Kinetics of carbon oxide evolution in temperature-programmed oxidation of carbonaceous laydown deposited on wet oxidation catalysts

The combustion kinetics of coke laydown on wet oxidation catalysts was studied by means of temperature-programmed oxidation and mass spectrometry within the temperature range (30–600°C). The coke deposits were formed over three different catalysts 1 wt.% Pt/Al₂O₃, MnO₂/CeO₂ and 1 wt.% Pt–MnO₂/CeO₂ during phenol deep oxidation in a three-phase slurry reactor at various reaction conditions (exposure time, temperature, oxygen pressure, catalyst loading). The carbon oxides, oxygen and water fluxes arising from the combustion of the carbonaceous deposits in a 5% O₂/He mixture, were continuously monitored. In all cases, unimodal quasi-Gaussian distributions were obtained for CO₂ while no CO was detected. These evolutions were successfully described by a modified “fractal power-law” grain model. The coke-dependence of the carbon dioxide profiles was related to the fractal dimension of the catalyst surface and to the oxygen partial order during coke burn-off. The corresponding change in O₂ partial order was ascribed to competition between three steps in the combustion mechanism: non-dissociative O₂ chemisorption, interaction of oxygen with undissociated dioxygen bearing surface species, physical desorption of the complex oxide as carbon dioxide.     

A series of NiMo/Al2O3 catalysts containing boron and phosphorus: Part II. Hydrodenitrogenation and hydrodesulfurization using heavy gas oil derived from Athabasca bitumen

The hydrodenitrogenation (HDN) and hydrodesulfurization (HDS) activity of a series of NiMo/Al₂O₃ catalyst containing boron (B) and phosphorus (P) were tested in a trickle bed reactor using heavy gas oil derived from Athabasca bitumen. Detailed characterization of these catalysts is given in Part I of this paper. Addition of B and P caused the formation of extremely strong acid sites on the catalyst and enhanced its HDN activity. The total (TN), basic (BN) and non-basic nitrogen (NBN) conversions increased from 61.9 to 78.0 wt.%, from 78.9 to 93.0 wt.% and from 52.8 to 70.0 wt.%, respectively, with the increase in B concentration from 0 to 1.7 wt.% to NiMo/Al₂O₃ catalyst. Similarly, TN, BN and NBN conversions increased from 61.9 to 78.4 wt.%, from 78.9 to 91.0 wt.%, and from 52.8 to 71.6 wt.% with the addition of 2.7 wt.% P. Though the addition of B and P to NiMo/Al₂O₃ catalyst did not show any significant effect on S conversion, the HDN and HDS activities of the catalyst containing 1.7 wt.% B and the one containing 2.7 wt.% P are comparable to those of a commercial catalyst. The activity over extended period indicated that catalysts L and K were more stable (lower deactivation rate) in terms of nitrogen removal activity than catalyst B (reference catalyst). On the other hand, the stability for sulfur removal was comparable with catalyst B. Selected catalysts after use were characterized using BET surface area, TPR, TPD and SEM techniques which were correlated further with their activities.     

过氧化氢氧化苯制苯酚的催化剂研究进展

综述了过氧化氢直接氧化苯制苯酚过程中相关催化剂的研究进展,重点介绍了含钛、钒、铁、铜的催化剂,同时给出了各种催化剂所达到的收率和选择性及其工业化前景。     

n-butane isomerization on sulfated zirconia. Deactivation and regeneration as studied by Raman,UV-VIS diffuse reflectance and ESR spectroscopy

n-butane isomerization on sulfated zirconia was studied in the temperature range 393–473 K. Rapid deactivation occurs, when the reaction is carried out in He carrier gas. In contrast, stable stationary activity was observed in H₂ carrier gas. In situ Raman and UV-VIS diffuse reflectance spectroscopy and ESR showed that the deactivation is caused by the formation of allylic and polyenylic cations and polycyclic aromatic compounds, the formation of which is largely prevented in the presence of H₂. Deactivated catalysts can be fully regenerated by treatment at 723–753 K in flowing O₂. The regeneration process was also followed by in situ spectroscopies.     

Characterization of Mo–Sn–O system by means of Raman spectroscopy and electrical conductivity measurements

Mo–Sn–O systems were characterized by Raman spectroscopy and electrical conductivity measurements. The catalysts were obtained from precipitation of SnCl₄ by ammonia in the presence of (NH₄)₂Mo₇O₂₄ using four different levels of Mo concentration. The electrical conductivity measurements showed that particles are formed by agglomeration of SnO₂ crystals aggregated by polymolybdate. Raman spectroscopy suggested that four-coordinated species are dispersed at the external surface while six-coordinated species are inside the particles. For high Mo concentration (Mo >10%), octahedral coordinated species are also on the surface. Bulk MoO₃ oxide was not observed. These results confirm the model previously proposed.     

辛烯醛气相加氢制辛醇催化剂及其工艺的研究

介绍了一种铜锌系辛烯醛气相加氢制辛醇的催化剂,并对催化剂的制备方法及加氢工艺条件进行了考察,确定了最佳的工艺条件。     

Characterization of a coating layer on glass fibre used as reinforcing material in a polyepoxide matrix by means of FTIR spectroscopy and vapour phase interaction studies with monofunctional model compounds

Coatings on glass fibres, used to reinforce polyepoxide matrices, were examined by Fourier transform infra-red spectroscopy and by their reaction with styrene oxide, aniline, and also water in the vapour phase which was followed calorimetrically and gravimetrically. The coatings comprised an adhesive (of the DGEBA epoxy prepolymer type) applied on its own or together with a coupling agent (γ aminopropyltriethoxysilane). In all tests, these fibres were compared with untreated fibres of a similar type. The results of the studies indicate that the combination of the two coatings forms a reactive mixture within themselves which may inhibit uniform coating of the glass. It is also shown that the coating products on the glass control the process of water diffusion.