Catalytic hydrodesulfurization of a light gas oil over a NiMo catalyst: kinetics of selected sulfur components

The hydrotreating of a real light gas oil feedstock over a commercial NiMo catalyst has been investigated in a pilot plant reactor operating at industrial conditions. The sulfur containing species in the oil and hydrotreated product have been characterized using a sulfur-sensitive gas chromatography technique, and the behavior of several individual components has been followed. The slow-reacting components all belong to the class of dibenzothiophenes, like dibenzothiophene (DBT), 4-methyl-DBT (4-MDBT) and 4,6-dimethyl-DBT (4,6-DMDBT). The individual kinetic behavior of these components was analyzed, and pseudo-first-order rate constants were obtained. The relative rates of HDS decrease in the order DBT>4-MDBT>4,6-DMDBT, the ratio between the rates of these components is shown to be strongly dependent on the reaction temperature. The behavior of 4,6-DMDBT with increasing temperature indicates a limitation on the HDS rate in an agreement with a reversible reaction, suggesting this component has to be hydrogenated before the carbon–sulfur bond is broken.     

Effect of nitrogen removal from light cycle oil on the hydrodesulphurization of dibenzothiophene, 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene

Five light cycle oil feeds (LCO) with nitrogen contents ranging from 744.9 to 16.5 mg/L were prepared by removing organic nitrogen compounds gradually through adsorption on a silica column. These feeds were hydrotreated over a commercial Ni-Mo/Al₂O₃ catalyst to study the effect of nitrogen compounds on the hydrodesulphurization (HDS) of dibenzothiophene, 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene. It was found that nitrogen compounds had the most negative impact on the HDS of 4- and/or 6-substituted dibenzothiophenes. The temperatures to achieve 50% HDS conversion were 5, 20 and 25 °C lower for dibenzothiophene, 4-methyldibenzothiphene and 4,6-dimethyldibenzothiophene, respectively, when the nitrogen content in the feed was reduced from 744.9 to 16.5 mg/L. Our results also revealed that, at lower temperatures, about 20% of the nitrogen compounds from the original light cycle oil were adsorbed on the catalyst's surface. The HDS of 4,6-dimethyldibenzothiophene was retarded until the HDN rate became greater than the adsorption rate, which might have freed some hydrogenation sites for adsorption. This phenomenon was not observed for the HDS of DBT. Our results suggest that nitrogen compounds and 4,6-dimethyldibenothiophene competed for the same type of active sites, and dibenzothiophene also could have been converted over a different site. In addition, the hydrodenitrogenation activity was also enhanced by the removal of nitrogen compounds. The experimental data was fitted to a Langmuir–Hinshelwood type of kinetic equation by assuming that the inhibition only affected the hydrogenation pathway.     

Upgrading of gas oils: the HDS kinetics of dibenzothiophene and its derivatives in real gas oil

The hydrodesulphurization (HDS) of dibenzothiophene (DBT), 4-methyl dibenzothiophene (4 M-DBT), 4,6-dimethyl dibenzothiophene (4,6 DM-DBT) and 4,6-diethyl dibenzothiophene (4,6 DE-DBT) as real gas oil components on NiMo/Al₂O₃ catalyst was investigated. On the basis of the first order rate constants of HDS of the individual sulphur compounds reactivities of the investigated compounds decreased in the order DBT ≫ 4 M-DBT > 4,6 DE-DBT ≈ 4,6 DM-DBT. Apparent activation energies of HDS of above sulphur compounds increased from 80.0 to 120.5 kJ/mol.     

The effect of heavy aromatic sulfur compounds on sulfur in cracked naphtha

The scope of the present study was to elucidate the effect of heavy sulfur compounds, commonly found in the gas oils, on the percentage of sulfur in gasoline range during the Fluid Catalytic Cracking (FCC) process. Five model sulfur compounds commonly found in the gas oils were studied: benzothiophene, 2-methyl-benzothiophene, 3-decyl-thiophene, dibenzothiophene and 4,6-dimethyl-dibenzothiophene. In order to maintain a realistic hydrocarbon environment each one of the heavy sulfur model compounds were diluted in conventional gas oil. Their cracking behaviour were studied using a steamed deactivated FCC catalyst, while the run tests were performed in an automated Short Contact Time Microactivity Test Unit (SCT-MAT) operated at 560 °C and 12 s run time. The experimental results indicated that the long chain alkyl-thiophene (3-decyl-thiophene) is mainly responsible for the increase of sulfur amount in the gasoline range during cracking, through dealkylation and side cracking reactions for the production of thiophene and shorter chain alkyl-thiophenes, respectively. That sulfur compound was also the most reactive one with respect to desulfurization, since it was highly cracked to H₂S and decomposed to S in coke. On contrary, the polycyclic sulfur compounds did not affect the sulfur amount in gasoline, while their reactions were strongly related to their chemical structure. Thus, the main reaction pathway of the alkylated 2-methyl-benzothiophene and 4,6-dibenzothiophene during the FCC process was isomerization, while for benzothiophene and dibenzothiophene alkylation reactions were dominated.     

Desulfurization of liquid fuels by air assisted peracid oxidation system in the presence of Fe-ZSM-5 catalyst

Catalytic oxidative desulfurization of the model oil or synthetic sulfur oil (SSO) and the different real/industrial industrial oil fractions was investigated using air assisted hydrogen peroxide and formic acid oxidation in the presence of Fe-ZSM-5 as catalyst. The reactivity of the different model sulfur compounds increased in the order of thiophene< dibenzothiophene (BT)<4-methyl dibenzothiophene (4-MDBT). The desulfurization yield in case of the model oil was increased in the presence of Fe-ZSM-5 and the sulfur content of the model oil was reduced from 1275 to less than 50 ppm in 60 min at 60 °C temperature. The catalyst also performed efficiently in ODS of real industrial oil fractions, i.e., untreated naphtha (UN), light gas oil (LGO), cooker derived combined heavy gas oil (HGO) and Athabasca oil sands derived bitumen (At. Bit.), and sulfur removal of 80, 78, 62 and 60% was attained, respectively. Kinetic investigation revealed that the ODS catalyzed by Fe-ZSM-5 followed the first-order kinetics.     

Hydrodesulfurization activity of CoMo and NiMo supported on Al2O3–TiO2 for some model compounds and gas oils

Catalytic activities of Al₂O₃–TiO₂ supporting CoMo and NiMo sulfides (CoMoS and NiMoS) catalysts were examined in the transalkylation of isopropylbenzene and hydrogenation of naphthalene as well as the hydrodesulfurization (HDS) of model sulfur compounds, conventional gas oil (GO), and light cycle oil (LCO). Al₂O₃–TiO₂ supporting catalysts exhibited higher activities for these reactions except for the HDS of the gas oil than a reference Al₂O₃ supporting catalyst, indicating the correlation of these activities. Generally, more content of TiO₂ promoted the activities. Inferior activity of the catalyst for HDS of the gas oil is ascribed to its inferior activity for HDS of dibenzothiophene (DBT) in gas oil as well as in model solvent decane, while the refractory 4,6-dimethyldibenzothiophene (4,6-DMDBT) in gas oil as well as in decane was more desulfurized on the catalyst. Characteristic features of Al₂O₃–TiO₂ catalyst are discussed based on the paper results.     

甲醇生产中精脱硫工艺及脱硫剂的选择

评述了不同原料制取甲醇合成气时有机硫转化催化剂与硫吸收剂的合理搭配方式,给出了近年在国内甲醇生产厂实际使用时的脱硫效果和存在问题。当以重（渣）油或煤为原料部分氧化法制气时,在近室温下水解催化剂串接氧化锌脱硫剂可确保总硫脱除到0.01ppm以下,具有最佳节能和精脱硫效果。     

Deep desulfurization of full range and low boiling diesel streams from Kuwait Lower Fars heavy crude

Information on feed quality and, in particular, various types of sulfur compounds present in the diesel (gas oil) fractions produced form different crudes and their HDS reactivities under different operating conditions are of a great value for the optimization and economics of the deep HDS process. This paper deals with deep desulfurization of gas oils obtained from a new heavy Kuwaiti crude, namely, Lower Fars (LF) which will be processed in the future at Kuwaiti refineries. Comparative studies were carried out to examine the extent of deep HDS, and the quality of diesel product using two gas oil feeds with different boiling ranges. The results revealed that the full range diesel feed stream produced from the LF crude was very difficult to desulfurize due to its low quality caused by high aromatics content (low feed saturation) together with the presence of high concentrations of organic nitrogen compounds and sterically hindered alkyl DBTs. The low-boiling range gas oil showed better desulfurization compared with the full range gas oil, however, deep desulfurization to 50 ppm sulfur was not achieved even at a temperature as high as 380 °C for both feeds. The desulfurized diesel product from the low-boiling gas-oil feed was better in quality with respect to the S, N and PNA contents and cetane index than the full-range gas-oil feed.     

Hydrodesulfurization of Diesel Feeds by Association of a Catalytic Process and a Separation Process Using Charge-Transfer Complexes

While deep hydrodesulfurization of gas oil is more and more important, elimination of sulfur compounds such as 4,6-dialkyldibenzothio-phenes still attracts considerable attention. A new process based on the association of a separation process by charge-transfer complex (CTC) formation and classical catalytic hydrotreating (HDT) was evaluated. The results indicated that a CTC pretreatment allows the rate of hydrodesulfurization (HDS) to increase and the final sulfur level to decrease. This process is even more efficient for feeds difficult to desulfurize.     

Simulation of hydrodesulfurization using artificial neural network

Artificial neural network (ANN) is applied to investigate the hydrodesulfurization (HDS) process with light‐cycle oil as feed and NiMo/Al₂O₃ as catalyst. ANN models frequently work as a “black box” which makes the model invisible to users and always need significant data for training. In this work, a new ANN is proposed. The Langmuir–Hinshelwood kinetic mechanism is incorporated into the model so that the proposed ANN model is forced to follow the given reaction mechanisms. Both advantages of self‐learning ability of ANN and the existing knowledge of HDS were taken into account. Lengthy training process is minimised. Effects of operating temperature, pressure, and LHSV on the sulfur removal rate are studied. The inhibition of nitrogen compounds is also investigated. It is shown that the presence of nitrogen can significantly reduce the conversion rate of sulfur components, in particularly, hard sulfur such as 4,6‐DMDBT.     

间歇式给料的生物质快速热解制油的实验研究

设计了间歇式给料的鼓泡流化床反应器,对生物质在不同的反应温度、不同的流化气速以及不同的床层高度等条件下的生物质热解进行了研究。结果表明热解温度是生物质产油率的主要影响因素,流化气流速和床层高度对产油率也有一定的影响。在最佳的反应条件下,生物质油的产率可达65%,其主要组分为有机酸和呋喃。     

Deep desulfurization of diesel fuels: kinetic modeling of model compounds in trickle-bed

Five catalysts with different hydrodesulfurization (HDS) and hydrogenation activity were tested in HDS of fresh crude heavy atmospheric gas oil (HAGO) (1.33 wt% S), two partially hydrotreated HAGO (1100 and 115 ppm S) and two model compounds, dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (DMDBT), dissolved in model solvents and HAGO. Aromatic compounds in the liquid decreased significantly the HDS rate of 4,6-DMDBT, especially for catalysts with high hydrogenation activity. H₂S displayed a similar inhibition effect with all catalysts. These effects were extremely pronounced in HAGO where the DBT HDS rate decreased by a factor of 10 while 4,6-DMDBT – of 20 relative to paraffinic solvent. The feasibility of using a highly active hydrogenation catalyst for deep HDS of HAGO is diminished by the strong impact of aromatics.     

On-line multivariable adaptive control of a binary distillation column

An experimental evaluation of the simultaneous control of top and bottom product compositions of a binary distillation column utilizing multi-variable self-tuning control algorithms is presented. The study was carried out using an 8-tray, 22.86 cm diameter methanol–water pilot scale column with continuous capacitance analysis of top product composition and bottom composition analyzed on a 3 minute cycle, by a gas chromatograph. Column control is studied for ±25% step disturbances in feed flow rate. Terminal composition regulation using both ‘positional’ and ‘incremental’ forms of a generalized minimum variance self-tuning control algorithm is compared with that achieved using a conventional digital PI/PID multiloop control strategy.     

MCM-41-supported Co-Mo catalysts for deep hydrodesulfurization of light cycle oil

Light cycle oil (LCO), a by-product of the fluid catalytic cracking (FCC) process in a petroleum refinery, can be used as a blendstock for the production of diesel and jet fuels. Regulatory and operational issues result in need for new and more active catalysts for the deep hydrodesulfurization (HDS) of diesel feedstocks, such as LCO. This paper reports the activity of a mesoporous molecular sieve MCM-41-supported Co-Mo catalyst in comparison to a commercial γ-alumina (Al₂O₃)-supported Co-Mo catalyst for the desulfurization of a LCO with a sulfur content of 2.19 wt.%. The HDS of dibenzothiophene, 4-methyldibenzothiophene, and 4,6-dimethyldibenzothiophene—polyaromatic sulfur compounds present in LCO—and their relative reactivities in terms of conversion were examined as a function of time on stream in a fixed-bed flow reactor. The MCM-41-supported catalyst demonstrates consistently higher activity for the HDS of the refractory dibenzothiophenic sulfur compounds, particularly 4,6-dimethyldibenzothiophene. The presence of a large concentration of aromatics in LCO appears to inhibit the HDS of the substituted dibenzothiophenes.     

Microbial desulfurization of modeland straight‐run diesel oils

The desulfurization kinetics of Nocardia globerula R‐9 was investigated initially in a model system consisting of dibenzothiophene (DBT) dissolved in dodecane. The ability to desulfurize straight‐run diesel oil by resting cells of this strain was also evaluated. The course of desulfurization of DBT in dodecane could be represented by the Michaelis–Menten equation. The desulfurization of DBT and 4,6‐dimethyl dibenzothiophene (4,6‐DMDBT) in a mixture of the two proceeded simultaneously without preference for either of them. The sulfur content of the straight‐run diesel oil could be reduced from 1807 to 741 mg dm^?3 by treatment with resting cells of this strain, at a mean rate of 5.1 mmol sulfur kg^?1 h^?1. This showed that Nocardia globerula R‐9 could be a potential bacterium for reducing the sulfur content of petroleum products. Copyright © 2003 Society of Chemical Industry     

INTEGRATING ALBEMARLE RESOLVE DESULFURIZATION TECHNOLOGY WITH NOVEL PETRO-CANADA PROCESS CONCEPTS IN COMMERCIAL FCCU OPERATIONS

The gasoline and distillate sulfur regulations promulgated throughout the world to reduce tail-pipe emissions are now strongly impacting refinery operations and investments. FCC gasoline is recognized as the principal contributor of sulfur to the gasoline pool and has become the focus for meeting the new specifications. The difficulty in removing sterically hindered sulfur species in the fluid catalytic cracking unit (FCCU) cycle oil drives up the hydrogen and investment costs for treating the distillates. Although installation of pre- and post-treatment facilities is planned by many refiners, other non-capital approaches such as undercutting are being evaluated to meet interim and future sulfur levels. Even when expensive treatment facilities are installed, operating costs can be lowered and the flexibility of the facility increased with improvements in the ability to remove sulfur in the FCCU. In this article, we detail Petro-Canada's experience in integrating Albemarle's RESOLVE sulfur reduction technology with a combination of innovative process ideas. These concepts include heavy naphtha recycle, coprocessing of hydrogen donor feeds, and recycle of light cycle oil (LCO) to a specially designed stripper reactor. Special attention is paid to the interaction of deep FCC feed hydrodesulfurization with the FCC performance. The results demonstrate that very low FCC gasoline sulfur levels can be achieved without significant capital investment through novel approaches to recycle, creative integration of cat feed hydrotreating unit (CFHTU)-FCCU designs and operations, and application of state-of-the-art sulfur reduction additive technology. An added benefit of the RESOLVE 950 sulfur reduction technology is the substantial elimination of sulfur oxides in the FCC flue gas. This has been observed in Petro-Canada operations and numerous other RESOLVE 950 applications around the world.     

Extraction conditions for removal of oxidized sulfur compounds in gas oil

An experimental study was conducted to investigate the extraction of oxidized sulfur compounds from gas oil. Solvents used for this purpose included acetone, acetonitrile, methanol and propanol. The effect of solvent concentration, solvent to gas oil ratio, temperature, time and number of stages was studied. To select the best solvent and conditions for extraction, two criteria were considered: high desulfurization and more hydrocarbon recovery. Results showed that extraction time and temperature have no significant effect. Methanol for low ability of extraction of oxidized sulfur compounds and propanol for low hydrocarbon recovery were excluded from further experiments. After the tests, the optimum conditions for extraction were determined to be 85% acetone, solvent/feed ratio of 1, two stages extraction in ambient temperature and enough time for mixing. In this condition 85% of sulfur compounds of gas oil containing 1,670 ppmw S were separated and 95% of gas oil was recovered.     

Energy‐efficient complex distillation sequences: Control properties

Four thermally coupled distillation systems were designed for the separation of five‐component mixtures (the light‐ends separation section of a crude distillation plant); their steady‐state design was obtained by starting from a conventional distillation sequence and then optimizing for minimum energy consumption. The thermally coupled distillation systems were compared to sequence based on conventional columns design. Comparison was based on controllability properties under open and closed loop operation, following the dynamic behaviour after common industrial operating disturbances. Simulation results were analyzed by the singular value decomposition technique and with the performance examination of elimination of feed disturbances using PI controllers. It was found that thermally coupled distillation systems are controllable and, sometimes, they exhibit dynamic responses that are easier to manage than in the case of conventional distillation sequences; this result is innovative in the study of this kind of systems.     

PY-GC法研究渣油中硫化物的热裂解性能

采用裂解气相色谱（PY-GC）方法研究渣油中的大分子硫化物的裂解性能。首先对（PY-GC）的实验条件进行优化,在此基础上,得到了可以反应渣油样品中硫化物组成和结构的裂解色谱图;通过标准物对比并结合文献对渣油裂解产物中硫化物的组成进行定性。研究发现,渣油高温裂解产物中的硫化物主要有：H2S、噻吩类、苯并噻吩类和二苯并噻吩类系列的化合物。根据模型化合物的裂解色谱分析结果,推测出渣油裂解产物中的H2S不仅来源于重油分子中硫醚类结构的裂解,而且与重油分子中噻吩、苯并噻吩和二苯并噻吩类结构的裂解有关,而渣油裂解产物中的噻吩、BT和DBT系列化合物主要来自于重油中的大分子噻吩、BT和DBT类化合物的裂解。     

Microbial desulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene in dodecane and straight-run diesel oil

The desulfurization of dibenzothiophene (DBT), 4,6-dimethyldibenzothiophene (4,6-DMDBT) and their mixture by lyophilized cells ofPseudomonas delafieldii R-8 was studied in the presence of dodecane. The desulfurization rate for 4,6-DMDBT was found to be about 40% in comparison with that for DBT. The desulfurization process for DBT and 4,6-DMDBT proceeded simultaneously without preference for either one. The desulfurization rate for each compound was decreased when they were mixed together. The extent of desulfurization of 4,6-DMDBT was increased with the increase of cell concentration and the decrease of the volume ratio of oil-to-water used. The specific desulfurization rate for 4,6-DMDBT could be reached to 10.4 mmol sulfur kg⁻¹ (cell) h⁻¹ [approximately 0.33 mg sulfur g⁻¹ (cell) h⁻¹].Pseudomonas delafieldii R-8 showed high desulfurization capability for straight-run diesel oil (containing 1,807 mg/L of sulfur). About 1,000 mg/L of sulfur in diesel oil was removed by resting cells of this strain in 24 h of reaction. The specific desulfurization rate was 8.75 mmol sulfur kg⁻¹ (cell) h⁻¹.