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Highly Active and Selective Metal-modified Zeolite Catalysts for Low Temperature Conversion of Methanol and Dimethyl Ether to Gasoline-range Branched Hydrocarbons

National Renewable Energy Laboratory

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Technology Marketing Summary

Recent investigations by a number of groups have shown that a beta zeolite catalyst (and other solid Brønsted acids) will convert methanol and/or dimethyl ether (DME) to iso-alkanes such as triptane (2,2,3-trimethylbutane), with uniquely high selectivity to C4 and C7 (termed the DME to high octane gasoline process or DTHOG). In comparison, the Exxon-Mobil methanol to gasoline (MTG) process produces a broader mixture of hydrocarbons, which is heavy in benzene, toluene, and xylene (BTX). DTHOG is milder than MTG (350-450 °F vs. 650-950 °F and 130 psia vs. 315 psia), thus offering the benefit of reduced capital and operating costs for the reactor. However, similar to MTG, this new low-temperature, selective production of alkanes is still a hydrogen-deficient process. That is, to produce alkanes, a quantitative production of aromatics is required to maintain stoichiometry—a result of oxygen from methanol or DME being rejected as water.

Description

Scientists at the National Renewable Energy Laboratory (NREL) have developed a catalyst formulation and structure that is capable of incorporating hydrogen from gaseous co-fed H2 into methylation and alkylation products without altering aliphatic hydrocarbon selectivity or lowering reaction rates. Volumetric and gravimetric activities are increased and the rate of formation of heavy aromatic residues is decreased. The catalysts are comprised of a beta zeolite modified with Cu, Ga, other non-noble metals, and combinations thereof. The metals provide sites for H2 dissociation, hydrogen addition, and hydrogen abstraction, all of which modulate critical reaction steps—providing H for alkane formation and H removal for alkene formation, bringing products back into the carbon chain growth pathway and minimizing side-reactions that produce unwanted byproducts. The metals work with the Brønsted acids of the zeolite, which act as the catalyst for alkene methylation and carbon chain growth. Physical mixtures of the metal catalyst and zeolite do not yield the same benefits.  Metal loadings are low (< 5 wt%) and include metals in metallic clusters, oxide clusters, and cationic forms.

Benefits
  • Lower temperature operation compared to MTG process, resulting in significantly reduced aromatic production and higher yield to gasoline-range branched alkanes and alkenes
  • Allows, in principle, recycle of intermediate products that are not activated/upgraded (i.e., are dead-end products) on similar catalysts, improving yield to higher-value products
  • Incorporates H2 from the gas phase to ‘fix’ the oxygenate to alkane stoichiometric imbalance instead of expensive hydrogen transfer agents like adamantane while maintaining the attractive product selectivity of similar catalysts
  • Increases desired hydrocarbon yield compared to similar catalysts
  • Reduces deactivation and the frequency of regeneration cycles by reducing the net rate of formation of heavy aromatic residues
Applications and Industries
  • Biofuels
  • Methanol/DME to hydrocarbons
  • C4 alkylation, butane/butene upgrading
  • Gas to Liquids (GTL)
  • Octane enhancement/gasoline blending
  • Avigas
  • Jet/Biojet (via oligomerization of products over acid resin catalysts)
Patents and Patent Applications
ID Number
Title and Abstract
Primary Lab
Date
Patent 9,714,387
Patent
9,714,387
Catalysts and methods for converting carbonaceous materials to fuels
Catalysts and processes designed to convert DME and/or methanol and hydrogen (H.sub.2) to desirable liquid fuels are described. These catalysts produce the fuels efficiently and with a high selectivity and yield, and reduce the formation of aromatic hydrocarbons by incorporating H.sub.2 into the products. Also described are process methods to further upgrade these fuels to higher molecular weight liquid fuel mixtures, which have physical properties comparable with current commercially used liquid fuels.
National Renewable Energy Laboratory 07/25/2017
Issued
Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated
NREL ROI 14-49ProposedAvailable12/08/201501/05/2016

Contact NREL About This Technology

To: Eric Payne<eric.payne@nrel.gov>