Zhichao Tao

Study of Manganese Promoter on a Precipitated Iron-Based Catalyst for Fischer-Tropsch Synthesis

Abstract The effects of Manganese (Mn) incorporation on a precipitated iron-based Fischer-Tropsch synthesis (FTS) catalyst were investigated using N2 physical adsorption, air differential thermal analysis (DTA), H2 temperature-programmed reduction (TPR), and Mossbauer spectroscopy. The FTS performances of the catalysts were tested in a slurry phase reactor. The characterization results indicated that Mn increased the surface area of the catalyst, and improved the dispersion of α-Fe2O3 and reduced its crystallite size as a result of the high dispersion effect of Mn and the Fe-Mn interaction. The Fe-Mn interaction also suppressed the reduction of α-Fe2O3 to Fe3O4, stabilized the FeO phase, and (or) decreased the carburization degree of the catalysts in the H2 and syngas reduction processes. In addition, incorporated Mn decreased the initial catalyst activity, but improved the catalyst stability because Mn restrained the reoxidation of iron carbides to Fe3O4, and improved further carburization of the catalysts. Manganese suppressed the formation of CH4 and increased the selectivity to light olefins (C=2–4), but it had little effect on the selectivities to heavy (C5+) hydrocarbons. All these results indicated that the strong Fe-Mn interaction suppressed the chemisorptive effect of the Mn as an electronic promoter, to some extent, in the precipitated iron-manganese catalyst system.

Effect of A12O3 Binder on the Precipitated Iron-Based Catalysts for Fischer-Tropsch Synthesis

Abstract A series of iron-based Fischer-Tropsch synthesis (FTS) catalysts incorporated with Al 2 O 3 binder were prepared by the combination of co-precipitation and spray drying technology. The catalyst samples were characterized by using N 2 physical adsorption, temperature-programmed reduc-tion/desorption (TPR/TPD) and Mossbauer effect spectroscopy (MES) methods. The characterization results indicated that the BET surface area increases with increasing Al 2 O 3 content and passes through a maximum at the Al 2 O 3 /Fe ratio of 10/100 (weight basis). After the point, it decreases with further increase in Al 2 O 3 content. The incorporation of Al 2 O 3 binder was found to weaken the surface basicity and suppress the reduction and carburization of iron-based catalysts probably due to the strong K-Al 2 O 3 and interactions. Furthermore, the H2 adsorption ability of the catalysts is enhanced with increasing content. The FTS performances of the catalysts were tested in a slurry-phase continuously stirred tank reactor (CSTR) under the reaction conditions of 260 °C, 1.5 MPa, 1000 h −1 and molar ratio of H2/CO 0.67 for 200 h. The results showed that the addition of small amounts of Al 2 O 3 affects the activity of iron-based catalysts to a little extent. However, with further increase of Al 2 O 3 content, the FTS activity and water gas shift reaction (WGS) activity are decreased severely. The addition of appropriate Al 2 O 3 do not affect the product selectivity, but the catalysts incorporated with large amounts of Al 2 O 3 have higher selectivity for light hydrocarbons and lower selectivity for heavy hydrocarbons.

Effect of Sulfate on an Iron Manganese Catalyst for Fischer-Tropsch Synthesis

Abstract The effect of sulfate on Fischer-Tropsch synthesis performance was investigated in a slurry- phase continuously stirred tank reactor (CSTR) over a Fe-Mn catalyst. The physiochemical properties of the catalyst impregnated with different levels of sulfate were characterized by N 2 physisorption, X-ray photoelectron spectroscopy (XPS), H 2 (or CO) temperature-programmed reduction (TPR), Mossbauer spectroscopy, and CO 2 temperature-programmed desorption (TPD). The characterization results indicated that the impregnated sulfate slightly decreased the BET surface area and pore volume of the catalyst, suppressed the catalyst reduction and carburization in CO and syngas, and decreased the catalyst surface basicity. At the same time, the addition of small amounts of sulfate improved the activities of Fischer- Tropsch synthesis (FTS) and water gas shift (WGS), shifted the product to light hydrocarbons (C 1 –C 11 ) and suppressed the formation of heavy products (C 12+ ). Addition of SO 2 − 4 to the catalyst improved the FTS activity at a sulfur loading of 0.05–0.80 g per 100 g Fe, and S-05 catalyst gave the highest CO conversion (62.3%), and beyond this sulfur level the activity of the catalyst decreased.

Effects of SiO2 and Al2O3 on performances of iron-basedcatalysts for slurry Fischer–Tropsch synthesis

Abstract Two spherical iron-based catalysts (Fe/Cu/K/SiO2 and Fe/Cu/K/Al2O3) were prepared by the combination of coprecipitation and spray drying method for the application of slurry Fischer–Tropsch synthesis (FTS). The effects of SiO2 and Al2O3 on the reduction and the carburization behaviors of iron-based catalysts were studied using temperature-programmed desorption (TPD) in H2 and CO, isothermal reduction in syngas, and Mossbauer-effect spectroscopy (MES). The results indicate that SiO2 suppresses the H2 adsorption, facilitates the CO adsorption, and the carburization as compared with Al2O3. The FTS performances of the catalysts were evaluated in a slurry reactor under the industrial relevant reaction conditions of 260°C, 1.5 MPa, H2/CO = 0.67, and a space velocity of 2000 h−1. This indicates that SiO2-supported catalyst has higher FTS activity, higher water-gas shift reaction (WGS) reactivity, and higher selectivities to heavy hydrocarbons. Furthermore, the run stability of Al2O3 supported, iron-based catalyst is better than SiO2 supported catalyst.

Effect of Manganese Incorporation Manner on an Iron-Based Catalyst for Fischer-Tropsch Synthesis

Abstract A systematic study was undertaken to investigate the effects of the manganese incorporation manner on the textural properties, bulk and surface phase compositions, reduction/carburization behaviors, and surface basicity of an iron-based Fischer-Tropsch synthesis (FTS) catalyst. The catalyst samples were characterized by N2 physisorption, X-ray photoelectron spectroscopy (XPS), H2 (or CO) temperature-programmed reduction (TPR), CO2 temperature-programmed desorption (TPD), and Mossbauer spectroscopy. The FTS performance of the catalysts was studied in a slurry-phase continuously stirred tank reactor (CSTR). The characterization results indicated that the manganese promoter incorporated by using the coprecipitation method could improve the dispersion of iron oxide, and decrease the size of the iron oxide crystallite. The manganese incorporated with the impregnation method is enriched on the catalysts surface. The manganese promoter added with the impregnation method suppresses the reduction and carburization of the catalyst in H2, CO, and syngas because of the excessive enrichment of manganese on the catalyst surface. The catalyst added manganese using the coprecipitation method has the highest CO conversion (51.9%) and the lowest selectivity for heavy hydrocarbons (C12+).

Structural Properties, Reduction and Carburization Behaviors of Fe/Cu/K/Al2O3 Catalyst for Fischer-Tropsch Synthesis

Abstract An Fe/Cu/K/Al 2 O 3 catalyst for Fischer-Tropsch synthesis (FTS) was prepared by using a combination of co-precipitation and spray-drying method. Thermal gravity (TG), N 2 physisorption, X-ray diffraction (XRD), H 2 temperature programmed reduction (H 2 -TPR), CO temperature programmed reduction (CO-TPR), and Mossbauer effect spectroscopy (MES), were used to investigate the effects of different calcination temperatures on the structural properties, reduction, and carburization behaviors of the iron-based catalyst. The results indicated that an increase in calcination temperature facilitated the carbonate decomposition and H 2 O removal and promoted the reduction of the catalyst. With further increasing the calcination temperature, the BET surface area of the catalyst decreased, and the size of the catalyst crystallite and the average pore diameter increased. Furthermore, high calcination temperature enhanced the metal-support interaction, which weakened the promotional effect of CuO and K 2 O, and therefore, severely suppressed the reduction and carburization behaviors of the catalyst.采用连续共沉淀与喷雾干燥成型技术相结合的方法制备了微球状Fe/Cu/K/Al2O3催化剂,结合TG、N2物理吸附、XRD、H2-TPR、CO-TPR、Mssbauer谱等表征手段,研究焙烧温度对Fischer-Tropshc（F-T）合成铁基催化剂的结构性质、还原行为和碳化行为的影响.结果表明,较高的焙烧温度有利于碳酸盐的分解和结晶水的脱除,促进了催化剂的还原.随着焙烧温度的进一步升高,催化剂的比表面积减小,平均孔径增大,α-Fe2O3晶粒的粒径增大,催化剂中金属与载体的相互作用增强,从而削弱了CuO、K2O助剂的作用,严重抑制了催化剂的还原和碳化.

Synthesis of nano-sized LTL zeolite by addition of a Ba precursor with superior n-octane aromatization performance

A nano-sized LTL-type zeolite was successfully synthesized using a facile and commercially viable hydrothermal method by the addition of a small amount of Ba precursor to the conventional synthesis mixture regardless of the types of Ba precursors used. The results showed that the Ba added can be used to finely tune LTL particle sizes in the range of 0.1–1 μm and shorten the synthesis time, indicating that Ba had a significant effect on the crystallization process of LTL-type zeolite. By comprehensively tracing the evolution of two systems, namely KL and BaKL, it was found that the crystallization of KL zeolite took place by a chain of processes including the appearance of worm-like particles (WLPs), their random aggregation/coalescence and crystallization of these aggregates. On the other hand, the Ba added can accelerate the coordination between monosilicate and alumina species. Therefore, LTL zeolites with small crystal sizes were quickly produced by rapid crystallization of the amorphous phase to the final products. The Pt/LTL catalysts were obtained by impregnating the obtained zeolites with Pt and then evaluated in n-octane aromatization reactions. Compared with conventional LTL zeolite, the nano-sized LTL zeolite-supported Pt catalyst exhibited superior catalytic performance with an about 3-fold prolonged catalytic lifetime and higher selectivity for aromatics due to the shorter diffusion path of the primary aromatic products in nano-sized zeolites, which inhibited the secondary undesirable reactions (coke formation and hydrogenolysis).

Effect of impregnation methods on nickel-tungsten catalysts and its performance on hydrocracking Fischer-Tropsch wax

Abstract Three hydrocracking catalysts were prepared by impregnation method with different incorporation manners of Ni/W metals on HY/Al 2 O 3 support. The effect of combination methods on acidity, hydrogenation capability of the catalysts and its hydrocracking performance on FT wax was studied. The balance between hydrogenation performance and cracking performance could be modulated by adjusting the metal-support combination methods. Ni/W pre-impregnated on HY can increase the hydrogenation capability of the catalyst and simultaneously lower the acidity of the support. The results show that the coordination of high hydrogenation capability and low acidity of catalyst can inhibit the formation of secondary cracking on some extent, and increase the selectivity of diesel. While Ni/W metals supported on HY/Al 2 O 3 can achieve a relative balance of hydrogenation and cracking, thus the catalysts have a higher activity and the more flexible ability to modulate reaction.