EFFECTS OF SUPPORTS ON THE ACTIVITY OF NICKEL CATALYST FOR CH4 REFORMING WITH CO2

Nickel catalyst is an effective catalyst for reforming CH₄ with CO₂. The reaction between CO₂ and CH₄ at 1073 K. in the pressure of 0·1 MPa has been studied over different materials supported nickel metal in a fixed-bed reactor. Different catalysts before and after reaction were characterized by SEM, XRD, XPS. Results shows that CO and H₂ are basically produced at the same ratio. When the feed ratio CO₂/CH₄ is less than 0·5, less C₂~C₄ hydrocarbons are detected. When the feed ratio CO₂/CH₄ is 1, Ni/a- Al₂O₃ catalyst has the highest activity. However, when the feed ratio CO₂/CH₄ is greater than 1, Ni/y- A1/O₃, Ni/a- A1₂O₃, Ni/SiO₂ and Ni/HZSM-5 had higher activity; Ni/clinoptilolite basically no activity. Different kinds of carbon deposit are established.     

Effect of methanol, ethanol, and formaldehyde addition on the steam conversion of methane in the presence of nickel catalysts of various porous structure

The effect of CH₂O, CH₃OH, and C₂H₅OH on the methane conversion and the CO, CO₂, and coke yield in the methane steam conversion on commercial nickel catalysts for steam reforming C 11-9-09 (12.8 wt % Ni/α-Al₂O₃) and hydrogenation (54.0 wt % Ni/kieselguhr) was studied at a temperature of 750°C and an H₂O:CH₄ ratio of 1.5–2.0. The action of these compounds was studied both individually and for their joint presence in the methane-steam mixture. Their effect on the reaction depends on the pore structure of the catalyst. Using the catalyst C 11-9-09 as an example, it was found that the introduction of formaldehyde into steam suppressed the methane conversion into C_s and high-boiling-point carbon compounds and gave the desired products with a yield close to the equilibrium value. When all three additives were present in the steam, ethanol was responsible for the formation of C_s.     

Effect of Recycle Gas Composition of the Performance of Fischer-Tropsch Catalyst

Abstract

In this study, the influence of CO₂ and CH₄ on the performance and selectivity of Co-Ru/Al₂O₃ catalyst is investigated by injection of these gases (0–20 vol.% of feed) to the feed stream. The effect of temperature and feed flow rate are also inspected. The results show that low amounts of CO₂ in the feed stream do not change the catalyst activity, but increasing the amount of CO₂ (more than 10 vol.%), causes the CO conversion to decrease and the selectivity of heavy components to increase. Methane acts as an inert gas and does not affect the catalyst performance. Increasing feed flow rate has a negative effect on both CO conversion and heavy component selectivity. By raising the temperature, CO conversion will increase but there are more volatile components in the product. The effect of CO₂ on catalyst deactivation is also investigated and a mechanism is suggested to explain the negative influence of CO₂ on catalyst deactivation.     

煅烧还原一步制备Ni基催化剂及在CH4-CO2重整反应中的应用

采用大豆油研磨法制备了Ni/C-SiO_2系列催化剂,并用于CH_4-CO_2重整反应。通过XRD、TG-DTG、BET、H_2-TPR、CO_2-TPD等对催化剂进行了物理性能表征,利用固定床连续反应对催化剂进行了催化性能测试。结果表明,研磨法制得的催化剂前驱体在惰性气氛N2中煅烧后,催化剂上的镍元素全部转变成了Ni~0,实现了煅烧还原一步制备中孔Ni基催化剂。CH_4-CO_2重整反应后的催化剂上存在两种炭,一种是催化剂制备时残留的碳源炭,另一种是重整反应过程中产生的可致催化剂失活的积炭。考察了助剂CeO_2、ZrO_2、La_2O_3对催化剂性能的影响,结果表明,与Ni/C-SiO_2催化剂相比,Ni-CeO_2/C-SiO_2、Ni-ZrO_2/C-SiO_2、Ni-La_2O_3/C-SiO_2催化剂中Ni~0的粒径降低了,Ni-CeO_2/C-SiO_2、Ni-La_2O_3/C-SiO_2催化剂的反应活性提高了,反应后Ni-ZrO_2/C-SiO_2、Ni-La_2O_3/C-SiO_2催化剂上的积炭减少了。助剂La_2O_3不仅提高了催化剂活性,而且降低了催化剂上的积炭量,使用Ni-La_2O_3/C-SiO_2催化剂进行CH_4-CO_2重整反应,总碳转化率达到了52%。     

Effects of Impregnation Solvents on Catalytic Performance of Co-Ru-ZrO2/γ-Al2O3 Catalyst for Fischer-Tropsch Synthesis

Abstract

Used ZrO₂ modified γ-Al₂O₃ as support, Co-Ru catalysts were prepared by incipient impregnation method. The effects of impregnation solvents on the performances of catalysts were examined. The catalyst was prepared with ethanol solution and high Co dispersion was obtained, exhibiting highest activity of CO hydrogenation, very low methane selectivity, and high heavy hydrocarbon C₅ ⁺ selectivity. The catalysts were prepared with aqueous solution and methanol solution, and the reaction behaviors were similar. The solvent isopropanol caused the lowest catalytic activity and highest methane selectivity. Increasing the reaction temperature enhanced the CO hydrogenation rate, and the CO conversion slightly increased the CO₂ selectivity and favored the formation methane and light hydrocarbons, while the chain growth probability decreased. For the catalyst prepared with ethanol, the CO conversion, the CH₄ selectivity, and the C₅ ⁺ selectivity were 94.16%, 5.65%, and 88.2%, respectively, and the chain growth probability was 0.87 at 493 K, 1.5 MPa, 800 h^?1, and n(H₂):n(CO) = 2.0 in feed.     

CATALYTIC REACTION OF CO4 WITH CH4OVER NICKEL CATALYST

ABSTRACT

The reaction between CO₂and CH₄was carried out in a fixed-bed continuous flow reactor over y-alumina supported nickel metal, reaction temperature was 773-1073°K and reaction pressure 0.1-0.13MPa with different ratios of CH₄C0₂. Catalysts were characterized by SEM, XRD, XPS and IJTA. It was found that Ni/y-alumina had higher activity, selectivity and stability when it was made in strong acid(pH?2) or strong base (pH?ll) solution. In this reaction syngas with lower ratios of H₂/CO was produced.     

Oxidative Desulfurization of Fuel Catalyzed by Amphiphilic Peroxomolybdate

Abstract

The oxidation of sulfur-containing compounds (benzothiophene [BT], dibenzothiophene [DBT], and 4,6-dimethyldibenzothiophene [4,6-DMDBT]) was studied in an emulsion system composed of model oil, hydrogen peroxide, and an amphiphilic catalyst [C₇H₇C₁₂H₂₅(CH₃)₂N]₂Mo₂O₃(O₂)₄. The most suitable conditions were suggested: n (DBT): n (catalyst): n (H₂O₂) = 1:0.1:10, at 60°C for 2 hr. Under optimized experimental conditions, the removal of DBT, BT, and 4,6-DMDBT could reach 98.0, 94.0, and 62.7%, respectively. The oxidation product sulfones could be readily separated by extraction. The catalyst could be recycled five times without a significant decrease in catalytic activity.     

Dissociation behavior of （CH4 ＋ C2H4） hydrate in the presence of sodium dodecyl sulfate

Separation of a mixture of CH4+C2H4 gas by forming hydrate in ethylene production has become of interest,and the dissociation behavior of(CH4+C2H4) hydrate is of great importance for this process. The hydrate formation rate could be increased by adding a small amount of sodium dodecyl sulfate(SDS) into water. In this work,the kinetic data of CH4(18.5 mol%) +C2H4(81.5 mol%) hydrate decomposition in the presence of 1000 mg·L-1 SDS at different temperatures and pressures were measured with the depressurizing m...     

Ni/ZSM-5 CATALYST FOR CH4 REFORMING WITH CO2

Abstract

For good physical and chemical proprieties of ZSM-5 and its selectivity to higher hydrocarbons it is selected as support carrier. In this paper CH₄ reforming with CO₂ to synthesize heavier hydrocarbons over Ni/ZSM-5 catalyst is investigated. The reforming reaction is operated at 1073K under the ambient pressure in a fixed-bed tabular reactor. As promoter rare earth oxides, La₂O₃, CeO₂, Pr₆O₁₁ and Nd₂O₃ are separately added to Ni/ZSM-5 and Ni-La/ZSM-5(NZL), Ni-Ce/ZSM-5(NZC), Ni-Pr/ZSM-5(NZP) and Ni-Nd/ZSM-5(NZN) are formed accordingly. For convenience, they are recorded as Ni-RE/ZSM-5. When these catalysts are used in the reforming reaction the yield of heavier hydrocarbons is obviously increased. The structure of Ni-RE/ZSM-5 catalysts before and after reaction is systematically characterized by XRD, XPS, TEM, SEM, ICP and FTIR. After 10 hours reaction there are more carbon deposit on Ni-RE/ZSM-5 catalyst than Ni/ZSM-5, but their structure are not destroyed and carbon deposit is easy gasified.     

Effect of process conditions on Fischer–Tropsch synthesis product selectivity over an industrial iron-based catalyst in slurry reactor

The authors present the application of the statistical model in CO hydrogenation to CH₄, C₂-C₄ and C₅₊ over industrial iron-based catalyst (100 Fe/5 Cu/4.2 K/25 SiO₂) in a 1-L stirred tank slurry reactor. The effect of different reaction conditions, including temperatures (T = 493, 513 and 533 K), pressures (P = 0.8, 1.5, 2.25, and 2.5 MPa), synthesis gas feed molar ratios (H₂/CO = 0.67 and 2), and gas space velocity (GSV) from 0.52 to 23.5 Ndm³/g-Fe/h on selectivity investigated via a statistical models. The proposed selectivity model is very useful in the oil, gas, and petrochemical industries and can be used for interpretation of experimental data, comparison of performance of different reactor conditions, and reactor modeling and simulation studies. Furthermore, interaction between operating parameters such as pressure, temperature, H₂/CO, and GSV was investigated in selectivity models. A CUBIC polynomial was successfully fitted to the experimental data. It was concluded that C₅₊ selectivity shifts to higher with increasing total pressure (H₂/CO) ratio and decreasing temperature. Decreased H₂/CO ratio and temperature and increasing in the reactor pressure cause CH₄ formation decrease. Temperature and pressure fluctuations vary product distribution. As it is observed, the insignificant term in C₂-C₄ selectivity is pressure. With the models obtained from regression we can reach to the optimum condition for favorite products such as C₂-C₄ or C₅₊. So that optimization must be done to illustrate the optimum conditions. It was obtained that the maximum amount of C₅₊ and C₂-C₄ and minimum amount of methane achieved in T = 528.97 K, P = 1.23 bar, H₂/CO = 2, and GSV = 23.49 Ndm³/g-Fe/h.     

Optimization of Oxidative Desulfurization of Dibenzothiophene Using a Coordinated Ionic Liquid as Catalytic Solvent

Abstract

Oxidative desulfurization (ODS) of dibenzothiophene (DBT) in n-octane with hydrogen peroxide/acetic acid using a quaternary ammonium coordinated ionic liquid (IL) (C₄H₉)₄NBr · 2C₆H₁₁NO as catalytic solvent has been studied. The ODS mechanism by coordinated ionic liquid [(C₄H₉)₄NBr · 2C₆H₁₁NO] was also carried out. The sulfur-containing compounds in model oil were extracted into ionic liquid phase and oxidized to their corresponding sulfones by H₂O₂. The effect factors for desulfurization of model oil were investigated in detail by means of monofactorial and orthogonal experiments (L₁₆(4)⁴). The results showed that the desulfurization efficiency of model oil could reach 98.6% under the optimal conditions of oxidation time, oxidation temperature, molar ratio of H₂O₂/sulfur (O/S), and volume ratio of model oil to coordinated ionic liquid were 30 min, 50°C, 16, and 1, respectively. The influences to the desulfurization efficiency of DBT decreased in the following order: volume ratio of model oil to coordinated ionic liquid (C₄H₉)₄NBr · 2C₆H₁₁NO (V_{model oil}/V_IL) > molar ratio of O/S > oxidation temperature > oxidation time, according to extreme analysis of the orthogonal test. The coordinated ionic liquid (C₄H₉)₄NBr · 2C₆H₁₁NO can be recycled 5 times without a significant decrease in desulfurization.     

AN EXPERIMENTAL STUDY OF THE EFFECT OF PARAFFINIC SOLVENTS ON THE ONSET AND BULK PRECIPITATION OF ASPHALTENES

ABSTRACT

Asphaltene onset concentration and bulk deposition were measured for a typical live reservoir oil titrated with n-C₆H₁₄, n-C₅H₁₂, n-C₄H₁₀, C₃H₈, C₂H₆, CH₄ and CO₂ at 100° C (212 ° F) and 29.9 MPa (4340 psia). The concentration of titrant at asphaltene onset was observed to decrease approximately in a linear fashion with decreasing molecular weight of the paraffinic solvent; CH₄ did not induce any asphaltene precipitation. Bulk deposition experiments were performed using a solvent: oil volume ratio of 10:1; the results indicated that the weight percent of asphaltenes precipitated increased exponentially with decreasing molecular weight of the paraffinic solvents. More importantly, the asphaltene molecular weight showed a maximum for n-C₄H₁₀ precipitated asphaltenes. Possible explanations for this unusual result are presented.     

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).     

Evolution of active ingredients and catalytic properties of Pt-Sn/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts in the selective deoxygenation reaction of vegetable oils

The evolution of the structure of Pt–Sn/Al₂O₃ catalysts and their catalytic properties in the reaction of the reductive deoxygenation of rapeseed oil fatty acid triglycerides (FATGs) have been studied. The catalysts were prepared by deposition from an organic solution of a mixture of platinum and tin compounds, as well as a heterometallic (PPh₄)₃[Pt(SnCl₃)₅] complex, in which platinum and tin atoms are linked by a metal–metal bond. It has been shown that the use of the heterometallic complex as a precursor with a tin to platinum molar ratio of 5 results in the formation of clusters of nanosized tin (2+; 4+) oxides and particles of a metastable PtSn_{3 ± δ} alloy on the surface of the catalyst after reductive activation. In the presence of this catalyst, the exhaustive conversion of the feed FATGs and the selectivity for hydrocarbons above 98% have been achieved. The gaseous products CO, CO₂, and CH₄ are formed in trace quantities. The results show that the deoxygenation occurs not via the known decarboxylation and decarbonylation route, but also through the step of the selective reduction of oxygen and almost complete suppression of cracking of the organic moieties of FATGs.     

Synthesis and gas separation properties of metathesis poly(5-ethylidene-2-norbornene)

High molecular weight metathesis poly(5-ethylidene-2-norbornene) (PENB) has been synthesized in the presence of the 1st generation Grubbs catalyst at a high monomer/catalyst ratio (3000/1 and higher). The yields of the corresponding polymer have been more than 90% at all monomer/catalyst ratios and molecular weights (M _w ) of PENB have been higher than 3 × 10⁵. The gas permeability of different gases (He, H₂, O₂, N₂, CO₂, and CH₄) through PENB films has been studied, and diffusivity and selectivity coefficients have been determined. It has been found that PENB is more permeable than unsubstituted metathesis polynorbornene and cycloalkyl-substituted polynorbornene dicarboximides, but it is less permeable than some Si-containing polynorbornenes. Despite the fact that PENB is more permeable than metathesis polynorbornene and cycloalkyl-substituted polynorbornene dicarboximides, it is close to these polymers in ideal selectivities for some gas pairs.     

Evaluation and modeling of Fischer-Tropsch synthesis in presence of a Co/ZrO2 catalyst

Abstract

The present work focused on the application of response surface methodology (RSM), Box–Behnken design (BBD), for prediction of products distribution of Fischer-Tropsch synthesis (FTS) using a Co/ZrO₂ catalyst in a fixed bed reactor. The effect of four independent operating variables such as reaction temperature, pressure, space velocity and H₂/CO ratio on the responses (CH₄ and C₅⁺ selectivities) in FTS were investigated. The analysis of variance (ANOVA) results showed that the suggested quadratic models could well predict CH₄ and C₅⁺selectivities. The optimized operating condition was temperature 200.73?°C, pressure 20?bar, space velocity 1662.58?h^?1 and H₂/CO ratio 1.93.     

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.     

STRUCTURAL CHARACTERIZATION OF SOLID n-PARAFFIN COMPONENTS DERIVED FROM MUKTA CRUDE OIL

ABSTRACT

The total solid paraffins (boiling 270°C+) separated from Mukta crude by urea adduction and its narrow fractions were analysed for their structural composition by proton NMR, infrared spectroscopy and gas chromatography. It has been observed that CH2/CH3 ratio in these samples varies from 7·9 to 13·8 while their average carbon number ranges from 17 to 29·6. The CH₂/CH₃ ratio and chain length of paraffins increases with increase in boiling range of the fractions.     

Sulfuration Pretreatment of Ni/Al2O3 Catalyst to Remove Butadiene in FCC C4 Fraction

Abstract

The Ni-based catalysts have more advantages than the most widely used Pd-based catalysts in selective hydrogenating of the butadiene in fluid catalytic cracking (FCC) C₄ fraction. But the selectivity and stability of the Ni-based catalysts aren't good. The sulfuration pretreatment is an effective process to improve the performance of the Ni/Al₂O₃ catalysts. The sulfuration conditions of the Ni/Al₂O₃ catalyst have been studied in this article. The results showed the fittest conditions are that the catalyst was in-situ presulfurized for 60 min by the solution of S concentration 0.07 mol/L. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis indicated that the presulfurization declined the Ni crystal dimension.     

旋转弧放电等离子体重整乙醇制氢

目的 为了抑制炭沉积、优化操作条件和提高产氢效率,基于绿色制氢和现场制氢的理念,研究了一种用等离子体重整制氢的新型制氢技术,优化设计了一套等离子体气相重整乙醇制氢装置.方法 以空气作为工作气体,研究了氧醇物质的量比(以下简称氧醇比)、乙醇流量、放电电压和放电间距对重整结果的影响.结果 氧醇物质的量比过大或者过小都不利于...