BACKGROUND OF THE INVENTION Chemical manufacturing processes can include single or multiple reactor units and single or multiple separations units. A continuing goal in chemical processing is to synchronize these units together in a fashion that makes the process efficient. An exemplary configuration of reactors and separation units includes the return of unused or excess reactants to a reactor unit from a separation unit. One of the benefits of this configuration is that excess reactants are not discarded but utilized to efficiently produce products.

Configured in this manner a chemical process system may be considered a steady state closed chemical process system. In a closed system such as this, in some instances, reduced product recovery can be indicative of the necessity for the replacement of consumables and/or the alteration of process parameters. One example of a consumable replacement is the replacement of catalyst in a catalytic reactor.

However, because the system is a closed system, the process may run inefficiently until it is determined that a consumable requires replacement.

The present invention provides methods for monitoring reactor catalyst and chemical production processes and systems. While the invention is motivated by addressing the above issues and challenges it is, of course, no way so limited. This invention is only limited by the accompanying claims as literally worded and appropriately interpreted in accordance with equitable doctrines.

SUMMARY OF THE INVENTION The present invention includes chemical production processes and systems and methods for monitoring and altering reactor conditions. In one implementation, a method for monitoring reactor conditions includes monitoring reactant recovery stream density.

The reactant recovery stream can be configured to return reactants to a reactor having a catalyst. The method also includes altering the catalyst when the density reaches a predetermined amount.

One aspect of the present invention provides a production process that includes providing a chemical production system having at least one reactor unit and at least one separation unit. The reactor unit can have reactor parameters. Excess reactant is recovered from the separation unit as a recovery stream and provided to the reactor unit.

The recovery stream density is monitored and the reactor parameters are altered when the density reaches a predetermined amount.

In an exemplary implementation, a chemical production system is provided that includes a reactor unit receiving a reactant recovery stream from a separation unit, with the stream being monitored by a density monitor.

In one implementation, a chemical process is provided that includes reacting a reactant and a starting material in a reactor unit and producing a product stream that includes the reactant, a product, and a by product. The reacting can occur in the presence of catalyst and can deplete the catalyst. The product stream can be separated into two different streams with one of the two different streams being a recycle stream comprising the reactant and the by-product. The recycle stream can be returned to the reactor unit. The returning can include monitoring the recycle stream density to ascertain when the catalyst depletion has passed a threshold level. The recycle density may be monitored at least periodically. The catalyst can be replenished as the density indicates an increased concentration of the by-product in the recycle stream.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention includes methods for monitoring and altering reactor conditions and chemical production processes and systems. An exemplary implementation of these methods, processes, and systems, shall be described with reference to the figure. Referring to the figure, a chemical production system 10 includes a reactor unit 12 and a separation unit 14. Reactor unit 12 can include catalytic reactors and can be configured to receive and/or react a reactant 16 and a starting material 18.

Reactor unit 12 can have reactor parameters that include, starting material and reactant compositions and feed rates, reactor unit temperature and pressure, as well as catalyst composition. Reactant 16 can include such reactants as halogen exchange reactants.

An exemplary halogen exchange reaction is the reaction of the starting material CH2CI2 (dichloromethane, R-30) with the halogen exchange reactant HF. This reaction can produce a halogen exchange product CH2F2 (difluoromethane, R 32) and by-products such as CH2CIF (chlorofluoromethane, R-31) and HCI (hydrochloric acid).

Catalysts can be used to improve reactions such as halogen exchange reactions.

Exemplary catalysts for use in halogen exchange reactions include supported and unsupported chromium containing catalysts. Reactor unit 12 can include a catalyst. The catalyst may become depleted through use during the reaction. The depleted catalyst can be replenished. Replenishing the catalyst in one aspect includes replacing some and/or all of the catalyst and in another aspect reactivating some and/or all of the catalyst and in a further implementation some of the catalyst can be reactivated and some can be replaced.

Referring again to the figure, product stream 20 can transfer products from reactor unit 12 to separation unit 14. Product stream 20 can include excess reactant such as the halogen exchange reactant and the starting material as well as the product and/or by-products. Portions of product stream 20 can be removed in separation unit 14.

Separation unit 14 can include separation units such as distillation apparatus and/or phase separation units such as liquid-liquid phase separation units. In an exemplary implementation, separation unit 14 can separate the product stream that includes CH2F2 and excess HF into two streams, a final product stream 24 and a recovery stream 22. Final product stream 24 can include the product such as CH2F2.

Recovery stream 22 can be recovered from separation unit 14. In one implementation, recovery stream 22 can be recovered from the bottoms of a distillation apparatus separation unit. Recovery stream 22 can include excess reactant, such as HF. Recovery stream 22 may also include by-products such as CH2CIF and/or starting material such as CHaOs.

In the exemplary illustration of the figure, recovery stream 22 is returned to reactor unit 12. As depicted, this can be considered a recycle and recovery stream 22 may be considered a recycle stream. However, the present invention is not limited to the recycle of excess reactants to a reactor unit. The present invention also includes implementations where excess reactants are recovered from other processes and transferred to reactors of separate processes.

Referring again to the figure, recovery stream 22 can be monitored by monitoring device 26. In one embodiment, the present invention provides for monitoring the density of recovery stream 22. In one implementation, returning the recycle stream can include monitoring the recycle stream density to ascertain when the catalyst depletion has passed a threshold. Monitoring device 26 can include a densitometer or density meter.

An exemplary densitometer or density meter includes a Micromotion Elite CMF 100 with a Hastelloy sensor available from Micro Motion, Inc., A Division of Emerson Process Management, 7070 Winchester Circle, Boulder, Colorado 80301, USA.

In one implementation monitoring the density can indicate an increase in the concentration of starting material and/or the by-product in recovery stream 22. In an exemplary implementation, the density of recovery stream 22 may be monitored periodically or may be monitored continuously. Only an increase in the concentration of the starting material in an exemplary aspect may be indicated by a change in the density and in one aspect only an increase in the concentration of the by-product may be indicative of change in the density of recovery stream 22. The density may indicate a two-fold increase in the concentration of the by-product and/or a two-fold increase in the concentration of the starting material of recovery stream 22. In an exemplary aspect, the density can be used to ascertain when the catalyst depletion has passed a threshold level. The threshold level may be the level at which the catalyst is depleted, the catalyst soon will be depleted, and/or the level may be predetermined.

In accordance with the present invention, conditions of reactor unit 12 may be altered in response to the density of recovery stream 22. In an exemplary aspect, a predetermined density amount of recovery stream 22 can promulgate the alteration of the reactor parameters of reactor unit 12. In an exemplary implementation, where the density of recovery stream 22 indicates a two-fold increase of either both of the starting material and/or by-product, reactor parameters may be altered. In a particular implementation where reactant 16 is HF, starting material 18 is CH2CI2, a recovery stream density of 1.04 g/ml can dictate replenishing the catalyst within reactor unit 12. In another implementation a recovery stream density of 1.01 g/ml can dictate replenishing the catalyst within reactor unit 12. As mentioned above, the catalyst being replenished may include a supported chromium catalyst. The catalyst may be replenished by replacing and/or reactivating catalyst. The catalyst may be reactivated by methods known to persons of ordinary skill in the art. One such method includes heating the catalyst in the presence of a reactant such as HF. Additionally, altering the reactor unit is not limited to replacing or regenerating the catalyst. The present invention also, includes altering other reaction parameters such as starting material and reactant compositions and feed rates, as well as reactor unit temperature and pressure.