AF-5分子筛催化剂上苯气相乙基化反应的失活动力学研究——(Ⅰ)实验研究

在绝热固定床实验反应器中对苯和乙烯在 AF-5分子筛催化剂上进行的烷基化反应的失活动力学作了研究。初步考察表明乙烯和苯都会引起失活,但乙烯引起的失活是主要的。在和工业反应器类似的操作条件下系统测定了由催化剂失活引起的乙烯转化率随操作时间的变化。所得数据将用于建立失活动力学模型。     

AF—5分子筛催化剂上苯气相乙基化反应的失活动力学研究…

在绝热固定床实验反应器中对苯和乙烯在ＡＦ－５分子筛催化剂上进行的烷基化反应的失活动力学作了研究。初步考察表明乙烯和苯都会引起失活，但乙烯引起的失活是主要的。在和工业反应器类似的操作条件下系统测定了由催化剂失活引起的乙烯转化率随操作时间的变化，所得数据将用于建立失活动力学模型。     

透氧膜反应器提效甲烷芳构化

近日,中科院青岛生物能源与过程研究所膜分离与催化团队负责人江河清研究员与德国汉诺威大学、尤利西研究中心、拜耳公司等机构研究人员合作,在透氧膜反应器中尝试进行了甲烷芳构化反应,生成了苯及其衍生物。据介绍,甲烷芳构化是将甲烷直接转化为液体产品的有效途径之一,在催化科学、工业应用等方面具有重要意义。其早期研究主要集中在开发高活性、高稳定性的催化剂。Mo/ZSM-5催化剂是目前被广泛研究和使用的催化剂。但该类催化剂存在易积炭失活、甲烷转化率低等问题。研究人员尝试在该体系中引入一定量氧气     

N2O一步氧化苯制苯酚FeZSM-5分子筛的失活与再生

将离子交换法制备并经水热处理的FeZSM-5分子筛应用于N2O一步氧化苯制苯酚反应中.在固定床反应器上研究了导致催化剂失活的原因,考察了失活催化剂的再生条件,并采用热重-差热综合热分析法(TG-DTA)、N2吸附比表面测定法(BET)和程序升温氧化法(TPO)等对失活前后的催化剂进行了表征.结果表明,FeZSM-5分子筛催化剂在N2O一步氧化苯制苯酚反应中具有较高的初始活性,但失括较快.失活催化剂上存在两种形式的积炭,C与H比不同的低温炭和高温炭是催化剂失活的主要原因.再生实验结果表明,失活催化剂在450℃下,在N2O气氛中烧炭再生处理40 min后,催化剂的活性可完全恢复,此时催化剂表面的积炭率仍保持在30%左右.     

氯化氢催化氧化制氯气催化剂的失活与再生

对浸渍法制备的Cu含量为8%的HCl催化氧化制Cl2催化剂的失活机理和再生方法进行了研究. 在温度400℃、压力0.12 MPa、摩尔比HCl/O2=1及HCl空速为0.8 h-1的条件下,在石英管固定床反应器中对催化剂进行了300 h的寿命评价. 结果表明,新鲜催化剂活性较好,HCl转化率在70%以上,而反应300 h后HCl转化率降到约50%. 催化剂活性下降的原因是CeO2晶粒聚并和活性组分流失. 较低温度下氯化可使失活催化剂再生,再生后催化剂可使HCl转化率恢复到70%以上.     

丙烷脱氢固定床反应器的动态模拟与优化

在丙烷脱氢制丙烯反应过程中,由于焦的沉积使催化剂活性不断降低,而且失活速度很快。本文建立了径向绝热固定床反应器丙烷脱氢 失活过程的动态模型,在Pt-Sn催化剂动力学基础上对脱氢过程进行了模拟和分析。得到了不同时刻反应器内的压力、温度、催化剂活性等的分布情况以及转化率、选择性、收率等的变化规律,并在分析反应器入口温度、流量及压力对过程影响的基础上对反应的操作条件进行了优化。     

丙烯醛与异丙醇均相氢转移制烯丙醇反应中催化剂失活及再利用研究

采用异丙醇铝为催化剂,丙烯醛与异丙醇进行均相氢转移反应合成烯丙醇,对催化剂的再利用及催化剂的失活原因进行了研究。研究发现,采用减压蒸馏的方法,可分离出催化剂。若在反应过程中加入高沸点溶剂,催化剂的第一次及第二次反应性能均有显著提高,并且随溶剂沸点升高,转化率及选择性呈上升趋势。当以邻二甲苯为溶剂时,第一次反应转化率、选择性分别为91%、92%;第二次反应转化率、选择性分别为80%、85%,可部分实现催化剂的再利用。催化剂失活的原因在于,原料中以及反应过程中产生的水对催化剂结构有破坏作用;另外,反应过程中产生的重组分副产物对催化剂的配合或包裹是造成催化剂失活的主要原因。     

糠醛在Pd-Cu膜反应器中催化加氢合成糠醇

以糠醛催化加氢合成糠醇作为模型反应,采用共沉淀法制备的Cu/MgO-K₂O作为催化剂,考察了Pd-Cu膜反应器的加氢性能.膜反应器由双套管组成,采用分别进料的方式操作.即糠醛气化后由载气带入中心膜管的催化床层,而氢气则进入管壳层通过Pd-Cu合金膜渗透到反应区.在不同条件下分别进行糠醛催化加氢反应,考察了糠醛转化率、产品糠醇选择性和收率,并与传统的共进料填充床反应器进行比较.研究结果显示,膜反应器比传统的填充床反应器具有产品收率高、选择性好和副产物少的特点.此外,本文结合催化剂的组成、结构和表面形貌的表征对催化剂的催化活性和失活行为进行了讨论.     

合成气一步法制二甲醚工艺条件研究

研究了三相床反应器中合成气一步法制二甲醚的工艺条件,催化剂是由甲醇合成催化剂与甲醇脱水催化剂均匀混合组成的双功能催化剂.在温度220～265℃、压力4～5MPa、空速1～2 L/(g·h)的条件下,分别考察了温度、压力和空速对二甲醚合成反应中CO转化率及二甲醚选择性的影响.结果表明,在上述各因素相应的范围内,,随着反应温度的升高,CO转化率、DME选择性逐渐增加;随着压力的升高,CO转化率、DME选择性逐渐增加;CO转化率、DME选择性随空速的提高而逐渐减小.与固定床实验结果相比,三相床反应器中CO转化率略低于固定床反应器.     

改性ZSM-5上苯与乙醇烷基化反应条件的考察及再生评价

通过离子交换法制备出-种钛改性的分子筛,并在连续流动固定床反应器上对其进行了苯与乙醇烷基化反应条件和催化剂的失活再生评价.通过XRD,BET、NH3-TPD、py-IR和ICP方法对催化剂进行了表征,结果表明,改性后催化剂的比表面积、微孔孔容和孔径均减少,B酸/L酸比值增加,改性元素含量8.56%.反应评价结果显示,改性后乙苯选择性略有降低,苯的转化率增加,乙醇利用率增加.改性催化剂的最佳反应条件:温度360～460℃,质量时空速3～5 h-1,苯醇摩尔比3～5.催化剂4次再生评价效果良好,再生后酸性没有太大改变,是-种具有良好工业应用前景的催化剂.     

Deactivation mechanism of beta-zeolite catalyst for synthesis of cumene by benzene alkylation with isopropanol

The alkylation of benzene with isopropanol over beta-zeolite is a more cost-effective solution to cumene production.During the benzene alkylation cycles,the cumene selectivity slowly increased,while the benzene conversion presented the sharp decrease due to catalyst deactivation.The deactivation mechanism of beta-zeolite catalyst was investigated by characterizing the fresh and used catalysts.The XRD,SEM and TEM results show that the crystalline and particle size of the beta-zeolite catalyst almost remained stable during the alkylation cycles.The drop in catalytic activity and benzene conversion could be explained by the TG,BET,NH3-TPD and GC-MS results.The organic matters mainly consisted of ethylbenzene,p-xylene and 1-ethyl-3-(1-methyl) benzene produced in the benzene alkylation deposited in the catalyst,which strongly reduced the specific surface area of beta-zeolite catalyst.Moreover,during the reaction cycles,the amount of acidity also significantly decreased.As a result,the catalyst deactivation occurred.To maintain the catalytic performance,the catalyst regeneration was carried out by using ethanol rinse and calcination.The deactivated catalyst could be effectively regenerated by the calcination method and the good catalytic performance was obtained.     

Alkylation of benzene with 1- dodecene over usy zeolite catalyst: Effect of pretreatment and reaction conditions

Catalytic activity, stability and selectivity of USY zeolite catalyst for alkylation of benzene with 1-dodecene were investigated using a continuous fixed bed high pressure microreactor. It is found that the catalytic activity and stability depend closely on the pretreatment temperature of catalyst and reaction conditions. The best result was obtained at 120 °C and 3.0MPa with 8 molar ratio of benzene to 1-dodecene, and 4 h-1 weight hourly space velocity of reactant over the catalyst with the pretreatment temperature of 500 °C. Under this condition, the reaction conversion was nearly 100% and no deactivation was observed within the employed 50 h of time on stream with the selectivity of 2-phenyldodecene being 22%. This paper is dedicated to Professor Wha Young Lee on the occasion of his retirement from Seoul National University. On a research leave from Department of Chemical Engineering, Nanjing University of Technology, Nanjing 210009, China.     

Methane aromatization using Mo-based catalysts prepared by microwave heating

Mo/HZSM-5 and Cu–Mo/HZSM-5 catalysts for the non-oxidative aromatization of methane have been prepared by microwave heating method. The effects of Mo loading, the molar ratio of Cu/Mo and preparation method on the catalytic performance of catalysts were studied. The results were compared with those for the methane aromatization over catalysts prepared by conventional heating. Both two kinds of catalysts have the maximum methane conversion when the Mo loading is 6%. The catalysts prepared by microwave heating exhibited higher selectivity to benzene than that prepared by conventional heating. The addition of metal Cu to Mo/HZSM-5 catalyst prepared by microwave heating enhanced the lifetime of catalyst, and gave rise to a little increase in methane conversion. The molar ratio of Cu/Mo influenced the methane conversion, and the maximum value was attained when Cu/Mo = 0.05, whereas no significant influence on the benzene selectivity was observed with the increase molar ratio of Cu/Mo. N₂ adsorption results showed that the catalysts prepared by microwave heating have the larger surface area and the similar pore volume compared with the catalysts prepared by conventional heating. This fact revealed that the more Mo species located on the outer surface of catalysts prepared by microwave heating is the main reason why they have better catalytic performance. XRD analysis indicated that the Mo species are highly dispersed on HZSM-5 zeolite. The addition of Cu influenced the dispersion. The actual active phase Mo₂C can be identified on the catalyst surface after reaction. TEM analysis revealed the carbonaceous deposition to have the form of carbon nanotube after reaction, with a uniform size range of 10–20 nm. TG analysis indicated that carbonaceous deposition on the catalysts prepared by microwave heating is lower than that by conventional heating, and the metal Cu further prompts the stability of catalyst. Most of the carbonaceous deposition on catalysts prepared by microwave heating is formed at low temperature and it is easy to burn-off. Coke accumulation at high temperature is the main reason of catalyst deactivation. The carbonaceous deposition formed on the catalysts for non-oxidative aromatization of methane is different from those formed on the catalysts for partial oxidation of methane.     

Reaction Kinetics and Coking Behavior for Furan Deoxygenation via Catalytic Pyrolysis Using Methane

The effective deoxygenation of oxygenates remains a major challenge that needs to be overcome for industrial‐scale conversion of biomass to fuels. Present technology uses expensive gaseous hydrogen for deoxygenation. This work looks at the possibility of using methane or natural gas as an alternative for the deoxygenation process. Catalytic pyrolysis studies were carried out using furan as the model oxygenate in the presence of methane in a fixed‐bed reactor over 5 % Ni/HZSM‐5 as catalyst. The effects of temperature and space velocity on the catalyst activity, reaction kinetics, and deactivation behavior were studied. It was found that the deoxygenation of furan was first and second order with respect to furan and methane concentration, respectively. Deactivation studies suggested that catalyst deactivation takes place through poisoning, fouling, and sintering.     

PED-01乙苯脱氢催化剂的评价试验

自主开发的PED-01乙苯脱氢催化剂在100 mL等温评价装置上进行了重复试验和稳定性试验,在反应温度620 ℃、空速1.0 h^-1、水蒸汽与乙苯质量比2∶1和常压条件下,催化剂的乙苯平均转化率为79.51%,苯乙烯平均选择性为95.91%,苯乙烯平均收率为76.25%。侧线装置上条件试验和稳定性试验结果表明,PED-01催化剂的乙苯转化率和苯乙烯平均收率均优于进口催化剂,失活速率比进口催化剂慢,具有更好的稳定性。     

玄武岩催化甲烷裂解制 C2 烃

以天然玄武岩为甲烷裂解催化剂,通过XRF、XRD、SEM及XPS对催化剂组成、结构、表面活性物种进行了研究。利用固定床反应装置考察了不同反应温度、空速条件下玄武岩催化甲烷裂解制C_2烃的效果。结果表明,在气体空速为4 L·h-1条件下,当反应温度为1 225 K时,甲烷的转化率为7.66%,C_2烃的选择性为33.64%;当反应温度升至1 325 K时,甲烷的转化率可达17.13%,同时C_2烃的选择性为27.21%。相同温度下,气体空速越大,乙烷的选择性越高,乙炔的选择性越低。催化剂活性因表面积炭的产生而降低,积炭类型为芳烃积炭。     

Some technological aspects of methane aromatization (direct and via oxidative coupling)

The investigations on transformation of methane to benzene and naphthalene have been carried out in aim to verify and supplement earlier reported data and on this basis to estimate real industrial perspectives of the CH₄ aromatization concept, the main challenges and barriers. Methane aromatization (direct and via oxidative coupling) has been studied over Mo/HZSM-5 catalyst used both for direct methane dehydroaromatization and for aromatization of methane oxidative coupling (OCM) products. The effects of Mo content in the catalyst, temperature, space velocity, the presence of CO₂, CO, H₂O, C₂H₄, C₂H₆ and their mixtures in the feed have been studied. The effectiveness of the catalyst regeneration in the air was also examined. All results were confronted with the literature data and analyzed from technological point of view. It was confirmed that direct CH₄ aromatization process was characterized by a low CH₄ single-pass conversion, low single-pass yields of the main products (benzene, hydrogen and naphthalene) and a low catalyst stability (rapid catalyst deactivation). Various possible technological schemes were analyzed. It was concluded that real industrial chances of direct methane aromatization or aromatization via OCM would depend largely on the advancement in the cost-effective separation techniques. The methane aromatization concept was also confronted with other methane conversion processes.     

Study of W/HZSM-5-Based Catalysts for Dehydro-aromatization of CH4 in Absence of O2. I. Performance of Catalysts

With incorporation of Zn (or Mn, La, Zr ) into the W/HZSM-5 catalyst, highly active and heat-resisting W/HZSM-5-based catalysts were developed and studied. Under reaction conditions of 0.1 MPa, 1073 K, GHSV of feed-gas CH₄+10% Ar at 960 h^–1, the conversion of methane reached 18–23% in the first 2 h of reaction, and the corresponding selectivity to benzene, naphthalene, ethylene and coke was 56–48, 18, 5 and 22%, respectively. Addition of a small amount of CO₂ (2%) to the feed-gas was found to significantly enhance the conversion of methane and the selectivity of benzene, and to improve the performance of coke-resistance of the W/HZSM-5-based catalysts. Heavy deposition of carbon on the surface of the functioning catalyst was the main reason leading to deactivation of the catalyst. Reoxidation by air may regenerate the deactivated catalyst effectively. In comparison with the Mo/HZSM-5 catalyst, the promoted W/HZSM-5-based catalyst can operate under reaction temperature of 1073 K, and gain a methane conversion approximately two times as high as that of the Mo/HZSM-5 catalyst operating at 973 K. It can also operate at 973 K and have about the same methane conversion as that of the Mo/HZSM-5 catalyst at the same reaction temperature. Its main advantage is its heat-resistant performance; the high reaction temperature did not lead to loss of W component by sublimation.     

Sb-SBA-15催化剂上二苯甲烷的合成

采用浸渍法制备了Sb-SBA-15催化剂,通过XRD、N₂吸附-脱附、FTIR对其进行表征,结果表明,Sb-SBA-15催化剂仍具有六方介孔结构。考察了苯/氯化苄的摩尔比、反应时间、催化剂用量、反应温度对Sb-SBA-15催化苯与氯化苄苄基化反应的影响,并研究了反应的动力学。实验结果表明,Sb-SBA-15对苯与氯化苄的苄基化反应具有良好的催化性能,最佳反应条件为:苯与氯化苄的摩尔比8、反应时间3h、催化剂用量0.1g、反应温度120℃。在最佳条件下,氯化苄的转化率可达96.78%,二苯甲烷的选择性高达99%以上。     

CFD study on partial oxidation of methane in fixed-bed reactor

Partial oxidation of methane (POM) is a preferred method for synthesis gas, which usually occurs in fixed bed reactors. In this paper, the discrete element method (DEM) is used to reconstruct the structure of a reactor bed via simulating the process of filling the reactor with catalyst. The particle resolved CFD physical model with the detailed micro-kinetcis of the POM reaction was established to study the interaction among reactant flow, heat and mass transfer, and reaction in the fixed bed. The gas composition and temperature distribution in the reactor were obtained based on the simulation results. The effects of the space velocity and the reaction temperature on the CH₄ conversion, catalyst selectivity, and catalyst surface coke formation were analyzed. The simulation results show that the temperature hot spots of the catalyst in the bed occur at the inlet and the temperature increases further near the wall. With the increase in space velocity, the conversion rate of CH₄ decreases gradually, and the selectivity does not change significantly. As the temperature increases, the conversion rate of CH₄ gradually increases and the selectivity decreases. The risk of coke formation on the catalyst surface rises axially and the C species concentration is relatively higher near the outlet. Appropriately increasing the gas velocity and increasing the temperature helps to reduce the surface coke accumulation of the catalyst.