脂肪醇催化胺化制叔胺工艺技术现状及前景

脂肪醇催化胺化制叔胺的工艺是目前生产脂肪叔胺的主要方法,和传统的酸法工艺相比具有明显的优势。该工艺的技术关键为胺化催化剂及工艺放大。催化剂的开发水平已经能够满足工业化生产的要求,但基础理论研究不够广泛的深入。要想进一步提高催化剂的水平。要从基础理论入手。工程放大主要是解决气、液、固三相之间的传质问题,可以通过反应器形式的改进来实现,如采用环路反应器及固定床反应器等。要从根本上解决国内目前叔胺生产厂家多但规模小的问题,需要在工程化问题上有所突破。     

异丙醇直接氨化合成异丙胺

采用浸渍法制备Cu -Ni-Zn -Mg/Al2 O3 催化剂 ,用于异丙醇氨化制异丙胺反应。研究了催化剂中铜、镍加入量及反应压力、温度、空速、氨与异丙醇摩尔比等对氨化反应的影响。在适宜的催化剂组成及操作条件下 ,异丙醇单程转化率达到 70 % ,异丙胺选择性达到 95 % ,具有较好的工业应用价值。     

Lewis Acid‐Catalyzed Direct Amination of Benzhydryl Alcohols

The Lewis acid‐mediated direct amination of benzylic alcohols is described, providing various benzylic amine derivatives in good yields under mild and environmentally benign conditions. Among the different Lewis acids tested, gold(III) proved to be the catalyst of choice for both chemical (yield, conversion) and practical reasons (a filtration over a silica pad is generally sufficient to obtain the corresponding benzylic amine in analytically pure form).     

制备胺基离子交换纤维的反应条件优化研究

以聚丙烯接枝苯乙烯纤维为原料,采用乙酰化及胺基化两步法反应,制备多胺基离子交换纤维。研究了反应时间和温度、催化剂及乙酰氯用量对乙酰化反应条件的影响。利用正交实验法研究了胺酰摩尔比、胺醛摩尔比、胺酸摩尔比及反应时间对胺化反应影响。所制备的胺基纤维对Cu2+吸附容量可达2.00mmol/g。     

端氨基聚醚的合成

研究了以改性雷尼镍为催化剂、聚醚和液氨为原料,临氢高压催化氨化制备端氨基聚醚的工艺路线,考察了反应温度、催化剂用量、氨醇比、氢醇比对反应的影响.结果表明,温度220℃、氨醇摩尔比10 ～ 12、氢醇摩尔比0.6～0.8、催化剂质量分数为7％～11％、反应时间4～5h时,聚醚氨化制备端氨基聚醚的转化率大于97％.     

Structural Determinants for the Non‐Canonical Substrate Specificity of the ω‐Transaminase from Paracoccus denitrificans

Substrate binding pockets of ω‐transaminase (ω‐TA) consist of a large (L) pocket capable of dual recognition of hydrophobic and carboxyl substituents, and a small (S) pocket displaying a strict steric constraint that permits entry of a substituent no larger than an ethyl group. Despite the unique catalytic utility of ω‐TA enabling asymmetric reductive amination of carbonyl compounds, the severe size exclusion occurring in the S pocket has limited synthetic applications of ω‐TA to access structurally diverse chiral amines and amino acids. Here we report the first example of an ω‐TA whose S pocket shows a non‐canonical steric constraint and readily accommodates up to an n‐butyl substituent. The relaxed substrate specificity of the (S)‐selective ω‐TA, cloned from Paracoccus denitrificans (PDTA), afforded efficient asymmetric syntheses of unnatural amino acids carrying long alkyl side chains such as L ‐norvaline and L ‐norleucine. Molecular modeling using the recently released X‐ray structure of PDTA could pinpoint an exact location of the S pocket which had remained dubious. Entry of a hydrophobic substituent in the L pocket was found to have the S pocket accept up to an ethyl substituent, reminiscent of the canonical steric constraint. In contrast, binding of a carboxyl group to the L pocket induced a slight movement of V153 away from the small‐pocket‐forming residues. The resulting structural change elicited excavation of the S pocket, leading to formation of a narrow tunnel‐like structure allowing accommodation of linear alkyl groups of carboxylate‐bearing substrates. To verify the active site model, we introduced site‐directed mutagenesis to six active site residues and examined whether the point mutations alleviated the steric constraint in the S pocket. Consistent with the molecular modeling results, the V153A variant assumed an elongated S pocket and accepted even an n‐hexyl substituent. Our findings provide precise structural information on substrate binding to the active site of ω‐TA, which is expected to benefit rational redesign of substrate specificity of ω‐TA.

     

管道化氨解合成1-氨基蒽醌新工艺

采用管道化氨解工艺合成1-氨基蒽醌,将1-硝基蒽醌的40%甲苯溶液、液氨及催化剂氯化铵的1%正丁醇溶液以流量比9.25:1:1.85经预混合器后以0.15 mL/s的总流量流经外径6mm,内径3 mm,总长50 m的管道反应器进行反应,反应温度200℃,反应压力15 MPa,反应停留时间40 min,减压精馏得1-氨基...     

Reductive amination of n-hexanol to n-hexylamine over Ni–Ce/γ-Al2O3 catalysts

The amination of alkyl alcohols is one of the most promising paths in synthesis of aliphatic amines. Herein, cerium doped nickel-based catalysts were synthesized and tested in a gas-phase amination of n-hexanol to n-hexylamine. It was found that the activity of the Ni/γ-Al₂O₃ catalyst is significantly improved by doping an appropriate amount of cerium. The presence of cerium effectively inhibits the agglomeration of nickel particle, resulting in better Ni dispersion. As Ni particle size plays critical role on the catalytic activity, higher turnover frequency of n-hexanol amination was achieved. Cerium doping also improves the reduction ability of nickel and enhances the interactions between Ni and the catalyst support. More weak acid sites were also found in those cerium doped catalysts, which promote another key step—ammonia dissociative adsorption in this reaction system. The overall synergy of Ni nanoparticles and acid sites of this Ni–Ce/γ-Al₂O₃ catalyst boosts its superior catalytic performance in the amination of n-hexanol.     

Compatibilization of poly(methyl methacrylate) and cellulose nanocrystals through co-continuous phase to enhance the thermomechanical properties

The present study focuses on enhancing the thermomechanical properties of poly(methyl methacrylate) (PMMA), a transparent and biocompatible polymer known for its high strength but limited toughness. The approach involves the development of PMMA/cellulose nanocrystals (CNCs) composites. To improve the interfacial compatibility between PMMA and CNCs, a two-step process is employed. Initially, the CNCs undergo oxidation using sodium periodate, followed by the introduction of amino groups through reductive amination. The aminated CNCs are then covalently bonded to PMMA via an amidation reaction using the “grafting onto” approach. Subsequently, the grafted CNCs are incorporated into the PMMA matrix using the solvent casting method. The resulting composites are extruded into filaments. Elemental composition analysis confirms CNC modification, revealing the presence of 1.6% nitrogen. The modified CNCs exhibit a higher degradation temperature than unmodified CNCs, showing a 50°C increase. The composites' dynamic mechanical analysis (DMA) reveals a 20% improvement in storage modulus (E′) upon incorporating 1.5% of the grafted CNCs into the PMMA matrix. This enhancement is attributed to the formation of co-continuous phases in the composite structure.