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Methaforming: Novel Process for Producing High-Octane Gasoline from
Naphtha and Methanol at Lower CAPEX and OPEX. Stephen Sims, Adeniyi Adebayo, Elena Lobichenko, Iosif Lishchiner, Olga Malova
New Gas Technologies – Synthesis LLC, USA/Russia
Authors’ Introduction
Stephen Sims: President, New Gas Technologies – Synthesis North America. Energy Advisor at Houston Technology Center. He previously served in technical and management roles at Exxon, Citgo and ConocoPhillips. Stephen has over 40 years’ industry experience in more than 15 countries spanning the entire value chain of the downstream sector.
Adeniyi Adebayo: Research Engineer, New Gas Technologies – Synthesis LLC M.Sc. in Energy Science and Technology, Skoltech (Russia)/MIT (USA). Prior to joining New Gas Technologies – Synthesis LLC, Adeniyi conducted research in enhanced oil recovery, receiving accolades for his research including the 2014 SPE International Award for graduate students.
Elena Lobichenko: Research Engineer, New Gas Technologies – Synthesis LLC M.Sc. Materials Science, Skoltech (Russia)/MIT (USA). Elena has over 5 years’ experience in chemical analysis and synthesis, working at major chemistry laboratories of the Moscow State University.
Iosif Lishchiner: Chief Technologist, New Gas Technologies – Synthesis LLC Head of Laboratory, High Temperatures Institute of the Russian Academy of Sciences. Dr. Lishchiner has extensive experience of over 30 years in research and development of novel refining technologies in the downstream sector. He is the author of 25 patents.
Olga Malova: Head of Catalysis, New Gas Technologies – Synthesis LLC Assistant Professor, Department of Organic Chemistry, Gubkin Russian State University of Oil and Gas. Prof. Malova is the co-developer of the Methaforming process catalyst. Prior to her current role at New Gas Technologies – Synthesis LLC, Prof. Malova worked with Bayer and Eni in developing refining catalysts.
Corresponding author: Stephen Sims, [email protected]
1. Introduction
Gasoline should continue to be the major automobile transportation fuel for the
foreseeable future. The International Energy Agency predicts a 30% increase in global energy
demand to 2040 which the agency reckons will be fueled by an increase in the consumption of
all modern fuels (International Energy Agency, 2016). Even though there has been a gradual
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decline in gasoline consumption in developed countries, global gasoline consumption continues
to be spurred by growth in automobile markets in China, India and other rapidly urbanizing
countries. Oil consumption is up 33%, in non-OECD countries since 2005 (Covert et al., 2016).
Concurrently with this growth in demand for gasoline, stricter environmental regulations are
being enforced in most countries to regulate benzene content, vapor pressure, content of olefins
and dienes in gasoline. While shale-derived oil will have some impact on overall crude oil
quality, the average quality of global crude oil is expected to gradually decline. This, among
other factors, may force refineries to utilize streams with increasing sulfur content and lower
octane. This scenario can put a strain on existing technologies to economically meet product
requirements. This provides the incentive to develop novel catalytic processes for producing
high-octane, low-olefin streams.
New Gas Technologies – Synthesis (NGTS) Methaforming process converts a wide range
of low octane naphtha streams with methanol into a high-octane gasoline blend-stock. The
process yields low benzene content and can handle feeds containing up to 1000 ppm of sulfur,
removing up to 90 % of sulfur without the need for hydrogen.
Methaforming uses a proprietary novel zeolite catalyst in a process flow scheme similar
to naphtha hydrotreating. Methaforming yields and associated octane numbers are comparable to
isomerization + continuous catalyst regeneration (CCR) reforming. However, Methaforming is a
one-step process that can replace naphtha desulfurization, reforming, isomerization and benzene
removal thereby reducing costs to as little as a third of typical costs of conventional technologies.
In Methaforming, low-octane naphtha streams are contacted with NGTS’ zeolite-based
catalyst and methanol at 660-730oF and 50-150psi. Methanol is dehydrated in an exothermic
reaction releasing the methyl radical which alkylates benzene into toluene and converts other
aromatics into alkyl aromatics. Just like in reforming, normal paraffins and naphthenes are
converted into aromatics in an endothermic reaction. Unlike reforming, however, Methaforming
can tolerate sulfur content of up to 1000 ppm in the feedstock. Special feed preparation for
sulphur-containing streams is usually not necessary. Also, feed olefins and dienes do not
significantly impact the catalyst’s activity or lifetime. The product stream from a Methaformer is
a high-octane gasoline blending stream rich in high-octane isoparaffins and aromatics, low in
benzene and olefins.
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For refiners with a wide range of low-octane naphtha streams, NGTS’ Methaforming
provides an effective and profitable alternative solution with minimal feed preparation and
modest capital and operating costs to achieving high-octane product yields. Additionally, the
process can be easily implemented by revamping an idle hydrotreater or semi-regenerative
reformer into a Methaformer.
2. Process Description
Most refineries upgrade naphtha by producing high-octane blendstocks using
isomerization and reforming. The feeds need to be hydrotreated to remove essentially all sulfur
before being sent to reformers or isomerization units. The whole range of activities mean several
units are required to achieve the required gasoline specifications. On the other hand, the
Methaforming process uses only one unit, reducing both capital and operating costs. The general
process scheme consists of the Methaforming reactor and the product stabilization column.
Figure 1 - Simplified Methaforming Process Flow Diagram
The Methaforming process is based on extensive R&D in catalysis and process design
conducted over several years by the NGTS scientists. One of the most important aspects of the
Methaforming process is the patented reactor section. The Methaforming reactor is a multi-stage
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fixed-bed adiabatic reactor with methanol injection between each catalyst bed. In the upper part
of each reactor bed, predominantly exothermic reactions occur, mainly dehydration of methanol.
Endothermic reactions occur in the bottom part of each bed. The total thermal effect is slightly
endothermic or exothermic depending on the ratio of methanol to naphtha. The oxygenate
dehydration reaction, which is exothermic, is faster than the endothermic naphthene
dehydrogenation reaction. This results in a temperature rise early in each catalyst bed followed
by a decline. Methanol is injected at multiple stages of the reactor to minimize temperature
gradients. This increases the selectivity of the process and enhances the life of the catalyst and its
time between regenerations.
While methanol is the primary oxygenate used in the Methaforming process, other
oxygenates can be used with or instead of methanol. Also, light olefins such as FCC dry gas can
be used with or instead of methanol. This possibility makes Methaforming a very attractive
choice for refineries with oxygenate or olefin-rich streams such as ethanol and FCC gas.
Another important distinguishing feature of Methaforming is that the catalyst requires no
precious metals. In most analogous processes, the need for precious metals makes their use both
expensive as well as more complicated due to the sensitivity of these catalysts to poisons and
high temperatures.
Given the foregoing, the Methaforming process reactor was designed to achieve the
desired conversion results while maintaining an acceptable temperature profile as well as to
attain a uniform distribution of flow across the reactor eliminating hotspots that can impair the
process performance. While the process operating conditions will depend on final application,
the following provides a range of process parameters that may be applied.
• Temperature of reactor inlet: 662-788° F (350-420 C)
• High-pressure separator: 94 - 174 psia (0.65-1.2 MPa)
• Space velocity, liquid volume: 0.7 – 1.5 h-1
3. Scalability and Performance Data
The simplicity of the Methaforming process greatly enhances scalability across a wide
range of naphtha feedstock. Lab and pilot plant testing has been conducted for over five years
with the process demonstrating excellent performance on full range naphtha, light naphtha,
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condensate, FCC naphtha, LPG, FCC olefin-rich gas and pyrolysis gasoline. The tests were
conducted in 3 units: 0.0012 BPD, 0.012 BPD and 0.23 BPD. Currently, a 100 BPD demo unit in
Russia is being completed for operation in the first quarter of 2017.
The 2 larger laboratory test units are shown in the figure below.
0.012 BPD lab unit
0.23 BPD lab unit
Figure 2. NGTS’ Methaforming test units
Design parameters are optimized by conducting parametric studies on each feedstock.
Optimal parameters are a combination of: temperature, pressure, space velocity and methanol
fraction. By conducting the process over a wide range of parameters and correlating the yield and
RON of the methaformate obtained, the optimal process parameters are determined to guide
further development and scale-up.
Results of parametric studies for one typical feedstock are presented below.
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Figure 3. Results of parametric studies on NGTS’ Methaforming pilot plants
The graphs above demonstrate the constraining factors of the Methaforming process.
Increasing the temperature of the process increases octane obtained but lowers yield. At higher
temperatures, aromatization reactions are favored, leading to the production of a higher volume
of aromatics in the product and hence higher octane number. Increasing methanol fraction in the
feed increases both yield and octane number. However, for the other factors, namely
temperature, pressure and space velocity, optimal processing conditions is a compromise
decision on either increasing yield or octane number. Based on parametric studies, optimal
processing conditions have been determined for several feeds including full range naphtha, light
virgin naphtha, FCC naphtha, raffinate from aromatic extraction and a number of non-standard
‘orphan’ feeds. This extensive testing has shown that Methaforming can be used to process most
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naphtha feeds in the C4-C10 range into high-octane, low-olefin gasoline blendstock. Depending
on refining needs, Methaforming is easily adaptable to limit the quantity of aromatics produced
by tuning process parameters to suit desired product characteristics.
The selectivity and yield advantages of the Methaforming process can be demonstrated
by examining pilot plant data. As an example, given below are the standard yields obtained for
the Methaforming of full range naphtha. Typical yields of Methaformate of full range naphtha is
between 83 - 93% depending on process parameters.
Table 1. Standard yields for the Methaforming of Full Range Naphtha from NGTS’ library
Feedstock Units Feed name FRN True boiling point range ° С IBP-150 PONA wt. % 66 /1 /24 /9 RON/MON 75/61 Total Sulfur ppm 180.0
Parameters Units Т (reactor inlet) ° С 360 Pressure atm 5 Space velocity: liquid hourly, W h-1 1.20
BALANCE Units Feeds
Methanol mt 0.283 Naphtha feed mt 1.0 Ethanol mt - Ethylene mt - Total mt 1.283
Products Methaformate (С5+ + 3% C4) mt 0.926 LPG (90% C3 + 10% C4) mt 0.082 С4 pure mt 0.103 Fuel gas mt (0.003) Hydrogen mt 0.001 Water mt 0.159 RF & L mt 0.015 RON 90 Total mt 1.283 Added value* $ 236
*calculated based on December 2016 price assumptions.
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4. Process Chemistry
Naphtha from different sources vary greatly in their hydrocarbon composition and
therefore in the ease of conversion in isomerization/reforming as well as Methaforming. The
composition of the product stream and the ease of conversion depend on the mix of paraffins,
olefins, naphthenes and aromatics of the feedstock. Methaforming will convert most of the
normal paraffins, naphthenes and olefins while retaining most of the isoparaffins. The resulting
product is rich in aromatics (up to 30-45% depending on process parameters) and dual branched
isoparaffins.
The shift in chemical compositions of the pilot tests conducted, shows that Methaforming
aromatizes normal paraffins while retaining most of the high-octane isoparaffins. A feedstock-
product comparison of one of the test runs on full range naphtha is shown in the chart below.
Figure 4. Feed-product comparison for Methaforming of Full Range Naphtha (total
aromatics content is controlled based on refinery needs)
As can be seen from the chart above for Full Range Naphtha, Methaforming converts
72% of the normal paraffins while retaining more than 70% of the isoparaffins. Naphthenes are
reduced through dehydrogenation and 38% of the product is made up of high-octane aromatics.
The aromatics mix for this run is shown in the table below.
Table 2 - Aromatics composition from Methaforming of full range naphtha
Component Naphtha feed, % wt
Product (Methaformate), %wt
Benzene 1.0 0.9
24.37.0
1.4
2.7
41.0
29.3
24.6
23.0
8.7
38.0
Naphtha Methaformate
aromatics
naphthenes
isoparaffins
olefins
n-paraffins
100% 100%
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Component Naphtha feed, % wt
Product (Methaformate), %wt
Toluene 2.4 6.9
C8 aromatics 3.0 16.0
C9 aromatics 1.6 8.4
C10 aromatics 0.6 2.4
C11 aromatics 0.1 2.5
C12 aromatics 0.0 0.9
Total in stream 8.7 38.0
As the data above demonstrates, Methaforming avoids benzene while increasing the
yields of toluene, xylene and C9 aromatics.
There are numerous chemical reactions that occur during the Methaforming process.
Some of these reactions are highlighted below. As expected, methanol plays a vital part in
upgrading hydrocarbons. Upon contact with the zeolite catalyst, methanol yields a methyl
radical. The methyl radical can react with itself to yield ethyl radical which can ethylate aromatic
groups or be further converted to higher olefins and aromatics. The methyl radical can also
directly react with aromatics present in the feed to form high-octane alkyl aromatics:
Apart from the alkylation of aromatic rings, methanol itself is converted into a mix of high
octane aromatics, naphthenes and paraffins (simplified reaction pathway for methanol
conversion is shown below).
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Every step indicated in the above simplified scheme is an equilibrium reaction and hence
the products of the conversion process will depend on process parameters.
Olefins and dienes present in the feedstock follow a similar conversion pathway. Newly
formed aromatics can be further alkylated; paraffins and naphthenes can be further converted to
isoparaffins and aromatics.
Paraffins are converted into aromatics and isoparaffins. The aromatization of paraffins
occur through intermediate formation of cycloalkanes:
Naphthenes in the Methaforming process undergo dehydrogenation, yielding aromatics:
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Methaforming shows extended catalyst life cycle because the catalyst, unlike analogues,
is tolerant to steam and sulfur. The expected lifetime of the catalyst is 5 years with a run length
between regenerations of a month. Also, due to the properties of the NGTS’ zeolite catalyst, the
content of fused-ring aromatics (e.g. naphthalene) in the product remains below 0.5%. By using a
process scheme that allows for a distributed feed supply of methanol, increased conversion and
selectivity is achieved.
5. Process Economics & Comparison
For new plant applications, the major benefit of Methaforming is its cost. Both initial
capital cost and operating costs are lower in comparison to the combined processes of hydro
treatment, isomerization, benzene reduction and catalytic reforming. Also, it is important to note
that Methaforming is a green technology with very low greenhouse gas (GHG) emissions. In the
USA, the refining industry is the third largest producer of greenhouse gas emissions (Plagakis,
2013). These emissions come from traditional refining infrastructure including furnaces, boilers,
steam reforming process for H2 generation etc., with oil and gas fuel firing of furnaces and
boilers accounting for 65% of total refinery CO2 emissions (Elgowainy et al., 2014). As
explained above, Methaforming is a one-step process, using an adiabatic multi-bed reactor with
no reheat furnaces and no need for hydrogen. The Methaforming process configuration and
chemistry yields better heat management and consequently lead to significant reduction in GHG
emissions.
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Methaforming yields and associated octane numbers of products can be comparable to a
combined isomerization and CCR reforming; and can be significantly better than
isomerization/semi-regen reforming. As a result, Methaforming offers a low-cost approach to
improve yields and to debottleneck gasoline production for existing semi-regen reformers. This
yield advantage is worth $57 million/year at a retrofit cost of about $20 million for a 20 K BPD
unit. The retrofit is done at the associated naphtha hydrotreater with the major cost being
replacement of the existing reactor with two larger ones.
Refiners with fluid catalytic cracking (FCC) can increase Methaformer profitability by
$100 per ton ($7 per barrel) by using light olefins from the FCC dry gas to replace the methanol
in a Methaformer. For example, a 50K BPD FCC produces enough ethylene to replace about half
of the methanol in a 25K BPD Methaformer generating economic added value of over $40
million/year.
A number of use cases are described below.
a. Use case 1 - upgrade light virgin naphtha.
The conventional solution available to upgrade light virgin naphtha is to use isomerization
possibly with recycle. The refiner will need to factor in energy costs of recycle and ensuring the
feed is free of sulfur. The presence of sulfur typically requires hydrotreating just as before the
reformer before it can be sent to the isomerization unit. An alternative is using Methaforming.
Light virgin naphtha (LVN) contains C5, C6 and C7 in a ratio of 50/40/10. The multi-branch
isomers present in the LVN are relatively unreactive in Methaforming. The cyclic paraffins are
further converted into aromatics and alkyl aromatics according to the reaction schemes presented
earlier. Further, the use of FCC dry gas is very economically attractive. The FCC dry gas
contains up to 20% wt. ethylene, which is the key intermediate product of the Methaforming
process. The net economic comparison of the two approaches for a 10K BPD plant is illustrated
in Table 3.
Table 3 - Economic comparison of Methaforming with Isomerization unit with recycle
New 10 K bpd unit (400 K tpa)
Methaforming with FCC dry gas
Alternative (isom with recycle)
∆ Methaforming- Alternative
Yields, $MM/yr 120 110 10
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Methaforming is clearly the better choice in this use case as it gives $12 million per year higher
profit and has a $20 million lower capital expenditure than the alternative.
b. Use case 2 – Grassroots Methaformer to process raffinate and dry FCC gas
For a refiner with 60 RON raffinate from aromatics extraction, the traditional choice is to
blend the raffinate into the gasoline pool. This obviously reduces the pool’s octane number.
Raffinate contains mostly paraffinic hydrocarbons which are converted in a Methaformer into
high octane isoparaffins and aromatics. This stream which includes C6 to C10 may be processed
in a Methaformer giving very attractive economics. Methaforming of the raffinate can be carried
out using methanol or using dry FCC gas to replace methanol. FCC dry gas is often used as fuel
gas. Table 4 below provides a comparison between these two choices evaluated for a 2K BPD
unit.
Table 4 - Processing low octane raffinate and FCC dry gas with Methaforming
New 2 K bpd unit (88 K tpa)
Methaforming (with FCC dry gas)
Alternative (blend into gasoline)
∆ Methaforming- Alternative
Yields, $MM/yr 89 60 29
OpEx, $MM/yr 2 0 2 CapEx, $MM 17 0 17 Total NPV at 12% 575 408 + 167
c. Use case 3 - upgrade existing semi-regen reformer
A semi-regen reformer has lower yields than either a CCR reformer or Methaformer. This
provides an economic opportunity for conversion. However, the capital cost for replacing a semi-
regen with CCR is substantial. On the other hand, the semi-regen reformer may be very
economically converted into a higher yield Methaformer. This approach involves retrofitting the
naphtha hydrotreater in front of the semi-regen reformer into a Methaformer by adding dual
OpEx, $MM/yr 4 6 -2
CapEx, $MM 30 50 -20
Total NPV at 12% 860 750 110
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reactors. Based on Methaforming pilot plant testing on full range naphtha, the following
economics are expected.
Table 5 - Replacing a semi-regen reformer with a Methaformer
New 20 K bpd unit (860 K tpa)
Methaforming semi-regen reformer ∆ Methaforming- Alternative
Yields, $MM/yr 206 149 57
OpEx, $MM/yr 7 14 -7
CapEx, $MM 20 0 20
Total NPV at 12% 1330 920 410
d. Use case 4 - Grassroots Methaformer instead of traditional naphtha processing suite
The traditional complete naphtha processing suite includes hydrodesulphurization,
catalytic reforming and isomerization unit. A refiner looking to build or expand its reforming
capacity can opt for a grassroots Methaformer over the traditional suite. The clear advantages of
using a Methaformer are highlighted in the table below. Methaforming has a remarkably lower
CapEx. This is achieved because Methaforming is a one-step process, using fewer units and
requiring lower operating costs.
Table 6. Grassroots Methaformer instead of a traditional naphtha processing suite
For 20 K BPD unit (860 K tpa) Methaforming Alternative
(combined process) ∆ Methaforming- Alternative
Yields, $MM/yr 206 202 + 4
OpEx, $MM/yr 7 21 - 14
CapEx, $MM 50 156 - 106
Total NPV, $MM 1 300 1 080 + 220
A 20K BPD Methaforming shows better performance in terms of economic returns. With
$14 million lower operating costs, and $4 million better yields, the profit margin advantage for
using Methaforming is $18 million per year.
6. Conclusion
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The results obtained from hundreds of pilot runs show that Methaforming of low octane
streams (Light virgin naphtha, Full range naphtha, non-standard low-value refinery naphtha
streams) presents an opportunity and alternative solution to improve the value of these streams.
The proprietary zeolite catalyst used in the process is tolerant to high sulphur content (up to 1000
ppm) and steam.
The Methaforming process runs under relatively mild operating conditions in a reactor
design similar to proven hydroprocessing reactor design. The reactor design and process
parameters ensure that Methaforming can be run with minimal technical risks, either by
revamping an idle hydrotreater or building a grassroots Methaformer. The components of the
Methaforming process are well proven and therefore carry minimal inherent risks. The
Methaforming process flow is similar to a hydrotreater except that methanol is used instead of
hydrogen. This process configuration allows for a hydrotreater or reformer to be revamped for
Methaforming. Since hydrotreaters and reformers as well as other fixed bed gas phase processes
have well established reactor designs, there are low technical risks associated with implementing
Methaforming. The process is further simplified because there is no recycle compressor. Also,
the process configuration has no reheat furnaces, thereby, leading to energy savings and reducing
the carbon footprint.
Currently, NGTS is overseeing the completion of the first pilot-scale demonstration plant.
The 0.5 m3 reactor producing 100 BPD, located in Russia, will go online in the first quarter of
2017 to validate the predicted yields and scale up factors of the process. The plant is expected to
generate income because of favorable Methaforming economics, giving more than $200/ton
uplift on initial feeds.
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Figure 2 - The 0.5 m3 reactor, 100 BPD Methaforming unit
References
1. Covert, T., Greenstone, M., Knittel, C.R., 2016. Will We Ever Stop Using Fossil Fuels?
J. Econ. Perspect. 30, 117–138. doi:10.1257/jep.30.1.117
2. Elgowainy, A., Han, J., Cai, H., Wang, M., Forman, G.S., DiVita, V.B., 2014. Energy
Efficiency and Greenhouse Gas Emission Intensity of Petroleum Products at U.S.
Refineries. Environ. Sci. Technol. 48, 7612–7624. doi:10.1021/es5010347
3. International Energy Agency, 2016. World Energy Outlook 2016 (Executive Summary).
IEA WEO.
4. Plagakis, S., 2013. Oil and Gas Production a Major Source of Greenhouse Gas
Emissions, EPA Data Reveals.