以类水滑石为前驱体的Cu/ZnO/Al2O3催化剂用于COx加氢合成甲醇：CO在反应混合物中的作用(英文)

近年来,催化CO₂加氢合成甲醇被视为有望解决温室效应和燃料枯竭的有效途径。目前,铜基催化剂因具有较高的反应活性被广泛应用于工业生产。然而,竞争逆水煤气变换反应产生的CO导致甲醇选择性较低,同时副产物水引起Cu发生不可逆烧结,进而降低甲醇产率。众所周知,CO能够调整分子的表面竞争吸附和活性位的氧化还原行为,本工作拟向原料气中掺入具有还原性的CO以抑制逆水煤气变换反应和防止表面氧化中毒。另一方面,通常认为铜基催化的CO₂加氢制甲醇是结构敏感性反应,不同的前驱体能够显著影响催化剂结构和形貌,进而影响催化活性。因此,我们首先通过共沉淀法和蒸氨法制备了含有类水滑石前驱体(CHT-CZA)和复合物前驱体(CNP-CZA)结构的Cu/ZnO/Al₂O₃催化剂。随后,为探究CO掺杂后反应机理,在250°C,5 MPa的反应条件下,含有不同比例CO的原料气中(CO₂:CO:H₂:N₂=x:(24.5_-x):72.5:3)评价两种催...     

老化时间对Cu/ZnO/Al2O3合成甲醇催化剂性能的影响

并流共沉淀法制备了CuO/ZnO/Al2O3催化剂前驱体及催化剂,用XRD、TG－DTG、TPR、N2吸附及加压微反活性评价技术,考察了母料老化时间对催化剂前驱体物相组成及焙烧后物料中CuO－ZnO间的作用和物化性能的影响,提出了催化剂母料物相随老化时间的变化。研究表明,老化时间对催化剂活性的影响是通过改变催化剂比表面积及形成CuO ZnO固溶体的结果。     

加料方式对CuO/ZnO/Al2O3系催化剂前驱体性质的影响

用XRD、TG-DTG、TPR技术研究了不同加料方式对CuO/ZnO/Al2O3系催化剂前驱体物相组成及其结晶情况的影响，用加压微反装置考察了催化剂合成甲醇反应活性。结果表明, 加料方式对Cu2+形成的中间化合物的物相组成及结晶度影响显著,对Zn2+及Al3+的沉淀物相的影响很小。不同加料方式对催化剂前驱体物相组成及催化剂性能的影响主要是形成的初始前驱体中Cu的物相及结晶度不同。正加法主要形成Cu2(OH)3NO3,并流法主要形成无定形Cu2CO3(OH)2,后者与Zn5(CO3)2(OH)6相互作用转化为(Cu,Zn)2CO3(OH)2和（Cu,Zn）5(CO3)2(OH)6，由它们分解形成的CuO-ZnO固溶体是合成甲醇反应的活性相。并流法能最大程度的形成CuO-ZnO固溶体，有利于CuO粒子的细化，其催化活性较好。     

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…     

Cu含量对以水滑石为前驱体的Cu/Co/Mn/Al催化剂高级醇合成性能的影响

A series of Cu/Co/Mn/Al catalysts derived from hydrotalcite precursors with different Cu/Co molar ratios (0, 0.1, 0.5, 1.0, and 2.0) were prepared and used for the synthesis of higher alcohols from syngas. N₂ physical adsorption desorption, inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray diffraction (XRD), scanning electron microscopy (SEM), hydrogen temperature-programmed reduction (H₂-TPR), thermogravimetry (TG), and high-resolution transmission electron microscopy (HRTEM) techniques were employed to investigate the physical and chemical properties of the Cu/Co/Mn/Al catalysts. The results show that the optimum Cu content can increase specific surface area, improve reducibility, and form regular layered structure to provide more uniform distribution of active sites, thereby enhancing catalytic activity and alcohol selectivity. When the Cu/Co molar ratio was 0.5, the yield of alcohol and the alcohol selectivity reached the maximum values of 0.071 g·g^-1·h^-1 and 35.9%, respectively.     

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.     

表面助剂改性对Cu/ZnO/Al2O3甲醇合成催化剂性能的影响

采用共沉淀-后浸渍方法制备了表面助剂改性的Cu/ZnO/Al₂O₃ (CZA)甲醇合成催化剂, 在固定床反应器上以合成气为原料分别考察了三种助剂(Zr、Ba和Mn)对CZA催化剂性能的影响; 以Zr为助剂时反应温度的影响; 并进行了催化稳定性试验. 利用粉末X射线衍射(XRD)、低温氮气吸脱附(N₂-sorption)、氧化亚氮(N₂O)反应吸附技术、X射线光电子能谱(XPS)、氢气程序升温吸脱附(H₂-TPD)、扫描电子显微镜(SEM)和高分辨透射电子显微镜(HR-TEM)技术对催化剂进行了表征.结果显示: 以Zr或Ba作为助剂能够明显提高CZA催化剂耐热前后的甲醇时空收率(STY); Mn的引入降低了CZA催化剂的耐热前活性; Zr的引入降低了CZA催化剂最高活性温度点, 增强了CZA催化剂的催化稳定性; 还原态CZA催化剂表面Cu⁰和ZnO都能吸附活化氢气, Cu⁰与ZnO的强相互作用有利于提高催化剂的性能, 耐热后催化剂性能的降低归因于Cu晶粒的长大. 在实验和表征结果基础上,提出了CZA催化剂上合成气制甲醇的“双向同步催化反应历程”.     

尿素水解均匀沉淀法制Cu/ZnO/Al2O3甲醇合成催化剂

甲醇是富氯液体，可通过水蒸气重整制氢用于燃料电池的氢源，是最有希望成为燃料电池电动汽车的燃料，目前这方面的研究颇受重视。现代甲醇工业是通过合成气在催化剂作用下反应制得的，所用催化剂主要为Cu／ZnO／Al2O3。为了进一步提高催化剂的性能，近年来关于催化剂制备方法的文献发表较多。吴晓晖等考察了草酸盐胶体法制备Cu／ZnO／Al2O3甲醇合成催化剂的性能，洪中山等用凝胶网格共沉淀法制得Cu／ZnO／Al2O3甲醇合成催化剂，郭宪吉等则考察了添加Mn助剂对Cu／ZnO／Al2O3甲醇合成催化剂的影响。     

Cu/ZnO/Al2O3催化剂的共沉淀-蒸氨法制备及其对二氧化碳加氢制甲醇的研究

分别以碳酸铵为沉淀剂采用共沉淀-蒸氨法(CAE)和以碳酸铵(CCA)、碳酸钠(CCS)为沉淀剂采用常规共沉淀法制备了三种Cu/ZnO/Al2O3催化剂,并运用XRD,BET,TPR和N2O滴定技术对催化剂进行了表征.结果表明:采用共沉淀-蒸氨法制备的催化剂具有较小的颗粒尺寸、较大的Cu(0)比表面积;以碳酸铵为沉淀剂常...     

微波辐照促进的甲醇水蒸汽重整制氢Cu/ZnO/Al2O3催化剂

微波介电加热具有高效和节能等特点,近年来利用其独特的“体相加热”效应制备结构特异及性能优越的催化材料在多相催化领域中已引起关注,本文报道微波辐照处理对传统Cu／ZnO／Al2O3催化剂在甲醇水蒸汽重整制氢反应中的促进作用,研究结果表明,微波辐照处理对传统Cu／ZnO／Al2O3催化剂的微结构性质具有调控作用,可大大改善其低温催化活性及制氢选择性。     

Adaptation of Cu/ZnO/Al2O3 to Temperature Change in Methanol Synthesis from CO2 Hydrogenation

The induction behavior in CO2 hydrogenation was studied by varying the reaction temperatureto investigate the adaptation of the Cu/ZnO/Al2O3 catalyst to the temperature change. The resultsindicated that a used catalyst had a tendency to keep the last running state in new reaction conditionsfor MeOH formation, and that this tendency was related to the difference in Cu/Cun+ ratio caused byCO2 and CO produced at different reaction temperatures. However, the reverse water-gas shift reaction(RWGS) induced at four temperatures was completely different from that of methanol synthesis. It impliedthat the two so-called competitive reactions in CO2+H2, RWGS and methanol synthesis, have differentactive centers.     

Adaptation o Cu／ZnO／Al2O3 to Temperature Change in Methanol Synthesis from CO2 Hydrogenation

The induction behavior in CO2 hydrogenation was studied by varying the reaction temperature to investigate the adaptation of the Cu/ZnO/Al2O3 catalyst to the temperature change,The results indicated that a used catalyst had a tendency to keep the last running state in new reaction conditions for MeOH formation,and that this tendency was related to the difference in Cu/Cu^n ration caused by CO2 and CO produced at different reaction temperatures,However,the reverse water-gas shift reaction (BWGS) induced at four temperatures was completely different from that of methanol synthesis,It implied that the two so-called competitive reactions in CO2 H2,RWGS and methanol synthesis,have different, active centers.     

沉淀还原法制备高性能CO2加氢合成甲醇Cu/ZnO/Al2O3催化剂

由铜基催化剂催化CO2+H2合成甲醇是有效利用CO2的潜在途径[1～5]. 但传统的催化剂对该反应的催化活性及选择性均很低[3～5], 因而寻求具有高活性及高选择性的新型催化剂已成为重要研究课题[4,6]. Cu/ZnO系列催化剂的制备方法和助剂对催化剂的性质及CO2加氢合成甲醇的反应性能有显著影响[6～10], 传统的气相还原活化铜基催化剂的过程常伴随强烈的热效应, 导致催化剂活化过程存在耗时长及还原条件难以控制等问题[11]. 本文采用沉淀-还原法, 用KBH4溶液对新鲜制备的碳酸盐共沉淀进行液相化学还原处理, 直接得到高活性及高选择性的还原态Cu/ZnO/Al2O3甲醇合成催化剂, 并可通过改变催化剂表面Cu+/Cu0活性物种的相对比例来改善催化剂的活性及选择性.     

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.     

EXAFS研究合成甲醇催化剂Cu／ZnO／MxOy

有关CO。＋H。合成甲醇催化剂的研究已有许多报道［‘－’j，但目前对活性中心及反应机理的认识仍不～致，其中对活性中心的看法归纳起来有3种：（1）Cll为活性中心“‘；（2）Cll”为活性中心［’j；（3）Cll－CtJ”为活性中心［‘1．研究发现，第三组分（如AI刀。）的加入可防止Cu粒子的烧结［’］，使Cu产生无序及缺陷结构，有利于CO。的吸附、活化［‘j及起到高分散Cu／Zno的稳定剂的作用［’j．由于三组分催化剂结构的多相性和准非晶态性，通常的XRD方法难以明确了解其结构，而EXAFS方法对研究局部有序结构特别有效．本文以Z…     

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     

以类水滑石为前驱体的Cu/Zn/Al/(Zr)/(Y)催化剂制备及其催化CO_2加氢合成甲醇的性能

采用共沉淀法合成了Cu:Zn:Al:Zr:Y原子比分别为2:1:1:0:0、2:1:0.8:0.2:0、2:1:0.8:0:0.2和2:1:0.8:0.1:0.1的Cu/Zn/Al/(Zr)/(Y)类水滑石化合物.将前驱体材料在空气中500°C焙烧后得到复合金属氧化物,并将其用于CO2加氢合成甲醇反应.采用X射线衍射(XRD)、热重(TG)分析、N2吸附、氧化亚氮(N2O)反应吸附、氢气程序升温还原(H2-TPR)和H2/CO2程序升温脱附(H2/CO2-TPD)技术对所制备的样品进行表征.结果表明,Zr和Y的引入使得催化剂BET比表面积大幅增加,金属铜的比表面积和分散度均按以下顺序依次增加:Cu/Zn/AlCu/Zn/Al/ZrCu/Zn/Al/YCu/Zn/Al/Zr/Y,然而,强碱位数目占总碱位数目的比例的变化顺序为:Cu/Zn/AlCu/Zn/Al/YCu/Zn/Al/Zr/YCu/Zn/Al/Zr.活性评价结果揭示CO2转化率取决于金属铜的比表面积,甲醇选择性则随强碱位比例的增加而线性增加.因而,Zr和Y的引入有利于甲醇的合成,Cu/Zn/Al/Zr/Y催化剂上的甲醇收率最高.     

制备方法对超细Cu／ZnO／Al2O3催化剂上CO2＋H2合成甲醇的影响

制备方法对超细Ｃｕ／ＺｎＯ／Ａｌ_２Ｏ_３催化剂上ＣＯ_２＋Ｈ_２合成甲醇的影响张玉龙，王欢，邓景发（复旦大学化学系，上海，２００４３３）关键词超细粒子，合成甲醇，Ｃｕ／ＺｎＯ／Ａｌ_２Ｏ_３催化剂，ＣＯ_２＋Ｈ_２ＣＯ２＋Ｈ２合成甲醇是目前的热门课题［１～...