(624d) Process Intensified and Direct Production of Gasoline from Syngas

An Abstract Submission to 2017 AICHE
Meeting

Session: Process Intensification By Enhanced Heat and Mass Transfer

Topical Area: Process Intensification

Process Intensified and Direct Production of Gasoline
from Syngas

Xinquan Cheng^a,
William R. Yantz Jr.^a, and Bruce J. Tatarchuk^{a, b,}*

^a Center for
Microfibrous Materials Manufacturing, Department of Chemical Engineering, 212
Ross Hall, Auburn University, AL 36849

^b IntraMicron Inc.,
368 Industry Dr., Auburn, AL 36832, USA

* Corresponding
author. Tel.: +1 334 844 2023; fax: +1 334 844 2065; E-mail address:
Tatarbj@auburn.edu

Abstract

The
increasing demand for liquid fuels draw people’s attentions to the synthetic
fuels. Currently, there are mainly two approaches to synthesize liquid fuels
from syngas. One is Fischer-Tropsch synthesis (FTS) and another one is
syngas-to-methanol first and followed up with methanol-to-gasoline (MTG). Those
two approaches are well-known techniques for converting syngas to liquid fuels.
However, FTS process produces a broad spectrum of products, which requires
complex and expensive subsequent processes to upgrade the initial products in
order to meet liquid fuel specifications. The MTG approach is a multiple step
process. Typically, in the first reactor syngas is converted to methanol, and
followed with methanol dehydration reactor to produce the intermediate product
dimethoxyethane (DME), and then DME successively converted to hydrocarbons in
the reactor packed with zeolite. It must be noticed that all those reactions
are highly exothermic reactions, which producing extremely amount of heat
during the reaction processes. Therefore, the reaction thermal management is
always a big issue for syngas to liquid fuels.

Here,
we present a single reactor system to directly convert syngas-to-gasoline (STG)
by using a novel catalyst structure called Microfibrous Entrapped Catalyst
(MFEC) structure. The MFEC structure was developed by our group, which is a
catalyst network supported by micron-sized metal fibers with high thermal
conductivity. By supporting small catalyst particles into a high voidage matrix
of microfibers the catalyst is suitable for fixed bed applications without
severe pressure drop or bed channeling encountered in small particle packed
beds. Previous efforts on this unique catalyst structure have shown significant
enhancement in intra-bed heat transfer and mass transfer.^[1-4]
Basically, we packed a large tubular reactor (34.0 mm I.D.) in three zones by
using Cu MFEC. As we can see from Figure 1, the first zone (Zone-1) is a mixed
catalyst zone for the production of DME from syngas. The second zone (Zone-2) is
a relative inert zone mainly used to separate Zone-1 from Zone-3 since those
two zones have different temperature. In order to convert all the unreacted
methanol from Zone-1, we packed γ-Al₂O₃ in Zone-2 as
a methanol dehydration catalyst. The third zone (Zone-3) is a zeolite zone
packed with ZSM-5 to convert the DME to gasoline. This kind of multi-zone
reactor design can separate the zeolite from the methanol synthesis catalyst,
because the proximity of those two catalyst components is crucial factor for
the product selectivity of STG process.^[5] If those two components are
close to each other, the lower olefins, which are the essential intermediates
from methanol to aromatics, diffuse from the zeolite to the methanol synthesis
catalyst, where they are easily hydrogenated to lower paraffins. It turns out
that most of the products are short chain paraffins.^[6]

However,
with this simple multi-zone reactor design, the olefinic intermediates are
preserved for subsequently oligomerization reactions. Under a typical reaction
conditions (P=30 atm, GHSV=1000 h^-1, H₂:CO=1:1), the C₅
– C₁₀ hydrocarbon selectivity can reach 39.0 wt% with a relative
high CO conversion (73.2 %). In addition, the Cu MFEC structure demonstrated a
very low radial temperature gradient (around 5 ºC) for a 34.0 mm I.D. reactor and
insignificant amount of pressure drop. While with the same test conditions, the
comparative packed bed reached a very high radial temperature gradient (around
140 ºC) and significant amount of pressure drop. Considering these attributes
and advantages, the Cu MFEC multi-zone reactor system is a very efficient
process intensification technique for the direct production of gasoline from
syngas.

Figure 1. The STG reactor design
(all the catalysts particles entrapped in Cu MFEC in Zone-1, Zone-2, and Zone-3
are in 60 – 80 mesh)

References:

[1] M.
Sheng, H.Y. Yang, D.R. Cahela, B.J. Tatarchuk, J. Catal. 281 (2011) 254-262.

[2] M.
Sheng, H.Y. Yang, D.R. Cahela, W.R. Yantz Jr., C.F. Gonzalez, B.J. Tatarchuk, Appl. Catal.
A-Gen. 445-446 (2012) 143-152.

[3] M.
Sheng, D.R. Cahela, H.Y. Yang, C.F. Gonzalez, W.R. Yantz Jr., D.K. Harris, B.J.
Tatarchuk, Int. J. Heat Mass Tran. 56 (2012) 10-19.

[4] X.Q. Cheng, H.Y. Yang, B.J. Tatarchuk, Catal.
Today 273 (2016) 62-71.

[5] S. Sartipi, M. Makkee, F. Kapteijn, J. Gascon,
Catal. Sci. Technol. 4 (2014) 893-907.

[6] K. Fujimoto, H. Saima, H. Tominaga, J. Catal. 94, (1985)
16-23.