Analysis of Travel Hot Spots of Taxi Passengers Based on Community Detection

It is an important content of smart city research to study the activity track of urban residents, dig out the hot spot areas and spatial interaction patterns of different residents’ activities, and clearly understand the travel rules of urban residents' activities. This study used community detection to analyze taxi passengers’ travel hot spots based on taxi pick-up and drop-off data, combined with multisource information such as land use, in the main urban area of Nanjing. The study revealed that, for the purpose of travel, the modularity and anisotropy rate of the community where the passengers were picked up and dropped off were positively correlated during the morning and evening peak hours and negatively correlated at other times. Depending on the community structure, pick-up and drop-off points reached significant aggregation within the community, and interactions among the communities were also revealed. Based on the type of land use, as passengers' travel activity increased, travel hot spots formed clusters in urban spaces. After comparative verification, the results of this study were found to be accurate and reliable and can provide a reference for urban planning and traffic management

Synthesis of micron-particle-size HZSM-5 zeolite with different Si/Al ratio and its catalytic activity for toluene methanol alkylation reaction

HZSM-5 molecular sieve is one of the commonly used catalysts for the alkylation of toluene with methanol to para-xylene (PX). This study introduces a one-step method to directly prepare microscale HZSM-5 catalysts with suitable pore structure and acidity. Specifically, this paper combined crystal seed regulation of the morphology of HZSM-5 and adjusted the Si/Al ratios of the precursor solution for HZSM-5 synthesis to regulate the acidic phase of the HZSM-5. It analyzed the phase composition, pore structure parameters, microstructure, and acidity of HZSM-5 molecular sieve through X-ray diffraction, N2 adsorption desorption, SEM, NH3 temperature programmed desorption, pyridine infrared spectroscopy, etc. This study investigated the catalytic performance of HZSM-5 in the alkylation of toluene with methanol to PX, and explored the effects of pore structure and acidity on the catalytic performance. Results indicate that in the hydrothermal crystallization method, the crystal seeds and aluminum content in the synthesis solution have a significant impact on the acidity and morphology structure of the HZSM-5 molecular sieve. The HZSM-5 (150)molecular sieve catalyst with 5μm grain size exhibits 60% PX selectivity and 11% toluene conversion rate in the evaluation reaction of toluene methanol alkylation due to its longer diffusion path and more suitable acidic sites. By fine-tuning the pores and acidic sites of HZSM-5 molecular sieve, the selectivity for PX has been effectively improved, providing new methods and approaches for the design of shape-selective catalysts

Effects of Silicalite-1 Coating on the p-Xylene Selectivity and Catalytic Stability of HZSM-5 in Toluene Methylation with Methanol

The methanol–toluene alkylation process over zeolites catalysts offers a promising route for the production of p-xylene from low-cost feedstocks. Herein, we present a catalyst by preparing a core-shell aluminosilicate zeolite with an epitaxial silicalite-1 shell that passivates acid sites on the exterior surfaces. The para-selectivity was obviously increased due to the inhibition of the unselective isomerization of p-xylene over the external acid sites, and the open porous structure of the silicalite-1 shell ensured the mass transfer of reactants and products. Meanwhile, the carbon deposition was suppressed over HZSM-5@silicalite-1 catalysts, as a result of the decreased external acid sites. Furthermore, pulse chromatographic experiments revealed that the silicalite-1 coating could also improve the separation efficiency of p-xylene over o-xylene and m-xylene, due to the steric hindrance and extended diffusion path, resulting in a higher selectivity for p-xylene compared to that of the parent HZSM-5. The HZSM-5@4%S-1 catalyst showed the highest p-xylene selectivity (>80%) and methanol efficiency (66%), with good catalytic stability throughout the 170 h reaction time

Effects of Silicalite-1 Coating on the <i>p</i>-Xylene Selectivity and Catalytic Stability of HZSM-5 in Toluene Methylation with Methanol

The methanol–toluene alkylation process over zeolites catalysts offers a promising route for the production of p-xylene from low-cost feedstocks. Herein, we present a catalyst by preparing a core-shell aluminosilicate zeolite with an epitaxial silicalite-1 shell that passivates acid sites on the exterior surfaces. The para-selectivity was obviously increased due to the inhibition of the unselective isomerization of p-xylene over the external acid sites, and the open porous structure of the silicalite-1 shell ensured the mass transfer of reactants and products. Meanwhile, the carbon deposition was suppressed over HZSM-5@silicalite-1 catalysts, as a result of the decreased external acid sites. Furthermore, pulse chromatographic experiments revealed that the silicalite-1 coating could also improve the separation efficiency of p-xylene over o-xylene and m-xylene, due to the steric hindrance and extended diffusion path, resulting in a higher selectivity for p-xylene compared to that of the parent HZSM-5. The HZSM-5@4%S-1 catalyst showed the highest p-xylene selectivity (>80%) and methanol efficiency (66%), with good catalytic stability throughout the 170 h reaction time