2,3-二甲氧基-1,3-丁二烯的合成研究

选用新型催化剂及溶剂体系,通过相转移催化法在低温下合成了2,3-二甲氧基-1,3-丁二烯,采用减压蒸馏和柱层析的分离方法提高了产品纯度,通过在反应前引入吩噻嗪阻聚剂有效防止了产物聚合。实验表明:反应以十六烷基三甲基溴化铵作催化剂,v(2,3-丁二酮)∶v(原甲酸甲酯)=1∶3.5,并且在溶剂CH2Cl2中回流10h时,总收率达到77%。与文献相比,反应条件更温和,收率更高。     

乙醇法制备1,3-丁二烯的研究进展

丁二烯是重要的有机化工原料,是合成橡胶的重要单体,采用乙醇合成丁二烯意义重大。介绍了乙醇制备1,3-丁二烯的生产方法,对其催化剂的研究状况进行了论述,并介绍了可能的反应机理。最后对当前乙醇法制备丁二烯过程存在的问题进行了总结,提出了可行的研究方向,并对其应用前景进行了展望。     

ZrO2/SiO2催化乙醇乙醛制备1,3-丁二烯

采用干混法、浸渍法、溶胶凝胶法3种制备方法制备ZrO₂/SiO₂,在固定床微型反应器中进行催化剂的活性评价。通过溶胶凝胶法制备的ZrO₂/SiO₂对丁二烯选择性最高,达到64.77%。采用氨气程序升温脱附(NH₃-TPD)、X射线衍射(XRD)、透射电镜(TEM)等手段对催化剂表面酸性以及表面结构进行了表征,结果表明锆在二氧化硅表面均匀分布有利于乙醇乙醛转化率以及对1,3-丁二烯选择性的提高,同时1,3-丁二烯的生成需要合适的酸性位。以溶胶凝胶法制备的ZrO₂/SiO₂为催化剂,对其制备条件进行了优化,得出最佳制备条件为焙烧温度650℃、硝酸浓度2mol/L、混合温度30℃。     

环氧化液体丁二烯-苯乙烯共聚物的制备

采用阴离子聚合制备了线型和星型液体丁二烯-苯乙烯嵌段共聚物(LBSC)、含渐变段共聚物和无规共聚物。采用甲酸-H_2O_2原位法对上述LBSC进行了环氧化反应。考察了H_2O_2用量、环氧化反应时间和温度、相对分子质量、苯乙烯含量和序列结构等对LBSC环氧化反应的影响;研究了环氧化液体丁苯共聚物(ELBSC)偶联剂对聚丁二烯活性链末端偶联反应的影响。结果表明:控制H_2O_2用量可以得到环氧值可控的ELBSC,当H_2O_2与丁苯共聚物中聚丁二烯双键的摩尔比为0.6,反应时间在120 min,温度在50℃时可达到最大环氧值;随着ELBSC用量的增加,偶联效率逐渐增大,相对臂数逐渐减小,在环氧基团与锂的摩尔比为1.0时偶联效率最大。     

1,3-丙二醇分批发酵动力学模型

在分批发酵中，研究了Klebsiella pneumoniae的生长、底物甘油消耗及1,3-丙二醇的产生特性. 基于Logistic方程和Luedeking-Piret方程，得到了描述1,3-丙二醇分批发酵过程的动力学模型及模型参数，该组模型能很好地拟合发酵过程，并在初始甘油浓度变化较大的范围内表现出很好的适用性. 同时，所建立的模型也基本反映了Klebsiella pneumoniae分批发酵过程的动力学特征. 基于分批发酵动力学模型，提出了以甘油为单一碳源时的底物流加策略，通过与其他流加策略条件下的发酵对比实验表明，通过基于动力学模型的流加策略可获得更高的1,3-丙二醇浓度及生产强度.     

负载钛催化丁二烯-异戊二烯共聚合反应动力学的研究

研究了TiCl4 /MgCl2 负载型高效催化剂催化丁二烯 -异戊二烯共聚合的动力学特征 ,并对影响聚合速率的因素进行了考察。首先通过计算排除了扩散控制对反应总聚合速率的影响 ,测定了单体浓度和催化剂浓度的反应级数和表观活化能 (2 2 .8kJ/mol) ,建立的聚合速率方程为 :R =kp·f·[Ti]·[M]。     

铋钼催化剂上丁烯氧化脱氢制丁二烯的本征动力学

采用水热法制备了Bi2MoO6纳米片催化剂、共沉淀法制备了BiMoV0.15催化剂,在固定床反应器中研究了两种催化剂上丁烯氧化脱氢制丁二烯的本征动力学.采用幂函数模型对不同条件下测得的动力学数据进行了拟合,建立了本征动力学模型,并得到了活化能和反应级数等相关参数.结果表明:由于不同的反应温度区间拥有不同的速率控制步骤,...     

二乙烯基苯-丁二烯-苯乙烯负离子聚合动力学行为

用气相色谱法对正丁基锂为引发剂、环已烷为溶剂、ＴＦ为极性调节剂的二乙烯基苯－丁二烯－苯乙烯负离子聚合动力学进行了研究,求得了体系内各单体表观增长反应速率常数（ｋｐ＂）。结果表明,各单体ｋｐ＂的大小依次为：ｐ－ＤＢＶ,ｍ－ＤＢＶ,Ｂｄ,Ｓｔ,ｍ－ＥＶｇ,ｍ－ＥＶＢ,ｐ－ＥＶｂ。     

丁二烯在氧气中的氧化反应特性及产物

采用小型密闭压力容器试验(MCPVT)装置,考察丁二烯的氧化特性,用碘量法测定氧化过程的过氧化值,探讨丁二烯的初期可能氧化反应生成,用顶空(进样)-气相色谱-质谱联用(HS-GC-MS)技术测定反应产物。结果表明,在氮气氛围中,即使到达105℃也未检测到丁二烯发生反应,在氧气氛围中,45℃下能测定过氧化物生成,65℃反应26 h,过氧化值达到9.1 mmol/kg。在70～100℃下,MCPVT能观察到显著的化学反应产生,压力减少。丁二烯在氧气中的反应是复杂的,主要产物有丙烯醛、呋喃、2,5二氢呋喃、2,3二氢呋喃、反式1,2-二乙烯基环丁烷、4-乙烯基环己烯、1,5-环辛二烯等。     

A kinetic model of the cycloaddition reactions between cyclopentadiene and 1,3-butadiene for synthesis of 5-vinyl-2-norbornene

Under high temperature and pressure, a continuous tubular reactor was successfully utilized to investigate the kinetics of 5-vinyl-2-norbornene (VNB) production. The process involved multiple cycloaddition reactions between cyclopentadiene (CPD) and 1,3-butadiene (BD). The results, spanning a wide range of operating conditions, indicate that higher temperature (180°C) and proper residence time (72 min) were conducive to efficient synthesis of VNB. The apparent kinetic parameters, including activation energies and pre-exponential factors, were acquired by fitting experimental data under integral operating conditions. The kinetic model was proven effective from a practical point of view in predicting the concentration changes of each product in the range 140 to 180°C and 30 to 80 wt.% concentration. This work provides a solid basis for the optimization of the VNB synthesis process.     

Experimental study of the structure of a rich premixed 1,3-butadiene/CH4/O2/Ar flame

The structure of a laminar rich premixed 1,3-butadiene/CH₄/O₂/Ar flame has been investigated, 1,3-butadiene, methane, oxygen, and argon mole fractions being 0.033, 0.2073, 0.3315, and 0.4280, respectively, for an equivalence ratio of 1.80. The flame has been stabilized on a burner at a pressure of 6.7 kPa. The concentration profiles of stable species have been measured by gas chromatography after sampling with a quartz probe. The quantified species include carbon monoxide and dioxide, methane, oxygen, hydrogen, ethane, ethylene, acetylene, propyne, allene, propene, cyclopropane, 1,3-butadiene, butenes, 1-butyne, vinylacetylene, diacetylene, C₅ compounds, benzene, and toluene. The temperature distribution in the flame has also been measured. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 6, pp. 89–95, November–December, 2006.     

A novel microfabricated Pd/SiO2 model catalyst for the hydrogenation of 1,3-butadiene

The hydrogenation of 1,3-butadiene was successfully demonstrated using a microfabricated catalyst. The reaction was carried out at atmospheric pressure and 100°C with a hydrogen to hydrocarbon ratio of 125. Data from a thin film Pd/silica catalyst is also presented for comparison. The conversion for the microfabricated catalyst is more stable and slightly lower than that for the thin film catalyst; however, the geometric surface area of the thin film catalyst is 7.5 times greater than that of the microfabricated catalyst. The selectivity of the reaction products is greatly different between the two catalysts. The microfabricated catalyst has a much lower selectivity for 1-butene and favors the 2-butenes more so than does the thin film catalyst.     

Polymerization of 1,3-butadiene with MgCl2-supported cobalt catalysts activated by ordinary alkylaluminums

MgCl₂-supported CoBr₂ catalysts were prepared from mixture of MgCl₂ and CoBr₂L₂ (L = triphenylphosphine or pyridine) in toluene. Polymerization of 1,3-butadiene was conducted over the catalysts combined with ordinary alkylaluminums as cocatalyst. The CoBr₂(PPh₃)₂/MgCl₂ catalyst gave polybutadiene with approximately 80% of 1,2 units, whereas cis-1,4-poly-butadiene was obtained with the CoBr₂(C₅H₅N)₂/MgCl₂ catalyst. Addition of triphenylphospine to the latter catalyst caused a marked increase in the content of 1,2 units. The content of 1,2 units could be thus controlled in the range from 0 to 80% by changing the amount of triphenylphosphine. On the other hand, the CoBr₂(PPh₃)₂/MgCl₂ catalyst with very low content of CoBr₂(PPh₃)₂ hardly displayed any activity. Addition of dimethoxydiphenylsilane to the catalyst gave polybutadiene containing 90 % of 1,2 units with a fairly high activity.     

Selectivity controlling in the hydrogenation of 1,3-butadiene on Tl-modified Pd catalyst

The selectivity and reactivity in the hydrogenation of 1,3-butadiene catalyzed by Tl-modified 5 wt% Pd/Al₂O₃ catalysts vary with amounts of Tl loading and with the reduction temperatures, that is, the main product was 1-butene and trans-2-butene for values of Tl loading of 0.5 and 2 in Tl/Pd atomic ratio, respectively, when the catalysts were reduced at 673 K. 1,3-butadiene was hydrogenated selectively towards 1-butene and trans-2-butene when the Tl modified 5 wt% Pd/Al₂O₃ catalyst of Tl/Pd = 2 was reduced at 300 and 373 K or above, respectively. On the catalyst with Tl/Pd = 2 reduced at 373 K or above, the butenes formed are not hydrogenated to butane, even after a long reaction time. These results suggest the formation of Pd-Tl alloy or intermetallic compounds during the reduction procedure which is responsible for the selectivity controlling in the reaction. TPR and XRD results were in consistence with the reaction data.     

六氟丁二烯的合成方法研究综述

六氟丁二烯是一种优异的蚀刻气体,应用前景广阔。介绍了六氟丁二烯的性质和应用,根据不同的制备关键中间体对其合成方法进行了分类评析,指出了各种制备方法的优缺点。综合各方法的特点,指出了今后制备六氟丁二烯的方向。     

Synthesis of poly(2,3-dimethyl-1,3-butadiene) and its hydrogenation using a metallocene/n-butyllithium catalyst system

Poly(2,3-Dimethyl-1,3-butadiene) (PDMB) with varying contents of 1,4-and 1,2-structures has been anionically synthesized using either n-butyllithium or sec-butyllithium as an initiator. The addition of tetrahydrofuran could enhance the rate of synthesis and effect the microstructure. The T_m was higher for PDMB with a lower content of 1,2-structure, and the T_g was lower. This PDMB was then hydrogenated with a nickelocene/n-butyllithium catalyst system leading to the formation of HPDMB. The trans 1,4-structure unit was more difficult to hydrogenate due to its steric hindrance. Repetitive hydrogenation was necessary in order to achieve a high degree of hydrogenation. The hydrogenated PDMB is an amorphous elastomeric material. The T_g’s were found to decrease with an increase in the degree of hydrogenation, concurrent with a gradual disappearance of the T_m’s. Since a HPDMS with a low content of 1,2-structure resembles a head-to-head polypropylene, our data suggest that the T_g of an atactic head-to-head polypropylene lie between −30 and −35 °C.     

Sizeable deactivation effect for the 1,3-butadiene hydrogenation on vapor-deposited Pd aggregates on graphite

The catalytic activity of Pd aggregates vapor-deposited on graphite has been measured in the 1,3-butadiene hydrogenation. It is generally decreasing with particle size. But, such a decrease is largely depending upon the hydrogen and the hydrocarbon pressure. Indeed, with low hydrocarbon pressure (about 1 Torr) and in presence of large excess of hydrogen (P h ₂/P c ₄ h ₆=100) the activity of the smaller aggregates is comparable to that of larger particles. The different behaviour is consequently attributed to a size dependent deactivation. Such a deactivation could be due to carbon deposits generated by dehydrogenation of the diene admolecules. This behaviour is tentatively related with marked differences observed by XPS on the smaller aggregates, both with respect to the core level energies and to the density of states into the valence band.     

Oxidation reaction kinetics of Athabasca bitumen

The oxidation reaction kinetics of bitumen from Athabasca oil sands have been investigated in a flow-through fixed bed reactor using gas mixtures of various compositions. The system was modelled as an isothermal integral plug-flow reactor. The oxidation of bitumen was found to be first order with respect to oxygen concentration. Two models were examined to describe the kinetics of bitumen oxidation. In the first, the Athabasca bitumen is considered to be a single reactant and the oxidation reaction a single irreversible reaction. The activation energy for the overall reaction was found to be 80 kJ mol^?1. This model is limited to calculating the overall conversion of oxygen. Because the fraction of oxygen reacting to form carbon monoxide and carbon dioxide increases with temperature, a more sophisticated model was proposed to take this into account. The second model assumes that the bitumen is a single reactant and that the oxidation of bitumen may be described by two simultaneous, parallel reactions, one producing oxygenated hydrocarbons and water, the other producing CO and CO₂. The activation energy for the first reaction was found to be 67 kJ mol^?1, and for the second, 145 kJ mol^?1. This more sophisticated model explains the result that at higher temperatures more oxygen is consumed in the oxidation of carbon, because this reaction has a higher activation energy than the reaction leading to the production of oxygenated hydrocarbons and water. This model can also predict the composition of the product gases at various reaction conditions.