SiBCN陶瓷先驱体的制备和应用研究进展

综述了SiBCN陶瓷前驱体制备过程中在硅氮烷上引入硼元素的3种方法(采用环硼氮烷引入硼元素、采用硼氢化反应引入硼元素、采用BCl3引入硼元素);介绍了SiBCN陶瓷前驱体在制备介孔骨架、涂覆碳纳米管、制备无定形涂层上的应用;以及先驱体转化的SiBCN陶瓷的结晶化过程及陶瓷结构分析(无定形SiBCN陶瓷的结晶化过程,不同SiBCN陶瓷前驱体生成的陶瓷结构的对比)。     

硼氢化反应合成聚硼硅氮烷和热压成型-热解制备SiBCN陶瓷

对甲基乙烯基二氯硅烷(MeViSiCl2)进行氨解形成聚甲基乙烯基硅氮烷(PMVS),进而用二甲基硫醚硼烷(BH3-SMe2)和PMVS进行硼氢化反应,合成出SiBCN陶瓷的前驱体聚硼硅氮烷(polyborosilazane,PBSZ)。Fourier红外光谱分析表明:合成的PBSZ中有C-B-C和Si-N特征吸收峰,分别对应HC-B(CH)-CH和≡Si-NH-基团;11B和29Si的核磁共振分析产物中有BC3,SiN2C2,SiN3C和SiC3N等结构单元,这些光谱结果表明合成的产物为PBSZ。对PBSZ热压成型,在1000℃氩气中热解制备出SiBCN陶瓷体。PBSZ的热重分析表明:氩气中1300℃热解的陶瓷产率为52.6%。陶瓷局部致密,表明用前驱体热解法有望获得致密的SiBCN陶瓷体。     

聚醚与二乙胺的临氢胺化反应研究

以聚醚PEP-600与二乙胺为主要原料,雷尼镍为催化剂,通过临氢胺化反应制备了端叔胺基聚醚。反应产物通过滴定分析,确定为伯、仲、叔胺的混合物。对轻组分的GC-MS及GC分析表明:临氢胺化制备叔胺时,二乙胺发生了自身的缩合反应,生成氨气、一乙胺、二乙胺和三乙胺。     

Si-C-N陶瓷前驱体聚硅氮烷合成的研究进展

综述了合成Si—C—N陶瓷前驱体聚硅氮烷的主要方法，即氨／Q解氯硅烷法、硅氮烷低聚物交联法、硅氮烷低聚物与氯硅烷反应法及氯硅氯烷和氯硅烷脱氯编聚法，并介绍了用铝、硼、钛、钇等元素对聚硅氮烷进行改性，以提高Si—C—N陶瓷性能的方法。     

某些仲胺配位体的合成

用β-支链醇、仲醇、氯代十二烯及环氧乙烷烷基化仲碳伯胺,合成了8个仲胺配位体。为此目的专门制备了铜镍型催化剂。这些仲胺化合物可用于稀有元素的分离。     

中间体O-3-氯-2-丙烯基羟胺的合成研究

O-3-氯-2-丙烯基羟胺肟法合成的操作简单,反应安全,产品收率高,被广泛应用工业生产。不可避免生成的杂质影响了产品质量和收率,杂质前驱体在醚化反应中产生,对杂质前驱体形成机理进行了合理推测,中间产物N-乙酰基-O-(3-氯-2-丙烯基)羟胺与反式-1,3-二氯丙烯反应生成了三级胺。确定了醚化反应的最佳反应条件减少杂质前驱体生成,使用羟胺水溶液参与反应,在反应温度60℃、投料比n(羟胺)∶n(NaOH)∶n(反式-1,3二氯丙烯)=1∶2.1∶1.0时得最高产品收率87.6%。     

用红外光谱法研究环氧树脂固化过程

一、引 言 环氧树脂是玻璃钢手糊工艺最常用的树脂之一,研究其固化过程,对工艺制度的合理选择、产品性能的提高和质量的评定都有一定意义。 手糊成型玻璃钢使用的环氧树脂,通常都以脂肪族伯胺作固化剂。环氧树脂与伯胺的固化反应,一般认为是环氧基团与连接在伯胺氮原子上的氢原子反应,转变成仲胺,再由仲胺转变成叔胺。反应过程中环氧基团逐渐消失,羟基逐渐生成。由于固化反应中化学结构的变化和某些基团的消失或生成情况可以直接反映固     

反应条件对甲基氯硅烷合成的影响

以硅粉、氯甲烷为原料,借助搅拌床反应器模拟工业装置合成甲基氯硅烷,研究了反应温度、硅粉平均粒径、氯甲烷质量流量3个因素对甲基氯硅烷合成的影响。结果表明:反应温度对合成的影响最显著。以二甲选择性为评价指标时的最佳工艺条件为反应温度300℃、硅粉平均粒径110μm,氯甲烷质量流量为625 g/h;以触体产率为评价指标时的最佳工艺条件为反应温度320℃、硅粉平均粒径60μm,氯甲烷质量流量为625 g/h。     

脂肪族仲烷基胺的生产技术

介绍了仲烷基胺的工业生产方法及由长链烃制备一系列脂肪仲胺的专利。讨论了由脂肪醇及伯胺合成仲炕基胺中各种因素对辛醇-1与甲胺胺化反应的影响.     

Mannich反应及N—羟甲基胺的制备

含α—H 的酸性成份与醛(常用甲醛)和胺(仲胺、伯胺)缩合生成在酸性成份的α-碳上连有—CH_2NR_2的化合物—Mannich 碱。亦即使酸性成份发生胺甲基化的反应—Mannich 反应。     

Influence of operating temperature on CO<Subscript>2</Subscript>-NH<Subscript>3</Subscript> reaction in an aqueous solution

Although aqueous ammonia solution has been focused on the removal of CO₂ from flue gas, there have been very few reports regarding the underlying analysis of the reaction between CO₂ and NH₃. In this work, we explored the reaction of CO₂-NH₃-H₂O system at various operating temperatures: 40 °C, 20 °C, and 5 °C. The CO₂ removal efficiency and the loss of ammonia were influenced by the operating temperatures. Also, infrared spectroscopy measurement was used in order to understand the formation mechanism of ion species in absorbent, such as NH₂COO⁻, HCO₃⁻, CO₃²⁻, and NH₄⁺, during CO₂, NH₃, and H₂O reaction. The reactions of CO₂-NH₃-H₂O system at 20 °C and 40 °C have similar reaction routes. However, a different reaction route was observed at 5 °C compared to the other operating temperatures, showing the solid products of ammonium bicarbonates, relatively. The CO₂ removal efficiency and the formation of carbamate and bicarbonate were strongly influenced by the operating temperatures. In particular, the analysis of the formation carbamate and bicarbonate by infrared spectroscopy measurement provides useful information on the reaction mechanism of CO₂ in an aqueous ammonia solution.     

Polymerization of lactides and lactones. III. Ring-opening polymerization of DL-lactide by the (η3-C3H5)2Sm(μ2-Cl)2(μ3-Cl)2Mg(tmed)(μ2-Cl)Mg(tmed) complex

Ring-opening polymerization of DL -lactide (LA) has been initiated with the (η³-C₃H₅)₂Sm(μ₂-Cl)₂(μ₃-Cl)₂Mg(tmed)(η₂-Cl)Mg(tmed) complex both in bulk and solution. The effects of reaction conditions, such as reaction time, reaction temperature, and monomer/initiator molar ratio on the polymerization has been discussed. The results showed that (η³-C₃H₅)₂Sm(μ₂-Cl)₂(μ₃-Cl)₂Mg(tmed)(μ₂-Cl)Mg(tmed) was more effective for the polymerization of LA, and high molecular weight of polylactide was obtained by this initiator. The solvent affected the polymerization significantly. The polymerization mechanism was in agreement with the coordination mechanism. The polymer was characterized by FTIR, ¹H-NMR, and DSC. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2857–2862, 1999     

Evolution of metal nitriding and hydriding reactions during ammonia plasma-assisted ball milling

Nanocrystalline metal nitride and hydride powders were prepared using plasma-assisted ball milling in ammonia gas (NH₃-P-milling) via an in situ synthesis reaction. The gas–solid reactions were triggered by a short duration of plasma milling of Mg and Ti under a constant pressure of ammonia gas, and the products in the two systems were nanocrystalline Mg₃N₂ and TiN, TiH₂ after 10?h, respectively. During the NH₃-P-milling of Ti powder, TiH₂ and TiN were formed during the initial stages of milling, and then, the TiH₂ decomposed during further milling upon reaction with N radicals, transforming into the TiN phase. In contrast, no chemical reaction occurred between NH₃ and Mg/Ti after 10?h of C-milling. The discharge plasma activated and decomposed the ammonia gas and activated the surface of the powders, which, together with the mechanical effect of high-energy ball milling, accelerated the gas–solid reactions.     

Thermodynamic analysis on calcium dissolution in the system of Ca(II)-NH3-NH4Cl-H2O

Based on the principles of ionic balance, electro-neutrality and the existing thermodynamic data, the thermodynamics equilibrium on calcium dissolution in the system of Ca(II)-NH₃-NH₄Cl-H₂O was theoretically calculated. The results show that the equilibrium pH values in the system vary from 11.43 to 12.59, and the solubility of Ca(II) is significant in the system of NH₄Cl-NH₃-H₂O. The c(NH₄OH) has little influence on c(Ca²⁺)_T and when the ammonia concentration is kept constant, the total calcium concentration (c(Ca²⁺)_T) with a maximum concentration of 2.03 mol/L increases linearly with the increase of concentration of c(NH₄Cl). Calcium mainly presents in the form of calcium-bearing complexes instead of calcium ion in the system. The reaction degrees of Ca²⁺ with ammonium hydroxide and H₂O are less in the system. The absolute average error of calcium equilibrium concentration between the experimental and theoretical calculated values is 7.07% in confirmatory experiments. The results are helpful to clarify the leaching behaviour of calcium ions in the system of Ca(II)-NH₃-NH₄Cl-H₂O and provide the theoretical foundation to improve the calcium yield and remove impurities in the leaching stage of the indirect aqueous CO₂ sequestration process.     

Plasma polymerization in mixture system of tetramethyltin and ammonia gas

Summary Plasma polymerization in a mixture system of tetramethyltin (TMT) and ammonia (NH₃) gas was investigated by elemental analysis, IR spectroscopy, and ESCA in comparison with that in a mixture system of tetramethylsilane (TMS) and NH₃ gas. NH₃ gas contributed to the formation of polymers containing much tin, less carbon and hydrogen, and negligible nitrogen element. IR and ESCA spectra showed acceleration in dehydrogenation and /or dealkylation of carbon chains and in oxidation of tin element by NH₃ gas. While, plasma polymerization in the TMS/NH₃ mixture system showed incorporation of nitrogen residues as amido and amino groups as well as dehydrogenation and dealkylation. This descrepancy in chemical structure between polymerizations in the TMT/NH₃ and the TMS/NH₃ system might result from Sn-N bonds susceptible to moisture to form oxidized Sn.     

Ammonia decomposition in coal gasification atmospheres

Ammonia present in the product gas from coal gasification may increase NO_x emissions from IGCC systems. A fixed bed reactor was used to study the effect of calcined limestone (CaO) on NH₃ decomposition and reaction of NH₃ and NO. Reactions at temperatures to 900°C in helium and in gas compositions typical of air-blown gasifiers were studied. Although CaO enhanced ammonia decomposition in helium, reaction in the gasification atmosphere resulted in the loss of this catalytic activity. Increasing the total pressure further reduced the rate of NH₃ decomposition. CaO enhanced conversion of NO to NH₃ in gasification atmospheres.     

Nitridation of MgO-loaded MCM-41 and its beneficial applications in base-catalyzed reactions

Nitrogen-containing MgO-MCM-41 solid base material is prepared by nitridation of MgO-loaded mesoporous MCM-41. The ordered mesoporous structure and high surface area of MCM-41 are well preserved after MgO impregnation and nitridation, as proved by the XRD, TEM and nitrogen adsorption/desorption analysis. FTIR spectra the bridging -NH- groups and terminal -NH₂ groups are incorporated into the framework of MgO-MCM-41 by nitridation, and the base strength is expected to be enhanced due to the replacement of oxygen by nitrogen with lower electronegativity. FTIR spectra with the adsorption of different probe molecules, e.g. CO, CD₃CN and ¹³CO₂, are employed for the characterization of surface acidic-basic properties of MgO-MCM-41 before and after nitridation. It is revealed that the acidic hydroxyls in MgO-MCM-41 are greatly reduced through nitridation process. Compared with MgO-MCM-41, the nitridized MgO-MCM-41 material exhibits improved basic catalytic performances in Knoevenagel condensation reaction, Claisen-Schmidt reaction and dehydrogenation reaction of 2-propanol.     

Experimental study on capturing CO2 greenhouse gas by mixture of ammonia and soil

This paper presents our study on removal of carbon dioxide (CO₂) greenhouse gas emissions by using the mixture of ammonia and soil. CO₂ capture capacity using this method is 15% higher than the sum of ammonia chemical absorption capacity and soil physical adsorption capacity. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) are utilized to study this synergism. The removal effect is not only reflected in ammonia chemical reaction with CO₂. CO₂ can also be absorbed by ammonium bicarbonate (NH₄HCO₃) crystal, which is the main component of the product, or wrapped in the pore of the crystal or packed in the gap between the crystal and the soil. CO₂ can be permanently deposited as carbonated minerals in the subsoil earth layers.     

Immobilization of <Emphasis Type="Italic">Candida</Emphasis> sp.99-125 lipase onto silanized SBA-15 mesoporous materials by physical adsorption

SBA-15-NH₂ and SBA-15-Cl Mesoporous Materials were prepared by modifying SBA-15 with silane coupling agent 3-aminopropyltriethoxysilane and 3-chloropropyltriethoxysilane using the post-synthesis method. The mesoporous samples were characterized by Fourier transform infrared spectra and nitrogen adsorption. Compared with SBA-15-NH₂, SBA-15-Cl has suitable pore opening for further utilization in the immobilization of Candida sp.99-125 lipase by physical adsorption. The influences of lipase concentration and immobilizing time on the immobilization efficiency were investigated. Meanwhile, the lipase immobilized on SBA-15-Cl showed higher thermal, pH and storage stability than that of free lipase. Further study demonstrated that lipase immobilized on SBA-15-Cl could be used eight times without significant decrease of enzyme activity. The phenomenon was associated with the shrinkage of the pore opening of SBA-15-Cl keeping lipase from leaping out.     

CO_2-NH_3复叠与NH_3制冷系统的流程参数比较

设计了典型的CO2-NH3复叠式制冷流程和NH3两级压缩制冷流程,对流程进行了模拟计算,比较了两者的关键参数,并分析了换热器的热流分布及氨系统的参数优化。结果表明:在蒸发温度-45℃的条件下,复叠式系统的压缩机总功耗、制冷剂NH3流量小于氨系统,但氨系统具有较大规模的中温制冷量,其总制冷系数COP大于复叠式系统。复叠式系统冷凝蒸发器的两相流间换热温差较小,而氨系统中间冷却器的换热温差较大。随着低压级排气压力的上升,以及中间温度的降低,氨两级压缩机的总功耗呈下降趋势。