非晶态Ni-Mo-P催化剂上硝基苯加氢为苯胺及催化剂失活机理

引言苯胺是一种重要的有机中间体,广泛应用于聚氨酯、橡胶助剂和医药等领域[1-3]。硝基苯催化加氢法合成苯胺是目前应用较为广泛的工艺之一。其生产方法主要有硝基苯Fe粉还原法、苯酚氨碱法和硝基苯催化加氢法[4],其中,硝基苯催化加氢法     

碱性矿物水镁石催化臭氧化—机理与应用

文章系统综述了碱性矿物水镁石及其煅烧产物在臭氧化净水中的应用及其机理。以活性艳红染料、硝基苯、苯胺、苯酚为例,分别研究了水镁石煅烧前后对不同类型的有机污染物的催化臭氧化降解效果。文章在前文实验的基础上,提出了水镁石煅烧前后的不同催化机理,进一步发展了臭氧化催化理论,为碱性矿物水镁石及其煅烧产物的利用提供了理论上的指导。     

染料颜料中间体发展重点

业界分析 ,我国染料颜料中间体今后的工作重点为 :1 )现有品种合成新工艺、新技术的运用。亟待采用的主要新工艺如下 :硝基苯加氢转位生产对氨基苯酚 ;邻硝基氯苯催化加氢生产 3 ,3 二氯联苯胺 ;溶剂法生产 2 ,3酸 ;间二异丙基苯氧化分解生产间苯二酚 ;间苯二酚胺化生产间氨基苯酚 ;间氨基苯酚烷基化合成间羟基 Ｎ ,Ｎ 二乙基苯胺 ;苯胺直接磺化合成邻氨基苯磺酸 ;苯胺与对硝基氯苯直接缩合法生产 4 硝基二苯胺 ,再经加氢还原生产ＲＴ培司 ;采用三氧化硫磺化、溶剂氧化及加氢还原等先进的单元反应技术生产ＤＳＤ酸 ;色酚ＡＳ系列产品催化…     

高度氧化法的特性及其在废水处理中的应用

论述了新兴化学氧化法－－高度氧化法（ＡＰＯ法）的氧化能力、反应选择性和氧化效率,并以苯酚和２,４－二氯苯酚为目标污染物进行了试验。结果表明：ＡＰＯ法比普通化学氧化法氧化效率高,无反应选择性,反应彻底,是一种处理含难降解有机污染物废水的高争化方法,值得推广。     

酸性中心对复合氧化物催化苯酚羟基化反应的影响

铁基复合氧化物催化苯酚羟基化反应具有明显的诱导期,适当引入酸性中心,在氧化还原活性位的共同存在下,可以迅速缩短羟基化反应的诱导期;酸性中心弱或没有采用酸改性的复合氧化物催化剂,对苯酚羟基化反应催化作用活性低,催化剂用量大,反应诱导期不稳定。乙酸、乙酸酐等有机弱酸可以直接加入羟基化反应体系。对复合氧化物催化剂进行后处理改性,引入适当的酸性中心,有助于提高催化剂的活性,缩短甚至消除羟基化反应诱导期,避免由于未反应过氧化氢的积累增加反应器运行的风险,提高过氧化氢有效利用率和目标产物选择性。将5.3g苯酚、0.051g催化剂、过氧化氢与苯酚的物质的量比为0.33,在65℃下,于10.6g溶剂水中反应,时间为30min,反应诱导期仅5min,苯酚转化率达21.2%,苯二酚选择性为92.9%,过氧化氢有效利用率为59.6%。分析了直接加入酸性中心和对复合氧化物催化剂进行酸改性所带来的问题,推测了苯酚羟基化反应的机理。     

超临界水氧化含芳香族有机物废水的研究

利用自行建立的管式平推流反应装置,对含苯酚或含硝基苯的不同废水的超临界水氧化反应进行了研究。考察了温度、停留时间对二者氧化效率的影响,实验结果表明,硝基苯比苯酚要稳定得多,此外还对苯酚进行了反应动力学研究,得到了苯酚消失速率方程,并与文献报导结果进行了比较。     

铁掺杂PbO2/Ti电极电催化氧化苯酚的实验研究

以苯酚为目标化合物,研究了新型铁掺杂PbO2/Ti阳极电催化氧化有机污染物的特性,结果表明,该电极对苯酚的降解显示了良好的电催化活性,有较好的环保应用前景。同时,初步探讨了反应的动力学和氧化机理。     

苯胺-硝基苯联合分离技术

<正>一、项目简介苯胺是重要的化工原料,主要用于医药和橡胶硫化促进剂,也是制造树脂和涂料的原料。本技术适合于由硝基苯经活性铜催化氢化制备和氯苯及氨在高温和氧化铜催化剂存在下反应得到的苯胺粗液的分离与提纯。本技术分硝基苯的精制和苯胺精制两大部分。分别采用三塔连续精馏技术,反应粗液经初馏、精制和汽提后得到纯度很高的硝基苯和苯胺产品。     

臭氧/分子筛氧化降解水中微量的硝基苯

本文以硝基苯为目标反应物,对臭氧／分子筛氧化和臭氧氧化去除水中微量有机污染物的效果进行了比较。发现与单独的臭氧氧化相比,臭氧／分子筛氧化工艺可以提高水中硝基苯的降解效果。在本次实验条件下,单独臭氧氧化和臭氧／分子筛氧化对硝基苯的去除率都随着温度的升高而增加,随着pH值的升高越来越大;此外还考察了分子筛对硝基苯去除率的影响,初步分析了分子筛在臭氧氧化过程中的作用。     

关于二氟马来酸苯胺盐的合成试验研究

了解二氟马来酸苯胺盐的合成试验,首选需要对五氟苯酚进行氧化,把五氟苯酚在过氧乙酸中进行充分氧化,然后在苯胺的作用下,就能得到二氟马来酸苯胺盐,总收率在40%。本文主要阐述了合成二氟马来酸苯胺盐的原料配比、反应的时间以及温度对产物收率的影响等。     

难降解芳烃化合物在超临界水中氧化的COD去除率的研究

Some aromatic compounds, phenol, aniline and nitrobenzene, were oxidized in supercritical water. It was experimentally found that the chemical oxygen demand (COD) removal efficiency of these organic compounds can achieve a high level more than 90% in a short residence time at temperatures high enough. As temperature, pressure and residence time increase, the COD removal efficiencies of the organic compounds would all increase. It is also found that temperature and residence time offer greater influences on the oxidation process than pressure. The difficulty in oxidizing these three compounds is in the order of nitrobenzene > aniline > phenol. In addition, it is extremely difficult to oxidize aniline and nitrobenzene to CO2 and H2O at the temperature lower than 873.15 K and 923.15 K, respectively. Only at the temperature higher than 873.15 K and 923.15 K, respectively, the COD removal efficiencies of 90% of aniline and nitrobenzene can be achieved.     

Promotion of the electrochemical hydrogenation of nitrobenzene at hydrogen storage alloys studied using a solid electrolyte method

The electrocatalytic properties of an AB₅-type hydrogen storage alloy towards the electrochemical hydrogenation of unsaturated organic compounds have been studied by a solid electrolyte method using electrochemical hydrogenation of nitrobenzene as a model reaction. Voltammetric studies reveal that the kinetics of the nitrobenzene electro-reduction on the hydrogen storage alloy electrode is similar to that on a Ni electrode. Aniline and p-aminophenol are produced as the reaction products. Compared to the Ni electrode, the production of aniline is considerably promoted on the hydrogen storage alloy electrode. Modifying the alloy surface with a thin layer of Cu enhances the reaction selectivity and current efficiency for aniline formation. Compared to a Cu electrode, the electrochemical hydrogenation of nitrobenzene to aniline is promoted on the Cu-modified alloy electrode. The hydrogenation promotion effect is attributed to the chemical reaction between nitrobenzene and metal hydrides that are electrochemically generated in situ. Hydrogen storage alloys therefore make it possible to intensify the electrochemical hydrogenation process of unsaturated organic compounds.     

Catalyst preparation and deactivation issues for nitrobenzene hydrogenation in a microstructured falling film reactor

Hydrogenation of nitrobenzene to aniline in ethanol was performed continuously in a microstructured falling film reactor at 60 °C, 1–4 bar hydrogen pressure and residence time 9–17 s. Palladium catalyst was deposited as films or particles via sputtering, UV-decomposition of palladium acetate, incipient wetness or impregnation. Deactivation was observed and was particularly pronounced for the sputtered and UV-decomposed catalysts. Catalysts prepared through incipient wetness or impregnation were more stable and activity could be recovered by oxidation at 130 °C. The main causes of deactivation were determined to be deposition of organic compounds and palladium loss.     

Rapid Hydrogenation of Aromatic Nitro Compounds in Supercritical Carbon Dioxide: Mechanistic Implications via Experimental and Theoretical Investigations

An exceptionally rapid hydrogenation of nitrobenzene to aniline [TOF=252,000 h⁻¹] over palladium containing MCM‐41 (Pd/MCM‐41) with excellent yield of >99% can be achieved in supercritical carbon dioxide at 50 °C and a hydrogen pressure of 2.5 MPa. It has been observed that this promising method preferred a single phase between liquid substrate and carbon dioxide‐hydrogen system. The ascendancy of the supercritical carbon dioxide medium is established in comparison with the conventional organic solvent and solvent‐less conditions. Changes in the reaction parameters such as carbon dioxide and hydrogen pressure, temperature and the reaction time do not affect the selectivity. A combined experimental and theoretical study has elucidated the mechanism under the studied reaction condition because experimental observations revealed a direct conversion of nitrobenzene to aniline. However, density functional theory (DFT) calculation shows that the direct conversion is energetically unfavourable; hence, a stepwise mechanism has been proposed. Theoretical predictions and experimental observations suggested that the rate‐limiting step of nitrobenzene conversion is different from that of the liquid phase hydrogenation. This catalytic process can also be successfully extended to the hydrogenation of other aromatic nitro compounds with different substituents. Easy separation of the liquid product from catalyst and the use of an environmentally friendly solvent make this procedure a viable and an attractive green chemical process.     

硝基苯法合成4-氨基二苯胺中间体的研究

以苯胺和硝基苯为原料,在复合催化剂作用下合成了4-氨基二苯胺的中间体。对影响反应的主要因素进行了优化．其最佳工艺条件为：催化剂加入量155g,苯胺与硝基苯的摩尔比6：1,滴加时间120min,保温时间70min,反应温度75℃．硝基苯转化率99％以上,选择性达到96％以上。     

纳米Ni/Fe对水中硝基苯的催化还原特性

采用自制的纳米Ni/Fe对水中硝基苯进行催化还原处理。探讨了硝基苯的还原降解途径,考察了溶液pH、纳米Ni/Fe用量和Ni含量对还原效果的影响。结果表明,纳米Ni/Fe对水中硝基苯的去除是纳米Ni/Fe的吸附作用和还原作用的协同作用的结果,两者对硝基苯去除率的贡献分别为33.7%和66.3%。纳米Ni/Fe可将硝基苯还原为苯胺和中间产物亚硝基苯,亚硝基苯进一步被还原为最终产物苯胺。还原产物苯胺的生成率随溶液pH的升高而降低;随纳米Ni/Fe用量的增加而升高;Ni含量的适当增大有利于硝基苯还原为苯胺,但Ni含量过高时会导致苯胺生成率降低,适宜的Ni含量为1.85%。纳米Ni/Fe对硝基苯的催化还原过程遵循一级反应动力学规律,反应速率常数为0.0226 min-1。     

硝基苯在Cu-SPE复合电极上的电还原反应特性研究

以国产NF - 1型离子膜为SPE膜材料 ,采用浸渍还原法制备了Cu SPE复合电极 ,研究了硝基苯在此电极上的电还原反应及其主要影响因素 ,并建立了相应的扩散模型。结果表明 :Cu SPE复合电极对硝基苯的电还原反应具有较高的电催化活性 ,硝基苯及其产物在SPE膜内的扩散是反应的控制步骤 ,反应主要发生在Cu SPE界面的内表面 ,其扩散系数D0 =8.1× 10 -7cm2 /s ;经HPLC分析表明电还原产物主要为苯胺。     

Sorption of aqueous organic contaminants onto dodecyl sulfate intercalated magnesium iron layered double hydroxide

Dodecyl sulfate anion (DS⁻) intercalated magnesium iron layered double hydroxide (DS–Mg–Fe LDH) was firstly prepared by the co-precipitation method, and was characterized by the means of X-ray diffraction (XRD), Fourier infrared (FT-IR), Total Organic Carbon analysis (TOC), themogravimetric and differential thermal analysis (TG-DTA) and surface characteristics analysis (BET-N₂). The sorption characteristics and mechanisms of hydrophobic organic contaminants (naphthalene, nitrobenzene, acetophenone) and hydrophilic contaminant (aniline) on DS–Mg–Fe LDH were investigated, and were subsequently compared with that on the inorganic magnesium iron layered double hydroxides (CO₃–Mg–Fe LDH and NO₃–Mg–Fe LDH). The greater sorption amount of organic contaminants on DS–Mg–Fe LDH than on CO₃–Mg–Fe LDH and NO₃–Mg–Fe LDH indicated that organic modified LDHs were potential sorbents for the abatement of organic contaminants. Sorption mechanism on DS–Mg–Fe LDH varied with the types of organic contaminants. The uptake curves of naphthalene, nitrobenzene and acetophenone on DS–Mg–Fe LDH were linear, and sorption capacities for three hydrophobic compounds were in the sequence of their hydrophobicity (refers to water solubility or K_ow). These results suggested that the sorption mechanism was the partition between water and the organic interlayer phase composed of the alkyl chain of DS⁻. After eliminating the influence of the hydrophobicity, the polar compounds (nitrobenzene and acetophenone) exhibited higher affinity to DS–Mg–Fe LDH than nonpolar compound (naphthalene), which demonstrated that both the hydrophobicity and polarity benefited the sorption of hydrophobic compounds on organic LDHs. For hydrophilic compound, aniline, its uptake curve was nonlinear. The sorption process of aniline was the cooperation of the adsorption on hydroxide surface through forming the hydrogen bonding and the weak partition to the interlayer organic phase.     

Heterogeneous Photocatalysis in Microreactors for Efficient Reduction of Nitrobenzene to Aniline: Mechanisms and Energy Efficiency

Aniline was synthesized from nitrobenzene through photo‐induced reduction in microreactors under UV irradiation. Nitrobenzene solution and the nanofluid prepared by a TiO₂ nanocatalyst, PEG‐400, and deionized water were mixed in a capillary microreactor. The effects of catalyst composition, residence time, and substrate concentration on the reaction performance were systematically investigated. The conversion of nitrobenzene and the yield of aniline reached high values under optimized conditions. The excellent reusability of the photocatalyst was realized for four runs. A mechanism was proposed for this photocatalytic reduction process based on reaction kinetics. Both photo‐induced electrons and ^?CO₂^? could reduce nitrobenzene to aniline. The photonic efficiency in the microreactor was still much higher than that obtained in batch reactors, which was mainly attributed to the much larger effective radiation area of the microreactor.