百里香酚的研究进展

本文介绍百里香酚的天然来源和合成方法.介绍了由间甲酚经过异丙基化、由薄荷醇脱氢和由α-蒎烯合成百里香酚等合成路线的研究现状,重点介绍了新型高转化率、高选择性的固体催化剂在合成中的应用.     

模板剂在分子筛合成中的作用

本文着重介绍了模板剂在分子筛合成中的应用,对采用模板剂合成的ZSM和SAPO系列分子筛的结构及模板剂对合成分子筛的影响作了重点介绍,并对国内外分子筛合成中常用的模板剂作了较为系统地介绍.     

1,3,5-三嗪类似物的合成路线研究概况

1,3,5-三嗪类似物在化学工业中应用相当广泛,它的应用范围主要包括橡胶工业、塑料工业、医药工业、纺织工业。同时还具有许多生物活性,可以用作杀虫剂、酶抑制剂。人们对三嗪衍生物的研究一直保持着浓厚的兴趣,介绍了1,3,5-三嗪类似物的两种合成路线,分别是对称合成方法与非对称合成法。其中对称合成法介绍了5种合成路线,非对称合成法介绍了4种合成路线。     

石墨制合成炉的现状和发展

介绍了多种形式的石墨制合成炉,重点介绍了组合式"二合一"HCl石墨合成炉,下点火式"三合一"石墨合成炉、下点火式"四合一"石墨合成炉。     

苯甲醛电合成技术的新进展

简述了苯甲醛电合成的发展概况,详细地介绍了间接电合成法、成对电合成法和超声电合成法3种苯甲醛合成技术,并着重介绍了Mn3+/Mn2+电解媒质作为氧化还原电对间接电合成苯甲醛的应用情况,指出超声电合成法将是合成苯甲醛很有前景的方法。     

二氧化碳化工开发的新工艺

本文介绍了以二氧化碳为原料,正在开发研究的新工艺路线:合成天然气、合成烃类、合成甲醇、合成羧酸及其衍生物、合成烷基胺类化合物、芳烃烷基化以及合成高分子化合物等。此外还介绍了用二氧化碳作为选择性萃取剂,用液体二氧化碳输送煤炭等。     

氟化石墨烯的制备与应用进展

简要介绍了氟化石墨烯的物化性质和合成背景。综述了氟化石墨烯的合成方法和反应机理,重点介绍了化学法合成氟化石墨烯的具体工艺,指出了当前氟化石墨烯合成工艺的难点和发展前景。     

松节油在农药增效剂及杀虫剂中的应用与进展

介绍松节油合成农药增效剂单萜烯基酰亚胺的一般合成机理和合成工艺。并对松节油在传统杀虫剂和非杀生性杀虫剂保幼激素类似物方面的研究进展进行了论述,同时还介绍国内外利用松节油合成的一些典型杀虫剂和新产品、及其一般的合成方法。     

维生素K的合成及其废液处理

介绍了维生素Ｋ的合成路线，重点介绍了合成中含铬废液的处理方法。     

端伯氨基氧化丙烯聚醚的合成与应用进展

介绍了一种端伯氨基聚醚的合成方法,对各种合成方法的特点作了简要的介绍,并且分析了两大类合成方法的优缺点。     

桥键烷基酚及其衍生物用于合成橡胶防老剂的研究进展

分析了2,6-二叔丁基-4-甲基苯酚(BHT)作为合成橡胶防老剂存在易迁移、易挥发、抗老化效率低等问题,阐述了BHT与桥键烷基酚类防老剂的作用机理,介绍了桥键烷基酚类防老剂的优势、合成方法,指出用桥键烷基酚及其衍生物取代BHT是合成橡胶防老剂发展的方向.     

A New Antioxidant Active Film Based on HDPE and Peppermint Essential Oil for Packaging Soybean Oil

In this research, the effect of antioxidant active package was studied on oxidative stability of soybean oil at 40 °C during 2‐month storage. A synthetic antioxidant [Butylatedhydroxytoluene (BHT), 200 ppm] and peppermint essential oil (200 and 400 ppm) were added to antioxidant free soybean oil. To prepare active packages, the oil was filled in antioxidant active high‐density polyethylene (HDPE) bottles containing synthetic antioxidant (3700 ppm) and the essential oil (3700 and 8400 ppm). Regarding peroxide and thiobarbituric acid values, the essential oil added to the oil delayed the oil oxidation more than BHT. In active packages, the synthetic and natural antioxidants migrated from the package to the oil (with 68 and 100 % migration rate, respectively) and retarded its oxidation over the storage time. However, no significant difference was observed between essential oil and BHT in antioxidant capacity for active packages. This study demonstrated that active packages containing antioxidants could be introduced as a good replacement for direct addition of synthetic antioxidants to the oil.     

Canola extract as an alternative natural antioxidant for canola oil

The antioxidative activity of ethanolic extracts of canola meal at 100, 200, 500 and 1000 ppm on refined-bleached (RB) canola oil was examined and compared with commonly used synthetic antioxidants, such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), BHA/BHT/monoglyceride citrate (MGC) andtert-butyl-hydroquinone (TBHQ). Stability of RB oil was monitored under Schaal oven test conditions at 65°C over a 17-d period. Progression of oxidation was monitored by weight gain, peroxide, conjugated diene, 2-thiobarbituric acid and total oxidation values. Canola extracts at 500 and 1000 ppm were more active than BHA, BHT and BHA/BHT/MGC and less effective than TBHQ at a level of 200 ppm.     

复合型受阻酚抗氧剂的制备及清除DPPH·活性研究

以二苯基氯化磷和2,2′亚甲基双(4甲基6叔丁基苯酚)为原料,合成具有亚磷酸酯及受阻酚结构的复合型抗氧剂2(2羟基3叔丁基5甲基苄基)4甲基6叔丁基苯基二苯基亚磷酸酯,产率为65.12 %,产物经FT-IR表征,符合理论设计构型。将产物与商用抗氧剂2,6二叔丁基4甲基苯酚(BHT)进行热稳定性及DPPH自由基清除能力的对比测试,结果表明,产物较抗氧剂BHT分子量更高,热稳定性更好;同时其对DPPH自由基具有良好的清除效果,其抗氧化能力强于抗氧剂BHT。     

Protection of biodiesel against oxidation

The importance of using synthetic antioxidants to improve oxidation stability and shelf life of biodiesel is today generally accepted. In our investigations which started early with the development of biodiesel we have looked at the course of stability, ageing of biodiesel, and the use of synthetic antioxidants. We have shown for the first time that oxidative stability of biodiesel is lower than that of the rape seed oil from which it was produced. The natural stability of biodiesel relates mainly to the content of tocopherols which survive the transesterification process. Biodiesel freed from tocopherols has no stability and will be destroyed immediately in air. Synthetic antioxidants like BHT and the newly developed stronger “Bis‐BHT” dramatically improve oxidative stability and prolong shelf life. Biodiesel rich in polyunsaturated fatty acid methyl ester needs strong antioxidants to be sufficiently protected. The class of hindered phenolic antioxidants from which the BHT and “Bis‐BHT” derive are well suited as industrial biodiesel stabilizer because of their ready availability, sufficient effectiveness and proven safety in diesel fuel. Surprisingly, none of the approved international biodiesel and biodiesel blend specifications refer to shelf life as a quality parameter. There is no definition of shelf life available, although it is well understood that biodiesel ages and loses its oxidative stability over time. We propose to consider the time span from production until the biodiesel reaches zero oxidative stability and becomes rancid and detrimental for the engine as the “shelf life” of biodiesel. From the perspective of a customer running their car on biodiesel blends, shelf life should become a more important issue.     

Antioxidant Activity of Oat Malt Extracts in Accelerated Corn Oil Oxidation

Oat cultivar AC Vermont was malted to concentrate antioxidants, milled to fractionate only the endosperm portion and extracted with methanol to isolate the crude antioxidants. The oat malt antioxidant fraction was assessed as a natural antioxidant based upon enhancing the stability of corn oil against oxidation and compared to the synthetic antioxidant butylated hydroxytoluene (BHT). The induction time (time required for the formation of 10 meq hydroperoxide per kilogram corn oil thermally oxidized) was used to measure antioxidant activity of oat antioxidant or BHT. The protection factor achieved by crude oat malt antioxidant extract concentrate at 0.26% (2,600 μg/g) was comparable to BHT (75 μg/g). The antioxidant activity of the oat and barley malt extract concentrates was not significantly different. However, the extract concentrate of oat malt had 44% less color compared to that of barley malt at equal concentrations showing its potential as a natural food antioxidant.     

Antioxidant Activity of Osage Orange Extract in Soybean Oil and Fish Oil during Storage

The food industry is seeking natural antioxidants for edible oils that have comparable activity to synthetic counterparts. In this study, Osage orange extract (OOE) rich in osajin (42.9%) and pomiferin (30.0%) was obtained after hexane extraction of the fruit, and its antioxidant activity was examined in stripped soybean oil (SBO) and fish oil (FO), in which antioxidants and polar compounds were removed. The antioxidant activity of OOE was compared with commercial natural antioxidants (i.e., rosemary extract and mixed tocopherols) and a synthetic antioxidant, butylated hydroxytoluene (BHT), during storage at 25 and 40 °C. The 0.1% OOE had stronger antioxidant activity than 0.1% rosemary extract and 0.1% mixed tocopherols in both oils at 25 and 40 °C. Its activity was similar to 0.02% BHT in SBO and was similar or slightly stronger than 0.02% BHT in FO. When OOE was studied at 0.05, 0.1, and 0.2%, there was a weak dose–response in SBO but a stronger dose–response in FO. Headspace volatile analysis using solid phase micro-extraction (SPME) combined with GC–MS indicated that 0.1% OOE was very effective in preventing the formation of volatile oxidation products in both oils. Although it should be further tested for safety before the actual use, this study shows that OOE can be developed as an antioxidant for edible oils.     

Effectiveness of antioxidants on lipid oxidation and lipid hydrolysis of cod liver oil

The capacity of the natural antioxidant from barley husks to retard oxidation of PUFA in cod liver oil (Gadus morhua) was investigated and compared to synthetic antioxidants. The results confirm the efficacy of a natural antioxidant derived from barley husks to slow down the progress of lipid hydrolysis and increase oxidative stability in cod liver oil. The rates of lipid hydrolysis and lipid oxidation were slowed down with increasing concentration of natural antioxidant used. Using 100 mg of the natural antioxidant was more effective than some synthetic antioxidants (BHA 200 mg and BHT 200 mg) against primary and secondary oxidation. The use of propyl gallate (PG) as an antioxidant (200 mg/kg in cod liver oil) was the most effective antioxidant employed in reducing the production of primary and delaying secondary oxidation products. The formation of free fatty acids (FFA) was significantly lower in samples with natural antioxidant (BE200 and BE100) than in the control samples. BHA and BHT were the most effective antioxidants employed to delay the lipid hydrolysis. Practical applications: The use of barley husks, which are residues of the brewing process, was optimized to obtain a crude antioxidant extract. Natural extracts of phenolic compounds with high antioxidant activity were obtained after prehydrolysis and delignification of barley husks. The raw extracts show more than two‐fold antioxidant capacity compared to BHT in terms of EC50. The results demonstrate the efficacy of a natural antioxidant derived from barley husks. The extract could be used in fatty foods (such as butter, oil, etc.) to prevent rancidity.     

Study of the biodiesel B100 oxidative stability in mixture with antioxidants

Antioxidants are an alternative to prevent or retard biofuel degradation. This study assessed the oxidative stability of biodiesel B100, made from soybeans, in the presence of three synthetic antioxidants, butylhydroxyanisole (BHA), terbutylhydroquinone (TBHQ) and butylhydroxytoluene (BHT), pure or in mixture, from the simplex-centroid design. Results revealed that when the three oxidants were employed separately, as well as the ternary mixture, they presented induction period over 6 h, at 110 °C, being in accordance with specifications of the norm EN1412. Besides that, depending on the temperature, the BHA, TBHQ and BHT oxidants act in different ways, highlighting that BHA and TBHQ presented higher efficiency in the prevention of the oxidative process of the biofuel B100.     

The influence of antioxidants on the oxidation stability of biodiesel

Oxidation stability of bodiesel is an important issue because FA derivatives are more sensitive to oxidative degradation than mineral fuel. Therefore, in the most recent European Specifications for biodiesel, a minimum value of 6 h for the induction period at 110°C, measured with a Rancimat instrument, is specified. To guarantee this value at the filling station, the use of additional antioxidants will be necessary. In this paper we show the influence of different synthetic and natural antioxidants on the oxidation stability, using the specified test method. Biodiesel produced from rapeseed oil, sunflower oil, used frying oil, and beef tallow, both undistilled and distilled, was investigated. The four synthetic antioxidants pyrogallol (PY), propylgallate (PG), TBHQ, and BHA produced the greatest enhancement of the induction period. These four compounds and the widely used BHT were selected for further studies at concentrations from 100 to 1000 mg/kg. The induction periods of methyl esters from rapeseed, oil, used frying oil, and tallow could be improved significantly with PY, PG, and TBHQ, whereas BHT was not very effective. A good correlation was found between the improvement of the oxidation stability and the FA composition.