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采用电化学原位红外光谱技术研究了多晶Pt电极上甲酸的分解反应. 研究发现,在恒电位下(0.4 V vs. RHE)从不含甲酸的支持电解质溶液切换到含甲酸的溶液时,COad的生成速率在切换的最初也就是甲酸根的覆盖度为零最大,切换后的1 s内甲酸根的覆盖度达到平衡,而COad的生成速率逐步降低. E由0.75 V变至0.35 V的电位阶跃实验显示:电位阶跃后的瞬间,甲酸根的红外光谱强度迅速降低,而COad的生成强度随时间缓慢增加. 实验表明甲酸根不是甲酸脱水生成CO的反应活性中间体. 相似文献
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An in situ dehydration kinetics study of gypsum under water-saturated condition was performed in the temperature and pressure ranges of 383–423?K and 343–1085?MPa by using a hydrothermal diamond anvil cell and Raman spectroscopy. Kinetic analysis shows that the dehydration rate k increases with pressure, suggesting a negative pressure dependence on dehydration rate. The elevation of temperature can contribute to the dehydration. The n values increase with pressure, indicating that the nucleation process becomes slower relative to the growth process. According to the n values of ~1.0, the dehydration of gypsum is dominated by an instantaneous nucleation and diffusion-controlled growth mechanism. The obtained average activation volume ?V is equal to 5.69?cm3/mol and the calculated activation energy Ea and the pre-exponential factor A are 66.9?kJ/mol and 4.66?×?105?s?1. The activation energy may be dependent upon grain size, shape, temperature and pressure, and surrounding water. 相似文献
406.
《Journal of Coordination Chemistry》2012,65(21):3493-3500
A three-dimensional complex, [CuL2(H2O)]2 (HL?=?3-hydroxy-1-adamantanecarboxylic acid), C44H64Cu2O14, was synthesized under hydrothermal conditions from CuCO3?·?Cu(OH)2 and HL. The crystal structure of the complex was determined by X-ray crystallography and its thermal behavior and IR spectra examined. The non-isothermal dehydration kinetics of the complex were investigated using the Achar differential method. 相似文献
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《化学:亚洲杂志》2017,12(24):3178-3186
Carbon‐based solid acid catalysts were successfully obtained via one‐step hydrothermal carbonization (HTC) of water hyacinth (WH) in the presence of p ‐toluenesulfonic acid (PTSA). Increasing the HTC temperature from 180 to 240 °C resulted in carbonaceous materials with increased sulfur content and less adsorbed water. The material obtained at 220 °C (WH‐PTSA‐220) contains the highest amount of acid sites and promotes the highest initial rate of two transformations, that is, methanolysis of oleic acid and dehydration of xylose to furfural. While all PSTA‐treated WH catalysts gave comparable fatty acid conversions (≈97 %) and furfural yields (≈60 %) after prolonged reaction times, the WH‐PTSA‐240 system bearing a relatively low acid density maintains the most favorable reusability profile. Higher HTC temperatures (220–240 °C) improved the catalyst reusability profiles due to graphitization and hydrophobicity of the carbon surface. The catalyst systems derived herein from biomass may have potential applications in biorefining platforms, utilizing the conversion of waste biomass to chemicals. 相似文献
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An operationally simple, efficient, and environmentally benign preparation of nitriles in good to excellent yields from various aldoximes in the presence of recyclable poly(ethylene glycol)–bound sulfonyl chloride is described. 相似文献
409.
Alcohol Dimer is Requisite to Form an Alkyl Oxonium Ion in the Proton Transfer of a Strong (Photo)Acid to Alcohol
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Dr. Sun‐Young Park Young Min Lee Dr. Kijeong Kwac Prof. Dr. Yousung Jung Prof. Dr. Oh‐Hoon Kwon 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(13):4340-4344
Alcohols, the simplest amphiprotic organic compounds, can exhibit either acidic or basic behavior by donating or accepting a proton. In this study, proton dissociation of a model photoacid in solution is explored by using time‐resolved spectroscopy, revealing quantitatively for the first time that alcohol acts as a Brønsted base because of H‐bonded cluster formation to enhance the reactivity. The protonated alcohol cluster, the alkyl oxonium ion, can be regarded as a key reaction intermediate in the well‐established alcohol dehydration reaction. This finding signifies, as in water, the cooperativity of protic solvent molecules to facilitate nonaqueous acid–base reactions. 相似文献
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