Methods of deoxygenation of tall oil and production of polymerizable monomers therefrom
A method of deoxygenation of tall oil as well as methods for the production of aliphatic hydrocarbons and polymerizable monomers from tall oil. Sulphurous crude tall oil together with hydrogen gas is fed into a reactor comprising a catalyst bed. The oil is catalytically deoxygenated by hydrogen in the bed by use of a sulfided metal catalyst, e.g. a NiMoS catalyst. The flow exiting the reactor is cooled down and a hydrocarbon-bearing liquid phase is separated from a gas phase, followed by subjecting the liquid phase to distillation for removal of useless aromatic hydrocarbons and then to steam cracking to form a product containing olefins such as ethylene or propylene. By regulation of the deoxygenation temperature to be at least 270° C. but less than 360° C. the yield is rich in linear and cyclic aliphates that usefully turn to olefins in the steam cracking, while formation of napthalenes is reduced.
1. A method for the production of polymerizable olefins from tall oil, the method comprising the steps of:
feeding sulphurous crude tall oil and hydrogen gas into a catalyst bed, the sulphurous crude tall oil having a content of 30 to 70 weight-% of fatty acids and a content of 20 to 50 weight-% of resin acids;
catalytically deoxygenating the sulphurous crude tall oil by hydrogen in the catalyst bed in a temperature of 280° C. to 320° C. in the presence of a sulfided metal catalyst;
cooling the flow which has exited the catalyst bed, and separating a hydrocarbon bearing-liquid phase from a gas phase;
removing aromatic hydrocarbons from the hydrocarbon-bearing liquid phase to produce a hydrocarbon-bearing liquid distillate; and
subjecting the hydrocarbon-bearing liquid distillate to steam cracking to form a product containing polymerizable olefins.
2. The method of claim 1 , wherein water is separated from the hydrocarbon-bearing liquid phase before feeding the liquid into steam cracking.
3. The method of claim 1 , wherein the aromatic hydrocarbons are removed from the hydrocarbon-bearing liquid phase before the steam cracking step by distilling the hydrocarbon-bearing liquid phase to separate the aromatic hydrocarbons from the hydrocarbon-bearing distillate.
4. The method of claim 1 wherein ethylene and/or propylene are produced by the steam cracking.
5. The method of claim 1 , wherein the gas phase comprises contaminants, hydrogen gas, and C 1 to C 4 hydrocarbons, and wherein the gas phase is washed with diethyl amine to remove the contaminants, the hydrogen gas is circulated to the deoxygenation stage to be used as hydrogen-bearing gas, and the C 1 to C 4 hydrocarbons are recovered and passed to steam cracking.
6. The method of claim 1 , wherein the sulphurous crude tall oil contains 0.05 to 0.5 weight-% of sulphur.
7. The method of claim 1 , wherein the deoxygenation catalyst is a sulfided NiMo or CoMo catalyst.
8. The method of claim 1 , wherein the hydrogen pressure at the deoxygenation step is 30 to 100 bar.
9. The method of claim 1 , wherein the catalyst bed is a fixed bed formed by fixed bed material.
10. The method of claim 1 , wherein the flows in the catalyst bed run from top to bottom.