Characterization of the active phase of NiMo/Al2O3 hydrodesulfurization catalysts

The active phase of the NiMo/Al₂O₃ catalyst for hydrodesulfurization reactions has been investigated in this work. Special attention has been focused on the effect of the order of metal impregnation on the formation of the active phase in the reaction. The Mo and Ni oxides and their sulfides on the alumina were investigated by XPS and DRS analyses. The Ni-Mo oxides or precursor of the active phase which are chemically bonded between Mo and Ni were also confirmed from the binding energy shifts of the XPS peaks. The amount of Ni-Mo oxides was determined after the formation of metal oxides during calcination. The Ni-Mo sulfide (active phase) was then induced through sulfidation. It was important that Mo should be located at the tetrahedral sites on the alumina with a high Mo dispersion. These results indicated that there are two important factors in preparing highly efficient Ni-Mo catalysts; one is that Mo should be located at the tetrahedral coordination on Al₂O₃ in high dispersion (Mo/Al₂O₃) and the other is that the Ni species should be supported on MoAl₂O₄ to form Ni-Mo oxides which change into the Ni-Mo sulfide active sites by sulfidation.     

Intermetallic PdxIny/Al2O3 catalysts with isolated single-atom Pd sites for one-pot hydrogenation of diphenylacetylene into trans-stilbene

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光照对Pt/Al2O3光热CO2加氢反应的增强作用（英文）

在传统热催化材料的研究领域中,光照技术已经得到了广泛的应用,从而使传统热催化剂的催化反应活性和选择性得到优化.然而,在光热协同催化反应过程中,光照因素对催化反应过程的影响尚未得到很好地研究和理解.本文通过浸渍法制得Pt/Al2O3催化剂,并应用于光热协同催化CO2加氢反应.结果证明,在光热协同CO2加氢催化反应中, Pt/Al2O3催化剂表现出光热协同效应.本文结合原位漫反射红外光谱(operandoDRIFTS)和密度泛函理论计算(DFT)对光照因素对该催化反应过程的作用机制进行了进一步深入研究.结果表明, CO气体分子从Pt纳米颗粒上的脱附过程为CO2加氢反应的重要步骤;CO气体分子在Pt纳米颗粒上脱附的位置包含台阶位置(Ptstep)和平台位置(Ptterrace).结果表明,反应过程中CO气体分子从Pt表面的脱附有利于催化剂暴露出Pt反应活性位点.值得注意的是,在光热协同催化CO2加氢反应过程中,光照和温度因素对CO气体分子的脱附过程具有不同影响.吸附能的计算结果证明, CO气体分子吸附在Ptstep和Ptterrace上的吸附能分别为-1.24和-1.43eV.由此可见, CO气体分子与Pt纳米颗粒上的Ptstep吸附位点之间相互作用更强.在无光照作用的条件下对催化剂进行加热, CO气体分子更容易从Ptterrace吸附位点发生脱附;但是在对应的温度下加入光照作用后,吸附在Ptstep位点上的CO气体分子会先转移到Ptterrace吸附位点上,随后脱附,从而促进CO2加氢反应的进行.     

Sonochemical asymmetric hydrogenation of isophorone on proline modified Pd/Al2O3 catalysts

The sonochemical asymmetric hydrogenation of isophorone (3,3,5-trimethyl-2-cyclohexenone) by proline-modified Pd/Al2O3 catalysts is described; presonication of a commercial Pd/Al2O3-proline catalytic system resulted in highly enhanced enantioselectivities (up to 85% ee).     

Selective phenol hydrogenation under mild condition over Pd catalysts supported on Al2O3 and SiO2

Research on Chemical Intermediates - Cyclohexanone (CHONE) is the key intermediate in the manufacture of nylon-6 and nylon-66. Selective hydrogenation of phenol into CHONE was investigated over...     

KOH修饰Au/Al2O3催化剂的低温CO氧化催化反应性能

采用等体积浸渍法制备了KOH-Au/Al<,2>O<,3>系列催化剂,考察了催化剂对低温CO氧化反应的初始活性和干、湿气氛下连续反应的稳定性能,并用电感耦合等离子发射光谱、红外光谱、高分辨透射电镜、紫外漫反射光谱等技术对催化剂进行了结构表征.结果表明:与母体催化剂(Au/Al<,2>O<,3>)相比,修饰催化剂(KOH...     

新型Ni-Mo/Al2O3加氢脱硫催化剂的研究

采用溶胶凝胶技术,制备了双结构Al2O3载体,用此改性载体制备了Ni-Mo/Al2O3催化剂,在中压固定床微反装置上考察了载体改性对催化剂上噻吩加氢脱硫(HDS)活性的影响,并用X射线粉末衍射、透射电镜、吡啶-红外光谱等分析方法对改性载体和催化剂进行了表征。结果表明,由铝溶胶改性载体制备催化剂的加氢脱硫活性均高于未改性载体制备的催化剂的催化活性。XRD和TEM结果表明氧化铝表面负载的铝溶胶经过干燥、焙烧后以纳米尺度的η-Al2O3状态存在,吡啶-红外光谱结果表明,改性氧化铝载体制备催化剂的弱B酸和弱L酸的酸量均提高,强L酸的酸量也明显增加。酸性、酸量的提高和纳米尺度η-Al2O3的存在是催化剂活性提高的主要原因。     

Plasma catalytic reaction of natural gas to C2 product over Pd-NiO/Al2O3 and Pt-Sn/Al2O3 catalysts

The decomposition of natural gas over Pd-NiO/Al₂O₃ and Pt-Sn/Al₂O₃ is carried out in a microwave catalytic reaction at room temperature. The decomposition of methane is caused by collision by excitation of unstable electronic state. Measuring the flow rate and plasma power can provide kinetic data and indicate the mechanism. The conversion of C₂ products increases from 47 to 63.7% in the microwave plasma catalytic reaction with electric field. Comparing the activities of catalysts, Pd-NiO/Al₂O₃ bimetallic catalyst is more active than Pt-Sn/Al₂O₃ catalyst because of modification of the surface of catalysts by carbon formation. The kinetic modeling of plasma of methane conversion seems related to the power of the electric discharge. It was also revealed that proper coking or polymeric carbon formation improves the catalytic activity; therefore, the conversion of methane may increase over Pd-Ni/Al₂O₃ catalyst in the plasma system.     

Co-Mo/Al2O3催化剂上裂解汽油中单烯烃加氢宏观动力学

采用绝热管式固定床积分反应器,在2.0MPa~4.0MPa、524K~644K、氢/裂解汽油摩尔比1.5~3.5和反应器入口环戊烯、3 乙基 1 戊烯、苯乙烯和1 己烯的分压分别为0.87kPa~5.60kPa、1.09kPa~7.01kPa、1.14kPa~7.35kPa和0.25kPa~0.97kPa下,对Co Mo/Al2O3催化剂上裂解汽油中单烯烃催化加氢的宏观动力学特性进行了系统研究。以Powell优化法和Merson迭代法对动力学实验数据进行非线性参数估值,建立了与实验数据吻合良好、裂解汽油中单烯烃催化加氢的幂函数型宏观动力学模型。其中,环戊烯、3 乙基 1 戊烯、苯乙烯和1 己烯的反应级数分别为1.725、0.685、0.7和0.655,对应的加氢反应宏观活化能依次为63455 J·mol－1, 61781 J·mol－1, 52105 J·mol－1和54181 J·mol－1。实验所用Co Mo/Al2O3催化剂对环戊烯、3 乙基 1 戊烯和苯乙烯加氢具有明显的催化作用,对1 己烯加氢具有一定的催化作用,但对1 庚烯加氢基本无催化活性。加氢反应压力控制在3.5MPa左右更为适宜。     

Active sites in CO2 hydrogenation over confined VOx-Rh catalysts

Science China Chemistry - Metal oxide-promoted Rh-based catalysts have been widely used for CO2 hydrogenation, especially for the ethanol synthesis. However, this reaction usually suffers low CO2...     

Laser-induced luminescence of model Fe/Al2O3 and Cr/Al2O3 catalysts

The laser-induced luminescence of Cr³⁺ impurity ions in model Fe/Al₂O₃ and Cr/Al₂O₃ catalysts with different calcination temperatures was studied. It was found that an additional luminescence band at 770 nm appeared in the luminescence spectra of low-temperature samples as a result of the interaction of octahedrally coordinated Cr³⁺ ions with Fe³⁺ impurity ions. In the θ-Al₂O₃ phase with a concentration of Cr³⁺ ions higher than 0.1 wt %, the interaction of the Cr³⁺-Cr³⁺ ion pairs in the immediate surroundings resulted in the appearance of N _θ lines due to the splitting of R _θ lines. The differences of these lines from the N _α lines of α-Al₂O₃ were related to the individuality of the crystal lattice of the θ phase and the coordination of Cr³⁺ impurity ions in the immediate surroundings, which is different from that in the α phase. Based on the laser-induced luminescence spectroscopic data, it was found that regions with a local Cr³⁺ concentration higher than the average Cr³⁺ concentration in the bulk of a catalyst by one order of magnitude were formed in the α-Al₂O₃-Fe₂O₃ system with the bulk Fe and Cr concentrations of 2.5 and 0.04 wt %, respectively, which was calcined at 1220°C, as a result of the diffusion of chromium and iron ions.     

Characterization of electron donor sites on Al2O3 surface

Formation of radical anions after adsorption of 1,3,5-trinitrobenzene (TNB) on electron donor sites of fully oxidized Al(2)O(3) samples with different phase compositions is studied by EPR. It is shown that the maximum concentration of the radical anions does not substantially depend on the choice of solvent and reaction temperature, and can be used to measure the total concentration of the donor sites. The donor sites are observed in almost the same concentration about 5 × 10(16) m(-2) on all alumina polymorphs except for α-Al(2)O(3). The formation rate of the TNB radical anions and the activation energy of this process are found to depend on the donor properties of the solvent. The EPR in situ experiments showed that a substantial amount of the adsorbate forming a liquid phase is required for generation of the radical anions. These results prove that the sites measured by the formation of the TNB radical anions are not genuine electron donor sites capable of direct electron transfer to the adsorbed TNB molecules. A model of the observed paramagnetic species based on the obtained experimental data and the results of quantum chemical simulations is suggested. According to this model, a TNB radical anion substitutes a hydroxyl group forming a neutral ion pair with a surface aluminum cation. The suggested mechanism for the formation of such ion pairs involves the migration of simple radicals and does not require long-distance charge separation. It is supposed that the donor site where the process is initiated includes a negatively charged surface hydroxyl group.     

尖晶石型衍生的Ni/Al2O3催化剂低温催化顺酐加氢合成丁二酸酐

开发高活性的顺酐加氢制丁二酸酐和γ-丁内酯催化剂具有重要的工业意义.顺酐加氢多采用Cu基和Ni基催化剂,但一般Cu基和Ni基催化剂存在反应温度高(170–260℃)和稳定性差等缺点,很有必要开发高活性的顺酐加氢催化剂.我们以拟薄水铝石作为Al2O3载体的前驱体,采用浸渍法制备了一系列镍铝尖晶石型衍生的不同Ni含量的Ni/Al2O3催化剂,并研究了它们在顺酐加氢反应中的催化性能.还原前Ni/Al2O3催化剂的X射线衍射结果表明,催化剂含有NiAl2O4物种.氮吸附结果显示,不同Ni含量的催化剂均具有介孔结构.氢-程序升温还原研究发现,Ni/Al2O3催化剂经750℃还原2 h后,其表面上NiAl2O4物种能被高效还原.X射线粉末衍射结果表明,750℃还原的Ni/Al2O3催化剂中金属Ni颗粒尺寸随着Ni负载量升高而增大.利用一氧化碳-程序升温脱附对750℃还原的Ni/Al2O3催化剂进行研究,发现750℃还原的催化剂上金属Ni物种含量从高到低依次为:Ni(7.5%)/Al2O3>Ni(5%)/Al2O3>Ni(2.5%)/Al2O3.采用CO化学吸附获得的Ni(2.5%)/Al2O3,Ni(5%)/Al2O3和Ni(7.5%)/Al2O3催化剂上金属Ni颗粒尺度分别为8.0,12.8和15.7 nm.活性研究结果表明,750℃还原的Ni(5%)/Al2O3催化剂具有最高的催化活性,这可能是由于Ni(5%)/Al2O3催化剂具有较多的Ni活性位点和较合适的Ni颗粒粒度所致.进一步研究发现,在650–750℃还原温度下,Ni(5%)/Al2O3催化剂的还原度随着还原温度的升高而升高,Ni分散度随着还原温度的升高而降低.活性结果研究表明,700℃还原的Ni(5%)/Al2O3催化剂具有较多的Ni活性位点和较合适的Ni颗粒粒度,具有最高的加氢催化活性,其在120℃,H2压力为0.5 MPa和质量空速为2 h?1的反应条件下,能获得近100%的顺酐转化率和90%的丁二酸酐选择性,同时该催化剂具有优良的稳定性.以上结果表明,尖晶石型衍生的Ni/Al2O3催化剂是一个十分有应用前景的顺酐加氢催化剂.     

EXAFS characterization of Ti/Al2O3 supports and Co/Ti/Al2O3 catalysts

The structure of Ti/Al₂O₃ supports (0–14 wt% Ti) and Co/Ti/Al₂O₃ catalysts (3 wt% Co) was examined by EXAFS. The results indicated that the Ti was present primarily as a highly dispersed surface phase. The Ti EXAFS results indicated that the Ti species were octahedrally coordinated. Evidence of Ti—Ti interactions was found for all loadings (2–14 wt% Ti) suggesting that the Ti surface species are present as small clusters of TiO₂.The Co EXAFS results showed evidence for several structurally different Co surface phases as a function of Ti loading. Evidence of a Co species interacting with the Ti surface phase was observed for the 3% Co/2% Ti-3%Co/6%Ti catalysts. At the highest loadings studied, 3%Co/8%Ti and 3%Co/14%Ti, evidence was found for a CoTiO₃-like phase.     

Catalytic hydrogenation of aromatic aldehydes and ketones over ruthenium catalysts

Catalytic hydrogenations of acetophenone, benzaldehyde, and cinnamaldehyde using a catalyst of 5% wt. Ru/activ. carbon in hexane and/or 2-propanol were studied. Basic kinetic parameters were evaluated. The influence of the reactants’ structure and the kind of solvent used on the course of the reaction were also discussed.     

裂解汽油中噻吩硫在Co-Mo/Al2O3上的催化加氢宏观动力学

采用绝热管式固定床积分反应器，在2.5MPa~3.9MPa、513K~655K、氢/裂解汽油摩尔比1.8~3.5和裂解汽油中噻吩、单甲基噻吩和双甲基噻吩质量分数为838×10－6、137×10－6~723×10－6和192×10－6~723×10－6下，对Co-Mo/Al2O3催化剂上裂解汽油催化加氢脱硫的宏观动力学进行了研究。以Powell优化法和Merson迭代法对动力学实验数据进行非线性参数估值，建立了良好吻合实验数据的、裂解汽油催化加氢脱硫的幂函数型宏观动力学模型。噻吩、单甲基噻吩和双甲基噻吩的反应级数分别为0.721、0.735和0.87，对应的加氢反应宏观活化能依次为70.0kJ·mol－1、67.9kJ·mol－1和59.9kJ·mol－1。各噻吩基硫的转化率均随反应压力的提高而增加，3.5MPa以上时，增加的趋势减缓；反应温度的提高有利于噻吩基硫转化率的增加；593K以上时，各硫化物的转化率随温度的增加呈现线性增加的趋势。     

Characterization of La-promoted Ni/Al2O3 catalysts for hydrogen production from glycerol dry reforming

In the current paper, dry (CO₂)-reforming of glycerol, a new reforming route, was carried out over alumina (Al₂O₃)-supported, non-promoted and lanthanum-promoted nickel (Ni) catalysts. Both sets of catalysts were synthesized via a wet co-impregnation procedure. Physicochemical characterization of the catalysts showed that the promoted catalyst possessed smaller metal crystallite size, hence higher metal dispersion compared to the virgin Ni/Al₂O₃ catalyst. This was also corroborated by the surface images captured by the FESEM analysis. From temperature-programmed calcination analysis, the derivative weight profiles revealed two peaks, which represent a water elimination peak at a temperature range of 373 to 473 K followed by nickel nitrate decomposition from 473 to 573 K. In addition, BET surface area measurements gave 85.0 m²·g⁻¹ for the non-promoted Ni catalyst, whilst the promoted catalysts showed an average of 1% to 6% improvement depending on the La loadings. Significantly, reaction studies at 873 K showed that glycerol dry reforming successfully produced H₂. The 2%La-Ni/Al₂O₃ catalyst, which possessed the largest BET surface area, gave an optimum H₂ generation (9.70%) at a glycerol conversion of 24.5%.     

Pt/Al2O3和Pt-Cu/Al2O3催化CCl4氢化脱氯反应

制备了Al2O3负载Pt单金属催化剂和负载Pt-Cu双金属催化剂,比较了二者不同还原温度对其催化CCl4氢化脱氯反应性能的影响。 单金属Pt催化剂上主要生成CHCl3,而双金属Pt-Cu催化剂上产物随催化剂制备时的还原温度不同而异,当催化剂经400 ℃用H2还原后产物主要为CHCl3,而当催化剂经800 ℃用H2还原后产物主要为CCl2CCl2。 由于CCl4氢化反应是强放热反应,催化剂表面局部过热使得在反应中生成的C2等产物聚合结焦,覆盖了催化剂的活性中心,导致催化剂失活。 因此,通过加入甲醇作为稀释剂以带走部分反应热可提高催化剂的稳定性。 同时也降低了CHCl3的选择性,提高了CCl2CCl2的选择性。     

Hydrazine decomposition over Irn/Al2O3 model catalysts prepared by size-selected cluster deposition

Hydrazine decomposition chemistry was probed over a temperature range from 100 to 800 K for a series of model catalysts prepared by mass-selected Ir(n)(+) deposition on planar Al(2)O(3)/NiAl(110). Two sets of experiments are reported. Temperature-programmed desorption (TPD) was used to study hydrazine desorption and decomposition on Al(2)O(3)/NiAl(110) and on a model catalyst prepared by deposition of Ir(+) on Al(2)O(3)/NiAl(110) at a density large enough (5 x 10(14) cm(-2)) that formation of a distribution of small Ir(n) clusters on the surface is expected. This model catalyst was found to have hydrazine decomposition properties qualitatively similar to those observed on single-crystal Ir and polycrystalline Rh. This catalyst was also studied by X-ray photoelectron spectroscopy (XPS), to probe TPD-induced changes in the samples. A substantial decrease in the Ir XPS intensity suggests that considerable sintering takes place when the samples are heated to 800 K. In addition, a significant fraction of the nitrogen contained in the hydrazine is converted to an aluminum nitride (or mixed Al(x)O(y)N(z)) compound. Continuous flow experiments were used to probe relative reactivity at 300 and 400 K of samples prepared by depositing differently sized Ir(n)(+) clusters. At 300 K, samples prepared with preformed Ir(n)(+) (n = 5, 7, 10) are about twice as active, per Ir atom, as samples prepared with Ir(+) deposition, and there is a weaker trend to higher activity with increasing cluster size. At 400 K the trends are similar, but weaker, suggesting that thermal modification of the samples is already significant.