甲醇水蒸气重整制氢Cu/ZnO/Al2O3催化剂的研究

燃料电池作为一种无污染、高效率的能源引起世界各大汽车公司的广泛关注[1,2]。用于燃料电池的燃料目前研究较多的是氢气,用氢气作燃料存在储存、安全、运输等问题,寻求合适贮氢方法或替代燃料,实现车载制氢是解决问题的办法。甲醇作为液体燃料,因具有高能量密度,低碳含量,以及运输和贮存等优势成为车载制氢的理想燃料,甲醇水蒸气重整制氢反应也成为研究的热点[3～10]。车载制氢对甲醇水蒸气重整制氢反应体系中的产氢速率,氢气和CO的含量都有一定的要求。尤其对CO含量要求更为苛刻,因CO易引起燃料电池阳极催化剂中毒[11,12]。因此,开…     

凝胶网格共沉淀法制备Cu/ZnO/Al2O3合成甲醇催化剂

随着工业污染和温室效应等环境问题及能源危机和资源危机的日益严重,以二氧化碳为原料催化合成甲醇等化学品已成为C;化工研究中最重要的前沿课题之一[‘－’j．CO。加氢合成甲醇的研究虽已有     

ZnO或K_2O助剂对Cu/SiO_2-Al_2O_3催化剂上丙三醇和苯胺气相催化合成3-甲基吲哚反应的促进作用

研究了ZnO或K2O助剂对Cu/SiO2-Al2O3上丙三醇和苯胺气相催化合成3-甲基吲哚反应的促进作用,采用X射线衍射、透射电子显微镜、H2程序升温还原、NH3程序升温脱附以及热重-差热分析等技术对催化剂进行了表征.结果表明,适量ZnO或K2O的加入可明显提高催化剂的活性、选择性和稳定性,其中以ZnO的促进作用更强.ZnO不仅能增强活性组分Cu与SiO2-Al2O3载体之间的相互作用、提高Cu在载体表面的分散度,而且可有效抑制反应过程中Cu粒子的烧结;而K2O的加入却降低了Cu分散度,但也对反应过程中Cu粒子的烧结有所抑制.ZnO或K2O的加入均不同程度地增加了Cu/SiO2-Al2O3催化剂的弱酸中心数量,从而促进3-甲基吲哚的生成.     

AHTD法铜基催化剂合成甲醇的研究——Ⅰ.催化剂的催化性能

自从ICI低压、低温甲醇合成过程取代高压过程以来,人们对该过程所使用的Cu/ZnO/Al_2O_3或Cu/ZnO/Cr_2O_3催化剂有极大的兴趣。Herman、Klier等人已证明这种低压、低温下的活性应归属于Cu-ZnO间的相互作用,在相同的条件下,单纯的铜或氧化锌的活性几乎可以忽略不计,而氧化铝或氧化铬主要起结构助剂的作用。由此可见,控制适宜的Cu-ZnO间的相互作用是提高甲醇合成活性的关键,因此,如何才能产生这种适宜的相互作用就成了人们极为重视的研究课题。到目前为止,人们普遍采用沉淀法制备铜基甲醇合成催化剂,试图通过改变各种制备条件来开发更好的     

New process of low-temperature methanol synthesis from CO/CO_2/H_2 based on dual-catalysis

A new process of low-temperature methanol synthesis from CO/CO2/H2 based on dual-catalysis has been developed. Some alcohols, especially 2-alcohol, were found to have high catalytic promoting effect on the synthesis of methanol from CO hydrogenation. At 443 K and 5 MPa, the synthesis of methanol could process high effectively, resulting from the synergic catalysis of Cu/ZnO solid catalyst and 2-alcohol solvent catalyst. The primary results showed that when 2-butanol was used as reaction solvent, the one-pass average yield and the selectivity of methanol, in 40 h continuous reaction at temperature as low as 443 K and 5 MPa, were high up to 46.51% and 98.94% respectively. The catalytic activity was stable and the reaction temperature was 80 K or so lower than that in current industry synthesis process. This new process hopefully will become a practical method for methanol synthesis at low temperature.     

New process of low-temperature methanol synthesis from CO/CO2/H2 based on dual-catalysis

A new process of low-temperature methanol synthesis from CO/CO₂/H₂ based on dual-catalysis has been developed. Some alcohols, especially 2-alcohol, were found to have high catalytic promoting effect on the synthesis of methanol from CO hydrogenation. At 443 K and 5 MPa, the synthesis of methanol could process high effectively, resulting from the synergic catalysis of Cu/ZnO solid catalyst and 2-alcohol solvent catalyst. The primary results showed that when 2-butanol was used as reaction solvent, the one-pass average yield and the selectivity of methanol, in 40 h continuous reaction at temperature as low as 443 K and 5 MPa, were high up to 46.51% and 98.94% respectively. The catalytic activity was stable and the reaction temperature was 80 K or so lower than that in current industry synthesis process. This new process hopefully will become a practical method for methanol synthesis at low temperature.     

Ca对Cu/B/Ca/Al_2O_3结构及其催化醋酸仲丁酯加氢反应性能的影响

以γ-Al2O3为载体采用分步浸渍法制备了不同Ca O含量的Cu/B/Ca/Al2O3催化剂,并测试了其催化醋酸仲丁酯加氢制备仲丁醇的反应性能.Ca O含量对催化剂的结构、氧化还原性能、酸碱性和金属铜分散度的影响分别采用XRD、H2-TPR、XPS、NH3-TPD和N2O-H2氧化还原滴定实验进行分析.结果表明,适量氧化钙的引入对金属铜的分散度无明显影响,过量的氧化钙(20%)降低催化剂的比表面积,进而导致金属铜分散度的降低;但钙作为给电子助剂能够补偿电子从铜向氧化硼之间的迁移,提高催化剂的酯加氢活性.同时,氧化钙的引入能够有效消除Cu/B/Ca/Al2O3催化剂表面的强酸性位点并降低催化剂的酸量,减少醋酸仲丁酯加氢反应中酸催化副产物以及催化剂表面积碳的生成.     

二氧化碳加氢直接合成二甲醚催化剂的研究Ⅱ铜/锌对复合催化剂结构和性能的影响

制备了具有不同铜/锌(氧化物质量比)的CuO-ZnO-Al2O3/HZSM-5复合型催化剂,考察了其对CO2加氢直接合成二甲醚的催化性能,并采用H2-TPR、XRD、BET、IR及XPS等表征方法对催化剂的物化性质进行了表征。结果表明,催化剂中的铜/锌对催化剂的反应性能、晶相结构以及还原难易程度等均有一定程度的影响。在所制备的四种不同铜/锌的复合催化剂中,以Cu/Zn＝1/2的催化剂反应性能最为理想,虽然它们的还原峰位置和比表面积相差不大,但在反映催化剂各组分间相互作用的IR谱图中则表现出较明显的差别。XPS结果表明,活性组分铜以Cu+和Cu0两种形态存在,支持Cu+和Cu0共同组成合成甲醇活性中心的观点。     

氧化铈气凝胶担载氧化铜催化剂上的一氧化碳氧化

 以一氧化碳氧化为探针反应,考察了氧化铈气凝胶担载氧化铜催化剂的催化活性,研究了催化剂中氧化铜的含量、载体及催化剂的焙烧温度对催化剂活性的影响．结果表明,氧化铈气凝胶担载的氧化铜催化剂对一氧化碳氧化反应呈现出高催化活性,适当温度下焙烧载体及催化剂有利于提高催化剂的催化活性;随着催化剂中氧化铜含量的增加,一氧化碳完全转化的温度降低,但当w（CuO）＞12％时,过量的氧化铜以体相形式而不是以高分散形式存在,对催化剂活性的影响很小．     

Vapor phase synthesis of N-butylaniline over copper-based catalysts

Cu-based catalysts, such as Cu/SiO2, Cu/γ-Al2O3 and Cu/SiO2-Al2O3, for the vapor phase synthesis of N-butylaniline from aniline and 1-butanol were investigated and the catalysts were characterized by BET, H2-TPR, XRD and NH3-TPD techniques. The results indicated that the dispersion of copper on support was greatly influenced by the interaction between Cu and the support. Copper-based catalyst with larger amounts of acidic sites did not favor the synthesis of N-butylaniline because more by-products were prod...     

添加表面活性剂两步沉淀法制备甲醇催化剂

采用添加表面活性剂两步沉淀法制备了具有高表面铜相对浓度的超细甲醇合成催化剂。以组成为H2/CO/CO2/N2=66/27/3/4(体积比）的原料气对催化剂进行了活性评价。结果表明,该催化剂比传统并流沉淀法制备的铜基催化剂活性提高47.9%,比两步沉淀法和添加表面活性剂并流沉淀法制备的铜基催化剂活性分别提高9.3%和16.8%。利用SEM、XRD及XPS方法对催化剂的结构、形貌和表面金属组成进行了表征。     

CeO_2改性Cu/Zn-Al水滑石衍生催化剂对甲醇水蒸气重整制氢性能的影响

采用原位合成法在γ-Al2O3表面合成了锌铝水滑石,再采用顺次浸渍法制备了Ce/Cu/Zn-Al催化材料;将其应用于甲醇水蒸气重整制氢,探讨了Ce含量对Cu/Zn-Al催化剂催化性能的影响.催化剂表征结果表明,CeO_2的引入改善了活性组分铜的分散度、铜的比表面积以及催化剂的氧化还原性质,进而提高了催化剂的催化活性和产氢率.当Ce含量为4%时,催化剂活性最佳,在250℃时,甲醇转化率达到100%,CO摩尔分数为0.39%,与Cu/Zn-Al催化剂相比,甲醇转化率提高了近40%.     

无表面活性剂条件下一锅法制备金属/氧化锌复合材料用于催化二氧化碳加氢制甲醇反应

Catalytic hydrogenation of CO₂ to methanol is an important chemical process owing to its contribution in alleviating the impacts of the greenhouse effect and in realizing the requirement for renewable energy sources. Owing to their excellent synergic functionalities and unique optoelectronic as well as catalytic properties, transition metal/ZnO (M/ZnO) nanocomposites have been widely used as catalysts for this reaction in recent years. Development of size-controlled synthesis of metal/oxide complexes is highly desirable. Further, because it is extremely difficult to achieve the strong-metal-support-interaction (SMSI) effect when the M/ZnO nanocomposites are prepared via physical methods, the use of chemical methods is more favorable for the fabrication of multi-component catalysts. However, because of the requirement for an extra H₂ reduction step to obtain the active metallic phase (M) and surfactants to control the size of nanoparticles, most M/ZnO nanocomposites undergo two- or multi-step synthesis, which is disadvantageous for the stable catalytic performance of the M/ZnO nanocomposites. In this work, we demonstrate facile one-pot synthesis of M/ZnO (M = Pd, Au, Ag, and Cu) nanocomposites in refluxed ethylene glycol as a solvent, without using any surfactants. During the synthesis process, Pd and ZnO species can stabilize each other from further aggregation by reducing their individual surface energies, thereby achieving size control of particles. Besides, NaHCO₃ serves as a size-control tool for Pd nanoparticles by adjusting the alkaline conditions. Ethylene glycol serves as a mild reducing agent and solvent owing to its capacity to reduce Pd ions to generate Pd crystals. The nucleation and growth of Pd particles are achieved by thermal reduction, while the ZnO nanocrystals are formed by thermal decomposition of Zn(OAc)₂. X-ray diffraction patterns of the M/ZnO and ZnO were analyzed to study the phase of the nanocomposites, and the results show that no impurity phase was detected. Transmission electron microscopy (TEM) was used to study the morphology and structural properties. In addition, X-ray photoelectron spectroscopy analysis was performed to further confirm the formation of M/ZnO hybrid materials, and the results confirm SMSI between Pd and ZnO. Inductively coupled plasma mass spectrometry was used to check the actual elemental compositions, and the results show that the detected atomic ratios of Pd/Zn were consistent with the values in the theoretical recipe. To investigate the effects of the Pd/Zn molar ratios and the added amount of NaHCO₃ on Pd size, the average sizes of Pd particles were calculated, and the results were confirmed by TEM observation. The Cu/ZnO/Al₂O₃ composite is a widely known catalyst for hydrogenation of CO₂ to methanol, and other M/ZnO composites are also catalytic for this reaction. Therefore, different M/ZnO hybrids were further studied as catalysts for hydrogenation of CO₂ to methanol, among which Pd/ZnO (1 : 9) demonstrated the best performance (30% CO₂ conversion, 69% methanol selectivity, and 421.9 g_methanol·(kg catalyst·h)^-1 at 240 ℃ and 5 MPa. The outstanding catalytic performance may be explained by the following two factors: first, Pd is a good catalyst for the dissociation of H₂ to give active H atoms, and second, SMSI between Pd and ZnO favors the formation of surface oxygen vacancies on ZnO. Moreover, most M/ZnO composites exhibit excellent performance in methanol selectivity, especially the Au/ZnO catalyst, which has the highest methanol selectivity (82%) despite having the lowest CO₂ conversion. Hopefully, this work would provide a simple route for synthesis of M/ZnO nanocomposites with clean surfaces for catalysis.     

不同改性组分对Cu-ZnO基催化剂低温甲醇合成性能的影响

通过共沉淀法制备了Al、Zr和Ce改性的Cu-ZnO基低温甲醇合成催化剂,采用氮气物理吸附、H2-TPR、CO2-TPD、N2O滴定、XRD和TEM等技术对其进行了表征,并考察了改性组分和煅烧温度对其在170℃下合成气制甲醇催化性能的影响。结果表明,经Zr改性的Cu-ZnO基催化剂,其低温甲醇合成性能较好;随着煅烧温度的降低,Cu在催化剂表面的分散度逐渐变大、颗粒逐渐变小,所得到的催化剂其活性也较高;其中,未经煅烧的Cu-ZnO/ZrO2催化剂的活性最佳,其甲醇时空产率为106.02 g/(kg·h),选择性达87.04%。     

NaBH4处理LaCuZnX(X=Zr、Al、Zr+Al)(类)钙钛矿型催化剂及其CO2加氢合成甲醇性能的研究

采用共沉淀法分别制备了不同F-T组分(Fe、Co、Ni)改性的KCuZrO_2催化剂,并用于催化CO加氢合成异丁醇。通过BET、XRD、TEM、XPS、H_2-TPR、CO-TPD以及in-situ DRIFTS对催化剂进行了表征。结果显示,F-T组分的加入促进了乙醇和丙醇的形成,但是对异丁醇选择性影响不同。结果表明,Fe促进了催化剂中各组分的分散,活性组分Cu在催化剂表面发生了富集,提高了H_2/CO活化吸附;另外,KFeCuZrO_2的催化剂表面含有较多的C_1物种,有利于乙醇和丙醇进一步发生β-加成反应得到异丁醇,而Co和Ni改性的催化剂上缺少足够的C_1物种,因此,异丁醇的选择性并未明显增加。Co的引入对催化剂结构以及Cu的分散影响不大,但是Co改性后催化剂性能有所下降,其原因是催化剂发生了失活;Ni添加后催化剂比表面积有所减小,且催化剂表面Cu/Zr物质的量比也降低到0.19,催化剂粒径增大,Cu-Zr之间相互作用减弱,异丁醇选择性降低。     

甲醇水蒸气重整制氢的高效碳纳米管改性Cu/ZnO/Al2O3催化剂

以碳纳米管为助剂,制备用于甲醇水蒸气重整制氢的新型高效Cu/ZnO/Al₂O₃催化剂,并与传统Cu/ZnO/Al₂O₃催化剂在相同条件下的催化性能进行了比较.结果表明,添加适量碳纳米管可显著提高催化剂的低温催化活性和选择性,在大幅度提高产氢速率的同时有效降低了重整产气中CO的含量.SEM和XRD分析证实适量碳纳米管的添加有效促进了Cu/ZnO/Al₂O₃催化剂结构特性的改善,有利于活性铜物种的分散,从而显著提高了催化剂的低温催化性能.     

Pd-基金属-酸-碱多功能催化剂的制备及其丙酮一步法合成MIBK性能研究

甲基异丁基酮 (MIBK) 是一种重要的化学品, 广泛应用于涂料以及有机合成领域, 下游产品包括特种涂料溶剂、高品质脱蜡溶剂和高性能橡胶防老剂等. 近年来随国民经济的快速发展, 甲基异丁基酮的年需求量与价格逐年上升, 应用领域也不断拓宽. 因此, 开展 MIBK 绿色合成工艺的研究对提高原子经济性、打破国际技术壁垒以及满足国内市场需求具有重要意义. 目前生产 MIBK 最绿色、高效的生产方法是丙酮一步法, 包括缩合、脱水以及加氢等一系列反应过程, 该工艺顺利实施的关键在于所使用的催化剂. 根据丙酮一步法合成 MIBK 反应特点, 所用催化剂表面必须具备多种催化活性中 心, 从而保证缩合、脱水以及加氢反应的顺利进行, 实现从反应物到产物的高效转化. 因此, 高活性和高选择性多功能催化剂的制备是提高 MIBK 生产效率的有效途径.本文采用浸渍法将具有加氢活性的贵金属 Pd 负载在表面具有丰富酸性位点或碱性位点的固体酸或固体碱氧化物载体上, 制备了 Pd/MOx(M = Ti, Ce, Al, Si, La, Ca和Mg) 双功能催化剂, 并用于丙酮一步法合成 MIBK 反应中. 结果表明, Pd基金属-酸/碱双功能催化剂均可以催化该连串反应的进行, 其性能高于 Pd 基金属-酸双功能催化剂, 其中 Pd/MgO 催化剂上丙酮转化率为30.67%, MIBK 产率可达27.61%. 构效关系研究显示, 催化剂表面酸性位点和碱性位点对于该连串反应的各反应步骤催化性能有所不同, 其中碱性位点有利于丙酮缩合反应, 而酸性位点有利于二丙酮醇脱水反应, 且强路易斯碱性中心位点可以更好的催化缩合反应的进行, 同时中强度路易斯酸性中心位点具有最佳的催化脱水反应的能力. 此外, 表面具有最强路易斯碱性中心位点 Pd/La2O3催化剂并未表现出最高的MIBK产率, 说明在丙酮一步法合成MIBK反应中, Pd基双功能催化剂表面各位点间的协同对其催化性能具有重要的影响.本文进一步采用水热法和沉淀沉积法制备了系列MgTiOx、MgAlOx和CaTiOx二元复合氧化物 (MMO) 以及 CaMgAlOx和 TiMgAlOx三元MMO, 并以其为载体, 通过浸渍焙烧还原制备 Pd 基多功能催化剂, 并用于丙酮一步法合成MIBK反应中,发现Pd/MgAl-MMO多功能催化剂具有最高的催化活性及 MIBK 产率. 对其表面多功能位点数量进行调变, 并通过 XRD、CO2-TPD、NH3-TPD、吡啶红外、CO2红外和HRTEM等进行表征, 结果表明, 经过450 ℃焙烧酸碱中心摩尔量比为0.4的0.1%Pd/Mg3Al-MMO多功能协同催化剂三种催化活性中心位点协同作用最佳, 其丙酮转化率为38.20%, MIBK产率可达31.63%. Pd/Mg3AlMMO多功能协同催化剂三种活性位点接近性研究表明, 在多功能催化剂中分离酸中心活性位点、碱中心活性位点以及加氢活性位点后, 获得的双功能催化剂产率均明显下降, 说明Pd/Mg3Al-MMO多功能催化剂在三种活性位点相互接近时才能更好催化反应的进行. 根据多功能催化剂构效关系研究结果, 对各催化活性中心的密度及分布进行调控, 结果显示, 通过沉淀沉积法制备的Pd/Mg3Al-MMO催化剂性能进一步提高, 丙酮转化率为42.11%, 产率高达37.20%.     

高效甲醇水蒸气重整制氢的SBA-15改性的Cu/ZnO/Al2O3催化剂

以介孔SBA-15为结构助剂, 制备出用于甲醇水蒸气重整制氢的新型高效氧化硅掺杂的Cu/ZnO/Al₂O₃催化剂, 并与传统Cu/ZnO/Al₂O₃催化剂在相同条件下的催化性能进行了比较. 结果表明, 添加适量介孔SBA-15可显著提高催化剂的催化活性和选择性, 在大幅度提高甲醇转化率的同时有效降低了重整产气中CO的含量. 原位XRD分析证实适量介孔SBA-15的添加对传统Cu/ZnO/Al₂O₃催化剂的微结构性质可产生重要的调控作用, 从而大大改善其催化活性和制氢选择性.     

探究Cu/ZnO相互作用对CO2加氢制甲醇反应性能的影响

Using renewable green hydrogen and carbon dioxide (CO₂) to produce methanol is one of the fundamental ways to reduce CO₂ emissions in the future, and research and development related to catalysts for efficient and stable methanol synthesis is one of the key factors in determining the entire synthesis process. Metal nanoparticles stabilized on a support are frequently employed to catalyze the methanol synthesis reaction. Metal-support interactions (MSIs) in these supported catalysts can play a significant role in catalysis. Tuning the MSI is an effective strategy to modulate the activity, selectivity, and stability of heterogeneous catalysts. Numerous studies have been conducted on this topic; however, a systematic understanding of the role of various strengths of MSI is lacking. Herein, three Cu/ZnO-SiO₂ catalysts with different strengths of MSI, namely, normal precipitation Cu/ZnO-SiO₂ (Nor-CZS), co-precipitation Cu/ZnO-SiO₂ (Co-CZS), and reverse precipitation Cu/ZnO-SiO₂ (Re-CZS), were successfully prepared to determine the role of such interactions in the hydrogenation of CO₂ to methanol. The results of temperature-programmed reduction (H₂-TPR) and X-ray photoelectron spectroscopy (XPS) characterization illustrated that the MSI of the catalysts was considerably affected by the precipitation sequence. Fourier transform infrared reflection spectroscopy (FT-IR) results indicated that the Cu species existed as CuO in all cases and that copper phyllosilicate was absent (except for strong Cu-SiO₂ interaction). Transmission electron microscopy (TEM), X-ray diffraction (XRD), and N₂O chemical titration results revealed that strong interactions between the Cu and Zn species would promote the dispersion of Cu species, thereby leading to a higher CO₂ conversion rate and improved catalytic stability. As expected, the Re-CZS catalyst exhibited the highest activity with 12.4% CO₂ conversion, followed by the Co-CZS catalyst (12.1%), and the Nor-CZS catalyst (9.8%). After the same reaction time, the normalized CO₂ conversion of the three catalysts decreased in the following order: Re-CZS (75%) > Co-CZS (70%) > Nor-CZS (65%). Notably, the methanol selectivity of the Re-CZS catalyst was found to level off after a prolonged period, in contrast to that of Co-CZS and Nor-CZS. Investigation of the structural evolution of the catalyst with time on stream revealed that the high methanol selectivity of the catalyst was caused by the reconstruction of the catalyst, which was induced by the strong MSI between the Cu and Zn species, and the migration of ZnO onto Cu species, which caused an enlargement of the Cu/ZnO interface. This work offers an alternative strategy for the rational and optimized design of efficient catalysts.     

CaO对Cu-ZnO-ZrO_2催化CO_2加H_2合成甲醇性能影响

用CaO作为改性助剂,采用并流共沉淀法制备了CuO∶ZnO∶ZrO_2为5∶4∶1(物质的量比),CaO添加量为0、1%、2%、4%、8%、16%(摩尔分数)的六组催化剂。用X射线衍射(XRD)、微商热重(TG-DTG)、傅里叶红外(FT-IR)、N2吸附脱附(BET)、X射线光电子能谱(XPS)、氢气程序升温还原(H_2-TPR)、CO_2程序升温脱附(CO_2-TPD)、NH_3程序升温脱附(NH_3-TPD)对催化剂进行了表征。用自制固定床评价了催化剂活性。结果表明,添加CaO后,催化剂路易斯酸性和表面碱性增强;催化剂母体中高温碳酸盐含量增加,热稳定性增强,CuO颗粒粒径变小,Cu-Zn协同作用增强,Cu比表面积增大,分散性变好。催化剂活性受到表面酸碱性、铜比表面积、Cu-Zn协同作用和铜分散性共同影响。当CaO为2%时,铜比表面积为79.3 m2/g、铜分散度为34.8%、CO_2转化率为24.55%、甲醇选择性为19.01%、甲醇收率为0.044 g/(gcat·h),催化剂活性最好。过量CaO占据催化剂孔道和覆盖表面活性位,使催化剂路易斯酸性和表面碱性过强,CuO与H_2有效接触减少,CO_2难以脱附,催化活性下降。因此,适量CaO(2%)添加可促进CO_2加氢反应合成甲醇。