Environment-friendly synthesis of N-phenylpiperidine from aniline and 1,5-pentanediol over γ-Al2O3 catalyst

An efficient environment-friendly synthesis of N-phenylpiperidine was developed from aniline and 1,5-pentanediol over γ-Al2O3 catalyst under atmospheric pressure. The conversion of 1,5-pentanediol reached 97% and the selectivity for N-phenylpiperidine attained 94%. The structure of the catalyst was characterized by NH3-TPD and BET. The influences of calcination temperature of the catalyst and reaction temperature on activity and selectivity of the catalyst were investigated.     

Relationship between surface microstructure and properties of supported catalyst Rh/Ys

The inner structure of Rh/Ys,a novel high efficiency supported catalyst,and the spreading of Rh on the Ys surface were analyzed through electron transmission microscopy and scanning tunnel microscopy.The relationship between the distribution of Rh over the support and the preparation temperature of th catalyst was determined.The formation of Rh-C bond was confirmed by XPS and far-IR spectra.The loss of Rh from the surface of the support and the catalytic activity under different preparation conditions have been compared.The internal factors for the high activity and high stability of the novel Rh/Ys catalyst have been discussed.     

Surface Structure and Catalytic Behavior of MnO_(1+x) Radiated by Microwave

Introduction The surface structure, distribution and strength of the active centers of a catalyst would directly affect its catalytic activity and selectivity. In principle all the techniques and methods which can modify the surface and body structure of a catalyst, or influence its physicochemical properties can be used to change the activity and selectivity of a practical catalyst.     

Effects of Temperature and Catalyst to Oil Weight Ratio on the Catalytic Conversion of Heavy Oil to Propylene Using ZSM-5 and USY Catalysts

It is useful for practical operation to study the rules of production of propylene by the catalytic conversion of heavy oil in FCC (fluid catalytic cracking). The effects of temperature and C/O ratio (catalyst to oil weight ratio) on the distribution of the product and the yield of propylene were investigated on a micro reactor unit with two model catalysts, namely ZSM-5/Al2O3 and USY/Al2O3, and Fushun vacuum gas oil (VGO) was used as the feedstock. The conversion of heavy oil over ZSM-5 catalyst can be comparable to that of USY catalyst at high temperature and high C/O ratio. The rate of conversion of heavy oil using the ZSM-5 equilibrium catalyst is lower compared with the USY equilibrium catalyst under the general FCC conditions and this can be attributed to the poor steam ability of the ZSM-5 equilibrium catalyst. The difference in pore topologies of USY and ZSM-5 is the reason why the principal products for the above two catalysts is different, namely gasoline and liquid petroleum gas (LPG), repspectively. So the LPG selectivity, especially the propylene selectivity, may decline if USY is added into the FCC catalyst for maximizing the production of propylene. Increasing the C/O ratio is the most economical method for the increase of LPG yield than the increase of the temperature of the two model catalysts, because the loss of light oil is less in the former case. There is an inverse correlation between HTC (hydrogen transfer coefficient) and the yield of propylene, and restricting the hydrogen transfer reaction is the more important measure in increasing the yield of propylene of the ZSM-5 catalyst. The ethylene yield of ZSM-5/Al2O3 is higher, but the gaseous side products with low value are not enhanced when ZSM-5 catalyst is used. Moreover, for LPG and the end products, dry gas and coke, their ranges of reaction conditions to which their yields are dependent are different, and that of end products is more severe than that of LPG. So it is clear that maximizing LPG and propylene and restricting dry gas and coke can be both achieved via increasing the severity of reaction conditions among the range of reaction conditions which LPG yield is sensitive to.     

Deactivation Mechanism for COS Hydrolysis over TGH Catalyst——FT-IR Study of the Adsorption Behavior of COS,O_2 and H_2S

The adsorptions of COS, H2S and O2 were investigated over the TGH catalyst in this paper. It was found that the numbers of basic centers and basic intensities were reduced over the deactivated TGH catalyst. The PT-IR results of COS+H2S+O2 co-adsorption on the TGH catalyst show that the main causes of catalyst deactivation is the formation of element sulfur and trace sulfate.     

A Study on the Effects of Carrier Gases on the Structure and Morphology of Carbon Nanotubes Prepared by Pyrolysis of Ferrocene and C2H2 Mixture

Carbon nanotubes （CNTs） were prepared using different carrier gases, with ferrocene as the catalyst precusor and acetylene as the carbon source. The effects of ammonia and nitrogen as carrier gases on the structure and morphology of CNTs were investigated. Transmission electron microscope （TEM）, high-resolution electron microscope （HRTEM）, scanning electron microscope （SEM） and X-ray diffraction （XRD） were employed to characterize the products and the catalyst. Experiment results show that the CNTs grown in N2 gas exhibited cylindrical and tubular structure, while a bamboo-like structure was observed for the CNTs grown in NH3 gas. Moreover, vertically aligned CNTs were obtained on an A12O3 disk when NH3 was used as the carrier gas. The carrier gas also exerted influence on the shape of the catalyst. Based on the theory of active centers of catalysis and combined with the particle shape of the catalyst, a growth model for the vertically aligned CNTs on the substrate is given.     

Preparation, Characterization and Catalytic Properties of S2O8^2-／ZrO2 Supported by Tungsten Carbide

A WC-supported S2O8^2-/ZrO2(PSZ) catalyst was prepared and characterized by means of XRD, BET, FTIR and XPS. The isomerization of n-pentane over the catalyst was investigated as well. The results show that the skeletal isomerization and the crack of n-pentane proceed simultaneously on WC-supported S2O8^2-/ZrO2 catalyst. The addition of tungsten carbide showed a significant enhancement in the activity and stability of the catalyst for n-pentane isomerization. The catalyst showed evidently a better activity than S2O8^2-/ZrO2 supported by Pt and WO3. The results can be interpreted by the existence of the tungsten oxycarbide compound(WCxOy) with carbidic, oxide and acidic sites.     

A sulfonate-based Cu(Ⅰ) metal-organic framework as a highly efficient and reusable catalyst for the synthesis of propargylamines under solvent-free conditions

A new highly efficient and reusable Cu(Ⅰ)-MOF has been developed for the synthesis of propargylamine compounds via the three-component reaction of secondary amines,alkynes.and aromatic aldehydes under solvent-free conditions.The desired propargylamines were obtained in good to excellent yields with a low catalyst loading.The catalyst may be recovered and reused for up to 5 cycles without major loss of activity.This protocol has the advantages of excellent yields,low catalyst loading,and catalyst recyclability.     

A Novel Carbon Nanotube-Supported NiP Amorphous Alloy Catalyst and Its Hydrogenation Activity

A carbon nanotube-supported NiP amorphous catalyst (NiP/CNT) was prepared by induced reduction. Benzene hydrogenation was used as a probe reaction for the study of catalytic activity. The effects of the support on the activity and thermal stability of the supported catalyst were discussed based on various characterizations, including XRD, TEM, ICP, XPS, H2-TPD, and DTA. In comparison with the NiP amorphous alloy, the benzene conversion on NiP/CNT catalyst was lower, but the specific activity of NiP/CNT was higher, which is attributed to the dispersion produced by the support, an electron-donating effect, and the hydrogen-storage ability of CNT. The NiP/CNT thermal stability was improved because of the dispersion and electronic effects and the good heat-conduction ability of the CNT support.     

Comparing the deactivation behaviour of Co/CNT and Co/γ-Al2O3 nano catalysts in Fischer-Tropsch synthesis

An extensive study of Fischer-Tropsch (FT) synthesis on cobalt nano particles supported on γ-alumina and carbon nanotubes (CNTs) catalysts is reported.20 wt% of cobalt is loaded on the supports by impregnation method.The deactivation of the two catalysts was studied at 220 C,2 MPa and 2.7 L/h feed flow rate using a fixed bed micro-reactor.The calcined fresh and used catalysts were characterized extensively and different sources of catalyst deactivation were identified.Formation of cobalt-support mixed oxides in the form of xCoO yAl2O3 and cobalt aluminates formation were the main sources of the Co/γ-Al2O3 catalyst deactivation.However sintering and cluster growth of cobalt nano particles are the main sources of the Co/CNTs catalyst deactivation.In the case of the Co/γ-Al2O3 catalyst,after 720 h on stream of continuous FT synthesis the average cobalt nano particles diameter increased from 15.9 to 18.4 nm,whereas,under the same reaction conditions the average cobalt nano particles diameter of the Co/CNTs increased from 11.2 to 17.8 nm.Although,the initial FT activity of the Co/CNTs was 26% higher than that of the Co/γ-Al2O3,the FT activity over the Co/CNTs after 720 h on stream decreased by 49% and that over the Co/γ-Al2O3 by 32%.For the Co/γ-Al2O3 catalyst 6.7% of total activity loss and for the Co/CNTs catalyst 11.6% of total activity loss cannot be recovered after regeneration of the catalyst at the same conditions of the first regeneration step.It is concluded that using CNTs as cobalt catalyst support is beneficial in carbon utilization as compared to γ-Al2O3 support,but the Co/CNTs catalyst is more susceptible for deactivation.     

Synthesis of Dimethyl Carbonate from Methanol and Carbon Dioxide Catalyzed by Potassium Hydroxide under Mild Conditions

The synthesis of dimethyl carbonate （DMC） from methanol and carbon dioxide using potassium hydroxide as catalyst in the presence of CH3I and the effect of ionic liquid on the reaction were investigated. The results showed that KOH is an effective catalyst; the high selectivity and raised yield of DMC formation under mild conditions were achieved. However, the addition of the ionic liquid, l-ethyl-3-methylimidazolium bromide （emimBr）, can evidently accelerate the conversion of methanol and yield of the product.     

A Novel Non-phosgene Process for the Synthesis of Methyl N-Phenyl Carbamate from Methanol and Phenylurea： Effect of Solvent and Catalyst

A novel environmentally benign process for the synthesis of methyl N-phenyl carbamate (MPC) from methanol and phenylurea was studied. Effect of solvent and catalyst on the reaction behavior was investigated. The IR spectra of methanol and phenylurea dissolved in different solvents were also recorded. Compared with use of methanol as both a reactant and a solvent, phenylurea conversion and selectivity to MPC increased by using toluene, benzene or anisole as a solvent, while phenylurea conversion decreased slightly by using n-octane as a solvent. The phenylurea conversion declined nearly 50% when dimethyl sulfoxide (DMSO) was used as a reaction media, and MPC selectivity decreased as well. The catalytic reaction tests showed that a basic catalyst enhanced the selectivity to MPC while an acidic catalyst promoted the formation of methyl carbamate and aniline. Moderate degree of basicity showed the best catalytic performance in the cases studied.     

Studies on Tripolycyanamide Formaldehyde Resin-Pd Complex and Its Use in the Synthesis of the Branch of Paclitaxel

A novel method was developed to prepare the branch of paclitaxel using 2,4-dichlorophenylaldehyde as the starting material.The branch was synthesized through condensation, cydoaddltion and catalyzing hydrogenation of dichlorophenyl intermediate. Tripolycyanamide formaldehyde resin-Pd complex as hydrogenation catalyst has been studied. The influence of temperature and N/Pd atomic ratio of the catalyst on the effect of catalytic hydrogenation was investigated and the optimum conditious were found. Because of the mild cyclization reaction condition, convenient asymmetric resolution operation and high yield, the synthetic route was practical.     

Screening of MgO——and Ce02-Based Catalysts for Carbon Dioxide Oxidative Coupling of Methane to C2＋ Hydrocarbons

The catalyst screening tests for carbon dioxide oxidative coupling of methane (CO2-OCM)have been investigated over ternary and binary metal oxide catalysts.The catalysts are prepared by doping MgO-and CeO2-based solids with oxides from alkali(Li2O),alkaline earth (CaO),and transition metal groups (WO3 or MnO).The presence of the peroxide (O2^2-)active sites on the Li2O2,revealed by Raman spectroscopy,may be the key factor in the enhanced performance of some of the Li2O/MgO catalysts.The high reducibility of the CeO2 catalyst,an important factor in the CO2-OCM catalyst activity,may be enhanced by the presence of manganese oxide species. The manganese oxide species increases oxygen mobitity and oxygen vacancies in the CeO2 catalyst.raman and Fourier Transform Infra Red (FT-IR)spectroscopies revealed the presence of lattice vibrations of metal-oxygen bondings and active sites in which the peaks carresponding to the buld crystalline structures of Li2O,CaO,WO2 and MnO are detected.The performance of 5%MnO/15?O/CeO2 catalyst is the most potential among the CeO2-based catalysts,although lower than the 2%Li2O/MgO catalyst.The 2%Li2O/MgO catalyst showed the most promising C2 hydrocarbons selectivity and yield at 98.0%and 5.7%,respectively.     

Influence of Catalyst Residues on Thermo-oxidative Aging and Thermal Stability of Poly（butene-1）

Isotactic poly（butene-1） （iPB） with spherical morphology was synthesized successfully with bulk precipitation polymerization without post-treatment of the products. The bulk precipitation polymerization process made it possible for iPB to be used as general plastic due to the acceptable decreased cost compared with the solution polymerization process. The influence of catalyst residues on the aging and thermal stability of iPB synthesized by bulk precipitation polymerization method was investigated by gel permeation chromatography, mechanical performance testing, thermogravimetric analysis and infrared spectroscopic analysis. Commercial iPB and the lab-made iPB with varied catalyst residue contents were studied. The results demonstrated that the catalyst residues played an important role in the aging process of the iPB. A possible mechanism of aging promotion by catalyst residues was proposed.     

Esterification and Selective Esterification in the Presence of TiCl4

A series of carboxylic acids was esterified to the corresponding esters with TiCl_4 as catalyst at room temperature,in high yields.This catalyst was highly effective for the selective esterification of primary alcohols with carboxylic acids,in the presence of secondary alcohols,and for the selective esterification of saturated acid with alcohol in the presence of conjugated acid or aromatic acid.On account of the high yield,high chemoselectivity,mild condition,and being free of other dehydrants,this is an efficient method.     

纳米二氧化锆在甲醇合成催化剂Cu/Ga2O3/ZrO2中的作用

The introduction of mesoporous nanosize zirconia to the catalyst for methanol synthesis dedicates the nanosized catalyst and mesoporous duplicated properties. The catalyst bears the larger surface area, larger mesoporous volume and more uniform diameter, more surface metal atoms and oxygen vacancies than the catalyst prepared with the conventional coprecipitation method. The modification of microstructure and electronic effect could result in the change of the reduced chemical state and decrease of reducuction temperature of copper, donating the higher activity and methanol selectivity to the catalyst. The results of methanol synthesis demonstrate that the Cu^＋ is the optimum active site. Also, the interaction between the copper and zirconia shows the synergistic effect to fulfil the methanol synthesis.     

N-Sulfonic acid poly(4-vinylpyridinium) chloride as a highly effcient and reusable catalyst for the Biginelli reaction简

A mild, simple and efficient procedure for the preparation of 3,4-dihydropyrimidin-2（1H）-ones and -thiones is described using N-sulfonic acid poly（4-vinylpyridinium） chloride （NSPVPC） as a heterogeneous and efficient catalyst under solvent-free conditions. Simple methodologies, easy work-up procedure, easy preparation of the catalyst, excellent yields and very short reaction times are among the other advantages of this work. Further, the catalyst can be reused and recovered for several times without significant decrease in its activity.     

Polymerization Kinetics of Propylene with the MgCl_2-Supported Ziegler-Natta Catalysts——Active Centers with Different Tacticity and Fragmentation of the Catalyst

The catalytic activity and stereospecificity of olefin polymerization by using heterogeneous TiCl_4/MgCl_2 Ziegler-Natta(Z-N) catalysts are determined by the structure and nature of active centers, which are mysterious and fairly controversial. In this work, the propylene polymerization kinetics under different polymerization temperatures by using Z-N catalysts were investigated through monitoring the concentration of active centers [C*] with different tacticity. SEM was applied to characterize the catalyst morphologies and growing polypropylene(PP) particles. The lamellar thickness and crystallizability of PP obtained under different polymerization conditions were analyzed by DSC and SAXS. The PP fractions and active centers with different tacticity were obtained with solvent extraction fractionation method. The catalytic activity, active centers with different tacticity and propagation rate constant k_p, fragmentation of the catalyst, crystalline structure of PP are correlated with temperature and time for propylene polymerizations. The polymerization temperature and time show complex influences on the propylene polymerization. The higher polymerization temperature(60 ℃) resulted higher activity, k_p and lower [C*], and the isotactic active centers C_i* as the majority ones producing the highest isotactic polypropylene(iPP) components showed much higher k_p when compared with the active centers with lower stereoselectivity. Appropriate polymerization time provided full fragmentation of the catalyst and minimum diffusion limitation. This work aims to elucidate the formation and evolution of active centers with different tacticity under different polymerization temperature and time and its relations with the fragmentation of the PP/catalyst particles, and provide the solutions to the improvement of catalyst activity and isotacticity of PP.     

The synthesis and structure of pyridine-oxadiazole iridium complexes and catalytic applications:Non-coordinating-anion-tuned selective C—N bond formation

Several novel pyridine-oxadiazole iridium complexes were synthesized and characterized through X-ray crystallography.The designed iridium.complexes revealed surprisingly high catalytic activity in C-N bondformation of amides and benzyl alcohols with the assistance of non-coordinating anions.In an attempt to achieve borrowing hydrogen reactions of amides with benzyl alcohols,N,N'-(phenylmethylene)dibenzamide products we re unexpectedly isolated under non-coordinating anion conditions,whereas N-benzylbenzamide products were achieved in the absence of non-coordinating anions.The mechanism explorations excluded the possibility of"silver effect"(silver-assisted or bimetallic catalysis)and revealed that the reactivity of iridium catalyst was varied by non-coordinating anions.This work provided a convenient and useful methodology that allowed the iridium complex to be a chemoselective catalyst and demonstrated the first example of non-coordinating-anion-tuned selective C-N bond formation.