No abstract

Ranzi, E.; Dente, M.; Pierucci, S.; Barendregt, S.: Cronin, P. Oil Gas Shah, Y. T.; Stuart, E. B.; Sheth, K. D. Ind. Eng. Chem. Process Des. Trimm, D. L. Catal. Reu.-Sci. Eng. 1977, 16(2), 155. Trimm, D. L.; Holmen, A,; Lindvag, 0. J . Chem. Technol. Biotech-265-325.

Since net feedstock cost is the most significant item of olefins production cost, selection of cracking conditions conducive to high yields of the desired products is a very important feature of an economically successful olefins manufacturing venture.For any specific feedstock, residence time, temperature, degree of conversion and hydrocarbon partial pressure are the variables that influence the product distribution achieved in a steam-pyrolysis process. Of these, residence time and temperature are the most significant variables and the mechanism and kinetics of the thermal cracking of hydrocarbons indicate that optimum selectivity to olefins and maximum feedstock utilization should result from operations carried out at high temperatures and short contact times.Advances in tube metallurgy have made it possible for furnace designers to reduce contact times for commercial pyrolysis plants.Thus over the past decade, design contact times have been reduced in several stages from over 2 seconds to 0.25 seconds, with each step providing an increase in ethylene yield and a decrease in relative tail gas production.In the early stages of pyrolysis development, Kellogg designed a conventional pilot plant reactor (1) (0.25 to 1.5 seconds) in order to study the effect of temperature and contact time on product yields from the pyrolysis of pure hydrocarbons and complex mixtures, ranging from light naphthas to heavy vacuum gas oils. Yields and operating conditions obtained from this pilot plant have been used successfully to design many commercial olefins plants.The accuracy of the operating conditions and yields measured and predicted from this 373

Light gas oil and heavy gas oil from Paraho shale oil and their mixtures with a petroleum light gas oil were pyrolyzed in the presence of steam at 880-900 OC and contact times between 60 and 90 ms in a nonisothermal bench-scale pyrolysis reactor. Blending of petroleum LGO into the shale oil feeds provided product yields that were the weighted linear combination of the yields of the individual components of the blends. Partial denitrogenation and a pronounced decrease in the rate of coke deposition on the reactor walls were observed when petroleum gas oil was blended with the shate gas oils.

A new theory of multilayer physical adsorption is developed ,using a modified form of the significant structurie theory of liquids. With adsorption limited to three layers, isotherm equations are developed in which the adsorption process is described from zero surface coverage up to three adsorbed layers. These isotherm equations are used to fit the multilayer adsorption data for the system Ar-hexagonal boron nitride at three different temperatures. The predicted temperature dependence of the theoretical isotherms agrees quite well with the experimental data. The theory not only correctly predicts condensation of Ar in the first adsor'bed layer, but in the second layer as well, with the critical temperature in each layer dependent on the degree of lateral interaction of Ar in that layer. All molecular parameters except the gas-solid interaction parameters are taken from outside sources. The gas-solid interaction parameter used in the first layer agrees well with previously used values. There are no independent sources of the gas-solid interaction parameters in the second and third layers.