Higher Gasoline Yield Research Articles

Digital simulation of industrial fluid catalytic cracking units—V. Static and dynamic bifurcation

A dynamic model, whose steady-state version has been verified against industrial units in earlier parts of this series, is used to investigate the static and dynamic bifurcation behaviour of an industrial fluid catalytic cracking (FCC) unit. The investigation concentrates on fixed point and periodic attractors of this industrially important unit. The results show some of the important static and dynamic features of the unit and also point-out to means of stabilizing the unstable high gasoline yield operating points. In certain cases operating the unit on a periodic attractor can give higher gasoline yields, however more work is needed to identify regions of design and operating parameters where this possibility can be realized without the practical problems associated with it.

Catalytic Cracking of an Australian Coal-Derived Liquid Heavy Feedstock on HY and HZSM-5 Zeolites

The catalytic reactions of a severely hydrotreated CDL heavy feed were investigated on HY and HZSM-5 zeolites at 480 C over a range of catalyst-to-feed ratios. The formation of gaseous (<C5) and gasoline range (C5-ClO) products was closely followed. A higher gasoline yield was observed from cracking on HY zeolite, reaching a maximum of -40 wt % at 70% feed conversion (compared with -15 wt % over HZSM-5 at 40% conversion). Greater gas yields were observed from reaction on the pentasil. Although a reduced gasoline yield was obtained from reaction on HZSM-5, it had a higher octane rating compared with that obtained from reaction on the faujasite, possibly due to the higher concentration of alkenes and aromatics produced on the pentasil. The concentration of selected aromatics falling outside the gasoline range was found to increase with conversion, while the reactivity of linear alkanes (originally present in the starting feedstock) increased with chain length. Observed differences in product yield and selectivity from reaction on HY and HZSM-5 were attributed to the different pore diameters, acidity, and hydrogen-transfer potential of the two zeolites.

Catalytic cracking of hexadecane over ZSM-5 modified with SiCl 4, BCl 3, NH 4F and LaCl 3

In this investigation ZSM-5 has been modified with SiCl 4 BCl 3 NH 4F and LaCl 3. Modified ZSM-5 were characterized using infrared (IR), X-ray diffraction (XRD) and temperature-programmed decomposition (TPD) techniques and model reaction. Experimental results show that the physico-chemical properties and cracking performance of modified ZSM-5 are connected to the methods used for modification. Of the four modification methods used the one with LaCl 3 seems to be the most favourable owing to the high cracking activity of LaCl 3-modified ZSM-5 and its high gasoline yield in the cracking of hexadecane. On the basis of the experimental results it is proposed that the La (III) ion is probably exchanged into the ZSM-5 during the modification with LaCl 3 solution.

Octane enhancement in fluid catalytic cracking: I. Role of ZSM-5 addition and reactor temperature

Addition of ZSM-5 to an ultra-stabilized fluid catalytic cracking (FCC) catalyst leads to significant losses in gasoline yield, the gasoline being cracked preferentially to propylene, iso-butane and butylene. The octane boost resulting from ZSM-5 addition is due to an increase in gasoline aromatics concentration as well as a decrease in molecular weight. Rather than being due to a particular reaction mechanism, the increase in aromatics concentration is in essence a concentration effect resulting from preferential removal of the non-cyclic gasoline components through cracking. No increase in gasoline component branching is observed on ZSM-5 addition. Of particular importance is the effect of ZSM-5 addition on the octane potential of the low-octane gasoline heart-cut (b.p. 70–130°C) from the FCC unit. A boost in motor octane number (MON) is observed due to cracking of low-MON components, e.g. olefins, to gas. However, no effect on heart-cut research octane number (RON) is seen, since these olefins have a significant RON contribution. A comparative study has been made of the effects of ZSM-5 addition and operation at higher reactor temperatures on gasoline octane enhancement in fluid catalytic cracking. Higher FCC reactor temperatures give rise to higher research octane levels than ZSM-5 addition does due to the catalytic formation of gasoline aromatics and preservation of olefins; the latter are preferentially cracked out in the presence of ZSM-5. Hence, a higher gasoline yield is realized, even at high motor octane levels. One detrimental factor, however, is the increased production of dry gas.

METHANOL TO GASOLINE: IMPROVED GASOLINE YIELDS

ABSTRACT The role played by the catalyst in the mehhanol-to-gasoline process under varying conditions is significant. The mobil ZSM-5 catalyst yielded dimethyl ether as a major product in earlier experiments conducted in the Chemical Engineering Department. This prompted us to ascertain those parameters which yielded a high percentage of gasoline and minimized or eliminated dimethyl ether. A number of parameters like residence time, reaction temperature, and methanol catalyst weight ratio were studied and knowledge regarding how best a high gasoline yield could be produced was obtained. Product characterization was done by gas chromatographic analysis. GC-MS proved to be an extremely beneficial tool.

Mobil Methanol-to-Gasoline Process

This paper explains that 2 major concerns in the development of the methanol-to-gasoline (MTG) process are heat removal from the reactor and the formation of durene (1-,2-,4-,5-tetramethylbenzene). Conversion of methanol to gasoline is highly exothermic (about 1510-1740 kJ/kg of methanol converted) and the adiabatic temperature rise would be almost 600C. Within Mobil, 2 types of reactor configurations were adopted for development: an adiabatic fixed-bed and a fluid-bed reactor. The fixed-bed reactor is ready for immediate commercialization and is more suitable for smaller scale operation. The fluid-bed reactor is under development and possesses the following potential advantages over the fixed-bed reactor: reaction heat removal is simplified by using the superior heat transfer characteristics of a fluid bed; when coupled with alkylation, the fluid bed gives a higher gasoline yield than the fixed bed; and constant catalyst activity, gasoline selectivity, and gasoline quality can be maintained with the fluid-bed operation. Fixed-bed is cyclic.

Effect of hydro-thermal treatment on properties of aluminosilicate catalysts in cracking of petroleum fractions

1. 1. Hydrothermal treatment of gel during the synthesis of aluminosilicate catalysis increases catalytic activity in cracking of a kerosine-gas oil fraction by 3–7% of gasoline yeild. 2. 2. Aluminosilicate catalysts subjected to hydro-thermal tretment produce less coke and have a higher rate of oxidative recovery, compared with an industrial cracked catalyst containing zeolite. 3. 3. A catalyst obtained from a matrix subjected to hydro-thermal treatment and containing zeolite has a higher gasoline yield (46.4–51.0%) than AShNTs-3 spherical and zeolite-containing industrial aluminosilicate catalysts (39.0–45.4%).