FT-IR spectroscopic study of the oxidation of chlorobenzene over Mn-based catalyst

Adsorption and oxidation of chlorobenzene on Al(2)O(3), TiO(2)-Al(2)O(3), and MnO(x)/TiO(2)-Al(2)O(3) have been studied by in situ Fourier transform infrared (FT-IR) spectroscopy. At room temperature, chlorobenzene is only physisorbed on Al(2)O(3), TiO(2)-Al(2)O(3), and MnO(x)/TiO(2)-Al(2)O(3), and gives the same IR spectrum as that for liquid-phase chlorobenzene. On Al(2)O(3) no further interaction and reaction take place with treatment, at higher temperatures (up to 773 K), while phenolates are observed for TiO(2)-Al(2)O(3) and MnO(x)/TiO(2)-Al(2)O(3) at 773 K. When the adsorbed chlorobenzene coexists with oxygen, formates are detected for Al(2)O(3), while acetates are additionally observed for TiO(2-)Al(2)O(3) above 573 K. For MnO(x)/TiO(2-)Al(2)O(3), maleates are present at 573 And 673 K, while formates and acetates develop at 473 and 573 K. Almost all IR bands due to formates, acetates, and maleates disappear at 773 K, indicating that these oxygen-containing species are potential intermediates for the total oxidation of chlorobenzene.

ATR FT-IR absorption enhancement of a thin film under the photon-tunneling condition

A simple, yet very powerful technique for the spectral acquisition of an extremely thin film with enhanced absorption was explored. An infrared absorption of an extremely thin film confined between media of high refractive indices was greater than that of its bulk when the spectrum was acquired under the attenuated total reflection (ATR) condition with parallel (p) polarized radiation. The absorption enhancement was not observed under perpendicular (s) polarized radiation. Theoretical investigations indicated that the absorption enhancement was proportional to the integration of the mean square evanescent field within the film. The field integration under p-polarized radiation increased, while that under s-polarized radiation decreased as the thickness of the confined film became thinner. The maximum enhancement was observed when the film was sufficiently thinner than the penetration depth. The phenomena were experimentally investigated, and the results agreed very well with theoretical predictions.

Análise de queilite actínica por espectroscopia micro FT-IR

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Prehistoric hand stencils at Fern Cave, North Queensland (Australia): environmental and chronological implications of Raman spectroscopy and FT-IR imaging results

Raman spectroscopy and FT-IR imaging analyses of cave wall pigment samples from north Queensland (Australia) indicate that some hand stencils were undertaken during a dry environmental phase indicating late Holocene age. Other, earlier painting episodes also took place during dry environmental periods of the terminal Pleistocene and/or early Holocene. These results represent a rare opportunity to attain chronological information for rock art in conditions where insufficient carbon is present for radiocarbon dating.

An in situ high pressure FT-IR study of CO2/H2 interactions with model ZnO/SiO2, Cu/SiO2 and Cu/ZnO/SiO2 methanol synthesis catalysts

In situ FT-IR spectroscopy allows the methanol synthesis reaction to be investigated under actual industrial conditions of 503 K and 10 MPa. On Cu/SiO2 catalyst formate species were initially formed which were subsequently hydrogenated to methanol. During the reaction a steady state concentration of formate species persisted on the copper. Additionally, a small quantity of gaseous methane was produced. In contrast, the reaction of CO2 and H2 on ZnO/SiO2 catalyst only resulted in the formation of zinc formate species: no methanol was detected. The interaction of CO2 and H2 with Cu/ZnO/SiO2 catalyst gave formate species on both copper and zinc oxide. Methanol was again formed by the hydrogenation of copper formate species. Steady-state concentrations of copper formate existed under actual industrial reaction conditions, and copper formate is the pivotal intermediate for methanol synthesis. Collation of these results with previous data on copper-based methanol synthesis catalysts allowed the formulation of a reaction mechanism

Two-Dimensional Correlation Analysis of Temperature-Dependent FT-IR Spectra of Oleic Acid

In the present study, variable temperature FT-IR spectroscopic investigations were used to characterize the spectral changes in oleic acid during heating oleic acid in the temperature range from -30 degrees;C to 22 degrees C. In order to extract more information about the spectral variations taking place during the phase transition process, 2D correlation spectroscopy (2DCOS) was employed for the stretching (C?O) and rocking (CH2) band of oleic acid. However, the interpretation of these spectral variations in the FT-IR spectra is not straightforward, because the absorption bands are heavily overlapped and change due to two processes: recrystallization of the ?-phase and melting of the oleic acid. Furthermore, the solid phase transition from the ?- to the a-phase was also observed between -4 degrees C and -2 degrees C. Thus, for a more detailed 2DCOS analysis, we have split up the spectral data set in the subsets recorded between -30 degrees C to -16 degrees C, -16 degrees C to 10 degrees C, and 10 degrees C to 22 degrees C. In the corresponding synchronous and asynchronous 2D correlation plots, absorption bands that are characteristic of the crystalline and amorphous regions of oleic acid were separated.

用NMR、FT-IR、DSC和AFM的方法研究PP-b-PE的结构与性能

聚丙烯是一种优异的高分子材料，但其低温抗冲击性能欠佳，因而限制了其应用范围。采用PP与PE嵌段共聚来改善PP的抗冲击性能是世界上目前行之有效的方法，因而引起人们的重视。由于聚丙烯嵌段共聚物（PP-b-PE）是由多组分组成的复杂体系，对其组成和链的结构仍不十分清楚。因此，本工作选取国外（6组）和国内（5组）共计11组PP-b-PE样品，分别对其结构、性能及其影响因素进行了研究，为实际应用提供了依据。为了保证能将PP-b-PE中的橡胶成分抽提出来，先将PP-b-PE样品用二甲苯溶解，之后加入甲醇沉淀、过滤、干燥，最后用正庚烷抽提，使得PP-b-PE样品中正庚烷的不可溶物与可溶物完全分离。其中，可溶物即为橡胶，不可溶物为塑料。再利用高温核磁共振谱仪（NMR）、示差扫描量热仪（DSC）和傅立汗卜变换红外谱仪（FT-IR）等先进的分析技术手段进行结构分析，并用原子力显微镜（AFM）观察生产过程中样品的形貌。实验和分析结果表明：在正庚烷可溶物中含有低熔点的聚丙烯和嵌段长度不同且能结晶的聚乙烯；并且还含有属于乙丙无规共聚物橡胶部分的n值小于4的（-CH2-）n结构，以及嵌有结晶性的丙烯和乙烯链节。正庚烷的不可溶物主要为聚丙烯，及少量聚乙烯。对于不同物性的PP-b-PE而言，正庚烷不可溶物决定了其刚性，正庚烷可溶物决定了其韧性，并由其粘度比决定了橡胶在聚丙烯中的分布情况。用AFM来研究PP-b-PE中的橡胶颗粒的分布情况是非常好的分析方法。PP-b-PE样品中橡胶的含量及其组成成分将对PP-b-PE的性能产生很大的影响。国内用浆液法生产的PP-b-PE样品中橡胶含量相对于用液一气相法和气相法生产的要少，但在其正庚烷不可溶物中含有较多的乙烯。从而可以用控制乙烯的含量来改善其抗冲击性能，这是浆液法与液一气相法和气相法的最大区别。液一气相法和气相法生产的PP-b-PE样品中的正庚烷可溶物的含量和结构十分接近。结果表明，本文采用多种不同的先进的分析方法和实验手段对PP-b-PE的结构与性能的研究是一条有效可行的实验途径。

Adsorption and reaction of thiophene and H2S on Mo2C/Al2O3 catalyst studied by in situ FT-IR spectroscopy

The reactions of both thiophene and H2S onMo(2)C/Al2O3 catalyst have been studied by in situ FT-IR spectroscopy. CO adsorption was used to probe the surface sites of Mo2C/Al2O3 catalyst under the interaction and reaction of thiophene and H2S. When the fresh Mo2C/Al2O3 catalyst is treated with a thiophene/H-2 mixture above 473 K, hydrogenated species exhibiting IR bands in the regions 2800-3000 cm(-1) are produced on the surface, indicating that thiophene reacts with the fresh carbide catalyst at relatively low temperatures. IR spectra of adsorbed CO on fresh Mo2C/Al2O3 pretreated by thiophene/H-2 at different temperatures clearly reveal the gradual sulfidation of the carbide catalyst at temperatures higher than 473 K, while H2S/H-2 can sulfide the Mo2C/Al2O3 catalyst surface readily at room temperature (RT). The sulfidation of the carbide surface by the reaction with thiophene or H2S maybe the major cause of the deactivation of carbide catalysts in hydrotreating reactions. The surface of the sulfided carbide catalyst can be only partially regenerated by a recarburization using CH4/H-2 at 1033 K. When the catalyst is first oxidized and then recarburized, the carbide surface can be completely reproduced.

In situ FT-IR spectroscopic studies of CO adsorption on fresh Mo2C/Al2O3 catalyst

The surface sites of supported molybdenum carbide catalyst derived from different synthesis stages have been studied by in situ FT-IR spectroscopy using CO as the probe molecule. Adsorbed CO on the reduced passivated Mo2C/Al2O3 catalyst gives a main band at 2180 cm(-1), which can be assigned to linearly adsorbed CO on Mo4+ sites. The IR results show that the surface of reduced passivated sample is dominated by molybdenum oxycarbide. However, a characteristic IR band at 2054 cm-1 was observed for the adsorbed CO on MoO3/Al2O3 carburized with CH4/H-2 mixture at 1033 K (fresh Mo2C/Al2O3), which can be assigned to linearly adsorbed CO on Modelta+ (0 < delta < 2) sites Of Mo2C/Al2O3, Unlike adsorbed CO on reduced passivated Mo2C/Al2O3 catalyst, the IR spectra of adsorbed CO on fresh Mo2C/Al2O3 shows similarity to that on some of the group VIII metals (such as Pt and Pd), suggesting that fresh carbide resembles noble metals. To study the stability Of Mo2C catalyst during H-2 treatment and find proper conditions to remove the deposited carbon species, H-2 treatment of fresh Mo2C/Al2O3 catalyst at different temperatures was conducted. Partial amounts of carbon atoms in Mo2C along with some surface-deposited carbon species can be removed by the H, treatment even at 450 K. Both the surface-deposited carbon species and carbon atoms in carbide can be extensively removed at temperatures above 873 K.

In-situ microscopic FT-IR spectroelectrochemical investigation of polythiophene film modified electrode

A polythiophene film was electrochemically deposited on a Pt micro-plate electrode and investigated by cyclic voltammetry and in-situ reflection microscopic FTIR spectroscopy. The FTIR analysis showed that the electropolymerization of thiophene on the Pt surface was affected Lv the surface adsorption processes of thiophene molecules. Two adsorption modes were identified. Two structure models of the polythiophene chain were observed simultaneously. It was proposed that the good conductibility of the polythiophene film was originated from a co-vibratory equilibrium of the link part of model I and model II.