Bhagyesha S. Patil , Alejandra Torres-Velasco , Hashim A. Alzahrani , Skylar Pratt , Juan J. Bravo-Suárez
{"title":"原位 DDR-UV-Vis 和拉曼光谱研究二氧化钛对二氧化硅支撑的钨催化剂在增强丙烯偏析中的促进作用","authors":"Bhagyesha S. Patil , Alejandra Torres-Velasco , Hashim A. Alzahrani , Skylar Pratt , Juan J. Bravo-Suárez","doi":"10.1016/j.cattod.2024.115138","DOIUrl":null,"url":null,"abstract":"<div><div>Tungsten based catalysts supported on silica (<em>z</em>WO<sub>X</sub>/SiO<sub>2</sub>) and silica promoted by titania (<em>z</em>WO<sub>X</sub>/<em>y</em>TiO<sub>X</sub>/SiO<sub>2</sub>) were studied for their catalytic activity towards propylene metathesis. The catalysts were prepared by a simple incipient wetness impregnation method using a large pore SiO<sub>2</sub> of intermediate surface area (∼50 m<sup>2</sup>/g). Catalytic activity studies carried out in a fixed-bed reactor (723 K, 101 kPa propylene) indicated that propylene conversion increased with increasing W loading in <em>z</em>WOx/SiO<sub>2</sub> catalysts (<em>z</em> = 0.5−6 W/nm<sup>2</sup>). It was shown that the catalytic activity of a poorly WO<sub>X</sub> dispersed 6WO<sub>X</sub>/SiO<sub>2</sub> catalyst could be enhanced and maximized by an optimum titania promotion of 2 wt% TiO<sub>2</sub> (∼3 Ti/nm<sup>2</sup>). In situ differential diffuse reflectance (DDR) UV-Vis spectroscopy at reaction conditions showed that TiO<sub>X</sub> domain size increased with increases in titania loading from isolated TiO<sub>X</sub> to TiO<sub>X</sub> clusters to TiO<sub>2</sub> nanocrystals. The UV-Vis results also evidenced the existence of highly dispersed isolated WO<sub>X</sub> species, WO<sub>X</sub> clusters, and WO<sub>3</sub> nanoparticles in the 6WO<sub>X</sub>/<em>y</em>TiO<sub>X</sub>/SiO<sub>2</sub> (<em>y</em> = 0.5−6 wt% TiO<sub>2</sub> or ∼0.7–9 Ti/nm<sup>2</sup>) catalysts. In situ DDR-UV-Vis, Raman, and mass spectrometry during propylene metathesis, and catalyst oxidation and reduction revealed the reasons for an optimum amount of titania promoter in 6WO<sub>X</sub>/2TiO<sub>X</sub>/SiO<sub>2</sub>. They were the result of a balanced interplay between two factors: (1) enhanced WOx species dispersion due to the presence of a trimeric TiO<sub>X</sub> cluster and (2) absence of catalyst deactivation (present at high TiO<sub>2</sub> loadings) due to the trimeric TiO<sub>X</sub> cluster poor reactivity towards coke formation.</div></div>","PeriodicalId":264,"journal":{"name":"Catalysis Today","volume":"447 ","pages":"Article 115138"},"PeriodicalIF":5.2000,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"In Situ DDR-UV-Vis and Raman spectroscopic study of titania promoting effect on silica supported tungsten catalysts for enhanced propylene metathesis\",\"authors\":\"Bhagyesha S. Patil , Alejandra Torres-Velasco , Hashim A. Alzahrani , Skylar Pratt , Juan J. Bravo-Suárez\",\"doi\":\"10.1016/j.cattod.2024.115138\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><div>Tungsten based catalysts supported on silica (<em>z</em>WO<sub>X</sub>/SiO<sub>2</sub>) and silica promoted by titania (<em>z</em>WO<sub>X</sub>/<em>y</em>TiO<sub>X</sub>/SiO<sub>2</sub>) were studied for their catalytic activity towards propylene metathesis. The catalysts were prepared by a simple incipient wetness impregnation method using a large pore SiO<sub>2</sub> of intermediate surface area (∼50 m<sup>2</sup>/g). Catalytic activity studies carried out in a fixed-bed reactor (723 K, 101 kPa propylene) indicated that propylene conversion increased with increasing W loading in <em>z</em>WOx/SiO<sub>2</sub> catalysts (<em>z</em> = 0.5−6 W/nm<sup>2</sup>). It was shown that the catalytic activity of a poorly WO<sub>X</sub> dispersed 6WO<sub>X</sub>/SiO<sub>2</sub> catalyst could be enhanced and maximized by an optimum titania promotion of 2 wt% TiO<sub>2</sub> (∼3 Ti/nm<sup>2</sup>). In situ differential diffuse reflectance (DDR) UV-Vis spectroscopy at reaction conditions showed that TiO<sub>X</sub> domain size increased with increases in titania loading from isolated TiO<sub>X</sub> to TiO<sub>X</sub> clusters to TiO<sub>2</sub> nanocrystals. The UV-Vis results also evidenced the existence of highly dispersed isolated WO<sub>X</sub> species, WO<sub>X</sub> clusters, and WO<sub>3</sub> nanoparticles in the 6WO<sub>X</sub>/<em>y</em>TiO<sub>X</sub>/SiO<sub>2</sub> (<em>y</em> = 0.5−6 wt% TiO<sub>2</sub> or ∼0.7–9 Ti/nm<sup>2</sup>) catalysts. In situ DDR-UV-Vis, Raman, and mass spectrometry during propylene metathesis, and catalyst oxidation and reduction revealed the reasons for an optimum amount of titania promoter in 6WO<sub>X</sub>/2TiO<sub>X</sub>/SiO<sub>2</sub>. They were the result of a balanced interplay between two factors: (1) enhanced WOx species dispersion due to the presence of a trimeric TiO<sub>X</sub> cluster and (2) absence of catalyst deactivation (present at high TiO<sub>2</sub> loadings) due to the trimeric TiO<sub>X</sub> cluster poor reactivity towards coke formation.</div></div>\",\"PeriodicalId\":264,\"journal\":{\"name\":\"Catalysis Today\",\"volume\":\"447 \",\"pages\":\"Article 115138\"},\"PeriodicalIF\":5.2000,\"publicationDate\":\"2024-11-20\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Catalysis Today\",\"FirstCategoryId\":\"92\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0920586124006321\",\"RegionNum\":2,\"RegionCategory\":\"化学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"CHEMISTRY, APPLIED\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Catalysis Today","FirstCategoryId":"92","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0920586124006321","RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"CHEMISTRY, APPLIED","Score":null,"Total":0}
In Situ DDR-UV-Vis and Raman spectroscopic study of titania promoting effect on silica supported tungsten catalysts for enhanced propylene metathesis
Tungsten based catalysts supported on silica (zWOX/SiO2) and silica promoted by titania (zWOX/yTiOX/SiO2) were studied for their catalytic activity towards propylene metathesis. The catalysts were prepared by a simple incipient wetness impregnation method using a large pore SiO2 of intermediate surface area (∼50 m2/g). Catalytic activity studies carried out in a fixed-bed reactor (723 K, 101 kPa propylene) indicated that propylene conversion increased with increasing W loading in zWOx/SiO2 catalysts (z = 0.5−6 W/nm2). It was shown that the catalytic activity of a poorly WOX dispersed 6WOX/SiO2 catalyst could be enhanced and maximized by an optimum titania promotion of 2 wt% TiO2 (∼3 Ti/nm2). In situ differential diffuse reflectance (DDR) UV-Vis spectroscopy at reaction conditions showed that TiOX domain size increased with increases in titania loading from isolated TiOX to TiOX clusters to TiO2 nanocrystals. The UV-Vis results also evidenced the existence of highly dispersed isolated WOX species, WOX clusters, and WO3 nanoparticles in the 6WOX/yTiOX/SiO2 (y = 0.5−6 wt% TiO2 or ∼0.7–9 Ti/nm2) catalysts. In situ DDR-UV-Vis, Raman, and mass spectrometry during propylene metathesis, and catalyst oxidation and reduction revealed the reasons for an optimum amount of titania promoter in 6WOX/2TiOX/SiO2. They were the result of a balanced interplay between two factors: (1) enhanced WOx species dispersion due to the presence of a trimeric TiOX cluster and (2) absence of catalyst deactivation (present at high TiO2 loadings) due to the trimeric TiOX cluster poor reactivity towards coke formation.
期刊介绍:
Catalysis Today focuses on the rapid publication of original invited papers devoted to currently important topics in catalysis and related subjects. The journal only publishes special issues (Proposing a Catalysis Today Special Issue), each of which is supervised by Guest Editors who recruit individual papers and oversee the peer review process. Catalysis Today offers researchers in the field of catalysis in-depth overviews of topical issues.
Both fundamental and applied aspects of catalysis are covered. Subjects such as catalysis of immobilized organometallic and biocatalytic systems are welcome. Subjects related to catalysis such as experimental techniques, adsorption, process technology, synthesis, in situ characterization, computational, theoretical modeling, imaging and others are included if there is a clear relationship to catalysis.