吸附强化蒸汽重整制氢中CO2固体吸附剂的研究进展

吸附强化蒸汽重整（SESR）制氢技术是集重整反应（H₂生产）和选择性分离（CO₂吸附）于一体的新型技术。该技术的特点为采用固体吸附剂在高温下对CO₂进行原位脱除,以改变反应的正常平衡极限,提高烃类转化率,提高H₂产量,减少CO₂排放。在整个SESR制氢技术中,吸附剂的选择与反应条件至关重要。本文探讨了CaO、水滑石、Li₂ZrO₃、Li₂SiO₃以及双功能吸附剂在SESR制氢过程中的性能,总结了提高这些吸附剂吸附性能的不同方法。确定了固体吸附剂的反应条件,如温度、压力、水蒸气量等因素的影响及相关的反应机理。分析表明,CaO基吸附剂由于其低廉的价格及较高的吸附能力,被认为是最具潜力的吸附剂,然而在SESR制氢过程中,CaO基吸附剂面临着多次循环再生后吸附能力衰减的挑战。集吸附与催化双重功能的吸附催化材料由于可以克服SESR制氢中不同固体催化剂和吸附剂的匹配问题、降低所用固体材料的成本,从而使其在吸附强化蒸汽重整制氢方面具有巨大优势,并成为该领域未来研究的一个重要方向。     

废轮胎热解炭低温催化焦油重整制备富氢气体的研究

以全钢型废旧轮胎为原料,通过热解、活化、浸渍、焙烧的流程制备了三种热解炭催化剂,分别为轮胎热解炭（Raw char）、轮胎热解活性炭（AC）和负载Zn的活性炭（Zn/AC）。采用N₂吸/脱附、SEM、EDS、XRD等表征方法对催化剂进行了一系列表征和分析,发现CO₂/H₂O活化可显著提高催化剂BET比表面积,最高可达380 m²·g^-1,有效改善催化剂表面结构性质,同时浸渍法使催化剂表面负载大量ZnO活性位。对三种催化剂在纤维素热解焦油重整制氢过程中的催化性能进行了研究,发现Raw char（600℃）具有最佳催化效果,相较于空白组（500℃）,热解气中H₂体积分数提高了12.4%,达到19.3%,其次为Zn/AC（500℃）组的17.8%,实现了低温下催化纤维素焦油热解制得高产率H₂。     

焦油渣制取活性炭吸附汽油中有机硫的研究

采用焦油渣制取的活性炭,以硝酸铈为改性剂改性,分别考察不同铈添加量、焙烧时间和焙烧温度对直馏汽油的脱硫性能。结果表明,稀土添加可以有效地提高活性炭的脱硫性能,在一定的焙烧时间和焙烧温度下,可以得到脱硫效果较好的活性炭样品。     

生物质焦油重整催化剂的研究进展

生物质热解制备富氢合成气是当前的研究热点,催化重整生物质焦油不仅能够有效地去除焦油,而且可以增加气相中H₂和CO的含量。本文综述了近几年关于生物质焦油重整催化剂的研究,讨论了镍基催化剂、非镍过渡金属催化剂和碱金属催化剂的优劣势。镍基催化剂使用时通常需要载体,虽然具有较高的催化活性,但是易通过积炭和镍烧结而失活。非镍过渡金属催化剂中的贵金属催化剂虽然具有极高的活性和稳定性,但是价格昂贵。碱金属催化剂易挥发而永久失活。     

流化床二氧化碳吸附强化甘油重整的数值模拟

生物甘油催化重整技术为制氢工业的发展提供了广阔的前景,而二氧化碳吸附强化重整因能降低能耗和促进氢气产量被广泛关注。基于欧拉-欧拉双流体模型,结合化学反应动力学,对流化床反应器中二氧化碳吸附强化甘油重整过程开展了数值模拟,评估了催化剂和吸附剂颗粒在反应器中的流动行为,分析了操作压力对气体产物分布的影响。结果表明,催化剂和吸附剂在床中形成了典型的内循环流动结构,压力的增加会促进吸附反应,但在一定程度上减少了氢气的纯度。     

吸附强化乙醇水重整制氢的工艺条件

采用吸附强化技术强化了乙醇水重整制氢过程。考察了温度、水醇比、液空速对无强化乙醇水重整制氢反应特性的影响,在此基础上研究了吸附强化乙醇水重整制氢反应特性。通过响应面法确定了吸附强化乙醇水重整制氢最优工艺条件为温度422～444 ℃、水醇比10.2～10.8、液空速0.13 h?1,在此条件下的氢产率为3.2 mol/mol,同比提高了51.7%,氢含量为88.91%,同比提高了22.9%,反应温度降低了178 ℃,降低了能耗,控制了CO2排放。     

流化床二氧化碳吸附强化甘油重整的数值模拟

生物甘油催化重整技术为制氢工业的发展提供了广阔的前景,而二氧化碳吸附强化重整因能降低能耗和促进氢气产量被广泛关注。基于欧拉-欧拉双流体模型,结合化学反应动力学,对流化床反应器中二氧化碳吸附强化甘油重整过程开展了数值模拟,评估了催化剂和吸附剂颗粒在反应器中的流动行为,分析了操作压力对气体产物分布的影响。结果表明,催化剂和吸附剂在床中形成了典型的内循环流动结构,压力的增加会促进吸附反应,但在一定程度上减少了氢气的纯度。     

吸附强化的甲烷水蒸汽重整制氢反应特性

在实验室固定床反应器上研究了采用复合催化剂的吸附强化甲烷水蒸汽重整制氢反应,对吸附强化制氢反应条件进行了考查,得到了实验室条件下的最佳反应条件为温度600～640 ℃,压力0.2 MPa,水碳比4～5.在600 ℃,0.2 MPa,水碳比5的条件下,吸附强化段H2含量高达95.39%,吸附强化段CH4转化率达到81.37%,相对于理论平衡值的吸附强化因子达到26.76%.     

吸附强化甲醇水重整制氢工艺条件研究

研究了吸附增强技术对甲醇水重整制氢过程的作用效果。对商业水滑石、Ca基吸附剂、负载型MgO吸附剂3种吸附剂进行了CO2-TPD考察。考察了反应温度、液空速、水醇摩尔比对甲醇水重整制氢的影响。在此基础上,选择Ca基吸附剂,利用响应面法,进行了吸附强化甲醇水重整制氢条件考察。研究结果表明,适宜的工艺条件为反应温度245~247℃,液空速0.30~0.31 h-1,水醇摩尔比3.15~3.19。在此条件下,与无强化的甲醇水重整制氢相比,氢产率为2.528 mol/mol,提高了32.77%,氢含量为92.1451%,提高了26.49%,氢产率相同则反应温度可降低57℃,是一条高效节能减排的制氢路线。     

Hydrogen production by the partial oxidation and steam reforming of tar from hot coke oven gas

Hot coke oven gas (COG) with a temperature of about 1050 K was produced from a test unit for coke production, the capacity of which was 80 kg of coal. The COG was introduced into an experimental unit with a tar converter where oxygen and steam were injected. Over 98% of the total carbon in the hot COG was partially oxidized, reformed with steam and converted to hydrogen and CO. About 1 Nm³/h of hydrogen was continuously produced for 5 h in this experiment. The experimental results suggest that three to five times the amount of hydrogen and CO that were present in the original COG could be recovered by this technology, utilizing the heat of the hot COG for the reaction. The feasibility study showed that hydrogen can be produced by this technology at a lower cost and higher efficiency than by the separation of cold COG.     

Hydrogen production from fluidized bed steam reforming of hydrocarbons

Steam reforming of methane, kerosene and heavy oil over a nickel/alumina commercial catalyst and other materials such as limestone, dolomite and iron ore, was studied using a 5 cm i.d. fluidized bed reactor. The effects of operating parameters on conversion, hydrogen yield, product gas composition and elutriation of fine catalysts were investigated. It was found that a fluidized bed is flexible enough to handle various feedstocks, including hydrocarbons heavier than naphtha, because it permits the addition of catalyst to, or withdrawals of, coked catalyst from the bed. The yield of hydrogen obtained from fluidized bed steam reforming of heavy oil at 800‡C over limestone was similar to that obtained over commercial nickel-based catalyst. This indicates that limestone could be a promising catalyst for the production of hydrogen from heavy oil. However, hydrogen yield decreased with reaction time in the experiments using the limestone catalyst. The main cause of the decrease in hydrogen yield was elutriation of fine catalysts from the bed during the reaction.     

用于PEMFC的天然气水蒸气制氢系统

针对质子交换膜燃料电池（PEMFC）的应用要求,开发了一个包括天然气水蒸气重整、CO变换和变压吸附净化的制氢工艺过程,并着重对重整反应和变压吸附的操作条件进行了实验研究。考察了温度、空速和水碳比对重整反应的影响,得到适宜的工艺操作条件,实验结果表明：温度650℃、水碳比6、空速42h^-1时,氢气含量为70.21%,甲烷转化率为77.41%;分析了温度、流速对变压吸附脱除CO效果的影响,结果表明：在0.2MPa、40℃和吸附、脱附时间120s的条件下,产品气中CO浓度接近于1×10^-6,经过多次循环后产品气质量稳定,可以连续获得满足80W质子交换膜燃料电池要求的高纯度氢气。     

Hydrogen production for fuel cells from the catalytic ethanol steam reforming

Alumina-supported rhodium catalysts were shown to be active, selective and stable catalysts in the catalytic ethanol steam reforming when the reaction is carried out under pressure (1.1 MPa). Both the nature of the metal precursor salt, the metal loading and the reaction conditions were shown to influence the activity, the selectivity and the stability of the catalysts. Some trends observed when the reaction is carried out under moderate pressure were shown to be different from the conclusions drawn from earlier results obtained at atmospheric pressure. In fact, rhodium catalysts derived from a chlorinated metal precursor were shown to be the most active, selective and stable.

     

Hydrogen production via catalytic steam reforming of fast pyrolysis bio-oil in a two-stage fixed bed reactor system

Hydrogen production was prepared via catalytic steam reforming of fast pyrolysis bio-oil in a two-stage fixed bed reactor system. Low-cost catalyst dolomite was chosen for the primary steam reforming of bio-oil in consideration of the unavoidable deactivation caused by direct contact of metal catalyst and bio-oil itself. Nickel-based catalyst Ni/MgO was used in the second stage to increase the purity and the yield of desirable gas product further. Influential parameters such as temperature, steam to carbon ratio (S/C, S/CH₄), and material space velocity (W_BHSV, GHSV) both for the first and the second reaction stages on gas product yield, carbon selectivity of gas product, CH₄ conversion as well as purity of desirable gas product were investigated. High temperature (> 850 °C) and high S/C (> 12) are necessary for efficient conversion of bio-oil to desirable gas product in the first steam reforming stage. Low W_BHSV favors the increase of any gas product yield at any selected temperature and the overall conversion of bio-oil to gas product increases accordingly. Nickel-based catalyst Ni/MgO is effective in purification stage and 100% conversion of CH₄ can be obtained under the conditions of S/CH₄ no less than 2 and temperature no less than 800 °C. Low GHSV favors the CH₄ conversion and the maximum CH₄ conversion 100%, desirable gas product purity 100%, and potential hydrogen yield 81.1% can be obtained at 800 °C provided that GHSV is no more than 3600 h^− 1. Carbon deposition behaviors in one-stage reactor prove that the steam reforming of crude bio-oil in a two-stage fixed bed reaction system is necessary and significant.     

Hydrogen production from ethanol steam reforming over Rh/CeO2 catalyst

Hydrogen production from ethanol steam reforming over an Rh/CeO₂ catalyst was investigated with a stoichiometric feed composition. Ethanol was entirely converted to hydrogen and C₁ products (CO, CO₂, CH₄) at 400 °C due to the remarkable C–C bond cleavage capacity of Rh species. The Rh/CeO₂ catalyst exhibited stable activity and selectivity without the obvious deactivation during 70 h on stream test. Structural analysis of the aged catalysts indicated that the strong interaction between Rh and ceria support efficiently inhibited Rh particles sintering (stable at around 2 nm) and coke formation to guarantee catalyst stability.     

Hydrogen production via dry reforming of butanol: Thermodynamic analysis

Dry reforming of butanol for hydrogen production has been studied by Gibbs free energy minimization method. The calculation results showed that the formation of hydrogen and carbon monoxide was through a multi-step pathway via the dehydrogenation, dehydration, decomposition and carbon dioxide reforming of butanol. The optimum conditions for hydrogen production are identified: reaction temperatures between 1150 and 1200 K and carbon dioxide-to-butanol molar ratios between 3.5 and 4.0 at 1 atm. Under the above conditions, 100% conversion of butanol, 34.91-37.98% concentration of hydrogen and 57.34−57.87% concentration of carbon monoxide could be achieved in the absence of coke formation. The butanol dry reforming with carbon dioxide is suitable for providing fuels for Solid Oxide Fuel Cell (SOFC). The coke-formed and coke-free regions are found, which are useful in guiding the search for suitable catalysts for the reaction.