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- 저자 : Zeeshan, Sara (검색결과 209 건)
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Zeeshan Nawaz,Fei Wei 한국공업화학회 2011 Journal of Industrial and Engineering Chemistry Vol.17 No.3
The addition of Al_2O_3 up to 20% (as cementing agent) in SAPO-34 support significantly integrates metal functions of Pt–Sn-based catalyst, ultimately improves catalytic performance for direct propane dehydrogenation to propylene. Superior propane conversion (initially above 40%) and propylene selectivity (around 95%) is obtained experimentally over Pt–Sn/Al_2O_3–SAPO-34. The results were found promising and compared with Pt–Sn/SAPO-34 under identical operating conditions. Better platinum dispersion and higher active platinum sites are characterized by TEM and hydrogen-chemisorption analysis. Moreover, the possible metal interactions with different supports were configured. Therefore,light alkane dehydrogenation to alkene was enhanced using surface modified support Al_2O_3–SAPO-34for Pt–Sn-based catalysts.
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Zeeshan Nawaz,Fei Wei 한국공업화학회 2010 Journal of Industrial and Engineering Chemistry Vol.16 No.5
Catalyst’s regeneration is unavoidable part during dehydrogenation. The hydrothermal treatment influence on the performance of Pt–Sn-based SAPO-34 supported novel catalyst, used for propane dehydrogenation to propylene is investigated in this study. The catalyst shows excellent stability for mild steaming (nitrogen mixed steam), during four consecutive runs (reaction–regeneration mode). On the other hand, Pt–Sn/ZSM-5 was largely affected on mild steaming due to severe dealumination. In order to get into mechanistic understanding, severe hydrothermal treatment was carried our using pure steam. The substation loss in catalyst activity was noted. Both fresh and severe hydrotreated catalysts were characterized by XRD, XRF, O2-pulse analysis of coke, NH3-TPD, IR spectrum of adsorbed ammonia,H2-TPR, HR-TEM and XPS, to explore reasons for change in catalytic properties. The texture/topology is found stable. Changes in surface ensembles occur due to the loss of Sn, Al, formation of SnOx species and in particular Pt sintering. This leads Pt active sites (zeolite–SnO–Pt) to inactive sites (zeolite–Pt, zeolite–PtO–Sn, Pt–Sn alloy, etc.) formation and reduced catalyst activity. TEM micrographs and H2-chemisorption analysis confirms Pt particles agglomeration and/or sintering. About 98% catalyst activity is recovered by re-dispersed Pt using chlorination technique and credit goes to hydrothermally stable support (SAPO-34). 2010 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
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Zeeshan Nawaz,Shu Qing,Gao Jixian,Xiaoping Tang,Fei Wei 한국공업화학회 2010 Journal of Industrial and Engineering Chemistry Vol.16 No.1
The performance of Pt–Sn-based catalyst, supported on ZSM-5 of different Si/Al ratios were investigated for simultaneous dehydrogenation and cracking of n-butane to produce light olefins. The catalysts were characterized by number of physio-chemical techniques including XRF, TEM, IR spectra, NH3-TPD and O2-pulse analysis. Increase in Si/Al ratio of zeolite support ZSM-5 significantly increased light olefin’s selectivity, while feed conversion decreases due to lower acidity of support. The results indicated that both the n-butane cracking and dehydrogenation activity to light olefin’s over Pt–Sn/ZSM-5 samples with increasing Si/Al ratios greatly enhanced catalytic performance. The catalysts were deactivated with time-on-stream due to the formation of carbon-containing deposits. A coke deposition was significantly related to catalyst activity, while at higher Si/Al ratio catalyst the coke precursors were depressed. These results suggested that the Pt–Sn/ZSM-5 catalyst of Si/Al ratio 300 is superior in achieving high total olefins selectivity (above 90 wt.%). The Pt–Sn/ZSM-5 also demonstrates resistance towards hydrothermal treatment, as analyzed through the three successive reaction-regeneration cycles.
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Zeeshan Nawaz,Faisal Baksh,Jie Zhu,Fei Wei 한국공업화학회 2013 Journal of Industrial and Engineering Chemistry Vol.19 No.2
The objective of this work is to discuss the performance of Pt-Sn/slit-SAPO-34 novel catalyst for selective C3–C4 dehydrogenation to corresponding light olefins. The metallic contents, acidity, active metallic sites and metallic dispersion were determined using a number of physico-chemical techniques as it gives a justification for superior catalytic activity for dehydrogenation reaction. The Pt-Sn/slit-SAPO-34 catalyst was analyzed for dehydrogenation activity under optimized operating conditions; at atmospheric pressure, hydrogen to alkane (feed) molar ratio is 0.2, weight hourly space velocity 5 h1 and temperature 585 8C. Around 40% light alkane conversion and above 95% of total olefins selectivity with 94% propene, 92% n-butene and about 84% iso-butene selectivity were achieved over Pt-Sn/slit-SAPO-34novel catalyst. The catalyst was parametrically characterized over the above said operating conditions and effects of operating conditions on product distribution were discussed. The coke formation was inherently related to catalyst activity in dehydrogenation reaction and related to surface intermetallic ensemble effects; and ultimately the prominent stakeholder in catalyst deactivation. The novel catalysts also showed very good hydrothermal stability in a continuous reaction–regeneration cycles due to silicabased acidic structure of support. The results obtained over Pt-Sn/slit-SAPO-34 novel catalyst were compared with other Pt-Sn-based ZSM-5 and SAPO-34 supported catalysts of similar active metallic content under identical operating conditions.
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Zeeshan, Rozina,Irfan, Syed Mohammed,Sultan, Sadia,Bhimani, Sanjana Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.4
Background: Chronic lymphoid leukemia (CLL) is the most frequent type of adult leukemia. The Rai and Binet staging systems have been well recognized as standards for assessing the treatment requirements and overall survival in CLL patients. However, there is a need to seek newer prognostic markers to identify stable or progressive forms of CLL that will facilitate risk-adapted treatment strategies. Currently a molecular biomarker ZAP-70 has attracted interest as providing prognostic information in CLL patients. Objective: To determine the frequency of ZAP-70 positivity in B-CLL patients at disease presentation. Materials and Methods: From January 2011 to September 2014, 89 patients were diagnosed to have chronic lymphoid leukemia. Complete blood count was done on an automated analyzer (Cell Dyne, Abott Architect, USA), while immunophenotyping was conducted for each patient to establish the diagnosis of the disease. ZAP-70 expression was evaluated by flow cytometry. Data were compiled and analyzed by SPSS version 21. Results: Out of the total of 89 B-CLL patients, 62 (69.7%) were male and 27 (30.3%) were females with a male to female ratio of 2:1. The mean age was $57.5{\pm}12.1years$. The frequency of ZAP-70 positivity in our B-CLL patients was found to be 13.5%. ZAP-70 positivity was significantly correlated with stage III disease and high absolute lymphocytic count (P<0.05). No correlation of ZAP-70 could be established with age and gender (p>0.05). Conclusions: The frequency of ZAP-70 in our patients appears low. It is approximately half that in international data. We would recommend to screen all the newly diagnosed patients with CLL for ZAP-70 protein expression for risk stratification, family counseling and to predict overall survival.
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Zeeshan Rashid,Cecilia Devi Wilfred,Regupathi Iyyaswami,Arunagiri Appusamy,Murugesan Thanabalan 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.79 No.-
Dispersion of asphaltene in crude oil using ionic liquids (ILs) is being considered as a viable solution, inextraction and transportation processes. In this work, the interplay between asphaltene and ILs has beenstudied systematically to understand the effect of structural variation of ILs on asphaltene solubility. Theactivity coefficient of the total of 1517 ILs with different combinations of cation and anion of ILs forrepresentative asphaltene molecule (asphaltene) was estimated via COSMO-RS (Conductor-likeScreening Model for Real Solvents). COSMO_RS predictions were validated using experimental dataon asphaltene solubility. Among the studied ILs, asphaltene showed high solubility in imidazolium-basedILs with hydrophobic anions. The present approach paved a way forward to rationally understand theimpact of structural variation of ILs on their interaction with asphaltene molecule and to design new ILsfor the dispersion and stabilization of asphaltene.
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Performance Analysis of Path Planning Algorithms for Fruit Harvesting Robot
Zeeshan Sadaf,Aized Tauseef 한국농업기계학회 2023 바이오시스템공학 Vol.48 No.2
Purpose Path planning is an essential part in designing of an agricultural robot. The path planning algorithms for fruit harvesting robots vary in performance, based on diff erent environments, obstacles, and constraints. This research aims to analyze and evaluate the most commonly used path planning algorithms by fruit harvesting robots in the past 10 years to assess the robot’s performance. The primary objective behind the comparative analysis of path planning algorithms is to ascertain which algorithm demonstrates better performance in terms of reaching the target fruit in the shortest time, requiring the least amount of computing resources, and being able to navigate around obstacles eff ectively. Hence, the study determines which path planning algorithm is the most effi cient for the application of fruit harvesting robot. Method In this study, four common path planning algorithms were evaluated namely A-star, Probabilistic Road Map, Rapidly exploring Random Tree, and improved Rapidly exploring Random Tree. Three cases were examined for performance. The fi rst case deals with performance based on varying orientations of fruit within the workspace. The second case investigates the performance in the presence of obstacles in the path, and the third case caters to performance due to varying distances of robot and the fruit. Matlab software was used for creating simulation environment for testing. Run time, path length, standard deviation, and total task time were obtained for each case and statistical analysis was done. Results It was found that improved Rapidly exploring Random Tree performed better in terms of path length and gave an optimal path as compared to the other algorithms due to its rewiring feature by an average of 21%. Run time of Rapidly exploring Random Tree was better than the other three algorithms. Conclusion Four most commonly used path planning algorithm were analyzed for performance for fruit harvesting robot for three diff erent cases. Despite the variations in performance across diff erent scenarios, the results confi rmed that the improved Rapidly exploring Random Tree algorithm outperformed all other algorithms under the given constraints.
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