COMPARATIVE REACTION STUDY OF METHYLCYCLOHEXANE AND 3-METHYLHEXANE IN H2 AND N2 ON Pt/Al2O3 CATALYST

The reaction of methylcyclohexane and 3-methylhexane were studied in a pulse microcatalytic reactor using H₂ and N₂ carriers on Pt/Al₂O₃ catalyst at temperatures from 350 to 500°C, contact times (W/F) of 1.25 × 10^-3-3.75 × 10^-3 g min/ml and a total pressure of 4.0 kg/cm². In N₂, there was complete conversion of methylcyclohexane to methane, benzene and toluene while similar products were produced for 3-methylhexane, albeit with diminished conversion level. In H₂, methane was produced from 3-methylhexane conversion while aromatization without demethylation was obtained in addition to some cracking for methylcyclohexane at the low temperature range (350-400°C); a higher temperature range (460-500°C) resulted in complete fragmentation for methylcyclohexane. In H₂-N₂ mixtures, the presence of N₂ of not less than 50% in the carrier gas stream yielded an aromatic catalyst at conditions where only cracking activity was previously evident. The differences in product distribution and/or product types for the two reactants in H₂ and N₂ suggest a different reaction mechanism for both reactants.     

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.     

The study of catalytic performance of silica-supported three metallic Fe–Co–Ce catalyst prepared using impregnation procedure for Fischer–Tropsch synthesis

We apply the wet impregnation procedure to prepare the Fe–Co–Ce catalyst supported by silica. The effects of operational conditions such as temperature, pressure, and the feed ratios of reaction on the selectivity and yield were studied. The production of light olefins from syngas (CO and H₂) over this catalyst in a fixed bed reactor via Fischer–Tropsch synthesis (FTS) was investigated. The reactor tests were determined through the design experiments.The optimum condition was determined in a way that the selectivity of methane was the least and other olefins have the maximum selectivity. The results indicated that the catalyst at 350°C, 3 bar, and syngas with H₂/CO ratio 1/1 has shown the better catalytic performance for FTS.     

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.     

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.     

Editorial: Emerging Technologies for Petroleum Waste Management

ABSTRACT

An estimate of the quantity of toxic coke deposited on fresh and regenerated Pt/Alj₂O₃ catalyst has been determined for methylcyclopentane (MCP) reforming in a Berty CSTR at 390°C, W/F=0·11 g min cm^-3, total pressure of 1 atm and MCP partial pressure of 9·2 × 10^-2 atm in H₂ or N₂ carrier. Eleven cycles consisting each of catalyst deactivation, regeneration and reduction were investigated with 3 in H₂ and 8 in N₂. Oxidizable (primary) coke deposits were higher in N₂. However, higher levels of toxic (secondary) coke were deposited in H₂. The ratio of oxidizable to toxic coke lies between 1?15×10³ in H₂ and 22 ? 55 × 10³ in N₂ The coke-time profiles for secondary coke removal exhibited maxima suggestive of three types of secondary coke with varying reactivity in H₂. Furthermore, the results strongly suggest that the cokes were layered on acidic coke forming sites with the solid phase transformation of primary to secondary coke occurring at the catalyst-coke interface.     

Oxidative Dehydrogenation of Methanol on Chromium Oxide/Montmorillonite K10 Catalysts

Abstract

Methanol conversion was carried out on a mesoporous material—chromia/montmorillonite K10 (MK10)—in a pulse microcatalytic system. Methanol was converted to formaldehyde and ethylene by two different mechanisms. Methanol dehydrogenation increases by increasing reaction temperature (300–400°C) and as chromia loading decrease. On the other hand, the dehydration of methanol occurs at a higher temperature (400–500°C) and as chromia loading increase, 3–18% Cr. Redox and exposed nonredox Cr³⁺ are responsible for formaldehyde formation. There is a relationship between increased C₂H₄ production and the increase of Cr⁶⁺ phase according to the acidity of chromia catalysts 34 and 76 μL tert-Butylamine/g catalyst for 3% Cr and 18% Cr, respectively. Formaldehyde formation is diffusionally controlled at high temperatures (400–500°C) and kinetically controlled at a lower reaction temperature (300–400°C), while methanol dehydration to ethylene is surface reaction controlled at 400–500°C.     

Mechanistic Kinetic Models for n-Heptane Reforming on Platinum/Alumina Catalyst

Abstract

The kinetics of the reforming of n-heptane on a platinum/alumina catalyst has been studied in a pulse microcatalytic reactor at a total pressure of 391.8 kPa over a relatively wide temperature range of 420°C–500°C. The differential and integral methods were used for the kinetic analyses of the reforming reaction. Twenty-nine reaction rate equations of the Langmuir-Hinselwood-Hougen-Watson type, based on molecular and atomic adsorption of hydrogen, were developed. Parameter estimates for the n-heptane reforming reactions were obtained by application of the Nelder-Mead simplex optimization technique to the predicted and observed conversion/production rates of the reaction components. Discrimination among rival kinetic models was based upon physicochemical criteria, analysis of the residuals, and statistical and thermodynamic tests. The rate-determining step was found to be the surface reaction of adsorbed iso-heptane to adsorbed methylcyclohexane with dissociative adsorption of hydrogen on the catalyst surface during dehydrocyclization of iso-heptane to methylcyclohexane. Hence, the surface reaction on the metallic function is rate-determining for the n-heptane reforming on the Pt/Al₂O₃ catalyst.     

MILD HYDROCRACKING OF VACUUM GAS OILS TO IMPROVE FCC PERFORMANCE AND MAXIMIZE DISTILLATE YIELDS

ABSTRACT

A pilot plant study was conducted on mild hydrocracking of heavy vacuum gas oils derived from two different crude sources over a commercially available catalyst to determine the possibility of utilizing mild hydrocracker bottoms as fluidized catalytic cracking feedstock along with improved middle distillate yields. The mild hydrocracking experiments were conducted at 390°C, 60 kg/cm², 1.0/h liquid hourly space velocity and H₂/oil ratio of 390 l/l in a pilot plant trickle bed reactor using two catalyst beds for pretreatment and mild hydrocracking reactions. The experimental results showed that mild hydrocracking would result in valuable middle distillates with low sulphur and nitrogen content. With research octane number of 78, the naphtha obtained from mild hydrocracking was found to be a good blending stock for gasoline pool. The middle distillate fraction (140–370°C) obtained from mild hydrocracking product was found to have cetane number in the range of 48–54. The bottom product from mild hydrocracking of heavy vacuum gas oils was found to be a good feedstock for fluidized catalytic cracking unit because of its low sulphur, nitrogen and aromatic contents. The data obtained from pilot plant studies showed that the processing of mild cracker bottom in FCC unit would result in better quality fuels.     

HYDROLIQUEFACTION OF TEXAS LIGNITE IN COAL- AND PETROLEUM-DERIVED SLURRY OILS

ABSTRACT

Hydroliquefaction of Texas lignite (68.5%. C daf) was conducted in a batch autoclave under hydrogen in a coal–derived slurry oil at 90 bar initial pressure for temperatures of 380–460^° C and residence time of 15–60 minutes, or a vacuum distillate from petroleum at 435^° C for 60 minutes and initial H₂–pressure of 60–150 bar, or a vacuum residue from the same petroleum at 435 and 460^° C for 60 minutes and initial H₂–pressure of 90–150 bar or tetralin at 435^°C, 60 minutes and 90 bar initial H₂–pressure. Red mud plus sodium sulfide were added as a catalyst for all experiments. Lignite conversion ranged from 50 to 83%. The products were separated into gases, residue, asphaltenes, oils B,P. above 200^° C, oils B.P. below 200^° C. Total liquid products from coal reached 57% in coal-derived slurry-oil, 56% in vacuum distillate and 64% in vacuum residue at optimum conditions with 32% of product oil B.P. below 200^° C in vacuum distillate and 24% in vacuum residue. When coprocessing lignite with vacuum residue at 120 bar initial pressure, 435^°C and 60 minutes residence time the total mass balance presented an oil yield of 73%. with 32% boiling below 200^°C.     

The features of the catalytic synthesis of methanethiol from dimethyl sulfide

The characteristic features of methanethiol synthesis from dimethyl sulfide and H₂S in the presence of Al₂O₃ at atmospheric pressure and T = 320–500°C have been studied. It has been shown that the yield of methanethiol increases with an increase in the temperature, the H₂S-to-dimethyl sulfide ratio, and the contact time, attaining equilibrium values. The methanethiol formation rate is proportional to the dimethyl sulfide partial pressure raised to a power of 0.4 and the H₂S partial pressure raised to a power of 0.8. An increase in the specific surface area and the volume of transport pores and a decrease in the particle sizes of Al₂O₃ facilitate the augmentation of the catalyst activity in methanethiol formation. At T ～ 400°C, a low H₂S concentration, and a long contact time, the side reaction of dimethyl sulfide cracking occurs to result in the release of methane and the deposition of sulfur-containing and carbonaceous compounds on the surface, which lower the activity of alumina. The deactivated catalyst can be regenerated by oxidation.     

REFORMING OF N-OCTANE ON A Pt/Al2O 3 CATALYST. 1. PRODUCT DISTRIBUTION AND KINETIC ANALYSIS.

ABSTRACT

The conversion of n-octane on Pt/Al₂O₃ catalyst to hydrocracked products, isooctane, ethylbenzene, o-,p-,m-xylene and toluene was investigated in hydrogen in a Berty CSTR at three different partial pressures of n-octane, 101·325 KPa total pressure, temperatures between 400°C-460°C and W/F values up to 0·33gmincm^-3. The hydrocracked products were the most predominant. Of the other products, isooctane was present in the highest yield. A sequence of elementary steps based on the suggested reaction network of Ako and Susu (1986) was found to predict the experimental conversion-W/F data with the conversion of adsorbed isooctane to adsorbed o-xylene as the rate determining step. The activation energies for the forward and backward reactions of this step were determined to be 21·2 and 14·3 Kcal/gmol, respectively.     

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.     

Dibenzothiophene Hydrodesulfurization Activity of MoS2 Supported in Sol–Gel ZrO2–TiO2 Mixed Oxides

Abstract

In this work, we report the effect of support composition on the properties of MoS₂ impregnated in sol–gel ZrO₂–TiO₂ mixed oxides as dibenzothiophene hydrodesulfurization catalyst. The supports calcined at 500°C were characterized by N₂ physisorption and X-ray diffraction (electronic radial distribution function). The oxidic impregnated materials (2.8 Mo atoms/nm²) were sulfided at 400°C under a H₂S/H₂ stream. The sample impregnated on the equimolar support showed the highest activity per mass of catalysts whereas the one with TiO₂ carrier was superior in a per mass of Mo basis. Marked differences in products selectivity were observed by TiO₂ addition in the supports. The hydrodesulfurization route to partially hydrogenated compounds was favored over the mixed oxides-supported catalysts meanwhile the direct desulfurization (to biphenyl) was promoted on the ZrO₂-supported solid. It is suggested that among other properties the dispersion and morphology of the MoS₂ phase could influence that behavior.     

The effect of H<Subscript>2</Subscript>S on the selectivity of light alkenes in the FE-Mn-catalyzed Fischer-Tropsch synthesis

Iron-manganese oxides are prepared using a co-precipitation procedure and studied for the conversion of synthesis gas to light olefins. In particular, the effect of a range of preparation variables is investigated in details. In this investigation, sulfur absorption and effect of sulfur poisoning on Fe-Mn catalysts have been studied. In the Fischer-Tropsch synthesis process, the poisoning of the catalyst is one of the important parameters causing a decrease in the catalyst activity, declaring the sulfur compounds as virulent poisons in this process. In the present investigation, poisoning of Fe-Mn catalysts were performed in a gas circulation system and H₂S was injected into a circulation loop. The prepared catalysts were exposed to a mixture of H₂S and N₂ at about 450°C in the stainless-steel micro reactor via co-precipitation method. H₂S was produced by addition of H₂SO₄ to Na₂S × H₂O and this gas was mixed with an inert carrier gas (N₂). Comparing the activity and selectivity of fresh and poisoned catalysts, indicates that the selectivity and CO conversion are affected by high-level sulfur adsorbed on the catalysts. The results show that the CO conversion and selectivity with respect to methane production and coke formation were decreased, but the selectivity of light alkenes such as propylene was increased over poisoned catalysts. Characterization of both precursors and calcined catalysts by powder X-ray diffraction, BET specific surface area and thermal analysis methods such as TGA and DSC showed that the poisoning of Fe-Mn catalysts influenced the catalyst structure.     

DEEP DESULPHURISATION OF A DIESEL BLEND IN A PILOT PLANT TRICKLE BED REACTOR

ABSTRACT

A pilot plant investigation was conducted to study the influence of hydrotreating conditions on conversion and characteristics of diesel blend and to determine the severity of operating conditions required to meet the proposed product specifications for diesel fuel in India. A typical diesel blend derived from various refinery streams with sulphur content of 2·06 wt% was hydrodesulphurised over a commercial NiO-MoO₃/Al₂O₃ catalyst in a pilot plant trickle bed reactor. The experiments were conducted at 300–370°C, 30–50 kg/cm², 2·0 3·0 hr^-1 liquid hourly space velocity and constant H₂/oil ratio of 185 m³/m³. The data showed that the diesel blend could be hydrotreated to meet revised product specifications of 0·25 wt% sulphur, 46 cetane number by increasing the severity of operation. The cetane number and aromatic saturation were limited by thermodynamic equilibrium at temperatures above 360°C. The influence of temperature was found to be more pronounced than that of pressure in the range of operating conditions studied.     

THE EFFECTS OF HIGH PRESSURE ON OIL‐TO‐GAS CRACKING DURING LABORATORY SIMULATION EXPERIMENTS

The effects of high pressures on the yield and kinetics of gas generated by the cracking of crude oil were investigated in laboratory simulation experiments. Samples of a low‐maturity non‐marine oil were recovered from the Paleogene Shahejie Formation in the Dongying depression, Bohai Bay Basin, eastern China. The oils were cracked to gas under different pressure and temperature conditions in an autoclave. Initial temperatures of 300 °C were increased to 650 °C at rates of either 30 or 100 °C/h. Reaction products were analysed at the end of each 50 °C temperature increase. Pressure conditions were either 0.1 MPa (i.e. atmospheric) or 20 MPa. Results show that high pressures inhibit or delay oil‐to‐gas cracking and retard the initiation of the cracking process. The temperature at which oil was cracked and the activation energy of the formation of C_1–5 hydrocarbons increased under high pressure conditions, demonstrating the effects of pressure on the kinetics of the oil‐to‐gas cracking process. High pressures and high temperatures inhibited the conversion of C_2–5 hydrocarbons to methane during secondary cracking. In addition, high pressures retarded the generation of N₂, H₂ and CO during cracking of oil. The presence of water increased the yields of total cracked gas, C_2–5 hydrocarbons and CO₂ in high‐pressure conditions. The simulation results show that CO₂ and C_2–5 hydrocarbons have similar yields during oil‐to‐gas cracking. Using the kinetic parameters determined from the laboratory experiments, the yield and production rate of gas generated during the cracking of oil from Member 4 of the Paleogene Shahejie Formation in the Minfeng‐Lijin sag (Dongying depression) were calculated. The results indicate that only limited volumes of natural gas in this area were derived from the cracking of oil, and that most of the gas was derived from the thermal decomposition of kerogen.     

An improved gravimetric method applied to co-processing of polyethylene terephtalate and petroleum blend using HY zeolite as a catalyst

The co-processing of petroleum and polyethylene terephthalate (PET) was carried out in the presence and absence of a catalyst in an open vessel batch reactor at temperatures of 200, 300, 400, and 500 °C, which corresponds to temperatures of distillation and cracking. The catalyst used was the acidic HY zeolite, which is widely used in petroleum refining. The catalytic co-processing was carried out with the PET–oil charge, at a mass ratio of 1:1, containing 10% of HY zeolite. The conversion degree was measured by knowing the initial sample mass and amount of degraded material for each temperature and reaction time, using an improved gravimetric method consisting of a precision balance and an oven with a heating rate controller. The conversion values obtained were compared for petroleum and PET samples with and without the zeolite catalyst. At temperatures of 200 and 300 °C, the PET showed low conversions, about 5–10%. However, for the catalytic co-processing of PET–oil/HY at these same temperatures, an increase in conversion to about 25–30% was observed. At temperatures of 400 and 500 °C, conversions above 90% were obtained for the two samples, with a subsequent reduction in the activation energy, from 76 kJ mol^?1 (PET) to 56 kJ mol^?1 (PET–oil/HY). The decrease in the activation energy proved the efficiency of the HY zeolite and the synergistic effect when PET was blended to the oil for the catalytic co-processing, proving to be a viable alternative for the chemical recycling of PET in the petroleum industry.     

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.     

Study on flame propagation of premixed N2O–NH3/N2O–NH3–C3H8 in cylindrical vessels

The flame propagation behavior of premixed N₂O–NH₃/N₂O–NH₃–C₃H₈ was experimentally investigated in elongated vented cylindrical vessels with central ignition. The effect of vessel diameter and propane concentration ([C₃H₈] = 1.96–7.41 wt.%) on the process of flame acceleration was studied and discussed. The results revealed that the maximum value of flame acceleration rate was found in the cylindrical vessel with an inner diameter of 7 mm, followed by 5 mm, 10 mm, and 15 mm. At a constant vessel diameter, the rate of flame acceleration was noticeably improved by adding propane ([C₃H₈] = 1.96–3.85 wt.%) to the premixed N₂O–NH₃. However, a further increase in the propane fraction up to 5.66%, caused a decline in the flame acceleration rate, probably as a consequence of a combined effect between the reduction of oxygen and greater dilution of the ammonia in the total concentration.