国内乙烯装置丙烯加氢精制工艺研究进展

石油烃裂解分离的碳三(C3)馏分催化选择加氢脱丙炔(MA)和丙二烯(PD)是工业上乙烯装置丙烯精制以制备聚合级丙烯的方法.碳三催化选择加氢工艺有气相、液相(包括气-液相)和催化精馏三种类型,其中以液相工艺应用最广,催化精馏工艺未见工业化报道.综述了近年来国内在碳三加氢反应动力学、加氢工艺及催化剂失活和再生方面取得的进展.动力学研究表明,丙炔和丙二烯的加氢速率与其浓度和氢气的分压成正比关系,而丙烯的加氢速率则仅与氢气的分压有关.国内碳三液相加氢工艺和催化剂不仅在国内装置上应用,而且已经出口国外.除了砷、一氧化碳和水是导致催化剂失活的原因以外,碳三馏分中的碳四组分浓度也是造成加氢催化剂失活的主要原因之一.采用低温空气氧化法取代传统的蒸汽-空气法实现催化剂再生具有再生周期长等优点.     

Stability of transition metals on Mg(0001) surfaces and their effects on hydrogen adsorption

The interactions of a hydrogen atom with clean, vacancied, and transition metal-doped (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Au, Pt) Mg(0001) surfaces are investigated using first-principles calculations. The H adsorption on Mg(0001) with TMs doped within the second layer is generally more stable than that on clean Mg but clearly weaker than that on Mg surfaces with TM in the first layer. We find, however, that all these TM atoms prefer to substitute for the Mg atoms in the second layer rather than for those in the outermost layer of the Mg surface. To enhance the catalytic effect of the TM dopants, we investigated various co-doping conditions of TMs, and we found that i) Ti is a good “assistant” that stabilizes co-doped Co, Ni, Pd, Ag, Pt, and Au within the first layers and that ii) Ni and Co are more easily incorporated into the first layer of a Mg surface when co-doped with Ti, V, and Nb. These observations may lead to a possible approach to stabilize the TM dopants within the first layer and thus promote the hydrogenation of Mg accordingly.     

Theoretical investigation of solvent effects on the selective hydrogenation of furfural over Pt(111)

It was well known that solvent effect plays a very important role in the catalytic reaction. There are many theoretical studies on the solvent effect in homogeneous catalysis while there are few theoretical studies on the solvent effect in the heterogeneous catalytic reaction and there has been no work to investigate the solvent effect on furfural transformation in heterogeneous catalysis. In the present work, both the density functional calculations and the microkinetic analysis were performed to study the selective hydrogenation of furfural over Pt(111) in the presence of methanol as well as toluene and compared with that in the gas condition. The present results indicated that the methanol can enhance the adsorption strength of furfural and other oxygen-containing reaction species due to its relatively strong polarity properties and this can be a main reason for solvent-induced high activity and selectivity. Another reason is that reaction paths study showed that the presence of methanol solvent makes the dehydrogenation of furfural less thermochemical due to the fact that furfural is more stabilized than that of dehydrogenation species, and methanol also has an inhibition effect on the dehydrogenation of furfural in the kinetic aspect, and further energetic span theory proves highest activity and selectivity for hydrogenation in methanol solvent of vapor, methanol and toluene. Moreover, microkinetic model simulation demonstrated that the activity and selectivity of hydrogenation in methanol is both higher than that in vapor and toluene. The much higher activity in methanol is due to the stabilized adsorbed reactants in the surface, which leads to a higher surface coverage of furfural. It might be proposed based on the present work that a solvent with relatively strong polarity may be favorable for the high selective hydrogenation of furfural.     

Hydrocarbon hydrogen carriers for catalytic transfer hydrogenation of guaiacol

Polycyclic hydrocarbons are known to be efficient hydrogen carriers capable of yielding high purity H₂ upon dehydrogenation. Due to their high hydrogen density, high boiling point, and stability, these compounds demonstrate the potential to be used as hydrogen donors under catalytic transfer hydrogenation (CTH) conditions. In this work, the potential of a suite of hydrogen carriers to donate hydrogen, as well as the mechanisms affecting their hydrogen transfer, are assessed through the CTH of guaiacol, on Pd/Al₂O₃, as a model system. The results indicated the following descending order of transfer hydrogenation rate: bicyclohexyl > tetralin » hydrogenated terphenyl (HTP) > cyclohexylbenzene. Among the products, cyclohexanone and phenol are the most abundant, directly resulting from CTH. Detailed analysis of the hydrogen carrier conversion and selectivity clearly shows that the potential for CTH is highly linked to the molecular structure of the donor, rather than the amount of hydrogen available for transfer. A density functional theory (DFT) study, supported by experimental data, reveals that when unsaturated hydrocarbons are utilized, such as tetralin, cyclohexylbenzene, and HTP, the effective CTH rate to guaiacol is limited, despite dehydrogenation being more favorable for those molecules than from fully saturated donors, such as bicyclohexyl.     

Controllable synthesis of mesoporous alumina as support for palladium catalysts and reconstruction of active sites during methane combustion

Uniform mesoporous alumina (MA) nanospheres with excellent thermal stability and controllable pore size distribution were facilely obtained through ultrasonic assisted sol-gel method then taken as carriers for synthesizing a series of supported palladium catalysts. Results evidenced that the pore size distribution of MA significantly affected the catalytic performance of as-prepared catalysts. More importantly, the methane pretreatment tuned valence state of palladium species and distribution of surface oxygen species, along with promoting the adsorption of CH₄ on catalysts and the generation of CH₃1 group to form methane-derived adsorbates. Moreover, the synergistic effect of PdO and surface adsorbed oxygen effectively activated CH₄ and invoked the oxidation of methane-derived adsorbates, hence boosting the catalytic activity with the 90% CH₄ conversion temperature (T₉₀) decreased by 40 °C relative to the unpretreated catalyst. Noticeably, the T₉₀ of Pd/MA(CH₄) catalyst could be attained at 380 °C after subsequent long term and cyclic stability test.     

Comprehensive review of Cu-based CO2 hydrogenation to CH3OH: Insights from experimental work and theoretical analysis

Developing the technology of CO₂ hydrogenation into methanol can not only alleviate environmental problems such as greenhouse effect, but also effectively promote the utilization of CO₂ resources. In general, Cu-based catalysts have been extensively studied due to its low cost and the effective synthesis of methanol. Thus, this review is to be reported based on Cu-based catalysts for methanol synthesis from CO₂ hydrogenation. The specific goal of this review is to provide some insights into the structural and surface properties of Cu-based catalysts and their functions on the reaction mechanisms, and further affecting on the catalytic selectivity, stability, and activity for the CO₂ hydrogenation to methanol. A vital issue discussed is the fundamental understanding of active sites, reaction mechanisms, and interactions (active metal-support, active metal-promoter, bimetal) in determining the catalytic performance. Through a comprehensive overview on Cu-based systems for CO₂ hydrogenation to methanol from both experimental and theoretical perspectives, it could provide some useful information to go into CO₂ hydrogenation to methanol for the outsider, and promote the design and synthesis of novel and efficient catalysts.     

石灰石脱硫反应对喷氨脱硝反应影响的实验研究

在循环流化床锅炉炉膛尾部或旋风分离器入口喷入氨气可以降低烟气中的NOx含量。在循环流化床锅炉中,为脱硫而加入的石灰石会影响喷氨脱硝反应。通过实验研究了石灰石热解产物和脱硫产物对喷氨脱硝反应的影响,发现石灰石的热解产物在脱硫前,比表面积较大,CaO对喷氨脱硝反应显示出一定的催化活性,能够促进喷氨脱硝反应;石灰石的脱硫产物,对喷氨脱硝反应影响较小,但在T>1 200 K以上时,能够促进NH3的氧化,降低NH3的逸出,对喷氨脱硝反应有利。     

FHDO技术在混合二甲苯脱烯烃中的工业应用

催化重整生成油中富含芳烃和少量烯烃,要想生产合格的芳烃产品,必须脱除其中的烯烃。目前,广泛采用的脱除烯烃的方法是白土吸附和加氢精制工艺。抚顺石油化工研究院开发的FHDO技术,在成功应用于重整生成油苯、BTX等馏分脱烯烃基础上,首次在安庆石化1.0Mt/a催化重整装置混合二甲苯精制单元实现工业化应用。FHDO技术在较低反应温度(120~170℃)、反应压力(1.0~1.8MPa)、反应空速2~4h-1和氢油比(200~500∶1)下,生产出符合GB/T3407—2010的混合二甲苯产品。运行结果表明,HDO-18催化剂具有良好的活性和选择性,适用于催化重整生成油混合二甲苯馏分选择性加氢脱烯烃,FHDO技术可以有效替代常规的白土吸附和加氢精制工艺,从而彻底解决了常规混合二甲苯脱烯烃工艺中白土使用寿命短、需要频繁更换和废弃白土污染环境问题,以及加氢精制工艺在深度加氢脱烯烃过程中,带来的芳烃损失偏高等问题。FHDO技术的成功应用,填补了国内在催化重整生成油混合二甲苯馏分选择性加氢领域的空白,也是今后芳烃脱烯烃工艺的发展趋势。     

Improved hydrogen adsorption of ZnO doped multi-walled carbon nanotubes

Hydrogen storage is still one of the most important problems to improve hydrogen energy usage widespread. New materials capable of storing hydrogen with high efficiency must be introduced to overcome this problem. In recent years, addition of metals or inorganic compounds to multiwalled carbon nanotubes (MWCNTs) has been generally used for hydrogen uptake studies to enhance adsorption property of the nanotubes. In this study, Zinc oxide (ZnO) nanoparticles doped MWCNTs (ZnO-MWCNTs) have been produced as new reversible hydrogen storage materials, and we have investigated characterization of ZnO-MWCNTs by XRD, SEM, TGA, TEM and BET analyses. The functionalized MWCNTs and ZnO doped MWCNTs were subjected to hydrogenation step by dynamic gas sorption analyser under pressure of 5–50 bar. The hydrogen uptake capacities of the materials under different pressures were measured gravimetrically. It was indicated that by controlling the pressures for hydrogenation of ZnO-MWCNTs induces the spillover of ZnO nanoparticles in the layer of MWCNTs which in return with high hydrogen adsorption capacity. Consequently, the hydrogen adsorption of the functionalized MWCNTs (f-MWCNTs) and the ZnO-MWCNTs were achieved to be 1.05 wt% and 2.7091 wt% under pressure of 50 bar as maximum.     

Pt/C containing different platinum loadings for use as electrocatalysts in alkaline PBI-based direct glycerol fuel cells

This study shows the influence of the Pt percentage in Pt catalysts (Pt/C) on their application in Direct Glycerol Fuel Cells (DGFC). Catalysts with 20, 30, 40 and 60% Pt were prepared by formic acid reduction. X-Ray Diffraction (XRD) confirmed the formation of Pt fcc nanocrystals (with average sizes between 3 and 4 nm). Thermogravimetric analysis (TGA) corroborated the Pt loadings and the Transmission Electron Microscopy (TEM) images show a homogeneous distribution of the Pt nanoparticles, with larger particles at higher Pt percentages. Electrochemical measurements reveal that higher Pt percentages promote the activity of the glycerol electroxidation reaction, resulting in lower onset potentials, higher current densities and reduced poisoning of the Pt surface. Single cell tests confirm these results, with greater maximum power density at higher Pt percentages, although the glycerol crossover effect starts to become significant in the 60% Pt/C catalyst, owing to the reduced thickness of this catalytic layer. A final product selectivity analysis indicates that tartronate is the preferential glycerol electroxidation product, along with glycerate and oxalate in lower proportions, with minor amounts of glycolate and mesoxalate. In general, a thicker catalytic layer is associated with the formation of more oxidized products.     

Effect of carbon allotropes on the structure and hydrogen sorption during reactive ball-milling of Mg–C powder mixtures

Hydrogen sorption by magnesium–carbon composites during reactive high-energy ball milling under hydrogen was investigated. Mg-based composites absorb up to 5 wt.% of hydrogen during milling. It was found that reactive ball milling of magnesium with the different carbon allotropes (graphite, ultrafine diamonds, carbon nanotubes and amorphous carbon powder produced by electric breakdown of organic liquids) leads to a significant increase of hydrogen sorption rate. Morphology and phase composition of the synthesized Mg–C composites have been studied by TEM and XRD. Special attention was focused on the study of structural changes in the carbon additives. The hydrogenation rate of magnesium-carbon composites during reactive ball milling is strongly affected by the nature of carbon additives and their dispersion in an initial state.     

Boosting the hydrogenation activity of dibenzyltoluene catalyzed by Mg-based metal hydrides

Hydrogenation of dibenzyltoluene (DBT) is of great significance for the application in liquid organic hydrogen carriers (LOHCs). We successfully develop Mg-based metal hydrides (Mg₂NiH₄, MgH₂, and LaH₃) reactive ball-milling for the hydrogenation of DBT. Mg-based metal hydrides milled with 500 min exhibit the best catalytic activity, the hydrogen uptake of DBT can reach 4.63 wt% at the first 4 h and finally achieve 5.70 wt% through 20 h, which is the first time to use hydrogen storage material as a catalyst for the hydrogenation of DBT. The excellent catalytic hydrogenation performance of Mg-based metal hydrides mostly originates from numerous catalytic activity centers formed at the surfaces of Mg₂NiH₄ nanoparticles in the MgH₂ matrix. Inspired by this mechanism, more general metal hydrides can be explored for catalyzing the hydrogenation of LOHCs. The new application of Mg-based metal hydrides is beneficial to developing efficient LOHC based hydrogen storage systems and offers novel insights to hydride-based catalysts.     

Hydrogenation of CO2 over Co supported on carbon nanotube,carbon nanotube-Nb2O5, carbon nanofiber,low-layered graphite fragments and Nb2O5

CO₂ hydrogenation was studied with catalysts containing 1.5–35 wt% Co supported on carbon nanotubes, nanofibers, low-layered graphite fragments and composites of carbon nanotube-Nb₂O₅. All catalytic processes with Co/supported catalysts were investigated using XRF, DSC, TGA, H₂-TPR, TEM, SEM and XPS. Based on obtained results, it is indicated that the products from CO₂ hydrogenation were CH₄ and/or CO under reaction conditions pressure of 1.5 MPa and temperature of 200–500 °C, as well as the size of the particles of Co and their phase state directly affected on the catalysts activity. 3 wt% Co catalyst supported on carbon nanotubes has shown catalytic inactivity due to amorphous state of metal. It is possible to activate them during Co crystallization after thermal treatment. It is shown, that the size of Co particles supported on carbon nanotubes is 4–6 nm. The methods of fictionalization the surface of carbon nanomaterials ensuring an additional stability of metal nanoparticles is recommended.     

Mathematical modelling and simulation of nitrite hydrogenation in a membrane microreactor

Nitrite hydrogenation using heterogeneous catalysis is an important process for purification of wastewater or potable water. The main aim of this study is to explore a new mechanistic model and simulation for a heterogeneously catalysed reaction in a microporous catalytic layer. The system studied involves a liquid solution containing certain amount of nitrite, and a membrane reactor in which the nitrite penetrates into the catalytic layer to react with hydrogen. The developed model considers coupling between equations of momentum transfer in free and porous media and convection-diffusion of nitrite. It was found that there is great agreement between measured data and modelling values. Increasing velocity was the main reason for reduction of nitrite conversion and also there was a slight increase in nitrite conversion with increasing the thickness and porosity of catalytic layer. Furthermore, it was found that the diffusion mass transfer mechanism is favourable for nitrite hydrogenation while convective mass transfer of fluid flow has negative impact on nitrite hydrogenation.     

Nanostructured hydrogen storage materials prepared by high-energy reactive ball milling of magnesium and ferrovanadium

Hydrogen storage nanocomposites prepared by high energy reactive ball milling of magnesium and vanadium alloys in hydrogen (HRBM) are characterised by exceptionally fast hydrogenation rates and a significantly decreased hydride decomposition temperature. Replacement of vanadium in these materials with vanadium-rich Ferrovanadium (FeV, V80Fe20) is very cost efficient and is suggested as a durable way towards large scale applications of Mg-based hydrogen storage materials. The current work presents the results of the experimental study of Mg–(FeV) hydrogen storage nanocomposites prepared by HRBM of Mg powder and FeV (0–50 mol.%). The additives of FeV were shown to improve hydrogen sorption performance of Mg including facilitation of the hydrogenation during the HRBM and improvements of the dehydrogenation/re-hydrogenation kinetics. The improvements resemble the behaviour of pure vanadium metal, and the Mg–(FeV) nanocomposites exhibited a good stability of the hydrogen sorption performance during hydrogen absorption – desorption cycling at T = 350 °C caused by a stability of the cycling performance of the nanostructured FeV acting as a catalyst. Further improvement of the cycle stability including the increase of the reversible hydrogen storage capacity and acceleration of H₂ absorption kinetics during the cycling was observed for the composites containing carbon additives (activated carbon, graphite or multi-walled carbon nanotubes; 5 wt%), with the best performance achieved for activated carbon.     

Promotion effect of different lanthanide doping on Co/Al2O3 catalyst for dry reforming of methane

In this paper, a series of cobalt catalysts modified by different lanthanide metals were synthesized via co-impregnation method using inexpensive industrial-grade alumina as a support for dry reforming of methane. The effect of lanthanide metals as accelerators of cobalt-based catalysts on catalytic performance and anti-coking properties was mainly investigated. The textural relationships between the catalytic performance and physicochemical properties of cobalt-based catalysts doped with different lanthanide metals were further investigated. Different characterization techniques demonstrate the positive effect of lanthanide metals on the physicochemical properties of catalysts. The results show that the electron transfer between cobalt species and lanthanide metal oxides is significantly enhanced due to the introduction of lanthanide elements. The process generates more active sites, which is favorable for the adsorption and activation of methane. In addition, the abundant medium basic sites and oxygen vacancies on the surface of cobalt-based catalysts with the effect of lanthanides promoted the adsorption and activation of carbon dioxide and the gasification of carbon accumulation, which greatly improved the anti-carbon accumulation performance of the catalysts. Therefore, the prepared cobalt-lanthanum-based catalysts showed the best catalytic effect and have great potential for application.     

Thermal conductivity improvement of stearic acid using expanded graphite and carbon fiber for energy storage applications

The influence of expanded graphite (EG) and carbon fiber (CF) as heat diffusion promoters on thermal conductivity improvement of stearic acid (SA), as a phase change material (PCM), was evaluated. EG and CF in different mass fractions (2%, 4%, 7%, and 10%) were added to SA, and thermal conductivities of SA/EG and SA/CF composites were measured by using hot-wire method. An almost linear relationship between mass fractions of EG and CF additives, and thermal conductivity of SA was found. Thermal conductivity of SA (0.30 W/mK) increased by 266.6% (206.6%) by adding 10% mass fraction EG (CF). The improvement in thermal conductivity of SA was also experimentally tested by comparing melting time of the pure SA with that of SA/EG and SA/CF composites. The results indicated that the melting times of composite PCMs were reduced significantly with respect to that of pure SA. Furthermore, the latent heat capacities of the SA/EG and SA/CF (90/10 wt%) composite PCMs were determined by differential scanning calorimetry (DSC) technique and compared with that of pure SA. On the basis of all results, it was concluded that the use of EG and CF can be considered an effective method to improve thermal conductivity of SA without reducing much its latent heat storage capacity.     

Highly selective electrocatalytic hydrogenation of cinnamaldehyde over tin dioxide-supported palladium nanocatalysts

Selective hydrogenation of α, β-unsaturated aldehydes has always been a hot research topic owing to favorable thermodynamics in CC hydrogenation. In this work, a series of Pd/SnO₂ nanocatalysts were facilely synthesized under mild conditions, via the reduction of Na₂PdCl₄ by dimethylaminoborane. Under galvanostatic electrolysis at 3.33 mA cm^?2 for 8 h, the selective conversion of cinnamaldehyde (CAL) was achieved over Pd/SnO₂-coated carbon fiber in neutral phosphate buffer, giving the cinnamyl alcohol (COL) selectivity of 78.85% at the conversion of 84.88%. The Pd/SnO₂ nanocatalysts outperform commercial Pd/C catalysts, showing high COL selectivity and faradaic efficiency. The cathodic reduction potential of CAL over Pd_4·3/SnO₂ occurs at ?0.92 V. The SnO₂ support is beneficial to promote the CO adsorption of CAL and lower the HER activity of Pd nanocatalysts, thereby contributing to superior activity of Pd_4·3/SnO₂ for selective hydrogenation of CAL.     

Electrospun ultrafine composite fibers of binary fatty acid eutectics and polyethylene terephthalate as innovative form‐stable phase change materials for storage and retrieval of thermal energy

In this study, four fatty acids of lauric acid (LA), myristic acid (MA), palmitic acid (PA), and stearic acid (SA) were selected to prepare six binary fatty acid eutectics of LA‐MA, LA‐PA, LA‐SA, MA‐PA, MA‐SA, and PA‐SA; thereafter, electrospun ultrafine composite fibers with the binary fatty acid eutectics encapsulated in the supporting matrices of polyethylene terephthalate (PET) were prepared as innovative form‐stable phase change materials for storage and retrieval of thermal energy. The morphological structures and thermal energy storage properties of the ultrafine composite fibers were characterized by scanning electron microscope (SEM) and differential scanning calorimeter (DSC), respectively. The SEM results indicated that the fibers had the cylindrical morphology with diameters of 1–2 µm; some had smooth surfaces, while others had wrinkled surfaces with grooves. The DSC results indicated that the phase transition temperatures of binary fatty acid eutectics were lower than those of individual fatty acids; the enthalpy values associated with melting and crystallization for the eutectics encapsulated in the composite fibers were considerably reduced, whereas there were no appreciable changes on the phase transition temperatures. Copyright © 2012 John Wiley & Sons, Ltd.     

Promoting stability and activity of PtNi/C for oxygen reduction reaction via polyaniline-confined space annealing strategy

Studies indicated that the existing carbon supported Pt-based nanoalloys may exhibit instability and lose activity under acidic conditions due to particle aggregation, leaching/dissolution of the non-precious metals and carbon corrosion, which impeded the practical use of these nanomaterials for fuel cell electrocatalysts. This work presents a polyaniline (PANI)-confined space annealing strategy to efficiently promote the stability and activity of solution phase synthesized PtNi nanoparticles. By virtue of an in situ formed PANI coating layer, PtNi NPs can be developed to be more stable and active at thermal annealing process without serious agglomeration. Simultaneously, high temperature forces the carbonization of PANI, featuring the final obtained PtNi NPs with a nitrogen-doped carbon (NC) coating layer. XPS analysis attributed the enhanced catalytic performance of as-constructed PtNi/C@NC composite to the unique electronic interaction between Pt atoms and NC outer layer, which is beneficial for stabilizing PtNi NPs under fuel cell working condition.