苯酚液相原位加氢合成环己酮和环己醇

基于吸热的甲醇水相重整制氢反应和放热的苯酚液相催化加氢反应使用相同类型的催化剂,比较接近的反应温度和压力,且都在液相状态下进行的特点,提出在Raney Ni催化剂的作用下,将甲醇水相重整制氢反应产生的氢气原位地应用于苯酚加氢合成环己酮和环己醇的反应,实现了水相重整制氢和液相催化加氢两个反应的耦合。消除了传统方法中需要专门的氢气制备、存储和输送等环节,简化了工艺、降低了生产成本。通过这两个反应的耦合,甲醇水相重整过程中甲醇转化率和氢气选择性都得到明显提高;同时,在Raney Ni催化剂[JP2]作用下实现了苯酚的高选择性还原(环己酮和环己醇总选择性达99％以上),比传统的氢气还原法具有更好的效果。     

木糖Raney—Ni催化加氢宏观动力学研究

在改装的高压釜中，测定两种粒径Ｒａｎｅｙ－Ｎｉ催化剂用于木糖水溶液加氢反应的动力学规律。反应温度３８３Ｋ、氢压范围１．０－６．０ＭＰａ，借助模型计算对反应过程进行分析，并讨论了实验结果     

Raney镍上松香催化加氢本征动力学

测定在不同类型搅拌器下高压釜的持气量和反应效果 ,认识到松香在Raney镍上催化加氢反应受到外扩散的严重影响 ,利用加入 2 0 0号溶剂油、改造搅拌器类型、提高搅拌速度的方法消除外扩散 ,使反应处于化学动力学控制区 ,然后采集动力学数据 ,经对 17种可能的反应机理模型进行筛选 ,推测的反应机理为 :松香中的主要成分枞酸分子不吸附 ,枞酸分子与催化剂表面上被吸附的氢原子进行反应 ,氢原子的吸附为控制步骤 ,据此导出其本征动力学方程 .     

Raney镍上松香催化加氢反应动力学研究

以松香为原料、Raney镍为催化剂和200#油为溶剂进行松香催化加氢反应研究。在消除松香加氢过程内外扩散影响的条件下,利用毛细管气相色谱法在线跟踪分析压力为5.0 MPa、温度为423~453 K下反应物浓度随时间的变化关系,对反应过程进行拟均相动力学研究,结果表明,松香催化加氢的反应速率与枞酸浓度呈0.5级反应,其动力学方程为r=5.68×105e-7.T5997c0A.5,表观活化能为63.18 kJ/mol。     

新型固定床Raney Ni催化剂的制备、表征及苯加氢活性评价

将镍铝合金粉、拟薄水铝石和田菁粉捏合、成型,在空气中高温焙烧,然后用苛性碱溶液充分浸取,制备出可应用于固定床加氢的活性Raney Ni催化剂.实验结果表明,成型合金焙烧过程中,富铝合金相逐渐转化为贫铝相,同时小部分金属铝氧化生成α-Al₂O₃,可提高催化剂的颗粒强度.BET和SEM分析表明,催化剂表面具有较宽的缝隙和丰富的大孔结构.苯加氢活性评价表明,在一定反应条件下,该新型固定床Raney Ni催化剂活性高于传统负载型镍催化剂,也高于按照专利方法制备的同类型催化剂.     

改性Raney Ni催化剂用于加氢合成间苯二甲胺

采用改性RaneyNi催化剂 ,研究了溶剂、温度、压力、催化剂用量对间苯二甲腈 (IPN)加氢合成间苯二甲胺 (m XDA)反应的影响。结果表明 ,该催化剂在以甲醇、甲苯为混合溶剂 ,V(甲醇 )∶V(甲苯 )=1∶2 ,当m(溶剂 )∶m(IPN) =3∶1,反应温度 70℃、压力 6 0～ 7 0MPa、催化剂用量为原料质量 10 %时 ,IPN转化率接近 10 0 % ,m XDA收率达 97%。失活催化剂经再生 ,即能恢复其性能。     

Ca助剂对钯负载催化剂在苯酚液相原位加氢反应中的影响

利用等体积浸渍法制备了一系列不同助剂的Pd／Al2O3催化剂,并利用固定床管式反应器考察了以上催化剂在“苯酚＋甲醇＋水”耦合反应体系中的性能。结果表明Ca的促进作用较明显,进一步考察了Ca助剂的含量对催化剂活性的影响,并通过BET和CO吸附表征探讨了Ca助剂对催化剂结构以及Pd分散度的影响。     

木糖Raney-Ni催化加氢本征反应动力学

用细粉末Ｒａｎｅｙ－Ｎｉ催化剂研究了木糖水溶液加氢的本征反应动力学。在考察的温度（３７３～３９３Ｋ）、压力（１～６ＭＰａ）和木糖浓度（０．０２～１．３ｍｏｌ／ｄｍ３）范围内,速率与木糖浓度成１级。氢压低于４～５ＭＰａ时,符合Ｌａｎｇｍｕｉｒ－Ｈｉｎｓｈｅｗｏｏｄ形式的方程,用非线性优化法关联其参数,得到本征速率方程。反应机理推测为吸附氢原子与吸附木糖分子反应,表面反应生成的中间物被木糖解吸而成产物是控制步骤。３７３Ｋ以上在高压区出现的速率剧增现象可能与低能吸附位的激活有关     

Raney镍上α-蒎烯催化加氢本征动力学

测定在不同类型搅拌器下高压釜的持气量和反应效果，认识到α－蒎烯在雷尼镍上催化加氢反应严重受到外扩散的影响，利用改造搅拌器类型和提高搅拌转速的方法消除外扩散；改变Raney镍的粒度，消除内扩散影响，使反应处于化学动力学控制区，然后采集动力学数据，经对17种可能的反应机理模型进行筛选，认为最可几的反应机理为：催化剂表面上被吸附的氢原子和α蒎烯分子间的表面反应为控制步骤，据此推导其本征动力学方程。     

Raney Ni催化剂的制备及应用研究

Raney-Ni催化剂是一种十分重要的骨架型催化剂,由于其具有的高活性及高选择性,被广泛应用于有机反应。本文简述了Raney Ni催化剂的制备方法,阐述了铝镍合金晶体结构、第三金属、残余铝、活化条件和催化剂粒度对活性的影响,并对Raney Ni催化剂在氢化反应、脱硫、脱卤反应、硝基加氢反应、氨解反应等方面的应用作了概括说明。     

Maltose hydrogenation to maltitol over industrial Raney Ni catalyst: Kinetics and mechanism

The kinetics and mechanisms of selective maltose hydrogenation over Raney Ni remain poorly understood, which hinders the industrial advancement of maltitol production for biorefining. Herein, the impact of hydrogenation conditions and in-depth mechanistic characterizations were carefully investigated in this research. Optimization of reaction conditions illustrated that maltitol formation was favored by moderate reaction temperatures (≤130°C), high hydrogen pressures (>7 MPa), and near-neutral sodium phosphate buffer (pH = 6.47). Kinetic studies demonstrated the E_a of 45.5 kJ/mol for the hydrogenation of maltose. The in situ IR revealed that the hydrogenation of maltose over Raney Ni occurs in the order of ring opening and adsorption via CO of the aldose form followed by hydrogenation. The UV–vis spectra demonstrated the near-neutral setting (pH = 6.47) promoted the production of open-chain aldose conformation and selective CO hydrogenation to the corresponding alcohols. The present study on concentrated-maltose hydrogenation paves the way for the industrial development of maltitol manufacturing.     

骨架镍催化对苯二胺液相加氢动力学

用骨架镍作催化剂,在排除内外扩散影响条件下,研究了以水为溶剂对苯二胺加氢反应的动力学.通过测定实验过程中对苯二胺浓度,得出浓度对数随时间变化的曲线,获取该反应中对氢气和对苯二胺的反应级数、速率常数、活化能和指前因子等动力学参数,并反映了氢气压力和反应温度等因素对反应的影响.催化剂加氢动力学方程为- dc对苯二胺/dt=...     

Modelling of kinetics and mass transfer in the hydrogenation of xylose over Raney nickel catalyst

This paper discusses the modelling of xylose hydrogenation kinetics over Raney nickel in aqueous solutions, the determination of the hydrogen solubility in the reaction mixture as well as evaluation of mass transfer effects in the reaction system. The hydrogenation experiments were carried out batchwise in an automatic laboratory‐scale reactor. The reactor system operated at a pressure range of 40–70 bar and at temperatures between 80 and 140 °C. The catalyst‐to‐xylose ratio was approximately 5 wt‐% of the xylose weight normally. The reactor contents were analysed off‐line with a high performance liquid chromatograph. Hydrogen solubility in the reaction medium was determined with a gas‐chromatographic system. The solubility was found to remain fairly constant during the hydrogenation. Only a slight increase in the hydrogen solubility was detected as xylose was hydrogenated to xylitol. The overall hydrogen solubility in the reaction mixture was significantly lower than in pure water, as expected. The main hydrogenation product was xylitol, but small amounts of xylulose and arabinitol were detected as by‐products. A semi‐competitive kinetic model, based on hydrogen and xylose adsorption, was developed. The model accounts for the very different areas covered by a hydrogen atom and an organic species on the catalyst surface. The parameters of the kinetic model were determined with non‐linear regression analysis. It turned out that the kinetic model is able to describe the formation of both xylitol and the by‐products. The mass transfer effects in the batch hydrogenation were evaluated by using measured viscosities and estimated diffusion and mass transfer coefficients. A process simulator, utilizing the kinetic and mass transfer effects, was developed to predict the behaviour of industrial reactors. © 1999 Society of Chemical Industry     

苯甲酸甲酯气相原位加氢制苯甲醛

提出了苯甲酸甲酯气相原位加氢制苯甲醛的路线。在常压固定床反应器上研究了浸渍法制备的Cu-MnO/γ-Al₂O₃双功能催化剂催化苯甲酸甲酯气相原位加氢制苯甲醛的反应性能,考察了催化剂的组成、反应温度、进样速率、酯/醇/水摩尔比等因素对苯甲酸甲酯转化率和苯甲醛选择性的影响。在优化的反应条件（苯甲酸甲酯/甲醇/水摩尔比为0.5/40/40、反应温度为420℃、进样速率为0.1 ml•min^-1）下,苯甲醛选择性可达到88.5%,苯甲酸甲酯的转化率为79.6%,且Cu-MnO/γ-Al₂O₃催化剂具有较好的稳定性。根据产物分布提出了苯甲酸甲酯原位加氢的反应机理。该反应体系不需要外部供应氢气,避免了氢气的生产和运输,简化了反应工艺。     

骨架镍催化剂制备及其催化烯基芳烃加氢性能的研究

考察了成型时拟薄水铝石和合金粉的比例、胶溶剂硝酸质量分数,水粉比及焙烧温度对骨架镍催化剂侧压强度的影响,采用XRD和TG-DTA等手段对催化剂进行表征。结果表明,催化剂侧压强度随着拟薄水铝石和合金粉的比例、胶溶剂硝酸质量分数、水粉比以及焙烧温度的提高呈现先增加后减小的规律,在拟薄水铝石与合金粉质量比1.5、胶溶剂硝酸质量分数6%和水粉比0.21 mL.g-1条件下成型,860℃空气中焙烧,得到侧压强度最好的催化剂,以苯乙烯、甲基苯乙烯加氢为探针反应,对催化剂的加氢性能进行评价,结果表明,在反应压力2 MPa、温度80℃、原料空速2 h-1和V(H2)∶V(油)=300∶1条件下,苯乙烯与甲基苯乙烯在考察的500 h运转周期内,转化率接近100%,且催化剂活性保持稳定。     

磁性载体在Raney Ni催化加氢中的应用

通过引入利用磁性载体在反应过程中固定雷尼镍催化剂的方法,克服催化剂流失的问题;减少了搅拌剪切力对雷尼镍催化剂的影响,以延长催化剂的使用寿命,在邻硝基乙苯加氢体系中催化剂的使用寿命可以达到未加磁性载体的300％;同时,使催化剂在反应结束后易于与反应体系分离,对催化剂的回收可以达到加入量的98％～99％,方便催化剂的后处理。     

Electrocatalytic hydrogenation of phenol in aqueous solutions at a Raney nickel electrode in the presence of cationic surfactants

The electrocatalytic hydrogenation (ECH) of phenol at a Raney nickel cathode was studied in aqueous solutions. At 30 °C, without surfactants, cyclohexanol was obtained with low or medium yields. The best results were observed in alkaline solutions (pH 9). At pH 2 the efficiency of the hydrogenation reaction is significantly improved by low amounts of didodecyldimethylammonium bromide (DDAB). This surfactant effect is studied in relation to the substrate and hydrogen adsorption phenomena.     

Enantio-differentiating hydrogenation of methyl acetoacetate over modified Raney nickel catalysts prepared by two-step modifications

Two-step modifications of the Raney nickel were examined for the enantio-differentiating hydrogenation of methyl acetoacetate. Among the two-step modifications attempted in this study, the combination of ‘pre-modification with disodium tartrate and NaBr in water’ and ‘in-situ modification with tartaric acid’ resulted in the highest optical yield (84%). This modification process is a greener process than the conventional one carried out under weakly acidic conditions, because this process generated almost no Ni²⁺ ions. The pre-modification with the tartrate and NaBr preferentially eliminated Al³⁺ from the Raney nickel surface.