甲醇合成催化剂的工艺参数优化及反应机理探讨

引用本文

杨盼盼, 邱正璞, 张雪冰, 张凡, 缪平, 张玉龙, 孙琦. 甲醇合成催化剂的工艺参数优化及反应机理探讨[J]. 工业催化, 2019,27(2): 67-71.
Yang Panpan, Qiu Zhengpu, Zhang Xuebing, Zhang Fan, Miao Ping, Zhang Yulong, Sun Qi. Process parameter optimization and reaction mechanism investigation of a methanol-synthesis catalyst[J]. Industrial Catalysis, 2019,27(2): 67-71. 复制到剪切板

DOI:10.3969/j.issn.1008-1143.2019.02.010
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甲醇合成催化剂的工艺参数优化及反应机理探讨

杨盼盼, 邱正璞, 张雪冰, 张凡, 缪平, 张玉龙^*, 孙琦

北京低碳清洁能源研究院,北京 102211

通讯联系人:张玉龙,“千人计划”专家,教授级高级工程师,主要从事石油化工、煤炭化工的催化过程以及环境催化方面的研究。

作者简介:杨盼盼,男,博士。

收稿日期: 2018-08-28

摘要

对自主研制的甲醇合成催化剂进行工艺参数优化,同时根据实验结果对合成气条件下甲醇合成的反应机理进行探讨。实验采用16通道反应器,考察反应温度和接触时间对合成甲醇反应速率的影响,确定适宜的催化剂工艺条件。结果表明,在较长接触时间下,随着温度的升高,CO转化率、H₂转化率和甲醇相对含量先升高后降低,CO₂转化率降低。在较低温度下,CO₂转化率随接触时间延长基本不变,表明甲醇中碳元素主要来自于CO,而CO₂浓度处于水汽变换反应与加氢形成甲醇反应之间的平衡状态。

关键词: 有机化学工程; 甲醇合成; 工艺条件; 反应机理; CO₂作用

中图分类号:TQ223.12⁺1;TQ426.94 文献标志码:A 文章编号:1008-1143(2019)02-0067-05

Process parameter optimization and reaction mechanism investigation of a methanol-synthesis catalyst

Yang Panpan, Qiu Zhengpu, Zhang Xuebing, Zhang Fan, Miao Ping, Zhang Yulong^*, Sun Qi

National Institute of Clean-and-Low-Carbon Energy,Beijing 102211,China

Abstract

The process parameters of a self-designed methanol-synthesis catalyst were optimized and reaction mechanisms involved were investigated.The effect of reaction temperature and contact time on reaction rate was studied in reactor with 16 channels,and the suitable process conditions were obtained.Results showed that with high contact time,conversions of CO and H₂,and relative content of CH₃OH increased and then decreased when reaction temperature increased,while CO₂ conversion decreased gradually.Under low temperature,CO₂ conversion was basically unchanged with the increase of contact time,which indicated that carbon in CH₃OH was generally from CO,while CO₂ concentration was in equilibrium formed by water-gas shift reaction and CO₂ hydrogenation to methanol.

Keyword: organic chemical engineering; methanol synthesis; process conditions; reaction mechanism; function of CO₂

文章图片

我国煤炭资源丰富, 随着社会对生态环境的日益重视, 煤炭的清洁利用受到越来越多关注。作为一条洁净煤炭利用途径, 煤炭气化及其下游的合成气合成工业吸引了众多学者探索研究。甲醇是一种重要的化工原料、清洁的液体燃料和有潜力的氢气载体。以煤炭气化获得的合成气生产甲醇, 再经甲醇转化为其他依赖石油化工的产品是一条有前景的煤代替油技术路线。工业上用合成气生产甲醇一般采用Cu/ZnO/Al₂O₃催化剂, 在(5~10) MPa和(230~280) ℃条件下进行。目前, 国内市场上大型甲醇生产装置一般采用国外催化剂, 如Kataclo51-9催化剂和MK121催化剂^[1]。自20世纪90年代以来, 国内学者对铜基甲醇合成催化剂进行了多方面研究^{[2, 3, 4, 5, 6, 7, 8, 9, 10]}, 推动了国产甲醇合成催化剂的工业应用。

催化剂的工艺参数优化是催化剂开发到实际工业应用的必要基础数据, 可靠的工艺参数数据有助于催化剂性能的改进及反应操作条件的优化。甲醇合成的反应机理, 如甲醇的直接碳源和加氢过程中的中间产物, 现在仍然有争议^{[11, 12, 13]}。本工作在接近工业原料组成的合成气条件下, 对一种自主研制的合成甲醇催化剂进行工艺参数优化的实验, 考察反应温度和接触时间对合成甲醇反应速率的影响, 同时根据反应过程中各组分的变化情况对合成甲醇的反应机理进行探讨。

1 实验部分

1.1 实验设计

实验采用德国HTE公司16通道微型多管组合式反应装置, 如图1所示。

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	图1 16通道微型多管组合式反应器简图Figure 1 Diagram of high throughput micro-reactor

该装置通过毛细管分流系统, 将一路原料气体均匀分流成16路, 分配到16根管式反应器中, 各反应管内原料气体流速相同, 组分具有很好的一致性。实验压力为4 MPa, 反应温度为(190~260) ℃, 在催化剂装填量为0.8 g时的空速为8 000 h^-1。实验在230 ℃通过逐步增加流速、同时增加催化剂装填量保持空速不变的方式消除外扩散作用的影响, 确定合适的流速。设计的原料气组成为:x(CO)=13%, x(CO₂)=1.2%, x(H₂)=80%, x(Ar)=5.8%, 气体由北京氦普北分气体工业有限公司提供。

通过改变催化剂装填量调节空速, 催化剂装填情况如图1所示。为保证数据准确性, 催化剂装填量为0.3 g、0.4 g、0.5 g、0.6 g、0.7 g和0.8 g的实验分别使用两根反应管, 催化剂装填量为0.2 g的实验使用3根反应管, 其中, 6^#反应管未添加催化剂, 而是填充同粒度石英砂, 用于在线检测原料气体组成。催化剂粒径为(60~100)目, 装填时采用同粒度石英砂与催化剂相互掺混。在230 ℃通过逐步增加催化剂目数的方式考察内扩散作用的影响, 确定合适的催化剂粒径。

催化剂还原后, 通入的原料气在催化剂作用下发生反应, 反应后气体包括甲醇进入到气相色谱仪分析气体组成。通过加热带加热稳定气体产物温度在120 ℃。实验选择8个停留温度点190 ℃、200 ℃、210 ℃、220 ℃、230 ℃、240 ℃、250 ℃和260 ℃, 在每个温度点, GC分析系统轮流对每一个反应管出口处的气体样品取样并进行检测, 每根反应管轮流重复取样检测6次。

1.2 实验数据处理

实验数据处理包括实时原料气体组成的确定、CO、H₂和CO₂转化率的计算、甲醇产率计算以及CO和CO₂转化速率计算。

(1) 实时原料气体组成。通过对6^#反应管出口处气体样品检测分析, 并对多次取样结果求平均值, 获得实时原料气体组成为:x(H₂)=79.82%, x(CO)=12.68%, x(CO₂)=1.29%, x(Ar)= 6.21%。

(2) CO、H₂和CO₂转化率计算。以Ar为标准气体计算CO、H₂和CO₂转化率:

$x_{i} = \frac{y_{i, 0} - \frac{y_{i} y_{Ar, 0}}{y_{Ar}}}{y_{i, 0}} \times 100 %$

式中, x_i为CO、H₂或CO₂的转化率; y_{i, 0}为原料气体中CO、H₂、CO₂或Ar物质的量分数; y_i为出口气体产物中CO、H₂、CO₂或Ar物质的量分数。

(3) 甲醇相对含量计算。以Ar为标准气体, 对出口气体产物中甲醇相对物质的量分数进行计算:

x_m= $\frac{y_{m} y_{Ar, 0}}{y_{Ar}}$ × 100%

式中, x_m为甲醇相对物质的量分数; y_m为出口气体产物中甲醇物质的量分数。

2 结果与讨论

2.1 CO转化率、H₂转化率和甲醇相对含量

在x(H₂)=79.82%、x(CO)=12.68%、x(CO₂)=1.29%、x(Ar)= 6.21%和压力4 MPa条件下, 考察反应温度和接触时间对合成甲醇反应的影响, 结果见图2。

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	图2 CO转化率、H₂转化率以及甲醇相对含量随接触时间和温度变化曲线Figure 2 Effects of contact time and reaction temperature on CO, H₂conversion, and relative content of CH₃OH

从图2可以看出, CO转化率为0~74%, 反应温度较低时, 随着接触时间的延长, CO转化率增加。反应温度增至240 ℃时, CO转化率的增加开始变得缓慢。进一步升高反应温度, CO转化率随着接触时间延长开始保持不变甚至略有下降。从250 ℃和260 ℃下的CO转化率趋向于稳定的现象可以推断, 随着接触时间的延长, 两个反应温度下的气体组成逐渐达到热力学平衡, 这也是在较长接触时间下250 ℃的CO转化率略高于260 ℃的原因。260 ℃时的CO转化率随接触时间延长略降的可能原因是部分甲醇在催化剂作用下发生分解^[14]。

H₂转化率为0~18%。H₂转化率随接触时间和反应温度的变化规律与CO转化率有很好的一致性。随着反应温度升高, 在短接触时间条件下, CO转化率逐步增加, 而在长接触时间条件下, 开始出现先升高后降低的趋势, 并且各接触时间下出现的CO转化率峰值随接触时间延长向低温偏移。本实验条件下, 最高CO转化率出现在接触时间0.45 s和反应温度(230~240) ℃。合成气制甲醇是放热反应, 受热力学平衡的影响, CO平衡转化率随着反应温度的升高而下降。CO转化率随反应温度增加先升高后降低的现象同样也是热力学限制所致。可以看出, 接触时间越长, 达到热力学平衡时的温度点越低。

尾气中甲醇相对含量为0~8%。甲醇生成与CO转化具有非常好的对应关系, 这也体观了本实验条件下CO向甲醇转化反应的良好选择性。

2.2 CO₂转化率及机理探讨

在x(H₂)=79.82%、x(CO)=12.68%、x(CO₂)=1.29%、x(Ar)= 6.21%和压力4 MPa条件下, 考察CO₂转化率随接触时间和反应温度的变化规律, 结果见图3。

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	图3 CO₂转化率随接触时间和反应温度变化曲线Figure 3 Effects of contact time and reaction temperature on CO₂ conversion

从图3可以看出, CO₂转化率为5%~17%。较低反应温度下, CO₂转化率随着接触时间的延长基本保持稳定或在一个很小的范围内(± 1%)波动, 从这一现象可以推断, 此条件下CO₂的消耗(式2)和生成(式3)处于一个动态平衡的状态。合成气合成甲醇主要发生的化学反应有:

CO+2H₂⇌CH₃OH (1)

CO₂+3H₂⇌CH₃OH+H₂O (2)

CO+H₂O⇌CO₂+H₂ (3)

一般认为, 在铜基催化剂条件下水汽变换反应(式3)快于CO₂加氢反应(式2), 即式2是这一转化过程的速率控制步骤, 水汽变换反应处于平衡状态。CO₂加氢反应生成的水参与水汽变换反应, 被迅速消耗转化为CO₂, 通过这样一个循环使体系中CO₂浓度可以维持基本不变。260 ℃条件下, CO₂转化率随着接触时间延长出现较明显下降。原因可能是260 ℃的反应温度使反应体系容易达到平衡, 再延长接触时间, 甲醇与水蒸汽反应(式2逆反应)分解生成CO₂。

随着反应温度的增加, CO₂转化率呈现较为明显下降的趋势。反应温度升高有利于CO₂加氢反应速率的提高, 促进CO向甲醇的转化。在相同接触时间下, 反应温度越高, CO浓度越低, 而甲醇浓度越高, 反应体系越趋近于平衡, 有利于促进甲醇与水蒸汽的反应(式2逆反应); 同时甲醇分解反应是吸热反应, 反应温度升高有利于反应的进行。这可能是体系中CO₂转化率随反应温度升高而降低的原因。本实验条件下, CO是形成甲醇的主要碳源, CO₂起到的是一种类似中间媒介的作用, 为CO提供一条加氢形成甲醇的反应路径。

图4显示了甲酸盐机理解释水汽变换反应与CO₂加氢合成甲醇反应的路径。CO₂经过吸附加氢转化, 形成甲酸根中间物种HCOO-, HCOO-向甲氧根(CH₃O-)的转化被认为是反应的速控步骤^[14], 这一转化形成的表面氢氧根(-OH)是CO发生水汽变换的重要物种。当反应体系中CO浓度未达到平衡时, CO₂转化形成反应的中间媒介-OH, 促进CO的转化。CO浓度逐渐接近平衡时, 甲醇渐渐开始与体系中的水蒸汽反应^[15], 使体系中的CO₂浓度回归到接近于初始水平。

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	图4 甲酸盐机理解释水汽变换反应与CO₂加氢合成甲醇反应Figure 4 Reaction mechanism of water-gas shift reaction and CO₂ hydrogenation to methanol with formate as intermediate

3 结论

采用自主研制的合成甲醇催化剂, 考察反应温度(190~260)℃和接触时间(0.112 5~0.45) s对合成甲醇反应的影响。在接触时间0.45 s和反应温度(230~240) ℃下, 最高CO转化率约74%。CO是合成甲醇的主要碳源, CO先经过水汽变换反应转化为CO₂, 再加氢转化为甲醇是主要的反应路径。

The authors have declared that no competing interests exist.

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2017

0.0

... 目前,国内市场上大型甲醇生产装置一般采用国外催化剂,如Kataclo51-9催化剂和MK121催化剂^[1] ...

2000

0.0

... 自20世纪90年代以来,国内学者对铜基甲醇合成催化剂进行了多方面研究^{[2,3,4,5,6,7,8,9,10]},推动了国产甲醇合成催化剂的工业应用 ...

2000

0.0

... 自20世纪90年代以来,国内学者对铜基甲醇合成催化剂进行了多方面研究^{[2,3,4,5,6,7,8,9,10]},推动了国产甲醇合成催化剂的工业应用 ...

2006

0.0

房德仁, 刘中民, 徐秀峰, 等. 老化时间对Cu/ZnO/Al₂O₃合成甲醇催化剂性能的影响[J]. 燃料化学学报, 2006, 34(1): 96-99.

Fang

Deren

, Liu

Zhongmin

, Xu

Xiufeng

, et al. Influence of aging time on the properties of CuO/ZnO/ Al₂O₃ catalysts for methanol synthesis[J]. Journal of Fuel Chemistry and Technology, 2006, 34(1): 96-99.

The aging process of copperzincaluminum precursors was studied by XRD, TGDTG and TPR techniques. The catalytic activity of CuO/ZnO/Al2O3 catalyst for methanol synthesis were tested using continues flow type fixedbed reactor. For the precursors prepared at the precipitating condition of pH=8.0 and temperature=80℃, the initial phases of the precipitate was a mixture of copper nitrate hydroxide Cu2(OH)3NO3, georgeite(amorphous Cu2CO3(OH)2) and hydrozincite Zn5 (CO3)2(OH)6. By increasing duration of its aging time, the phase of Cu2(OH)3 NO3first transited to georgeite, then interdiffused with Zn5(CO3)2(OH)6, resulting in two new phases: rosasite (Cu,Zn)2CO3(OH)2 and aurichalcite (Cu,Zn)5(CO3)2(OH)6. It was found that the composition and structure of the precursors altered obviously after the colour transition point. The research results demonstrate that the BET surface area and the amounts of CuOZnO solidsolution of the catalyst increased as the aging time extending which in turn to influence the catalytic activity of the catalyst.

1. Dalian Institute of Chemical Physics, The Chinese Academy of Sciences, Dalian 116023, China; 2. Institute of Applied Catalysis of Yantai University, Yantai 264005, China

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。

... 自20世纪90年代以来,国内学者对铜基甲醇合成催化剂进行了多方面研究^{[2,3,4,5,6,7,8,9,10]},推动了国产甲醇合成催化剂的工业应用 ...

2006

0.0

岑亚青, 李小年, 刘化章. 酸-碱交替沉淀法制备铜基甲醇合成催化剂[J]. 催化学报, 2006, 27(3): 210-216.

Cen

Yaqing

, Wu

Zaiguo

, Liu

Huazhang

. Optimized preparation and characterization of copper-based catalyst by acid-alkali alternate precipitation method for methanol synthesis[J]. Chinese Journal of Catalysis, 2006, 27(3): 210-216.

A new copper-based catalyst for methanol synthesis was prepared by acid-alkali-based alternate precipitation (AP) method. The catalyst activity is the highest when the pH value of the mother solution alters in the range of 5.0 and 9.5 for three times. Compared with the catalysts prepared by other methods, the activity and thermal stability of the catalyst prepared by the AP method is the best. About 88% activity of the catalyst is remained after the thermal test, which is 8%～20% higher than that of other catalysts. Furthermore, the activity of this catalyst after the thermal test is higher than that of other catalysts before the thermal test. The catalysts were characterized by X-ray diffraction (XRD), N2 adsorption, differential thermogravimetric analysis (DTG), and scanning electron microscopy (SEM). XRD patterns show that the characteristic peaks of CuO and ZnO are far more broadened for the catalyst prepared by the AP method. From SEM photographs it is found that the grains of the catalyst prepared by the AP method are smaller, and the distribution of the grains is symmetrical. The crystal size of this catalyst is small. DTG patterns show that this catalyst requires the lowest reduction temperature. The primary reason for the high activity and thermal stability of the catalyst prepared by the AP method is that an amorphous sosoloid of CuO and ZnO is formed, which can increase the dispersion of the active components and the BET surface area of the catalyst.

State Key Laboratory Breeding Base of Green Chemistry-Synthesis Technology, Institute of Industrial Catalysis, Zhejiang University of Technology, Hangzhou 310032, Zhejiang , China

采用酸-碱交替沉淀法(AP法)制备了一种新型的低压甲醇合成催化剂. 研究了母液pH值和交替次数对催化剂性能的影响. 结果表明, pH值交替范围为5.0～9.5, 交替次数为3时制备的催化剂活性最好. 与其它制备方法相比, AP法制备的催化剂具有最高的活性和耐热性,耐热后活性保留率达88%, 比其它催化剂高8%～20%, 而且耐热后活性甚至高于其它催化剂的初活性. X射线衍射(XRD)、热重分析、低温N2吸附和扫描电子显微镜等结果表明, AP法制备的催化剂的XRD谱中铜和锌的特征峰最为宽化、弥散, CuO与ZnO 峰交织在一起,峰强度最弱; 同时催化剂的粒度较小,粒径尺寸分布较均匀,结晶度相对较低; 而且催化剂的还原温度最低,铜锌组分间的协同作用最强. 这表明AP法制备的催化剂具有高活性、高耐热性和易还原的主要原因是该制备方法使催化剂中的铜锌组分形成了无定形状态的铜锌固溶体,提高了活性组分的分散度和比表面积.

... 自20世纪90年代以来,国内学者对铜基甲醇合成催化剂进行了多方面研究^{[2,3,4,5,6,7,8,9,10]},推动了国产甲醇合成催化剂的工业应用 ...

2007

0.0

郭宪吉, 李利民, 刘淑敏, 等. 并流淤浆混合法制备铜基甲醇合成催化剂及助剂Al₂O₃的作用研究[J]. 燃料化学学报, 2007, 35(3): 329-333.

Guo

Xianji

, Li

Limin

, Liu

Shumin

, et al. Preparation of CuO/ZnO/γ-Al₂O₃ catalysts for methanol synthesis using parallel-slurry-mixing method[J]. Journal of Fuel Chemistry and Technology, 2007, 35(3): 329-333.

Abstract A series of CuO/ZnO/γ-Al 2 O 3 catalysts with different Al 2 O 3 contents were prepared using the parallel-slurry-mixing method, in which an aqueous solution of Cu 2+ and Zn 2+ mixed nitrates and an aqueous solution of Na 2 CO 3 were poured into a precipitation vessel containing γ-Al 2 O 3 slurry in a parallel-flow manner. The catalyst structure and its performance for methanol synthesis were investigated. The results indicated that Al 2 O 3 as a structural promoter can inhibit CuO and ZnO crystallites from enlarging during calcination. The catalyst with a Cu/Zn/Al ratio of 4/5/1 (molar ratio) exhibits the highest catalytic activity. With an increase in Al content, the amount of (Cu 0.3 Zn 0.7 ) 5 (CO 3 ) 2 (OH) 6 phase in the catalyst precursor before calcination decreases, whereas that of Cu 2 CO 3 (OH) 2 phase increases; (Cu 0.3 Zn 0.7 ) 5 (CO 3 ) 2 (OH) 6 in the precursor is beneficial to the catalytic activity of the final Cu/ZnO/γ-Al 2 O 3 catalyst.

... 自20世纪90年代以来,国内学者对铜基甲醇合成催化剂进行了多方面研究^{[2,3,4,5,6,7,8,9,10]},推动了国产甲醇合成催化剂的工业应用 ...

2009

0.0

李忠, 郭启海, 张小兵, 等. 前驱体物相转变对浆态床合成甲醇催化剂活性的影响[J]. 高等学校化学学报, 2009, 30(11): 2215-2221.

Zhong

, Guo

Qihai

, Zhang

Xiaobing

, et al. Influence of the precursor phase transition on the catalyst activity in slurry methanol synthesis[J]. Chemical Journal of Chinese Universities, 2009, 30(11): 2215-2221.

The CuO/ZnO/Al 2 O 3 catalyst precursor were prepared by co-current precipitation and the crystal composition and phase-transition of the precursor prepared at different aging temperature were investigated in order to study the effect of the crystal composition and phase-transition of the precursor on the catalyst activity for slurry methanol synthesis. The results show that phase-transition of precursors are prominent influence on catalytic activity for slurry methanol synthesis. The (Cu,Zn) 2 CO 3 (OH) 2 and(Cu,Zn) 5 (CO 3 ) 2 (OH) 6 crystal phase are critical precursor to produce the catalytic active centre. The degree of substitution between Cu 2+ and Zn 2+ is increased with increasing Cu 2+ /Zn 2+ entering crystal lattices of Zn 5 (CO 3 ) 2 (OH) 6 /Cu 2 (CO 3 )(OH) 2 , and the ratio of copper to zinc in Rosasite and Aurichalcite is unchangeable. The calcined catalyst has more specific surface area and strong interaction between CuO-ZnO, and gets high activity in slurry methanol synthesis.

Institude of Coal Chemical Engineering, Key Laboratory of Coal Science and Technology of Ministry of Education and Shanxi Province, Taiyuan University of Technology, Taiyuan 030024, China

采用并流共沉淀法, 通过考察老化温度, 研究CuO/ZnO/Al 2 O 3 催化剂前驱体晶相及组成的变化对浆态床催化合成甲醇的反应活性的影响. 结果表明, 前驱体的物相转变对浆态床合成甲醇活性影响显著, 单斜晶系锌孔雀石(Cu,Zn) 2 CO 3 (OH)2和斜方晶系绿铜锌矿(Cu,Zn) 5 (CO 3 ) 2 (OH) 6 晶体是产生高活性催化剂的主要物相. 随着Cu 2+ /Zn 2+ 进入Zn 5 (CO 3 ) 2 (OH) 6 /Cu 2 CO 3 (OH) 2 晶格, 离子同晶取代量增加, 催化剂前驱体中形成了固定铜锌比的锌孔雀石和绿铜锌矿物相. 焙烧后催化剂比表面积增大, CuO-ZnO固溶体协同作用加强, 浆态床催化合成甲醇的活性提高.

... 自20世纪90年代以来,国内学者对铜基甲醇合成催化剂进行了多方面研究^{[2,3,4,5,6,7,8,9,10]},推动了国产甲醇合成催化剂的工业应用 ...

2010

0.0

林胜达, 唐浩东, 吕兆坡, 等. 沉淀方法对铜基甲醇合成催化剂前驱体及其性能的影响[J]. 催化学报, 2010, 31(10): 1257-1262.

Lin

Shengda

, Tang

Haodong

, Lu

Zhaobo

, et al. Influence of precipitation methods on precursors and properties of Cu-based catalyst for methanol synthesis[J]. Chinese Journal of Catalysis, 2010, 31(10): 1257-1262.

Cu/ZnO/Al 2 O 3 catalyst samples for methanol synthesis were prepared by co-precipitation (CP), two-stage precipitation (TP), and fractional precipitation (FP) methods, respectively. The evaluation results showed that the methanol yields over the catalyst prepared by FP is the best, which is 46.3% higher than that over the catalyst prepared by CP and 9.3% higher than that over the catalyst prepared by TP. The catalyst samples and their precursors were characterized by X-ray diffraction, thermogravimetry, infrared spectroscopy, N 2 adsorption-desorption, temperature-programmed reduction, and N 2 O titration. The results revealed that the precursor prepared by FP has higher amounts of (Cu,Zn) 2 CO 3 (OH) 2 and (Zn,Cu) 5 (CO 3 ) 2 (OH) 6 phases and a lower amount of the (Cu,Zn) 6 Al 2 (OH) 16 CO 3 •4H 2 O phase. Therefore, after calcination the catalyst has a higher amount of CuO-ZnO solid solution and carbonate formed at high temperature.

State Key Laboratory of Green Chemistry-Synthesis Technology, Institute of Industrial Catalysts, Zhejiang University of Technology, Hangzhou 310032, Zhejiang, China

分别采用共沉淀法 (CP)、两步沉淀法 (TP) 和分步沉淀法 (FP) 制备了 Cu/ZnO/Al 2 O 3 甲醇合成催化剂. 结果发现, FP 催化剂上甲醇收率比 CP 催化剂上高 46.3%, 比 TP 催化剂上高 9.3%. 采用 X 射线衍射、微分热重分析、红外光谱、N 2 吸附-脱附、程序升温还原及 N 2 O 滴定等方法表征了催化剂. 结果表明, FP 催化剂前驱体中 (Cu,Zn) 2 CO 3 (OH) 2 和 (Zn,Cu) 5 (CO 3 ) 2 (OH) 6 两种高活性物相较多, 而 (Cu,Zn) 6 Al 2 (OH) 16 CO 3 •4H 2 O 物相较少, 焙烧后形成了较多的 CuO-ZnO 固溶体, 同时形成了较多的碳酸盐, 因而催化活性更高.

... 自20世纪90年代以来,国内学者对铜基甲醇合成催化剂进行了多方面研究^{[2,3,4,5,6,7,8,9,10]},推动了国产甲醇合成催化剂的工业应用 ...

2013

0.0

... 自20世纪90年代以来,国内学者对铜基甲醇合成催化剂进行了多方面研究^{[2,3,4,5,6,7,8,9,10]},推动了国产甲醇合成催化剂的工业应用 ...

2017

0.0

... 自20世纪90年代以来,国内学者对铜基甲醇合成催化剂进行了多方面研究^{[2,3,4,5,6,7,8,9,10]},推动了国产甲醇合成催化剂的工业应用 ...

2015

0.0

... 甲醇合成的反应机理,如甲醇的直接碳源和加氢过程中的中间产物,现在仍然有争议^[11,12,13] ...

2011

0.0

... 甲醇合成的反应机理,如甲醇的直接碳源和加氢过程中的中间产物,现在仍然有争议^[11,12,13] ...

2013

0.0

... 甲醇合成的反应机理,如甲醇的直接碳源和加氢过程中的中间产物,现在仍然有争议^[11,12,13] ...

1997

0.0

孙琦, 张玉龙, 马艳, 等. CO₂/H₂和(CO/CO₂)+H₂低压合成甲醇催化过程的本质[J]. 高等学校化学学报, 1997, 18(7): 1131-1135.

Sun

, Zhang

Yulong

, Ma

Yan

, et al. Comparison studies on the catalysis process of methanol synthesis from CO₂+H₂ and (CO/CO₂)+H₂[J]. Chemical Journal of Chinese Universities, 1997, 18(7): 1131-1135.

The catalytic processes of methanol synthesis from CO 2 +H 2 , CO+H 2 and (CO/CO 2 ) +H 2 have been studied.The results indicate that methanol is primarily formed fromCO 2 hydrogenation for both CO 2+ H 2 and (CO/CO 2 ) +H 2 . Due to the limitation of thermaldynamics, the yield of methanol is low for CO 2 hydrogenation.In the process of (CO/CO 2 )+H 2 , methanol selectivity and formation rate are promoted greatly due to the recycle processof methanol synthesis from CO 2+ H 2 and reverse water-gas shift reaction.As a result, thelimitation of thermodynamic equilibrium of methanol synthesis from CO 2 , hydrogenation ismoved to the favorable side of methanol synthesis.Anovel reaction mechanism is proposed.

1. Dept.of Chem., Fudan Univ., Shanghai 200433; 2. DePt.of Chem., Tong .Univ., Shanghai 200092

通过在Cu/ZnO/Al 2 O 3 催化剂上CO 2 ＋H 2 、CO＋H 2 和(CO/CO 2 )＋H 2 催化反应动力学研究,对合成甲醇动力学和反应机理进行了细致分析,提出合成甲醇的反应机理,解释了在(CO/CO 2 )＋H 2 合成甲醇过程中少量CO 2 的作用及合成甲醇的直接碳源.

... 260 ℃时的CO转化率随接触时间延长略降的可能原因是部分甲醇在催化剂作用下发生分解^[14] ...

... CO₂经过吸附加氢转化,形成甲酸根中间物种HCOO-,HCOO-向甲氧根(CH₃O-)的转化被认为是反应的速控步骤^[14],这一转化形成的表面氢氧根(-OH)是CO发生水汽变换的重要物种 ...

2010

0.0

... CO浓度逐渐接近平衡时,甲醇渐渐开始与体系中的水蒸汽反应^[15],使体系中的CO₂浓度回归到接近于初始水平 ...