甘油氢解Cu/Cr催化剂制备方法对性能的影响

Cu/Cr催化剂由于Cu对C—C键氢解活性很低,对C—O键氢解活性很高而成为甘油氢解制1,2-丙二醇效果最好的固体催化剂。采用5种方法制备了Cu/Cr催化剂,并用于甘油的催化氢解反应,发现Cu/Cr催化剂的制备方式极大地影响着其对甘油的催化氢解性能。以5种方法制备的Cu/Cr催化剂中,对甘油的催化氢解性能依次是:铜氨络合沉淀法Adkins法碳酸钠沉淀法硅藻土浸渍法干混法。运用XRD、TG、BET、FTIR、TPR等表征手段对制备的催化剂结构进行了表征,详细分析了不同方式制备的催化剂的结构差异,将催化剂的结构表征结果与催化反应性能进行关联分析和讨论,并从理论上解释了催化剂结构差异和催化氢解性能的关系。     

催化加氢

1、催化加氢的含意是什么? 气态氢在催化剂存在下与有机化合物进行加成或还原反应,生成新的有机化合物统称为催化加氢。它一般包含两个内容,即氢化与氢解。化合物与氢反应只拆开π键的称为氢化。如烯烃与氢反应生成相应的烷烃。在反应中拆散σ键的称为氢解。例如硝基化合物与氢反应生成相应的氨基化合物。     

加氢脱氮反应研究进展

介绍了油品加氢脱氮反应机理;详细综述了非杂环类化合物、碱性杂环化合物、非碱性杂环化合物等含氮化合物的加氢脱氮反应网络;还从活性组分、载体的改性、助剂的选择等加氢脱氮催化剂改性途径方面作了论述.     

ZrO2纳米颗粒催化借氢反应研究

以醇为烷基化试剂，与羰基化合物反应实现羰基α位烷基化的C-烷基化反应，或者与胺反应实现胺基烷基化的N-烷基化反应是一锅多步串联的借氢反应。这种绿色的借氢反应近年来得到广泛关注，但目前报道的该反应的催化剂均为贵金属基催化剂，开发廉价的非贵金属多相催化剂对于此类借氢反应的工业化应用具有重要意义。采用廉价易得的ZrO₂纳米颗粒催化剂催化这两种类型的借氢反应，构建的C—N键形成借氢反应产率高达97.5%,C—C键形成借氢反应产率92.1%。初步研究结果表明，金属氧化物纳米颗粒ZrO₂具有优良的催化借氢反应能力。同时ZrO₂纳米颗粒表现出较大的底物适用性和很高的稳定性，在重复使用五次后催化活性损失不大。     

钯催化卤代芳烃氨解反应的研究进展

钯催化卤代芳烃进行氨解反应是构建C-N键的重要方法,由于该方法所需的催化剂量少、反应条件温和、应用范围广和操作简单,因而被广泛应用于芳香胺类化合物的制备与生产。本文对该反应机理进行了简介,对近年来钯催化卤代芳烃与氨、伯胺、仲胺和其他含氮化合物的氨解反应研究进展进行了综述。指出迄今为止高活性和高选择性的催化剂依然有限,氨作为氨解剂和低廉的氯代芳烃作为氨解底物的使用都还不够广泛。寻找新的配体、设计新的催化体系、提高反应选择性和改善反应对敏感官能团的容忍性,是钯催化卤代芳烃氨解反应领域未来的发展方向。另外,仔细研究反应机理将会加深对反应的理解。     

有机含氮化合物对深度加氢脱硫反应的影响

从燃料油中含氮化合物和含硫化合物特点出发,介绍了含氮化合物对加氢脱硫（HDS）催化剂活性、选择性以及失活等性能的影响。研究表明,含氮化合物主要通过与含硫化合物在催化剂表面的竞争吸附,强烈抑制HDS催化剂活性。含氮化合物对含硫化合物加氢（HYD）和氢解（HYG）两条并行反应路径均有抑制作用,但对HYD反应路径的抑制作用更为强烈。含氮化合物还能通过毒化催化剂酸中心进而影响催化剂HDS活性和选择性,而其在催化剂表面的强烈吸附也是引发催化剂结焦和失活的重要因素。     

异丙醇在催化转移氢化反应中的应用

催化转移氢化反应在有机合成中具有重要的应用价值。异丙醇作为有机氢源应用于催化转移氢化反应,包括有机物中含碳不饱和键的还原,含氮、硫不饱和键的还原和无机盐中不饱和键的还原等。综述了各个不同类型的催化转移氢化反应的反应式,并列出了反应的催化剂,最后对异丙醇在催化氢转移中的应用前景进行展望。     

生物催化C—N成键反应合成手性胺的研究进展

生物催化C—N键的成键反应主要是用于合成手性胺类化合物,它广泛应用于食品、精细化学品和药物中间体的制备过程中。酶法生产手性胺具有高对映体选择性、转化率和时空产率的特点。主要介绍了C—N键成键的三种方式,分别为还原胺化反应、氢胺化反应和转氨化反应。并根据不同的反应类型对相关的酶进行了归纳总结。     

IB和IIB族金属催化氢胺化反应的研究进展

氢胺化反应是将氮氢键直接加成到碳碳不饱和键上的原子经济性反应，是一种合成胺类化合物的重要路径，在合成含氮化合物方面具有重要意义。本文首先介绍了氢胺化反应的机理，从活化胺类和活化不饱和烃类两个氢胺化反应机理的视角，详细阐述了IB族中的Au、Ag、Cu和IIB族中的Zn 4种金属在氢胺化反应过程中活化底物的方式，并指出了IB和IIB两族金属在氢胺化反应的热催化体系中存在的优缺点，在均相体系中反应温度较低，但操作步骤繁琐，催化剂不能循环利用，而在多相体系中可以实现催化剂的循环利用，但又面临着反应温度高的问题，因此开发温和条件下高效绿色的催化体系显得至关重要。此外，对光催化技术在氢胺化反应中的应用前景进行了展望，而非贵金属利用可见光在温和条件下实现高效催化氢胺化反应是未来的一个重要发展方向。     

加氢脱氮催化剂及反应机理研究进展

介绍了各馏分油品中含氮化合物的分布规律和特点,概述了加氢脱氮反应过程中含氮化合物进行加氢和C-N键断裂的反应机理及典型含氮化合物的反应网络;总结了传统加氢脱氮催化剂及其载体的制备、改性和调变方法,论述了新型金属碳化物、氮化物、磷化物催化剂的结构特性及各类催化剂的加氢脱氮反应性能.关联了催化剂的物理化学性质对加氢脱氮反应的影响,提出了高活性加氢脱氮催化剂的研制思路和途径.     

A multi-functional Ru Mo bimetallic catalyst for ultra-efficient C3 alcohols production from liquid phase hydrogenolysis of glycerol

Ru and Mo bimetallic catalysts supported on active carbon modified by phosphotungstic acid (PW) were designed and applied in glycerol hydrogenolysis reaction. The physicochemical properties of the catalysts were characterized and the presence of active sites was investigated from the perspective of the glycerol hydrogenolysis performance. The MoO_x is highly selective for the C—O bond cleavage of glycerol molecules, which can reasonably regulate the strong C—C bond cleavage activity of Ru nanoparticles. By using sequential deposition of Ru and Mo supported on mesoporous PW-C, the characterization results show that the combination of isolated low-valence MoO_x with metal Ru particles can form “MoO_x-Ru-PW”, which provides highly catalytic activity toward C—O bond cleavage, selectively producing more C3 alcohols (mainly 1,2(3)-propanediol). The glycerol conversion of 1% Mo/Ru/PW-C catalyst was 59.6%, the selectivity of C3 alcohol was 96.1%, and the selectivity of propanediol (1,2(3)-propanediol) was 94.9%. It is noteworthy that the selectivity of 1,3-propanediol reached 20.7% when the PW was 21.07% (mass). This study provides experimental evidence for the tandem dehydration and hydrogenation mechanism of the multifunctional Mo/Ru/PW-C catalyst.     

噻吩和苯并噻吩在原位氢存在下的还原脱硫

研究了噻吩和苯并噻吩在原位氢和硼化镍存在下的还原脱硫。实验对操作条件进行了优化;研究了可能的反应机理。结果表明,六水合氯化镍与还原剂于质子溶剂中反应的对硫化物脱硫,产生的原位氢脱硫活性较高;还原剂用量为0.64 g时,脱硫率可达99%以上。噻吩和苯并噻吩脱硫主要发生直接氢解反应;少量苯并噻吩脱硫经由加氢途径进行,硫化物主要通过S原子"端连吸附"在硼化镍表面。推测反应机理为,反应中大量原位氢吸附在硼化镍表面并活化;硼化镍中富电子镍介入硫化物分子中C—S键形成加合物,与活性原位氢进一步作用,使C—S和C—C键断裂。     

A selectivity study of 2,4-pentanediol hydrogenolysis combining experiments and computer simulation

In the current work, the process of 2,4-PD hydrogenolysis is studied in a combined effort of experiments and computer simulation, to understand the mechanism and factors controlling the C-C vs. C-O bond cleavage selectivity of this process. It is expected that the results from this study will be useful in control of the selectivity of sugar hydrogenolysis, as the bond cleavage mechanism in sugar hydrogenolysis is the same as in 2,4-pentanediol hydrogenolysis. In this capacity, the effects of reaction conditions, including temperature, base concentration, hydrogen pressure, catalyst amount and catalyst type, on the C-C vs. C-O bond cleavage selectivity of 2,4-pentanediol hydrogenolysis are investigated both experimentally and via simulation. The simulation study strengthens the experimental investigation in several aspects. It allows the process to be explored in a larger range of reaction conditions, the mechanism and factors controlling the selectivity to be understood at a deeper level, and the features of catalysts critical to improving the selectivity to be identified. However, the experimental data are useful in providing a baseline for the simulation results to be compared.     

四乙酰基二硝基六氮杂异伍兹烷分子结构研究

四乙酰基二硝基六氮杂异伍兹烷(TADNIW)是合成六硝基六氮杂异伍兹烷(HNIW)的中间体。该文用Gaussian 98软件包,采用密度泛函理论B3LYP和标准基组6-31G对所选构型进行了全优化计算,在结构上对TADNIW的键长、键角、二面角、Mu lliken电荷及集居数进行了理论分析,发现笼形化合物的六元环成船式构象,硝基处于桥头,骨架以亚稳态存在。结构分析表明,六元环上N—NO2键相对较稳定,采用一般的硝解条件反应不能进行,作者提出了新的反应机理,即水解-硝化假设:含有酰胺基团的一类化合物在含水的硝化介质中首先发生水解生成相应的仲胺,碱性较强的仲胺再在氮硝化催化剂的作用下,迅速硝化成硝胺。计算得到TADNIW分子总能量为-1 583.375 682 a.u.,前线轨道能量差ΔE(ELUMO-EHOMO)为4.123 eV。计算IR谱图与实验IR谱图对比,误差小于20 cm-1。     

苯酚-尿素-乙二醛树脂的合成工艺研究

为从根本上消除木材胶合制品的甲醛释放对环境和人体健康的危害及改善尿素-乙二醛(UG)树脂的性能,选择无毒、低挥发的乙二醛代替甲醛,与尿素、苯酚反应制备苯酚-尿素-乙二醛(PUG)共缩聚树脂木材胶黏剂。研究了在反应的不同阶段加入苯酚以及苯酚的加入量对树脂性能的影响,并通过傅里叶变换红外光谱法(FTIR)对树脂的结构进行了表征。结果表明:在所研究的合成条件下,PUG树脂的pH和状态受苯酚加入量和加入时间的影响不大,苯酚的加入量为尿素总量的10%为宜;树脂中主要含有氮氢(N—H)、氧氢(O—H)、羰基(C=O)、饱和碳氢(C—H)、醚键(C—O—C)及碳氮(C—N)键等主要官能团。     

Inhibition of nitrogen compounds on the hydrodesulfurization of substituted dibenzothiophenes in light cycle oil

The influence of nitrogen compounds on the hydrodesulfurization (HDS) activities of a series of substituted dibenzothiophenes in light cycle oil (LCO) was studied over a NiMo/Al₂O₃ commercial catalyst. Three types of light cycle oil with nitrogen compounds of different concentrations and chemical natures were used as feed—an original fluid catalytic cracking light cycle oil (LCO), LCO with most of its basic nitrogen removed, and an ultra-low nitrogen LCO. Experiments were conducted in a fixed-bed microreactor at a total pressure of 70 atm, temperatures between 330 and 400 °C, and liquid hourly space velocities (LHSV) in the range of 1.0 to 3.5 h⁻¹. The inhibition effects of nitrogen compounds on the HDS reactivity of the three sulfur groups—total sulfur, hard sulfur, easy sulfur—and 14 specific mono-, di- and tri-alkyl substituted dibenzothiophenes were investigated. The results showed that the HDS rate significantly increased using ultra-low nitrogen LCO. Pseudo first-order rate constants were estimated for the 14 mono-, di- and tri-alkyl substituted dibenzothiophenes. The HDS rates could be classified into three groups based on the position of the substituents. It was found that 4 and 6 substituted dibenzothiophenes had the lowest HDS rates. The HDS rate of the 14 substituted dibenzothiophenes were all increased when the ultra-low nitrogen feed was used. The improvement was greater for 4 and 6 substituted dibenzothiophenes than for those with one of the substituents at either the 4 or 6 positions. This finding indicates that the hydrogenation route is more strongly suppressed than hydrogenolysis route by nitrogen compounds since the hydrogenation route is believed to be the predominant reaction pathway for 4 and 6 alkyl-substituted dibenzothiophenes.     

Synthesis and pyrolysis of Ti‐containing precursors for advanced Si/C/N/Ti‐based ceramics

A new kind of polytitanosilazane (PTSZ) precursor for Si/C/N/Ti‐based ceramic was synthesized from the condensation reaction of silazane lithium salts and titanium tetrachloride (TiCl₄). Titanium in the precursors was bonded to silazane compounds in the Si—N—Ti bond. The obtained PTSZs were characterized by Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), and elemental analyses. The PTSZs were pyrolyzed at 900 to 1300°C under nitrogen, argon, and ammonia atmosphere, respectively, to give amorphous inorganic products. The results indicated that ceramic yields of PTSZs were much higher than that of their corresponding silazane oligomers and ceramic yields increased with the increase in Ti content in PTSZs. Precursors containing reactive vinyl groups gave higher pyrolytic yields. The pyrolytic yield under ammonia is lower than that under nitrogen and argon. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2733–2739, 2004     

环己烷绿色氧化合成环己醇/环己酮(KA油)催化剂及机理研究进展

环己烷绿色氧化合成环己醇/酮(KA油)一直是饱和C—H氧化领域的研究热点。本文综述了近十年来过氧化氢环己烷氧化和分子氧液相环己烷氧化的催化研究情况,指出过氧化氢环己烷氧化反应虽然条件温和、环己烷转化率和KA油选择性高,但活性较高的反应体系一般为包含昂贵配合物、酸、溶剂和氧化剂的复杂均相体系,不利于产物和催化剂分离,同时过氧化氢利用率较低,氧化剂成本高。液相分子氧环己烷氧化采用多相催化剂,操作简单,其中金和纳米氧化物有望成为潜在的工业催化剂。对环己烷氧化机理成果进行分析,指出除了金属卟啉的氧异裂非自由基机理,环己烷氧化按自由基机理进行,为自催化反应,但催化剂可促进活性自由基产生,活化C—H键,提高反应速率。最后指出开发有潜力的环己烷氧化多相催化剂和探索反应机理是今后的研究方向。     

生物基1,6-己二醇的研究进展

传统的以石油化工产品为原料的石化基1,6-己二醇(1,6-HDO)的生产存在能耗高、反应产物分离困难、污染环境等缺点,以5-羟甲基糠醛(5-HMF)为原料制备生物基1,6-HDO可以克服这些缺点。本文介绍了国内外制备生物基1,6-HDO的研究进展,总结并讨论了由5-HMF制备1,6-HDO的不同反应路径,并从反应物吸附、金属粒径、活性组分协同作用、载体等角度对比了不同催化剂体系及其催化机理,探讨了各种催化剂促进C=O加氢、呋喃环C=C加氢、呋喃环C—O氢解开环反应,抑制呋喃环、呋喃环侧链C—C氢解断裂反应的性能。与多步法相比,一步法制备1,6-HDO的反应步骤简单,但1,6-HDO的产率相对较低,因此开发高效的催化剂体系和反应工艺将是今后研究的重点。