Hydrogen Storage, Distribution, and Transportation: Developments in Hydrogen Carriers

According to the joint EPO-IEA report summarizing patent trends in the hydrogen economy  (summarized here), technologies related to storage, distribution, and transportation of hydrogen are among the most critical challenges for large-scale deployment. Standardized infrastructure for hydrogen trade is essential to allow the market to function and flow.

While trends show that established technologies have generated high levels of patent-related activities, emerging technologies such as the use of hydrogen carriers are key to encouraging widespread hydrogen distribution systems. Patent filings in the fields of liquid organic hydrogen carriers (LOHCs) and ammonia cracking, two example hydrogen carriers discussed below, have increased since 2011.

Conventional storage and transportation of hydrogen relies on liquid-compressed hydrogen, which is stored at either extremely high pressures or extremely low temperatures. LOHCs and ammonia cracking enable hydrogen to bond with a stabilized carrier, which allows for safer and more economical transportation. The two examples below illustrate the types of improvements that have been patented recently.

Ammonia Cracking

Ammonia cracking is the process of using ammonia as an energy carrier for transporting hydrogen. In this process, hydrogen is first produced through means such as electrolysis, and then combined with nitrogen extracted from ambient air using an air separator to produce green ammonia, which can be transported using conventional means. Once the green ammonia arrives at its destination, the compound is separated into hydrogen and nitrogen using an ammonia cracking process.

Topsoe A/S recently received US Patent No. 11,511,991 (‘991 Patent) issued 29 November 2022, entitled “Autothermal Ammonia Cracking Process.” The ‘991 Patent discloses a process for ammonia cracking that reduces or eliminates the need to remove residual nitrogen oxides from the cracked gas. Nitrogen oxides (NOx), a common byproduct of ammonia cracking, are gases that contribute to air pollution and present health hazards.

The process of the ‘991 Patent includes (i) noncatalytic partial oxidation of ammonia with an oxygen-containing gas to a process gas containing nitrogen, water, amounts of NOx, and residual amounts of ammonia; (ii) cracking the residual amounts of ammonia to hydrogen and nitrogen in the process gas by contact with a nickel-containing catalyst while simultaneously reducing the amounts of NOx to nitrogen and water by reaction with a part of the hydrogen formed during cracking of the process gas by contacting the process gas with the nickel-containing catalyst; and (iii) withdrawing the hydrogen and nitrogen containing product gas.

When using a nickel-containing catalyst during the ammonia cracking of the process gas, NOx are reduced to nitrogen and water to reduce or eliminate the need for further processing to remove NOx. The amount of NOx generated in the noncatalytic partial oxidation stem is purportedly reduced by between 80% and 100% as limited by thermodynamic equilibrium due to the contact with the nickel containing catalyst.

Liquid Organic Hydrogen Carriers

LOHCs are organic compounds that can absorb and release hydrogen through chemical reactions and act as a storage media for hydrogen. Example LOHCs include toluene/methylcyclohexane, n-ethyl carbazole, and dibenzyltoluene. The process typically includes an endothermal hydrogenation of the LOHC at elevated temperatures and pressures to form a compound that can be easily stored or transported. Prior to use, the compound undergoes a hydrogen purification step to strip the hydrogen from the LOHC.

Hydrogenious LOHC Technologies recently received US Patent No. 11,383,974 (‘974 Patent) on 12 July 2022, entitled “Method and Apparatus for Dehydrogenating a Hydrogen Carrier Medium.” The ‘974 Patent outlines purported improvements to the step of releasing the hydrogen using a dehydrogenation catalyst. Typically, the dehydrogenation of the hydrogen carrier medium occurs at high temperatures and is uneconomical at temperatures below 250°C. The processes disclosed in the ‘974 Patent claim to provide an increased release rate of hydrogen from the LOHC at reduced temperatures.

The technology of the ‘974 Patent utilizes a metal-containing catalyst material that is mixed with a partially loaded hydrogen carrier medium and a metal-free reaction accelerator substance. The metal-containing catalyst has the ability to activate the LOHC-bound hydrogen and transfer it to the metal-free reaction accelerator substance and then release it from there.

The metal-free reaction accelerator substance is provided initially in a hydrogen-depleted form. The hydrogen carrier medium is contacted directly with the metal-containing catalyst and the metal-free reaction accelerator substance such that the hydrogen is released at lower temperatures, thereby ostensibly minimizing the overall energy expenditure. 

In our next post on the EPO-IEA’s report, “Hydrogen Patents for a Clean Energy Future: A Global Trend Analysis of Innovation Along Hydrogen Value Chains,” we will dive into the third technology segment of the hydrogen value chain. Having discussed the first segment of hydrogen production previously here and the second segment of storage, distribution, and transformation above, the next topic will be end-use industrial applications.

By: Clare Frederick and Jason Engel