有机钛-硅催化剂合成聚酯的动力学研究

为开发稳定且具有较高活性的钛系催化剂,用制备得到的系列新型钛硅（Ti-Si）复合催化剂催化合成聚对苯二甲酸乙二醇酯,研究了聚合反应动力学及催化剂的用量、缩聚温度对聚合反应和聚酯切片性能的影响,将其与传统锑系催化剂三氧化二锑（Sb2O3 ）、钛系催化剂Ti（X）进行对比。结果表明：在研究范围内,Ti-Si 催化剂的最佳用量为19 μg/g,缩聚温度为281 ℃;Ti-Si 催化剂对酯化和缩聚反应均有催化作用,可降低酯化反应的活化能,活化能仅为42.49/mol,提高了酯化反应速度;Ti-Si 催化剂具有较高的催化活性,其缩聚时间比Sb2O3、Ti(X) 均缩短约40 min,缩聚活化能也低于Sb2O3 ,且与 Ti(X) 相近;采用Ti-Si 催化剂制得的聚酯切片在热性能、力学性能方面均与Ti(X)相似,但优于Sb2O3合成的;在色度上,Ti-Si 催化剂合成的聚酯的亮度优于Sb2O3的,b 值与Ti(X)的相似。     

新型稀土固体超强酸S2O82-/Sb2O3/La3+催化合成乙酸辛酯

采用金属醇盐水解法制备稀土固体超强酸S2O2-8/Sb2O3/La<3 >催化剂.以稀土固体超强酸S2O2-8/Sb2O3/La<3 >为催化剂,以冰乙酸和正辛醇为原料,在微波辐射下合成乙酸辛酯.考察催化剂制备条件及合成条件对酯化率的影响,结果表明,催化剂最佳制备条件:用1.5 mol/L的(NH4)2S2O8和2.71%La(NO3)3混合溶液浸渍前体氧化物Sb2O3,经110℃烘干,于500℃焙烧3 h;最佳合成条件:n(正辛醇):n(冰乙酸)=1.2:1、催化剂用量为0.6 g、辐射时间为20 min、微波功率为528 W,酯化率达82.3%.用IR对产品进行确证.     

CaO/(Mg-Fe-O)固体碱的制备及其酯交换催化活性研究

采用共沉淀、浸渍及高温焙烧的方法制备了Ca O/(Mg-Fe-O)固体碱催化剂,以蓖麻油转化率为催化剂活性评价指标,采用正交实验考察了制备条件对催化剂酯交换催化活性的影响。得到的优化条件为:Mg/Fe摩尔比3∶1,Ca(Ac)2浸渍液质量分数15%,浸渍时间12 h,焙烧温度800℃,焙烧时间2 h。以优化条件下制备的Ca O/(Mg-Fe-O)固体碱为催化剂,用于蓖麻油和甲醇酯交换反应,蓖麻油转化率可达94.74%。采用TG-DTA、FTIR、BET及XRD技术对催化剂及其前驱体进行了表征。结果表明:当温度超过750℃时,Ca(Ac)2/(Mg-Fe水滑石)几乎不再失重;Ca O/(Mg-Fe-O)固体碱和Ca(Ac)2/(Mg-Fe水滑石)相比,其—OH和CO2-3的红外吸收峰显著下降;负载于Ca O/(Mg-Fe-O)固体碱催化剂介孔中的Ca O起主要催化作用;Ca O/(Mg-Fe-O)固体碱中的Ca O以无定形或微晶的形式高度分散于Mg Fe2O4及Mg O表面。     

CaO/Co-Al-O固体碱的制备、表征及其油脂醇解活性

采用共沉淀、浸渍及高温焙烧的方法制备了Ca O/Co-Al-O固体碱催化剂。采用正交实验考察了制备条件对Ca O/Co-Al-O固体碱油脂醇解活性的影响,得到固体碱催化剂的优化制备条件为:Co与Al摩尔比3∶1、顺加法、Ca(Ac)2浸渍液质量分数0.25、焙烧温度700℃、焙烧时间6 h。以优化条件下制备的Ca O/Co-Al-O固体碱为催化剂,在甲醇与蓖麻油摩尔比9∶1、催化剂与蓖麻油质量比0.04∶1、搅拌速率400 r/min、反应温度65℃、反应时间3 h的条件下,蓖麻油转化率为94.74%。采用TG-DTA、FT-IR、BET及XRD技术对固体碱催化剂及其前驱体进行了表征。结果显示:固体碱催化剂前驱体Ca(Ac)2/Co-Al水滑石TG曲线有3个失重台阶,分别出现在100~200℃、200~300℃及680~730℃;Ca O/Co-Al-O固体碱催化剂的BET比表面积为42.7 m2/g,BJH脱附累积孔容为0.29 cm3/g,BJH脱附平均孔半径为11.4 nm;Ca O/Co-Al-O固体碱中的活性组分Ca O以无定形或微晶的形式高度分散于Co Al2O4及Co3O4表面。     

国内PET缩聚催化剂醋酸锑的研制现状

本文根据所掌握的资料,对国内外醋酸锑的制备方法及几家主要生产厂的醋酸锑质量予以综述对比,并根据已作的部分实验,主要就美国M＆T化学公司生产的醋酸锑与国内几家已生产和试制的醋酸锑在聚酯缩聚反应中的催化效应进行比较,通过对各研制单位以不同方法制备的、质量规格不尽相同的Sb(OAc)_3,在相同条件下催化缩聚反应后制得的产品PET质量规格的测试结果分析,客观地对国产催化剂醋酸锑的质量提出一些粗浅的看法,以期促进聚酯缩聚催化剂Sb(OAc)_3的生产和应用国产化。     

羟基锡酸锌/Sb_2O_3对聚氯乙稀复合建筑膜材的协同阻燃性能

为提高聚氯乙烯(PVC)复合膜材的阻燃性能并降低Sb2O3的使用量,制备了羟基锡酸锌(ZHS);利用X射线粉末衍射仪、傅里叶红外光谱仪和场发射扫描电镜对制备的样品进行了测试。结果显示,制备的样品为边长1μm左右的立方体ZHS。将ZHS等助剂添加到PVC糊料中制备了具有阻燃作用的膜材涂层材料,通过测试极限氧指数、热重分析及扫描电镜对炭渣形貌分析等方法,探讨了PVC复合涂层材料的阻燃作用。结果表明:添加ZHS的PVC材料的残炭量高于添加Sb2O3的PVC材料且炭渣表面更致密;而添加ZHS/Sb2O3的PVC材料的极限氧指数(LOI值)高于二者单独使用,即ZHS和Sb2O3对PVC涂料存在协同阻燃效应,从而降低Sb2O3在阻燃PVC涂层材料中的使用量。     

PBT／PET共聚酯的结构表征和热转变

本文用红外光谱(IR),~1H,~(13)C核磁共振谱(NMR),动态力学谱(DMM),热分析(DSC),热重分析(TGA)方法鉴定了用混合缩聚法制得的PBT/PET共聚酯的化学结构和热转变温度。结果表明:PBT/PET共聚酯是无规共聚物。共聚酯的熔点(T_m)和用力学方法测得的玻璃化温度(T_9)随其化学组成的变化呈“V”字形。共聚酯的热稳定性与缩聚催化剂Sb的关系不大。     

氧气-离子液体预处理对麦草酶解效率的影响

以麦草为原料,探讨了氧气(O2)-离子液体(1-乙基-3-甲基咪唑醋酸盐,[Emim]Ac)预处理工艺条件,以期提高麦草的酶解效率。结果显示,较适宜的O2-[Emim]Ac预处理条件为:固液比1∶1.5,氧压0.4 MPa,温度130℃,处理时间6 h。在此条件下,经过O2-[Emim]Ac预处理的麦草酶解(酶解条件为:纤维素酶用量30 U/g原料,酶解时间72 h)还原糖得率为65.1%,高于未经预处理麦草酶解还原糖得率5倍以上。扫描电镜、X射线衍射和红外光谱分析表明,O2-[Emim]Ac预处理后麦草纤维表面粗糙,孔隙增加,结构疏松,结晶度降低12.6%。     

分光光度法测定催化剂浆料中的Sb2O3含量

本方法利用KI-抗坏血酸溶液为显色剂,在440nm的波长下,用分光光度计来测定催化剂浆料中Sb2O3的含量,能够得到准确、稳定的结果.     

介孔K2CO3/SBA-15固体碱催化大豆油制备生物柴油性能研究

采用浸渍法制备了固体碱K2CO3/SBA-15催化剂,通过单因素试验考察了焙烧温度、焙烧时间、K2CO3负载量、催化剂用量和反应时间对利用大豆油制备生物柴油产率的影响.通过X射线衍射(XRD)、扫描电镜(SEM)和透射电镜(TEM)等方法对催化剂进行了表征.结果表明:催化剂通过焙烧产生了新的活性中心K2O;K2CO3/...     

Solubility and toxicity of antimony trioxide (Sb2O3) in soil

Antimony trioxide (Sb2O3) is a widely used chemical that can be emitted to soil. The fate and toxicity of this poorly soluble compound in soil is insufficiently known. A silt-loam soil (pH 7.0, background 0.005 mmol Sb kg(-1)) was amended with Sb2O3 at various concentrations. More than 70% of Sb in soil solution was present as Sb(V) (antimonate) within 2 days. The soil solution Sb concentrations gradually increased between 2 and 35 days after Sb2O3 amendment but were always below that of soils amended with the more soluble SbCl3 at the lower Sb concentrations. The soil solution Sb concentrations in freshly amended SbCl3 soils (7 days equilibration) were equivalent to those in Sb2O3-amended soils equilibrated for 5 years at equivalent total soil Sb. Our data indicate that the Sb solubility in this soil was controlled by a combination of sorption on the soil surface, Sb precipitation at the higher doses, and slow dissolution of Sb2O3, the latter being modeled with a half-life ranging between 50 and 250 days. Toxicity of Sb to plant growth (root elongation of barley, shoot biomass of lettuce) or to nitrification was found in soil equilibrated with Sb2O3 (up to 82 mmol Sb kg(-1)) for 31 weeks with 10% inhibition values at soil solution Sb concentrations of 110 microM Sb or above. These concentrations are equivalent to 4.2 mmol Sb per kg soil (510 mg Sb kg(-1)) at complete dissolution of Sb2O3 in this soil. No toxicity to plant growth or nitrification was evident in toxicity tests starting one week after soil amendment with Sb2O3, whereas clear toxicity was found in a similar test using SbCl3. However, these effects were confounded by a decrease in pH and an increase in salinity. It is concluded that the Sb(V) toxicity thresholds are over 100-fold larger than background concentrations in soil and that care must be taken to interpret toxicity data of soluble Sb(III) forms due to confounding factors.     

Kinetic studies on Sb(III) oxidation by hydrogen peroxide in aqueous solution

Knowledge of antimony redox kinetics is crucial in understanding the impact and fate of Sb in the environment and optimizing Sb removal from drinking water. The rate of oxidation of Sb(III) with H2O2 was measured in 0.5 mol L(-1) NaCl solutions as a function of [Sb(III)], [H2O2], pH, temperature, and ionic strength. The rate of oxidation of Sb(III) with H2O2 can be described by the general expression: -d[Sb(III)]/dt= k[Sb(III)][H2O2][H+](-1) with log k = -6.88 (+/- 0.17) [kc min(-1)]. The undissociated Sb(OH)3 does not react with H2O2: the formation of Sb(OH)4- is needed for the reaction to take place. In a mildly acidic hydrochloric acid medium, the rate of oxidation of Sb(III) is zeroth order with respect to Sb(III) and can be described by the expression -d[Sb(III)]/dt = k[H2O2][H+][Cl-] with log k = 4.44 (+/- 0.05) [k. L2 mol(-2) min(-1)]. The application of the calculated rate laws to environmental conditions suggests that Sb(III) oxidation by H2O2 may be relevant either in surface waters with elevated H2O2 concentrations and alkaline pH values or in treatment systems for contaminated solutions with millimolar H2O2 concentrations.     

Iron-mediated oxidation of antimony(III) by oxygen and hydrogen peroxide compared to arsenic(III) oxidation

Antimony is used in large quantities in a variety of products, though it has been declared as a pollutant of priority interest by the Environmental Protection Agency of the United States (USEPA). Oxidation processes critically affect the mobility of antimony in the environment since Sb(V) has a greater solubility than Sb(lll). In this study, the cooxidation reactions of Sb(lIl) with Fe(ll) and both O2 and H2O2 were investigated and compared to those of As(III). With increasing pH, the oxidation rate coefficients of Sb(lll) in the presence of Fe(ll) and O2 increased and followed a similar pH trend as the Fe(ll) oxidation by O2. Half-lives of Sb(lll) were 35 and 1.4 h at pH 5.0 and pH 6.2, respectively. The co-oxidation with Fe(ll) and H2O2 is about 7000 and 20 times faster than with Fe(ll) and O2 at pH 3 and pH 7, respectively. For both systems, *OH radicals appear to be the predominant oxidant below approximately pH 4, while at more neutral pH values, other unknown intermediates become important. The oxidation of As(lll) follows a similar pH trend as the Sb(lll) oxidation; however, As(lll) oxidation was roughly 10 times slower and only partly oxidized in most of the experiments. This study shows that the Fe(ll)-mediated oxidation of Sb(Ill) can be an important oxidation pathway at neutral pH values.     

Contamination of bottled waters with antimony leaching from polyethylene terephthalate (PET) increases upon storage

Antimony concentrations were determined in 132 brands of bottled water from 28 countries. Two of the brands were at or above the maximum allowable Sb concentration for drinking water in Japan (2 microg/L). Elevated concentrations of Sb in bottled waters are due mainly to the Sb2O3 used as the catalyst in the manufacture of polyethylene terephthalate (PET(E)). The leaching of Sb from PET(E) bottles shows variable reactivity. In 14 brands of bottled water from Canada, Sb concentrations increased on average 19% during 6 months storage at room temperature, but 48 brands of water from 11 European countries increased on average 90% under identical conditions. A mineral water from France in PET(E), purchased in Germany, yielded 725 ng/L when first tested, but 1510 ng/L when it was stored for 6 months at room temperature; the same brand of water, purchased in Hong Kong, yielded 1990 ng/L Sb. Pristine groundwater containing 1.7+/-0.4 ng/L Sb (n = 6) yielded 26.6+/-2.3 ng/L Sb (n = 3) after storage in PET(E) bottles from Canada for 6 months versus 281+/-38 ng/L Sb (n = 3) in PET(E) bottles from Germany. Tap water bottled commercially in PET(E) in December 2005 contained 450+/-56 ng/L Sb (n = 3) versus 70.3+/-0.3 ng/L Sb (n = 3) when sampled from a household faucet in the same village (Bammental, Germany), and 25.7+/-1.5 ng/L Sb (n = 3) from a local artesian flow.     

Antimony speciation in alkaline sulfide solutions: role of zerovalent sulfur

Antimony is subject to a lower drinking water standard than arsenic, its notorious group 15 cohort in the periodic table. Both elements often co-vary in nature and are fairly soluble under reducing, alkaline conditions. Of the two, much less is known about the environmental chemistry of Sb. Measurements of Sb solubility in sulfidic solutions equilibrated with stibnite (Sb2S3) and orthorhombic sulfur reveal the existence of two new complexes that may control Sb behavior in many reducing environments. Formation reactions and stability constants (23 +/- 2 degrees C) are HS- + S(s) + Sb2S3(s) <==> HSb2S5-, log K = -1.47 +/- 0.17; and HS- + 2S(s) + Sb2S3(s) <==> Sb2S6(2-) + H+, log K = -9.55 +/- 0.07. The first complex is a mixed-valence Sb(III,V) complex; the second is an Sb(V) complex. Their stability in sulfidic solutions may explain previously puzzling evidence of Sb(V) in natural anoxic environments. Owing to these complexes, zerovalent S can enhance stibnite solubility up to 3 orders of magnitude. In neutral-to-alkaline, reducing environments, less than 7 microM HS- will transform O-coordinated, electrically neutral Sb(OH)3o to predominantly anionic S-coordinated complexes. This transformation could diminish the adsorption of Sb to negatively charged mineral surfaces, lowering retardation factors in anoxic aquifers.     

Chemical characterisation of saccharides in the milk of a reindeer (Rangifer tarandus tarandus)

Although reindeer milk is utilised as a food in some areas in the world, including Mongolia, the saccharides in this milk have thus far not been explored. In this study, the structures of the separated saccharides were characterised by ¹H-nuclear magnetic resonance spectroscopy to be as follows: Gal(β1-3)Gal(β1-4)Glc (3′-galactosyllactose, 3′-GL), Gal(β1-6)Gal(β1-4)Glc (6′-galactosyllactose, 6′-GL), Gal(β1-4)Glc (lactose), Neu5Ac(α2-6)Gal(β1-4)Glc (6′-N-acetylneuraminyllactose, 6′-SL), Neu5Ac(α2-6)Gal(β1-4)GlcNAc(β1-3)Gal(β1-4)Glc (sialyllacto-N-tetraose c, LST c) and uridine 5′-diphospho-α-N-acetyl-D-glucosamine (UDP-GlcNAc). In addition, monosaccharide-α-1-phosphate and some other UDP-mono or oligosaccharides were found, but Neu5Ac(α2-3)Gal(β1-4)Glc (3′-N-acetylneuraminyllactose, 3′-SL) was not detected. Lactose was the predominant saccharide. It may be concluded that, in this milk, the concentration of phosphorylated or UDP-saccharides was higher than that of Neu5Ac containing oligosaccharides; this should be a significant feature of this species milk.     

Chemical characterisation of oligosaccharides in commercially pasteurised dromedary camel (Camelus dromedarius) milk

It has been suggested that bactrian camel milk and colostrum may be a good source of biologically significant oligosaccharides but, although the oligosaccharides found in bactrian camel milk and colostrum have been characterised, those in dromedary camel milk have not. In this study, seven oligosaccharides from commercially available pasteurised dromedary camel milk were characterised using ¹H nuclear magnetic resonance spectroscopy. The following oligosaccharides were detected: Gal(β1-3)Gal(β1-4)Glc (3′-galactosyllactose), Gal(β1-4)GlcNAc(β1-3)[Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc (lacto-N-neohexaose), Neu5Ac(α2-3)Gal(β1-4)Glc (3′-sialyllactose), Neu5Ac(α2-6)Gal(β1-4)Glc (6′-sialyllactose), Neu5Ac(α2-3)Gal(β1-3)Gal(β1-4)Glc (sialyl-3′-galactosyllactose), Neu5Ac(α2-3)Gal(β1-3)[Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc (sialyllacto-N-novopentaose a) and Neu5Ac(α2-6)Gal(β1-4)GlcNAc(β1-3)[Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc (monosialyllacto-N-neohexaose).