19 research outputs found

    Tailoring acidity of HZSM-5 nanoparticles for methyl bromide dehydrobromination by Al and Mg incorporation

    Get PDF
    Three kinds of HZSM-5 nanoparticles with different acidity were tailored by impregnating MgO or varying Si/Al ratios. Both the textural and acidic properties of the as-prepared nanoparticles were characterized by nitrogen adsorption-desorption measurements, X-ray diffraction (XRD), scanning electron microscopy (SEM), ammonia temperature-programmed desorption (NH(3)-TPD) and Fourier transform infrared spectroscopy (FTIR or Py-FTIR). It was found that the intensity of Lewis acid sites with weak strength was enhanced by impregnating MgO or reducing Al concentration, and such an enhancement could be explained by the formation of Mg(OH)(+) or charge unbalance of the MgO framework on the surface of HZSM-5 support. The effect of HZSM-5 nanoparticles' acidity on methyl bromide dehydrobromination as catalyst was evaluated. As the results, MgHZ-360 catalyst with the highest concentration of Lewis acid sites showed excellent stability, which maintained methyl bromide conversion of up 97% in a period of 400 h on stream. Coke characterization by BET measurements and TGA/DTA and GC/MS analysis revealed that polymethylated naphthalenes species were formed outside the channels of the catalyst with higher acid intensity and higher Brønsted acid concentration during the initial period of reaction, while graphitic carbon formed in the channels of catalyst with lower acid intensity and higher Lewis acid concentration during the stable stage

    A Comparison of Laboratory Simulation Methods of Iron Contamination for FCC Catalysts

    No full text
    Two different methods of simulating iron contamination in a laboratory were studied. The catalysts were characterized using X-ray diffraction, N2 adsorption–desorption, and SEM-EDS. The catalyst performance was evaluated using an advanced cracking evaluation device. It was found that iron was evenly distributed in the catalyst prepared using the Mitchell impregnation method and no obvious iron nodules were found on the surface of the catalyst. Iron on the impregnated catalyst led to a strong dehydrogenation capacity and a slight decrease in the conversion and bottoms selectivity. The studies also showed that iron was mainly in the range of 1–5 μm from the edge of the catalyst prepared using the cycle deactivation method. Iron nodules could be easily observed on the surface of the catalyst. The retention of the surface structure in the alumina-rich areas and the collapse of the surface structure in the silica-rich areas resulted in a continuous nodule morphology, which was similar to the highly iron-contaminated equilibrium catalyst. Iron nodules on the cyclic-deactivated catalyst led to a significant decrease in conversion, an extremely high bottoms yield, and a small increase in the dehydrogenation capacity. The nodules and distribution of iron on the equilibrium catalyst could be better simulated by using the cyclic deactivation method

    A Comparison of Laboratory Simulation Methods of Iron Contamination for FCC Catalysts

    No full text
    Two different methods of simulating iron contamination in a laboratory were studied. The catalysts were characterized using X-ray diffraction, N2 adsorption–desorption, and SEM-EDS. The catalyst performance was evaluated using an advanced cracking evaluation device. It was found that iron was evenly distributed in the catalyst prepared using the Mitchell impregnation method and no obvious iron nodules were found on the surface of the catalyst. Iron on the impregnated catalyst led to a strong dehydrogenation capacity and a slight decrease in the conversion and bottoms selectivity. The studies also showed that iron was mainly in the range of 1–5 μm from the edge of the catalyst prepared using the cycle deactivation method. Iron nodules could be easily observed on the surface of the catalyst. The retention of the surface structure in the alumina-rich areas and the collapse of the surface structure in the silica-rich areas resulted in a continuous nodule morphology, which was similar to the highly iron-contaminated equilibrium catalyst. Iron nodules on the cyclic-deactivated catalyst led to a significant decrease in conversion, an extremely high bottoms yield, and a small increase in the dehydrogenation capacity. The nodules and distribution of iron on the equilibrium catalyst could be better simulated by using the cyclic deactivation method

    Effect of Transition Metal Nickel on the Selectivity of Light Olefins in n-Hexane Cracking of Ni/IM-5 Zeolite

    No full text
    The production of light olefins by catalytic cracking is aresearch hotspot in the petrochemical industry. Herein, nickel was usedto modify IM-5 zeolite to improve the performance in catalyticcracking. Properties of the Ni/IM-5 zeolites with different nickelloadings were characterized. It was demonstrated that nickel specieswere mainly located on the external surface of impregnated IM-5zeolite, only a few Ni2+ions were distributed in the ion exchange site ascompensation cations. Pyridine infrared results indicated that theintroduction of nickel could modulate the acidity of IM-5 zeolite andincrease the amount of Lewis acid sites. Compared with IM-5, Ni/IM-5exhibited higher olefin selectivity, especially ethylene, inn-hexanecracking reactions. It was considered that nickel could providedehydrogenation active sites and promote the formation of lightolefins. Thus, the selectivity of light olefins can be improved by controlling the amount and distribution of nickel in IM-5 zeolite

    Effect of Transition Metal Nickel on the Selectivity of Light Olefins in n-Hexane Cracking of Ni/IM-5 Zeolite

    No full text
    The production of light olefins by catalytic cracking is aresearch hotspot in the petrochemical industry. Herein, nickel was usedto modify IM-5 zeolite to improve the performance in catalyticcracking. Properties of the Ni/IM-5 zeolites with different nickelloadings were characterized. It was demonstrated that nickel specieswere mainly located on the external surface of impregnated IM-5zeolite, only a few Ni2+ions were distributed in the ion exchange site ascompensation cations. Pyridine infrared results indicated that theintroduction of nickel could modulate the acidity of IM-5 zeolite andincrease the amount of Lewis acid sites. Compared with IM-5, Ni/IM-5exhibited higher olefin selectivity, especially ethylene, inn-hexanecracking reactions. It was considered that nickel could providedehydrogenation active sites and promote the formation of lightolefins. Thus, the selectivity of light olefins can be improved by controlling the amount and distribution of nickel in IM-5 zeolite

    Catalytic function of boron to creating interconnected mesoporosity in microporous Y zeolites and its high performance in hydrocarbon cracking

    No full text
    Connectivity of mesopores in zeolites, which is a key factor for the high efficiency catalyst design, is still a challenge to be generated without using organic template. Herein, a hierarchical porous Y zeolite (USYB) was synthesized by introducing catalytic amounts of boron into the framework of NaY, followed by steaming. The introduction of framework boron promoted the hydrolysis of the surrounding Si-O-Al and Si-O-B bonds in steaming treatment. When the boron was dislocated from framework, it could further create more mesopores by steaming. It was deemed that boron played catalytic like role for leading to generate well interconnected mesoporosity. As a result, the mesopore volume of the zeolite increased by 46% relatively. The influence of the generated interconnected mesoporosity on the higher activity was evidenced in both iso-octane (i.e. 2,2,4-trimethylpentane) and 1,3,5-triisopropylbenzene (TIPB) cracking over USYB zeolite. Compared with conventional USY zeolite, there would be 2.1% increase in the yield of gasoline for the cracking of heavy oil over USYB catalyst. (C) 2017 Elsevier Inc. All rights reserved
    corecore