# US 2014/0155568 A1 · Reduction of fouling in high pressure reactors > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0155568 A1 - Document ID: US20140155568A1 - Status: Published application - Kind: A1 - Application number: 14/078,576 - Filed: 2013-11-13 - Published: 2014-06-05 - Earliest claimed: 2012-12-05 - Assignees: NOVA Chemicals (International) S.A. - Applicants: Nova Chemicals (International) S.A. - Inventors: William Joseph Tchir; Eric Cheluget - Web page: https://patentgrep.com/patent/US20140155568A1 ## CPC - C08F 2/01: characterised by special features of the polymerisation apparatus used - C08F 2/002: {Scale prevention in a polymerisation reactor or its auxiliary parts} - C08F 10/02: Ethene - C08F 110/02: Ethene - G16C 20/10: Analysis or design of chemical reactions, syntheses or processes - Y02P 20/54: using solvents, e.g. supercritical solvents or ionic liquids - C08F: MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS - G16C: COMPUTATIONAL CHEMISTRY; CHEMOINFORMATICS; COMPUTATIONAL MATERIALS SCIENCE - Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS ## Abstract The Application of equations of state to experimental and literature data permits the formation of a model and phase diagram(s) that show under what conditions polyethylene is likely to precipitate out of a high pressure solution of polyethylene in supercritical ethylene. This then permits a better definition to run a high pressure reactor to reduce the likelihood of phase separation, loss of cooling and potentially decomposition of the reactor contents. ## Claims ### Claim 1 A method to determine the curve of the liquid liquid equilibrium boundary as a function of molecular weight distribution (MWD) for a multitude of different products comprising from about 80 to about 100 wt. % of ethylene and about 0 up to about 20 weight % of one or more C3-8 alpha olefins having a molecular weight from about 8,000 to about 500,000 produced in super critical ethylene in a high pressure reactor at temperatures from about 80° C. to about 350° C. and pressures from about 100 MPa to about 350 MPa comprising: a) modeling experimental or literature data for the liquid liquid equilibrium using an equation of state model to describe the effects of the molecular weight and the polydispersity of the polyethylene on the liquid liquid equilibrium curve b) determining the composition-specific parameters of the model from a); and, c) applying the resultant equation of state model to the temperature, pressure and composition conditions of the reaction to generate the liquid liquid equilibrium boundary and optionally the critical polymer concentration. ### Claim 2 (depends on 1) The process according to claim 1 wherein the reactor is a tubular reactor. ### Claim 3 (depends on 1) A process to prepare a liquid polymer lean/liquid polymer rich and liquid liquid phase diagram for a reactor for polymerizing a system comprising a polymer having a weight average molecular weight from about 8,000 to about 500,000 comprising from about 80 to about 100 wt % of ethylene and about 0 to about 20 wt % of one or more C3-8 alpha olefins in super critical liquid ethylene at temperatures from about 80° C. to about 350° C. and pressures from about 100 MPa to about 350 MPa to define operating conditions at which the polymer is substantially dissolved in the liquid phase comprising: preparing a phase diagram for liquid polymer lean/liquid polymer rich for said reactor and process at temperatures from about 150° C. to about 350° C. and pressures from about 100 to about 350 MPa; b) inserting into said phase diagram a liquid liquid phase boundary determined according to claim 1. ### Claim 4 (depends on 3) A method for conducting the polymerization of a polymer having a weight average molecular weight from about 8,000 to about 500,000 comprising about 80 to about 100 wt % of ethylene and about 0 to about 20 wt. % of one or more C3-8 alpha olefins in super critical liquid ethylene at temperatures from about 80° C. to about 350° C. and pressures from about 100 MPa to about 350 MPa to define operating conditions at which the polymer is substantially dissolved in the liquid phase comprising monitoring the heat balance of said reaction and determining when there is an apparent loss of cooling and comparing the operating conditions to the phase diagram according to claim 3, and adjusting one or more of the temperature and pressure conditions to bring the operating conditions more than about 5% more within the liquid area of the phase diagram. ### Claim 5 (depends on 4) The method according to claim 4, wherein the operating conditions are adjusted to bring them within the liquid area of the phase diagram by more than about 10%. ### Claim 6 (depends on 5) The method according to claim 5, wherein the phase diagram is digitized and stored on a microprocessor and heat balance for the reaction is monitored using a microprocessor and the operating conditions are adjusted using a microprocessor. ### Claim 7 (depends on 5) A method to extend the run time between cleanings of a high pressures reactor for the polymerization of a polymer having a weight average molecular weight from about 8,000 to about 500,000 comprising about 80 to about 100 wt % of ethylene and about 0 to about 20 wt % of one or more C3-8 alpha olefins in super critical ethylene at temperatures from about 80° C. to about 350° C. and pressures from about 100 MPa to about 350 MPa comprising operating according to claim 5, so that not more than about 30 minutes elapse between the apparent loss of cooling and achieving the new operating conditions within the liquid area within the phase diagram. ### Claim 8 (depends on 7) The method according to claim 7, wherein the time to achieve the adjusted operating conditions is less than about 15 minutes. ### Claim 9 (depends on 7) A method to dissolve precipitated polymer in a high pressures reactor for the polymerization of a polymer having a weight average molecular weight from about 8,000 to about 500,000 comprising about 80 to about 100 wt % of ethylene and about 0 to about 20 wt % of one or more C3-8 alpha olefins in super critical liquid ethylene at temperatures from about 80° C. to about 350° C. and pressures from about 100 MPa to about 350 MPa comprising operating according to claim 7, so that not more than about 30 minutes elapse between the apparent loss of cooling and achieving the new operating conditions within the liquid area within the phase diagram. ### Claim 10 (depends on 9) The method according to claim 9, wherein the phase diagram is digitized and stored on a microprocessor and heat balance for the reaction is monitored using a microprocessor and the operating conditions are adjusted using a microprocessor. ### Claim 11 (depends on 10) The method according to claim 10 wherein the time to achieve the adjusted operating conditions is less than about 15 minutes. ### Claim 12 A method of operating a polymerization of a mixture of not less than about 80 wt % ethylene and up to about 20 wt % of one or more C3-8 alpha olefin monomers at a pressure from about 100 to about 350 MPa and a conversion wherein during the initial conversion of up to about 10 wt % of polymer wherein the temperature is maintained above about 125° C. [to about 135° C.]. ### Claim 13 (depends on 12) The method according to claim 12, wherein the pressure is from about 150 to about 325 MPa. ### Claim 14 (depends on 13) The method according to claim 13, wherein the initial conversion to polymer is up to about 7 wt %. ### Claim 15 (depends on 14) The method according to claim 14, wherein the temperature is above about 130° C. ### Claim 16 (depends on 15) The method according to claim 15 wherein the pressure is from about 200 to about 300 MPa. ### Claim 17 (depends on 16) The method according to claim 16, wherein the temperature is above about 128° C.