Bp Chemicals Limited

Christian Sait

Alain Pinede

Gacem Benazzouz

Gacam Benazzouz

Eric Arrivat

Jacques Heritier

A process for maintaining a property P of a polyisobutene around a target value V during a continuous polymerisation of isobutene in a reactor containing a boiling liquid reaction phase in equilibrium with a gas phase above the liquid phase. The process comprises continuously introducing, into the reactor, a catalyst and a C4 hydrocarbon feed and continuously withdrawing, from the reactor, the liquid reaction phase which is subsequently subjected, continuously, to at least one purification step to isolate the polyisobutene. The property P is chosen amongst the viscosity and the average molecular mass of the polyisobutene. The property P is maintained around the target value V (i) by measuring the isobutene partial pressure (PiC4) in the gas phase of the reactor, (ii) by calculating the isobutene concentration (CiC4) in the boiling liquid reaction phase by means of a first model predicting the value of CiC4from the measured value of PiC4 and being based on liquid/vapor equilibrium law, (iii) by calculating an instantaneous value Pinst of the property P by means of a second model predicting the value of Pinst from the calculated value of CiC4and including at least one function of the isobutene polymerisation kinetics, and (iv) by varying at least one process parameter so as to make the instantaneous value Pinst tend towards the target value V.

Process for the polymerisation of isobutene

The present application relates to a process for the continuous polymerization of isobutene while maintaining at a constant desired value a property P (viscosity or average molecular mass) of the polymer produced. The polymerization is conducted in a reactor comprising a boiling liquid reaction phase which contains the monomer and the polymer being formed, in equilibrium with a gas phase on top of the said liquid phase, by continuous introduction into the reactor of a catalyst and of a C4 hydrocarbon feed mixture comprising the monomer, and by continuous withdrawal from the reactor of the liquid reaction phase, which is subsequently subjected continuously to at least one purification step which is intended to isolate the polyisobutene produced. The process comprises the determination of a target value V of the partial pressure piC4 of the isobutene in the gas phase of the reactor corresponding to the property P, by virtue of an empirical relationship established beforehand between the property P of the polyisobutene produced and piC4. During the polymerization, piC4 is measured and held constant at around the target value V by acting on the flow rate Qc of the catalyst introduced into the reactor and/or on the flow rate Qh of the C4 hydrocarbon feed mixture.

Isobutene polymerization process

Isobutene polymerization process wherein a property P (viscosity or average molecular weight) of the polyisobutene product is maintained constant. The polymerization is conducted continuously in a reactor comprising a boiling liquid reaction phase in equilibrium with a gas phase, by continuous introduction into the reactor of a catalyst and of a C4 hydrocarbon feed mixture comprising the monomer, and by continuous withdrawal from the reactor of the liquid reaction phase. The process comprises the determination of a target value V of the partial pressure, PiC4, of the isobutene in the reactor gas phase corresponding to the desired value of the property P, by virtue of an empirical relationship established beforehand between the property P of the polyisobutene product and PiC4. During the polymerization, PiC4 is measured and a corrected value of PiC4, (PiC4) , is calculated and is held constant at around the target value V, by acting on the flow rate Qc of the catalyst and/or on the flow rate Qh of the C4 hydrocarbon feed mixture.

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Cornillon-Confoux, France

Christian Sait