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XPS analysis for Pt on 0.5-Pt-1-Sn/SBA-100 catalyst: (a) fresh sample; (b) reduced sample; under reaction at (c) 60 min, (d) 180 min, (e) 300 min.
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Catalytic propane dehydrogenation is an attractive method to produce propylene while avoiding the issues of its traditional synthesis via naphtha steam cracking of naphtha. In this contribution, a series of Pt-Sn/SBA-16 catalysts were synthesized and evaluated for this purpose. Bimetallic Pt-Sn catalysts were more active than catalysts containing o...
Similar publications
Propane dehydrogenation (PDH) over Pt catalyst operated in a moving-bed mode is becoming the dominant process for the on-purpose production of propylene worldwide ¹⁻³ . Sintering and coking deactivations of Pt catalysts, which greatly decrease the durability and efficiency of this scarce and costly noble metal, are the most challenging issues for t...
Citations
... The used HNZ-5-30 showed a mass loss of 16.67 % in the range of 450-600°C, suggesting a high H/C ratio related to so-called "soft coke" in the catalyst pore system. [48] The weight loss of spent CZSM-5 (48.3 %) was more pronounced than that of spent HNZ-5-30, which indicated that coke formed much more rapidly in the microporous CZSM-5 zeolite than in the hierarchical zeolite HNZ-5-30. [38] This coke corresponded to adsorbed hydrocarbon molecules inside the catalyst pores that had been generated by coke precursors. ...
A series of hierarchical ZSM‐5 nanocrystalline aggregates (HNZ‐5) was synthesized using a hydrothermal method with tetrapropylammonium hydroxide as a structural guide. The HNZ‐5 samples having different Si/Al molar ratios all showed suitable hierarchical architectures and the maximum surface area was found to be 329 m²/g. The SEM image displayed the width of the individual crystal particles was ~100 nm, and its nanocrystalline clusters generated intercrystalline pores. Temperature‐programmed desorption with NH3 indicated that the total acidity of this material increased with increases in the Al³⁺ content to a maximum of 0.47 mmol/g at a Si/Al ratio of 15. In addition, ²⁷Al magic angle spinning nuclear magnetic resonance spectra showed that the acid sites were associated with tetrahedral and octahedral Al sites. This HNZ‐5 was applied to the catalytic cracking of waste cooking oil model compound and gave a light olefin yield as high as 43.9 % at 550 °C. Extending the reaction time to 6000 min provided a yield of light olefins in excess of 30 %, which was higher than that achieved using traditional ZSM‐5. These data confirmed that the hierarchical pore structure of HNZ‐5 resulting from the self‐assembly of nanocrystals, together with exposed acidic sites, promoted the catalytic conversion of large molecules.
... The spent ZK-80 catalyst showed weight loss over the range of 450-600°C, attributed to adsorbed hydrocarbon molecules with a high H/C ratio (soft coke) inside the catalyst pore system, which had formed from the coke precursor. 44 Samples of spent ZK-80-6000 min (after 6000 min of reaction) showed mass loss over the range of 600-700°C, which is associated with the polymerization of soft coke to more bulky carbonaceous compounds with a low H/C ratio (i.e., hard coke). 45 The weight loss of spent ZSM-5 was more pronounced than that of spent ZK-80, possibly because ZSM-5 had a greater number of strong acid sites. ...
BACKGROUND
A series of ZSM‐5@KIT‐6 composite molecular sieve catalysts was prepared by encapsulating ZSM‐5 as a substrate in the mesoporous material KIT‐6. The intent was to use these catalysts to promote the catalytic cracking of a waste cooking oil model compound (WCOMC) to produce light olefins.
RESULTS
The morphology, structural characteristics and acidity of each of the resulting catalysts were characterized by X‐ray diffraction, transmission electron microscopy, N2‐Brunauer–Emmett–Teller (N2‐BET) surface area analysis and temperature‐programmed ammonia desorption. The results showed that ZSM‐5 was successfully coated with KIT‐6. The BET surface areas of these catalysts ranged from 345 to 792 m² g⁻¹ and the specimens had average pore sizes in the range of 2.37–5.51 nm. Total acidity increased with increases in the mass‐based proportion of ZSM‐5 in the material.
CONCLUSION
The catalytic cracking of WCOMC was studied in a lab‐scale fixed‐bed apparatus. Trials at a reaction temperature of 600 °C using the material having a mass‐based ZSM‐5 proportion of 80.0% (ZK‐80) gave the highest gas‐phase yield of light olefins of 43.8%. After 6000 min, the catalytic performance of this material remained stable, demonstrating a resistance to carbon deposits. The superior activity of the present composite catalysts can be ascribed to improvements in pore structure and acid strength distribution. © 2023 Society of Chemical Industry (SCI).
... Consequently, the catalytic dehydrogenation of propane to propylene (PDH, C 3 H 8 ↔ C 3 H 6 + H 2 ) is of great importance because of the growing demand all around the world [5]. For instance, supported Pt and CrO x catalysts have been successfully and commercially employed for the dehydrogenation of propane in chemical production [6][7][8]. However, the high price and scarcity of Pt and the potential toxicity of CrO x restrict their further development in the PDH industry. ...
Propane dehydrogenation to propylene, one of the most significant compounds in the chemical industry, has attracted tremendous attention worldwide. A series of V doped graphitic carbon nitride composites (V-g-C3N4) were synthesized via a combination of thermal polymerization of urea and thermal decomposition of NH4VO3. After doping VOx species, the V doped g-C3N4 catalysts achieved an optimal propylene yield of 16.16% with a propylene selectivity of 68.6% at 600 °C, compared with undoped g-C3N4 (a propylene yield of 5.42% with a propylene selectivity of 53.9%) at the same condition. Subsequently, various characterization techniques, including XRD, TEM, FTIR, Raman, XPS, N2 adsorption–desorption, etc., were unitized to investigate the chemical properties and crystalline structures of the prepared catalysts. The essence of catalytic enhancement, such as crystallinity, the main active VOx species, and the newly emerging V–N bonds in V-g-C3N4 catalysts, has been discussed, providing a tentative reaction pathway for CH3(*CH)CH3 and CH3CHCH2* species on V active sites. In general, this work offers a research basis for the bran-new materials design for propane dehydrogenation.
Graphical Abstract
... It has been suggested that the coke formed on PtSn-based catalysts in PDH reaction mainly consists of three kinds of species: aliphatics, aromatics and pregraphite, with the aliphatic one constituting most of the deposit, with the C/H ratio of around 1.5 [95]. Raman studies on exhausted Pt-Sn/SBA-16 catalysts have shown an increase in coke crystal size from 60 to 180 min on stream and from 180 to 300 min under reaction [96]. These results are consistent with the so-called "coke migration phenomenon", attributed to the coke movement near the particle to the support, or to the sintering of the metallic particle. ...
Propylene is one of the most important feedstocks in the chemical industry, as it is used in the production of widely diffused materials such as polypropylene. Conventionally, propylene is obtained by cracking petroleum-derived naphtha and is a by-product of ethylene production. To ensure adequate propylene production, an alternative is needed, and propane dehydrogenation is considered the most interesting process. In literature, the catalysts that have shown the best performance in the dehydrogenation reaction are Cr-based and Pt-based. Chromium has the nonnegligible disadvantage of toxicity; on the other hand, platinum shows several advantages, such as a higher reaction rate and stability. This review article summarizes the latest published results on the use of platinum-based catalysts for the propane dehydrogenation reaction. The manuscript is
based on relevant articles from the past three years and mainly focuses on how both promoters and supports may affect the catalytic activity. The published results clearly show the crucial importance of the choice of the support, as not only the use of promoters but also the use of supports with tuned acid/base properties and particular shape can suppress the formation of coke and prevent the deep dehydrogenation of propylene.
Public health, production and preservation of food, development of environmentally friendly (cosmeto-)textiles and plastics, synthesis processes using green technology, and improvement of water quality, among other domains, can be controlled with the help of chitosan. It has been demonstrated that this biopolymer exhibits advantageous properties, such as biocompatibility, biodegradability, antimicrobial effect, mucoadhesive properties, film-forming capacity, elicitor of plant defenses, coagulant-flocculant ability, synergistic effect and adjuvant along with other substances and materials. In part, its versatility is attributed to the presence of ionizable and reactive primary amino groups that provide strong chemical interactions with small inorganic and organic substances, macromolecules, ions, and cell membranes/walls. Hence, chitosan has been used either to create new materials or to modify the properties of conventional materials applied on an industrial scale. Considering the relevance of strategic topics around the world, this review integrates recent studies and key background information constructed by different researchers designing chitosan-based materials with potential applications in the aforementioned concerns.
The dehydrogenation of propane was carried out with feed gas containing different proportions of propylene, and the coking behavior of Pt-based catalyst under propene-rich condition was investigated. The results show that the presence of propylene in the raw material accelerates the rate of coke deposition, shortens the time of dynamic equilibrium of coke deposition on the support, and promotes the formation of coke on the surface area of the active phase and the subsequent graphitization. At the same time, the increase the amount of unsaturated aliphatic compounds, thus promoting the generation of aromatic carbon and graphitized carbon, while the catalyst structure is not destroyed. In the process of propane dehydrogenation, the coke “Peak I” appears on the surface of the active phase, and the “Peak II” moves to the high-temperature region, when the propylene content increase to 1.5%. With the alkene content increasing to 3.0%, Peak I and Peak II merge into a larger peak, the area of which increases significantly. When the coke content exceeds 10.26%, the graphitization degree of the catalyst becomes higher and higher. The increase of the propylene content accelerates the saturation process of the coke holding capacity of the carrier, meaning the increasing amount of coke deposit under the same reaction time.
Propane dehydrogenation (PDH) is an industrial technology for direct propylene production, which has received extensive attention and realized large-scale application. At present, the commercial Pt/Cr-based catalysts suffer from fast deactivation and inferior stability resulting from active species sintering and coke depositing. To overcome the above problems, several strategies such as the modification of the support and the introduction of additives have been proposed to strengthen the catalytic performance and prolong the robust stability of Pt/Cr-based catalysts. This review firstly gives a brief description of the development of PDH and PDH catalysts. Then, the advanced research progress of supported noble metals and non-noble metals together with metal-free materials for PDH is systematically summarized along with the material design and active origin as well as the existing problems in the development of PDH catalysts. Furthermore, the review also emphasizes advanced synthetic strategies based on novel design of PDH catalysts with improved dehydrogenation activity and stability. Finally, the future challenges and directions of PDH catalysts are provided for the development of their further industrial application.
