Regeneration of H<Subscript>3</Subscript>PW<Subscript>12</Subscript>O<Subscript>40</Subscript> catalyst in the direct preparation of dichloropropanol (DCP) from glycerol and hydrochloric acid gas

Methods for regenerating H₃PW₁₂O₄₀ catalyst in the solvent-free direct preparation of dichloropropanol (DCP) from glycerol and hydrochloric acid gas were investigated. Regenerated H₃PW₁₂O₄₀ catalyst was then applied to the solvent-free direct preparation of DCP. In the solvent-free direct preparation of DCP, selectivity for DCP over H₃PW₁₂O₄₀ catalyst regenerated by method I (recovery of solid H₃PW₁₂O₄₀ catalyst by evaporating homogeneous liquidphase product solution) significantly decreased with increasing recycling run, while that over H₃PW₁₂O₄₀ catalyst regenerated by method II (regeneration of H₃PW₁₂O₄₀ catalyst by oxidative calcination of solid product recovered by method I) was slightly decreased with no significant catalyst deactivation with respect to recycling run. On the other hand, selectivity for DCP over H₃PW₁₂O₄₀ catalyst regenerated by method III (regeneration of H₃PW₁₂O₄₀ catalyst by recrystallization and subsequent oxidative calcination of solid product recovered by method II) was the same as that over fresh catalyst without any catalyst deactivation with respect to recycling run. Thus, method III was found to be the most efficient method for the regeneration of H₃PW₁₂O₄₀ catalyst.     

Increase in the thermal stability during the methanation of CO2 over a Rh catalyst prepared from an amorphous alloy

The hydrogenation of CO₂ was investigated over a Rh catalyst prepared from an amorphous Rh₂₀Zr₈₀ alloy. After the reaction, the catalyst was regenerated by oxidation in air and reduction in H₂. It was observed that the reaction activity increased with the repetition of regeneration. We also prepared the Rh/ZrO₂ catalyst by the conventional impregnation method. The difference in the turnover frequency between the alloy-precursor catalyst and the conventionally prepared catalyst was small. For the alloy-precursor catalyst, however, the conversion and CH₄ selectivity were stable at 723 K, whereas the conversion and CH₄ selectivity decreased with time-on-stream even at 673 K for the catalyst prepared by the conventional impregnation method.     

Effect of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-ZrO<Subscript>2</Subscript> xerogel support on hydrogen production by steam reforming of LNG over Ni/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-ZrO<Subscript>2</Subscript> catalyst

An Al₂O₃-ZrO₂ xerogel (AZ-SG) was prepared by a sol-gel method for use as a support for a nickel catalyst. The Ni/AZ-SG catalyst was then prepared by an impregnation method, and was applied to hydrogen production by steam reforming of LNG. A nickel catalyst supported on commercial alumina (A-C) was also prepared (Ni/A-C) for comparison. The hydroxyl-rich surface of the AZ-SG support increased the dispersion of nickel species on the support during the calcination step. The formation of a surface nickel aluminate-like phase in the Ni/AZ-SG catalyst greatly enhanced the reducibility of the Ni/AZ-SG catalyst. The ZrO₂ in the AZ-SG support increased the adsorption of steam onto the support and the subsequent spillover of steam from the support to the active nickel sites in the Ni/AZ-SG catalyst. Both the high surface area and the well-developed mesoporosity of the Ni/AZ-SG catalyst improved the gasification of adsorbed surface hydrocarbons in the reaction. In the steam reforming of LNG, the Ni/AZ-SG catalyst showed a better catalytic performance than the Ni/A-C catalyst. Moreover, the Ni/AZ-SG catalyst showed strong resistance toward catalyst deactivation.     

Effects of ZnO Contained in Supported Cu-Based Catalysts on Their Activities for Several Reactions

The specific activity of Cu-based catalyst supported on Al₂O₃, ZrO₂ or SiO₂ for methanol synthesis and reverse water–gas shift reactions was improved by the addition of ZnO to the catalyst. On the other hand, the specific activity of the supported Cu-based catalyst for methanol steam reforming and water–gas shift reactions was not improved by the addition of ZnO to the catalyst.     

介质阻挡放电等离子体处理载体对CO甲烷化Ni/SiO2催化剂性能的改进

以经介质阻挡放电等离子体处理的SiO₂为载体,用浸渍法制备了Ni/SiO₂催化剂,并进行了CO甲烷化反应评价。与载体未经处理的常规Ni/SiO₂催化剂相比,载体经处理的催化剂在400℃下的CO与H₂转化率均提高了约6%,且在经700℃烧结6 h后,活性仍高于常规催化剂。XRD、TEM和H₂-TPR结果表明,载体经处理的催化剂,Ni颗粒粒径更小、粒径分布更集中,Ni与SiO₂之间的相互作用更强,证明等离子体处理使SiO₂更有利于促进Ni的分散。     

Preparation of SnO2-CNTs supported Pt catalysts and their electrocatalytic properties for ethanol oxidation

SnO₂-carbon nanotubes (CNTs) composites were prepared by sol-gel method, and characterized by scanning electron microscopy and X-ray diffraction. Due to high stability in diluted acidic solution, SnO₂-CNTs composites were selected as the catalyst support and second catalyst for ethanol electrooxidation. The electrocatalytic properties of the SnO₂-CNTs supported platinum (Pt) catalyst (Pt/SnO₂-CNTs) for ethanol oxidation have been investigated by typical electrochemical methods. Under the same mass loading of Pt, the Pt/SnO₂-CNTs catalyst shows higher electrocatalytic activity and better long-term cycle stability than Pt/SnO₂ catalyst. Additionally, the effect of the mass ratio of CNTs to SnO₂ on the electrocatalytic activity of the electrode for ethanol oxidation was investigated, and the optimum mass ratio of CNTs to SnO₂ in the Pt/SnO₂-CNTs catalyst is 1/6.3.     

Comparison of physically mixed and separated MgO and WO<Subscript>3</Subscript>/SiO<Subscript>2</Subscript> catalyst for propylene production via 1-butene metathesis

We examined the catalyst bed design of MgO and WO₃/SiO₂ for production of propylene via metathesis of 1-butene. WO₃/SiO₂ was used as a bi-functional catalyst for isomerization and metathesis reactions. Addition of MgO was proposed to help improve the isomerization activity and hence the propylene yield. Experimental studies were carried out to determine activity and reaction kinetics of 1-butene isomerization over MgO isomerization catalyst and 1-butene metathesis over WO₃/SiO₂ bi-functional catalyst for designing a suitable catalyst bed. Two types of catalyst bed arrangement—physically mixed bed and separated bed—were considered and compared by computer simulation. The simulations reveal that adding MgO in the separated bed by packing MgO before WO₃/SiO₂ offers superior propylene yield to the physically mixed bed. The appropriate %MgO loading in catalyst bed which offers a maximum propylene yield was found to vary (3 and 23%), depending on operating condition.     

Catalytic Behaviors of Amorphous Co-B Catalysts in Hydroformylation of 1-Octene

An amorphous Co-B catalyst was prepared by chemical reduction method and characterized by isothermal N₂ adsorption/desorption, XRD, ICP-AES and HR-TEM. The catalytic activity of the Co-B catalyst in the hydroformylation of 1-octene was evaluated in a 100 mL stainless autoclave. Fresh amorphous Co-B catalyst showed a relatively high activity in the hydroformylation of 1-octene. The thermal stability of fresh Co-B catalyst was also examined. When fresh Co-B catalyst was thermally treated in N₂ or H₂ atmosphere at 200–500 °C for 2 h, the specific surface area and the catalytic activity of the Co-B catalyst decreased. When Co-B was supported on SiO₂, the activity of the catalyst increased obviously. Compared with conventional supported Co/SiO₂ catalyst, Co-B/SiO₂ showed much higher activity than Co/SiO₂. The influences of solvents and reaction conditions on the catalytic activity of the amorphous Co-B catalyst were also studied. The recycle test of the amorphous Co-B catalyst was done.     

Reactivation of spent Pd/AC catalyst by supercritical CO2 fluid extraction

In this article, we reported a nondestructive and environmentally friendly method for the reactivation of a spent Pd/AC catalyst for the hydrogenation of benzoic acid by using supercritical CO₂ (scCO₂) fluid extraction. The effects of reactivation conditions, such as extraction temperature, pressure, CO₂ flow rate, and time, on the activity of the reactivated Pd/AC catalyst, were presented. The catalyst was characterized by N₂ physisorption, laser particle size analysis, and transmission electron spectroscopy, and the liquid extract was analyzed by GC-MS. It is found that scCO₂ fluid extraction was very efficient in eliminating organic substances blocking the pores of the catalyst, while did not affect noticeably the granule size of the catalyst and the particle size of Pd. The reactivated Pd/AC catalyst regained more than 70% of the activity of the fresh 5.0 wt % Pd/AC catalyst, and has been successfully used in an industrial unit for the hydrogenation of benzoic acid. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Modification of a heterogeneous catalyst: Sulfonated graphene oxide coated by SiO2 as an efficient catalyst for Beckmann rearrangement

In this work and in continuation of our strategy for improving the performance of heterogeneous catalysts, the SiO₂@GO-OSO₃H catalyst was applied as a very efficient solid acid catalyst for the Beckmann rearrangement. This catalyst effectively catalyzed the liquid-phase Beckmann rearrangement of cyclohexanone oxime to caprolactam in high yield under very mild conditions. The improvement of GO-OSO₃H catalyst in regard to its separation from reaction mixture is achieved by coating it with a mesoporous SiO₂ layer. The influence of the operating parameters on the performance of the catalyst namely solvent, temperature, amount of catalyst, and time was studied.     

Preparation of a new precipitated iron catalyst for Fischer–Tropsch synthesis

It is well known that a typical precipitated iron catalyst was prepared by iron(III) nitrate (Fe(NO₃)₃). The modified iron catalyst was prepared by iron(II) sulfate in our laboratory. The results from catalytic performance tests showed that the iron catalyst prepared from iron sulfate (cat-S) has the higher activity for Fischer–Tropsch synthesis (FTS) than the catalyst prepared from iron nitrate (cat-N). The results from XRD of catalyst before use showed the difference definitely. The XRD patterns of these catalysts indicate that the main phase of cat-N is Fe₂O₃, whereas the phases of cat-S are a mixture of Fe₂O₃ and Fe₃O₄. It is considered that magnetite was directly formed during precipitation and contained in the catalyst before use enhances the activity for FTS.     

Fischer–Tropsch synthesis over Co/TiO2 catalyst: Effect of catalyst activation by CO compared to H2

Co/TiO₂ catalyst activation for Fischer–Tropsch (FT) reaction by CO in comparison to H₂ has been performed. The catalyst, prepared by incipient wetness impregnation, has been characterized using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses after separate reduction using CO and H₂ respectively. Temperature programmed reduction (TPR) analyses were also conducted to study the reduction behaviour of the catalyst in presence of H₂ and CO respectively. CO improved catalyst reduction and produced a more stable and active catalyst with higher selectivity and yield for C_5 + hydrocarbons at extended time-on-stream.     

Selective Isopropylation of Biphenyl to 4,4′-DIPB over Mordenite (MOR) Type Zeolite Obtained from a Layered Sodium Silicate Magadiite

Molybdenum carbide catalysts for water–gas shift (WGS) reaction were investigated to develop an alternate commercial LTS (Cu-Zn/Al₂O₃) catalyst for an onboard gasoline fuel processor. The catalysts were prepared by a temperature-programmed method and were characterized by N₂ physisorption, CO chemisorption, XRD and XPS. It was found that the Mo₂C catalyst showed higher activity and stability than the commercial LTS catalyst, even though both catalysts were deactivated during the thermal cycling runs. The optimum carburization temperature for preparing Mo₂C was in the range of 640–650 °C. It was found that the deactivation of the Mo₂C catalyst was caused by the transition of Mo^δ+ (IV < δ⁺ < VI, MoO_xC_y), Mo^IV and Mo₂C on the surface of the Mo₂C catalyst to Mo^VI (MoO₃) with the reaction of H₂O in the reactant. It was identified that molybdenum carbide catalyst is an attractive candidate for the alternate Cu-Zn/Al₂O₃ catalyst for automotive applications.     

Partial oxidation of alkenes by a membrane catalyst conducting H+ and e−

Partial oxidation of C₂H₄ to MeCHO (>95% selectivity) with O₂ by a new type of membrane catalyst was studied at 353 K. Reaction system was (C₂H₄, H₂O | membrane catalyst | O₂, NO). The membrane catalyst was assembled from three sheets, porous catalyst for oxidation of C₂H₄, mixed conductor of H⁺ and e⁻, porous catalyst for the reduction of O₂. NO functioned as a co-catalyst for reduction of O₂ to H₂O. This three-layered membrane catalyst functioned as a hydrogen permeation membrane.     

Synergic effect of Pd/γ-alumina and Cu/ZSM-5 on the performance of NO x storage reduction catalyst

NO _x reduction with a combination of catalysts, Pd catalyst, NO _x storage reduction (NSR) catalyst and Cu/ZSM-5 in turn, was investigated to elucidate for the high NO _x reduction activity of this catalyst combination under oxidative atmosphere with periodic deep rich operation. The catalytic activity was evaluated using the simulated exhaust gases with periodically fluctuation between oxidative and reductive atmospheres, and it was found that the NO _x reduction activity with this catalyst combination was apparently higher than that of the solely accumulation of these individual activities, which was caused by the additional synergic effect by this combination. The Pd catalyst upstream of the NSR catalyst improved NO _x storage ability by NO₂ formation under oxidative atmosphere. The stored NO _x was reduced to NH₃ on the NSR catalyst, and the generated NH₃ was adsorbed on Cu/ZSM-5 downstream of the NSR catalyst under the reductive atmosphere, and subsequently reacted with NO _x on the Cu/ZSM-5 under the oxidative atmosphere.     

Regeneration of Lamina TS-1 Catalyst in the Epoxidation of Propylene with Hydrogen Peroxide

The deactivation and regeneration of the lamina titanium silicalite (TS-1) catalyst for the epoxidation of propylene with dilute H₂O₂was investigated in a fixed-bed reactor. In the scale-up experiment, the dosage of the lamina TS-1 catalyst is 2. 5 kg, after 1000 h reaction the catalyst still exhibits good performance and further increases the reaction time, the conversion of H₂O₂begins to decrease. TG and BET analyses of the deactivated catalysts show that the main species occluded within the zeolite pore are propylene oxide oligomers, and these species occupying the active Ti site and blocking the pores of the lamina TS-1 are the main reason for the deactivation of catalyst. The deactivated catalyst can be regenerated by different regeneration methods. The activity of deactivated catalysts regenerated by dilute H₂O₂or heat treatment by using air or nitrogen as a calcination media can be fully recovered, but a decline in propylene oxide (PO) selectivity of the regenerated catalyst has been observed during the first hours of reaction. However, water vapor treatment of the deactivated catalyst can improve the PO selectivity with the same activity as that of the fresh lamina TS-1 catalyst.     

Synthesis and activity of the Pt catalyst supported on CNT

Carbon nanotubes (CNT) were obtained by the decomposition of methane on a Ni catalyst supported on Al₂O₃. After the removal of the catalyst materials from CNT, a CNT-supported Pt catalyst was prepared, and this catalyst was characterized by XRD, XPS, and TEM. Activity of the CNT-supported Pt catalyst for hydrogenation of carbon–carbon double bonds at room temperature under the atmospheric pressure of hydrogen was examined. The CNT-supported Pt catalyst showed higher activity than the commercial Pt catalysts supported on activated carbon.     

Effect of H2SO4 concentration in washing solution on regeneration of commercial selective catalytic reduction catalyst

Commercial SCR catalysts used in a coal-fired power plant were regenerated by H₂SO₄ solution. The characterization study of the catalysts was carried out by using various analytical techniques. Major deactivating elements for the SCR catalyst were determined and the optimal condition for regeneration of the catalyst was investigated. The catalyst regenerated with 0.5 wt% H₂SO₄ solution showed a high catalytic activity due to an increase in the polymeric vanadates and acid sites by surface sulfates. A higher H₂SO₄ concentration than 2.5 wt% in the washing solution leads to a loss of active components out of the catalyst by dissolution and a dramatic decrease in the surface area.     

Effects of Pretreatments of Cu/ZnO-Based Catalysts on Their Activities for the Water–Gas Shift Reaction

The effects of the pretreatments of Cu/ZnO-based catalysts prepared by a coprecipitation method on their activities for the water–gas shift reaction at 523K were investigated. The activity of a Cu/ZnO/ZrO₂/Al₂O₃ catalyst for the water–gas shift reaction was less affected by calcination at temperatures ranging from 673-973K and by H₂ treatment at 573 or 723K than that of a Cu/ZnO/Al₂O₃ catalyst. The catalyst activity could be correlated mainly to the Cu surface area of the catalyst.     

Process Optimisation of In Situ H2 Generation From Ammonia Using Ni on Alumina Coated Cordierite Monoliths

A catalyst of Ni supported on alumina coated monolith has been prepared, characterized and tested in NH₃ decomposition. The characterization of the catalyst by XPS and TPR showed that there is no formation of aluminates after catalyst use. It is studied the effect of the space velocity, by varying the feed flow rate and the catalyst??s length. Some evidences are shown about the reaction inhibition by produced H₂ and about the reasons for the better performance of the monolith than packed bed catalyst.