Sustainable Oxidative Cleavage of Vegetable Oils into Diacids by Organo-Modified Molybdenum Oxide Heterogeneous Catalysts

Exploiting vegetable oils to produce industrially valuable diacids via an eco‐friendly process requires an efficient and recyclable catalyst. In this work, a novel catalytic system based on organo‐modified molybdenum trioxide was synthesized by a green hydrothermal method in one simple step, using Mo powder as precursor, hydrogen peroxide, and amphiphilic surfactants cetyltrimethylammonium bromide (CTAB) and tetramethylammonium bromide (TMAB) as capping agents. The synthesized materials were first characterized by different techniques including XRD, SEM, TGA, and FT‐IR. Interestingly, various morphologies were obtained depending on the nature of the surfactants and synthetic conditions. The synthesized catalysts were employed in oxidative cleavage of oleic acid, the most abundant unsaturated fatty acid, to produce azelaic and pelargonic acids with a benign oxidant, H₂O₂. Excellent catalytic activities resulting in full conversion of initial oleic acid were obtained, particularly for CTAB‐capped molybdenum oxide (CTAB/Mo molar ratio of 1:3) that gave 83 and 68% yields of production of azelaic and pelargonic acids, respectively. These are the highest yields that have been obtained for this reaction by heterogeneous catalysts up to now. Moreover, the CTAB‐capped catalyst could be conveniently separated from the reaction mixture by simple centrifugation and reused without significant loss of activity up to at least four cycles.     

Enzyme‐catalyzed copolymerization of oxiranes with dicarboxylic acid anhydrides

Ring‐opening copolymerizations of the oxiranes glycidyl phenyl ether (GPE) and diglycidyl ether of bisphenol A (DGEBA) with a dicarboxylic acid anhydride [methyl hexahydrophthalic anhydride, nadic anhydride, maleic anhydride (MA), or itaconic anhydride (IA)] were carried out with the lipases Candida cylindracea (CCL), Lipozyme TL‐IM (LIM), and Novozyme 435 (N435) as catalysts. The CCL‐catalyzed reaction of DGEBA with MA or IA (at a 1:2 molar ratio) at 80°C resulted in only partial curing. We monitored the reactions by Fourier transform infrared spectroscopy and by following the changes in the intensities of carbonyl stretching frequencies of the anhydride and ester groups. The reactivity of the oxirane group in GPE was higher than that in DGEBA; this may have been due to the higher viscosity of DGEBA. The reactivities of the enzymes for the copolymerization of the oxiranes and dicarboxylic acid anhydride were in the order LIM > CCL > N435. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 697–704, 2005     

Reaction mechanisms and kinetics of xylo‐oligosaccharide hydrolysis by dicarboxylic acids

Hydrothermal pretreatment of lignocellulosic materials generates a liquid stream rich in pentose sugar oligomers. Cost‐effective hydrolysis and utilization of these soluble sugar oligomers is an integral process of biofuel production. We report integrated rate equations for hydrolysis of xylo‐oligomers derived from pretreated hardwood by dicarboxylic maleic and oxalic acids. The highest xylose yield observed with dicarboxylic acids was 96%, and compared to sulfuric acid, was 5–15% higher with less xylose degradation. Dicarboxylic acids showed an inverse correlation between xylose degradation rates and acid loadings unlike sulfuric acid for which less acid results in less xylose degradation to aldehydes and humic substances. A combination of high acid and low‐temperature leads to xylose yield improvement. Hydrolysis time course data at three different acid concentrations and three temperatures between 140 and 180°C were used to develop a reaction model for the hydrolysis of xylo‐oligosaccharides to xylose by dicarboxylic acids. © 2012 American Institute of Chemical Engineers AIChE J, 59: 188–199, 2013     

Enzyme‐catalyzed regioselective synthesis of sucrose‐based esters

Sucrose‐based esters are nonionic biosurfactants, which can be synthesized from the enzyme‐catalyzed esterification/transesterification of sucrose. The multi‐hydroxyl groups of sucrose and the immiscibility of sucrose with the acyl donors are the main bottlenecks in obtaining highly regioselective sucrose‐based esters. In this mini‐review, the effects of reaction conditions such as biocatalysts, design of solvent systems used as reaction media, modification and denaturation of substrates, and coupling with external auxiliary physical fields such as microwave irradiation and ultrasonic waves on the yield of sucrose esters and regioselectivity of products are highlighted. The existing problems in the field of enzymatic synthesis of sucrose esters as well as its future perspectives were pointed out. Copyright © 2011 Society of Chemical Industry     

The formation of hydroxy monocarboxylic acids and dicarboxylic acids by alkaline thermochemical degradation of cellulose

Treatment of cotton cellulose with 3 M sodium hydroxide solution at 260°C and 280°C gave a mixture of carboxylic acids with a yield of > 95%. The identified 50 carboxylic acids included both hydroxy monocarboxylic acids and dicarboxylic acids; their routes of formation are discussed. Among the main compounds were lactic, glycolic, 2-hydroxy-2-methylpropanoic, 2-hydroxybutanoic, 3,4-dideoxypentonic, anhydroisosaccharinic, 2,3-dideoxypentaric, and 3,4-dideoxyhexaric acids. Technical utilisation of this kind of acid mixture requires further studies. Investigations of the cyclic compounds, formed in small amounts only, resulted in identification of mainly alkyl-substituted 2-cyclopenten-1-ones.     

Lipase‐catalyzed synthesis of quinate and glucuronate fatty esters

The lipase‐catalyzed synthesis of fatty alcohol esters of quinic and glucuronic acid was investigated. The results showed that although a direct esterification process was possible, a strategy involving short‐chain alkyl ester intermediates was advantageous. 2‐Methyl‐2‐butanol was chosen as solvent and parameters such as substrate ratios and concentrations were optimized. Octyl, decyl and hexadecyl esters of quinic and glucuronic acids could be obtained with this process. However, reaction rates were rather slow and it could be shown that the completely chemically catalyzed synthesis of the same products using ion exchange resins was advantageous.     

Biotechnological synthesis of long‐chain dicarboxylic acids as building blocks for polymers

An important field in sustainable industrial chemistry is the development of new applications for fats and oils. One of the promising applications is the use of fatty acid derivatives, e.g. dicarboxylic acid (DCA), as polymer building blocks. In contrast to conventional plastics, bioplastics are polymers derived from renewable biomass sources. In addition to their contribution to the conservation of fossil resources and reduction in CO₂ emissions by waste incineration, many bioplastics are biodegradable. The majority of industrial DCA production for polyamide (PA) and polyester (PE) synthesis is still done via chemical synthesis. While short‐chain DCA can be synthesized in high yields, costs of long‐chain DCA production rise significantly due to the generation of various by‐products and are connected mostly to a costly purification. Thus biotechnology provides novel biochemical approaches for long‐chain DCA synthesis that can provide an eco‐efficient process alternative. In the present article, strategies for the development of high‐level production strains for long‐chain DCA are illustrated. Basic strategies for strain development, in order to achieve an effective enrichment of DCA, require the knowledge of the respective biochemical pathways. These are discussed in detail. Furthermore an overview of fermentation strategies and characteristics of corresponding polymers is given.     

相转移催化法合成取代苯甲酸乳糖酯

采用相转移催化法合成了7个取代苯甲酸乳糖酯,通过IR、^1HNMR、元素分析确证了糖酯的结构,通过对糖酯化合物的^1HNMR图谱中糖环碳1位质子的化学位移及偶合常数,并结合红外图谱中糖环C-H的弯曲振动吸收,确证糖酯化合物均为β型异构体。     

催化合成脂肪族二元酸烷氧基酯的反应动力学研究

脂肪族二元酸烷氧基酯是一类性能优良的耐寒性增塑剂产品。以二元羧酸及乙二醇丁醚为原料,在硫酸催化下合成烷氧基酯,测定了表观速率常数,并建立了反应体系的酯化反应动力学模型。实验结果表明,在453.15～473.15K,合成脂肪族二元酸烷氧基酯的宏观动力学符合三级不可逆反应特征,以C5至C8的二元羧酸为原料的酯化过程其反应表观活化能在220～250kJ/mol内。     

Gold‐Catalyzed Benzylation of Arenes and Heteroarenes

Friedel–Crafts type benzylation of arenes and heteroarenes with benzylic acetates, alcohols, and carbonates is effectively promoted under mild reaction conditions using catalytic amounts of gold salts. The resulting 1,1‐diarylalkanes and 1‐aryl‐1‐heteroarylalkanes are obtained in high yields and with high selectivity. The utility of the method is demonstrated by a short synthesis of beclobrate {ethyl 2‐[4‐(4‐chlorobenzyl)‐phenoxy]‐2‐methylbutyrate ( 3 )}, a fibric acid derivative.     

Double Gold‐Catalysed Annulation of Indoles by Enynones

The gold‐catalysed double functionalisation of indoles is presented. Enynones are used to annulate indoles via a double sodium tetrachloroaurate‐catalysed process involving a mixture of C H activation and alkyne activation modes of promotion. Good yields for the formation of medicinally relevant [6,5,7]‐tricyclic indoles are realised.     

Oxidation of 5-hydroxymethylfurfural over supported Pt, Pd and Au catalysts

Supported Pt, Pd, and Au catalysts were evaluated in the aqueous-phase oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) at 295 K and high pH in a semibatch reactor. The intermediate reaction product 5-hydroxymethyl-2-furancarboxylic acid (HFCA) was formed in high yield over Au/C and Au/TiO₂ at 690 kPa O₂, 0.15 M HMF and 0.3 M NaOH, but did not continue to react substantially to FDCA at the specified O₂ pressure and base concentration. In contrast, the final reaction product FDCA was formed over Pt/C and Pd/C under identical conditions. The initial turnover frequency of HMF conversion was an order of magnitude greater on Au catalysts compared to either Pt or Pd. Increasing the O₂ pressure and NaOH concentration facilitated the conversion of HFCA to FDCA over the supported Au. The significant influence of base concentration on the product distribution indicates an important role of OH⁻ in the activation, oxidation and degradation of HMF.     

A new method of synthesis of alkyl-glycidyl esters of dicarboxylic acids in high yields

A series of new alkyl-glycidyl esters of dicarboxylic acids which could be used as PVC plasticizers were synthesized. The method adopted is a new synthetic process which can be carried out in two stages. During the first stage, the carboxylic acid anhydride reacts with the salt of the alcohol, and the sodium salt produced reacts with epichlorhydrin in the presence of a catalyst to yield an alkyl-glycidyl ester. The specific reactions give pure products in high yields. The reaction of phthalic acid bisodium salt with epichlorhydrin, as well as the reaction of phthaloyl chloride with glycidol, gave diglycidyl phthalate in 36% and 22% yields, respectively.     

Heterogeneous base catalyzed synthesis of 2-oxazolidinones/2-imidiazolidinones via transesterification of ethylene carbonate with β-aminoalcohols/1,2-diamines

Several heterogeneous basic metal oxide catalysts were screened for the synthesis of 2-oxazolidinones and 2-imidiazolidinones via transesterification of ethylene carbonate with different β-aminoalcohols or 1,2-diamines. Among the several catalysts screened, MgO was found to be the best catalyst, as it has excellent recyclability. Various reaction parameters were studied in detail. Excellent yields of the products were obtained using MgO as catalysts at 80 °C within 6 h in ethanol. Basic properties of the metal oxide catalysts were compared using temperature programmed desorption (TPD) studies with CO₂. The relationship between the catalyst performance and the basic property of each catalyst has been discussed.     

壬二酸联合氧化法的合成与反应机理初探

对以过氧化氢和臭氧联合为氧化剂,油酸为原料制备壬二酸的工艺进行了研究,考察了不同的过氧化氢的质量分数、通入臭氧的流速以及不同种类钨化合物与季铵盐组成的相转移催化体系催化氧化油酸的反应活性,实验结果表明:以20 g油酸为原料,加入0.6 g磷钨酸,0.7 g CTAB,滴加ω(H2O2)=30%60 mL,温度70℃,通入臭氧8 h,壬二酸的收率为71%.初步研究了臭氧-过氧化氢联合氧化法制备壬二酸的反应杌理,发现·0H是一个重要的反应物.     

固体酸催化合成丁二酸二乙酯研究进展

固体酸能够代替硫酸作为酯化催化剂。评述了对甲苯磺酸、强酸性阳离子交换树脂、六水合三氯化铁、氯化亚锡、四水硫酸铈、一水硫酸氢钠、固体超强酸和杂多酸等固体酸催化合成丁二酸二乙酯的方法。认为强酸性阳离子交换树脂、一水硫酸氢钠、固载固体酸、固体超强酸和杂多酸是合成丁二酸二乙酯的良好催化剂。     

Comparative Study of Ship-in-a-Bottle and Anchored Heterogenized Mn Complexes

Metal schiff base catalyst can be immobilized with the heteropoly acid as the anchor or by flexible ligand route. The immobilized Mn schiff base catalysts overY molecular sieves prepared by these two methods were characterized by IR, DTA-TGA thermal analysis and XPS. The catalysts were used in the oxidation of cyclohexene under ambient conditions using molecular dioxygen as oxidant and isobutyraldehyde as sacrificial reagent. For the oxidation of cyclohexene the heterogenized catalysts showed the advantages of easy handling and recycling and the immobilized catalyst with the heteropoly acid as the anchoring agent showed higher turnover number than that prepared by the flexible ligand route. Morever, the anchored catalyst was still active after reused for six times, attributed to the lower leaching speed of Mn complex from the heterogenized catalyst.     

Gold‐Catalyzed Synthesis of 1‐Naphthylcarbenoids and Their Synthetic Utilization in Cyclopropanation Reactions

1‐Naphthylcarbenoids are generated via 1,2‐acyl migration and subsequent carbene shift from simple, easily available diyne starting materials. These highly reactive species were allowed to react with differently substituted alkenes in both intermolecular and intramolecular fashions. In the intermolecular cases even a simple 1:1 ratio of the starting materials delivered the corresponding cyclopropylnaphthalenes in high yields by the use of a gold(III) catalyst. The methodology offers a completely new approach to these valuable targets, the new route represents an efficient alternative to common methods that are based on cross‐coupling strategies.

     

Electrochemical study of 1,2-dihydropyridazine-3,6-dione in protic and aprotic solvents: Oxidative ring cleavage and reduction

The electrochemical behavior of 1,2-dihydropyridazine-3,6-dione (3,6-dihydroxypyridazine) on glassy carbon electrode in aqueous and some organic solvents was investigated. The results indicate that the electrochemically generated pyridazine-3,6-dione is unstable and via oxidative ring cleavage converts to maleic acid. Also, the results show that the rate of oxidative ring cleavage depends on electrolysis media. In addition, the observed homogeneous rate constant of oxidative ring cleavage of 1,2-dihydropyridazine-3,6-dione was estimated by comparing the experimental cyclic voltammetric responses with the digital simulated results in aprotic solvents. Furthermore, some kinetic parameters related to irreversible cathodic electron transfer process of 1,2-dihydropyridazine-3,6-dione was estimated in aqueous solutions.