Feb-2020

Developments in refining catalysts

New catalyst technologies underpin increasing flexibility in refineries’ response to changes in demand for their output.

MICHAEL CLEVELAND
Honeywell UOP

Article Summary

Stunning technological advances have occurred since UOP introduced catalysis to the refining industry in 1933. It graduated the science of refining from a series of processes governed by pressure, temperature, and time to one where catalysts could be employed to perform specific functions, to break and rearrange molecular bonds to make predetermined products. As catalytic science became more sophisticated, catalysts could be engineered to perform those functions more selectively and efficiently.

By merely coming into contact with a catalyst, hydrocarbon molecules can be induced to break apart, join together, and rearrange themselves into intended new forms. But despite all the achievements in catalytic science in the last 87 years, the industry still has only scratched the surface of what catalysts can do.

Most of the developments in catalysts resulted from the invention of new materials that do not exist naturally. These materials were designed to be manufactured with repeating crystalline structures with advanced properties. For example, acid catalysts were developed with greater acid site density and strength, lower diffusion paths, and other qualities to make them more efficient. Novel metal catalysts featured new nanomaterials, or atomic-level compositions, with superior electronics that gave them new capabilities. All of these developments are the product of highly developed core competencies in the design of new materials, and the manufacturing expertise to uniformly synthesise them.

While the industry has developed thousands of new materials, including hundreds of new zeolites, a second competency is necessary to scale up production from a few grams in a lab to continuous quantities that may number in the hundreds of metric tons.

Today, much of the development in catalysts focuses on process intensification designing catalysts that are more efficient than existing catalysts, or that perform more than one chemical conversion in a single step. This allows them to process more feedstock with fewer and smaller units, requiring less land, steel, and energy.

Because catalysts are integral to process technology, this profoundly improves the economics of refineries and petrochemical plants by reducing their utilities requirements and water use, avoiding production of low value byproducts, and even allowing them to use a wider range of feedstocks. These processes, enabled by more capable and efficient catalysts, can lower capital requirements and operating costs.

Catalysts also are at the heart of the Refinery of the Future, a framework of asset development and molecule management that helps ensure optimal economic efficiency, profitability, and environmental leadership over time. It is an approach to capital investment that is unique to each refinery. Different combinations of technologies are built in carefully timed stages to meet changing market conditions, take advantage of changing feedstocks, and meet evolving regulatory constraints and competitive threats with the goal of maintaining optimal profitability.

One of the overriding trends in the industry today is the widely forecast peak in global demand for transportation fuels in the mid-2030s, due to the introduction of more fuel-efficient engines and the growing number of vehicles powered by alternative fuels. At the same time, new environmental regulations threaten to strand refining capacity for fuels that do not meet stricter emissions standards.

This has caused many refiners to upgrade their fuels refining capacity while bridging into petrochemicals, where product demand and margins remain strong, due to 4% growth in global GDP driven in part by population growth in developing economies.

More efficient processes based on more sophisticated catalysts offer great competitive advantages in terms of operating margins and slate flexibility, with the ability to direct molecules to processes where they can produce the greatest value. The best solutions are catalysts that are designed to operate under these new conditions using existing capital assets. In this sense, they are akin to reprogramming a refinery, in the same way you would install a software upgrade to a computer. The refinery is essentially the same, but now it can do more.

For example, a new catalyst with some modifications to operating conditions can change a hydrocracking unit from production of distillate to production of naphtha. With the staged investment of a CCR Platforming unit, the naphtha can be converted into aromatics and LPG which, with the addition of a PDH unit, can be the feed for producing olefins.

While existing refineries are investigating these paths, new world-scale refineries already are being built that will convert half or more of their feedstock into petrochemicals. In fact, refineries that produce only petrochemicals probably are not far behind.

Where economics favour larger operations, new catalyst designs also make it possible to design larger units with greater capacities. In cases where processes are hydrodynamically limited, a catalyst can be made denser or stronger, or given a more efficient shape or some other property to accommodate greater production capacity, without risking pressure drop, pinning, or void blowing.

The design of advanced catalysts today requires advanced characterisation techniques, employing electron microscopes to verify the composition of the material and even ensure metals have been properly dispersed. Without the ability to actually inspect what has been created, we cannot know exactly why a new catalyst formulation behaves the way it does.

Aromatics conversion
One of the processes used to selectively convert lower value toluene and C9+ aromatics into benzene and xylene products is the Tatoray process. In this process, toluene is combined with C9 and C10 aromatics and converted to benzene and xylenes in a simple transalkylation reactor system, more than doubling the yield of paraxylene from a given naphtha feedstock.

But to further increase yields of paraxylene from an aromatics complex — and allow the use of even heavier feeds UOP developed the TA-42 catalyst for the Tatoray process. This catalyst employs a true nano-zeolite which is highly stable, active, and selective because the reactions are controlled by mass transfer. The dimensions of the zeolite pores are smaller, giving it more active sites and greater selectivity to the molecules without getting clogged by heavier C9 and C10 aromatics. As a result of its higher activity, yields of paraxylene per unit of energy and overall processing capacity — are higher. The ability to scale up this zeolite was made possible by the invention of a new material.

Bottoms upgrading
One of the persistent problems with upgrading vacuum residue, or so-called ‘bottoms’, is the volume of carbon byproduct, or pet coke.