介质阻挡放电条件下甲烷水蒸气重整和部分氧化反应制氢

构建了CH_4-O_2-N_2-H_2O反应体系,对介质阻挡放电条件下甲烷水蒸气重整和部分氧化制氢反应过程进行了研究,考察了H2O/CH4物质的量比、O_2/N_2物质的量比、气体总流量、放电电压及放电频率等参数对制氢效率的影响,并基于发射光谱原位诊断法分析了反应机理。结果表明,甲烷转化率和氢气产率随着H_2O/CH_4物质的量比、O_2/N_2物质的量比和放电电压的增加而增加,而随着反应气体总流量的增加而减小,随着放电频率的增加先增大后减小,在9.8 kHz处取得最大值。在H_2O/CH_4物质的量比1.82、O_2/N_2物质的量比2.1、总流量136 mL/min、放电电压18.6 kV及放电频率9.8 kHz的条件下,甲烷转化率与氢气产率分别达47.45%和21.33%。甲烷和水蒸气等反应物分子通过电子解离产生CH_x·、H·、OH·、O·等自由基,进而通过自由基间的碰撞反应生成H_2;H·自由基一方面来源于CH_4的电子解离;另一方面来源于水蒸气一次解离以及OH·的进一步离解。部分氧化反应主要表现为O_2电子解离形成的O·自由基以及水蒸气一次反应产物OH·自由基进一步离解形成的O·自由基对CH_2·自由基的氧化。     

介质阻挡放电等离子体甲烷部分氧化重整制氢

在自制的介质阻挡放电等离子体重整制氢装置上进行了甲烷部分氧化重整制氢的实验研究. 本文研究了氧碳(O/C)摩尔比, 进气流量, 放电间隙, 放电区间长度, 填充物的直径、形状和材料, 放电电压和放电频率对甲烷转化率、氢产率和产物的选择性(H₂、CO和CO₂)的影响. 实验结果表明: 放电区域的参数对甲烷转化率有较大的影响. 甲烷转化率随着放电区域长度的增大而增大, 当放电区域长度从5 cm增大到20 cm时, 甲烷转化率从6.87%增大到22.26%, 增大率为224%. 同时, 放电区域的填充物对产氢效果有较大的影响. 当反应器填充颗粒时, 甲烷转化率比无填充物时高. 选择适当介电常数的填充物具有巨大的实际工程意义. 另外, 氢产率和氢气的选择性随着放电频率的增大而增大, 当放电频率从1.5 kHz 增大到7.0 kHz 时, 氢产率从1.10%增大到9.49%, 氢气的选择性从21.18%增大到30.06%. 实验结果将对碳氢燃料等离子体重整制氢的车载应用提供实验依据.     

纳秒脉冲介质阻挡放电等离子体合成氨工艺条件优化

氨(NH₃)作为重要的化工原料对农业及国计民生发展有直接影响。工业合成氨需高温高压、能耗高和污染重。低温等离子体技术是一种可持续,有潜力的合成氨途径,已成为国内外研究热点。本工作以氮气和氢气为原料,在低温常压下采用纳秒脉冲介质阻挡放电等离子体合成氨,通过单因素实验系统研究脉冲峰值电压、脉冲重复频率、气体总流量、N₂和H₂体积比(V(N₂)∶V(H₂))等因素对合成氨速率及能量产率的影响规律。进一步通过正交实验评价确定影响合成氨反应速率因素的主次顺序为:脉冲峰值电压>脉冲重复频率>气体体积比>气体总流量。影响合成氨能量产率因素的主次顺序为:脉冲峰值电压>气体体积比>脉冲重复频率>气体总流量。结合两部分实验,最终得到合成氨的优选条件:脉冲峰值电压16 kV、脉冲重复频率6 kHz、脉冲上升沿100 ns、V(N₂)∶V(H₂)=1∶1、气体总流量200 mL/min。此时NH₃合成...     

生物油水蒸气气化实验研究

利用固定床反应器对生物油的水蒸气非催化气化性能进行了实验研究,考察了温度和水蒸气的加入量对气化过程的影响,对气化所得粗合成气的组成分布进行了分析。结果表明,升高温度有利于生物油向合成气转化,1 200 ℃时,生物油的碳转化率可达97.8%,合成气有效成分(H₂+CO)的产率可达77%,其中H₂/CO摩尔比为1.19;水蒸气的加入可以提高合成气中的H₂/CO摩尔比,当S/C(水碳比)=4时,合成气中的H₂/CO摩尔比可达3.69,与此同时,水蒸气的加入不利于合成气有效成分产率的提高;生物油气化所得气体为中热值气体。     

垃圾衍生燃料热解半焦气化过程中HCl与H2S析出规律

通过水平管式气化炉和化学吸收法,对比研究了矿化垃圾热解半焦（ARC）和常规垃圾热解半焦（NRC）在水蒸气和CO₂气化过程中腐蚀性气体（HCl和H₂S）的析出特性,考察了气化温度、气化介质类型和流量对腐蚀性气体析出特性的影响。当气化温度升至950℃,ARC在水蒸气气化过程中的碳气化率、HCl和H₂S产率分别为66.1%、100%和74.9%,而其在CO₂气化过程中的碳气化率、HCl和H₂S产率分别为77.8%、100%和2.9%;NRC在水蒸气气化过程中的碳气化率、HCl和H₂S产率分别为98.8%、100%和53.7%,而其在CO₂气化过程中的碳气化率、HCl和H₂S产率分别为100%、96.2%和10.3%。以NRC为原料,考察了水蒸气和CO₂流量对其HCl和CO₂析出特性的影响。NRC的HCl和H₂S产率均随水蒸气流量增加而增加,但当水碳比大于等于3.3时,其促进作用不再明显。NRC的HCl产率随CO₂流量的增加而增加,而H₂S产率随CO₂流量的增加而减小。     

两段式固定床富氧－水蒸气气化实验研究

以玉米芯颗粒为原料在两段式固定床气化装置上进行了气化实验,考察了当量比ER、富氧浓度OC和水蒸气配比S/B对气化温度、气化气组分、低位热值、气体产率、气化效率和碳转化率等参数的影响,并比较了两段式固定床与传统下吸式固定床的气化特性。实验结果表明,当量比为0.27时H₂的体积分数、CO的体积分数和气化效率达到最大值;增加富氧浓度能优化气化效果,但富氧浓度大于90%后,燃气质量和气化效率均提高不大;增加S/B能提高H₂的体积分数,但同时会降低CO的体积分数、气体热值、气化效率;当S/B为0.6时,氢气的体积分数达最高值33.3%,H₂/CO比为1.32;相比于传统固定床,两段式固定床气化可明显提高气化温度、氢气的体积分数、碳转化率和气化效率,降低焦油含量。     

介质阻挡放电等离子体催化天然气偶联制C2烃

在常压、室温的介质阻挡放电连续流动反应器中, 对介质阻挡放电等离子体作用下天然气偶联反应制C₂烃进行了研究. 考察了放电频率、放电的电极结构、放电电压、放电的电极数目、氢气、甲烷进料流量和催化剂等参数对甲烷转化率和产物(碳二烃和碳三烃)的选择性影响规律, 同时探讨了反应过程. 结果表明合适的工艺条件为: 电源频率20 kHz, 电极结构为两个电极上都覆盖绝缘介质的b型, 放电电压20~40 kV, 进料流量20~60 mL·min^-1, H₂/CH₄为1/4; 甲烷的转化率随电压的升高而增大, 随甲烷进料流量的增大而减小, 碳二烃的选择性随电压的升高而减小, 随甲烷进料流量的增大而增大. 甲烷的转化率可达45%, 碳二烃选择性可达76%, 产品(碳二烃和碳三烃)的总选择性接近100%; 连续反应100 h无积碳; 催化剂可改善产品碳二烃的选择性; 碳二烃和碳三烃的生成主要是通过自由基和甲烷分子反应获得的.     

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。     

IM-5分子筛在Ni-Cu催化剂甲烷热裂解制氢反应中的作用研究

甲烷热裂解制氢并生成高附加值的纳米碳材料,被认为是极具发展前景的氢气生产途径,但高性能催化剂的研发仍存在诸多挑战.我们选择多种载体(TS-1、 IM-5、 Y、介孔SiO₂、 γ-Al₂O₃、 CNTs),采用浸渍法制备Ni-Cu负载催化剂,通过低温N2吸附-脱附、 XRD、 SEM和H₂-TPR等系列表征方法对样品进行分析,考察不同载体对催化剂甲烷裂解制氢和纳米碳材料的影响.实验结果发现,分子筛载体独特的孔道结构有利于金属颗粒的分散,能有效避免反应中界面效应导致的催化剂失活,可提高催化剂反应活性并延长反应寿命,也显著提高了其碳产率.其中以IM-5分子筛为载体的催化剂表现最佳,在反应温度为700℃时, NiCu/IM-5催化剂甲烷转化率高达80%,氢气选择性达100%,反应400 min后活性未见明显降低. NiCu/IM-5催化剂碳产率高达1 446 g_C/g_cat,是NiCu/SiO₂催化剂的5.7倍, NiCu/γ-Al     

Ni/Al2O3改性催化剂催化重整生物油模拟物制氢研究

制备了Ni/Al₂O₃、Ni-Cu/Al₂O₃、Ni-Co/Al₂O₃和Ni-Co-Cu/Al₂O₃催化剂,研究了Co和Cu对生物油水蒸气催化重整的影响。实验表明,Co 能促进水汽变换(WGS)反应,提高氢气的产率,Cu能抑制反应中焦炭的形成,提高催化剂的稳定性。对催化剂Ni-Co-Cu/Al₂O₃进行工艺条件考察,当900 ℃、水油比为6 g/g、质量空速(WHSV)为1 h^-1时,碳选择性达到87.5%,氢气产率达到84.2%,潜在氢气产率达到92.4%。     

大气压等离子体射流重整CH4-CO2制合成气

采用大气压等离子体射流,以CH₄和CO^₂直接作为放电气体进行常压下重整制合成气的实验研究,考察了等离子体射流的放电特征及放电距离、放电功率、原料气配比和流量对反应的影响。结果表明,该等离子体具有放电稳定、均匀的特征。重整反应的主要产物为合成气,只有少量的H₂O和积炭生成。优化的反应条件为放电距离为9mm,CH₄和CO₂的摩尔比为4/6。当原料气流量为1000mL/min,放电功率为88.4W时,CH4和CO₂的最高转化率为分别为94.99%和87.23%。甲烷和二氧化碳的转化率随放电功率的增加而增加,随流量的增加而减少。     

Reforming of Carbon Dioxide to Methane and Methanol by Electric Impulse Low-Pressure Discharge with Hydrogen

Basic phenomena of the reduction of carbon dioxide to reusable organic materials including methane and methanol were investigated by using a radio frequency impulse discharge in a low gas pressure range without catalysis. The discharge took place under different discharge parameters such as voltage, gas flow rate, gas-mixing ratio, and gas residence time, where the carbon dioxide was mixed with hydrogen at total gas pressure of 1–10 Torr. Organic materials such as methane and methanol were observed. Carbon monoxide was a major product from carbon dioxide. Methane was the dominant organic species produced by the discharge. The concentration of methane increased with discharge voltage, and its volume fraction attained 10–20% of the products containing carbon that came from carbon dioxide. This fraction was also dependent on the mixing ratio of carbon dioxide and hydrogen. We also observed the formation of methanol, though its fraction was low, a few %, compared with methane.     

循环流化床富氧气化实验研究

在循环流化床富氧气化实验台上,通过调节水蒸气流量使气化温度基本稳定在910℃,研究了不同氧气浓度及气化当量比对煤气组分、产气率、冷煤气效率及碳转化率的影响。结果表明,氧气浓度从25%增加至40%时,N2体积分数从48.82%降低至33.83%,H2从21.47%不断增加至27.59%,CH4基本不变;受水蒸气流量影响,氧气浓度高于35%时,CO体积分数降低,CO2体积分数增加;氧气浓度40%时的煤气热值为空气气化煤气热值的1.84倍,产气率随氧气浓度增加从2.35 m3/kg降至2.13 m3/kg,冷煤气效率和碳转化率不断增大;当气化当量比从0.20增加至0.29时,N2体积分数先降低后升高,H2体积分数从24.01%增加到25.46%后基本保持不变,CO和CH4持续减小,CO2不断增加,产气率由1.94 m3/kg升高到2.29 m3/kg;受水蒸气和气化当量比综合影响,冷煤气效率先增大后减小,碳转化率持续增加。     

甲醇水蒸气重整制氢CuO/CeO2-ZrO2/SiC整体催化剂的研究

采用浸渍法和溶胶凝胶法制备了CuO/CeO₂-ZrO₂/SiC整体催化剂，并将其用于甲醇水蒸气重整制氢反应中。结果表明，与CuO/CeO₂-ZrO₂颗粒催化剂相比，CuO/CeO₂-ZrO₂/SiC整体催化剂催化活性较好，产氢速率较快且重整气中CO体积分数较低。进一步探究了涂层涂覆量和CuO负载量对催化性能的影响，结果表明，当CeO₂-ZrO₂复合氧化物涂层涂覆量在15%±1%，CuO负载量为5%±1%时，催化性能较好；当反应温度为340℃，水醇物质的量比为1.2，甲醇水蒸气气体空速为4840 h^-1时，甲醇转化率为86.0%，产氢速率为1490.0 L/（m³·s），重整气中CO体积分数为1.55%。最后通过单因素实验法探究了甲醇水蒸气气体空速、水醇物质的量比和反应温度对反应的影响。结果表明，随着气体空速变大，甲醇转化率下降，产氢速率上升，重整气中CO体积分数下降。随着水醇物质的量比增加，甲醇转化率先上升后下降，产氢速率先上升后下降，重整气中CO体积分数下降。随着反应温度的升高，甲醇转化率、产氢速率和重整气中CO体积分数均上升。     

Ni/TiO2 Catalyst for Partial Oxidation of Methane to Syngas

Ni/TiO₂ catalyst was firstly used for the partial oxidation of methane to produce synthesis gas. The reaction was carried out in a fixed-bed continuous flow quartz reactor at atmospheric pressure. The flow rate was regulated by a mass controller with a space velocity of 1.5×10⁵ h^-1 and a CH₄/O₂ molar ratio of 2/1. Prior to the introduction of feed gas, the Ni/TiO₂ catalyst was activated in flowing H₂ at 700℃ for 30 min. TiO₂ is known to be a poor support for partial oxidation because which can easily result in complete oxidation. But at 700℃, Ni/TiO₂ catalyst exhibited a better performance than Ni/SiO₂ and Ni/ZrO₂. The conversion of methane was 81.5, and the selectivity of hydrogen and carbon monoxide were 93.4 and 89.4 respectively. After 6h of continuous reaction, the conversion of methane descended a little and then remained a steady yield on the whole,but the selectivity of H₂ and CO gradually declined, as far as to a constant. The selectivity of H₂ was always higher than that of CO and the ratio of H₂/CO wouldn't change with the increasing of reaction time.     

Conversion of natural gas to C_2 hydrocarbons through dielectric-barrier discharge plasma catalysis

The experiments are carried out in the system of continuous flow reactors with dielectric-barrier discharge (DBD) for studies on the conversion of natural gas to C2 hydrocarbons through plasma catalysis under the atmosphere pressure and room temperature. The influence of discharge frequency, structure of electrode, discharge voltage, number of electrode, ratio of H2/CH4, flow rate and catalyst on conversion of methane and selectivity of C2 hydrocarbons are investigated. At the same time, the reaction process is investigated. Higher conversion of methane and selectivity of C2 hydrocarbons are achieved and deposited carbons are eliminated by proper choice of parameters. The appropriate operation parameters in dielectric-barrier discharge plasma field are that the supply voltage is 20-40 kV (8.4-40 W), the frequency of power supply is 20 kHz, the structure of (b) electrode is suitable, and the flow of methane is 20-60 ml · min-1. The conversion of methane can reach 45%, the selectivity of C2 hydrocarbons i     

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.     

煤和生物质共气化制备富氢气体的实验研究

在煤处理量为8kg/h的小型流化床反应器上,以富氧空气和水蒸气为气化介质,对煤和生物质共气化制取富氢燃气进行了实验研究。在850℃～1 050℃主要考察了空气当量比、水碳比、生物质比例和生物质种类对燃气组成和气体产率的影响。结果表明,对煤和稻草混合体系,稻草质量比为33%时,空气当量比增加,CO2含量显著增加,H2、CO和CH4含量减少,气体产率增加;水碳比增加,CO2和CH4含量增加,CO和H2含量减小,气体产率先增加后减小;生物质比例增加,CO2、H2和CH4含量增加,CO含量降低,气体产率先增加后减小,当生物质比例小于50%时,可以实现体系的稳定运行。对于三种不同的煤与生物质混合体系,煤与高粱秆共气化所得煤气中H2含量最高,气体产率的顺序为:煤/木屑煤/高粱秆煤/稻草煤。实验中H2在煤气中的体积分数最高可达37.25%,最大产率为0.54m3/kg。     

Reaction parameters influence on the catalytic performance of copper-silica aerogel in the methanol steam reforming

Steam reforming of methanol was carried out on the copper-silica aerogel catalyst.The effects of reaction temperature,feed rate,water to methanol molar ratio and carrier gas flowrate on the H_2 production rate and CO selectivity were investigated.M ethanol conversion was increased considerably in the range of about 240-300,after which it increased at a slightly lower rate.The used feed flowrate,steam to methanol molar ratio and carrier gas flowwere 1.2-9.0 m L/h,1.2-5.0 and 20-80 m L/min,respectively.Reducing the feed flowrate increased the H_2 production rate.It was found that an increase in the water to methanol ratio and decreasing the carrier gas flowrate slightly increases the H2production rate.Increasing the water to methanol ratio causes the lowest temperature in which CO formation was observed to rise,so that for the ratio of 5.0 no CO formation was detected in temperatures lower than 375℃.In all conditions,by approaching the complete conversion,increasing the main product concentration,increasing the temperature and contact time,and decreasing the steam to methanol ratio,the CO selectivity was increased.These results suggested that CO was formed as a secondary product through reverse water-gas shift reaction and did not participate in the methanol steam reforming reaction mechanism.