质子梯度转移酸性复合物及其在乙酸香叶酯合成中的催化能力（英文）

萜烯酯是一类重要的化学中间体和产品,广泛应用于香料、食品和医药等领域.酸催化的酯化反应是目前工业合成萜烯酯最流行的反应之一.已有用于合成萜烯酯催化剂的报道,并且大多数催化剂具有较高的催化活性,但多数催化剂没有在催化活性、选择性、稳定性和回收性等综合性能上表现出突出优势.质子型离子液体具有结构可调、易合成及易与产物分离的特点,被认为是酯化反应的绿色催化剂和分离剂.早期的质子型离子液体催化酯化研究主要集中在低碳链饱和有机酸酯的合成,对于易氧化的萜烯醇酯化研究较少.因为Brnsted碱上的N原子含有一个孤对电子,在质子型离子液体阳离子形成的过程中,酸上的质子传递到这个N原子上时会伴随着较大的吉布斯自由能改变.这个质子与Bronsted碱紧紧键合着,并使其酸性与游离酸相比减弱.众所周知,离子液体的催化活性强烈依赖于其酸强度.所以与游离酸相比,质子型离子液体在酯化反应中的催化活性常常被削弱.本课题组合成了一类新型的"质子梯度转移酸性复合物(PGTACs)"催化剂,通过核磁共振、质谱、红外光谱及元素分析等表征方法,发现其具有有别于常规质子型离子液体的键合模型,即同时具有一个N-H共价键和一个N…H氢键.这主要是由于阳离子1,10-邻菲罗啉具有高度的对称结构,且阳离子上的两个N原子位置较近.当第一个酸上的质子与碱上的第一个N原子键合后会对第二个酸上的质子与碱上的第二个N原子的键合造成较大的空间位阻,从而使后者以氢键键合方式存在.此外,为了进一步了解键合的两个质子的差异性,我们通过理论计算对其结构进行了优化,同样证明了N-H共价键和N…H氢键的存在,并得到它们的键长分别为1.032-1.036和3.068-3.571.本文对PGTACs的催化能力进行了系统研究,发现该类催化剂兼具强酸催化剂的高催化活性和弱酸催化剂的高选择性两方面优势,可选择性地高效催化合成乙酸香叶酯.当催化剂加入量为2%摩尔分数,反应时间为2 h,反应温度为50℃时,香叶醇转化率和乙酸香叶酯选择性分别高达99.5%和96.9%;而对于易氧化的萜烯酯(如乙酸芳樟酯、乙酸-α-松油酯和乙酸-4-松油酯等)仍有高于85%的收率.此外,研究还发现PGTACs催化剂是一类反应诱导自分离催化剂,反应初期可快速溶于反应体系中形成均相,反应结束后自动与产物分离,形成液液双相.此反应过程不仅有效解决了固体催化剂的传质阻力限制,还强化了反应,实现了反应与分离的耦合.最后,我们采用拟均相模型(PH model)对实验数据进行了拟合,为后续过程设计提供了宝贵的基础数据.     

相转移催化合成乙酸异戊酯

乙酸异戊酯是无色透明液体,具有香蕉和梨的香味,可用作食用香精,也是很好的有机溶剂,广泛用于医药、涂料、印染行业。合成乙酸异戊酯的经典方法是用浓Ｈ２ＳＯ４为催化剂酯化制得,但由于硫酸严重腐蚀设备和易引起副反应,使产品纯度低,后处理过程复杂,因而促使人们研究其它合成方法。自１９８１年黄化民等报道用无机硫酸盐作催化剂以来,不少研究者采用了用不同的无机盐超强酸、固体酸、杂多酸、离子交换树脂作为催化剂进行了广泛研究。但这些催化剂也有其自身的缺点。以季铵盐作为乙酸异戊酯的酯化反应催化剂尚未见文献报道,笔者采…     

硫酸氢钠催化合成乙酸β-萘酯

乙酸 β-萘酯可用做评价酯酶、或模拟酯酶活性的底物 [1,2 ] ,此类化合物可用乙酰氯在胺的作用下与酚反应制得 ,但用有机胺溶剂时后处理不方便 [3] .浓硫酸催化酸或酸酐与醇 (酚 )反应也可制得乙酸酯 ,但该法对设备腐蚀大 ,且反应体系为均相 ,存在催化剂和产物的分离问题 .近年来 ,人们开发了各种取代浓硫酸的催化剂 ,其中多相催化剂特别引人注目 [4 ] .本文考察了硫酸氢钠催化乙酸 β-萘酯的合成 ,发现其是有效的多相酯化催化剂 ,该法基本具备绿色化学的要求 .尚未见有文献报道 .醋酸酐、β-萘酚、Na HSO4 ·H2 O均为分析纯 .Na HSO4 …     

聚苯乙磺酰氯与三氯化铁复合物的合成及其对乙酸和正丁醇酯化…

聚苯乙烯磺酰氯树脂１与三氯化铁或三氯化铁的六水合物在二氯乙烷的回流温度下分别制得了复合树脂２和复合树脂３。这责任中树脂在二氯乙烷中分别用无水ＨＣｌ处理分别得到复合树脂４和复合树脂５。     

螯合型二甘醇钛酸酯的合成及其催化性能研究

报导了两种新的螯合型二甘醇钛酸酯的合成方法，进行了ＩＲ和ＵＶ鉴定，并作为酯化反应催化剂催化合成了邻苯二甲酸二辛酯。研究了酯化反应转化率与反应时间、反应温度及催化剂用量的关系，探讨了催化剂结构与催化性能的关系。     

乙酸苄酯在H-β沸石上的催化合成

β沸石是一种高硅大孔沸石^[1],H－β沸石已用于催化某些有机反应,例如芳醚的酰化^[2],歧化反应^[3]等。酯化反应通常用浓硫酸或Lewis酸作催化剂,但传统的方法有催化剂易流失,反应产物难纯制,腐蚀性和有毒废物等缺点,用HZSM－5等固体酸催化剂^[4,5]能显克服这些,本报道用H－β沸石作催化剂合成乙酸苄酯的结果。     

PPY催化合成乙酸沉香酯

利用吡啶与二氯亚砜反应 ,制成双吡啶盐 ,进而与四氢吡咯反应 ,一步法合成 4 ( 1 四氢吡咯 )吡啶(PPY)。利用PPY为催化剂进行沉香醇的酰化反应 ,并对影响反应的诸因素进行了讨论 ,醇的转化率为 99% ,酯的收率为 88.2 %。     

相转移催化法合成芳氧基乙酸芳酯及硫赶酸苯酯

用液-液相转移催化法合成了35个芳氧基乙酸芳酯,5个芳氧基硫赶乙酸苯酯,与经典方法相比,相转移催化法有产率较高,反应条件温和,操作简便等优点。     

乙酸苄酯合成中接枝型三相相转移催化剂的活性及催化反应动力学

采用"接出(grafting from)"方式,将苯乙烯(St)接枝聚合在微米级硅胶表面,然后对接枝的聚苯乙烯进行了氯甲基化(CM)反应,制得了氯甲基聚苯乙烯/硅胶微粒(CMPS/SiO2);使三丁胺与三苯基膦分别与CMPS大分子链上的苄氯基团发生季铵化与季鏻化反应,分别制得了固载有季铵盐与季鏻盐的接枝微粒QN-PSt/SiO2与QP-PSt/SiO2,即制得了两种接枝型三相相转移催化剂.将该催化剂用于苄氯与乙酸钠合成乙酸苄酯的相转移催化反应,并重点考察了催化剂的活性与催化动力学.实验结果表明,两种接枝型三相相转移催化剂QN-PSt/SiO2与QP-PSt/SiO2对乙酸苄酯的合成都具有明显的催化活性,在液-固-液之间可有效地实现反应物种乙酸根的转移;两者相比,季鏻盐型的催化剂QP-PSt/SiO2的催化活性更高;当水相中乙酸钠用量大大过量时,在有机相中苄氯与乙酸根的反应属准一级反应;两个相转移反应体系相比,以QP-PSt/SiO2为催化剂时反应的表观活化能更低.     

稻壳炭基固体酸催化剂的制备及其催化酯化反应性能

以热解稻壳炭为原料, 浓硫酸为磺化剂制备了固体酸催化剂. 采用X射线衍射、X射线光电子能谱、元素分析、孔结构分析和热重-质谱联用等手段对其进行了表征. 以油酸和甲醇的酯化为探针反应, 考察了磺化温度和时间对催化剂活性的影响, 探讨了反应条件对油酸转化率的影响, 并对所制催化剂的稳定性进行了研究. 结果表明, 制备该催化剂的适宜磺化温度和时间分别为90℃和0.25 h, 在该条件下制得的催化剂为无定形碳结构, 磺酸基密度为0.7 mmol/g. 该催化剂表现出较高的催化酯化反应活性, 在催化剂用量为5%、甲醇/油酸摩尔比为4、酯化温度和时间分别为110℃和2 h的条件下, 油酸的酯化率可达98.7%. 该催化剂具有较好的稳定性, 经7次连续反应后, 油酸的酯化率仍可达96.0%.     

Contrast performance in catalytic ability—new cinchona phase transfer catalysts for asymmetric synthesis of α-amino acids

Two new cinchona phase transfer catalysts are prepared from dihydrocinchonidine using 13-picenylmethyl bromide and 1-pyrenylmethyl bromide, respectively. A total contrast in catalytic efficiency is observed during the asymmetric alkylation of glycinate esters; with one catalyst, the reaction is either incomplete or the enantioselectivity is very poor (15% ee) while the other catalyst afforded high selectivity up to 94% ee.     

Study of catalytic hydrodeoxygenation performance for the Ni/KIT-6 catalysts

Ni/KIT-6 catalysts loaded with different amounts of metallic Ni were prepared by impregnation method. The prepared catalysts and their precursors were investigated through wide- and low-angle XRD, TEM, BET, H₂-TPR, and H₂-TPD analyzes. The catalytic hydrodeoxygenation performance of the catalysts was evaluated using ethyl acetate as a model bio oil compound. Results indicate that the catalytic hydrodeoxygenation performance of the prepared catalysts was directly related to hydrogen storage properties, hydrogen desorption properties, dispersion of the active component Ni, and so on. The ethyl acetate conversion and ethane selectivity of 25?wt% Ni/KIT-6 catalyst were 100 and 96.8%, respectively, at 300?°C, which shows the best performance. The hydrodeoxygenation activity of ethyl acetate was higher than that of methyl acetate and isopropyl acetate because of the effect of molecular polarity and size. And, this reaction is a structure sensitive reaction.     

A facile synthesis of cellulose acetate reinforced graphene oxide nanosheets as proton exchange membranes for fuel cell applications

In this work, for the first time, a simple casting process is used to create an efficient and highly stable cellulose acetate (CA) based membrane with dispersive graphene oxide nanosheets (GO). The successful preparation of GO and its integration into the polymer matrix was verified by structural and morphological characterization using FTIR, TEM, SEM, and XRD. Furthermore, the impact of GO nanosheets and their content on the composite membranes' physicochemical properties is investigated. The water uptake increased up to 24% as the concentration of GO increased, while the ion exchange capacity increased threefold compared to the blank CA membrane. Additionally, increasing GO loading also enhanced the proton conductivity and the tensile strength of the developed membranes. The homogeneous CA/GO nanocomposite membranes with GO filler amounts ranging from 0.3 to 0.8 wt% were found to have excellent proton conductivity varying from 9.2 to 15.5 mS/cm compared to 6.94 mS/cm for Nafion 212. Further, as systematically studied and compared in membrane performance, the overall power density of the membrane electrode assembly (MEA) with GO content was increased up to 519 mW/cm² compared to 401 mW/cm² for Nafion 212 with significantly lower cost. The encouraging outcomes of this study pave the way for a simple, environmentally friendly, and cost-effective approach for developing nanocomposite membranes for application in PEMFCs.     

Novel synthesis of polymeric phase transfer catalysts containing N,N-dialkylacrylamide unit and their catalytic activity

Soluble polymeric phase transfer catalysts (PTCs) containing benzyltributylphosphonium chloride moieties and polar N,N-dialkyl-acrylamide with long alkyl groups such as N,N-dipropylacrylamide, N,N-dibutylacrylamide, N,N-dihexylacrylamide, and N,N-dioctylacrylamide were prepared via two-step reactions from p-chloromethylstyrene and the corresponding N,N-dialkylacrylamide. When the obtained polymers were added, the phase transfer catalyzed reaction of benzylchloride with solid potassium acetate to proceed smoothly. The catalytic activity was strongly affected by the content of phosphonium chloride and the varieties of comonomer unit in the polymeric PTC. The polymeric PTC containing the N,N-dihexylacrylamide unit showed excellent high catalytic activity in a low polar solvent such as the mixed solvent of toluene with 70 vol % n-tridecane. Therefore, the polymer containing lipophilic long chains such as the hexyl group is desirable for polymeric PTC. © 1996 John Wiley & Sons, Inc.     

磁性纳米复合氧化物固体酸催化剂的制备及酯化性能

固体酸催化剂的无腐蚀、环境友好和可循环使用等特点使其成为无机液体酸的最佳替代物.磁性纳米固体酸具有优于常规固体酸催化剂的催化活性及分离简单的特性.用共沉淀法分别合成了一系列三组分TiO2-Al2O3-Fe3O4(TAF)和CeO2-Al2O3-Fe3O4(CAF)及四组分ZrO2--Al2O3-Fe3O4(ZACF)磁性纳米复合氧化物固体酸催化剂,通过电感耦合等离子体原子发射光谱、比表面积测定、X射线衍射、透射电镜、热重分析和红外光谱等对其进行了表征,并利用酯化反应作为探针反应评价了其催化性能.结果表明,合成的磁性纳米固体酸催化剂在酯化反应中表现出很好的催化活性.     

Cobalt(II) phenoxy-imine complexes in radical polymerization of vinyl acetate: The interplay of catalytic chain transfer and controlled/living radical polymerization

A series of cobalt(II) phenoxy-imine complexes (Co^II(FI)₂) have been synthesized to mediate the radical polymerization of vinyl acetate (VAc) and methyl acrylate (MA) to evaluate the influence of chelating atoms and configuration to the control of polymerization. The VAc polymerizations showed the properties of controlled/living radical polymerization (C/LRP) with complexes 1a and 3a , but the catalytic chain transfer (CCT) behaviors with complexes 2a , 1b , 2b , and 3b . The control of VAc polymerization mediated by complex 1a could be improved by decreasing the reaction temperature to approach the molecular weights that not only linearly increased with conversions but also matched the theoretical values and relatively narrow molecular weight distributions. The catalytic chain transfer polymerizations (CCTP) mediated by complexes 2a , 1b , 2b , and 3b were characterized by Mayo plots and the polymer chain end double bonds were observed by ¹H NMR spectra. The tendency toward C/LRP or CCTP in VAc polymerization mediated by Co^II(FI)₂ could be determined by the ligand structure. Cobalt complex coordinated by the ligand with more steric hindered and less electron-donating substituents favored the controlled/living radical polymerization. In contrast, the efficiency of CCT process could be enhanced by less steric hindered, more electron-donating ligands. The controlled/living radical polymerization of MA, however, could not be achieved by the mediation of these cobalt(II) phenoxy-imine complexes. Associated with the results of polymerization mediated by other cobalt complexes, this study implied that the configuration and spin state of cobalt complexes were more critical than the chelating atoms to the control behavior of radical polymerization. © 2019 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 101–113     

ZSM-5分子筛的粒径可控合成及其在甲醇转化中的催化作用

以四丙基氢氧化胺为模板剂、聚乙二醇为添加剂,水热合成了粒径在0.1～14 μm且分布均一的ZSM-5分子筛,并采用XRD、SEM、BET、Py-IR、NH₃-TPD和ICP等技术对其进行了表征,考察了不同粒径分子筛在甲醇转化制碳氢化合物反应中的催化作用。结果表明,通过调变PEG添加量、硅源种类和水含量以及控制陈化和晶化条件,可以在较大范围内调变分子筛晶粒尺寸。随着粒径的减小,ZSM-5晶粒的聚集程度、比表面积和Si/Al比提高,而结晶度、BrØnsted酸浓度和总酸量有所下降。在甲醇催化转化制碳氢化合物的反应中,粒径为0.1 μm的分子筛催化稳定性最好;随着粒径的增大,其稳定性逐渐下降,粒径为14 μm的分子筛催化剂寿命明显降低。同时,粒径对甲醇转化产物分布也有较大影响;小粒径分子筛有利于生成轻质烃类(C₁～C₄),而大粒径分子筛对C₅以上烷烃和芳烃的选择性较高。     

低温等离子体制备低碳醇合成用KNiMo基催化剂及其结构性能表征

采用低温等离子体法在温和条件下制备了低碳醇合成（HAS）用的高性能KNiMo基催化剂,利用XRD、氮吸附、TEM、H₂-TPD、CO-TPD和原位CO吸附DRIFTS等技术对其进行了表征。结果表明,与传统的热法制备相比,低温等离子体法不仅缩短了制备时间,而且得到的KNiMo基催化剂层数少、粒径小、分散度高,有利于形成更薄和更短的片层,并暴露大量位于边、角位的催化活性位,促进CO转化和醇的形成,表现出优异的低碳醇合成催化性能。其中,采用低温等离子体直接制备的KNiMo-DPS催化剂,在5 MPa、350℃、空速为5000 h^-1的反应条件下,CO转化率达到32.3%,总醇选择性为75.1%,总醇中C₂₊醇的选择性为65.2%。     

Preparation of microporous polymer-encapsulated Pd nanoparticles and their catalytic performance for hydrogenation and oxidation

Palladium nanoparticles (Pd NPs) encapsulated by conjugated microporous polymers (CMPs) were prepared by the Pd-catalyzed polymerization followed by a thermal treatment with N₂ or H₂. The Pd catalysts were embedded in the porous network during polymerization and used as a precursor for the generation of Pd NPs in CMP. Although no Pd NPs were formed in the as-synthesized Pd/CMPs, Pd NPs with 1.6–3.5 nm size were formed after the thermal treatment. The obtained Pd/CMP-N₂ and -H₂ catalysts were highly selective in the hydrogenation of 4-nitrostyrene to 4-ethylnitrobenzene, whereas Pd NPs supported on carbon (Ketjen black) gave a fully reduced product, 4-ethylaniline. Substituents in CMP framework could change the catalytic activity of Pd NPs; hydroxy-substituted CMP encapsulated Pd NPs showed higher catalytic activity than Pd/CMP-H₂ for benzyl alcohol oxidation.