Cracking catalysts hydrogen content

The revolutionary zeolite cracking catalyst (synthetic Linde X and Y) was introduced commercially over 28 years ago, but considerable effort is still being expended on the improvement of its stability and catalytic properties. Decreasing the aluminum content of the zeolite framework and the replacing the rare-earth with the hydrogen form have greatly increased activity at the expense of stability. The thermal stability of the faujasites is fairly well understood, while the reasons for the increased catalytic activitity are still not fully known. 

The cracking and hydrogenation balance in the catalyst depends on acid center/metal ratio. In our case, the main target is the diesel quality. The results of diesel PNA analysis are shown in Table 6 for catalysts Cl, CII and CIII operating at 380 °C. The analysis shows that the steam-ammonia treatment increases the paraffins content and decreases naphthenes and aromatics content. This indicates a higher hydrogenation-hydrogenolisis activity in CIII than in CII and Cl. In addition, the NMR analysis indicates... 

Cracking. - Eberly et aP studied the coke formed on a cracking catalyst with IR. The fundamental C-H stretches in the 3100 to 2800 cm were important. The aromatic C-H absorption appears at 3050 cm and methylene groups at 2930 and 2860 cm The ratio of the absorbance of the infrared bands at 3050 and 2930 cm is a meassure of the aromaticity of the coke. In this case, it was found that the coke was formed by highly condensed aromatics of low hydrogen content. 

Furnace carbon black is produced from the incomplete combustion of what is called carbon black oil feedstock, which consists of heavy aromatic residue oils. In the United States this oil is commonly the bottoms from catalytic cracker units. They are commonly referred to as cat cracker bottoms and contain relatively low hydrogen content (and conversely high carbon content). In Europe and other locations, the carbon black oil used is commonly a byproduct of high-temperature steam cracking of such products as naphtha, gas condensate, and gas oil to produce ethylene, propylene, and other olefins. Here, no catalysts are used in the cracking process. These types of carbon black oils are mainly unsaturated hydrocarbons. A third source of carbon black feedstock is coal tar, which is commonly used in China to manufacture carbon black. 

These new constraints on gasoline formulation focused attention on the decreased octane levels of gasoline produced with REY-zeolite cracking catalysts and the octane dip, or low octane number, of C6-C10 paraffins. To compensate, the aromatic content of the gasoline pool was increased from about 20% in 1973 to almost 40%, but the need for new octane catalysts was soon an important objective for refiners and catalyst producers. Octane catalysts require a suitable zeolite that can limit the hydrogen transfer reactions that convert olefins to paraffins. 

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