- Highly-selective solvent-free catalytic isomerization of α-pinene to camphene over reusable titanate nanotubes
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Titanate nanotubes, prepared by the hydrothermal reconstitution and modification with hydrochloric acid, were tested as solid acid catalysts in the isomerization of α-pinene under solvent free conditions. The results showed that titanate nanotubes have be
- Huang, Geng,Liu, Jian,Su, Shengpei,Yin, Dulin,Zhou, Shuolin
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Read Online
- Monoterpenes etherification reactions with alkyl alcohols over cesium partially exchanged Keggin heteropoly salts: effects of catalyst composition
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In this work, cesium partially exchanged Keggin heteropolyacid (HPA) salts were prepared, characterized, and evaluated as solid catalysts in monoterpenes etherification reactions with alkyl alcohols. A comparison of the activity of soluble HPAs and their insoluble cesium salts showed that among three different Keggin anions the phosphotungstate was the most efficient catalyst. Assessments on the effects of the level of the protons exchange by cesium cations demonstrated that Cs2.5H0.5PW12O40 solid salt was the most active and selective phosphotungstate catalyst, converting β-pinene to α-terpinyl methyl ether. The influences of the main reaction parameters such as reaction temperature, time, catalyst load, substrate nature (i.e., alcohols and monoterpenes) were investigated. We have demonstrated that the simultaneous presence of the cesium ions and protons in the catalyst plays an essential role, being the 2.5–0.5 the optimum molar ratio. The Cs2.5H0.5PW12O40 salt was efficiently recovered and reused without loss of catalytic activity. Graphic abstract: [Figure not available: see fulltext.]
- da Silva, Márcio José,Lopes, Neide Paloma Goncalves,Ferreira, Sukarno Olavo,da Silva, Rene Chagas,Natalino, Ricardo,Chaves, Diego Morais,Texeira, Milena Galdino
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p. 153 - 168
(2020/07/21)
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- Discovering Monoterpene Catalysis Inside Nanocapsules with Multiscale Modeling and Experiments
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Large-scale production of natural products, such as terpenes, presents a significant scientific and technological challenge. One promising approach to tackle this problem is chemical synthesis inside nanocapsules, although enzyme-like control of such chemistry has not yet been achieved. In order to better understand the complex chemistry inside nanocapsules, we design a multiscale nanoreactor simulation approach. The nanoreactor simulation protocol consists of hybrid quantum mechanics-molecular mechanics-based high temperature Langevin molecular dynamics simulations. Using this approach we model the tail-to-head formation of monoterpenes inside a resorcin[4]arene-based capsule (capsule I). We provide a rationale for the experimentally observed kinetics of monoterpene product formation and product distribution using capsule I, and we explain why additional stable monoterpenes, like camphene, are not observed. On the basis of the in-capsule I simulations, and mechanistic insights, we propose that feeding the capsule with pinene can yield camphene, and this proposal is verified experimentally. This suggests that the capsule may direct the dynamic reaction cascades by virtue of π-cation interactions.
- Pahima, Efrat,Zhang, Qi,Tiefenbacher, Konrad,Major, Dan T.
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p. 6234 - 6246
(2019/04/25)
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- A porous Br?nsted superacid as an efficient and durable solid catalyst
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The development of catalysts able to assist industrial chemical transformations is a topic of high importance. In view of the versatile catalytic capabilities of acid catalysts, extensive research efforts are being made to develop porous superacid materials with a high density of accessible active sites to replace molecular acid catalysts. Herein, we report the rational development of a porous Br?nsted superacid by combining important elements that target high strength acidity into one material, as demonstrated by grafting the sulfonic acid group onto a highly fluorinated porous framework, where the acid strength and stability are greatly enhanced by an electron-withdrawing environment provided by the polymer backbone, reminiscent of that seen in Nafion resin. In addition, the densely arranged acid groups that are confined in the three-dimensional nanospace facilitate the transfer of hydrons, thereby further increasing the acidity. By virtue of the pore structure and strong acidity, this system exhibits excellent performance for a wide range of reactions, far outperforming commercial acid resins under repeated batch and flow reaction conditions. Our findings demonstrate how this synthetic approach may instruct the future design of heterogeneous acid catalysts with advantageous reaction capabilities and stability.
- Sun, Qi,Hu, Kewei,Leng, Kunyue,Yi, Xianfeng,Aguila, Briana,Sun, Yinyong,Zheng, Anmin,Meng, Xiangju,Ma, Shengqian,Xiao, Feng-Shou
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supporting information
p. 18712 - 18719
(2018/10/15)
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- Bifunctional catalyst Pd-Al-MCM-41 for efficient dimerization-hydrogenation of β-pinene in one pot
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A new type of bimetallic palladium and aluminum incorporated mobile crystalline materials (Pd-Al-MCM-41) as bifunctional catalysts has been hydrothermally synthesized. Characterization shows that these molecular materials exhibit an ordered mesoporous structure, high surface area and a good dispersion of palladium in the frame. The catalytic activity of the Pd-Al-MCM-41 for the dimerization-hydrogenation reaction system of β-pinene in one pot has been systematically studied. Pd0.5-Al30-MCM-41 (SiO2/Al2O3 = 30, 0.5 wt% palladium content) was found to be the best catalyst which gave a dimer yield of up to 64.7%. It is worth noting that palladium shows a good synergic catalytic effect with aluminum in the dimerization reaction and enhances the dimerization yield. Furthermore, the bifunctional catalyst displayed a good activity over 4 runs.
- Zhang, Song,Xu, Chao,Zhai, Guoqing,Zhao, Mingliang,Xian, Mo,Jia, Yuxiang,Yu, Zongjiang,Liu, Fusheng,Jian, Fangfang,Sun, Weizhi
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p. 47539 - 47546
(2017/10/19)
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- Catalytic and physicochemical properties of modified natural clinoptilolite
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A natural specimen from the deposit at Ku?in (Slovakia), rich in clinoptilolite type zeolite, was dealuminated using HCl solutions of increasing concentration (0.05-11.5 M). The samples were characterized by XRD, sorption of nitrogen, TPD of ammonia, FT IR and NMR spectroscopies. The preparations modified under mild conditions (acid concentration, temperature of dealumination) retained largely their crystallinity and acidity, and were active in the liquid phase isomerization of α-pinene. Upon more severe treatments, the samples became partially amorphous and lost their catalytic activity. The kinetics of α-pinene isomerization was studied over the most active catalysts. The reaction rate constants and apparent energies of activation were obtained. Initial reaction rates over the clinoptilolite type catalysts were compared with other acidic catalysts, including ferrierite-type zeolites.
- Dziedzicka, Anna,Sulikowski, Bogdan,Ruggiero-Miko?ajczyk, Ma?gorzata
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- Acidic functionalized ionic liquids as catalyst for the isomerization of α-pinene to camphene
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An acidic functionalized ionic liquids (ILs) [HSO3-(CH2)3-NEt3]Cl-ZnCl2 was synthesized and used to catalyze the isomerization of α-pinene in a homogeneous system. The optimum conditions for isomerization were obtained as follows: n(α-pinene):n(ILs) = 9:1, reaction temperature 140 °C, and reaction time 4 h, α-pinene 0.04 mol. Under the optimal conditions, the conversion of α-pinene was 97.6 % and the selectivity for camphene could reach 64.8 %. In addition, the catalyst could be easily separated by centrifugation after the isomerization completely finished. When the ILs were repeatedly used for four times, the conversion of α-pinene and the selectivity for camphene were still excellent, indicating the superb recycle ability of the acidic functionalized ILs catalyst.
- Liu, Yue,Li, Lu,Xie, Cong Xia
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p. 559 - 569
(2016/04/26)
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- Selective methoxylation of α-pinene to α-terpinyl methyl ether over Al3+ ion-exchanged clays
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In this study, we report the use of clay-based catalysts in the methoxylation of α-pinene, for the selective synthesis of α-terpinyl methyl ether, TME. The main reaction products and intermediates were identified by GC-MS. The reaction conditions (stirring rate and catalyst load) that afford a kinetic regime were established. SAz-1 (Cheto, Arizona, USA) source clay and a montmorillonite (SD) from Porto Santo, Madeira Archipelago, Portugal, were modified by ion-exchange with Al3+ to produce catalysts with markedly different acidities and textural properties. The catalysts based on the high layer-charge SAz-1 montmorillonite proved to be the most active. Ion-exchange with Al3+, followed by thermal activation at 150°C, afforded the highest number of Br?nsted acid sites - a significant proportion of which were located in the clay gallery - and this coincided with the maximum catalytic activity. The influence of various reaction conditions, to maximize α-pinene conversion and selectivity, was studied over AlSAz-1. When the reaction was performed for 1 h at 60°C, the conversion reached 65% with 65% selectivity towards the mono-ether, TME. Similar conversions and selectivities required up to 50 h over zeolites and other solid acid catalysts. The kinetic dependencies of this reaction on temperature and reagent concentration, over the selected clays were also investigated. It was established that, in the temperature and reagent concentration regime studied, the reaction was first order with respect to α-pinene. The apparent activation energies over the two catalysts, calculated from Arrhenius plots, were almost identical at 72 kJ mol-1.
- Catrinescu,Fernandes,Castilho,Breen
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p. 171 - 179
(2015/05/05)
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- Effect of high-temperature calcination on the generation of Bronsted acid sites on WO3/Al2O3
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The acid properties of a series of alumina-supported tungsten oxide (WO3/Al2O3) catalysts with loadings of 5-50 wt% WO3 calcined at various temperatures were investigated by acid-catalyzed reactions (benzylation of anisole and isomerization of α-pinene) and FTIR spectroscopy. The relationships between acid properties, structures, and catalytic performances were evaluated. Both the catalytic activity and amount of Bronsted acid sites depend on the calcination temperature and WO3 loading. High-temperature calcination (1123 K) generated Bronsted acid properties, and 20 wt% WO 3/Al2O3 calcined at 1123 K exhibited the highest activity among the catalysts tested. The activities for the benzylation of anisole and α-pinene isomerization over WO3/Al 2O3 calcined at 1123 K were proportional to the Bronsted acidity, which indicates that these reactions occurred on the Bronsted acid sites. Tungsten oxide, which has distorted octahedral symmetry, was loaded as 2D monolayer domains below 20 wt%, and these domains covered most of the alumina surface at 20 wt%. If the WO3 loading was sufficient to form 2D tungsten oxide monolayer sheets (>20 wt%), some of the Bronsted acid sites on WO3/Al2O3 were obscured by monoclinic WO3 that has no Bronsted acid sites, which resulted in a decrease of the catalytic activity. This suggests that Bronsted acid sites are generated at the boundaries between tungsten oxide monolayer domains.
- Kitano, Tomoyuki,Hayashi, Tomohiro,Uesaka, Toshio,Shishido, Tetsuya,Teramura, Kentaro,Tanaka, Tsunehiro
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p. 2011 - 2020
(2014/08/05)
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- Hydrothermal synthesis of single-crystalline mesoporous beta zeolite assisted by N-methyl-2-pyrrolidone
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Highly crystalline beta zeolite with large intracrystalline mesopores has been facilely synthesized via the introduction of low-cost N-methyl-2- pyrrolidone (NMP) into common TEAOH-based zeolite synthesis mixtures, which exhibited remarkably higher catalytic activity contrast than conventional porous catalysts (ZSM-5, beta and Al-MCM-41) in acid-catalyzed reactions involving large molecules.
- Liu, Lijia,Wang, Hongbin,Wang, Runwei,Zeng, Shangjing,Ni, Ling,Zhang, Daliang,Zhu, Liangkui,Zou, Houbing,Qiu, Shilun,Zhang, Zongtao
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p. 39297 - 39300
(2014/11/08)
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- Superacidity in sulfated metal-organic framework-808
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Superacids, defined as acids with a Hammett acidity function H0 ≤ -12, are useful materials, but a need exists for new, designable solid state systems. Here, we report superacidity in a sulfated metal-organic framework (MOF) obtained by treating the microcrystalline form of MOF-808 [MOF-808-P: Zr6O5(OH)3- (BTC)2(HCOO)5(H2O)2, BTC = 1,3,5-benzenetricarboxylate] with aqueous sulfuric acid to generate its sulfated analogue, MOF-808-2.5SO4 [Zr6O5(OH)3(BTC)2- (SO4)2.5(H2O)2.5]. This material has a Hammett acidity function H0 ≤ -14.5 and is thus identified as a superacid, providing the first evidence for superacidity in MOFs. The superacidity is attributed to the presence of zirconiumbound sulfate groups structurally characterized using single-crystal X-ray diffraction analysis.
- Jiang, Juncong,Gándara, Felipe,Zhang, Yue-Biao,Na, Kyungsu,Yaghi, Omar M.,Klemperer, Walter G.
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supporting information
p. 12844 - 12847
(2015/12/26)
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- Synthesis of mesoporous Beta and Sn-Beta zeolites and their catalytic performances
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Mesoporous Beta zeolite has been successfully prepared through hydrothermal synthesis in the presence of cationic ammonium-modified chitosan as the meso-template. Through a subsequent solid-gas reaction between highly dealuminated mesoporous Beta zeolite and SnCl4 steam at an elevated temperature, mesoporous Sn-Beta has been facilely obtained. It was revealed that the addition of cationic chitosan induced the nanocrystal aggregation to particle sizes of ～300 nm, giving rise to the intercrystalline/interparticle mesoporosity. In the Sn-implanting procedure, Sn species were demonstrated to be doped into the framework of the resulting mesoporous Beta zeolite in a tetrahedral environment without structural collapse. Due to the micro/mesoporous structures, both mesoporous Beta and Sn-Beta exhibited superior performances in α-pinene isomerization, Baeyer-Villiger oxidation of 2-adamantanone by hydrogen peroxide and the isomerization of glucose in water, respectively. the Partner Organisations 2014.
- Jin, Junjiang,Ye, Xinxin,Li, Yongsheng,Wang, Yanqin,Li, Liang,Gu, Jinlou,Zhao, Wenru,Shi, Jianlin
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p. 8196 - 8204
(2014/06/09)
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- Synthesis of zirconia porous phosphate heterostructures (Zr-PPH) for Prins condensation
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Porous phosphate heterostructure materials with zirconia galleries have been prepared. Their acid properties were studied via 2,6-di-tert-butyl-pyridine adsorption, infrared spectra of pyridine adsorption and potentiometric titration. The samples prepared in alcohol media are more thermal stable than those prepared in aqueous media. They are very active and selective for the Prins condensation of β-pinene with paraformaldehyde because of large amount of Lewis acid sites as well as proper L/B ratio. The selectivity towards Nopol can be further improved by ion-exchanging with sodium cations, due to the elimination of Br?nsted acid sites which suppresses the by-reactions such as isomerization of β-pinene.
- Wang, Xueyan,Wang, Tao,Hua, Weiming,Yue, Yinghong,Gao, Zi
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- Alkylation of 2,4-dimethylphenol with (+)-α- and (-)-β-pinenes in the presence of aluminum xylenolate
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Alkylation of 2,4-dimethylphenol with (+)-α- and (-)-β-pinenes in the presence of aluminum 2,4-dimethylphenoxide generated in situ led to the formation of mixtures of products, from which optically active compounds were isolated. The structure of 2-bornyl
- Chukicheva,Krylova,Buravlev,Suponitskii,Kutchin
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p. 589 - 595
(2014/06/10)
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- Continuous production of the renewable ρ-cymene from α-pinene
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The aim of this work was to demonstrate the feasibility to produce ρ-cymene, an important commodity chemical, in a continuous, one-pot reaction system from abundant α-pinene, available e.g. as a by-product of pulping industry. The isomerization reactions of α-pinene over bimetallic heterogeneous catalysts, 3 and 5 wt% Pd-Zn (1:1, 1:4, 4:1, 1:0, and 0:1), supported on Al-SBA15 were studied. The principal reaction products were identified as ρ- and m-cymenes, limonene, camphene, and ρ-menthene, respectively. The highest concentration of ρ-cymene reached 77 wt% under the optimized reaction conditions: 300 C and α-pinene feed of 0.03 mL/min. Two main reaction pathways toward ρ- and m-cymenes were described, and a mechanistic kinetic model, based on a plausible reaction network in line with Langmuir-Hinshelwood approach, was developed. The catalyst characterization revealed the reduction in Pd(II) sites, catalyst coking, and decline of surface area over the course of time. The catalyst recovery and reuse was addressed.
- Golets,Ajaikumar,Mohln,Waerna,Rakesh,Mikkola
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p. 305 - 315
(2013/09/24)
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- Synthesis of terpinyl acetate using octadecylamine ethoxylate ionic liquids as catalysts
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Terpinyl acetate, an important natural flavor, can be synthesized by esterification of α-pinene with acetic acid under acidic conditions. In this work, seven acidic ionic liquids were first synthesized, using octadecylamine ethoxylates (AC 1810, AC 1815, AC 1820, and AC 1830) as the cations, and characterized by FT-IR, 1H NMR, and 13C NMR spectroscopy. The ionic liquids were then used as catalysts in the synthesis of terpinyl acetate. The effect of preparation conditions on catalyst performance was examined. It was found that the acidic ionic liquid 1-(3-sulfonic acid)propyl-3-poly(ethylene glycol) octadecylamine polyoxyethylene ether tetrafluoroborate ([PAC1815]+[BF4]-) was an excellent catalyst for synthesis of terpinyl acetate. The effects of the conditions used for preparation of terpinyl acetate were examined in detail, and the optimum preparation conditions were obtained. Under the optimum conditions, the yield of terpinyl acetate reached 35.70 %. When the catalyst was reused for the 5th time, the yield of terpinyl acetate was still 32.00 %. The results showed that effective separation and recycling of catalyst could contribute to developing a new strategy for synthesis of terpinyl acetate.
- Li, Lu,Liu, Shiwei,Shi, Yanjing,Yu, Shitao,Xie, Congxia,Qi, Chunjie
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p. 2095 - 2105
(2013/06/05)
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- Supported H4SiW12O40 catalysts for α-pinene isomerization
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The heterogeneous isomerization of α-pinene was studied at 100, 130 and 160°C using 10% supported H4SiW12O40 (SiW) on SiO2, TiO2 and HZSM-5. The effect of the reaction temperature and the concentratio
- Szuecs-Balazs, Jozsef-Zsolt,Coros, Maria,Woiczechowski-Pop, Adrian,Blanita, Gabriela,Vlassa, Mircea
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p. 1208 - 1217
(2012/11/13)
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- Microwave-assisted α-pinene acidic catalytic isomerisation
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A comparative study of microwave assisted α-pinene acidic catalytic isomerisation reactions with near-critical water procedure under microwave irradiation is presented. This study can be performed because in both cases the mechanism is similar, namely an acidiccatalyzed rearrangement. The non-critical method technique is milder using a lower temperature and pressure and a shorter reaction time than near-critical water conditions. The general aspect of the selectivity of the reaction products is changed, being higher for α-terpinolene and γ-terpinolene and lower for limonene and camphene compared to the non-critical conditions.
- Szuecs-Balazs, Jozsef Zsolt,Coros, Maria,Molnar, Diana,Vlassa, Mircea
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p. 209 - 213
(2013/03/13)
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- Liquid phase acetoxylation of α-pinene over Amberlyst-70 ion-exchange resin
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Heterogeneously-catalyzed and solvent-catalyzed liquid phase acetoxylation of α-pinene with acetic acid acting as both a solvent and a reagent was studied. Both solvent-catalyzed and catalytic experiments were carried out and various reaction conditions were studied. The influence of temperature, pressure, solvent and gas milieu were taken into account. Bornyl, fenchyl, verbenyl as well as α-terpinyl acetates, limonene, camphene and γ-terpinene were found among reaction products. The addition of the catalyst allowed for maximization of the yield of bornyl acetate. The predominant products obtained were α-terpinyl, verbenyl and bornyl acetates. The reaction pathways were identified and evaluated. The aim of this work was to study the feasibility of batch acetoxylation of α-pinene. The analysis of the complex product distribution is not trivial and, consequently, resolving the reaction network was important. The optimized reaction conditions were searched for aiming at an efficient conversion of α-pinene to a mixture of valuable products.
- Golets,Ajaikumar,Blomberg,Grundberg,W?rn?,Salmi,Mikkola
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scheme or table
p. 43 - 50
(2012/10/18)
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- Transformations of monoterpene hydrocarbons on ferrierite type zeolites
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Transformations of α-pinene and limonene over hydrogen forms of commercial ferrierite type zeolites of different origin (Tosoh Corp. and Zeolyst Intern.) have been studied in the liquid phase at 313-363 K. The catalysts were characterized by XRD, sorption
- Rachwalik,Hunger,Sulikowski
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scheme or table
p. 98 - 105
(2012/07/14)
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- Isomerization of α-Pinene over Immobilized AlCl3 Catalysts
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Immobilized AlCl3 catalysts supported on γ-Al2O3 and SiO2 were prepared by a two-step vapor method and their catalytic activities were evaluated by the liquid phase isomerization of α-pinene for the first time. The results showed that the immobilized AlCl3 catalyst gave excellent catalytic performance for the isomerization of α-pinene. The AlCl3/SiO2 catalyst gave 98.4% conversion of α-pinene and 93.7% selectivity for the main products such as camphene, limonene, and terpinolene at a reaction temperature of 40 °C. The AlCl3/γ-Al2O3 catalyst gave much higher activity, 95.5% conversion of α-pinene and 94.4% selectivity for the main products even at temperatures as low as 30 °C. The excellent catalytic performance of the immobilized AlCl3 catalysts is due to their strong acidity.
- Wu, Yihui,Tian, Fuping,He, Min,Cai, Tianxi
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p. 1138 - 1142
(2016/04/19)
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- α-Pinene isomerisation over heteropoly acid catalysts in the gas-phase
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The isomerisation of α-pinene was studied in the gas phase over solid heteropoly acid (HPA) catalysts in a fixed-bed continuous flow reactor at 200 °C and ambient pressure. The catalysts included bulk and SiO 2-supported H3PW12O40 and bulk Cs2.5H0.5PW12O40 possessing strong Br?nsted acid sites, as well as composites prepared by supporting 15 wt% H3PW12O40 on Nb2O5, ZrO2 and TiO2 possessing both Br?nsted and Lewis acid sites of moderate strength. The reaction yielded camphene as the main product in a mixture with monoterpene by-products such as limonene, terpinolenes, terpinenes, β-pinene, p-cymene and others. The HPA catalysts with strong Br?nsted acid sites exhibited high initial activities, but suffered from catalyst deactivation, resulting in low camphene yields. Conversely, the HPA catalysts supported on Nb2O5, ZrO 2 and TiO2, although weaker acids, showed more stable performance in α-pinene isomerisation. The HPA catalyst supported on TiO2 gave a camphene yield of 51% and a total camphene and limonene yield of 58%.
- Alsalme, Ali,Kozhevnikova, Elena F.,Kozhevnikov, Ivan V.
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experimental part
p. 219 - 224
(2011/12/15)
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- Selective vapour-phase α-pinene isomerization to camphene over gold-on-alumina catalyst
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The vapour-phase isomerization of α-pinene for the first time was studied over a supported Au catalyst. α-pinene was isomerized to camphene over the 2.2% Au/γ-Al2O3 catalyst at 463-483 K using a solution of the reagent in n-octane as the initial reaction mixture and H2 or N2 as a carrier gas. Under these conditions, the selectivity to camphene reaches 60-80% at 99.9% conversion of α-pinene. The reaction is found to be first-order with respect to α-pinene, the apparent activation energy being similar to that observed with the conventional TiO2 catalyst. The prominent catalyst deactivation has been observed at increased α-pinene concentrations in the inlet reaction mixture (≥4 vol% in n-octane solution). According to HRTEM and TPO results, the deactivated catalyst contains the carbonaceous deposits that may block the catalyst surface. Almost complete regeneration was done in flowing O2 at temperature up to 923 K required to totally eliminate the coke deposits.
- Simakova,Solkina, Yu.S.,Moroz,Simakova,Reshetnikov,Prosvirin,Bukhtiyarov,Parmon,Murzin, D.Yu.
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experimental part
p. 136 - 143
(2010/11/18)
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- Desilication of ZSM-5 and ZSM-12 zeolites: Impact on textural, acidic and catalytic properties
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Two zeolites of different topology: ZSM-5 and ZSM-12 were subjected to desilication in the NaOH solutions of increasing concentrations. Changes in the properties of modified zeolites were investigated by several methods ( 29Si and 27
- Gil, Barbara,Mokrzycki, ?ukasz,Sulikowski, Bogdan,Olejniczak, Zbigniew,Walas, Stanis?aw
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experimental part
p. 24 - 32
(2010/10/19)
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- Methoxylation of α-pinene over heteropolyacids immobilized in silica
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The methoxylation of α-pinene was studied using heteropolyacids immobilized on silica as catalysts, at 60 °C, being the α-terpinyl methyl ether the main product. Tungstophosphoric acid (PW), molybdophosphoric acid (PMo), tungstosilicic acid (SiW) and molybdosilicic acid (SiMo) were immobilized on silica by sol-gel method. It was observed that the catalytic activity of the silica-supported heteropolyacids decreases in the series: PW2_S > SiW_S > PMo_S > SiMo_S. A series of PW immobilized on silica with different PW loading were prepared. It was observed that the catalytic activity increases with the amount of PW immobilized on silica. However, at high amount of PW on silica, a decrease of the catalytic activity was observed. Good values of selectivity to α-terpinyl methyl ether (about 60% near complete conversion) were obtained with all catalysts. Catalytic stability of the PW2_S was evaluated by performing consecutive batch runs with the same catalyst sample. After the third batch it was observed a stabilisation of the initial activity. A kinetic model was developed assuming that the α-pinene is consumed according to the parallel reaction network. It was observed that the kinetic model fits the experimental concentration data quite well.
- Pito,Matos,Fonseca,Ramos,Vital,Castanheiro
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body text
p. 140 - 146
(2010/10/01)
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- Photocatalytic removal of monoterpenes in the gas phase. Activity and regeneration
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We show the photocatalytic removal of various monoterpenes such as β-pinene, α-pinene, camphene and limonene in the gas phase as a function of the reaction temperature, from room temperature to 80°C, taking also into account the thermal catalytic isomeriz
- Salem, Ibtissam,Keller, Nicolas,Keller, Valerie
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experimental part
p. 966 - 973
(2010/04/23)
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- Structural studies of high dispersion H3PW12O 40/SiO2 solid acid catalysts
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Highly dispersed H3PW12O40/SiO2 catalysts with loadings between 3.6 and 62.5 wt% have been synthesised and characterised. The formation of a chemically distinct interfacial HPW species is identified by XPS, attributed to pertubation of W atoms within the Keggin cage in direct contact with the SiO2 surface. EXAFS confirms the Keggin unit remains intact for all loadings, while NH3 adsorption calorimetery reveals the acid strength >0.14 monolayers of HPW is loading invariant with initial ΔHads = ～-164 kJ mol-1. Lower loading catalysts exhibit weaker acidity which is attributed to an inability of highly dispersed clusters to form crystalline water. For reactions involving non-polar hydrocarbons the interfacial species where the accessible tungstate is highest confer the greatest reactivity, while polar chemistry is favoured by higher loadings which can take advantage of the H3PW 12O40 pseudo-liquid phase available within supported multilayers. the Owner Societies 2006.
- Newman, Andrew D.,Brown, D. Robert,Siril, Prem,Lee, Adam F.,Wilson, Karen
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p. 2893 - 2902
(2008/02/08)
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- Structure-reactivity correlations in sulphated-zirconia catalysts for the isomerisation of α-pinene
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A range of mesoporous sulphated zirconias with tuneable structural and catalytic properties have been prepared by direct impregnation. The surface sulphate coverage can be readily varied, achieving a maximum value of ～0.2 monolayers. High-temperature calcination induces the crystallisation of tetragonal zirconia while suppressing the monoclinic phase and enhances surface acidity. Superacid sites only appear above a critical threshold SO4 coverage of 0.08 mL (corresponding to 0.44 wt% total S). Sulphated zirconias show good activity towards α-pinene isomerisation of under mild conditions. Conversion correlates with the number Bronsted acid sites, while the selectivity towards mono- versus polycyclic products depends on the corresponding acid site strength; superacidity promotes limonene formation over camphene.
- Ecormier, Muriel A.,Wilson, Karen,Lee, Adam F.
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- Hydrogenation and Skeleton Rearrangements of α-Pinene on Heterogeneous Catalysts
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Hydrogenation and isomerization of α-pinene on heterogeneous catalysts were studied, and conditions were found for hydrogenation of pinene to cis-pinane on nickel catalysts and for its dehydrogenation to p-cymene on decationized zeolite Y.
- Bazhenov,Kas'yanova,Bokin,Kutepov,Khazipova,Travkin,Shchadneva,Khusnutdinov,Dzhemilev
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p. 234 - 237
(2007/10/03)
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- Thermal transformation of monoterpenes within thionin-supported zeolite Na-Y. Acid-catalyzed or electron transfer-induced?
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Several monoterpenes (monocyclic, bicyclic or acyclic) isomerize and finally transform to p-cymene in the dark upon loading within thionin-supported zeolite Na-Y. The same reactions occur in Na-Y dried under the same conditions as thionin/Na-Y. It is postulated that the thermal treatment of Na-Y generates 'electron holes' (probably acidic sites). The transformation of monoterpenes occurs more likely via an electron transfer-induced reaction subordinated to the occurrence of the acidic sites. The radical cation of the more thermodynamically stable monoterpene, α-terpinene, eventually dehydrogenates to p-cymene. For comparison, the same reactions were performed within methyl viologen-supported Na-Y. Copyright
- Stratakis, Manolis,Stavroulakis, Manolis,Sofikiti, Nikoletta
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- Reaction of α-pinene with haloacetic acids
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The reactions of α-pinene with chloro-, bromo-, and trichloroacetic acids, accompanied by isomerization of α-pinene, were studied.
- Radbil',Zolin,Shkapova,Radbil'
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p. 310 - 314
(2007/10/03)
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- DERMATOLOGICAL COMPOSITIONS AND METHODS
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Disclosed are methods and compositions for regulating the melanin content of mammalian melanocytes; regulating pigmentation in mammalian skin, hair, wool or fur; treating or preventing various skin and proliferative disorders; by administration of various compounds, including alcohols, diols and/or triols and their analogues.
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- Dehydration of Alcohols Catalysed by Heteropolyacids Supported on Silica
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Keggin type heteropolyacids supported on silica efficiently dehydrate secondary and tertiary alcohols under mild conditions and in good yields to afford the correspondent alkenes.
- Alesso, Elba,Torviso, Rosario,Finkielsztein, Liliana,Lantano, Beatriz,Moltrasio, Graciela,Aguirre, Jose,Vazquez, Patricia,Pizzio, Luis,Caceres, Carmen,Blanco, Mirta,Thomas, Horacio
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p. 1232 - 1245
(2007/10/03)
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- Acid-catalyzed alkoxylation and hydration of camphene
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Camphene alkoxylation in the presence of various acid catalysts was studied. With heteropolyacids H4SiW12O40 and H3PW12O40 as catalyst the reaction afforded in high yield alkyl isobornyl ethers The mechanism of camphene hydration in water - alcohol mixtures catalyzed with acids was discussed.
- Radbil',Kulikov,Sokolova,Kartashov,Zolin,Radbil'
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p. 1618 - 1622
(2007/10/03)
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- Treatment of neurodegenerative diseases
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Disclosed are methods for increasing the differentiation of mammalian neuronal cells for purposes of treating neurodegenerative diseases or nerve damage by administration of various compounds including alcohols, diols and/or triols and their analogues.
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- Monoterpene synthase activities in leaves of Picea abies (L.) Karst. and Quercus ilex L.
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In addition to direct ecological functions in the interaction of plants with the environment, the emission of monoterpenes, especially from the foliage of evergreen trees, is of great importance for the production of ozone and photochemical oxidants in the troposphere. In the present work, we established a reproducible non-radioactive standard enzyme assay and characterized monoterpene synthase activities in needles of Norway spruce (Picea abies (L.) Karst.) and in leaves of holm oak (Quercus ilex L.). In Norway spruce, the dominant monoterpenes formed were α-pinene, camphene, and to a lesser extent β-pinene and limonene. In holm oak, α-pinene, sabinene, and β-pinene were the main products, while limonene was a minor component. Under optimum conditions, in both Norway spruce and holm oak, monoterpene formation remained constant up to 180 min and 90 min, respectively, and varied with the buffer and Mg2+ and Mn2+ concentrations used. Optimum temperature for monoterpene synthase activity was 40°C in both species; optimal pH ranged between 6.5 and 7.5 in both species. Apparent Michaelis- constants for the substrate GDP were ca. 17.9 ± 5.1 μM for Norway spruce and ca. 69.4 ± 22.1 μM for holm oak. Molecular weight determination by FPLC indicated that the monoterpene synthases in Norway spruce and holm oak have native molecular weights of ca. 59 and 50 kDa, respectively. (C) 2000 Elsevier Science Ltd.
- Fischbach, Robert J.,Zimmer, Ina,Steinbrecher, Rainer,Pfichner, Andreas,Schnitzler, Joerg-Peter
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p. 257 - 265
(2007/10/03)
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- Alkoxylation and hydration of camphene in the presence of acid catalysts
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The alkoxylation of camphene in the presence of various acid catalysts is studied. Alkylisobornyl ethers are obtained in high yields if the heteropolyacids H4SiW12O40 and H3PW12O40 are used
- Radbil',Kulikov,Sokolova,Kartashov,Zolin,Radbil'
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p. 524 - 528
(2007/10/03)
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- Treatment of diseases mediated by the nitric oxide/cGMP/protein kinase G pathway
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Disclosed are methods and compositions for stimulating cellular nitric oxide (NO) synthesis, cyclic guanosine monophosphate levels (cGMP), and protein kinase G (PKG) activity for purposes of treating diseases mediated by deficiencies in the NO/cGMP/PKG signal transduction pathway, by administration of various compounds including alcohols, diols and/or triols and their analogues.
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- Isomerization of α-pinene over clinoptilolite
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The kinetics of the liquid-phase isomerization of α-pinene over a natural zeolite-clinoptilolite has been studied at 100-180°C and nitrogen pressures at 1-20 bar. Up to 80-85 wt% of conversion selectivity toward reaction products was constant with camphene and limonene as the main products. Only at relatively high conversions were other monocyclic and tricyclic products formed. The consumption rate of α-pinene followed first-order kinetics. Temperature dependence of the first-order kinetic constant obeyed Arrhenius dependence with the activation energy equal to 80.9 kJ/mol. Selectivities at particular conversions were seen to be independent of temperature and pressure. A reaction network and mechanism are advanced and the corresponding kinetic equations are derived. The kinetic model gave a good correlation between the theoretical and the experimental data.
- Allahverdiev, Ayaz I.,Irandoust, Said,Murzin, Dmitry Yu.
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p. 352 - 362
(2007/10/03)
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- Acidic Property of FSM-16. 2. Generation of Lewis Acid Sites and Catalysis
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Catalysis over Lewis acid sites on siliceous mesoporous FSM-16 was confirmed. Acidic property of FSM-16 was studied by pyridine TPD measurements, and catalyses of α-pinene isomerization and methylamine synthesis. FSM-16 possess both Br?nsted and Lewis acid sites, and another Lewis acid site formed on FSM-16 when a catalyst was pretreated above 873 K. α-Pinene isomerization was catalyzed over Br?nsted acid sites, the activity of which is the highest when FSM-16 is pretreated at 673 K. Lewis acid sites on FSM-16 catalyze methylamine synthesis, and the initial rates are enhanced with increasing pretreatment temperature up to 1273 K. The structure of FSM-16 was completely retained throughout a pretreatment at 1273 K and a reaction procedure for methylamine synthesis at 673 K.
- Yamamoto, Takashi,Tanaka, Tsunehiro,Inagaki, Shinji,Funabiki, Takuzo,Yoshida, Satohiro
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p. 6450 - 6456
(2007/10/03)
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- Generation of acid sites on silica-supported rare earth oxide catalysts: Structural characterization and catalysis for α-pinene isomerization
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Silica-supported rare earth oxide catalysts (Ln/SiO2; Ln = La, Ce, Pr, Sm, Eu, Tb, Yb and Y), loading amounts of which were 3.4 mmol g (support)- 1, were characterized by α-pinene isomerization, temperature-programmed desorption (TPD), Fourier transform infrared (FTIR), X-ray diffraction (XRD), X-ray absorption fine structure (XAFS), thermogravimetric-differential thermal analysis (TG-DTA) and Raman spectroscopy. In the lanthanoid series, the catalytic activity increased with atomic number from 57La to 70Yb, except for Ce. All the Ln/SiO2 catalysts, except for Ce, were amorphous. On the surface of the catalyst, Ln-O-Si and Ln-O-Ln linkages formed, the ratio of which varied with the loaded element. The ratio of Ln-O-Si linkage increases with stronger affinity among LnO(n) units and SiO4 tetrahedra, and the affinity depends on the size of Ln3+. With increasing ratio of Ln-O-Si to Ln-O-Ln linkage, the catalytic activity increases. Silica-supported yttrium oxide catalyst, the trivalent ion radius of which is quite similar to that of ytterbium, exhibited the same activity as that of Yb/SiO2. Raman spectroscopic characterization revealed that excess loading of Yb atoms on SiO2-support block Yb-O-Si linkage to form Yb2O3 fine particles. When Yb/SiO2 was pretreated at 1273 K, fine ytterbium silicate crystallites formed. Ln-O-Si linkage without a long-ranged ordering structure was the active site for α-pinene isomerization.
- Yamamoto, Takashi,Matsuyama, Takahiro,Tanaka, Tsunehiro,Funabiki, Takuzo,Yoshida, Satohiro
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p. 2841 - 2849
(2007/10/03)
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- An unprecedented elimination-driven migration: The reductive dihalobornane-camphene rearrangement
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An organometallic counterpart of the Wagner-Meerwein rearrangement, the incarnation of an carbocationic alkyl 1,2-migration, has now been discovered. However, the structural reorganization does not occur through carbanionic intermediates, but can only be brought about by a push-pull process via 1a (see scheme).
- Garamszegi, Laszlo,Schlosser, Manfred
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p. 3173 - 3175
(2007/10/03)
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- Liquid-phase isomerization of α-pinene on a natural clinoptilolite
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The liquid-phase isomerization of α-pinene on a suspended powder (50-100 μm) of a natural clinoptilolite is studied. It is found that thermoevacuation at 500°C decreases the catalyst's activity and selectivity. The surface acidity decreases, whereas the surface concentration of Fe2+ ions increases. The reaction mechanism is proposed.
- Allakhverdiev,Sokolova,Gunduz,Kul'kova
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p. 1647 - 1650
(2007/10/03)
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- Acidic property of FSM-16
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Siliceous FSM-16 possesses acid sites to catalyze but-1-ene isomerization to produce but-2-ene (cis/trans = 1.4-1.7) at 323 K and 2,6,6- trimethylbicyclo[3.1.1]hept-2-ene (α-pinene) isomerization at 303 K. Catalytic activity was dependent upon heat treatment and reached a maximum at 673 K. The maximum acid strength was invariably H0 = -3.0 independent of the pretreatment temperatures. The acidity was much reduced by calcination at higher temperatures, but restored by water treatment at 353 K as long as the FSM-16 retained its structure.
- Yamamoto, Takashi,Tanaka, Tsunehiro,Funabiki, Takuzo,Yoshida, Satohiro
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p. 5830 - 5839
(2007/10/03)
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- Isomerization of α-pinene to camphene
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The catalytic isomerization reaction of α-pinene to camphene over a clinoptilolite catalyst was investigated in a batch reactor open to the atmosphere between 130 and 155°C. The catalyst was selective to the isomerization of α-pinene to camphene. The effects of several variables, such as reaction temperature, amount of catalyst, stirring speed and catalyst particle size, on the conversion of α-pinene and selectivity to camphene were determined. The reaction fits a first-order parallel reaction with rate constants of k1 = 3.020·10-2 e-33381.6/RT for the production of camphene and of k2 = 1.576·10-2 e-31096.53/RT for the production of limonene.
- Findik,Guenduez
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p. 1145 - 1151
(2007/10/03)
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- Reaction of Hydrazones with Methoxy(tosyloxy)iodobenzene (MTIB): Tosylate Formation under Oxidative Conditions
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Treatment of aromatic hydrazones 1 containing electron-withdrawing, reduction sensitive substituents with MTIB gives the corresponding tosylates 2 in high yield. When the tosylate is particularly reactive the thermodynamically more stable methyl ether 3 is isolated. Analogous reactions with DAIB give acetates 4 in high yield. Dialkyl hydrazones give olefinic products (e.g. 7 and 8). (+)-Camphor hydrazone 1k with either MTIB or DAIB gives both camphene 12 (major product) and tricyclene 11 (minor product) suggesting that a carbene pathway accounts for some of the material formed in these oxidations.
- Ramsden, Christopher A.,Rose, Helen L.
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- Synthesis of (±)-2,3,5-trichloro-4,4-dimethoxycyclopent-2-en-1-one
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At 20°C, (±)-1,3,4-trichloro-2-isobornyloxy-5,5-dimethoxycyclopentadiene slowly decomposes to give (±)-2,3,5-trichloro-4,4-dimethoxycyclopent-2-en-1-one.
- Kuznetsov,Torosyan,Vostrikov,Miftakhov
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p. 2658 - 2659
(2007/10/03)
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- Reactions of Thianthrene Cation Radical with Acyclic and Cyclic Alcohols
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Thianthrene cation radical perchlorate (Th(.+)*ClO4(-)) reacted readily with cycloalkanols (C5, C7, C8, and C12), alkan-2-ols (C3, C5, C6, and C8), 3-hexanol, neopentyl alcohol, a number of benzyl alcohols, dl- and (S)-1-phenylethanol, cyclopentyl- and cyclohexylmethanols, the exo- and endo-borneols, and norborneols.Reactions were carried out with an excess of the alcohol in acetonitrile solution containing 2,6-di-tert-butyl-4-methylpyridine.Products were alkenes, ethers, and N-substituted acetamides, depending on the structure of the alcohol.Thianthrene (Th) and its 5-oxide (ThO) were formed in equal amounts.The sum of amounts of products from the alcohol was equal to the amount of ThO.All reactions are interpretable on the basis of the ultimate formation and further reactions of a 5-alkoxythianthreniumyl ion (ROTh(+)).The predominant formation of nortricyclene from the norborneols is striking and is discussed.Swern-Moffatt-type oxidations of the alcohols were not observed.
- Shine, Henry J.,Yueh, Wang
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p. 3553 - 3559
(2007/10/02)
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Reaction of alkyl hydroperoxides (1(ary), 2(ary) or 3(ary)) upon tertiary alkyl trichloroacetimidates under acidic catalysis yielded unsymmetrical dialkyl peroxides with yields in the range 30-70%.
- Bourgeois,Montaudon,Maillard
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p. 2477 - 2484
(2007/10/02)
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