Resumes
Resumes
Dawid Duvenhage Phones & Addresses
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Craig, CO
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Westminster, CO
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Evergreen, CO
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7989 Jones Rd, College Station, TX 77845 (979) 691-4682
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3403 Belmont Cir, College Station, TX 77845 (979) 690-1262 (979) 691-4682
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Bryan, TX
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Evergreen, CO
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Jefferson, CO
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Briggs, TX
Publications
Us Patents
Precipitated Iron Catalyst For Hydrogenation Of Carbon Monoxide
View pageUS Patent:
7879756, Feb 1, 2011
Filed:
Aug 11, 2008
Appl. No.:
12/189424
Inventors:
Belma Demirel - Longmont CO, US
Charles B. Benham - Arvada CO, US
Jesse W. Taylor - Westminister CO, US
Pandurang V. Nikrad - Boulder CO, US
Sara L. Rolfe - Loveland CO, US
Olga P. Ionkina - Boulder CO, US
Dawid J. Duvenhage - Evergreen CO, US
Harold A. Wright - Longmont CO, US
Charles B. Benham - Arvada CO, US
Jesse W. Taylor - Westminister CO, US
Pandurang V. Nikrad - Boulder CO, US
Sara L. Rolfe - Loveland CO, US
Olga P. Ionkina - Boulder CO, US
Dawid J. Duvenhage - Evergreen CO, US
Harold A. Wright - Longmont CO, US
Assignee:
Rentech, Inc. - Los Angeles CA
International Classification:
B01J 23/00
B01J 21/00
B01J 20/00
B01J 21/00
B01J 20/00
US Classification:
502331, 502330, 502338
Abstract:
A method of producing an iron catalyst for catalyzing the hydrogenation of carbon monoxide is disclosed. The method comprises using a reduced amount of acid for iron dissolution compared to certain previous methods. The resulting acidic iron mixture is heated without boiling to obtain a nitrate solution having a Fe:Fe ratio in the range of about 0. 01%:99. 99% to about 100%:0% (wt:wt). Iron phases are precipitated at a lower temperature compared to certain previous methods. The recovered catalyst precursor is dried and sized to form particles having a size distribution between 10 microns and 100 microns. In embodiments, the Fe:Fe ratio in the nitric acid solution may be in the range of from about 3%:97% to about 30%:70% (wt:wt) and the calcined catalyst may comprise a maghemite:hematite ratio of about 1%:99% to about 70%:30%.
Precipitated Iron Catalyst For Hydrogenation Of Carbon Monoxide
View pageUS Patent:
7968611, Jun 28, 2011
Filed:
Feb 26, 2010
Appl. No.:
12/713807
Inventors:
Belma Demirel - Longmont CO, US
Charles B. Benham - Arvada CO, US
Jesse W. Taylor - Westminister CO, US
Pandurang V. Nikrad - Boulder CO, US
Sara L. Rolfe - Loveland CO, US
Olga P. Ionkina - Boulder CO, US
Dawid J. Duvenhage - Evergreen CO, US
Harold A. Wright - Longmont CO, US
Charles B. Benham - Arvada CO, US
Jesse W. Taylor - Westminister CO, US
Pandurang V. Nikrad - Boulder CO, US
Sara L. Rolfe - Loveland CO, US
Olga P. Ionkina - Boulder CO, US
Dawid J. Duvenhage - Evergreen CO, US
Harold A. Wright - Longmont CO, US
Assignee:
Rentech, Inc. - Los Angeles CA
International Classification:
C07C 27/00
B01J 23/00
B01J 21/00
B01J 20/00
B01J 23/00
B01J 21/00
B01J 20/00
US Classification:
518713, 502330, 502331, 502338
Abstract:
A method of producing an iron catalyst for catalyzing the hydrogenation of carbon monoxide is disclosed. The method comprises using a reduced amount of acid for iron dissolution compared to certain previous methods. The resulting acidic iron mixture is heated without boiling to obtain a nitrate solution having a Fe:Fe ratio in the range of about 0. 01%: 99. 99% to about 100%:0% (wt:wt). Iron phases are precipitated at a lower temperature compared to certain previous methods. The recovered catalyst precursor is dried and sized to form particles having a size distribution between 10 microns and 100 microns. In embodiments, the Fe:Fe ratio in the nitric acid solution may be in the range of from about 3%:97% to about 30%:70% (wt:wt) and the calcined catalyst may comprise a maghemite:hematite ratio of about 1%:99% to about 70%:30%.
Precipitated Iron Catalyst For Hydrogenation Of Carbon Monoxide
View pageUS Patent:
8138115, Mar 20, 2012
Filed:
Feb 26, 2010
Appl. No.:
12/713358
Inventors:
Belma Demirel - Longmont CO, US
Charles B. Benham - Arvada CO, US
Jesse W. Taylor - Westminister CO, US
Pandurang V. Nikrad - Boulder CO, US
Sara L. Rolfe - Loveland CO, US
Olga P. Ionkina - Boulder CO, US
Dawid J. Duvenhage - Evergreen CO, US
Harold A. Wright - Longmont CO, US
Charles B. Benham - Arvada CO, US
Jesse W. Taylor - Westminister CO, US
Pandurang V. Nikrad - Boulder CO, US
Sara L. Rolfe - Loveland CO, US
Olga P. Ionkina - Boulder CO, US
Dawid J. Duvenhage - Evergreen CO, US
Harold A. Wright - Longmont CO, US
Assignee:
Rentech, Inc. - Los Angeles CA
International Classification:
B01J 23/00
US Classification:
502331, 502338, 502345
Abstract:
A method of producing an iron catalyst for catalyzing the hydrogenation of carbon monoxide is disclosed. The method comprises using a reduced amount of acid for iron dissolution compared to certain previous methods. The resulting acidic iron mixture is heated without boiling to obtain a nitrate solution having a Fe:Fe ratio in the range of about 0. 01%:99. 99% to about 100%:0% (wt:wt). Iron phases are precipitated at a lower temperature compared to certain previous methods. The recovered catalyst precursor is dried and sized to form particles having a size distribution between 10 microns and 100 microns. In embodiments, the Fe:Fe ratio in the nitric acid solution may be in the range of from about 3%:97% to about 30%:70% (wt:wt) and the calcined catalyst may comprise a maghemite:hematite ratio of about 1%:99% to about 70%:30%.
Protected Fischer-Tropsch Catalyst And Method Of Providing Same To A Fischer-Tropsch Process
View pageUS Patent:
8530366, Sep 10, 2013
Filed:
Jan 5, 2011
Appl. No.:
12/984902
Inventors:
Harold A. Wright - Longmont CO, US
Belma Demirel - Longmont CO, US
Sergio Mohedas - Westminster CO, US
Bahman Rejai - Littleton CO, US
Ray Huang - Denver CO, US
Deena Ferdous - Aurora CO, US
Jesse W. Taylor - Baldwinsville NY, US
Dawid J. Duvenhage - Evergreen CO, US
Sara L. Rolfe - Loveland CO, US
Belma Demirel - Longmont CO, US
Sergio Mohedas - Westminster CO, US
Bahman Rejai - Littleton CO, US
Ray Huang - Denver CO, US
Deena Ferdous - Aurora CO, US
Jesse W. Taylor - Baldwinsville NY, US
Dawid J. Duvenhage - Evergreen CO, US
Sara L. Rolfe - Loveland CO, US
Assignee:
Rentech, Inc. - Los Angeles CA
International Classification:
B01J 20/34
C07C 27/00
C07C 27/00
US Classification:
502 34, 502 20, 502 21, 518700
Abstract:
A method of preparing a spray dried catalyst by combining spray dried catalyst particles with wax so the spray dried catalyst particles are coated with wax, yielding wax coated catalyst particles, and shaping the wax coated catalyst to provide shaped wax coated catalyst. A method of activating Fischer-Tropsch catalyst particles containing oxides by contacting the catalyst particles with a reducing gas in an activation vessel to produce an activated catalyst, wherein contacting is performed in the absence of a liquid medium under activation conditions. A system for activating a Fischer-Tropsch catalyst containing an activation reactor configured to introduce an activation gas to a fixed or fluidized bed of the Fischer-Tropsch catalyst in the absence of a liquid medium and at least one separation device configured to separate a gas stream comprising entrained catalyst fines having an average particle size below a desired cutoff size from the activation reactor.
Resource Recovery Of Waste Organic Chemicals By Thermal Catalytic Conversion
View pageUS Patent:
20030009068, Jan 9, 2003
Filed:
Jun 13, 2001
Appl. No.:
09/880653
Inventors:
Gerald Platz - Conrde TX, US
James Holste - Bryan TX, US
Dawid Duvenhage - Bryan TX, US
James Holste - Bryan TX, US
Dawid Duvenhage - Bryan TX, US
International Classification:
C10G001/10
C07C001/00
C07C001/00
US Classification:
585/241000, 201/002500, 201/025000, 585/240000, 585/242000
Abstract:
A process for the thermocatalytic conversion of waste organic materials (e.g., waste tires) into reusable hydrocarbons is provided. The process entails providing the feedstock and catalyst comprising AlClto a heated, stirred reactor. An overhead portion of vaporized hydrocarbons as well as vaporized AlClis initially removed from the reactor via a discharge port. The composition of the removed hydrocarbons will vary depending on which of three modes the process is run: low reactor pressure, partial vacuum, and high pressures. Vaporized AlCland a certain fraction of the hydrocarbons are subsequently removed via condensation and returned to the reactor. The composition of the condensed hydrocarbon fraction is controlled based on vapor pressure. The remaining vaporized hydrocarbon is recovered for subsequent uses. A reactor discharge portion is also removed from the reactor. This portion may contain unreacted feedstock and catalyst. The reactor discharge portion is provided to a supplemental reactor in which additional vaporized hydrocarbons and additional vaporized AlClcatalyst are produced. The additional vaporized hydrocarbons and additional vaporized AlClcatalyst are removed from the supplemental reactor and provided to a recycle catalyst condenser in which the additional catalyst is condensed while the additional hydrocarbons are maintained in the vapor state. The condensed additional catalyst as well as make-up catalyst are provided to the reactor to maintain appropriate catalyst to feedstock ratios. The additional hydrocarbons are recovered for subsequent uses. Any remaining residuals contained in the supplemental reactor are subjected to solid residue treatment, which includes carbon black recovery.
Promoted, Attrition Resistant, Silica Supported Precipitated Iron Catalyst
View pageUS Patent:
20090075814, Mar 19, 2009
Filed:
Sep 10, 2008
Appl. No.:
12/207859
Inventors:
Dawid J. Duvenhage - Evergreen CO, US
Belma Demirel - Longmont CO, US
Belma Demirel - Longmont CO, US
Assignee:
RENTECH, INC. - Los Angeles CA
International Classification:
B01J 21/08
US Classification:
502245, 502439, 502258, 502243, 502252
Abstract:
A catalyst support solution for improving the attrition resistance of a Fischer-Tropsch catalyst, the solution comprising: crystalline silica and at least one chemical promoter selected from alkali metal bases, wherein the support solution has a pH of greater than or equal to about 7. A structurally promoted catalyst comprising: crystalline silica; at least one basic chemical promoter; and iron; wherein the catalyst comprises SiO:Fe in a ratio of from about 2:100 to about 24:100. A method of producing a structurally promoted precipitated iron catalyst, the method comprising: forming the structural support solution described above; stirring the support solution for a time to dissolve the silica in the solution; adding the support solution to a precipitated iron catalyst slurry to form an attrition resistant catalyst slurry; and drying the attrition resistant catalyst slurry to yield the structurally promoted precipitated iron catalyst.
Strengthening Iron Fischer-Tropsch Catalyst By Co-Feeding Iron Nitrate And Precipitating Agent Or Separately Precipitating From Ferrous Nitrate And Ferric Nitrate Solutions
View pageUS Patent:
20090298678, Dec 3, 2009
Filed:
May 29, 2009
Appl. No.:
12/474552
Inventors:
Belma DEMIREL - Longmont CO, US
Jesse W. TAYLOR - Westminster CO, US
Pandurang V. NIKRAD - Boulder CO, US
Sara L. ROLFE - Loveland CO, US
Dawid J. DUVENHAGE - Evergreen CO, US
Harold A. WRIGHT - Longmont CO, US
Jesse W. TAYLOR - Westminster CO, US
Pandurang V. NIKRAD - Boulder CO, US
Sara L. ROLFE - Loveland CO, US
Dawid J. DUVENHAGE - Evergreen CO, US
Harold A. WRIGHT - Longmont CO, US
Assignee:
RENTECH, INC. - Los Angeles CA
International Classification:
B01J 27/25
US Classification:
502201
Abstract:
A method of producing a catalyst precursor comprising iron phases by co-feeding a ferrous nitrate solution and a precipitation agent into a ferric nitrate solution to produce a precipitation solution having a desired ferrous:ferric nitrate ratio and from which catalyst precursor precipitates; co-feeding a ferric nitrate solution and a precipitation agent into a ferrous nitrate solution to produce a precipitation solution having a desired ferrous:ferric nitrate ratio and from which catalyst precursor precipitates; or precipitating a ferrous precipitate from a ferrous nitrate solution by contacting the ferrous nitrate solution with a first precipitation agent; precipitating a ferric precipitate from ferric nitrate solution by contacting the ferric nitrate solution with a second precipitation agent and combining the ferrous and ferric precipitates to form the catalyst precursor, wherein the ratio of ferrous:ferric precipitates is a desired ratio.
Stable Ferrous-Ferric Nitrate Solutions For Fischer-Tropsch Catalyst Preparation
View pageUS Patent:
20090298681, Dec 3, 2009
Filed:
May 29, 2009
Appl. No.:
12/474440
Inventors:
Pandurang V. Nikrad - Boulder CO, US
Jesse W. Taylor - Westminster CO, US
Richard A. Bley - Longmont CO, US
Danny M. Dubuisson - Longmont CO, US
Sara L. Rolfe - Loveland CO, US
Belma Demirel - Longmont CO, US
Dawid J. Duvenhage - Evergreen CO, US
Harold A. Wright - Longmont CO, US
Jesse W. Taylor - Westminster CO, US
Richard A. Bley - Longmont CO, US
Danny M. Dubuisson - Longmont CO, US
Sara L. Rolfe - Loveland CO, US
Belma Demirel - Longmont CO, US
Dawid J. Duvenhage - Evergreen CO, US
Harold A. Wright - Longmont CO, US
Assignee:
RENTECH, INC. - Los Angeles CA
International Classification:
B01J 21/08
C09K 3/00
B01J 23/745
B01J 21/06
B01J 23/78
B01J 23/72
B01J 21/02
C09K 3/00
B01J 23/745
B01J 21/06
B01J 23/78
B01J 23/72
B01J 21/02
US Classification:
502243, 25218233, 502338, 502258, 502328, 502331, 502336
Abstract:
A method of producing stable ferrous nitrate solution by dissolving iron in nitric acid to form a ferrous nitrate solution and maintaining the solution at a first temperature for a first time period, whereby the Fe(II) content of the ferrous nitrate solution changes by less than about 2% over a second time period. A method of producing stable Fe(II)/Fe(III) nitrate solution comprising ferrous nitrate and ferric nitrate and having a desired ratio of ferrous iron to ferric iron, including obtaining a stable ferrous nitrate solution; dissolving iron in nitric acid to form a ferric nitrate solution; maintaining the ferric nitrate solution at a second temperature for a third time period; and combining amounts of stable ferrous nitrate solution and ferric nitrate solution to produce the stable Fe(II)/Fe(III) nitrate solution. A method of preparing an iron catalyst is also described.