Performance of a tubular oxygen-permeable membrane reactor for partial oxidation of CH4 in coke oven gas to syngas

A gas-tight BaCo0.7Fe0.2Nb0.1O3-δ (BCFNO) tubular membrane was fabricated by hot pressure casting. And a membrane reactor with BCFNO tubular membrane and Ag-based sealant was readily constructed and applied to partial oxidation of CH4 in coke oven gas. At 875 ℃, 95% of methane conversion, 91% of H2 and as high as 10 ml·cm-2·min-1 of oxygen permeation flux were obtained. There was a good match in the coefficient of thermal expansion between Ag-based alloy and BCFNO membrane materials. The tubular BCFNO membrane reactor packed with Ni-based catalysts exhibited not only high activity but also good stability in hydrogen-enriched coke oven gas (COG) atmosphere.     

Partial oxidation of ethane to syngas in an oxygen-permeable membrane reactor

A perovskite-type oxide of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ (BSCFO) with mixed electronic and oxygen ionic conductivity at high temperatures was used as an oxygen-permeable membrane. A tubular membrane of BSCFO made by extrusion method has been used in the membrane reactor to exclusively transport oxygen for the partial oxidation of ethane (POE) to syngas with catalyst of LiLaNiO/γ-Al₂O₃ at temperatures of 800–900 °C. After only 30 min POE reaction in the membrane reactor, the oxygen permeation flux reached at 8.2 ml cm⁻² min⁻¹. After that, the oxygen permeation flux increased slowly and it took 12 h to reach at 11.0 ml cm⁻² min⁻¹. SEM and EDS analysis showed that Sr and Ba segregations occurred on the used membrane surface exposed to air while Co slightly enriched on the membrane surface exposed to ethane. The oxygen permeation flux increased with increasing of concentration of C₂H₆, which was attributed to increasing of the driving force resulting from the more reducing conditions produced with an increase of concentration of C₂H₆ in the feed gas. The tubular membrane reactor was successfully operated for POE reaction at 875 °C for more than 100 h without failure, with ethane conversion of ∼100%, CO selectivity of >91% and oxygen permeation fluxes of 10–11 ml cm⁻² min⁻¹.     

Partial oxidation of simulated hot coke oven gas to syngas over Ru-Ni/Mg（Al）O catalyst in a ceramic membrane reactor

Hydrogen amplification from simulated hot coke oven gas (HCOG) was investigated in a BaCo0.7Fe0.2Nb0.1O3−δ (BCFNO) membrane reactor combined with a Ru-Ni/Mg(Al)O catalyst by the partial oxidation of hydrocarbon compounds under atmospheric pressure. Under optimized reaction conditions, the dense oxygen permeable membrane had an oxygen permeation flux around 13.3 ml/(cm2·min). By reforming of the toluene and methane, the amount of H2 in the reaction effluent gas was about 2 times more than that of original H2 in simulated HCOG. The Ru-Ni/Mg(Al)O catalyst used in the membrane reactor possessed good catalytic activity and resistance to coking. After the activity test, a small amount of whisker carbon was observed on the used catalyst, and most of them could be removed in the hydrogen-rich atmosphere, implying that the carbon deposition formed on the catalyst might be a reversible process.     

Planar and tubular perovskite-type membrane reactors for the partial oxidation of methane to syngas

Dense planar and tubular oxygen separation membranes of La_0.6Ca_0.4Fe_0.75Co_0.25O_3– were investigated as reactors for the partial oxidation (POX) of methane to syngas. Their permeation properties were measured in an air/argon pO₂ gradient as a function of temperature. At 900 °C, the oxygen flux through a 1.26-mm-thick membrane was 0.075 mol/cm²·s and through a 0.25-mm-thick tube, 0.24 mol/cm²·s.For the POX measurements, a catalyst was added to the membrane and methane was introduced on the argon side. This resulted in a gradual increase of the oxygen flux with increasing concentration of methane, reaching 2 mol/cm²·s at 900 °C with pure methane. For the planar reactor, the CO selectivity reached 99% and the CH₄ conversion 75% at 918 °C with pure methane. For the tubular reactor, the CO selectivity and CH₄ conversion were 83 and 99%, respectively, under the same conditions. After 1,400 h of operation in a tubular POX reactor, the membrane was examined revealing phase demixing and local decomposition.Presented at the OSSEP Workshop Ionic and Mixed Conductors: Methods and Processes, Aveiro, Portugal, 10–12 April 2003     

The oxidative stream reforming of methane to syngas in a thin tubular mixed-conducting membrane reactor

The oxidative stream reforming of methane (OSRM) to syngas, involving coupling of exothermic partial oxidation of methane (POM) and endothermic steam reforming of methane (SRM) processes, was studied in a thin tubular Al₂O₃-doped SrCo_0.8Fe_0.2O_3−δ membrane reactor packed with a Ni/γ-Al₂O₃ catalyst. The influences of the temperature and feed concentration on the membrane reaction performances were investigated in detail. The methane and steam conversions increased with increasing the temperature and high conversions were obtained in 850–900 °C. Different from the POM reaction, in the OSRM reaction the temperature and H₂O/CH₄ profoundly influenced the CO selectivity, H₂/CO and heat of the reaction. The CO selectivity increased with increasing the temperature or decreasing the H₂O/CH₄ ratio in the feed owing to the water gas shift reaction (H₂O + CO → CO₂ + H₂). And the H₂ selectivity based on methane conversion was always 100% because the net steam conversion was greater than zero. The H₂/CO in product could be tuned from 1.9 to 2.8 by adjusting the reaction temperature or H₂O/CH₄. Depending on the temperature or H₂O/CH₄, furthermore, the OSRM process could be performed auto-thermally with idealized reaction condition.     

Hydrogen production from coke oven gas over LiNi/γ-Al2O3 catalyst modified by rare earth metal oxide in a membrane reactor

The performance of LiNi/r-Al2O3 catalysts modified by rare earth metal oxide (La2O3 or CeO2) packed on BCFNO membrane reactor was discussed for the partial oxidation of methane (POM) in coke oven gas (COG) at 875 ◦C. The NiO/r-Al2O3 catalysts with different amounts of La2O3 and CeO2 were prepared with the same preparation method and under the same condition in order to compare the reaction performance (oxygen permeation, CH4 conversion, H2 and CO selectivity) on the membrane reactor. The results show that the oxygen permeation flux increased significantly with LiNiREOx/r-Al2O3 (RE = La or Ce) catalysts by adding the element of rare earth especially the Ce during the POM in COG. Such as, the Li15wt%CeO29wt%NiO/ -Al2O3 catalyst with an oxygen permeation flux of 24.71 ml·cm−2·min−1 and a high CH4 conversion was obtained in 875 ◦C. The resulted high oxygen permeation flux may be due to the added Ce that inhibited the strong interaction between Ni and Al2O3 to form the NiAl2O4 phase. In addition, the introduction of Ce leads up to an important property of storing and releasing oxygen.     

Microwave effect on partial oxidation of methane to syngas

In this paper the results of the partial oxidation of methane over Ni-based and Co-based catalysts activated by two different heating modes (conventional and microwaves) are reported. Compared with a conventional heating mode, the temperature of the catalytic bed is much lower and there is a higher selectivity of CO and H₂ with microwave irradiation.     

Oxidative dehydrogenation of propane in a dense tubular membrane reactor

Oxidative dehydrogenation of propane (ODP) to propylene was investigated in a dense tubular membrane reactor made of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ (BSCF) at 700^oC and 750^oC. The propylene selectivity in the membrane reactor (44.2%) is much higher than that in the fixed-bed reactor (15%) at the similar propane conversion (23-27%). Higher propylene selectivity in the membrane reactor was attributed to the lattice oxygen (O^2-) supplied through the membrane. This revised version was published online in June 2006 with corrections to the Cover Date.     

Numerical study on soot removal in partial oxidation of methane to syngas reactors

The serious carbon deposition existing in catalytic partial oxidation of methane (CPOM) to syngas process is one of the key problems that impede its industrialization. In this study, 3-dimensional unsteady numerical simulations of the soot formation and oxidation in oxidation section in a heat coupling reactor were carried out by computational fluid dynamics (CFD) approach incorporating the Moss-Brookes model for soot formation. The model has been validated and proven to be in good agreement with experiment results. Effects of nozzle type, nozzle convergence angle, channel spacing, number of channels, radius/height ratio, oxygen/carbon ratio, preheat temperature and additional introduction of steam on the soot formation were simulated. Results show that the soot formation in oxidation section of the heat coupling reactor depends on both nozzle structures and operation conditions, and the soot concentration can be greatly reduced by optimization with the maximum mass fraction of soot inside the oxidation reactor from 2.28% to 0.0501%, and so that the soot mass fraction at the exit reduces from 0.74% to 0.03%.     

Coke formation during high pressure catalytic partial oxidation of methane to syngas

Summary Carbonization of the surface of alumina-based catalysts has been studied with respect to the composition of the catalysts and conditions of the propionitrile ammonolysis. It was shown that the surface concentration of carbon increases with the increase in temperature and with time of the reaction and depends on the catalysts nature in the order: Al-Zr(5)-O < Al-Zr(40)-O < Al-O < Al-Mg-O. The surface concentration of the Brönsted acidic sites follows the same sequence.     

Modeling of microreactor for syngas production by catalytic partial oxidation of methane

Fixed-bed reactors for the catalytic partial oxidation of methane (CPOM) to produce synthesis gas still pose hot spots problems. Microreactor is a good alternative reactor proposed to resolve these problems. In this paper, synthesis gas (hydrogen and carbon monoxide) production was investigated by a two-dimensional numerical model of single microchannel. CFD modeling with detailed chemistry was conducted to understand the CPOM on platinum (Pt) catalyst. Gas inlet velocity, microchannel pressure, and fuel to air ratio (F/A) are selected as the effective parameters on microchannel performance. Study results show that Reynolds number has considerable effect on methane conversion, hydrogen to carbon monoxide ratio (H2/CO), and product distribution. Increasing gas inlet velocity causes all the above parameters to decrease. It is noted that increasing microchannel pressure and decreasing the ratio of fuel to air cause the decrease of the H2/CO ratio.     

氟修饰的含Ni类水滑石在甲烷部分氧化制合成气中的应用研究

通过共沉淀法合成了含Ni/Mg/Al的类水滑石,并利用水滑石的"重构性能"将F^-引入到水滑石层间。焙烧该类水滑石后得到Ni/Mg/Al/O-F催化剂,采用XRD、SEM、CO₂-TPD、H₂-TPR、N₂吸附-脱附等手段对其结构进行了表征。结果表明,焙烧后的催化剂为方镁石结构,并具有丰富的介孔,Ni/Mg/Al/O-F较之不含F^-的复合氧化物Ni/Mg/AlO具有更小的比表面积、颗粒粒径和结晶度,但是碱密度明显增大,并且在甲烷部分氧化(POM)反应中表现出更高的活性和稳定性,反应120h后,活性没有下降。这是因为F^-的引入提高了催化剂碱性和活性组分Ni的分散,从而改善了催化剂的抗积炭和烧结能力。     

Ce-Fe-Zr-O/MgO整体型氧载体用于化学链部分氧化甲烷制合成气

以MgO为载体,采用球磨法制备了Ce-Fe-Zr-O/MgO粉末状氧载体,进而采用挤压成型法制备了整体型氧载体。研究了两种氧载体化学链部分氧化甲烷制合成气的性能,并通过XRD、H₂-TPR对氧载体进行表征。结果表明,粉末状氧载体中的储氧组分以Ce-Fe-Zr-O固溶体形式存在,而整体型氧载体的制备过程会导致Zr、Fe游离氧化物的形成。粉末状氧载体和整体型氧载体上均存在表面晶格氧和体相晶格氧,其中,体相晶格氧具有高选择性氧化甲烷的性能,可以将甲烷转化成CO和H₂。粉末状氧载体与甲烷反应活性较高,但其存在高含量的表面氧,易导致甲烷的完全氧化。整体型氧载体上体相晶格氧占据优势,可将甲烷选择性氧化为CO和H₂。氧化还原循环实验表明,粉末状氧载体在还原反应发生短时间内容易引起甲烷裂解导致产物气中的H₂/CO物质的量比显著大于2.0,同时产生大量积炭,制约了其循环性能。而整体型氧载体经10次循环实验后,全程反应过程中合成气H₂/CO物质的量比一直维持在2.0附近,显示了较高的循环稳定性能。     

Improving photoreduction of CO_2 with water to CH_4 in a novel concentrated solar reactor

CO_2 photoreduction is an attractive process which allows the storage of solar energy and synthesis of solar fuels. Many different photocatalytic systems have been developed, while the alternative photo-reactors are still insufficiently investigated. In this work, photoreduction of CO_2 with H_2O into CH_4 was investigated in a modified concentrating solar reactor, using TiO_2 and Pt/TiO_2 as the catalysts. The TiO_2 and Pt/TiO_2 samples were extensively characterized by different techniques including powder X-ray diffraction(XRD), N_2 adsorption/desorption and UV–vis absorption. The catalytic performance of the TiO_2 and Pt/TiO_2 samples in the gas phase was evaluated under unconcentrated and concentrated Xe-lamp light and nature solar light with different concentrating ratios. Various parameters of the reaction system and the catalysts were investigated and optimized to maximize the catalytic performance of CO_2 reduction system. Compared with the normal light irradiation, the TiO_2 and Pt/TiO_2 samples show higher photocatalytic activity(about 6–7 times) for reducing CO_2 into CH_4 under concentrated Xe-lamp light and nature solar light. In the range of experimental light intensity, it is found that the concentration of the light makes it suitable for the catalytic reaction, and increases the utilization efficiency of the TiO_2 and Pt/TiO_2 samples while does not decrease the quantum efficiency.     

Temperature dependence of catalytic cyclohexane partial oxidation in a polytetrafluoroethylene reactor

Polymer-supported Co(II) catalyst was prepared and its activity and selectivity in the partial oxidation of cyclohexane was determined at several temperatures in a polytetrafluoroethylene reactor (PTFE). The catalyst was characterized by means of SEM-EDX, FTIR, diffuse reflectance UV-Vis, N₂ sorption, and mecury porosimetry. Activation energies were determined under steady state conditions for the net production of cyclohexanone and cyclohexanol and for cyclohexane and oxygen net consumption. Some activation energies were lower than the ones reported for the uncatalyzed process, indicating that the catalyst played an important role in the initiation of the free-radical reaction. The text was submitted by the authors in English.     

Effect of Cu promoter on Ni-based SBA-15 catalysts for partial oxidation of methane to syngas

A series of Ni/SBA-15 catalysts with 5wt% to 15wt% Ni content as well as a series of 12.5%Ni/Cu/SBA-15 catalysts with 1% to 10% copper content were prepared by the impregnation method. The catalytic performance for partial oxidation of methane was investigated in a continuous flow microreactor under atmospheric pressure. The textural and chemical properties of the catalysts were characterized by XRD, TEM, BET and H2-TPR techniques. The results indicated that the catalysts modified with Cu promoter showed better performance than those without modification. For the 12.5%Ni/2.5%/Cu/SBA-15 catalyst, at 850 ◦C the conversion of CH4 reached 97.9% and the selectivity of CO and H2 reached 98.0% and 96.0%, respectively. In XRD patterns of the Ni/Cu/SBA-15 catalyst with 7.5 to 10% Cu contents there were CuO characteristic peaks beside NiO characteristic peaks. The mesoporous structure of SBA-15 was retained in all of the catalysts. TPR analysis of the catalysts revealed that a strong interaction between Ni, Cu promoter and SBA-15 support may be existed. This interaction enhanced significantly the redox properties of the catalysts resulting in the higher catalytic activity.     

磷酸三丁酯萃取脱硫废液中硫氰酸根的初步研究

焦炉煤气含污染物H_2S 5g/m~3-8gm~3、HCN1g/m~3-2.5g/m~(3[1]),目前主要用催化氧化-氨水吸收法(NH_3-OMC)工艺处理.由此产生的脱硫脱氰废液中主要含有NH_4SCN、(NH_4)_2S_2O_3等无机盐,其中,SCN~-及S_2O_3~(2-)浓度均影响脱硫催化剂的效率,规定其总浓度不得超过250g/L.     

Ni-Cu /La2O3催化剂上甲烷部分氧化制合成气

用浸渍法制备了不同Cu质量分数的Ni Cu/La2O3双金属催化剂,考察了金属浸渍顺序和Cu质量分数对催化剂甲烷部分氧化性能的影响,并通过BET、XRD、TPR和SEM等技术对催化剂进行了表征。结果表明,在甲烷部分氧化制合成气反应中,Cu助剂的添加对Ni/La2O3催化剂的活性有一定的改进作用,其中浸渍顺序对催化剂的性能影响很大,共浸渍制备的催化剂活性相对较好;Cu质量分数为5%~7%时催化剂有较好的活性和稳定性;XRD等测试表明,Cu和Ni金属由于相同的晶型结构及离子半径在制备过程中形成了双金属固溶体,提高了活性组分Ni的分散度,减少了Ni晶粒的烧结聚集长大,从而提高了催化剂的活性和稳定性。     

Low-temperature utilization of CO_2 and CH_4 by combining partial oxidation with reforming of methane over Ru-based catalysts

Combination of partial oxidation of methane (POM) with carbon dioxide reforming of methane (CRM) has been studied over Ru-based catalysts at 550℃.POM,CRM and combined reaction were performed over 8wt%Ru/γ-Al2O 3 and the results show that both POM and CRM contribute to the combined reaction,between which POM plays a more important role.Moreover,the addition of Ce to Ru-based catalyst results in an improvement in the activity and CO selectivity under the adopted reaction conditions.The Ce-doped catalyst was characterized by N2 adsorption-desorption,SEM,XRD,TPR,XPS and in situ DRIFTS.The mechanism has been studied by in situ DRIFTS together with the temperature distribution of catalyst bed.The mechanism of the combined reaction is more complicated and it is the combination of POM and CRM mechanisms in nature.The present paper provides a new catalytic system to activate CH4 and CO2 at a rather low temperature.