Characterization of Pt-Sn/Al2O3 Catalyst and Coke Formation During Propane Dehydrogenation PDF Download
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Author: Kah Sing Ho Publisher: ISBN: Category : Catalysts Languages : en Pages : 76
Book Description
The problems faced in propane dehydrogenation, PDH process are lack of information on the commercially obtained Pt-Sn/Al2O3 catalyst and formation of coke. Therefore, this research deals with characterization of regenerated Pt-Sn/Al2O3 catalyst obtained from PDH plant and coke formation during propane dehydrogenation process at different temperature. Analyses of these characteristics were performed using nitrogen adsorption method, X-Ray Diffraction, Field Emission Scanning Electron Microscopy, X-Ray Photoelectron Spectroscopy and Fourier Transform Infrared Spectroscopy. Effect of temperatures on coke formation is identified by studying the fraction of products formed over the catalyst using Temperature Programmed Reaction. XPS was able to pick up traces of carbon in regenerated catalyst with percentage of atomic composition of 7.750%. FTIR had suggested that most of the carbon exist in the form of alkane and alkene where ethylene and methane records the highest fraction of side products formed by TPR. The regenerated Pt-Sn/Al2O3 catalyst has a surface area of 103.554 m2/g and mean pore radius of 12.695 nm with highest crystallite sizes of 20.0 nm. As for the effect of temperature towards coke formation, more carbon precursors were produced at higher temperature suggesting that more coke will be formed on the catalyst resulting in less propylene formed at higher temperatures. Spent catalyst yields a lower surface area of 78.943 m2/g and means pore radius of 10.151 nm compared to regenerated catalyst. Besides, the coke formed on the catalyst forms a crystal which was detected by XRD with its size of 25.7 nm. The increment of carbon content in the spent catalyst was traced by XPS where the percentage of atomic concentration increased to 31.75%.
Author: Kah Sing Ho Publisher: ISBN: Category : Catalysts Languages : en Pages : 76
Book Description
The problems faced in propane dehydrogenation, PDH process are lack of information on the commercially obtained Pt-Sn/Al2O3 catalyst and formation of coke. Therefore, this research deals with characterization of regenerated Pt-Sn/Al2O3 catalyst obtained from PDH plant and coke formation during propane dehydrogenation process at different temperature. Analyses of these characteristics were performed using nitrogen adsorption method, X-Ray Diffraction, Field Emission Scanning Electron Microscopy, X-Ray Photoelectron Spectroscopy and Fourier Transform Infrared Spectroscopy. Effect of temperatures on coke formation is identified by studying the fraction of products formed over the catalyst using Temperature Programmed Reaction. XPS was able to pick up traces of carbon in regenerated catalyst with percentage of atomic composition of 7.750%. FTIR had suggested that most of the carbon exist in the form of alkane and alkene where ethylene and methane records the highest fraction of side products formed by TPR. The regenerated Pt-Sn/Al2O3 catalyst has a surface area of 103.554 m2/g and mean pore radius of 12.695 nm with highest crystallite sizes of 20.0 nm. As for the effect of temperature towards coke formation, more carbon precursors were produced at higher temperature suggesting that more coke will be formed on the catalyst resulting in less propylene formed at higher temperatures. Spent catalyst yields a lower surface area of 78.943 m2/g and means pore radius of 10.151 nm compared to regenerated catalyst. Besides, the coke formed on the catalyst forms a crystal which was detected by XRD with its size of 25.7 nm. The increment of carbon content in the spent catalyst was traced by XPS where the percentage of atomic concentration increased to 31.75%.
Author: Joanna Jo Ean Chye Publisher: ISBN: Category : Catalysis Languages : en Pages : 91
Book Description
Propylene is widely used in industry as a starting material for many downstream petrochemical productions in particular polypropylene. It is produced by catalytic dehydrogenation process near atmospheric pressure and 580-650 °C over Pt-Sn/Al2O3 catalyst. However, there are also many undesired reactions occur notably formation of carbon due to high temperature hydrocarbon decomposition. Physicochemical characters including element quantity and quality, nature, morphology, structure and location of coke deposited on used Pt-Sn/Al2O3 catalyst were studied by several characterization techniques i.e. Liquid Nitrogen Physisorption, X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), Field Emission Scanning Electron Microscope (FESEM) and Thermogravimetric Analysis (TGA). XPS analysis detected the constituents of the catalyst and also other elements i.e. K, S, Cl and Fe. FTIR identified the presents of various hydrocarbon species particularly dehydrogenated species; olefins and aromatics while crystallite pre-graphite which indicates the coke was detected by XRD. FESEM images also proved the presents of coke in amorphous, whiskers-like form. BET surface for coked catalyst was only 78.943 m2 g-1. The coke formed was altered by Sn promoter towards the bulk alumina support as discovered by TGA. Subsequently, for carbon removal analysis, the highest gasification obtained as oxygen and followed by air. Nitrogen gasified coke with the lowest rate and the activation energy for nitrogen is higher than oxygen and air. Air is suitable gasifying agent as it can removed carbon content like oxygen but in a mild condition with lower heat released. Different heating ramps did not affect the gasification mechanism.
Author: Michel Boudart Publisher: Elsevier ISBN: 1483183971 Category : Science Languages : en Pages : 263
Book Description
Kinetics of Chemical Processes details the concepts associated with the kinetic study of the chemical processes. The book is comprised of 10 chapters that present information relevant to applied research. The text first covers the elementary chemical kinetics of elementary steps, and then proceeds to discussing catalysis. The next chapter tackles simplified kinetics of sequences at the steady state. Chapter 5 deals with coupled sequences in reaction networks, while Chapter 6 talks about autocatalysis and inhibition. The seventh chapter describes the irreducible transport phenomena in chemical kinetics. The next two chapters discuss the correlations in homogenous kinetics and heterogeneous catalysis, respectively. The last chapter covers the analysis of reaction networks. The book will be of great use to students, researchers, and practitioners of scientific disciplines that deal with chemical reaction, particularly chemistry and chemical engineering.
Author: Jason Wu Publisher: ISBN: Category : Languages : en Pages : 135
Book Description
The production of light alkenes comprises a 250 million ton per year industry due to their extensive use in the production of plastics, rubbers, fuel blending agents, and chemical intermediates. While steam cracking and fluid catalytic cracking of petroleum crude oils are the most common methods for obtaining light alkenes, rising oil prices and low selectivities toward specific alkenes have driven the search for a more economical and efficient process. Catalytic dehydrogenation of light alkanes, obtained from natural gas feedstock, presents an attractive alternative that offers high selectivity and greater flexibility in the alkene pool to address changing demands. Platinum is the most effective metal to catalyze the reaction, but by itself, suffers from catalyst deactivation due to the buildup of carbonaceous deposits. The addition of a secondary metal to form a bimetallic alloy has been of high interest due to its ability to suppress coking and increase selectivity. This dissertation has focused on developing a deeper understanding of promotion effects of various metals and elucidating the mechanism behind coking on Pt catalysts. The use of Sn as a promoter was first investigated, and the effects of particle size and composition on the ethane dehydrogenation performance were determined using a colloidal method to prepare model catalysts. At high conversions, catalyst deactivation from coke formation was a strong function of particle size and Sn/Pt, in agreement with previous high resolution transmission electron microscopy studies (HRTEM) studies. Deactivation decreased significantly with decreasing particle size and increasing addition of Sn. For a fixed average particle size, the activity and selectivity to ethene increased with increasing content of Sn in the Pt-Sn particle. For Pt and Pt3Sn compositions, the turnover frequency increased with increasing particle size, while the selectivity to ethene was not strongly affected. For uncovering the mechanism by which Pt catalysts deactivate, carbon formation on MgO-supported Pt nanoparticles was studied by in situ HRTEM in order to obtain time-resolved images of a single nanoparticle during the dynamic coking process. An electron dose rate dependence on the rate of carbon growth was found, and a suitable imaging strategy was adopted in order to minimize beam-induced artifacts. Multi-layer carbon growth around the nanoparticle was investigated, and significant restructuring of the particle was also observed. In particular, step formation was captured in various images, supporting evidence that the nucleation and growth of carbon during coking on Pt catalysts often requires low coordination sites such as step sites. This is in agreement with scanning tunneling microscopy (STM) experiments, which illustrate a slight preference for carbon atoms to nucleate at the step sites on a Pt(111) crystal. Other promoters for light alkane dehydrogenation were then investigated. The thermal dehydrogenation of n-butane to butene and hydrogen was carried out over Pt nanoparticles supported on calcined hydrotalcite containing indium, Mg(In)(Al)O. The optimal In/Pt ratio was found to be between 0.33 and 0.88, yielding> 95% selectivity to butenes. Hydrogen co-fed with butane was shown to suppress coke formation and catalyst deactivation, with a ratio of H2/C4H10 = 2.5 providing the best catalytic performance. In addition, a Pt-Ir alloy was investigated for ethane and propane dehydrogenation. Following characterization to confirm formation of a bimetallic alloy, intrinsic rate measurements at low feed residence time revealed the following trend in activity: Pt3Sn> Pt3Ir> Pt. DFT calculations carried out on tetrahedral clusters (Pt4, Pt3Ir, Pt3Sn) show that this trend in activity can be attributed to variations in the HOMO-LUMO gap of the cluster.
Author: Susannah L. Scott Publisher: Springer Science & Business Media ISBN: 0387306412 Category : Science Languages : en Pages : 341
Book Description
With the recent advent of nanotechnology, research and development in the area of nanostructured materials has gained unprecedented prominence. Novel materials with potentially exciting new applications are being discovered at a much higher rate than ever before. Innovative tools to fabricate, manipulate, characterize and evaluate such materials are being developed and expanded. To keep pace with this extremely rapid growth, it is necessary to take a breath from time to time, to critically assess the current knowledge and provide thoughts for future developments. This book represents one of these moments, as a number of prominent scientists in nanostructured materials join forces to provide insightful reviews of their areas of expertise, thus offering an overall picture of the state-- the art of the field. Nanostructured materials designate an increasing number of materials with designed shapes, surfaces, structures, pore systems, etc. Nanostructured materials with modified surfaces include those whose surfaces have been altered via such techniques as grafting and tethering of organic or organometallic species, or through various deposition procedures including electro, electroless and vapor deposition, or simple adsorption. These materials find important applications in catalysis, separation and environmental remediation. Materials with patterned surfaces, which are essential for the optoelectronics industry, constitute another important class of surface-modified nanostructured materials. Other materials are considered nanostructured because of their composition and internal organization.
Author: Guy B. Marin Publisher: Academic Press ISBN: 0124199941 Category : Technology & Engineering Languages : en Pages : 254
Book Description
Advances in Chemical Engineering was established in 1960 and is the definitive serial in the area. It is one of great importance to organic chemists, polymer chemists, and many biological scientists. Written by established authorities in the field, the comprehensive reviews combine descriptive chemistry and mechanistic insight and yield an understanding of how the chemistry drives the properties. This volume covers the topic of catalysis and kinetics and aspects in chemical engineering. - Control and optimization of process systems - Polyelectrolytes - Propane dehydrogenation and selective oxidation of hydrogen - Chromium catalysts for ethylene polymerization and oligomerization - Computational simulation of rare Earth catalysis
Author: M. Guisnet Publisher: World Scientific ISBN: 1848166370 Category : Science Languages : en Pages : 359
Book Description
In chemical processes, the progressive deactivation of solid catalysts is a major economic concern and mastering their stability has become as essential as controlling their activity and selectivity. For these reasons, there is a strong motivation to understand the mechanisms leading to any loss in activity and/or selectivity and to find out the efficient preventive measures and regenerative solutions that open the way towards cheaper and cleaner processes. This book covers in a comprehensive way both the fundamental and applied aspects of solid catalyst deactivation and encompasses the state-of-the-art in the field of reactions catalyzed by zeolites. This particular choice is justified by the widespread use of molecular sieves in refining, petrochemicals and organic chemicals synthesis processes, by the large variety in the nature of their active sites (acid, base, acid-base, redox, bifunctional) and especially by their peculiar features, in terms of crystallinity, structural order and textural properties, which make them ideal models for heterogeneous catalysis. The aim of this book is to be a critical review in the field of zeolite deactivation and regeneration, by collecting a series of contributions by experts in the field which describe the factors, explain the techniques to study the causes and suggest methods to prevent (or limit) catalyst deactivation. At the same time, an anthology of commercial processes and exemplar cases provides the reader with theoretical insights and practical hints on the deactivation mechanisms and draws attention to the key role played by the loss of activity on process design and industrial practice.
Author: Michel Che Publisher: John Wiley & Sons ISBN: 3527326871 Category : Technology & Engineering Languages : en Pages : 1313
Book Description
This two-volume book provides an overview of physical techniques used to characterize the structure of solid materials, on the one hand, and to investigate the reactivity of their surface, on the other. Therefore this book is a must-have for anyone working in fields related to surface reactivity. Among the latter, and because of its most important industrial impact, catalysis has been used as the directing thread of the book. After the preface and a general introduction to physical techniques by M. Che and J.C. Vedrine, two overviews on physical techniques are presented by G. Ertl and Sir J.M. Thomas for investigating model catalysts and porous catalysts, respectively. The book is organized into four parts: Molecular/Local Spectroscopies, Macroscopic Techniques, Characterization of the Fluid Phase (Gas and/ or Liquid), and Advanced Characterization. Each chapter focuses upon the following important themes: overview of the technique, most important parameters to interpret the experimental data, practical details, applications of the technique, particularly during chemical processes, with its advantages and disadvantages, conclusions.
Author: Marcello De Falco Publisher: Springer Science & Business Media ISBN: 0857291513 Category : Technology & Engineering Languages : en Pages : 244
Book Description
Membrane Reactors for Hydrogen Production Processes deals with technological and economic aspects of hydrogen selective membranes application in hydrogen production chemical processes. Membrane Reactors for Hydrogen Production Processes starts with an overview of membrane integration in the chemical reaction environment, formulating the thermodynamics and kinetics of membrane reactors and assessing the performance of different process architectures. Then, the state of the art of hydrogen selective membranes, membrane manufacturing processes and the mathematical modeling of membrane reactors are discussed. A review of the most useful applications from an industrial point of view is given. These applications include: natural gas steam reforming, autothermal reforming, water gas shift reaction, decomposition of hydrogen sulphide, and alkanes dehydrogenation. The final part is dedicated to the description of a pilot plant where the novel configuration was implemented at a semi-industrial scale. Plant engineers, researchers and postgraduate students will find Membrane Reactors for Hydrogen Production Processes a comprehensive guide to the state of the art of membrane reactor technology.
Author: Javier García-Martínez Publisher: John Wiley & Sons ISBN: 3527335749 Category : Technology & Engineering Languages : en Pages : 608
Book Description
Authored by a top-level team of both academic and industrial researchers in the field, this is an up-to-date review of mesoporous zeolites. The leading experts cover novel preparation methods that allow for a purpose-oriented fine-tuning of zeolite properties, as well as the related materials, discussing the specific characterization methods and the applications in close relation to each individual preparation approach. The result is a self-contained treatment of the different classes of mesoporous zeolites. With its academic insights and practical relevance this is a comprehensive handbook for researchers in the field and related areas, as well as for developers from the chemical industry.
Author: Kah Sing Ho
Author: Kah Sing Ho
Author: Joanna Jo Ean Chye
Author: Michel Boudart
Author: Jason Wu
Author: Susannah L. Scott
Author: Guy B. Marin
Author: M. Guisnet
Author: Michel Che
Author: Marcello De Falco
Author: Javier García-Martínez