistic effect of the catalyst in the CL reaction was systematically investigated in the presence of hydrogen peroxide using ultraviolet–visible and CL spectroscopy. Studies showed that the sensitivity of the catalyst could be amplified by adjusting several parameters such as pH of the medium and concentrations of the base and luminol. The sensitivity of the novel-type catalyst was examined through the validation of hydrogen peroxide levels in commercial hair dye samples. Markedly, the catalyst displayed ultrasensitivity to hydrogen peroxide as the limit of detection of hydrogen peroxide using this catalyst was determined to be 0.02 μM under optimized conditions. In general, the proposed inexpensive, ecofriendly, and nontoxic catalyst could enable the determination of hydrogen peroxide for diverse analytical applications.     

Transesterification of palm oil to methyl ester on activated carbon supported calcium oxide catalyst

In this study, methyl ester (ME) was produced by transesterification of palm oil (CPO) (cooking grade) using activated carbon supported calcium oxide as a solid base catalyst (CaO/AC). Response surface methodology (RSM) based on central composite design (CCD) was used to optimize the effect of reaction time, molar ratio of methanol to oil, reaction temperature and catalyst amount on the transesterification process. The optimum condition for CPO transesterification to methyl ester was obtained at 5.5 wt.% catalyst amount, 190 °C temperature, 15:1 methanol to oil molar ratio and 1 h 21 min reaction time. At the optimum condition, the ME content was 80.98%, which is well within the predicted value of the model. Catalyst regeneration studies indicate that the catalyst performance is sustained after two cycles.     

Cyclodextrin trimers as receptors for arranging ester and catalyst at optimized location to achieve enhancement of hydrolytic activity

Two novel trimer receptor molecules (AC and AD trimers) consisting of two alpha-cyclodextrins (alpha-CDs) and one beta-cyclodextrin (beta-CD) have been designed and synthesized in order to make an optimum arrangement between a substrate and a catalyst. In the reaction systems that use trimer receptors as host molecules, the substrate and the catalyst are thought to be accommodated by two alpha-CDs and one beta-CD, respectively. The rate for the hydrolytic reaction of a long-shaped ester was largely increased, when the trimer receptors were used as receptor molecules or molecular flasks, which provided optimum location between the substrate and the catalyst.     

5-(pyrrolidin-2-yl)-1H-tetrazole and 5-[(pyrrolidin-2-yl)methyl]-1H-tetrazole: proline surrogates with increased potential in asymmetric catalysis

Catalytic enantioselective methodology has dramatically been enriched by the re-discovery of the simple amino acid proline as a chiral catalyst in the year 2000. Although no catalyst offers such a simple and broad access to quite complex reaction products, as does proline, its synthetic potential is not unrestricted, what is especially connected to its poor solubility in organic media. Exchange of the carboxylic moiety by a tetrazole unit leads to proline surrogates, that by far outperform proline with respect to yield, enantioselectivity, reaction time, substrate and solvent scope, catalyst loading, and stoichiometry of the compounds used in excess. These factors are discussed and critically compared with selected representative proline-catalyzed reactions.