Improved catalytic performance of Ni catalysts for steam methane reforming in a micro-channel reactor

Milliseconds process to produce hydrogen by steam methane reforming （SMR） reaction, based on Ni catalyst rather than noble catalyst such as Pd, Rh or Ru, in micro-channel reactors has been paid more and more attentions in recent years. This work aimed to further improve the catalytic performance of nickel-based catalyst by the introduction of additives, i.e., MgO and FeO, prepared by impregnation method on the micro-channels made of metal-ceramic complex substrate. The prepared catalysts were tested in the same micro-channel reactor by switching the catalyst plates. The results showed that among the tested catalysts Ni-Mg catalyst had the highest activity, especially under harsh conditions, i.e., at high space velocity and/or low reaction temperature. Moreover, the catalyst activity and selectivity were stable during the 12 h on stream test even when the ratio of steam to carbon （SIC） was as low as 1.0. The addition of MgO promoted the active Ni species to have a good dispersion on the substrate, leading to a better catalytic performance for SMR reaction.     

Hydrogen production from the aqueous phase derived from fast pyrolysis of biomass

Hydrogen production from the aqueous phase derived from fast pyrolysis of biomass was carried out by catalytic steam reforming in a fluidized bed reactor. The effects of reaction conditions such as reaction temperature, steam-to-carbon ratio (S/C) and weight hourly space velocity of the aqueous phase (WHSV) on the results of hydrogen yield, potential hydrogen yield and carbon selectivity of product gases were investigated. The effect of reaction temperature on the carbon deposition on catalyst was also studied. The hydrogen yield of 64.6%, potential hydrogen yield of 77.6% and the carbon selectivity for product gases of 84.3% can be obtained at the optimized conditions of reaction temperature 800 °C, S/C 10 and WHSV 1.0 h⁻¹.     

Methanol steam reforming in a dense Pd–Ag membrane reactor: The pressure and WHSV effects on CO-free H2 production

In this experimental work, a dense tubular Pd–Ag membrane reactor is used for carrying out the methanol steam reforming reaction for producing a CO-free hydrogen stream. A non-commercial Cu/Zn/Mg-based catalyst is used in the lumen side of the membrane reactor and the experimental tests are performed at a reaction temperature of 300 °C and H₂O/CH₃OH feed molar ratio of 3/1. In both co-current and counter-current flow configurations, the effect of the weight hourly space velocity (WHSV) as well as the reaction pressure on the membrane reactor performances in terms of CO-free hydrogen recovery, hydrogen yield and hydrogen selectivity are proposed and discussed.     

生物油水溶性组分的水蒸气催化重整制氢实验研究

利用固定床反应器对生物油水溶性组分重整制氢反应进行了考察,研究了温度、吸收剂的加入对反应过程的影响。结果表明,在常压条件下生物油水溶性组分的最佳重整温度为800℃,此时H2体积分数为60%、CO体积分数为10%。加入CO₂吸收剂后,H₂体积分数提高了25%,H₂产率提高了10%。在常压条件下,以CaO作为吸收剂时,最佳的反应温度为600℃,此时H₂体积分数最高可达85%。650℃时CaO对CO₂的吸收能力减弱导致其对生成H₂反应的促进作用急剧降低。     

Cu/ZrO2催化剂上乙醇水蒸气重整反应的研究Ⅰ催化剂性能及其制备参数的影响

研究了Cu/ZrO2催化剂在乙醇水蒸气重整反应中的催化性能。用常规沉淀法、醇凝胶法制备了ZrO2载体;用浸渍法或共沉淀法制备了Cu/ZrO2催化剂。考察了ZrO2载体的制备方法以及Cu/ZrO2的制备参数对催化剂性能的影响。采用BET、XRD、TEM及XRF等方法对催化剂的比表面积、孔容、晶相、表面形貌以及活性组分等进行了表征。同时,制备并比较了Ni/ZrO2、Cu/10MgO-90ZrO2和Cu/10CaO-90ZrO2催化剂的性能,考察了活性组分Cu、Ni的差异以及ZrO2载体的影响。在Cu/ZrO2催化剂(Cu的质量分数为8%)上,500 ℃~600 ℃乙醇转化率达到98%~100％、H2选择性为2.0~2.6（摩尔比）。 Cu/ZrO2与Ni/ZrO2机械混合有助于H2选择性的提高。在催化剂载体中添加MgO、CaO碱性物质可以使H2选择性提高1.3倍~2.0倍。浸渍法制备的Cu/ZrO2催化剂的性能优于共沉淀法。     

Three-step macrokinetic model of butane and propane steam conversion to methane-rich gas

Low-temperature steam conversion (LTSC) of a methane-butane mixture (95% methane and 5% butane) into a methane-rich gas over an industrial Ni-based catalyst has been studied with the following reaction conditions: temperature 200–320°C, pressure 1 bar, gas hour space velocity 1200–3600 h^–1, and steam to carbon ratio 0.64. A three-step macrokinetic model has been suggested based on the kinetic parameters found. The model includes the following reactions: (1) irreversible steam reforming; (2) CO₂ methanation, which occurs in a quasi-equilibrium mode at temperatures above 260°C; (3) hydrogenolysis of propane and butane, which is essential at temperatures below 260°C. Steam reforming was shown to limit the overall reaction rate, whereas hydrogenolysis and CO₂ methanation determined the product distribution in low- and high-temperature regions, respectively. Temperature dependencies of the product distribution for the LTSC of a model ternary methane-propane-butane mixture (85% methane, 10% propane, and 5% butane) have been successfully simulated using the three-step model suggested.     

Maximum Hydrogen Production by Autothermal Steam Reforming of Bio-oil With NiCuZnAl Catalyst

Autothermal steam reforming (ATR) of bio-oil, which couples the endothermic steam reform-ing reaction with the exothermic partial oxidation, offers many advantages from a technical and economic point of view. Effective production of hydrogen through ATR of bio-oil was performed at lower temperature with NiCuZnAl catalyst. The highest hydrogen yield from bio-oil reached 64.3% with a nearly complete bio-oil conversion at 600 oC, the ratio of steam to carbon fed (S/C) of 3 and the oxygen to carbon ratio (O/C) of 0.34. The reaction con-ditions in ATR including temperature, O/C, S/C and weight hourly space velocity can be used to control both hydrogen yield and products distribution. The comparison between the ATR and common steam reforming of bio-oil was studied. The mechanism of the ATR of bio-oil was also discussed.     

镍基整体式催化剂上生物质粗燃气重整调变的特性研究

采用浸渍法制备了Ni基整体式催化剂,考察了不同条件(温度、时间、空速、水蒸气添加等)对催化剂上生物质粗燃气重整反应性能的影响。结果表明,催化剂在较低温度下(≤500 ℃)只具有CO加氢反应活性,随着反应温度的升高粗燃气重整反应逐渐进行,在800 ℃以上,CH₄和C₂转化率均高达95 %以上,CO₂转化率达到92%,但随着反应空速和水蒸气添加量的增加,CH₄和CO₂等转化率呈现缓慢降低的趋势。此外,通过改变水蒸气添加量可对合成气中H₂/CO体积比在0.85~4.00进行较好调节。结合XRD表征发现,Ni基整体式催化剂中Ni°的生成可较好地促进重整反应的进行。     

共沉淀镍催化剂用于膜反应器中高碳烃类燃料水蒸气重整反应

 采用共沉淀法制备了NiO/La-Al2O3催化剂,利用低温N2物理吸附、程序升温还原、 H2-O2化学吸附和X射线衍射对催化剂进行了表征,并将该催化剂应用于Pd膜反应器中高碳烃类燃料水蒸气重整反应. 结果表明,催化剂中NiO与载体间存在较强的相互作用. 与常规固定床反应器相比,在膜反应器中,由于高渗透性能的Pd金属复合膜能选择分离氢气,结果氢气产率得到了明显的提高,甲烷的生成得到了有效抑制,并且在接近实用的反应条件下,依然能够得到高的氢气产率和回收率. 高碳烃类燃料水蒸气重整反应制氢的过程可以在一个膜反应器中,利用一种催化剂在反应温度低于823 K的温和条件下实现.     

Hydrogen production by steam reforming of glycerol over Ni/Ce/Cu hydroxyapatite-supported catalysts

Hydroxyapatite-supported Ni-Ce-Cu catalysts were synthesised and tested to study their potential for use in the steam reforming of glycerol to produce hydrogen. The catalysts were prepared by the deposition-precipitation method with variable nickel, cerium, and copper loadings. The performance of the catalysts was evaluated in terms of hydrogen yield at 600°C in a tubular fixed-bed microreactor. All catalysts were characterised by the BET surface area, XRD, TPR, TEM, and FE-SEM techniques. The reaction time was 240 min in a fixed-bed reactor at 600°C and atmospheric pressure with a water-to-glycerol feed molar ratio of 8: 1. It was found that the Ni-Ce-Cu (3 mass %-7.5 mass %-7.5 mass %) hydroxyapatite-supported catalyst afforded the highest hydrogen yield (57.5 %), with a glycerol conversion rate of 97.3 %. The results indicate that Ni/Ce/Cu/hydroxyapatite has great potential as a catalyst for hydrogen production by steam reforming of glycerol.     

Studies of the Methane Steam Reforming Reaction at High Pressure in a Ceramic Membrane Reactor

The effects of temperature and pressure on the steam reforming of methane 3H2+CO) were investigated in a membrane reactor (MR) with a hydrogen permeable membrane. The studies used a novel silica-based membrane prepared by using the chemical vapor deposition (CVD) technique with a permeance for H2 of 6.0×l0-8 mol·m-2·s-1·Pa-1 at 923 K. The results in a packed-bed reactor (PBR) were compared to those of the membrane reactor at various temperatures (773-923 K) and pressures (1-20 atm, 101.3-2026.5 kPa) using a commercial Ni/MgAl2O4 catalyst. The conversion of methane was improved significantly in the MR by the countercurrent removal of hydrogen at all temperatures and allowed product yields higher than the equilibrium to be obtained. Pressure had a positive effect on the hydrogen yield because of the increase in driving force for the permeance of hydrogen. The yield of hydrogen increased with pressure and reached a value of 73×10-6 mol·g-1·s-1 at 2026.5 kPa and 923 K which was higher by 108% than the value of 35×10-6 mol·g-1·s-1 obtained for the equilibrium yield. The results obtained with the silica-based membrane were similar to those obtained with various other membranes as reported in the literature.     

介孔Ni/MgO催化剂催化水蒸气重整生物质油制氢

采用水热法制备了介孔MgO作为催化剂的载体,并制备了介孔Ni/MgO催化剂。利用N_2吸附-脱附、XRD、H_2-TPR等对样品进行表征,并考察了介孔Ni/MgO催化水蒸气重整糠醛、生物质油模型物和两种商用生物质油制氢的活性。结果表明,在介孔Ni/MgO催化剂催化水蒸气重整糠醛制氢反应中,随着反应温度的提高,水蒸气重整糠醛中糠醛的转化率、氢气的产率和氢气的选择性,都呈现递增的趋势。在反应温度提高到600℃时,糠醛的转化率和氢气的产率分别达到94.9%和83.2%。Ni/MgO催化水蒸气重整二组分模拟生物质油,糠醛/乙酸、糠醛/羟基丙酮制氢的反应中,氢气的产率分别达到87.3%和86.8%,均高于水蒸气重整糠醛反应中氢气的产率。由此表明,乙酸或羟基丙酮的存在,提高了模拟生物质油中主要有机物组分糠醛的转化率,并相应地提高了氢气的产率。在水蒸气重整商用生物质油制氢反应中,随着反应物水碳比(S/C(molar ratio)=5、10、15、20、25)的提高,主要有机物的转化率、氢气的产率和选择性呈现出增加的趋势。在水碳比为20时,两种生物质油的主要有机物组分(糠醛、乙酸和羟基丙酮)的转化率均可达90%以上,氢气的产率也达到81.0%以上。由此可知,Ni催化剂对于水蒸气重整商用生物质油也具有较高的催化活性。     

C12A7-Mg催化剂水蒸汽重整生物油、石脑油和CH4制氢

Hydrogen production by catalytic steam reforming of the bio-oil, naphtha, and CH4 was investigated over anovel metal-doped catalyst of (Ca24Al28O64)4+￠4O-/Mg (C12A7-Mg). The catalytic steam reforming wasinvestigated from 250 to 850 ±C in the ˉxed-bed continuous °ow reactor. For the reforming of bio-oil, theyield of hydrogen of 80% was obtained at 750 ±C, and the maximum carbon conversion is nearly close to95% under the optimum steam reforming condition. For the reforming of naphtha and CH4, the hydrogenyield and carbon conversion are lower than that of bio-oil at the same temperature. The characteristics ofcatalyst were also investigated by XPS. The catalyst deactivation was mainly caused by the deposition ofcarbon in the catalytic steam reforming process.     

甲醇POSR制氢的反应网络热力学分析和有效因子的估算

在Cu/ZnO/Al2O3催化剂上对甲醇部分氧化蒸汽重整制备氢气反应的动力学过程进行了研究。在常压和473 K～1 073 K温度范围内对该反应网络中的甲醇部分氧化、甲醇蒸汽重整、甲醇分解和水煤气反应的化学平衡进行了分析。在对这些反应的催化剂Cu/ZnO/Al2O3动力学研究的基础上，根据有效因子的基本概念，考虑催化剂颗粒内的扩散限制，对每个反应沿反应器床层的有效因子进行了估算。     

A review on butanol steam reforming for renewable hydrogen production

Butanol is a renewable bio-oxygenate that can be prepared by fermentation of lignocellulosic biomass. Steam reforming of bio-derived butanol is an attractive and feasible option for producing renewable hydrogen. In the present work, all the studies on butanol steam reforming are reviewed comprehensively. The thermodynamics for the reaction, the optimized reaction conditions such as temperature, pressure, steam to carbon (S/C) ratio and the innovations in catalyst designs are described in depth. Based on the type of catalyst and support, different reaction routes for butanol reforming are possible. Ni, Co, Rh and Pt catalyst are more appropriate for butanol reforming. The challenges associated in utilizing bio-butanol as feed and design of cost effective and coke resistant catalyst are discussed. Such discussions on butanol reforming are still missing and the present work will fill this gap.     

负载NiO-Fe2O3的凹凸棒石对生物油模型物催化重整制氢性能的影响

利用共沉淀法,制备一系列在凹凸棒土上负载不同含量的NiO-Fe₂O₃催化剂。以乙酸、乙醇和苯酚的水溶性溶液为生物油模型物,在自制的三段式固定床反应器中,考察了NiO-Fe₂O₃的负载量、反应温度、水碳比(S/C)对生物油模型物重整制氢的影响。结果表明,所获得的氢气产率最高的工艺条件为,在650℃条件下,以水碳比8~10的生物油模型为实验原料,使用自制的50%NiO-50%Fe₂O₃/PG型催化剂,可使气体产物中H₂的相对含量达到最大66.15%。     

Membrane reactor performance of steam reforming of methane using hydrogen-permselective catalytic SiO2 membranes

Hydrogen production by steam reforming of methane using catalytic membrane reactors was investigated first by simulation, then by experimentation. The membrane reactor simulation, using an isothermal and plug-flow model with selective permeation from reactant stream to permeate stream, was conducted to evaluate the effect of permselectivity on membrane reactor performance – such as methane conversion and hydrogen yield – at pressures as high as 1000 kPa. The simulation study, with a target for methane conversion of 0.8, showed that hydrogen yield and production rate have approximately the same dependency on operating conditions, such as reaction pressure, if the permeance ratio of hydrogen over nitrogen ((H₂/N₂)) is larger than 100 and of H₂ over H₂O is larger than 15. Catalytic membrane reactors, consisting of a microporous Ni-doped SiO₂ top layer and a catalytic support, were prepared and applied experimentally for steam reforming of methane at 500 °C. A bimodal catalytic support, which allows large diffusivity and high dispersion of the metal catalyst, was prepared for the enhancement of membrane catalytic activity. Catalytic membranes having H₂ permeances in the range of 2–5 × 10⁻⁶ m³ m⁻² s⁻¹ kPa⁻¹, with H₂/N₂ of 25–500 and H₂/H₂O of 6–15, were examined for steam reforming of methane. Increased performance for the production of hydrogen was experimentally obtained with an increase in reaction-side pressure (as high as 500 kPa), which agreed with the theoretical simulation with no fitting parameters.     

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.     

Effect of O_2 and H_2O on the tri-reforming of the simulated biogas to syngas over Ni-based SBA-15 catalysts

A series of Ni/SBA-15 catalysts with Ni contents from 7.5 wt% to 15 wt% were prepared by impregnation method.The effect of O2 and H2O on the combined reforming of the simulated biogas to syngas was investigated in a continuous flow fixed-bed micro-reactor.The stability of the catalyst was tested at 800 ?C.The results indicated that 10wt%Ni/SBA-15 catalyst exhibited the highest catalytic activities for the combined reforming of the simulated biogas to syngas.Under the reaction conditions of the feed gas molar ratios CH4/CO2/O2/H2O = 2/1/0.6/0.6,GHSV = 24000 ml gc?a1t h?1 and the reaction temperature T = 800 ?C,the conversions of CH4 and CO2 were 92.8% and 76.3%,respectively,and the yields of CO and H2 were 99.0% and 82.0%,respectively.The catalytic activities of the catalyst did not decrease obviously after 100 h reaction time on stream.     

在Ni/HZSM-5催化剂上低温水蒸汽重整生物油制氢

We investigated high catalytic activity of Ni/HZSM-5 catalysts synthesized by the impregna-tion method, which was successfully applied for low-temperature steam reforming of bio-oil. The influences of the catalyst composition, reforming temperature and the molar ratio of steam to carbon fed on the stream reforming process of bio-oil over the Ni/HZSM-5 catalysts were investigated in the reforming reactor. The promoting effects of current passing through the catalyst on the bio-oil reforming were also studied using the electrochemical catalytic re-forming approach. By comparing Ni/HZSM-5 with commonly used Ni/Al₂O₃ catalysts, the Ni₂₀/ZSM catalyst with Ni-loading content of about 20% on the HZSM-5 support showed the highest catalytic activity. Even at 450 oC, the hydrogen yield of about 90% with a near complete conversion of bio-oil was obtained using the Ni₂₀/ZSM catalyst. It was found that the performance of the bio-oil reforming was remarkably enhanced by the HZSM-5 supporter and the current through the catalyst. The features of the Ni/HZSM-5 catalysts were also investigated via X-ray diffraction, inductively coupled plasma and atomic emission spectroscopy, hydrogen temperature-programmed reduction, and Brunauer-Emmett-Teller methods.