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E ngineering an A lternate R oute to S tyrene Project Proposal and Feasibility Study Team 7: Chemical Engin-EARS Larae Baker Maxine Bent Jonathan Bush Michael Heslinga Adam Jones Advisor: J.A. Sykes December 9, 2005

Engineering an Alternate Route to Styrene - Calvin … an Alternate Route to Styrene ... the cost of production can be significantly reduced and ... ethylbenzene used in 90% of commercial

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Page 1: Engineering an Alternate Route to Styrene - Calvin … an Alternate Route to Styrene ... the cost of production can be significantly reduced and ... ethylbenzene used in 90% of commercial

Engineering an Alternate Route to Styrene

Project Proposal and Feasibility Study

Team 7: Chemical Engin-EARS

Larae Baker

Maxine Bent

Jonathan Bush

Michael Heslinga

Adam Jones

Advisor: J.A. Sykes

December 9, 2005

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Abstract: The production of styrene is a 28 billion dollar industry worldwide.14 There is a significant demand for it and cutting costs even a few cents per pound will yield large savings. These savings can then be passed to the consumer and will ultimately make styrene products (like polystyrenes and ABS polymers) available to more people worldwide. We believe it is feasible to simulate a process for producing styrene that will make this possible. The idea is to use cheaper raw materials, namely ethane instead of ethylene, and utilize the fundamentals of the process, such as a dehydrogenation unit, to convert the ethane to ethylene in the process.

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Table of Contents

1. Introduction 3 2. Problem Statement 3 3. Project Objectives 3

3.1. Academic 3 3.2. Economic 3

4. Alternate Solutions 3 4.1. Chemistry 3 4.2. Alkylation Reactor Design 4 4.3. Alkylation Reactor Catalyst Design 4 4.4. Dehydrogenation Reactor Design 4 4.5. Dehydrogenation Reactor Catalyst Design 5 4.6. Separations (Inhibitors) 5 4.7. Optimal Location 5

5. Feasibility Study 5 5.1. Time Feasibility 5 5.2. Chemical Feasibility 5

5.2.1. Reactor Modeling Feasibility 5 5.2.2. Separations Modeling Feasibility 6 5.2.3. Byproducts and Trace Materials 6

5.3. Cost Feasibility 7 5.3.1. Plant Production 7 5.3.2. Report/Project Production 7

6. Method of Approach 8 7. Christian Perspectives on the Project 9

7.1. Cultural Appropriateness/Justice 10 7.2. Justice 10 7.3. Transparency 10 7.4. Stewardship 10

7.4.1. Environmental 10 7.4.2. Human 10

7.5. Caring 11 8. Task Breakdown and Time Schedule 11 9. Cost Estimates 12

9.1. Equipment Costs 12 9.2. Labor Costs 12 9.3. Utility Costs 13 9.4. Material Costs 13 9.5. Actual 13

10. Preliminary Design 13 11. Conclusion 14 References 15 Figure 2: Process Flow Diagram 17 Table 2: HYSYS Stream Tables 18 Reaction Chemistry 28 Figure 3: Process Flow Diagram Old Chemistry from Patent #2,376,532 29 Figure 4: Critical Path Network 30

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1. Introduction: During 2000 in the U.S. 12.1 billion pounds of styrene are sold per year.17 Most often it is used to make polymers such as polystyrene or acryonitrile-butadiene-styrene. These polymers are used in a wide variety of everyday products. They are used for food storage, electronics casings, and as packaging when shipping fragile items. They are used as injection moldings in car doors to improve safety and to make many different foams which are well known for their insulating abilities.13 These polymers are an essential part of modern life. These products that are so crucial to food storage, safety, and everyday life are not available to everybody around the world. If styrene could be made at a lower cost, then it could be sold at a lower price; thus the availability of these vital plastics could be extended to people of all walks of life.

2. Problem Statement: The current method for producing styrene utilizes ethylene as a starting material. While this process works well, it is hard to break into the styrene market without building a plant of massive capacity. If a new, cheaper starting material can be used, the cost of production can be significantly reduced and the market undercut with less capital cost than by sheer capacity.

3. Project Objectives Our project has objectives both for our course work at Calvin and for the project to produce styrene.

3.1. Academic: Our project is to design and optimize a full scale industrial plant to produce styrene from benzene and ethane precursors using data from Dow Chemical and Snamprogetti's patents on the chemistry. We will also design the process to produce the catalyst for this reaction. The process and plant will be evaluated economically and environmentally. If time allows, it will be compared to the design of the old process of styrene from ethylene.

3.2. Economic: Our plant will be optimized to produce styrene below the current production cost by utilizing new technology and building a plant of large enough capacity to be cost efficient. The optimal location will be determined for the plant.

4. Alternative Solutions: It is important to consider as many different solutions to the design challenge in the Problem Statement as possible. Our final design is essentially the summation of many different designs, specifically the chemistry, the reactors, the separations equipment, and the process equipment such as compressors and pumps. Therefore, to examine the many different alternate solutions available it is appropriate to break our design into seven components: chemistry, alkylation reactor design, alkylation reactor catalyst design, dehydrogenation reactor design, dehydrogenation reactor catalyst design, separations, and optimal location.

4.1. Chemistry: There are two routes to produce styrene used in industry. One of them is a dehydrogenation of ethylbenzene used in 90% of commercial production facilities. This is a straight-forward procedure, generally beginning with petroleum products. It proceeds as follows:15

1.) 52564266 HCHCHCHC →←+

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2.) 232565256 HHCHCHCHC +→←

However, styrene can be industrially produced by what is known as PO-SM Coproduction, where propylene oxide and styrene are made simultaneously. It proceeds as follows:

3.) OOHCHCHHCOCHCHHC )( 35623256 →←+

4.)

3235632356 )()( COCHCHHOHCHCHHCCHCHCHOOHCHCHHC +→←=+

5.) OHCHCHHCOHCHCHHC 2256356 )( +=→

One downside to the PO-SM Coproduction is that the production capacity is dictated by the demand for propylene oxide. Since it is a more complex series of reactions makes it is less attractive to operate in industry.

4.2. Alkylation Reactor Design: The alkylation reactor is where benzene and ethylene will undergo a reaction similar to a Friedel-Crafts alkylation. This reaction will be very similar to what is currently done in industry with the exception that some ethane will be present. The feed will not enter in a 1:1 mole ratio, but with a significant excess of benzene so as to discourage polyalkylations and force the reaction towards the products. The excess ratio is yet to be determined and must be optimized. The reaction can be run in the liquid or gas phase and this will have a large impact on the reactor design. The type of reactor the alkylation will take place in is a packed-bed reactor. The temperatures at which it will operate are in the range of 450-600°C and will need to be optimized for the best conversion and selectivity.1 The temperature will need to be increased over time to compensate for the degradation of the catalyst. This temperature increase will be favorable for more side reactions and polyalkylations to take place. How this will vary is dependant on the life-time and type of catalyst.

4.3. Alkylation Reactor Catalyst Design: The catalyst plays a major role in how well the desired reaction proceeds. In industry, an aluminum chloride catalyst is used to do a Freidel-Crafts alkylation.18 This catalyst can be optimized to get good conversion and final purity. One of the biggest problems with this catalyst is that it alkylates excessively and polyalkylbenzenes are formed. This has the drawback that a distillation and transalkylation unit is often required to convert these polyalkylbenzenes back to ethylbenzene. Another catalyst used in industry contains iron oxides. The newest catalysts in use are zeolite catalysts.1 These are considered molecular sieves and have the advantages that they are highly selective and achieve good conversion. They are also non-corrosive and environmentally benign. In fact, the conversion can be modeled as though all of the ethylene reacted. Specific zeolite catalysts contain high SiO2 to Al2O3 ratios like ZSM-5 or Lewis acids.

15

4.4. Dehydrogenation Reactor Design: The design of the dehydrogenation reactor will be based off the information given in the patents. There are three theoretical reactors for the dehydrogenation unit. These are a fluidized packed-bed reactor, a membrane reactor, and a fluidized catalyst cracking reactor (FCC). The pros and cons of these are discussed in section 5.2.1. This reaction vessel is different than any current industrial design because it will simultaneously dehydrogenate ethane and ethylbenzene to create ethylene and styrene respectively. Ranges for the reaction parameters are given in the patents,

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and they will have to be optimized. The kinetics will either have to be determined from an analogous reaction through researching the literature or by a round-about method explained in 5.2.1.

4.5. Dehydrogenation Reactor Catalyst Design: The catalyst for the dehydrogenation reactor is unique in that it will dehydrogenate ethane and ethylbenzene in one vessel.8,11 There are two potential catalysts listed in the patents for this reaction. One is primarily gallium oxide with imbedded platinum and potassium suspended on alumina and modified with silica. The other is a chromium oxide mixed with tin oxide and alkaline oxides.1,2 The effectiveness and regeneration rates of each will be crucial to deciding which catalyst will be used.

4.6. Separations (Inhibitors): The separation chain for the process is standardized.15 The only difference between our process and the old process is that ours will contain unreacted ethane in the distillate along with ethylene. This whole stream will be recycled to the alkylation unit. One decision we will have to make with the separations is the inhibitor type and quantities. Typically dinitrophenol and dinitrocresol are added, but others include SFR and STYREX, developed by Uniroyal Chemical and Betz Process Chemicals respectively.15

4.7. Optimal Location: The optimal location of the plant is another key design alternative. The plant should be placed close to the suppliers and preferably close to potential consumers. A location in the United States where ethane is inexpensive is preferred. However, this is a contradiction. Ethane is 90% cheaper in the Middle East than on the Gulf Coast.19 It may be economically favorable to build in the Middle East.

5. Feasibility Study: The parameters that dictate the process design are the amount of time we have available to accomplish the design, the chemical reactions which govern the process, the economics in terms of industrial profitability and our expenditures, and the resources available to us to fill in missing data. These will all be analyzed in detail below.

5.1. Time Feasibility: This project, while very challenging, will be feasible in our given time frame. Since the chemicals used in this process can all be found in our modeling software, HYSYS, we will be able to make a computer simulation of the process. The challenge of the design will be in determining the kinetics of the reactions involved. In order to obtain this information, much library research will be needed. Most of this research will be done to determine the optimal size, shape, and composition of the catalyst along with operating temperatures and sizes.

5.2. Chemical Feasibility: Dow Chemical has this process patented, thus it is chemically feasible. The process has never been done on an industrial scale, but since it is chemically feasible and fairly similar to the current process, we are confident that it can be done.

5.2.1. Reaction Modeling Feasibility: There are two reaction vessels we will have to design. The first reactor alkylates recycled ethylene with raw benzene by the following reaction:

6.) 52564266 HCHCHCHexcessC →←+

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This reaction essentially uses up all of the ethylene feed.15 The temperature range for this reaction is specified in the patents and is typically 450-650°C.1,2,10 Data is available for aluminum chloride, iron oxide, and new zeolite catalysts. This alkylation is how the precursor to styrene, ethylbenzene, has been made for the past 65 years. Thus the kinetics of this reaction are well established. There is the possibility of ethylene polyalkylating the benzene to form diethylbenzenes, triethylebenezenes, tetraethylbenzenes, etc. The industrial practice has been to distill out these side products and then run them through a transalkylation reactor. This is where a diethylbenzene would react with excess benzene to form two ethylbenzenes. These are in high yield and purity, and are combined with the ethylbenzene stream.15 Ethylbenzene and raw ethane are then brought into a dehydrogenation reactor. In this reactor the catalyst is a key component. If a catalyst can simultaneously dehydrogenate ethylbenzene and ethane than it can be used for this process. The catalyst listed in the patents is comprised of gallium oxide, platinum, and potassium on alumina modified with silica.20 The optimization of this catalyst is known only to Dow Chemical, so the specific kinetics will be impossible to acquire. There is literature available on catalysts similar to the one of interest. The best way to design this reactor is to research current reactors in use in the industry to determine the parameters in ours. The flow through the reaction vessel is limited by how fluidized the bed can become (i.e. there is a maximum velocity) and by its maximum dimensions (i.e. height limited by air-traffic). These will also be controlled by how fast the catalyst can be regenerated and how much catalyst can be used. Once these parameters can be determined and a flow régime established a residence time can be bracketed. If the assumption of equilibrium conversion is applied (which is a viable assumption) then the kinetics will be indirectly determined.12 Some estimates as to other values such as catalyst inventory will need to be made. One heuristic is that catalyst regeneration can be estimated as proceeding half as fast as the reaction, and possibly as low as an order of magnitude slower. Any slower than two orders of magnitude is unprofitable, which we know is not the case.12 Another estimated value is the ratio of dehydrogenated styrene to dehydrogenated ethylene. Examining activation energies and applying heuristics for these reactions will help to determine this. Another heuristic is that the larger a molecule is, the easier it will be to dehydrogenate.12 We are also considering several different types of reactors for our process. For the dehydrogenation we are considering a fluidized packed-bed reactor, a membrane reactor, and a fluidized catalyst cracking reactor (FCC). The fluidized packed-bed reactor greatly limits the velocity of the flow through the vessel. This is because the catalyst’s physical properties are analogous to fine-grain beach sand and when the bed is fluidized the catalyst will crash against the reactor wall, essentially “sand-blasting” the reactor.12 The reaction vessel cannot withstand this punishment for 8000 hours a year over twenty years. Membrane reactors are not yet used for this process in industry. The major draw of a membrane reactor is that as hydrogen is produced it is taken out of the process and the equilibrium is pushed even further towards the products. However, there are three major drawbacks to using membrane reactors. The first is that the materials used in them are fracture prone to the point where if there was an accident (i.e. an employee dropping a heavy wrench on the reactor) a catastrophic failure could occur. Another problem is that they can foul overtime and may lose its robustness, causing insufficient flux. The third problem is with sealing. A ceramic vessel must be used to withstand reactions at 700°C and be surrounded by a metal, but there is no way to seal ceramic to metal.12 Therefore, the most feasible reactor is the FCC and is used in industry for this process.

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5.2.2. Separations Modeling Feasibility: The major difficulty in the separations for the process lies in how similar the chemicals are to each other. For example, styrene and ethylbenzene are different by a double bond, so the relative volatility is small.15 Fortunately, data for the materials in the process are available in the literature. In fact, the separations for this process are essentially the same as the old process which is well established and not under patent. The difference will be that unreacted ethane in the product stream will have to account for. When the ethylene is separated from the product stream out of the dehydrogenation unit, the ethane will go with it. Recycling ethane back through our alkylation unit will not affect that chemistry. Thus ethane does not pose a significant problem to the separations. Another problem with the separations is that styrene may polymerize in the distillation chain.11 The polymers and other heavy aromatics should leave from the bottoms of the distillation chain and be purged or used as a fuel.15

5.2.3. Byproducts and Trace Materials: The major byproduct noted in the patents is toluene. Toluene is created by the following reactions:1,10

7.) 435623256 2 CHCHHCHHCHC +→←+

8.) CCHHCHCHC +→← 3563256

The carbon produced in the second reaction is deposited on the catalyst, so the catalyst will have to be regenerated. The process for this is catalyst-specific, but most generally is:15

9.) 222 22 HCOOHC +→←+

There are also inhibitors added to the process so that once styrene is formed, it will not polymerize. These inhibitors are most notably dinitrophenol and dinitrocresol for the distillation chain and 4-tert-butylcatechol for shipping and storage. These have been added to the process since the discontinuation of sulfur in the seventies.15 Despite using inhibitors there will still be trace amounts of polymerized styrene which will leave out the bottom of the distillation chain to be purged. Other heavier aromatics will leave out this purge stream as well. These include, but are not limited to: cumene, α-methylstyrene, allylbenzene, phenylacetylene, xylenes, vinyl toluenes, n-propylbenzene, ethyl toluenes and butylbenzenes. Fortunately, these are present in extremely trace amounts and for the design can be considered to be a zero-factor.12 They will not change the selectivity by a measurable quantity. However, a side reaction forming benzene can have an impact. The reaction is:

10.) 426623256 HCHCHHCHC +→←+

This can account for a loss of yield up to one percent.15 The other source of impurities could be in the raw materials. Fortunately, both benzene and ethane are available at very pure conditions. In benzene the biggest impurity is toluene generally ranging from 50-1000ppm.15 Ethane is available from Aldrich at 99.99% purity, ethylene has 200-2000ppm ethane impurity.

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5.3. Economic Feasibility: As Christians, we are not driven solely by the economics or profitability of a process. However, our goal is still to minimize the cost of production. If styrene is cheaper, then styrene polymers will be cheaper. This allows people everywhere to have access to plastic products that make life easier. Therefore, the economic feasibility of the process is important.

5.3.1. Plant Production: The purpose of our project is to determine if it is economically advantageous to build a plant producing styrene through this new process, however, due to the cost structure of a plant, this will not be determined until the design is nearly complete. Nonetheless, this process has made its way into chemical magazines and others have done projects similar to this. For example, SRI Consulting has analyzed the process and concluded, “Operating and capital cost charges related to the separation and recycle of the ethane/ethylene from the dehydrogenation system offsets the favorable price differential between ethane and ethylene.” The group director, Russel Heinen stated, “Based on current pricing in the Gulf Coast, it appears that the spread between ethylene and ethane would put these processes on about a breakeven basis.” He added, “Clearly Dow’s intention is to use this process in areas like the Middle East where ethane is priced 90% lower than the Gulf Coast, which result in about a 16% reduction in total raw material cost of the process. Factoring in the additional capital costs of the process, the cost of producing styrene after the 25% return on capital is about 10% lower than the ethylene-based process.”19 Based on these preliminary studies, the new process has minimal economical advantage if located in the United States because the additional operating costs would off-set the cheaper raw materials.

5.3.2. Report/Project Production: We will be able to stay within our budget of 300 dollars because the only planned costs are for the printing of our reports. Further down the road some costs may arise if we look to acquire private reports. Most notably, SRI Consulting has published research very applicable to the new process as well as several others that can be helpful to us. This is just one example of costs that we are not yet able to predict.

5.4. Laboratory Work Feasibility: The patents list a lot of ranges for the parameters governing our process. The literature may have some studies of reactions similar to ours, but we have found none that yield any data specific to the kinetics for our catalysts. Therefore, in order to fill in the holes in our acquirable information we would like to be able to do lab research. We would set up a continuous process and run a couple of small scale reactions using a catalyst-packed microreactor. This would be the ideal case. However, we do not have the equipment available to run a continuous process and acquiring it would be expensive. We also would have to buy the raw materials (benzene and ethane) for the process, which are expensive to purchase and store. Also, to acquire kinetics we would have to purchase the gallium oxide catalyst with platinum imbedded and try several different catalyst designs to determine the optimum. This alone would be well above our $300 budget. Therefore, doing laboratory work to acquire information is not feasible.

5.5. Assumptions and Educated Guesses: Since we may not be able to find all the data we need in the literature and doing labwork is not feasible, we will need to make some assumptions about our process. At this stage in the design there are only a few foreseeable assumptions. We will have to assume something about the dehydrogenation unit chemistry. A heuristic for this specific process is that the dehydrogenation reaction will essentially go to equilibrium.12 An educated guess will need to be made for the

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ethylbenzene conversion to ethane conversion. We can also rule out a transalkylation unit, as selectivites for ethylbenzene run very high.12 This means we will essentially assume that the alkylation unit has no polyalkylation byproducts or rather that when a polyalkylation occurs there is a sufficient excess of benzene to the point where it will quickly transalkyate back to ethylbenzene. For our purposes, these are reasonable assumptions.

6. Method of Approach: Since the process has been determined to be feasible, some path or method must be employed in the design of equipment and process operations. Our method of approach to the task of designing a styrene plant is to work backwards from the final goals of the project. First, we determine the final goals of the project. The goal is to design a styrene plant that utilizes a new chemistry that we hope will be competitive in the market.

Second, we decide what fundamental areas to be designed are vital to the overall process. These are two reactions, alkylation of benzene to ethylbenzene and dehydrogenation of ethylbenzene to styrene, and the separation of our product from byproducts and leftover reactants. Third, we determine what information will be needed to design the reactions and separations. The essential information is a kinetic rate law for the reactions and the separations parameters. Fourth, the tasks of determining this information were divided among the team members. Figure 1 below shows the division of this work.

Figure 1: Task Division. Each person is responsible for their particular area of research, but is also involved in the overall design. In this way each person develops expertise in a certain area of the project, which will be useful for the design of the equipment along with a general idea of the overall design process. Also, different team members are in charge of the operational aspects of the project. For example, Larae is charge in charge of updating the website, while Maxine is in charge of managing the meeting minutes and schedule. Fifth, we design the key parts of the process: the reactors and separations units. The other pieces of equipment support these major processes, so it makes sense to start with what is important. Sixth, we design all the other pieces of equipment to fill in unknown information for all streams and for the pricing of the plant.

Team

Advisor:

J. A. Sykes

Mike

Heslinga

Micro-

reactors

Maxine

Bent

Fluidized

Bed

Reactors

Jonathan

Bush

Catalyst

Properties

Adam

Jones

Patents and

HYSYS

Larae

Baker

Separations

Equipment

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Seventh and last, we optimize the economics of the whole process by modifying operating conditions and equipment.

7. Christian Perspectives on the Project: Calvin stresses that not only are we to be good engineers, we are to be good engineers that view all life through our Christianity. As we work out our design of the styrene plant, we must consider how what we are doing impacts people and the world in which we live. Some design norms that we must consider are cultural appropriateness, justice, transparency, and stewardship.

7.1. Cultural appropriateness: One of our concerns with the plant to be designed is the location of the final design. Most of our starting materials are manufactured along the gulf coast, so building in the same area makes economical and cultural sense. Alternatively, if we were to build the plant in a location with no demand for styrene or availability of raw material, such as South America, the location would not be appropriate. This is due not only to economic reasons, but also due to the fact that the local people may be accustomed to using other materials instead of styrene (polystyrene). Thus, styrene would not be culturally appropriate.

7.2. Justice: As designers, we have a duty to consider the rights and needs of all people and not only the people directly involved in the business. People of the community that the plant is located in are also stakeholders in the business; they will have ties to what goes on in the styrene plant. For example, it is important to ask that if the plant were to be built in Grand Rapids, MI, would there be strong community opposition and for what reason(s)? Even though we will design a plant that is environmentally friendly, there is still a fear of safety hazards of having a large scale chemical plant and these fears must be addressed.

7.3. Transparency: The dangers inherent in this large scale chemical process must not be hidden, but acknowledged to the general public. This honesty is something that we owe to the stakeholders who depend on us. Additionally, the equipment and process we design must be consistent and reliable. Our customers and suppliers rely heavily on knowing that the process will be able to run continuously.

7.4. Stewardship: As Christians we have a cultural mandate to rule over and care for the earth and all that is in it. This includes people around us and the rest of the environment.

7.4.1. Environmental: Our plant will strive to produce styrene as efficiently as possible. All of our equipment will be optimized so that the least amount of energy needed will be used. Additionally, our design includes several recycle streams to make sure that our starting materials are fully utilized. Our catalyst is also regenerated so that it can be reused and recycled in our process, allowing us to use less feed catalyst.

7.4.2. Human: We also consider many safety precautions so that we minimize the effect in the case of an accident. This shows respect for the employees and neighbors of the plant, respecting their property and their lives shows great stewardship with the resources God has given. This includes planning for worst-case scenarios both for steady-state conditions and unsteady-

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state conditions that occur at start-up and shut-down. Many of the chemicals involved in the process, including styrene, are hazardous and flammable.

7.5. Caring: Styrene is a product that is a precursor for a product that is widely used throughout the world. Polystyrene is used to create a lot of safety and health equipment including insulation for food products and medical gloves. If styrene can be produced at a lower cost, the use of styrene for these cases can be expanded to those of lower economic standing.

8. Task Breakdown and Time Schedule Table 1: Task Schedule

Task Completion Dates

Team Definition 9/14

Project Objectives 9/28

Project Poster 9/30

Alternative Solutions 10/7

First Presentation Delivered 10/12

Preliminary Task Specifications 10/17

Preliminary Evaluation of Feasibility 10/28

Preliminary Budget 11/1

Refined Task Specifications 11/4

Preliminary Project Schedule 11/7

Project Brief with Industrial Consultant 11/15

Print out project plan and Gantt chart 11/9

Print out design component sheets 11/11

Deliver Brief 11/15

Second Presentation Delivered 11/23

PPFS Draft 1 11/10

PPFS Draft 2 11/28

Research 12/5

Microreactors 12/5

Catalyst Properties 12/5

Fluidized Bed Reactors 12/5

Patents 12/5

Separations Parameters 12/5

Hand in PPFS 12/9

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Tentative dates of completion

HYSYS 3/21/06

base case 12/16/05

Piping 2/9/06

Heat Exchangers 2/20/06

Compressors 3/1/06

Reactors 3/10/06

Separations Equipment 3/21/06

Comparison of Old Process 4/4/06

Artistic Plant Design 4/28/06

PFD (animated) 4/28/06

PPFS 1 4/28/06

Economics 4/28/06

Website 5/5/06

Layout 11/4/05

Update 5/5/06

Budget 4/18/06

9. Cost Estimates: Based on data obtained about plant capacity, this styrene plant should produce more than 2 billion pounds of styrene per year to be viable in the styrene production market. The goal is to produce styrene at a lower cost by increasing plant capacity and by using a new process. The budget for this project consists of the design and operation of a major chemical plant, which can be broken down into four major areas: equipment and capital investment, wages and benefits for employees, energy and utility costs, and material costs.

9.1. Equipment Costs: The cost of each piece of equipment depends on size and duty. The process of production has not yet been optimized, so the type of equipment, the number of pieces of equipment, and the size and duty of each piece of equipment is yet to be determined. The process involved in the commercial synthesis of styrene will include reactors, heat exchangers, pumps, compressors, mixers, and separations equipment.

9.2. Labor Costs: Employees for operating a large-scale chemical plant will be needed to oversee operation, repair or replace broken equipment, and solve problems that may arise. Each of these employees will be compensated. The number of employees and their compensation will need to be projected.

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9.3. Utility Costs: Industrial chemical production plants require large amounts of energy to run equipment. This includes electricity to power compressors, perhaps natural gas or steam to fire heaters or reactors, and cooling water for heat exchangers and reactors. Utility costs vary with the prices of these materials/energies (natural gas, electricity, process water) and the amounts of these materials/energies depend on the duties on pieces of equipment that need to be optimized. The prices vary with the location of the plant as well. Also, the process may involve making steam or waste gas that can be used outside the plant. In this case, these costs can be deducted from the total utility cost.

9.4. Material Costs: Raw materials are needed as inputs to chemical processes. In this case, benzene and ethane need to be purchased and transported to the site of the styrene plant. Therefore, the prices at which benzene and ethane might be purchased needs to be determined. Also, the cost of transportation needs to be included in this material cost. Another material that needs to be purchased is the catalyst. The process includes a method of replenishing the catalyst (i.e., decoking it), but some catalyst will be lost over time and more will need to be purchased. Another material cost includes the processing of any wastes that are produced. This includes waste water or other streams that need to be treated. Feedstock ethane fluctuates between $0.16/lb and $0.20/lb yearly since the demand increases during the winter. Feedstock benzene can be purchased for $0.37/lb Contract prices on styrene are approximately $0.72/lb. These prices are as of June 2005.4 Total production capacity in the United States was 12.1 billion pounds as of 2000. Canada has a production capacity of 1.9 billion pounds as of 2000. Mexico has a capacity of 0.3 billion pounds as of 2000. There were no planned capacity increases in the next few years. Demand in the US was 10.8 billion pounds in 2000 and forecast at 11.9 billion pounds in 2004. Imports were 1.3 billion pounds and exports were 2.7 billion pounds in 2000.16 Then demand in US that we can sell at is (demand – imports) and capacity for US is (capacity – exports). So, the actual demand is 9.2 billion pounds and actual supply is 9.8 billion pounds with a demand growth projected as a constant at 2.6% per year. Therefore, the current styrene plants in the US run at about 94% capacity.16

9.5. Actual Costs: Actual expenses for our project include the artistic plant design, printing, and binding of the final report. These out of pocket expenses will be minimal, less than $50.

10. Preliminary Design, the Base Case: From the patents acquired from the U.S. Patent Office and held by Snamprogetti and Dow Chemical, a base case for a styrene production plant was created using HYSYS computer simulation software. For this first simulation only the equipment needed for the liquid and gas handling systems were included in the development of the flow sheet. This restriction on the process as modeled was followed because HYSYS would be able to easily model this and our current HYSYS does not include the dynamics license which is required for modeling some of the solid handling equipment.

The process flow diagram for the base case can be seen in the appendix. This simulation accounts for the majority of the equipment stated in Snamprogetti’s patents (excluding the solid handling equipment). The entering starting materials in this base case: benzene, ethane, and air, are assumed to be entering at standard temperature and pressure (298.15K and 101.325Kpa). These temperatures and pressures will have to be examined at a later stage of development to take into account location and

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method of feed (pipeline, semi-truck, or on-site storage).

The basic process flow can be seen from the diagram to start with pure benzene flowing into the first reactor, the alkylation reactor, with a recycled steam of ethylene and ethane. The product from this reactor, ethylbenzene, is then mixed with pure ethane and recycled ethylbenzene before being heated and pressurized into the second reactor. In the second reactor the ethylbenzene reacts to become styrene and the ethane reacts to be come ethylene. These products are then cooled and filtered before being put into the separations portion of the plant. Here products are separated into different steams: ethane with ethylene and benzene to be recycled to reactor 1, ethylbenzene to be mixed with products from reactor 1 before reactor 2, by-products that are not being modeled in the base case, light hydrocarbons to be recycled to the regeneration unit for the catalyst, and styrene. In order to model this process in HYSYS however some rules must be assumed or be seen as valid.

One such assumption that was made in this base case was that there were no by-products produced. In normal operation the Snamprogetti patents report that up to 65% conversion can be achieved with 90% by weight selectivity for the dehydrogenation reaction. Thus in this base case 60% conversion is used in the reactor without by-product reactions, thus 100% selectivity. Later simulations will include side reactions and kinetics based reactions instead of conversion based.

For this base case, the dehydrogenation reaction is modeled as if it is occurring in only one reaction. This model is good for a base case because of its simplicity but is not a realistic model for the reactor. In reality, the catalyst used in the dehydrogenation reaction needs to be decoked in order to maintain its effectiveness. To decoke the catalyst, the catalyst needs to be removed from the reactor in one of several different ways. One option is to create a series of reactors. These reactors would rotate being taken out of the line and the catalyst regenerated. The exact number of reactors would have to be optimized, but this would prevent the shut down of the plant in order to regenerate the catalyst and would also incorporate redundancy in our process. Redundancy will allow maintenance to be performed on any reactor without interruption in production.

A second option would be to have a catalyst recycle stream. This would allow the catalyst to continually be regenerated. This would probably be the most cost effective way to run the reaction because it involves fewer reactors, but it would not create the same redundancy that would result from multiple reactors. The catalyst recycle stream was suggested in the patents, but without commercial scale optimizations and considerations for redundancy, a decision cannot be made. This means that both options will be seriously considered.

11. Conclusion: We have shown that the major parameters that govern the feasibility of our project will not hinder it from being completed. Our biggest hurdle is not being able to do laboratory work to find any missing data. However, we believe we can use our knowledge of the process and the chemistry to make viable estimates. Therefore, our project is feasible. Further evidence of this is that we have completed a base case simulation. Many assumptions had to be made, but over time we will be able to eliminate most of these and develop an accurate model of the real process.

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References

1Buonomo, Franco; Donati, Dianni; Micheli, Emilio; Tagliabue, Lorenzo. “Process for the Production of Styrene” listed in US Patent #6,031,143; Feb 29, 2000.

2Buonomo, Franco; Sanfilippo, Domenico; Iezzi, Rodolfo; Micheli, Emilio. “Catalytic System and Proces for Dehydrogenating Ethylbenzene to Stryene” listed in US Patent # 6,242,660; June 5, 2001.

3Chen, Kaidong, Alexis T. Bell, and Enrique Iglesia. "Kinetics and Mechanism of Oxidative Dehydrogenation of Propane on Vandium, Molybdenum, and Tungsten Oxides." J. Phys. Chem 104 (2000): 1292-99.

4Chemical Industry Intelligence - Chemical Pricing Reports. www.icislor.com.

5Dessau, Ralph M. “Dehydrogenation and Dehydrocyclization Using a Non-Acidic NU-87 Catalyst” listed in US Patent # 5,254,787.

6Egloff, Gustav. “Production of Styrene” listed in US Patent # 2,376,532; May 22, 1945.

7Frash, M V., and R A. Santen. "Activation of Small Alkanes in Ga-Exchanged Zeolites: A Quantum Chemical Study of Ethane Dehydrogenation." J. Phys. Chem 104 (2000): 2468-75.

8Iezzi, Rodolfo; Barolini, Andrea; Buonomo, Franco. “Process for Activating Catalyst Precursors for the Dehydrogenation of C2-C5 Paraffins, and a Catalytic Composition Activated by the Process” listed in US Patent # 5,308,822; May 3, 1994.

9Iezzi, Rodolfo; Buonomo, Franco, Sanfilippo, Domenico. “Catalytic Composition for the Dehydrogenation of C2-C5 Paraffins” listed in US Patent # 5,143,886; Sept 1, 1992.

10Iezzi, Rodolfo; Sanfilippo, Domenico. “Process for the Dehydrogenation of Ethylbenzene to Styrene” listed in US Patent # 6,841,712; Jan 11, 2005.

11Iezzi, Rodolfo; Bartolini, Andrea; Buonomo, Franco. “Process for Activating Catalyst Percursors for the Dehydrogenation of C2-C5 Paraffins, and a Catalytic Composition Activated by the Process” listed in US Patent # 5,414,182; May 9, 1995.

12Jones, Mark. Personal Interview. 8 Dec. 2005.

13Polystyrene Packaging Council Homepage. http://www.polystyrene.org/.

14SIRC: International Styrene Industry Forum. 9 Dec. 2005

http://www.styrene.org/international.html.

15"Styrene." Vol. 22. In Kirk-Othmer Concise Encyclopedia of Chemical Technology, edited by Jacqueline I. Kroschwitz. New York: John Wiley & Sons, 1997.

16Styrene Producers Price Capacity. http://www.the-innovation-

group.com/ChemProfiles/Styrene.htm.

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17Tullo, Alexander H. "Spotlight on Polymers." Chemical and Engineering News, 12 September 2005, 19-24.

18Watson, Keith. Calvin College, Grand Rapids, MI. 5 Oct.

19Wood, Andrew. "Dow Joins Snamprogetti to Develope Ethane-Based Styrene Process." Chemical Week, 20 April 2005, 17.

20Wood, Andrew. "Celanese, Dow Revisit Catalytic Route from Ethane to Ethylene." Chemical Week, 15 June 2005, 25.

21Zhou, Ying; Cavis, Stephen M. “Dehydrogenation Catalysts and Process for Preparing the Catalysts” listed in US Patent # 5,219,816; June 15, 1993.

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Figure 2: Project Flow Diagram

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Table 2: HYSYS Flow Streams

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Reaction Chemistry

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

10.as

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1

Catalyst

Chamber

Separator

Separator

Figure 3: Process Flow Diagram For Old Process as Shown in Patent #2,376,532

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Figure 4: Critical Path Network

Economic

Optimization

Optimal

Location

HYSYS Final Case

Dehydrogenation

Alkylation

Separations

Other Equipment

HYSYS Base

Case

Catalysts Kinetics

Reactor

Types

Separations

Parameters

Thermodynamics

Old Process

Patent

Research

Contact Mark

Market Research

Optimization