Effects of ammonium exchange and Si/Al ratio on the conversion of methanol to propylene over a novel and large partical size ZSM-5

One type of ZSM-5 zeolite with large partical size was prepared and characterized by XRD, SEM, N2 adsorption-desorption, XRF, Py-IR and NH3-TPD techniques. Effects of ammonium exchange and SiO2/Al2O3 molar ratios on the reaction of methanol to propylene (MTP) over Na-ZSM-5 and H-ZSM-5 zeolites have been studied in a fixed-bed flow reactor under the operating conditions of T = 500 °C, P = 1 atm, and WHSV = 6 h-1. Ammonium exchange led to a rapid decrease in Na content for Na-ZSM-5 zeolite. The reaction results indicated that Na-ZSM-5 and H-ZSM-5 with different SiO2/Al2O3 molar ratios all exhibited high activity for methanol conversion. Ammonium exchange and the decreased SiO2/Al2O3 molar ratio of ZSM-5 zeolite led to an increase both in strong acid sites and weak acid sites. Na-ZSM-5 with high SiO2/Al2O3 molar ratio was favorable for the formation of propylene. The highest propylene selectivity (45.9%) was obtained over Na-ZSM-5 zeolite catalyst with SiO2/Al2O3 molar ratio of 220.     

COx-Free Hydrogen and Carbon Nanofibers Produced from Direct Decomposition of Methane on Nickel-Based Catalysts

Direct decomposition of methane was carried out using a fixed-bed reactor at 700℃for the production of COx-free hydrogen and carbon nanofibers. The catalytic performance of NiO-M/SiO2 catalysts (where M=AgO, CoO, CuO, FeO, MnOx and MoO) in methane decomposition was investigated. The experimental results indicate that among the tested catalysts, NiO/SiO2 promoted with CuO give the highest hydrogen yield. In addition, the examination of the most suitable catalyst support, including Al2O3, CeO2, La2O3, SiO2, and TiO2, shows that the decomposition of methane over NiO-CuO favors SiO2 support. Furthermore, the optimum ratio of NiO to CuO on SiO2 support for methane decomposition was determined. The experimental results show that the optimum weight ratio of NiO to CuO fell at 8:2 (w/w) since the highest yield of hydrogen was obtained over this catalyst.     

INFLUENCE OF SURFACE ACIDITY ON THE CATALYTIC PERFORMANCE IN OLIFIN OXIDATION OVER MO-Te BASED MIXED OXIDES

Partial oxidation of propylene and isobutene was performed over avariety of Mo-Te based mixed oxides.Results indicated that catalytic behaviorfor propylene and isobutene was different over the same catalyst.The differ-ence depended on surface acid-base properties of the catalyst.The relation ofsurface acidity to activity/selectivity can be explained on the basis of mecha-nism of oxidation over mixed oxide catalyst.     

Role of support nature （γ-Al2O3 and SiO2-Al2O3） on the performances of rhenium oxide catalysts in the metathesis of ethylene and 2-pentene

The metathesis of ethylene and 2-pentene was studied as an alternative route for propylene production over Re2O7/γ-Al2O3 and Re2O7/SiO2-Al2O3 catalysts. Both NH3 temperature-programmed desorption (NH3-TPD) and H2 temperature-programmed reduction (H2-TPR) results showed that Re2O7/SiO2-Al2O3 exhibited stronger acidity and weaker metal-support interaction than Re2O7/γ-Al2O3. At 35 60℃, isomerization free metathesis was observed only over Re2O7/γ-Al2O3, suggesting that the formation of metal-carbene metathesis active sites required only weak acidity. Our results suggest that on the Re2O7/SiO2-Al2O3, hydrido-rhenium species ([Re]-H) were formed in addition to the metathesis active sites, resulting in the isomerization of the initial 1-butene product into 2-butenes. A subsequent secondary metathesis reaction between these 2-butenes and the excess ethylene could explain the enhanced yields of propylene observed. The results demonstrate the potential for high yield of propylene from alternative feedstocks.     

Synthesis of Pt-SnOx/TS-1@SBA-16 Composites and Their High Catalytic Performance for Propane Dehydrogenation

A novel composite material of TS-1@SBA-16 was synthesized by enwrapping TS-1 zeolite crystals with mesoporous SBA-16 silica. This composite was used as catalyst support for loading Pt-SnOx in the propane dehydr genation(PDH) reaction. Catalysts were characterized by means ofN2 adsorption-desorption, XRD, SEM, TEM, XPS, UV-Vis, and Raman spectroscopy. The effect of different contents of TS-1 on PDH was investigated, and the optimal amount of TS-1 was determined to be 10%. The catalyst with TS-1 content of 10% showed the highest PDH activity and the initial conversion of propane over it can achieve 54.5%, higher than those over TS-1 or SB A-16-supported ones. The superior catalytic performance of Pt-SnOx/TS-1 @SBA-16 is related to the synergistic effect of the excellent mass transfer performance through the hierarchical porous structure, suitable acid acidity and electronic effect of Ti species.     

TiO2 supported cobalt-manganese nano catalysts for light olefins production from syngas

Cobalt-manganese nano catalysts were prepared by sol-gel method. This research investigated the effects of different cobalt-manganese (Co/Mn = 1/1) loading, pH and calcination conditions on the catalytic performance of Co-Mn/TiO2 catalysts for Fischer-Tropsch synthesis (FTS) in a fixed bed reactor. It was found that the catalyst containing 30wt%(Co-Mn)/TiO2 was an optimal catalyst for the conversion of synthesis gas to light olefins especially propylene. The activity and selectivity of optimal catalyst were studied under different operational conditions. The results showed that the best operational conditions were H2 /CO = 1/1 molar feed ratio at 250℃ and GHSV = 1300 h-1 under atmospheric pressure. Characterization of catalysts was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption-desorption measurements.     

Study on Chemisorption, Catalytic Behavior, and Stability of Supported Au Catalyst for the Propylene Epoxidation Reaction

The supported Au/TiO2 and Au/TiO2-SiO2 catalysts were prepared by deposition precipitation method. The TPD study reveals that propylene oxide competes with propylene to be adsorbed on the same adsorptive center-Tin site on the surface of the catalyst and that the adsorbing capacity of the catalyst for propylene oxide is larger than that for propylene. Catalytic behavior for propylene epoxidation with H2 and O2 was tested in a micro-reactor. Under typical conditions, the selectivity for propylene oxide is over 87%. The TG curves show that PO successive oxidation cause carbon deposition on the active center and deactivation of the Au catalysts. Because the amounts of Tin site decrease significantly, and consequently the separation between Tin sites increases, the Au/TiO2-SiO2 catalyst is more stable than Au/TiO2.     

Spectroscopic Studies of a Three-dimensional,Five-coordinated Copper(Ⅱ） Complex via Hydrogen Bonds:[Cu(PPD)(H2O)2](H2PDA=Pyridine-2,6-dicarboxylic Acid)

A new copper(Ⅱ） complex[Cu(PDA)(H2O)2] was synthesized and its structure was determined.Cu(Ⅱ）is five-coordinated in a tetragonal pyramid geometry.The two coordinating water molecules are different and the two Cu-O bond lengths differ by nearly 0.02nm.The whole crystal is linked to form a three-dimensional network by means of hydrogen bonds.The X-band ESR spectrum shows three different g tensors with a well-resolved hyperfine structure in the gz signal,giving the ESR parameters gx=2.05,gy=2.065 and gz=2.29.The covalency of the coordinate bonds and the deviation from tetragonal pyramid geometry for the complex are discussed based on the ESR spectra.     

STUDIES ON THE KINETICS OF PROPYLENE POLYMERIZATION WITH THE COMPLEXTYPE TiCl_3 CATALYST

The active center concentration C_p, the rate constant k_p, and the activation energy of chain propagation E_p in the polymerization of propylene with complex-type TiCl_3-(C_2H_5)_2AlCl catalyst system were studied. The Mn was corrected by (?) value determined by GPC. The values thus obtained for C_p, k_p, and E_p at 50℃were 3.01 mol/mol Ti, 6.27 1/mol·sec, and 5.10 Kcal/mol respectively.The kinetic parameters were compared with those obtained from conventional TiCl_3·AlCl_2 catalyst, showing that the higher activity of the complex-type catalyst over the conventional catalyst is not only due to the higher C_p of the former, but to a greater extent due to the increase of the k_p value.     

Hydrogenation of phenylpyruvic acid to phenylalanine catalyzed by Ni-B/SiO2

Phenylalanine （Phe） is a significant amino acid that cannot be synthesized by human themselves but must be taken from environment. It was initially found that the nanosized amorphous Ni-B/SiO2 alloy prepared by the chemical reduction method was an effective catalyst for the preparation of Phe from phenylpyruvic acid （PPA） by amination and hydrogenation. It has been found that the amorphous Ni-B/SiO2 alloy catalyst exhibits superior activity and selectivity to the traditional catalysts Raney Ni and Urushibara nickel. The effects of reaction time, amounts of catalysts and ammonia solution, reaction temperature, and H2 pressure on the reaction have been investigated systematically. The results indicated that the yield of Phe was 97.9%, and the selectivity for Phe reached 98.9% when the reaction was carried out for 3 h at 333 K and 2.0 MPa of H2 with m（Cat.） ： m（PPA） = 0.6 ： 1.0 and n（NH3） ： n（PPA） = 3 ： 1. The catalysts were characterized by XRD, AAS, XPS, BET, and TEM, and the relationship between the catalyst structure and the catalytic activity was discussed in detail. It was found that the reason why Ni-B/SiO2 amorphous alloy catalyst was much more active for the preparation of Phe could be accounted for by the presence of electron-rich Ni due to electron donation from alloying B; the smaller size of Ni-B particles, the larger specific surface area of Ni-B/SiO2.     

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.