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 )).     

硅对铁基费-托合成催化剂的影响

用共沉淀法制备了一系列不同硅含量的铁基催化剂,采用N2吸附和原位X射线衍射对催化剂进行了表征,在固定床反应器中考察了催化剂的费-托合成反应活性、选择性和稳定性.结果表明,含硅的催化剂具有较大的比表面积和较小的平均孔径,在CO还原及费-托合成反应中生成的碳化铁物种的稳定性比不含硅的催化剂高.在费-托合成反应中,不含硅的催化剂具有较高的初始活性,但易失活;含硅的催化剂具有较低的初始活性,但稳定性较高.Fe7C3是活性最高的碳化铁物种.随着硅含量的增加,催化剂的费-托合成反应更易生成低碳数产物.     

钾助剂对F-T合成铁基催化剂浆态床反应性能的影响

 采用连续共沉淀与喷雾干燥成型技术相结合的方法制备了不同K助剂含量的系列微球形Fe/Cu/K/SiO2催化剂(K/Fe质量比为0.010～0.058),采用低H2/CO比的合成气于典型的工业反应条件下(523～533 K, 1.5 MPa, H2/CO=0.67)进行了长期的浆态相F-T合成(FTS)反应性能评价. 结果表明: K助剂的添加可增大催化剂活性,提高C5+、总的烯烃、有机含氧化合物及CO2的选择性,并促进水煤气变换反应,但过高的K含量易使催化剂反应稳定性变差. 适中的K含量为K/Fe＝0.030,该K含量催化剂的660 h浆态床FTS反应性能评价结果显示,该催化剂具有较高的催化活性和C5+选择性,产物分布较合理,长期运行稳定性好,反应后卸载下的催化剂形貌观测表明该催化剂还具有较好的抗磨损性能. 除K助剂的化学效应起主导作用外,催化剂的织构性质尤其是孔结构可能对催化剂的催化性能也有一定的影响,并引起K/Fe＝0.045时铁基催化剂对FTS产物选择性和水煤气变换反应活性的部分调变.     

浸渍钠对铁基催化剂F-T合成浆态床反应性能的影响

以FeCuK/Si O2为母体催化剂,通过乙酸钠浸渍得到一组不同Na含量的费托合成铁基催化剂.采用原子发射光谱、低温N2吸附、程序升温还原和M ssbauer谱等技术对催化剂进行了表征.在H2/CO摩尔比为0.67,空速为2 000 h-1,压力为1.5 MPa和温度为250℃的条件下进行了浆态床F-T合成反应性能评价实验.结果表明,浸渍少量Na能提高催化剂的比表面积,促进铁物相的分散,而浸渍大量Na却大大降低了催化剂的比表面积,使催化剂中的铁物相聚集形成较大的颗粒;浸渍Na抑制了催化剂在H2中的第一步还原,但促进了催化剂在CO中的碳化;在原位合成气还原过程中,浸渍Na有利于催化剂的碳化.在500 h的运行实验中,浸渍Na的催化剂均表现出不同程度的失活现象.反应结果表明,浸渍Na对水煤气变换反应活性影响不大,对费托合成反应活性和烃产物选择性有较大的影响.在铁基催化剂上浸渍Na有利于C12 重质烃和低碳烯烃的生成.     

Effect of Sulfate on an Iron Manganese Catalyst for Fischer-Tropsch Synthesis

The effect of sulfate on Fischer-Tropsch synthesis performance was investigated in a slurry- phase continuously stirred tank reactor(CSTR)over a Fe-Mn catalyst.The physiochemical properties of the catalyst impregnated with different levels of sulfate were characterized by N_2 physisorption,X-ray photoelectron spectroscopy(XPS),H_2(or CO)temperature-programmed reduction(TPR),Mφssbauer spectroscopy,and CO_2 temperature-programmed desorption(TPD).The characterization results indicated that the impregnated sulfate slightly decreased the BET surface area and pore volume of the catalyst, suppressed the catalyst reduction and carburization in CO and syngas,and decreased the catalyst surface basicity.At the same time,the addition of small amounts of sulfate improved the activities of Fischer- Tropseh synthesis(FTS)and water gas shift(WGS),shifted the product to light hydrocarbons(C_1-C_(11)) and suppressed the formation of heavy products(C_(12 )).Addition of SO_4~(2-)to the catalyst improved the FTS activity at a sulfur loading of 0.05-0.80 g per 100 g Fe,and S-05 catalyst gave the highest CO conversion(62.3%),and beyond this sulfur level the activity of the catalyst decreased.     

Ru助剂对Co/SiO2催化剂费托合成反应性能的影响

 考察了 Ru 助剂 (0.17%?9.96%) 对 Co/SiO2 催化剂结构及其费托合成反应性能的影响. 结果表明, Ru 助剂可降低 Co/SiO2 催化剂的还原温度, 从而提高其还原度. 光电子能谱和扩展 X 吸收射线精细结构研究表明, 即使 Ru 含量高达 9.96%, 在 Co/SiO2 催化剂焙烧过程中也未观察到 Ru 物种与 Co 物种作用形成的化合物. 还原后催化剂中 Ru 趋向于与 Co 物种紧密接触且分散在催化剂表面. H2 程序升温脱附结果表明, 随着 Ru 含量的增加, 位于反应温度附近的 H2 脱附峰面积增加, 即此时催化剂吸附 H2 能力提高, 因此反应活性单调增加, 但存在最佳 Ru 含量, 此时 C5+选择性最高.     

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.     

SO4^2-对铁基催化剂上费托合成反应的影响

以FeCuK/SiO2为母体催化剂,用不同浓度的NH4HSO4水溶液进行等体积浸渍,制备了不同SO42-含量的费托合成(FTS)铁基催化剂.采用原子发射光谱、低温N2吸附、X射线光电子能谱、程序升温还原和穆斯堡尔谱等技术对催化剂进行了表征,并在H2/CO摩尔比0.67,WHSV=2 000 h-1,压力1.5 MPa和温度250℃条件下进行了浆态床FTS反应.结果表明,少量SO42-能促进催化剂在H2中的还原;在合成气还原过程中,少量SO42-对催化剂的碳化程度影响不大,但大量SO42-严重抑制催化剂的碳化.在约500 h的运行实验中,各催化剂样品表现出的催化活性有所差异,但均呈现较好的稳定性.SO42-可抑制水煤气变换反应活性,且随着SO42-含量的增加,抑制作用愈加明显;同时,催化剂上浸渍少量SO42-可有效抑制CH4的生成,提高低碳烯烃的选择性.     

La2O3对费-托合成沉淀铁催化剂的影响

制备了一系列不同La2O3含量(100Fe/2.8Si/nLa,n=0,0.5,1,2,4,原子比)的沉淀铁费-托合成催化剂,通过原位X射线衍射、一氧化碳程序升温还原和N2吸附-脱附等手段对催化剂进行了表征.催化剂费-托反应评价在固定床反应器中进行.结果表明,少量La2O3助剂(La/Fe≤0.01,原子比)的加入显著降低了Fe2O3颗粒大小,增加了催化剂的比表面积和分散度,有利于碳化铁的形成,从而导致费-托合成催化活性的提高.随着La2O3含量的进一步增加(La/Fe≥0.02),催化剂表面大量La2O3的覆盖和LaFeO3化合物的形成降低了铁碳化物的形成,反应活性反而降低.因此,最适宜的La2O3含量为La/Fe=0.01.La2O3的加入提高了甲烷的选择性,抑制了C5+碳氢化合物的形成.     

铁基催化剂成型方式对浆态床费-托合成反应性能的影响

采用连续共沉淀方法制备了无定形Fe-Cu-K-SiO2催化剂,利用连续共沉淀与喷雾干燥成型技术相结合的方法制备了不同粒径的微球形Fe-Cu-K-SiO2催化剂.在接近反应工况的条件下对催化剂进行了浆态床费-托合成(FTS)反应性能评价,并对催化剂进行了物性表征.表征结果表明,无定形催化剂没有规整的外形和均一的粒径分布,微球形催化剂的表面光滑,球形度好,颗粒分布均匀.浆态床FTS反应评价结果表明,尽管无定形催化剂的初活性及最高活性较高,但蜡产物与催化剂的在线分离困难;随着成型时平均粒径的增大,微球形催化剂的活性降低,但失活速率减慢,烃产物选择性向轻组分方向偏移,容易实现蜡产物与催化剂的在线分离.     

Effect of Al2O3 Binder on the Precipitated Iron-Based Catalysts for Fischer-Tropsch Synthesis

A series of iron-based Fischer-Tropsch synthesis (FTS) catalysts incorporated with Al2O3 binder were prepared by the combination of co-precipitation and spray drying technology. The catalyst samples were characterized by using N2 physical adsorption, temperature-programmed reduc-tion/desorption (TPR/TPD) and Mossbauer effect spectroscopy (MES) methods. The characterization results indicated that the BET surface area increases with increasing Al2O3 content and passes through a maximum at the Al2O3/Fe ratio of 10/100 (weight basis). After the point, it decreases with further increase in Al2O3 content. The incorporation of AI2O3 binder was found to weaken the surface basicity and suppress the reduction and carburization of iron-based catalysts probably due to the strong K-Al2O3 and Fe-Al2O3 interactions. Furthermore, the H2 adsorption ability of the catalysts is enhanced with increasing Al2O3 content. The FTS performances of the catalysts were tested in a slurry-phase continuously stirred tank reactor (CSTR) under the reaction conditions of 260℃, 1.5 MPa, 1000 h-1 and molar ratio of H2/CO 0.67 for 200 h. The results showed that the addition of small amounts of Al2O3 affects the activity of iron-based catalysts to a little extent. However, with further increase of Al2O3 content, the FTS activity and water gas shift reaction (WGS) activity are decreased severely. The addition of appropriate Al2O3 do not affect the product selectivity, but the catalysts incorporated with large amounts of Al2O3 have higher selectivity for light hydrocarbons and lower selectivity for heavy hydrocarbons.     

费托合成 Fe基催化剂中铁物相与活性的关系

 采用连续共沉淀和喷雾干燥相结合的方法制备了微球形 Fe 基催化剂, 采用 N2 吸附-脱附、X 射线衍射和穆斯堡尔谱等手段, 考察了催化剂在不同还原条件下铁物相的转变, 并在浆态床反应器中评价了催化剂的费-托合成 (FTS) 反应性能. 结果表明, Fe 基催化剂在合成气气氛下首先从α-Fe2O3 转变为 Fe3O4, 然后转变为铁碳化物 (FexC); 还原压力的增大有利于 α-Fe2O3 向 Fe3O4 的转变, 而抑制 Fe3O4 向 FexC 的转变; 还原空速的增加则促进 Fe3O4 转变为 FexC. 催化剂的 FTS 反应活性随着催化剂中 Fe3O4 含量的增加而逐渐下降, 而随着 FexC 含量的增加而逐渐上升.     

Study on iron-manganese catalysts for Fischer-Tropsch synthesis

Iron-manganese catalysts were prepared by co-precipitation method.Characterization of catalysts was carried out by using X-ray diffraction(XRD),scanning electron microscopy(SEM),temperature program reduction(TPR),N2 adsorption-desorption measurements.The results from catalytic performance tests in Fischer-Tropsch synthesis showed that the iron-manganese catalysts are supersensitive to catalyst composition and materials source.It was found that C2~4 light olefins increased while CH4 and CO2 decreased by using iron-manganese catalyst prepared from iron(II) sulfate(A catalyst).The activity and selectivity of A catalyst was studied in different operational conditions.The results showed that the best operational conditions for C2~4 light olefins production were H2/CO=1/1(GHSV=2400h-1) at 260℃ under 0.3MPa total pressure.     

La2O3助剂对Co/AC催化剂上费-托合成反应性能的影响

 通过改变稀土助剂La2O3的负载量,考察了La2O3助剂对活性炭负载Co基催化剂(Co/AC)上费-托合成性能的影响,并通过XRD, SEM, TPR和CO-TPD对催化剂进行了表征. 结果表明, La2O3的加入可提高催化剂的活性,降低产物中甲烷的选择性. 对于15%Co/AC催化剂,加入少量的La2O3(w(La)=0.7%～1.7%)可使CO转化率从27%升高到56%, 甲烷选择性从16.5%下降到7.8%,C5+选择性从55.4%升高到74.7%; 但加入过多的La2O3(w(La)=8.1%～12.4%)时,甲烷选择性反而升高. XRD和SEM结果表明, La2O3的加入提高了催化剂中Co的分散度. TPR和CO-TPD结果表明, La2O3与Co之间存在着相互作用,并使催化剂的还原度下降,尤其是La2O3负载量高的催化剂还原度下降更加明显,导致Co/AC催化剂上CO的高温吸附量的增加.     

Effect of La2O3 on a Precipitated Iron Catalyst for Fischer-Tropsch Synthesis

A series of La₂O₃-promoted precipitated iron catalysts (100Fe/2.8Si/nLa, n = 0, 0.5, 1, 2, and 4, atomic ratio) were prepared and characterized by in situ X-ray diffraction, CO temperature-programmed reduction, and N₂ adsorption-desorption. The catalytic performance for Fischer-Tropsch synthesis was studied in a fixed-bed reactor. It was found that the addition of a small amount of La₂O₃ (La/Fe ≤ 0.01) gave a large decrease in the particle size of Fe₂O₃, which increased the specific surface area and dispersion of the catalysts. This also favored the formation of iron carbides, which gave a high catalytic activity in Fischer-Tropsch synthesis. With increasing La₂O₃ content (La/Fe ≥ 0.02), a high La₂O₃ coverage and the formation of a LaFeO₃ compound decreased the formation of iron carbides, and the reaction activity decreased. The optimum La₂O₃ content was La/Fe = 0.01. The addition of La₂O₃ increased the selectivity for methane and suppressed the formation of C₅₊ hydrocarbons.     

Mn助剂对CuFeZrO2低碳醇合成催化剂的修饰作用

利用程序升温还原和原位漫反射红外光谱技术研究了Mn修饰的CuFeZrO2催化剂的结构特性,并测试了催化剂的CO加氢合成低碳醇的反应性能.研究表明，适量添加锰助剂有利于提高催化剂的反应活性,提高产物中C2＋醇的含量,抑制甲烷的生成,但随锰含量的增加催化剂的活性和选择性呈现先增加后下降的趋势.程序升温还原的测试表明,锰助剂通过与铜的相互作用使铜的还原变得困难,影响铜在催化剂上的状态,随锰的加入量的增加这种作用得到加强.铜分散度的测定表明锰促进了铜的分散,利用探针分子CO在催化剂上吸附的漫反射红外光谱研究发现,锰助剂可以提高组分间的相互作用,影响铜的电子性质,从而增加了CO在铜上的吸附.     

Cr 助剂对 Fe 基催化剂结构和费托合成性能的影响

 采用 N2 吸附-脱附、X 射线衍射、穆斯堡尔谱、X 射线光电子能谱、程序升温还原和热重分析等技术研究了助剂 Cr 含量对 Fe 基费托合成催化剂的织构性质、还原行为以及物相变化的影响. 在 H2/CO = 2.0, 260~300 oC, 1.5 MPa 和 2 000 ml/(g•h) 条件下, 在固定床反应器中考察了 Cr 含量对 Fe 基催化剂费托合成反应活性和产物烃选择性的影响. 结果表明, 在氧化态催化剂中, Cr 助剂与 Fe 物相存在较强的相互作用, 形成固溶体相 α-(Cr1-xFex)2O3; 随着 Cr 含量的增加, 逐渐由单一的富 Fe 相 α-(Fe1-xCrx)2O3 向富 Fe 相和富 Cr 相 α-(Cr1-yFey)2O3 两相过渡. Fe-Cr 固溶体的生成显著抑制了催化剂的还原, 导致催化剂还原度降低, 因而催化剂活性下降. 同时, Cr 的添加提高了甲烷和轻质烃选择性, 但抑制了水煤气变换活性.     

费托合成反应中纳米铁催化剂上La和Ba助剂的协同效应(英文)

Effect of promoters such as Barium and Lanthanum has been investigated on the conventional nanostructured iron catalyst in Fischer-Tropsch synthesis (FTS). The nanosized iron-based catalysts were prepared by a microemulsion method with the general formulation of 100Fe/4Cu, 100Fe/4Cu/2La, 100Fe/4Cu/ 1La/1Ba, and 100Fe/4Cu/2Ba. The phase, structure, and morphology of the catalysts were characterized by X-ray diffraction, N2 adsorption, transmission electron microscopy, temperature-programmed desorption of CO2, and temperature- programmed reduction. The results indicated that the addition of promoters could improve the activity of Fe catalysts for FTS and WGS (water-gas shift reaction) and lower the gas fraction at the outlet. In addition, both Ba- and La-promoted Fe catalysts exhibit the highest activity due to the synergetic effect.     

Study on the Precursor Phase Composition of Fused Iron Catalyst for Fischer-Tropsch Synthesis

The effect of the precursor composition of fused iron catalyst on the performance of Fischer-Tropsch synthesis was investigated. XRD, BET and CO2 adsorption experiments were carried out to provide better insight into the relationship therein. The results showed that the selectivity of C5＋ hydrocarbon products was dependent on the mole ratio of Fe^2＋/Fe^3＋, which was represented by a hump-shaped curve. Catalysts with precursors containing Fe3O4 phase favored the magnetite spinal formation during F-T reaction, while Fe（1-x）O-based catalysts were more likely to favor the formation and growth of the iron carbide crystals.     

焙烧温度对费托合成铁基催化剂还原动力学的影响

采用沉淀法和喷雾干燥技术制备了一个典型的费托合成铁基催化剂(100Fe/3K/6SiO_2,质量比)所得样品在不同温度下焙烧5 h.分别利用N_2吸附和穆斯保尔谱表征了催化剂的织构和物相性质,同时利用热重分析仪记录了催化剂在H2气氛中的还原过程,并利用气固反应模型对还原曲线进行了动力学模拟.结果表明,300~600℃焙烧后催化剂的还原过程可用相同的模型拟合,其中由α-Fe_2O_3还原为Fe_3O_4的过程可用一维晶相形成与生长模型或三维相界面反应模型描述,Fe_3O_4还原为α-Fe的过程受二维晶相形成与生长模型控制.而对于700℃焙烧后的催化剂,其还原过程可能受晶相形成与生长模型和收缩核模型共同影响.随着焙烧温度的提高,催化剂的还原能力减弱,还原过程活化能升高.这可能是由于焙烧温度的提高导致晶粒尺寸增大和晶格缺陷减少所致.