Pub Date : 2015-02-01DOI: 10.1179/2055075814Y.0000000006
J. Kennedy, W. Jones, D. Morgan, M. Bowker, Li Lu, C. Kiely, P. Wells, N. Dimitratos
Abstract We have investigated polyvinylalcohol stabilized Au and Ag based nanoparticles supported on titania prepared via sol immobilisation for the anaerobic, ambient temperature reforming of methanol with water for the photocatalytic production of hydrogen. The catalytic activity of the Au/TiO2 catalysts was strongly affected by the metal loading and calcination temperature. Here, we report the preparation and use of supported Au–Ag nanoparticles, based on either the co-reduction or the consecutive reduction of the two metals. Au–Ag supported catalysts were more active than monometallic Au and Ag catalysts and the preparation methodology had a pronounced effect in terms of catalytic activity of the Au–Ag catalysts. In fact, using a consecutive reduction where Au was firstly reduced followed by reduction of Ag gave materials which exhibited the highest catalytic performance.
{"title":"Photocatalytic hydrogen production by reforming of methanol using Au/TiO2, Ag/TiO2 and Au-Ag/TiO2 catalysts","authors":"J. Kennedy, W. Jones, D. Morgan, M. Bowker, Li Lu, C. Kiely, P. Wells, N. Dimitratos","doi":"10.1179/2055075814Y.0000000006","DOIUrl":"https://doi.org/10.1179/2055075814Y.0000000006","url":null,"abstract":"Abstract We have investigated polyvinylalcohol stabilized Au and Ag based nanoparticles supported on titania prepared via sol immobilisation for the anaerobic, ambient temperature reforming of methanol with water for the photocatalytic production of hydrogen. The catalytic activity of the Au/TiO2 catalysts was strongly affected by the metal loading and calcination temperature. Here, we report the preparation and use of supported Au–Ag nanoparticles, based on either the co-reduction or the consecutive reduction of the two metals. Au–Ag supported catalysts were more active than monometallic Au and Ag catalysts and the preparation methodology had a pronounced effect in terms of catalytic activity of the Au–Ag catalysts. In fact, using a consecutive reduction where Au was firstly reduced followed by reduction of Ag gave materials which exhibited the highest catalytic performance.","PeriodicalId":43717,"journal":{"name":"Catalysis Structure & Reactivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1179/2055075814Y.0000000006","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"65871718","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}
Pub Date : 2015-02-01DOI: 10.1179/2055075814Y.0000000002
Y. Hao, Xiaodong Wang, N. Perret, F. Cárdenas-Lizana, M. Keane
Abstract The role of the support in the gas phase hydrogenation of butyronitrile over Pd/Al2O3 and Pd/C (2.5–3.0 nm mean Pd size) has been studied, taking bulk Pd as benchmark. Catalyst activation by temperature programmed reduction was monitored and the metal and acid functions characterized by H2 and NH3 chemisorption/temperature programmed desorption and electron microscopy (STEM/TEM). Butyronitrile hydrogenation was stable with time on-stream to deliver butylamine where consecutive condensation with the intermediate butylidenimine generated dibutylamine and tributylamine. Condensation can occur on bulk Pd but selectivity is influenced by the support and reaction over Pd/Al2O3 generated dibutylamine as principal product. Preferential tertiary amine formation was observed over Pd/C and attributed to greater surface acidity that favors the condensation step. Increased hydrogen spillover and acidity (associated with Pd/C) elevated butyronitrile consumption rate.
{"title":"Support effects in the gas phase hydrogenation of butyronitrile over palladium","authors":"Y. Hao, Xiaodong Wang, N. Perret, F. Cárdenas-Lizana, M. Keane","doi":"10.1179/2055075814Y.0000000002","DOIUrl":"https://doi.org/10.1179/2055075814Y.0000000002","url":null,"abstract":"Abstract The role of the support in the gas phase hydrogenation of butyronitrile over Pd/Al2O3 and Pd/C (2.5–3.0 nm mean Pd size) has been studied, taking bulk Pd as benchmark. Catalyst activation by temperature programmed reduction was monitored and the metal and acid functions characterized by H2 and NH3 chemisorption/temperature programmed desorption and electron microscopy (STEM/TEM). Butyronitrile hydrogenation was stable with time on-stream to deliver butylamine where consecutive condensation with the intermediate butylidenimine generated dibutylamine and tributylamine. Condensation can occur on bulk Pd but selectivity is influenced by the support and reaction over Pd/Al2O3 generated dibutylamine as principal product. Preferential tertiary amine formation was observed over Pd/C and attributed to greater surface acidity that favors the condensation step. Increased hydrogen spillover and acidity (associated with Pd/C) elevated butyronitrile consumption rate.","PeriodicalId":43717,"journal":{"name":"Catalysis Structure & Reactivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1179/2055075814Y.0000000002","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"65871893","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}
Pub Date : 2015-02-01DOI: 10.1179/2055075814Y.0000000003
E. van Steen, M. Claeys
Abstract The role of copper in iron based Fischer–Tropsch catalysts was investigated using DFT with χ-Fe5C2(100)0.25 as a model surface. The presence of atomic copper on the iron-rich χ-Fe5C2(100)0.25-surface is more favorable than its presence in surface. Nevertheless, the segregation of copper from the surface yielding fcc-Cu remains an exergonic process. Carbon monoxide at a coverage of 2.2 CO per nm2 stabilizes atomic copper on this surface. The presence of copper results in the redshift in the stretching frequency of adsorbed CO. The mobility of copper atoms was investigated on χ-Fe5C2(100)0.25 in the presence of CO. The hopping frequency is reduced due to the presence of CO, although never enough to avoid formation of fcc-Cu on a shorter time scale than typically required for the formation of hydrocarbons in the Fischer–Tropsch synthesis.
以χ-Fe5C2(100)0.25为模型面，采用离散傅里叶变换研究了铜在铁基费托催化剂中的作用。原子铜在富铁的χ-Fe5C2(100)0.25表面的存在比在表面的存在更有利。尽管如此，铜从表面的分离产生fcc-Cu仍然是一个随工过程。2.2 CO / nm2的一氧化碳覆盖率稳定了这个表面上的原子铜。铜的存在导致吸附CO的拉伸频率红移。在CO存在下，铜原子的迁移率在χ-Fe5C2(100)0.25上进行了研究。由于CO的存在，跳频降低，尽管不足以避免在比费托合成中形成碳氢化合物通常所需的更短的时间尺度上形成fcc-Cu。
{"title":"Promoting χ-Fe5C2(100)0.25 with copper – a DFT study","authors":"E. van Steen, M. Claeys","doi":"10.1179/2055075814Y.0000000003","DOIUrl":"https://doi.org/10.1179/2055075814Y.0000000003","url":null,"abstract":"Abstract The role of copper in iron based Fischer–Tropsch catalysts was investigated using DFT with χ-Fe5C2(100)0.25 as a model surface. The presence of atomic copper on the iron-rich χ-Fe5C2(100)0.25-surface is more favorable than its presence in surface. Nevertheless, the segregation of copper from the surface yielding fcc-Cu remains an exergonic process. Carbon monoxide at a coverage of 2.2 CO per nm2 stabilizes atomic copper on this surface. The presence of copper results in the redshift in the stretching frequency of adsorbed CO. The mobility of copper atoms was investigated on χ-Fe5C2(100)0.25 in the presence of CO. The hopping frequency is reduced due to the presence of CO, although never enough to avoid formation of fcc-Cu on a shorter time scale than typically required for the formation of hydrocarbons in the Fischer–Tropsch synthesis.","PeriodicalId":43717,"journal":{"name":"Catalysis Structure & Reactivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1179/2055075814Y.0000000003","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"65871979","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}
Pub Date : 2015-02-01DOI: 10.1179/2055075814Y.0000000004
S. Jones, A. Kolpin, S. Tsang
Abstract Formic acid is proposed as a storage material to supply hydrogen gas for small portable fuel cell devices. However catalysts for its decomposition must be highly active and selective to provide a high quantity of hydrogen and carbon dioxide at ambient conditions but prevent any CO formation that can poison the catalysts. In this paper we report the functionalization of high surface area metal oxides with amine groups, which are then utilized as catalyst support to host Pd nanoparticles. It is demonstrated that the electronic and geometric properties of Pd nanoparticles can be substantially modified by these functionalized supports, resulting in improved activity and selectivity performance for the formic acid dehydrogenation.
{"title":"Modification of Pd for formic acid decomposition by support grafted functional groups","authors":"S. Jones, A. Kolpin, S. Tsang","doi":"10.1179/2055075814Y.0000000004","DOIUrl":"https://doi.org/10.1179/2055075814Y.0000000004","url":null,"abstract":"Abstract Formic acid is proposed as a storage material to supply hydrogen gas for small portable fuel cell devices. However catalysts for its decomposition must be highly active and selective to provide a high quantity of hydrogen and carbon dioxide at ambient conditions but prevent any CO formation that can poison the catalysts. In this paper we report the functionalization of high surface area metal oxides with amine groups, which are then utilized as catalyst support to host Pd nanoparticles. It is demonstrated that the electronic and geometric properties of Pd nanoparticles can be substantially modified by these functionalized supports, resulting in improved activity and selectivity performance for the formic acid dehydrogenation.","PeriodicalId":43717,"journal":{"name":"Catalysis Structure & Reactivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1179/2055075814Y.0000000004","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"65871590","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}
Pub Date : 2015-01-08DOI: 10.1179/2055075814Y.0000000009
Chuntian Qiu, Chen C Chen, S. Ishikawa, Zhenxin Zhang, T. Murayama, W. Ueda
Abstract Crystalline Mo–V–W–O complex oxides with the orthorhombic or trigonal structure were synthesized by a hydrothermal method. Those Mo–V–W–O samples with various amounts of tungsten were characterized by inductively coupled plasma atomic emission spectroscopy, TEM, STEM–EDX, X-ray diffraction, Rietveld analysis, and a N2 adsorption method. It was found for the first case that an additional metal such as W can be successfully incorporated into the trigonal Mo–V–O structure by using (CH3CH2NH3)2Mo3O10.The alkylammonium cation acted as a structural stabilizer that was requisite for the formation of a trigonal structure when additional metal ions were present. For the orthorhombic Mo–V–W–O structure, introduction of W into the orthorhombic structure caused a rod segregation effect by which nanoscale crystals formed and the external surface area greatly increased. Additionally, these Mo–V–W–O materials were applied as catalysts for the gas phase selective oxidation of acrolein to acrylic acid. The best catalyst was assigned to the orthorhombic Mo–V–O–W7.5, which possessed an ordered arrangement of heptagonal and hexagonal channels and a large external surface area.
{"title":"Synthesis of crystalline Mo–V–W–O complex oxides with orthorhombic and trigonal structures and their application as catalysts","authors":"Chuntian Qiu, Chen C Chen, S. Ishikawa, Zhenxin Zhang, T. Murayama, W. Ueda","doi":"10.1179/2055075814Y.0000000009","DOIUrl":"https://doi.org/10.1179/2055075814Y.0000000009","url":null,"abstract":"Abstract Crystalline Mo–V–W–O complex oxides with the orthorhombic or trigonal structure were synthesized by a hydrothermal method. Those Mo–V–W–O samples with various amounts of tungsten were characterized by inductively coupled plasma atomic emission spectroscopy, TEM, STEM–EDX, X-ray diffraction, Rietveld analysis, and a N2 adsorption method. It was found for the first case that an additional metal such as W can be successfully incorporated into the trigonal Mo–V–O structure by using (CH3CH2NH3)2Mo3O10.The alkylammonium cation acted as a structural stabilizer that was requisite for the formation of a trigonal structure when additional metal ions were present. For the orthorhombic Mo–V–W–O structure, introduction of W into the orthorhombic structure caused a rod segregation effect by which nanoscale crystals formed and the external surface area greatly increased. Additionally, these Mo–V–W–O materials were applied as catalysts for the gas phase selective oxidation of acrolein to acrylic acid. The best catalyst was assigned to the orthorhombic Mo–V–O–W7.5, which possessed an ordered arrangement of heptagonal and hexagonal channels and a large external surface area.","PeriodicalId":43717,"journal":{"name":"Catalysis Structure & Reactivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1179/2055075814Y.0000000009","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"65872347","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}
Pub Date : 2015-01-07DOI: 10.1179/2055075814Y.0000000010
Glenn Jones
Abstract Computational results are presented from density function theory (DFT) that describe the reactivity of Al and early transition metal doped, sponge Ni catalysts. To develop an understanding of the catalytic activity of these materials, the direct reduction of acetaldehyde has been studied as a test system. Use of the scaling paradigm proposed by Norskov and co-worker shows the influence of dopant atoms upon the atomic adsorption energy of C and O and consequently adsorption energies of reaction intermediates. Construction of a simple kinetic model (parameterized from DFT) demonstrates that the presence of Al improves catalytic performance of carbonyl hydrogenation by increasing the reactivity towards O containing molecules, whilst at the same time decreasing the affinity towards C. Comparison is made to acetylene hydrogenation, where the activity is dependent on the C affinity of the catalysts. It is thus suggested that should one desire to selectively hydrogenate a carbonyl group in the presence of an alkene then the use of early transition metal dopants may facilitate this selectivity. Alternatively, one could use a dopant that is able to reduce the affinity for C but maintains a high O affinity. The origin of the activity change due to doping is shown to be the intrinsic electronic structure of the dopant rather than a perturbation of the lattice constant due to the dopant atom.
{"title":"Origin of catalytic activity in sponge Ni catalysts for hydrogenation of carbonyl compounds","authors":"Glenn Jones","doi":"10.1179/2055075814Y.0000000010","DOIUrl":"https://doi.org/10.1179/2055075814Y.0000000010","url":null,"abstract":"Abstract Computational results are presented from density function theory (DFT) that describe the reactivity of Al and early transition metal doped, sponge Ni catalysts. To develop an understanding of the catalytic activity of these materials, the direct reduction of acetaldehyde has been studied as a test system. Use of the scaling paradigm proposed by Norskov and co-worker shows the influence of dopant atoms upon the atomic adsorption energy of C and O and consequently adsorption energies of reaction intermediates. Construction of a simple kinetic model (parameterized from DFT) demonstrates that the presence of Al improves catalytic performance of carbonyl hydrogenation by increasing the reactivity towards O containing molecules, whilst at the same time decreasing the affinity towards C. Comparison is made to acetylene hydrogenation, where the activity is dependent on the C affinity of the catalysts. It is thus suggested that should one desire to selectively hydrogenate a carbonyl group in the presence of an alkene then the use of early transition metal dopants may facilitate this selectivity. Alternatively, one could use a dopant that is able to reduce the affinity for C but maintains a high O affinity. The origin of the activity change due to doping is shown to be the intrinsic electronic structure of the dopant rather than a perturbation of the lattice constant due to the dopant atom.","PeriodicalId":43717,"journal":{"name":"Catalysis Structure & Reactivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1179/2055075814Y.0000000010","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"65872422","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}
Pub Date : 2015-01-07DOI: 10.1179/2055075814Y.0000000008
M. Nadeem, I. Majeed, Geoffrey I N Waterhouse, H. Idriss
Abstract The effect of Au particle size and loading (over TiO2 anatase and rutile) on the reaction selectivity and conversion of ethanol has been studied using temperature programmed desorption. The addition of Au onto TiO2 had three main effects on the reaction. First, a gradual decrease is observed in the reaction selectivity of the dehydration (to ethylene) in favor of dehydrogenation (to acetaldehyde) with increasing Au loading on both polymorphs of TiO2. Second, a gradual decrease is seen in the desorption temperature of the main reaction products also with increasing Au loading. Third, secondary reaction products [mainly C4 (crotonaldehyde, butene, furan) and C6 (benzene) hydrocarbons] increased considerably with increasing Au loading reaching about 60% for benzene for the 8 wt-%Au/TiO2 anatase. An inverse relationship between the interface lengths of Au particles on TiO2 and desorption temperatures of reaction products is found.
{"title":"Study of ethanol reactions on H2 reduced Au/TiO2 anatase and rutile: effect of metal loading on reaction selectivity","authors":"M. Nadeem, I. Majeed, Geoffrey I N Waterhouse, H. Idriss","doi":"10.1179/2055075814Y.0000000008","DOIUrl":"https://doi.org/10.1179/2055075814Y.0000000008","url":null,"abstract":"Abstract The effect of Au particle size and loading (over TiO2 anatase and rutile) on the reaction selectivity and conversion of ethanol has been studied using temperature programmed desorption. The addition of Au onto TiO2 had three main effects on the reaction. First, a gradual decrease is observed in the reaction selectivity of the dehydration (to ethylene) in favor of dehydrogenation (to acetaldehyde) with increasing Au loading on both polymorphs of TiO2. Second, a gradual decrease is seen in the desorption temperature of the main reaction products also with increasing Au loading. Third, secondary reaction products [mainly C4 (crotonaldehyde, butene, furan) and C6 (benzene) hydrocarbons] increased considerably with increasing Au loading reaching about 60% for benzene for the 8 wt-%Au/TiO2 anatase. An inverse relationship between the interface lengths of Au particles on TiO2 and desorption temperatures of reaction products is found.","PeriodicalId":43717,"journal":{"name":"Catalysis Structure & Reactivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1179/2055075814Y.0000000008","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"65871844","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}
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