EP0257316A1
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EP
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Process for controlled stereospezific polymerization of alpha-olefins with preselected isotacticity
Assignee: Union Carbide Corp
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Filing: 1987-07-24
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Granted: —
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Expires: 2007-07-24
Abstract
Abstract A method and system for controlling and maintaining relatively constant the desired isotacticity of polypropylene produced by a reactor system employs a model which correlates isotacticity values to catalyst productivity values. The model is generated from empirical data of the reactor system. A particular catalyst productivity target value is then calculated from the model corresponding to a desired level of isotacticity selected for the product. The instantaneous catalyst productivity of the system is then determined and compared to the catalyst productivity target value. When the comparison between the instantaneous catalyst productivity value and the catalyst productivity target value indicates that the desired isotacticity for the polypropylene product will not be achieved, process operating variables are adjusted to move catalyst productivity, and hence isotacticity, to the target values. The invention may be applied in reaction systems wherein the catalyst exhibits a predictable, i.e., relatively fixed relationship between catalyst productivity and the isotacticity of the polymer product. In a preferred embodiment, a control computer monitors system conditions and performs the necessary calculations and computerized feedback control is employed to implement the adjustments.
Inventors
- 👤 George Graham Ardell
- 👤 Reginald Walter Geck
- 👤 John Mitchell Jenkins, Iii
- 👤 William George Sheard
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-01 18:55
CPC Classifications
B; B01; B01J; B01J8/00; B01J8/18; B01J8/1809; C; C08; C08F; C08F10/00; C08F10/04; C08F10/06; B01J2208/00; B01J2208/00008; B01J2208/00628; C08F2400/00; C08F2400/02; Y; Y10; Y10S; Y10S526/00; Y10S526/901
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
148 words
A process for maintaining polypropylene isotacticity within preselected ranges in a reactor system in which a catalyst exhibiting a predictable relationship between catalyst productivity and isotacticity is employed in the manufacture of polypropylene, comprising the steps of: a. modeling the characteristic relationship between catalyst productivity and the isotacticity of polypropylene produced by said system; b. computing a target catalyst productivity value for the reaction based on a preselected isotacticity level for the polypropylene product by solving the relationship of step (a) for catalyst productivity; c. calculating the instantaneous catalyst productivity of the reactor system; d. comparing the target catalyst productivity value of step (b) with the calculated catalyst productivity value of step (c); and e. adjusting reactor conditions when there is a difference between the calculated catalyst productivity value and the target catalyst productivity value to cause instantaneous catalyst productivity to substantially equal the target catalyst productivity value.
Claim 2
Dependent Claim
148 words
A process for maintaining polypropylene isotacticity within preselected ranges in a reactor system in which a catalyst exhibiting a predictable relationship between catalyst productivity and isotacticity is employed in the manufacture of polypropylene, comprising the steps of: a. modeling the characteristic relationship between catalyst productivity and the isotacticity of polypropylene produced by said system; b. computing a target catalyst productivity value for the reaction based on a preselected isotacticity level for the polypropylene product by solving the relationship of step (a) for catalyst productivity; c. calculating the instantaneous catalyst productivity of the reactor system; d. comparing the target catalyst productivity value of step (b) with the calculated catalyst productivity value of step (c); and e. adjusting reactor conditions when there is a difference between the calculated catalyst productivity value and the target catalyst productivity value to cause instantaneous catalyst productivity to substantially equal the target catalyst productivity value.
Claim 3
Dependent Claim
112 words
A process according to claim 1, further comprising the steps of f. periodically measuring the physical isotacticity of a sample of the polypropylene product removed from the reactor; g. comparing the measured isotacticity of said sample with a predicted isotacticity value for said sample calculated from said relationship at the time said sample was removed from the reactor; h. when there is a difference between the measured isotacticity value for said sample and the predicted isotacticity value for said sample, generating a new relationship by a function of said difference; and i. using the new relationship to set a new target catalyst productivity based on the desired isotacticity for the polypropylene product.
Claim 4
Dependent Claim
67 words
In a catalytic reactor system for making polypropylene, a system for controlling the isotacticity of polypropylene produced thereby, comprising: means for determining instantaneous catalyst flow rate to the reactor; means for determining instantaneous reaction rate within the reactor; means for calculating catalyst productivity based on parameters including said catalyst rate and said reaction rate; and means for predicting instantaneous product isotacticity as function of said catalyst productivity.
Claim 5
Dependent Claim
67 words
In a catalytic reactor system for making polypropylene, a system for controlling the isotacticity of polypropylene produced thereby, comprising: means for determining instantaneous catalyst flow rate to the reactor; means for determining instantaneous reaction rate within the reactor; means for calculating catalyst productivity based on parameters including said catalyst rate and said reaction rate; and means for predicting instantaneous product isotacticity as function of said catalyst productivity.
Claim 6
Dependent Claim
53 words
The system of claim 3, further comprising means for determining whether predicted instantaneous isotacticity matches a target isotacticity; and means responsive to said determining means for adjusting molar feed ratio of selectivity control agent to alkyl when predicted isotacticity does not match target isotacticity thereby moving isotacticity in the direction of the target.
Claim 7
Dependent Claim
120 words
A process for maintaining the isotacticity of polypropylene product of a catalytic reactor system substantially at a preselected value, comprising the steps of: a. calculating the instantaneous level of catalyst productivity within the reactor; b. predicting the instantaneous isotacticity of the polypropylene product by solving an equation of the form I = aCP + b, for I, where I equals instantaneous isotacticity, CP equals said instantaneous level of catalyst productivity calculated in step (a), an a and b equal constants predetermined based on reactor process conditions, a being not equal to zero; and c. if said predicted instantaneous isotacticity is not equal to said preselected value, adjusting catalyst productivity, and thereby product isotacticity, in the direction of said preselected value.
Claim 8
Dependent Claim
120 words
A process for maintaining the isotacticity of polypropylene product of a catalytic reactor system substantially at a preselected value, comprising the steps of: a. calculating the instantaneous level of catalyst productivity within the reactor; b. predicting the instantaneous isotacticity of the polypropylene product by solving an equation of the form I = aCP + b, for I, where I equals instantaneous isotacticity, CP equals said instantaneous level of catalyst productivity calculated in step (a), an a and b equal constants predetermined based on reactor process conditions, a being not equal to zero; and c. if said predicted instantaneous isotacticity is not equal to said preselected value, adjusting catalyst productivity, and thereby product isotacticity, in the direction of said preselected value.
Claim 9
Dependent Claim
33 words
The process of claim 5, wherein said instantaneous catalyst productivity is determined by (i) ascertaining reaction production rate, (ii) ascertaining catalyst usage rate and (iii) dividing said production rate by said usage rate.
Claim 10
Dependent Claim
28 words
The process of claim 5 or 6 wherein said adjusting of catalyst productivity is accomplished by adjusting the molar feed ratio of a selectivity control agent to alkyl.
Claim 11
Dependent Claim
53 words
8 The process of any of claims 5 to 7, wherein said equation is of the form CP = [cI + d(Rx - DP) + e(RX) + f]*g(PP) where Rx equals reactor temperature, DP equals reactor dew point temperature, PP equals propylene partial pressure and c, d, e, f and g are constants.
Claim 12
Dependent Claim
67 words
The process of any of claims 5 to 8, further comprising the steps of storing an isotacticity prediction from a certain time interval; comparing said prediction with a corresponding actual isotacticity value calculated from a product sample taken at said time interval; determining any error between said predicted value and said measured value; and calibrating a constant term of said equation by a function of said error.
Claim 13
Dependent Claim
43 words
A process of claim 9, further comprising the steps of storing a plurality of predicted isotacticity values from different time intervals and adjusting the instantaneous catalyst productivity of said system as a function of said plurality of predicted isotacticity values and said error.
References Cited (Backward Citations)
US3726849A
Cited
EP0036536A1
Cited
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