Ni2P/SiO2-Al2O3催化剂的制备、表征及其对4,6-二甲基二苯并噻吩加氢脱硫反应的催化性能

 以硅酸钠为原料,以大孔Al2O3为基载体,采用水解沉积法制备了SiO2-Al2O3复合载体. 进而以非晶态镍基合金为前驱体,在低温下通过PH3处理制备了Ni2P/SiO2-Al2O3催化剂. 用X射线衍射、红外光谱、扫描电镜、电感耦合等离子体发射光谱和N2吸附技术对复合载体和催化剂进行了表征,并以4,6-二甲基二苯并噻吩为探针在小型连续流动固定床反应器上考察了催化剂的加氢脱硫性能. 结果表明,在γ-Al2O3载体表面引入SiO2能够明显减少γ-Al2O3表面四配位的Al3+离子,从而减弱Ni2P/SiO2-Al2O3催化剂中Ni2P和γ-Al2O3载体表面的强相互作用. 加入适量的SiO2后, SiO2-Al2O3复合载体仍能保持大孔γ-Al2O3载体孔结构的优势. 在实验范围内, Ni2P/SiO2-Al2O3催化剂表现出很好的加氢脱硫性能.     

Pt对Ni2P/MCM-41催化剂加氢脱硫性能的影响

以MCM-41为载体, 采用程序升温还原法制备了含有少量Pt的Ni-P/MCM-41催化剂, 并用氢气程序升温还原(H₂-TPR)、 X射线衍射(XRD)、 N₂吸附比表面积、 X射线光电子能谱(XPS)和透射电子显微镜(TEM)对催化剂的结构和性能进行了表征. 考察了P/Ni摩尔比及Pt含量对Ni-P/MCM-41催化剂催化二苯并噻吩(DBT)加氢脱硫(HDS)性能的影响. 结果表明, Pt能降低Ni₂P催化剂的还原温度, 并有助于Ni₂P相的生成, 抑制团聚现象, 提高催化剂的HDS活性. 当Pt的质量分数为0.6%, P/Ni摩尔比为2时, 催化剂具有最佳加氢脱硫活性, 在340 ℃, 3.0 MPa, 氢油体积比为500, 质量空速(WHSV)为2.0 h^-1的条件下, 二苯并噻吩转化率为100%, 且催化剂加氢脱硫活性在120 h内基本保持稳定.     

柠檬酸对Ni2P/TiO2-Al2O3催化剂加氢脱硫性能的影响

采用溶胶-凝胶法制备了TiO2-Al2O3复合载体,以柠檬酸(CA)为络合剂采用浸渍法制备了Ni2P负载的TiO2-Al2O3复合载体催化剂,并用X射线衍射(XRD)、N2吸附比表面积测定、H2程序升温氢还原(H2-TPR)、程序升温氧化(TPO)、X射线光电子能谱(XPS)技术对催化剂的结构和性质进行了表征,考察了CA/Ni摩尔比对在Ni2P/TiO2-Al2O3催化剂上进行的二苯并噻吩(DBT)加氢脱硫(HDS)性能的影响.结果表明:适量的CA可以丰富催化剂的孔道,提高催化剂的比表面积.当n(CA)/n(Ni)=2:1时,催化剂的比表面积达到126.75m2·g-1,与不加CA时相比,提高了57.05m2·g-1.调节n(CA)/n(Ni)能够改善活性相的分布,改变活性相的种类;引入CA使Ni和P前驱体的还原温度明显降低,促进活性相Ni2P的生成,一定程度上能够抑制催化剂表面炭的形成和沉积,提高其稳定性.n(CA)/n(Ni)=2:1时,催化剂具有最好的加氢脱硫活性,在360°C,3.0MPa,氢油比为500(V/V),液时体积空速为2.0h-1的条件下,二苯并噻吩转化率为99.5%,可将模拟油中硫含量由2%(w)降低到0.01%(w).     

Ni_2P/TiO_2-Al_2O_3催化剂的制备及其加氢脱硫、脱氮性能

采用溶胶-凝胶法制备了TiO2-Al2O3复合载体,采用浸渍法制备了Ni2P/TiO2-Al2O3催化剂,并用X射线衍射(XRD)、N2吸附比表面积(BET)测定、热重-差热分析(TG-DTA)、X射线光电子能谱(XPS)等技术对催化剂的结构和性质进行了表征.催化剂加氢脱硫(HDS)和脱氮(HDN)活性评价在实验室固定床连续反应装置上,以噻吩和吡啶为模型反应物进行.考察了不同载体、Ni2P负载量、标称Ni/P摩尔比、催化剂焙烧温度对Ni2P/TiO2-Al2O3催化剂上同时进行的噻吩加氢脱硫和吡啶加氢脱氮性能的影响.结果表明,TiO2含量为80%(w)的TiO2-Al2O3复合氧化物为载体,Ni2P负载量为30.0%(w),标称Ni/P摩尔比为1/2,催化剂焙烧温度为500℃时,Ni2P/TiO2-Al2O3催化剂加氢脱硫脱氮活性最高.在360℃,3.0MPa,氢油比800(V/V),液时体积空速1.5h-1的条件下,噻吩HDS和吡啶HDN转化率分别为61.32%和64.43%.     

TiO2-Al2O3载体的制备及Ni2P/TiO2-Al2O3催化剂上的同时加氢脱硫和加氢脱氮反应

 以溶胶-凝胶法制备的 TiO2-Al2O3 复合氧化物为载体, 采用浸渍法制备了 Ni2P/TiO2-Al2O3 催化剂, 并用 X 射线衍射、N2 吸附脱附、红外和 X 射线光电子能谱等技术对催化剂进行了表征, 考察了载体中 TiO2 含量、焙烧温度及其制备方法对 Ni2P/TiO2-Al2O3 催化剂上同时进行噻吩加氢脱硫和吡啶加氢脱氮反应的影响. 结果表明, 以 Ni/P 摩尔比为 1/2 的前驱体制备的催化剂表面仅出现 Ni2P 物相; 当载体中 TiO2 的含量为 80%, 焙烧温度为 550 oC 时, Ni2P/TiO2-Al2O3 催化剂上加氢脱硫和加氢脱氮的活性最高. 在 360 oC, 3.0 MPa, 氢/油体积比 500, 液时体积空速 2.0 h?1 的条件下, 噻吩和吡啶转化率分别为 61.3%和 64.4%.     

磷镍物质的量比对溶剂热法制备的磷化镍催化剂加氢脱硫性能的影响

以三苯基膦(PPh3)为磷源,以三正辛胺(TOA)为液相反应体系,采用溶剂热法制备了负载型Ni-P(x)/MCM-41催化剂(x为初始P/Ni物质的量比),并用X射线衍射(XRD)、N2吸附比表面积测定(BET)、CO吸附、X射线光电子能谱(XPS)和TEM对催化剂进行了结构表征。以含质量分数1%二苯并噻吩(DBT)的十氢萘溶液为原料,在连续固定床反应装置上,研究了初始P/Ni物质的量比对加氢脱硫(HDS)性能的影响。结果表明,在初始P/Ni物质的量比为0.5时,生成的磷化镍物相为以Ni12P5为主,含有少量Ni2P的混合相;初始P/Ni物质的量比大于0.5时,可得到纯Ni_2P相,且随着P/Ni物质的量比的提高,Ni2P晶粒粒径减小,分散度提高。在反应温度613 K,压力3.0 MPa,H_2/oil体积比500,质量空速2.0 h-1时,Ni-P(6)/MCM-41和Ni-P(10)/MCM-41催化剂的DBT转化率接近100%。     

Ni2P/SBA-15催化剂的结构及加氢脱硫性能

以硝酸镍为镍源, 磷酸氢二铵为磷源, 介孔分子筛SBA-15为载体, 用共浸渍法制备了含磷化镍前驱体的样品, 然后在氢气流中采用程序升温还原法, 制备了Ni2P质量分数为5%-40%的Ni2P/SBA-15催化剂. 用X射线衍射(XRD)、N2吸附脱附、透射电子显微镜(TEM)、傅立叶变换红外光谱(FTIR)等分析测试技术对催化剂的结构进行了表征, 以噻吩和二苯并噻吩(DBT)为模型化合物, 在微型固定床反应器上对催化剂的加氢脱硫(HDS)性能进行了评价. 结果表明, Ni2P/SBA-15催化剂中SBA-15 的介孔结构依然存在, 活性组分Ni2P具有良好的分散性, 但随Ni2P含量的增加, 催化剂的比表面积、孔容和孔径均有明显减小. 当反应温度为320 ℃时, Ni2P含量为15%-25%(w)的催化剂就具有很好的加氢脱硫催化性能; 反应温度在360 ℃以上时, 所有催化剂都具有优异的深度脱硫催化性能. Ni2P/SBA-15催化剂对二苯并噻吩的加氢脱硫(HDS)主要以直接脱硫机理(DDS)进行.     

Ni-Al类水滑石的制备及其Ni/Al2O3加氢脱硫研究

采用共沉淀方法合成了不同Ni/Al比的镍铝类水滑石,将其作为催化剂前驱体,制备了Ni/Al2O3加氢脱硫催化剂.通过X射线衍射法(XRD),程序升温还原(H2-TPR),热重分析(TG),傅里叶变换红外光谱(FT-IR)等技术对催化剂进行了表征.利用10 mL固定床装置在不同温度,压力,体积空速和氢油比条件下对Ni/Al2O3催化剂的加氢脱硫活性进行了评价.结果表明,XRD图和FT-IR图中均出现了Ni-Al类水滑石的特征峰,TG图呈现出两个明显阶段的失重,在Ni-Al2O3-HT的XRD图中最强的衍射角对应单质金属Ni粒子的(111)晶面.脱硫结果显示Ni-Al类水滑石作为前驱体在适当的条件下,FCC汽油的硫含量降至10 ppm以下.类水滑石作为前驱体的Ni/Al2O3加氢脱硫活性很好,说明类水滑石作为前驱体在加氢脱硫领域有好的应用前景.     

TiO_2-Al_2O_3载体的制备方法对其负载的磷化镍催化剂加氢脱氮反应性能的影响

采用共沉淀法和原位溶胶-凝胶法制备了TiO2-Al2O3复合载体,其负载的磷化镍催化剂采用等体积浸渍法和H2原位还原法制备.通过N2吸附(BET)、X射线衍射(XRD)、透射电镜(TEM)、程序升温还原(TPR),X射线光电子能谱(XPS)和等离子体发射光谱(ICP-AES)表征技术对催化剂进行了表征,并通过喹啉的加氢脱氮反应评价了催化剂的加氢脱氮性能.结果表明,原位溶胶-凝胶法制成的复合载体基本保留了原有的γ-Al2O3的孔特征,具有较大的比表面积和较宽的孔分布,TiO2主要以表面富集的形式分散在管状的γ-Al2O3表面,其负载的磷化镍催化剂还原后所形成的活性相为Ni2P和Ni12P5;而共沉淀法制成的复合载体比表面积较小,孔径分布更加集中,TiO2趋于在块状的Al2O3表面均匀分散,其负载的磷化镍催化剂具有更好的可还原性,还原后所形成的活性相为Ni2P.不同的载体制备方法和不同的钛铝比对催化剂加氢脱氮性能影响较大,当n(Ti)/n(Al)=1/8时,共沉淀法载体负载的催化剂表现出最佳的加氢脱氮性能,在340℃,3 MPa,氢油体积比500,液时空速3 h-1的反应条件下,喹啉的脱氮率可以达到91.3%.     

Ni2P/SBA-15催化剂的结构及加氢脱硫性能

以硝酸镍为镍源,磷酸氢二铵为磷源,介孔分子筛SBA-15为载体,用共浸渍法制备了含磷化镍前驱体的样品,然后在氢气流中采用程序升温还原法,制备了Ni2P质量分数为5%-40%的Ni2P/SBA-15催化剂.用X射线衍射(XRD)、N2吸附脱附、透射电子显微镜(TEM)、傅立叶变换红外光谱(FTIR)等分析测试技术对催化剂的结构进行了表征,以噻吩和二苯并噻吩(DBT)为模型化合物,在微型同定床反应器上对催化剂的加氧脱硫(HDS)性能进行了评价.结果表明,Ni2P/SBA-15催化剂中SBA-15的介孔结构依然存在,活性组分Ni2P具有良好的分散性,但随Ni2P含量的增加,催化剂的比表面积、孔容和孔径均有明显减小.当反应温度为320℃时,Ni2P含量为15%-25%(w)的催化剂就具有很好的加氢脱硫催化性能;反应温度在360℃以上时,所有催化剂都具有优异的深度脱硫催化性能.Ni2P/SBA-15催化剂对二苯并噻吩的加氢脱硫(HDS)主要以直接脱硫机理(DDS)进行.     

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.