Handbook of petroleum refining processes
Collected by BEHTA MIRJANY, STC. Co. Email : behtam@yahoo.com ALKYLATION AND POLYMERIZATION P ● A ● R ● T ● 1 Source: HANDBOOK OF PETROLEUM REFINING PROCESSES Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Collected by BEHTA MIRJANY, STC. Co. Email : behtam@yahoo.com 1.3 CHAPTER 1.1 NExOCTANE™ TECHNOLOGY FOR ISOOCTANE PRODUCTION Ronald Birkhoff Kellogg Brown & Root, Inc. (KBR) Matti Nurminen Fortum Oil and Gas Oy INTRODUCTION Environmental issues are threatening the future use of MTBE (methyl-tert-butyl ether) in gasoline in the United States. Since the late 1990s, concerns have arisen over ground and drinking water contamination with MTBE due to leaking of gasoline from underground storage tanks and the exhaust from two-cycle engines. In California a number of cases of drinking water pollution with MTBE have occurred. As a result, the elimination of MTBE in gasoline in California was mandated, and legislation is now set to go in effect by the end of 2003. The U.S. Senate has similar law under preparation, which would eliminate MTBE in the 2006 to 2010 time frame. With an MTBE phase-out imminent, U.S. refiners are faced with the challenge of replacing the lost volume and octane value of MTBE in the gasoline pool. In addition, uti- lization of idled MTBE facilities and the isobutylene feedstock result in pressing problems of unrecovered and/or underutilized capital for the MTBE producers. Isooctane has been identified as a cost-effective alternative to MTBE. It utilizes the same isobutylene feeds used in MTBE production and offers excellent blending value. Furthermore, isooctane pro- duction can be achieved in a low-cost revamp of an existing MTBE plant. However, since isooctane is not an oxygenate, it does not replace MTBE to meet the oxygen requirement currently in effect for reformulated gasoline. The NExOCTANE technology was developed for the production of isooctane. In the process, isobutylene is dimerized to produce isooctene, which can subsequently be hydro- genated to produce isooctane. Both products are excellent gasoline blend stocks with sig- nificantly higher product value than alkylate or polymerization gasoline. Source: HANDBOOK OF PETROLEUM REFINING PROCESSES Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. 1.4 ALKYLATION AND POLYMERIZATION HISTORY OF MTBE During the 1990s, MTBE was the oxygenate of choice for refiners to meet increasingly strin- gent gasoline specifications. In the United States and in a limited number of Asian countries, the use of oxygenates in gasoline was mandated to promote cleaner-burning fuels. In addi- tion, lead phase-down programs in other parts of the world have resulted in an increased demand for high-octane blend stock. All this resulted in a strong demand for high-octane fuel ethers, and significant MTBE production capacity has been installed since 1990. Today, the United States is the largest consumer of MTBE. The consumption increased dramatically with the amendment of the Clean Air Act in 1990 which incorporated the 2 percent oxygen mandate. The MTBE production capacity more than doubled in the 5-year period from 1991 to 1995. By 1998, the MTBE demand growth had leveled off, and it has since tracked the demand growth for reformulated gasoline (RFG). The United States con- sumes about 300,000 BPD of MTBE, of which over 100,000 BPD is consumed in California. The U.S. MTBE consumption is about 60 percent of the total world demand. MTBE is produced from isobutylene and methanol. Three sources of isobutylene are used for MTBE production: ● On-purpose butane isomerization and dehydrogenation ● Fluid catalytic cracker (FCC) derived mixed C 4 fraction ● Steam cracker derived C 4 fraction The majority of the MTBE production is based on FCC and butane dehydrogenation derived feeds. NExOCTANE BACKGROUND Fortum Oil and Gas Oy, through its subsidiary Neste Engineering, has developed the NExOCTANE technology for the production of isooctane. NExOCTANE is an extension of Fortum’s experience in the development and licensing of etherification technologies. Kellogg Brown & Root, Inc. (KBR) is the exclusive licenser of NExOCTANE. The tech- nology licensing and process design services are offered through a partnership between Fortum and KBR. The technology development program was initialized in 1997 in Fortum’s Research and Development Center in Porvoo, Finland, for the purpose of producing high-purity isooctene, for use as a chemical intermediate. With the emergence of the MTBE pollution issue and the pending MTBE phase-out, the focus in the development was shifted in 1998 to the conver- sion of existing MTBE units to produce isooctene and isooctane for gasoline blending. The technology development has been based on an extensive experimental research program in order to build a fundamental understanding of the reaction kinetics and key product separation steps in the process. This research has resulted in an advanced kinetic modeling capability, which is used in the design of the process for licensees. The process has undergone extensive pilot testing, utilizing a full range of commercial feeds. The first commercial NExOCTANE unit started operation in the third quarter of 2002. PROCESS CHEMISTRY The primary reaction in the NExOCTANE process is the dimerization of isobutylene over acidic ion-exchange resin catalyst. This dimerization reaction forms two isomers of NExOCTANE™ TECHNOLOGY FOR ISOOCTANE PRODUCTION Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. NExOCTANE™ TECHNOLOGY FOR ISOOCTANE PROCUCTION 1.5 trimethylpentene (TMP), or isooctene, namely, 2,4,4-TMP-1 and 2,4,4-TMP-2, according to the following reactions: TMP further reacts with isobutylene to form trimers, tetramers, etc. Formation of these oligomers is inhibited by oxygen-containing polar components in the reaction mixture. In the Isobutylene 2 2,4,4 TMP-1 CH 2 = C - CH 3 CH 3 CH 2 = C - CH 2 - C - CH 3 CH 3 CH 3 CH 3 CH 2 - C = CH 2 - C - CH 3 CH 3 CH 3 CH 3 2,4,4 TMP-2 NExOCTANE process, water and alcohol are used as inhibitors. These polar components block acidic sites on the ion-exchange resin, thereby controlling the catalyst activity and increasing the selectivity to the formation of dimers. The process conditions in the dimer- ization reactions are optimized to maximize the yield of high-quality isooctene product. A small quantity of C 7 and C 9 components plus other C 8 isomers will be formed when other olefin components such as propylene, n-butenes, and isoamylene are present in the reaction mixture. In the NExOCTANE process, these reactions are much slower than the isobutylene dimerization reaction, and therefore only a small fraction of these components is converted. Isooctene can be hydrogenated to produce isooctane, according to the following reaction: CH 2 – C – CH 2 – C – CH 3 CH 3 CH 3 CH 3 IsooctaneIsooctene CH 2 = C – CH 2 – C – CH 3 + H 2 CH 3 CH 3 CH 3 NExOCTANE PROCESS DESCRIPTION The NExOCTANE process consists of two independent sections. Isooctene is produced by dimerization of isobutylene in the dimerization section, and subsequently, the isooctene can be hydrogenated to produce isooctane in the hydrogenation section. Dimerization and hydrogenation are independently operating sections. Figure 1.1.1 shows a simplified flow diagram for the process. The isobutylene dimerization takes place in the liquid phase in adiabatic reactors over fixed beds of acidic ion-exchange resin catalyst. The product quality, specifically the distri- NExOCTANE™ TECHNOLOGY FOR ISOOCTANE PRODUCTION Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. bution of dimers and oligomers, is controlled by recirculating alcohol from the product recov- ery section to the reactors. Alcohol is formed in the dimerization reactors through the reaction of a small amount of water with olefin present in the feed. The alcohol content in the reactor feed is typically kept at a sufficient level so that the isooctene product contains less than 10 percent oligomers. The dimerization product recovery step separates the isooctene product from the unreacted fraction of the feed (C 4 raffinate) and also produces a concentrated alco- hol stream for recycle to the dimerization reaction. The C 4 raffinate is free of oxygenates and suitable for further processing in an alkylation unit or a dehydrogenation plant. Isooctene produced in the dimerization section is further processed in a hydrogenation unit to produce the saturated isooctane product. In addition to saturating the olefins, this unit can be designed to reduce sulfur content in the product. The hydrogenation section consists of trickle-bed hydrogenation reactor(s) and a product stabilizer. The purpose of the stabilizer is to remove unreacted hydrogen and lighter components in order to yield a product with a specified vapor pressure. The integration of the NExOCTANE process into a refinery or butane dehydrogenation complex is similar to that of the MTBE process. NExOCTANE selectively reacts isobuty- lene and produces a C 4 raffinate which is suitable for direct processing in an alkylation or dehydrogenation unit. A typical refinery integration is shown in Fig. 1.1.2, and an integra- tion into a dehydrogenation complex is shown in Fig. 1.1.3. NExOCTANE PRODUCT PROPERTIES The NExOCTANE process offers excellent selectivity and yield of isooctane (2,2,4- trimethylpentane). Both the isooctene and isooctane are excellent gasoline blending compo- nents. Isooctene offers substantially better octane blending value than isooctane. However, the olefin content of the resulting gasoline pool may be prohibitive for some refiners. The characteristics of the products are dependent on the type of feedstock used. Table 1.1.1 presents the product properties of isooctene and isooctane for products produced from FCC derived feeds as well as isooctane from a butane dehydrogenation feed. The measured blending octane numbers for isooctene and isooctane as produced from FCC derived feedstock are presented in Table 1.1.2. The base gasoline used in this analy- 1.6 ALKYLATION AND POLYMERIZATION Dimerization Product Recovery Hydrogenation Reaction Stabilizer Isobutylene C 4 Raffinate Alcohol Recycle Isooctane Hydrogen Fuel Gas Isooctene DIMERIZATION SECTION HYDROGENATION SECTION FIGURE 1.1.1 NExOCTANE process. NExOCTANE™ TECHNOLOGY FOR ISOOCTANE PRODUCTION Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. sis is similar to nonoxygenated CARB base gasoline. Table 1.1.2 demonstrates the signif- icant blending value for the unsaturated isooctene product, compared to isooctane. PRODUCT YIELD An overall material balance for the process based on FCC and butane dehydrogenation derived isobutylene feedstocks is shown in Table 1.1.3. In the dehydrogenation case, an isobutylene feed content of 50 wt % has been assumed, with the remainder of the feed NExOCTANE™ TECHNOLOGY FOR ISOOCTANE PROCUCTION 1.7 FCC ALKYLATIONDIMERIZATION Hydrogen Isooctane Isooctene HYDROGENATION C 4 C 4 Raffinate NExOCTANE FIGURE 1.1.2 Typical integration in refinery. HYDROGE- NATION DEHYDRO Hydrogen Isooctan e Isoocten e DIMERIZATION iC 4 = NExOCTANE Butane HYDROGEN TREATMENT RECYCLE TREATMENT ISOMERI- ZATION DIB C 4 Raffinate FIGURE 1.1.3 Integration in a typical dehydrogenation complex. NExOCTANE™ TECHNOLOGY FOR ISOOCTANE PRODUCTION Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. mostly consisting of isobutane. For the FCC feed an isobutylene content of 22 wt % has been used. In each case the C 4 raffinate quality is suitable for either direct processing in a refinery alkylation unit or recycle to isomerization or dehydrogenation step in the dehy- drogenation complex. Note that the isooctene and isooctane product rates are dependent on the content of isobutylene in the feedstock. UTILITY REQUIREMENTS The utilities required for the NExOCTANE process are summarized in Table 1.1.4. 1.8 ALKYLATION AND POLYMERIZATION TABLE 1.1.1 NExOCTANE Product Properties FCC C 4 Butane dehydrogenation Isooctane Isooctene Isooctane Specific gravity 0.704 0.729 0.701 RONC 99.1 101.1 100.5 MONC 96.3 85.7 98.3 (R ϩ M) / 2 97.7 93.4 99.4 RVP, lb/in 2 absolute 1.8 1.8 1.8 TABLE 1.1.2 Blending Octane Number in CARB Base Gasoline (FCC Derived) Isooctene Isooctane Blending BRON BMON (R ϩ M) / 2 BRON BMON (R ϩ M) / 2 volume, % 10 124.0 99.1 111.0 99.1 96.1 97.6 20 122.0 95.1 109.0 100.1 95.1 97.6 100 101.1 85.7 93.4 99.1 96.3 97.7 TABLE 1.1.3 Sample Material Balance for NExOCTANE Unit Material balance FCC C 4 feed, lb/h (BPD) Butane dehydrogenation, lb/h (BPD) Dimerization section: Hydrocarbon feed 137,523 (16,000) 340,000 (39,315) Isobutylene contained 30,614 (3,500) 170,000 (19,653) Isooctene product 30,714 (2,885) 172,890 (16,375) C 4 raffinate 107,183 (12,470) 168,710 (19,510) Hydrogenation section: Isooctene feed 30,714 (2,885) 172,890 (16,375) Hydrogen feed 581 3752 Isooctane product 30,569 (2,973) 175,550 (17,146) Fuel gas product 726 1092 NExOCTANE™ TECHNOLOGY FOR ISOOCTANE PRODUCTION Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. NExOCTANE TECHNOLOGY ADVANTAGES Long-Life Dimerization Catalyst The NExOCTANE process utilizes a proprietary acidic ion-exchange resin catalyst. This catalyst is exclusively offered for the NExOCTANE technology. Based on Fortum’s exten- sive catalyst trials, the expected catalyst life of this exclusive dimerization catalyst is at least double that of standard resin catalysts. Low-Cost Plant Design In the dimerization process, the reaction takes place in nonproprietary fixed-bed reactors. The existing MTBE reactors can typically be reused without modifications. Product recov- ery is achieved by utilizing standard fractionation equipment. The configuration of the recovery section is optimized to make maximum use of the existing MTBE product recov- ery equipment. High Product Quality The combination of a selective ion-exchange resin catalyst and optimized conditions in the dimerization reaction results in the highest product quality. Specifically, octane rating and specific gravity are better than those in product produced with alternative catalyst systems or competing technologies. State-of-the-Art Hydrogenation Technology The NExOCTANE process provides a very cost-effective hydrogenation technology. The trickle-bed reactor design requires low capital investment, due to a compact design plus once-through flow of hydrogen, which avoids the need for a recirculation compressor. Commercially available hydrogenation catalysts are used. Commercial Experience The NExOCTANE technology is in commercial operation in North America in the world’s largest isooctane production facility based on butane dehydrogenation. The project includes a grassroots isooctene hydrogenation unit. NExOCTANE™ TECHNOLOGY FOR ISOOCTANE PROCUCTION 1.9 TABLE 1.1.4 Typical Utility Requirements Utility requirements FCC C 4 Butane dehydrogenation per BPD of product per BPD of product Dimerization section: Steam, 1000 lb/h 13 6.4 Cooling water, gal/min 0.2 0.6 Power, kWh 0.2 0.03 Hydrogenation section: Steam, 1000 lb/h 1.5 0.6 Cooling water, gal/min 0.03 0.03 Power, kWh 0.03 0.1 NExOCTANE™ TECHNOLOGY FOR ISOOCTANE PRODUCTION Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. CHAPTER 1.2 STRATCO EFFLUENT REFRIGERATED H 2 SO 4 ALKYLATION PROCESS David C. Graves STRATCO Leawood, Kansas INTRODUCTION Alkylation, first commercialized in 1938, experienced tremendous growth during the 1940s as a result of the demand for high-octane aviation fuel during World War II. During the mid-1950s, refiners’ interest in alkylation shifted from the production of aviation fuel to the use of alkylate as a blending component in automotive motor fuel. Capacity remained relatively flat during the 1950s and 1960s due to the comparative cost of other blending components. The U.S. Environmental Protection Agency’s lead phase-down pro- gram in the 1970s and 1980s further increased the demand for alkylate as a blending com- ponent for motor fuel. As additional environmental regulations are imposed on the worldwide refining community, the importance of alkylate as a blending component for motor fuel is once again being emphasized. Alkylation unit designs (grassroots and revamps) are no longer driven only by volume, but rather by a combination of volume, octane, and clean air specifications. Lower olefin, aromatic, sulfur, Reid vapor pressure (RVP), and drivability index (DI) specifications for finished gasoline blends have also become driving forces for increased alkylate demand in the United States and abroad. Additionally, the probable phase-out of MTBE in the United States will further increase the demand for alkylation capacity. The alkylation reaction combines isobutane with light olefins in the presence of a strong acid catalyst. The resulting highly branched, paraffinic product is a low-vapor-pres- sure, high-octane blending component. Although alkylation can take place at high temper- atures without catalyst, the only processes of commercial importance today operate at low to moderate temperatures using either sulfuric or hydrofluoric acid catalysts. Several dif- ferent companies are currently pursuing research to commercialize a solid alkylation cat- alyst. The reactions occurring in the alkylation process are complex and produce an alkylate product that has a wide boiling range. By optimizing operating conditions, the 1.11 Source: HANDBOOK OF PETROLEUM REFINING PROCESSES Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. [...]... reserved Any use is subject to the Terms of Use as given at the website Source: HANDBOOK OF PETROLEUM REFINING PROCESSES CHAPTER 1.3 UOP ALKYLENE™ PROCESS FOR MOTOR FUEL ALKYLATION Cara Roeseler UOP LLC Des Plaines, Illinois INTRODUCTION The UOP Alkylene process is a competitive and commercially available alternative to liquid acid technologies for alkylation of light olefins and isobutane Alkylate... is subject to the Terms of Use as given at the website Source: HANDBOOK OF PETROLEUM REFINING PROCESSES CHAPTER 1.4 UOP HF ALKYLATION TECHNOLOGY Kurt A Detrick, James F Himes, Jill M Meister, and Franz-Marcus Nowak UOP Des Plaines, Ilinois INTRODUCTION The UOP* HF Alkylation process for motor fuel production catalytically combines light olefins, which are usually mixtures of propylene and butylenes,... relative to those of other moving catalyst processes The reaction time is on the order of minutes for the completion of the primary reactions and to minimize secondary reactions The catalyst and hydrocarbon are intimately mixed during the reaction, and the catalyst is easily disengaged from the hydrocarbon product at the top of the reactor The catalyst is reactivated by a simple hydrogenation of the heavier... consumption is minimal as the quantity of heavy alkylate on the HAL-100 catalyst is very small The reactivation process is highly effective, restoring the activity of the catalyst to nearly 100 percent of fresh The liquid-phase operation of the Alkylene process results in less abrasion than in other catalyst circulation processes due to the lubricating effect of the liquid Furthermore, the catalyst... fractionation section of the alkylation unit is not simply a product separation section; it also provides a recycle isobutane stream To meet overall gasoline pool RVP requirements, many of the recent alkylation designs require an alkylate RVP of 4 to 6 lb/in2 (0.28 to 0.42 kg/cm2) To reduce the RVP of the alkylate, a large portion of the n-butane and isopentane must be removed Low C5ϩ content of the n-butane... units for new installations, and refiners had begun to gradually phase out the operation of existing polymerization plants The importance of the HF Alkylation process in the refining situation of the 2000s has been increased even further by the scheduled phase-out of MTBE and the increased *Trademark and/or service mark of UOP 1.33 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)... from a single olefin constitutes only a percentage of the alkylate because of the variety of concurrent reactions that are possible in the alkylation environment Compositions of pilot-plant products produced at conditions to maximize octane from pure-olefin feedstocks are shown in Table 1.4.1 Reaction Mechanism Alkylation is one of the classic examples of a reaction or reactions proceeding via the carbenium... optimization of the reaction conditions The design of the internal feed distributor has been modified to ensure concurrent contact of the acid catalyst and olefin/isobutane mixture at the point of initial contact The Contactor reactor hydraulic head has been modified to include a modern, cartridgetype mechanical seal system This results in a reliable, easy-to-maintain, and long-lasting seal system STRATCO offers... operation of reaction zones in autorefrigerated reactors Reliability One of the primary factors affecting the reliability of an alkylation unit is the number and type of mechanical seals required in the reaction zone Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of. .. distribution to allow for good mass transfer of reactants and products into and out of the catalyst The catalyst has been commercially produced and demonstrates high physical strength and very low attrition rates in extensive physical testing Catalyst attrition rates are several orders of magnitude lower than those experienced in other moving-bed regeneration processes in the refining industry HAL-100 has been . understanding of the reaction kinetics and key product separation steps in the process. This research has resulted in an advanced kinetic modeling capability,. in the Contactor reactor tube bundle as the net effluent stream removes the heat of reaction. The two-phase net effluent stream flows to the suction trap/flash