H-MCM-22 zeolitic catalysts modified by chemical liquid deposition for shape-selective disproportionation of toluene

Catalysts were prepared by dealumination of H-MCM-22 zeolite with oxalic acid leaching, followed by shaping and liquid phase modification with siloxane. The catalytic performance was measured with selective disproportionation of toluene in a fixed-bed reactor. The unmodified H-MCM-22 zeolite exhibited much higher initial activity than H-ZSM-5 with a thermodynamic equilibrium distribution of xylene products. The oxalic acid treatment of H-MCM-22 improved the selectivity for para-xylene by 10–18%. The modification by siloxane of the oxalic acid treated H-MCM-22 turned out to be highly selective for para-xylene, however, with the expense of the conversion. It is proposed that the high para-selectivity was closely associated with the contraction of micropore windows and the elimination of acid sites at the external surface by the deposited silica. Therefore, the modified H-MCM-22 is a potential catalyst for the selective disproportionation of toluene with a high para-selectivity.     

H-MCM-22 zeolitic catalysts modified by chemical liquid deposition for shape-selective disproportionation of toluene

Catalysts were prepared by dealumination of H-MCM-22 zeolite with oxalic acid leaching, followed by shaping and liquid phase modification with siloxane. The catalytic performance was measured with selective disproportionation of toluene in a fixed-bed reactor. The unmodified H-MCM-22 zeolite exhibited much higher initial activity than H-ZSM-5 with a thermodynamic equilibrium distribution of xylene products. The oxalic acid treatment of H-MCM-22 improved the selectivity for para-xylene by 10–18%. The modification by siloxane of the oxalic acid treated H-MCM-22 turned out to be highly selective for para-xylene, however, with the expense of the conversion. It is proposed that the high para-selectivity was closely associated with the contraction of micropore windows and the elimination of acid sites at the external surface by the deposited silica. Therefore, the modified H-MCM-22 is a potential catalyst for the selective disproportionation of toluene with a high para-selectivity.     

脱水处理对HZSM-5分子筛甲苯择形歧化性能的影响

通过²⁷Al MAS NMR、NH₃-TPD和FT-IR等表征手段研究了脱水处理对HZSM-5分子筛催化剂的结构和催化性能的影响。HZSM-5分子筛经过371 ℃水蒸汽处理后,分子筛的部分骨架铝脱出,形成非骨架铝物种,该非骨架铝物种对甲苯择形歧化反应具有较大影响。HZSM-5分子筛的酸性变化主要是由于非骨架铝物种SiAl（OH）的变化而引起,随着脱水温度的升高,HZSM-5分子筛酸中心的强度下降,但酸中心数量增加,当脱水温度为400 ℃时,HZSM-5分子筛的酸中心强度和数量达到最佳,甲苯转化率为28.2%。脱水过程中,甲苯的引入可以阻止HZSM-5分子筛催化剂进一步脱水,起到稳定催化剂活性中心的作用,使催化剂的性能较为稳定。     

SD-01甲苯择形歧化催化剂的工业应用

上海石油化工研究院研制开发的高空速、低氢烃比甲苯择形歧化催化剂SD—01在中石化股份公司天津分公司进行工业应用。本文介绍了国内首次进行甲苯择形歧化催化剂SD-01工业应用的开车过程和催化剂反应性能，结果表明该催化剂技术指标达到或超过国际公开报道的同类催化剂工业应用性能水平。     

聚苯基甲基硅氧烷改性ZSM-5分子筛上的甲苯择形歧化反应

以聚苯基甲基硅氧烷为改性剂,采用化学液相沉积法对ZSM-5分子筛催化剂进行改性修饰,考察改性催化剂的甲苯择形歧化反应性能。采用XRD、BET、NH 3-TPD表征改性催化剂的孔结构和酸性质。结果表明,聚苯基甲基硅氧烷作为改性剂可以增加催化剂的弱酸中心和中强酸中心酸量,同时缩小催化剂的平均孔径,改性程度与改性次数有关。改性催化剂用于甲苯歧化反应可以增加对二甲苯的选择性,对二甲苯选择性的增加程度与改性次数有关,改性次数增多,对二甲苯选择性增加越显著,同时甲苯转化率越低,副反应越多。     

HZSM-5 modified by silica CVD for shape-selective production of p-xylene: Influence of in situ and ex situ preparation conditions of the zeolite

HZSM-5 prepared in situ or ex situ from the NH₄-type one was modified by chemical vapor deposition (CVD) of silica for the shape-selective production of p-xylene from methylation of toluene, and the influence of preparation conditions upon the obtained selectivity was studied. The external surface of the ex situ prepared HZSM-5 deteriorated partially, maybe, due to the dealumination caused by moisture contained in the atmosphere. Because of the deteriorated external surface, the CVD could not sufficiently produce a uniform structure of silica to finely control the pore-opening size. On the other hand, the in situ prepared HZSM-5 which was not exposed to the atmosphere kept a fine structure of the external surface on which the silica could be deposited with a regulated structure. Fine control of the pore-opening size was thereby realized more uniformly on the in situ prepared HZSM-5. In situ preparation of H-form zeolite was thus found to be preferential for the CVD modification.     

改性HZSM-5分子筛在甲醇制汽油中的研究进展

甲醇制汽油(MTG)在生物质、合成气和煤制取高辛烷值汽油中应用广泛。MTG工艺技术既可以解决甲醇产能过剩问题,又可以降低对石油的依赖程度。MTG工艺的核心是HZSM-5分子筛催化剂,提高HZSM-5分子筛催化剂的汽油选择性和催化寿命是MTG工艺过程中的关键。对传统的HZSM-5分子筛改性是提高其催化性能的有效方式。综述了负载过渡金属、制备多级介孔、合成纳米颗粒以及复合其他材料等改性方法制备的HZSM-5分子筛对MTG反应催化性能的研究进展。着重说明了这些改性方法对HZSM-5分子筛酸性、孔径和表面积等性质的影响,同时对改性后的HZSM-5分子筛的汽油选择性和催化寿命进行了比较。指出了各种改性方法的优缺点和对汽油品质的影响,并对今后的研究方向进行了展望。     

磷镁改性的ZSM-5分子筛催化性能研究

研究了磷、镁改性对ZSM-5分子筛的孔结构和酸性的影响。采用甲苯的歧化反应为探针反应,考察了改性后分子筛催化甲苯选择歧化反应的活性和选择性。结果表明,磷、镁单独改性时,随着负载质量分数的增加,转化率逐渐增加,且大于相同工艺条件下HZSM-5的转化率。当磷质量分数达到3％～5％ 或镁质量分数达到1％时,转化率达到最大值,这时对二甲苯为平衡组成,基本没有选择性。磷镁复合改性时,既可以提高催化剂的选择性,又可以使催化剂的活性不至于降得很低。在磷质量分数为9％、镁质量分数为1％时,改性效果最好。     

磷镁改性HZSM-5催化剂甲苯甲醇烷基化性能研究

采用浸渍法制备了系列磷镁改性ZSM-5催化剂,考察了磷镁改性对HZSM-5催化剂甲苯甲醇烷基化反应活性和选择性的影响。并对其进行了NH3-TPD,Py—IR,XRD等表征,研究了改性氧化物在ZSM-5分子筛表面的分布状态以及其对催化剂的酸性质的影响,结果表明磷元素改性有效降低了催化剂的酸强度,抑制了甲苯歧化反应;MgO质量含量低时,主要以无定形状态高度分散在分子筛外表面上,含量较高时形成结晶态MgO。MgO改性主要作用是覆盖了催化剂外表面酸性活性中心,堵塞了孔口,提高了反应产物的对位选择性。     

A facile preparation of hausmannite as a high-performance catalyst for toluene combustion

Mesoporous transition metal oxide catalysts are well-used in the elimination of volatile organic compounds. In this study, we developed an efficient method for the preparation of mesoporous-Mn₃O₄ (m-Mn₃O₄) without the use of templates or surfactants. In this method, KCl protects oxygen defects on the surface of fresh Mn₃O₄ crystallites. m-Mn₃O₄ shows higher ameliorative catalytic activity than bulk-Mn₃O₄ (b-Mn₃O₄) and calcined-Mn₃O₄ (c-Mn₃O₄), achieving toluene catalytic oxidation of T₁₀ and T₉₀ (the temperature at a conversion rate of about 10% and 90%) at 191 ℃ and 230 ℃, respectively (WHSV = 40,000 ml·g^-1·h^-1). Based on various characterizations, the prepared m-Mn₃O₄ has large specific surface area and abundant oxygen defects, and thus can provide more surface active sites, which give it superior toluene combustion activity.     

金属改性甲醇芳构化催化剂的制备及性能研究

甲醇制芳烃是中国煤基甲醇深加工技术的重点发展方向之一,目前甲醇芳构化催化剂存在芳烃选择性低、收率低等问题。鉴于此,采用等体积浸渍法制备了一系列氧化锌、氧化镍复合改性催化剂,通过X射线荧光光谱（XRF）、氮气物理吸-脱附以及氨的程序升温脱附（NH₃-TPD）等方法对催化剂进行表征分析,通过固定床小试评价装置对催化剂的甲醇芳构化反应性能进行考察,并通过300 t/a固定床中试评价装置对优选催化剂的反应稳定性进行考察。小试实验结果表明,当氧化锌与氧化镍负载比例为2.0（质量比）、负载总量为6.2%（质量分数）时,催化剂具有最佳的甲醇芳构化性能,芳烃选择性为62.98%、收率为19.46%。中试实验结果表明,180 h内甲醇转化率保持100%、芳烃选择性不低于73%、芳烃收率不低于32%。以中国丰富的甲醇资源为原料,生产中国短缺的芳烃产品,一方面可以完善煤化工产业链、优化产品结构,另一方面可以缓解中国石油基芳烃供应不足的局势。     

镍改性HZSM-5催化乙醇脱水制备乙烯

在前期研究工作的基础上,通过正交实验对离子交换法制备Ni-HZSM-5的离子交换液浓度、交换温度和交换次数3个因素进行了考察。结果表明:硝酸镍溶液浓度为0.4 mol/L,交换温度为80℃,交换次数为2次时,制备的Ni-HZSM-5催化乙醇脱水制乙烯的效果最好。其中硝酸镍浓度对乙醇转化率和乙烯选择性的影响都最大。选取了3个催化剂和未改性的HZSM-5分别进行了XRD、BET和Py-TPD表征。最后对最佳条件下制备的Ni-HZSM-5进行了稳定性测试,15 h内乙醇转化率和乙烯选择性保持大于95%,催化性能得到显著提高。     

Selective toluene ethylation in supercritical CO2 using chemical liquid deposition modified HZSM-5 pellets

Pellets consisting of the para-selective HZSM-5 crystals prepared by the chemical liquid deposition (CLD) with tetraethyl orthosilicate (TEOS) were used as the catalyst for alkylation of toluene with ethylene in supercritical carbon dioxide. The pellets were formed by compressing the CLD modified HZSM-5 crystals with and without addition of the binder alumina. When the binder was used, the CLD was applied again right after the compression. For the addition of 0.1 ml of TEOS per gram of pellet, p-ethyltoluene yield and selectivity were found to be sufficiently close to those using the modified crystals and the compressed pellets without containing the binder. The alkylation was carried out in a tubular reactor packed with the prepared HZSM-5 pellets. From a study of the operating variables including temperature, pressure, weight hourly space velocity of toluene, and molar ratio of toluene to ethylene, the highest yield and selectivity of p-ethyltoluene were determined as 70 and 97%, respectively, at a temperature of 623 K, a pressure of 13.1 MPa, a weight hourly space velocity of 5.0 (g of toluene)/(g of catalyst)/h and a molar ratio of toluene to ethylene of 5. The obtained results indicate a pronounced shape-screening effect of the prepared HZSM-5 pellets and an applicability of using supercritical CO₂ as the carrier.     

Roles of ZSM-5 modifier agents in selective toluene disproportionation

Selective toluene disproportionation has been studied over ZSM-5 zeolites modified with P, Si and Cs compounds. For the P and Si modified samples, p-xylene proportion in the primary product was 100% due to the diffusional control on the internal xylene isomerization. The number and strength of the acid sites are reduced by the three modifier agents but a relationship between para-selectivity and the decrease of the acid strength has not been observed. The most para-selective samples have been those modified with Si which has been related to the deposition of this agent on the external surface of the zeolite crystals avoiding the primary product isomerization.     

A facile preparation of the superhydrophobic polydimethylsiloxane materials and its performances based on the supercritical fluid foaming

The supercritical foaming (SCF) method was proposed to conveniently fabricate superhydrophobic polydimethylsiloxane (PDMS) surface. The effect of foaming parameters on the cellular structure, wettability, mechanical properties and thermal properties was investigated. This work indicates that the microstructure plays an important role in the superhydrophobicity of the PDMS materials. When the cell size and cell wall size, respectively, reach to 103.6 and 29.7 μm, the water contact angle (WCA) of the microcellular PDMS foams can achieve the maximum value 158°, and the air occupies about 90.6% of the contact areas. Meanwhile, the tensile strength of superhydrophobic PDMS materials can reach to 0.81 MPa, indicating that the superhydrophobic PDMS materials are useful. Moreover, the superhydrophobic PDMS materials show good thermal stability and excellent adiabatic property. And the method is simple and convenient, which can be used for the preparation of the superhydrophobic surfaces.     

Selective ion-exchange in MAPO-36 and its application in toluene disproportionation

MAPO-36 was synthesized hydrothermally by isomorphic substitution of Mg²⁺ in the framework of AlPO-36 and ion-exchanged with Fe³⁺, Zn²⁺, La³⁺ and Ce³⁺ by wet method. The materials were characterized by XRD, TGA, TPD (ammonia) and SEM-EDX. XRD revealed absence of structural degradation after ion-exchange. TPD (ammonia) showed selective ion-exchange of strong acid sites in ion-exchanged MAPO-36. The weight loss around 550 °C in TGA for Fe, La and CeMAPO-36 suggested conversion of M(OH)₂⁺ to MO⁺. Toluene disproportionation was carried over all catalysts in which diphenyl methane derivative was suggested to be the principle intermediate in the formation of p-xylene and other products. The time on stream study showed exclusive formation of p-xylene after 6 h.     

Hydrothermal stability of HZSM-5 catalysts modified with Ni for the transformation of bioethanol into hydrocarbons

The hydrothermal stability of catalysts prepared from HZSM-5 zeolites doped with Ni (by impregnation) has been studied in the transformation of bioethanol into hydrocarbons, in order to remove the main barrier for the use of HZSM-5 zeolite catalysts in this process, which is the irreversible deactivation by dealumination of the zeolite above 400 °C with water in the reaction medium. The main effect of doping is the attenuation of the zeolite acid strength from 135 to 125 kJ (mol of NH₃)⁻¹ for a Ni content of 1 wt.%. The catalysts maintain a high level of activity and a high selectivity of propene and butenes, and Ni doping significantly attenuates irreversible deactivation of the catalyst by dealumination of the zeolite. The zeolite catalyst doped with 1 wt.% of Ni maintains its kinetic behaviour in reaction-regeneration cycles when the reaction step is carried out at 500 °C and with 5 wt.% of water in the feed. This catalyst allows operating at 400 °C without irreversible deactivation with bioethanol containing 75 wt.% of water.     

硅油-硝酸镧复合改性ZSM-5催化剂上甲苯甲醇选择性烷基化反应性能

以HZSM-5为改性基体,甲基硅油为改性剂,采用浸渍法制备硅油改性催化剂SiHZ(3.0)和复合改性催化剂SiHZ(3.0)/La₂O₃,考察硅油-硝酸镧复合改性ZSM-5催化剂上甲苯甲醇选择性烷基化的反应性能,并与单纯硅油改性的ZSM-5催化剂进行比较,结合催化剂酸性和孔结构的表征,研究硅油-硝酸镧复合改性对催化剂性能的影响。结果表明,在反应初期复合改性SiHZ(3.0)/La₂O₃催化剂上,甲苯转化率略低于单纯硅油改性的SiHZ(3.0)催化剂,对二甲苯选择性相近;反应100 h后,SiHZ(3.0)/La₂O₃催化剂活性和选择性均高于SiHZ(3.0)催化剂,说明复合改性催化剂中La₂O₃在硅油修饰外表面和孔口的基础上,进一步调变孔道内酸性质,降低强酸中心量和B酸酸量,从而显著提高催化剂稳定性。     

铜基催化剂中助组分对二甲胺歧化性能的影响

配置了A、B两组混合硝酸盐溶液，采用两步滴定共沉淀法制得5种多元铜基催化剂，在固定床微反-色谱联用装置上对制得的催化剂进行了二甲胺歧化性能的研究。结果表明：若不通过B溶液加任何组分，制得催化剂对应的歧化反应平衡需68．7h；若在B中加入Ni-Ba-Al、Ni、Ni-Ba、Ni-Mg-Al，对应的歧化平衡分别需要36．9h、33．0h、29．4h、25．3h，催化剂中Ni还原程度分别为1．63％、30．24％、59．20％、92．22％。加入不同组分，催化剂性能不同，二甲胺催化歧化活性与催化剂中Ni的还原性能密切相关，从反应机理中探讨了它们的关系。     

La改性多级孔HZSM-5在线催化提质生物油

采用Na₂CO₃溶液对HZSM-5分子筛进行预处理，然后采用浸渍法对预处理后的HZSM-5进行不同负载量的La改性，通过XRD、BET、SEM-EDS和Py-IR等方法对改性前后的HZSM-5进行表征。利用改性前后的HZSM-5在两段式固定床反应器上进行生物质热解产物在线催化实验，对得到的生物油有机相进行理化特性和组成成分分析。结果表明，经过Na₂CO₃溶液处理后，使HZSM-5分子筛形成了含有微-介孔的多级孔孔道结构，La的改性未改变HZSM-5的MFI结构，但改变了分子筛的酸分布。随着La负载量的增加，生物油有机相产率、密度、运动黏度及氧含量先减小后增加，含氧化合物和羰基类化合物含量同样呈现先减小后增加的变化趋势。经过最佳质量分数为5%的La负载后的多级孔HZSM-5分子筛制得的生物油中，有机相高位热值高达37.7 MJ/kg，烃类物质含量达到了49.86%，含氧化合物和羰基类化合物含量分别减少了32.43%和57.03%。