Continuous synthesis process of methanol at low temperature from syngas using alcohol promoters

A continuous process for low-temperature methanol synthesis from CO/CO₂/H₂ based on the promoting effect of alcohol solvent has been developed. 2-butanol, acting as a promoter, with the aid of Cu/ZnO solid catalyst, realized the high efficient synthesis of methanol with one-pass methanol yield of 47.0% and methanol selectivity of 98.9% at temperature as low as 443 K and 50 bar, which can be a very promising method for methanol production at low temperature.     

Evidence for the migration of ZnOx in a Cu/ZnO methanol synthesis catalyst

The behavior and role of ZnO in Cu/ZnO catalysts for the hydrogenations of CO and CO₂ were studied using XRD, TEM coupled with EDX, TPD and FT-IR. As the reduction temperature increased, the specific activity for the hydrogenation of CO₂ increased, whereas the activity for the hydrogenation of CO decreased. The EDX and XRD results definitely showed that ZnO _x (x = 0–1) moieties migrate onto the Cu surface and dissolve into the Cu particle forming a Cu-Zn alloy when the Cu/ZnO catalysts were reduced at high temperatures above 600 K. The content of Zn dissolved in the Cu particles increased with reduction temperature and reached 18% at a reduction temperature of 723 K. The CO-TPD and FT-IR results suggested the presence of Cu⁺ sites formed in the vicinity of ZnO _x on the Cu surface, where the Cu⁺ species were regarded as an active catalytic component for methanol synthesis.     

Cu/ZnO/Zn-Al水滑石催化剂的制备及在富CO_2合成气制甲醇反应中的催化性能

传统Cu/ZnO/Al_2O_3(CZA)甲醇合成催化剂在富CO_2合成气制甲醇反应中的性能不高。为了提高CZA催化剂的性能,采用并流沉淀-水热老化法制备Zn-Al水滑石(Zn-Al-HT)载体,与Cu-Zn母体复合得到Cu-ZnO/Zn-Al-HT(HCZA)催化剂。对载体以及催化剂进行表征,考察不同水滑石含量的HCZAx(x=1~4)催化剂在富CO_2合成气制甲醇反应中的催化性能,并在HCZA3催化剂上进行120h稳定性试验。结果表明,还原态催化剂上Cu比表面积越大,催化剂上总碳转化率越高;催化剂中Zn-Al-HT相含量越高,液相有机相中甲醇含量越高;HCZA3催化剂具有良好的催化稳定性。     

The active site for methanol synthesis on a Cu/ZnO/SiO2 catalyst

This note rectifies serious omissions from the references included in a recent paper by Fujitani et al. concerned with methanol synthesis over Cu/SiO₂ containing ZnO. This revised version was published online in July 2006 with corrections to the Cover Date.     

改进的二步共沉淀法制备Cu/ZnO/Al2O3甲醇合成催化剂

采用改进的二步共沉淀法制备了Cu/ZnO/Al₂O₃甲醇合成催化剂。用XRD、SEM和BET等手段对催化剂结构和形貌进行了表征。采用流动固定床微型反应器在5.0 MPa和空速5 000 h^-1条件下,考察了其催化合成气合成甲醇的活性,并在同一条件下用一种工业催化剂做对比测试。结果表明,改进的二步法制备的甲醇合成催化剂结晶度较低,基本以无定形状态的固溶体形式存在,铜锌之间的协同作用大,催化剂粒度较小,尺寸分布较均匀,比表面积较大,催化剂单位面积活性达98.54 mg·m^-2。     

Preparation of Cu/ZnO/Al2O3 catalyst under microwave irradiation for slurry methanol synthesis

Cu/ZnO/Al₂O₃ catalysts with Cu/Zn/Al ratios of 6/3/1 were precipitated and aged by conventional and microwave heating methods and tested in the slurry phase reactor for methanol synthesis. The effect of technological condition of precipitation and aging process under microwave irradiation on the catalytic performance was investigated to optimize the preparing condition of Cu/ZnO/Al₂O₃ catalyst. The results showed that the microwave irradiation during precipitation process could improve the activity of the catalyst, but had little effect on the stability. While the microwave irradiation during aging process has a great benefit to both the activity and stability of the catalyst, the catalyst aged at 80°C for 1 h under microwave irradiation possessed higher methanol space time yield (STY) and more stable catalytic activity. The activity and stability of the catalyst was further enhanced when microwave irradiation was used in both precipitation and aging processes; the optimized condition for the catalyst precursor preparation was precipitation at 60°C and aging at 80°C under microwave irradiation.     

Deactivation of Cu/ZnO catalyst during dehydrogenation of methanol

The deactivation of Cu/ZnO catalyst during methanol dehydrogenation to form methyl formate has been studied. The Cu/ZnO catalyst was seriously deactivated under the reaction conditions: various temperatures of 493, 523 and 553 K, atmospheric pressure and methanol GHSV of 3000 ml (STP)/g-cat h. The weight loss due to reduction of ZnO in the Cu/ ZnO catalyst was monitored by a microbalance. X-ray induced Auger spectroscopy of Zn(L₃M_4,5M_4,5) showed the increase in the concentration of metallic Zn on the catalyst surface after the reaction. Temperature-programmed reduction (TPR) of the Cu/ZnO catalyst with methanol demonstrated that the reduction of ZnO in Cu/ ZnO was suppressed by introduction of CO₂ into the stream of helium-methanol. As the concentration of CO₂ in the feed gas increased, the weight loss of the Cu/ZnO catalyst due to the reduction of ZnO decreased. The deactivation of the Cu/ZnO catalyst in the methanol dehydrogenation was also retarded by the addition of CO₂. In particular, oxygen injection into the reactant feed regenerated the Cu/ ZnO catalyst deactivated during the reaction. Based on these observations, the cause of deactivation of the Cu/ZnO catalyst has been discussed.     

机械研磨燃烧法制备Cu/ZnO/Al2O3甲醇合成催化剂

引言Cu/ZnO/Al2O3催化剂近年来广泛应用于低压甲醇合成、二甲醚合成和水煤气变换等领域[1-2],该催化体系具有活性高、使用寿命长、反应温度及     

Preparation and characterization of carbon nanotube-promoted Co–Cu catalyst for higher alcohol synthesis from syngas

A cobalt–copper catalyst promoted by “herringbone-type” multiwalled carbon nanotubes (CNTs) was developed. This catalyst displayed excellent performance for higher alcohol synthesis (HAS) from syngas, with the (C_2–8-alc. + DME)-STY reached 760 mg/(g·h) under the reaction conditions of 5.0 MPa and 573 K, which was 1.78 times that of the CNT-free host, Co₃Cu₁. The addition of a minor amount of the CNTs to the Co₃Cu₁ host did not cause a marked change in apparent activation energy for the HAS, but led to an increase at the surface of the catalyst of the concentration of catalytically active Co-species, CoO(OH), a kind of surface Co-species related closely to the selective formation of the higher alcohols. Excellent adsorption performance of this kind of CNTs for H₂ generated a surface micro-environment with a high concentration of H-adspecies on the functioning catalyst, thus increasing the rate of surface hydrogenation reactions in the HAS. Moreover, synergistic action of the high surface-concentration H-adspecies with CO₂ in the feed-gas led to a greater inhibition for the WGS side-reaction. All these factors contribute considerably to an increase in the yield of alcohols.     

Mechanism of the formation of precursors for the Cu/ZnO methanol synthesis catalysts by a coprecipitation method

Precursors of Cu/ZnO catalysts with various Cu/Zn molar ratios were prepared by a coprecipitation method. It was found that amorphous copper hydroxycarbonate and sodium zinc carbonate were intermediates for the formation of various precursors such as hydrozincite, malachite and aurichalcite. Aurichalcite having a high Cu/Zn ratio was prepared from a mechanical mixture of these intermediates.     

Cu/ZnO/AlOOH catalyst for methanol synthesis through CO<Subscript>2</Subscript> hydrogenation

Catalytic conversion of CO₂ to methanol is gaining attention as a promising route to using carbon dioxide as a new carbon feedstock. AlOOH supported copper-based methanol synthesis catalyst was investigated for direct hydrogenation of CO₂ to methanol. The bare AlOOH catalyst support was found to have increased adsorption capacity of CO₂ compared to conventional Al₂O₃ support by CO₂ temperature-programmed desorption (TPD) and FT-IR analysis. The catalytic activity measurement was carried out in a fixed bed reactor at 523 K, 30 atm and GHSV 6,000 hr^?1 with the feed gas of CO₂/H₂ ratio of 1/3. The surface basicity of the AlOOH supported Cu-based catalysts increased linearly according to the amount of AlOOH. The optimum catalyst composition was found to be Cu : Zn : Al=40 : 30 : 30 at%. A decrease of methanol productivity was observed by further increasing the amount of AlOOH due to the limitation of hydrogenation rate on Cu sites. The AlOOH supported catalyst with optimum catalyst compositions was slightly more active than the conventional Al₂O₃ supported Cu-based catalyst.     

Creation of the active site for methanol synthesis on a Cu/SiO2 catalyst

The effect of ZnO/SiO₂ in a physical mixture of Cu/SiO₂ and ZnO/SiO₂ on methanol synthesis from CO₂ and H₂ was studied to clarify the role of ZnO in Cu/ZnO-based catalysts. An active Cu/SiO₂ was prepared by the following procedure: the Cu/SiO₂ and ZnO/SiO₂ catalysts with a different SiO₂ particle size were mixed and reduced with H₂ at 523-723 K, and the Cu/SiO₂ was then separated from the mixture using a sieve. The methanol synthesis activity of the Cu/SiO₂ catalyst increased with the reduction temperature and was in fairly good agreement with that previously obtained for the physical mixture of Cu/SiO₂ and ZnO/SiO₂. These results indicated that the active site for methanol synthesis was created on the Cu/SiO₂ upon reduction of the physical mixture with H₂. It was also found that ZnO itself had no promotional effect on the methanol synthesis activity except for the role of ZnO to create the active site. The active site created on the Cu/SiO₂ catalyst was found not to promote the formation of formate from CO₂ and H₂ on the Cu surface based on in situ FT-IR measurements. A special formate species unstable at 523 K with an OCO asymmetric peak at ~1585 cm^-1 was considered to be adsorbed on the active site. This revised version was published online in July 2006 with corrections to the Cover Date.     

O-846型合成气低温脱氧催化剂的性能研究

开发了一种用于合成气的O-846型低温脱氧催化剂,该催化剂以氧化铝为载体,以贵金属Pd为主活性组分,采用浸渍工艺制备,使用前无需活化。在贵金属和多种非贵金属氧化物助剂协同催化作用下,于空速3 500 h-1、反应压力0.5 MPa和反应温度63℃条件下,将合成气中体积分数为0.2%的O2脱至0.5×10-6以下。1 032 h寿命试验结果表明,O-846型合成气低温脱氧催化剂的活性及稳定性良好,具有工业应用前景。     

The effect of the reduction temperature on the structure of Cu/ZnO/SiO2 catalysts for methanol synthesis

The structure of Cu/SiO₂ and Cu/ZnO/SiO₂ catalysts was studied after reduction at 450–1300 K. The influence of the ZnO promoter on the exposed Cu surface area and metal cluster size was determined by N₂O chemisorption and X-ray diffraction. After reduction at 450 K, the metal surface area amounted to 9 m²/g_cat for both catalysts. Oxygen uptake during N₂O chemisorption increased significantly up to reduction temperatures of 800–900 K. This increase was most prominent for the ZnO-promoted catalyst, although no oxygen uptake was observed for a similarly treated ZnO/SiO₂ sample. The behaviour of the promoted catalyst can be explained by formation of Zn⁰, surface alloying, and segregation of ZnO_x species on top of Cu clusters. The high thermostability of the catalysts was confirmed by in situ XRD measurements. The Cu crystallite size in both catalysts was about 4 nm, and did not increase when the reduction temperature was raised to 1100 K for 1 h.     

低压甲醇合成催化剂的保护

通过对低压法甲醇合成催化剂失活机理的分析研究 ,提出只要注意在催化剂装填前将设备和管道清理、吹扫干净 ,装填时在催化剂上加保护剂 ,还原过程出水平稳 ,优化工艺操作条件 ,就可以对催化剂进行有效的保护 ,延长催化剂的使用寿命     

Activity and stability of Cu/ZnO/Al2O3 catalyst promoted with B2O3 for methanol synthesis

The addition of B₂O₃ to a Cu/ZnO/Al₂O₃ catalyst increased the activity of the catalyst for methanol synthesis after an induction period during the reaction. The stability of the B₂O₃-containing Cu/ZnO/Al₂O₃ catalyst was greatly improved by the addition of a small amount of colloidal silica to the catalyst. This revised version was published online in July 2006 with corrections to the Cover Date.     

水煤浆气化两段低温甲醇洗净化合成气

介绍水煤浆制合成气净化工艺的选择及其经济性；鲁奇两段低温甲醇洗涤酸性气体的工业生产流程．可供联产Ｃ１化工产品的综合利用，提高合成气中Ｃ１的利用率，减免ＣＯ２排入大气的污染等参考。     

Effects of space velocity on methanol synthesis from Co2/Co/H2 over Cu/ZnO/Al2O3 catalyst

The space velocity had profound and complicated effects on methanol synthesis from CO₂/CO/H₂ over Cu/ZnO/Al₂O₃ at 523 K and 3.0MPa. At high space velocities, methanol yields as well as the rate of methanol production increased continuously with increasing CO₂ concentration in the feed. Below a certain space velocity, methanol yields and reaction rates showed a maximum at CO₂ concentration of 5–10%. Different coverages of surface reaction intermediates on copper appeared to be responsible for this phenomenon. The space velocity that gave the maximal rate of methanol production also depended on the feed composition. Higher space velocity yielded higher rates for CO₂/ H₂ and the opposite effect was observed for the CO/H₂ feed. For CO₂/CO/H₂ feed, an optimal space velocity existed for obtaining the maximal rate.     

Remarks on the assignments of temperature programmed desorption peaks for the surface species formed on Cu/ZnO and ZnO in the methanol synthesis from CO

Temperature programmed desorption (TPD), IR spectroscopy and chemical trapping of the surface species with H₂O revealed that the TPD peak of CO frequently assigned to zinc formate species, which were formed in the course of the methanol synthesis from CO-H₂, arose from zinc methoxide species.     

Structural change of Cu/ZnO by reduction of ZnO in Cu/ZnO with methanol

The reducibility of ZnO was investigated in the temperature range of 523–623 K in a stream of a reducing agent such as H₂, CO, and methanol. ZnO was reduced only in the presence of copper in the vicinity of ZnO with CO and methanol, but it was not reduced with H₂. Methanol was a stronger reducing agent in the reduction of ZnO than CO, while CO was stronger in the reduction of CuO than methanol. Two types of brass were observed resulting from the reduction of ZnO in the Cu/ZnO sample by XRD. Zanghengite brass started to be formed at 573 K in addition to α-brass which was observed at the temperature above 523 K in the temperature range of 523–623 K during the ZnO reduction with methanol. The carbon monoxide chemisorption showed that the copper surface areas decreased during the reduction of ZnO with methanol. This revised version was published online in July 2006 with corrections to the Cover Date.