Catalytic cracking feedstock quality

The performance analysis and product analysis results confirm previous findings (3,8) that hydrotreating improves the quality of catalytic cracker feedstock and the resultant products. In addition, it was shown that the quality of the liquid products and the yields of the coke and the heavy cycle oil (HCO) from cracking of the severely hydrotreated feedstock (WM-2-9) were independent of the conditions of the cracking process. These results imply that there exists a degree of pretreatment hydrotreating above which... 

Gravimetric Results of Catalytic Cracking. Experiments were conducted to assess the effects of temperature, cat-to-oil ratio, and feedstock composition. In addition to the effect of variables on product yields, it was also important to identify the relative influence of thermal reactions, since free-radical reactions may adversely affect product quality. A series of experiments was conducted in the temperature range of 412°-415°C because this is the temperature of maximum increase in production from thermal cracking and catalytic vs. thermal effects are more easily discernible at this temperature. 

In the program of feedstock quality analysis, the goal was to predict the product distribution that can be expected from the reduced crude conversion of each feedstock. In this paper the results of slurry oil and coke yield predictions will be discussed. The next section gives a brief overview of the chemistry of catalytic cracking and some of the basic concepts which were used to guide the development of the slurry oil and coke yield predictions. 

Distillates from coal tar (carbochemical oils), or residual oils that are created by catalytic cracking of mineral oil fractions and olefin manufacture by the thermal cracking of naphtha or gas-oil (petrochemical oil) can also be used as a source of raw material. Quality is the main criteria to favor a specific feedstock. Here a variety... 

Pyrolysis is a tertiary or feedstock recycling technique capable of converting plastic waste into fuels, monomers, or other valuable materials by thermal and catalytic cracking processes. This method can be applied to transform both thermoplastics and thermosets in high-quality fuels and chemicals. Moreover it allows the treatment of mixed, unwashed plastic wastes. 

In catalytic cracking a heavy oil is pyrolyzed on an aluminosilicate catalyst at 700-1000 K, to produce a range of lighter products. The gasoline so produced has a high proportion of aromatics and alkenes. Other cracking processes produce similar, but lower quality products from heavier feedstocks. 

Feedstocks to the coker generally consist of vacuum resids along with some slops (refinery or petrochemical waste streams) heavy FCC (fluid catalytic cracking) slurry oils, which contain unconverted hydrocarbons and traces of catalyst fines entrained from the reactor and asphalts. The coker is often the final disposition for many poor quality refinery process streams. As a result, the feedstock to the coker contains high levels of impurities. 

Of the many factors which influence product yields in a fluid catalytic cracker, the feed stock quality and the catalyst composition are of particular interest as they can be controlled only to a limited extent by the refiner. In the past decade there has been a trend towards using heavier feedstocks in the FCC-unit. This trend is expected to continue in the foreseeable future. It is therefore important to study how molecular types, characteristic not only of heavy petroleum oil but also of e.g. coal liquid, shale oil and biomass oil, respond to cracking over catalysts of different compositions. 

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