Newsletter 10 Zeolite And Fuel

FCC Network News March 2001 Volume 10 UPDATE ON NPRA ANNUAL MEETING The National Petrochemical and Refiners (NPRA) annual meeting was held from March 18th to the 20th in New Orleans, Louisiana. Key themes for the meeting included FCC gasoline desulfurization, technologies for producing ultra low sulfur diesel, refining management and financial trends, and technology trends for clean fuels production and hydrocarbon processing. Although there seemed to be a less extensive selection of technical papers related to fluid catalytic cracking, there were a number of papers that provided good technical information on advances in both process and catalyst technology. All FCC related papers were reviewed by the editors and key highlights from several were selected for presentation in this edition. Additional papers will be reviewed in April and May. ENGELHARD DESCRIBES NEW NAPHTHAMAX ™ TECHNOLOGY NPRA Paper AM-01-58, written by Joseph McLean and David Stockwell, details the NaphthaMax™ FCC catalyst technology recently introduced by Engelhard Corporation. Engelhard reports that NaphthaMax™ represents a breakthrough catalyst technology for short contact time (SCT) FCC applications. It is well known that for most SCT applications, coke and dry gas are reduced and the yields of desirable products are increased. However, because of reduced contact time, it is typically necessary to increase catalyst activity by 3 to 5 numbers and use a more selective matrix for bottoms conversion. NaphthaMax™ has been developed by Engelhard from the FACT platform and combines the new Distributed Matrix Structure (DMS) and the PyrochemPlus zeolite to provide a unique catalyst structure. It is commonly accepted that an important role of the catalyst matrix is to pre-crack heavy oil molecules so that they can diffuse to the crystalline zeolite for conversion to gasoline and lighter products. While effective at pre-cracking large molecules, current amorphous alumina or silica-alumina matrix materials can also produce significant by-product coke and gas. NapthaMax™ introduces a new concept, the zeolite DMS structure, which provides enhanced diffusion of feed molecules to pre-cracking sites located on the external, exposed surface of highly dispersed crystals. The feed then pre-cracks on zeolite rather than amorphous material. This approach is designed to provide high bottoms conversion with low coke and higher yields of gasoline and light olefin products.

FCC Network News – Page 2 ENGELHARD PRESENTS COMMERCIAL RESULTS FOR NAPHTHAMAX ™ The Engelhard paper, AM-01-58, presented results for three refinery trials. In all three cases, unit conversion increased with total C3+ liquid yields increasing by 3 to 6 volume %. Yields of gasoline and light olefins increased, while both slurry yield and slurry gravity dropped. In the second and third cases, slurry gravity was reduced to levels of –3 and –4, respectively. Regenerator temperature dropped in all three cases (full combustion) and dry gas yields were the same or lower. We hope to post a copy of the paper on the site soon. IRON CAN SIGNIFICANTLY IMPACT FCC CATALYST PERFORMANCE NPRA Paper AM-01-58, written by George Yaluris and several of his colleagues at Davison Catalysts, highlights the results of recent work in the area of FCC catalyst iron contamination. Tramp iron in feed has been shown to be fairly benign in FCC units, but iron that is finely dispersed or bound into organic molecules can cause problems with FCC catalyst performance. Davison researchers found that as FCC catalyst iron content increases significantly, apparent bulk density can actually decrease. Electron probe studies show that iron and calcium in combination with components of the catalyst surface can form a glass phase on the outer surface of the catalyst particle that covers the entire surface with a thickness of 1 to 3 microns. Depending on composition, the glassy phase can melt at temperatures as low as 932F, thereby forming surface nodules that prevent catalyst particles from coming in close contact with one another. This reportedly causes the observed reduction in catalyst bulk density. In certain instances, Davison found that the glass phase flowed into the outer pores of the catalyst, resulting in reduced molecular access and lost cracking activity. Davison presented results showing that this effect is predominant with silica-rich surfaces, while aluminarich surfaces seem to form higher melting point phases that do not result in pore blockage. The paper outlined steps for monitoring and reducing the impact of iron contamination in FCC. Feed quality should be monitored and if possible, high iron components should be reduced in or eliminated from FCC feed blends. Carefully consider the usage of high acid content feeds that may cause corrosion and result in finely dispersed iron. Also, consider desalting feed to remove the sodium and calcium fluxing agents that combine with iron to form the glassy crust. Finally, The FCC Network contains several papers describing the MagnaCat™ process for magnetic separation of FCC catalyst. This process will selectively remove the most metals-laden (including high iron particles) from the circulating inventory.

FCC Network News – Page 3 FCC GASOLINE DESULFURIZATION TECHNOLOGY COMMERCIALIZED NPRA Paper AM-01-43, written by representatives of Phillips Petroleum and Fluor Daniel, describes the project to install the Phillips S Zorb process at the Phillips Borger refinery. Previous issues of FCC Network News cover the principles of this fluidized bed process in detail. The paper focused on the details of project execution, while the presentation provided additional details regarding project status. Fluidization studies were completed in a cold flow model. The S Zorb unit at Borger will process FCC gasoline derived from cracking hydrotreated resid. Cat gasoline sulfur levels are expected to range from 250 to 1000 ppm with olefin content of 20% to 25%. Octane loss is expected to be less than 0.5 numbers, with hydrogen consumption of 50 SCFB. The unit is mechanically complete and has been pressure tested. The gas compressor is circulating nitrogen, gasoline is circulating through the stabilizer and the reactor is hot. It is anticipated that feed will be in the unit by the end of March. NPRA Paper AM-01-11, written by representatives of CDTech and Motiva Enterprises, LLC, details the 2000 start-up of the first CDHDS® Unit at the Motiva refinery in Port Arthur, Texas. The unit was mechanically complete in March 2000. Heavy cat naphtha (HCN) with 450F EP and 5200 ppm sulfur was introduced to the unit on May 14, 2000. The core of the process is a proprietary structure containing conventional HDS catalyst installed in a column where simultaneous reaction and distillation take place. Desulfurization levels of 97% to 98% were achieved with octane loss averaging slightly less than one number. Mercaptan levels in the HCN have been low enough for blending with no further treatment required. Since start-up, the feed surge drum has been modified with a coalescing element to eliminate water carryover. NPRA Paper AM-01-39, written by representatives of Irving oil and CDTech, describes the start-up of the first CDHYDRO®/CDHDS® unit at the Irving Oil refinery in Saint John, New Brunswick. In this process, full range catalytic naphtha (FRCN) is fractionated in the CDHYDRO column into light catalytic naphtha (LCN) and a combined medium and heavy cat naphtha (MCN/HCN). The top of the fractionating column contains a bed of nickel catalyst and hydrogen wherein mercaptans in the LCN are converted to high boiling sulfides that condense into the MCN/HCN. CDHYDRO column bottoms are fed to a CDHDS column where feed is fractionated in beds of structured packing containing Co-Mo catalyst into MCN and HCN cuts. This process configuration results in significantly less mercaptan in the reactor overhead compared with conventional HDS. Desulfurization was maintained at 80% during initial

FCC Network News – Page 4 FCC GASOLINE DESULFURIZATION (Continued) operation, with an average octane loss of one number. CDTech is improving the design of the catalyst CDModules to facilitate quicker unloading and reloading. These improvements will be utilized for a new CDHydro/CDHDS installation at Texaco Pembroke later this year. WHAT ARE THE ADVANTAGES OF PACKING A CATALYST STRIPPER? NPRA Paper AM-01-65, written by Warren Letzsch of Stone & Webster Engineering, describes the commercial impact of recent advances in fluid catalytic cracking technology. Much of the paper is devoted to the proposed advantages of packing a catalyst stripper. In a completely empty stripper vessel, at a mass flux of 1200 pounds per square foot per minute, superficial catalyst velocity would be 0.5 feet per second. When the disc and donut internals are installed at a the same mass flux (1200), maximum catalyst velocity can increase to as high as 1.5 feet per second because of the reduction in open flow area. At a catalyst velocity of 1.5 feet second, smaller gas bubbles (up to 1.8 inches in diameter) would be entrained downward and potentially carried to the regenerator with the catalyst. With structured packing, the stripper open flow area is greater, thereby reducing both catalyst velocity and bubble retention. The paper contained limited data from a commercial application showing that hydrogen in coke dropped from 7% to 6% by weight. Additional data was presented showing that the level of hydrocarbon in the flue gas dropped from an average 1.0 mol% to about 0.5 mol%. The refiner has taken advantage of this improved stripper performance by increasing unit the feed rate. The paper also described developments in feed injection, riser termination, axial spent catalyst introduction into the regenerator and catalyst cooling. USE PROCESS CHEMICALS TO SOLVE MANY FCC UNIT PROBLEMS Nalco-Exxon Energy Chemicals web site (www.nalcoexxon.com) has been upgraded with lots of great information regarding the use of process chemicals and monitoring programs to solve FCC operating and product problems. The site provides detailed information and many useful case studies on the following FCC related topics and describes solutions for many other refining problem areas.







Use of Settling Aids to Reduce Cat Fines and Make Carbon Black Oil Improve FCC Gasoline and Diesel Fuel Stability Control Corrosion in FCC Overhead Systems Control of Fouling in the FCC Slurry Circuit Metals Passivation to Improve FCC Operating Performance Use of Salt Dispersant to Improve Tower Performance

FCC Network News – Page 5 NEW FCC UNIT TROUBLESHOOTING FORUM Refining Process Services, a leader in providing technical training to the petroleum refining industry, will be offering a new unique public seminar program focused on solving common operating problems on the Fluid Catalytic Cracking Unit. The program will offer those in attendance the opportunity to interact with a panel of experts on a variety of FCC topics in an open discussion format. Topics covered will include start-up, feed injection, stripping, fractionation and gas plant, cyclones, refractory, expansion joints, air distributors, turnaround planning, rotating equipment, circulation problems, slide and plug valves, corrosion and environmental issues. Fluid Catalytic Cracking is an extremely complex process and as a result, operators and engineers can encounter numerous and difficult problems. An impressive team of experts has been assembled for this forum, with the experience to address and resolve virtually all types of FCC related problems. The forum will provide participants with an opportunity to utilize the panel’s experience and to receive advice, guidance and assistance from some of the best sources in the industry. In addition, those in attendance will be encouraged to relate their operating experiences to the group, facilitating the sharing of innovative solutions to difficult FCC design, operating and equipment problems. The FCC Unit Troubleshooting Forum will be offered in Houston Texas during September 13 and 14, 2001. For further information, please contact Refining Process Services via email at [email protected]. MONTHLY FEATURE PROVIDES ANSWERS TO YOUR QUESTIONS Each month we hope to post one question submitted by members of The FCC Network. This month’s question is: What is the effect of FCC unit conversion on FCC gasoline sulfur content? As FCC conversion increases, more of the feed sulfur molecules crack. Most of the converted sulfur ends up as H2S, but some goes to LCO and gasoline. As conversion increases, some gasoline sulfur will crack to H2S, but some heavier sulfur molecules will convert to gasoline range sulfur molecules. So with increasing conversion, gasoline sulfur is both created and destroyed. Therefore, the impact of higher conversion on gasoline sulfur is a function of many factors including type of sulfur species in feed, catalyst type, level of conversion, reaction temperature (catalytic vs. thermal cracking), contact time and cat-to-oil ratio. Generally, raising conversion by increasing cat-to-oil ratio will result in a slight decrease in gasoline sulfur content. However, if conversion is increased by raising both feed and reaction temperature simultaneously at constant cat-to-oil,

FCC Network News – Page 6 CONVERSION IMPACT ON GASOLINE SULFUR (Continued) then gasoline sulfur content will tend to increase. Trends observed for a specific FCC unit are dependent on feed sulfur species and operating conditions, which determine the relative rates of gasoline sulfur molecule creation and destruction. Two of the best papers on the subject include a 1971 paper titled “Sulfur Distribution in FCC Products” by E. G. Wollaston et al (API meeting paper) and “Feed-Sulfur Distribution in FCC Product” by G. Huling (Oil and Gas Journal – May 19, 1975). The Wollaston paper shows gasoline sulfur increasing as a function of conversion in the middle range of 50 to 65 volume %, but then dropping as conversion is increased to 70 volume % and beyond. Data in the Huling paper show gasoline sulfur either increasing or decreasing as a function of increased conversion, depending on feed type. For a severely hydrotreated gas oil, gasoline sulfur content increased significantly with higher conversion. However, for an unhydrotreated good quality ATB feed, gasoline sulfur dropped as conversion increased. In the end, like many other aspects of FCC, the impact of conversion on FCC gasoline sulfur content is a function of feedstock, catalyst, design and operating characteristics of each FCC unit. EXPANDING COVERAGE OF FCC PRODUCT RECOVERY ISSUES The FCC Network is working with Process Consulting Services, Inc. of Houston, TX to expand technical coverage of topics related to FCC product recovery. Process Consulting Services assists refiners in improving refinery operating performance through effective revamp design, optimization and troubleshooting assistance and equipment modification. A series of their technical papers has been added to the site. The primary focus of these papers is the recovery of FCC product in the main fractionator and recovery sections. To access these papers, visit the Technical papers section and scroll down the pull-down subject menu until you reach the very last subject on the list, FCC Product Recovery. “FCC Main Fractionator Revamps” “Improved Control Strategies Correct Main Fractionator Operating Problems” “Temperature, Pressure Measurements Solve Column Operating Problems” “Revamping FCCs – Process and Reliability” “FCC Gasoline Fractionation” “Improve the Reliability and Maintenance of FCCU Main Fractionator Internals” “Increase FCC Propylene Production and Recovery” “Pushing Plant Limits, Test Runs, Plant Expectations, Performance Confidence” “Simple Engineering Changes Fix Product Recovery Problems” “Case Studies Reveal Common Design, Equipment Errors in Revamp” Thanks for reading our newsletter. Staff of The FCC Network