高频燃烧红外分析法测定混凝土中的硫含量

采用高频红外碳硫仪快速测定混凝土中的硫含量.通过试验确定了适宜的分析条件:以水泥标准物质校正仪器,以铁屑、钨粒加锡粒为助熔剂,称样量为0.03～0.2g.用该法对4种混凝土样品进行测定,测定结果与化学法测定结果相吻合,5次测定结果的相对标准偏差不大于4%,精密度较为理想.     

高频燃烧–红外吸收法测定低合金钢中的碳含量

采用高频红外碳硫分析仪测定低合金钢中的碳含量。分别考察了取样量、助熔剂种类、助熔剂用量对测量结果的影响。结果显示当取样量为400 mg、钨助熔剂用量为样品取样量的1.2倍时,测定低合金钢中的碳含量效果最好,测定结果的相对标准偏差为0.9%(n=10),加标回收率在97.5%~102.7%之间。     

ICP-AES法测定水泥及熟料中三氧化硫

在水泥硬化过程中水泥中硫酸盐与固态水化铝酸钙形成水化硫铝酸钙 ,使体积膨胀 ,造成水泥的安定性不良 ,甚至崩裂。所以水泥及制备水泥的熟料中三氧化硫的测定对于水泥质量具有十分重要的意义。国家标准中规定三氧化硫的测试必须使用化学法 [1,2 ]目前化学测试方法多采用硫酸钡重量法 ,其操作复杂 ,分析周期长。本文采用 GB1 76- 87中的试样分解方法 ,研究了用 ICP- AES法直接测试硫的含量 ,然后换算成三氧化硫。本法简单、快速、结果准确 ,适用于硅酸盐水泥、普通硅酸盐水泥、矿渣硅酸盐水泥、火山灰硅酸盐水泥、粉煤灰硅酸盐水泥以及…     

氯化银比浊法测定镍钴锰三元素氢氧化物中氯离子

建立了氯化银比浊法测定镍钴锰三元素氢氧化物中氯离子含量的测定方法。选择了合适的测定波长,并对硝酸用量、沉淀剂用量、稳定时间对测定结果的影响进行了试验,确定了较优的分析条件。样品加标回收率在95%~103.3%,氯离子浓度在0~4μg/mL与浊度值有良好线性关系。方法为控制镍钴锰三元素氢氧化物中氯离子提供了检测依据。     

原子荧光法测定复配食品添加剂中的铅

应用原子荧光光谱法测定了复配食品添加剂中铅的含量。采用混酸湿法消解,探讨并优化了样品预处理过程、载流和还原剂用量,重点研究了铁氰化钾的用量以及样品最终酸度的判断对测定结果的影响。方法的检出限为0.17 ng/mL,测定结果的相对标准偏差为1.9%(n=7),线性范围为0.4～30 ng/mL,样品加标回收率为80.72%～102.5%。该法可以满足复配食品添加剂中铅的测定要求。     

钼蓝分光光度法测定铅精矿中二氧化硅

采用钼蓝分光光度法测定铅精矿中二氧化硅的含量,研究了显色酸度、钼酸铵用量、加入钼酸铵后的稳定时间、还原液用量以及加入还原液后稳定时间等因素对测定的影响,确定了最佳测定条件。方法加标回收率在97.01%~103.8%,相对标准偏差(RSD)在1.3%~8.5%。方法操作简单,流程短,干扰少,具有较好的精密度和准确度,能够满足铅精矿中二氧化硅含量的测定。     

水溶性聚合物改性水泥的研究 Ⅱ.水溶性聚合物对水泥水化过程的影响

从聚合物改性水泥的水化速率、水化热及水化生成物三方面讨论了聚合物对水泥水化的影响。水泥溶液ｐＨ 值和电导率及水泥凝结时间的研究结果表明,非离子聚合物聚丙烯酰胺、聚乙烯醇减慢水泥的初期水化,具有缓凝作用,而阴离子聚合物水解聚丙烯酰胺、聚丙烯酸、磺化聚丙烯酰胺及磺化聚苯乙烯则加速水泥的初期水化,具有促凝作用;水化放热测量结果表明,掺加聚合物均滞缓水泥的后期水化;ＸＲＤ 分析表明,ＨＰＡＭ 抑制水泥中晶体的早期生长,有利于晶体后期形成。在水泥中掺加１ ％ ～２ ％ 的ＨＰＡＭ、ＰＡＡ、ＳＰＳ或ＰＶＡ,抗折强度和抗压强度均有明显提高。     

聚羧酸共聚物侧链结构对水泥水化及硬化过程的影响

以聚乙二醇系列、丙烯酸、顺酐、丙烯酸羟乙酯为原料合成聚羧酸减水剂,讨论聚羧酸共聚物侧链长度对水泥分散性能和水化过程的影响,并测试掺加减水剂的混凝土性能.实验结果表明:通过调整聚羧酸共聚物中侧链链长的比例使其具有最佳的分散性.实验合成的聚羧酸共聚物聚乙二醇侧链为nPEG600∶nPEG400=1∶1时,分散效果最好,水泥浆体的流动度及分散力最佳,分别为289 mm和10.36.聚羧酸减水剂具有缓凝特性,能够显著延缓水泥水化及硬化过程,使水泥石的后期水化更充分、水化产物结构更紧密更有力量,各龄期混凝土抗压强度都有较大提高.在水泥中添加0.3%聚羧酸减水剂(PEG600∶400),32.5#水泥3 d,7 d和28 d的抗压强度分别提高了50.4%,40.8%,35.1%,42.5#水泥3 d,7 d,28 d的抗压强度分别提高了16.7%,31.0%和22.3%.     

咔唑比色法测定造纸法再造烟叶中的果胶含量

采用咔唑分光光度法对造纸法再造烟叶中的果胶含量进行了测定,通过实验对测定条件进行了优化。得到了最优的水解条件(H2SO4加入量6 mL、85℃水解15 min)和显色条件(咔唑乙醇溶液用量0.2 mL、25℃显色2h)。稳定性、精密度和加标回收实验均表明该法在造纸法再造烟叶果胶含量的测定中可以得到满意的结果。     

影响改性聚苯乙烯废塑料高效水泥减水剂减水增强性能因素的研究

通过化学改性反应将废旧聚苯乙烯塑料改性成为可提高水泥混凝土流动性能和强度的高效水泥减水增强剂。研究了改性废旧聚苯乙烯塑料减水剂中离子含量、减水剂的添加量对水泥混凝土的减水率和水泥强度的影响     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.