气态丙烯酸光致脱羧反应AM1法研究

半经验的自洽场分子轨道法(AM1)被用来研究激发单态(~1ππ~*)和三态(~3ππ~*)丙烯酸的脱羧反应. 计算结果支持Robert等人提出的光解机理. 与实验结合. 进一步推测, 丙烯酸光致脱羧反应的第一步, 是沿单态途径进行, 第二步沿三态途径进行. 单态和三态反应途径中的反应物、过渡态、中间体和产物都用能量梯度技术进行了优化. 对于过渡态和中间体, 还作了振动分析, 确证它们分别是一级鞍点和能量极小值点.     

HNCO+OH->H2O+NCO的反应机理

采用从头算分子轨道法 (UHF/6 31G 水平 ,并用MP4加以相关能校正 )研究了HNCO OHH2 O NCO反应机理 .同时用Morokuma数值法获得了反应途径即内禀反应坐标 (IRC) .沿着IRC ,运用反应途径哈密顿理论 ,获得反应途径动态学信息 .在此基础上 ,根据过渡态理论和相应隧道效应校正 ,计算了在不同温度下的反应速率常数 ,得到了和实验相一致的结果 .计算结果表明 ,此反应是一步直接型的抽提H反应 .     

HNCO+OH→H2O+NCO的反应机理

采用从头算分子轨道法(UHF/6-31G**水平,并用MP4加以相关能校正)研究了HNCO+OH→H2O+NCO反应机理.同时用Morokuma数值法获得了反应途径即内禀反应坐标(IRC).沿着IRC,运用反应途径哈密顿理论,获得反应途径动态学信息.在此基础上,根据过渡态理论和相应隧道效应校正,计算了在不同温度下的反应速率常数,得到了和实验相一致的结果.计算结果表明,此反应是一步直接型的抽提H反应.     

CaO对Pt/C催化硬脂酸脱羧反应性能的影响

以硬脂酸(C₁₇H₃₅COOH)脱羧为探针反应,研究了亚临界水中CaO对Pt/C催化脱羧反应性能的影响.实验表明,CaO可以促进脱羧反应,对十七烷选择性没有影响.CaO/硬脂酸物质的量比为0.5时,在330 ℃反应1 h,硬脂酸转化率由未添加CaO时的46.06%提高到66.99%.硬脂酸催化脱羧的最佳反应温度为350 ℃,高于这一温度时,烷基链上碳碳键断裂的副反应增加,导致十七烷选择性降低.亚临界水中硬脂酸脱羧反应符合一级动力学,建立的动力学方程可以较好地预测不同反应条件下十七烷的产率.根据实验结果推测,氧化钙与硬脂酸反应生成硬脂酸钙,催化剂表面的吸附态羧酸盐增加,从而提高了脱羧反应的速率.     

NAMI-A乙基取代衍生物水解机理的DFT研究

采用密度泛函理论(DFT)方法,并结合导体极化连续模型(CPCM)研究了[(N-EtIm)H][trans-RuⅢCl4(DMSO)(N-EtIm)](N-EtIm=N-乙基咪唑)分别在中性及酸性条件下的水解反应过程.同时,为提高溶剂化能的精确度,在中性条件下水解反应的计算中采用3个水分子的溶剂化模型.计算得到水解反应过程中相应的结构特征和详细的热力学能量及速率常数.首先,在中性条件下,对于第一步水解,液相中配合物的活化能垒为109.9kJ/mol,速率常数为3.3×10-7 s-1,与实验中测得的第一步水解反应的速率常数(4.4×10-7 s-1)一致.对于第二步水解,反应的活化能垒为117.9kJ/mol,这符合实验中观察到的第二步水解比第一步水解反应慢的现象.其次,计算结果表明,酸性条件下,DMSO基团易于水解,Cl-水解困难,这也与实验结果相吻合.     

丙烯酸聚醚聚氨酯合成反应中的氢键效应及其反应动力学研究

以红外光谱法研究了丙烯酸聚醚聚氨酯合成反应(其中有氢键效应存在)及其反应动力学。结果表明:由于丙烯酸聚氨酯分子链结构中含有-CO-O-;-NH-和-O-三种主要极性基因,导致在反应中存在明显的氢键变化。在第一步聚氨酯预聚体合成中,氢键距离R随反应进行而逐渐减小,反映出-NHCO-O-结构增加,聚集加强,氢键作用加强,并趋向稳定;其中不同结构聚氨酯预聚体氢键距离R不同:R_(MDI)>R_(HDI)>R_(TDP),链段结构中有序程度依次降低。在第二步丙烯酸聚氨酯合成中,存在明显键效应,其链段结构中有序程度较原来预聚体稳定或略有下降。在二步合成反应过程中,1/1-P_(NCO)和t之间呈现很好的线性关系,表明这两步合成均属二级反学动力学。其区别在于第一步反应速率常数(k_1)较第二步反应速率常数(k_2)小一个数量级。     

二氯甲基硅烷醇解的量化计算

采用溶剂法和B3LYP/6-31G(d)基组研究了甲基含氢二氯硅烷的醇解反应.结果表明，反应分二步进行，其一步和二步醇解均为放热反应，并得出了反应的最佳温度、醇与硅烷的最佳配比、最佳进样方式、主反应和副反应的活化能及其可能的反应途径曲线.计算结果和实验结果较为一致.     

室温下铜催化丙烯酸与膦氧类化合物的脱羧偶联反应（英文）

发展了一种简单而又温和的铜催化芳基丙烯酸与膦氧类化合物脱羧偶联反应,提供了一种合成烯基膦类化合物的途径;以空气中的氧气作为氧化剂,反应生成β-酮基膦化合物为主的产物.这两类反应的显著特点包括:优秀的化学反应选择性、良好的官能团兼容性以及温和的反应条件(如便宜的氧化剂、无配体参与和室温环境等).     

O(3P)与卤代甲基反应的理论研究--Ⅰ.O(3P)+CH2Cl的反应机理

用量子化学从头算法对氧原子与CH2 Cl自由基的反应进行了研究 ,采用G2MP2方法计算了势能面上各驻点的构型参数、振动频率和能量 .给出了O( 3 P)与CH2 Cl反应的明确机理 .反应首先形成富能中间体OCH2 Cl,而后经各种复杂的解离或异构化途径生成产物 .计算的各个通道的反应热与实验结果相符 ,预测H CHClO和Cl CH2 O是反应的主要通道 .根据从头算的结果 ,用过渡态理论计算了反应的总速率常数 .反应速率常数与压力无关 ,在低温下有弱的负温度效应 .计算值与实验值符合很好 .     

C_2H_2~＋＋H_2→C_2H_3~＋＋H反应振动选态速率常数的理论研究

用从头计算法辅以能一梯度法优化了反应Ｃ_２Ｈ＋Ｈ_２→Ｃ_２Ｈ＋Ｈ的过渡态，用福井谦一的理论求出反应途径，用反应途径哈密顿理论及正则变分过渡态理论计算沿反应途径的动力学性质和反应速率常数。在此基础上对涉及振动激发的选态反应速率常数进行计算，所得结果与现有的实验结果相符合。     

N,N-二甲基苄胺催化合成丙烯酸间苯二酚环氧酯的机理

Ｎ，Ｎ－二甲基苄胺催化合成丙烯酸间苯二酚环氧酯的机理高俊刚，王洪芳，袁翠红（河北大学化学系，保定０７１００２）关键词丙烯酸间苯二酚环氧酯，Ｎ，Ｎ－二甲基苄胺，催化反应机理不饱和酸环氧酯是由不饱和核酸与环氧化合物进行环氧化反应形成的一种化合物，它在涂料...     

Oxidation of propane to acrylic acid and acetic acid over alkaline earth-doped Mo-V-Sb-O_x catalysts

Alkaline earth metal (Mg,Ca,Sr and Ba)-doped Mo-V-Sb-O x catalysts,prepared by a dry-up method,have been investigated for their catalytic performance in the oxidation of propane under different reaction conditions.The catalysts have been characterized by N2 adsorption-desorption,temperature-programmed desorption (TPD) of NH3,SEM and XRD.Influence of water vapor on the catalytic performance,particularly on the selectivities to acetic acid and acrylic acid,has also been studied.The selectivity to acrylic acid was improved significantly by the doping of alkaline earth metals to Mo-V-Sb-O x catalysts.The surface acidic sites of the catalyst decreased with the doping of the catalyst with alkaline earth metals,which ultimately was found to be beneficial for obtaining high selectivity to acrylic acid.The catalytic activity and product selectivities were found to be influenced by the reaction temperature,C3H8/O2 ratio and space velocity.A significant improvement in the selectivity to acrylic acid has also been observed by the addition of water vapor in the feed of propane and oxygen in the oxidation of propane.     

Polymerisation radiochimique de l''acide methacrylique en solution

The polymerization of methacrylic acid was investigated in various solvents under the action of gamma-rays. It was found that, as in the case of acrylic acid, solvents could be divided into groups according to the observed effects. The addition of methanol or dioxane up to 50 per cent does not significantly alter the polymerization rate. These two solvents do not dissociate the plurimolecular aggregates of methacrylic acid, the presence of which is demonstrated by the high viscosity of the medium. In the presence of either toluene or n-hexane, the rate gradually decreases and the aggregates are dissociated. Chloroform and CCl₄ also dissociate the aggregates but lead to acceleration of the reaction. This effect which was not observed with acrylic acid presumably results from an energy transfer process. The polymerization of methacrylic acid in bulk and in solution has a very small overall activation energy, 1·0–1·5 kcal/mole between 16 and 60°. All conversion curves are linear in contrast to the case of acrylic acid where auto-accelerated conversion curves were observed in most mixtures. A comparison of these results shows that the initial rates of polymerization of acrylic acid follow relationships similar to those observed for methacrylic acid except for the chlorinated solvents. It is concluded that the molecular aggregates produce the same influence on the polymerization of methacrylic acid as on the initial stages of the reaction for acrylic acid, but the “matrix effect” of poly(acrylic acid) does not appear in the case of poly(methacrylic acid).     

PHOTOINDUCED GRAFTING OF ACRYLIC AND ALLYL MONOMERS ON POLYETHYLENE SURFACE

Photoinduced grafting of acrylic and allyl monomers on polyethylene surface wasgenerally studied by using benzophenone (BP) as a photoinitiator. The grafting process wascarried out either in vapor-phase or in solution of the monomers. In the vapor-phase reactionwith a filter used to cut off the short wavelength UV light, allyl amine is the most reactive ofthe four monomers used and acrylic amide is comparatively more reactive than acrylic acid andallyl alcohol. Acetone, as a solvent and carrier for initiator and monomers, however, showsits reactivity to participate the reaction. The solution grafting with a filter is much faster thanthe corresponding vapor-phase reaction, and a fully covered surface by the grafted polymercan be achieved in this way.     

Chemically initiated graft copolymerization of acrylic acid onto acrylonitrile-butadiene-styrene (ABS) terpolymer and its constituent polymers

The graft copolymerization of acrylic acid onto acrylonitrile-butadiene-styrene terpolymer (ABS), has been initiated by the use of both benzoyl peroxide and azobisisobutyronitrile. Addition occurs in the butadiene region of the polymer, either by the loss of a vinylic hydrogen and subsequent radical formation and addition of monomer or by addition to the double bond. The amount of acrylic acid which may be added is dependent upon the time and temperature of the reaction and the concentration of monomer and initiator. Thermal analysis of the grafted samples show that the residue is less than that expected based upon the composition of the copolymer; similar results have been previously obtained for acrylic acid grafted by another technique. © 1996 John Wiley & Sons, Inc.     

Effect of diluent and reaction parameter on selective oxidation of propane over MoVTeNb catalyst using nanoflow catalytic reactor

The selective oxidation of propane to acrylic acid over an MoVTeNb mixed oxide catalyst, dried and calcined before reaction has been studied using high-throughput instrumentation, which is called nanoflow catalytic reactor. The effects of catalyst dilution on the catalytic performance of the MoVTeNb mixed oxide catalyst in selective oxidation of propane to acrylic acid were also investigated. The effects of some reaction parameters, such as gas hourly space velocity （GHSV） and reaction temperature, for selective oxidation of propane to acrylic acid over diluted MoVTeNb catalyst have also been studied. The configuration of the nanoflow is shown to be suitable for screen catalytic performance, and its operating conditions were mimicked closely to conventional laboratory as well as to industrial conditions. The results obtained provided very good reproducibility and it showed that preparation methods as well as reaction parameters can play significant roles in catalytic performance of these catalysts.     

The Preparation and Properties of Acrylic and Methacrylic Acid Grafted Cellulose Prepared by Ceric Ion Initiation. Part I. Preparation of the Grafted Cellulose

The ceric ion method has been used to graft acrylic acid directly onto cellulose with a minimum amount of homopolymer. The method utilizes the pretreatment of the cellulose with ceric ammonium nitrate followed by washing out any excess of the catalyst. Oxygen can be present with the pretreatment step, but must be excluded during the grafting reaction itself. The process, which is entirely aqueous in nature, would appear to be quite practical on a large scale. Wet strengthened papers which are essential for the use of the grafted products as ion-exchange media can also be grafted but with adequate but lower yields than with the untreated paper. Apart from ion exchange, the products are of considerable potential value as water sorbing agents. Methacrylic acid gave lower grafting yields than acrylic acid, but these were much improved at higher temperatures.     

Oxidation of propane to acrylic acid and acetic acid over alkaline earth-doped Mo-V-Sb-Ox catalysts

Alkaline earth metal (Mg, Ca, Sr and Ba)-doped Mo-V-Sb-Ox catalysts, prepared by a dry-up method, have been investigated for their catalytic performance in the oxidation of propane under different reaction conditions. The catalysts have been characterized by N2 adsorption-desorption, temperature-programmed desorption (TPD) of NH3, SEM and XRD. Influence of water vapor on the catalytic performance, particularly on the selectivities to acetic acid and acrylic acid, has also been studied. The selectivity to acrylic acid was improved significantly by the doping of alkaline earth metals to Mo-V-Sb-Ox catalysts. The surface acidic sites of the catalyst decreased with the doping of the catalyst with alkaline earth metals, which ultimately was found to be beneficial for obtaining high selectivity to acrylic acid. The catalytic activity and product selectivities were found to be influenced by the reaction temperature, C3H8/O2 ratio and space velocity. A significant improvement in the selectivity to acrylic acid has also been observed by the addition of water vapor in the feed of propane and oxygen in the oxidation of propane.     

ABSORPTION OF METAL IONS AND SWELLING PROPERTIES OF POLY(ACRYLIC ACID-CO-ITACONIC ACID) HYDROGELS

Hydrogels of acrylic acid and itaconic acid has been synthesized with different monomers ratios. The swelling process of the different xerogels immersed in water and salt solutions has been studied. The swelling of hydrogels loaded with metal cations (Cu²⁺, Zn²⁺) was also investigated. The swelling process was monitored by the increase in the weight of hydrogel as a function of time. The absorption properties of metal ions were studied by using the hydrogel, and different concentrations of copper and zinc solutions (prepared from sulphate salts). The influence of pH on the absorption process was studied. For the absorption of metal ions, the amount of ions absorbed within the hydrogel can be calculated from the initial and equilibrium concentrations of the metal ions in aqueous phase, the weight of the hydrogel, and the volume of solution used. Metal absorption increased when pH, salt concentration in external solution and itaconic acid content is levelled.

The swelling isotherms which consisted of an initial fast increase levelled off asymptotically to the equilibrium swelling limit. The experimental data clearly suggest that our hydrogels follow a second-order kinetics for both cases (unload and metal loaded). The kinetics rate constant and the equilibrium water content, K, have been calculated for every monomer ratio from the experimental data according to the kinetics equation. Both magnitudes decreased as the itaconic acid content decreases in the xerogels.     

阴离子交换离子色谱法测定乳酸催化制备的丙烯酸

通过乳酸催化脱水制备丙烯酸具有良好的应用前景。为了对其中的催化过程进行有效、及时的监控,建立了一种同时测定乳酸及丙烯酸的阴离子交换色谱法(AEC)。选择Metrohm A Supp 5阴离子交换柱(150 mm×4.0 mm),以2 mmol/L Na2CO3+2 mmol/L NaHCO3混合水溶液为流动相,采用化学抑制电导检测技术,乳酸和丙烯酸在6 min内即可实现完全分离。乳酸和丙烯酸工作曲线的线性范围分别为0.1～500 mg/L和0.1～200 mg/L,检出限分别为0.030 mg/L和0.035 mg/L,加标回收率分别为100.7%～106%和99.6%～103%,相对标准偏差分别为2.16%~2.49%和2.42%~2.48%。该方法准确、快速、灵敏、重现性好。