ERTC Newspaper 2022

ERTC 2022

Using reactivated hydroprocessing catalysts in TGTUs for financial and sustainability rewards

Brian Visioli Evonik

Both these options, however, involve a processing cost and neither leverages the value of the technology inherent in the catalyst particle for the refiner’s benefit. Which brings us to the third option:  Reactivation for reuse This involves oxidation under controlled conditions to remove carbon and sulphur compounds but preserve catalyst qualities for certain applications. An additional chemical treat- ment (commonly referred to as ‘rejuvena- tion’) may also be employed. This is the superior of the three options for dealing with spent hydroprocessing catalysts, as it allows the refiner to leverage the maximum value of their spent catalyst, avoids dis- posal to landfill, and gives the active metal components which comprise a hydro- processing catalyst a ‘fresh start’. And crucially, regenerating and reusing the cat- alyst in this way reduces the refining indus- try’s dependence on freshly mined metals. From hydroprocessing to tail gas treating There are several similarities between tail gas treating catalysts and hydroprocess- ing catalysts. Both applications commonly employ metals such as cobalt and molyb- denum, supported on a carrier containing aluminum, silicon, zeolites, or combina- tions thereof. Both need to be converted to a metal- sulphide state for activity toward the

• Operating limit of other reactor control parameter • Catalyst bed fouling • Equipment failure • Coordinating timing with other operating units at the refinery At the end of its life cycle, the catalyst is removed from the reactor, with the spent catalyst then classified as hazardous. A spent hydroprocessing catalyst can be disposed of in one of three main ways:  Disposal in a hazardous waste landfill However, this is the least desirable method for several reasons: the refiner loses the value inherent in the spent catalyst and an additional fee must be paid for the spent catalyst to be disposed of in landfill. The fact that this places environmentally haz- ardous materials into a landfill must also be factored into considerations.  Processing for metal reclamation , where oxidation removes much of the carbon and sulphur compounds in preparation for recovery of valuable metal components (e.g. molybdenum). This approach is an improve- ment upon disposal in landfill, as the refiner is typically credited for a fraction of the value of certain components reclaimed from the spent catalyst. This method still requires a thermal treatment and leaves a final waste stream containing the less-valuable compo- nents of the catalyst particles (e.g. alumina), which must be disposed of in turn.

For over 40 years, the global petroleum refining industry has successfully been reusing hydroprocessing catalysts through ex situ reactivation, to capitalise on the economic and environmental benefits such technologies deliver. The process provides more cost-effective catalyst configurations whilst continuing to deliver performance lev- els equivalent to fresh catalysts. However, these gains have been exclusive to refinery hydroprocessing units – that is, until now. Following the successful installation and operation of reactivated hydroprocessing catalysts in the tail gas treating units at two US refineries, this is now changing. This fresh approach is already producing sev- eral benefits, namely: lower replacement catalyst costs, increased circularity, and increased activity levels (which has resulted in reduced SO₂ and CO₂ emissions), and less spent catalyst hazardous waste. Moreover, it has demonstrated a reduced dependence on fresh cobalt and molybde- num metals. Consequently, refiners can reap the double benefit of decreasing their carbon footprint and enhancing circular- ity without any adverse effect on perfor- mance levels. The extension of this technology to tail gas treating has been made possible thanks to Evonik’s unique experience in both hydroprocessing catalyst recovery and sulphur recovery catalysis. Patent cov- erage is held by the company for the use of reactivated hydroprocessing catalysts in tail gas treating units, consolidating its reputation for industry-leading innovation. Manufacturing catalysts Until recently, tail gas treating catalysts have been produced from basic raw mate- rial building blocks, including alumina, cobalt, and molybdenum. Each of these catalyst precursors is derived from a nat- urally occurring ore. The ‘upstream’ pro- cesses of mining, ore processing, and ore purification each require a significant energy input. These processes also have significant environmental and societal impacts, which though more difficult to quantify, should not be ignored. Four decades ago, the majority of hydro- processing catalysts also came from simi- lar raw materials. Since then, we have seen significant advances in the technologies and methods involved in catalyst reactiva- tion, which is why the use of reactivated hydroprocessing catalysts has become a central part of many oil refinery operating companies’ strategies today. Catalyst reactivation (regeneration and rejuvenation) Eventually, hydroprocessing catalysts will reach the end of their active life. This could be caused by several factors, such as: • Loss of catalytic activity/selectivity due to process upset • Operating limit of reactor feed heater

Catalyst reuse technologies reduce environmental footprint

Total CO e CO

Electricity

61% reduction Natural gas

67% reduction Diesel fuel

80% reduction

>60% reduction

desired reactions, and both consume hydro- gen as a reactant in the desired reactions. In both applications, extruded catalysts are quite common, although spherical tail gas treating catalysts have been introduced to provide lower pressure drop. That said, there are also important dif- ferences between the two types of cata- lysts. For example, the quantity of active metal applied to hydroprocessing catalysts is commonly much greater than that on tail gas treating catalysts, and hydroprocess- ing catalysts do not typically come in con- tact with species containing oxygen atoms when processing fossil fuels. Moreover, the operating pressure is significantly greater in hydroprocessing (up to 2000+ psig/140+ bar) compared to tail gas treating. Case Study: Catalyst in Context EcoMax™ TG catalyst was selected by a US Gulf Coast refinery for installation in its tail gas treating unit. The subject unit is a conven- tional temperature TGTU which processes Claus tail gas from one upstream SRU. The catalyst was sulphided in situ and operated for four months prior to performance testing. Performance testing was completed by a well-known SRU/TGU performance test- ing company. Gas samples were taken at the inlet and outlet of the tail gas reactor at a variety of conditions and analysed by gas chromatography. Reactor bed tempera- tures ranged from the baseline of 271°C to as low as 254°C, corresponding to reactor inlet temperatures from 263°C to as low as 248°C. The gas chromatography analysis indicated that no SO₂ was present at the tail gas reactor outlet throughout the testing, and conditions in the quench water system confirmed that complete SO₂ conversion was taking place in the tail gas reactor. The operating conditions were challenging. Very high levels of CS₂ were observed at the reactor inlet, ranging from 8,000 to 25,000 ppmv. Throughout the testing, zero CS₂ was observed in the tail gas reactor effluent, indi- cating complete conversion over the catalyst at all conditions tested. Unlocking potential It would be prudent for operators in the sul- phur recovery industry to investigate using our patented reactivated hydroprocessing catalysts in their tail gas treating units, given the raft of potential benefits – both financial and environmental – that these technologies can provide. References available on request. Contact: brian.visioli@evonik.com

THree considerations to maximising the valuation of catalyst assets When a refiner purchases a hydroprocessing catalyst, they are investing in an asset. That asset is composed of the physical constituents as well as the technology inher- ent in the catalyst particles which together yield activity. The value of the catalyst does not completely disappear over its active life, nor does the value suddenly evapo- rate when the catalyst reaches the end of its life and becomes classified as a spent catalyst. The spent catalyst maintains value which should be considered by the refiner when determining what to do with it.  Paying an unnecessary premium for new? A refiner who considers only fresh catalyst when it is time for catalyst replacement typically does so for reasons of perceived performance advantage in terms of con- version, selectivity, pressure drop, or active life. However, advances in catalyst reuse technology have eliminated the gap on each of these parameters while requiring a lower level of investment in the catalyst itself.  Catalyst activity and energy efficiency Operating the tail gas reactor at lower temperature conditions results in energy sav- ings, whether the reactor feed heater is indirect (e.g. steam or hot oil heat exchanger) or direct (reducing gas generator). In the TGTU, this has an added benefit of eliminating the need for a waste heat reclaimer downstream of the TGTU reactor, as is the norm for conventional (high tem- perature) TGTU designs. Elimination of this piece of equipment represents real Capex savings for new units.  Sustainability and corporate social responsibility Sustainability is a strategic focus for today’s refining industry, as evidenced by the front page of every major oil refiner’s website. Sustainable practices and concepts like the ‘circular economy’ yield real financial benefits, positive media coverage, improved reputation, and reduced environmental impact. Catalyst reuse is one way that sustainability can be incorporated into an oil refinery operating company’s strategy.