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1.
使用模型化合物在微型反应釜中研究了载体炭黑对渣油内部氢转移反应的影响。结果表明,炭黑可以明显地促进四氢萘到蒽的氢转移反应。使用等体积浸渍法制备了Fe/炭黑、Ni/炭黑催化剂并对Fe/炭黑催化剂进行了XRD、SEM表征,结果表明,金属硫化物附着在炭黑颗粒的表面,直径为1μm左右。在高压反应釜中研究了载体炭黑和以炭黑为载体的催化剂对克拉玛依常压渣油430℃加氢反应的影响,并于传统的水溶性分散型催化剂的抑焦性能进行了对比。 结果表明,Fe/炭黑、Ni/炭黑催化剂可以明显地抑制渣油加氢反应的生焦,水洗后的催化剂效果比未经水洗的催化剂抑制生焦的效果好;Ni/炭黑催化剂抑焦效果比Fe/炭黑催化剂好;Fe/炭黑催化剂比同等浓度的水溶性Fe催化剂抑焦效果好。对反应产物馏分的分析表明,Fe/炭黑催化剂可以有效地抑制渣油缩合生焦,同时在一定程度上抑制裂化反应。  相似文献   

2.
在对βMo2N0.78催化剂加氢脱硫催化性能进行考察的基础上,对反应使用后催化剂的组成、结构变化、以及反应后催化剂再处理对活性的影响等几方面进行了研究。结果表明,在噻吩加氢脱硫条件下,βMo2N0.78 催化剂的氮含量下降,表层被硫化,而且钝化过程中产生的氮氧化物被消耗,但体相结构没有发生变化,表现了较强的抗硫化性能;脱硫反应前后催化剂的氢还原处理不能改善催化剂的活性,但预硫化催化剂在反应起始的活性与钝化催化剂在反应稳定时活性相近,加氢脱硫反应后催化剂的再次氮化处理,可以较大程度的恢复催化剂的初始活性。  相似文献   

3.
木质素催化转化制取苯、甲苯和二甲苯   总被引:1,自引:0,他引:1  
对HZSM-5、HY和MCM-22三种催化剂进行了比较,其中HZSM-5催化裂解木质素制备苯、甲苯和二甲苯(BTX)的结果最优.确定了木质素催化裂解的最佳反应条件,包括反应温度、载气流速、催化剂/木质素配比.当反应温度为550-600℃,载气流速为300mL/min,催化剂/木质素配比为2时,使用HZSM-5催化裂解制备BTX的最高C产率和芳香选择性分别可达25.3%和90.9%。  相似文献   

4.
对以芳香醛、乙酰丙酮及碳酸氢铵为原料,苯甲酰胺吡咯烷为催化剂,合成1,4-二氢吡啶的反应进行了研究。考察了催化剂、溶剂、温度、时间和氮源对产率的影响。结果表明,反应温度70℃,芳香醛、乙酰丙酮和碳酸氢铵的摩尔比0.5∶1∶0.5,催化剂Ⅳ的用量10(mol)%时,产率最高,可达93%。催化剂循环使用3次,产率基本不变。该反应具有催化剂经济易得、反应条件温和、环境友好和操作简单等优点。  相似文献   

5.
以大孔聚苯乙烯氯球为原料,在氮气保护及氢化钠存在下,将其与4 氨基吡啶及硫酸二甲酯反应,制成聚苯乙烯支载N 苄基 N 甲基氨基吡啶(BMAP)催化剂.与文献相比,该法具有反应时间短,价格低,制备的BMAP活性高等特点.经过元素分析、FTIR及MAS1H NMR对其结构进行表征.利用该催化剂进行了芳樟醇的乙酰化反应,对影响反应的诸因素如反应物料比,反应时间,反应温度等进行了讨论,芳樟醇的转化率为99%以上,总酯率为95%左右,其中芳樟酯的产率为60%以上(目前工业上使用H3PO4催化剂芳樟酯产率为50%左右).催化剂通过再生连续使用五次,活性无明显下降.  相似文献   

6.
李贵贤  王建民  胡东成  闫亮  索继栓 《分子催化》2005,19(3):182-187,i002
以Dawson型磷钼钒杂多酸盐为相转移催化剂,用过氧化氢水溶液为氧化剂,研究了苯甲醇液相选择氧化制苯甲醛的反应.系统考察了催化剂的类型、催化剂用量、反应温度和反应时间等因素对反应的影响.结果表明:(Cpry)6HP2Mo17VO62/H2O2/H2O是一可循环使用的苯甲醇选择氧化制苯甲醛的高效环境友好催化剂体系,适宜的反应条件为,催化剂用量2μmol,H2O2 10mmol,反应温度80℃,反应时间8h.  相似文献   

7.
钱华  叶志文 《应用化学》2009,26(6):676-680
使用负载型杂多酸为催化剂,N2O5为硝化剂的新型硝化体系,对氯苯的硝化反应进行研究。文章分别考察了杂多酸类型、载体种类、杂多酸负载量及催化剂循环使用次数等因素对硝化反应的影响。结果证明,N2O5硝化反应属于酸催化反应,负载型杂多酸能显著提高N2O5的硝化能力;催化剂回收后可直接重复使用,催化活性没有明显的降低。在优化条件下,氯苯硝化反应得率为26%,对位选择性达到68.8%,表明N2O5是一种具有应用前景的硝化试剂,可取代传统的硝硫混酸硝化法,减少废酸处理,符合绿色环保要求。  相似文献   

8.
两种甲醇水蒸气重整制氢催化剂的研究   总被引:1,自引:3,他引:1  
对采用共沉淀法制备的CuZnAlO类铜系催化剂和采用水滑石类层柱材料(LDHs)前驱体制备的催化剂在甲醇水蒸气重整制氢反应中的性能进行了研究。对共沉淀法制备的CuZnAlO类铜系催化剂考察了ZrO2助剂的加入对催化剂反应性能的影响,发现Zr的质量分数为10%的催化剂显著提高CuZnAlO催化剂的反应性能。该催化剂的最佳反应条件:0.1 MPa、250 ℃、H2O/MeOH摩尔比1.0~1.3、3.56 h-1。在此反应条件下进行了COPZr2催化剂150 h稳定性实验。结果表明,该催化剂具有很好的反应稳定性。甲醇转化率和氢产率分别约为88%和83%,产物湿基组成中H2和CO的质量分数分别为>63%和0.20%~0.31%。对LDHs前驱体制备的催化剂,进行了70 h反应稳定性实验,结果表明,催化剂虽具有较高的起始活性,但随反应进行,活性有所下降,30?h后基本保持稳定,甲醇转化率和产氢率分别为73%和66%,产物湿基组成中H2和CO的质量分数分别为>55%和0.07%~0.08%。该类催化剂的反应稳定性虽较差,但却可以显著降低产物湿基组成中CO的摩尔分数。对LDHs前驱体制备的催化剂进行XRD和SEM表征结果表明,ZrO2的加入使催化剂中CuO晶粒分散更为均匀,颗粒更细。  相似文献   

9.
二氧化硅负载磷钨酸铵催化苯酚氧化溴代反应   总被引:1,自引:0,他引:1  
以溶胶-凝胶法制备的二氧化硅负载磷钨酸铵为催化剂,溴化钾为溴源,双氧水为氧化剂,冰醋酸为溶剂,实现了苯酚的催化氧化溴代反应。 探讨了催化剂负载量、催化剂用量和反应时间等反应参数对氧化溴代反应的影响。 结果表明,溶胶-凝胶法制备的负载磷钨酸铵仍具有典型的Keggin结构;在室温的温和条件下,该催化剂表现出较强的催化苯酚氧化溴代反应活性和较高的对溴苯酚选择性,在实验优化条件下,苯酚转化率达到95.4%,对邻比达到3.2;而且催化剂易回收,重复4次使用后,催化活性有所降低,苯酚转化率为87.4%,对邻比为1.6。  相似文献   

10.
以蔗糖为原料通过羟基的选择性保护、脱保护及迁移合成了三氯蔗糖的中间体2,3,6,3’,4’-五氧乙酰基蔗糖(6-PAS)。在蔗糖羟基的选择性保护反应中采用4.二甲氨基吡啶(DMAP)为催化剂,有效地提高了产率.并利用HPLC对选择性脱保护和乙酰基迁移2步反应进行跟踪,确定了较优的合成路线。并用核磁共振和红外光谱对产品进行表征。羟基选择性保护最佳反应条件为:使用质量分数为10%的催化剂,三苯甲基化反应在50℃进行4h,乙酰化反应在105℃进行3h。在该条件下进行反应,产率为81.9%。  相似文献   

11.
A three-phase reactor mathematical model was set up to simulate and design a three-phase bubble column reactor for direct synthesis of dimethyl ether (DME) from syngas, considering both the influence of part inert carrier backmixing on transfer and the influence of catalyst grain sedimentation on reaction. On the basis of this model, the influences of the size and reaction conditions of a 100000 t/a DME reactor on capacity were investigated. The optimized size of the 10000 t/a DME synthesis reactor was proposed as follows: diameter 3.2 m, height 20 m, built-in 400 tube heat exchanger (φ38×2 mm), and inert heat carrier paraffin oil 68 t and catalyst 34.46 t. Reaction temperature and pressure were important factors influencing the reaction conversion for different size reactors. Under the condition of uniform catalyst concentration distribution, higher pressure and temperature were proposed to achieve a higher production capacity of DME. The best ratio of fresh syngas for DME synthesis was 2.04.  相似文献   

12.
二甲醚气相色谱相对重量校正因子的测定   总被引:1,自引:0,他引:1  
陈吉平  张乐沣  杨立新  蔡光宇 《色谱》1997,15(3):248-249
 用冰冷却水吸收二甲醚配制样品,将TCD和FID串联使用,测定出二甲醚在TCD和FID上相对于甲醇的重量校正因子分别为0.86和0.55,并通过用甲醇催化脱水生成的二甲醚和水的化学计量关系,在线间接测定二甲醚在TCD上相对于甲醇的重量校正因子,从而使上述测定结果得到佐证。  相似文献   

13.
A model is proposed for the kinetics of the direct conversion of synthesis gas to dimethyl ether (DME) on a bifunctional catalyst in a flow reactor. Calculations for the yield of methanol and DME were carried out using literature data for the kinetics of methanol synthesis and methanol dehydration.  相似文献   

14.
运用电化学循环伏安法(CV)和原位傅立叶变换红外(FTIR)反射光谱, 研究了不同pH值溶液中二甲醚(DME)在Pt电极上的解离吸附和氧化过程. 稳态CV结果给出, 在0.1 mol·L-1 H2SO4溶液中, 当电位处于0.05-0.35 V (vs RHE)区间, 约70%的Pt表面位被DME的解离吸附产物占据. DME电氧化反应的活性随pH值增加而下降, 在0.1 mol·L-1 NaOH溶液中, 氢的吸脱附几乎不受抑制且观察不到明显的氧化电流, 表明DME醚键上氧原子的质子化是其发生解离吸附和氧化的必要条件. 原位FTIR光谱研究给出DME解离吸附和氧化过程的分子水平信息, 指出DME在低电位区间解离生成线型吸附态CO(COL)毒性中间体. 当电位高于0.55 V(vs RHE)时, COL开始氧化为CO2; 在0.75-1.00 V(vs RHE)的电位区间则可同时发生经活性中间体(HCOOH)的氧化过程.  相似文献   

15.
The formation of primary olefins from dimethyl ether (DME) was studied over ZSM-5 catalysts at 300°C using a novel step response methodology in a temporal analysis of products (TAP) reactor. For the first time, the TAP reactor framework was used to conduct single- and multiple-step response cycles of DME (balance argon) over a shallow bed with the continuous flow panel. Propylene is the major primary olefin and portrays an S-shaped profile with a preceding induction period when it is not observed in the gas phase. Methanol and water portray overshoot profiles due to their different rates of generation and consumption. DME effluent shows a rapid rise halfway to its steady-state value leading to a slow rise thereafter because of its high desorption rates followed by subsequent reactions involving DME in further steps during the induction period. To analyze the experimental data quantitatively, nine reaction schemes were compared, and kinetic parameters were obtained by solving a transient plug flow reactor model with coupled dispersion, convection, adsorption, desorption, and reaction steps. The methoxymethyl pathway involving dimethoxyethane and methyl propenyl ether gives the closest match to experimental data in agreement with recent density functional theory studies. Gaseous dispersion coefficients of ca. 10−9 m2 s−1 were obtained in the TAP reactor. The novel experimental data validated against the transient kinetic model suggests that after the formation of initial species, the bottleneck in propylene formation is the transformation of the initial C–C bond, that is dimethoxyethane formed initially from DME and methoxymethyl groups. DME adsorption on ZSM-5 catalyst generates surface methoxy groups, which further react with the feed to give methoxymethyl groups. These methoxymethyl groups are regenerated through a series of reactions involving intermediates such as dimethoxymethane and methyl propenyl ether before propylene formation.  相似文献   

16.
Regioselective anodic monofluorination of 4-oxo-2-pyrimidyl sulfides was investigated under various electrolytic conditions. Anodic fluorination was successfully carried out using Et(4)NF.4HF in dimethoxyethane (DME) to provide the corresponding alpha-fluorinated products in good yields. In contrast, acetonitrile (MeCN) was not suitable for the anodic fluorination due to the severe anode passivation during the electrolysis. A mixed solvent of DME and MeCN was found to be also effective for the fluorination, and the product yield increased with an increase of the ratio of DME to MeCN. The superiority of DME can be explained mainly in terms of the suppression of the anode passivation and enhancement of the nucleophilicity of the fluoride ions. Such marked solvent effects on the anodic fluorination were discussed in detail.  相似文献   

17.
As a solvent, ethanol can extract a wide range of polar substances, but its consumption is sometimes avoided for religious and cultural reasons. In this study, liquefied dimethyl ether (DME) was used to extract curcumin and antioxidants from highly moist, untreated turmeric. Higher amounts of curcumin (7.94 mg/g dry weight (DW)) were extracted using liquified DME compared with ethanol (6.77 mg/g DW). Almost all the water and 5.10 mg/g DW of lipids were extracted from raw turmeric using liquefied DME, corresponding to 56 % the amount extracted using ethanol. In addition, microscopic and spectroscopic analyses revealed that liquefied DME neither destroyed cell walls nor extracted cellulose. However, liquefied DME had a slightly lower extraction capacity for total phenolic compounds than ethanol and slightly lower antioxidant effect. DME extracts an equivalent amount of curcumin as ethanol and only slightly fewer antioxidants while simultaneously avoiding sun-drying degradation and prolonged freeze-drying.  相似文献   

18.
Leiming Pan 《Acta Physico》2008,24(10):1739-1744
Dissociative adsorption and electrooxidation of dimethyl ether (DME) on a platinum electrode in different pH solutions were studied using cyclic voltammetry (CV) and in situ FTIR reflection spectroscopy. The coverage of the dissociative adsorbed species was measured about 70% from hydrogen adsorption-desorption region (0.05-0.35 V (vs RHE)) of steady-state voltammogram recorded in 0.1 mol·L−1 H2SO4 solution. It was found that the electrochemical reactivity of DME was pH dependent, i.e., the larger the pH value was, the less the reactivity of DME would be. No perceptible reactivity of DME in 0.1 mol·L−1 NaOH solution could be detected. It was revealed that the protonation of the oxygen atom in the C-O-C bond played a key role in the electrooxidation of DME. In situ FTIR spectroscopic results illustrated that linearly bonded CO (COL) species determined at low potential region were derived from the dissociative adsorption of DME and behaved as ‘poisoning’ intermediate. The COL species could be oxidized to CO2 at potential higher than 0.55 V (vs RHE) and in the potential range from 0.75 to 1.00 V (vs RHE) DME was oxidized simultaneously via HCOOH species that were identified as the reactive intermediates.  相似文献   

19.
We have conducted a high-level quantum chemistry study of the interactions of 1,2-dimethoxyethane (DME) with water for complexes representing both hydrophilic and hydrophobic hydration. It was found that our previous quantum chemistry-based force field for poly(ethylene oxide) (PEO) and its oligomers in aqueous solution did a poor job in describing the hydrophobic binding of water to the ether, consistent with our recent calculations of the excess free energy and entropy of hydration of DME. Our original force field was revised to more accurately reproduce the interaction of water with the carboneous portions of DME. Molecular dynamics simulations of aqueous DME solutions using the revised quantum chemistry-based potential yielded good agreement with experiment for excess free energy, enthalpy, and volume as well as excess solution viscosity and the self-diffusion of water. Comparison with our original potential revealed that the relatively hydrophobic ether-water interactions in the new potential strongly reduced the favorable excess free energy and enthalpy but have relatively little influence on the excess entropy for dilute DME solutions. Other properties of DME and PEO solutions including conformational populations and dynamics, solution viscosity, hydrogen bonding, water translational and rotational diffusion and neutron structure factor as a function of solution composition were found to be largely unchanged from those obtained using the original potential.  相似文献   

20.
以Al2O3/堇青石蜂窝陶瓷为载体,氧化锰八面体分子筛(OMS-2)为活性组分,采用涂覆法制备了系列整体式催化剂。考察了黏合剂种类和活性组分涂覆次数对二甲醚(DME)催化燃烧性能的影响,并对催化剂进行XRD、BET、SEM、H2-TPR、O2-TPD等表征。结果表明,以甲氧基聚乙二醇为黏合剂经一次涂覆制备的整体式催化剂的性能最佳,活性组分OMS-2以相互交织的簇体均匀分布在载体上,并与Al2O3之间存在较强的相互作用。涂层的添加有效增加了催化剂的比表面积,提高了催化剂的性能,最佳催化活性t90为257 ℃。  相似文献   

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