碳化钼催化剂的制备及噻吩加氢脱硫性能

以MoO₃为前躯体,CH₄/H₂为还原碳化气,采用自制的程序升温还原碳化反应装置制备出Mo₂C催化剂,并用XRD、BET进行表征.借助原位TG-DTA方法研究了MoO₃在CH₄/H₂气氛中的还原碳化历程和适宜的还原碳化温度.以噻吩/环己烷溶液为模型反应物,采用高压微反-色谱实验装置考察了制备的碳化钼催化剂的噻吩加氢脱硫反应性能.结果表明：程序升温条件下的局部规整反应可提高催化剂的比表面积,且制备的碳化钼催化剂具有较高的噻吩加氢脱硫反应活性,在体积分数为5%的噻吩/环己烷溶液中,反应压力为3.0 MPa,空速为6 h^-1,H₂/原料液体积比500∶1的反应条件下, 370℃时的噻吩转化率达到98%以上,明显高于相应的硫化钼催化剂.还原碳化终温的提高,导致碳化钼催化剂比表面积的减少和表面积炭的增多,进而使其加氢脱硫反应活性降低.MoO₃在CH₄/H₂气氛中的还原碳化历程应为MoO₃→MoO₂→MoO_xC_y→Mo₂C,实验确定的适宜还原碳化温度为675℃.     

Characteristics of intermetallic NdNi5 as an unsupported catalyst in thiophene hydrodesulfurization

A systematic research is carried out on intermetallic NdNi₅ for the hydrodesulfurization (HDS) of thiophene. The effect of calcination and presulfidation of intermetallic NdNi₅ on thiophene HDS was examined and property changes of the catalyst during calcination, presulfidation, and reaction were observed by XRD, SEM, and surface area techniques. The intermetallic compound of NdNi₅ is disintegrated to fine powder and recrystallized to Nd/Ni oxide and sulfide by calcination, presulfidation, and reaction. A model for the surface area increase of the catalyst during calcination, presulfidation, and reaction was proposed and the role of neodymium was explained.     

Preparation of Agy zeolites using microwave irradiation and study on their adsorptive desulphurisation performance

Sorbents with Ag loading supported on NaY were synthesised by a liquid‐phase ion exchange method taking advantage of microwaves irradiation. The adsorption desulphurisation activity of the AgY adsorbent exchanged with AgNO₃ solution of 0.2 mol L^?1, microwave irradiation time 20 min with power 240 W as well as calcined at 500°C exhibited the best performance. Equilibrium isotherm shows that the adsorption of thiophene over the as‐prepared AgY can be represented by the Langmuir model. Kinetics of adsorptive desulphurisation followed the pesudo‐second‐order model and the equilibrium adsorption capacity q₂ = 0.893 mmol g^?1. © 2012 Canadian Society for Chemical Engineering     

A model for the rate of hydrodesulfurization of thiophene in a continuous catalytic fixed bed reactor

Hydrodesulfurization of thiophene in n-heptane, using a mixture of cobalt and molybdenum oxides as catalyst, has been studied in a fixed bed integral reactor, 200 mm long, 30 mm outer diameter and 20 mm inner diameter. It has been shown that, under experimental conditions employed in this study, neither external nor internal diffusion had been effective in the process and isothermal conditions prevailed in both gas and solid phases. A three step mechanism has been proposed for the hydrodesulfurization of thiophene. According to such a mechanism the diluent (n-heptane) acts as an inhibitor by occupying free active sites. In further steps, thiophene is adsorbed on the catalyst surface and then undergoes reaction with hydrogen gas. Based on this scheme a rate model has been derived and verified by experimental results.     

Synergism between Brønsted acid sites and metal sulfide particles in the hydrodesulfurization of thiophene on ultrastable Y zeolite catalysts W/USY and Ni/USY

The influence of the acidity of ultrastable Y (USY) zeolite-supported tungsten or nickel sulfide catalysts, prepared at different pH values, on thiophene hydrodesulfurization activity has been studied. The acidity affects the catalysts' deactivation. The results of the initial activity clearly show a synergic effect between the metal sulfide centers and the Brønsted acid sites present in the zeolites. © 1998 SCI     

Support effect on the formation of catalytic site precursors in the thiophene hydrodesulfurization

The TiO₂ and Al₂O₃ supported FeMo catalysts (6 and 12 wt.% Mo) have been prepared using (NH₄)₃Fe(OH)₆Mo₆O₁₈ salt (FeMo₆). They have been studied by the IR, TPR, XPS and MS methods and tested in thiophene conversion. The initial salt transforms in analog of the TiMo acid anion on the titania support and alumina heteropolymolybdate anion on the alumina support. Higher thiophene conversion is observed on the TiO₂ supported catalysts.     

The activity of transition metal nitrides for hydrotreating quinoline and thiophene

An investigation has been conducted of the activity of AlN, BN, TiN, VN, Mo₂N, and W₂N as catalysts for quinoline hydrodenitrogenation (HDN). The activity of Mo₂N and VN for thiophene hydrodesulfurization (HDS) and the concurrent hydrotreatment of quinoline and thiophene have also been examined. Bulk AlN, BN, and TiN were obtained with low surface areas and found to be inactive for the HDN of quinoline. Bulk Mo₂N, W₂N, and VN could be obtained with high surface area. Each of these nitrides exhibited high activity for quinoline HDN, the turnover frequency for this reaction decreasing in the order Mo₂N>W₂N>VN. Highly dispersed VN supported on SiO₂ was found to have a specific activity for quinoline HDN identical to that of bulk VN. Both bulk Mo₂N and 27% VN/SiO₂ exhibit high activity for the HDS of thiophene. The behavior of these two catalysts for the concurrent hydrotreatment of quinoline and thiophene is also discussed.     

MoS2基催化剂加氢脱硫反应活性相和作用机理研究进展

加氢脱硫工艺在清洁油品生产过程中发挥着重要作用，而MoS₂基催化剂是加氢脱硫的主要催化剂，因此对MoS₂基催化剂活性相和催化反应机理的深入研究有助于从原子层面上对催化剂进行优化设计。本文首先介绍了国内外有关MoS₂基催化剂活性相形貌结构的研究，着重探讨了硫化气氛、助剂和载体类型对活性相结构的影响，以及现有表征技术在MoS₂基催化剂活性相形貌结构研究中所面临的挑战，总结了不同条件下活性相的微观结构特征；同时，从MoS₂基催化剂的活性相组成和结构角度分析了噻吩的加氢脱硫机理，发现了加氢脱硫活性与催化剂微观结构之间的紧密联系；最后展望了理论计算在设计和开发高效加氢脱硫催化剂过程中的重要指导作用。     

Simultaneous hydrodesulfurization of thiophene and hydrogenation of cyclohexene over dimolybdenum nitride catalysts

A series of unsupported dimolybdenum nitride (γ-Mo₂N) catalysts differing in surface area were prepared by temperature programmed reduction of MoO₃ with a mixture of NH₃:N₂ (90:10). Characterization of catalysts by BET, XRD, TPR and XPS techniques was carried out. The samples were used as catalysts in hydrotreating reactions (simultaneous hydrodesulfurization of thiophene and hydrogenation of cyclohexene). Low surface area γ-Mo₂N materials show much higher specific conversions than those with higher surface area. These results indicate that HDS and HYD reactions over γ-Mo₂N seem to be structure-sensitive. The relative exposure extent of crystalline planes (1 1 1) and (2 0 0) over the different catalysts can be associated with their hydrogen adsorption capacities and with their catalytic performances. The catalytic activities are significantly affected by the catalyst pretreatment conditions.     

Synthesis of silica nanoparticles in a continuous-flow microwave reactor

Monodispersed silica colloidal spherical nanoparticles were synthesized from the hydrolysis and condensation of tetraethylorthosilicate (TEOS) by using a continuous microwave synthesis process. The flow rate was varied from 43 to 101 mL/min in order to establish the optimum conditions required to obtain unagglomerated silica nanopowders. The results were compared with those obtained in batch systems. In particular the mean particle diameter became smaller than 50 nm as the residence time was decreased by increasing the flow rate to 101 mL/min.     

Reaction of thiophene on Co?Mo/A12O3 catalysts of various loading at low hydrogen excess

Co-Mo/Al₂0₃ catalysts of various CoMo loadings were examined in the hydrodesulfurization (HDS) reaction of thiophene and tetrahydrothiophene at near stochiometric hydrogen: thiophene ratio. Good compensation plots were found for both reagents and all catalysts. Reversibly bound H₂S blocks active sites of HDS. The most important reaction pathway leads to but-1-ene; more Co gives more but-2-ene. The hydrogenation of buta-1, 3-diene is about 100 times more rapid than that of but-1-ene. The activity of two neighboring sites with twofold coordinative unsaturation is suggested in buta-1, 3-diene hydrogenation. The possible effect of Al₂0₃ support on active sites is discussed.     

Aminolytic depolymerization of poly(ethylene terephthalate) waste in a microwave reactor

The aminolytic depolymerization of poly(ethylene terephthalate) (PET) taken from waste soft‐drink bottles, under microwave irradiation, is proposed as a recycling method with possible substantial energy savings. The reaction was carried out with ethanolamine and without the use of any other catalyst in a sealed microwave reactor in which the pressure and temperature were controlled and recorded. Experiments under constant temperature or microwave power were carried out for several time periods. The main product, bis(2‐hydroxyethyl) terephthalamide, was identified from Fourier transform infrared (FTIR) spectra and DSC measurements. It was found that PET depolymerization is favoured by increasing temperature, time and microwave power. The average molecular weight of the PET residues, determined using viscosity measurements, was found to decrease with the percentage of PET degradation, indicating a random chain scission mechanism to some extent. From a simple kinetic model, the activation energy of the reaction was evaluated. Complete depolymerization was found to occur in less than 5 min when the irradiation power applied was 100 W or the temperature was 260 °C. These results support the use of microwave‐assisted aminolytic degradation as a very beneficial method for the recycling of PET wastes. Copyright © 2010 Society of Chemical Industry     

Reactions of benzene and ammonia in a continuous-flow microwave discharge reactor

Gaseous mixtures of benzene and ammonia have been passed through a continuous-flow microwave discharge reactor. The principal reaction products were hydrogen cyanide, hydrogen, nitrogen and acetylene. Aniline and butadiene were produced in smaller amounts. At a pressure of 4 × 10^?2 bar, no reaction occurred unless the molar ratio of ammonia to benzene exceeded 1 : 1. At 9.3 × 10 ^?2 bar, no reaction occurred unless the reactant ratio exceeded 2:1. The presence of nickel wire affected the distribution of reaction products. The conversions of benzene were less than those which had previously been found in pure benzene. The maximum conversions of ammonia were much higher than the conversions obtained in pure ammonia. The consumption of both benzene and ammonia were found to be zero order rate processes. The consumption rates of the reactants varied linearly with power absorption in the reactor.     

Reactions of acetylene and ammonia in a continuous-flow microwave discharge reactor

Both pure acetylene and mixtures of acetylene and ammonia have been passed continuously through a microwave discharge reactor. The reaction products from the gas mixtures were hydrogen cyanide, hydrogen and nitrogen. When the input reactant ratio (ammonia to acetylene) was below a critical value, the extent of reaction was negligible. When the critical ratio was exceeded, high conversions were obtained. When reaction did occur, the conversions of both reactants were linear functions of the power absorption in the discharge. The conversion of acetylene to hydrogen cyanide varied linearly with the input volumetric flow rate. Comparison of the present work with previous studies shows that hydrogen cyanide is not produced exclusively by the route when mixtures of benzene and ammonia react in a microwave discharge.     

催化裂化汽油中特征硫化物噻吩的催化氧化脱硫

以负载金属铈的分子筛为催化剂,在H2O2-HCOOH体系中,对催化裂化（FCC）汽油中特征硫化物噻吩（C4H4S）的正庚烷溶液进行了氧化脱硫研究。考察了氧化剂用量、溶剂、氧化时间、氧化温度、相转移剂等因素对噻吩脱除效果的影响,并对对噻吩的氧化反应历程进行了初步的探讨。实验结果表明：以负载金属铈的分子筛为催化剂,在反应温度50℃,反应60min, H2O2：S＝10：1（mol/mol）,H2O2：HCOOH＝1：1（V/V）的条件下,正庚烷溶液C4H4S的脱除率达到了78.2％,加入乳化剂OP可使C4H4S的脱硫率达到94.5％,但四丁基溴化胺（TBAB）的加入使氧化后的样品中出现了噻吩的溴代产物。     

微波强化铁炭微电解预处理含油废水的试验研究

以预处理的铁炭混合物作为催化诱导剂,采用微波诱导法预处理含油废水.最佳反应条件如下:铁炭质量比为2∶1、铁炭投加量为15％、微波功率800 W、废水pH值为3、微波反应时间为10 min.在此条件下,原水CODCr的质量浓度为2 600 mg/L,处理出水CODCr的质量浓度为780 mg/L左右,平均去除率在70％左...     

磷添加方式对NiMo/Al2O3催化剂加氢脱硫性能的影响

采用分步浸渍法制备了不同磷添加方式改性的NiMo/Al₂O₃催化剂,在固定床微反装置上考察了该系列催化剂对焦炉煤气中噻吩加氢脱硫（HDS）性能的影响,采用BET、X射线衍射（XRD）、H₂程序升温还原（H₂-TPR）、NH₃程序升温脱附（NH₃-TPD）、C₄H₄S(H₂)程序升温脱附[C₄H₄S(H₂)-TPD]、X射线光电子能谱（XPS）、高清透射电镜（HRTEM）和拉曼（Raman）等分析手段对催化剂进行表征。结果表明,不同磷添加方式制备NiMo/Al₂O₃催化剂的HDS性能存在较大差异。其中,催化剂PNi-Mo/Al和PMo-Ni/Al表面弱吸附解离活性位增强,对焦炉煤气中噻吩有较好的低温加氢脱硫活性,以含292.5mg/m³噻吩的模拟焦炉煤气为原料时,PNi-Mo/Al在250℃下对噻吩的脱硫率达61%。对于PNi-Mo/Al和PMo-Ni/Al催化剂,先浸渍P、Ni或者P、Mo时,P优先和载体Al₂O₃作用,减弱了活性金属组分Ni、Mo与载体间的相互作用,而又防止Ni或者Mo与载体间相互作用过低而聚集,提高了Ni、Mo在载体表面的均匀分散,生成能够促进硫化形成Ⅱ型活性相Ni-Mo-S的NiMoO₄物种。NiMoO₄和MoO₃之间的协同作用提高了催化剂的硫化度,使HDS活性得以提高。     

Kinetics of catalytic hydrodesulfurization of a petroleum residue in a batch-recycle trickle bed reactor

The kinetics of catalytic hydrodesulfurization of an atmospheric residuum were investigated in a batch-recycle trickle bed reactor with a commercial catalyst. The global rate equation determined was R = Catalyst effectiveness factors η, remaining activity ε, effective pore diffusivities D_e and activation energies E have been determined quantitatively. The data have also been interpreted in terms of the two parallel, first-order reactions model and the respective parameters have been determined. Solid—liquid chromatography fractions of three hydrocarbon and sulfur compound groups have been determined in addition to the asphaltenes content of the feedstock and the hydrotreated product. These data are discussed and conclusions are drawn with respect to their behaviour during HDS and a reaction network is proposed which explains the complicated interrelations involved.     

Experimental study on the heating effects of microwave discharge caused by metals

The heating effects of discharge triggered at the appearance of metals are important under microwave irradiation but special studies have rarely been carried out. In our experiments, the heat generation was successfully isolated by embedding metal in quartz sand and measured through an indirect calorimetric method. All the experiments and analyses indicate that the discharge triggered by metals under microwave irradiation has remarkable heating effects. The microwave power, irradiation time, metal amount, and atmosphere are all important factors to influence the discharge intensity and then the heating effects. The understanding of the effects of metal discharge will help us to further research on the treatment of solid waste, such as the microwave pyrolysis of electrical waste. It may also be a good idea to use the discharge phenomena and their heating effects by embedding some metals to the microwave field in some certain applications. © 2012 American Institute of Chemical Engineers AIChE J, 2012