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1.
The performance characteristics of isothermal fluidized bed syngas methanation for substitute natural gas are investigated over a self-made Ni–Mg/Al2O3 catalyst. Via atmospheric methanation in a laboratory fluidized bed reactor it was clarified that the CO conversion varied in 5% when changing the space velocity in 40–120 L·g?1·h?1 but the conversion increased obviously by raising the superficial gas velocity from 4 to 12.4 cm·s?1. The temperature at 823 K is suitable for syngas methanation while obvious deposition of uneasy-oxidizing Cγoccurs on the catalyst at temperatures around 873 K. From a kinetic aspect, the lowest reaction temperature is suggested to be 750 K when the space velocity is 60 L·g?1·h?1. Raising the H2/CO ratio of the syngas increased proportionally the CO conversion and CH4 selectivity, showing that at enough high H2/CO ratios the active sites on the catalyst are sufficient for CO adsorption and in turn the reaction with H2 for forming CH4. Introducing CO2 into the syngas feed suppresses the water gas shift and Boudouard reactions and thus increased H2 consumption. The ratio of CO2/CO in syngas should be better below 0.52 because varying the ratio from 0.52 to 0.92 resulted in negligible increases in the H2 conversion and CH4 selectivity but decreased the CH4 yield. Introducing steam into the feed gas affected little the CO conversion but decreased the selectivity to CH4. The tested Ni–Mg/Al2O3 catalyst manifested good stability in structure and activity even in syngas containing water vapor.  相似文献   

2.
甲苯与叔丁醇在补铝HM沸石催化剂上的烷基化反应   总被引:1,自引:0,他引:1       下载免费PDF全文
The realuminated H-mordenite catalysts (HM1-4) treated with different concentrations of NaOH and NaAlO2 aqueous solutions were prepared, and characterized by inductively coupled plasma (ICP), X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR) and temperature-programmed desorption of ammonia, They are of lower Si/Al ratio and higher acid amount while keeping a high relative crystallinity. Their catalytic performances were evaluated with the liquid-phase tert-butylation of toluene with tert-butyl alcohol in a 100 ml stainless steel batch reactor equipped with a stirrer. HM2 zeolite catalyst, obtained by treating HM in 0.1 mol•L-1 NaOH followed by 0.05 mol•L-1 NaAlO2 aqueous solution, shows a higher catalytic activity because of its highest acid amount. For HM2 catalyst the influences of reaction conditions on catalytic performance were investigated. The conversion of toluene is 50.3% and the selectivity of p-tert-butyltoluene is 74.7% at a temperature of 180°C, 2 of molar ratio of tert-butyl alcohol to toluene, 4h of reaction time and 0.2 of M(catalyst)/M(toluene).  相似文献   

3.
Under oxygen transfer limitation and kinetic control, liquid-phase catalytic oxidation of toluene over metalloporphyrin was studied. An improved technique of measuring dissolved oxygen levels for gas-liquid reaction at the elevated temperature and pressure was used to take the sequential data in the oxidation of toluene catalyzed by metalloporphyrin. By this technique the corresponding control step of toluene oxidation could be obtained by varying reaction conditions. When the partial pressure of oxygen in the feed is lower than or equal to 0.070 MPa at 463 K, the oxidation of toluene would be controlled by oxygen transfer, otherwise the reaction would be controlled by kinetics. The effects of both oxygen transfer and kinetic control on the toluene conversion and the selectivity of benzaldehyde and benzyl alcohol in biomimetic catalytic oxidation of toluene were systematically investigated. Three conclusions have been made from the experimental results. Firstly, under the oxygen transfer limitation the toluene conversion is lower than that under kinetic control at the same oxidation conditions. Secondly, under the oxygen transfer limitation the total selectivity of benzaldehyde and benzyl alcohol is lower than that under kinetic control with the same conversion of toluene. Finally, under the kinetics control the oxidation rate of toluene is zero-order with respect to oxygen. The experimental results are identical with the biomimetic catalytic mechanism of toluene oxidation over metalloporphyrins.  相似文献   

4.
Gas-phase dehydration of glycerol to produce acrolein was investigated over commercial catalysts based onγ-Al2O3, viz. A-64, A-56, I-62, AP-10, AP-56, AP-64 and KR-104. To understand the effect of Cl?anions, HCl-impregnated sup-ports have been investigated in the dehydration reaction of glycerol at 375 °C. For comparison, various H-zeolites were also examined. It was found that the glycerol conversion over the solid acid catalysts was strongly dependent on their acidity and surface area. And the relationship between the catalytic activity and the acidity of the catalysts was discussed. The outstanding properties of Pt/γ-Al2O3 catalyst systems for the dehydration of glycerol were revealed. Pt/γ-Al2O3 catalyst (AP-64) showed the highest catalytic activity after 50 h of reaction with an acrolein selectivity of 65%at a conversion of glycerol of 90%. Based on these results, catalysts based onγ-Al2O3 appear to be most promising for gas phase dehydration of glycerol.  相似文献   

5.
Heterogeneous oxidation of cyclohexane by tert-butyl hydroperoxide (TBHP) was carried out over ZSM-5 catalysts with different Si/Al ratios in ionic liquids and organic molecular solvents. Higher yield and selectivity of the desired products were found in ionic liquids than in molecular solvents. The conversion of cyclohexane exhibits a decrease from 15.8% to 10.8% with the increase of Si/Al ratio of the HZSM-5 catalyst, and all the catalysts exhibit good selectivity of monofunctional oxidation products at around 97%. The activity of catalyst is found strongly de-pendent on the alkyl chain length of ionic liquid.  相似文献   

6.
In this study, isobutane dehydrogenation to isobutene reaction was carried out in a series of Pt-Cu bimetallic catalysts prepared by co-impregnation method. The catalysts were characterized by means of several techniques, including XRD, N_2 adsorption–desorption, TEM, XPS, H_2-TPR and TG. The results show that the existence of LaAlO_3 perovskite can enhance the dispersion and sintering resistance of metal nanoparticles and facilitate the transfer of carbon deposits from active sites to the support. Interestingly,the perovskite nanoparticles can also inhibit the reduction of CuOxand the formation of PtCu alloys,resulting in the suitable interaction between Pt and Cu. The Pt-Cu/LaAlO_3/SiO_2 catalyst exhibits the optimal dehydrogenation performance with an isobutane conversion of 47% and isobutene selectivity of 92% after 310 min reaction, which was ascribed to the unique role of LaAlO_3 perovskite as well as the appropriate Pt-Cu interaction.  相似文献   

7.
An efficient catalyst SO_4~(2-)-TiO_2(ST) from industrial metatitanic acid has been successfully prepared to catalyze hydrolysis of ball-milling cellulose. The results show that the highest catalytic efficiency is obtained for ST calcined at 450 °C(ST-450) with the yield of 21.8% glucose, 13.0% 5-HMF and 4.2% furfural at 200 °C for30 min. The ball milling of cellulose and solid acid catalyst significantly enhances the cellulose hydrolysis. The high Lewis to Br?nsted acid sites ratio for ST-450 induced by bidentate ligands between SO_4~(2-)and TiO_2 benefits high organics yield, and high total acid sites contribute to the high cellulose conversion. The large pore volume of0.29 cm~3·g~(-1) and appropriate pore size of 7.35 nm of ST-450 also contribute to the high performance. High reaction temperature over 200 °C exhibits negative effect on glucose and 5-HMF yield due to undesired side reactions, while furfural product is stable in the reaction system. The bidentate ligands between SO_4~(2-)and TiO_2 are considered as active acid sites for cellulose hydrolysis in water–ethanol solvents.  相似文献   

8.
Hierarchical single-crystal ZSM-5 zeolites with different Si/Al ratios(Hier-ZSM-5-x,where x=50,100,150 and 200)were synthesized using an ordered mesoporous carbon-silica composite as hard template.Hier-ZSM-5-x exhibits improved mass transport properties,excellent mechanical and hydrothermal stability,and higher catalytic activity than commercial bulk zeolites in the benzyl alcohol self-etherification reaction.Results show that a decrease in the Si/Al ratio in hierarchical single-crystal ZSM-5 zeolites leads to a significant increase in the acidity and the density of micropores,which increases the final catalytic conversion.The effect of porous hierarchy on the diffusion of active sites and the final catalytic activity was also studied by comparing the catalytic conversion after selectively designed poisoned acid sites.These poisoned Hier-ZSM-5-x shows much higher catalytic conversion than the poisoned commercial ZSM-5 zeolite,which indicates that the numerous intracrystalline mesopores significantly reduce the diffusion path of the reactant,leading to the faster diffusion inside the zeolite to contact with the acid sites in the micropores predominating in ZSM-5 zeolites.This study can be extended to develop a series of hierarchical single-crystal zeolites with expected catalytic performance.  相似文献   

9.
A series of carboxylated long chain polyethylene glycols(abbreviated as PEGCOOH) has been synthesized and used to support chloroplatinic acid.These supported catalysts were then tested for their efficiency in the hydrosilylation of alkenes.The factors affecting their catalytic properties,e.g.relative molecular mass of polyethylene glycol,reaction temperature,platinum content,and type of alkenes,have been studied.It was found that the activity of the platinum catalyst decreased with increasing length of the polyethylene glycol chain,and increased with reaction temperature.Moreover,these catalysts could be reused several times without a noticeable decrease in activity or selectivity.The reaction pathway leading to excellent selectivity for the β-adduct of hydrosilylation of alkenes with triethoxysilane catalyzed by this catalysis system was discussed.  相似文献   

10.
The batch reaction experiments have been made for the first time to investigate the effect of ionic structure on the reactivity and selectivity of the trioxane-forming reaction catalyzed by a Br?nsted-acidic ionic liquid (IL). The ILs considered include 1-cyclohexyl-2-pyrrolidinonium trifluoromethanesulfonate ([NCyP][TfO]), 1-cyclohexyl-2-pyrrolidinonium benzenesulfonate ([NCyP][BSA]), 1-cyclohexyl-2-pyrrolidinonium p-toluenesulfonate ([NCyP][p-TSA]), 1-octyl-2-pyrrolidinonium 2,4-dinitrobenzenesulfonate ([NOP][DNBSA]), 1-octyl-2-pyrrolidinonium benzenesulfonate ([NOP][BSA]), 1-octyl-2-pyrrolidinonium methanesulfonate ([NOP][MSA]), and 1-octyl-2-pyrrolidinonium trifluoromethanesulfonate ([NOP][TfO]). It is found that the yield of trioxane in the reaction solution correlates inversely with the Hammett acidity function H0 of the aqueous solution of the corresponding ILs. Variation of the cation structure from [NCyP]+to [NOP]+exerts little influence on the yield and the selectivity of trioxane in the reaction solution. Using [TfO]?or [DNBSA]?in place of [MSA]?or [BSA]?apparently increases the yield of trioxane, but only slightly increases the concentration of formic acid in the reaction solution. The contin-uous production experiments have been made to investigate the performance of [NOP][MSA], [NOP][DNBSA], [NCyP][TfO], and H2SO4 as an extraction distil ation agent. Such effect of [NCyP][TfO] considerably overrides that of H2SO4. The yield and the selectivity of trioxane are both increased when [NCyP][TfO] is used instead of H2SO4 at a reaction time 5 h.  相似文献   

11.
The liquid phase alkylation of catechol with tert-butyl alcohol to produce 4-tert-butyl catechol(4-TBC)was carried out over MCM-41,HZSM-5,H-exchanged montmorillonite and novel acidic porous montmorillonite heterostructures(PMHs).Upon all catalysts tested,4-TBC is the main product and 3-tert-butyl catechol(3-TBC)and 3,5-di-tert-butyl catechol are the side products.The synthetic PMHs showed higher conversion of catechol and better selectivity to 4-TBC compared to other solid acid catalysts tested.Over the PMHs derived from H-exchanged montmorillonite through template extraction processes,the suitable reaction temperature is ca 410 K,the ratio of catechol to tert-butyl alcohol is 1:2.Increasing the amount of catalyst(lower weight hourly space velocity)can improve the conversion of catechol and influence the selectivity slightly.The reasonable reaction time is ca 8 h.The type and strength of acidity of H-montmorillonite and PMH were determined by pyridine adsorption FT-IR and ammonia temperature-programmed desorption techniques.The medium and strong acid sites are conducive to producing 4-TBC and the weak acid sites to facilitating the 3-TBC formation.The differences between the PMHs from calcination and those from extraction are attributed to proton migration and acidity change in the gallery surface.  相似文献   

12.
对叔丁基邻苯二酚的合成研究   总被引:2,自引:0,他引:2  
以邻苯二酚、异丁烯为原料,混酸作催化剂催化合成对叔丁基邻苯二酚的新工艺,探讨了工艺条件对反应结果的影响,确定了优惠条件:反应温度125℃,反应时间2h,物料比n(邻苯二酚)∶n(异丁烯)=1∶0.65,催化剂用量为邻苯二酚的0.1%(m/m),对叔丁基邻苯二酚收率可达93%以上。  相似文献   

13.
t-Butylation of 1,2-dihydroxybenzene (DHB) with isobutene as alkylating agent was carried out over various acidic zeolites such as USH-Y, H-beta, and H-ZSM-5. USH-Y zeolite exhibits the highest catalytic activity and considerable selectivity of 4-t-butylcatechol (4-TBC). The selectivity of 4-TBC is increased in the order of H-ZSM-5>USH-YH-beta. 3-t-Butylcatechol (3-TBC) is well produced over catalyst with high SiO2/Al2O3 ratio and large pore aperture. 3,5-Di-t-butylcatechol (3,5-DTBC) selectivity is maximum in zeolite which contains strong acidity and large pore channel. The influences of various reaction parameters such as reaction temperature, space velocity, reactant molar ratio are discussed. In order to improve 4-TBC formation and decrease in 3,5-DTBC selectivity simultaneously, USH-Y zeolite was silylated by tetraethylorthosilicate (TEOS) resulting in the decrease of 3,5-DTBC selectivity over modified catalysts by about 25%. USH-Y zeolite shows high stability in the t-butylation for at least 350 h. The coke formed during the reaction was identified by FT-IR and the USH-Y zeolite could be regenerated through oxidative thermal treatment.  相似文献   

14.
Several solid acid catalysts were prepared by exchanging metal cations such as Zn2+, Fe3+ and Al3+ with montmorillonite clay. Among these, Al-montmorillonite showed the highest acidity determined by the pyridine-IR as well as NH3-TPD methods. A systematic comparison of the performance of these catalysts along with parent montmorillonite was carried out for the hydroxyalkylation of p-cresol with formaldehyde to give 2, 2′-methylenebis (4-methyl phenol) (DAM). It was found that the activity of these catalysts was in accordance with the increase in acidity of parent montmorillonite after the exchange of cations in the order of Zn2+, Fe3+ and Al3+. The selectivity pattern was also influenced by the exchanged cations. Since Al-montmorillonite showed the highest conversion of 51% with 98% selectivity to DAM, the effects of various reaction parameters, namely, mole ratio, catalyst concentration, temperature, reaction time on conversion and selectivity pattern were also studied using the same catalyst. This catalyst also showed an excellent stability as evidenced by its eight times reuse.  相似文献   

15.
郑稳  林陵  曾崇余 《工业催化》2011,19(5):26-29
分别以硅藻土、γ-Al2O3和MgO为载体,采用均相沉淀一超声浸渍法,制备用于1,2-环己二醇脱氢制备邻苯二酚的镍基催化剂,利用SEM和BET对催化剂进行表征,并对催化活性和选择性进行考察.研究表明,超声浸渍法制备的催化剂,表观形貌规整,颗粒大小均匀,具有较大比例利于生成邻苯二酚的中孔结构,表现出良好的活性和选择性.在...  相似文献   

16.
以硝酸镍为镍源,分别以NH3.H2O,NH4HCO3,NH3.H2O+NH4HCO3为沉淀剂采用沉淀法制备镍/硅藻土催化剂,用于1,2-环己二醇脱氢制备邻苯二酚,考察了不同沉淀剂、焙烧温度、沉淀温度制备的催化剂对1,2-环己二醇脱氢反应性能的影响,并通过XRD,BET,CO2-TPD(热设计功耗)等方法对催化剂进行了表征。结果表明:不同的沉淀剂对镍的分散度、孔结构及表面碱量都有影响,以NH3.H2O+NH4HCO3复合沉淀剂制备的镍/硅藻土催化剂上活性组分镍晶粒度小、分散度较高,催化剂平均孔径较大,催化剂表面碱中心数目多、碱量大,表现出良好的催化活性和邻苯二酚选择性。另外,催化剂适宜沉淀温度为90℃、焙烧温度为350℃。上述适宜条件制备的催化剂在320℃下用于1,2-环己二醇脱氢制备邻苯二酚,1,2-环己二醇转化率达到99.1%,邻苯二酚选择性达到86.8%。  相似文献   

17.
Catalytic performances of various dealuminated mordenite catalysts for the isopropylation of naphthalene by isopropyl alcohol with decalin or cyclohexane as a solvent were investigated in a high-pressure fixed-bed flow reactor. It was found that dealumination of H-mordenite could substantially improve the catalytic conversion, selectivity and stability. The catalyst with steam treatment at 700 °C followed by acid leaching was revealed to exhibit high and comparatively stable conversion of ca. 37% with the high 2,6-/2,7-DIPN ratio of ca. 3. Reaction conditions, such as reaction temperature, pressure, space velocity and solvent, could significantly influence the catalytic performance, except for the 2,6-/2,7-DIPN ratio. The catalytic behavior is discussed in relation with catalyst porosity and acidity.  相似文献   

18.
The properties of catalysts with (i) Brønsted-type acidity (H-mordenite and Al/P mixed oxide), (ii) Lewis-type acidity (Al trifluoride) or (iii) basic characteristics (Mg/Fe mixed oxide) were investigated in the gas-phase methylation of catechol. When methanol was used as the methylating agent, H-mordenite and AlF3 gave high selectivities to guaiacol (the product of O-methylation) under mild reaction conditions, that is at very low catechol conversions. An increase in temperature led to the transformation of guaiacol to phenol and cresols, and to considerable catalyst deactivation. The basic catalyst Mg/Fe/O also favored an extensive degradation of guaiacol to phenol. On the mildly acidic catalyst Al/P mixed oxide a stable catalytic performance and a high selectivity to guaiacol at 40% catechol conversion were obtained. When methylformate, a more reactive methylating agent, was used with AlF3 and Mg/Fe mixed oxide as catalysts, higher catechol conversions and slower deactivation rates could be achieved under mild reaction conditions, with a low extent of guaiacol degradation. However, methylformate rapidly decomposed when temperatures above 350 °C were used. Finally, tests were made by reacting catechol and diethoxymethane with acid catalysts, with the aim of synthesizing methylenedioxybenzene. The latter product was obtained with high selectivity, but with very low yield, due to both catalyst deactivation and decomposition of diethoxymethane.  相似文献   

19.
杨宇 《广州化工》2009,37(4):104-106,113
在微型固定床连续流动反应装置上评价催化剂,研究了碱金属离子对合成愈创木酚催化剂AlPTiSbO性能的影响,结果显示碱金属离子对催化剂有较大的影响。优化了催化剂中钠离子的含量,发现最佳的钠铝原子比为0.045。在此催化剂上,280℃,常压下,愈创木酚的选择性为98%,邻苯二酚的转化率达到92%,催化剂稳定性也明显增加。采用BET,XRD,XPS和NH3-TPD等技术对催化剂进行了表征。结果显示,添加钠离子后,催化剂的比表面积有所增加;催化剂中磷酸盐(钠)含量增加;催化剂的表面酸强度降低。  相似文献   

20.
以临安钠基蒙脱土为原料,制备了铁交联和铁镧复合交联蒙脱土催化剂,利用物理吸附(BET)、扫描电镜(SEM)和X-射线衍射(XRD)对催化剂进行表征,并以铁镧复合交联蒙脱土(Fe/La-PILC)为催化剂,质量分数为30%的过氧化氢水溶液为氧化剂,考察反应时间、催化剂用量和过氧化氢用量对苯甲醇催化氧化制苯甲醛的影响.结果表明:铁镧复合交联蒙脱土形成了比较均一的中孔骨架结构;当苯甲醇与过氧化氢物质的量之比为1:2,Fe/La(200)-PILC(Fe与La物质的量之比为200)质量分数为4%,反应5 h时,苯甲醇转化率和苯甲醛选择性分别为62.1%和86.4%.研究铁镧交联蒙脱土催化剂的催化氧化机理,发现Fe/La-PILC催化氧化苯甲醇的活性氧来自于Fe/La-PILC所吸附的氧.  相似文献   

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