Support Effects on Thiophene Hydrodesulfurization over Co-Mo-Ni/Al_2O_3 and Co-Mo-Ni/TiO_2-Al_2O_3 Catalysts

A carbon-based sulfonated catalyst was prepared by direct sulfonation and carbonization （in moderate conditions：200 ＆#176;C, 12 h） of red liquor solids, a by-product of paper-making process. The prepared sulfonated cata-lyst （SC） had aromatic structure, composed of carbon enriched inner core, and oxygen-containing （SO3H, COOH, OH） groups enriched surface. The SO3H, COOH, OH groups amounted to 0.74 mmol·g^-1, 0.78 mmol·g^-1, 2.18 mmol·g^-1, respectively. The fresh SC showed much higher catalytic activity than that of the traditional solid acid catalysts （strong-acid 732 cation exchange resin, hydrogen type zeolite socony mobile-five （HZSM-5）, sulfated zir-conia） in esterification of oleic acid. SC was deactivated during the reactions, through the mechanisms of leaching of sulfonated species and formation of sulfonate esters. Two regeneration methods were developed, and the catalytic activity can be mostly regenerated by regeneration Method 1 and be fully regenerated by regeneration Method 2, respectively.

Effects of ZrO_2 on the Performance of CuO-ZnO-Al_2O_3/HZSM-5 Catalyst for Dimethyl Ether Synthesis from CO_2 Hydrogenation

A series of composite catalysts were prepared by the wet mixing method, and the mass ratio of CuO-ZnO-Al2O3-ZrO2 component to HZSM-5 zeolite （molar ratio of SiO2 to Al2O3 being 25） was 2：1. The CuO-ZnO-Al2O3-ZrO2 （CuO/ZnO/Al2O3=3/6/1 by weight） component was prepared by a modified ＇two-step＇ co-precipitation method. The effects of ZrO2 on the performance of CuO-ZnO-Al2O3/HZSMo5 catalyst for dimethyl ether synthesis from CO2 hydrogenation were investigated. It was found that ZrO2 improved the properties of CuO-ZnO-Al2O3/HZSM-5 as a structural promoter.

Characterization of CuO Species and Thermal Solid-Solid Interaction in CuO/CeO_2-Al_2O_3 Catalyst by In-Situ XRD, Raman Spectroscopy and TPR

Transference of CuO species and thermal solid-solid interaction in CuO/CeO2-Al2O3 catalyst prepared by an impregnation method were characterized by in-situ XRD, Raman spectroscopy and H2-TPR techniques. For the catalyst calcined at 300℃, two kinds of CuO species coexist on the surface, that is, highly dispersed and bulk CuO crystalline phase. Four kinds of CuO species are present for the catalyst calcined at 600 ℃, ： （1） highly dispersed CuO, （2） bulk CuO on the surface, （3） bulk CuO in the internal layer of CeO2, and （4） CuAl2O4 formed from CuO-Al2O3 interaction. For the catalyst calcined at 800 ℃,C, besides very little highly dispersed and bulk CuO on the surface, most of the CuO has transferred into the internal layer of CeO2 and the mass of CuAl2O4 are increased. At 900 ℃,, all of CuO has diffused into the internal layer of CeO2 and formed CuAl2O4. The results show that the distribution of CuO species in the catalysts depends on the calcination temperature; the different CuO species can be effectively confirmed by in-situ XRD, Raman spectroscopy and H2-TPR techniques.

Oligomerization of 1-Decene: Catalyzation by Immobilized AlCl_3/γ-Al_2O_3 Catalyst in Fixed-bed Reactor

1-Decene was oligomerized over the supported AlCl3/γ-Al2O3 catalyst in a fixed-bed reactor. The effects of temperature and LHSV on oligomerization of 1-decene were investigated and the synthetic PAO was characterized with GC technique. Furthermore, the life of immobilized catalyst was tested and the mechanism of catalyst deactivation was discussed. The results showed that with an increasing temperature, the PAO yield increased and the kinematic viscosity of oil decreased. The GC results indicated that the synthesized PAO was a mixture consisting of dimers, trimers, tetramers and pentamers. The results of chloride content measurements and BET tests showed that catalyst deactivation could be mainly attributed to the loss of active components.

CeO_2-ZrO_2-La_2O_3-Al_2O_3 composite oxide and its supported palladium catalyst for the treatment of exhaust of natural gas engined vehicles

Composite supports CeO2-ZrO2-Al2O3（CZA） and CeO2-ZrO2-Al2O3-La2O3（CZALa） were prepared by co-precipitation method. Palladium catalysts were prepared by impregnation and their purification ability for CH4, CO and NOx in the mixture gas simulated the exhaust from natural gas vehicles （NGVs） operated under stoichiometric condition was investigated. The effect of La2O3 on the physicochemical properties of supports and catalysts was characterized by various techniques. The characterizations with X-ray diffraction （XRD） and Raman spectroscopy revealed that the doping of La2O3 restrained effectively the sintering of crystallite particles, maintained the crystallite particles in nanoscale and stabilized the crystal phase after calcination at 1000 ℃. The results of N2-adsorption, H2-temperatnre-programmed reduction （H2-TPR） and oxygen storage capacity （OSC） measurements indicated that La2O3 improved the textural properties, reducibility and OSC of composite supports. Activity testing results showed that the catalysts exhibit excellent activities for the simultaneous removal of methane, CO and NOx in the simulated exhaust gas. The catalysts supported on CZALa showed remarkable thermal stability and catalytic activity for the three pollutants, especially for NOx. The prepared palladium catalysts have high ability to remove NOx, CH4 and CO, and they can be used as excellent catalysts for the purification of exhaust from NGVs operated under stoichiometric condition. The catalysts reported in this work also have significant potential in industrial application because of their high performance and low cost.

Synthesis and applications of mesoporous Cu-Zn-Al_2O_3 catalyst for dehydrogenation of 2-butanol

A series of mesoporous Cu-Zn-Al2O3 materials have been synthesized at ambient temperature and their structure was characterized by XRD, N2 physical adsorption and TPR techniques. Their catalytic applications for the dehydrogenation of 2-butanol to methyl ethyl ketone （MEK） were evaluated in a fixed-bed flow reactor at atmospheric pressure. It is demonstrated from the XRD patterns that both the as-synthesized samples and calcined samples have the typical XRD patterns of meso-structured materials and the results of N20 chemical adsorption showed that Cu was embedded in the framework of the mesoporous materials and homogeneously dispersed in the mesoporous Cu-Zn-Al2O3 materials. The catalytic activity of 2-butanol dehydrogenation was varied in the order of CZA（10） 〈 CZA（CP） 〈 CZA（20） 〈 CZA（30）; while the selectivity of MEK was increased in the order of CZA（CP） 〈 CZA（10） 〈 CZA（20） 〈CZA（30）.

Research on KOH/La-Ba-Al_2O_3 catalysts for biodiesel production via transesterification from microalgae oil

Alumina supports modified by lanthanum （La） and barium （Ba） were prepared by peptization. Catalysts with different KOH contents supported on modified alumina were prepared by impregnation method. Various techniques, including N2 adsorption-desorption （Brunauer-Emmet-Teller method, BET）, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and fourier transform infrared absorption spectroscopy （FT-IR）. Catalytic activity for microalgae oil conversion to methyl ester via transesterification was evaluated and analyzed by GC-MS and GC. BET results showed that the support possessed high specific surface area, suitable pore volume and pore size distribution. Activity results indicated that the catalyst with 25 wt% KOH showed the best activity for microalgae oil conversion. XRD and SEM results revealed that Al-O-K compound was the active phase for microalgae oil conversion. The agglomeration and changing of pore structure should be the main reasons for the catalyst deactivation when KOH content was higher than 30 wt%.

Autothermal reforming of methane over Ni catalysts supported over ZrO2-CeO2-Al2O3

Ni catalysts supported on Al2O3, ZrO2-Al2O3, CeO2-Al2O3 and ZrO2-CeO2-Al2O3 were prepared by coprecipitation method, and their catalytic performances for autothermal reforming of methane to hydrogen were investigated. The Ni-supported catalysts were characterized by XRD, TPR and XPS. The relationship between the structures and catalytic activities of the catalysts was discussed. The results showed that the catalytic activity and stability of the Ni/ZrO2-CeO2-Al2O3 catalyst was better than those of other catalysts with the highest CH4 conversion, H2/CO and H2/COx ratio at 750 ℃. The catalyst showed a little deactivation along the reaction time during its 72 h on stream with the mean deactivation rate of 0.08%/h. The catalytic performance of the Ni/ZrO2-CeO2-Al2O3 catalyst was also affected by reaction temperature, no2 ： nCH4 molar ratio and nH2O ： nCH4 molar ratio. TPR, XRD and XPS measurements indicated that the formation of ZrO2-CeO2 solid solution could improve the dispersion of NiO, and inhibit the formation of NiAl2O3, and thus significantly promoted the catalytic activity of the Ni/ZrO2-CeO2-Al2O3 catalyst.

Performance of Pd/CeO_2-ZrO_2-Al_2O_3 catalyst for motorcycle

The Pd-only catalysts for motorcycle were prepared by impregnating CeO2-ZrO2-Al2O3 and CeO2-ZrO2+Al2O3 with PdCl2 aqueous solution and characterized by X-ray diffraction (XRD), oxygen storage capacity (OSC) and H2-temperature-programmed reduction (H2-TPR) methods. The XRD result indicated that the CeO2-ZrO2-Al2O3 compound prepared by co-precipitation formed a single solid solution and had good thermal stability, and Pd phase was not observed in all catalysts. The TPR results showed that the reduction temperature of Pd/CeO2-ZrO2-Al2O3 catalyst was lower than that of Pd/CeO2-ZrO2+Al2O3 catalyst whether they were fresh or aged catalysts. The Pd/CeO2-ZrO2-Al2O3 exhibited high three-way catalytic activity at low temperature, high thermal stability, and wide working window, suggesting a great potential for applications.

DBD coupled with MnOx/γ-Al2O3 catalysts for the degradation of chlorobenzene

This paper investigates the degradation of chlorobenzene by dielectric barrier discharge(DBD)coupled with MnOx/γ-Al2O3 catalysts.MnOx/γ-Al2O3 catalysts were prepared using the impregnation method and were characterized in detail by N2 adsorption/desorption,x-ray diffraction and x-ray photoelectron spectroscopy.Compared with the single DBD reactor,the coupled reactor has a better performance on the removal rate of chlorobenzene,the selectivity of COx,and the inhibition of ozone production,especially at low discharge voltages.The degradation rate of chlorobenzene and selectivity of COx can reach 96.3%and 53.0%,respectively,at the specific energy density of 1350 J l-1.Moreover,the ozone concentration produced by the discharge is significantly reduced because the MnOx/Al2O3 catalysts contribute to the decomposition of ozone to form oxygen atoms for the oxidation of chlorobenzene.In addition,based on analysis of the byproducts,the decomposition mechanism of chlorobenzene in the coupled reactor is also discussed.

Syngas production by combined carbon dioxide reforming and partial oxidation of methane over Ni/α-Al_2O_3 catalysts

Ni/α-Al2O3 catalysts were found to be active in the temperature range 600 ～ 900℃ for both CO2 reforming and partial oxidation of methane.The effects of Ni loading,reaction temperature and feed gas ratio for the combination of CO2 reforming and partial oxidation of CH4 over Ni/α-Al2O3 were investigated.Catalysts of xwt%Ni/α-Al2O3（x=2.5,5,8 and 12） were prepared by wet impregnating the calcined support with a solution of nickel nitrate.XRD patterns and activity tests have verified that the 5wt%Ni/α-Al2O3 was the most active catalyst,as compared with the other prepared catalyst samples.An increase of the Ni loading to more than 5wt% led to a reduction in the Ni dispersion.In addition,by combining the endothermic carbon dioxide reforming reaction with the exothermic partial oxidation reaction,the loss of catalyst activity with time on stream was reduced with the amount of oxygen added to the feed.

Evaluation of H2 Influence on the Evolution Mechanism of NOx Storage and Reduction over Pt–Ba–Ce/c-Al2O3 Catalysts

In this investigation, Pt–Ba–Ce/c-Al2O3 catalysts were prepared by incipient wetness impregnation and experiments were performed to evaluate the influence of H2 on the evolution mechanism of nitrogen oxides (NOx) storage and reduction (NSR). The physical and chemical properties of the Pt–Ba–Ce/c- Al2O3 catalysts were studied using a combination of characterization techniques, which showed that PtOx, CeO2, and BaCO3, whose peaks were observed in X-ray diffraction (XRD) spectra, dispersed well on the c-Al2O3, as shown by transmission electron microscope (TEM), and that the difference between Ce3+ and Ce4+, as detected by X-ray photoelectron spectroscopy (XPS), facilitated the migration of active oxygen over the catalyst. In the process of a complete NSR experiment, the NOx storage capability was greatly enhanced in the temperature range of 250–350℃, and reached a maximum value of 315.3μmol·gcat^-1 at 350℃, which was ascribed to the increase in NO2 yield. In a lean and rich cycling experiment, the results showed that NOx storage efficiency and conversion were increased when the time of H2 exposure (i.e., 30, 45, and 60 s) was extended. The maximum NOx conversion of the catalyst reached 83.5% when the duration of the lean and rich phases was 240 and 60 s, respectively. The results revealed that increasing the content of H2 by an appropriate amount was favorable to the NSR mechanism due to increased decomposition of nitrate or nitrite, and the refreshing of trapping sites for the next cycle of NSR.

Cross metathesis of butene-2 and ethene to propene overMo/MCM-22-Al_2O_3 catalysts with different Al_2O_3 contents

A series of 3.0Mo/MCM-22-Al2O3 catalysts with γ-Al2O3 contents in the range of 0-100 wt% were prepared and applied in the metathesis reaction of ethene and butene-2. Addition of γ-Al2O3did not affect the structure of MCM-22 zeolite as evidenced by XRD and N2 adsorption measurements. It was deduced from TPR experiments that γ-Al2O3 phase favored the formation of polymolybdate or multilayered Mo oxide, while more Al2（MoO4）3 species were generated over MCM-22 zeolites. Alumina content in the support was directly related to the metathesis activity of ethene and butene-2 to propene. Mo species with higher valence （Mo6＋or Mo5＋） contributed more to the excellent performance of catalyst than metallic Mo. The best catalyst activity and stability was obtained over 3.0Mo/（MCM-22-30%Al2O3） under the reaction condition of 1.0 MPa and 125℃ using N2 as the pretreatment gas.

Effect of Fe_2O_3 Loading Amount on Catalytic Properties of Monolithic Fe_2O_3/Ce_(0.67)Zr_(0.33)O_2-Al_2O_3 Catalyst for Methane Combustion

Ce0.67Zr0.33O2-Al2O3 solid solution was prepared by the co-precipitation method. Fe2O3-based catalysts supported on the solid solution were obtained by the impregnation method. The article revealed that the optimal loading amount of Fe2O3 on Ce0.67Zr0.33 O2-Al2O3 in our experimental condition for catalytic combustion of methane was 8% （ mass fraction）. The prepared catalysts were characterized by BET, TPR, XRD analyses, and their catalytic activity was investigated after being calcined at 873 K and after being aged in water gas at 1273 K. When the loading amount of Fe203 was 8% （ mass fraction）, the catalyst held the highest activity, and the best temperature speciality and thermal stability. The complete-conversion temperature of methane for fresh and aged sample was 788 and 838 K, respectively. The range between the light-off temperature and the complete-conversion temperature was only 15 K. The characterization results of XRD indicated that Fe2O3 was well dispersed on the Ce0.67Zr0.33O2-Al2O3 matrix. The results of BET and TPR were in good harmony with the catalytic activity results.

Selective catalytic reduction of NO with NH_3 over sol-gel-derived CuO-CeO_2-MnO_x/γ-Al_2O_3 catalysts

Granular CuO-CeO2-MnOx/γ-Al2O3 catalysts were synthesized by the sol-gel method. The performance of the CuO-CeO2-MnOx/γ-Al2O3 catalysts for the selective catalytic reduction (SCR) was studied in a fixed bed system. Preliminary tests were carried out to analyze the behavior of NH3 and NO over catalyst in the presence of oxygen. The optimum temperature range for SCR over the CuO-CeO2-MnOx/γ-Al2O3 catalysts is 300-400 ℃ . The catalysts maintain nearly 100% NO conversion at 350 ℃. The NH3 oxidation experiments show that both NO and N2O are produced gradually with the increase of temperature. The catalysts in this experiment have a stronger oxidation property on NH3, which improves the denitrification activity at low temperature. The over-oxidation of NH3 at high temperature is the main cause leading to a decrease in the NO conversion. The NH3 and NO desorption experiments show that NH3 and NO can be adsorbed on CuO-CeO2-MnOx/γ-Al2O3 granular catalysts. The transient response of NH3 and NO indicates that the SCR reaction proceeds in accordance with the Eley-Rideal mechanism. The adsorbed NO has little influence on the denitrification activity in SCR process.

Methane Coupling Using Hydrogen Plasma and Pt/γ-Al_2O_3 Catalyst

In this paper, methane coupling at ambient temperature, under atmospheric pressure and in the presence of hydrogen was firstly investigated by using pulse corona plasma and Pt/g-Al2O3 catalyst. Experimental results showed that Pt/g-Al2O3 catalyst has catalytic activity for methane coupling to C2H4. Over sixty percent of outcomes of C2 hydrocarbons were detected to be ethylene.

Effect of Ball-Milling Time on the Performance of Ni-Al2O3 Catalyst for 1,4-Butynediol Hydrogenation to Produce 1,4-Butenediol

The Ni-Al2O3 catalyst was prepared by the mechanochemical method in combination with a planetary ballmilling machine.Effect of milling time on the crystal structure,the reduction characteristics and the catalytic performance of Ni-Al2O3 catalyst for hydrogenation of 1,4-butynediol to produce 1,4-butenediol were investigated.The catalysts were characterized by PSD,EDX,XRD,H2-TPR,BET,TEM,and NH3-TPD methods.Results showed that the MCt2.5 catalyst treated at a ball milling time of 2.5 h could form a smallest particle size of 191.0 nm.The evaluation experiments revealed that the activity of the prepared catalyst increased at first and then reached a constant value with the extension of ballmilling time.The BYD conversion,BED selectivity and yield on the MCt2.5 catalyst reached 35.63%,33.48%and 32.46%,respectively,which were higher than those obtained by other samples.The excellent performance of MCt2.5 sample is mainly related to the following three reasons from characterization results.Firstly,it has a smallest particle size of 191.0 nm;and then,the surface acidity(in terms of strong acids)of the catalyst was weaker than other catalysts;and eventually,the loading amount(23.84%)of the active component Ni exceeded the theoretical value(20%).

A comparative study on different regeneration processes of Pt-Sn/γ-Al2O3 catalysts for propane dehydrogenation

Three different regeneration processes including hydrogen or nitrogen purging and coke-burning treatment were used to restore the Pt-Sn/γ-AlOcatalysts, through which propane dehydrogenation reaction was performed in a consecutive reaction-regeneration mode. It was found that the catalyst using hydrogen regeneration showed the best stability compared with those regenerated by nitrogen purging and coke-burning treatment, suggesting that hydrogen regeneration is an effective approach for maintaining the performance of Pt-Sn/γ-AlOcatalysts in propane dehydrogenation reaction. The effect of different regeneration atmospheres on the metal active center and the coke deposition was investigated by XRD,TEM, N-physisorption, TPO, TG and Raman technologies, and the results revealed that hydrogen or nitrogen regeneration resulted in little impact on the size and structure of metal active center, retaining the effective Pt Sn phase over the catalyst. Moreover, hydrogen regeneration not only removed the low dense components of the coke, but also altered the property of the residual coke through hydrogenation, leading to a higher mobility of coke, and thus a higher accessibility of the metal active centers. Whereas nitrogen regeneration only removed the low dense components of the coke. Although coke-burning regeneration caused a thorough coke removal, the catalyst subjected to repeated redox exhibited poor stability due to metal agglomeration, phase segregation and the resulting large PtSn particle and core-shell structure with a Sn-rich surface.

二苯并噻吩和4-甲基二苯并噻吩在Mo和CoMo/γ-Al_2O_3催化剂上加氢脱硫的反应机理

研究了二苯并噻吩(DBT)和4-甲基二苯并噻吩(4-MDBT)在Mo/γ-Al_2O3和CoMo/γ-Al_2O_3上加氢脱硫反应的产物分布及其可能的反应网络,并通过反应压力和温度对产物分布的影响,揭示了加氢脱硫反应的可能机理。DBT在Mo/γ-Al_2O_3上的加氢脱硫反应主要通过直接氢解路径和加氢路径进行,两种途径的作用相近;在CoMo/γ-Al_2O_3催化剂上的加氢脱硫主要通过直接氢解路径进行。4-MDBT在Mo/γ-Al_2O_3和CoMo/γ-Al_2O_3上的加氢脱硫反应主要通过加氢路径进行。Co的加入有助于提高Mo/γ-Al_2O_3催化剂的加氢脱硫活性,尤其是直接氢解脱硫活性。4-MDBT加氢脱硫反应中加氢路径的相对作用显著大于DBT加氢脱硫反应的加氢路径,间接证明4-MDBT的加氢脱硫过程存在对“端连吸附”的空间位阻。4-MDBT分子中甲基的供电子作用有利于促进苯环的加氢反应,从而有助于缩小与DBT分子间加氢脱硫活性的差别。在DBT和4-MDBT加氢脱硫反应中,反应压力和温度对加氢路径的影响大于对氢解路径的影响。

Enhanced catalytic performance for direct synthesis of dimethyl ether from syngas over a La_2O_3 modified Cu-ZrO_2/γ-Al_2O_3 hybrid catalyst

A series of hybrid catalysts were made by physically mixing Cu-ZrO2 and γ-A12O3, for former it was modified with different loadings of La2O3 prepared by co-precipitation method. The catalysts were characterized by BET, XRD, N2O-adsorption, EXAFS, H2-TPR, NH3-TPD techniques and evaluated in the synthesis of dimethyl ether from syngas. The results show that La2O3 promoted catalysts displayed a significantly better catalytic performance compared with Cu-ZrO2#y-A12O3 catalyst in CO conversion and DME selectivity, and the optimum catalytic activity was obtained when the content of La2O3 was 12 wt%. The characterizations reveal that high copper dispersion, facile reducibility of copper particles and appropriate amount of acidic sites are responsible for the superior catalytic performance.