Enantioselective catalysis for agrochemicals. The case histories of (S)–metolachlor, (R)–metalaxyl and clozylacon

The application of enantioselective catalytic methods for the technical preparation of chiral agrochemicals is illustrated for three active ingredients of the acylanilide type. The key step for the technical synthesis of the herbicide (S)–metolachlor (trade name DUAL MAGNUM^®) is the enantioselective hydrogenation of an imine intermediate using a novel iridium ferrocenyl–diphosphine catalyst that exhibited an unprecedented high activity (average turnover frequency up to 350,000 h^-1) with an enantioselectivity of 80%. (R)–metalaxyl and clozylacon were synthesized with > 95% and 99% enantiomeric purity, respectively. The enantioselective hydrogenation of the corresponding enamides with Rh or Ru/binap catalysts was the key step in both cases. Some conclusions regarding the development of the catalyst system are made and important prerequisites for the use of enantioselective catalysts for the production of agrochemicals are discussed.     

Pilot run,plant design and cost analysis for reductive ozonolysis of methyl soyate

Preparation of methyl azelaaldehydate dimethyl acetal (MAzDA) from methyl soyate was investigated on a pilot scale via the sequence ozonization, hydrogenation, acetalization and fractional distillation. A water-methyl soyate emulsion for the ozonization step was preferred to methanolic solution or neat methyl soyate for reasons of cost and safety. Ozonization of the water-methyl soyate emulsion (1.63:1 ratio) in a six-plate sieve tower produced 1271 lb aqueous peroxidic emulsion during 12 days of continuous operation. Because a continuous hydrogenation facility was not available, reduction was done in 200 lb batches. Since batch hydrogenation of the peroxidic emulsion in this quantity was difficult to control and optimum conditions were difficult to maintain, maximum yield of the product was only 56%. The average yield for seven batches was 48.3%. However laboratory hydrogenation under optimum conditions of periodic samples taken from the sieve tower discharge indicated an overall yield of 74.5% (average of eight monitor samples). A plant designed to produce 10 million lb annually should be capable of producing MAzDA at a total manufacturing cost of 39 cents/lb or a net manufacturing cost of 27 cents/lb with byproduct credit conservatively estimated. Methyl soyate ozonolysis products are not sensitive to detonation, and their exothermic decomposition is greatly moderated by the presence of water. Presented in part at the AOCS Meeting, New Orleans, May 1967; see Abstr. 117, JAOCS 44:139A (1967). ARS, USDA.     

Low-temperature synthesis of DME from CO2/H2 over Pd-modified CuO–ZnO–Al2O3–ZrO2/HZSM-5 catalysts

Three series of Pd-modified CuO–ZnO–Al₂O₃–ZrO₂/HZSM-5 catalysts were prepared and characterized by BET, XRD and TPR analysis. The catalytic system was evaluated in the development of direct synthesis of dimethyl ether (DME) from carbon dioxide hydrogenation at low temperature (T=200 °C, P=3.0 MPa). The results indicated that the addition of palladium markedly enhanced the DME synthesis and retarded the CO formation. An explanation of this promoting effect of Pd on the DME synthesis could be attributed to the spillover of hydrogen from Pd⁰ to the neighboring phase.     

V-modified CuO–ZnO–ZrO2/HZSM-5 catalyst for efficient direct synthesis of DME from CO2 hydrogenation

A series of V-modified CuO–ZnO–ZrO₂/HZSM-5 catalysts for direct synthesis of dimethyl ether (DME) from CO₂ hydrogenation were prepared by an oxalate co-precipitation method. The catalysts were also characterized by XRD, BET, H₂-TPR, N₂O chemisorption, NH₃-TPD, and XPS techniques. The results show that the catalytic performances of the catalysts are strongly dependent on the content of V added in the preparation.     

二甲醚的生产工艺及其下游产品的开发

综述了二甲醚的性质、生产方法、应用及其下游产品的开发,通过比较二甲醚生产方法的优缺点,指出一步法生产二甲醚具有较高经济价值,而CO2加氢制取DME是发展方向。由二甲醚可开发出一系列具有高附加值的产品,其发展前景广阔。     

己二酸二甲酯加氢反应热力学分析及动力学研究

采用基团贡献法计算了己二酸二甲酯（DMA）和1,6-己二醇（HDOL）的热力学相关数据,在不同反应条件下,计算了DMA加氢生成HDOL反应的焓变、熵变、Gibbs自由能变和平衡常数,探讨了反应温度、压力对Gibbs自由能变和平衡常数的影响。利用固定床管式反应器,对DMA加氢反应本征动力学进行研究,采用幂函数型动力学方程对实验结果进行拟合,得到了反应的活化能为63.55 kJ·mol^-1,DMA和H₂的反应级数分别为0.63和0.40。统计学检验结果表明,该模型能较好地描述DMA加氢反应。     

Pt-Promoted Cu/SBA-15 Catalysts with Excellent Performance for Chemoselective Hydrogenation of Dimethyl Oxalate to Ethylene Glycol

Cu/SBA-15 catalysts containing a small amount of Pt (Cu–Pt/SBA-15) were prepared by sequential adsorption–reduction method and examined for chemoselective hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG). The Cu–Pt/SBA-15 catalyst with an optimal Cu/Pt atomic ratio of 10 showed a DMO conversion close to 100 % with a 98 % selectivity to EG at a temperature as low as 463 K. The results showed that the best Cu–Pt/SBA-15 enhanced the space time yield of EG by about 1.47 times compared with Cu/SBA-15. The introduction of Pt with stronger ability for H₂ adsorption and activation substantially enhanced the reducibility of the Cu²⁺ species and further promoted the chemisorption capacity of H₂. After reduction, a portion of Cu was alloyed with Pt, which was beneficial for the generation and stabilization of a balanced Cu⁺/Cu⁰ ratio during the hydrogenation process.     

合成气经二甲醚/乙酸甲酯制无水乙醇的研究进展

乙醇是一种重要的清洁能源,可以作为燃油替代品或者含氧添加剂使用,市场潜力巨大。由合成气出发,经二甲醚羰基化合成乙酸甲酯、乙酸甲酯加氢制乙醇是近年来备受关注的乙醇合成新工艺。该工艺选择性高、反应条件温和、催化剂价廉易得,且避免了乙醇-水共沸物的产生,节省了分离的能耗,是典型的绿色化学工艺。围绕这一工艺的两步核心反应(羰基化和加氢)的研究现状进行了综述,着重介绍了催化剂开发、反应机理方面的进展。该工艺路线的研究和推广,对促进我国能源多元化、清洁化发展有重要的意义。     

An overview of dehydration, aldol-condensation and hydrogenation processes for production of liquid alkanes from biomass-derived carbohydrates

We present results for the conversion of carbohydrate feedstocks to liquid alkanes by the combination of dehydration, aldol-condensation/hydrogenation, and dehydration/hydrogenation processing. With respect to the first dehydration step, we demonstrate that HMF can be produced in good selectivity from abundantly available polysaccharides (such as inulin, sucrose) containing fructose monomer units using a biphasic batch reactor system. The reaction system can be optimized to achieve good yields to 5-hydroxymethylfurfural (HMF) from fructose by varying the contents of aqueous-phase modifiers such as dimethylsulfoxide (DMSO) and 1-methyl-2-pyrrolidinone (NMP). Regarding the aldol-condensation/hydrogenation step, we present the development of stable, solid base catalysts in aqueous environments. We address the effects of various reaction parameters such as the molar ratio of reactants and temperature on overall product yield for sequential aldol-condensation and hydrogenation steps. Overall, our results show that it is technically possible to convert carbohydrate feedstocks to produce liquid alkanes by the combination of dehydration, aldol-condensation/hydrogenation, and dehydration/hydrogenation processing; however, further optimization of these processes is required to decrease the overall number of separate steps (and reactors) required in this conversion.     

An overview of aqueous-phase catalytic processes for production of hydrogen and alkanes in a biorefinery

In this overview we discuss how aqueous-phase catalytic processes can be used to convert biomass into hydrogen and alkanes ranging from C₁ to C₁₅. Hydrogen can be produced by aqueous-phase reforming (APR) of biomass-derived oxygenated hydrocarbons at low temperatures (423–538 K) in a single reactor over supported metal catalysts. Alkanes, ranging from C₁ to C₆ can be produced by aqueous-phase dehydration/hydrogenation (APD/H). This APD/H process involves a bi-functional pathway in which sorbitol (hydrogenated glucose) is repeatedly dehydrated by a solid acid (SiO₂–Al₂O₃) or a mineral acid (HCl) catalyst and then hydrogenated on a metal catalyst (Pt or Pd). Liquid alkanes ranging from C₇ to C₁₅ can be produced from carbohydrates by combining the dehydration/hydrogenation process with an upstream aldol condensation step to form C–C bonds. In this case, the dehydration/hydrogenation step takes place over a bi-functional catalyst (4 wt.% Pt/SiO₂–Al₂O₃) containing acid and metal sites in a specially designed four-phase reactor employing an aqueous inlet stream containing the large water-soluble organic reactant, a hexadecane alkane sweep stream, and a H₂ inlet gas stream. The aqueous organic reactant become more hydrophobic during dehydration/hydrogenation, and the hexadecane sweep stream removes these species from the catalyst as valuable products before they go on further to form coke.     

草酸二甲酯气相选择性加氢铜基催化剂研究进展

乙二醇是重要的化工原料,广泛应用于各种行业。煤经草酸二甲酯加氢制乙二醇符合我国"富煤少油"能源特点,具有良好的发展前景。对于草酸二甲酯气相选择性加氢合成乙二醇反应中催化剂的开发是实现该路线工业化的关键。重点介绍Cu基催化剂非均相气相加氢的研究进展,包括Cu基催化剂的活性中心、载体以及助剂,展望草酸二甲酯加氢Cu基催化剂的研究方向。     

Reaction mechanism of methyl nitrite dissociation during co catalytic coupling to dimethyl oxalate: A density functional theory study

Dissociation of methyl nitrite is the first step during CO catalytic coupling to dimethyl oxalate followed by hydrogenation to ethyl glycol in a typical coal to liquid process. In this work, the first-principle calculations based on density functional theory were performed to explore the reaction mechanism for the non-catalytic dissociation of methyl nitrite in the gas phase and the catalytic dissociation of methyl nitrite on Pd(111) surface since palladium supported on alpha-alumina is the most effective catalyst for the coupling. For the non-catalytic case, the calculated results show that the CH_3O–NO bond will break with a bond energy of 1.91 eV, and the produced CH_3O radicals easily decompose to formaldehyde, while the further dissociation of formaldehyde in the gas phase is difficult due to the strong C–H bond. On the other hand, the catalytic dissociation of methyl nitrite on Pd(111) to the adsorbed CH_3O and NO takes place with a small energy barrier of 0.03 eV. The calculated activation energies along the proposed reaction pathways indicate that(i) at low coverage, a successive dehydrogenation of the adsorbed CH_3O to CO and H is favored while(ii) at high coverage, hydrogenation of CH_3O to methanol and carbonylation of CH_3O to methyl formate are more preferred. On the basis of the proposed reaction mechanism,two meaningful ways are proposed to suppress the dissociation of methyl nitrate during the CO catalytic coupling to dimethyl oxalate.     

C5馏分分离技术现状及发展趋势

概述了关于C5馏分分离的一些现有情况。其中包括像二甲基甲酰胺法、乙腈法、N-甲基吡咯烷酮法的传统技术,还有这些传统技术在发展中近一步改进的状况,以及出现的一些尚在研究中的新型分离技术,像催化加氢除炔、反应精馏技术以及化学吸收法、膜分离方法等,而这些新型分离技术就是未来C5馏分分离技术的发展趋势。     

Enantioselective hydrogenation of N-acetyl dehydrophenylalanine methyl ester using cinchonine-modified Pd/TiO2 catalysts

The enantioselective hydrogenation of N-acetyl dehydrophenylalanine methyl ester (NADPME) to N-acetyl phenylalanine methyl ester is investigated using cinchonine-modified Pd/TiO₂ catalysts. The catalysts were prepared using deposition–reduction and wet impregnation methods and were evaluated for reaction using methanol as solvent with various cinchonine/NADPME molar ratios. Enantioselectivity was sensitive to this ratio and comparison with Pd/γ-Al₂O₃ showed that the Pd/TiO₂ gave marginally higher enantioselectivity when tested under comparable conditions. The effect of Pd loading and dispersion was investigated and the maximum enantiomeric excess observed was dependent on the dispersion; the role of the Pd particle size is discussed in the context of cinchonine adsorption. The reactions were carried out in solvents (methanol and dimethyl formamide) and mixed solvents (methanol–water and dimethyl formamide–water); the enantiomeric excess was significantly enhanced using dimethyl formamide. The addition of water does not have a significant effect for the Pd/TiO₂ catalysts. In this paper we report the highest enantiomeric excess for the hydrogenation of a prochiral ester using an immobilised catalyst.     

Stereoselective Hydrogenation of Folic Acid Dimethyl Ester Benzenesulfonate: A New Access to Optically Pure L‐Tetrahydrofolic Acid

Folic acid was converted to the corresponding dimethyl ester benzenesulfonate and stereoselectively hydrogenated in organic solvents. An extended screening with rhodium‐ and iridium‐diphosphine catalysts was performed. Under optimized conditions the asymmetric hydrogenation provided a solution of tetrahydrofolic acid dimethyl ester with up to 44% de. The de could be increased to 98% by fractional crystallization of L ‐tetrahydrofolic acid dimethyl ester benzenesulfonate from the hydrogenation mixture. Hydrolysis of the ester afforded optically pure L ‐tetrahydrofolic acid, which can be isolated or converted into its 5‐ or 10‐ or 5,10‐substituted derivatives.     

Iodine-modified Pt nanoparticles accelerate the hydrogenative ring-opening of furfurals to linear alcohols

The hydrogenative ring-opening of furfurals (furfural and 5-methylfurfural) to linear diols (1,4-pentanediol and 2,5-hexanediol) is of great significance for bioderived fine chemical synthesis. Unfortunately, the catalytic activity and selectivity are unsatisfactory because of the interference of various side reactions, such as overhydrogenation to tetrahydrofurans. Herein, the preparation of an iodine (I) modified Pt-based catalyst with abundant Pt-I pairs is reported for the first time and shows high catalytic efficiency for linear diol synthesis with a yield of 80%–90% via the hydrogenative ring-opening route, whereas bare Pt counterpart only shows tetrahydrofuran synthesis via the overhydrogenation route. The catalytic reaction mechanism shows the in-situ hydrogen spillover-promoted H⁻-Pt-I-H⁺ pairs not only supply hydrogenation sites for the C=O hydrogenation step but also provide Brønsted acidic sites for the ring-opening step. This work presents a feasible and convenient strategy for bifunctional catalysis with powerful linear diol synthesis over iodine-modified noble metals.     

草酸二甲酯加氢合成乙二醇Cu/SiO_2催化剂的稳定性试验研究

合成气经草酸二甲酯加氢制乙二醇技术在工业应用过程中存在一些技术难题,其中草酸二甲酯加氢制乙二醇催化剂的稳定性是制约该技术发展的瓶颈。以Cu/SiO_2草酸二甲酯加氢催化剂A为研究对象,通过2 600 h的稳定性实验研究,考察反应温度对草酸二甲酯转化率、乙二醇选择性以及产物中乙醇酸甲酯含量的影响,为合成气经草酸二甲酯制乙二醇技术的工业应用优化提供重要的技术支持。结果表明,当反应压力2.8 MPa、空速(0.3~0.5)h-1、氢酯物质的量比120~140和反应温度216℃时,草酸二甲酯转化率近100%,乙二醇选择性大于95.0%,产物中乙醇酸甲酯质量分数小于0.5%,Cu/SiO_2催化剂A稳定性较好。     

Hydroprocessing of Aromatics Using Sulfide Catalysts Supported on Ordered Mesoporous Phenol–Formaldehyde Polymers

Ni–W sulfide catalysts for the hydroprocessing of aromatic hydrocarbons were synthesized by the in situ decomposition of tetrabutylammonium nickel thiotungstate complex supported on ordered mesoporous phenol–formaldehyde polymer. Catalysts obtained with and without additional sulfidation with dimethyl disulfide were characterized by X-ray photoelectron spectroscopy and transmission electron microscopy. The catalytic activity has been studied using naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, and anthracene as examples. It is shown that the system used in this study proved to be active in hydrogenation and hydrocracking of polyaromatic hydrocarbons.     

Organische Phosphorverbindungen. XII [1]. Zum Hydrolyseverhalten von O,O-Dimethyl-O-(1,2-dibrom-2,2-dichlorethyl)-phosphat (Naled)

Organic Phosphorus Compounds. XII. The Hydrolytic Behaviour of O,O-Dimethyl O-(1,2-Dibromo-2,2-dichloroethyl) Phosphate (Naled) The hydrolysis of Naled 2 , an organophosphorus pesticide accessible by bromination of the enolphosphate Dichlorvos 1 , in unbuffered aqueous solution does not only lead — as hitherto described — to dimethyl phosphate 3 and bromodichloroacetaldehyde 4 (path A), but also via intermediate formation of Desmethylnaled 5 to monomethyl phosphate 6 (path B). Kinetic measurements show that in the temperature range of 20–30°C both reactions proceed with similar velocities, and the primary step 2 → 5 determines the rate of path B. In comparison to Dichlorvos 1 the hydrolytic stability of Naled 2 has been found to be markedly lower. — The information on the degradation of Naled in unbuffered aqueous solution is completed by studies on the pH-dependence of the hydrolysis and on the alkylation capacity of this pesticide.