ELUCIDATION OF HYDRODESULFURIZATION AND HYDROGENATION MECHANISMS USING RADIOISOTOPE TRACER METHODS

To meet the specification of sulfur and aromatic contents in diesel fuel, it is necessary for refiners to develop a new catalyst with high activity of hydrodesulfurization and hydrogenation. In the present study, the properties of noble metal catalysts for hydrodesulfurization and hydrogenation in the presence of sulfur compounds have been investigated. The hydrogenation activity of phenanthrene (PHE) on single noble metal and double noble metal catalysts-Pt/Al2O3, Pd/Al2O3 and Pd-Pt/Al2O3 in the presence of dibenzothiophene (DBT) was performed in a fixed bed flow reactor. The Pt based catalysts revealed the similar HDS activities and higher HYD activity compared with convertional Mo based catalysts. The maximum activity was obtained around 320℃ for both catalyst types. The Pt based catalysts produced perhydrophenanthrene as a major product at the maximum activity in the hydrogenation of PHE while the Mo based catalysts produced octahydrophenanthrene. A ^35S radioisotope pulse tracer method (^35S RPTM) was used to estimate the behavior of sulfur on the working catalysts and to clarity the differences between Pt and Mo based catalysts. Very little amount of labile sulfur was accumulated on the Pt and Pd catalysts in the HDS of [^35S]DBT (PtS0.25 or PdS0.25). This indicates that the mechanism of DBT HDS on noble metal catalysts is significantly different from that on conventional Mo based catalysts where Mo is present as MoS2 less than 60% of which can be labile in the case of Co-Mo/Al2O3. Another Ru-Cs/Al2O3 catalysts were also prepared and the behavior of sulfur on the working catalyst was compared with those of Mo based catalysts and Pt and Pd catalysts. The values of labile sulfur in the kIDS reaction for Ru-Cs catalysts approximately correspond to RS0.5-0.74. These amounts of labile sulfur are much higher than those for Pt and Pd catalysts. The result suggests that the oxidation state of Ru species is present between the oxidation states of Pt or Pd and Mo, and can change in the wide range during the HDS reaction, different from PtS0.25 (PdS0.25) and MoS2 which is unchangeable under the usual HDS conditions. From the approach of using [^35S]H2S it was found that the labile sulfur was hardly formed during the presulfiding procedure but was formed only during the actual HDS. This is also a unique character of Ru catalysts.     

Influence of Additives on Hydrodesulfurization Activity of Fe-Mo/Al2O3 Catalysts

Based on the study relating to the influence of additives on the hydrodesulfurization performance of Fe-Mo-Al2O3 catalysts, it was found out that the introduction of additives could increase considerably the activity of Fe-Mo/Al2O3 catalysts in the reaction of hydrodesulfurization of gasoline and diesel fractions. The introduction of zeolites （HY, HZSM） and other additives could lead to an increase of the concentration of acid centers, which were able to react with sulfur compounds, along with an increase of total catalysts＇ pore volume, which could improve the capability of catalyst to adsorb the hydrogen and feed oil.     

Research Progress of Palladium Catalysts for Methane Combustion

Recent research progress and development of the palladium catalysts for methane combustion are described in this study.The influence of active species,precursor,solvent,preparation methodologies,support and dopant on the catalytic activity and thermal stability of the palladium catalysts was discussed.Results of deactivation and poisoning of palladium catalysts were analyzed.Furthermore,possible kinetic models and reaction mechanism were indicated for Pd catalysts.     

天然气－CO2－O2转化制合成气催化剂的研究

The activity stability and resistance to carbon deposition of Ni－based catalysts prepared by different methods were investigated using a continuous flowing fixed－bed reactor．The result shows an optimum mass percentage of Ni 3.5％～6.0％，RE₂O₃ 5.6％～6.0％，MgO 6.2％～7.1％．The addition of an appropriate amount of MgO can improve the dispersity of active Ni component and thereby improve the catalyst’s activity and resistance to carbon deposition．The mutual effects of the active components were determined by TPR and XRD techniques．The performance of the catalyst has been demonstrated with the results．     

水热法合成MoO2单体和负载型MoO2催化剂应用于DBT氧化脱硫反应

A novel method for obtaining spherical MoO2 nanoparticles and SiO2-Al2O3 supported MoO2 by hydrothermalreduction of Mo （VI） species was studied. The obtained MoO2 catalysts show very high catalytic activity in the oxidativedesulfurization （ODS） process. The effect of hydrothermal temperature and crystallization temperature on ODS activity wasinvestigated. The ODS activity of supported MoO2 catalysts with various MoO2 contents were also investigated. The mechanismfor formation of MoO2 involving oxalic acid was proposed.     

浸渍顺序对PtSnNa/ZSM-5催化剂丙烷脱氢性能的影响

The effects of the sequence for impregnation of metal precursors on the performance of PtSnNa/ZSM-5 catalyst for propane dehydrogenation to propene were studied in this paper. Some methods such as XRD, TPDA, BET, H2-TPR, XPS, ICP, TEM and hydrogen chemisorption were used to characterize the catalysts. The structure of ZSM-5 zeolite was not destroyed by the introduction of metal components. Meanwhile the different impregnation sequence of metal precursors could affect the behavior of Sn4＋ species entering the ZSM-5 channel, and the interaction between platinum and tin species, as well as the degree for reduction of Pt and Sn components. As a result, the prepared catalysts exhibited different reac- tion activity and selectivity. Compared with the co-impregnation treated catalyst, the catalysts prepared by the sequential impregnation method showed better catalytic activity in propane dehydrogenation, especially the one prepared through impregnation with tin precursor at first. Finally, a model for the effect of impregnation sequence on the distribution of Pt and Sn species in PtSnNa/ZSM-5 catalyst was proposed.     

Catalytic Oxidative Desulfurization of Gasoline Using Vanadium（V）-substituted Polyoxometalate/H2O2/Ionic Liquid Emulsion System

Aiming at deep desulfurization of gasoline,three amphiphilic catalysts [C18H37N(CH3)3]3+x [PMo12-xVxO40](x=1,2,or 3) were prepared and characterized.The amphiphilic vanadium(V)-substituted polyoxometalates were dissolved in water-immiscible ionic liquid([Bmim]PF6),forming a H2O2-in-[Bmim]PF6 emulsion desulfurization system with 30 m% H2O2 serving as the oxidant.The catalytic oxidation of sulfur-containing model oil has been studied in detail under various reaction conditions using this system.The ionic liquid emulsion system showed high catalytic oxidative activity in the treatment of commodity gasoline.Furthermore,the mechanism of catalytic oxidative desulfurization was also elaborated.     

纯载体和担载KVO3催化剂裂解正丁烷制低碳烯烃的研究

Supported KVO3 catalysts were prepared by impregnating different kinds of.supporters (α-Al2O3,γ-Al2O3 and SiO2 powders) with a KVO3 solution. The activity of the bare supporters and supported catalysts were evaluated in a continuous micro-reactivity test unit, with n-butane as a raw material. The results show that KVO3 has no catalytic activity, but it can increase the selectivity to light olefins. The supporter of γ-Al2O3 has good catalytic performance for nbutane cracking when the reaction temperature is below 700℃.     

镓对PtSnNa/ZSM-5催化剂丙烷脱氢反应性能的影响

PtSnNaGa/ZSM-5 catalysts with different contents of Ga were prepared and characterized by X-ray diffraction (XRD), nitrogen adsorption, hydrogen chemisorption, ammonia temperature-programmed desorption (NH3-TPD), hydrogen temperature-programmed reduction (H2-TPR), and temperature-programmed oxidation (TPO) techniques. The performances of these catalysts for propane dehydrogenation were investigated. The test results indicated that the addition of Ga not only could improve the catalytic stability and propene selectivity, but also could effectively prevent the catalysts from coking. It was found that the PtSnNaGa(0.5 m%)/ZSM-5 catalyst exhibited the best performance in terms of propene selectivity and propane conversion. The high catalytic performance was most probably attributed to the presence of Ga that could strength- en the interaction between metals and the support to stabilize the catalytic active sites.     

Effect of LaPO4 Introduction as a Vanadium Trap for Preventing USY Zeolite Destruction

The use of lanthanum phosphate as a vanadium trap for preventing destruction of USY zeolite was studied.The effect of deposited vanadium on the hydrothermal destruction of zeolite was investigated by the solid-state NMR technique.LaPO4 species can inhibit the zeolite framework structure from being collapsed by vanadium after steaming treatment.The EPR results show the oxidation-reduction reaction in LaPO4 and V2O5 system and inhibition of zeolite destruction by V5+.The catalysts prepared from USY and LaPO-USY zeolites were also tested in the catalytic reactions of heavy oil.The assessment results indicated that the USY modified with LaPO4 could bring about remarkably high dehydrogenation ability.     

The surface properties of aluminated meso–macroporous silica and its catalytic performance as hydrodesulfurization catalyst support

Aluminated mesoporous silica was prepared by multiple post-grafting of alumina onto uniform mesoporous SiO_2 ,which was assembled from monodisperse SiO_2 microspheres.Hydrodesulfurization(HDS)catalyst was prepared by loading Ni and Mo active components onto the aluminated uniform mesoporous SiO_2 ,and its HDS catalytic performance was evaluated using hydrodesulfurization of dibenzothiophene as the probe reaction at 300°C and 6.0 MPa in a tubular reactor.The samples were characterized by N_2 physisorption,scanning electronic microscopy,Fourier transform infrared spectrum,X-ray diffraction(XRD),temperature-programmed desorption of ammonia(NH_3-TPD),~(27)Al nuclear magnetic resonance(~(27)Al-NMR)and high-resolution transmission electron microscopy(HRTEM).The results showed that the Si–OH group content of SiO_2 was mainly dependent on the pretreatment conditions and had significant influence on the activity of the Ni Mo catalyst.The surface properties of the aluminated SiO_2 varied with the Al_2O_3-grafting cycles.Generally after four cycles of grafting,the aluminated SiO_2 behaved like amorphous alumina.In addition,plotting of activity of Ni Mo catalysts supported on aluminated meso–macroporous silica materials against the Al_2O_3-grafting cycle yields a volcano curve.     

Hydrocracking of Low-Temperature Coal Tar over CoMo Catalysts Supported on ZrO_2-Al_2O_3 Composite Oxides

A series of CoMo/ZrO__2-Al__2O__3 catalysts with different contents of ZrO_2 were prepared and characterized through XRD, XPS, NH_3-TPD, H_2-TPR, HR-TEM, and N_2 adsorption–desorption technologies. The performance of the catalysts for low-temperature coal tar(LTCT) hydrocracking reaction was investigated. The interaction between active metals and Al_2 O_3 was weakened with the introduction of ZrO_2, which increased the MoS_2 content and the stack layer number of MoS_2 slabs to further promote the catalytic performance. At the same time, the amount of acid sites increased with an increasing ZrO_2 content. When the ZrO_2 content reached 32%, the pore volume of the catalyst decreased significantly. This phenomenon reduced the content of MoS_2 and the stack layer number of MoS_2 slabs, which were not conducive to improving the catalytic performance. The catalyst containing 24% of ZrO_2 exhibited the best catalytic performance for hydrocracking reaction, with the residue conversion and the total yield of gasoline and diesel fractions reaching 60.64% and 66.54%, respectively, which could fulfill the requirements for hydrocracking LTCT.     

Selective Oxidation of PM over Li Doped Potassium Titanate Catalysts

K2Ti2O5 and LixK2-xTi2O5 samples with varying K contents (x=0.125, 0.15, 0.3), targeted on removal of two main environmental pollutants: PM and NOx, were synthesized by the solid state method using TiO2, KNO3 and LiOH·H2O as starting materials and were characterized by X-ray diffractometry, scanning electron microscopy, and BET. The catalytic activity of titanate catalysts on PM oxidation was evaluated using the temperature programmed oxidation (TPO) method. The test results showed that the perovskite structure of K2Ti2O5 was still retained after doping a small amount of Li, and the catalytic performance of LixK2-xTi2O5 had been improved significantly compared with that of K2Ti2O5. Li0.15K1.85Ti2O5 catalyst had the highest catalytic activity with an ignition temperature of 210 ℃ and a peak temperature of 290 ℃. The catalytic activity of both K2Ti2O5 and LixK2-xTi2O5 under intimate contact was higher than that under loose contact. When the exhaust gas flow rate was around 100 mL/min, the catalyst samples showed a highest activity. The Li doped K2Ti2O5 could be an excellent candidate for PM oxidation due to its high oxidation activity, water stability, resistance to sulfur poisoning and economical advantages.     

Catalytic Dehydrogenation of n-Butane over V/SiO2 Catalyst： A Comparison with Cr/SiO2 Catalyst

V/SiO2 catalysts compared to Cr/SiO2 catalysts were studied for dehydrogenation of n-butane to butenes. Several methods for characterization of catalysts such as FT-IR, UV-vis and Raman spectroscopies were used. Some differences between two catalysts were showed, including the performances of catalysts, distribution of products and mechanism of reactions. The results showed that prepared catalysts with 12m% of active component loading all demonstrated best conversion of n-butane to butene at a reaction temperature of around 590 ℃. Two different reaction mechanisms were mentioned to well explain why iso-butene was produced on V/SiO2 catalysts but not on Cr/SiO2 catalysts.     

Pd nanoparticles immobilized on MIL-53(Al) as highly e ective bifunctional catalysts for oxidation of liquid methanol to methyl formate

A series of Pd/MIL-53(Al) heterogeneous bifunctional catalysts with di erent Pd contents were prepared by an impregnation method. The prepared metal–organic frameworks MIL-53(Al) and catalysts were characterized by XRD, SEM, HRTEM,FT-IR and N2 adsorption/desorption techniques. The results showed that MIL-53(Al) was synthesized successfully, and the structure was unchanged during and after the preparation of the catalysts. The Pd nanoparticles(NPs) with an average particle size of 4.6 nm were uniformly dispersed on the MIL-53(Al). The catalyst exhibited good catalytic activity in the selective oxidation of liquid methanol to methyl formate. Under the conditions of 150 °C, 2 MPa O_2 and solvent-free for5 h, the conversion of methanol could reach 60.3%, and the selectivity of methyl formate was up to 62.2%. In addition, the Pd/MIL-53(Al) bifunctional catalyst exhibited excellent stability and maintained high catalytic activity after five cycles.     

ZrOCl2?8H2O: 一种低廉高效的催化剂在酯化反应中的应用

The esterification of lauric acid with methanol could be efficiently catalyzed by ZrOCl2·8H2O, and this reaction was studied to develop a green method for biodiesel production. The influencing factors, such as amount of catalyst, reaction time and molar ratio of acid to methanol, were investigated. The results indicated that the ZrOCl2·8H2O catalyst showed high catalytic activity, and gave a 97.0% methyl laurate conversion rate under the following optimized conditions, viz.: a lauric acid/methanol molar ratio of 1:10, a catalyst dosage of 4%, and a reaction duration of 2 h at methanol refluxing temperature. The catalyst could be easily recovered while its activity could be well retained after three cycles. The ZrOCl2·8H2O catalyst also exhibited excellent catalytic activity for the esterification of different free long-chain fatty acids(including nonedible oils with high acid value) with different short carbon chain alcohols. Therefore, the ZrOCl2·8H2O catalyst has good potential for the synthesis of biodiesel from low-cost feedstocks such as waste vegetable oils and non-edible oils.     

Study on Removing Trace Olefins in Aromatic Hydrocarbons with HPMo-loaded Y Zeolites

HPMo-loaded Y-zeolites were prepared for the removal of trace olefins from aromatic hydrocarbons. The temperature of calcination and the proportion of phospho-molybdic acid in the catalyst were studied. The catalytic activity for olefins removal and the service life of the catalyst were tested in a fixed bed microreactor. The results showed that the catalyst containing 3% phospho-molybdic acid, which was calcined at 550℃, demonstrated the best activity for olefins removal. The catalyst could be regenerated and could perform still very well. Catalyst characterization was performed by XRD and measured by pyridine-FTIR spectrometry. The test results indicated that the activity of the catalyst was related with the effect of acid concentration and acid strength. Besides, the deactivation of the catalyst was associated with the formation of coke deposits and the deactivated catalyst could recover its activity by oxidation with air under a proper temperature.     

渣油催化临氢热转化钼铁双金属催化剂的研究

Replacement of precious single metal catalysts with cost-effective, highly-dispersed composite catalysts for catalytic hydrothermal conversion of residue holds tremendous promise for the residue upgrading technologies. Organic metals were added to the feed as the oil-soluble precursors, and transformed into the catalytic active phases in this work. Physical properties and structures of the composite catalysts had been investigated by X-ray fluorescence spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscope and transmission electron microscopy. The composite catalysts were found to be highly efficient in the catalytic hydrothermal conversion of both model compound and residue. Increased metal dispersion and synergistic effects of two metals played indispensable roles in such catalytic system. Results showed that under the test conditions in the article, the catalyst had the best catalytic performance when the mass ratio of molybdenum to iron was 1.5.     

Pd nanoparticles immobilized on MIL-53(Al) as highly effective bifunctional catalysts for oxidation of liquid methanol to methyl formate

A series of Pd/MIL-53(Al) heterogeneous bifunctional catalysts with different Pd contents were prepared by an impregnation method. The prepared metal–organic frameworks MIL-53(Al) and catalysts were characterized by XRD, SEM, HRTEM, FT-IR and N₂ adsorption/desorption techniques. The results showed that MIL-53(Al) was synthesized successfully, and the structure was unchanged during and after the preparation of the catalysts. The Pd nanoparticles (NPs) with an average particle size of 4.6 nm were uniformly dispersed on the MIL-53(Al). The catalyst exhibited good catalytic activity in the selective oxidation of liquid methanol to methyl formate. Under the conditions of 150 ℃, 2 MPa O₂ and solvent-free for 5 h, the conversion of methanol could reach 60.3%, and the selectivity of methyl formate was up to 62.2%. In addition, the Pd/MIL-53(Al) bifunctional catalyst exhibited excellent stability and maintained high catalytic activity after five cycles.     

Effect of CeO2 on Activity of Catalysts CuO/ZnO/Al2O3/CeO2 for Synthesis of Methanol

The size of the nanoparticles and the number of oxygen vacancies have a significant effect on the catalytic activity of copper-based catalysts used for the synthesis of methanol from syngas. In this study, the authors prepared a series of catalysts CuO/ZnO/Al₂O₃/CeO₂(CZAC) with CuO particles of different sizes and varying number of oxygen vacancies on the surface by changing the added volume of CeO₂ by using the co-precipitation method. The properties ...