AgCeY分子筛吸附剂的制备及性能研究

以NaY分子筛为载体,通过液相离子交换法制备了经Ag、Ce双金属离子改性的AgCeY吸附剂,并利用UV-vis、XRD、BET、ICP、XPS和FT-IR技术对吸附剂进行了表征。以噻吩/苯并噻吩/正辛烷/甲苯体系为汽油模拟体系,考察了制备条件和吸附条件对吸附剂脱硫性能的影响以及吸附剂再生性能。结果表明,AgCeY吸附剂上Ag、Ce这两种金属元素分别以Ag⁺、Ce⁴⁺形式存在,AgCeY吸附剂具有类似于AgY的高的脱硫性能,又具有类似于CeY的高的吸附选择性,AgCeY对噻吩(TP)和苯并噻吩(BT)的吸附选择性顺序为BT > TP;最适宜的制备条件为先交换Ag后交换Ce离子、离子交换24 h、Ce/Ag物质的量比为2.5、500 ℃焙烧;在原料20 mL、AgCeY吸附剂用量0.2 g、吸附温度50 ℃、吸附时间60 min下,噻吩脱硫率可达到59.0%,苯并噻吩脱硫率达到96.5%。     

改性Y型分子筛对FCC汽油脱硫性能的研究

采用液相离子交换法制备了Cu(I)Y、NiY、CeY分子筛,利用XRD、ICP/MS、N₂吸附脱附等技术对其物化性质进行了表征,使用固定床技术和色谱-硫化学发光检测(SCD)偶联技术系统考查了改性Y分子筛对FCC汽油的选择性吸附脱硫性能,着重探讨了FCC汽油选择性吸附脱硫过程中硫化物的脱除规律。结果表明,不同金属阳离子改性的Y分子筛对FCC汽油中不同硫化物选择性有所不同,对CeY分子筛:2-甲基-5-乙基噻吩<噻吩3硫醇< C₂噻吩<2或3-甲基噻吩<苯并噻吩<3,4-二甲基噻吩≈2,3,4-三甲基噻吩<四氢噻吩,而NiY与Cu(I)Y选择性相同:C₃硫醇<2-甲基-5-乙基噻吩2噻吩<2或3-甲基噻吩<噻吩<苯并噻吩<3,4-二甲基噻吩≈2,3,4-三甲基噻吩<四氢噻吩,改性Y分子筛对噻吩及小分子烷基取代噻吩类硫化物的选择性较差。     

苯和1-辛烯对Ce（Ⅳ）Y分子筛选择性吸附脱硫的影响

选取苯和1-辛烯作为模拟汽油中的芳烃和烯烃,分别研究它们对Ce(Ⅳ)Y分子筛选择性吸附脱硫的影响.结果表明,吸附剂的选择性吸附脱硫性能随着模拟油中苯和1-辛烯含量的增加而显著降低.借助傅立叶变换红外光谱(FT-IR)、紫外漫反射光谱(UV-DRS)技术研究发现.Ce(Ⅳ)Y分子筛对苯和1-辛烯的吸附模式及影响脱硫的机理是不同的.Ce(Ⅳ)Y分子筛阳离子和苯形成π络合作用,作用力较弱,容易脱附;而与1-辛烯的双键发生σ-π络合,不容易脱附.在Ce(Ⅳ)Y分子筛选择性吸附含苯模拟油中的硫化物时,由于苯的存在,苯和噻吩在分子筛表面存在严重竞争吸附,影响了吸附剂的选择性脱硫.而在含1-辛烯的模拟油中,由于1-辛烯直接和分子筛发生强相互作用,占据了吸附剂的活性位,导致Ce(Ⅳ)Y分子筛的脱硫性能显著降低.     

苯和1-辛烯对Ce(IV)Y分子筛选择性吸附脱硫的影响

选取苯和1-辛烯作为模拟汽油中的芳烃和烯烃, 分别研究它们对Ce(IV)Y分子筛选择性吸附脱硫的影响. 结果表明, 吸附剂的选择性吸附脱硫性能随着模拟油中苯和1-辛烯含量的增加而显著降低. 借助傅立叶变换红外光谱(FT-IR)、紫外漫反射光谱(UV-DRS)技术研究发现, Ce(IV)Y分子筛对苯和1-辛烯的吸附模式及影响脱硫的机理是不同的. Ce(IV)Y分子筛阳离子和苯形成π络合作用, 作用力较弱, 容易脱附; 而与1-辛烯的双键发生σ-π络合, 不容易脱附. 在Ce(IV)Y分子筛选择性吸附含苯模拟油中的硫化物时, 由于苯的存在, 苯和噻吩在分子筛表面存在严重竞争吸附, 影响了吸附剂的选择性脱硫. 而在含1-辛烯的模拟油中, 由于1-辛烯直接和分子筛发生强相互作用, 占据了吸附剂的活性位, 导致Ce(IV)Y分子筛的脱硫性能显著降低.     

CuNaY分子筛上汽油馏分中含硫组分的选择吸附及其红外光谱研究

本文从基础研究的角度出发,以红外光谱技术为主要研究手段,以噻吩为汽油馏分中含硫有机分子的模型化合物,首次给出了噻吩分子在吸附剂表面的吸附方式和吸附位,以及芳烃对噻吩吸附的影响等红外光谱信息.为避免吸附剂的强酸性可能引起的干扰,采用NaY分子筛为原料进行液相离子交换制备吸附剂.     

介孔材料MCM-41上汽油吸附深度脱硫

 研究了不同硅铝比的MCM-41介孔材料作为吸附剂对模型汽油以及真实FCC汽油的脱硫性能. 结果表明,在室温和常压下,MCM-41介孔材料对模型溶液中噻吩的吸附随着吸附剂中铝含量的增加而显著提高. 吡啶吸附的红外光谱显示,噻吩吸附容量的提高与吸附材料酸性的明显增大有直接关系. 但在对FCC汽油的吸附脱硫实验中,随着MCM-41中铝含量的提高,脱硫率并未增大. 这主要是由于在FCC汽油中存在大量性质与噻吩类含硫化合物十分相近的芳烃和烯烃,竞争吸附导致MCM-41对有机硫化物的吸附能力显著降低.     

原位傅里叶变换红外光谱研究Y型分子筛表面酸性对吸附有机分子的影响

采用吡啶原位吸附傅里叶变换红外(Py-FTIR)光谱对液相离子交换(LPIE)和固相离子交换(SSIE)法制备的CeY分子筛以及HY和NaY的酸性进行了测定. 在原位条件下采用单探针分子噻吩、环己烯和苯对其在分子筛上的吸附过程进行了研究; 以噻吩和环己烯、噻吩和苯组成的双探针分子对吸附过程中存在的竞争吸附、催化反应以及吸附机理进行了系统研究. 结果表明, HY和L-CeY 分子筛表面强Brönsted (B)酸性位可导致吸附在其表面的噻吩发生低聚反应以及吸附的环己烯产生二聚环己烯碳正离子. 低聚的噻吩和吸附的环己烯在分子筛上发生强的化学吸附, 进一步抑制和阻碍噻吩硫化物与分子筛吸附活性中心发生作用, 从而降低了吸附剂的选择性以及吸附硫化物的能力. 吸附剂表面Lewis (L)酸中心是吸附的主要活性中心, 大量弱的L 酸, 有利于噻吩吸附. 并且, S-CeY分子筛表面弱的L酸对吸附噻吩具有一定的选择性, 它受到环己烯的影响较小, NaY吸附剂对噻吩、环己烯和苯选择性较差, 它只与吸附质作用的先后有关.     

NiY分子筛选择性吸附脱硫性能及作用机理

用液相离子交换法制备了NiY分子筛,并用XRD、TEM、ICP、N2吸附和吡啶吸附原位红外技术等表征手段对其进行了表征. 利用固定床、气相色谱-硫发光检测器（GC-SCD）及傅里叶红外光谱（FT-IR）等方法系统研究了NiY分子筛对噻吩、2-甲基噻吩、3-甲基噻吩、四氢噻吩、苯并噻吩、二苯并噻吩、4-甲基二苯并噻吩、4,6-二甲基二苯并噻吩8种有机硫化物的选择性吸附脱硫性能和吸附机理. 结果表明,NiY分子筛对硫化物的穿透吸附硫容量顺序为四氢噻吩﹥苯并噻吩≈二苯并噻吩≈4,6-二甲基二苯并噻吩﹥4-甲基二苯并噻吩﹥2-甲基噻吩≈3-甲基噻吩﹥噻吩,说明有机硫化物的空间位阻效应不是其在NiY分子筛上吸附的决定因素. 红外结果表明,不同硫化物与NiY分子筛的作用机理并不相同,但主要以硫原子与金属离子配位作用（S-M作用）为主. 噻吩及其烷基取代物在NiY吸附剂上表面酸性作用下发生催化反应,噻吩环的共轭体系遭到破坏形成硫化物大分子或聚合物,导致分子筛孔道的堵塞,严重影响吸附剂的吸附脱硫能力. NiY的选择性吸附脱硫性能是硫化物与吸附中心的作用模式及吸附剂表面酸性综合作用的结果.     

NiY分子筛表面酸性影响其选择性吸附脱硫性能的机理研究

采用原位红外光谱技术,以噻吩、环己烯和苯为模型探针分子,分别考察单一烃分子在NiY分子筛上的吸附与反应行为以及噻吩与烯烃、芳烃间的竞争吸附和催化反应行为。单一探针分子吸附研究发现,NiY分子筛中与Ni物种相关的Lewis(L)酸位是噻吩的选择性吸附活性位;噻吩和环己烯在NiY分子筛中Brnsted(B)酸位上发生的质子化和低聚反应明显弱于HY分子筛。双探针分子竞争吸附研究发现,环己烯二聚体在NiY中强B酸位上的强化学吸附与噻吩存在显著的竞争吸附行为。另外,苯和噻吩在NiY上的竞争吸附现象在373K时明显减弱。由此,在选择性吸附脱硫过程中,减少吸附剂表面B酸中心可降低烯烃对噻吩的竞争吸附,另外适当提高吸附体系的温度可以有效避免芳烃对噻吩的竞争吸附。     

改性NaY分子筛吸附模拟油中噻吩的研究

用静态吸附方法研究了CuY分子筛、CeY分子筛和CeCuY分子筛对3种含噻吩的模拟油的吸附。实验结果表明,在相同条件下,以上3种分子筛对模拟油A、B的脱硫率为95%左右,对含环己烯的模拟油C的脱硫率均低于63%。运用BET对分子筛孔结构进行表征和运用IR对吸附模拟油后的分子筛情况进行考察,分析结果表明,Cu和Ce离子交换后的分子筛,BET比表面积下降,微孔比表面积下降,由此影响对模拟油A、B中噻吩的吸附。IR谱图表明,以上3种分子筛都会吸附环己烯,是导致其对模拟油C脱硫率下降的主要原因。     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

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.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.