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采用红外光谱法、凝胶色谱法、超导核磁共振波谱法、皂化滴定法以及气相色谱-质谱法等对国内外10种常用柴油降凝剂进行了成分分析,以寻找其成分对降凝剂性能的影响。结果表明:10种柴油降凝剂均属乙烯-乙酸乙烯酯聚合型降凝剂,样品聚合物部分相对分子质量较低,乙酸乙烯酯聚合物的质量分数一般在27%~37%之间,样品溶剂为重芳烃、以C10为主的烷烃或者它们的混合物。其中,国外产品的相对分子质量较高(Mr>3 700),乙酸乙烯酯聚合物质量分数大于30%,且溶剂添加了少量含氮类分散剂。 相似文献
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正在卷烟生产中用于粘结烟纸、滤嘴及包装纸的水基胶是重要的卷烟辅助材料之一[1]。目前国内烟草行业使用的水基胶大多是化学合成的白乳胶。白乳胶是以乙酸乙烯酯为主要原料在引发剂作用下经聚合反应而制得的一种热塑性粘合剂[2],主要有聚乙酸乙烯均聚乳液(PVAC)、乙酸乙烯-乙烯共聚乳液(VAE)和乙酸乙烯-丙烯酸丁酯共聚乳液(VAB)等。烟用水基胶中的乙酸乙烯酯在卷烟生产过程中受生产原料、操作工艺等条件的影响会因转化不完 相似文献
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用乙酸乙烯酯(VAc)和丙烯酸(AA)进行溶液聚合制备(乙酸乙烯酯-co-丙烯酸)共聚物[P(VAc-co-AA)],研究了不同单体投料比时的聚合反应速率,结果表明:反应时间一定,随AA含量增加,聚合反应速率降低,转化率降低;反应5小时后,不同AA含量体系的转化率差别减小;傅里叶变换红外吸收光谱(FTIR)和核磁共振氢谱(1H-NMR)测试结果表明AA与VAc发生共聚.用氢氧化钠(NaOH)作为催化剂对P(VAc-co-AA)进行醇解制得产物聚乙烯醇(PVA),通过X-射线衍射(XRD)测定了醇解产物结晶度,进一步考察了醇解产物在70℃水中的溶解性.结果表明:与聚乙酸乙烯酯(PVAc)的醇解产物相比,P(VAc-co-AA)的醇解产物结晶度有所下降,在水中的溶解性提高. 相似文献
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水溶性聚合物和两亲聚合物:21.丙烷酸/乙酸乙烯酯共聚物对… 总被引:1,自引:0,他引:1
研究了晶种存在下丙烯酸/乙酸乙烯酯无人聚物对碳酸钙从过饱和水溶液中结晶的影响。发现我们的实验条件下碳酸钙结晶包括溶液本体成核结晶和晶种上晶体生长两种不同过程,丙烯酸/乙酸乙烯酯共聚物同时具有明显抑制溶液成核结晶和抑制晶种上体的双重作用, 相似文献
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离子液体中脂肪酶催化拆分外消旋烯丙酮醇反应 总被引:2,自引:0,他引:2
以离子液体为溶剂,考察了溶剂类型、水活度、温度、 pH值和共溶剂等因素对脂肪酶催化拆分外消旋烯丙酮醇(R,S)-4-羟基-3-甲基-2-(2-丙烯基)-2-环戊烯-1-酮反应的影响,并与常用于外消旋烯丙酮醇拆分的有机溶剂乙酸乙烯酯进行了比较. 结果表明,在离子液体[bmim]PF6中脂肪酶的催化性能较好,酶初始反应速率为18.48 μmol/(g·min), 半衰期为74.53 h, 高于在乙酸乙烯酯中的相应值(9.18 μmol/(g·min)和64.29 h). 但离子液体中拆分反应的转化率低于在乙酸乙烯酯中的转化率,可以通过向离子液体中补加酰基供体来提高外消旋烯丙酮醇的转化率. 两种反应介质中最佳酶反应条件均为水活度0.17, 温度40 ℃和pH=7, 但加入共溶剂后,离子液体中脂肪酶催化拆分外消旋烯丙酮醇的效率降低,而在乙酸乙烯酯中则有所提高. 相似文献
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A novel cataluminescence (CTL) sensor using nanosized MgO as the sensing material for determination of the trace of vinyl acetate in air was proposed in the present study. Eight catalysts were examined and the results showed that the CTL intensity on MgO nanoparticles was the strongest. Under the optimized conditions, the linear range of the CTL intensity versus the concentration of vinyl acetate vapor was 2-2000 ppm with a detection limit of 1.0 ppm (3σ) and a relative standard deviation (R.S.D.) of 1.18% for five times determination of 1000 ppm vinyl acetate. There were no CTL emissions when foreign substances, including ammonia, benzene, acetic acid, formaldehyde and ethyl acetate, passed through the sensor. CTL emissions were detected for methanol, ethanol and acetaldehyde at levels around 5.5%, 10.1% and 13.4% compared with the responsed vinyl acetate. The sensor had a long lifetime more than 100 h. 相似文献
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The reactions of methoxymethyl cations generated from dimethyl ether with propene, butene-2, vinyl methyl ether, acetaldehyde and acetone have been studied. The collision complexes, generated with the olefines, may eliminate an olefine, a methanol and a formaldehyde molecule as shown by double resonance experiments. From deuterium labelling it is found, that in the cases of propene and butene-2 the elimination of an olefine is accompanied by an extensive H/D interchange in the collision complexes, which has been shown not to occur in the long-lived reactant methoxymethyl cations if the internal energy of the methoxymethyl cations is less than 2.3 eV. The H/D interchange in these collision complexes is reduced in the elimination of methanol and is almost completely suppressed in the elimination of formaldehyde. In reactions with vinyl methyl ether, however, the eliminations of methanol and formaldehyde from the corresponding collision complexes appear to proceed with extensive H/D interchange. These observations point to acyclic collision complexes rather than 4-membered ring complexes. The collision complexes generated with acetaldehyde and acetone decompose by elimination of formaldehyde only. Deuterium labelling has shown that the formaldehyde molecule contains the original methylene group of the reactant methoxymethyl cations. In addition, 18O labelling in acetone has shown that the original oxygen atom of the methoxymethyl cations is retained completely in the eliminated formaldehyde. These observations exclude any formation of 4-membered ring collision complexes and can only be explained by acyclic complexes. Possible mechanisms of all reactions mentioned are discussed in the light of these results. 相似文献
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建立了高效液相色谱法同时测定卷烟醋酸纤维滤棒中甲醛、乙醛和丙酮含量的方法,采用Acclaim(R)Explosive E2 C18色谱柱,流动相为乙腈/水梯度洗脱,流速为0.5 mL/min,检测波长为352 nm,对甲醛、乙醛和丙酮的分析取得满意的效果.甲醛、乙醛、丙酮的回收率分别为95.3%~105.6%、86.1... 相似文献
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Na Wang Wei Zhang Long-Hua Zhou Qing-Feng Deng Zong-Bo Xie Xiao-Qi Yu 《Applied biochemistry and biotechnology》2013,171(7):1559-1567
A facile tandem route to α,β-unsaturated aldehydes was developed by combining the two catalytic activities of the same enzyme in a one-pot strategy for the aldol reaction and in situ generation of acetaldehyde. Lipase from Mucor miehei was found to have conventional and promiscuous catalytic activities for the hydrolysis of vinyl acetate and aldol condensation with in situ formed acetaldehyde. The first reaction continuously provided material for the second reaction, which effectively reduced the volatilization loss, oxidation, and polymerization of acetaldehyde, as well as avoided a negative effect on the enzyme of excessive amounts of acetaldehyde. After optimizing the process, several substrates participated in the reaction and provided the target products in moderate to high yields using this single lipase-catalyzed one-pot biotransformation. Figure
One-pot tandem approach for the synthesis of α,β-unsaturated aldehydes was developed under the catalysis of lipase from M. miehei (MML), firstly. MML displayed conventional and promiscuous catalytic activities for hydrolysis of vinyl acetate and aldol condensation with in situ formed acetaldehyde. 相似文献
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Formaldehyde, acetaldehyde, acetone, and propionaldehyde may be identified and determined in concentrations of parts per million by reduction to the corresponding alcohol followed by gas chromatography of the alcohols on porous polyaromatic resin beads. The method may be used for determining the position of double bonds in, e.g., vinyl and isopropylidene groups by prior ozonolysis. The method is limited in sensitivity chiefly by the levels of these lower carbonyl compounds in the atmosphere. 相似文献
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Five different copolymer membranes, i.e. copolymer of acrylonitrile with 2-hydroxyethyl methacrylate (PANHEMA), vinyl acetate (PANVAC) and methyl methacrylate (PANMMA) and styrene with vinyl acetate PSTYVAC) and methyl methacrylate (PSTYMMA) were synthesized, each with two different copolymer compositions (i.e. PANHEMA-1, PANHEMA-2, etc.). The copolymer membranes were synthesized on the basis of their relative solubility parameters with respect to acetone and hydrophilicity with respect to water. These membranes were used for pervaporative dehydration of acetone over the entire concentration range of 0–100 wt% water as well as acetone separation over 0–44 wt% acetone in feed. The acrylonitrile copolymers showed water selectivity with maximum water flux and selectivity for PANHEMA-2 copolymer (29.3 g/(m2 h), 16.73, respectively, for 2.5 wt% water in feed) while the styrene copolymers showed maximum acetone selectivity with reasonable acetone flux for PSTYMMA-1 copolymer (7.12 g/(m2 h), 12.61, respectively, for 1.6 wt% acetone in feed) membrane. The influence of one permeant on permeation of the other permeant was also studied in terms of permeation factor. 相似文献
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利用烟雾箱模拟装置,研究了异戊二烯与OH自由基反应的二次有机气溶胶(SOA)的生成.反应中生成的气相产物通过质子转移反应质谱仪(PTR-MS)测定,SOA的浓度及粒径谱分布通过高分辨率粒径谱仪(EEPS3090)测定.研究表明:甲基丙烯醛(MAC)/甲基乙烯基酮(MVK)、乙醛、甲醛、甲醇、甲酸/乙醇、乙醇醛、甲基乙二醛、丙酮/丙醛等为主要气相产物,各组实验中MAC/MVK和乙醛浓度达到最大时,其产率分别介于13.78%~37.72%和5.38%~9.34%(以C计)范围内;SOA生成量及其中值粒径随异戊二烯反应量的增加而增加,气相物质稳定后,SOA产率在5.6%~11.7%范围内,粒径在22~165nm范围内. 相似文献
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Alberto Sturaro Giorgio Parvoli Lucio Doretti Cristina Bancomina Carlo Neonato 《Journal of mass spectrometry : JMS》1994,29(10):575-577
The determination of vinyl acetate at parts per 109 by volume (ppbv) levels in air by gas chromatography/mass spectrometry (GC/MS) was achieved by optimizing the GC conditions and choosing specific extraction solvents that are sufficiently pure. The ideal solvent should not give rise to fragment ions at m/z 43, in order to rule out any possible interference during the monitoring of the same vinyl acetate ion. Traces of acetone and butan-2-one in solvents suitable for this GC/MS determination may also mislead the detection of vinyl acetate. A 440 μl volume of a mixture of tetrachloroethylene containing 9% acetonitrile allowed the recovery of more than 90% of the ester with a detection limit of 1.5 ppbv in air together with a good linearity of response. 相似文献
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Gas-liquid chromatography (GLC) was used to measure Henry's law constants for ethylene, ethane, carbon dioxide, sulfur dioxide, methyl chloride, vinyl acetate, isopropyl alcohol, methyl ethyl ketone, and acetone in liquid poly(vinyl acetate) in the region 125 to 200°C. Retention-time differences were measured relative to nitrogen and corrections for nitrogen's finite solubility were applied; these corrections are significant when measuring the solubilities of sparingly soluble solutes by the GLC method. The effect of GLC column diameter is discussed. 相似文献