Synthesis of Vanadium Catalysts Supported on Cerium Containing TiO<Subscript>2</Subscript> Nanotubes for the Oxidative Dehydrogenation of Propane

Cerium containing TiO₂ nanotubes (CeTNTs) were successfully synthesized through the hydrothermal method and applied as support for vanadium catalyst in the oxidative dehydrogenation of propane. The impregnation method was employed to load 2, 5 and 8 wt % vanadium on the CeTNT surface. The catalysts were labeled as xV/CeTNT which x refers to the amount of vanadium loading. For a comparison, pure TNT was also synthesized and impregnated with 5 wt % vanadium. Based on TGA, XRD and TEM analyses, it was concluded that the addition of Ce increased the thermal stability of TNT. The Raman results showed that the 5V/CeTNT sample with a higher surface area hosted a higher number of monomeric VO_x species compared to 5V/TNT. On the other hand, it was shown that the population of monomeric VO_x species decreased as the vanadium loading increased. Catalytic results showed that propane conversion increased while propylene selectivity decreased as the vanadium loading increased. The best catalytic performance belonged to the 5V/CeTNT sample with propylene yield of about 10.6 wt % at the reaction temperature of 500°C.     

水蒸气对Pt-Sn-Ce催化剂的丙烷脱氢性能的影响

 摘要：以γ-Al2O3为载体, 采用连续等体积浸渍法制备了0.3%Pt/γ-Al2O3、0.3%Pt-0.9%Sn/γ-Al2O3和0.3%Pt-0.9%Sn/2.2%Ce-γ-Al2O3 3种Pt金属催化剂。考察了在C3H8催化脱氢制C3H6的体系中, 引入不同量的水蒸气对3种催化剂的催化脱氢性能的影响。结果表明,水蒸气的存在加速了0.3%Pt/γ-Al2O3和0.3%Pt-0.9%Sn/γ-Al2O3催化剂的失活, 同时降低了C3H6的选择性, 但对0.3%Pt-0.9%Sn/2.2%Ce-γ-Al2O3催化剂的稳定性影响较小。在0.3%Pt-0.9%Sn/2.2%Ce-γ-Al2O3体系中,水蒸气可以明显地提高C3H8的脱氢反应转化率和降低催化剂上的积炭量。对水蒸气处理后的Pt催化剂进行H2-化学吸附量测定的结果表明, Ce可以通过与活性中心Pt的强相互作用, 提高Pt粒子在水蒸气气氛下的抗烧结能力。C3H8脱氢转化率的提高是由于CeO中的活泼O与活泼H反应产生OH基团,OH基团参与了C3H8的β-H的消除反应, 提高了C3H8的脱氢速率。以γ-Al₂O₃为载体, 采用连续等体积浸渍法制备了0.3%Pt/γ-Al₂O₃、 0.3%Pt-0.9%Sn/γ-Al₂O₃和0.3%Pt-0.9%Sn/2.2%Ce-γ-Al₂O₃3种Pt 金属催化剂。考察了在丙烷（C₃H₈）催化脱氢制丙烯（C₃H₆）的体系中,引入不同量的水蒸气对3种催化剂的催化脱氢性能的影响。结果表明,水蒸气的存在加速了0.3%Pt/γ-Al₂O₃和0.3%Pt-0.9%Sn/γ-Al₂O₃催化剂的失活,同时降低了C₃H₆的选择性,但对0.3%Pt-0.9%Sn/2.2%Ce-γ-Al₂O₃催化剂的稳定性影响较小。在0.3%Pt-0.9%Sn/2.2%Ce-γ-Al₂O₃体系中,水蒸气可以明显地提高 C₃H₈的脱氢反应转化率和降低催化剂上的积炭量。对水蒸气处理后的 Pt 催化剂进行 H₂-化学吸附量测定的结果表明,Ce 可以通过与活性中心 Pt 的强相互作用,提高 Pt 粒子在水蒸气气氛下的抗烧结能力。C₃H₈脱氢转化率的提高是由于CeO 中的活泼O 与活泼H 反应产生OH 基团,OH 基团参与了 C₃H₈的 β-H 的消除反应, 提高了C₃H₈的脱氢速率。     

丙烷脱氢与逆水煤气变换耦合制丙烯——碱性助剂对Cr/SiO_2体系催化性能的影响

研究了丙烷脱氢与逆水煤气变换耦合制丙烯反应中碱性助剂对Cr/SiO2体系催化性能影响。运用XRD、TPR和吸附量热等技术考察了金属氧化物助剂对Cr/SiO2催化剂物相、氧化还原性以及表面酸性的影响,结果表明,碱金属和碱土金属助剂的加入,中和了催化剂表面的强酸中心,催化剂还原温度升高,丙烷脱氢转化率下降。但碱性助剂的加入,可提高丙烯的选择性和收率。5%Cr 0 4%K/SiO2催化剂的活性高,在650℃、V(CO2)/V(C3H8)=3 6的条件下,丙烷转化率为31%,丙烯的选择性和收率分别为91%和29%。     

Catalytic Cracking of <Emphasis Type="Italic">n</Emphasis>-Hexane and <Emphasis Type="Italic">n</Emphasis>-Heptane over ZSM-5 Zeolite: Influence of SiO<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Ratio

The performance of two types of ZSM-5 zeolite catalysts (MFI-type zeolite, SiO₂/Al₂O₃ = 50 and 300) was studied in the catalytic cracking of n-hexane and n-heptane as a model compound of light naphtha for production of light olefins at 500, 550, and 600°C. The physicochemical properties of ZSM-5 catalysts were characterized by means of XRD, BET, SEM and NH₃-TPD. The influence of SiO₂/Al₂O₃ molar ratio was investigated on conversion and product selectivity. ZSM-5 zeolite yielded higher conversion in the cracking of n-hexane compared to n-heptane and maximum conversion was achieved over ZSM-5(50) at 600°C. ZSM-5(50) showed higher alkane selectivity rather than olefins. It was found that ZSM-5(300) was more desirable in terms of having significant selectivity to light olefins as well as producing high propylene to ethylene ratio. The maximum propylene to ethylene ratio of 2.7 and 2.48 was observed over ZSM-5(300) at 500°C for n-hexane and n-heptane cracking, respectively.     

PRODUCTION OF ETHYLENE AND PROPYLENE FROM ETHANE,PROPANE, AND N-BUTANE MIXED WITH STEAM IN A MICROWAVE-IRRADIATED SILICON-CARBIDE LOADED REACTOR

ABSTRACT

We studied the production of ethylene (C2") and propylene (C3") by the decomposition of pure ethane, propane, and n-butane, mixed with steam, in a microwave-irradiated fixed bed reactor packed with silicon carbide. We found that ethylene production was maximized using ethane as the feed, with per pass yields as high as 63% at an ethane conversion level of 74%. With propane and n-butane feeds, more ethylene than propylene was produced, but the propylene amounts were significant. Combined per pass yields of C2" and C3" were 56% at a butane conversion of 99%, and 50% at a propane conversion of 93%. This microwave process appears to be a viable way of producing ethylene and propylene.     

丙烷在MoCexOy催化剂上氧化脱氢制丙烯

以钼酸铵、硝酸铈为原料,硅胶为载体,采用浸渍法制备了不同负载量的MoCexOy催化剂。在丙烷氧化脱氢制丙烯固定床反应器中,评价了催化剂的性能。结果表明,最佳工艺条件为：Ce离子／Mo离子（摩尔比）0．15,负载量（质量分数）10％,反应温度420℃,空速120h^-1。在此条件下,丙烷转化率为11．2％,丙烯选择性为94．5％。     

Synthesis of hierarchical SAPO-34 and its enhanced catalytic performance in methanol to propylene conversion process

ABSTRACT

Hierarchical SAPO-34 molecular sieve was synthesized hydrothermally in the presence of different concentrations of n-propylamine (NPA) as the mesoporous generating agent. It has been found that the mesoporous structure and morphology of the hierarchical SAPO-34 was depended to the amount of NPA used. The catalytic activity of the synthesized materials for methanol to propylene conversion were evaluated. A high selectivity for propylene (44.5%) compared to a conventional microporous SAPO-34 (28.7%) was observed with propylene to ethylene (P/E) ratio (3.6) which was attributed to the less total acidic sites measured by NH3-TPD and the optimal combination of mesoporous and microporous reaction paths. The synthesized hierarchical SAPO-34 catalysts were characterized by XRD, FE-SEM, BET, NH₃-TPD and TGA techniques.     

The effect of H<Subscript>2</Subscript>S on the selectivity of light alkenes in the FE-Mn-catalyzed Fischer-Tropsch synthesis

Iron-manganese oxides are prepared using a co-precipitation procedure and studied for the conversion of synthesis gas to light olefins. In particular, the effect of a range of preparation variables is investigated in details. In this investigation, sulfur absorption and effect of sulfur poisoning on Fe-Mn catalysts have been studied. In the Fischer-Tropsch synthesis process, the poisoning of the catalyst is one of the important parameters causing a decrease in the catalyst activity, declaring the sulfur compounds as virulent poisons in this process. In the present investigation, poisoning of Fe-Mn catalysts were performed in a gas circulation system and H₂S was injected into a circulation loop. The prepared catalysts were exposed to a mixture of H₂S and N₂ at about 450°C in the stainless-steel micro reactor via co-precipitation method. H₂S was produced by addition of H₂SO₄ to Na₂S × H₂O and this gas was mixed with an inert carrier gas (N₂). Comparing the activity and selectivity of fresh and poisoned catalysts, indicates that the selectivity and CO conversion are affected by high-level sulfur adsorbed on the catalysts. The results show that the CO conversion and selectivity with respect to methane production and coke formation were decreased, but the selectivity of light alkenes such as propylene was increased over poisoned catalysts. Characterization of both precursors and calcined catalysts by powder X-ray diffraction, BET specific surface area and thermal analysis methods such as TGA and DSC showed that the poisoning of Fe-Mn catalysts influenced the catalyst structure.     

Mathematical Modelling of the Methane Conversion to Heavier Hydrocarbons in a Plasma Reactor

In this study, mathematical modeling of fixed-bed plasma reactor operated under isothermal condition was investigated. In this process, methane and acetylene were the inputted feed and ethane, ethylene, propylene, propane, i-butane, and n-butane were the output products. The amount of methane conversion obtained was 12.7% for the former feed, however, if pure methane was inputted this conversion rose to 13.8%. Furthermore, the plasma process enhanced the conversion as well as the selectivity toward the desired product and yield. In the present study, when methane and acetylene were fed at a molar ratio of CH₄/C₂H₂ = 10 to the reactor, the selectivity of C₂, C₃, and C₄ hydrocarbons was determined to be 30%, 24%, and 44%; respectively. A comparison between the thermal and the plasma process showed that the methane conversion and production yield in the plasma process were higher than in the thermal process under the same operating conditions. On the other hand, product selectivity in the plasma process was determined to be lower than that of the thermal process. Finally, results of the methane conversion processes in the plasma phase were compared with those available in the open literature.     

正己烷在FAU和MFI型分子筛催化剂上的转化途径

 以正己烷在分子筛催化剂上的转化途径和各转化产物平均摩尔选择性为基础, 建立了正己烷在分子筛催化剂上转化反应的独立反应方程, 通过关联独立反应议程和转化产物平均摩尔选择性计算出独立反应的摩尔选择性. 结果表明, 一旦正己烷的C-C键或C-H键被质子所戟生成Carbonium ion后, 该C6 Carbonium ion 随后发生的α异裂的位置更货币于在靠近链中的位置. 正己烷在MFI型, 复合FAU型和FAU型分子筛催化剂上的转化反应中, 单分子反应的比例分别为75.87%, 32.01%和31.46%. 正己烷反应产物中的丙烷和丙烯等较大分子的来源不仅是双分子反应, 同时还有单分子反应, 两者的比例受分子筛催化剂类型的影响. 以正己烷和H质子进行验证表明独立反应方程的建立和独立反应摩尔选择性的计算是有效的.     

负载型V_2O_5/AlPO_4催化剂在丙烷氧化脱氢中的催化作用

采用浸渍法在自制的无定型磷酸铝ＡｌＰＯ４载体上负载０．６％～６．０％的Ｖ２Ｏ５，所制的催化剂在丙烷氧化脱氢反应中具有较好的催化性能，如３．０％Ｖ２Ｏ５／ＡｌＰＯ４催化剂在丙烷转化率为１４．２％时，丙烯选择性可达４９．１％，丙烯收率达７．０％。考察了不同反应条件下催化剂的性能，ＸＲＤ、ＩＲ和Ｒａｍａｎ光谱表明，Ｖ２Ｏ５在ＡｌＰＯ４上主要是以高度分散的钒氧物种存在；ＥＳＲ结果证明催化剂中存在Ｖ４＋物种，暗示Ｖ５＋／Ｖ４＋氧化还原偶参与了氧化还原反应。     

Oxidative dehydrogenation of butenes over Ni-V-Sb/γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> oxide catalyst

The process of the oxidative dehydrogenation of butenes over a nickel-vanadium-antimony supported catalyst proceeds with a higher conversion and selectivity as compared to the dehydrogenation of n-butane. It was found that the maximum yield of divinyl per pass from the butylene fraction reaches 44% at a 68% selectivity. The maximum selectivity of the process (75%) is achieved at a divinyl yield of no more than 40%. The addition of nickel oxide to antimony vanadate results in the simultaneous formation of both nickel vanadate and antimonate, which are responsible for the conversion of butylenes to divinyl. Systems based on the supported Ni-V-Sb oxide matrix were analyzed with the use of the BET, X-ray photoelectron spectroscopy, diffuse reflection spectroscopy, X-ray diffraction, and hydrogen temperature-programmed reduction techniques. The formation of the NiV₂O₆ nickel vanadate phase results in the most selective catalyst with an increased amount of mobile oxygen in the lattice due to the presence of vanadium.     

不同金属改性的ZSM-5分子筛正己烷裂解性能

轻烃催化裂解具有裂解温度低、产物分布可调以及可多产丙烯等优点而备受关注。采用等量浸渍法制备了一系列不同金属改性的ZSM-5分子筛催化剂,在固定床微型反应器中评价了其催化正己烷裂解性能。实验结果表明,4种不同金属（Ni,Fe,Cr,Co）改性的ZSM-5分子筛催化剂上正己烷转化率都显示出下降趋势,但下降幅度不同,而且乙烯、丙烯选择性随不同金属的引入变化规律也不同。其中,Fe和Cr的引入对正己烷转化率的影响较小,而Co的引入导致正己烷转化率的下降幅度更大。就丙烯和乙烯选择性而言,随着金属的引入都有所增加。Co的添加对丙烯选择性提高幅度最大。因此,需要更高丙烯选择性时,可以牺牲正己烷转化率获得更多丙烯。     

丙烷均相氧化脱氢及其应用

丙烷在８００￣８４０Ｋ、Ｏ２／Ｃ３＾０比０．４４￣１．６５、停留时间６．０￣１３．５ｓ的条件下进行均相氧化脱氢。在丙烷转化率为４０％时，丙烯选择性为４２．５％，产率为１７．０％。用自丙烯生产丙烯醛的Ｍｏ－Ｃｏ－Ｒｅ－Ｂｉ－Ｏ催化剂，将上述反应产物在５９０￣６１５Ｋ、Ｏ２／Ｃ３＾０综合比０．６５￣１．１３、停留时间２．４￣４．２ｓ的条件下氧化，得到丙烯醛按丙烷衡算的选择性〉３３．５％，产率〉１３．５     

PRODUCTION OF ETHYLENE AND PROPYLENE FROM ETHANE, PROPANE, AND N-BUTANE MIXED WITH STEAM IN A MICROWAVE-IRRADIATED SILICON-CARBIDE LOADED REACTOR

We studied the production of ethylene (C2") and propylene (C3") by the decomposition of pure ethane, propane, and n-butane, mixed with steam, in a microwave-irradiated fixed bed reactor packed with silicon carbide. We found that ethylene production was maximized using ethane as the feed, with per pass yields as high as 63% at an ethane conversion level of 74%. With propane and n-butane feeds, more ethylene than propylene was produced, but the propylene amounts were significant. Combined per pass yields of C2" and C3" were 56% at a butane conversion of 99%, and 50% at a propane conversion of 93%. This microwave process appears to be a viable way of producing ethylene and propylene.     

Conversion of Mixed Lower Olefins and Paraffins on Galloaluminosilicate

At many oil refineries and gas processing plants, the C₂–C₅ fractions obtained as by–products do not have any qualified application. These hydrocarbons can be converted into valuable products on zeolite–based catalysts from the pentasil family. The characteristics of conversion of mixed C₂–C₄ olefins and paraffins into aliphatic and aromatic C₅₊ hydrocarbons in the presence of a galloaluminosilicate catalyst with the structure of pentasil were investigated. The temperature intervals of formation of isoparaffins from ethylene and propylene and aromatic hydrocarbons from mixed C₂–C₄ olefins and paraffins were found. Key words: C₂–C₄ olefins and paraffins, aliphatic and aromatic hydrocarbons, zeolites of the pentasil family, galloaluminosilicates.     

Product control in catalytic aromatization of C2+ hydrocarbons

Aromatization of light hydrocarbons (propane, butane, propane-propene mixture, and cat-cracker off-gases) on ZnO-zeolite and lanthanide-zeolite catalysts based on zeolite TsVM (SiO₂/Al₂O₃ = 62) and industrial catalyst SGK-1 was studied. It was shown that the modification of catalysts with lanthanides leads to an increase in both the total yield of xylenes and the p-xylene selectivity, a change that is explained by the formation of branched intermediates and steric specifics of their further conversion.     

Structure and Reactivity of Vanadia/Dolomite Catalysts

Abstract

Supported vanadium oxide catalysts containing surface vanadia species on oxide supports are extensively employed as catalysts for many hydrocarbon oxidation reactions. This article studies the structure and reactivity of surface vanadia species supported on purified natural dolomite. CaO-MgO oxide support was derived from purified calcined dolomite mineral. Ammonium metavanadate was used as a source of V₂O₅, and the vanadia contents were varied from 10–18 wt%. The CaO-MgO support and the prepared vanadia catalysts (V₁, V₂, V₃) were characterized by means of X-ray, FTIR, and scanning electron microscopy. The activity of the prepared catalysts and the influence of vanadium loading on the catalytic performance for oxy-dehydrogenation of methyl cyclohexane were investigated at reaction temperatures ranging from 250°C to 450°C and under atmospheric pressure.     

The Catalytic Dehydration of Bio-ethanol to Ethylene on SAPO-34 Catalysts

SAPO-34 catalysts were synthesized by hydrothermal method, and characterized by X-ray diffraction (XRD), NH₃ temperature-programmed desorption (NH₃-TPD) and thermogravimetric-differential thermal analysis (TG-DTA). The synthesized catalysts were tested for dehydration of bio-ethanol to ethylene in comparison with commercial ZSM-5 and γ-Al₂O₃. The home-made SAPO-34 catalysts exhibited similar bio-ethanol conversion and ethylene selectivity at 60°C and 110°C lower compared to commercial ZSM-5 and γ-Al₂O₃ catalysts, respectively, indicating higher low-temperature activity. It was found that the crystallinity and surface acidity of synthesized SAPO-34 decreased after 4 h on stream, which is attributed to the carbonaceous deposits on catalyst confirmed by TG-DTA.     

不同载体的PtSn催化剂上丙烷脱氢性能的研究

考察了丙烷在Ａｌ２Ｏ３、ＭｇＡｌ２Ｏ４、ＺｎＡｌ２Ｏ４等载体负载的Ｐｔ及ＰｔＳｎ催化剂上的脱氢反应性能,讨论了催化剂中锡组分的存在状态与丙烷脱氢性能的关系,指出只有锡以氧化态存在且未覆盖活性铂簇团时才有利于催化剂脱氢性能的改善