化学循环重整甲烷制合成气LaB03钙钛矿型氧载体研究

采用溶胶-凝胶法制备了不同B位可变价离子的La-B-O复合氧载体（B=Cr、Ni）,采用XRD、BET、FT-IR、H2-TPR及CH4-TPSR等进行了表征,并用于化学循环重整（CLR）CH4反应中.结果表明,LaNiO3氧化物更易于与CH4发生深度氧化和选择氧化,LaCrO3氧化物则利于CH4裂解,其氧物种氧化CH4的能力较弱.在连续流动CLR反应中,LaNiO3具有较高的供氧量和持续供氧能力,能将CH4选择氧化为H2/CO=1.45的合成气,其CH4转化率和CO选择性分别达到23.4%和86.9%,且其结构保持了较高的稳定性.     

LaMO3纳米复合钙钛矿氧载体化学循环重整甲烷制合成气

采用溶胶-凝胶法制备了不同B位可变价离子的LaMO3 (M= Cr,Mn,Fe,Co)复合氧化物氧载体,采用X射线衍射、N2吸附-脱附、扫描电镜及CH4程序升温表面反应等手段对氧载体进行了表征,并用于直接选择氧化CH4的反应中.结果表明,Cr,Mn,Fe 和Co均能形成LaMO3纳米复合钙钛矿结构,其氧物种氧化能力大小...     

晶格氧用于甲烷氧化制合成气的研究：—氧化铁的氧化还原性能

制备了氧化铁剂,对其进行了程序升温实验（O2－TPD、空气－TPO和CH4－TPR）和不同温度下的多次CH4－空气脉冲循环反应,并对催化剂进行了XRD表征,研究结果表明,Fe2O3不仅具有较高的稳定性,还具有良好的氧化还原性能,可使CH4氧化为CO2和H2O。在750－850℃范围内,Fe2O3具有良好的提供晶格氧的能力;在900℃以上,供氧速度减慢,供氧和补氧能力明显降低,XRD测试结果表明,高于900℃时,脉冲空气不能将与脉冲CH4反应后的氧化铁氧化为Fe2O3晶格,导致了氧化铁供氧量下降。     

无气相氧条件下La0.8Sr0.2Fe0.9Co0.1O3钙钛矿氧化物的氧物种直接氧化甲烷

以La0.8Sr0.2Fe0.9CO0.1O3钙钛矿氧化物作氧载体,采用连续流动反应和连续顺序Redox反应考察了氧物种氧化甲烷的反应性能.结果表明,连续流动反应中La0.8Sr0.2Fe0.9CO0.1O3氧化物的氧物种能选择氧化甲烷生成合成气.在适宜的再氧化条件下,通过连续顺序Redox反应实现了La0.8Sr0.2Fe0.9CO0.1O3氧化物的氧物种氧化甲烷连续生成合成气,消耗的氧物种可通过与气相氧反应而得到补充.但随着Redox反应的进行,氧化物的持续供氧性能下降,钙钛矿结构被破坏.     

流化床中 CH4/C3H8 自热重整制合成气

 在流化床反应器中, 考察了 Ni/SiO2 催化剂上 CH4 或 CH4-C3H8 临氧 CO2 重整 (自热重整) 制合成气反应性能. 结果表明, 在 CH4-C3H8 混合气自热重整反应中, Ni 粒径较小催化剂的活性和抗积炭性能较高, CH4 和 CO2 转化率分别达 75.5% 和 72.6%. C3H8 比 CH4 更易解离及被氧化, 部分 C3H8 解离出来的中间产物 CHx 物种可与吸附 H 结合为 CH4, 因而降低了 CH4 的表观转化率; CHx 也可与吸附的 CO2 物种反应生成 H2 与 CO, 从而促进了 CO2 的转化.     

钙钛矿型La0.8Sr0.2FeO3中的晶格氧用于甲烷选择氧化取合成气

用自燃烧法制备了钙钛矿型La0.8Sr0.2FeO3催化剂。用H2－TPR考察了催化剂表面的氧消耗过程，用程序升温表面反应（TPSR）研究了甲烷与催化剂表面氧物种的反应，用在线质谱脉冲反应和甲烷／氧切换反应研究了催化剂的晶格氧选择氧化甲烷制合成气。结果表明，催化剂上存在两种氧物种，无气相氧存在时，强氧化性氧物种首先将甲烷氧化为CO2和H2O；而后提供的氧化性较弱的晶格氧具有良好的甲烷部分氧化选择性，可将甲烷氧化为合成气CO和H2（选择性可达95％以上）。在900℃一的CH4／O2切换反应结果表明，甲烷能与La0.8Sr0.2FeO3中的晶格氧反应选择性地生成CO和H2，失去晶格氧的La0.8Sr0.2FeO3能与气相氧反应恢复其晶格氧。在合适的反应条件下，用La0.8Sr0.2FeO3催化剂的晶格氧化替分子氧按Redox模式实现甲烷选择氧化制合成气是可能的。     

钙钛矿型La0.8Sr0.2FeO3中的晶格氧用于甲烷选择氧化制取合成气

 用自燃烧法制备了钙钛矿型La0．8Sr0．2FeO3催化剂．用H2－TPR考察了催化剂表面的氧消耗过程，用程序升温表面反应（TPSR）研究了甲烷与催化剂表面氧物种的反应，用在线质谱脉冲反应和甲烷／氧切换反应研究了催化剂的晶格氧选择氧化甲烷制合成气．结果表明，催化剂上存在两种氧物种，无气相氧存在时，强氧化性氧物种首先将甲烷氧化为CO2和H2O；而后提供的氧化性较弱的晶格氧具有良好的甲烷部分氧化选择性，可将甲烷氧化为合成气CO和H2（选择性可达95％以上）．在900℃下的CH4／O2切换反应结果表明，甲烷能与La0．8Sr0．2FeO3中的晶格氧反应选择性地生成CO和H2，失去晶格氧的La0．8－Sr0．2FeO3能与气相氧反应恢复其晶格氧．在合适的反应条件下，用La0．8Sr0．2FeO3催化剂的晶格氧代替分子氧按Redox模式实现甲烷选择氧化制合成气是可能的．     

Rh/SiO_2催化剂上甲烷部分氧化制合成气的反应机理

采用原位Raman光谱技术,在原料气中的O2未完全耗尽的条件下,对CH4部分氧化制合成气反应的Rh/SiO2催化剂床层前部贵金属物种的化学态以及由CH4解离所生成的碳物种进行了表征.在此基础上采用脉冲反应和同位素示踪技术,比较了CH4的部分氧化及其与H2O和CO2的重整等反应对催化剂床层氧化区内CO和H2生成的相对贡献,并将实验结果与Ra-man光谱表征结果进行了关联.结果表明,在600°C下将还原后的4%Rh/SiO2催化剂切入CH4:O2:Ar=2:1:45原料气,催化剂床层前部未检测到铑氧化物的Raman谱峰,但可清晰检测到源于CH4解离的碳物种;在700°C和接触时间小于1ms的条件下,催化剂床层的氧化区内已有大量CO和H2生成,在相同的实验条件下,CH4与H2O或CO2重整反应对氧化区内合成气生成的贡献则很小;以CH4:16O2:H218O:He=2:1:2:95为原料气的同位素示踪实验结果表明,在原料气中16O2未完全耗尽的情况下,反应产物中C16O的含量占CO生成总量的92.3%,表明CO主要来自CH4的部分氧化反应.上述结果均表明,在O2存在下Rh/SiO2催化剂上CO和H2可以通过CH4直接解离和部分氧化机理生成.     

LaBO3钙钛矿型复合氧化物同时消除柴油机尾气炭颗粒和NO

采用柠檬酸络合燃烧法制备了LaBO3(B=V,Cr,Mn,Fe,Co,Ni,Cu)复合氧化物.采用X射线衍射、紫外-可见漫反射光谱、傅里叶变换红外吸收光谱、氢程序升温还原及扫描电镜等手段对催化剂进行了表征,并对其在同时消除柴油机尾气中炭颗粒和NO反应中的催化活性进行了评价.结果表明,在制备的七种复合氧化物中,除La-V-O和La-Cu-O外,均形成钙钛矿结构.LaBO3钙钛矿型氧化物氧化能力由强到弱的顺序为LaCoO3≈LaNiO3>LaMnO3>LaFeO3>LaCrO3,在同时消除炭颗粒和NO的催化反应中,钙钛矿复合氧化物催化剂的催化活性与其氧化能力直接相关.其中LaCoO3和LaNiO3样品对炭颗粒的氧化催化活性较好,在炭颗粒与催化剂松散接触的条件下,炭颗粒燃烧温度较低,分别为421和431℃,生成CO2的最大选择性高,分别为99.1%和99.7%,NO生成N2的转化率分别为17.2%和20.1%.     

Cu离子A位掺杂对LaSrCoO4复合氧化物氧化性能的影响

采用聚丙烯酰胺法制备了La1-xCuxSrCoO4(x=0.2-0.8)复合氧化物,考察了Cu离子掺杂量(x)对CO及C3H8氧化反应活性的影响,并运用XRD、IR、TPR和TPD等多种手段对复合氧化物催化剂进行了表征。结果表明,催化剂活性随x的变化而变化,Cu部分取代A位La能提高LaSrCoO4催化剂的CO及C3H8氧化反应活性,当x=0.4时La1-xCuxSrCoO4催化剂的晶格氧和Co3 含量较多,晶格氧的活动性较高,催化活性最佳。     

Partial Oxidation of Methane to Syngas Using Lattice Oxygen of La1-xSrxFeO3

Catalytic partial oxidation of methane to syngas using the lattice oxygen of La1-xSrxFeO3 perovskite oxide catalysts in place of molecular oxygen was studied. La1-xSrxFeO3 (x＝0, 0.1, 0.2,0.5) perovskite oxides were prepared by the "auto-combustion method". XRD analysis showed that all La1-xSrxFeO3 samples have a single-phase perovskite-type oxide. The redox properties of the catalysts were investigated by temperature programmed reduction with hydrogen (H2-TPR). Reducibility of the catalysts increase with the increasing of the Sr2+ content. The oxygen species of the catalysts and their reaction with CH4 were studied by the temperature programmed surface reaction (CH4-TPSR). In the absence of gas phase oxygen, there exist two kinds of oxygen species on the catalysts. One kind of the oxygen species with strong oxidative ability is produced first, which can oxidize CH4 completely to CO2 and H2O.Then, the second oxygen species with weak oxidative ability is formed, which can oxidize CH4 partially to CO and H2 with high selectivity. The number of the oxygen species with strong oxidative ability in the CH4-TPSR tends to become zero at low x values (x≤0.1). Under suitable reaction conditions, switching alternatively the reactions of 11% O2-Ar and 11% CH4-He over a La0.sSr0.2FeO3 catalyst at 900 ℃ allows methane to be selectively converted to synthesis gas (CH4 conversion ～90%, CO selectivity ＞93%) using the lattice oxygen of the perovskite oxide catalyst in a redox mode.     

Partial Oxidation of Methane into Syngas with Oxygen Permeating Ceramic Membrane Reactors

Partial oxidation of methane (CH₄ +1/2O₂ CO + 2H₂) is considered as an alternative reforming reaction to steam reforming for production of syngas. This reaction is a slightly exothermic reaction and produces syngas of H₂/CO = 2, which is suitable for the synthesis of hydrocarbon or methanol. In this paper, the catalytic partial oxidation of CH₄ with a membrane reactor using oxygen permeating ceramic, in particular, LaGaO₃-based oxide, is reported. Supported Ni or Rh catalysts are active and selective for this reaction. On the other hand, a mixed ionic and electronic conducting (MIEC) ceramic membrane is useful for obtaining pure oxygen from air when the gradient in oxygen partial pressure is obtained. As for a MIEC membrane, mixed electronic–oxide ionic conductors of Fe- or Co-based perovskite oxides are widely investigated. However, the improvement in stability in a reducing atmosphere is critically required for the MIEC membrane for the application to the membrane reactor for CH₄ partial oxidation. Perovskite oxides of LaGaO₃ doped with Sr for a La site and a Fe, Co, or Ni for a Ga site, respectively, are promising as the oxygen-separating membrane for CH₄ partial oxidation because of high stability in a reducing atmosphere as well as high permeability of oxygen. The partial oxidation of CH₄ with solid oxide fuel cells (SOFCs) is also described. Simultaneous generation of electrical power and syngas is demonstrated by the fabricated fuel cell type reactor using a LaGaO₃-based oxide electrolyte.     

Simultaneous syngas production with different H_2/CO ratio in a multi-tubular methane steam and dry reformer by utilizing of CLC

For syngas production, the combustion of fossil fuels produces large amounts of CO2 as a greenhouse gas annually which intensifies global warming. In this study, chemical looping combustion(CLC) has been utilized for the elimination of CO2 emission to atmosphere during simultaneous syngas production with different H2/CO ratio in steam reforming of methane(SR) and dry reforming of methane(DR) in a CLC-SR-DR configuration. In CLC-SR-DR with 184 reformer tubes(similar to an industrial scale steam reformer in Zagros Petrochemical Company, Assaluyeh, Iran), DR reaction occurs over Rh-based catalysts in 31 tubes. Also, SR reaction is happened over Ni-based catalysts in 153 tubes. CLC via employment of Mn-based oxygen carriers supplies heat for DR and SR reactions and produces CO2 and H2O as raw materials simultaneously. A steady state heterogeneous catalytic reaction model is applied to analyze the performance and applicability of the proposed CLC-SR-DR configuration. Simulation results show that combustion efficiency reached 1 at the outlet of fuel reactor(FR). Therefore,pure CO2 and H2O can be recycled to DR and SR sides, respectively. Also, CH4 conversion reached 0.2803 and 0.7275 at the outlet of SR and DR sides, respectively. Simulation results indicate that, 3223 kmol h-1syngas with a H2/CO ratio equal to 9.826 was produced in SR side of CLC-SR-DR. After that, 1844 kmol h-1syngas with a H2/CO ratio equal to 0.986 was achieved in DR side of CLC-SR-DR. Results illustrate that by increasing the number of DR tubes to 50 tubes and considering 184 fixed total tubes in CLC-SR-DR, CH4 conversions in SR and DR sides decreased 2.69% and 3.31%, respectively. However, this subject caused total syngas production in SR and DR sides(in all of 184 tubes)enhance to 5427 kmol h-1. Finally, thermal and molar behaviors of the proposed configuration demonstrate that CLC-SR-DR is applicable for simultaneous syngas production with high and low H2/CO ratios in an environmental friendly process.     

天然铁矿石为氧载体的生物质化学链气化制合成气实验研究

在一个小型鼓泡流化床反应器上以Ar气为流化介质,对以天然铁矿石为氧载体的生物质化学链气化制合成气过程进行了研究。考察了反应温度对合成气组分、气体产率、碳转化率以及气化效率的影响,反应时间对合成气组分的影响;探讨了氧载体存在对生物质气化过程的影响。结果表明,天然铁矿石可以作为生物质化学链气化制合成气反应过程的氧载体,代替富氧空气或高温水蒸气作为生物质气化的气化剂;随着温度的升高,产物气体中CO、H₂的浓度逐渐增加,CO₂、CH₄浓度缓慢降低;随着反应时间的延长,合成气中H₂、CO、CH₄的相对浓度缓慢增加,而CO₂相对浓度逐渐降低;氧载体的存在能显著提高气体产率和碳的转化率及气化效率。扫描电镜-能谱(SEM-EDS)分析表明,当超过850 ℃时,铁矿石氧载体颗粒表面烧结现象明显,但反应前后,颗粒表面的成分及含量基本保持不变。     

CeO2 as the Oxygen Carrier for Partial Oxidation of Methane to Synthesis Gas in Molten Salts： Thermodynamic Analysis and Experimental Investigation

A new technique -- the direct partial oxidation of methane to synthesis gas using lattice oxygen in molten salts medium has been introduced. Using CeO2 as the oxygen carrier, thermodynamic data were calculated in the reaction process, and the results indicated that direct partial oxidation of methane to synthesis gas using lattice oxygen of cerium oxide is feasible in theory. In a stainless steel reactor, the effects of temperature and varying amounts of γ-Al2O3 supported CeO2 on cn4 conversion, H2 and CO selectivity, were investigated, respectively. The results show that 10% CeO2/γ-Al2O3 has the maximal reaction activity at a temperature of 865 ℃ and above, the H2/CO ratio in the gas that has been produced reaches 2 and the CH4 conversion, H2 and CO selectivity reached the following percentages： i.e. 61%, 89%, and 91% at 870 ℃, respectively. In addition, increase of reaction temperature is favorable for the partial oxidation of methane.     

Hydrogen production from a combination of the water-gas shift and redox cycle process of methane partial oxidation via lattice oxygen over LaFeO3 perovskite catalyst

A redox cycle process, in which CH4 and air are periodically brought into contact with a solid oxide packed in a fixed-bed reactor, combined with the water-gas shift (WGS) reaction, is proposed for hydrogen production. The sole oxidant for partial oxidation of methane (POM) is found to be lattice oxygen instead of gaseous oxygen. A perovskite-type LaFeO3 oxide was prepared by a sol-gel method and employed as an oxygen storage material in this process. The results indicate that, under appropriate reaction conditions, methane can be oxidized to CO and H2 by the lattice oxygen of LaFeO3 perovskite oxide with a selectivity higher than 95% and the consumed lattice oxygen can be replenished in a reoxidation procedure by a redox operation. It is suggested that the POM to H2/CO by using the lattice oxygen of the oxygen storage materials instead of gaseous oxygen should be possibly applicable. The LaFeO3 perovskite oxide maintained relatively high catalytic activity and structural stability, while the carbonaceous deposits, which come from the dissociation of CH4 in the pulse reaction, occurred due to the low migration rate of lattice oxygen from the bulk toward the surface. A new dissociation-oxidation mechanism for this POM without gaseous oxygen is proposed based on the transient responses of the products checked at different surface states via both pulse reaction and switch reaction over the LaFeO3 catalyst. In the absence of gaseous-phase oxygen, the rate-determining step of methane conversion is the migration rate of lattice oxygen, but the process can be carried out in optimized cycles. The product distribution for POM over LaFeO3 catalyst in the absence of gaseous oxygen was determined by the concentration of surface oxygen, which is relevant with the migration rate of lattice oxygen from the bulk toward the surface. This process of hydrogen production via selective oxidation of methane by lattice oxygen is better in avoiding the deep oxidation (to CO2) and enhancing the selectivity. Therefore, this new route is superior to general POM in stability (resistance to carbonaceous deposition), safety (effectively avoiding accidental explosion), ease of operation and optimization, and low cost (making use of air not oxygen).     

Ni/Al2O3催化剂上甲烷部分氧化制合成气反应机理

用变应答／质谱在线检测技术研究了Ｎｉ／Ａｌ２Ｏ３催化剂上甲烷部分氧化制合成气的反应要理，研究结果指出，在常压９７３Ｋ条件下，Ｎｉ／Ａｌ２Ｏ３催化剂上甲烷部分氧化制合成气按直接氧化机理进行，Ｈ２和Ｃ烛甲烷部分氧化的一次产物，其主要反应可表示如下：１．ＣＨ４＋ｘＮｉ－ＮｉｘＣ＋２Ｈ２，２．Ｏ２＋２Ｎｉ－２ＮｉＯ，３．ＮｉｘＣ＋ＮｉＯ－ＣＯ＋（ｘ＋１）Ｎｉ。     

Cofeeding of Methane and Ethane to Produce Syngas over a LiLaNiO/γ-Al_2O_3 Catalyst

There are abundant supplies of mixture gases containing CH, and C,H, from natural gas,FCC (Fluidized Catalytic Cracking) dry gas, refinery gas, elc. Commonly, the amount ofC,H, is relatively lower than that of CH,. With regard to the utilization of methane,partial oxidation of methane to syngas over nickel based catalysts has received intensiveallention l'2. For mixture gases containing CH# and C,H,, their conversion to syngas isalso of significance (but has not gained adequate attentio…     

生物质气化重整合成二甲醚

以松木粉为原料，采用空气 水蒸气气化制备了富氢气化气，通过添加甲烷重整富氢气化气，调整了合成气化学当量比，在260 ℃、4 MPa、12 000 h－1条件下，对生物质合成气一步法合成二甲醚进行了实验研究。结果表明：引入甲烷重整，活化了富氢气化气中过量的CO2，甲烷的最佳加入量为CH4/CO2=1，生物质碳转化率达到70%以上，尾气中二甲醚选择性达到69.6%。