Yield Of Unsaturated Hydrocarbons Research Articles

Effect of Hydrogen Atmosphere on Radiation- Induced Gas Evolution from Polyisoprene

Polyisoprene was irradiated in hydrogen atmosphere by 60Co γ-rays. The evolved gases were methane, ethane, ethylene, propane, propylene and butane. With respect to saturated hydrocarbons, the yields increased with increasing pressure of hydrogen. On the contrary, the yields of unsaturated hydrocarbons decreased. The G-value of methane in hydrogen of 1 MPa was about four times larger than that in vacuum for irradiation of cis-polyisoprene (Cis) at 160 kGy. The gas evolution from trans-isomer (Trans) was about the same as that from Cis. The yields of gases from gloves made of natural rubber were smaller than those from Cis or Trans.

Effect of the conditions of n-decane dehydrogenation on deactivation of the alumina-platinum catalyst

1. Deactivation of the alumina-platinum catalyst in the n-decane dehydrogenation increases with an increase in temperature (430–500°C), and decreases with an increase in either the presence of hydrogen (1·105−2.3·105 Pa) or the molar dilution of the hydrocarbon with hydrogen (4–16). 2. Under all conditions, the degree of deactivation of the catalyst, the accumulation of carbon on the catalyst surface, and combined yield of olefins and diolefins vary in parallel. 3. The degree of deactivation of the catalyst in n-decane dehydrogenation depends on both the amount of coke formed on the catalyst surface, decreasing as the latter increases. 4. Any alteration of parameters (temperature, space velocity, partial pressure of hydrogen, hydrogen dilution) which increases the yield of monoolefins and diolefins in the n-decane dehydrogenation reduces the stability of operation of the catalyst. By varying two of these parameters simultaneously it is possible to increase the yield of unsaturated hydrocarbons and to decrease the degree of deactivation of the catalyst.

Dehydrogenation of hydrocarbons over alumina-chromia catalysts containing additions of certain metal oxides

1. A study was made of the dehydrogenation of isopentane, hexane, and cyclohexane in presence of an alumina-chromia catalyst containing additions of lithium, sodium, potassium, rubidium, cesium, zinc, and lead oxides at 500° at a space velocity of 0.5 hour−1. 2. Catalysts containing sodium, potassium, rubidium, and cesium oxides are almost identical in activity in the dehydrogenation of isopentane and hexane: the yields of unsaturated hydrocarbons were 36–39% from isopentane and 9–12% from hexane (on the amount of hydrocarbon passed). 3. The catalysts with the highest dehydrocyclizing power were those with additions of potassium, rubidium, and cesium oxides; the yields of benzene were 35–38% on the amount of hexane passed. 4. Of all the catalysts investigated, the alumina-chromia-lithia and the alumina-chromia-litharge catalysts were the best from the point of view of high yields of unsaturated hydrocarbons (16–17% on the hydrocarbon passed) and low yields of benzene (13–15%).

Dehydrogenation of hydrocarbons over a lumina -chromia and alumina-chromia-potassia catalysts prepared in various ways

1. An investigation was made of the effect of the method of preparation of alumina-chromia and alumina-chromia-potassia catalysts on their dehydrogenating and dehydrocyclizing activities. 2. The methods investigated for the preparation of catalysts affect the course of the dehydrogenation of isopentane least of all. In the dehydrocyclization of hexane the dependence is more marked. The dependence on the method of preparing the catalysts is still more marked in the dehydrogenation of cyclohexane. 3. The introduction of K2O into alumina -chromia catalysts, however this may be effected, raises their activities and stabilities in the dehydrogenation of isopentane and cyclohexane and also in the dehydrogenation of hexane; it also reduces the yields of unsaturated hydrocarbons from hexane. 4. Of all the catalyst investigated, the best from the point of view of the obtaining of maximum yields of hexenes and the minimum yields of benzene is the alumina-chromia catalyst prepared by impregnation of alumina with ammonium dichromate solution (23% of unsaturated hydrocarbons and 16% of benzene).