CO2加氢合成甲醇的超细Cu-ZnO-ZrO2催化剂的表征

采用原位顺磁共振（ＥＰＲ）、原位Ｘ射线光电子能谱（ＸＰＳ）和程序升温还原（ＴＰＲ）等手段,对ＣＯ２加氢合成甲醇用的不同粒度的超细Ｃｕ－ＺｎＯ－ＺｒＯ２催化剂各组分的相互作用进行了研究。结果表明,ＺｒＯ２的加入改变了催化剂的表面结构和配位状态,增加了活性组分的分散度,提高了催化剂的稳定性。实验还发现,催化剂的粒度对各组分的相互作用有着重大的影响,催化剂的粒度较小时,Ｃｕ＾２＋主要以团簇的形式存在,易     

Pd-Cu/ZrO2催化CO2加氢制甲醇的性能

采用溶胶-凝胶法制备了n(Cu):n(Zr)=1:1、1:2、1:4和1:8的Cu/ZrO₂催化剂。 实验结果表明,当n(Cu):n(Zr)=1:4时,催化剂表现出较高的CO₂转化率(8.0%)和甲醇选择性(59.5%),为了增加CO₂的转化率,提高甲醇选择性,在n(Cu):n(Zr)=1:4的催化剂中添加质量分数1%的Pd,采用浸渍法制备了Pd-Cu/ZrO₂催化剂。 在250 ℃、2 MPa、12000 mL/(g·h)和V(H₂):V(CO₂)=3:1的反应条件下,CO₂转化率和CH₃OH收率相比Cu/ZrO₂催化剂(n(Cu):n(Zr)=1:4)分别提高了40.0%和80.9%。 通过X射线衍射仪(XRD)、傅里叶变换红外光谱仪(FT-IR)、N₂吸附-脱附(BET)、X射线光电子能谱仪(XPS)和程序升温还原化学吸附仪(H₂-TPR)等仪器表征证明Pd的添加提高了催化剂的分散性和比表面积。 催化剂中Pd和Cu之间强相互作用,使Cu2p轨道结合能向低处偏移,还原温度的降低,说明Pd-Cu/ZrO₂催化剂还原能力增强,使得CO₂加氢活性提高。     

用于CO2加氢合成甲醇超细CuO-ZnO/SiO2-ZrO2催化剂

用溶胶－凝胶法制备了ＣｕＯ－ＺｎＯ／ＳｉＯ２－ＺｒＯ２复合氧化物催化剂，使用ＩＲ，ＸＲＤ，ＴＥＭ和ＢＥＴ等手段对催化剂的结构及表面性能进行了表征，考察了ＺｒＯ对该体系的表面性质，结构，ＣｕＯ分散状态以及二氧化碳加氢合成甲醇的催化性能的影响。结果表明，该体系催化剂的比表面积大，活性组分分散均匀。     

Cu/Zn/TiO2负载型催化剂上CO2加氢合成甲醇

采用溶胶-凝胶法和浸渍法制备Cu/Zn/TiO2负载型催化剂,研究了不同Cu、Zn负载量对催化剂性能的影响,采用BET、XRD、TPR对催化剂进行了表征.考察了反应温度、压力和催化剂组成对CO2加H2催化合成甲醇的影响.     

ZnO逆修饰小尺寸Cu/SiO2催化剂及其在CO2加氢制甲醇中的应用

Cu-ZnO is broadly used as a catalyst in CO₂ reduction to produce methanol, but fabricating small-sized Cu-ZnO catalysts with strong Cu-ZnO interactions remains a challenge. In this work, a simple, low-cost method is proposed to synthesize small-sized Cu-ZnO/SiO₂ with high activity and controllable Cu-ZnO interactions derived from copper silicate nanotubes. A series of Cu-ZnO/SiO₂ samples with different amounts of ZnO were prepared. The activities of the as-prepared catalysts for methanol synthesis were tested, and the results revealed a volcano relationship with the weight fraction of ZnO. At 523 K, the methanol selectivity increased from 20% to 67% when 14% ZnO was added to the Cu/SiO₂ catalyst, while the conversion of CO₂ increased first and then decreased with the addition of ZnO. The optimum space time yield (STY) of 244 g·kg^-1·h^-1 was obtained on C-SiO₂-7%ZnO at 543 K under 4.5 MPa H₂/CO₂. Furthermore, the synergistic effect of Cu and ZnO was studied by high resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), in situ diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS), and temperature-programmed reduction (TPR) analyses. The HRTEM images showed that the Cu particles come in contact with ZnO more frequently with increased addition of ZnO, indicating that the catalysts with higher ZnO contents have a greater probability of formation of the Cu-ZnO interface, which promotes the catalytical activity of Cu-ZnO/SiO₂. Meanwhile, the HRTEM images, XRD patterns, and TPR results showed that the addition of excess ZnO leads to an increase in the size of the Cu particles, which in turn decreases the total number of active sites and further degrades the activity of the catalysts. The activation energy (E_a) for methanol synthesis and reverse water gas shift (RWGS) was calculated based on the results of the catalytical test. With the addition of ZnO, E_a for methanol synthesis decreased from 72.5 to 34.8 kJ·mol^-1, while that for RWGS increased from 61.3 to 102.7 kJ·mol^-1, illustrating that ZnO promotes the synergistic effect of Cu-ZnO. The results of XPS and in situ DRIFTS showed that the amount of Cu⁺ species decreases with the addition of ZnO, indicating that the Cu-ZnO interface serves as the active site. The Cu surface area and the turnover frequency (TOF) of methanol were calculated based on the H₂-TPR curves. The TOF of methanol on the Cu-ZnO/SiO₂ catalysts at 543 K increased from 1.5 × 10^-3 to 3.9 × 10^-3 s^-1 with the addition of ZnO, which further confirmed the promotion effect of the Cu-ZnO interface on the methanol synthesis. This study provides a method to construct Cu-ZnO interfaces based on copper silicate and to investigate the influence of ZnO on Cu-ZnO/SiO₂ catalysts.     

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.     

CO对CO2加氢合成甲醇的影响

甲醇是重要的有机化工原料，同时它也已被确认为尾气污染少、辛烷值高的汽、柴油接烧的洁净燃料和大功率燃料电池的燃料[1]．随着世界石油贮量的枯竭，甲醇汽车将快速发展，所以CO2加氢合成甲醇具有广阔的应用前景和深远的理论意义．铜基催化剂上CO2加氢主要存在二个竞争反应[2     

助剂对超细CuO－ZnO－SiO_2催化剂性质和CO_2加氢反应性能的影响

研究了９种助剂对用于ＣＯ２加氢反应的超细ＣｕＯ－ＺｎＯ－ＳｉＯ２催化剂性能的影响，并进行了ＸＲＤ和ＴＰＲ表征．结果表明，助剂影响超细催化剂的性质和催化性能，ＴｉＯ２、ＣｅＯ２、ＭｇＯ和Ｌａ２Ｏ３是ＣＯ２加氢合成甲醇的超细ＣｕＯ－ＺｎＯ－ＳｉＯ２催化剂体系的优良助剂．在含有不同助剂的ＣｕＯ－ＺｎＯ－ＳｉＯ２催化剂体系内存在ＣｕＯ和ＺｎＯ晶相，但除ＣｅＯ２以外，其它的助剂都可能以微晶或无定型的形式存在．ＴＰＲ研究表明，添加的助剂除ＣｅＯ２以外，都使超细ＣｕＯ－ＺｎＯ－ＳｉＯ２催化剂的还原温度提高，而且助剂对ＣｕＯ－ＺｎＯ－ＳｉＯ２催化剂活性的影响，按照助剂对ＣｕＯ－ＺｎＯ－ＳｉＯ２催化剂还原温度的影响进行了探讨     

CO2加氢合成甲醇催化反应中CO的作用

研究了铜基催化剂上CO₂加氢合成甲醇反应中掺人CO的作用,结果表明,在原料中添加少量CO,甲醇的选择性提高38%,收率提高25%;TPD-MS和TPSR-MS结果表明,CO能抑制催化剂表面起逆水汽变换作用的活性位对CO₂的吸附,从而提高了CO₂加氢合成甲醇的选抒性.     

在负载铼催化剂上由CO2/H2合成甲醇的研究

CO加H₂合成甲醇的工作已应用于工业化生产,其中多采用锌、铬、铜基催化剂。而CO₂加H₂合成甲醇研究工作尚不很多,其催化剂多数是在CO/H₂制甲醇催化剂基础上发展而来。     

Cu/Zn/Al/Mn催化剂上CO/CO2加氢合成甲醇特性研究

利用共沉淀法制备了四组分的Cu-Zn-Al-Mn和Cu-Zn-Al-Ce催化剂以及三组分的Cu-Zn-Al催化剂。利用组成H2/CO/CO2/N2=66/27/3/4(体积比)的富CO原料气对催化剂进行了活性评价，并研究了温度、压力和空速等反应条件对催化剂活性的影响。结果发现添加适量的锰助剂能显著提高催化剂的活性和热稳定性。利用SEM和XRD方法进行了催化剂的结构和形貌表征，同样表明锰助剂可以起到阻止CuO晶粒长大和促进CuO分散作用。利用富CO2的生物质原料气体积比为H2/CO/CO2/N2=50/25/20/5对Cu-Zn-Al-Mn催化剂进行的评价表明：Cu-Zn-Al-Mn催化剂上CO/CO2加氢合成甲醇的甲醇产率和选择性均有下降，在试验范围内，甲醇产率下降11％～25％，选择性为93％～95％。     

Characterization and performance of Cu/ZnO/Al_2O_3 catalysts prepared via decomposition of M(Cu,Zn)-ammonia complexes under sub-atmospheric pressure for methanol synthesis from H_2 and CO_2

Methanol synthesis from hydrogenation of CO2 is investigated over Cu/ZnO/Al2O3 catalysts prepared by decomposition of M(Cu,Zn)-ammonia complexes (DMAC) at various temperatures.The catalysts were characterized in detail,including X-ray diffraction,N2 adsorption-desorption,N2O chemisorption,temperature-programmed reduction and evolved gas analyses.The influences of DMAC temperature,reaction temperature and specific Cu surface area on catalytic performance are investigated.It is considered that the aurichalcite phase in the precursor plays a key role in improving the physiochemical properties and activities of the final catalysts.The catalyst from rich-aurichalcite precursor exhibits large specific Cu surface area and high space time yield of methanol (212 g/(Lcat·h);T=513 K,p=3MPa,SV=12000 h-1).     

Promoting effect of polyoxyethylene octylphenol ether on Cu/ZnO catalysts for low-temperature methanol synthesis

Cu/ZnO catalysts were prepared by the co-precipitation method with the addition of OP-10 (polyoxyethylene octylphenol ether) and were chemically and structurally characterized by means of XRD, BET, H₂-TPR, CO-TPD and N₂O-titration. The effect of OP-10 addition on the activity of Cu/ZnO for the slurry phase methanol synthesis at 150 °C was evaluated. The results showed that Cu/ZnO prepared with addition of 8% OP-10 (denoted as C8) exhibited the promoted activity for the methanol synthesis. The conversion of CO and the STY (space time yield) of methanol were 42.5% and 74.6% higher than those of Cu/ZnO prepared without addition of OP-10 (denoted as C0), respectively. The precursor of C8 contained more aurichalcite and rosasite, and the concerted effect of Cu-Zn in C8 was found to be stronger than that in C0. Compared with C0, C8 showed smaller particle size, lower reduction temperature and larger BET and Cu surface areas.     

液相还原法制备Cu/Zn/Al/Zr催化剂用于CO2加氢合成甲醇

近年来,由于大气CO2浓度增加引起的温室效应正日益威胁着人类的生存与发展,CO2的捕获与利用是有望解决温室效应和能源危机的有效途径.CO2催化转化为甲醇成为众多研究者关注的焦点,这是因为甲醇不仅是一种重要的基本化工原料,也是一种洁净的绿色燃料和能源载体.Cu基催化剂广泛应用于CO2加氢合成甲醇反应,并表现出良好的催化性能.通常,金属催化剂的制备是采用H2对金属氧化物进行还原.然而,传统的气相还原过程伴随着强烈的热效应,且需要在高温(473-573 K)下进行,会引起表面铜颗粒长大并加速其聚集烧结,使得活性组分利用率下降.近年来,以NaBH4为还原剂的液相还原法逐渐受到人们的重视,该方法操作简单、快捷且条件可控,反应在低温下进行,放出的热量可在液相环境中迅速得到转移,大大抑制了铜颗粒的聚集.因此,液相还原法可制备出高铜分散度、高活性的催化剂.焙烧温度对铜基催化剂结构和催化性能的影响已得到广泛探究,但这仅限于含二价铜物种催化剂,焙烧温度对含多种铜价态催化剂的影响未见报道.由于液相还原法制备的催化剂含有还原态的铜物种(Cu0和Cu+),它们比Cu2+具有更强的流动性,因此在后续的焙烧过程中催化剂更容易发生烧结和聚集.本文采用液相还原法合成了Cu/Zn/Al/Zr催化剂,分别于423,573,723和873 K焙烧后用于CO2加氢合成甲醇反应,考察了焙烧温度对制备的铜基催化剂结构性质和催化性能的影响,并与传统共沉淀法制备的催化剂进行了对比.结果显示,随着焙烧温度升高,铜物种聚集作用增强,金属铜颗粒尺寸增大,873 K时烧结出现显著增强.由于比表面积随焙烧温度升高而减小,高温度焙烧的催化剂具有小的表面碱性位数目.焙烧温度会影响催化剂中铜物种与其它组分的相互作用,进而影响催化剂的还原.随着焙烧温度的升高,催化剂的还原温度逐渐降低,表面Cu+/Cu0的比例先增后减.CO2加氢活性评价显示,液相还原法制备的催化剂具有更高的催化活性,尤其是甲醇选择性;随着焙烧温度升高,催化剂的CO2转化率和甲醇选择性先增后减,CZAZ-573催化剂具有最高活性,且在1000 h长周期活性测试中表现稳定.CO2转化率与催化剂暴露金属铜的比表面积密切相关.相比Cu0,产物甲醇更容易在Cu+表面催化生成,催化剂表面的Cu+/Cu0比与甲醇选择性的变化规律一致.通过调控焙烧温度可得到高Cu比表面积以及高Cu+/Cu0比的催化剂,有利于CO2加氢生成甲醇.     

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…     

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...     

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。     

Cu/ZnO催化糠醛气相加氢制2-甲基呋喃的研究

通过共沉淀法制备一系列铜锌催化剂,用于固定床上糠醛气相加氢制2-甲基呋喃的研究。采用X射线衍射仪(XRD)、N_2吸附-脱附、扫描电子显微镜(SEM)、H_2-程序升温还原(H_2-TPR)、NH_3-程序升温脱附(NH_3-TPD)表征,分析催化剂中Cu0和ZnO在催化反应中的作用。结果表明,Cu~0是糠醛加氢的活性中心,氧化锌的加入减小了催化剂晶粒粒径、增大了催化剂比表面积、利于催化剂还原和增加催化剂表面弱酸性位。当Cu/Zn物质的量比为1∶2时,Cu_1Zn_2催化剂具有适宜氧化还原活性中心及弱酸位数量,对2-甲基呋喃表现出较高的选择性。Cu_1Zn_2催化剂在常压、反应温度为200℃、氢醛物质的量比为4∶1、糠醛体积空速为0.3 h-1条件下,糠醛转化率100.0%,2-甲基呋喃选择性最高为93.6%。反应稳定运行200 h后,糠醛转化率仍为100.0%,2-甲基呋喃选择性为80.0%,糠醇选择性为11.4%。     

CO2加氢合成甲醇Cu/ZrO2催化剂的失活因素

采用低温氮气吸脱附、X射线衍射(XRD)、电镜(TEM)以及热重差热(TG-DSC)等手段,对不同反应时间下Cu/ZrO₂催化剂的物理结构、微观形貌以及积炭情况进行了表征,分析了催化剂的失活原因。结果表明,造成催化剂失活的主要因素是活性组分烧结;其次,表面积炭覆盖其活性中心也造成催化剂活性在一定程度上的降低;而催化剂比表面积对其活性的影响较小。     

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.