Hydrocracking Of Vacuum Gas Oil Research Articles

Hydrothermal Cracking of Vacuum Gas Oil for Producing Middle Distillates.

A novel process in which hydrogen and catalyst (in this study, NiMo supported nonacidic catalyst) coexisted and cooperated was developed. It was named hydrothermal cracking process. It was employed to perform liquid-phase cracking of vacuum gas oil (VGO) under 713K and 8.0MPa in a batch reactor. The results obtained were compared with those by simple thermal cracking under the same reaction conditions. The new process suppressed the naphtha yield (from 22.4 to 13.5wt%) but promoted the middle distillate yield (from 44.3 to 49.3wt%) while keeping similar conversion level (-65%). At the same conversion level, the yield ratio of middle distillates to naphtha for the new process was two times higher than that for the acid-catalyzed hydrocracking process. The hydrocracking of VGO over USYsupported NiMo proceeded at much lower temperatures but gave higher naphtha yields. Both the thermal cracking and hydrothermal cracking of n-dodecylbenzene (C6H5(CH2)11CH3) yielded toluene as the major aromatic product, whereas the hydrocracking of n-dodecylbenzene with NiMo/USY yielded benzene as the major aromatic product. The reaction mechanism of this process was assumed to consist of thermal cracking of hydrocarbon molecules via the free radical chain mechanism and catalytic hydroquenching of free radicals.

Hydrocracking of Vacuum Gasoil on the Novel Mesoporous MCM-41 Aluminosilicate Catalyst

The performance of NiMo (12 wt% MoO 3, 3 wt% NiO) supported on the mesoporous crystalline MCM-41 aluminosilicate for mild hydrotreating of a vacuum gasoil has been compared with that of an amorphous silica-alumina and a USY zeolite with the same Ni and Mo loadings. The MCM-41-based catalyst was seen to give superior HDS, HDN, and HC activities to the latter two catalysts in a one-stage operation using an untreated gasoil. The better performance of the former catalyst is explained by its higher surface area, the presence of uniform pores in the mesopore range, mild acidity, and stability. In the case of a two-stage operation using a pretreated feed, the MCM-41 catalyst showed a lower HC activity than USY, but higher than the amorphous silica-alumina while preserving its better selectivity to middle distillates.

Modeling of a hydrocracking reactor

A three parameter model has been developed for a two-stage vacuum gas oil hydrocracker unit. The feed and the products were lumped into 23 pseudocomponents, each characterized by its boiling range and specific gravity. The model assumes that each pseudocomponent can only form lighter products by a pseudohomogeneous first order reaction. The model parameters were determined using information from literature and plant data. Given the feed characterization and the inlet conditions, the concentration and temperature profiles throughout the reactors, the amount of recycle and hydrogen consumption can be calculated. The model was validated against plant data and the agreement was generally good. The effect of variation in the model parameters and operating conditions has also been discussed.

High pressure hydrocracking of vacuum gas oil to middle distillates

Hydrocracking of heavier petroleum fractions into lighter ones is of increasing importance today to meet the huge demand, particularly for gasoline and middle distillates. Much work on hydrocracking of a gas oil range feed stock to mainly gasoline using modified zeolite catalyst-base exchanged with metals (namely Ni, Pd, Mo, etc.) has been reported. In India, however, present demand is for a maximum amount of middle distillate. The present investigation was therefore aimed to maximize the yield of middle distillate (140–270°C boiling range) by hydrocracking a vacuum gas oil (365–450°C boiling range) fraction from an Indian Refinery at high hydrogen pressure and temperature. A zeolite catalyst-base exchanged with 4.5% Ni was chosen for the reaction. A high pressure batch reactor with a rocking arrangement was used for the study. No pretreatment of the feed stock for sulphur removal applied as the total sulphur in the feed was less than 2%. The process variables studied for the maximum yield of the middle distillate were temperature 300–450°C, pressure 100–200 bar and residence period 1–3 h at the feed to catalyst ratio of 9.3 (wt/wt). The optimum conditions for the maximum yield of 36% middle distillate of the product were: temperature 400°C, pressure 34.5 bar (initially) and residence period 2 h. A carbon balance of 90–92% was found for each run.

Studies on hydrodesulfurization of heavy distillates. Part 3. Physical and chemical properties of product oils.

Vacuum gas oil was hydroprocessed over a Co-Mo-Al2O3 catalyst at temperatures of 380, 400, and 420°C and at pressures of 4.0 and 7.9MPa. The physical and chemical properties of the product oils, viz., middle distillate and vacuum gas oil fractions were correlated. Also the properties of these oils were correlated with reaction conditions and with the results of cracking, desulfurization, and denitrogenation conversions. It was expected that the middle distillate produced by mild hydrocracking of vacuum gas oil would be less suitable as fuel oil and that the vacuum gas oil fraction in the product is a suitable feedstock for such upgrading process as fluidized catalytic cracking.

Studies on hydrodesulfurization of heavy distillates. Part 2. Reaction kinetics of hydrocracking, hydrodesulfurization, and hydrodenitrogenation.

Kinetic studies on hydrocracking (HC), hydrodesulfurization (HDS), and hydrodenitrogenation (HDN) reactions of vacuum gas oil derived from mixed Middle Eastern crude oils have been made. Hydroprocess experiments were carried out over a Co-Mo/Al2O3 catalyst at temperatures of 380, 400, and 420°C and at pressures of 4.0 and 7.9MPa. The HC and HDN reactions have been found to be of first order kinetics. However, the order of reaction for HDS reaction decreases with increasing temperature. The sensitivity of these reaction rates to pressure decreases in the following order: HDN>HDS>HC. In addition, with increase in temperature, the effect of pressure on the HC and HDS reaction rates decreases, whereas its effect on the HDN reaction rate is unvaried. These observations are interpreted by assuming that HC and HDS reactions follow at least two parallel reaction routes, which are differently influenced by pressure, and that the selectivity between the parallel reaction routes varies with temperature.

Evaluation study of hydrocracking of raw distillate

1. The economic efficiency of the hydrocracking process at 50 atmospheres has been fully demonstrated. The most favorable technical and economic indices are obtained with a combination of hydrocracking of vacuum gas oil and catalytic cracking of the hydrocracking residue. The hydrocracking residue can also be used as low-sulfur component of fuel oil or for lubricant oil production. 2. At the present stage of planning developments, the process of two-stage hydrocracking at 150 atmospheres under our conditions gives less favorable indices compared with catalytic cracking and hydrorefining of petroleum products.