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1.
SAPO-34 zeolite is considered to be an effective catalyst for methanol or dimethyl ether conversion to olefins. In this study, we developed the in situ synthesis technology to prepare SAPO-34 zeolite in kaolin microspheres as a catalyst for fluidized methanol or dimethyl ether to olefins process. The silicoaluminophosphate zeolite was first time reported to be synthesized in kaolin microspheres. The SAPO-34 content of synthesized catalyst was about 22% as measured by three different quantitative methods (micropore area, X-ray fluorescence and energy dispersive spectroscopy element analysis). Most of the SAPO-34 zeolites were in nanoscale size and distributed uniformly inside the spheres. The catalytic performance was evaluated in fixed bed and fluidized bed reactors. Compared with the conventional spray-dry catalyst, SAPO/kaolin catalyst showed superior catalytic activities, better olefin selectivities (up to 94%, exclusive coke), and very good hydrothermal stability. The in situ synthesis of SAPO-34 in kaolin microspheres is a facile and economically feasible way to prepare more effective catalyst for fluidized MTO/DTO (methanol to olefins/dimethyl ether to olefins) process.  相似文献   

2.
Ni/Al2O3 aerogel catalysts were synthesized by a sol-gel method combined with a supercritical drying route. The catalytic performances of the catalysts in methane reforming with CO2 were investigated in a quartz micro-reactor. The results indicated that the aerogel catalyst showed higher specific surface area and higher dispersivity of nickel species than those of impregnation catalyst. The excellent catalytic performances and stabilities were achieved over the aerogel catalysts in the fluidized bed reactor. Comprehensive characterization with TG, XRD and FESEM revealed that the aerogel catalyst in the fluidized bed had much lower carbon deposition than that in the fixed bed. The fluidization of the aerogel catalyst greatly improved the contact efficiency of gas-solid phase, which accelerated the gasification of the deposited carbon. In contrast, the deactivation of the aerogel catalyst was caused by the carbon deposition due to the catalyst without moving in the fixed bed. Moreover, decreasing activity of the impregnation catalyst in the fluidized bed resulted from the poor fluidization state of catalyst particles and low effective active sites on surface of catalyst.  相似文献   

3.
The fluidization characteristics of a nanoparticle catalyst were investigated in a fluidized bed assisted with an axial magnetic field. It showed that slugging and channeling, commonly observed when processing nanoparticles via conventional fluidized bed reactors, could be effectively eliminated, and the size of the agglomerates and bubble diameter could also be reduced with the aid of the magnetic field, leading to much improved gas-solid contact efficiency. Due to the improved gas-solid contact efficiency, the performance of the CH4-CO2 catalytic reforming has been significantly enhanced, where the initial conversion of CH4 was 7.6% and 24.3% higher than those obtained in a conventional fluidized bed reactor and a fixed bed reactor. The catalytic deactivation, caused by carbon deposition on catalyst surfaces, is also slower in the magnetic fluidized bed operation, where the CH4 conversion is 11.7% and 42.6% greater as compared with those in the conventional fluidized bed operation and the fixed bed operation. The present investigations demonstrated that carbon deposition can be much suppressed through improving the gas-solid contact efficiency with the assistance of the magnetic field.  相似文献   

4.
甲醇制烯烃工艺近年来已成为煤化工领域的研究热点。不同的甲醇制烯烃催化剂将导致不同的反应过程,以SAPO-34为催化剂时,甲醇主要遵循烃池机理,通过快速的平行反应直接生产乙烯和丙烯(MTO)等低碳烯烃;以ZSM-5为催化剂时,甲醇主要遵循双循环机理中的烯烃循环机理,通过甲基化-裂解等多步反应间接生产丙烯(MTP)。这种反应特征的不同也决定着反应器类型和工艺条件的不同:SAPO-34催化剂易失活的特性决定了工业MTO过程通常采用易再生的流化床反应器从甲醇一步生成乙烯和丙烯,而具有良好抗结焦能力的ZSM-5催化剂使得工业MTP过程通常选择易放大的固定床反应器,通过大量烯烃循环与分离逐步获得丙烯。针对SAPO-34催化剂上MTO过程以及ZSM-5催化剂上MTP过程的不同反应情况,综述了近年来甲醇制烯烃代表性的反应工艺、反应机理以及反应动力学等方面的研究进展,并根据其存在的问题提出了相应的发展方向。  相似文献   

5.
The SAPO-34/ZrO2 composite catalysts using ZrO2 as a binder were prepared and their performance was investigated for the dimethyl ether to olefins (DTO) reaction. The composite catalysts showed higher catalytic lifetimes than the free SAPO-34 catalyst, while maintaining high selectivity toward light olefins. This suggests that the binder-filled space between the SAPO-34 crystals can provide additional diffusion paths for mass transfer. In the SAPO-34/ZrO2 composite catalysts with different ZrO2 contents, the SAPO-34(11 wt%)/ZrO2 composite catalyst showed the highest catalytic lifetime. It can be concluded that ZrO2 is one of the best binders for the preparation of SAPO-34/binder composite catalysts.  相似文献   

6.
采用流化床两相模型描述甲醇制烯烃(MTO)过程,采用拉格朗日颗粒跟踪方法模拟催化剂上的积炭与反应,考察了相间传质、催化剂停留时间及返混对MTO过程的影响。结果表明,湍动流化床相间传质速率小于催化反应速率,是MTO过程的速率控制步骤;强化传质和延长催化剂停留时间都能显著提高催化剂的积炭量,有利于提高乙烯与丙烯的选择性;而减小催化剂返混或采用多级串连操作对反应选择性的改善作用不大,采用气固多级逆流操作反而会导致选择性显著下降。  相似文献   

7.
张奇  王涯  陈胜利  高玉李  蒋永杰 《工业催化》2014,22(10):775-779
SAPO-34分子筛用于催化甲醇转化制烯烃,乙烯和丙烯选择性高,是很好的甲醇制烯烃催化剂。由于SAPO-34分子筛失活速率快,甲醇制烯烃反应器通常是连续循环再生的流化床反应器,SAPO-34分子筛必须喷雾成型并达到一定抗磨强度后才能使用。在50 L反应釜合成了SAPO-34分子筛,并在中试喷雾装置上,以SAPO-34为活性组分喷雾成型甲醇制烯烃催化剂。结果表明,喷雾成型甲醇制烯烃催化剂的抗磨损指数为1.58%·h-1,抗磨性能达到工业应用要求,与两种工业甲醇制烯烃催化剂对比,喷雾成型甲醇制烯烃催化剂寿命最长,达260 min,乙烯、丙烯选择性以及乙烯+丙烯总选择性在对应的各个反应时间点均最高,260 min分别达到49.09%、35.05%和84.98%。  相似文献   

8.
The dimethyl ether to olefins process is very important for converting coal to chemicals. A SAPO-34 molecular sieve with a particle size up to 50 μm has been synthesized with morpholine as the template. The cold model fluidization experiment indicates that the SAPO-34 catalyst with average size of 45–50 μm is of good fluidization properties. After high temperature steam treatment at 1073 K for 8 h, this large fluidizable catalyst showed good reactivity and selectivity for the dimethyl ether to olefins (DTO) reaction in a micro-reactor. X-ray diffraction characterization showed that the structure of the catalyst was maintained well. A fluidized reactor of 50 mm inner diameter was used to carry out the DTO reaction, which showed that the fluidizable SAPO-34 is a selective catalyst for light olefin production.  相似文献   

9.
Chaoquan Hu   《Catalysis communications》2009,10(15):2008-2012
Ultrafine Cu0.1Ce0.5Zr0.4O2−δ catalyst operated in a fluidized bed reactor was found to be very effective for complete oxidation of dilute benzene in air. The complete conversion of benzene could be achieved at reaction temperature as low as 220 °C. The mechanism of benzene oxidation over the Cu0.1Ce0.5Zr0.4O2−δ catalyst was investigated by conducting pulse reaction of pure benzene in the absence of O2 over the catalyst and the results indicated the involvement of lattice oxygen from the catalyst in benzene oxidation.  相似文献   

10.
A comparative study was conducted for laboratory syngas methanation over a self-made Ni–Mg/Al2O3 catalyst to demonstrate the technical advantages of fluidized bed over fixed bed reactor. At different reaction temperatures, gas velocities and pressures, the CO conversion and selectivity to CH4 in fluidized bed were shown to be higher than in fixed bed, and much closer to the thermodynamic equilibriums. The spent catalysts from fluidized bed methanation had distinctively low and easy-oxidizing deposited carbon in comparison with that from fixed bed. The results were attributed to the bigger effective catalytic surface, better heat and mass transfer in fluidized bed reactor.  相似文献   

11.
Light olefins(C_2–C_4) are fundamental building blocks for the manufacture of polymers, chemical intermediates,and solvents. In this work, we realized a composite catalyst, comprising Mn_xZr _yoxides and SAPO-34 zeolite,which can convert syngas(CO + H_2) into light olefins. Mn_xZr_yoxide catalysts with different Mn/Zr molar ratios were facilely prepared using the coprecipitation method prior to physical mixing with SAPO-34 zeolite. The redox properties, surface morphology, electronic state, crystal structure, and chemical elemental composition of the catalysts were examined using H_2-TPR, SEM, XPS, XRD, and EDS techniques, respectively. Tandem reactions involved activation of CO and subsequent hydrogenation over the metal oxide catalyst, producing methanol and dimethyl ether as the main reaction intermediates, which then migrated onto SAPO-34 zeolite for light olefins synthesis. Effects of temperature, pressure and reactant gas flow rate on CO conversion and light olefins selectivity were investigated in detail. The Mn_1Zr_2/SAPO-34 catalyst(Mn/Zr ratio of 1:2) attained a CO conversion of 10.8% and light olefins selectivity of 60.7%, at an optimized temperature, pressure and GHSV of 380 °C, 3MPa and 3000 h~(-1) respectively. These findings open avenues to exploit other metal oxides with CO activation capabilities for a more efficient syngas conversion and product selectivity.  相似文献   

12.
通过等体积浸渍法,制备得到碱金属(Li、Na、K、Rb、Cs)改性的SAPO-34催化剂。并在常压连续固定床反应器上评价了各催化剂的甲醇制低碳烯烃(MTO)的性能,同时对催化剂进行了XRD、FT-IR、NH3-TPD等表征分析。结果表明,碱金属负载量为2%时,除Cs离子改性的催化剂低碳烯烃的选择性和寿命有所降低外,其他碱金属离子改性的SAPO-34催化剂低碳烯烃的选择性和寿命都有了明显的提高,尤其是Li离子改性的催化剂乙烯+丙烯的选择性达77%左右,寿命相对延长了2.5倍;将该催化剂再生3次后乙烯、丙烯的选择性几乎保持不变。  相似文献   

13.
SAPO-11 molecular sieves were synthesized from nonaqueous media. The effects of Si and Al sources as well as solvents on the catalytic performance of SAPO-11 were investigated by the hydroisomerization reaction of n-dodecane. The samples were characterized by XRD, XRF, N2-adsorption, SEM, NH3-TPD, IR-NH3 and 29Si CP MAS NMR. The SAPO-11 samples synthesized with tetraethoxysilane as the Si source showed higher Si incorporation contents than the SAPO molecular sieves prepared with polymeric Si sources (fumed silica and Si colloidal gel). The reaction results showed that Pt/SAPO-11 catalysts synthesized from ethylene glycol and glycerol media with the monomeric Si and Al sources (tetraethoxysilane, aluminum isopropoxide) exhibited higher catalytic activities than those catalysts with the polymeric Si or Al (pseudo-boehmite) sources, due to the larger external surface area and higher acidity of the former ones. Especially, the catalyst synthesized in an ethylene glycol medium possessed the highest catalytic activity. Over this catalyst, 88% conversion of n-dodecane was achieved at a low temperature of 250 °C.  相似文献   

14.
ZSM-5 zeolite has been hydrothermally synthesized in-situ on the external surface of calcined kaolinite in the presence of n-butylamine. This supported zeolite was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy and N2 adsorption. Several synthesis variables were systematically investigated, including SiO2 to Al2O3 ratio, pH, crystallization time, and crystallization temperature. After mixing the ZSM-5 with a Fluid Catalytic Cracking (FCC) catalyst, catalytic performance was evaluated by cracking vacuum gas oil (VGO) in a micro-fixed bed reactor. ZSM-5 addition was favorable for the production of light olefins by catalytic cracking of VGO.  相似文献   

15.
分子筛催化剂上催化裂化汽油掺混甲醇的改质研究   总被引:1,自引:1,他引:0  
以实现甲醇制取低碳烯烃转化工艺和FCC汽油降烯烃工艺的有效组合为目的,在固定床微型反应装置上,使用SAPO-34、ZSM-5、DOCO以及分子筛组合催化剂,对FCC汽油掺混甲醇改质进行了研究。主要对反应温度、空速和混炼比等影响因素进行了考察。结果表明,SAPO-34分子筛上甲醇制取低碳烯烃效果较好,高烯烃含量汽油在SAPO-34分子筛上的氢转移和芳构化效果显著,ZSM-5分子筛上的芳构化反应效果和DOCO的异构化反应效果较显著,甲醇转化与汽油转化反应间的相互协同作用,既有利于甲醇转化成低碳烯烃又能提高汽油降烯烃转化深度。适宜的混炼条件:反应温度400℃,m(甲醇):m(汽油)=0.05,空速3h~(-1),组合催化剂上,产物汽油中烯烃含量较FCC粗汽油下降23%以上。  相似文献   

16.
A process for the preparation of ethylene and propylene from methanol on a microporous silica—alumina—phosphate SAPO-34 catalyst is described. The influence of the temperature and the nature and concentration of the diluting agent on the catalyst activity, its selectivity with respect to C2=-C4= olefins, and ability to be regenerated were studied. The SAPO-34 catalyst was shown to be highly effective in the selectivity of ethylene and propylene formation; the total yield of C2=-C4= olefins at 350–450°C was 77–84% and methanol conversion was up to 96–99%. In the conversion of methanol under helium at 450°C, the yield of ethylene (∼36%) was higher than at 375°C (∼29%), while the yield of propylene (∼30%) was lower (∼38%). The use of water and helium vapors as a diluent increased the yield of ethylene to ∼36% at 375°C and to ∼50% at 450°C. In the conversion of methanol at 450°C in water vapors without helium, the yield of ethylene reached ∼44–49% and the yield of propylene was 24–29%. The C3= to C2= ratio in the process varied from ∼0.5 to 1.5. The high efficiency of the SAPO-34 catalyst is the consequence of the microporous structure of zeolite and the high content of acid centers of medium strength. In the course of methanol conversion, the catalyst was deactivated due to coking. After regeneration with air at 550°C, the catalyst activity was completely restored, while the crystal structure and the acid properties did not change. The activity of the catalyst in a cycle is prolonged if water vapors are used as a diluent and the catalyst is processed at a high temperature with vapors. The industrial processes for the production of ethylene and propylene from nonpetroleum materials are not used in Russia. The results of this study are comparable to the data obtained from the UOP/Norsk Hydro process on the SAPO-34 catalyst. The catalyst can be recommended for further trials on an FCC type pilot plant with a moving catalyst bed.  相似文献   

17.
《Applied Catalysis A: General》2002,223(1-2):225-238
The effect of catalyst fluidization on the conversion of methane to syngas in methane reforming with CO2 and H2O in the presence of O2 under pressurized conditions was investigated over Ni and Pt catalysts. Methane and CO2 conversion in the fluidized bed reactor was higher than those in the fixed bed reactor over Ni0.15Mg0.85O catalyst under 1.0 MPa. This reactor effect was dependent on the catalyst properties. Conversion levels in the fluidized and fixed bed reactor were almost the same over MgO-supported Ni and Pt catalysts. It is suggested that this phenomenon is related to the catalyst reducibility. On a catalyst with suitable reducibility, the oxidized catalyst can be reduced with the produced syngas and the reforming activity regenerates in the fluidized bed reactor. Although serious carbon deposition was observed on Ni0.15Mg0.85O in the fixed bed reactor, it was inhibited in the fluidized bed reactor.  相似文献   

18.
In this work, oxidative coupling of methane over Mn/Na2WO4/SiO2 catalyst is studied in a two-zone fluidized-bed reactor (TZFBR) and its performance is compared with a fluidized-bed reactor (FBR). Diluted oxygen in argon was introduced into the bottom of the TZFBR through a quartz ferrite and methane was entered at higher positions along the fluidized bed. The catalyst circulated between the oxygen-rich and methane-rich zones in the TZFBR reactor. The effects of the main operating variables including bed temperature, the methane/oxygen ratio (Rmo), and the height at which methane was introduced into the reactor (Hm) were investigated. It is found that under some operating conditions the TZFBR gives a higher C2 selectivity than that obtained in the FBR reactor. Reaction of methane with lattice oxygen of the Mn/Na2WO4/SiO2 redox catalyst in the methane-rich zone may have led to the higher selectivity.  相似文献   

19.
A series of Cr incorporated SAPO-34 catalysts varying in Cr content and a Cr supported SAPO-34 catalyst were prepared by one-pot hydrothermal and incipient-wetness impregnation methods, respectively. The synthesized materials were characterized by XRD, FESEM, TEM, BET, EDX dot mapping, TPD-NH3 and FTIR, and tested in ethane dehydrogenation with CO2 reaction. The incorporation of Cr3+ into the SAPO-34 framework and impregnation of Cr species were proved by TEM technique. With increase in the incorporated Cr content, smaller cubic crystals and amorphous particles were obtained. However, the extra-framework species probably appeared. Chromium impregnation led to micropore blockage and surface coverage partly, resulting in morphology change somewhat, significant decrease of surface area and acidity as evidenced by FESEM, TEM, BET and TPD-NH3 analysis. However, one-pot synthesis not only preserved the structure of SAPO-34 but also allowed higher surface area, more effective surface acidity and better chromium dispersion to be achieved, features that account for superior catalytic performance and stability of directly synthesized Cr rich catalyst. The Cr incorporated SAPO-34 catalyst containing rich amount of Cr exhibited the best catalytic activity, showing 38% ethylene yield at 700 °C even after 5 h on-stream operation.  相似文献   

20.
Fluidized bed and slurry reactors were employed to increase the CO2 conversion and desirable product selectivity in the direct hydrogenation of CO2 to hydrocarbons over K-promoted iron catalysts, as it is beneficial for the removal of heat generated due to highly exothermic nature of the reaction. The iron catalysts (Fe-K/Al2O3 and Fe-Cu-Al-K) were characterized by BET surface area, CO2 and H2 chemisorption, temperature-programmed reduction (TPR), X-ray diffraction (XRD) and temperature-programmed hydrogenation (TPH). The results of TPR and TPH study clearly indicated that co-precipitated Fe-Cu-Al-K catalyst has much higher reducibility and catalytic activity of CO2 hydrogenation at low temperature than Fe-K/Al2O3. The performance of fluidized bed or slurry reactors was superior to that of fixed bed reactor for the CO2 hydrogenation over Fe-Cu-Al-K catalyst in terms of CO2 conversion and hydrocarbon productivity. Moreover, light olefins and heavy hydrocarbons were selectively synthesized in fluidized bed and slurry reactors, respectively. The optimum operation conditions and the effects of operating variables on the CO2 conversion and its product distribution in these catalytic reactors were also discussed.  相似文献   

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