Na对PtSn/ZSM-5催化丙烷脱氢反应性能的影响

以HZSM-5分子筛为载体, 利用分步浸渍法制得不同Na含量的PtSnNa/ZSM-5催化剂, 用于丙烷脱氢反应. 利用XRD、吡啶吸附红外光谱、NH3-TPD、氢化学吸附、TPR等手段, 研究了Na的添加对PtSn/ZSM-5催化剂物化性质的影响. 结果表明: Na的添加对PtSn/ZSM-5催化剂的反应性能影响明显. 适量Na的添加不仅降低了催化剂中的Brönsted酸中心和Lewis中强/强酸中心, 抑制了积碳的发生, 提高了催化反应的稳定性; 而且提高了催化剂表面的Pt金属裸露度, 增加了反应活性. 当Na含量为1.0%(w)时, 催化剂的丙烯选择性和收率达到最大, 反应30 h后, 丙烷转化率仍然保持很高(36.4%). 继续增加Na含量, 催化剂中的Lewis弱酸中心有所增加, 同时Sn组分易于被还原成Sn0, 丙烷裂解、氢解等副反应增加, 不利于脱氢反应的进行.     

Evolution of MoTeOx/SiO2 and MoBiTeOx/SiO2 catalysts in the partial oxidation of propane to acrolein

A thorough investigation of the catalysts Mo₁Te₁O_x/SiO₂ and Mo₁Bi_0.05Te₁O_x/SiO₂ in the partial oxidation of propane is presented in this paper, in order to elucidate the nature and behavior of the active surface. The catalysts’ structures and redox properties were investigated by means of X-ray powder diffraction, Raman spectroscopy, in situ Raman spectroscopy, X-ray photoelectron spectroscopy, and H₂-TPR techniques. The results indicate that Te-polymolybdate is the main active phase on fresh catalysts. During reaction, the catalysts underwent a progressive reduction, resulting in the reconstruction of the active surface and the formation of a MoO₃ phase. The synergistic effect between Te-polymolybdate and MoO₃ was assumed to promote catalytic performance. The different stabilities of Mo₁Te₁O_x/SiO₂ and Mo₁Bi_0.05Te₁O_x/SiO₂ catalysts are also discussed.     

The first high-resolution analysis of the low-lying ν9 band of propane

The ν₉ fundamental band (C-C-C deformation) of propane (C₃H₈) at 369 cm⁻¹ has been studied at high-resolution (0.0011 cm⁻¹) with spectra recorded using the synchrotron radiation from the French light source facility at SOLEIL coupled to a Bruker IFS 125HR Fourier transform spectrometer. A 2.526 m base multipass cell with optical paths from 10.296 to 151.78 m was used. In addition, a spectrum was also recorded using a conventional globar source. Comparison of these experimental spectra shows clearly the gain obtained on the signal-to-noise ratios with the synchrotron radiation. The spectra have been thoroughly analyzed and transitions up to J=65 and K_a=33 have been assigned. The upper-state rotational levels were fitted using an A-type Watson Hamiltonian written in the I^r representation. An accurate band center ν₀ (ν₉)=369.228080(25) cm⁻¹ as well as accurate rotational and centrifugal distortion constants have been obtained and used to simulate a synthetic spectrum. These parameters should be useful to simulate hot bands of propane involving the 9¹ vibrational level as their lower state.     

Infrared absorption cross sections for propane (C3H8) in the 3 μm region

Infrared absorption cross sections for propane have been measured in the 3 μm spectral region from spectra recorded using a high-resolution FTIR spectrometer (Bruker IFS 125 HR). The spectra of mixtures of propane with dry synthetic air were recorded at 0.015 cm⁻¹ resolution (calculated as 0.9/MOPD using the Bruker definition of resolution), at a number of temperatures and pressures appropriate for atmospheric conditions. Intensities were calibrated using two propane spectra (recorded at 278 and 293 K) taken from the Pacific Northwest National Laboratory (PNNL) IR database.     

Measurements and modeling of high-temperature,high-pressure density for binary mixtures of propane with n-decane and propane with n-eicosane

Binary mixture density data are reported for propane (C₃) with n-decane (C₁₀) and with n-eicosane (C₂₀) at T = (320 to 525) K and pressures to 265 MPa. The (C₃ + C₁₀) mixture density data are in good agreement with available literature data to 70 MPa, which is the maximum reported literature pressure. There are no available binary mixture density data to compare to the (C₃ + C₂₀) mixture density data reported in the present study. The mixture density data are correlated with the Tait equation to facilitate interpolation of the data at different experimental conditions. Equations of state that are suitable for reservoir simulations are used to model the reported data. These models include the Peng–Robinson equation of state (PREoS), a volume-translated PREoS fit to high temperature, high pressure (HTHP) pure component density data, the PC-SAFT EoS, and modifications of the PC-SAFT EoS developed for better representation of HTHP data. The models give superior density predictions for (C₃ + C₁₀) mixtures compared to (C₃ + C₂₀) mixtures.     

Co3O4-CeO2氧化物对丙烷完全氧化的催化性能（英文）

挥发性有机化合物(VOCs)是全球大气污染物的主要来源,近年来已造成严重的环境问题.催化氧化是一种有效的、经济可行的VOCs去除技术,其研究的关键在于开发高效、稳定的催化剂.在本文中,我们采用柠檬酸法合成了一系列具有不同Co/(Ce+Co)摩尔比的Co3O4-CeO2二元氧化物催化剂,研究了其对丙烷(低碳VOCs)的催化氧化性能.在催化活性测试中,反应气的组成为0.2 vol.%C3H8和5 vol.%O2,Ar为平衡气,气体总流速为200 mL min^-1.实验结果表明,Ce的掺入能够明显提高Co3O4的丙烷催化氧化性能,Co3O4-CeO2催化剂的丙烷催化氧化活性顺序为CoCeOx-70>CoCeOx-90>Co3O4>CoCeOx-50>CoCeOx-20>CeO2.当Co/(Ce+Co)摩尔比为70%时,CoCeOx-70催化剂的丙烷催化氧化性能最好.在丙烷转化率达到90%时,CoCeOx-70催化剂的反应温度为310℃(GHSV=120000mL h^-1 g^-1),相比于单一的Co3O4催化剂的反应温度降低了25℃.XRD和TEM表征结果显示,在Co3O4-CeO2二元氧化物催化剂中存在Co3O4和CeO2两种晶型,同时随着Ce的掺入,催化剂的粒径明显降低.Raman光谱图显示,Ce的掺入使催化剂的晶格发生畸变,促进催化剂表面氧空位的产生,为催化剂中氧的迁移提供晶格位点.H2-TPR和C3H8-TPSR结果表明,Co3O4与CeO2间存在相互作用,能够提高催化剂的低温还原性能,以促进催化剂的丙烷催化氧化.O2-TPD和O 1s XPS结果表明,Ce的掺入能够增加催化剂表面活性氧物种的产生,提高催化剂中氧的移动性,从而提高了催化剂对丙烷的催化氧化活性.在对Co3O4和CoCeOx-70催化剂进行in-situ DRIFTS表征和简单的动力学研究,我们发现Ce的掺入不改变催化剂的丙烷催化氧化反应路径,其存在能够促进丙烷在催化剂表面的吸附和活化,以提高催化剂的丙烷催化氧化活性.同时,丙酮和酯作为中间物参与到丙烷的催化氧化反应过程中.此外,我们考察了反应气氛中水蒸气和CO2的存在对催化剂催化性能的影响.结果表明,CO2和水蒸气的存在都抑制了催化剂的丙烷催化氧化活性,催化性能随着CO2和水蒸气浓度的增加而降低.在相同条件下,水蒸气对催化剂催化性能的抑制作用明显大于CO2的抑制作用,但这种抑制作用会随着反应气中水蒸气和CO2的消失而消失.在稳定性测试中,CoCeOx-70催化剂表现出优异的抗水蒸气和CO2性能.在反应气中存在5 vol.%水蒸气和5 vol.%CO2的条件下,CoCeOx-70催化剂在50 h的稳定性测试中均未出现明显的失活现象.同时,经过10次加热和降温循环测试后,催化剂的催化活性也没有发生明显变化,这为CoCeOx-70催化剂的未来工业化的应用提供了可能.     

Dehydrogenation of propane in the presence of carbon dioxide over oxide-based catalysts

In the present study, we show the advantages of CO₂ use for the dehydrogenation of propane to propene on the basis of thermodynamic considerations and some experimental results. Several metal oxides Ga₂O₃, Cr₂O₃, Fe₂O₃ unsupported and supported on g- Al₂O₃ and SiO₂ were tested. Ga₂O₃ catalyst was found to be an effective agent for dehydrogenation of propane to propene. The yield of propene at 873 K was 30.1 %. This revised version was published online in June 2006 with corrections to the Cover Date.     

Neural network-based correlations for the thermal conductivity of propane

An alternative approach, exploiting neural networks, is proposed to develop thermal conductivity correlation of propane for the first time. In order to test the accuracy of the proposed technique and demonstrate its utility in fitting the thermal conductivity surface of propane, we have established a thermal conductivity correlation in terms of temperature and density, and then compared its predictions with those obtained by the conventional method. The results obtained are so impressive that the neural network correlation has lower overall average absolute deviations (AADs) in each data set.     

Measurement of the (p, ρ, T) relation of propane, propylene, n-butane, and isobutane in the temperature range from (95 to 340) K at pressures up to 12 MPa using an accurate two-sinker densimeter

Comprehensive (p, ρ, T) measurements on propane. propylene, n-butane, and isobutane have been carried out in the homogenous gas and liquid phases and along the (vapour + liquid) coexistence curve. The results cover a temperature range from (95 to 340) K at pressures up to 12 MPa. The measurements were performed by using an accurate two-sinker densimeter based on the Archimedes’ buoyancy principle. The total uncertainty of the measurements in density is (0.01 to 0.02)% (level of confidence 95%), except for low gas densities. Values for the second and third virial coefficients have also been determined from the measurements in the homogeneous gas regions of the fluids. The experimental results have been compared with previous results of other experimentalists and with values calculated from current equations of state. Moreover, previously unpublished results of (p, ρ, T) measurements on propane in the temperature range from (340 to 520) K at pressures up to 30 MPa are listed in the appendix.     

Modifications induced by potassium addition on chromia/alumina catalysts and their influence on the catalytic activity for the oxidative dehydrogenation of propane

The oxidative dehydrogenation of propane was investigated on K-containing chromia/alumina catalysts, with nominal Cr and K loadings of 10 and 0-2 wt%, respectively. Their chemical composition, structure, texture, nature of surface species, redox features and surface acidity were determined. Catalytic behaviour was investigated in a continuous-flow micro-reactor under different conditions. Besides the nature and concentration of the chromium species, potassium addition was found to affect the reducibility of the catalysts as well as their acid surface features. Such modifications were found to condition the catalytic behaviour, which appeared somewhat peculiar in comparison with that of the catalytic systems reported in literature.