Synthesis of La-Modified Ultra Stable Zeolite L and Its Application to Catalytic Cracking Catalyst

A new type of zeolite La-USL （ultra stable zeolite L （zeolite USL） modified by La）, which has superior activity, stability and selectivity in catalytic cracking of hydrocarbons and thus can be used as an active catalyst component, is reported in this paper. The zeolite L with relative crystallinity of above 90% was synthesized by the hydrothermal crystallization method under optimum conditions and characterized by means of XRD, NH3-TPD and isotherm adsorption techniques. The in-situ synthesized zeolite L with a SiO2/Al2O3 mole ratio of 5-6 was modified by cation ion exchange, hydrothermal dealumination and chemical modifications with La in order to prepare La-containing USL with a higher framework SiO2/Al2O3 mole ratio of 15-30. The modified zeolite La-USL was used as an active additive component of fluid catalytic cracking （FCC） catalyst and the resulting catalysts were evaluated by microactivity test （MAT） and fixed-fluidized bed （FFB） experiments using heavy oil as feedstock. The influence of La content in La- USL on cracking product distribution, gasoline group composition and research octane number （RON） was investigated. The results showed that when La content in La-USL was 0.8 wt%, the addition of the corresponding La-USL could result in a FCC catalyst that produced significant improvement in product distribution and gasoline quality.

Research Advances on Cyclohexane Catalytic Cracking

This article elaborates on the research achievements of domestic and foreign researchers in exploring the conversion pathways and reaction mechanisms of cyclohexane catalytic cracking in recent years.It analyzes the effects of different catalysts and process conditions on the conversion laws of cyclohexane,summarizes the conversion pathways of cyclohexane,and discusses the chemical mechanisms of several main reactions of cyclohexane in catalytic cracking,such as cracking,isomerization,hydrogen transfer,dehydrogenation,and alkylation;Several advanced characterization methods and common research methods were listed,and prospects for future development in this field were proposed based on existing research.

Recovery of rare earths from spent FCC catalysts by solvent extraction using saponified 2-ethylhexyl phosphoric acid-2-ethylhexyl ester(EHEHPA)

A process to recover rare earth（RE） metals from spent fluid catalytic cracking（FCC） catalysts by solvent extraction was studied, using saponified 2-ethylhexyl phosphoric acid-2-ethylhexyl ester（EHEHPA or P507）. The recovery process involved three steps：（1） leaching REs（mainly lanthanum and cerium）;（2） solvent extraction by applying saponified P507-kerosene system;（3） stripping. Experiments to assure optimal operating conditions were conducted. Results indicated that RE metals could be recovered effectively from spent catalyst with saponified P507-kerosene-HCl system. At room temperature of 25 oC, 10 g spent catalyst with 110 m L of HCl（1 mol/L） could achieve a leaching efficiency of 85%. For extraction, initial pH value of 3.17, organic/aqueous ratio（O/A ratio） of 2：1 with an extractants＇ saponification rate of 20% could obtain 100% efficiency. In the stripping process, 1 mol/L HCl with O/A ratio of 1：1 led to a stripping efficiency of 96%. In the present study, RE metals from spent FCC catalysts were effectively recovered, which avoided wasting a large amount of RE resources. It provides a theoretical support for commercial recycling of RE resources.

CFD simulation of gas-solid flow patterns in a downscaled combustor-style FCC regenerator

To investigate the gas-solid flow pattern of a combustor-style fluid catalytic cracking regenerator, a laboratory-scale regenerator was designed. In scaling down from an actual regenerator, large-diameter hydrodynamic effects were taken into consideration. These considerations are the novelties of the present study. Applying the Eulerian-Eulerian approach, a three-dimensional computational fluid dynamics （CFD） model of the regenerator was developed. Using this model, various aspects of the hydrodynamic behavior that are potentially effective in catalyst regeneration were investigated. The CFD simulation results show that at various sections the gas-solid flow patterns exhibit different behavior because of the asymmetric location of the catalyst inlets and the lift outlets. The ratio of the recirculated catalyst to spent catalyst determines the quality of the spent and recirculated catalyst mixing and distribution because the location and quality of vortices change in the lower part of the combustor. The simulation results show that recirculated catalyst considerably reduces the air bypass that disperses the catalyst particles widely over the cross section. Decreasing the velocity of superficial air produces a complex flow pattern whereas the variation in catalyst mass flux does not alter the flow pattern significantly as the flow is dilute.