Methods for producing polyolefin polymers may use a predictive melt index regression to estimate the melt index of the polyolefin during production based on the composition of the gas phase and, optionally, the concentration of catalyst in the reactor or reactor operating conditions. Such predictive melt index regression may include multiple terms to account for concentration of ICA in the reactor, optionally concentration of hydrogen in the reactor, optionally concentration of comonomer in the reactor, optionally the catalyst composition, and optionally reactor operating conditions. One or more terms may independently be represented by a smoothing function that incorporates a time constant.

Methods for determining ethylene concentration in an ethylene oligomerization reactor using an ultrasonic flow meter are described, and these methods are integrated into ethylene oligomerization processes and related oligomerization reactor systems.

A process to react an oxygen containing regenerated catalyst stream prior to use in a fluidized bed reactor comprising providing a regenerated catalyst stream which comprises at least 0.001 wt % oxygen; reacting the regenerated catalyst stream with a fuel source thereby forming oxides and reducing the amount of oxygen in the regenerated catalyst stream to produce a usable regenerated catalyst stream; and injecting the usable regenerated catalyst stream into a hydrocarbon fluidized bed reactor is provided.

Methods for producing polyolefin polymers may use a predictive melt index regression to estimate the melt index of the polyolefin during production based on the composition of the gas phase and, optionally, the concentration of catalyst in the reactor or reactor operating conditions. Such predictive melt index regression may include multiple terms to account for concentration of ICA in the reactor, optionally concentration of hydrogen in the reactor, optionally concentration of comonomer in the reactor, optionally the catalyst composition, and optionally reactor operating conditions. One or more terms may independently be represented by a smoothing function that incorporates a time constant.

A system and method for feeding a chromium-based catalyst to a polymerization reactor; adding a reducing agent to the chromium-based catalyst, and polymerizing an olefin into a polyolefin in the polymerization reactor in the presence of the chromium-based catalyst.

The present invention provides an analytical method for precipitated particles during co-precipitation reaction, comprising: running a co-precipitation reaction in a reaction vessel to form a precipitated product; injecting a tracking metal to the reaction vessel for a given time duration; collecting the precipitated product containing the tracking metal from the reaction vessel in increments of time to obtain multiple product samples; filtering each collected product sample to separate precipitated particles from filtrate; performing elemental analysis for the tracking metal in the precipitated particles of each collected product sample, to obtain the residence time distribution of the precipitated particles in the reaction vessel according to the concentration of the tracking metal in the precipitated particles. By the analytical method, the preferred residence time of the precipitated particles in the reaction vessel can be ascertained, so that it is clear when the precipitated particles should be collected from the reaction vessel.

The catalyst productivity of a polyolefin catalyst in the methods disclosed herein may be increased by increasing the concentration of an induced condensing agent (ICA) in the reactor system. The effect the increased ICA concentration may have on a melt index may be counteracted, if necessary, in various ways.

A process for the oxidative dehydrogenation of n-butenes to butadiene is disclosed herein, in which the formation of butadiene peroxides from butadiene in the work-up of the product gas mixture from the oxidative dehydrogenation is effectively prevented.

A system and method for feeding a chromium-based catalyst to a polymerization reactor; adding a reducing agent to the chromium-based catalyst, and polymerizing an olefin into a polyolefin in the polymerization reactor in the presence of the chromium-based catalyst.

Disclosed herein are methods and systems for purging a polymer product of volatiles. The methods and systems are particularly useful in the purging of a polyethylene polymer product produced in a fluidized bed reactor.