Applied CatalysisPub Date : 1991-10-15DOI: 10.1016/0166-9834(91)80066-6
Tseng-Chang Tsai , Ikai Wang *
{"title":"Cumene disproportionation over zeolite β","authors":"Tseng-Chang Tsai , Ikai Wang *","doi":"10.1016/0166-9834(91)80066-6","DOIUrl":"10.1016/0166-9834(91)80066-6","url":null,"abstract":"<div><p>Two methods, silica deposition and steam pretreatment, have been developed to improve the catalytic stability of zeolite β for cumene disproportionation. It was found that deactivation resulted from coke formation deposited on the zeolite pore mouths. Two different mechanisms for these two stabilization methods are proposed. Steam pretreatment enhances the acid strength and results in the reduction of coke formation. Nevertheless, Si (OC<sub>2</sub>H<sub>5</sub>)<sub>4</sub> can only deposit and decompose on the sites at the external surface and/or near the pore mouth. Accordingly, pore mouth coking is eliminated.</p></div>","PeriodicalId":8091,"journal":{"name":"Applied Catalysis","volume":"77 2","pages":"Pages 209-222"},"PeriodicalIF":0.0,"publicationDate":"1991-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0166-9834(91)80066-6","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90828321","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Applied CatalysisPub Date : 1991-10-15DOI: 10.1016/0166-9834(91)80063-3
H.S. Gandhi, M. Shelef *
{"title":"Effects of sulphur on noble metal automotive catalysts","authors":"H.S. Gandhi, M. Shelef *","doi":"10.1016/0166-9834(91)80063-3","DOIUrl":"10.1016/0166-9834(91)80063-3","url":null,"abstract":"<div><p>The small amount of sulfur, ca. 300 ppm, in gasoline which is equivalent to ca. 20 ppm SO<sub>2</sub> in exhaust, has multiple effects on the operation of automotive catalysts. These effects are not widely appreciated. Firstly, there are large differences in the capacity of different noble metals to chemisorb sulfur dioxide and secondly, the dispersion of the noble metal influences the activity in the oxidation of sulfur dioxide to sulfur trioxide. The ability of the catalyst to oxidize SO<sub>2</sub> determines the resistance to poisoning by residual amounts of lead in the fuel and whether the surface of the catalyst support will store sulfur, as sulfate, under oxidizing conditions. The surface sulfate groups on the support enhance the oxidation of saturated hydrocarbons, which is very desirable for the attainment of the stringent regulatory limits on hydrocarbon emissions. On the other hand, the stored sulfur can be emitted as a transient spike of hydrogen sulfide if the engine operating conditions shift momentarily to the rich side of the stoichiometric air/fuel ratio, which is an undesirable phenomenon. The presence of sulfur species in the exhaust influences the partitioning of the products of nitric oxide reduction between dinitrogen and ammonia strongly suppressing the latter. The optimization of the composition of the three-way catalyst has to take into account the effect of sulfur compounds present in the exhaust.</p></div>","PeriodicalId":8091,"journal":{"name":"Applied Catalysis","volume":"77 2","pages":"Pages 175-186"},"PeriodicalIF":0.0,"publicationDate":"1991-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0166-9834(91)80063-3","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79296722","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Applied CatalysisPub Date : 1991-10-15DOI: 10.1016/0166-9834(91)80072-5
M. Koussathana, D. Vamvouka, H. Economou, X. Verykios *
{"title":"Slurry-phase hydrogenation of aromatic compounds over supported noble metal catalysts","authors":"M. Koussathana, D. Vamvouka, H. Economou, X. Verykios *","doi":"10.1016/0166-9834(91)80072-5","DOIUrl":"10.1016/0166-9834(91)80072-5","url":null,"abstract":"<div><p>The hydrogenation of benzene, naphthalene and biphenyl over monometallic (Pt, Rh, Ru) and bimetallic (Pt, Rh, Ru-Pd, Ir, Re ) catalysts supported on γ-Al<sub>2</sub>O<sub>3</sub> or TiO<sub>2</sub> is investigated in a three-phase slurry reactor at a temperature of 300 °C and a hydrogen pressure of 66 atm. Under the conditions employed in this study, of the primary metals investigated platinum was found to possess the highest specific hydrogenation activity while biphenyl was found to be the most reactive molecule. The hydrogenation of benzene over platinum and naphthalene over platinum and rhodium were found to be structure insensitive reactions. In most cases, bimetallic formulations were found to exhibit significantly higher hydrogenation activity as compared to their monometallic counterparts. The enhancement factor was found to be larger when the bimetallic formations were supported on TiO<sub>2</sub> as opposed to Al<sub>2</sub>O<sub>3</sub> carriers. Bimetallic catalysts, especially those containing rhenium were also found to exhibit enhanced resistance to sulfur poisoning.</p></div>","PeriodicalId":8091,"journal":{"name":"Applied Catalysis","volume":"77 2","pages":"Pages 283-301"},"PeriodicalIF":0.0,"publicationDate":"1991-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0166-9834(91)80072-5","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81037771","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Applied CatalysisPub Date : 1991-10-15DOI: 10.1016/0166-9834(91)80065-5
Tseng-Chang Tsai , Chin-Lan Ay, Ikai Wang *
{"title":"Cumene disproportionation over zeolite β","authors":"Tseng-Chang Tsai , Chin-Lan Ay, Ikai Wang *","doi":"10.1016/0166-9834(91)80065-5","DOIUrl":"10.1016/0166-9834(91)80065-5","url":null,"abstract":"<div><p>Cumene disproportionation has been demonstrated as an accurate probe reaction for zeolite structures. Over twelve-membered ring zeolites, cumene undergoes a bimolecular mechanism; but over ten-membered ring zeolites, it undergoes a monomolecular mechanism. Zeolite β, a highly siliceous twelve-membered ring zeolite, shows excellent activity, disproportionation selectivity and stability in cumene disproportionation and therefore has practical potential in the production of diisopropylbenzenes.</p></div>","PeriodicalId":8091,"journal":{"name":"Applied Catalysis","volume":"77 2","pages":"Pages 199-207"},"PeriodicalIF":0.0,"publicationDate":"1991-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0166-9834(91)80065-5","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82985494","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Applied CatalysisPub Date : 1991-10-15DOI: 10.1016/0166-9834(91)80071-4
A. Bernier, L.F. Admaiai, P. Grange
{"title":"Synthesis and characterization of titanium pillared clays Influence of the temperature of preparation","authors":"A. Bernier, L.F. Admaiai, P. Grange","doi":"10.1016/0166-9834(91)80071-4","DOIUrl":"10.1016/0166-9834(91)80071-4","url":null,"abstract":"<div><p>Detailed analysis of the experimental conditions necessary in order to prepare thermally stable titanium pillared clays are described. pH, temperature and titanium concentration of the suspension play an important role. In the optimal conditions, high surface area Ti PILC (327 m<sup>2</sup> g<sup>−1</sup> at 600 °C) are prepared. In addition, these microporous materials develop strong Lewis acidity evaluated by TPD of ammonia and FT-IR of pyridine.</p></div>","PeriodicalId":8091,"journal":{"name":"Applied Catalysis","volume":"77 2","pages":"Pages 269-281"},"PeriodicalIF":0.0,"publicationDate":"1991-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0166-9834(91)80071-4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77246958","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Applied CatalysisPub Date : 1991-10-15DOI: 10.1016/0166-9834(91)80064-4
Xiaofan Xie *, Hengbo Yin, Bosheng Dou, Jichuan Huo
{"title":"Characterization of a potassium-promoted cobalt- molybdenum/alumina water-gas shift catalyst","authors":"Xiaofan Xie *, Hengbo Yin, Bosheng Dou, Jichuan Huo","doi":"10.1016/0166-9834(91)80064-4","DOIUrl":"10.1016/0166-9834(91)80064-4","url":null,"abstract":"<div><p>A series of potassium-promoted CoMo/Al<sub>2</sub>O<sub>3</sub> has been investigated by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and temperature-programmed reduction (TPR). CoMoO<sub>4</sub> was found in the CoMo/Al<sub>2</sub>O<sub>3</sub> catalyst by XRD and is destroyed by the presence of potassium. The reducibility of molybdenum is enhanced by potassium in the CoMoK/Al<sub>2</sub>O<sub>3</sub> catalyst and is easier to reduce to Mo<sup>IV</sup> during sulfidation. In the oxidic state catalyst cobalt is increased on the surface by the addition of potassium. After sulfidation this phenomena disappeared, the distribution of cobalt remains at a constant level and is unaffected by the potassium content. The addition of potassium leads to a monotonical decrease of the molybdenum dispersion with the impregnating amount of potassium in the oxidic state catalyst but is more complicated after sulfidation. Potassium is well dispersed on the surface in both the oxidic and sulfided state. The activity in the water-gas shift reaction was correlated with the potassium content of CoMoK/Al<sub>2</sub>O<sub>3</sub>.</p></div>","PeriodicalId":8091,"journal":{"name":"Applied Catalysis","volume":"77 2","pages":"Pages 187-198"},"PeriodicalIF":0.0,"publicationDate":"1991-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0166-9834(91)80064-4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81441979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}