Apr-2024

Catalyst technology for maximum light olefins and ultra-low emissions

Bio-derived naphtha-to-olefins technology for today’s refinery and the future’s anticipated renewable fuels and chemicals refinery.

Ray Fletcher
Gasolfin

Article Summary

A catalytically driven naphtha-to-olefins technology, the Gasolfin process converts conventional and bio-derived naphthas into light olefins (ethylene, propylene, and butylene), reaching olefin yields up to 88 wt%. The process developed by Inovacat reduces CO₂ emissions by 50% or more compared to the catalytic cracking (FCC) and propane dehydrogenation (PDH) processes. Gasolfin’s catalyst converts naphtha boiling-range hydrocarbons, excluding aromatics, from butane through undecane (C₄-C11). The catalyst also converts pentane, recognised as the lowest valued and most refractive of gasoline components.

Inovacat’s technology is based upon a catalyst system protected by multiple patents. This technology has been in development since 2017 and has successfully passed both bench- and pilot plant-scale testing. The company is currently in collaboration with an Asian refiner to build and operate an 800-litre/day demonstration plant. This plant is expected to go into construction in mid-2024 and will be in production in late 2025. Gasolfin anticipates having the technology ready for deployment in 2027 with the following enhanced capabilities:
• The first ever catalytic light ends conversion process capable of converting low molecular weight paraffins, such as pentane, into high-valued ethylene, propylene, and butylene with product yields up to 27%, 46%, and 30%, respectively.
• Converting fossil- and bio-derived naphthas into light olefins and light bio-olefins, respectively.
• Light olefins production with 50-66% lower CO₂ emissions.

More specifically, Gasolfin produces polymer-grade propylene and ethylene at a very low 0.45 tons CO₂/ton olefin ratio. In comparison, an FCC unit produces propylene at 0.783-0.869 tons CO₂/ton olefins, while a steam cracker produces ethylene at 1.231 tons CO₂/ton olefins. The technology improves the flexibility of the fuels-based refinery and steam cracker-based chemical plant. The technology also converts any naphtha regardless of the source (crude unit, hydrotreater, or coker), as well as petrochemical plant intermediate and byproduct streams. It will also enable the facility to run harder.

Ultra-low CO₂ emissions
The Gasolfin process produces light olefins with significantly lower CO₂ emissions than the three leading propylene-producing technologies: FCC, steam cracking, and propane dehydrogenation (PDH). A benchmark paper for establishing GHG emissions for existing technologies was produced in 2013 titled, ‘Energy and GHG Reductions in the Chemical Industry via Catalytic Processes’.1,2 Gasolfin produces 0.45 tons of CO₂ for every ton of total olefin produced, which is annotated as ‘tCO₂/tHVC’, where ‘tHVC’ abbreviates ‘ton Highly Valued Chemical’. This is an excellent metric, which enables a side-by-side comparison of an FCC and a steam cracker.

The GHG Reductions paper places the GHG emissions of an FCC between 0.783 and 0.869 tCO₂/tHVC. A steam cracker processes naphtha at 0.700 and ethane at 0.964 for an average GHG emissions level of 0.832 tCO₂/tHVC. A PDH unit produces 1.231 tCO₂/tHVC.

Gasolfin’s GHG emissions are significantly lower than each of the existing technologies shown in Figure 1 due to the following primary factors:
• Lower heat of reaction: Gasolfin’s feedstock boils in the naphtha range, which has a much lower heat of reaction than for ethane cracking or PDH.
• Narrow feed slate: The Gasolfin unit cracks naphtha boiling molecules to extinction. Feed boiling over the naphtha range is excluded from the feed.
• Low coke selective catalyst: Gasolfin’s patented catalyst features an extremely low coke selectivity. FCC and PDH have coke yields of 4-5 wt%, while the Gasolfin coke yield is well below 0.5 wt%. The chemical CO₂ contribution is therfore an order of magnitude less than FCC or PDH.
• Hybrid product recovery section: The inclusion of cryogenic distillation for ethylene recovery and conventional distillation for propylene and butylene recovery offers significant heat integration capabilities not typically found in a polymer-grade propylene or polymer-grade ethylene operation.

Catalyst development
Catalyst studies began in 2017, utilising the Chemical Process Engineering Research Institute (CPERI) laboratories in Thessaloniki, Greece. The catalyst development work was initially carried out in a microactivity test (MAT) reactor with many catalyst formulations, including multiple zeolite and alumina types and sources, each with various metal types and levels. The catalysts were tested fresh and with incremental deactivation severities.

The bulk of the testing was carried out at end-of-life conditions to achieve near-constant olefin selectivities as the catalyst ages. Gasolfin carried out approximately 300 individual tests before selecting the final few catalyst formulations. These catalysts were then advanced to the pilot plant phase. The final catalysts were tested for approximately 100 days of pilot plant operations. The feedstocks selected for these tests were pentane, hexane, octane, light straight run (LSR), full range naphtha (FRN), and FCC naphtha.

Ease of cracking
Gasolfin has created a catalyst system to efficiently convert all naphtha boiling-range hydrocarbons, excluding aromatics, into light olefins. The catalyst produces ethylene, propylene, and butylene with a total olefin yield of 60-88 wt%. There are no higher molecular weight byproducts produced, such as diesel or heavier. The ethylene-to-propylene-to-butylene product ratio (EPB ratio) is feedstock dependent. Paraffinic feeds such as LSR and FRN present an EPB ratio of 21:50:29, while olefinic feeds such as FCC naphtha present an EPB ratio of 18:49:33.

More than 25 commercially derived feedstocks have been cracked at CPERI’s Thessaloniki, Greece, laboratory. These feeds include pentanes, LSR, medium straight run (MSR), FRN, light FCC naphtha (LCN), full range FCC naphtha (HCN), pyrolysis naphtha (PN), Fischer-Tropsch naphtha (FTN), bio-naphtha (BN), and various petrochemical intermediate streams. The petrochemical intermediate streams included various paraffinic naphthas, olefinic naphthas, oxygenated naphthas, and naphtha streams bearing a mix of both olefinic and oxygenated components. The EPB ratios of these streams were all consistent with the typical ranges stated above.