Hydrocarbon Processing - August 2021 - 59

Hydrogen
in this step, which contributes to the efficiency
of the hydrogen process. Toluene
losses within the process are minimal.
Produced methylcyclohexane is then
transported to the site of H2
use. H2
is
recovered from the methylcyclohexane
via catalytic dehydrogenation. The dehydrogenation
process can be described as
follows: The methylcyclohexane feed is
vaporized in the vaporizer (11) and superheated
in the charge heater (12) before entering
the catalyst-packed tubes of the dehydrogenation
reactor (13). This reactor
is a tubular, quasi-isothermal reactor design
similar to that employed in the hydrogenation
process. The dehydrogenation
catalyst was specially developed in-house
for this process. Since dehydrogenation is
an endothermic reaction, an external heating
source is required. Typically, a hot oil
system is applied (14) to supply the necessary
reaction heat.
The dehydrogenation plant is ideally colocated
within an existing complex where
available waste heat at a suitable temperature
level can be utilized. Reactor effluent
and condensed
gas is cooled to separate H2
toluene (16). In the reactor, methylcyclohexane
is reconverted to toluene and H2
The recovered H2
.
is separated from the
toluene and is subsequently compressed
and purified, if necessary, to meet relevant
product H2
specifications (18). Toluene
is then transported back to the site of the
hydrogenation plant for re-hydrogenation.
Catalyst development. Key to the success
of the trademarked hydrogen processa
was
the development of a dehydrogenation
catalyst that was not only robust,
but also exhibited superior selectivity and
stability. As depicted in FIG. 5, methylcyclohexane
conversion of greater than 95%
was eventually achieved at a selectivity of
99.9%, which provides for a very low level
of reaction byproducts.
Accelerated, long-term testing showed
remarkable stability even after 10,000 hr
onstream. Commercially, a catalyst life of
2 yr could be reasonably expected. Once
a suitable candidate catalyst was developed,
the next steps to eventual commercialization
included scale-up for manufacturing
and pilot-level demo of both the
catalyst and the equipment.
From April 2013-November 2014,
10,000 hr of pilot plant operation were
successfully completed, and the expected
performance and life of the catalysts
FIG. 5. Dehydrogenation catalyst development and performance.
2
Cooling
medium
3
1
Toluene
5
4
11
6
Methylcyclohexane
Methylcyclohexane
H2 supply side
H2 demand side
FIG. 4. Hydrogenation and dehydrogenation processes for the trademarked hydrogen process.a
15
16
Toluene
13
H2
7
Hydrogenation process
Recycle H2
12
Heating
medium
14
Product
H2
17
18
treatment
H2
Dehydrogenation process
FIG. 6. Demonstration plant in Yokohama, Japan showing dehydrogenation/hydrogenation
for the trademarked hydrogen process.a
were confirmed. In the pilot-scale test
facility, methylcyclohexane and toluene
were continuously dehydrogenated and
rehydrogenated at a consistent rate of
50 Nm3
/hr of H2 (FIG. 6).
Demonstration projects. The authors'
company, along with its partners Mitsubishi,
Mitsui and Nippon Yusen, established
the Advanced Hydrogen Energy Chain
Association for Technology DevelopHydrocarbon
Processing | AUGUST 2021 59

Hydrocarbon Processing - August 2021

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