Oct-2011

Improved performance from reforming

Process and equipment solutions help to improve the profitability and reliability of reforming units

Anthony Poparad, Beatrix Ellis, Bryan Glover and Stephen Metro
UOP LLC, A Honeywell Company

Article Summary

Catalytic reforming continues to play an important role in meeting the world’s demands for high octane gasoline, petrochemicals and hydrogen. Due to shifting market demands and ageing equipment, many of today’s reforming units are operating under a much different set of conditions than for what they were originally designed.

Since its inception in the 1940s, catalytic reforming has played an important role in helping refiners convert heavy naphtha feedstock into high octane reformate for gasoline blending and high purity hydrogen for use in hydrotreating and hydrocracking applications. The first reforming units were operated in a semi-regenerative fashion and needed to be taken offline 
periodically to regenerate the monometallic platinum-containing reforming catalyst. To maximise cycle lengths, the first fixed-bed reforming units operated at relatively high pressures (up to 500 lb/ in2g), since reforming catalyst stability increases with rising pressure. In reforming, however, catalyst selectivity to desired products increases with decreasing pressure.  So low pressures are desirable to maximise catalyst selectivity. Through the 1950s and 1960s, advances were made to increase the stability of reforming catalysts by adding stability-enhancing rhenium to the catalyst. This allowed for operation at lower pressures (generally 200 to 300 lb/in2g), which improved the selectivity to desired products considerably. The new bimetallic reforming catalysts also allowed for higher severity operations while maintaining acceptable cycle lengths.¹ A block flow diagram of a UOP Fixed-Bed Platforming Process unit is shown in Figure 1.

Despite further catalyst innovations to improve catalyst stability, by the mid-1960s fixed-bed reforming units could not keep up with the increasing demand for octane barrels of reformate. Other technology licensors developed the cyclic reforming process, where individual reactors can be swung offline, regenerated and returned to service without the need to shut down the entire unit. UOP responded by developing a new reforming process with continuous catalytic regeneration, the CCR Platforming Process. The first CCR Platforming Process unit was started up in 1971. In CCR reforming, catalyst flows through the reactors in series instead of remaining static in fixed beds of individual reactors. Spent catalyst is continuously removed from the last reactor, transferred to the regeneration section, regenerated in a controlled environment and transferred back to the first reactor. Since the catalyst is regenerated much more frequently in CCR reforming than in fixed-bed reforming, much higher severity operation is possible. In addition to making high octane reformate for gasoline blending, many CCR reforming units are used to create feedstocks for aromatics complexes, since the reformate product contains a high concentration of C6-C10 range aromatics.

Modern CCR Platforming units operate at pressures as low as 35 lb/in2g, which allows for a high selectivity to desired products (C5+ reformate and hydrogen) and a minimal production of undesired products (methane, ethane and LPG).¹ Since the first CCR Platforming unit was started up, UOP has developed and continues to develop many significant innovations to the process configuration and individual pieces of equipment. CCR reforming catalysts still contain platinum, which is required to catalyse important reforming reactions. The level of platinum required on the catalyst has been considerably reduced over time as feedstock contaminant levels and regeneration quality have improved. Rhenium is not used, since CCR reforming catalysts do not need to be as stable as fixed-bed reforming catalysts. However, CCR reforming catalysts do use other metals, most notably tin, to enhance catalyst selectivity. While most CCR reforming catalysts are bimetallic (containing platinum and tin), other proprietary promoter metals are also used in some catalysts, with their objective being catalyst selectivity enhancement. More than 300 CCR reforming units have been licensed throughout the world,² with more than 250 of those being UOP CCR Platforming Process units. A block flow diagram of a typical CCR Platforming Process unit is shown in Figure 2.

Recent shifts in the demand for reformate (used for both gasoline blending and petrochemicals production) and hydrogen have caused many reforming unit operators to have to adjust their operations considerably from their initial designs. This has caused many reforming units to be operated in a less efficient manner. Many reforming units that were designed decades ago are also more prone to reliability issues.

Gasoline demand and utilisation
Reformate is an aromatics-rich, high octane intermediate that is produced in catalytic reforming units from heavy naphtha feedstock. Its two primary applications include use as a high octane blending component in gasoline and as an aromatics-rich petrochemical feedstock. We will review the reformate market to better understand the market situation and issues facing today’s reforming units. The reformate market is really a subset of the gasoline and aromatics markets, which, are in turn, subsets of the refining and petrochemicals markets. This section focuses on reformate produced for the gasoline market. 

Current worldwide gasoline consumption exceeds 22 million 
b/d. Growth is expected to be moderate, with a projected compounded annual growth rate (CAGR) of 1.30% from 2010 to 2016, based upon data from the Purvin & Gertz Global Petroleum Market Outlook (GPMO).3 Almost half of the gasoline produced today is being consumed in North America. Other regions such as Europe, Asia Pacific, China, Middle East and Latin America are consuming 1–3 million BPSD each. Product demand for these various regions is shown in Figure 3 and Table 1^.3

Gasoline demand in North America is relatively flat and declining in Europe, while the major growth is occurring in emerging regions such as China (7.7%), India (6.8%) and the Middle East (3.3%). These trends also track regional demand for refined product, as shown in Table 1.

In China, gasoline demand is projected to grow from 1.6 to 2.5 million b/d between 2010 and 2016. To satisfy this increase in demand, China would have to add approximately five CCR reforming units annually over the next five years. Based upon capacity projections and average unit sizes, the rest of the world would also need to add approximately five similar CCR reforming units annually over the next five years.