Residue Cracking Catalysts

Notwithstanding these limitations, a very effective residual cracking catalyst was developed, produced in large commercial quantity and demonstrated to be very effective commercially. 

DFCr systems appear to have the necessary metals tolerance to process residual oils and the abundant, cheaper, but heavily vanadium-contaminated, Venezuelan and Mexican crudes (1-4). Therefore, the dual function fluid cracking catalyst (DFCC) concept could lead to the generation of important catalysts for U.S. refineries should Middle East politics cause another sudden escalation in crude oil prices and availability. The concept is... 

In response to recent federal and local environmental concerns (e.g., industrial emission controls and lead phase-out) and to the growing interest of refiners in cracking residual fuels, researchers have generated new families of cracking catalysts. There is now a need to review the merits of these newly developed materials. This volume contains contributions from researchers involved in the preparation and characterization of cracking catalysts. Other important aspects of fluid catalytic cracking, such as feedstocks and process hardware effects in refining, have been intentionally omitted because of time limitations and should be treated separately in future volumes. 

Generally speaking, resid FCC (RFCC) catalysts should be very effective in bottoms cracking, be metals tolerant, and coke and dry gas selective. Based on many years of fundamental research and industrial experiences, a series of RFCC catalysts, such as Orbit, DVR, and MLC, have been developed by the SINOPEC Research Institute of Petroleum Processing (RIPP) and successfully commercialized [1]. These catalysts are very effective in paraffinic residue cracking. However, in recent years more and more intermediate-based residue has been introduced into FCC units, and the performances of conventional RFCC catalysts are now unsatisfactory. Therefore, novel zeolites and matrices have been developed to formulate a new generation of RFCC catalysts with improved bottoms cracking activity and coke selectivity. 

A more recent development in fixed bed residue processing is the use of zeolitic cracking catalysts. These have been developed primarily in Japan, and are quite stable according to the literature (64). 

If cracking catalysts are used to support the cracking process, the sulfur and metal contaminants must be removed upstream since they poison the catalyst, such as in the residue FCC process [3]. 

Char acts as a vapour cracking catalyst so rapid and effective separation from the pyrolysis product vapours is essential. Cyclones are the usual method of char removal and two are usually provided - the first to remove the bulk of the material and the second to remove as much of the residual fines as possible. However, some fines always pass through the cyclones and collect in the liquid product where they accelerate aging and exacerbate the instability problem, which is described below. 

Various industrial processes have been developed to convert heavy crude oils into transport fuels [3,4], Most of those in use are based on residual cracking or on hydroprocessing over cobalt-molybdenum, nickel-molybdenum or nickel-tungsten based catalysts [3], Given the nature of the feed and the severity of the processing, it is not surprising that catalyst deactivation is a major problem. 

At present, the aforementioned patent techniques have been industrialized for preparation of Si-rich zeolites. The industrial equipment based on the CHZ-3 residual oil cracking catalyst prepared using the corresponding zeolite as the active component has been in operation for heavy-oil catalytic cracking (RFCC). 

From the operation results of the RFCC industrial apparatus it is seen that in comparison with the commonly used residual oil cracking catalyst CHZ-2, the CHZ-3 catalyst with the Si-rich zeolite as the active component increases the content of low-pressure residual oil by 8.02%, whereas it decreases the oil pulp yield by 1.34% under circumstances where the coke yield remains constant. Meanwhile, the light-oil component yield increases by 1.10%, whereas the combined yeild of liquefied gas + light oil increases by 1.73% if CHZ-3 catalyst is used, indicating that this catalyst has excellent activity-stability as well. 

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