Impact of Hydrogenolysis on the Selectivity of the Fischer–Tropsch Synthesis: Diesel Fuel Production over Mesoporous Zeolite‐Y‐Supported Cobalt Nanoparticles

Selectivity control is a challenging goal in Fischer–Tropsch (FT) synthesis. Hydrogenolysis is known to occur during FT synthesis, but its impact on product selectivity has been overlooked. Demonstrated herein is that effective control of hydrogenolysis by using mesoporous zeolite Y‐supported cobalt nanoparticles can enhance the diesel fuel selectivity while keeping methane selectivity low. The sizes of the cobalt particles and mesopores are key factors which determine the selectivity both in FT synthesis and in hydrogenolysis of n‐hexadecane, a model compound of heavier hydrocarbons. The diesel fuel selectivity in FT synthesis can reach 60 % with a CH₄ selectivity of 5 % over a Na‐type mesoporous Y‐supported cobalt catalyst with medium mean sizes of 8.4 nm (Co particles) and 15 nm (mesopores). These findings offer a new strategy to tune the product selectivity and possible interpretations of the effect of cobalt particle size and the effect of support pore size in FT synthesis.     

IR spectral study of the effect of the reaction medium on the state of cobalt in a 10% Co/Al2O3 catalyst for aliphatic hydrocarbons from CO and H2

Diffuse scattering IR spectroscopy was used to study the 10% Co/Al₂O₃ catalyst for the synthesis of aliphatic hydrocarbons from CO and H₂. Ionic and metallic cobalt forms were identified in the IR spectroscopy. The adsorption of CO on these forms is accompanied by the appearance of linear and bridged complexes. After prolonged treatment of the catalyst by a CO + 2H₂ mixture, the ions and surface of metallic cobalt remain available for the adsorption of CO. Modification of the surface of metallic cobalt occurs upon the action of the reaction medium. This modification is seen in a bathochromic displacement of the IR bands for the adsorbed and linear CO forms. This displacement is accompanied by a reduction in the strength of the metal-carbon bond in the Co^o-CO complex.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2640–2643, November, 1990.     

Application of Thermal Analysis in Radiocarbon Dating

Thermal analysis combined with mass spectrometry was applied to radiocarbon dating procedures (age determination of carbon containing samples) to determine the optimal temperature range for the reduction of CO₂ over metallic cobalt of various particle sizes. Experiments were carried out to show the different catalytic activities of cobalt of particle sizes 1, 1–45 and 44 μm. The morphology of the cobalt samples and the deposited carbon were investigated. The quantification of CH₄ and CO formed during the reduction of CO₂ was done by means of pulse thermal analysis. This revised version was published online in July 2006 with corrections to the Cover Date.     

Co/SiO2催化剂催化费托合成中CeO2助剂的作用

 在Co/SiO2催化剂中加入少量CeO2助剂, 能够提高其催化费托(FT)反应的活性和液态烃(Ｃ5+)的选择性,特别是可以生成优质的高附加值柴油及润滑油基础油(C12+), 但助剂CeO2对Co/SiO2催化剂的作用目前仍存在争议. 本文利用X射线衍射、程序升温还原、程序升温脱附、程序升温表面反应、 X射线光电子能谱、扫描电镜和同位素脉冲反应结合H-D同位素交换等方法对催化剂进行了表征,并采用微反评价考察了催化剂的催化性能. 表征结果表明,少量CeO2助剂的添加提高了活性组分Co在催化剂表面的分散度,降低了催化剂表面Co的晶粒度,使催化剂对CO和H2的吸附性能发生了改变. 同位素脉冲反应结合H-D交换实验表明, CeO2的添加减弱了Co的金属性,提高了其吸附解离氢的能力和CO吸附量,增大了催化剂表面活性碳物种的浓度和聚合趋势,使FT合成的碳链增长几率增大至0.90, 产物中液态烃选择性和重质烃含量明显增加,说明CeO2的加入有利于生成高附加值的柴油和润滑油基础油.     

费托(FT)合成及相关反应的研究进展(英文)

按催化剂分类介绍了改性ＦＴ合成及与其相关反应的近期研究成果。即通过调制催化剂组成和反应条件,由合成气直接合成其他有价值的化工原料如醇、烯烃、芳香烃和石蜡等。分子筛,如ＡＩ－ＭＣＭ－４１和ＺＳＭ－５／磷铝分子筛等在ＦＴ及其相关反应中扮演着越来越重要的角色,但由于金属作为反应活性中心,所以金属催化剂如Ｆｅ,Ｃｏ、Ｐｄ、Ｒｈ和Ｎｉ,双金属如Ｆｅ－Ｉｒ和Ｐｔ－Ｍｏ仍然是人们研究的重点。另外,一些新的反应方法和新的材料也被采用,如超临界方法及超微粒催化剂等。     

Secondary reactions of ethylene and propylene in the Fischer-Tropsch synthesis on cobalt-aluminum and cobalt-chromium catalysts

The only secondary reaction of olefins in the Fischer-Tropsch synthesis on Co/SiO₂·Al(III) and Co/SiO₂·Cr(III) with 2.7·10⁻⁶ and 4.0·10⁻⁶ g-ion/m² cation concentration in the support matrix, respectively, is dimerization of ethylene to give a four-carbon intermediate, which participates in the growth of C-C bond chains according to the classical FT synthesis mechanism. When the chromium concentration is increased by a factor of 1.7, secondary ethylene reactions occurring on the acid sites of the catalyst are also observed. When the aluminum concentration is increased by a factor of 3.4, we observe the oligomerization of ethylene and propylene. The secondary reactions of ethylene mainly result in linear hydrocarbons, while oligomerization involving propylene gives a significant amount of branched hydrocarbons. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 44, No. 2, pp. 115–120, March–April, 2008.     

Influence of solvent on the yield of singlet oxygen upon the chloride ion-catalyzed decomposition of dimethyldioxirane

The excitation yield of the singlet molecular oxygen ¹Δ _g [φ(¹O₂)] in the reaction of the dimethyldioxirane with the chloride ion in benzene, acetone, methylene chloride, and acetonitrile solutions has been determined. The φ(¹O₂) value depends on the solvent nature and is in the range 50–84%. Correlation between the value of the singlet oxygen yield and the Kamlet-Taft parameter (α) characterizing the acidity of the solvent as a hydrogen bond donor has been established: the higher the α value, the higher the ¹O₂ yield.     

Thermoset Cure Kinetics by Isoconversional Methods

The curing kinetics of thermosets based on unsaturated polyester resin crosslinked with styrene was studied by differential scanning calorimetry (DSC). The isoconversional kinetic analysis was applied to non-isothermal data. The results obtained show a dependence of the activation energy (E_α) on conversion (α) that proves the existence of a multistep process and a complex kinetic scheme that must be interpreted in terms of chemical and physical mechanisms. The interrelationship of the Arrhenius parameters obtained from the isoconversional kinetic data has been used as a tool to investigate the production of free radicals by the action of a promoter (cobalt octoate) and the temperature on the initiator (methyl ethyl ketone peroxide). An optimum promoter/initiator ratio has been found. This revised version was published online in August 2006 with corrections to the Cover Date.     

One-step synthesis of 2-indolylalkylamines

An efficient one-step synthesis of 2-indolylalkylamines was proposed. The synthesis involves the Fischer reaction of phenylhydrazine with cyclic imines containing a CH₂ group in the α-position or with amino ketones containing two CH₂ groups in the α-position with respect to the C=O group.     

Effect of Re and Al 2 O 3 Promotion on the Working Stability of Cobalt Catalysts for the Fischer–Tropsch Synthesis

The results of the working stability studies of cobalt catalysts based on SiO2 and Al2O3 promoted with Re and Al2O3 in the synthesis of hydrocarbons from CO and H2 in continuous tests for 200–300 h are presented. The prepared catalysts were characterized by transmission electron spectroscopy, temperature-programmed reduction with hydrogen, temperature-programmed desorption of CO, and X-ray fluorescence spectroscopy and tested at a temperature 200°C, a pressure of 0.1 MPa, and a GHSV of 100 h–1. It was determined that a cobalt–silica catalyst promoted with Al2O3 had the highest activity. It was established that the addition of Al2O3 to a cobalt–silica catalyst increased the conversion of CO and selectivity for C5+ hydrocarbons and inhibited the agglomeration of Co particles under the action of a reaction atmosphere in the Fischer–Tropsch synthesis. It was found that the initial conversion of CO increased by a factor of 2 upon the introduction of 0.1 wt % rhenium into the Co/γ-Al2O3 catalyst; however, the rate of its deactivation increased in this case due to an almost twofold increase in the size of cobalt particles in the course of synthesis after operation for 300 h.     

An investigation of chain growth probability in Fischer-Tropsch synthesis over an industrial Fe?Cu?K catalyst

The chain growth probability of Fischer-Tropsch synthesis (FTS) was investigated on the basis of data from a set of experiments over an industrial coprecipitated Fe−Cu−K catalyst developed by the Institute of Coal Chemistry (China). The experimental results show that the ASF chain growth probability (α) depends on operation conditions, temperature (T) and H₂/CO ratio in the feed. α decreases with T or H₂/CO feed ratio increasing. The experimental results also show that chain growth probabilities of hydrocarbons are not constant, but a function of carbon number. This deviation from ASF assumption is further discussed.     

贵金属助剂对费-托合成用钴基催化剂的促进作用

贵金属助剂促进的费-托合成用钴基催化剂具有高活性和长链烃(C₅⁺)选择性优越等特点,被广泛应用于由合成气制清洁燃料的合成反应中。 本文重点讨论了贵金属助剂对活性钴物种的结构（还原度、分散度、双金属颗粒或合金的构成）, 钴基催化剂稳定性以及其对费-托合成的反应速率和产物选择性的影响规律。     

MOFs衍生炭负载的钴基催化剂的廉价制备及其CO加氢催化性能

以对苯二甲酸（H₂BDC）为配体、乙酸钴为Co源、水作溶剂,通过共沉淀法合成了金属有机框架材料（Co-BDC MOFs）;以其为前驱体分别在乙炔和氩气氛下采用化学气相沉积法制备了核壳结构Co@C催化剂。结合XRD、氮吸附、SEM、TEM、XPS、TGA和Raman光谱等手段对Co@C催化剂的结构和组成进行了表征,考察了该催化剂在费托合成反应中的活性及稳定性。结果表明,炭化气氛对炭层结构的石墨化程度有较大影响,而对金属Co核的物相结构和粒径影响较小;乙炔气氛有助于形成多孔的石墨炭壳,从而促进烃链的生长,Co@C-C₂H₂催化剂上的C₅₊烃产物选择性高达82.66%,反应过程中催化剂物相由单相金属Co转变为金属Co与Co₂C的混合相,且无失活现象发生,表明Co₂C具有较高的费托反应催化活性。     

Synthesis of hydrocarbons from Co and H2 in the presence of supported Co catalysts modified by palladium

A study has been made of the effect of Pd on the activity and selectivity of Co catalysts prepared by impregnating various supports (SiO₂, SiO₂-Al₂O₃, Al₂O₃) with cobalt carbonyl or nitrate in the synthesis of hydrocarbons from CO and H₂. It is shown that the addition of Pd leads to an increase in the yield of liquid hydrocarbons and to a change in their composition. It has been established by IR spectroscopy that the introduction of Pd into the composition of carbonyl catalysts affects the formation of their surface.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 521–524, March, 1990.     

Effect of epitaxial growth on the formation of the cobalt catalysts of the Fischer-Tropsch synthesis

Mixed oxides Co_xAl_yO₄ with different Al/Co ratios applied as supports for the catalysts of the Fischer-Tropsch synthesis were prepared using the solid-state chemical reaction. The Co_xAl_yO₄ supports were prepared by modifying gibbsite with various cobalt salts (acetate, nitrate, and basic carbonate). The use of basic cobalt carbonate gives the Co(20%)/Co_xAl_yO₄ catalyst, which provides an increased yield of hydrocarbons C₅₊ and a decreased methane content compared to the impregnation catalyst Co(30%)/Al₂O₃. The introduction of small amounts of rhenium additives makes it possible to enhance the yield of hydrocarbons C₅₊ (179 g m⁻³) and also to increase the selectivity with respect to the C₅–C₁₈ fraction. The introduction of basic cobalt carbonate into the support, most likely, creates favorable conditions for the epitaxial growth of the precursor of the active phase. Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1856–1860, September, 2007.     

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.     

Effect of the nature of the carrier on the properties of Co catalysts preheated in air in synthesis of hydrocarbons from CO and H2

A study has been made of the effect of preheating Co/Al₂O₃ and Co/SiO₂ catalysts in a stream of air on their susceptibility to reduction and catalytic properties in the synthesis of hydrocarbons from CO and H₂. It has been shown that as the pretreatment temperature increases there is a decrease in the extent of Co reduction for both systems together with a decrease in the yield of liquid synthesis products for Co/SiO₂ and an increase in yield for Co/Al₂O₃. It is proposed that interaction between cobalt oxide and Al₂O₃ during preheating produces additional active centers on the surface of the sample.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2450–2455, November, 1991.     

The effect of ball-milling on the thermal behavior of anatase-doped hematite ceramic system

High energy ball-milling methods were employed in the synthesis of anatase-doped hematite xTiO₂(a) · (1−x)α-Fe₂O₃ (x = 0.1, 0.5, and 0.9) ceramic system. The thermal behavior of as obtained ceramic system was characterized by simultaneous DSC–TG. The pure anatase phase was found to be stable below 800 °C, but there is a 10.36% mass loss due to the water content. Two exothermic peaks on DSC curves of pure anatase indicate the different crystallization rates. The pure hematite partially decomposed upon heating under argon atmosphere. Ball-milling has a strong effect on the thermal behaviors of both anatase and hematite phases. For x = 0.1 and 0.5, there is gradual Ti substitution of Fe in hematite lattice, and the decomposition of hematite is enhanced due to the smaller particle size after ball-milling. The crystallization of hematite was suppressed as the enthalpy values decreased due to the anatase-hematite solid–solid interaction. For x = 0.9, most of the anatase phase converted to rutile phase after long milling time. The thermal behavior of xTiO₂(a) · (1−x)α-Fe₂O₃ showed smaller enthalpy value of the hematite transformation to magnetite and anatase crystallization due to the small fraction of hematite phase in the system and hematite–anatase interaction, while the mass loss upon heating increased as a function of milling time due to more water content absorbed by the smaller particle size.     

Structure of cobalt hydroxoaluminate and catalytic properties of the products of its reduction

The structure of synthesized cobalt hydroxoaluminate (CHA) and course of thermolysis and reduction were investigated by XPA (including high-temperature x-ray diffraction), thermal chromatography, DTA, DTG, IR, and UV spectroscopy. It was shown that the activity the products of reduction activation of CHA in synthesis of hydrocarbons from CO and H₂ is a function of the temperature of reduction and synthesis. It was concluded that hydrocarbons are synthesized on Co/CoAl₂O₄. The production of CHA are active in the same reduction temperature range as the previously studied cobalt cement catalysts.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 759–765, April, 1991.     

Non-isothermal Studies on Mechanism And Kinetics of Thermal Decomposition of Cobalt(II) Oxalate Dihydrate

Thermal decomposition of CoC₂O₄⋅2H₂O was studied using DTA, TG, QMS and XRD techniques. It was shown that decomposition generally occurs in two steps: dehydration to anhydrous oxalate and next decomposition to Co and to CoO in two parallel reactions. Two parallel reactions were distinguished using mass spectra data of gaseous products of decomposition. Both reactions run according toAvrami–Erofeev equation. For reaction going to metallic cobalt parameter n=2 and activation energy is 97±14 kJ mol^–1. It was found that decomposition to CoO proceeds in two stages. First stage (0.12<α_II<0.41) proceeds according to n=2, with activation energy 251±15 kJ mol^–1 and second stage (0.45<α_II<0.85) proceeds according to parameter n=1 and activation energy 203±21 kJ mol^–1. This revised version was published online in August 2006 with corrections to the Cover Date.