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The catalytic reaction zone may either be a fixed bed or a fluid type, in which latter type operation the catalyst is maintained in powder form in a turbulent state. It is evident that the process may be operated in accordance with any of the usual techniques for high temperature catalytic conversions.
Thus, fixed catalyst beds may be used in alternate reaction and regeneration cycles; fluid catalyst operation may be used wherein catalyst is continuously withdrawn from the catalyst zone, regenerated and reintroduced into the catalyst zone after regeneration; fluidized fixed bed operation may also be used in which the catalyst particles remain in the reaction zone during alternate reaction and regeneration cycles; stirred catalyst beds as well as moving catalyst beds of the Thermofor type are other possible alternatives.
The particular conditions of reaction are best illustrated by reference to conditions involved in the reaction of an unsaturated acyclic hydrocarbon, such as butylene- 2 over chromia-alumina catalyst employing a fixed bed type of process technique.
Thiophenes (Best Synthetic Methods)
When charging butylene-2 over a chromia-alumina catalyst, the space velocity advantageously falls within the range of 0. It is to be understood that the specific conditions described as optimum are those which result in optimum yields of thiophene in a single pass operation. Where a continuous recycle process is used, it may be desirable to modify these conditions of reaction in order to obtain an optimum yield of the desired product. The process period for optimum thiophene production will depend to some extent upon the charge stock and the reaction conditions employed, but will generally be of longer duration than one hour.
In any case, periodic determination of thiophene yields will indicate the practical period of catalyst activity before regeneration. When the thiophene yields are found to fall off sharply, the catalyst may then be regenerated by conventional methods, such as regeneration with air at about P.
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For example, the reaction products containing unreacted charge stocks, sulfur, cracked products of the charge stock, diolefinic compounds, unreacted hydrogen sulfide may be passed through a caustic soda solution to dissolve the acid gases. If the caustic soda solution is maintained cold, the thiophene will condense as a supernatant layer. The thiophene layer can be drawn oif therefrom and distilled. If the caustic soda solution is maintained hot, the thiophene compounds will steam distill from the caustic solution and can then be separated from the water layer and purified by distillation.
The thiophene compounds may also be recovered in crude form by a simple condensation procedure which involves passing the products into a cool body of hydrocarbon oil, such as kerosene, in which the thiophene compounds will condense; thiophene compounds can later be recovered from the condensing oil by distillation. The process of the invention is illustrated by the following specific examples which clearly show the necessity of eifecting the thiophene-forming reaction at a contact time between 0.
Example I Butylene-2 and hydrogen sulfide in a mol ratio of about 1. The reactants were charged at a hydrocarbon space velocity of 0. The catalyst was maintained on stream for a period of about 75 minutes without reactivation. Crude thiophene of about purity was obtained in a yield of about Example 11 Butylene-2 and hydrogen sulfide in a mol ratio of about 1.
The catalytic reaction. The catatystwas maintained on stream fora period of about minutes without reactivation. The catalytic reaction chamber contained a catalyst which consisted of a mixture of molybdenum oxide, zinc oxide and alumina having the approximate composition of 9. M0O3 supported on. Zn AlQ2 The reactants were charged at ahydrocarb'on space velocityaofapproxi- :mately 08 weights of butylene-l ,per hour iper weight of catalyst and a contact time of about The catalyst was maintained on stream -.
Crude thiophene of.
Thiophenes by Salo Gronowitz, Anna-Britta Hornfeldt - xoreqigigype.gq
Example IV v Ethylene and hydrogen sulfide in a mol ratio of 1. The catalytic reaction chamber contained a catalyst which consisted of a mixture of chromic oxide and alumina havmg the approximate composition of 10 per cent CrzOs supported on A The reactants were charged at a hydrocarbon space velocity, of approximately 0.
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Crude thiophene of about 95 per cent purity was obtained in a yield of about 2 pounds per pounds of ethylene charged. Example V Normal butane and Has in a mol ratio of about 1. The reactants were charged at an hydrocarbon space velocity of 0. The catalyst was maintained on stream for a period of about 75 minutes.
The yield of crude liquid thiophene amounted to Example VI 1, g. The reactants were charged at a hydrocarbon space velocity of approximately 31 weights of butylene-2 per hour per weight of catalyst and a contact time of about 0. After 30 minutes no liquid product had been recovered. The efliuent gas was caustic washed for HzS removal; the caustic-washed gas had the following composition in volume per cent:. Catalytic reaction chamber contained a-. The reactants were'oharged. The yield of crude liquid thiophene. The reactants were charged at ahydrocarbon space velocity of 0. After a reaction period off minutes, there was obtained no liquid thiophene yield.
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