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

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

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

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

Waveguide invariant estimation based on correlation coefficient of tonal acoustic intensity interference fluctuation

The waveguide invariant is usually not extracted from the striation pattern of broadband continuous spectrum in the low frequency analysis and recording spectrum at low signal-to-noise ratio. In this paper, the correlation coefficient of multi-tonal acoustic intensity interference fluctuation is utilized to estimate waveguide invariant. Since the proportional relationship between the reference intensity interference fluctuation and the scaled intensity interference fluctuation is dependent on waveguide invariant, the waveguide invariant estimation can be done. Firstly, the tonal intensity interference fluctuation has been resampled in the new time domain under the radial and non-radial motion models respectively. Then, the similarity degree between the resampling reference tonal intensity interference fluctuation and the scaling tonal intensity interference fluctuation can be described by correlation coefficient, and the peak of correlation coefficient is corresponding to the true value. Finally, the numerical results and the experimental results prove the proposed method's effectiveness

A Feature-Level Fusion-Based Target Localization Method with the Hough Transform for Spatial Feature Extraction

Traditional two-step localization methods and direct localization methods have practical problems when they are used for underwater acoustic source localization. In this paper, a localization method based on the feature-level information fusion is proposed, in which the Hough Transform is exploited to detect the line characteristics of the spatial features of the target. A secondary accumulation procedure is proposed to extract and fuse the good features instead of fusing all features. The possibility to produce a ghost target is greatly reduced. Hence, the robustness of the proposed method in low SNR scenarios is improved. Experimental results validate the efficiency of exploiting the Hough Transform to eliminate interfering spatial features without sacrificing the localization accuracy