微米级HZSM-5分子筛催化剂在甲苯甲醇烷基化反应中的应用

采用浸渍法合成了不同硅铝比、晶粒大小的复合改性HZSM-5分子筛催化剂,采用XRD、SEM、NH3-TPD、TEM和低温N2吸附等手段对改性前后催化剂的结构进行了表征。在小型固定床等温反应器上考察了HZSM-5分子筛催化剂在甲苯与甲醇烷基化反应中的性能。实验结果表明,在反应温度440℃、重时空速2 h~(-1)、n(甲苯)∶n(甲醇)=2、n(H_2)∶n(H_2O)∶n(甲苯+甲醇)=8∶2∶1的优化反应条件下,具有大晶粒、高硅铝比的复合改性HZSM-5分子筛催化剂上甲苯转化率达26.2%、对二甲苯在异构体中的选择性为95.0%;在复合改性HZSM-5分子筛催化剂的基础上引入加氢金属后,催化剂的稳定性明显提高,在相同反应条件下,甲苯转化率为18%~26%,对二甲苯选择性为90%~96%,稳定运行1 700 h后催化剂未出现明显失活的现象。     

HZSM-5/Silicalite-1复合分子筛的甲苯甲醇烷基化反应的催化性能

采用水热合成法在商业HZSM-5分子筛表面生长了一层Silicalite-1纯硅分子筛层,在典型反应条件下评价了复合分子筛对甲苯甲醇烷基化反应的催化性能。考察了水热合成原料配比、晶化时间对催化活性的影响,在HZSM-5(n(SiO2)/n(Al2O3)=80)与Silicalite-1合成液固液配比为1:30g/mL,晶化温度为100℃,晶化时间为18h条件下合成的复合分子筛催化剂的对二甲苯选择性为56.66%。在HZSM-5外表面适当生长纯硅Silicalite-1分子筛,提高了对二甲苯产物选择性。     

Conditions for nonhydrodewaxing reaction of hydrocracking tail oil

Hydrocracking tail oil is used in hydrogenation modification in the hydrocracking process and is an ideal material to produce lube-based oil. Through investigating the effect of operation conditions on properties of dewaxing products under atmospheric pressure, the optimum operation conditions are that reaction temperature is 360°C, volume space velocity is 1.0 h^?1, and distillation temperature is 140°C. Under the optimum condition, the yield of liquid products is higher, and the flash point, pour point, and viscosity of white oil are stable and meet the factory product requirements. Especially, properties of alkane and white oil change little when reaction time is 20 h, which indicates that HZSM-5/Al₂O₃ has better stability. When HZSM-5 molecular sieve catalyst was loaded by pseudo-boehmite, HZSM-5/Al₂O₃ catalyst activity and stability improved and became more beneficial to nonhydrodewaxing reaction of hydrocracking tail oil.     

Nanocatalysts: Effect of Active-phase and Promoter on Catalytic Properties and Performance in the Hydrodesulfurization Reaction

The influence of various amounts of phosphorus addition on performance of NiMoP/Al₂O₃ and CoMoP/Al₂O₃ nanocatalysts was examined in hydrodesulfurization of thiophene. The nanocatalysts were synthesized via sonochemical technique. The prepared samples were characterized by XRD, FESEM, BET, and FTIR analysis. The catalytic activity in hydrodesulfurization reaction was investigated in a batch stirred slurry reactor at 160°C and atmospheric pressure. The characterizations confirmed highly dispersion of active phase and formation of amorphous AlPO₄ species on the support surface. The results obtained from thiophene hydrodesulfurization showed the nanocatalysts contained 1 wt% of phosphorus had the highest activity. The CoMoP/Al₂O₃ and NiMoP/Al₂O₃ nanocatalysts with optimum phosphorus loading nearly gave 100% conversion of thiophene, so that the sulfur compound concentration in final solution was less than 50 ppm.     

Catalytic Performance of Modified HZSM-5/Al2O3 Catalysts for Nonhydrodewaxing

The HZSM-5/Al₂O₃ molecular sieve catalyst was modified by phosphoric acid, tetraeth-oxysilane, tetrabutyl titanate, and boric acid, respectively. Properties of modified catalysts are characterized. The results show that the specific surface area declines and the acid density increases after modification of the catalysts, and the strong acid strength of Si/HZSM-5/Al₂O₃ catalyst enhanced. Modified catalysts performances are evaluated on fixed bed reactor using hydrocracking tail oil from a refinery as raw material. Results show that the Si/HZSM-5/Al₂O₃ catalyst has better catalytic dewaxing effect and stability than the other modified catalysts.     

Production of olefins from syngas over Al2O3 supported Ni and Cu nano-catalysts

The most important products that can be produced from syngas are methanol, dimethyl ether and light olefins (ethylene and propylene). The light olefins are the most important syngas products, because many of the chemicals are produced from them. The aim of this work was to study the olefins production from syngas over Al₂O₃-supported Ni-Cu nano-catalysts. In addition, the effect of various factors such as catalyst on olefin production and CO conversion has been investigated. The concentration of heavier olefins (C5) was greater than the remaining olefins, since the rate of reactions must be increased to form C1 to C4. In the case of a Ni/Al₂O₃ catalyst, C1 and C4 was initially increased and then decreased with an increase in Ni loading from 0% to 15%.     

镍盐前驱体对Ni改性HZSM-5择形催化甲苯与甲醇合成对二甲苯反应性能的影响

分别以硝酸镍、氯化镍、硫酸镍和乙酸镍为前驱体,采用浸渍法制备了Ni改性HZSM-5催化剂,并考察了其对甲苯甲醇烷基化反应合成对二甲苯的催化性能。采用XRD、TG-DTG、N₂吸附-脱附、H₂-TPR和NH₃-TPD手段对催化剂进行了表征。结果表明,由于镍盐前驱体中阴离子种类的不同,活性Ni物种在催化剂中的分散状态和存在形式不同,导致Ni改性催化剂具有不同的烷基化催化活性和加氢活性;与母体催化剂相比,催化甲苯甲醇烷基化反应的甲苯转化率降低,对二甲苯选择性呈现不同变化,并且Ni的加氢作用延缓了催化剂的积炭过程。以硝酸镍为前驱体制备的Ni改性催化剂中活性Ni物种晶粒尺寸较小,分散度较高,具有较高的烷基化催化活性和加氢活性,并且稳定性也比母体催化剂有所提高。     

The Effect of Pd Precursors on the Catalytic Activity of a Pd/Al2O3 Catalyst for Cumene Hydroperoxide Hydrogenation

Abstract

Abstract Pd/Al₂O₃ catalysts were prepared by wet impregnation using K₂PdCl₄, (NH₄)₂PdCl₄, and Pd(NO₃)₂ as precursors. All catalysts were characterized by means of inductively coupled plasma-atomic emission spectroscopy (ICP-AES), temperature-programmed reduction (TPR), X-ray diffraction (XRD), and CO chemisorption. The results obtained in the hydrogenation of cumene hydroperoxide (CHP) to α-cumyl alcohol (CA) showed that Pd/Al₂O₃ catalyst prepared from Pd(NO₃)₂ exhibited the highest turnover frequency (TOF) value and the greatest deactivation extent, whereas Pd/Al₂O₃ catalyst prepared from (NH₄)₂PdCl₄ displayed the lowest TOF value but the best stability.     

KINETIC INVESTIGATION OF METHYLCYCLOPENTANE REFORMING ON FRESH AND DEACTIVATING Pt/Al2O3 CATALYST

ABSTRACT

The conversion of methylcyclopentane (MCP) in hydrogen on fresh and deactivating Pt/Al₂O₃ catalyst to hydrogenolysis products (2-methylpentane, 3-methylpentane and n-hexane), cyclohexane and benzene was studied in a Berty CSTR at various partial pressures of MCP and H₂, and at a total pressure of 1 atm. For the kinetic studies, temperatures between 370 – 400° and W/F values up to 0.33 g min/cm³ were used. The conversion of MCP was found to increase with increase in temperature at all the MCP partial pressures investigated. The hydrogenolysis products and benzene composition generally increased with increase in temperature and W/F. The mechanism for the reforming of MCP was similar to that proposed by Dartigues et al. (1978) except that the formation of hydrogenolysis products was accounted for in this formulation. Eleven rate models were developed and tested and six satisfied the set criteria. Since hydrogenation/dehydrogenation and desorption steps are relatively rapid, the conversion step to hydrogenolysis products was deemed the only rate determining step with an activation energy of 36.31 kcal/gmol. For the deactivation studies, the model of Corella and Asua (1982) was used for the development of two deactivation models. The only model found to predict the deactivation behavior was the step leading to the formation of the coke precursor as rate controlling.     

甲苯与甲醇侧链烷基化合成苯乙烯KX催化剂失活现象的研究

考察了甲苯、甲醇侧链烷基化反应KX催化剂的稳定性及失活现象。并采用XRD、N2物理吸附、DTG、SEM、NH3-TPD、CO2-TPD和ICP等方法对反应前后的催化剂进行了表征。结果表明,反应前后活性位变化和积炭不明显,对催化剂失活影响很小。随着反应时间延长,反应过程中产生大量的水导致分子筛骨架脱铝,晶体结构被严重破坏,这是催化剂失活的主要原因。增强催化剂骨架的水热稳定性是解决催化剂失活问题的关键。     

甲苯、甲醇在碱性沸石上侧链烷基化反应的研究 Ⅱ.X型沸石交换度对侧链反应的影响

以催化剂的评价和表征结果为依据，探讨了交换度、总碱度和总产率三者的关系。认为随着沸石中钾离子交换度的提高，分子筛表面总碱度急剧上升，甲苯、甲醇的侧链反应性能逐渐增强，但总收率存在一峰值，这说明苯乙烯和乙苯的总产率不是无限制地随着沸石阳离子交换度的提高而提高。总碱度与总收率成正比关系，总碱量有一最大值，苯乙烯和乙苯的总产率有一峰值，最大值和峰值是相对应的。     

钒作为加氢催化剂活性组分的研究 Ⅱ 钒对NiMo/Al2O3催化剂渣油加氢活性的影响

 采用浸渍法制备了一系列含V的NiMo/Al₂O₃催化剂。对硫化态含V的NiMo/Al₂O₃催化剂进行了XPS和TEM表征;以科威特常压渣油为原料,考察了V对NiMo/Al₂O₃催化剂渣油加氢活性的影响。结果表明,由于渣油中金属和硫的存在形态不同,并且V-Mo-S相和V-S相对于加氢脱金属的催化作用大于加氢脱硫的催化作用,因此V能引起NiMo/Al₂O₃催化剂上渣油脱金属率的增加;但是V含量较高时,V会造成NiMo/Al₂O₃催化剂上渣油脱硫率的降低。     

CHEMICAL BASIS OF MIDDLE DISTILLATE FUEL INSTABILITY: Interactive Effects of Selected Nitrogen Heterocycles with Organic Bases in a Shale-Derived Diesel Fuel.

ABSTRACT

Fuel instability reactions are defined in terms of the formation of deleterious products such as filterable sediments and peroxides. Gravimetric stability tests have been carried out at 80^°C using two model nitrogen heterocycles: 2,5-dimethy1pyrrole, DMP, and 3-methylindole, 3-MI, in an otherwise stable shale derived middle distillate fuel. Potential interactive effects for these model nitrogen heterocycles have been described by the presence of organic base co-dopants. Organic bases employed included: tri-n-butylamine, N, N-dimethyl-aniline, and 4-dimethylaminopyridine. Simple organic amines exerted only minor interactive effects, usually an increase in filterable sediment in the range of 5–15%. However, the diamine species, 4-dimethylaminopyridine, interacted in a strong positive fashion to generate increased amounts, 22–44%, of sediment.     

Desulfurization of FCC Gasoline Over Mordenite Modified with Al2O3

Abstract

Mordenite modified with Al₂O₃ (Al₂O₃/mordenite) was synthesized and used for the desulfurization of FCC gasoline. The influences of operating parameters on the results were studied for the model solution composed of dibenzothiophene (DBT) and isooctane. Al₂O₃/mordenite exhibits higher sulfur capacity than other kinds of chemisorbents. The suitable composition of the chemisorbent is 30 wt% Al₂O₃ to 70 wt% mordenite. The optimal operating parameters are: temperature 160°C; velocity 3 h^?1 (WHSV). Under the stated conditions, desulfurization was carried out for the FCC gasoline with sulfur content of 220.4 μg/g. The chemisorbent can maintain the sulfur content under 50 μg/g for 40 h and has good regeneration ability after desorption using benzene.     

Hydrogen production by catalytic gasification of petroleum residue

The liquid fuel gasification to obtain a clean flue gas for power generation and produce chemicals such as methanol is a most promising attempt to reduce the greenhouse gas emissions and air pollutants. In this paper, an equilibrium model of liquid fuel gasification was developed by the method of Gibbs free energy minimization. Two kinds of catalysts: Ni/CeO₂/Al₂O₃ and Ni/Al₂O₃ were used to explore the influence of catalysts and operating conditions on hydrogen yield and char conversion. Over the ranges of operating conditions studied, the maximum hydrogen yield reached 52.47 vol%, whereas the char conversion varied between 45.2% and 98.5%. The results indicated that an appropriate reaction temperature is favorable for higher hydrogen production and char conversion. The model was validated with experimental data obtained from a fluidized bed gasifier.     

甲苯、甲醇在碱性沸石上侧链烷基化反应研究 Ⅰ.工艺参数、反应机理的探讨

研究了重量空速、反应温度、载气流速、反应时间等工艺条件对甲苯、甲醇在碱性沸石上侧链烷基化反应的影响。结果表明，虽然不同类型沸石催化剂特性不同，但工艺条件对其性能的影响是相似的。另外，基于实验结果，提出了可能的反应机理。     

Characterization of Al2O3–ZrO2 Mixed Oxide Supported Mo Hydrotreating Catalyst

Abstract

A series of molybdenum catalysts supported on Al₂O₃–ZrO₂ mixed oxide containing 50% ZrO₂ and 50% Al₂O₃ were prepared by incipient wetness technique and characterized by BET surface area, X-ray diffraction, temperature programmed reduction and oxygen chemisorption. The catalytic activities for hydrodesulphurization (HDS), hydrogenation (HYD), and hydrocracking (HYC) were determined using thiophene, cyclohexene, and cumene as model compounds, respectively. Results indicate that up to 8 wt% Mo loading, the catalyst is well dispersed and crystallite growth occurred beyond this loading. Also both oxygen uptake and catalytic activities increase with Mo loading up to 8 wt% and then decreases at higher loading. A linear correlation was obtained between oxygen uptake and all catalytic activities and the correlation coefficients obtained suggest that the order of catalytic activities for HDS, HYD, and HYC is: HDS > HYD > HYC. Furthermore, the catalytic activities of the mixed oxide supported catalyst for HDS, HYD, and HYC were higher than those supported on pure alumina and pure zirconia. The incorporation of 3% Co on 8% Mo catalyst was determined to result in enhanced activity for HDS, HYD, and HYC.     

Hydrogen production by catalytic methane decomposition over Ni,Co, and Ni-Co/Al2O3 catalyst

Hydrogen is a chief source of energy. Catalytic decomposition produces hydrogen and carbon. In this work, x%M/Al₂O₃ (where M is Ni, Co and combined Ni-Co, and x is 10%, 15%, and 30%) has been successfully employed as a catalyst. The effect of activation temperature and active metal type and loading on catalyst perfomance was investigated. The catalysts were characterized with BET, XRD, TPO, TPR, TEM, XPS, and Raman. The results displayed that the 30%Co/Al₂O₃ catalyst activated at 500°C provided the greatest catalytic performance toward methane conversion. 30%Co/Al₂O₃ catalyst activated at 500°C formed amorphous carbon.     

COMBINED EFFECT OF FLUORINE AND ZINC INCORPORATION ON THE HDS ACTIVITY OF Co-Mo CATALYSTS

Abstract

Conventional HDS-catalysts consist of Co and Mo supported on Y-Al₂O₃. The addition of Zn as a second promoter or the alumina acidification with F increase the catalitye activity in HDS of commercial feeds (Fierro et al., 1984; Boorman et al., 1984). In this paper the combined effect of both Zn and F incorporation is discussed. A series of Zn-Co-Mo catalysts supported on fluorinated alumina (0.0 –2.0 wt% F) was prepared and tested for HDS activity using a commercial gas-oil. The data gathered showed a decrease in HDS activity for intermediate F contents (0.4 – 1.0 wt%). This result could be tentatively explained through alumina surface deterioration during impregnation with NH₄HF₂ solutions al low pH.     

The direct dimethyl ether (DME) synthesis process from syngas II. Intrinsic kinetics and catalyst deactivation in one-step LPDMEtm process

In Part I of this series, it was seen that the favorable thermodynamic and kinetic coupling in the one-step LPDME^tm process – of methanol dehydration reaction (very rapid kinetics and at/near thermodynamic equilibrium) with the methanol synthesis reaction (slower kinetics and under thermodynamic limitation) – leads the beneficial “chemical synergy”.

In this part II of Series, we briefly discern the intrinsic kinetics of the LPMeOH^tm and LPDME^tm systems, and also shed light of the catalyst deactivation phenomena in these processes. Among the many reports on intrinsic kinetics of the one-step LPMeOH^tm and LPDME^tm processes, two illustrative kinetic studies, from the groups of University of Akron and Air Products and Chemicals, Inc. are highlighted and discussed further. For development of intrinsic kinetic models of LPMeOH^tm and LPDME^tm systems, a detailed thermodynamic framework has been developed which allows one to compute the liquid phase concentrations of reactive species, at phase equilibria and at chemical reaction equilibria. The intrinsic kinetic models of the LPDME^tm system are mainly based on the independent, component kinetic models of methanol synthesis (van den Bussche and Froment, 1996) and methanol dehydration (Bercic & Levec, 1992). From an overarching analysis of the deactivation of supported copper catalysts for methanol synthesis and other reactions (methanol decomposition and methanol steam reforming), we propose that thermal sintering, i.e., increase in Cu particle size and loss of metal surface area, is the only cause of catalyst deactivation in methanol synthesis reactions over Cu/ZnO/Al₂O₃ industrial-type methanol catalysts.