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.     

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.     

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.     

Efficacy ofapplication of zinc oxide on the surface of the NiO/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalytic system

The surface and catalytic properties of the NiO/Al₂O₃ system after deposition of 3 to 7% zinc oxide on its surface and heat treatment at 400, 600, and 800°C were investigated by X-ray diffraction analysis, nitrogen adsorption at −196°C, and catalytic oxidation of carbon monoxide by oxygen at 150-250°C. It was shown that calcination of the catalyst at 400°C decreases the specific surface area, while it increases it at 600 and 800°C. The decrease in the specific surface area is accompanied by an increase in the size of the NiO/Al₂O₃ crystallites. The activity of the catalysts calcined at 400°C in oxidation of carbon monoxide by oxygen, manifested by a constant reaction rate, increases with an increase in the zinc oxide content on the surface. After deposition of the zinc oxide, the mechanism of the oxidation reaction remains as before, but the concentration of active centers in the catalyst changes.     

Production of Lubricating Base Oil Using a Moist SiO2/γ-Al2 O3 Catalyst

Abstract

The catalyst SiO₂/γ-Al₂ O₃ treated by micro-wetness air to produce lubricating base oil was studied in this article. The satisfactory reaction temperature, the treatment temperature, and the proper content of active composition was researched. Under the best reaction conditions with a reaction temperature of 170°C, a reaction pressure at 6.0 Mpa, the volume velocity at 0.5 h^?1. The polymerization of α-olefin was performed at a microreactor and produced lubricating base oil with the kinetic viscosity at 38.19 mm² · s^?1, the bromine number at 5.78 g(Br) · (100 g)^?1, and the pour point at ?43.0°C. Then the structure of the catalyst was determined by Brunauer, Emmett and Teller (BET) technology. The result shows that when the optimal micro-wetness air was 45°C, the reaction temperature was 800°C, and the amount of active composition was 12%, and the catalyst has high catalytic activity and wide market prospect.     

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%.     

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.     

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.     

Oxidative Desulfurization of Dibenzothiophene Catalyzed by VO(acac)2 in Ionic Liquids at Room Temperature

A simple extraction and catalytic oxidative desulfurization (ECODS) system composed of VO(acac)₂, 30% H₂O₂, and 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF₄) has been found to be suitable for the deep removal of dibenzothiophene (DBT) in model oil at room temperature. The optimal conditions were as follows: [n(H₂O₂)/n(DBT)/n(catalyst) = 100:20:1], model oil = 5 mL, ionic liquid [IL] = 1 mL, T = 30°C, t = 2 hr. With the ECODS system, the sulfur removal of DBT could reach 99.6%, which was superior to that of the simple extraction with IL (15.6%) or oxidation without catalyst (17.1%). The IL could be recycled five times without a significant decrease in activity.     

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。     

Effect of operating conditions on alkylation of toluene with methanol

P-xylene (PX) is widely used as a raw material of synthesis of terephthalic acid (PTA) and polyester. With the demand of PTA and polyester, PX is demanded eagerly. The process for preparing PX through alkylation of toluene with methanol has been concerned widely. In an experiment HZSM-5/Al₂O₃ catalyst was prepared by loading pseudoboehmites on HZSM-5. The strength of B acid is adjusted, so side reactions can be controlled effectively. The optimum operating conditions are that molar ratio of toluene to methanol is 2.0, reaction temperature is 410°C, carrier gas flow is 7 mL/min, and WHSV is 1.0 h^?1 by investigating the effect of operating conditions on toluene conversion and PX selectivity. Toluene conversion and PX selectivity are up to 46.2% and 68.07%, respectively, under the optimum operating conditions.     

Role of Mn/Al2O3 catalyst in deep oxidative desulfurization of diesel

Abstract

In this work, a series of supported manganese catalyst has been synthesized and utilized in oxidative desulfurization to remove 4,6-dimethyldibenzothiophene (4,6-DMDBT), dibenzothiophene (DBT) and thiophene. The influences of catalyst parameters were investigated including manganese precursors, manganese loading and calcination temperature in details. The synthesized catalyst was characterized by scanning electron microscopy (SEM), N₂ adsorption/desorption and X-ray diffraction (XRD) techniques. 90.2% of 4,6-DMDBT, 98.5% of DBT and 95.5% of thiophene conversion were achieved under mild operational conditions using 3Mn(NO₃)₂/Al₂O₃ at 500?°C calcination temperature. A slight decrease in desulfurization activity was observed after Mn/Al₂O₃ catalyst being used in five cycles ODS.     

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.     

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.     

REFORMING OF N-OCTANE ON A Pt/Al2O3 CATALYST. II. KINETIC ANALYSIS OF HYDROGEN DEPENDENCE.

ABSTRACT

The conversion of n-octane on Pt/Al₂O₃ catalyst was found to pass through pronounced maxima with the variation of the partial pressure of hydrogen at temperatures between 420°C-460°C, P_N = 7·63 × 10^-3 atm and W/F = 0·11lg min cm_-3. The products of reaction were hydrocracked products, octane, ethylbenzene, o-.p-,m,-xylene and toluene. The order of appearance of the optimum PH for the various reactions were: Isooctane>Dehydrocyclized products>Hydrocracked products.

A sequence of elementary steps earlier postulated was found to predict the maximum in the n-octane P_H profiles for the three temperatures investigated. The rate determining steps for the two rate equations that were found suitable were conversion of adsorbed isooctane to adsorbed o-xylene and ethylbenzene.     

The role of sulfur in modification of active sites of reforming catalysts

The features of the interaction of hydrogen sulfide with the surface of supports (alumina and silica) and catalysts (Pt/SiO₂, Pt/Al₂O₃, Re/Al₂O₃, and Pt–Re/Al₂O₃) have been studied. It has been found that the adsorption of sulfur on the supports is completely reversible. The amount of irreversibly adsorbed sulfur (S_irrev) and S_irrev/metal ratios in the catalysts after treatment in a hydrogen atmosphere at 500°C have been determined. Sulfurization reduces the dispersion of platinum to 5% and increases the amount of ionic platinum on the catalyst surface. Regarding the dehydrocyclization reaction of n-heptane, the optimal amount of sulfur required for sulfurization of the catalyst with the composition 0.25% Pt 0.3% Re/γ-Al₂O₃ (0.3% Zr) is 0.072 wt %.     

Mathematical modeling of catalytic behavior of catalyst pellets in crude oils after blocking by liquid sulfur

The sulfur recovery unit converts H₂S to elemental sulfur by the Claus process. The process occurs during two combustion and catalytic reactions. Alumina (γ-Al₂O₃) and bauxite (Al₂O₃H₂O) are the main Claus catalysts in crude oils. The volume distribution of micro- and macropores and the parameter of Bethe lattice representing the complex structure of catalyst pellets pores are the most important parameters affecting catalyst performance. This research is aimed at evaluating these parameters impact on effective efficiency of catalyst bed after blocking by liquid sulfur for the second and third reactors. It can be done by considering micro- and macropores as a function of pellet diameter. The results show that pellets with a minimum coordination number or Bethe lattice parameter of 6 are more suitable to use in catalytic reactors. There is a great consistency between the modeling results and the industrial ones. In addition, a catalytic pellet with a diameter of 4.55 mm has the most optimal performance for sulfur recycling processes in industrial crude oil.     

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.     

Recovery of precious metals from spent Mo–Co–Ni/Al2O3 catalyst in organic acid medium: Process optimization and kinetic studies

In present study, the leaching kinetics of the spent Mo–Co–Ni/Al₂O₃ catalyst was investigated in the presence of formic acid as an organic leaching agent. Firstly, the spent catalyst was roasted in different roasting temperature (200–700?°C) and time (15–240?min), the maximum metal extraction was achieved that at 500?°C with 90?min. Then, the leaching experiments were carried out to determine the influences of process parameters following; particle size, liquid/solid ratio, formic acid concentration, leaching temperature, leaching time and stirring speed. According to the experimental results, the highest dissolution rates of molybdenum (Mo, 75.82%), cobalt (Co, 96.81%), nickel (Ni, 93.44%) and aluminum (Al, 19.46%) were reached under optimum experimental conditions; particle size +75???30?µm; liquid/solid ratio 10?ml/g; formic acid concentration 0.6?M; leaching temperature 80?°C; leaching time 90?min and stirring speed 300 r/min. Moreover, the leaching kinetics clearly reveal that the leaching reaction is controlled by liquid film diffusion and that the activation energy values (E_a) of Co, Ni, Mo and Al were to be 24.49, 25.98, 32.36 and 33.47?kJ/mol, respectively. In conclusion, the leaching process can be conducted in the presence of formic acid for the various industrial wastes in similar structure and composition to Mo–Co–Ni/Al₂O₃ spent catalyst.     

STUDIES ON DEPOSITS OF SPENT HYDRO-TREATING CATALYST: A STUDY BY COMBINED ANALYTICAL TECHNIQUES

ABSTRACT

Carbonaceous and non-carbonaceous deposits on a Ni-Mo catalyst, stemming from atmospheric residue upgrading in an ARDS unit were subjected to a combination of analytical techniques, i.e. SF extraction, TGA/DTA/MS, DRIFT, ^l3C CP-MAS NMR, XRD and elemental analysis. Since the spectroscopic features of several components of the deposit interfere with each other a detailed deposit characterization was only achieved by stepwise removal of certain components by SFE deoiling and calcination. SF extraction stripped about 22 wt % of the carbonaceous deposit of the spent catalyst increasing the sp²/(sp³ + sp²) ratio of the NMR-visible carbon from 0 63 to 0.67. TGA revealed three separate temperature ramps for stepwise driving off of deposited material- first ramp, 30° C - 280° C, loss of oil and sulfur from metal sulfides; second ramp, 280° C - 450° C, loss of carbonaceous material like coke; third ramp, 500° C - 680° C, loss of metal sulfates. Further calcination up to 1000° C has no effect on the metal content of the deposition but transforms the framework γ-Al₂O₃ into α-Al₂O₃. Entire burn-off of