Shengfu Ji

Effect of Ni Loading and CexZri-xO2 Promoter on Ni-Based SBA-15 Catalysts for Steam Reforming of Methane

Abstract A series of Ni/SBA-15 catalysts with Ni contents ranging from 5wt% to 20wt% as well as 10wt%Ni/10wt%Ce x Zr 1_x :O 2 /SBA-15 (x=0, 0.5, 1) were prepared. The structures of the catalysts were characterized using XR.D, TPR, TEM and BET techniques. The catalytic activities of the catalysts for steam reforming of methane were evaluated in a continuous flow microreactor. The results indicated that both the Ni/SBA-15 and the Ni/Ce x Zr 1_x ;O 2 /SBA-15 catalysts had good catalytic activities at atmospheric pressure. The 10wt%Ni/SBA-15 catalyst exhibited excellent stability at 800 °C for time on stream of 740 h. After the reaction, carbon deposits were not formed on the surface of the catalyst. There existed a regular hexagonal mesoporous structure in the Ni/SBA-15 and the Ni/Ce x Zr 1_x ;O 2 /SBA-15 catalysts. The nickel species and the Ce x Zr 1_x ;O2 component were all confined in the SBA-15 mesopores. The Ce x Zr 1_x ;O2 could promote dispersion of the nickel species in the Ni/Ce x Zr 1_x ;O 2 /SBA-15 catalysts.

Effect of MgO promoter on Ni-based SBA-15 catalysts for combined steam and carbon dioxide reforming of methane

Abstract A series of Ni/SBA-15 catalysts with Ni contents ranging from 5 wt% to 15 wt%, as well as another series of 10%Ni/MgO/SBA-15 catalysts, in which the range of the MgO content was from 1 wt% to 7 wt%, were prepared, and their catalytic performances for the reaction of combined steam and carbon dioxide reforming of methane were investigated in a continuous flow microreactor. The structures of the catalysts were characterized using the XRD, H2-TPR and CO2-TPD techniques. The results indicated that the CO selectivity for this reaction was very close to 100%, and the H2/CO ratio of the product gas could be controlled by changing the H2O/CO2 molar ratio of the feed gas. The simultaneous and plentiful existing of steam and CO2 had a significant influence on the catalytic performance of the 10%Ni/SBA-15 catalyst without modification. After reacting at 850 °C for 120 h over this catalyst, the CH4 conversion dropped from 98% to 85%, and the CO2 conversion decreased from 86% to 53%. However, the 10%Ni/3%MgO/SBA-15 catalyst exhibited a much better catalytic performance, and after reacting for 620 h, the CO2 conversion over this catalyst dropped from 92% to around 77%, while the CH4 conversion was not decreased. Oxidation of the Ni0 species as well as carbon deposition during the reaction were the main reasons for the deactivation of the catalyst without modification. On the other hand, modification by the MgO promoter improved the dispersion of the Ni0 species, and enhanced the CO2 adsorption affinity which in turn depressed the occurring of carbon deposition, and thus retarded the deactivation process.

Hydrogen generation from methanolysis of sodium borohydride over Co/Al2O3 catalyst

Co/Al2O3 catalyst is prepared with an impregnation-chemical reduction method and used to catalyze the methanolysis of sodium borohydride (NaBH4) for hydrogen generation. At solution temperature of 0 °C, the methanolysis reaction can be effectively accelerated using Co/Al2O3 catalyst and provide a desirable hydrogen generation rate, which makes it suitable for applications under the circumstance of low environmental temperature. The byproduct of methanolysis reaction is analyzed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The characterization results indicate that methanol can be easily recovered after methanolysis reaction by hydrolysis of the methanolysis byproduct, NaB(OCH3)4. The catalytic activity of Co/Al2O3 towards NaBH4 methanolysis can be further improved by appropriate calcination treatment. The catalytic methanolysis kinetics and catalyst reusability are also studied over the Co/Al2O3 catalyst calcined at the optimized temperature.

Effect of O2 and H2O on the tri-reforming of the simulated biogas to syngas over Ni-based SBA-15 catalysts

Abstract A series of Ni/SBA-15 catalysts with Ni contents from 7.5 wt% to 15 wt% were prepared by impregnation method. The effect of O2 and H2O on the combined reforming of the simulated biogas to syngas was investigated in a continuous flow fixed-bed micro-reactor. The stability of the catalyst was tested at 800 °C. The results indicated that 10wt%Ni/SBA-15 catalyst exhibited the highest catalytic activities for the combined reforming of the simulated biogas to syngas. Under the reaction conditions of the feed gas molar ratios CH4/CO2/O2/H2O = 2/1/0.6/0.6, GHSV = 24000 ml·gcat−1·h−1 and the reaction temperature T = 800 °C, the conversions of CH4 and CO2 were 92.8% and 76.3%, respectively, and the yields of CO and H2 were 99.0% and 82.0%, respectively. The catalytic activities of the catalyst did not decrease obviously after 100 h reaction time on stream.

Effect of Cu promoter on Ni-based SBA-15 catalysts for partial oxidation of methane to syngas

Abstract A series of Ni/SBA-15 catalysts with 5wt% to 15wt% Ni content as well as a series of 12.5%Ni/Cu/SBA-15 catalysts with 1% to 10% copper content were prepared by the impregnation method. The catalytic performance for partial oxidation of methane was investigated in a continuous flow microreactor under atmospheric pressure. The textural and chemical properties of the catalysts were characterized by XRD, TEM, BET and H 2 -TPR techniques. The results indicated that the catalysts modified with Cu promoter showed better performance than those without modification. For the 12.5%Ni/2.5%/Cu/SBA-15 catalyst, at 850 °C the conversion of CH 4 reached 97.9% and the selectivity of CO and H 2 reached 98.0% and 96.0%, respectively. In XRD patterns of the Ni/Cu/SBA-15 catalyst with 7.5 to 10% Cu contents there were CuO characteristic peaks beside NiO characteristic peaks. The mesoporous structure of SBA-15 was retained in all of the catalysts. TPR analysis of the catalysts revealed that a strong interaction between Ni, Cu promoter and SBA-15 support may be existed. This interaction enhanced significantly the redox properties of the catalysts resulting in the higher catalytic activity.

Ultrasonic-assisted ultra-rapid synthesis of monodisperse meso-SiO2@Fe3O4 microspheres with enhanced mesoporous structure.

A core-shell-type of meso-SiO2@Fe3O4 microsphere was synthesized via an ultrasonic-assisted surfactant-templating process using solvothermal synthesized Fe3O4 as core, tetraethoxysilane (TEOS) as silica source, and cetyltrimethyl ammonium bromide (CTAB) as templates. The samples were characterized by FT-IR, XRD, TEM, N2 adsorption-desorption technology, and vibrating sample magnetometer (VSM). The results show that as-prepared meso-SiO2@Fe3O4(E) and meso-SiO2@Fe3O4(C) microspheres, treated by acetone extraction and high temperature calcination, respectively, still maintain uniform core-shell structure with desirable mesoporous silica shell. Therein, the meso-SiO2@Fe3O4(E) microspheres possess a distinct pore size distribution in 1.8-3.0 nm with large specific surface area (468.6 m(2)/g) and pore volume (0.35 cm(3)/g). Noteworthily, the coating period of this ultrasonic-assisted method (40 min) is much shorter than that of the conventional method (12-24 h). The morphology of microspheres and the mesoporous structure of silica shell are significantly influenced by initial concentration of CTAB (CCTAB), ultrasonic irradiation power (P) and ultrasonic irradiation time (t). The acceleration roles of ultrasonic irradiation take effect during the whole coating process of mesoporous silica shell, including hydrolysis-condensation process of TEOS, co-assembly of hydrolyzed precursors and CTAB, and deposition of silica oligomers. In addition, the use of ultrasonic irradiation is favorable for improving the homogeneity of silica shell and the monodispersity of meso-SiO2@Fe3O4 microspheres.

Preparation of Ni‐Based Metal Monolithic Catalysts and a Study of Their Performance in Methane Reforming with CO2

A series of Ni/SBA-15/Al(2)O(3)/FeCrAl metal monolithic catalysts with Ni loadings varying between 3 % and 16 % were prepared, and their structure was characterized by various techniques. The catalytic activity of the catalyst for methane reforming with CO(2) leading to synthesis gas was evaluated using a fixed-bed reactor. The results indicate good catalytic activity of the Ni/SBA-15/Al(2)O(3)/FeCrAl samples under the reaction conditions. The catalyst with a Ni loading of 8.0 % displays excellent activity and stability at 800 degrees C over 1400 h time on stream. After reaction, the hexagonal mesoporous structure of SBA-15 is still present and the pore walls of SBA-15 prevent the aggregation of nickel. Interactions between NiO, SBA-15, and the Al(2)O(3)/FeCrAl support modify the redox properties of the Ni/SBA-15/Al(2)O(3)/FeCrAl catalysts.

Magnetically recyclable Pd/γ-AlOOH@Fe 3 O 4 catalysts and their catalytic performance for the Heck coupling reaction

Novel magnetically recyclable Pd/γ-AlOOH@Fe3O4 catalysts were prepared using γ-AlOOH@Fe3O4 as a magnetic supporter and nano-Pd particles as the active catalytic component. The structure of the catalysts was characterized by XRD (X-ray diffraction), TEM (transmission electron microscopy), N2 adsorption-desorption, and a VSM (vibration sample magnetometer). The catalytic activity and recyclability for the Heck coupling reaction were investigated. Results showed that the magnetic γ-AlOOH@Fe3O4 possessed a core-shell structure, as well as that the nano-Pd particles were 6–8 nm and had been well dispersed in the γ-AlOOH shell. In the Heck coupling reactions, the magnetic Pd/γ-AlOOH@Fe3O4 catalysts exhibited good catalytic activity and recyclability. For the (0.021 mol%)Pd/γ-AlOOH@Fe3O4 catalyst, the bromobenzene conversion and product yield reached about 100% and 96.3%, respectively, under a 120°C reaction temperature and 12 h reaction time. After being recycled 8 times, the conversion of bromobenzene and the recovery of the catalyst were about 90% and 93%, respectively. The nano-Pd particles were kept well dispersed in the used Pd/γ-AlOOH@Fe3O4 catalyst.

Catalytic steam reforming of biomass over Ni-based catalysts: Conversion from poplar leaves to hydrogen-rich syngas

Abstract A series of Ni/SBA-15 catalysts with Ni contents from 5 wt%-20 wt% and CaO-12.5%Ni/SBA-15 catalysts with CaO contents from 1.4 wt%-9.8 wt% have been prepared. The structure of the catalysts was characterized using X-ray diffraction (XRD), N 2 adsorption-desorption, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The performance of catalytic steam reforming of the poplar leaves to the hydrogen-rich syngas was tested in a fixed-bed reactor. The results indicate that the 7.0wt%CaO-12.5wt%Ni/SBA-15 catalyst exhibits the best performance for the catalytic steam reforming of poplar leaves to hydrogen-rich syngas. The ratio of H 2 :CO can reach ca 5:1 in the hydrogen-rich syngas. The yield of H 2 can reach 273.30 mL/g (poplar leaves). In the CaO-Ni/SBA-15 catalyst, Ni active component mainly fills the role of catalytic steam reforming of the poplar leaves, and CaO active component mainly plays the role as water-gas shift and CO 2 sorbent.

Oxidative coupling of methane in a dual-bed reactor comprising of particle/cordierite monolithic catalysts

Abstract A dual-bed reactor was constructed comprising of a 5%Na 2 WO 4 -2%Mn/SiO 2 particle catalyst and a 4%Ce-5%Na 2 WO 4 -2%Mn/SiO 2 /cordierite monolithic catalyst. The reaction performance of the oxidative coupling of methane (OCM) over the dual-bed reactor system was evaluated. The effects of the bed height and operation mode, as well as the reaction parameters such as reaction temperature, CH 4 /O 2 ratio and flowrate of feed gas, on the catalytic performance were investigated. The results indicated that the suggested dual-bed reactor exhibited a good performance for the OCM reaction when the feed gases firstly passed through the particle catalyst bed and then to the monolithic catalyst bed. A CH 4 conversion of 38.2% and a C 2 H 4 selectivity of 43.3% could be obtained using the dual-bed reactor with a particle catalyst bed height of 10 mm and a monolithic catalyst bed height of 50 mm. Both the CH 4 conversion and C 2 H 4 selectivity have increased by 2.5% and 12.8%, respectively, as compared with the 5%Na 2 WO 4 -2%Mn/SiO 2 particle catalyst in a conventional single-bed reactor and by 12.9% and 23.0%, respectively, as compared with the 4%Ce-5%Na 2 WO 4 -2%Mn/SiO 2 /cordierite monolithic catalyst in a single-bed reactor. The catalytic performance of the OCM in the dual-bed reactor system has been improved remarkably.