Effect of barium on reducibility and activity for cobalt-based Fischer-Tropsch synthesis catalysts

Barium modified Co/Al2O3 catalysts were prepared by incipient wetness impregnation. The catalysts were characterized by XRD, TPD and DRIFTS. The catalytic activity for Fischer-Tropsch synthesis was measured in a continuously stirred tank reactor. It was found that small amounts of BaO (≤ 2 wt%) improved the cobalt reducibility, which led to more cobalt active sites on the catalyst surface, and then resulted in higher CO conversion and C5+ selectivity. However, for the catalysts with high BaO loadings negative effects on the catalytic activity and selectivity for high hydrocarbons were observed because of low cobalt reducibility.     

焙烧温度对K改性Ag-Fe/ZnO-ZrO2催化剂结构和CO加氢合成低碳混合醇醚性能的影响

采用并流共沉淀法在不同焙烧温度下制备K改性Ag-Fe/ZnO-ZrO₂催化剂,考察不同焙烧温度对催化剂CO加氢合成低碳混合醇醚反应性能的影响。通过N₂物理吸附(N₂-adsorption)、X射线衍射(XRD)、氢气程序升温还原(H₂-TPR)、一氧化碳程序升温脱附(CO-TPD)等手段对催化剂进行表征。结果表明,250 ℃焙烧的催化剂,由于焙烧温度较低,表面尚未形成足够多的活性位,未能达到最佳的催化性能;300 ℃焙烧的催化剂,其CO转化率最高、醇醚选择性较高,醇醚时空产率达到最大值。随着焙烧温度进一步升高,CO转化率逐渐降低,醇选择性先降低后增大,二甲醚(DME)选择性逐渐增大,醇醚时空产率逐渐降低。催化剂性能主要与其比表面积、还原性能、所含银铁复合物分散度及CO吸脱附性能有关,即比表面积较大、易于被还原、银铁复合物分散度较高以及较多的CO吸脱附活性位,有利于催化剂CO加氢转化。催化剂表面活性位对CO的非解离吸附强度降低,有利于醇醚产物的生成;而对CO的解离吸附强度增强,则不利于烃类产物的生成。     

Synergistic effects of potassium promoter and carbon fibers on direct synthesis of isobutanol from syngas over Cu/ZnO/Al2O3 catalysts obtained from hydrotalcite-like compounds

The Cu/ZnO/Al₂O₃ catalysts (CuZnAl) can be utilized to directly synthesize higher alcohols from syngas under mild conditions. Carbon fibers (CFs) are widely used as a catalyst supporter, and potassium is usually used as a good electron assistant for charge transfer to the active phase of the catalyst. However, little is known about the combined effects of CFs and potassium on Cu/ZnO/Al₂O₃ catalysts. In this work, the CuZnAl catalysts supported on activated carbon fibers (ACFs) were prepared by a co-precipitation method, and then the catalysts were modified by potassium. The catalytic performances of K-modified CuZnAl and composites containing ACFs and CuZnAl were evaluated. Addition of ACFs and/or potassium increased CO conversion and selectivity for isobutanol compared with pure CuZnAl. All the samples were characterized by BET, XRD, SEM–EDS, CO–TPD, and Raman spectroscopy to further disclose the reason for better catalytic performance of the catalysts with ACFs and/or potassium. We found that addition of ACFs or potassium promotes moderate CO adsorption and formation of the active phase (CuO/ZnO solid solution) during alcohol synthesis, which facilitates synthesis of higher alcohols and CO conversion. As a result, ACFs and potassium exhibited synergistic effects on improvement of CO conversion and selectivity for isobutanol.     

Hydrogenation of Carbon Dioxide on Iron Manganese Catalysts

The synthesis of hydrocarbons from hydrogenation of carbon dioxide has been studied on a series of coprecipitated iron-manganese catalysts. Kinetic measurements, X-ray diffraction, Mössbauer spectroscopy, and temperature-programmed reaction of adsorbed species were used for activity tests and catalyst characterizations. The results showed that the yields of low-carbon olefins decrease, whereas the amount of methane increases with increasing manganese content in catalysts. The conversion to hydrocarbons is suppressed by the reverse water-gas shift (RWGS) reaction equilibrium. Mössbauer spectra and XRD patterns of catalysts after reaction indicate that catalysts are severely oxidized; it is speculated that the olefin producing surface structure in CO hydrogenation may be destroyed by this oxidation. A pulse-reactor study of the Boudouard reaction showed that manganese has the effect of suppressing CO dissociation and thus decreasing carbon content on catalysts. For CO₂ hydrogenation, the affinity to carbon on catalysts is important; therefore manganese is not a good promoter. Among all catalysts tested, pure iron has the best selectivity to olefinic and long-chain hydrocarbons.     

纳米二氧化锆催化剂上一氧化碳加氢合成异丁烯

 考察了纳米ZrO2的制备方法及Al2O3和KOH助剂的添加对ZrO2催化\r\nCO加氢合成异丁烯反应的影响．纳米ZrO2的制备方法对ZrO2的物理性质\r\n和催化性能有较大的影响．用超临界流体干燥法干燥并在流动N2气氛中\r\n焙烧制得的ZrO2催化剂对异丁烯具有较高的选择性．Al2O3和KOH助剂表\r\n现出非常优良的助剂效应，在大幅度提高催化剂对i－C4烃选择性的同\r\n时保持了和ZrO2同样高的催化活性．催化剂的酸碱性表征结果表明，酸\r\n碱性对催化剂的催化性能影响很大，催化剂上适宜的酸碱数量和酸碱比\r\n例是影响其催化CO加氢合成异丁烯性能的非常重要的因素．     

Selective CO methanation over amorphous Ni-Ru-B/ZrO2 catalyst for hydrogen-rich gas purification

Amorphous Ni-Ru-B/ZrO₂ catalysts were prepared by chemical reduction method. The effects of Ni-Ru-B loading and Ru/Ni mole ratio on the catalytic performance for selective CO methanation from reformed fuel were studied, and the catalysts were characterized by BET, ICP, XRD and TPD. The results showed that Ru strongly affected the catalytic activity and selectivity by increasing the thermal stability of amorphous structure, promoting the dispersion of the catalyst particle, and intensifying the CO adsorption. For the catalysts with Ru/Ni mole ratio under 0.15, the CO methanation conversion and selectivity increased significantly with the increasing Ru/Ni mole ratio. Among all the catalysts investigated, the 30 wt% Ni-Ru-B loading amorphous Ni₆₁Ru₉B₃₀/ZrO₂ catalyst with 0.15 Ru/Ni mole ratio presented the best catalytic performance, over which higher than 99.9% of CO conversion was obtained in the temperature range of 230°C～250°C, and the CO₂ conversion was kept under the level of 0.9%.     

Cu、K助剂对FeMn/SiO2催化费托合成的影响

研究了Cu、K助剂对共沉淀型FeMn/SiO2催化剂还原行为、吸附行为及费托(F-T)合成活性和选择性的影响. Cu助剂以与Fe、Mn、SiO2共沉淀的方式引入, 而K助剂是在喷雾干燥前均匀加入沉淀浆料引入的. 结果表明, Cu可明显提高催化剂的还原性能, K助剂能促进催化剂在CO中的还原但抑制在H2中的还原, 而同时加入Cu和K会进一步促进催化剂在H2或CO中的还原; Cu助剂能促进H2吸附而K助剂对H2吸附无明显影响; Cu在一定程度上提高了F-T合成活性, 缩短了反应诱导期, K明显促进了CO的转化而相对抑制了H2的转化, 并且延长了反应的诱导期, Cu与K协同作用不仅提高反应的转化率而且缩短了反应的诱导期; K使得烃产物平均分子量增加, Cu单独对烃产物分布影响不明显, 而与K共同作用会进一步增加烃产物的分子量.     

Effect of niobium promoter on iron-based catalyst for Fischer-Tropsch reaction

Niobium-promoted Fe/CNTs catalysts were prepared using a wet impregnation method.Samples were characterized by nitrogen adsorption,H2-TPR,TPD,XRD and TEM.The Fischer-Tropsch Synthesis(FTS) was carried out in a fixed-bed microreactor at 220 ℃,1 atm and H2/CO=2 for 5 h.Addition of niobium into Fe/CNTs increased the dispersion,decreased the average size of iron oxide nanoparticles and the catalyst reducibility.Niobium-promoted Fe catalyst resulted in appreciable increase in the selectivity of C5+ hydrocarbons and suppressed methane formation.These effects were more pronounced for the 0.04%Nb/Fe/CNTs catalyst,compared to those observed from other niobium compositions.The 0.04%Nb/Fe/CNTs catalyst enhanced the C5+ hydrocarbons selectivity by a factor of 67.5% and reduced the methane selectivity by a factor of 59.2%.     

Study of activated carbon supported iron catalysts for the Fischer-Tropsch synthesis

Summary Characterization (BET and TPD) and reaction studies were conducted with activated carbon supported iron catalysts (Fe/AC) used for the Fischer-Tropsch synthesis (FTS). The TPD study showed that there existed interactions between metals and the AC surface. Greater association of Cu and K promoters with the AC surface resulted in stronger promoter to surface interaction, which enhanced the H₂ desorption ability of the Cu and K promoted Fe/AC catalyst prepared under vacuum impregnation (VI). Catalytic behavior of a Fe/AC catalyst (VI-15 Fe/2 Cu/2 K/81 AC, in parts per weight) was studied in a 1-liter slurry phase continuous stirred tank reactor. The catalyst presented moderate syngas conversion (44.3-60.6%) and high gaseous selectivity (CH₄, 12.8-15.1% and C₂-C₄, 42.4-46.1%) under 304^oC, 3.0 MPa, 1.1 L(STP)/g-cat/h, and H₂/CO = 2.0 during 166 h of testing. Detectable hydrocarbons up to C₁₈ were formed on the Fe/AC catalyst.     

Effect of Manganese Incorporation Manner on an Iron-Based Catalyst for Fischer-Tropsch Synthesis

A systematic study was undertaken to investigate the effects of the manganese incorpo- ration manner on the textural properties,bulk and surface phase compositions,reduction/carburization behaviors,and surface basicity of an iron-based Fischer-Tropsch synthesis(FTS)catalyst.The cata- lyst samples were characterized by N_2 physisorption,X-ray photoelectron spectroscopy(XPS),H_2(or CO)temperature-programmed reduction(TPR),CO_2 temperature-programmed desorption(TPD),and M(?)ssbauer spectroscopy.The FTS performance of the catalysts was studied in a slurry-phase continuously stirred tank reactor(CSTR).The characterization results indicated that the manganese promoter incor- porated by using the coprecipitation method could improve the dispersion of iron oxide,and decrease the size of the iron oxide crystallite.The manganese incorporated with the impregnation method is enriched on the catalyst's surface.The manganese promoter added with the impregnation method suppresses the reduction and carburization of the catalyst in H_2,CO,and syngas because of the excessive enrichment of manganese on the catalyst surface.The catalyst added manganese using the coprecipitation method has the highest CO conversion(51.9%)and the lowest selectivity for heavy hydrocarbons(C_(12 )).     

甲烷氧化偶联反应催化剂碱性与反应性能的相关性

在催化剂甲烷氧化偶联反应性能研究的基础上，利用ＣＯ２－ＴＰＤ技术考察了不同的碱金属化合物－Ｌａ２Ｏ３／ＢａＣｏ３催化剂的表面碱性。结果表明，ＢａＣＯ３的协同作用，碱金属化合物的添加都增大了催化剂表面碱性的强度，也增加了碱性位的数量。     

Fe含量对Fe-Zn-M/HY复合催化剂上CO2加氢性能的影响

在340 ℃，5.0 MPa条件下，研究了Fe-Zn-M/HY(M=Cr、Al)复合催化剂上CO2的加氢性能。考察了催化剂中Fe含量对CO2转化率、烃类产物及异构烷烃选择性的影响, 并用CO2-TPD、H2-TPR研究了Fe-Zn-M对CO2的吸附和对H2的还原性能。结果表明, 随着Fe含量的增加, 复合催化剂的活性增强, 烃类产物的选择性降低, 异构烷烃在烃类中的选择性随Fe含量的增加而降低，CO2-TPD、H2-TPR结果表明，随Fe含量的增加，催化剂对CO2的活化吸附量随之增加, 而Fe含量的增加促进了催化剂的还原。     

Co在超细Mo-Co-K催化剂合成低碳醇中的作用

采用BET、XPS和TPD表征手段对超细Mo-Co-K催化剂的织构、表面结构和吸附行为进行了研究，结合催化剂的合成低碳醇性能，论证了Co在超细Mo-Co-K催化剂合成低碳醇中的作用。Co的加入提高了催化剂合成低碳醇的活性和选择性，同时也提高了催化剂的比表面并促进了微孔的形成，催化剂的催化性能与其织构之间呈现出很好的顺变关系。Co对催化剂中可能作为合成低碳醇活性中心的低价Mo物种的电子结合能值影响较小。Co的加入降低了H2和CO在催化剂表面的强吸附中心的吸附强度，从而有利于合成低碳醇反应的发生。研究结果表明，Co仅仅是作为结构助剂，通过调变催化剂的织构和催化剂表面的H2及CO的强吸附中心而影响其合成低碳醇性能的。     

Selective Transformation of Syngas into Gasoline‐Range Hydrocarbons over Mesoporous H‐ZSM‐5‐Supported Cobalt Nanoparticles

Bifunctional Fischer–Tropsch (FT) catalysts that couple uniform‐sized Co nanoparticles for CO hydrogenation and mesoporous zeolites for hydrocracking/isomerization reactions were found to be promising for the direct production of gasoline‐range (C_5–11) hydrocarbons from syngas. The Brønsted acidity results in hydrocracking/isomerization of the heavier hydrocarbons formed on Co nanoparticles, while the mesoporosity contributes to suppressing the formation of lighter (C_1–4) hydrocarbons. The selectivity for C_5–11 hydrocarbons could reach about 70 % with a ratio of isoparaffins to n‐paraffins of approximately 2.3 over this catalyst, and the former is markedly higher than the maximum value (ca. 45 %) expected from the Anderson–Schulz–Flory distribution. By using n‐hexadecane as a model compound, it was clarified that both the acidity and mesoporosity play key roles in controlling the hydrocracking reactions and thus contribute to the improved product selectivity in FT synthesis.     

K-Mo基催化剂的表面酸性与其合成醇选择性

对500℃和800℃焙烧制得的氧化态K－MoO3／γ－AlO3，K－MoO3／SiO2及非负载K－Mo催化剂进行硫化后，测试其合成醇活性．结果表明500℃焙烧制得的负载型催化剂显示较高的合成低碳烃活性和较低的合成低磷醇选择性，经800℃焙烧后，合成低磷醇的选择性大幅度提高．500℃焙烧的非负载K－Mo催化剂显示较高的合成醇选择性，经800℃焙烧后，促碳醇的选择性保持不变．用氨的吸附及TPD方法测定了各样品的酸性，并与催化剂活性对照，发现催化剂酸性越强，酸量越大，则其合成醇选择性越低．催化剂上的乙醇分解实验证实，催化剂的酸量大小与它的醇分解活性成正变关系，这些结果说明催化剂酸性对其合成醇性能有直接的影响．     

Synthesis of hydrocarbons from CO and H2 in the presence of Co-Ru and Co-Pd catalysts containing aluminum oxide

The influence of additions of 0.1–0.5% Pd or Ru in a 10% Co/Al₂O₃ catalyst on its activity and selectivity in the synthesis of liquid hydrocarbons from CO and H₂ has been studied. It has been shown that the bimetallic systems make it possible to carry out the synthesis of hydrocarbons with a higher extent of conversion of CO and a higher yield of C ₅ ⁺ carbons in comparison with the original Co catalyst. Co-Ru catalysts exhibit exceptionally high selectivity (up to 80%) with respect to the formation of liquid products. It has been demonstrated by temperature-programmed reduction (TPR) that the introduction of Pd an dRu promotes the reduction of Co at lower temperatures and the formation of cobalt aluminates.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 60–64, January, 1992.     

Promotion effect of adsorbed water/OH on the catalytic performance of Ag/activated carbon catalysts for CO preferential oxidation in excess H2

Activated carbon (AC) supported silver catalysts were prepared by incipient wetness impregnation method and their catalytic performance for CO preferential oxidation (PROX) in excess H₂ was evaluated. Ag/AC catalysts, after reduction in H₂ at low temperatures (≤200 °C) following heat treatment in He at 200 °C (He200H200), exhibited the best catalytic properties. Temperature-programmed desorption (TPD), X-ray diffraction (XRD) and temperature-programmed reduction (TPR) results indicated that silver oxides were produced during heat treatment in He at 200 °C which were reduced to metal silver nanoparticles in H₂ at low temperatures (≤200 °C), simultaneously generating the adsorbed water/OH. CO conversion was enhanced 40% after water treatment following heat treatment in He at 600 °C. These results imply that the metal silver nanoparticles are the active species and the adsorbed water/OH has noticeable promotion effects on CO oxidation. However, the promotion effect is still limited compared to gold catalysts under the similar conditions, which may be the reason of low selectivity to CO oxidation in PROX over silver catalysts. The reported Ag/AC-S-He catalyst after He200H₂00 treatment displayed similar PROX of CO reaction properties to Ag/SiO₂. This means that Ag/AC catalyst is also an efficient low-temperature CO oxidation catalyst.     

碱金属助剂对CoCu/TiO2催化剂上二氧化碳加氢合成长链烃的影响

大气中CO2浓度增加导致的温室效应以及化石燃料的匮乏正日益受到世界范围的关注. 由于CO2较强的惰性以及较高 C-C 偶联能垒, 迄今为止大部分研究都集中在CO2催化加氢制备各种 C1 化学品 (如 CH4, CH3OH, CO 等), 鲜有研究关注合成液态燃料 (C5+碳氢化合物). 目前,CO2加氢直接合成烃类主要通过CO2基费托合成反应 (CO2-FTS) 实现, 即先通过逆水煤气变换反应 (RWGS) 将CO2还原成 CO, 随后 CO 通过传统费托反应 (FTS) 加氢生成烃类化合物. 在两种工业化FTS 催化剂 (Fe 和 Co 基催化剂) 中, 钴基催化剂具有更高的反应活性和链增长能力, 以及较高的机械强度和稳定性. 然而,由于CO2的惰性, 造成催化剂表面物种的加氢程度更高, 使得甲烷更容易生成. 因而, 高反应活性、高选择性催化剂的开发是实现该过程的关键.本文采用沉积沉淀法制备了一系列双金属 CoCu/TiO2催化剂, 再通过初湿浸渍法对其进行碱金属助剂 (Li, Na, K, Rb和 Cs) 改性, 并用多种表征手段系统研究了碱金属助剂对催化剂物化性质及其催化CO2加氢制备长链烃反应的影响. 结果表明, 碱金属的加入对催化剂织构性质影响不大, 它们在催化剂表面发生富集, 且富集程度随碱金属原子序数的增加而降低. 另外, 碱金属的加入增强了CO2的吸附, 其中, Na 改性的 CoCu/TiO2催化剂的碱性最强; 同时还降低了 H2的脱附量,尤以 K, Rb 和 Cs 改性的催化剂为甚.在 250 oC, 5 MPa, 空速 3000 mL·gcat-1·h-1和 H2/CO2= 3 的反应条件下, 对不同碱金属助剂改性的催化剂进行评价. 结果表明, 不加助剂的 CoCu/TiO2催化剂上CO2转化率高达 23.1%, 但产物主要是 CH4, 此时CO2在 Co 活性中心上直接发生甲烷化反应; 碱金属助剂的引入显著抑制了 CH4的生成, 提高了长链烃的选择性, 但同时也降低了CO2转化率, 并且随着碱金属原子序数增大呈现先下降后上升的趋势, 表明合适的碱性强度可以更好地改性催化剂性能. 其中, Na 助剂改性的CoCu/TiO2催化剂的碱性最强, 且 H2的脱附量降低幅度较小, 因此, 该催化剂具有最高的 C5+烃类收率, 达到 5.4%; 同时CO2转化率为 18.4%, 烃类产物中 C5+烃类选择性为 42.1%. Na 助剂改性的 CoCu/TiO2催化剂还展现了良好的催化稳定性,反应 200 h 后,CO2转化率和 C5+选择性分别保持 18% 和 40%. 基于碱金属助剂对催化剂物化性质与反应性能的调变规律,可进一步指导CO2加氢直接合成长链碳催化剂的设计与合成.     

Characterization and catalytic behavior of EDTA modified silica nanosprings (NS)-supported cobalt catalyst for Fischer-Tropsch CO-hydrogenation

The effect of ethylene diamine tetraacetic acid(EDTA) modification on the physico-chemical properties and catalytic performance of silica nanosprings(NS) supported cobalt(Co) catalyst was investigated in the conversion of syngas(H~(2+) CO) to hydrocarbons by Fischer-Tropsch synthesis(FTS). The unmodified Co/NS and modified Co/NS-EDTA catalysts were synthesized via an impregnation method. The prepared Co/NS and Co/NS-EDTA catalysts were characterized before the FTS reaction by BET surface area,X-ray diffraction(XRD),transmission electron microscopy(TEM),temperature programmed reduction(TPR),X-ray photoelectron spectroscopy(XPS),differential thermal analysis(DTA) and thermogravimetric analysis(TGA) in order to find correlations between physico-chemical properties of catalysts and catalytic performance. FTS was carried out in a quartz fixedbed microreactor(H_2/CO of 2 ∶1,230 ℃ and atmospheric pressure) and the products trapped and analyzed by GC-TCD and GC-MS to determine CO conversion and reaction selectivity. The experimental results indicated that the modified Co/NS-EDTA catalyst displayed a more-dispersed phase of Co_3O_4 nanoparticles(10.9%) and the Co_3O_4 average crystallite size was about 12.4 nm. The EDTA modified catalyst showed relatively higher CO conversion(70.3%) and selectivity toward C_(6-18)(JP-8,Jet A and diesel) than the Co/NS catalyst(C_(6-14))(JP-4).     

Fischer–Tropsch Synthesis by Carbon Dioxide Hydrogenation on Fe-Based Catalysts

Impregnated and co-precipitated, promoted and unpromoted, bulk and supported iron catalysts were prepared, characterized, and subjected to hydrogenation of CO₂ at various pressures (1–2 MPa) and temperatures (573–673 K). Potassium, as an important promoter, enhanced the CO₂ uptake and selectivity towards olefins and long-chain hydrocarbons. Al₂O₃, when added as a structural promoter during co-precipitation, increased CO₂ conversion as well as selectivity to C₂₊ hydrocarbons. Among V, Cr, Mn and Zn promoters, Zn offered the highest selectivity to C₂–C₄ alkenes. The different episodes involved in the transformation of the catalyst before it reached steady-state were identified, on the co-precipitated catalyst. Using a biomass derived syngas (CO/CO₂/H₂), CO alone took part in hydrogenation. When enriched with H₂, CO₂ was also converted to hydrocarbons. The deactivation of impregnated Fe–K/Al₂O₃ catalyst was found to be due to carbon deposition, whereas that for the precipitated catalyst was due to increase in crystallinity of iron species. The suitability of SiO₂, TiO₂, Al₂O₃, HY and ion exchanged NaY as supports was examined for obtaining high activity and selectivity towards light olefins and C₂₊ hydrocarbons and found Al₂O₃ to be the best support. A comparative study with Co catalysts revealed the advantages of Fe catalysts for hydrocarbon production by F–T synthesis.