十二烷基硫酸钠对原位晶化制备小晶粒NaY的影响

研究了十二烷基硫酸钠对原位晶化制备小晶粒NaY的影响,并以包含小晶粒NaY的原位晶化产物为母体,通过铵交换和稀土离子交换制备出了REUSY催化剂.采用X射线衍射(XRD)、扫描电镜(SEM)、X射线荧光(XRF)及N₂物理吸附-脱附等手段对样品进行了表征,采用微反活性评价装置和小型固定流化床(ACE)评价了所制备催化剂在重油催化裂化反应中的催化性能.结果表明:在原位晶化合成NaY的体系中,添加高岭土微球质量5%的十二烷基硫酸钠,可以将分子筛的平均晶粒尺寸由540 nm减小到250 nm.相比于常规的原位晶化型流化催化裂化(FCC)催化剂,以包含小晶粒NaY的原位晶化产物为母体所制备出的催化剂,在反应原料的转化率、裂化产物的选择性以及抗积碳性能等方面均有明显的提高或改善.     

微波诱导快速合成纳米NaY分子筛

报导了一种在常压回流微波加热条件下,可使合成的NaY分子筛晶粒尺寸减小至100 nm以下的方法.添加柠檬酸的晶化速率接近添加稀土离子的晶化速率,合成60 min后两者得到的NaY分子筛的晶粒度和硅铝比接近,约为40 nm和5.2,晶粒度小且硅铝比高于在相同条件下没有添加合成得到的NaY分子筛.微波合成的NaY分子筛的晶粒度明显小于常规相同配比所得样品的晶粒度且晶化时间明显缩短,充分证明了微波加热快速均匀且能够得到较小晶粒度的特点.     

超微NaY分子筛的合成(Ⅰ)──添加轻稀土离子的影响

导向剂的陈化时间和反应胶的晶化温度可以影响NaY分子筛的晶化行为.随导向剂陈化时间的增加,NaY分子筛的晶化速度加快,晶粒尺寸减小;随晶化温度的升高,NaY分子筛的晶化速度加快,但晶粒尺寸增加.而向合成体系中添加轻稀土离子(Ln³⁺)对NaY分子筛的晶化行为影响更为明显.与未添加稀土离子时相比较,在一定的稀土离子添加量范围内[n(Ln³⁺)/n(Al³⁺)<0.2],NaY分子筛的晶化速度明显加快而晶粒尺寸显著减小,同时所合成出的NaY分子筛的n(SiO₂)/n(Al₂O₃)比也有较大的提高.添加稀土离子使合成体系中形成异晶晶种的Ln(OH)₃微晶,从而进一步引发NaY分子筛的成核.     

超微NaY分子筛的合成(Ⅱ)——添加铝络合剂的影响

NaY分子筛合成体系中添加铝的络合剂(乙二胺四乙酸、柠檬酸和醋酸),可有效地减小分子筛的晶粒尺寸及增加分子筛的晶化速度和SiO2/Al2Oa物质的量比.在添加柠檬酸的合成体系中,考察了柠檬酸的添加量对NaY分子筛晶化行为的影响.发现存在着一个最佳的柠檬酸的添加量范围,即n(柠檬酸)：n(氧化铝)≤2：1,在此范围内,NaY的晶化速率和硅铝比较高,而晶粒尺寸较小.     

纳米NaY分子筛的合成及其催化柴油加氢改质性能

在系统考察添加阳离子表面活性剂、凝胶陈化以及晶化温度和晶化时间等因素对NaY分子筛细化影响的基础上,对纳米NaY分子筛的合成规律进行了研究;合成出了n(SiO2)/n(Al2O3)=4.5,BET比表面积为620m2/g,孔容为0.34 cm3/g,微孔集中分布在0.55 nm附近,粒度分布范围在100 nm以内的纳米NaY分子筛.并采用XRD、BET、IR、TTEM和NH3-TPD等手段系统表征了纳米NaY分子筛的微观结构.分别采用合成的纳米NaY分子筛和微米NaY分子筛为原料制备负载型Ni-Mo-P催化剂,并以FCC柴油为原料,考察了催化剂的加氢改质性能,结果表明,与微米NaY分子筛基负载型Ni-Mo-P催化剂相比,纳米NaY分子筛基负载型Ni-Mo-P催化剂,在加氢脱氮率、密度和十六烷值相当的情况下,其加氢脱硫率较高,柴油收率较高.     

超微NaY分子筛的合成（II）—添加铝络合剂的影响

NaY分子筛合成体系中添加铝的络合剂（乙二胺四乙酸、柠檬本矣醋酸）,可有效地减小分子筛的晶粒尺寸及增加分子筛的晶化速度和SiO2/Al2O3物质的量比,在添加柠檬酸的合成体系中,考察了柠檬酸的添加量对NaY分子的筛晶化的影响,发现存在着一个最佳的柠檬酸的添加量范围,即n（柠檬酸）：n（氧化铝）≤2：1,在此范围内,NaY的晶化速率和硅铝比较高,而晶粒尺寸较小。     

甲醇催化转化制丙烯中HZSM-5分子筛的尺寸效应

甲醇催化制丙烯(MTP)是一个具有重要工业应用的研究课题, 目前普遍采用的催化剂是HZSM-5 分子筛. 通过调节分子筛合成原料的配比、晶化温度和晶化时间等参数, 对所制备的不同晶粒尺寸的HZSM-5 分子筛, 综合利用X射线衍射(XRD)、扫描电镜(SEM)、N₂吸附和氨气程序升温脱附(NH₃-TPD)等手段表征了其晶格结构、表观形貌、孔结构以及酸性质. 利用固定床反应装置对HZSM-5 分子筛甲醇催化制丙烯的活性和稳定性进行了评价, 并采用热重(TG)分析技术对催化剂的积炭性能进行了考察. 实验结果表明, HZSM-5 分子筛粒度的减小可以增加分子筛比表面积、孔体积, 同时有更多开放的孔口及短的孔道长度, 有利于反应物分子的吸附和传质,并降低了产物分子在孔道中的扩散距离及发生二次反应的几率, 提高了催化剂的抗积炭能力和容炭能力以及稳定性; 而且所合成的小尺寸分子筛单位质量的总酸量及强酸量均有不同程度的下降, 有利于提高目标产物丙烯的选择性.     

海泡石原位晶化合成NaY分子筛的研究

首次用海泡石为硅源、高岭土为铝源,在水热条件下原位晶化合成NaY分子筛,采用粉末X射线衍射仪、电子扫描电镜等测试手段对所合成样品进行表征分析,着重考察晶化温度和投料配比对产品相对结晶度的影响.研究结果表明,NaY分子筛的形成受晶化温度的影响最大,随温度的升高,产品的相对结晶度显著提高,晶化温度升至100℃时,得到结晶度较高的NaY分子筛晶体.在原位晶化体系中,随n(SiO2)/n(Al2O3)减小,其相对结晶度增大;增加体系的n(Na2O)/n(SiO2)和减小n(H2O)/n(Na2O)都增大产品的相对结晶度;n(SiO2)/n(Al2O3)在投料比影响因素中占主导地位.     

预吸附微波合成纳米NaY沸石晶种制备NaY型分子筛膜

在常压回流的微波加热体系中成功地合成出纳米尺寸的NaY分子筛,XRD和SEM等表征结果表明,分子筛具有40nm左右的平均晶粒尺寸.以其为晶种,预吸附在多孔氧化铝载体上,结合原位水热法进行二次晶化,制备出较为致密的NaY分子筛膜,该膜主要以孪生聚晶的形式存在.CO₂/N₂气体分离测试结果显示,随着温度的升高,分子筛膜的气体分离能力呈上升趋势,在140℃时真实选择分离系数达到最大值4.0.     

以氨水做碱源胶态晶种导向法合成小晶粒TS-1分子筛

TS-1分子筛具有MFI拓扑结构,因其独特的择形选择性和优异的催化氧化能力而广受关注.最早报道的TS-1合成方法采用大量四丙基氢氧化铵(TPAOH)作为有机结构导向剂, TPAOH价格昂贵,制约着TS-1分子筛大规模应用.开发廉价、环境友好的合成工艺是TS-1分子筛合成领域的重要课题.以价格相对较低的四丙基溴化铵(TPABr)代替TPAOH做有机结构导向剂,以氨水为碱源可合成TS-1分子筛,但产物晶粒尺寸远远大于以TPAOH做模板的合成结果,影响TS-1分子筛的传质和催化性能.因此,人们对该法进行了改进,选用有机胺作为碱源, TPABr为结构导向剂合成TS-1分子筛,但始终未能将其晶粒尺寸降至1μm以下.在合成体系中引入预先合成的TS-1分子筛或TS-1胶态前驱体作为晶种可以促进成核,缩短成核诱导期,有利于获得小晶粒尺寸的TS-1分子筛.此类方法往往需要辅助以大量有机胺等结构导向剂;胶态TS-1前驱体的制备需要特别小心以保证晶种中Ti的四配位状态,通常需要经历低温水解钛酸四丁酯(TBOT)和高温加热除醇等繁琐步骤.而胶态纯硅silicalite-1制备则相对简单,且已广泛用于导向合成同样具有MFI结构的ZSM-5沸石,但目前鲜有以silicalite-1做晶种合成TS-1分子筛的报道.基于此,本文以纯硅胶态silicalite-1为晶种,以氨水做碱源,辅助以少量TPABr做导向剂,合成了小晶粒TS-1分子筛,并以正己烯环氧化和环己酮氨肟化做探针反应考察了所得TS-1分子筛的催化氧化性能. X射线衍射结果表明,当晶种中SiO2占合成体系中SiO2的10 wt%(晶种引入TPAOH, TPAOH/SiO2=0.35),加入TPABr (TPABr/SiO2=0.03)做辅助结构导向剂,即合成体系中总(TPAOH+TPABr)/SiO2摩尔比低至0.07时,所得样品依然具有良好的结晶度.扫描电镜照片观察不到无定形物存在;晶种中SiO2占合成体系中SiO2的10 wt%时,所得TS-1晶粒尺寸约为250 nm ×150 nm ×50 nm;其他条件不变,胶态晶种用量增加到15 wt%时,初级晶粒尺寸基本保持不变,晶粒-晶粒之间交叉生长,形成孪生形貌;继续增加胶态晶种用量至20 wt%时,晶粒尺寸下降至仅100 nm左右;而用20 wt%胶态晶种所含相同量的TPAOH来代替胶态晶种,得到样品呈近10μm的大块状.与之对应的是,胶态silicalite-1晶种导向得到的小晶粒TS-1分子筛具有比直接用TPAOH得到的大块状样品更大的外比表面积和堆积孔体积.分析结果显示所得TS-1分子筛的体相TiO2/SiO2比在41–43.红外光谱和紫外可见光谱结果表明,胶态晶种导向法所得TS-1分子筛中的Ti主要以四配位状态存在,而直接用TPAOH合成的大块状样品则呈现显著骨架外Ti吸收峰,说明胶态晶种有助于Ti物种进入分子筛骨架.在催化正己烯环氧化反应时,用胶态silicalite-1晶种导向得到的小晶粒TS-1分子筛表现出与大块状TS-1相似的催化性能;而以环己酮氨肟化做探针反应时,小晶粒TS-1分子筛因具有外比表面积大和扩散路径短等优点而表现出远远高于大块状TS-1分子筛的催化活性.但与文献报道的相同SiO2/TiO2比的TS-1分子筛比较,本文所得小晶粒TS-1分子筛催化正己烯环氧化的活性略差.提高该小晶粒TS-1分子筛正己烯环氧化活性和建立构-效关系是下一步工作的重点.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.