Role of support nature （γ-Al2O3 and SiO2-Al2O3） on the performances of rhenium oxide catalysts in the metathesis of ethylene and 2-pentene

The metathesis of ethylene and 2-pentene was studied as an alternative route for propylene production over Re2O7/γ-Al2O3 and Re2O7/SiO2-Al2O3 catalysts. Both NH3 temperature-programmed desorption (NH3-TPD) and H2 temperature-programmed reduction (H2-TPR) results showed that Re2O7/SiO2-Al2O3 exhibited stronger acidity and weaker metal-support interaction than Re2O7/γ-Al2O3. At 35 60℃, isomerization free metathesis was observed only over Re2O7/γ-Al2O3, suggesting that the formation of metal-carbene metathesis active sites required only weak acidity. Our results suggest that on the Re2O7/SiO2-Al2O3, hydrido-rhenium species ([Re]-H) were formed in addition to the metathesis active sites, resulting in the isomerization of the initial 1-butene product into 2-butenes. A subsequent secondary metathesis reaction between these 2-butenes and the excess ethylene could explain the enhanced yields of propylene observed. The results demonstrate the potential for high yield of propylene from alternative feedstocks.     

微乳液法制备Pt-S2O82-/ZrO2-Al2O3型固体超强酸催化剂及其异构化性能

采用微乳液法负载Pt制备了Pt-S2O82-/ZrO2-Al2O3(Pt-SZA-M)固体超强酸催化剂, 以正戊烷异构化反应为探针, 对比了微乳液法和浸渍法负载Pt制备的催化剂(Pt-SZA)的异构化性能, 并采用XRD, FTIR, BET, TG-DTA, TPR和TEM对催化剂进行了表征. 结果表明, 与Pt-SZA催化剂相比, Pt-SZA-M催化剂中Pt粒子的粒径更小(4.5 nm)且尺寸更均一; Pt-SZA-M催化剂的比表面积(109.6 m2/g)比Pt-SZA催化剂(95.0 m2/g)增加了15.4%. Pt-SZA-M催化剂的初始还原温度比Pt-SZA催化剂降低了10~20℃, 表明微乳液法负载Pt可以提高催化剂的氧化活性, 提高氢分子在催化剂上的吸附解离能力. 异构化活性实验结果表明, 与Pt-SZA催化剂相比, Pt-SZA-M催化剂的低温活性得到明显改善, 在反应压力为2.0 MPa、 氢烃摩尔比为4: 1、 质量空速为1.0 h-1的条件下, Pt-SZA-M催化剂在反应温度为230℃时活性达到60.8%, 在100 h内异戊烷的收率可稳定在58.0%左右, 选择性在95.0%以上.     

The thermal reaction of 2-pentene around 500°C at low extent of reaction

The thermal reaction of 2-pentene (cis or trans) has been performed in a static system over the temperature range of 470°–535°C at low extent of reaction and for initial pressures of 20–100 torr. The main products of decomposition are methane and 1,3-butadiene. Other minor primary products have been monitored: trans-2-pentene, trans- and cis-2-butenes, ethane, 1,3-pentadienes, 3-methyl-1-butene, propylene, 1-butene, hydrogen, ethylene, and 1-pentene. The initial orders of formation, 0.8–1.1 for most of the products and 1.5–1.8 for 1-pentene, increase with temperature. The formation of the products and the influence of temperature on their orders can be essentially explained by a free radical chain mechanism. But cis–trans or trans–cis isomerization and hydrogen elimination from cis-2-pentene certainly involve both molecular and free radical processes. The formation of 1-pentene mainly occurs from the abstraction of the hydrogen atom of 2-pentene by resonance stabilized free radicals (C₅H₉.).     

High selectivity production of propylene from 2-butene: non-degenerate pathways to convert symmetric olefins via olefin metathesis

The first example of propylene production from 2-butene in promising yield is described by reacting trans-2-butene over tungsten hydrides precursor W-H/Al(2)O(3) at 150 °C and different pressures in a continuous flow reactor. The tungsten carbene-hydride active site operates as a "bi-functional catalyst" through the disfavoured 2-butene isomerisation on W-hydride and 2-butenes/1-butene cross-metathesis on W-carbene.     

Cross metathesis of butene-2 and ethene to propene over Mo/MCM-22-Al2O3 catalysts with different Al2O3 contents

A series of 3.0Mo/MCM-22-Al2O3 catalysts with γ-Al2O3 contents in the range of 0-100 wt% were prepared and applied in the metathesis reaction of ethene and butene-2. Addition of γ-Al2O3 did not affect the structure of MCM-22 zeolite as evidenced by XRD and N2 adsorption measurements. It was deduced from TPR experiments that γ-Al2O3 phase favored the formation of polymolybdate or multilayered Mo oxide, while more Al2(MoO4)3 species were generated over MCM-22 zeolites. Alumina content in the support was directly related to the metathesis activity of ethene and butene-2 to propene. Mo species with higher valence (Mo⁶⁺or Mo⁵⁺) contributed more to the excellent performance of catalyst than metallic Mo. The best catalyst activity and stability was obtained over 3.0Mo/(MCM-22-30%Al2O3) under the reaction condition of 1.0 MPa and 125 ℃ using N2 as the pretreatment gas.     

低硅铝比ZSM-5分子筛上C4烃的催化裂解反应

以低硅铝比(n(SiO2)/n(Al2O3)=20-45)的ZSM-5分子筛为催化剂, 研究了混合C4烃的催化裂解反应, 并对不同硅铝比的ZSM-5分子筛进行了酸性表征. 混合C4烃的催化裂解反应结果表明, 低硅铝比的ZSM-5分子筛具有较高的低温催化活性, 高硅铝比ZSM-5分子筛催化剂上乙烯和丙烯的收率高于低硅铝比ZSM-5分子筛催化剂, 低硅铝比ZSM-5分子筛上苯和甲苯的收率高于高硅铝比ZSM-5分子筛催化剂. 在反应温度为625 ℃时, 硅铝比为20的ZSM-5分子筛催化剂上乙烯、丙烯、苯和甲苯的总收率可达79.42%. 酸性表征结果表明, 硅铝比低的ZSM-5分子筛具有更多的Bronsted(B)酸酸量、Lewis(L)酸酸量及总酸酸量, 这是低硅铝比ZSM-5分子筛具有低温高活性及高的苯和甲苯收率的原因.     

Acyclic diene metathesis (ADMET) of vinylsilanes over Re2O7–Al2O3 catalyst

Tetravinylsilane and divinylsilanes have been successfully metathesized for the first time over Re₂O₇/Al₂O₃ catalyst promoted with tetrabutyltin under mild reaction conditions. All of the products were acyclic oligomers via intermolecular metathesis; the cyclic products via intramolecular metathesis were not formed.     

焙烧温度对微乳液法负载铂制备的Pt-S2O82-/ZrO2-Al2O3催化剂异构化性能的影响

过微乳液法负载Pt制备了Pt-S₂O₈^2-/ZrO₂-Al₂O₃(Pt-SZA-X) 催化剂,并采用XRD、BET、FT-IR、TPR、TEM等手段对催化剂进行了表征。以正戊烷异构化反应为探针,考察了焙烧温度对催化剂异构化性能的影响。结果表明,焙烧温度对Pt-SZA-X的还原温度影响不大,但催化剂表面S含量随着焙烧温度的升高而下降;焙烧温度为600~650℃时形成O=S=O结构,此时S与催化剂载体结合比较稳定;焙烧温度为650℃时,可得到单一的ZrO₂四方晶相,焙烧温度高于650℃时,比表面积迅速降低,催化剂表面S⁶⁺流失严重。在不同温度下焙烧得到的催化剂中,经650℃焙烧的催化剂具有适宜的超强酸位和比表面积,异构化活性最高。在反应温度为230℃、反应压力2.0 MPa、氢烃物质的量比4:1、质量空速1.0 h^-1时,催化异戊烷产率达到60.8%。     

Oxidative coupling of methane over BaCl2-TiO2-SnO2 catalyst

The performance of BaCl2-TiO2-SnO2 composite catalysts in oxidative coupling of methane reaction has been investigated. A series of BaCl2-TiO2, BaCl2-SnO2, TiO2-SnO2, and BaCl2-TiO2-SnO2 catalysts were prepared, and characterized by BET, XRD, XPS, CO2-TPD and H2-TPR, respectively. The synergistic effect among BaCl2, SnO2 and TiO2 compositions enhances the catalytic performance. The best C2 selectivity and ethylene yield are obtained on the catalyst with the equal molar amount of the three compositions (BaCl2 : TiO2 : SnO2 molar ratio of 1 : 1 : 1). The optimal reaction conditions are as follows: 800°C, 44 mL·min-1 for methane, 22 mL·min-1 for oxygen and a space velocity of 5000 mL·h-1 g-1, and the C2H4 yield over the catalyst is 20.1% with the CH4 conversion of 43.8% and C2 selectivity of 53.3%.     

NaOH改性WO3/SiO2催化剂催化2-丁烯和乙烯复分解制丙烯SurasaMaksasithorn,DamienP.Debecker,PiyasanPraserthdam,JoongjaiPanpranot,KongkiatSuriye,SirachayaKunjaraNaAyudhya简

A WO₃/SiO₂ catalyst is used in industry to produce propylene from 2-butene and ethylene metathesis. Catalysts with various WO₃ loading (4% to 10%) were prepared by impregnation and tested for the metathesis of ethene and trans-2-butene. Ion exchange of NaOH onto the WO₃/SiO₂ catalyst was used to mitigate the acidity of the catalysts in a controlled way. At low WO₃ loading, the treatment with large amounts of NaOH resulted in a significant decrease in metathesis activity concomitant with significant W leaching and marked structural changes (XRD, Raman). At higher WO₃ loading (6% to 10%), the treatment with NaOH mainly resulted in a decrease in acidity. FT-IR experiments after adsorption of pyridine showed that the Lewis acidic sites were poisoned by sodium. Nevertheless, the metathesis activity remained constant after the NaOH treatment. This suggested that the remaining acidity on the catalyst was enough to ensure the efficient formation of the carbene active sites. Interestingly, Na poisoning resulted in some modification of the selectivity. The mitigation of acidity was shown to favor propene selectivity over the formation of isomerization products (cis-2-butene, 1-butene, etc.). Moreover, treatment with NaOH led to a shorter induction period and reduced coke formation on the WO₃/SiO₂ catalyst.     

Formation of 1,4-disilyl-2-butenes from vinyl grignard reagent and chlorosilanes catalyzed by a titanocene complex

Symmetrical 1,4-disilyl-2-butenes 1 have been prepared by the reaction of vinyl Grignard reagent with chlorosilanes. This reaction proceeds efficiently in the presence of a catalytic amount of titanocene dichloride at 0 degrees C in THF. When dichlorodiphenylsilane was used, 1,1-diphenyl-1-silacyclo-3-pentene 2 was obtained in a good yield.     

Germanium and silicon compounds as promoters for Re2O7/SiO2-Al2O3 metathesis catalysts

The effect of replacement of R₄Sn by germanium and silicon derivatives as the promoter for the catalyst system Re₂O₇/SiO₂-Al₂O₃ in the metathesis of hex-1-ene, and the system Re₂O₇/B₂O₃/SiO₂-Al₂O₃ in the metathesis of methyl oleate, was studied. The new promoters react slowly with the rhenium oxide. An activation time of about 15 min at temperatures varying from 50 to 75 °C is required for obtaining a good catalytic activity. These promoters can replace the toxic tin compounds, although they give rise to lower turnover numbers in the metathesis of methyl oleate.     

Homo-polymerization of alpha-olefins and co-polymerization of higher alpha-olefins with ethylene in the presence of CpTiCl2(OC6H4X-p)/MAO catalysts (X = CH3, Cl)

Cyclopentadienyl-titanium complexes containing -OC6H4X ligands (X = Cl,CH3) activated with methylaluminoxane (MAO) were used in the homo-polymerization of ethylene, propylene, 1-butene, 1-pentene, 1-butene, and 1-hexene, and also in co-polymerization of ethylene with the alpha-olefins mentioned. The -X substituents exhibit different electron donor-acceptor properties, which is described by Hammett's factor (sigma).The chlorine atom is electron acceptor, while the methyl group is electron donor. These catalysts allow the preparation of polyethylene in a good yield. Propylene in the presence of the catalysts mentioned dimerizes and oligomerizes to trimers and tetramers at 25 degrees C under normal pressure. If the propylene pressure was increased to 7 atmospheres,CpTiCl2(OC6H4CH3)/MAO catalyst at 25 degrees gave mixtures with different contents of propylene dimers, trimers and tetramers. At 70 degrees C we obtained only propylene trimer.Using the catalysts with a -OC(6)H(4)Cl ligand we obtained atactic polymers with M(w) 182,000 g/mol (at 25 degrees C) and 100,000 g/mol (at 70 degrees C). The superior activity of the CpTiCl2(OC6H4Cl)/MAO catalyst used in polymerization of propylene prompted us to check its activity in polymerization of higher alpha-olefins (1-butene, 1-pentene, 1-hexene)and in co-polymerization of these olefins with ethylene. However, when homo-polymerization was carried out in the presence of this catalyst no polymers were obtained. Gas chromatography analysis revealed the presence of dimers. The activity of the CpTiCl2(OC6H4Cl)/MAO catalyst in the co-polymerization of ethylene with higher alpha-olefins is limited by the length of the co-monomer carbon chain. Hence, the highest catalyst activities were observed in co-polymerization of ethylene with propylene (here a lower pressure of the reagents and shorter reaction time were applied to obtain catalytic activity similar to that for other co-monomers). For other co-monomers the activity of the catalyst decreases as follows: propylene >1-butene > 1-pentene > 1-hexene. In the case of co-polymerization of ethylene with propylene, besides an increase in catalytic activity, an increase in the average molecular weight M(w) of the polymer was observed. Other co- monomers used in this study caused a decrease of molecular weight. A significant increase in molecular weight distribution (M(w)/M(n)) evidences a great variety of polymer chains formed during the reaction.     

柠檬酸对Ni2P/TiO2-Al2O3催化剂加氢脱硫性能的影响

采用溶胶-凝胶法制备了TiO2-Al2O3复合载体,以柠檬酸(CA)为络合剂采用浸渍法制备了Ni2P负载的TiO2-Al2O3复合载体催化剂,并用X射线衍射(XRD)、N2吸附比表面积测定、H2程序升温氢还原(H2-TPR)、程序升温氧化(TPO)、X射线光电子能谱(XPS)技术对催化剂的结构和性质进行了表征,考察了CA/Ni摩尔比对在Ni2P/TiO2-Al2O3催化剂上进行的二苯并噻吩(DBT)加氢脱硫(HDS)性能的影响.结果表明:适量的CA可以丰富催化剂的孔道,提高催化剂的比表面积.当n(CA)/n(Ni)=2:1时,催化剂的比表面积达到126.75m2·g-1,与不加CA时相比,提高了57.05m2·g-1.调节n(CA)/n(Ni)能够改善活性相的分布,改变活性相的种类;引入CA使Ni和P前驱体的还原温度明显降低,促进活性相Ni2P的生成,一定程度上能够抑制催化剂表面炭的形成和沉积,提高其稳定性.n(CA)/n(Ni)=2:1时,催化剂具有最好的加氢脱硫活性,在360°C,3.0MPa,氢油比为500(V/V),液时体积空速为2.0h-1的条件下,二苯并噻吩转化率为99.5%,可将模拟油中硫含量由2%(w)降低到0.01%(w).     

Selective catalytic oxidation of NO with O2 over Ce-doped MnOx/TiO2 catalysts

A series of Ce-doped MnOx/TiO2 catalysts were prepared by impregnation method and used for catalytic oxidation of NO in the presence of excess O2. The sample with the Ce doping concentration of Ce/Mn=1/3 and calcined at 300°C shows a superior activity for NO oxidation to NO2. On Ce(1)Mn(3)Ti catalyst, 58% NO conversion was obtained at 200°C and 85% NO conversion at 250°C with a GHSV of 41000 h-1, which was much higher than that over MnOx/TiO2 catalyst (48% at 250°C). Characterization results implied that the higher activity of Ce(1)Mn(3)Ti could be attributed to the enrichment of well-dispersed MnOx on the surface and the abundance of Mn3+ and Ti3+ species. The addition of Ce into MnOx/TiO2 could improve oxygen storage capacity and facilitate oxygen mobility of the catalyst as shown by PL and ESR, so that its activity for NO oxidation could be enhanced. The effect of H2O and SO2 on the catalyst activity was also investigated.     

Dry reforming reaction over nickel catalysts supported on nanocrystalline calcium aluminates with different CaO/Al2O3 ratios

Nanocrystalline calcium aluminates with different CaO/Al2O3 ratios were prepared by a facile co-precipitation method using Poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEG-PPG-PEG, MW: 5800) as a surfactant. They were employed as catalyst support for nickel catalysts in methane reforming with carbon dioxide. The prepared samples were characterized by X-ray diffraction (XRD), N2 adsorption (BET), temperature-programmed reduction and oxidation (TPR-TPO), and scanning electron microscopy (SEM) techniques. Catalysts showed a relatively high catalytic activity and stability. TPR analysis revealed that the catalysts with higher CaO content are more difficult to be reduced. TPO analysis showed that the 5 wt%Ni/CA and 5 wt%Ni/C12A7 catalysts with higher CaO amount were effective against coke deposition.     

Deactivation of H3PW12O40/TiO2 catalyst used in the production of camphene

Summary The deactivation of the H3PW12O40 (HPW) catalyst supported on TiO2 used in the isomerization reaction of a-pinene and its regeneration were studied. The regeneration of the deactivated catalyst was carried out with an air flow at 300 and 500ºC, with an ozone-enriched oxygen flow at 150ºC and by extraction with solvent and acid treatment. Only the last treatment permitted to recover its activity restoring it in 48% of its initial value.     

Kinetics of catalytic combustion in air over Pt/Al2O3/Al catalyst

Summary Catalytic combustion of toluene, propylene and CO over Pt/Al₂O₃ /Al catalyst was investigated. Strong inhibition effects are observed when the mixture of toluene, propylene and CO is oxidized. A reaction mechanism of catalytic combustion over Pt/Al₂O/Al is proposed. The results from kinetic models are in good agreement with the experimental data.     

纳米膜组装介孔Al2O3：合成及Pt/Al2O3的硝基苯催化加氢性能

以"乙酸乙酯(EA)-偏铝酸钠-水"体系在室温下合成了纳米膜组装介孔Al2O3。研究发现:合成反应时间、静置前搅拌时间、NaAlO2用量、EA用量及反应温度等对合成产物的形貌有影响;另外,与用商品γ-Al2O3制备的Pt/γ-Al2O3催化剂相比,纳米膜组装介孔Al2O3制备的Pt/Al2O3催化剂含有部分易被还原的PtOx物种。在硝基苯催化加氢反应中,用合成Al2O3为载体制备的Pt/Al2O3催化剂,比用商品γ-Al2O3制备的Pt/γ-Al2O3催化剂具有更好的催化活性。     

利用磁性可回收的Fe_3O_4纳米颗粒催化剂合成苯并咪唑的新方法(英文)

Magnetically recoverable Fe3O4 nanoparticles have been synthesized as a catalyst for the cyclocondensation of 1,2-phenylenediamines with orthoesters under solvent-free conditions.Catalyst loadings can be as low as 1 mol% to give high yields of the corresponding benzimidazole derivative at 80 °C.This green method offers significant advantages in terms of its simplicity,low catalyst loadings,high product yields,and non-toxic nature.The Fe3O4 nanoparticles were characterized by X-ray diffraction,transmission electron microscopy,and Fourier transform infrared spectroscopy.