Steam reforming of gaseous by-products from bitumen oil using various supported Ni-based catalysts

The steam reforming process is an efficient route for producing hydrogen gas which, along with lower costs compared to other methods, has an acceptable efficiency rate. In this study, by using an experimental setup we tried to investigate the effect of various catalysts on the amount of tar and produced hydrogen from steam reforming of gas by products from bitumen oil and to introduce effective parameters in the process of hydrogen production. As temperature increased, the amount of tar conversion to gas increases and the amount of hydrogen surged accordingly. With increase in temperatures from 400 to 900°C, tar elimination also improved from 39% to 99% for Ni/Al₂O₃, from 30.5 to 93.1 for Ni/olivine and from 25.7 to 83.6 for Ni/Fe₂O₃. As a result, it was concluded that the Ni/Al₂O₃ catalyst has been more successful in eliminating the tar, although there is not much difference between the activities of the three catalysts.     

Study on steam reforming of naphthalene in presence of supported catalysts

Due to the limitations of existing methods, steam reforming is the most important method of hydrogen production. In this study, we intend to investigate the potential of two Rh/Al₂O₃ and Cr/Al₂O₃ catalysts in the conversion of naphthalene in the steam reforming process. For this purpose, the experimental method was first described in a fluidized bed reactor. In the next step, the effect of various parameters such as catalysts, temperature and steam/carbon ratio on naphthalene conversion was investigated. With increase in temperature from 700°C to 850°C, the naphthalene conversion increased from 43.2% to 82.8% for Rh/Al₂O₃ and from 39.0% to 77.9% for Cr/Al₂O₃. Hydrogen production increased as the injection of steam into the reactor increased which can be explained based on the principle of Le Chatelier.     

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.     

水蒸气对Pt-Sn-Ce催化剂的丙烷脱氢性能的影响

 摘要：以γ-Al2O3为载体, 采用连续等体积浸渍法制备了0.3%Pt/γ-Al2O3、0.3%Pt-0.9%Sn/γ-Al2O3和0.3%Pt-0.9%Sn/2.2%Ce-γ-Al2O3 3种Pt金属催化剂。考察了在C3H8催化脱氢制C3H6的体系中, 引入不同量的水蒸气对3种催化剂的催化脱氢性能的影响。结果表明,水蒸气的存在加速了0.3%Pt/γ-Al2O3和0.3%Pt-0.9%Sn/γ-Al2O3催化剂的失活, 同时降低了C3H6的选择性, 但对0.3%Pt-0.9%Sn/2.2%Ce-γ-Al2O3催化剂的稳定性影响较小。在0.3%Pt-0.9%Sn/2.2%Ce-γ-Al2O3体系中,水蒸气可以明显地提高C3H8的脱氢反应转化率和降低催化剂上的积炭量。对水蒸气处理后的Pt催化剂进行H2-化学吸附量测定的结果表明, Ce可以通过与活性中心Pt的强相互作用, 提高Pt粒子在水蒸气气氛下的抗烧结能力。C3H8脱氢转化率的提高是由于CeO中的活泼O与活泼H反应产生OH基团,OH基团参与了C3H8的β-H的消除反应, 提高了C3H8的脱氢速率。以γ-Al₂O₃为载体, 采用连续等体积浸渍法制备了0.3%Pt/γ-Al₂O₃、 0.3%Pt-0.9%Sn/γ-Al₂O₃和0.3%Pt-0.9%Sn/2.2%Ce-γ-Al₂O₃3种Pt 金属催化剂。考察了在丙烷（C₃H₈）催化脱氢制丙烯（C₃H₆）的体系中,引入不同量的水蒸气对3种催化剂的催化脱氢性能的影响。结果表明,水蒸气的存在加速了0.3%Pt/γ-Al₂O₃和0.3%Pt-0.9%Sn/γ-Al₂O₃催化剂的失活,同时降低了C₃H₆的选择性,但对0.3%Pt-0.9%Sn/2.2%Ce-γ-Al₂O₃催化剂的稳定性影响较小。在0.3%Pt-0.9%Sn/2.2%Ce-γ-Al₂O₃体系中,水蒸气可以明显地提高 C₃H₈的脱氢反应转化率和降低催化剂上的积炭量。对水蒸气处理后的 Pt 催化剂进行 H₂-化学吸附量测定的结果表明,Ce 可以通过与活性中心 Pt 的强相互作用,提高 Pt 粒子在水蒸气气氛下的抗烧结能力。C₃H₈脱氢转化率的提高是由于CeO 中的活泼O 与活泼H 反应产生OH 基团,OH 基团参与了 C₃H₈的 β-H 的消除反应, 提高了C₃H₈的脱氢速率。     

Selective Oxidation of Cyclohexane Using a Co-M/Al2O3 Catalyst without Additives

Abstract

Without any organic solvent or activator, the selective oxidation of cyclohexane with air to afford cyclohexanol and cyclohexanone was investigated over Co/Al₂O₃ and Co-M/Al₂O₃ (M = Cu, Zn, and Ni) catalysts prepared by sol-gel method. The activity of the catalysts decreases in the following order: Co-Ni/Al₂O₃ > Co/Al₂O₃ > Co-Zn/Al₂O₃ > Co-Cu/Al₂O₃. The optimum contents of cobalt and nickel are 4.0 wt% and 3.0 wt% in Co-Ni/Al₂O₃ catalyst, respectively. The best result was obtained over Co-Ni/Al₂O₃ catalyst with a conversion of 9.9% and a selectivity of 94.6% and the ratio of cyclohexanone to cyclohexanol of 2.8 when the reaction was carried out at 443 K for 120 min under 4.5 MPa, and catalytic activity did not change after five consecutive reactions.     

Desulfurization by Oxidation/Adsorption Scheme over Ti3(PW12O40)4 Catalyst

Abstract

Due to the future specifications for sulfur content in gasoline, a lot of research work has been done to develop alternative methods for desulfurization. This work presents the results for the desulfurization by oxidation/adsorption scheme over Ti₃(PW₁₂ O₄₀)₄ catalyst. The desulfurization experiment was performed with hydrogen peroxide (H₂ O₂) as the oxidant in the presence of Ti₃(PW₁₂ O₄₀)₄/SiO₂-Al₂ O₃ catalyst and adsorbent prepared by the sol-gel method, by using dibenzothiphene (DBT) in petroleum ether as the model compound. The efficiency of Ti₃(PW₁₂ O₄₀)₄/SiO₂-Al₂ O₃ catalyst and adsorbent prepared by the sol-gel method towards DBT adsorption from model compound was studied. The effects of titanium content of the adsorbent and the reaction conditions, such as the reaction temperature, the amounts of adsorbent and hydrogen peroxide (H₂ O₂), and the reaction time, etc., on the desulfurization efficiency and regeneration performance of the catalyst were investigated. It was found that the Ti₃(PW₁₂ O₄₀)₄/SiO₂?Al₂ O₃ catalyst presented higher maximum desulfurization conversion than SiO₂-Al₂ O₃ solids. In addition, it showed higher desulfurization conversion after regeneration with N,N-dimethylamide. Optimal reaction conditions were determined as: a reaction temperature of 70°C, a Ti (titanium)/H(hydrogen) molar ratio of 3, an adsorbent amount of 5 wt%, a H₂ O₂/S molar ratio of 3, and a reaction time of 2 hr. As a result, the total sulfur content in the petroleum ether solution of DBT could be decreased after oxidation/adsorption scheme from an initial value of 200 μg/g to a value of 2 μg/g, and the desulfurization conversion reached 99%, which is a remarkable result. Further, the said adsorbent also had quite good regenerability.     

The effect of steam on the conversion of dimethyl ether to lower olefins and methanol over zeolite catalysts

The effect of steam on the catalytic properties of La-Zr-HZSM-5/Al₂O₃ and Mg-HZSM-5/Al₂O₃ in the synthesis of olefins from dimethyl ether (DME) has been studied. It has been found that the presence of steam has a significant effect on the ethylene-to-propylene ratio regardless of the nature of the modifier; the formation of methanol was observed only on Mg-HZSM-5/Al₂O₃. In situ high-temperature diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy has revealed that the formation of methanol on Mg-HZSM-5/Al₂O₃ occurs owing to the formation of methoxy groups on the surface of the zeolite during the interaction between DME and basic sites. The resulting methoxy groups can be easily converted to methanol in the presence of steam.     

Desulfurization using an oxidation/catalysis/adsorption scheme over H3PW12O40/SiO2−Al2O3 1

A desulfurization experiment was performed with tert-butyl hydroperoxide (t-BuOOH) as the oxidant in the presence of H₃PW₁₂O₄₀/SiO₂₋Al₂O₃ as the catalyst prepared by the sol-gel method, by using dibenzothiphene (DBT) in petroleum ether as the model compound. This work presents the results for the desulfurization by an oxidation/catalysis/adsorption scheme. The effects of catalyst amounts, t-BuOOH amounts, reaction temperature, and reaction time on the desulfurization efficiency and regeneration performance of the catalyst were studied. It was found that the H₃PW₁₂O₄₀/SiO₂-Al₂O₃ catalyst presented a higher maximum desulfurization conversion than SiO₂-Al₂O₃ solids also prepared by the sol-gel method. In addition, the H₃PW₁₂O₄₀/SiO₂-Al₂O₃ catalyst showed a higher desulfurization conversion after regeneration with N,N-dimethylamide. It was also found that the oxidation agent t-BuOOH resulted in a higher desulfurization conversion than hydrogen peroxide (H₂O₂). The text was submitted by the authors in English.     

Promoted catalysts for hydrogenation of bicyclic aromatic hydrocarbons obtained in situ from molybdenum and tungsten carbonyls

Promoted Мo and W catalysts have been prepared in situ via thermal decomposition of precursors, oil-soluble salts Mo(CO)₆, W(CO)₆, С°C₁₆H₃₀O₄, and NiC₁₆H₃₀O₄. TiO₂, Al₂O₃, and ZrO(NO₃)₂ · 6H₂O have been used as the acidic additives. Also, Mo and W unsupported sulfide catalysts have been prepared in the presence of elemental sulfur as the sulfiding agent. The catalysts have been characterized by transmission electron microscopy and X-ray photoelectron spectroscopy. The activity of the catalysts prepared in situ has been evaluated in the hydrogenation reaction of bicyclic aromatic hydrocarbons by the example of model mixtures of 10% solutions of naphthalenes (unsubstituted naphthalene, 1- and 2-methylnaphthalenes, and 1,5- and 2,3-dimethylnaphthalenes) in n-hexadecane. The effect of the precursor/acidic oxide ratio on the activity of the formed catalyst has been found. Hydrogenation of bicyclic aromatic hydrocarbons has been conducted at a hydrogen pressure of 2 and 5 MPa and a temperature of 380 and 400°C for 2 h. Hydrogenation of the unsubstituted aromatic ring has been preferable due to the absence of steric hindrances. The degree of conversion of n-hexadecane under the reaction conditions has been 1.5–7.5% depending on the reaction temperature. It has been found that the activity of the sulfided catalyst in the conversion of 1- and 2-methylnaphthalenes is inferior to the activity of the unsulfided analogue, while partial replacement of TiO₂ by Al₂O₃ results in a decrease in the conversion of the substrates as opposed to the unsulfided catalysts, in which the use of nanocrystalline Al₂O₃ promotes an increase in the conversion.     

Product distribution and catalytic performance of nano-sized H-ZSM-5 zeolites in the methanol-to-aromatics (MTA) reaction

A study of the effect of SiO₂/Al₂O₃ molar ratio on the activity and selectivity of H-ZSM-5 catalyst in the reaction of methanol to aromatics (MTA) has been carried out in this work. Aluminosilicate zeolite (ZSM-5) zeolites with different SiO₂/Al₂O₃ molar ratios were successfully synthesized by the hydrothermal method. The SiO₂/Al₂O₃ molar ratio of the prepared ZSM-5 zeolite particles could be easily controlled by changing the ratio of tetraethylorthosilicate to aluminum nitrate nonahydrate. The effect of SiO₂/Al₂O₃ molar ratio on the activity of nano-sized H-ZSM-5 zeolites in the MTA reaction was studied. The H-ZSM-5 zeolite catalyst with low SiO₂/Al₂O₃ molar ratios shows remarkable selectivity toward aromatics and benzene, toluene, and xylene (BTX) in the MTA reaction.     

Stability of La-Zr-HZSM-5/Al2O3 zeolite catalysts in the conversion of dimethyl ether to lower olefins

The stability of the zeolite component and a La-Zr-HZSM-5/Al₂O₃ catalyst synthesized on its basis in the synthesis of lower olefins from dimethyl ether (DME) has been studied. It has been shown that both the zeolite component and the catalyst based on it exhibit highly stable catalytic properties. A high-temperature treatment of the zeolite component and the finished La-Zr-HZSM-5/Al₂O₃ catalyst with air and steam, respectively, leads to a significant increase in the catalyst selectivity for olefins, particularly propylene, while the activity in the DME conversion slightly decreases as the steaming temperature increases from 500 to 750°C.     

Preparation and characterization of FeNi/Al2O3 catalysts for production of light olefins

The 24%Fe-36%Ni/Al₂O₃ catalyst was prepared using sol-gel method. This research investigated many variable factors for conversion synthesis gas to C₂?CC₄ light olefins by using Fisher-Tropsch synthesis. The effects of calcination atmospheres and calcination heating rates and also operation conditions such as the H₂/CO molar feed ratios, gas hourly space velocity (GHSV), temperatures and total reaction pressure on the catalytic performance of 24%Fe-36%Ni/Al₂O₃ catalyst was investigated. The stability of the catalyst for 240 h has been tested at optimal operating conditions (T = 260°C, H₂/CO = 2/1, GHSV = 3200 h^?1 and P = 3 bar). The results indicated that this catalyst was highly stable for production C₂?CC₄ light olefins. Characterization of precursors and calcined catalysts were carried out by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) specific surface area measurement, temperature program reduction (TPR) and thermal analysis methods such as thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC).     

Hydrotreating of vacuum gas oil on modified Ni–Mo/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts

The effect of the introduction of P₂O₅ into Ni–Mo/Al₂O₃ catalysts on their activity in the hydrotreating of vacuum gas oil has been studied. As the support, γ-Al₂O₃ prepared from aluminum hydroxide AlOOH powder of the TH-100 brand (Sasol) has been used. The catalytic properties of the catalysts obtained have been examined in the hydrotreating of vacuum gas oil in a continuous-flow unit under hydrogen pressure. The amounts of sulfur and polycyclic aromatic hydrocarbons, the hydrocarbon group composition, and the carbon residue of the feedstock and the hydrotreating product have been determined. The catalysts after testing have been studied using differential thermal analysis in combination with thermogravimetry (DTA–TGA); the influence of the amount of the modifier on the catalytic activity and coking of the catalysts has been shown.     

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%.     

复合催化剂Ni-Cu/ZnO-TiO_2催化乙醇水蒸气重整制氢

利用共沉淀法制备了Ni/TiO2,Ni/ZnO,Ni/ZnO-TiO2,Ni-Cu/ZnO-TiO2催化剂,活性组分Ni及Cu含量均为2%(w);对催化剂进行了BET,H2-TPR,XRD,SEM-EDS表征及乙醇水蒸气重整制氢性能评价。实验结果表明,在水与醇摩尔比13、反应温度300～550℃、液态空速23.8 h-1的反应条件下,ZnO及ZnO-TiO2负载的Ni催化剂有较好的催化性能,当反应温度高于450℃时,乙醇转化率均达90%以上。在450～550℃,Ni-Cu/ZnO-TiO2催化剂的氢产率最高、CO选择性较低且稳定性良好,550℃时Ni-Cu/ZnO-TiO2催化剂上最大氢产率为3.49 mol/mol(每mol反应乙醇生产的H2的物质的量)。表征结果显示,Ni/ZnO,Ni/ZnO-TiO2,Ni-Cu/ZnO-TiO2催化剂的活性组分分散良好;采用复合载体ZnO-TiO2及添加第二种活性组分Cu,改善了Ni-Cu/ZnO-TiO2催化剂的性能;反应后4种催化剂上均有丝状炭生成,但未出现明显的烧结与团聚现象。     

Design of Catalyst Support for Deep Hydrodesulfurization of Gas Oil

Abstract

Alumina-silica (Al₂O₃-SiO₂) composite supports were examined to find the optimum state of support (i.e., composition and morphology). SiO₂ content in the Al₂O₃-SiO₂ support induced a shift of the main peak to higher frequency ascribed to an increased amount of Mo₈O₂₆ ^4?. A 75 wt% Al₂O₃-25 wt% SiO₂ support had homogeneously dispersed alumina particles of smaller size with high crystallinity. Hydrodesulfurization (HDS) of straight-run gas oil and its conventionally hydrotreated straight-run gas oil was performed over NiMo sulfides supported on Al₂O₃-SiO₂ composites. The high crystallinity of NMASA2-27 may be related to the high HDS and hydrogenation activity of NiMo sulfides due to its moderate interaction with the alumina surface.     

Optimization of silica content in alumina-silica nanocomposites to achieve high catalytic dehydrogenation activity of supported Pt catalyst

The present work aims at obtaining a suitable and selective catalyst for catalytic dehydrogenation reactions through designing pore structures of silica-containing alumina nanocomposites by optimizing silica content in the structure. In this trend, series of silica-containing alumina nanocomposites with different molar ratios Al₂O₃/SiO₂ were prepared by the solvothermal method. According to surface characterization of silica-containing alumina nanocomposites, the sample with the highest molar ratio of Al₂O₃/SiO₂ (2.06) showed mesoporous structure with selective pore sizes of 3.7 and 4.6 nm. In addition, it had a high surface area value of 308 m²/g. Furthermore, SEM and TEM images of the same sample showed ultra fine sized particles in the nano size (7–17 nm). Dehydrogenation catalysts, as developed structures, were then achieved by loading 0.6 wt.% platinum metal over the prepared nanocomposites. Performances of the prepared nanocatalysts were investigated via the dehydrogenation of a model compound namely; cyclohexane. Experimental results showed that the Pt catalyst supported on the silica-containing alumina nanocomposites with the highest molar ratio of Al₂O₃/SiO₂, is an efficient and selective catalyst toward the dehydrogenation reaction. This was revealed in terms of 100% selectivity of this catalyst toward the conversion of cyclohexane at all ranges of temperatures with the conversion reaction being temperature dependent. Practically, the total conversion of cyclohexane increased with increasing reaction temperature and reached 100% at 450 °C while the prepared catalyst demonstrated absolute selectivity.     

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.     

The Role of Nitrogen in Facilitating Methylcyclohexane Aromatization on Pt/Al2O3 and Pt-Re/Al2O3 Catalysts

Abstract

The kinetics of methylcyclohexane aromatization on commercial Pt/Al₂O₃ and Pt-Re/Al₂O₃ catalysts was investigated in a micro-reactor using N₂ and/or H₂ as carrier gases at temperatures ranging between 300–500°C, W/F values ranging between 0.83–3.75 mg min/mL and at a total pressure of 4.0 kg/cm². On both catalysts in N₂ atmosphere, aromatization accompanied by demethylation was observed with the formation of cracked products, benzene and toluene. However, in H₂ methane was the predominant product of methylcyclohexane reforming on PtA1₂O₃ and Pt-Re/Al₂O₃ at 500°C and 400–500°C respectively, whereas at 350°C, aromatization was predominant on Pt/Al₂O₃ but on Pt-Re/Al₂O₃, aromatization was accompanied by fragmentation to methane. In N₂–H₂ mixtures, demethylation activity was observed to decrease with H₂ content of the mixture on Pt-Re/Al₂O₃. A preliminary test of the kinetic data using Sica's method of pulse kinetic analysis suggests a first order rate in methylcyclohexane with activation energies of 3.21 kcal/gmol in N₂ and 19.70 kcal/gmol in H₂ for the Pt/Al₂O₃ catalyst and 16.66 kcal/gmol in N₂ and 34.94 kcal/gmol in H₂ for the Pt-Re/Al₂O₃ catalyst. However, a more comprehensive kinetic analysis suggested an aromatization mechanism for Pt-Re/Al₂O₃, where adsorbed H₂ was a participant. A different aromatization mechanism for the reaction in N₂ where hydrogen was not needed explained the data on Pt/Al₂O_3. In both cases, the desorption of toluene was determined as the rate determining step.     

邻甲酚加氢脱氧还原型催化剂的实验研究

以邻甲酚为生物质热解油模型化合物,研究了几种还原型加氢催化剂的催化脱氧性能的差异。采用孔饱和浸渍法制备了Mo/Al₂O₃、CoMo/Al₂O₃和CoMoEDTA/Al₂O₃加氢脱氧催化剂,采用H₂ -TPR、XRD对它们进行了表征;在H2气氛下对催化剂进行了还原,并在连续流动固定床加氢微反装置中,考察了邻甲酚在不同还原态催化剂催化下加氢脱氧反应的转化率和产物的选择性。结果表明,在相同的加氢反应条件下,CoMoEDTA/Al₂O₃的催化活性和稳定性均比Mo/Al₂O₃和CoMo/Al₂O₃催化剂高;在反应过程中,Mo/Al₂O₃催化剂表现出较高的直接脱氧选择性,而CoMo/Al₂O₃和CoMoEDTA/Al2O3催化剂表现出较高的加氢脱氧选择性。