Cu/La2O3/Al2O3催化剂上甲醇水蒸气重整制氢反应

研究以并流共沉淀法制备Cu/La2 O3 /Al2 O3 系列催化剂催化甲醇水蒸气重整制氢反应过程 ,考察了La2 O3含量、反应温度、水醇比、液体空速 (WHSV)等因素对催化剂活性的影响。结果表明 :催化剂表现出较好的低温活性、高氢气选择性和稳定性。La2 O3 质量分数为 15 % ,在 2 5 0℃反应时 ,催化剂活性表现最佳 ,甲醇摩尔转化率为94 .5 % ,氢气选择性为 10 0 % ,CO摩尔分数为 1.0 5× 10 -7。     

Cu-Mn/γ-Al2O3催化剂上二甲醚水蒸气重整制氢

采用草酸盐胶态共沉淀-机械混合法制备了一系列Cu-Mn/γ-Al2O3催化剂,考察了CuMn摩尔比及助剂La、Al、Fe、Zn等对Cu-Mn/γ-Al2O3催化剂上二甲醚水蒸气重整制氢的催化性能的影响,并结合热重-差热扫描量热分析(TG-DSC)、N2吸附-脱附(BET)、X射线衍射(XRD)、H2程序升温还原(H2-TPR)等表征手段研究了助剂La的添加对Cu-Mn/γ-Al2O3催化剂微观结构的影响.研究表明:当Cu-Mn/γ-Al2O3催化剂中Cu/Mn摩尔比为1/2时,催化剂具有较高的初始活性;添加La、Al、Fe、Zn等助剂均不同程度地提高了Cu-Mn/γ-Al2O3催化剂的稳定性,其提高顺序为:La>Al>Fe>Zn;适量La的添加可以起到隔离和分散铜的作用,能阻碍活性组分的聚集长大,有助于活性组分细化,并增加表面高分散CuO的量,同时增强Cu-Mn以及金属铜和载体之间的相互作用,防止铜的团聚,从而提高催化剂的活性及稳定性.     

CuO-ZnO/γ-Al_2O_3催化剂分解N_2O的性能研究

以CuO为活性组分、ZnO为助剂、γ-Al_2O_3为载体,采用等体积浸渍法制备了一系列CuOZnO/γ-Al_2O_3型直接分解N_2O催化剂,考察了活性组分和助剂含量、烟气工况对催化剂分解N_2O活性的影响,开展了催化剂的稳定性测试,并对催化剂进行了表征.结果表明:CuO质量分数为15%时催化剂的分解活性最高,ZnO助剂的掺入可以明显提高催化剂对N_2O的转化率,烟气中O2和H_2O的存在则会抑制催化剂的活性.15Cu-30Zn/γ-Al_2O_3催化剂在650℃、空速为21 000h~(-1)、含O_2和H_2O的烟气条件下,在100h的连续测试中,N_2O转化率稳定维持在90%以上,具有良好的高温抗氧和抗水蒸气抑制性能以及稳定性.     

催化剂Ni/CeO2-ZrO2催化生物油水溶性组分重整制氢

利用固定床反应器对一系列自制催化剂Ni/CeO2-ZrO2和商业镍基催化剂Z417在生物油水溶性组分重整制氢反应中的催化性能进行考察,研究了活性金属Ni的负载量、反应温度、水油比对催化剂活性的影响.实验结果表明:Ni负载量为12wt％的催化剂Ni/CeO2-ZrO2在生物油水溶性组分重整制氢反应中表现出最佳催化活性,当反应温度为800C和水油比为4.9时,氢产率达到最大值67.8％,氢的选择性较高,为61.8％.     

基于Ni/Al2O3整体式催化剂的生物质气化合成气甲烷化研究

以生物质气化模拟合成气H2/CO/N2为原料气,以堇青石蜂窝陶瓷为基体制备Ni/Al2O3整体式催化剂,通过扫描电镜(SEM)、比表面积(BET)、X射线衍射(XRD)、程序升温反应法(TPR)、热重分析(TG)等表征分析手段,考察催化剂制备方法(浸渍法和溶胶-凝胶法)、温度(250~550℃)及空速GHSV(6000~14000 mL/(g·h))对催化剂甲烷化性能的影响。结果表明:浸渍法制备的Ni/Al2O3催化剂(DIP-Ni/Al2O3)与溶胶-凝胶法制备的Ni/Al2O3催化剂(SGNi/Al2O3)相比,前者甲烷化性能较好。在H2、CO、N2物质的量之比为3∶1∶1且空速为10000 mL/(g·h)条件下,浸渍法制备的Ni/Al2O3催化剂在400℃时甲烷化性能最佳,且该条件下CO转化率为98.6%,CH4选择性为90.9%。当H2、CO、N2物质的量之比为3∶1∶1且温度为400℃时,在实验空速范围内,浸渍法制备的Ni/Al2O3催化剂CO转化率和CH4选择性均基本稳定在90%,甲烷化性能较好。     

废甲醇催化剂综合利用技术进展

甲醇的产能在所有化工产品中仅次于乙烯和合成氨,每年产生的废甲醇催化剂数量巨大。合成甲醇催化剂经历了锌铬高压催化剂、铜基催化剂、合金催化剂及其他非铜基催化剂3个发展阶段,目前在工业中应用的主要为铜基催化剂,此类废催化剂的回收主要围绕Cu和Zn的分离及回收展开。回收工艺可分为酸浸、氨浸和酸浸-电解工艺。废催化剂预处理的关键是在800～1000℃进行焙烧,其目的一是去除有机物,二是脱硫,三是使其中的氧化铝或Cr2O3转化为酸难溶的晶型,四是使金属铜或氧化亚铜转化为氧化铜。预处理后的废催化剂可通过H2SO4酸浸-Zn还原法回收活性ZnO和CuSO4·5H2O,通过H2SO4酸浸-SO32-还原法回收活性ZnO和CuCl,通过HNO3酸浸-Zn还原法制备硝酸盐,通过H2SO4-NHO3联合酸浸法制备胆矾和铝铵矾;通过NH4＋铬合氨浸回收CuCl和活性ZnO,通过NH4＋-NH3复合氨浸回收Cu2O和ZnO;通过H2SO4酸浸-电解回收单质Cu。此外,还可以被制成微肥或作为脱硫剂使用。     

乙醇选择催化还原降低柴油机NOx排放的应用研究

以Ag/Al2O3作为催化剂、乙醇为还原剂的选择性催化还原(SCR)技术被认为是最有潜力降低稀燃NOx的技术之一。开发了基于开环控制的还原剂空气辅助喷射系统;在发动机台架上对乙醇选择性催化还原Ag/Al2O3催化剂的特性进行了性能评价试验;对与Ag/Al2O3组合使用的Cu/TiO2和Pt/TiO2氧化催化剂进行了匹配优选;对集成NOx排气后处理的整机进行了ESC工况测试试验;最后将集成的排气后处理系统装在一辆客车上,并进行了道路实车试验。台架试验结果表明:新鲜Ag/Al2O3催化剂具有很高的NOx转化效率,老化一段时间后NOx转化效率有所降低;与Ag/Al2O3 Cu/TiO2组合催化剂相比,Ag/Al2O3 Cu/TiO2 Pt/TiO2组合催化剂具有更好的NOx转化效率,并能抑制THC和CO排放升高;使用NOx集成排气后处理系统后,发动机在欧ⅢESC工况下,NOx从原机的13.06 g/(kW.h)降为4.63 g/(kW.h),整机的NOx、THC、CO排放都低于欧Ⅲ限值。道路实车试验表明,Ag/Al2O3催化剂需要进一步降低催化剂的起燃温度,以适应柴油车实际运行中低温变工况的需要。     

CuO/γ-Al2 O3干法烟气脱硫

采用自制的CuO／γ—Al2O3烟气脱硫剂，在固定床流动反应器上进行模拟烟气脱硫试验，定量研究了不同组分样品的脱硫活性，分析了载铜量、SO2浓度、空间速度、反应温度等对脱硫效果的影响．结果表明，CuO在载体上分布的阈值为0．47mg／m^2，当CuO分布低于阈值时，在脱硫温度400℃、空间速度11200h^-1，S／Cu摩尔比低于理论值1的情况下，其脱硫效率可高达95％以上．     

绒面ZnO:Al(ZAO)透明导电薄膜的制备

利用中频交流磁控溅射方法，采用氧化锌铝(98wt％ZnO 2wt％A12O3)陶瓷靶材制备了绒面ZAO(ZnO：Al)薄膜，考察了所制备的绒面ZAO薄膜与绒面SnO2：F薄膜在绒度、粗糙度、表面形貌以及电学性质的差异，利用原子力显徽镜对薄膜表面形貌进行了分析并计算出薄膜表面粗糙度，利用紫外可见分光光度计和电阻测试仪测量了薄膜的光学、电学特性。结果表明：所制备的绒面ZAO薄膜具有与绒面SnO2：F薄膜相比拟的各种性能，在非晶硅太阳电池中具有潜在的应用前景。     

Ni-CeO_2/γ-Al_2O_3催化甲苯水蒸气重整的实验研究

以单质镍为活性组分、CeO2为助剂、γ-Al2O3为载体制备了Ni-CeO2/γ-Al2O3催化剂,以甲苯为生物质气化焦油模型化合物,在固定床反应器上进行催化水蒸气重整实验,考察了反应温度、水/碳摩尔比(S/C)和CeO2负载量对甲苯转化率、产气组成及积碳生成的影响。结果表明,Ni-CeO2/γ-Al2O3催化剂具有较好的催化活性和抗积碳能力;在反应温度为850℃,S/C为3时,使用Ni-CeO2(3%)/γ-Al2O3催化剂,甲苯转化率可以达到90.4%,经反应后的催化剂含碳量仅为0.42%。     

Hydrogen production by steam reforming of methanol in a micro-channel reactor coated with Cu/ZnO/ZrO2/Al2O3 catalyst

Hydrogen production by steam reforming of methanol is studied over Cu/Zn-based catalysts (Cu/ZnO, Cu/ZnO/Al₂O₃, Cu/ZnO/ZrO₂/Al₂O₃). Cu/Zn-based catalysts are derived from hydrotalcite-like precursors prepared by a co-precipitation method. The catalysts are characterized by N₂O chemisorption, XRD, and BET surface area measurements. ZrO₂ added to the Cu/Zn-based catalyst enhances copper dispersion on the catalyst surface. Among the catalysts tested, Cu/ZnO/ZrO₂/Al₂O₃ exhibits the highest methanol conversion and the lowest CO concentration in the outlet gas. A micro-channel reactor coated with a Cu/ZnO/ZrO₂/Al₂O₃ catalyst in the presence of an undercoated Al₂O₃ buffer layer exhibits higher methanol conversion and lower CO concentration in the outlet gas than in the absence of an undercoated Al₂O₃ buffer layer. The micro-channel reactor with a undercoated Al₂O₃ buffer layer produces large amounts of hydrogen compared with one without a buffer layer. The undercoated Al₂O₃ buffer layer enhances the adhesion between catalysts and micro-channel walls, which leads to improvement in reactor performance.     

Steam reforming of methane over Ni catalyst in micro-channel reactor

A comprehensive study on the catalytic performance of Ni catalyst to implement millisecond steam reforming of methane (SRM) reaction in micro-channel reactors was conducted in this work. A new method to manufacture the metal-ceramics complex substrate as catalyst support was presented, that is, a layer of nano-particles, α-Al₂O₃, was thermally sprayed on a metallic substrate, usually FeCrAlloy. Ni or Rh catalyst was then impregnated on the substrate, forming firm and active catalyst coatings. The fall-off rate of the catalyst can be neglected after the plates experienced the high-temperature SRM reaction, showing the reliability in long-term use and the excellent catalytic performance for SRM reaction in micro-channel reactors. In comparison with the expensive Rh catalyst, Ni also showed wonderful performance to catalyze the SRM reaction in micro-reactors within milliseconds. Using the appropriate reactor design, CH₄ conversion reached above 90% when the residence time was as short as 32 ms for catalyst loading of 6.8 g/m². When the residence time was longer than 100 ms, CH₄ conversion was above 98%. Besides, catalyst deactivation was not detected for 500 h on stream with S/C ratio of 3.0, and for 12 h with S/C of 1.0 as well. Extensive characterizations on these Ni catalyst plates using XRD, SEM, TEM and XPS demonstrated that Ni catalysts prepared in this work did not show any sign of deactivation after being used in the micro-channel system under high-temperature operation.     

Influence of CuO/ZnO/Al2O3 wash-coating slurries on the steam reforming reaction of methanol

A micro-channel reactor for methanol steam reforming is a candidate to supply hydrogen on-site to fuel cells. Micro-channel beds wash-coated with poor quality slurry formulations lead to poorer performance than packed beds using pellet catalysts. This study explored the morphology, X-ray Diffraction (XRD) spectrum, BET surface area and activity of wash-coating catalyst layers from a series of catalyst slurries. All catalyst slurries were prepared from the commercial MDC-3 catalyst. Hydrogen production using wash-coating catalyst layers was performed under packed bed conditions. The results reveal that the solubility level of the MDC-3 catalyst during the slurry preparation process affected the activity of methanol steam reforming. It is difficult to reconstruct the original fine structure, as the MDC-3 catalyst had a higher solubility status after slurry preparation. The volume of the micro-channel catalyst bed was approximately 0.3 cm³. It can supply hydrogen to fuel cells that can produce approximately 8 W with 80% H₂ utilization and 60% fuel cell efficiency.     

S-scheme assisted Cu2O/ZnO flower-shaped heterojunction catalyst for breakthrough hydrogen evolution by water splitting

Zinc and copper are considered as excellent metals for oxidation and reducibility, respectively. This study aims to obtain a redox-coupled composite semiconductor, wherein oxides of Zn and Cu were obtained and junctioned, for application as a photocatalyst in hydrogen production. To create a large number of activated sites on the catalyst's surface, the morphologies of the catalysts were controlled and several angular parts were formed. During the junction process, Cu₂O and ZnO particles were controlled in cubic and starfish shapes, respectively, and the structure of the junctioned Cu₂O/ZnO composite was similar to that of a chrysanthemum flower. Kubelka–Munk and Mott–Schottky plots demonstrated that ZnO and Cu₂O have band gaps of 3.2 and 1.9 eV, respectively, and they are n- and p-type semiconductors, respectively. The TRPL and IMVS, as well as the photocurrent density and IMPS, confirmed that the recombination between electrons and holes in the junctioned Cu₂O/ZnO particles was very slow, and effective charge separation was achieved. As a result, the amount of hydrogen generated from the junction catalyst was significantly higher than that generated from the single catalysts. In particular, the accumulated amount of evolved hydrogen after 10 h in the 2Cu₂O/1ZnO junction catalyst was 2089.5 μmol. Results obtained from spin-trapping ESR experiments suggest that the charge-transfer mechanism in the redox-coupled 2Cu₂O/1ZnO junction catalyst follows the S-scheme with a stronger reducing power.     

Methane steam reforming: Kinetics and modeling over coating catalyst in micro-channel reactor

Kinetics of methane steam reforming for hydrogen production has been studied through experiment in a micro-channel reactor over coating catalyst. The catalyst coating prepared by cold spray on stainless steel substrate is based on a mixture of Ni–Al oxides which is normally employed in industry for methane primary steam reforming. Two kinetic laws namely parallel as well as inverse models have been derived at atmospheric pressure, and power law type kinetics have been established using non-linear least squares optimization. With the above kinetics, simulation study has been carried out to find out temperature distribution in the micro-channel over coating catalyst at two different types of boundary conditions. The results show a quite different “cold spot” character and reactants, products distribution character in the reaction channel due to its own distinct heat and mass transfer features. The kinetics and simulation study results can be applied in aid of micro-channel reactor design, and suggestion has been proposed for catalytic coating preparation and optimization.     

Highly efficient Zr-substituted catalysts CuZnAl1−xZrxO used for hydrogen production via dimethyl ether steam reforming

A series of CuZnAl_1−xZr_xO catalysts with different weight ratios of ZrO₂/(Al₂O₃ + ZrO₂) were prepared by co-precipitation and used for catalytic production of hydrogen via the route of dimethyl ether steam reforming (DME SR). Multiple techniques such as N₂ physisorption, X-ray diffraction (XRD), temperature-programmed reduction by hydrogen (H₂-TPR), N₂O chemisorption and X-ray absorption fine structure (XAFS, including XANES and EXAFS) were employed for catalyst characterization. It is found that the relative contents of Al and Zr greatly influence the catalytic performance of the catalysts including DME conversion, H₂ yield and CO/CO₂ selectivity. The catalyst CuZnAl_0.8Zr_0.2O shows not only the highest DME conversion but also the highest H₂ yield in the whole reaction temperature region of 300–425 °C. Poorly crystallized CuO and ZnO phases were identified by XRD for CuZnAl_1−xZr_xO catalysts. The crystallinity of them increases with the decrease of Al content. The partial substitution of Al by Zr improves both the reducibility and the dispersion of copper species as revealed by H₂-TPR results. The N₂O chemisorption and Cu K-edge XAFS results conformably indicate that the Cu species in CuZnAl_0.8Zr_0.2O possesses the highest dispersion. In addition, after used in DME SR reaction, the catalyst CuZnAl_0.8Zr_0.2O possesses the highest Cu⁺/Cu⁰ ratio, as calculated by Cu K-edge XANES fitting. The lowest CO selectivity during DME SR over this catalyst is highly related to the highest Cu⁺/Cu⁰ ratio.     

Effect of Cu loading on Cu/ZnO water–gas shift catalysts for shut-down/start-up operation

Cu/ZnO catalysts with Cu loadings of 44–5 wt% were prepared by coprecipitation and evaluated in temperature-dependant and shut-down/start-up water–gas shift (WGS) reactions using realistic reformate. These catalysts had similar Cu crystallite sizes, and the metallic Cu surface area and surface Cu content increased with the Cu loading. In temperature-dependent reactions, the CO conversion on the 25wt%Cu/ZnO catalyst slightly exceeded that on 44wt%Cu/ZnO. In shut-down/start-up operation, which is imperative for mobile and residential fuel cell applications, the catalysts with Cu loadings higher than 5 wt% suffered slight activity loss. Among them, the 15wt%Cu/ZnO catalyst deactivated the most reluctantly. As a result, after three shut-down/start-up cycles the CO conversion on 15wt%Cu/ZnO, 25wt%Cu/ZnO, and 44wt%Cu/ZnO became comparable. These results demonstrate the feasibility to lower the Cu loading without degrading the WGS performance of the Cu/ZnO catalyst in shut-down/start-up operation, which will guarantee the operation safety when the catalyst will be operated unattended for domestic small-scale fuel cell applications. Unexpectedly, the CO conversion was doubled on 5wt%Cu/ZnO after one shut-down/start-up cycle, which is interpreted as the redispersion of Cu nanoparticles based on transmission electron microscopy (TEM) and temperature-programmed reduction (TPR).     

Investigation of synthesized Fe2O3 and CuO–Fe2O3 for pure hydrogen production by chemical-loop reforming of methanol in a micro-channel reactor

Production of pure hydrogen from methanol was investigated by the chemical looping method in the presence of 0.1CuO–Fe2O3 and Fe2O3 at 350 °C in a micro-channel reactor. The x-ray diffraction and atomic absorption spectroscopy analysis confirmed the formation phases and the values of Fe2O3 and CuO.Considering the formation of coke due to methanol conversion reactions and as a result, the production of CO together with H2, the time of the reduction step (2 hours-11 min) has been controlled to minimize coke deposition. The results show that coke deposition was prevented by optimizing the reduction time to 11 min for both samples and the pure H2 flow was generated for fuel cell applications, which was 231.1% higher for the 0.1CuO–Fe2O3. Although the results show that improving the Cu content and the reduction temperature increases the reduction degree of the catalyst and yield of H2, but coke deposition cannot be prevented.     

Reforming of methanol to produce hydrogen over the Au/ZnO catalyst

Gold particle with an average size of d_Au ~ 4 nm was dispersed on ZnO by the deposition precipitation method. The fabricated Au/ZnO catalyst was used to produce hydrogen from reforming of methanol. Four reforming reactions, i.e., decomposition of methanol (DM), steam reforming of methanol (SRM), partial oxidation of methanol (POM) and oxidative steam reforming of methanol (OSRM), were evaluated in a fixed bed reactor. A reaction temperature of T_R > 623 K was required for catalyzing reactions of DM and SRM. Interestingly, high methanol conversion (C_MeOH > 90%) was found from reforming reactions of POM and OSRM at an amazing low temperature of T_R < 473 K. Besides, a presentable hydrogen yield (R_H2 ~ 2.4) and a low selectivity of CO (S_CO ~ 1%) were simultaneously attained from the reaction of OSRM. Therefore, the low temperature OSRM reaction over the Au/ZnO catalyst is suggested as a friendly reforming process for on-board production of hydrogen.     

Enhanced water-gas shift reaction performance of MOF-derived Cu/CeO2 catalysts for hydrogen purification

The water-gas shift (WGS) reaction has received renewed interest because it is one of the key reactions for producing hydrogen and renewable energy in contemporary technologies like fuel cells and bio-refineries. Catalysts play an important role in WGS reaction for achieving high CO conversion and hydrogen generation activity. Thus, the performance and stability of catalysts are vital for the WGS reaction. In the present work, the CuCe metal-organic framework (MOF) is used as a template to derive the nanostructured Cu/CeO₂ catalyst. The influence of CuCe-MOF templated approach on the WGS activity of Cu/CeO₂ has been established. Different Cu doping levels had a significant impact on WGS activity. Amongst, the Ce_0.8Cu_0.2O₂ (Cu2Ce) catalyst had a highest CO conversion (96%). The long-term stability tests further prove that the Cu2Ce catalyst had maintained high CO conversion over 100 h reaction time. XRD and TEM results suggest that different loadings of Cu content have a distinct impact on the dispersion of Cu and the catalytic properties. N₂O chemisorption results suggest that 20 wt.% of Cu loading resulted in high Cu dispersion (52%) compared to other loadings. The H₂-temperature programmed reduction (TPR) revealed that the superior catalytic activity of Cu2Ce catalyst could be attributed to the strong reducibility (i.e. lower redox temperature) derived from CuCe-MOF template. It further suggests well-dispersed copper oxide species at low Cu loadings and crystalline copper oxide species at high Cu loadings. This work emphasizes the significance of Cu/CeO₂ catalysts with exceptional catalytic activity and stability for the WGS process with MOF-precursor.