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1.
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... 相似文献
3.
采用共沉淀法制备CuZnAlO x(CZA)催化剂,通过浸渍法得到一系列不同硼(B)负载量的yB/CZA(y=0.28%、0.38%、0.73%、0.89%和4.10%,质量分数)催化剂,并将其用于甲醇水蒸气重整制氢反应。此外,为探究催化剂的构效关系,采用ICP、BET、SEM、N 2O化学吸附、TEM、XRD、H 2-TPR和XPS等手段对催化剂进行表征。结果表明,B引入主要影响催化剂的Cu分散性、还原性及Cu-B间相互作用,进而影响甲醇水蒸气重整制氢性能。其中,0.38B/CZA催化剂获得最高催化活性,这与其具有较高的Cu分散性与较强的Cu-B相互作用力有关;在反应温度为250℃,n(H 2O):n(CH 3OH)=3,空速为9000 mL/(g·h)时,CH 3OH转化率达到93%,CO选择性仅有0.3%,且反应102 h后仍未失活。 相似文献
4.
Nano ZrO 2 and MgO-ZrO 2 were prepared by a self-assembly route and were employed as the support for Ni catalysts used in hydrogen production from glycerol reforming in supercritical water (SCW). The reforming experiments were conducted in a tubular fixed-bed flow reactor over a temperature range of 600–800 °C. The influences of process variables such as temperature, contact time, and water to glycerol ratio on hydrogen yield were investigated and the catalysts were charactered by ICP, BET, XRD and SEM. The results showed that high hydrogen yield was obtained from glycerol by reforming in supercritical water over the Ni/MgO-ZrO 2 catalysts in a short contact time. The MgO in the catalyst showed significant promotion effect for hydrogen production likely due to the formation of the alkaline active site. Even when the glycerol feed concentration was up to 45 wt%, glycerol was completely gasified and transfered to the gas products containing hydrogen, carbon dioxide, and methane along with small amounts of carbon monoxide. At a diluted feed concentration of 5 wt%, near theoretical yield of 7 mole of H 2/mol of glycerol could be obtained. 相似文献
5.
采用等体积浸渍法制备了Al 2O 3、CeO 2、TiO 2及MgO负载Ni催化剂,考察了它们对甘油蒸汽重整制氢反应的催化性能。采用X射线衍射、N 2吸附、透射电镜及H 2程序升温还原等方法对催化剂进行了表征。结果表明,载体对Ni催化剂的活性有显著影响。在400 ℃下Ni/CeO 2的催化活性明显好于其他催化剂,活性次序为Ni/CeO 2> Ni/Al 2O 3 > Ni/TiO 2 ~ Ni/MgO。Ni/CeO 2也具有好的稳定性,反应20 h未见活性下降,甘油转化率70%,氢气收率69.2%。这与CeO 2的本性及其与活性组分的相互作用有关。Al 2O 3具有较大的比表面积与孔体积,有利于CO吸附及甲烷化反应的进行,使得Ni/Al 2O 3催化剂在较高温度下具有很高的甘油转化率85.7%,但H 2选择性较差。由于MgO载体与活性组分强的相互作用而生成NiMgO 2固溶体,导致Ni/MgO低温活性差。 相似文献
6.
考察了载体对Ni催化剂乙醇水蒸气重整制氢反应性能的影响。结果表明,Ni/CeO2催化剂具有较好的低温活性和氢气选择性。对Ni担载量和焙烧温度考察发现,400℃焙烧的15%NiCeO2催化剂具有较好的催化性能;继续升高焙烧温度引起NiO和CeO2粒子的显著增大,导致对氢气选择性的降低。较小的Ni和CeO2粒子有利于乙醇水汽重整反应的进行,而大的粒子倾向于乙醇的分解反应。 350℃时,在反应过程中分别添加CO、CO2和CH4的结果表明没有发生CO和CO2甲烷化反应,而发生了一定程度的CH4水汽重整反应。 相似文献
7.
采用等体积浸渍法和共沉淀法制备了Ni催化剂,在固定床反应器上考察了Ni负载量、焙烧温度、反应温度等因素对乙二醇低温重整制氢反应活性和选择性的影响。应用X射线衍射、氮物理吸附、H 2程序升温还原等技术对负载型Ni催化剂进行了表征。结果表明,共沉淀法制备的Ni/CeO 2催化剂具有较小的NiO颗粒与CeO 2载体颗粒粒径,催化活性较高。添加少量氧化钴到Ni/CeO 2催化剂中可使H 2收率达72.6%,EG转化率达93.1%。在CeO 2中添加Al 2O 3能提高负载Ni催化剂的活性,乙二醇转化率达94.0%,H 2收率达67.0%;但添加SiO 2则使其活性明显变差。 相似文献
8.
The steam reforming of glycerol has been studied at 500 and 600 oC using Co/SBA-15 and Co/M/SBA-15(M: Zr, Ce, or La) promoted catalysts. The prepared materials were characterized by inductively coupled plasma atomic emission spectroscopy(ICP-AES), X-ray powder diffraction(XRD), hydrogen temperatureprogramed reduction(H_2-TPR), ammonia temperature-programed desorption(NH_3-TPD), nitrogen physisorption analysis(N_2-BET), transmission electron microscopy(TEM) and thermogravimetric analysis(TGA). The incorporation of promoters like Zr, Ce and La on SBA-15 support and successive Co impregnation leaded to smaller cobalt crystallites improving metaldispersion. Besides, stronger metal-support interactions between Co species and M/SBA-15 supports were observed. Thanks to the incorporation of Zr, La and mainly Ce, promoted catalysts present higher glycerol conversion than Co/SBA-15 along 5 h of time on stream. Besides, at 600 oC, Co/M/SBA-15(M: Zr, Ce, or La) catalysts produce higher hydrogen amounts than Co/SBA-15. 相似文献
9.
The steam reforming of four bio-oil model compounds(acetic acid,ethanol,acetone and phenol) was investigated over Ni-based catalysts supported on Al2O3 modified by Mg,Ce or Co in this paper.The activation process can improve the catalytic activity with the change of high-valence Ni(Ni2O3,NiO) to low-valence Ni(Ni,NiO).Among these catalysts after activation,the Ce-Ni/Co catalyst showed the best catalytic activity for the steam reforming of all the four model compounds.After long-term experiment at 700°C and the S/C ratio of 9,the Ce-Ni/Co catalyst still maintained excellent stability for the steam reforming of the simulated bio-oil(mixed by the four compounds with the equal masses).With CaO calcinated from calcium acetate as CO2 sorbent,the catalytic steam reforming experiment combined with continuous in situ CO2 adsorption was performed.With the comparison of the case without the adding of CO2 sorbent,the hydrogen concentration was dramatically improved from 74.8% to 92.3%,with the CO2 concentration obviously decreased from 19.90% to 1.88%. 相似文献
10.
采用浸渍法制备出γ-Al2O3、SiO2和γ-Al2O3·SiO2负载的Ni-La催化剂,用XRD、TPR、XPS、H2-TPD、NH3-TPD和TG等手段对催化剂进行了表征,结果表明:这3种负载型催化剂中的活性组分Ni的分散度较高,La3 氧化物高度分散于载体表面.在温度为400℃、水醇比为4.0和液体空速为8.0 mL h-1 g-1cat的条件下,催化剂进行稳定性测试,结果表明:γ-Al2O3·SiO2负载的Ni-La催化剂在整个100 h稳定性测试过程中,氢气的选择性保持在67.0%左右,且稳定性良好.对经过稳定性测试后的Ni-La催化剂进行热重分析,发现γ-Al2O3·SiO2负载的Ni-La催化剂具有较少的积碳量,仅仅是0.86 g C·g-1cat,其中石墨碳占42.81%. 相似文献
12.
Selective production of hydrogen by oxidative steam reforming of methanol (OSRM) was studied over Cu/SiO 2 catalyst using fixed bed flow reactor. Textural and structural properties of the catalyst were analyzed by various instrumental methods. TPR analysis illustrates that the reduction temperature peak was observed between 510?K and 532?K at various copper loadings and calcination temperatures and the peaks shifted to higher temperature with increasing copper loading and calcination temperature. The XRD and XPS analysis demonstrates that the copper existed in different oxidation states at different conditions: Cu 2O, Cu 0, CuO and Cu(OH) 2 in uncalcined sample; CuO in calcined sample: Cu 2O and metallic Cu after reduction at 600?K and Cu 0 and CuO after catalytic test. TEM analysis reveals that at various copper loadings, the copper particle size is in the range between 3.0?nm and 3.8?nm. The Cu particle size after catalytic test increased from 3.6 to 4.8?nm, which is due to the formation of oxides of copper as evidenced from XRD and XPS analysis. The catalytic performance at various Cu loadings shows that with increasing Cu loading from 4.7 to 17.3?wt%, the activity increases and thereafter it decreases. Effect of calcination shows that the sample calcined at 673?K exhibited high activity. The O 2/CH 3OH and H 2O/CH 3OH molar ratios play important role in reaction rate and product distribution. The optimum molar ratios of O 2/CH 3OH and H 2O/CH 3OH are 0.25 and 0.1, respectively. When the reaction temperature varied from 473 to 548?K, the methanol conversion and H 2 production rate are in the range of 21.9–97.5% and 1.2–300.9?mmol?kg ?1?s ?1, respectively. The CO selectivity is negligible at these temperatures. Under the optimum conditions (17.3?wt%, Cu/SiO 2; calcination temperature 673?K; 0.25 O 2/CH 3OH molar ratio, 0.5 H 2O/CH 3OH molar ratio and reaction temperature 548?K), the maximum hydrogen yield obtained was 2.45?mol of hydrogen per mole of methanol. The time on stream stability test showed that the Cu/SiO 2 catalyst is quite stable for 48?h. 相似文献
13.
New highly conductive, active and stable Ni steam reforming catalysts were prepared through a method consisting of the calcination of a hydrotalcite-like compound electrodeposited in a single step on FeCrAlloy foams. 相似文献
14.
Hydrogen production by catalytic reforming of simulated hot coke oven gas (HCOG) with toluene as a model tar compound was investigated in a fixed bed reactor over Ni/Mg(Al)O catalysts. The catalysts were prepared by a homogeneous precipitation method using urea hydrolysis and characterized by ICP, BET, XRD, TPR, TEM and TG. XRD showed that the hydrotalcite type precursor after calcination formed (Ni, Mg)Al 2O 4 spinel and Ni-Mg-O solid solution structure. TPR results suggested that the increase in Ni/Mg molar ratio gave rise to the decrease in the reduction temperature of Ni 2+ to Ni 0 on Ni/Mg(Al)O catalysts. The reaction results indicated that toluene and CH 4 could completely be converted to H 2 and CO in the catalytic reforming of the simulated HCOG under atmospheric pressure and the amount of H 2 in the reaction effluent gas was about 4 times more than that in original HCOG. The catalysts with lower Ni/Mg molar ratio showed better catalytic activity and resistance to coking, which may become promising catalysts in the catalytic reforming of HCOG. 相似文献
15.
In this study, the main purpose is to develop low-cost catalysts with high activity and stability for high quality syngas production via steam reforming of biomass tar in biomass gasification process. The calcined waste scallop shell(CS) supported copper(Cu) catalysts are prepared for steam reforming of biomass tar. The prepared Cu supported on CS catalysts exhibit higher catalytic activity than those on commercial CaO and Al_2O_3. Characterization results indicate that Cu/CS has a strong interaction between Cu and CaO in CS support, resulting in the formation of calcium copper oxide phase which could stabilize Cu species and provide new active sites for the tar reforming. In addition, the strong basicity of CS support and other inorganic elements contained in CS support could enhance the activity of Cu/CS. The addition of a small amount of Co is found to be able to stabilize the catalytic activity of Cu/CS catalysts,making them reusable after regeneration without any loss of their activities. 相似文献
16.
用浸渍-热分解-氢还原法(IHDHR)和浸渍-热分解法(IHD)分别制备了两种纳米尺寸的Ni/Y2O3催化剂,并应用X-光电子能谱、X-射线衍射、BET比表面测试等分析技术对两种催化剂的结构进行了表征和比较。采用固定床反应器对两种催化剂的催化性能进行实验测试。结果表明,氢气预还原与否对该纳米Ni/Y2O3催化剂的催化性能有一定的影响,经过氢气预还原的催化剂对低温乙醇水蒸气重整反应表现出较高的活性和稳定性,250?℃时,乙醇的转化率达到81.9%;320 ℃时,乙醇的转化率达到95.3%,对氢气的选择性为53.6%。对经过氢预还原的Ni/Y2O3催化剂进行了60 h的稳定性测试。 相似文献
17.
用水热法制备微米尺寸CeO2花状微球粉体,并通过浸渍/热分解法在该粉体上担载纳米尺寸的NiO颗粒,制得催化剂NiO/CeO2。对催化剂进行了XRD、SEM、XES和BET物性表征。经固定床反应器对催化剂的催化性能进行测试。装载1.0 g催化剂,液体处理量0.05 mL/min。结果表明,该方法合成的催化剂NiO/CeO2对低温乙醇水蒸气重整反应表现出较高的活性和稳定性。同时通过微量Cr、Zn、Cu的加入在低温区抑制了CO、CH4的生成,提高了H2的产率和催化剂的抗积炭能力。该催化剂连续稳定性测试达到2 000 h;进行反复起动稳定性测试12次后,未表现出失活特征。 相似文献
18.
采用等体积浸渍的方式,在全硅Beta分子筛载体上担载Cu、Ni活性组分,制备出一系列xCuyNi-ABZ多功能乙醇水蒸气重整制氢催化剂。通过XRD、TEM、SEM-EDX以及XPS等多种表征手段,研究催化剂的结构特性、活性组分含量等因素对催化性能的影响,依据反应产物分布,揭示其作用机理。结果表明,以Beta分子筛为载体可促使活性组分以纳米颗粒的形式高度分散于载体表面,并且存在较强的载体-金属作用力。与传统SiO_2为载体催化剂相比,2.5Cu2.5Ni-ABZ催化剂具备良好的乙醇水蒸气重整催化性能,当反应温度为450℃,实现100%的乙醇转化率和67.23%的H_2选择性,且副产物CO(4.14%)、CH_4(5.65%)含量相对较低。这可归因于Cu和Ni活性组分间的高效协同作用,Cu具有良好的乙醇脱氢性能,生成反应中间体乙醛;在反应过程中,乙醛的重整和分解是两个受温度影响的竞争反应,Ni组分利用其较强的C-C键断裂能力,随温度的升高,乙醛重整反应占主导作用,生成目标产物H_2。通过对反应后样品分析表明,2.5Cu2.5Ni-ABZ催化剂具备良好的抗烧结和抗积炭催化性能。 相似文献
19.
In this article, nanocrystalline γ-alumina with high surface area (309 m2 g?1) and mesoporous structure with an average pore size of 4.3 nm was synthesized and employed as a carrier for the synthesis of Ni catalysts in steam reforming of methane. The results revealed that the metal–support interaction decreased by increasing the nickel loading and led to the movement of the Tmax of reduction temperature to lower temperatures. The results demonstrated that the synthesized catalysts exhibited high CH4 conversion and stability and increasing the nickel loading up to 10 wt% improved the CH4 conversion. The results revealed that the incorporation of MgO in nickel catalyst improved the resistance of the catalyst against carbon deposition and also enhanced the catalytic activity and the 10%Ni–5%MgO–Al2O3 catalyst exhibited high stability during 60 h. The high stability of the promoted catalyst was related to the high basicity of the catalyst. 相似文献
20.
Hydrogen production by catalytic reforming of simulated hot coke oven gas (HCOG) with toluene as a model tar compound was investigated in a fixed bed reactor over Ni/Mg(Al)O catalysts. The catalysts were prepared by a homogeneous precipitation method using urea hydrolysis and characterized by ICP,BET, XRD, TPR, TEM and TG. XRD showed that the hydrotalcite type precursor after calcination formed (Ni,Mg)Al2O4 spinel and Ni-Mg-O solid solution structure. TPR results suggested that the increase in Ni/Mg molar ratio gave rise to the decrease in the reduction temperature of Ni2+ to Ni0 on Ni/Mg(Al)O catalysts. The reaction results indicated that toluene and CH4 could completely be converted to H2 and CO in the catalytic reforming of the simulated HCOG under atmospheric pressure and the amount of H2 in the reaction effluent gas was about 4 times more than that in original HCOG. The catalysts with lower Ni/Mg molar ratio showed better catalytic activity and resistance to ceking, which may become promising catalysts in the catalytic reforming of HCOG. 相似文献
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