Dec-2012

Cracking the code

How advanced catalysts enhance hydrocracking processes, showing that profits can be advanced by platinum group metals recovery and refining

Kevin M Beirne
Sabin Metal Corporation

Article Summary

It is now more than seven decades since the practical introduction of large-scale catalytic cracking for the processing of crude oil. The technology has advanced significantly since then (it was first developed in Germany circa 1915 to provide coal-based liquid fuels), according to a recent article1 by Russell Heinen, a director at INS Chemical. Catalytic cracking of crude oil led to “an important process breakthrough” (the Houdry process, Figure 1) that “coupled the endothermic cracking reaction with the exothermic reaction of catalyst regeneration in a cyclic, continuous operation,” Heinen added. “Significant developments since the 1940s, however, have made catalytic processes even more important to the modern petroleum refining and petrochemical/chemical processing industries,” he continued. In his article. Heinen cited the global value of process catalysts as a $13 billion business, with resultant products produced with the aid of catalysts valued at $500–600 billion.

Development of modern hydrocracking
However, it was not until the early 19605 that “modern” hydrocracking became even more cost effective for many practical processing applications. This was because of the introduction of zeolite-based catalysts, which offered significantly better performance than previous catalysts, including lower pressure operation that helps lower costs of building and operating hydrocrackers, according to Heinen. As would be expected, concurrent with production economies and advancements in catalytic cracking over this period, feedstock refiners have continually sought improved catalysts to help speed up processing. lower costs, reduce pollution and produce higher-quality end products from lower-quality feedstock. In addition, as catalyst technologies have become more sophisticated, more beneficial uses for catalysts have also kept up with improvements; namely, uses for catalysts in many new hydrocarbon processing applications as well as for chemical and petrochemical products.

However, as the Heinen article points out, “petroleum refining...is the source for the largest share of industrial products. Upgrading crude oil technology consists almost entirely of catalytic processes...[with the] largest catalyst segment in terms of value being catalytic cracking”. New catalyst materials being developed are not only geared towards enhanced processing throughput and use of lower-quality feedstocks, but environmental pressures have also “become the major driving forces in catalysis and process design,” Heinen adds.

As new catalyst developments improve the technology, in part driven by environmental regulation pressures, large-scalehydrocracking has been able to help increase production throughput significantly. Efficiency of scale now makes it possible for a hydrocracking plant to easily produce 100 000 bpd of cleaner distillates from “increasingly difficult feedstocks such as FCC light cycle oil (LCO), heavy vacuum gas oils (HVGO), and heavy coke gas oils (HCGO)”.2 Since there is a direct correlation between economy, lower-quality (more difficult) feedstocks and process steps to produce a variety of end products, improved catalysts have also been a key factor in enhancing profitability. Essentially, today’s sophisticated catalysts have made great strides by allowing lower-grade feedstocks to be used for producing higher-grade distillates, as well as minimising pollution problems through the production of cleaner fuels. In fact, modern catalysts are critical for this process.

One article² pointed out that: “Typical hydrocracking feedstocks include heavy atmospheric and vacuum gasoils, and catalytically or thermally cracked gas oils. These products are converted to lower molecular weight products, mainly naphtha or distillates. Sulphur, nitrogen and oxygen removal and olefin saturation occurs simultaneously with the hydrocracking reaction; because of the high reaction temperatures and pressures (in the region of 475°C and 215 bar) more “highly developed catalysts” have been introduced into the hydrocracking process over the past few decades”. The trend indicates that this will continue for some time.

Essentially, the hydrocracking process removes various feed contaminants (which typically include sulphur and nitrogen along with other unwanted materials) in order to convert low-quality feedstocks into more commercially useful end products. The hydrogenation occurs in fixed hydrotreating catalyst beds to improve hydrocracking ratios and to remove unwanted contaminants. From there, the process continues into reactors containing fixed hydrocracking catalyst beds that dealkylate aromatic rings, open napthene rings and hydrocrack paraffin chains.

Catalyst design
The article went on to point out that: “Increased environmental regulations on gasoline and diesel have made hydrocracking an essential process, resulting in ever greater increases in worldwide capacity.” Its authors also stressed the importance of “optimum catalyst design” (to extend catalyst lifecycles by improving reactor operation). This coincides with many catalyst suppliers’ efforts to continually improve their products and offer users “longer cycles, higher throughput, and faster turnarounds, all with minimal capital investment”. Because hydrocracking allows refiners to process lower-grade feedstocks, there has been widespread attention in the catalyst market for development of advanced catalysts to ultimately improve profit margins. In fact, because of these advances, there have been nearly 100 new hydrocracking systems put online around the world in the past 10 years. Many of these “new refineries and refinery expansions are targeting operating capacities of 400 000 bpd or higher,” the article concluded.

Despite the global recession, there is still significant demand for gasoline and diesel fuels, especially in developing nations. Some estimates put the growth rate in China and India alone at approximately 40% over the next two decades. On the other hand, the demand for less refined products such as fuel oil is declining. This is one reason why many refiners are employing more sophisticated hydrocracking processes with more sophisticated catalyst materials. This trend is likely to continue.

Catalyst composition
Modern hydrocracking technology employs complex catalysts composed of one or more platinum group metals (PGMs), including platinum, palladium, ruthenium and rhodium, and occasionally rhenium, gold, silver or other precious metals, depending upon application. Catalyst compositions typically include soluble or insoluble alumina, silica/alumina or zeolites in configurations that include monolithic structures, beads, pellets, powders or extrudates, depending upon application (Figure 2). As a result of a continuous hydrocracking process (generally over a number of years), these catalysts lose their efficacy (mainly because of process contaminants) and must be replaced by “fresh” catalysts. When that occurs, their precious metals content must be recycled (recovered, refined and returned to their owners, either in the form of new metals or dollars) so as to acquire fresh catalysts to start the process over.