Methaforming: Novel Process for Producing High-Octane Gasoline from Naphtha and Methanol at Lower CAPEX and OPEX.

Transcription

1 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: Adeniyi Adebayo: Elena Lobichenko: Iosif Lishchiner: Olga Malova: 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. 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. 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. 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. 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, s.sims@ngts.us 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 1

2 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 o F and psi. 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. 2

3 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 3

4 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: F ( C) High-pressure separator: psia ( MPa) Space velocity, liquid volume: h 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, 4

5 condensate, FCC naphtha, LPG, FCC olefin-rich gas and pyrolysis gasoline. The tests were conducted in 3 units: BPD, BPD and 0.23 BPD. Currently, a 100 BPD demo unit in Russia is being completed for operation in the first quarter of The 2 larger laboratory test units are shown in the figure below 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. 5

6 Yield, % Yield, % Octane Temperature, o C Octane (RON) Yield, % Yield, % 75 Octane Pressure, atm Octane (RON) Yield, % Yield, % Octane Space velocity Octane (RON) Yield, % Yield, % Octane Fraction MeOH, % Octane (RON) 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 6

7 naphtha feeds in the C 4 -C 10 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 Parameters Units Т (reactor inlet) С 360 Pressure atm 5 Space velocity: liquid hourly, W h BALANCE Units Feeds Methanol mt Naphtha feed mt 1.0 Ethanol mt - Ethylene mt - Total mt Products Methaformate (С % C4) mt LPG (90% C3 + 10% C4) mt С4 pure mt Fuel gas mt (0.003) Hydrogen mt Water mt RF & L mt RON 90 Total mt Added value* $ 236 *calculated based on December 2016 price assumptions. 7

8 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 feedstockproduct comparison of one of the test runs on full range naphtha is shown in the chart below. 100% 100% aromatics naphthenes isoparaffins olefins n-paraffins Naphtha Methaformate 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

9 Component Naphtha feed, % wt Product (Methaformate), %wt Toluene C 8 aromatics C 9 aromatics C 10 aromatics C 11 aromatics C 12 aromatics Total in stream 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). 9

10 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: 10

11 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 H 2 generation etc., with oil and gas fuel firing of furnaces and boilers accounting for 65% of total refinery CO 2 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. 11

12 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 C 5, C 6 and C 7 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

13 OpEx, $MM/yr CapEx, $MM Total NPV at 12% 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 C 6 to C 10 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 Methaforming Alternative Methaforming- (88 K tpa) (with FCC dry gas) (blend into gasoline) Alternative Yields, $MM/yr OpEx, $MM/yr CapEx, $MM Total NPV at 12% 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 semiregen 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 13

14 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 OpEx, $MM/yr CapEx, $MM Total NPV at 12% 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 OpEx, $MM/yr CapEx, $MM Total NPV, $MM 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 14

15 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 m 3 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. 15

16 Figure 2 - The 0.5 m3 reactor, 100 BPD Methaforming unit References 1. Covert, T., Greenstone, M., Knittel, C.R., Will We Ever Stop Using Fossil Fuels? J. Econ. Perspect. 30, doi: /jep Elgowainy, A., Han, J., Cai, H., Wang, M., Forman, G.S., DiVita, V.B., Energy Efficiency and Greenhouse Gas Emission Intensity of Petroleum Products at U.S. Refineries. Environ. Sci. Technol. 48, doi: /es International Energy Agency, World Energy Outlook 2016 (Executive Summary). IEA WEO. 4. Plagakis, S., Oil and Gas Production a Major Source of Greenhouse Gas Emissions, EPA Data Reveals. 16