HANDBOOK OF PETROLEUM REFINING PROCESSES (www ebookbyte com)

Source: HANDBOOK OF PETROLEUM REFINING PROCESSES P ● A ● R ● T ● ALKYLATION AND POLYMERIZATION 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 Source: HANDBOOK OF PETROLEUM REFINING PROCESSES 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, utilization 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 production 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 hydrogenated to produce isooctane Both products are excellent gasoline blend stocks with significantly higher product value than alkylate or polymerization gasoline 1.3 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 PRODUCTION 1.4 ALKYLATION AND POLYMERIZATION HISTORY OF MTBE During the 1990s, MTBE was the oxygenate of choice for refiners to meet increasingly stringent 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 addition, 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 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 consumes 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 C4 fraction Steam cracker derived C4 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 technology 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 conversion 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 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 PRODUCTION 1.5 NExOCTANE™ TECHNOLOGY FOR ISOOCTANE PROCUCTION 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 CH3 CH3 CH2 = C - CH2 - C - CH3 CH3 CH3 2,4,4 TMP-1 CH2= C - CH3 CH3 Isobutylene CH3 CH2 - C = CH2 - C - CH3 CH3 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 dimerization reactions are optimized to maximize the yield of high-quality isooctene product A small quantity of C7 and C9 components plus other C8 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: CH3 CH3 CH2 = C – CH2 – C – CH3 + H2 CH3 Isooctene CH3 CH3 CH2 – C – CH2 – C – CH3 CH3 Isooctane 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- 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 PRODUCTION 1.6 ALKYLATION AND POLYMERIZATION C4 Raffinate Isooctene Isobutylene Dimerization Product Recovery Hydrogen Hydrogenation Reaction Fuel Gas Isooctane Stabilizer Alcohol Recycle DIMERIZATION SECTION HYDROGENATION SECTION FIGURE 1.1.1 NExOCTANE process bution of dimers and oligomers, is controlled by recirculating alcohol from the product recovery 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 (C4 raffinate) and also produces a concentrated alcohol stream for recycle to the dimerization reaction The C4 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 isobutylene and produces a C4 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 integration into a dehydrogenation complex is shown in Fig 1.1.3 NExOCTANE PRODUCT PROPERTIES The NExOCTANE process offers excellent selectivity and yield of isooctane (2,2,4trimethylpentane) Both the isooctene and isooctane are excellent gasoline blending components 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 analyDownloaded 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 PRODUCTION 1.7 NExOCTANE™ TECHNOLOGY FOR ISOOCTANE PROCUCTION C4 C4 Raffinate DIMERIZATION ALKYLATION FCC Isooctene Hydrogen HYDROGENATION Isooctane NExOCTANE FIGURE 1.1.2 Typical integration in refinery NExOCTANE Isooctene iC4= DEHYDRO Butane DIB DIMERIZATION HYDROGEN TREATMENT RECYCLE TREATMENT HYDROGENATION Isooctane Hydrogen C4 Raffinate ISOMERIZATION FIGURE 1.1.3 Integration in a typical dehydrogenation complex sis is similar to nonoxygenated CARB base gasoline Table 1.1.2 demonstrates the significant 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 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 PRODUCTION 1.8 ALKYLATION AND POLYMERIZATION TABLE 1.1.1 NExOCTANE Product Properties FCC C4 Butane dehydrogenation Isooctane Isooctene Isooctane 0.704 99.1 96.3 97.7 1.8 0.729 101.1 85.7 93.4 1.8 0.701 100.5 98.3 99.4 1.8 Specific gravity RONC MONC (R ⫹ M) / RVP, lb/in2 absolute TABLE 1.1.2 Blending Octane Number in CARB Base Gasoline (FCC Derived) Isooctene Isooctane Blending volume, % BRON BMON (R ⫹ M) / BRON 10 20 100 124.0 122.0 101.1 99.1 95.1 85.7 111.0 109.0 93.4 99.1 100.1 99.1 TABLE 1.1.3 BMON 96.1 95.1 96.3 (R ⫹ M) / 97.6 97.6 97.7 Sample Material Balance for NExOCTANE Unit Material balance Dimerization section: Hydrocarbon feed Isobutylene contained Isooctene product C4 raffinate Hydrogenation section: Isooctene feed Hydrogen feed Isooctane product Fuel gas product FCC C4 feed, lb/h (BPD) 137,523 30,614 30,714 107,183 (16,000) (3,500) (2,885) (12,470) 30,714 (2,885) 581 30,569 (2,973) 726 Butane dehydrogenation, lb/h (BPD) 340,000 170,000 172,890 168,710 (39,315) (19,653) (16,375) (19,510) 172,890 (16,375) 3752 175,550 (17,146) 1092 mostly consisting of isobutane For the FCC feed an isobutylene content of 22 wt % has been used In each case the C4 raffinate quality is suitable for either direct processing in a refinery alkylation unit or recycle to isomerization or dehydrogenation step in the dehydrogenation 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 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 PRODUCTION NExOCTANE™ TECHNOLOGY FOR ISOOCTANE PROCUCTION 1.9 TABLE 1.1.4 Typical Utility Requirements Utility requirements FCC C4 per BPD of product Butane dehydrogenation per BPD of product 13 0.2 0.2 6.4 0.6 0.03 Dimerization section: Steam, 1000 lb/h Cooling water, gal/min Power, kWh Hydrogenation section: Steam, 1000 lb/h Cooling water, gal/min Power, kWh 1.5 0.03 0.03 0.6 0.03 0.1 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 extensive 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 recovery is achieved by utilizing standard fractionation equipment The configuration of the recovery section is optimized to make maximum use of the existing MTBE product recovery 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 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 Source: HANDBOOK OF PETROLEUM REFINING PROCESSES CHAPTER 1.2 STRATCO EFFLUENT REFRIGERATED H2SO4 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 program in the 1970s and 1980s further increased the demand for alkylate as a blending component 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-pressure, high-octane blending component Although alkylation can take place at high temperatures without catalyst, the only processes of commercial importance today operate at low to moderate temperatures using either sulfuric or hydrofluoric acid catalysts Several different companies are currently pursuing research to commercialize a solid alkylation catalyst 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 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 ...Source: HANDBOOK OF PETROLEUM REFINING PROCESSES P ● A ● R ● T ● ALKYLATION AND POLYMERIZATION Downloaded from Digital Engineering Library @ McGraw-Hill (www. digitalengineeringlibrary .com) Copyright... subject to the Terms of Use as given at the website Source: HANDBOOK OF PETROLEUM REFINING PROCESSES CHAPTER 1.1 NExOCTANE™ TECHNOLOGY FOR ISOOCTANE PRODUCTION Ronald Birkhoff Kellogg Brown &... 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 Source: HANDBOOK OF PETROLEUM