- Insights into the doping effect of rare-earth metal on ZnAl2O4 supported PtSn catalyzed isobutane dehydrogenation
-
Isobutane dehydrogenation is a vital route for the production of isobutene, an important substance for methyl tert-butyl ether. However, the reaction is typically performed at relatively low pressure and high temperature, resulting in a facilitated coke formation. Here, we used rare-earth metals (Y, La, Ce) as dopants to modify the ZnAl2O4 support and studied their effects on Pt-Sn catalyzed dehydrogenation of isobutane. Combining the experimental and theoretical results, it is demonstrated that while Y and La tend to incorporate into the matrix of ZnAl2O4, separate CeO2 phase could be easily formed on ZnAl2O4 surface, leading to a decrease in both amount and strength of the Lewis acid sites. And for the La-ZnAl2O4, because of the large local deformation, oxygen vacancy can be readily formed, and results in a lot acid sites in the subsurface layer available for reactions. Deactivation rates of the catalysts in isobutane dehydrogenation is found to linearly correlate with the Lewis acid amounts over the modified supports. Compared with the catalysts of Pt-Sn/ZnAl2O4, Pt-Sn/La-ZnAl2O4 and Pt-Sn/Y-ZnAl2O4, Pt-Sn/Ce-ZnAl2O4 exhibits superior catalytic performance due to the low coke contents and high Pt dispersion. These results may provide additional insights on the design and optimization of isobutane dehydrogenation catalysts by tailoring the composition and structure of oxide supports.
- Liu, Jianfeng,Zhou, Wei,Jiang, Dongyu,Wang, Dong,Wu, Wenhai,Wang, Yue,Ma, Xinbin
-
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- Stabilizing Oxygen Vacancies in ZrO2by Ga2O3Boosts the Direct Dehydrogenation of Light Alkanes
-
The conversion of light alkanes to olefins (e.g., ethylene, propylene, or butylene) is crucial to the chemical industry. ZrO2 with oxygen vacancies has recently been regarded as a promising catalyst for the direct dehydrogenation of light alkanes. However, the intrinsic mechanism of the effect of oxygen vacancies on catalytic performance has not been completely understood yet, and ZrO2 without promoters generally displays poor activity toward the direct dehydrogenation of light alkanes. In this work, we demonstrate that the oxygen vacancies in ZrO2 can be poisoned by H atoms during the dehydrogenation of light alkanes, and we report a strategy for stabilizing the oxygen vacancies in ZrO2 by Ga2O3. Experimental results and theoretical calculations indicate that ZrO2 with oxygen vacancies is responsible for dehydrogenation, while Ga2O3 prevents the poisoning of oxygen vacancies by dissociated hydrogen atoms which, in the absence of the Ga2O3 component, blocks further dehydrogenation. Consequently, the optimal Zr0.26Ga1 catalyst exhibits superior propane dehydrogenation performance to the industrial Pt-Sn catalyst, the state-of-the-art catalyst for the direct dehydrogenation of light alkanes. We anticipate this work may shed light on both the fundamental research of catalysis and the chemical industry.
- Cao, Muhan,Hu, Huicheng,Li, Youyong,Lifshitz, Yeshayahu,Lin, Haiping,Liu, Lijia,McLeod, John,Sham, Tsun-Kong,Tang, Zeyuan,Wang, Xuchun,Wu, Linzhong,Xu, Yong,Yang, Di,Zhang, Qiao
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p. 10159 - 10169
(2021/08/24)
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- Synthesis and catalytic application of nanorod-like FER-type zeolites
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Nanosize dimensions have an important impact on zeolite properties and catalytic performance in particular. Herein, we develop a direct synthesis route to obtain a nanosized nanorod-like ferrierite (FER) zeolite with the assistance of ammonium fluoride (NH4F) and employing a conventional structure-directing agent (pyrrolidine). The resultant nanorod-like FER zeolite crystals exhibit a greatly reduced diffusion path along the c-axis. The physicochemical properties of nanorod-like FER and its conventional micronsized plate-like counterpart were analyzed by N2 adsorption-desorption, 27Al, 1H, 29Si MAS NMR, NH3-TPD, and in situ D3-acetonitrile and pyridine adsorption followed by FTIR. The nanorod-like FER zeolite possesses superior characteristics in terms of a larger external area, better accessibility to the acid sites, and a larger number of pore mouths per unit crystal surface than the micron-sized counterpart synthesized without NH4F. The improved properties provide the nanorod-like FER zeolite with high selectivity and low deactivation rates in 1-butene skeletal isomerization. The thermogravimetry analysis (TGA) of the coke amounts revealed a better capability of coke tolerance of the nanorod-like FER zeolite. The in situ ultraviolet-visible (UV/Vis) and Fourier transform infrared spectroscopy (FTIR) spectroscopy investigations of the organic intermediates formed on FER zeolite catalysts during the catalytic reaction further verified the enhanced catalytic activity and stability of the nanorod-like FER zeolite.
- Dai, Weijiong,Deng, Xin,Guan, Naijia,Li, Landong,Ruaux, Valérie,Tai, Wenshu,Valtchev, Valentin,Wu, Guangjun
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p. 24922 - 24931
(2021/11/27)
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- METHOD FOR DEHYDRATING ALCOHOLS TO OBTAIN OLEFINS, INVOLVING A STEP OF CATALYST SELECTIVATION
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The invention relates to a process for dehydrating alcohols to olefins, comprising a reaction step and a catalyst selectivation step.
- -
-
Paragraph 0055-0077
(2021/03/19)
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- Effect of the pore structure of an active alumina catalyst on isobutene production by dehydration of isobutanol
-
An alumina catalyst was prepared by mixing and pinching with pseudo-boehmite, and the catalyst was reamed with polyethylene glycol. The catalysts prepared were characterized by means of XRD, mercury injection and NH3-TPD, and the dehydration properties of the catalysts prepared with different amounts of reamer were evaluated in a 10 mL fixed bed reactor with 5% water as a raw material. The results showed that the addition of reamer did not affect the crystal structure and the amount of acid of the catalyst. With the increase of the amount of reamer, the pore volume of the catalyst increased continuously, the number of large pores increased, the conversion rate of isobutanol increased, and the selectivity of isobutene remained basically unchanged. When the amount of reamer is 30%, the isobutanol conversion rate is the best. The isobutanol conversion rate and the isobutene selectivity were 97% and 93% respectively under the conditions of 330 °C, 0.1 MPa and 12 h?1air velocity of the body liquid.
- Tian, Kaige,Li, Qin,Jiang, Weili,Wang, Xiaosheng,Liu, Shicheng,Zhao, Yapeng,Zhou, Guanglin
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p. 11952 - 11958
(2021/04/06)
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- Method for isobutylene from tert-butanol
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In the dehydration reaction of tert - butanol, the specific surface area is 30m. 2 Zirconia oxide (ZrO) above/g2 Using a solid acid catalyst. Provided is a process for preparing isobutylene which can show high conversion of tert - butanol and high selectivity to isobutylene while inhibiting oligomerization and side reactions of isobutylene. A method for producing isobutylene using tert - butanol is provided to obtain high purity isobutylene without adding a separate distillation process with high conversion of tert-butanol and isobutylene.
- -
-
Paragraph 0031-0045; 0054
(2021/07/06)
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- Aqueous Microdroplets Capture Elusive Carbocations
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Carbocations are short-lived reactive intermediates in many organic and biological reactions that are difficult to observe. This field sprung to life with the discovery by Olah that a superacidic solution allowed the successful capture and nuclear magnetic resonance characterization of transient carbocations. We report here that water microdroplets can directly capture the fleeting carbocation from a reaction aliquot followed by its desorption to the gas phase for mass spectrometric detection. This was accomplished by employing desorption electrospray ionization mass spectrometry to detect a variety of short-lived carbocations (average lifetime ranges from nanoseconds to picoseconds) obtained from different reactions (e.g., elimination, substitution, and oxidation). Solvent-dependent studies revealed that aqueous microdroplets outperform organic microdroplets in the capture of carbocations. We provide a mechanistic insight demonstrating the survival of the reactive carbocation in a positively charged aqueous microdroplet and its subsequent ejection to the gas phase for mass spectrometric analysis.
- Kumar, Anubhav,Mondal, Supratim,Banerjee, Shibdas
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supporting information
p. 2459 - 2463
(2021/02/16)
-
- HYDROTHERMAL PRODUCTION OF ALKANES
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Synthesizing an alkane includes heating a mixture including an alkene and water at or above the water vapor saturation pressure in the presence of a catalyst and one or both of hydrogen and a reductant, thereby hydrogenating the alkene to yield an alkane and water, and separating the alkane from the water to yield the alkane. The reductant includes a first metal and the catalyst includes a second metal.
- -
-
Paragraph 0022
(2021/04/17)
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- General Synthesis of Ordered Mesoporous Carbonaceous Hybrid Nanostructures with Molecularly Dispersed Polyoxometallates
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Hybrid nanomaterials with controlled dimensions, intriguing components and ordered structures have attracted significant attention in nanoscience and technology. Herein, we report a facile and green polyoxometallate (POM)-assisted hydrothermal carbonization strategy for synthesis of carbonaceous hybrid nanomaterials with molecularly dispersed POMs and ordered mesopores. By using various polyoxometallates such as ammonium phosphomolybdate, silicotungstic acid, and phosphotungstic acid, our approach can be generalized to synthesize ordered mesoporous hybrid nanostructures with diverse compositions and morphologies (nanosheet-assembled hierarchical architectures, nanospheres, and nanorods). Moreover, the ordered mesoporous nanosheet-assembled hierarchical hybrids with molecularly dispersed POMs exhibit remarkable catalytic activity toward the dehydration of tert-butanol with the high isobutene selectivity (100 %) and long-term catalytic durability (80 h).
- Chen, Chunhong,Fan, Zhanxi,Ge, Yiyao,Ma, Qinglang,Mao, Shanjun,Qi, Guodong,Tan, Chaoliang,Wang, Yong,Wang, Zhe,Xu, Jun,Zhang, Xiao
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supporting information
p. 15556 - 15562
(2021/06/11)
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- Mechanism and Kinetics of Acetone Conversion to Isobutene over Isolated Hf Sites Grafted to Silicalite-1 and SiO2
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Isolated hafnium (Hf) sites were prepared on Silicalite-1 and SiO2 and investigated for acetone conversion to isobutene. Characterization by IR, 1H MAS NMR, and UV-vis spectroscopy suggests that Hf atoms are bonded to the support via three O atoms and have one hydroxyl group, i.e, (SiO)3Hf-OH. In the case of Hf/Silicalite-1, Hf-OH groups hydrogen bond with adjacent Si-OH to form (SiO)3Hf-OH···HO-Si complexes. The turnover frequency for isobutene formation from acetone is 4.5 times faster over Hf/Silicalite-1 than Hf/SiO2. Lewis acidic Hf sites promote the aldol condensation of acetone to produce mesityl oxide (MO), which is the precursor to isobutene. For Hf/SiO2, both Hf sites and Si-OH groups are responsible for the decomposition of MO to isobutene and acetic acid, whereas for Hf/Silicalite-1, the (SiO)3Hf-OH···HO-Si complex is the active site. Measured reaction kinetics show that the rate of isobutene formation over Hf/SiO2 and Hf/Silicalite-1 is nearly second order in acetone partial pressure, suggesting that the rate-limiting step involves formation of the C-C bond between two acetone molecules. The rate expression for isobutene formation predicts a second order dependence in acetone partial pressure at low partial pressures and a decrease in order with increasing acetone partial pressure, in good agreement with experimental observation. The apparent activation energy for isobutene formation from acetone over Hf/SiO2 is 116.3 kJ/mol, while that for Hf/Silicalite-1 is 79.5 kJ/mol. The lower activation energy for Hf/Silicalite-1 is attributed to enhanced adsorption of acetone and formation of a C-C bond favored by the H-bonding interaction between Hf-OH and an adjacent Si-OH group.
- Bell, Alexis T.,Lu, Peng,Lund, Alicia,Qi, Liang,Zhang, Yanfei
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p. 8352 - 8366
(2021/06/27)
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- Alkylation of Phenol with tert-Butanol in a Draining-Film Reactor
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The alkylation of phenol with tert-butanol in a displacement draining-film reactor on a heterogeneous catalyst, Beta zeolite, was evaluated. Optimum process conditions ensuring the maximal p-tert-butylphenol yield were determined: phenol:tert-butanol molar ratio (3–3.5):1, superficial liquid velocity 1.0–1.5 m3 m–2 h–1, and temperature 100°C–110°C. A procedure ensuring 100% conversion of tert-butanol and isobutylene (a by-product formed from tert-butanol) was observed.
- Maksimov, A. L.,Mel’chakov, I. S.,Terekhov, A. V.,Zanaveskin, L. N.
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p. 569 - 575
(2021/07/26)
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- Multiple N-H and C-H Hydrogen Atom Abstractions through Coordination-Induced Bond Weakening at Fe-Amine Complexes
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We report the use of the reported Fe-phthalocyanine complex, PcFe (1; Pc = 1,4,8,11,15,18,22,25-octaethoxy-phthalocyanine), to generate PcFe-amine complexes 1-(NH3)2, 1-(MeNH2)2, and 1-(Me2NH)2. Treatment of 1 or 1-(NH3)2 to an excess of the stable aryloxide radical, 2,4,6-tritert-butylphenoxyl radical (tBuArO?), under NH3 resulted in catalytic H atom abstraction (HAA) and C-N coupling to generate the product 4-amino-2,4,6-tritert-butylcyclohexa-2,5-dien-1-one (2) and tBuArOH. Exposing 1-(NH3)2 to an excess of the trityl (CPh3) variant, 2,6-di-tert-butyl-4-tritylphenoxyl radical (TrArO?), under NH3 did not lead to catalytic ammonia oxidation as previously reported in a related Ru-porphyrin complex. However, pronounced coordination-induced bond weakening of both α N-H and β C-H in the alkylamine congeners, 1-(MeNH2)2 and 1-(Me2NH)2, led to multiple HAA events yielding the unsaturated cyanide complex, 1-(MeNH2)(CN), and imine complex, 1-(MeN═CH2)2, respectively. Subsequent C-N bond formation was also observed in the latter upon addition of a coordinating ligand. Detailed computational studies support an alternating mechanism involving sequential N-H and C-H HAA to generate these unsaturated products.
- Wang, Zongheng,Johnson, Samantha I.,Wu, Guang,Ménard, Gabriel
-
supporting information
p. 8242 - 8251
(2021/06/25)
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- Ni-Catalyzed Reductive Allylation of α-Chloroboronates to Access Homoallylic Boronates
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The transition-metal-catalyzed allylation reaction is an efficient strategy for the construction of new carbon-carbon bonds alongside allyl or homoallylic functionalization. Herein we describe a Ni-catalyzed reductive allylation of α-chloroboronates to efficiently render the corresponding homoallylic boronates, which could be readily converted into valuable homoallylic alcohols or amines or 1,4-diboronates. This reaction features a broad substrate scope with good functional group compatibility that is complementary to the existing methods for the preparation of homoallylic boronates.
- Lou, Yixian,Qiu, Jian,Yang, Kai,Zhang, Feng,Wang, Chenglan,Song, Qiuling
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supporting information
p. 4564 - 4569
(2021/06/28)
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- PROCESS AND SYSTEM TO MAKE SUBSTITUTED LACTONES
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A process for oxidizing iso-butane with oxygen to produce t-butyl hydroperoxide and t-butyl alcohol; dehydrating at least a portion of the t-butyl alcohol to produce di-tert-butyl ether and isobutylene; epoxidizing at least a portion of the isobutylene with the t-butyl hydroperoxide to produce isobutylene oxide and t-butyl alcohol; and carbonylating at least a portion of the isobutylene oxide with carbon monoxide to produce pivalolactone.
- -
-
Paragraph 0052; 0054
(2021/02/05)
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- Trioxatriangulenium (TOTA+) as a robust carbon-based Lewis acid in frustrated Lewis pair chemistry
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We report the reactivity between the water stable Lewis acidic trioxatriangulenium ion (TOTA+) and a series of Lewis bases such as phosphines and N-heterocyclic carbene (NHC). The nature of the Lewis acid-base interaction was analyzedviavariable temperature (VT) NMR spectroscopy, single-crystal X-ray diffraction, UV-visible spectroscopy, and DFT calculations. While small and strongly nucleophilic phosphines, such as PMe3, led to the formation of a Lewis acid-base adduct, frustrated Lewis pairs (FLPs) were observed for sterically hindered bases such as P(tBu)3. The TOTA+-P(tBu)3FLP was characterized as an encounter complex, and found to promote the heterolytic cleavage of disulfide bonds, formaldehyde fixation, dehydrogenation of 1,4-cyclohexadiene, heterolytic cleavage of the C-Br bonds, and interception of Staudinger reaction intermediates. Moreover, TOTA+and NHC were found to first undergo single-electron transfer (SET) to form [TOTA]·[NHC]˙+, which was confirmedviaelectron paramagnetic resonance (EPR) spectroscopy, and subsequently form a [TOTA-NHC]+adduct or a mixture of products depending the reaction conditions used.
- Shaikh, Aslam C.,Veleta, José M.,Moutet, Jules,Gianetti, Thomas L.
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p. 4841 - 4849
(2021/04/14)
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- Oxidative Addition of Aryl and Alkyl Halides to a Reduced Iron Pincer Complex
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The two-electron oxidative addition of aryl and alkyl halides to a reduced iron dinitrogen complex with a strong-field tridentate pincer ligand has been demonstrated. Addition of iodobenzene or bromobenzene to (3,5-Me2MesCNC)Fe(N2)2 (3,5-Me2MesCNC = 2,6-(2,4,6-Me-C6H2-imidazol-2-ylidene)2-3,5-Me2-pyridine) resulted in rapid oxidative addition and formation of the diamagnetic, octahedral Fe(II) products (3,5-Me2MesCNC)Fe(Ph)(N2)(X), where X = I or Br. Competition experiments established the relative rate of oxidative addition of aryl halides as I > Br > Cl. A linear free energy of relative reaction rates of electronically differentiated aryl bromides (ρ = 1.5) was consistent with a concerted-type pathway. The oxidative addition of alkyl halides such as methyl-, isobutyl-, or neopentyl halides was also rapid at room temperature, but substrates with more accessible β-hydrogen positions (e.g., 1-bromobutane) underwent subsequent β-hydride elimination. Cyclization of an alkyl halide containing a radical clock and epimerization of neohexyl iodide-d2 upon oxidative addition to (3,5-Me2MesCNC)Fe(N2)2 are consistent with radical intermediates during C(sp3)-X bond cleavage. Importantly, while C(sp2)-X and C(sp3)-X oxidative addition produces net two-electron chemistry, the preferred pathway for obtaining the products is concerted and stepwise, respectively.
- Rummelt, Stephan M.,Peterson, Paul O.,Zhong, Hongyu,Chirik, Paul J.
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p. 5928 - 5936
(2021/05/06)
-
- Tuning supported Ni catalysts by varying zeolite Beta heteroatom composition: effects on ethylene adsorption and dimerization catalysis
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The influence of zeolite heteroatom composition on the electron density and catalytic activity of a supported Ni cation is examined. Ni-[X]-Beta catalysts, where X = Al, Ga, Fe, or dealuminated, were synthesized and characterized with probe molecule adsorption with FTIR spectroscopy and C2H4dimerization catalysis. It was observedviaCO adsorption that supported Ni cations were increasing in electron density in the order: [Fe] > [Ga] > [Al]. C2H4dimerization activity increased with increasing electron density of the Ni cation. Despite similarities in reported acid site strength, the acid sites on [Fe]-Beta in this work had significantly lower activity than those on [Ga]-Beta for the skeletal isomerization of linear butenes as well as C2H4dimerization. Introducing H2as a reactant resulted in a decrease in dimerization activity for Ni-[Al]-Beta and Ni-[Ga]-Beta but an increase for Ni-[Fe]-Beta. The selectivity and activity of Ni-[DeAl]-Beta changed dramatically with the introduction of H2, which subsequently converted all C2H4withca.100% selectivity towards C2H6(even with a lower space velocity relative to without H2). These results demonstrate the ability of heteroatom composition to tune catalysis by using C2H4dimerization catalysis as a test reaction with zeolite Beta supported Ni catalysts.
- Meloni, Michael,Runnebaum, Ron C.
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p. 3393 - 3401
(2021/06/06)
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- RED SLUDGE USED AS A CATALYST FOR OLEFIN ISOMERIZATION
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The invention relates to systems and a method for isomerizing a charge to form a stream of alpha-olefin product. An example of a process includes calcination of red mud, flow of an olefin feedstock onto red sludge in an isomerization reactor, and separation of alpha-olefin from reactor effluent.
- -
-
Paragraph 0035
(2021/12/31)
-
- METHOD FOR PRODUCING ISOBUTYLENE
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PROBLEM TO BE SOLVED: To provide a method with relevant conventional technology as the background, for making it possible to produce isobutylene from isobutane at a relatively low temperature with a low-temperature high-activity dehydrogenation catalyst under economically advantageous conditions. SOLUTION: A method for producing isobutylene through direct dehydrogenation of isobutane includes the step of allowing a gas material containing isobutane to circulate in a catalyst layer filled with a dehydrogenation catalyst containing zeolite with platinum and iron supported thereon. SELECTED DRAWING: None COPYRIGHT: (C)2021,JPOandINPIT
- -
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Paragraph 0043-0076
(2020/12/09)
-
- Isobutane Dehydrogenation Assisted by CO2 over Silicalite-1-Supported ZnO Catalysts: Influence of Support Crystallite Size
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The ZnO catalysts supported on Silicalite-1 zeolites with different crystallite sizes (0.08, 0.35, 1 and 1.7 μm, respectively) and 5% Zn were synthesized via an incipient wetness method. The catalysts were characterized by XRD, N2 adsorption, SEM, TEM-EDX, DRIFT spectra and NH3-TPD, and their catalytic performance in isobutane dehydrogenation assisted by CO2 was investigated. The catalytic activity is strongly dependent on the crystallite size of Silicalite-1 support. The ZnO/S-1-0.35 catalyst with ca. 0.35 μm crystallite size displays the highest activity, affording an initial isobutane conversion of 51.0% and 74.5% isobutene selectivity. This can be attributed to a higher amount of acid sites present on this catalyst as well as the largest amount of nest silanols possessed by the S-1-0.35 support.
- Luo, Yajun,Wei, Chunling,Miao, Changxi,Yue, Yinghong,Hua, Weiming,Gao, Zi
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supporting information
p. 703 - 708
(2020/05/05)
-
- Iridium-Catalyzed Hydrochlorination and Hydrobromination of Alkynes by Shuttle Catalysis
-
Described herein are two different methods for the synthesis of vinyl halides by a shuttle catalysis based iridium-catalyzed transfer hydrohalogenation of unactivated alkynes. The use of 4-chlorobutan-2-one or tert-butyl halide as donors of hydrogen halides allows this transformation in the absence of corrosive reagents, such as hydrogen halides or acid chlorides, thus largely improving the functional-group tolerance and safety profile of these reactions compared to the state-of-the-art. This method has granted access to alkenyl halide compounds containing acid-sensitive groups, such as tertiary alcohols, silyl ethers, and acetals. The synthetic value of those methodologies has been demonstrated by gram-scale synthesis where low catalyst loading was achieved.
- Yu, Peng,Bismuto, Alessandro,Morandi, Bill
-
supporting information
p. 2904 - 2910
(2020/01/25)
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- Acid Properties of Cesium-Nickel-Zirconium Complex Phosphates: Effect on Isobutanol Dehydration
-
Abstract: The physicochemical and catalytic properties of Cs1 – 2xNixZr2(PO4)3 (x = 0, 0.15, 0.25, 0.50) systems are studied. Double and triple nickel-containing phosphates with the NASICON structure are obtained by the sol–gel method. It is shown that these phosphates are active and stable isobutanol dehydration catalysts. The relationship between the catalytic activity in the dehydration reaction over triple cesium-zirconium phosphates and their crystallographic characteristics and surface acidity is established. It is shown that upon partial or complete replacement of cesium ions with nickel ions an increase in dehydration activity correlates with an increase in the number of acid sites determined by the pyridine adsorption titration method.
- Akhmedova, L. S.,Fionov, Yu. A.,Knyazeva, E. I.,Pylinina, A. I.,Sokolova, E. A.
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p. 592 - 596
(2020/05/29)
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- NASICON Catalysts with Composition Na(Cs)1 – 2xMxZr2(PO4)3 for Transformations of Aliphatic Alcohols
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Abstract: The activity of solid electrolytes from the family of Na(Cs)–Mx–Zr phosphates (NZP and CZP) with dopant ions M+2 = Co+2 and Ni+2 synthesized by the sol–gel method is studied in the gas-phase transformations of isopropanol and isobutanol. It is found that the amount of M+2 and its nature, as well as the direction of a change in the catalyst temperature (heating or cooling in the range of 473?693 K), affects the activity of M-NZP and M-CZP. In the transformation of isopropanol, hysteresis of the acetone yield, counter-clockwise (type I) for Co-NZP and clockwise (type II) for Ni-NZP, is observed in the heating–cooling cycles. An increase in the activity of Co-NZP in the cooling mode (type I) is related to a rise in the apparent activation energy of alcohol dehydrogenation under conditions of the formation of new catalytically active sites in the form of a Co+2?Zr+4 → Co+3?Zr+3 ion pair with the oxidized form of M and the reduced form of Zr. Type I hysteresis of the total alcohol conversion is observed in the transformations of isobutanol to olefin and aldehyde over Co(Ni)-CZP. The hysteresis is associated with a decrease in the activation energy of alcohol dehydrogenation. The main reaction over the Co(Ni)-CZP catalysts is the dehydration of alcohol with an increase in the activation energy of the reaction upon cooling, for example, by 53 kJ/mol for Ni0.25-CZP.
- Knyazeva, E. I.,Mikhalenko, I. I.,Pylinina, A. I.
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p. 1176 - 1183
(2020/10/14)
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- Reductive activation of PdII-precatalysts: Via decarboxylation of pivalate in direct C-H arylation reactions
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The mechanism of the reductive activation of PdII pre-catalysts has been extensively studied, but remains poorly understood. Herein, a combined computational and experimental approach is employed to clearly identify a PdII reduction process that has not been considered thus far. Pivalate, assumed to be a general base, was found to decarboxylate and act as a reductant, suggesting an alternative explanation for the superior performance of pivalic acid as an additive in Pd-catalyzed direct C-H arylation reactions.
- Kim, Seoung-Tae,Baik, Mu-Hyun
-
supporting information
p. 13868 - 13871
(2020/11/18)
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- Tuning Catalytic Sites on Zr6O8 Metal-Organic Framework Nodes via Ligand and Defect Chemistry Probed with tert-Butyl Alcohol Dehydration to Isobutylene
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Metal-organic frameworks (MOFs) have drawn wide attention as candidate catalysts, but some essential questions about their nature and performance have barely been addressed. (1) How do OH groups on MOF nodes act as catalytic sites (2) What are the relationships among these groups, node defects, and MOF stability, and how do reaction conditions influence them (3) What are the interplays between catalytic properties and transport limitations To address these questions, we report an experimental and theoretical investigation of the catalytic dehydration of tert-butyl alcohol (TBA) used to probe the activities of OH groups of Zr6O8 nodes in the MOFs UiO-66 and MOF-808, which have different densities of vacancy sites and different pore sizes. The results show that (1) terminal node OH groups are formed as formate and/or acetate ligands present initially on the nodes react with TBA to form esters, (2) these OH groups act as catalytic sites for TBA dehydration to isobutylene, and (3) TBA also reacts to break node-linker bonds to form esters and thereby unzip the MOFs. The small pores of UiO-66 limit the access of TBA and the reaction with the formate/acetate ligands bound within the pores, whereas the larger pores of MOF-808 facilitate transport and favor reaction in the MOF interior. However, after removal of the formate and acetate ligands by reaction with methanol to form esters, interior active sites in UiO-66 become accessible for the reaction of TBA, with the activity depending on the density of defect sites with terminal OH groups. The number of vacancies on the nodes is important in determining a tradeoff between the catalytic activity of a MOF and its resistance to unzipping. Computations at the level of density functional theory show how the terminal OH groups on node vacancies act as Br?nsted bases, facilitating TBA dehydration via a carbocation intermediate in an E1 mechanism; the calculations further illuminate the comparable chemistry of the unzipping.
- Babucci, Melike,Gaggioli, Carlo Alberto,Gagliardi, Laura,Gates, Bruce C.,Ray, Debmalya,Yang, Dong
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p. 8044 - 8056
(2020/04/30)
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- Phosphonate-Modified UiO-66 Br?nsted Acid Catalyst and Its Use in Dehydra-Decyclization of 2-Methyltetrahydrofuran to Pentadienes
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Phosphorus-modified all-silica zeolites exhibit activity and selectivity in certain Br?nsted acid catalyzed reactions for biomass conversion. In an effort to achieve similar performance with catalysts having well-defined sites, we report the incorporation of Br?nsted acidity to metal–organic frameworks with the UiO-66 topology, achieved by attaching phosphonic acid to the 1,4-benzenedicarboxylate ligand and using it to form UiO-66-PO3H2 by post-synthesis modification. Characterization reveals that UiO-66-PO3H2 retains stability similar to UiO-66, and exhibits weak Br?nsted acidity, as demonstrated by titrations, alcohol dehydration, and dehydra-decyclization of 2-methyltetrahydrofuran (2-MTHF). For the later reaction, the reported catalyst exhibits site-time yields and selectivity approaching that of phosphoric acid on all-silica zeolites. Using solid-state NMR and deprotonation energy calculations, the chemical environments of P and the corresponding acidities are determined.
- Caratzoulas, Stavros,Chen, Tso-Hsuan,Dauenhauer, Paul,Dorneles de Mello, Matheus,Han, Songi-I,Jain, Sheetal K.,Kumar, Gaurav,Li, Xinyu,Scott, Susannah L.,Tabassum, Tarnuma,Tsapatsis, Michael,Vlachos, Dionisios G.
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supporting information
p. 13260 - 13266
(2020/06/08)
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- Deoxygenation of Epoxides with Carbon Monoxide
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The use of carbon monoxide as a direct reducing agent for the deoxygenation of terminal and internal epoxides to the respective olefins is presented. This reaction is homogeneously catalyzed by a carbonyl pincer-iridium(I) complex in combination with a Lewis acid co-catalyst to achieve a pre-activation of the epoxide substrate, as well as the elimination of CO2 from a γ-2-iridabutyrolactone intermediate. Especially terminal alkyl epoxides react smoothly and without significant isomerization to the internal olefins under CO atmosphere in benzene or toluene at 80–120 °C. Detailed investigations reveal a substrate-dependent change in the mechanism for the epoxide C?O bond activation between an oxidative addition under retention of the configuration and an SN2 reaction that leads to an inversion of the configuration.
- Maulbetsch, Theo,Jürgens, Eva,Kunz, Doris
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p. 10634 - 10640
(2020/07/30)
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- Impact of Zeolite Framework Composition and Flexibility on Methanol-To-Olefins Selectivity: Confinement or Diffusion?
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The methanol-to-olefins reaction catalyzed by small-pore cage-based acid zeolites and zeotypes produces a mixture of short chain olefins, whose selectivity to ethene, propene and butene varies with the cavity architecture and with the framework composition. The product distribution of aluminosilicates and silicoaluminophosphates with the CHA and AEI structures (H-SSZ-13, H-SAPO-34, H-SSZ-39 and H-SAPO-18) has been experimentally determined, and the impact of acidity and framework flexibility on the stability of the key cationic intermediates involved in the mechanism and on the diffusion of the olefin products through the 8r windows of the catalysts has been evaluated by means of periodic DFT calculations and ab initio molecular dynamics simulations. The preferential stabilization by confinement of fully methylated hydrocarbon pool intermediates favoring the paring pathway is the main factor controlling the final olefin product distribution.
- Boronat, Mercedes,Corma, Avelino,Ferri, Pau,Li, Chengeng,Martínez-Triguero, Joaquín,Millán, Reisel,Moliner, Manuel
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supporting information
p. 19708 - 19715
(2020/08/21)
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- Synthesis and catalytic performance of zeolite-Y supported on silicon carbide in n-heptane cracking
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In this work, we demonstrate a facile approach for the synthesis of zeolite-Y crystals (size, ca. ~400 nm) supported on silicon carbide (SiC) with the assistance of the cationic template (polydiallyldimethylammonium chloride, PDDA). The polymeric cationic template used to treat SiC particles induces a positive charge on SiC surface which electrostatically attracts negatively charged aluminosilicate seeds and promotes the growth of zeolite (ZY) particles over SiC, thus leading to the formation of stable ZY?SiC supported catalysts. The supported ZY catalysts with different weight ratio of ZY and SiC were synthesized and characterized by various techniques such as XRD, SEM, SEM-EDX, SEM-mapping, TEM, STEM, FT-IR, 27Al MAS NMR and N2 sorption. The characterization of the supported ZY catalysts suggests the uniform growth of ZY particles over SiC together with the creation of hierarchical micro-mesopores assembly. In the catalytic cracking of n-heptane, the catalyst ZY?SiC-50 displayed a remarkable improvement in reaction rate when compared to commercial zeolite-Y (CBV-600) amounting to 3.5 folds enhancement. Interestingly, the light olefins yield is also substantially improved. At WHSV of 8 h?1 and 475 °C, the highest light olefin yield (24–36 %) was achieved over ZY?SiC-50 whereas the reference catalyst, CBV-600 produced lower light olefins yield (7–17 %). Moreover, the supported ZY catalyst exhibited less deactivation rates. This improved performance is attributed to the hierarchical micro-mesopores assembly created by the homogeneous dispersion of zeolite crystals on SiC which offers fast diffusion pathways for the reactants and enhanced accessibility to active sites thus leading to higher observed reaction rates and fast diffusion of products thus minimizing the occurrence of side reactions.
- Alhassan, Saeed M.,Berthod, Mikael,Dabbawala, Aasif A.,Joseph, Tony,Khan, Shaihroz,Mittal, Hemant,Morin, Stephane,Singaravel, Gnana,Vaithilingam, Balasubramanian V.,Wahedi, Yasser Al
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- PROCESS AND CATALYSTS FOR THE PRODUCTION OF DIESEL AND GASOLINE ADDITIVES FROM GLYCEROL
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A method of producing one or more glycerol ethers, the method comprising contacting glycerol and tertiary butanol (TBA) in the presence of an acidic catalyst to produce one or more glycerol ethers selected from mono-tert butyl glycerol ethers, di-tert butyl glycerol ethers, tri-tert butyl glycerol ethers, or a combination thereof; separating water and a stream comprising isobutylene, unreacted TBA, or a combination thereof from the one or more glycerol ethers; and recycling at least a portion of the stream comprising isobutylene, unreacted TBA, or a combination thereof to the contacting. Also disclosed is a process of co-producing isooctene, wherein the process involves contacting glycerol and tertiary butanol in the presence of a dehydrating catalyst and dimerizing/oligomerizing the dehydrated products in the presence of an oligomerizing catalyst to form isooctene, a precursor of isooctane and isomers thereof.
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Paragraph 0043-0045
(2020/01/24)
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- CATALYST SYSTEMS THAT INCLUDE METAL OXIDE CO-CATALYSTS FOR THE PRODUCTION OF PROPYLENE
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Embodiments of methods of synthesizing a metathesis catalyst system, which include impregnating tungsten oxide on silica support in the presence of a precursor to produce a base catalyst; calcining the base catalyst; impregnating a metal oxide co-catalyst comprising a metal oxide onto the surface of the base catalyst to produce a doped catalyst; and calcining the doped catalyst to produce a metathesis catalyst system. Further embodiments of processes for the production of propylene, which include contacting a hydrocarbon feedstock comprising a mixture of 1-butene and 2-butene with embodiments of the metathesis catalyst system to produce, via metathesis conversion, a product stream comprising propylene.
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Paragraph 0069-0070
(2020/05/02)
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- Photooxidation Reactions of Ethyl 2-Methylpropionate (E2MP) and Ethyl 2,2-Dimethylpropionate (E22DMP) Initiated by OH Radicals: An Experimental and Computational Study
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The relative rate (RR) technique was used for the measurement of OH-initiated photooxidation reactions of ethyl 2-methylpropionate (E2MP) and ethyl 2,2-dimethylpropionate (E22DMP) in the temperature range of 268-363 K at 760 Torr. In addition to this, the
- Kaipara, Revathy,Rajakumar, B.
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p. 2768 - 2784
(2020/05/08)
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- Sn-Catalyzed Criegee-Type Rearrangement of Peroxyoxindoles Enabled by Catalytic Dual Activation of Esters and Peroxides
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We report here the Sn-catalyzed mild protocol for ring expansion of peroxyoxindoles to afford the series of substituted-2H-benzo[b][1,4]oxazin-3(4H)-one derivatives. In this protocol, we showed the in situ conversion of tert-butyl peroxy compounds into peresters with the aid of external esters, which then underwent the ring-expansion process, and the incipient carbocation was trapped with the alcohol residue generated from the esters. The reaction is also demonstrated in a continuous flow process to afford the rearranged product in 22 min of residence time.
- Chaudhari, Moreshwar B.,Gnanaprakasam, Boopathy,Jayan, Krishna
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supporting information
p. 3374 - 3382
(2020/03/23)
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- O-(tert-butyl) Se-phenyl selenocarbonate: A convenient, bench-stable and metal-free precursor of benzeneselenol
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A study by our laboratory shows that air, light and moisture stable O-(tert-butyl) Se-phenyl selenocarbonate could be employed as a safer, practical and efficient alternative to generate “in situ” benzeneselenol or benzeneselenolate anion under different and transition metal-free conditions. This procedure seems to be of general application since the nucleophilic selenium species obtained can be trapped by electrophiles such as alkyl halides, epoxides and electron-deficient alkenes and alkynes under different reaction conditions.
- Temperini, Andrea,Siciliano, Carlo
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- Rotation-Triggered Transmetalation on a Heterobimetallic Cu/Al N-Phosphine-Oxide-Substituted Imidazolylidene Complex
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A novel strategy for the preparation of heterobimetallic N-heterocyclic carbene (NHC) complexes is demonstrated using N-phosphine-oxide-substituted imidazolylidenes (PoxIms). In these heterobimetallic Cu/Al complexes, the Cu and Al centers can be either completely separated or brought near each other via the rotation of the N-phosphinoyl group in the PoxIm ligands. Triggered by this rotation, transmetalation to exchange the Cu-OtBu and Al-C6F5 bonds occurs on in situ-generated Cu/Al PoxIm complexes, and the Cu-C6F5 and Al-OtBu bonds are formed in excellent yield. On the basis of the results of mechanistic studies, including the isolation/in situ observation of key complexes and theoretical calculations, a plausible reaction mechanism for an intramolecular transmetalation is proposed to proceed via an activation complex that includes the simultaneous coordination of the phosphinoyl oxygen atom to the Cu as well as the Al centers. Furthermore, the formation of carbon-carbon bonds between Al(C6F5)3 and allyl bromide mediated/catalyzed by Cu/Al PoxIm complexes is demonstrated. Upon the consecutive transfer of three C6F5 groups from a single molecule of Al(C6F5)3, allyl pentafluorobenzene derivatives were obtained. The present results demonstrate the role of phosphine oxide in the activation of organoaluminum reagents for the transmetalation between Cu(I) complexes bearing NHCs as well as the benefit of constructing an intramolecular system based on a heterobimetallic complex to achieve efficient transmetalation by programming the encounter of two organometallic fragments.
- Asada, Takahiro,Hoshimoto, Yoichi,Ogoshi, Sensuke
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supporting information
p. 9772 - 9784
(2020/07/10)
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- A Cationic Oligomer as an Organic Template for Direct Synthesis of Aluminosilicate ITH Zeolite
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There are a large number of zeolites, such as ITH, that cannot be prepared in the aluminosilicate form. Now, the successful synthesis of aluminosilicate ITH zeolite using a simple cationic oligomer as an organic template is presented. Key to the success is that the cationic oligomer has a strong complexation ability with aluminum species combined with a structural directing ability for the ITH structure similar to that of the conventional organic template. The aluminosilicate ITH zeolite has very high crystallinity, nanosheet-like crystal morphology, large surface area, fully four-coordinated Al species, and abundant acidic sites. Methanol-to-propylene (MTP) tests reveal that the Al-ITH zeolite shows much higher selectivity for propylene and longer lifetime than commercial ZSM-5. FCC tests show that Al-ITH zeolite is a good candidate as a shape-selective FCC additive for enhancing propylene and butylene selectivity.
- Chen, Wei,Corma, Avelino,De Baerdemaeker, Trees,De Vos, Dirk E.,Dong, Zhuoya,Kolb, Ute,Lei, Chi,Müller, Ulrich,Ma, Yanhang,Marler, Bernd,Martínez, Cristina,Martínez-Triguero, Joaquín,Meng, Xiangju,Parvulescu, Andrei-Nicolae,Wu, Qinming,Xiao, Feng-Shou,Yokoi, Toshiyuki,Zhang, Weiping,Zheng, Anmin
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supporting information
p. 15649 - 15655
(2020/07/04)
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- Synthesis of Trialkylamines with Extreme Steric Hindrance and Their Decay by a Hofmann-like Elimination Reaction
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A number of amines with three bulky alkyl groups at the nitrogen, which surpass the steric crowding of triisopropylamine considerably, were prepared by using different synthetic methods. It turned out that treatment of N-chlorodialkylamines with organometallic compounds, for example, Grignard reagents, in the presence of a major excess of tetramethylenediamine offered the most effective access to the target compounds. The limits of this method were also tested. The trialkylamines underwent a dealkylation reaction, depending on the degree of steric stress, even at ambient temperature. Because olefins were formed in this transformation, it showed some similarity with the Hofmann elimination. However, the thermal decay of sterically overcrowded tertiary amines was not promoted by bases. Instead, this reaction was strongly accelerated by protic conditions and even by trace amounts of water. Reaction mechanisms, which were analyzed with the help of quantum chemical calculations, are suggested to explain the experimental results.
- Banert, Klaus,Hagedorn, Manfred,Heck, Manuel,Hertel, Raphael,Ihle, Andreas,Müller, Ioana,Pester, Tom,Shoker, Tharallah,Rablen, Paul R.
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p. 13630 - 13643
(2020/11/13)
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- Primary Sulfonamide Synthesis Using the Sulfinylamine Reagent N-Sulfinyl- O-(tert-butyl)hydroxylamine, t-BuONSO
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Sulfonamides have played a defining role in the history of drug development and continue to be prevalent today. In particular, primary sulfonamides are common in marketed drugs. Here we describe the direct synthesis of these valuable compounds from organometallic reagents and a novel sulfinylamine reagent, t-BuONSO. A variety of (hetero)aryl and alkyl Grignard and organolithium reagents perform well in the reaction, providing primary sulfonamides in good to excellent yields in a convenient one-step process.
- Davies, Thomas Q.,Hall, Adrian,Skolc, David,Tilby, Michael J.,Willis, Michael C.
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supporting information
p. 9495 - 9499
(2020/12/21)
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- Wet and dry processes for the selective transformation of phosphonates to phosphonic acids catalyzed by br?nsted acids
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A "wet"process and two "dry"processes for converting phosphonate esters to phosphonic acids catalyzed by a Bronsted acid have been developed. Thus, in the presence of water, a range of alkyl-, alkenyl-, and aryl-substituted phosphonates can be generally hydrolyzed to the corresponding phosphonic acids in good yields catalyzed by trifluoromethyl sulfonic acid (TfOH) at 140 °C (the wet process). On the other hand, with specific substituents of the phosphonate esters, the conversion to the corresponding phosphonic acids can be achieved under milder conditions in the absence of water (the dry process). Thus, the conversion of dibenzyl phosphonates to the corresponding phosphonic acids took place smoothly at 80 °C in toluene or benzene in high yields. Moreover, selective conversion of benzyl phosphonates RP(O)(OR′)(OBn) to the corresponding mono phosphonic acids RP(O)(OR′)(OH) can also be achieved under the reaction conditions. The dealkylation via the generation of isobutene of ditert- butyl phosphonate, and the related catalysis by TfOH took place even at room temperature to give the corresponding phosphonic acids in good to high yields. Nafion also shows high catalytic activity for these reactions. By using Nafion as the catalyst, phosphonic acids could be easily prepared on a large scale via a simple process.
- Li, Chunya,Saga, Yuta,Onozawa, Shun-Ya,Kobayashi, Shu,Sato, Kazuhiko,Fukaya, Norihisa,Han, Li-Biao
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supporting information
p. 14411 - 14419
(2020/12/29)
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- Hydrogenative metathesis of enynes via piano-stool ruthenium carbene complexes formed by alkyne gem-hydrogenation
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The only recently discovered gem-hydrogenation of internal alkynes is a fundamentally new transformation, in which both H atoms of dihydrogen are transferred to the same C atom of a triple bond while the other position transforms into a discrete metal carbene complex. [Cp?RuCl]4 is presently the catalyst of choice: the resulting piano-stool ruthenium carbenes can engage a tethered alkene into either cyclopropanation or metathesis, and a prototypical example of such a reactive intermediate with an olefin ligated to the ruthenium center has been isolated and characterized by X-ray diffraction. It is the substitution pattern of the olefin that determines whether metathesis or cyclopropanation takes place: a systematic survey using alkenes of largely different character in combination with a computational study of the mechanism at the local coupled cluster level of theory allowed the preparative results to be sorted and an intuitive model with predictive power to be proposed. This model links the course of the reaction to the polarization of the double bond as well as to the stability of the secondary carbene complex formed, if metathesis were to take place. The first application of "hydrogenative metathesis"to the total synthesis of sinularones E and F concurred with this interpretation and allowed the proposed structure of these marine natural products to be confirmed. During this synthesis, it was found that gem-hydrogenation also provides opportunities for C-H functionalization. Moreover, silylated alkynes are shown to participate well in hydrogenative metathesis, which opens a new entry into valuable allylsilane building blocks. Crystallographic evidence suggests that the polarized [Ru-Cl] bond of the catalyst interacts with the neighboring R3Si group. Since attractive interligand Cl/R3Si contacts had already previously been invoked to explain the outcome of various ruthenium-catalyzed reactions, including trans-hydrosilylation, the experimental confirmation provided herein has implications beyond the present case.
- Peil, Sebastian,Bistoni, Giovanni,Goddard, Richard,Fürstner, Alois
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supporting information
p. 18541 - 18553
(2020/11/17)
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- Synthesis and Catalytic Performance of a Dual-Sites Fe–Zn Catalyst Based on Ordered Mesoporous Al2O3 for Isobutane Dehydrogenation
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Abstract: Ordered mesoporous Zn/OMA-Fe materials were easily prepared via one pot evaporation induced self-assembly (EISA) method in combination with incipient wetness strategy. Dehydrogenation of isobutane to isobutene were carried out on these materials, the isobutane conversion of 50.7% and the yield of 37.8% were obtained over 13Zn/OMA-10Fe catalyst at 580?°C with 300?h?1 GHSV. The synthesized materials with large specific surface areas and uniform pore sizes were characterized by XRD, N2 adsorption–desorption, TEM, XPS, H2-TPR, M?ssbauer and NH3-TPD. A portion of Fe species were highly dispersed on the support surface and others incorporated into Al2O3 frameworks, Zn species existed in the form of hexagonal ZnO phase. The total acidity of these catalysts was increased by the introduction of Zn, facilitating the conversion of isobutane. Moreover, the conversion of Fe species might play a major role in improving isobutene selectivity. Graphical Abstract: [Figure not available: see fulltext.].
- Cheng, Ming,Zhao, Huahua,Yang, Jian,Zhao, Jun,Yan, Liang,Song, Huanling,Chou, Lingjun
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p. 1326 - 1336
(2019/03/02)
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- Facile synthesis of ordered mesoporous zinc alumina catalysts and their dehydrogenation behavior
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Ordered mesoporous Zn/Al2O3 materials with varying Zn content were simply prepared via an evaporation-induced self-assembly (EISA) method. Dehydrogenation of isobutane to isobutene was carried out on these materials; an isobutane conversion of 45.0% and isobutene yield of 39.0% were obtained over the 10%Zn/Al2O3 catalyst at 580?°C with 300 h?1 GHSV. The obtained materials with Zn content up to 10% possess large specific surface area and big pore volume and zinc species can be highly dispersed on the surface or incorporated into the framework. The acidity of these catalysts was changed by the introduction of Zn, the decrease of strong acid sites is conducive to the promotion of isobutene selectivity and the weak and medium acidic sites played an important role in isobutane conversion. In addition, these catalysts exhibited good catalytic stability, due to the effective inhibition of coke formation by the ordered mesoporous structure.
- Cheng, Ming,Zhao, Huahua,Yang, Jian,Zhao, Jun,Yan, Liang,Song, Huanling,Chou, Lingjun
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p. 9828 - 9837
(2019/04/01)
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- SULFUR INJECTION IN FLUIDIZATION BED DEHYDROGENATION ON CHROMIUM CATALYST FOR DEHYDROGENATION PROCESS IMPROVEMENT AND PROCESS SCHEME OPTIMIZATION
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Systems and processes for producing isomerized alkenes are disclosed. The systems mainly include an isomerization unit, a dehydrogenation unit, and a MTBE synthesis unit. A hydrocarbon stream is fed into the isomerization unit to form iso-alkanes in a sulfur free hydrocarbon stream. The sulfur free hydrocarbon stream is heated and then combined with a sulfur-containing hydrocarbon stream comprising sulfur containing compounds to form a reactant feed stream to the dehydrogenation unit. The iso- alkanes is dehydrogenated to form iso-alkenes. The formed iso- alkenes comprising isobutylene can be used as a feed stock for the MTBE synthesis unit.
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Paragraph 0025-0030; 0055-0059
(2019/07/13)
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- Targeted Synthesis of a Zeolite with Pre-established Framework Topology
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Given their great potential as new industrial catalysts and adsorbents, the search for new zeolite structures is of major importance in nanoporous materials chemistry. However, although innumerable theoretical frameworks have been proposed, none of them have been synthesized by a priori design yet. We generated a library of diazolium-based cations inspired from the organic structure-directing agents (OSDAs) recently reported to give two structurally related zeolites (PST-21 and PST-22) under highly concentrated, excess-fluoride conditions and compared the stabilization energies of each OSDA cation in ten pre-established hypothetical structures. A combination of the ability of the OSDA selected in this way with the excess-fluoride approach has allowed us to crystallize PST-30, the targeted aluminosilicate zeolite structure. We anticipate that our approach, which aims to rationally couple computational predictions of OSDAs with an experimental setup, will advance further development in the synthesis of zeolites with desired properties.
- Jo, Donghui,Hong, Suk Bong
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supporting information
p. 13845 - 13848
(2019/08/26)
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- METHOD OF PRODUCING ISOBUTENE
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PROBLEM TO BE SOLVED: To provide a production method enabling activity of γ-alumina catalyst to be maintained and enabling isobutene to be obtained from tert-butyl alcohol at high yield. SOLUTION: The method of producing isobutene is provided that includes a step of contacting tert-butyl alcohol with a γ-alumina catalyst having an Na content of less than 0.1 mass% in terms of Na2O. In the method of producing isobutene, it is preferable that Si content of the γ-alumina catalyst in terms of SiO2 is less than 0.5 mass%. It is also preferable that specific surface area of the γ-alumina catalyst is 100 to 300 m2/g. Further it is preferable that the tert-butyl alcohol and the γ-alumina catalyst are contacted with each other at a temperature in the range of 180 to 370°C. SELECTED DRAWING: None COPYRIGHT: (C)2020,JPOandINPIT
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Paragraph 0020-0026
(2019/12/03)
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- Synthesis of β-ketoiminate and β-iminoesterate tungsten (VI) oxo-alkoxide complexes as AACVD precursors for growth of WOx thin films
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The tungsten (VI) oxo-alkoxide complexes WO(OR)3L [R = tBu; L = acNac, etNac, tbNac, acNacMe, acNacEt] (1–5) and WO(OCH3)3(acNac) (6) have been synthesized. The isomeric purity of these complexes depends on the steric bulk of the substituent on the imino nitrogen of the chelating ligand. The thermal properties of the complexes have been evaluated to assess the effect of the β-ketoiminate or β-iminoesterate ligands. WO(OC(CH3)3)3(acNac) (1) has been used as a precursor for aerosol assisted chemical vapor deposition (AACVD) of WOx thin films at temperatures from 250 to 450 °C. The results of mass spectrometry and thermolysis studies have been used to propose possible precursor decomposition pathways during film deposition.
- Su, Xiaoming,Kim, Taehoon,Abboud, Khalil A.,McElwee-White, Lisa
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p. 548 - 557
(2018/11/10)
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- Visualizing Formation of Intermetallic PdZn in a Palladium/Zinc Oxide Catalyst: Interfacial Fertilization by PdHx
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Controllable synthesis of well-defined supported intermetallic catalysts is desirable because of their unique properties in physical chemistry. To accurately pinpoint the evolution of such materials at an atomic-scale, especially clarification of the initial state under a particular chemical environment, will facilitate rational design and optimal synthesis of such catalysts. The dynamic formation of a ZnO-supported PdZn catalyst is presented, whereby detailed analyses of in situ transmission electron microscopy, electron energy-loss spectroscopy, and in situ X-ray diffraction are combined to form a nanoscale understanding of PdZn phase transitions under realistic catalytic conditions. Remarkably, introduction of atoms (H and Zn in sequence) into the Pd matrix was initially observed. The resultant PdHx is an intermediate phase in the intermetallic formation process. The evolution of PdHx in the PdZn catalyst initializes at the PdHx/ZnO interfaces, and proceeds along the PdHx ?111? direction.
- Niu, Yiming,Liu, Xi,Wang, Yongzhao,Zhou, Song,Lv, Zhengang,Zhang, Liyun,Shi, Wen,Li, Yongwang,Zhang, Wei,Su, Dang Sheng,Zhang, Bingsen
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supporting information
p. 4232 - 4237
(2019/02/16)
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- Thermal analysis of salts from 4-nitrophenol and aliphatic amines
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Solid samples obtained from 4-nitrophenol and aliphatic amines, in excess of amine, were submitted to thermal analysis. The TGA/DTA showed two endothermic events, with exception of tert-butylamine, which showed three endothermic peaks. The first event was the melting of the ionic salt, which temperature does not follow a pattern, and is maxim for ethylammonium minimal for butylammonium salt. For methylammonium and ethylammonium, the fusion is followed by mass loss corresponding to one amine by 4-nitrophenol, while for the others ammonium salts, this event marks the beginning of the mass variation, that is maintained until the decomposition of the 4-nitrophenol at 485?K. The temperature of the event depends of the length of the chain of the amine, while the second occurs at the same temperature for all amines.
- Lazzarotto, Márcio,Nachtigall, Francine Furtado,de Siqueira, Geisa Liandra de Andrade,da Silveira Lazzarotto, Simone Rosa,Lazzarotto, Marcelo
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p. 351 - 357
(2019/04/17)
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- METHOD FOR PRODUCING CONJUGATED DIENE
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Provided is a method of producing a conjugated diene, including a step of dehydrating a γ,δ-unsaturated alcohol in the presence of a solid acid catalyst having a Hammett acidity function (H0) of ?12.2 or less.
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Paragraph 0058-0059
(2019/05/18)
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- Chemical Vapor Deposition of Phase-Pure Uranium Dioxide Thin Films from Uranium(IV) Amidate Precursors
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Homoleptic uranium(IV) amidate complexes have been synthesized and applied as single-source molecular precursors for the chemical vapor deposition of UO2 thin films. These precursors decompose by alkene elimination to give highly crystalline ph
- Straub, Mark D.,Leduc, Jennifer,Frank, Michael,Raauf, Aida,Lohrey, Trevor D.,Minasian, Stefan G.,Mathur, Sanjay,Arnold, John
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p. 5749 - 5753
(2019/04/16)
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