Dehydrocyclization of Diphenylamine to Carbazole over Platinum-Based Bimetallic Catalysts

 Gas phase dehydrocyclization of diphenylamine (DPA) to carbazole over monometallic and bimetallic 0.4 wt% Pt-based catalysts in a fixed bed reactor was studied in the presence of hydrogen at a temperature of 550 ^oC. Alumina and carbon supported Pt catalysts showed very high initial activity (> 95%). The selectivity for carbazole over carbon supported Pt catalysts was slightly lower. Doping of the catalyst with potassium led to an increase in the selectivity for carbazole by 15%. Bimetallic Pt-Sn catalysts prepared by co-impregnation were less selective than catalysts prepared by successive impregnation. The selectivity for carbazole over bimetallic Pt-Sn catalysts prepared by successive impregnation was 75%, but their activity decreased with increased Sn loading. Highly active and reasonably selective catalysts were Ir-doped bimetallic Pt-based catalysts. The conversion of diphenylamine over Pt-Ir catalysts was above 98% and the selectivity for carbazole was nearly 55%, while the lifetime was much longer.     

Selective Oxidation of CO in Excess H2 over Ru/Al2O3 Catalysts Modified with Metal Oxide

The Ru/Al_2O_3 catalysts modified with metal oxide(K_2O and La_2O_3)were prepared via incipient wetness impregnation method from RuCl_3·nH_2O mixed with nitrate loading on Al_2O3 support. The activity of catalysts was evaluated under simulative conditions for the preferential oxidation of CO (CO-PROX)from the hydrogen-rich gas streams produced by reforming gas,and the performances of catalysts were investigated by XRD and TPR.The results showed that the activity temperature of the modified catalysts Ru-K_2O/Al_2O3 and Ru-La_2O_3/Al_2O_3 were lowered approximately 30℃compared with pure Ru/Al_2O_3,and the activity temperature range was widened.The conversion of CO on Ru-K_2O/Al_2O_3 and Ru-La_2O_3/Al_2O_3 was above 99% at 140-160℃,suitable to remove CO in a hydrogen-rich gas and the selectivity of Ru-La_2O_3/Al_2O_3 was higher than that of Ru-K_2O/Al_2O_3 in the active temperature range. Slight methanation reaction was detected at 220℃and above.     

Effects of Citric Acid Concentration and Activation Temperature on the Synthesis of Carbon Nanotubes

A series of Ni-La-Mg catalyst samples were prepared by citric acid complex method, and carbonnanotubes were synthesized by catalytic decomposition of CH4 on these catalysts. The effects of the citricacid concentration and the activation temperature on catalytic activity were investigated by CO adsorption,TEM and XRD techniques. The experimental results showed that the particle size of the catalysts preparedthrough gel auto-combustion varied with the concentration of citric acid. Therefore carbon nanotubes with different diameters were obtained correspondingly. The effect of activation temperature on the activity of catalyst was negligible from 500 to 700℃, but it became pronounced at lower or higher temperatures.     

Additive effects of alkaline-earth metals and nickel on the performance of Co/γ-Al_2O_3 in methane catalytic partial oxidation

Nano-sized γ-alumina (γ-Al2O3) was first prepared by a precipitation method. Then, active component of cobalt and a series of alkaline- earth metal promoters or nickel (Ni) with different contents were loaded on the γ-Al2O3 support. The catalysts were characterized by N2 adsorption-desorption, X-ray diffraction (XRD) and thermogravimetry analysis (TGA). The activity and selectivity of the catalysts in catalytic partial oxidation (CPO) of methane have been compared with Co/γ-Al2O3, and it is found that the catalytic activity, selectivity, and stability are enhanced by the addition of alkaline-earth metals and nickel. The optimal loadings of strontium (Sr) and Ni were 6 and 4 wt%, respectively. This finding will be helpful in designing the trimetallic Co-Ni-Sr/γ-Al2O3 catalysts with high performance in CPO of methane.     

Ni/Al2O3 catalysts for syngas methanation: Effect of Mn promoter

Ni/Al2O3 catalysts with different amounts of manganese ranging from 1 to 3 wt% as promoter were prepared by co-impregnation method. The catalysts were characterized by N2 physisorption, XRD, TPR, SEM and TEM. Their catalytic activity towards syngas methanation reaction was also investigated using a fixed-bed integral reactor. It was demonstrated that the addition of manganese to Ni/Al2O3 catalysts can increase the catalyst surface area and average pore volume, but decrease NiO crystallite size, leading to higher activity and stability. The effects of reaction temperature, pressure and weight hourly space velocity (WHSV) on carbon oxides conversion and CH4 formation rate were also studied. High carbon oxides conversion, CH4 selectivity and formation rate were achieved at the reaction temperature range of 280 300℃.     

Effects of Calcination Temperature on the Acidity and Catalytic Performances of HZSM-5 Zeolite Catalysts for the Catalytic Cracking of n-Butane

The acidic modulations of a series of HZSM-5 catalysts were successfully made by calcination at different treatment temperatures, i.e. 500, 600, 650, 700 and 800 ℃, respectively. The results indicated that the total acid amounts, their density and the amount of B-type acid of HZSM-5 catalysts rapidly decreased, while the amounts of L-type acid had almost no change and thus the ratio of L/B was obviously enhanced with the increase of calcination temperature (excluding 800 ℃). The catalytic performances of modified HZSM-5 catalysts for the cracking of n-butane were also investigated. The main properties of these catalysts were characterized by means of XRD, N2 adsorption at low temperature, NH3-TPD, FTIR of pyridine adsorption and BET surface area measurements. The results showed that HZSM-5 zeolite pretreated at 800 ℃ had very low catalytic activity for n-butane cracking. In the calcination temperature range of 500-700 ℃, the total selectivity to olefins, propylene and butene were increased with the increase of calcination temperature, while, the selectivity for arene decreased with the calcination temperature.The HZSM-5 zeolite calcined at 700 ℃ produced light olefins with high yield, at the reaction temperature of 650 ℃ the yields of total olefins and ethylene were 52.8% and 29.4%, respectively. Besides, the more important role is that high calcination temperature treatment improved the duration stability of HZSM-5zeolites. The effect of calcination temperature on the physico-chemical properties and catalytic performance of HZSM-5 for cracking of n-butane was explored. It was found that the calcination temperature had large effects on the surface area, crystallinity and acid properties of HZSM-5 catalyst, which further affected the catalytic performance for n-butane cracking.     

Selective catalytic methanation of CO in hydrogen-rich gases over Ni/ZrO2 catalyst

Ni/ZrO2 catalysts were prepared by the incipient-wetness impregnation method and were investigated in activity and selectivity for the selective catalytic methanation of CO in hydrogen-rich gases with more than 20 vol% CO2. The result showed that Ni loadings significantly influenced the performance of Ni/ZrO2 catalyst. The 1.6 wt% Ni loading catalyst exhibited the highest catalytic activity among all the catalysts in the selective methanation of CO in hydrogen-rich gas. The outlet concentration of CO was less than 20 ppm with the hydrogen consumption below 7%, at a gas-hourly-space velocity as high as 10000 h-1 and a temperature range of 260 °C to 280 °C. The X-ray diffraction （XRD） and temperature programmed reduction （TPR） measurements showed that NiO was dispersed thoroughly on the surface of ZrO2 support if Ni loading was under 1.6 wt%. When Ni loading was increased to 3 wt% or above, the free bulk NiO species began to assemble, which was not favorable to increase the selectivity of the catalyst.     

Catalytic properties of Ni/ceria-yttria electrode materials for partial oxidation of methane

The catalytic properties of electrode materials Ni/Ce1-xYxO2-δ (x = 0.05, 0.10, 0.15 and 0.20) were investigated for partial oxidation of methane (POM). The CeO2-Y2O3 solid solutions were prepared by co-precipitaion method. The Ni-based catalysts supported on the solid solutions were obtained using the impregnation method. Structural, surface and redox characteristics of the prepared catalysts were systematically examined by means of X-ray diffraction (XRD), N2 adsorption-desorption (Brunauer-Emmet-Teller BET method), H2 temperature-programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS) methods. The results indicated that yttria doped in the ceria system, forming a good solid solution, readily induced more defects and oxygen vacancies that favored the improvement of catalytic activity and coking resistance. In the temperature range of 600-850 ℃, Ni/Ce0.90Y0.10O1.95 catalyst exhibited the best catalytic activity among the four tested catalysts, with the CH4 conversion, CO selectivity and H2 selectivity of 78.8%, 90.6% and 89.8%, respectively, at 850 ℃. And the H2/CO molar ratio in products of Ni/Ce0.90Y0.10O1.95 catalyst was closer to the theoretical value of 2.0. The excellent coking resistant behaviors for all catalysts were clearly manifested by Thermal Analysis.     

Effect of ultrasonic irradiation and /or halogenation on the catalytic performance of γ-Al2O3 for methanol dehydration to dimethyl ether

Dimethyl ether(DME) is amongst one of the most promising alternative,renewable and clean fuels being considered as a future energy carrier.In this study,the comparative catalytic performance of the halogenated γ-Al 2 O 3 prepared from two halogen precursors(ammonium chloride and ammonium fluoride) is presented.The impact of ultrasonic irradiation was evaluated in order to optimize both the halogen precursor for the production of DME from methanol in a fixed bed reactor.The catalysts were characterized by SEM,XRD,BET and NH 3-TPD.Under reaction conditions where the temperature ranged from 200 to 400 ℃ with a WHSV = 15.9 h-1was found that the halogenated catalysts showed higher activity at all reaction temperatures.However,the halogenated alumina catalysts prepared under the effect of ultrasonic irradiation showed higher performance of γ-Al 2 O 3 for DME formation.The chlorinated γ-Al 2 O 3 catalysts showed a higher activity and selectivity for DME production than fluorinated versions.     

Selective oxidation of ethane to aldehydes over SBA-15 supported molybdenum catalyst

SBA-15 supported Mo catalysts （Moy/SBA-15） were prepared by an ultrasonic assisted incipient-wetness impregnation method. The physical and chemical properties of the catalysts were characterized by means of N2-adsorption-desorption, XRD, TEM, UV-Vis, Raman, XANES and H2-TPR. The results showed that a trace amount of MoO3 was produced on high Mo content samples. Tum-over frequency （TOF） and product selectivity are dependent on the molybdenum content. Both Mo0.75/SBA-15 and Mo1.75/SBA-15 catalysts give the higher catalytic activity and the selectivity to the total aldehydes for the selective oxidation of C2H6. At the reaction temperature of 625℃, the maximum yield of aldehydes reached 4.2% over Mo0.75/SBA-15 catalyst. The improvement of the activity and selectivity was related with the state of MoOx species.     

Simultaneous Removal of COS and H_2S at Low Temperatures over Nanoparticle a-FeOOH Based Catalysts

Catalysts using a-FeOOH nanoparticles as the active ingredient were tested by a microreactor-chromatography assessing apparatus at atmospheric pressure between 25 and 60C with a gas hourly space velocity of 10,000 h-1, while the removal performance of H2S with catalysts was investigated using the thermal gravimetric method. The results show that the catalysts are highly active for COS hydrolysis at low temperatures (<60C) and high gas hourly space velocity, and the highest activity can reach 100%. The catalyst is particularly stable for 12 h, and no deactivation is observed. Nanoparticle a-FeOOH prepared using hydrated iron sulfate shows higher COS hydrolysis activity, and the optimum calcination temperature for the catalyst is 260C. In addition, the catalysts can remove COS and H2S simultaneously, and 60C is favorable for the removal of H2S. The compensation effect exists in nanoparticle-based catalysts.     

Catalytic oxidation of soot particulates over MnOx-CeO2 oxides prepared by complexation-combustion method

MnOx-CeO2 oxides prepared by complexation-combustion method were used for soot oxidation. The highest conversion rate of soot was obtained on a MnOx-CeO2 oxide prepared under mild acid condition of pH = 4, where the oxidation temperature corresponding to maximum activity was decreased more than 150℃ compared with that of un-catalytic soot oxidation. The structure and property of the catalysts were investigated by X-ray powder diffraction (XRD) and temperature programmed reduction (TPR). The results indicate...     

纳米贵金属插入的粘土用于催化选择性加氢反应

 The use of clay minerals in the synthesis of nanosized noble metal particles to give increased catalytic activity was investigated. Nanosized platinum and ruthenium catalysts intercalated in clay (montmorillonite/hectorite) were synthesised and their catalytic activity was evaluated for the selective hydrogenation of three different α,β-unsaturated aldehydes, namely, crotonaldehyde, cinnamaldehyde, and citral, in a gas phase microreactor. The metal nano-sol was prepared by the chemical reduction of its precursor by the micellar technique in the presence of cetyl trimethyl ammonium bromide (CTAB), and the micelle stabilized metal particles were intercalated in the clay mineral by ion exchange. TEM micrographs of the catalyst particles showed that the metal particles were in the nanometre range. The average diameters of the particles were 1–25 nm. The effects of temperature, metal loading, and hydrogen flow rate on the catalytic activity and selectivity for α,β- unsaturated alcohol were studied. The results were correlated with the structural properties of the catalysts. The products formed in each reaction over the different catalysts showed that the catalysts were very active for hydrogenation, and the selectivity for the desired product, namely, α,β-unsaturated alcohol, was good. The metal catalysts intercalated in montmorillonite showed better selectivity than that in hectorite because of its higher acidity. Increased selectivity for α,β-unsaturated alcohol was observed with increased flow rate of hydrogen.     

Study on iron-manganese catalysts for Fischer-Tropsch synthesis

Iron-manganese catalysts were prepared by co-precipitation method.Characterization of catalysts was carried out by using X-ray diffraction(XRD),scanning electron microscopy(SEM),temperature program reduction(TPR),N2 adsorption-desorption measurements.The results from catalytic performance tests in Fischer-Tropsch synthesis showed that the iron-manganese catalysts are supersensitive to catalyst composition and materials source.It was found that C2~4 light olefins increased while CH4 and CO2 decreased by using iron-manganese catalyst prepared from iron(II) sulfate(A catalyst).The activity and selectivity of A catalyst was studied in different operational conditions.The results showed that the best operational conditions for C2~4 light olefins production were H2/CO=1/1(GHSV=2400h-1) at 260℃ under 0.3MPa total pressure.     

Pd catalysts supported on modified Zr0.5Al0.5O1.75 used for lean-burn natural gas vehicles exhaust purification

Composite supports Zr0.5Al0.5O1.75 modified by metal oxides,such as La2O3,ZnO,Y2O3 or BaO,were prepared by co-precipitation method,and palladium catalysts supported on the modified composite supports were prepared by impregnation method.Their properties were characterized by X-ray diffraction(XRD),NH3 temperature-programmed desorption(NH3-TPD),H2 temperature-programmed reduction(H2-TPR),N2 adsorption/desorption,and CO-chemisorption.The catalytic activity and the resistance to water poisoning of the prepared Pd catalysts were tested in a simulated exhaust gas from lean-burn natural gas vehicles with and without water vapor.The results demonstrated that the modified supports had an apparent effect on the performance of Pd catalysts,compared with the Pd catalyst supported on the unmodified ZrAl.The addition of ZnO or Y2O3 promoted the conversion of CH4.In the absence of water vapor,Pd/ZnZrAl exhibited the best activity for CH4 conversion with the light-off temperature(T50) of 275℃ and the complete conversion temperature(T90) of 314℃,respectively.However,in the presence of water vapor,Pd/YZrAl was the best one over which the light-off temperature(T50) of methane was 339℃ and the complete conversion temperature(T90) was 371℃.These results indicated that Pd catalyst supported on the modified composite ZrAl support showed excellent catalytic activity at low temperature and high resistance to H2O poisoning for the exhaust purification of lean-burn natural gas vehicles.     

Characterization of Ni／AlMCM-41 Catalysts and Their Catalytic Performance in n-Dodecane Hydroconversion

A series of Ni/AIMCM-41 catalysts with different nickel contents was prepared via the incipient wetness impregnation method. The effects of the nickel content on the structure, acidity and metal function of the catalysts were studied by using different techniques. In the test of n-dodecane hydroconversion, it was found that the metal and acid functions were well balanced over a 2.0%Ni (mass fraction)/AIMCM-41 catalyst, which gave the maximal isomerization selectivity and a homolytic cleavage products.     

Selective Oxidation of Isobutane over NH4CsFePVMoAs Heteropolycompound Catalysts

A series of NH4Cs1.5Fe0.08HxPVMo11AsαOy heteropolycompound catalysts for the selective oxidation of isobutane, having Keggin structure, were synthesized by using co-precipitation method. The catalysts were characterized by FT-IR, H2-TPR, TG-DTA, SEM and XRD. Effects of the As content,reaction time, reaction temperature and molar ratio of isobutane to oxygen in feedstock on the activity and selectivity of the catalyst were investigated. The activation energy of the catalysts was measured by kinetics researches. Results showed the introduction of Cs^ into the catalysts shortened the stable period of them and enhanced their catalytic activity for the selective oxidation of isobutane. The highest conversion of isobutane and the total selectivity to liquid products were 18.6% and 81.2%, respectively,which were obtained at 380 *(3 with a space velocity of 975h^-1 over the NH4Cs1.5Fe0.08HxPVMo11 As0.3Oy heteropolycompound catalyst. It is confirmed that completely oxidized products were controlled well.     

Simultaneous Removal of COS and H2S at Low Temperatures over Nanoparticle α-FeOOH Based Catalysts

Catalysts using α-FeOOH nanoparticles as the active ingredient were tested by a microreactorchromatography assessing apparatus at atmospheric pressure between 25 and 60℃ with a gas hourly space velocity of 10,000h^-1,while the removal performance of H2S with catalysts was investigated using the thermal gravimetric method.The results show that the catalysts are highly active for COS hydrolysis at low temperatures(≤℃）and high gas hourly space velocity,and the highest activity can reach 100%.The catalyst is particularly stable for 12h,and no deactivation is observed.Nanoparticle α-FeOOH prepared using hydrated iron sulfate shows higher COS hydrolysis activity,and the optimum calcination temperature for the catalyst is 260℃.In addition,the catalysts can remove COS and H2S simultaneously,and 60℃ is favorable for the removal of H2S.The compensation effect exists in nanoparticle-based catalysts.     

Production of gasoline range hydrocarbons from methanol on hierarchical ZSM-5 and Zn/ZSM-5 catalyst prepared with soft second template

Nano hierarchical mesoporous ZSM-5 catalysts were prepared with cationic dimethyldiallyl ammonium chloride acrylamide copolymer(PDDA) as a soft second template. Using ZSM-5 catalyst as a matrix,Zn/ZSM-5 catalysts were also obtained by the wet impregnation method. The effect of the PDDA amount and Zn loadings on the properties of the catalysts,including crystallinity,morphology,textural properties,acid nature and catalytic activity in MTG reaction,was investigated by XRD,FESEM,TEM,Nitrogen adsorption–desorption isotherms and NH3-TPD method,respectively. The MTG reaction was performed in a fixed bed reactor,and the result revealed that the nano hierarchical ZSM-5 catalyst prepared with a PDDA/Si molar ratio of 0.070 possesses longer stable phase of 70 h with a liquid hydrocarbon selectivity of 29.8%.Zn/ZSM-5 catalyst with a Zn/ZSM-5 ratio of 0.07 wt.% shows the highest liquid hydrocarbon selectivity,reaching 62.5%.     

Stabilization of Cu/ZnO Based Catalysts by Nickel Additive in Methanol Decomposition

A series of Cu/Zn based catalysts with and without Ni, prepared by the co-precipitation method, has been studied for methanol decomposition. CO and H2 are the major products. The Cu/Zn catalysts show a low initial activity and a poor stability. The formation of the CuZn alloys was observed in the deactivated Cu/Zn catalysts which were used for methanol decomposition at 250 . When small amounts of Ni were added in the catalyst, the Cu/Zn/Ni(molar ratio 5/4/ x) catalysts showed a high activity at a low temperature. The activity and the stability of the catalyst depend on the nickel content. The activity of the Cu/Zn/Ni catalysts was maintained at a. relatively stable value of 78% conversion of methanol with 95% selectivity of H2, 93% selectivity of CO, and a more than 70% yield of hydrogen was obtained at 250 C when x >1. The stability of the Cu/Zn/Ni (molar ratio 5/4/x) catalysts showed the maximum (ca 88%) when x=1. The stabilization effect of nickel on the Cu/Zn based catalysts may lead to the increasin