Studies of the effects of the modification conditions on the hydrogenation rate for the enantio-differentiating hydrogenation of methyl acetoacetate over a tartaric acid–NaBr-modified nickel catalyst

The effects of the modification conditions on the hydrogenation rate and the enantio-differentiating ability (e.d.a.) for the enantio-differentiating hydrogenation of methyl acetoacetate were studied over an (R, R)-tartaric acid–NaBr-in-situ-modified nickel catalyst. It was revealed that a tartaric acid modification increased the hydrogenation rate irrespective of the presence of the auxiliary modifier, NaBr. In the presence of the tartaric acid, NaBr would have two roles, i.e., Na⁺ activates the enantio-differentiating sites through the interaction with tartaric acid, and Br⁻ deactivates both the enantio-differentiating sites and non-enantio-differentiating sites. The e.d.a. values and the hydrogenation rate would be determined by the combination of these effects of Na⁺ and Br⁻.     

Studies of the effect of pivalic acid on the hydrogenation rate and the enantio-differentiating ability for the hydrogenation of 2-octanone over a tartaric acid-NaBr-modified nickel catalyst

The effects of the addition of pivalic acid to the reaction media on the hydrogenation rate and the enantio-differentiating ability (e.d.a.) for the hydrogenation of 2-octanone were studied over an (R,R)-tartaric acid-NaBr-in-situ-modified nickel catalyst. It was revealed that the modification with both tartaric acid and NaBr was necessary for increasing the e.d.a. by the addition of pivalic acid to the reaction media. The role of pivalic acid in the enantio-differentiating hydrogenation of 2-octanone was different from that of acetic acid in the hydrogenation of methyl acetoacetate.     

卤醇脱卤酶催化合成(R)-1-氯-3-苯氧基-2-丙醇的工艺优化

以卤醇脱卤酶重组湿菌体E. coli BL21（pET28a-HHDH）为催化剂,催化外消旋的1-氯-3-苯氧基-2-丙醇的动力学拆分可以获得光学纯的(R)-1-氯-3-苯氧基-2-丙醇。本文系统地研究了卤醇脱卤酶催化合成光学纯(R)-1-氯-3-苯氧基-2-丙醇的影响因素,对反应pH、反应温度、菌体浓度、亲核试剂 {\mathrm{N}}_{\mathrm{3}}^{-} 浓度和底物浓度进行了探究。结果表明,卤醇脱卤酶催化合成(R)-1-氯-3-苯氧基-2-丙醇的最佳工艺条件为：pH为7.0,反应温度为28℃,菌体浓度为22.5g/L,亲核试剂NaN₃的浓度为50mmol/L,底物外消旋1-氯-3-苯氧基-2-丙醇的浓度为10mmol/L。在此工艺条件下,(R)-1-氯-3-苯氧基-2-丙醇的ee值和收率分别为100%和16.97%。     

Role of Acetic Acid Added to the Reaction Media for the Enantio-differentiating Hydrogenation of Methyl Acetoacetate Over a Tartaric Acid-modified Nickel Catalyst

The role of acetic acid added to the reaction media for the enantio-differentiating hydrogenation of methyl acetoacetate over a (R,R)-tartaric acid-in-situ-modified nickel catalyst was studied from the viewpoint of the hydrogenation rate during repeated runs. The hydrogenation of methyl acetoacetate on the “enantio-differentiating sites” of a tartaric acid-modified nickel catalyst was specifically accelerated by the acetic acid added to the reaction media to increase the enantio-differentiating ability of the catalyst. In order to increase the enantio-differentiating ability, the addition of acetic acid to the reaction media was required in each run during the repeated use of the catalyst.     

The Durability of the Enantio-Differentiating Ability of a Tartaric Acid–NaBr-Modified Reduced Nickel Catalyst Pre-Modified in Tetrahydrofuran

The enantio-differentiating hydrogenation of methyl acetoacetate was carried out over a (R,R)-tartaric acid–NaBr-modified reduced Ni catalyst. The reduced Ni was pre-modified in a tetrahydrofuran solution of tartaric acid and NaBr at atmospheric pressure or at a high hydrogen pressure. The enantio-differentiating ability of 70–90% was maintained during 40 runs over the reduced nickel catalyst pre-modified at 9 MPa hydrogen and 373 K. The results indicated that the durability of a high enantio-differentiating ability of an in-situ-modified catalyst would be attributed to the modification conditions at the high hydrogen pressure of 9 MPa and the high temperature of 373 K in the autoclave.     

手性修饰催化剂在多相不对称氢化中的研究进展

手性修饰金属催化剂是最具发展潜力的多相不对称催化剂之一。本文综述了近年来三个具有代表性的多相不对称氢化反应体系的研究进展,即酒石酸修饰镍催化剂催化β-酮酯不对称加氢体系、金鸡纳生物碱修饰铂催化剂催化α-酮酯不对称加氢体系以及金鸡纳生物碱修饰钯催化剂催化C=C和C=N双键不对称加氢体系。概述了催化体系的影响因素,探讨了酒石酸及金鸡纳生物碱修饰型催化剂的手性识别机理模型。指出开发高效催化剂,修正或提出手性识别机理模型仍是今后多相不对称催化氢化反应研究的方向。     

Hydrogenation of cyclohexanone on nickel-tungsten sulfide catalysts

Unsupported Ni-W sulfide catalysts were tested for cyclohexanone hydrogenation under atmospheric pressure conditions and showed a high selectivity towards cyclohexene. They were prepared employing ammonium thiotungstate complexes and nickel nitrate as metal-sulfide precursors. The data of catalytic activity show a synergetic effect as a function of stoichiometric composition, R=Ni/(Ni+W). A maximum synergetic effect occurred at R=0.7. The texture and surface composition characterization of the catalysts were carried out by BET surface area measurements, AES and XPS. The surface of catalysts was found to be nickel deficient, compared to the nominal values, as determined by AES and XPS. The electronic state of Ni changed as the catalyst stoichiometry varied, but the electronic state of W did not change.     

Preparation method for supported metal catalysts using w/o microemulsion: Study on immobilization conditions of metal particles by hydrolysis of alkoxide

It was previously found that the silica-supported rhodium catalyst prepared using water-in-oil microemulsion had rhodium particles partly, or wholly, embedded in silica. In this work, consequently, we investigated the effect of hydrolysis conditions of tetraethylorthosilicate, employed as the source of silica, on the atomic ratio of surface rhodium in contact with the gas phase, to total surface rhodium of nanoparticles. This ratio is denoted as R in this paper. R became higher when the catalyst was prepared under the following hydrolysis conditions: a shorter hydrolysis time and a smaller amount of tetraethylorthosilicate. On the other hand, R showed the minimum value when the water content in the preparation solution was 33 vol%. From these results, it is demonstrated that it was important to form silica as early as possible in hydrolysis of TEOS in order to increase R values. In addition, the effect of R on the catalytic behavior in CO hydrogenation was investigated. At R values below 30%, the turnover frequencies increased with a decrease in R.     

The importance of modifier pH in the generation of enantioselective nickel catalysts

Enantioselective Ni/SiO₂ catalysts have been prepared by modification with aqueous solutions of (R)-(+)-tartaric acid (TA) and used in the asymmetric hydrogenation of a prochiral -keto ester (methylacetoacetate) to a -hydroxy ester ((R)-(-)-methyl-3-hydroxybutyrate). The simultaneous adsorption of TA and corrosive leaching of surface nickel metal are graphically illustrated and the progress of TA buildup on the catalyst surface with the duration of modification is presented. Variations of modifier pH were found to strongly affect the modification process and influence the ultimate hydrogenation rate and enantioselectivity. The surface coverage by TA is correlated to the asymmetric activity and an optimum fractional coverage of 0.2 is identified; at higher coverages modification with basic TA solutions yielded superior enantioselectivities. While TA treatment in basic media was less corrosive, a proportion of the surface enantioselective nickel sites was leached into solution during the hydrogenation step. The difference in the response of nickel precursors, prepared by impregnation and homogeneous precipitation/deposition, to TA treatment is compared and discussed in terms of metal/support interaction.     

Enantioselective hydrogenation of isophorone and kinetic resolution of 3,3,5-trimethylcyclohexanone over Pd catalysts in the presence of (S)-proline

Enantioselective hydrogenation of isophorone and kinetic resolution of 3,3,5-trimethylcyclohexanone (TMCH) over Pd catalysts in the presence of (S)-proline revealed that the enantioselectivity for hydrogenation of isophorone was mainly originated from the kinetic resolution of TMCH. The rapid hydrogenation of isophorone primarily yielded racemic TMCH, and the followed kinetic resolution consumed the (R)-TMCH enantiomer, leaving the (S)-TMCH enantiomer in excess. The kinetic resolution of racemic TMCH is closely related to the acidic/basic properties of the support, and the addition of K₂CO₃ to Al₂O₃ provided more enantio-differentiating environment through the enhanced adsorption of (S)-proline on the catalyst surface. As a result, the Pd/Al₂O₃-K₂CO₃ catalyst with finely dispersed Pd particles and enhanced adsorption of (S)-proline gave very high enantioselectivities (e.e. value up to 98%) for the enantioselective hydrogenation of isophorone.     

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.     

共沉淀法制备Ni/Al2O3催化剂的研究

油脂加氢催化剂是以金属镍为活性组分、氧化铝为载体制备的Ni/Al2O3催化剂。在制备催化剂过程中,其合成条件直接影响着催化剂的最终活性。以工业硝酸镍、碳酸钠和自制氧化铝粉为原料,利用共沉淀的方法制备加氢催化剂,考察了反应温度、反应时间、反应液pH及反应过程中搅拌转速对催化剂活性的影响。通过实验数据汇总分析,最终确定制备Ni/Al2O3油脂加氢催化剂的最佳条件：反应温度为85 ℃、反应结束时溶液pH=8.0、反应时间为1.5 h、搅拌转速为600 r/min。在此条件下制备的Ni/Al2O3催化剂,经棕榈油加氢评价后测定的碘值最低。     

Study of the properties of nickel oxide and nickel as precursors for the tartaric acid-NaBr-modified nickel catalyst

Nickel oxide was prepared by the decomposition of nickel hydroxide and then the nickel oxide was reduced to form the nickel catalyst. The properties of the nickel oxide and the reduced nickel were studied in relation to the enantio-differentiating ability (e.d.a.) of a tartaric acid-NaBr-modified reduced nickel catalyst. The modified nickel catalyst prepared from nickel oxide with less non-stoichiometric oxygen produced a high e.d.a. for the hydrogenation of methyl acetoacetate. The high crystallinity of the nickel oxide and the resultant nickel would be required to attain a high e.d.a.     

The structure of tartaric acid adsorbed over nickel catalyst observed by FT-IRAS

The structure of the L-tartaric acid adsorbed on the surface of a nickel metal catalyst with or without NaBr was studied by FT-IRAS. The carboxylic acid and carboxylate type adsorbed species were observed on nickel surface which was treated with only tartaric acid, while only one type of carboxylate ion was observed on the nickel surface which was treated with tartaric acid and NaBr.     

Pt-Cu-Zn/C催化加氢制备DSD酸工艺

本文研究了4,4'-二硝基二苯乙烯-2,2'-二磺酸(DNS酸),在Pt/C催化剂存在下,Zn和Cu为抑制剂,水相体系中液相催化加氢制备DSD酸。Pt-Cu-Zn/C催化剂制备DSD酸具有很好的活性和选择性,能有效抑制苄基物及影响色度的杂质的生成。较佳的工艺条件为:DNS酸钠盐质量浓度为12~20%、Pt/C催化剂量为硝基物的0.5~0.7%,反应温度40~60℃、pH4~6、氢气压力1.0 MPa。DNS酸转化率100%,DSD酸选择性98.5%以上,收率98%,DSD酸含量均达到95%以上(氨基值法),苄基物含量低于0.1%(外标法),色度低于0.2。新工艺生产每吨DSD酸产生废水12吨,废水COD值为24 mg/L,无色透明。     

Dehydration of methyl phenyl carbinol catalyzed by modified active aluminum oxide

The effect of modification with metal salts and acids on the acid-base characteristics and the catalytic properties of active aluminum oxide in the reaction of methyl phenyl carbinol dehydration to styrene was studied using the IR spectroscopy of adsorbed base molecules. The surface treatment of γ-Al₂O₃ with chromium and nickel cations decreased the catalyst activity because of the occurrence of hydrogenation side reactions. The appearance of strong Bronsted and Lewis acid sites as a result of modification with sulfate, nitrate, and fluoride anions accelerated the deactivation of the catalyst. Upon modification with acetic acid solutions, additional Lewis acid sites with Q _CO = 33.5?34 kJ/mol were formed on the surface of aluminum oxide, and the concentration of strong basic sites with PA = 900 kJ/mol decreased; this facilitated an increase in the catalyst activity and a decrease in the rate of catalyst deactivation.     

Colloidal nickel(0)-carboxymethyl cellulose particles: A biopolymer-inorganic catalyst for hydrogenation of nitro-aromatics and carbonyl compounds

Colloidal solution of nickel(0) in carboxymethyl cellulose showed good catalytic efficiency in hydrogenation of aromatic nitro compounds, as well as aliphatic and aromatic ketones in aqueous medium yielding the respective aromatic amines and alcohols in excellent yield along with moderate to good reusability of the catalyst. The catalyst was isolated and characterized by powder XRD, EDX, SEM and TEM studies. The active phase of the catalyst consists of nickel nanoparticles entrapped in carboxymethyl cellulose (Col-Ni-CMC Nps). The ecofriendly synthesis was performed in water at room temperature by NaBH₄ reduction of nickel chloride in the presence of sodium carboxymethyl cellulose (CMC).     

采用多相放电反应技术加氢精制生物油的试验研究

针对目前生物油加氢技术中存在的催化剂易结焦、工艺过程不能连续等问题,采用多相放电反应对生物油进行加氢精制。构建了生物油/固体催化剂/H₂的多相放电体系,研究了催化剂类型、工作电压、气体流量、反应时间等条件对精制生物油的加氢脱氧效果的影响。研究结果表明：随着工作电压和气体流量的增大,多相放电催化加氢精制生物油的脱氧率（R）呈现出先增加后减少的趋势;随着反应时间的延长,呈现出先增加后稳定的趋势。在工作电压为22kV,气体流量为60mL/min,反应时间为120min的工艺条件下,脱氧率最高可达41%。与生物原油相比,多相放电催化加氢精制的生物油中醇类、酚类、酮类等物质的含量相对较低,而碳氢类物质显著增多。     

Die Wechselwirkung Fettsäuren/Ni-Katalysator bei der Hydrierung

Correlation Effect between Fatty Acids and Ni-Catalyst during Hydrogenation During hydrogenation of fatty acids by a Ni-catalyst besides the occasional saturation of the double bonds simultaneously a reaction of the carboxyl group of the fatty acids with the Ni-NiO-system of the catalyst takes place, forming fatty acid nickel salts, hydrogen and water. This reaction is reversible and proceeds in three phases. When the maximal concentration of Ni-soaps in the beginning of the hydrogenation is achieved, up to 80% of the total nickel is thus converted; those fatty acids which are hardened to a low iodine value contain 5–40% of the total nickel, as nickel soaps. The fact that the reaction is reversible is explained by activation of the hydrogen on the Ni-catalyst surface and by its effect on the formed Ni-soap. The course of the correlation effect fatty acids/Ni-catalyst is above all influenced by the reaction conditions, as e. g. temperature and concentration of the used catalyst in the reactor with unobjectionably washed catalyst particles and unobjectionable saturation with hydrogen under normal pressure. No significant influence of the degree of reduction on the character of this correlation could be found.     

镍系SBS加氢反应机理及加氢催化剂制备研究

对镍系SBS催化加氢机理进行了探讨,对催化剂制备工艺进行了优化。当催化剂组分质量浓度为2～4 g/L,陈化温度为50～70℃,n(Al)/n(Ni)为3～6时催化剂活性最高。向待加氢胶液中加入一定量破杂剂A可使催化剂活性及稳定性有一定程度提高。用该法制备的催化剂有较好的稳定性,常温下放置一个月其催化活性几乎没有变化。