正己烷在HZSM-5分子筛上的催化裂解研究

为筛选反应活性和烯烃选择性相对较高的催化剂用于研究吸热型碳氢燃料的催化裂解,以正己烷的催化裂解作为探针反应,探讨其在不同硅铝物质的量比HZSM-5［n(Si)∶n(Al)=25、36、100］分子筛上催化裂解的反应活性和产物分布。结果表明,正己烷在HZSM-5分子筛上的裂解转化率随温度的升高和分子筛中硅铝物质的量比的减小而增大;裂解产物中乙烯、丙烯和总烯烃的选择性均随裂解温度的升高和分子筛中硅铝物质的量比的增加而增加,在（300~550） ℃,HZSM-5［n（Si)∶n(Al)=36］上的总烯烃收率最高,芳烃含量随分子筛中硅铝物质的量比的增加而减小;基于裂解转化率、烯烃和芳烃收率等因素综合考虑,HZSM-5 n(Si)∶n(Al)=36］分子筛为优选催化剂。     

Catalytic cracking of tricyclo [5.2.1.0] decane over HZSM-5 molecular sieves

The catalytic cracking of a high density hydrocarbon fuel, tricyclo [5.2.1.0^2.6] decane (JP-10) over HZSM-5 molecular sieves with different Si/Al mole ratios of 25, 38, and 50 was investigated at the temperature range from 773 to 873 K. Compared with the thermal cracking and the catalytic cracking over ZSM-5, conversions of JP-10 from the catalytic cracking over HZSM-5 molecular sieves at the same temperature were evidently heightened. The predominant hydrocarbon products from the catalytic cracking, checked at room temperature and atmospheric pressure, were methane, ethane, ethene, propane and propylene in the gaseous phase and benzene, indene, naphthalene and their homologues in the liquid phase. The contents of ethane, propane and propene decrease with increasing Si/Al mole ratio of a catalyst while those of methane and ethene increase simultaneously with the increase of Si/Al mole ratio of HZSM-5. The contents of the main components in the liquid products produced on the catalyst surface at a given temperature also decreased with the increase of Si/Al mole ratio. To keep high yields of alkenes, the HZSM-5 catalyst with high Si/Al mole ratio could be chosen.     

轻汽油在HZSM-5分子筛上催化裂解制丙烯的研究

以催化裂化轻汽油（≤75 ℃）为原料，在小型固定床反应器上，考察了反应温度、反应空速、催化剂不同硅铝物质的量比及载体Al₂O₃含量对轻汽油的催化裂解性能及丙烯选择性的影响。实验结果表明，反应温度和空速对催化裂解的产物分布和丙烯收率有较大的影响，高硅铝比催化剂的丙烯选择性比低硅铝比催化剂好，适量Al₂O₃的添加有助于提高丙烯收率。选择合适的反应条件可以有效提高催化剂的裂化性能并能很好抑制氢转移反应的进行，从而提高丙烯的选择性。在550 ℃、0.2 MPa和空速4 h^－1条件下，高硅铝比n(SiO₂)∶n(Al₂O₃)=200］催化剂的丙烯收率为37.56％，当添加30%的Al₂O₃时，丙烯收率增至38.26%。     

Fe_2O_3/HZSM-5催化转化乙醇制备低碳烯烃

采用浸渍法制备了Fe2O3/HZSM-5分子筛催化剂,并用于乙醇脱水与低聚制备丙烯为主的低碳烯烃反应体系.在400～500℃范围内考察了HZSM-5的硅/铝比、氧化铁负载量、反应温度、催化剂氢气还原预处理对产物中烯烃收率的影响.结果表明,HZSM-5硅/铝比为140时,丙烯、丁烯收率最高;氧化铁负载能有效提高烯烃收率,当负载量为2.9%时丙烯收率最高,接近25%;反应初期升高温度可促进丙烯生成,但催化剂寿命缩短;氢气还原预处理能进一步促进乙烯、丙烯生成.     

Dehydrogenative Cracking of n-Butane over Modified HZSM-5 Catalysts

Dehydrogenative cracking reaction of n-butane was studied using HZSM-5 catalyst modified with various metal oxides. Alkaline earth (magnesium), transition metal (cobalt) and rare earth (lanthanum) elements are used for the modification. The selectivity of the products was studied at low conversion (20%). Methane, ethane, ethylene, propylene, butenes and butadiene were the main products. With the use of the cobalt- or magnesium-containing HZSM-5, dehydrogenative cracking was observed and the selectivity of ethylene was much larger than that of ethane. On the other hand, the selectivity of ethylene and ethane were almost the same in the reaction using the lanthanum-containing HZSM-5. It is considered that the cobalt- and magnesium-loaded sites on HZSM-5 played an important role in the dehydrogenative cracking.     

nMnOx·HZSM-5催化正丁烷裂解增产乙烯丙烯性能研究

采用等体积浸渍法制备nMnO_x·HZSM-5 系列催化剂,用XRD 、NH₃-TPD 、Py-IR 、BET 和SEM 等表征催化剂物相结构和表面性质。在固定床微型反应装置中,对nMnO_x·HZSM-5催化剂进行正丁烷裂解性能评价。结果表明,活性组分Mn借助固相反应以MnO_x 簇形式定位于HZSM-5 分子筛的直形和Z形孔道交叉处,并与其骨架氧结合形成nMnO_x·HZSM-5单相复合体,引起分子筛骨架收缩,晶胞参数及晶胞体积减小;nMnO_x·HZSM-5 催化剂样品总酸量和强酸中心酸量随活性组分Mn用量的增大逐渐减小,B酸/L酸逐渐下降;在反应温度625 ℃和空速5 600 h^-1条件下,Mn质量分数0.5%制备的nMnO_x·HZSM-5-0.5催化剂催化正丁烷裂解反应,正丁烷转化率为76.26%,略低于HZSM-5 分子筛,但乙烯和丙烯收率分别为13.68%和18.93%,分别提高 0.76 个百分点和 1.09 个百分点,表现出较好的增产乙烯和丙烯效果。     

Effect of process variables on product yield distribution in thermal catalytic cracking of naphtha to light olefins over Fe/HZSM-5

The effect of temperature, WHSV and Fe loading over HZSM-5 catalyst in thermal-catalytic cracking (TCC) of naphtha for the production of light olefins has been studied. The response surface defined by three most significant parameters is obtained from Box-Behnken design method and the optimal parameter set is found. The results show that ethylene increases with temperature, while propylene shows an optimum at 650 °C. Moderate WHSV is favorable for maximum production of light olefins. Addition of Fe to HZSM-5 has a favorable effect on the production of light olefins up to 6% of loading. Excess amount of loading decreases the conversion of naphtha, which leads to a drop in light olefin yields. The yield of light olefins (ethylene and propylene) at 670 °C, 44 hr⁻¹ and 6 wt% Fe has been increased to 5.43 wt% compared to the unmodified HZSM-5 and reaches to 42.47 wt%.     

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.     

改性HZSM-5甲醇制丙烯催化剂的研究

系统地研究了不同硅/铝比HZSM-5分子筛负载的La、Mg、Ce、P改性剂对甲醇制丙烯催化剂催化性能的影响。实验表明,La、Mg、Ce改性剂对HZSM-5催化剂合成丙烯选择性有良好的促进作用,HZSM-5分子筛的水蒸气处理条件、分子筛的硅/铝比及结晶状态对催化剂性能都有重要影响。在共浸渍法制备的1.5%La-3%Mg-HZSM-5(硅/铝=120)催化剂上,在600℃-24 h水蒸气处理条件下,丙烯选择性可达57%。     

Petrochemicals from ethanol over a W-Si-based nanocomposite bidisperse solid acid catalyst

Very high ethylene selectivity values approaching 100% and very high ethanol conversion values approaching 85% were obtained in dehydration of ethanol over a new W-silicate-based nanocomposite catalyst having both meso and macropores and containing a W/Si atomic ratio of 0.85. Silicotungsticacid was successfully incorporated into the catalyst structure following a one-pot hydrothermal synthesis procedure. This catalyst is highly stable and does not loose activity in polar solvents and it has a sufficiently high surface area for catalytic applications. Calcination temperature of the catalyst was found to have a very significant effect on the catalyst structure and also on its catalytic performance in ethanol dehydration. Maximum selectivity of the second major reaction product diethylether was obtained as 0.7 at 200 °C, with the catalyst which was calcined at 400 °C. Very high ethylene and diethylether yield values obtained in this study at different reaction conditions are highly promising for the production of petrochemicals from ethanol.     

Fe改性HZSM-5分子筛上甲醇耦合C4烃制低碳烯烃反应性能研究

用等体积浸渍法制备Fe改性HZSM-5分子筛催化剂（Fe/HZSM-5）。考察了Fe/HZSM-5在不同温度下对甲醇耦合C₄烃制低碳烯烃反应性能的影响,并利用紫外-可见漫反射光谱对Fe/HZSM-5进行了表征。结果表明,在低铁含量条件下,Fe改性HZSM-5分子筛上Fe（Ⅲ）主要以高分散隔离的形式存在于HZSM-5分子筛的表面,Fe改性提高了催化剂上的原料转化率以及乙烯和丙烯选择性,从而获得了较高的乙烯和丙烯总收率。在反应温度为550 ℃时,在Fe（Ⅲ）处理的HZSM-5分子筛上,乙烯和丙烯总收率最高可达42.1%,比未改性的HZSM-5提高了7％。     

Dehydrogenative cracking of n-butane using double-stage reaction

Dehydrogenation-cracking double-stage (tandem) reaction of n-butane was studied using a Pt-Sn type dehydrogenation catalyst and a cracking catalyst (rare earth-loaded HZSM-5). n-Butane was firstly dehydrogenated to n-butene (1- and 2-butene) over the Pt-Sn catalyst loaded at the upper part of the reactor. Then n-butene was successively converted to ethylene and propylene over the cracking catalyst loaded at the lower part of the reactor. The yield of light olefins (ethylene+propylene) was 58% at 650 °C. The key to obtaining ethylene and propylene in high yield was to determine how the bimolecular reactions of olefins to aromatic and heavier products can be inhibited. It was proved that the loaded rare earths played an important role in inhibiting the bimolecular reactions.     

CrHZSM-5 Zeolites – Highly Efficient Catalysts for Catalytic Cracking of Isobutane to Produce Light Olefins

The CrHZSM-5 catalysts with trace amount of Cr were firstly used for catalytic cracking of isobutane, and the effect of Cr-loading on the catalytic performances of CrHZSM-5 catalysts for the cracking of isobutane was also studied. The results suggested that when the loading of Cr in the CrHZSM-5 catalysts was less than 0.038 mmol/g Cr, especially at Cr loading of 0.004 mmol/g, both the reactivity of isobutane cracking and the selectivity to light olefins of CrHZSM-5 samples were greatly enhanced compared with the unpromoted HZSM-5, and very high yields of olefins(C₂+C₃) and ethylene were obtained. For instance, the yield of olefins(C₂+C₃) and ethylene reached 56.1% and 30.8%, respectively, at 625 °C when 0.004 mmol/g Cr was loaded on HZSM-5 sample.     

苯和乙烯一步法合成苯乙烯反应研究

首次采用苯和乙烯在无氧存在下, 于多种固体酸和金属负载HZSM-5分子筛催化剂上反应直接得到苯乙烯与其它固体酸相比, HZSM-5分子筛催化剂表现出最高的反应活性和较高的对苯乙烯的选择性。HZSM-5分子筛负载不同金属后, 苯乙烯的选择性均有明显提高, 其中以Co/HZSM-5、Fe/HZSM-5和Pd/HZSM-5催化剂显示出较高的反应活性和苯乙烯选择性。反应温度、苯烯比、金属负载量、液空速、催化剂的焙烧及还原温度均会不同程度地影响反应转化率和产物分布。     

催化裂化汽油裂解制丙烯

以催化裂化汽油为原料,水热处理后的HZSM-5分子筛为催化剂,催化裂解制丙烯。比较了水热处理后的HZSM-5分子筛催化剂上负载镧和未负载镧的催化裂化性能,并考察了镧的最佳负载量。结果表明,水热处理后负载镧提高了催化剂活性、稳定性和丙烯选择性,负载镧质量分数为8%时,催化裂化性能最佳。当反应温度550 ℃和空速4 h-1时,丙烯收率12.51%。     

Ammonolysis of ethanol on pure and zinc oxide modified HZSM-5 zeolites

Reaction between ethanol and ammonia have been studied on various zinc oxide modified HZSM-5 (Si/Al=225) catalysts under various conditions of temperature, C/N ratio of the reactants and their WHSV. Two pure zinc oxides were taken for the study. One was a highly active acidic form Z₁ and the other was a stoichiometric non acidic zinc oxide Z₂. The activity of the catalysts for ammonolysis reaction followed the order Z₂⪡Z₁⪡HZSM-5. However, for composite catalysts containing 10–40% Z₁ on HZSM-5, the activity increased synergistically and became maximum (∼81% conversion of alcohol) for the catalyst 40% Z₁/HZSM-5 and about 50% conversion for the catalyst 40% Z₂/HZSM-5. The products formed were mainly N-heterocycles. Some novel high molar mass N-heterocycles were also detected. The catalytic activity and product selectivity was crucially affected by the reaction conditions, particularly the effect of temperature; the optimum yield of the products was obtained at the catalyst temperature of 723 K, C/N ratio 0.3892 and WHSV of 2.5 h⁻¹.     

高温水蒸汽处理对HZSM-5分子筛催化甲醇制丙烯的影响

考察不同硅铝比的HZSM-5分子筛催化剂和经过高温水蒸汽处理后的HZSM-5分子筛催化剂在甲醇制丙烯反应中的催化性能,考察温度和空速对催化反应的影响。结果表明,随着HZSM-5分子筛硅铝比的增加,产物中丙烯选择性增大,可能是分子筛的酸性降低所致;经过高温水蒸汽处理后的HZSM-5分子筛表面酸性降低,提高了催化剂的催化性能。在反应温度450 ℃和空速1.0 h^-1条件下,600 ℃高温水蒸汽处理后的催化剂HT-600的丙烯选择性从改性前的26.8%提高到33.5%。     

HZSM-5催化剂上甲醇制丙烯反应条件的研究

以HZSM-5分子筛为催化剂,在固定床反应器中考察了反应温度和原料空速对甲醇制丙烯性能的影响。结果表明,随着反应温度的升高,乙烯和丙烯选择性均增加,但温度过高容易引起催化剂的失活;而随原料空速的增大,甲醇转化率、乙烯和丙烯的选择性均呈下降趋势。最佳的反应条件为反应温度为460°C,原料液时空速为1.4 kg(Methanol)/kg(cat.).h。对添加粘结剂与未添加粘结剂成型后的催化剂性能比较,表明添加粘结剂成型后,甲醇转化率和丙烯选择性有所下降。     

Aromatization of alkanes over Pt promoted conventional and mesoporous gallosilicates of MEL zeolite

Aromatization of hexane and propane was investigated over Pt promoted mesoporous gallium-containing HZSM-11 with controlled mesoporosity generated by desilication. Prepared catalysts were characterized by nitrogen adsorption, X-ray powder diffraction, scanning electron microscopy, Fourier transform infrared of chemisorbed pyridine, and NH₃ temperature programmed desorption confirming the development of intracrystalline mesoporosity of Ga-containing HZSM-11. The catalytic activities, which were compared in the aromatization of n-hexane and propane, increased upon desilication. The aromatization of n-hexane decreased in the following order, Pt/mesoporous GaZSM-11 ? Pt/conventional GaZSM-11 ? mesoporous GaZSM-11 > conventional GaZSM-11. Hexane conversion reached 70.1% over mesoporous Pt/GaZSM-11 with Si/Ga of 61, as compared with 29.6 and 24.9% for corresponding mesoporous and conventional GaZSM-11 (Si/Ga = 94), respectively, for experiments at liquid hour space velocity of 3.6 h⁻¹, and 540 °C. Comparison of BTX (benzene-toluene-xylene) selectivity at the conversion level of ∼21.0% revealed that Pt/mesoporous GaZSM-11 is more selective than corresponding mesoporous and conventional GaZSM-11. The BTX selectivity over Pt/mesoporous GaZSM-11 (Si/Ga = 94), which showed strong dependence on the conversion, reached 28.2%, whereas over corresponding mesoporous and conventional GaZSM-11catalysts reached 19.1% and 5.5%, respectively. A higher conversion and better selectivity can be attributed to the improved accessibility to the active extra-framework Ga species owing to the generation of mesopores inside the zeolite particles and shortening the contact time. It is worth mentioning that the prepared catalysts exhibited quite low activity in propane aromatization but exhibiting similar trends as for hexane aromatization.     

不同模板制备ZSM-5分子筛的酸性特征及催化裂解性能差异

分别以正丁胺、四丙基溴化铵为模板及无模板条件下制备了3种晶粒尺寸及硅铝比相近的ZSM-5分子筛,通过X射线衍射（XRD）、扫描电镜（SEM）、氨气程序升温脱附（NH₃-TPD）、N₂吸附/脱附对分子筛进行了表征,将其应用于正己烷裂解反应考察其性能差异。结果表明,实验控制三者ZSM-5样品具有相似的硅铝比,却仍显示出不同的酸性质及酸分布;在相同初始转化率下,不同模板制备的ZSM-5具有不同的产物选择性,正丁胺和四丙基溴化铵为模板制备的ZSM-5分子筛的双烯选择性高于无模板制备的ZSM-5分子筛,但无模板制备的ZSM-5分子筛表现出更高的裂解稳定性,转化率可在1200 min内保持在96%以上,远远高于其他模板制备的ZSM-5分子筛。