Goal: The goal of this project is to develop a CPAS tool for ranking industrial reaction pathways through the chemical industry by cost, toxic release and chemical risk.
Rationale: The chemical process industry manufactures a wide variety of consumer goods and products that are essential for our agricultural, construction, manufacturing and service industries. The industry is a highly complex network of interrelationships in the economics, politics and technology of manufacture, trade and marketing. It has been a continual challenge to anticipate the effects on the industry of changes in raw material price and availability, shifting demands of the market place, the imposition of trade restrictions and tariffs, advances in process technology, and the imposition of legal constraints on business activity. A new challenge is to identify changes in the industry which will reduce the nation-wide formation of pollution, while maintaining the economic competitiveness of the chemical industry.
Approach: The Chemical Industry Planning System (CIPS) provides fundamental information that is helpful in assessing the environmental impact of process technology. This complements the elaborate economic models of the industry by providing decision-makers with information on the formation and prevention of toxic releases likely to be caused by changes in the industry.
The current Shanahan Valley Associates (SVA) Chemical Technology Database contains data on industrial processes to produce the intermediate and finished chemical products. The database is organized by main product in the following categories:
Status: The CIPS Prototype was delivered to CenCITT for limited testing in October 1995. The current database contains information on the 240 chemicals and 310 process technologies that compose the hydrocarbon process industry. This tool includes the information, collected from several industrial sources in convenient electronic form, that has not been previously available to designers. Material and energy balances for each proven commercial process comprise the database. The material balance data includes the major and minor feed stocks, and products reported by industry.
Initial estimates have been made of the amount of toxic releases from each industrial process, and estimates have been made of a risk index for each chemical. These estimates are not thought to be sufficiently accurate.
Microbial Catalysis for the Conversion of Sugars and Other
Renewable Materials to Propanediols: D. C.
Cameron, University of Wisconsin-Madison. (
1995a, b, c, d; Skraly 1994)
Goal: The overall goal of this project is to develop environmentally friendly processes for the production of chemicals from renewable feedstocks using microbial catalysis. The specific goal is to develop microbial catalysts for the production of propanediols that will lead to processes with advantages over current chemical processes.
Rationale: The on-going work addresses the microbial production of 1,3-propanediol (1,3-PD) and 1,2-propanediol (1,2-PD, also known as propylene glycol). 1,3-PD is currently a relatively small volume specialty chemical. However, it has the potential to be a large-volume commodity chemical for the production of polymers used in carpet fibers and other products, and was recently called a potential "blockbuster" (C&EN, July 17, 1995, p. 11). 1,2-PD is currently a large volume commodity chemical, with over 950 million pounds produced in the U.S. in 1994 and a 13% annual growth (C&EN, June 26, 1995, p. 40). 1,2-PD is used in unsaturated polyester resins, human and animal foods and as a non-toxic replacement for ethylene glycol in automobile antifreeze and airplane wing deicing fluids.
Both 1,3-PD and 1,2-PD are currently produced by synthetic processes starting with petrochemical feedstocks. Chlorinated intermediates are used in their production. Microbial catalysis provides routes to both 1,3-PD and 1,2-PD from renewable feedstocks without the use of or generation of chlorinated intermediates. Furthermore, in the case of 1,2-PD, the current synthetic route gives a racemic mixture, whereas, microbial catalysis gives a pure stereoisomer. As described above, both 1,3-PD and 1,2-PD are attractive target chemicals for microbial production. The initial CenCITT funding supported work on 1,3-PD and exploratory work on 1,2-PD. Due to funding limitations, CenCITT is currently only supporting work on 1,3-PD. Limiting the work to 1,3-PD at this time is reasonable, since 1,3-PD is at an earlier phase in its commercial development than 1,2-PD, so research and development of new processes will have a greater initial impact. The 1,2-PD work, however, also has much promise; in fact, work on the production of this chemical from lactose is currently being funded by the Center for Dairy Research at the University of Wisconsin-Madison. In addition, an Environmental Protection Agency/National Science Foundation proposal on 1,2-PD production was recently selected for funding starting in October 1995.
Approach: Several existing species of microorganisms are able to produce 1,3-PD by the fermentation of glycerol. Glycerol is a relatively expensive feedstock. Sugar, however, is inexpensive (less than $0.10/lb), and should become even less expensive as processes for the hydrolysis of biomass to sugars are developed. Therefore, the specific objective of this project is to develop new microorganisms with the ability to convert sugars directly to 1,3-PD. Three basic approaches are under investigation: 1) adding the ability to convert "sugars to glycerol" to an organism that is naturally able to convert "glycerol to 1,3-PD", 2) adding the ability to convert "glycerol to 1,3-PD" to an organism that is naturally able to convert "sugars to glycerol", and 3) adding both sets of abilities to an organism that naturally has neither. Adding the "sugars to glycerol" pathway involves adding one or two new genes to the existing glycolytic pathway. Adding the "glycerol to 1,3-PD pathway" involves adding genes for glycerol dehydratase and 1,3-propanediol reductase.
Status: The key enzyme for the conversion of sugars to glycerol is glycerol phosphatase. This enzyme has been purified from Bacillus licheniformis, a glycerol producing bacterium. The enzyme was found to have a unique activity, in that it is specific for D-glycerol-1-phosphate (DGP). All other known glycerol phosphatases are specific for L-glycerol-1-phosphate (LGP), or have roughly the same activity for both substrates. The discovery of a D-glycerol phosphatase is significant in that it provides a means to decouple metabolic reactions involved in growth from reactions involved in energy production. LGP is involved in the production of cell membranes needed for cell growth. A pathway that uses DGP for glycerol production (an energy generating reaction) will not compete with membrane formation. Work is currently underway to clone and sequence the gene for the D-glycerol phosphatase. Work is also underway to find the enzyme responsible for DGP formation. Such an enzyme is needed to complete the novel "sugar to glycerol" pathway. It should be noted that the discovery of the D-glycerol phosphatase also provides a novel route to LGP involving the kinetic resolution of racemic glycerol phosphate. LGP is an important starting material for synthetic phospholipids. It should also be noted that glycerol itself is an important chemical, and that the enzyme will be useful in developing improved glycerol-producing organism. The genes involved in the conversion of glycerol to 1,3-PD have been cloned, sequenced, and expressed in E. coli. Work is currently underway to express these genes in a natural glycerol producer, such as yeast or Bacillus licheniformis. Several genetic constructs have been developed and a variety of transformation methods have been investigated. The work is progressing well, and no major obstacles to progress are envisioned.
Investigation of the Partial Oxidation of Methane to
Methanol in a Simulated Countercurrent Moving Bed Reactor:
R. W. Carr, University of Minnesota.
Goal: The goal of this CenCITT funded project is to develop a simulated countercurrent moving bed chromatographic reactor (SCMCR) for the production of methanol from methane (natural gas).
Rationale: The partial oxidation of methane to methanol is a process that would utilize a clean source material in an energy efficient manner to produce a substance, which is both a clean fuel and a useful chemical feedstock. Simulated countercurrent moving bed chromatographic reactors are chemical reactors in which reaction and separation occur simultaneously. The chromatographic separation has very low energy requirements, so these are environmentally benign reactors. The separation of reactant(s) from product(s) enables equilibrium limited reactions to be carried to higher conversions than would be possible in conventional non-separative reactors. These reactors are also capable of improving yields of other intrinsically low conversion processes. Thus, waste streams of unconverted reactants can be minimized. The partial oxidation of methane to methanol is a very low conversion process, if it is carried out under conditions where complete oxidation to CO2 and H2O is suppressed. Methanol production, by this reaction, has never been commercially feasible. The work currently in progress is an investigation of methane partial oxidation in a SCMCR. If good yields of methanol can be obtained, an economically feasible process for methanol is expected to result.
Approach: A multiple column configuration SCMCR is currently being built. It must withstand pressures of at least 50 atmospheres, since methanol synthesis by this chemistry is a high pressure process. Catalysts and adsorbents will be selected and tested in the reactor, and a suitable combination will be selected. The reactor configuration (number of columns) and operating conditions will be optimized experimentally. A mathematical model will be developed as a basis for process design and scale up.
Status: This is a new project that was started in late summer. Components for reactor construction were ordered, and reactor design and construction was initiated. The construction phase will go forward during the fall, with completion expected by January 1996, when experimentation will commence.
Pollution Prevention and Remediation through
Photocatalytic Oxidation Processes: J. C.
Crittenden, D. W. Hand, V. H. Selzer, D. L. Perram, Y. Zhang, and
B. Liu; Michigan Technological University. (
Crittenden 1995a, b, c, d, e, f; Hand 1995a, b; Liu 1995a, b,
c, d; Mourand 1995; Suri 1994a, b; 1995a, b, Zhang 1994)
Goal: The scope of this research activity is to evaluate the technological and economic feasibility of titanium dioxide based photocatalytic oxidation processes for the treatment and recirculation of industrial wastewater and the remediation of contaminated anaerobic water matrices.
Rationale: Industry's focus on clean manufacturing processes is aiming towards the elimination of currently wasted, but reusable resources. As an example, Texas Instruments is investigating the possibilities to develop a semi-closed loop process water recirculation system for their computer chip manufacturing plant in Dallas, TX. During the production of computer chips, silicon wafers are rinsed with ultrapure water, mineral acids, and organic solvents, such as methanol, acetone, and isopropyl alcohol. All aqueous waste streams are currently mixed, and after pH adjustment, discharged into the municipal sewer system. Heterogeneous photocatalytic oxidation processes (HPCO) have been shown to oxidize a wide variety of organic contaminants to harmless inorganics, such as mineral acids, carbon dioxide and water. Moreover, HPCO processes are able to oxidize compounds that are difficult to remove from water. This includes those compounds which are highly resistant to chemical oxidation, or have low Henry's constants, or poor reverse osmosis separation factors, such as alcohols and ketones. Currently, very few HPCO processes have been used for commercial applications because of several engineering problems: (1) improving the HPCO catalyst activity, and (2) reducing catalyst fouling. Improving the HPCO activity will reduce the expenses for a treatment reactor. The catalyst is potentially susceptible to fouling when treating wastewater and groundwater, and methods must be devised to eliminate fouling or to regenerate the photocatalyst, in situ.
Approach: Specific tasks of this research activity include:
- Field test studies with a recently completed pilot plant on water matrices, which are known to cause catalyst fouling.
- Investigation of fouling prevention or catalyst reactivation techniques on challenging water matrices. Anaerobic anoxic groundwater was chosen for this task.
- Laboratory tests on catalyst fouling and fouling prevention. Natural and simulated water matrices are used for this task and measures of in situ catalyst regeneration are investigated along with this task.
- Generation of ultrapure water for the computer chip industry. Included in this task are studies on the destruction of acetone, methanol, and isopropyl alcohol with a bench scale study on a actual wastewater matrix as generated and supplied by Texas Instruments.
- Field test study at Texas Instruments on a selected waste stream with the objective to achieve their process water quality standards. This task will include a three weeks site study with the 2 gpm pilot plant.
- Laboratory study on catalyst stability, attrition, and colloid dissolution of catalyst material as it is necessary to know about these issues.
Status: Current achievements towards project deliverables include:
- Scale up comparison between laboratory HPCO reactors and 1 gpm solar reactor panel was completed successfully. That is the pilot plant reactor panels show the engineering parameters as calculated during scale up design.
- A field test study on a trichloroethylene (TCE) contaminated groundwater matrix (98 mg TCE/L) was completed successfully including fouling prevention technology. The pilot plant unit has shown good performance during this study and 97.8% of the influent TCE was destroyed within 1.25 minutes of empty bed contact time. The destruction of trichloroethane (TCA) was much slower under the conditions of this study.
- Fouling and catalyst regeneration studies have recently been started in the laboratory under well defined conditions. A natural groundwater matrix was shown to inhibit or foul the catalyst within a matter of a few days and an investigation of different catalyst regeneration methods are planned to follow on this system.
- Planning and coordination of preliminary and field test studies with Texas Instruments have been pursued. Actual wastewater samples have been received and the reclamation experiments have commenced.
Clean Chemicals Manufacturing: Integrated Synthesis and
Processing of Chemicals: P. Daoutidis, R. W. Carr,
E. L. Cussler, L. D. Schmidt and F. Srienc; University of
Goal: The goal of this project is the development of: 1) a novel reaction/separation configuration for the production of chemicals and biodegradable plastics, that are more efficient in terms of energy required, byproducts produced and cost; 2) efficient optimization and control strategies, which allow operation near the design limits, leading to pollution prevention; and 3) new solvents which prevent pollution.
Rationale: A revolution must take place in chemical manufacturing in the United States to eliminate processes which produce unwanted and difficult to capture byproducts. This cannot simply involve the modification of old technologies to reduce pollution, but rather requires the replacement of old technologies by new ones with entirely different configurations and strategies. This project proposes a coordinated and comprehensive attack on the discovery and development of such technologies, in a program that combines theory and experimentation. It aims at establishing the scientific basis, and developing the engineering tools for pollution prevention, through clean chemistry, integrated reactor and separator processes, and novel, high-efficiency control strategies.
Approach: The project focuses on: 1) the study of processes that combine reaction, separation and heat transfer in a single process unit (chromatographic reactors, reactive distillation columns, rapid quench reactors), in order to achieve higher yield, selectivity and energy efficiency; 2) the development and study of new solvents which can be recycled and re-used with negligible emissions; and 3) the development of novel approaches for the synthesis of biodegradable plastics.
Status: Funding for this project has not yet been received.
Chemical Reaction Pathways for the Reactions of Isobutane
over Supported Platinum (Pt), Platinum/Tin (Sn), and
Platinum/Tin/Alkali Catalysts: D. F. Rudd, R. D.
Cortright, E. Bergene, J. A. Dumesic; University of
Borgard 1995; Chen 1994;
Cortright 1994a, b, 1995a, b, c; Gonzalez 1993; Handy 1993;
Rekoske 1993; Rudd 1993; Sharma 1993, 1994a, b; Shen 1994a, b;
Spiewak 1994, 1995a, b; Yaluris 1994, 1995a, b)
Goal: The goal of this project is to understand and utilize the effects of adding modifiers and promoters such as tin and alkali metals to supported platinum catalysts for the selective conversion of isobutane to isobutene.
Rationale: Industrial catalytic reaction pathways for production of methyl tert-butyl ether (MTBE), an important motor fuel oxygenate, typically involve 1) production of synthesis gas from hydrocarbon feedstocks, 2) conversion of synthesis gas into methanol, 3) production of isobutylene by the cracking, alkylation, isomerization and dehydrogenation of light hydrocarbons, and 4) conversion of methanol and isobutylene into MBTE. A critical process in this sequence of steps is the production of the isobutylene. Current technology utilizes an inefficient and dirty reaction which requires a chromium based catalyst that must be regenerated every half hour. Significant advances in pollution prevention could be achieved by the discovery of a clean and efficient catalytic technology for the production of isobutylene.
We have recently invented a new dehydrogenation catalyst which achieves these pollution prevention goals in the laboratory. This new catalyst is highly selective and active for the dehydrogenation of isobutane to isobutylene, with the formation of almost no pollutant by-products. Further, this catalyst is not based on chromium and requires only infrequent regeneration. A patent is being pursued for this new catalytic technology through the Wisconsin Alumni Research Foundation.
This new catalyst system requires four components to become highly active, selective and stable for isobutane dehydrogenation. It contains platinum which catalyzes the removal of hydrogen from isobutane to produce isobutylene. It requires the addition of tin to reduce the size of the surface platinum ensembles and to suppress isomerization and hydrogenolysis reactions. It utilizes alkali metals such as potassium to neutralize the support, to suppress isomerization and hydrogenolysis reactions, and to enhance the dehydrogenation rate. Finally, this catalyst employs L zeolite to stabilize small Pt/Sn particles as well as to stabilize adsorbed isobutyl species.
Approach: The combination of microcalorimetry, steady-state kinetic measurements, deuterium tracing kinetic studies, and infrared spectroscopic measurements is used to provide information about the isobutane reaction pathways over supported Pt catalysts. In addition, these techniques provide information on the effects of tin, potassium, and support on these reaction pathways.
Status: Steady-state kinetic measurements show that the rate of isobutane dehydrogenation becomes zero order with respect to hydrogen pressure over Pt/SiO2 at hydrogen pressures lower than 75 Torr at 723 K. However, the dehydrogenation reaction is negative order with respect to hydrogen over supported Pt/Sn and Pt/Sn/K catalysts. Furthermore, tracing experiments show that deuterium is readily incorporated into isobutylene in flowing gas mixtures of isobutane/D2 and isobutylene/D2 over supported Pt and Pt/Sn catalysts at 723 K. The combined results of the kinetic and microcalorimetric experiments suggest that the adsorption/desorption steps of hydrogen and isobutylene are equilibrated and that the rate-limiting step for isobutane dehydrogenation over supported Pt/Sn and Pt/Sn/K catalysts is the dissociative adsorption of isobutan e. Accordingly, the high activity for isobutane dehydrogenation over Pt/Sn/K-L catalysts may be attributed to stabilization of molecularly-adsorbed isobutane species by the zeolite pore structure and/or by excess potassium, which enhances the rate limiting dissociation of isobutane. Adsorption microcalorimetry of isobutane at low temperatures allows the investigation of the effects of pore structure and potassium on the formation of molecularly-adsorbed isobutane species. These microcalorimetric experiments are combined with infrared spectroscopic experiments conducted at the same conditions to identify the nature of the species formed on the catalyst surface.
Chemical Reaction Pathways for Clean Production of
Environmentally Benign Fluorochemicals: D. F.
Rudd, J. A. Dumesic; University of Wisconsin-Madison.
(References: Dumesic 1993)
Goal: The goal of this project is to conduct exploratory research in the use of heterogeneous catalysts for the clean production of specialty fluorochemicals.
Rationale: We are working jointly with the 3M Fluorochemical Technology Center to investigate the use of heterogeneous catalysts for the clean production of fluorochemical products. The 3M Company is a major producer of fluorochemical-based consumer products. These products comprise a $300 million per year business that is expected to grow at a rate of 10 to 15% per year. Fluorochemicals are commercially important because of high chemical inertness, high absorptivity of gases, excellent lubricating and solvating power, and good reactivity as monomer building units. These chemicals are essential ingredients in hundreds of commercial products. In addition, there is growing interest in selectively fluorinated molecules for biological applications.
The fluorochemical products of interest here are considered to be environmentally benign or can be made more nearly environmentally benign by hydrogenation and reduction reactions. These reactions are currently driven by chemical reducing agents, such as NaBH4, which generate as much waste material as finished products. A major challenge is to replace these dirty hydrogenation and reduction reactions which involve chemical reducing agents by clean catalytic reactions which involve hydrogen as a reducing agent.
Approach: We are investigating the catalytic hydrogenation and reduction of fluorochemicals over supported transition metal catalysts. Initially, the direct catalytic reduction of fluorocarbon-methyl esters to alcohols is being studied over supported metal catalysts. These investigations probe the chemical properties of the catalytic sites and elucidate the role of these sites in catalytic processes. Structural, chemical, and catalytic information about the catalytic sites is obtained from the combination of results from spectroscopic, microcalorimetric, and kinetic studies. Microcalorimetry is particularly useful because it can probe the distribution of surface sites on the catalyst, the effects of surface coverage on the properties of the surface and the influence on the surface properties of promoters, poisons and supports. The combination of microcalorimetry with reaction kinetics measurements provides a powerful method for elucidation of the essential catalytic chemistry. This information is vital to formulate quantitative correlations between the factors that control the generation, type, strength, and catalytic properties of active sites on catalysts.
Status: The 3M Company Fluorochemical Technology Center is providing intellectual collaboration, supplying sample fluorochemicals and funding the development of a catalytic fluorochemical reaction laboratory at the University of Wisconsin. We are currently constructing a flow-through kinetics apparatus and are in the planning stages for the construction of a trickle bed reactor which allows interaction between the three phases present in catalytic processing of fluorochemicals, (e.g., gaseous hydrogen, liquid fluorochemical, and the solid catalyst).
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