Catalytic Bitumen Partial Upgrading under Methane Environment over

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Catalytic Bitumen Partial Upgrading under Methane Environment over Ag-Mo-Ce/ZSM-5 Catalyst and Mechanistic Study Using N-butylbenzene as Model Compound Lulu Zhao, Peng He, Jack Jarvis, and Hua Song Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.6b02374 • Publication Date (Web): 10 Nov 2016 Downloaded from http://pubs.acs.org on November 16, 2016

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Catalytic Bitumen Partial Upgrading under Methane Environment over Ag-Mo-Ce/ZSM-5 Catalyst and Mechanistic Study Using N-butylbenzene as Model Compound

Lulu Zhao, Peng He, Jack Jarvis and Hua Song*

Department of Chemical and Petroleum Engineering, University of Calgary, 2500 University Dr. NW, Calgary, Alberta T2N 1N4, Canada.

*Corresponding author Fax: +1 (403) 284-4852; Tel: +1 (403) 220-3792; E-mail: [email protected] 1

ACS Paragon Plus Environment

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Graphical Abstract

A novel catalytic methanotreating process is reported to partially upgrade bitumen at mild reaction conditions (400 oC and 3 MPa) for pipeline transportation with reduced cost and minimized carbon footprint and methane involvement into bitumen upgrading is evidenced via model compound and isotopic labelling studies.

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Abstract Bitumen extracted from oil sands which is abundant in Canada needs to be partially upgraded to meet pipeline specifications before being sent to downstream refineries. Hydrotreating where expensive hydrogen is involved at high pressure (15~20 MPa) is commonly employed as the technique to satisfy the upgrading requirement. In this study, it is reported that a partially upgraded crude oil can be readily produced from bitumen under methane environment at mild conditions (400 oC and 3 MPa) without H2 engagement under the facilitation of 1%Ag-5%Mo-10%Ce/ZSM-5 (Si/Al=23:1). Moreover, methane participation into the upgrading process was evidenced by model compound reactions employing n-butylbenzene as a model compound to typify heavy oil and clearly observed in 1H and 2D NMR spectra when CD4 was engaged as the methane source. Through extensive catalyst characterizations using TEM, XRD, and XPS, the excellent catalytic upgrading performance might be closely related to the highly dispersed silver and molybdenum oxide on the zeolite support at reduced oxidation state for better methane activation and partially reduced cerium oxide for coke reduction owing to its high oxygen mobility. The outcomes from this research could not only create an innovative route for more profitable natural gas utilization, but also benefit bitumen partial upgrading in a more economical and environmentally friendly way.

Keywords: Bitumen; Natural gas; Methane activation; Upgrading; Catalyst

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1. Introduction Heavy oil and bitumen extracted from oil sands are abundant in Canada. However, such unconventional petroleum deposit cannot be directly sent to existing refineries, which are often located in US, as feedstock for fuels and lubricants production, due to its high viscosity, low hydrogen to carbon ratio, and high impurities content. Therefore, such heavy crude oil needs to be partially upgraded to meet the pipeline transportation specifications and lessen the burden of downstream upgrading which would further convert the partially upgraded oil into fuel and chemical feedstocks.[1] Fuel products are further separated into a few sub-groups based on their boiling points including gasoline and diesel by fractional distillation process. Gasoline often refers to the fuel for the internal combustion engine, while that used in diesel engines is denoted diesel. Traditionally, hydrogen thermal cracking (named hydrotreating) is widely practiced to break down the long carbon chain and especially the complicated polycyclic molecular structure of the high molecular weight residues, saturate the formed small molecules, and remove the impurities such as sulfur, nitrogen, and metal out from the partially upgraded crude oil.[2] However, the involvement of such expensive hydrogen resource at high pressure (e.g. 15~20 MPa) which is not naturally available results in the significant cost increase of this partial upgrading step. It is thus critical to find out an alternative substitute which is readily available and abundant in nature for prominent upgrading cost reduction, making the whole process more economically attractive. Currently over 50% of the world’s hydrogen production relies on the conversion of 4


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natural gas through steam reforming process.[3] Instead of using hydrogen, if natural gas can be directly utilized in the upgrading process as the reducing agent, the steam reforming process can be completely eliminated, leading to the upgrading process cost reduction. Furthermore, compared to the traditional hydrotreating process, such novel process can produce extra synthetic crude oil originating from the introduction of natural gas molecules into the carbon chain of cracked heavy crude oil, making the upgrading process even more economically favorable. Moreover, such carbon incorporation could lead to less greenhouse gas (i.e., CO2) emission to the surroundings, thus benefiting our environmental protection. Natural gas, mainly composed of methane, is chemically inert and is therefore predominantly applied to domestic heating. However, given the relatively recent discovery of large shale gas formations, natural gas finds itself in abundance throughout North America. Thus, the utilization of natural gas for other applications such as chemical upgrading for transportation and valuable products, has encouraged research in this area for over half a century. Despite this, a breakthrough in this area has yet to be seen and an effective technology capable of converting methane into valuable commodities remains highly sought after by both academia and industry. Therefore, the study reported here aims to develop a novel catalytic process named methanotreating where bitumen can be partially upgraded under methane environment. An effective catalytic system needs to be developed to reduce operating conditions (pressure and temperature) when considering methanotreating, to maintain economic 5


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interest as well as lower the energy barrier. The challenge, as mentioned before, lies with methane’s chemical and physical inertness in the form of strong bonding energies in its tetrahedral structure (~435 kJ mol-1). Thus, the catalyst in question must first activate methane through H3C-H bond cleavage so that it can participate in the desired upgrading reactions in the same capacity as would hydrogen in a hydrotreating system. By looking at literature provided over the last 30 years, the dedication of many researchers is evidenced in the area of catalytic systems for non-oxidative methane activation [4-10]. Despite seeing < 10% methane conversion to major aromatic products at temperatures above 700°C, among the most promising catalysts are zeolite supported Mo catalysts when concerned with higher hydrocarbons converted from methane. [11] Given that these conditions are not applicable to the requirements necessary for a proposed methanotreating process, more investigative work is needed. However, inspirational and no doubt pioneering work, as seen in the investigation of Choudhary, et al.

[12]

as well as a series of consequential publications

[13-21]

has indicated

that methane conversion in the presence of olefins can be improved significantly and is possible at much lower temperatures (400 ~ 600 oC) and pressures (1 atm). Under an appropriate catalyst and based on the reported synergetic effect, the co-existing cracked shorter carbon chain species formed from the thermal treatment of bitumen should help with the activation of methane and its subsequent conversion. As mentioned earlier, the cleaved C-H bond(s) will provide the following species; CHx and (4–x)H, allowing the now available hydrogens’ to become involved in the 6


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saturation and hetero atom removal of the cracked products. Under the facilitating catalyst, this process should also be accompanied by the reaction of cracked hydrocarbons with the aforementioned CHx moiety to produce yet more synthetic oil. It is thus assumed that when given a suitably charged catalytic system, a synergetic effect can be evidenced between heavy oil and methane during the methanotreating process.

This

has in fact been evidenced by various parties such as Ovalles et al.[22, 23] not to mention, within our own promising research in the area of methane environment facilitated heavy oil[24] and bio-oil[25-27] upgrading at a bench scale. Although the technical feasibility of bitumen catalytic methanotreating has been preliminarily evidenced with Ag-Zn/ZSM-5 in our earlier publication

[24]

, more

experimental results should be accumulated over modified catalyst systems to provide more direct confirmation and deliver the partially upgraded oil with better quality for meeting the pipeline transportation specifications and easing the downstream refining burden at the other end of the pipeline. In this study, Ag-Mo-Ce/ZSM-5 catalyst was synthesized using impregnation method and evaluated for triggering bitumen partial upgrading reaction under methane environment at 400 oC and 3 MPa. The formed crude synthetic oil was extensively analyzed for its quality control in terms of viscosity, acidity, density, water content, gasoline & diesel content, asphaltene content, heating value, stability, and elemental composition. Nt-butylbenzene was selected as the model compound for methane participation investigation through isotopic labelling study. In addition, versatile characterization techniques including TEM, XRD, and XPS were 7


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employed for identifying the correlations between the properties of the developed catalyst and its catalytic performance.

2. Experimental 2.1 Feedstock and chemicals Canadian Bitumen (Syncrude Canada Ltd.) was used as provided. Toluene (VWR International, > 99.5 wt.%) enabled the isolation of toluene-insoluble solids (such as catalyst and coke) in the bitumen and its associated products. Heptane (Sigma-Aldrich, 99% anhydrous) allowed the quantification of asphaltenes within oil samples. N-butylbenzene (Sigma-Aldrich, ≥99% purity) was used as a model compound for bitumen. 2.2 Catalyst synthesis NH4ZSM-5 (Alfa Aesar, SiO2/Al2O3 molar ratio of 23, specific surface area = 425 m2 g-1) was calcined for 5 hours in air at 600 °C to give HZSM-5. HZSM-5 then underwent incipient wetness impregnation (IWI) by use of silver nitrate (AgNO3), ammonium

molybdate

tetrahydrate

((NH4)6Mo7O24•4H2O)

and

cerium

nitrate

hexahydrate (Ce(NO3)3•6H2O) aqueous solutions all at > 99% from Alfa Aesar. IWI process provided 1 wt.% Ag-5 wt.% Mo-10 wt.% Ce/HZSM-5 catalyst which was then dried in the oven (92 oC) overnight. The catalyst was finally calcined for 3 hours in air at 600 °C and stored appropriately for later use.

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2.3 Catalytic performance test A leak test was conducted and post passing, bitumen (80g) and catalyst (1wt.%) was loaded into an autoclave (Parr 300mL), purged to remove air and pressurized (30 bar) with appropriate reactant gas (nitrogen or methane). The temperature was raised to 130°C from RT and held for 30 minutes under agitation (mechanic rotor associated with Parr 300 mL setup) to ensure thorough catalyst dispersion. Temperature was then raised to the desired reaction temperature (400 °C) and held for 20 minutes under maintained stirring. Upon reaction completion (dictated by experiment in question) the autoclave was plunged into a cold-water bath to quench. This technique was also used when applying the model compound to the reaction. For the convenience of isotopic labelling study, reaction between n-butylbenzene and CH4/CD4 (99% 2D, Cambridge Isotope Laboratories, Inc.) was conducted in a Parr® autoclave of 100 mL capacity. 0.5 g catalyst was charged into the reactor with a glass vial carrying 0.1 g n-butylbenzene. The reactor was pressurized to 3 atm by CH4 or CD4 after the air was purged by N2 at 1 atmospheric pressure. The reactor temperature was then ramped up with a rate of 20 oC/min to the designated temperature (400 oC) and held for 60 mins. After the reaction, the reactor was allowed to cool down to room temperature. The formed liquid product embedded into the charged solid catalyst was extracted out using 10.0 g CS2 (Sigma Aldrich, ≥99.9%) as solvent for the following NMR analysis. 2.4 Characterizations 9


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Liquid Product was quantified for water content by using Karl Fischer titration (Metrohm 870 Titrino Plus) and the average value of 3 runs obtained. The totle acid number (TAN) of the liquid product was also measured (Metrohm 848 Titrino Plus) and the average value of 3 runs was obtained. To measure the density of the liquid product at 15.6 oC, a gas displacement density analyzer was employed (AccuPyc II 1340, Micromeritics) and the temperature was controlled via a Cole-Palmer fabricated instrument (PolyScience® LS 51 compact recirculating chiller). A custom fabricated distillation apparatus setup was employed to perform diesel and gasoline separation, running at 217 oC, -860mbar and 350 oC, 1 atm respectively. Oil products were analyzed for compatibility and stability features by use of a spot tester (TriboAmix®) manufactured by TRIBOMAR GmbH and as defined by the ASTM D4740 procedure. Liquid product heating value was obtained by Parr 6100 compensated jacket calorimeter. The oil product viscosity was quantified by use of a Fungilab designed Viscolead one series L viscometer whilst at a temperature of 25°C maintained by use of a circulated hot water bath. Elemental analysis of the oil products was conducted using an elemental analyzer (Perkin Elmer 2400 Series). The weight percentages of C, H, N and S are reported by the instrument. The oxygen content is calculated as the balance assuming that only C, H, N, 10


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S and O are present in the product oil. Produced oil was dissolved in toluene to obtain a solution, which was then filtered and extracted via Soxhlet extractor until a colorless toluene solvent obtained. The filter paper was collected, dried for 2 hours in an oven at 100°C and weighed to determine coke yield. ASTM standard D 6560-00 was employed to determine asphaltene content of oil samples. A fraction of the oil sample was mixed with heptane and heated under reflux. The precipitate (asphaltenes, waxy substances and inorganic material) were then put to a filter paper and washed in an extractor with heptane to remove the waxy substances. A solute was then formed of the remaining mixture by use of hot toluene and the asphaltenes separated. The extracted solvent was then evaporated and the asphaltenes weighed. The 1H NMR experiments were conducted at 9.4 T (ν0(1H) = 400.1 MHz) on a BRUKER AVANCEⅢ 400 spectrometer with a BBFO probe. 1H NMR chemical shifts were referenced to CHCl3 at 7.24 ppm. A spectral width of 12 kHz and a pulse delay of 2 s were used to acquire 1H NMR spectra with 64 scans per spectrum. The NMR samples in the tubes were prepared by mixing 3.0 mL sample with 3.0 mL CDCl3. The 2D NMR experiments were conducted at 9.4 T (ν0(1H) = 61.4 MHz) on a BRUKER AVANCEⅢ 400 spectrometer with a BBFO probe. A spectral width of 2.5 kHz and a recycle delay of 7 s were used to acquire 2D NMR spectra with 512 scans per

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spectrum. The Transmission Electron Microscopy (TEM) images were acquired on a Philips Tecnai TF-20 TEM instrument operated at 200 kV. Ethanol was used to disperse the sample which was then supported by lacey-formvar carbon on a 200 mesh Cu grid.

The

TEM was equipped with an X-ray analyzer that collected EDX spectra for elemental analysis. The images were collected under STEM mode to improve the contrast between carbon and silver phases. The prepared catalysts underwent x-ray diffraction via Rigaku Multiflex diffractometer (Cu Kα irradiation, 20Kv, 40mA in 2θ of 5-50 o) to obtain composition in the crystalline phase. X-ray Photoelectron Spectroscopy (XPS) spectra were acquired using an AXIS His, 165 Spectrometer manufactured by Kratos Analytical with a monochromatized Al Kα X-ray source. A voltage of 2.3V was chosen to make the charge balance. The samples were put in a stainless steel sample holder. Survey scans were performed to identify all the elements within the sample and estimate the amount of each element, followed by more detailed regional scans for Ag 3d, Zn 2p, C 1s, and O 1s orbitals in order to collect high resolution spectra for these elements. A controlled-atmosphere transfer chamber was used to transfer the sample to the XPS instrument without exposure to atmosphere. The composition of the product oil was determined by the pre-calibrated Gas Chromatography-Mass Spectrometer (GC-MS: PerkinElmer GC Claus 680 and MS

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Clarus SQ 8T) equipped with a Paraffins-Olefins-Naphthenes-Aromatics (PONA) column (Agilent HP-PONA). The oven temperature of the GC was programmed to hold at 35 oC for 15 min, ramp to 70 oC at 1.5 oC/min, ramp to 150 oC at 3 oC/min and hold for 30 min, then ramp to 250 oC at 3 oC/min and hold for 2 min.

3. Results and discussion 3.1 Catalytic Performance of Bitumen Upgrading By inspection of Tables 1, 3, 4, and 5, a synergetic effect between methane and bitumen is clearly demonstrated during the partial upgrading process when the Ag-Mo-Ce/ZSM-5 catalyst is engaged under methane environment. This has led to the production of partially upgraded oil of the highest quality with regards to the following values: Lowest viscosity of (404 cP at 25 oC), highest diesel and gasoline contents of (37.1 wt.%), lowest density (0.9648 g/cm3 at 15.6 oC and equivalent API gravity of 15o), lowest acidity (0.02 mg KOH/g), highest heating value (41.4 MJ/kg), lowest asphaltene content (9.5 wt.%), and highest H/C atomic ratio (1.70). As well as this, a highest liquid yield of 98.2 wt.% is observed along with acceptable coke formation (0.38 wt.%) when compared to a series of control runs, indicating the most efficient carbon chain breakage and rearrangement once the catalytic methanotreating process is taking place. Given an initial methane pressure of 3.0 MPa and charged Ag-Mo-Ce/ZSM-5, a significant reduction in bitumen’s viscosity is observed; from a very high value of 848,080 cP to as low as 404 cP when under methane environment. It should be noted that this is lower than 13


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the viscosity reduction achieved over Ag-Zn/ZSM-5 over a reaction time of 150 min[24]. As put forward by both the Canadian and U.S. Governments for the transportation of oil via pipelines, the value of viscosity obtained in this paper is approaching that requirement. [28]

As well as this, and as previously mentioned, the high liquid yield (98.2 wt.%) and

low coke yield (0.38 wt.%) accompanies this low viscosity value when under the engagement of methane (3.0 MPa) and Ag-Mo-Ce/ZSM-5 catalyst (Table 1). When referring to Table 1, it is evident that upon the inclusion of methane presence in the reaction, a higher liquid yield is achieved with this effect becoming even more pronounced upon the addition of the charged Ag-Mo-Ce/ZSM-5 catalyst. This allows the suggestion that methane is incorporated into the resultant partially upgraded oil, especially upon the inclusion of the specially tailored catalyst. Deposition could possibly occur when given a 1 wt% of coke particulate and could in turn endanger the pipeline due to clogging. Thus, and as seen in this paper, low pressure methane (3 MPa) at a low temperature of 400°C when activated by Ag-Mo-Ce/ZSM-5 can be employed to reduce this coking effect and hence, increase the oils ability to flow along with reasonable stability. Ultimately, transportation via pipeline can be made more attractive and achievable for this unconventional petroleum resource as well as easing downstream refining work. The low coke formation (0.24 ~ 0.38 wt.%) when Ag-Mo-Ce/ZSM-5 is present might be closely related to the excellent oxygen storage capability (OSC) of the introduced cerium oxide in the framework of zeolite which would benefit oxidation of the deposited 14


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carbon to form CO or CO2 and thus lead to reduced coke formation. [29] Figure 1 displays the results obtained from spot tests conducted on the oil samples. This figure allows for a clearer picture when concerned with the compatibility and stability of oil products as seen in Table 1 as it demonstrates the oils ability to be stored for long periods of time as well its feasibility for long transportation. The barely present and blurred black inner ring in Figure 1f shows a lack of phase separation and referral to Table 2 and Figure 2 supports this, hence, the partially upgraded oil is of an improved quality for pipeline transportation when Ag-Mo-Ce/ZSM-5 is engaged under methane environment. When a closer look is given to Table 3 for the diesel and gasoline fractions of oil product (as reported in Table 1) it can be observed that the gasoline fraction from the partially upgraded bitumen (in the company of Ag-Mo-Ce/ZSM-5 and a methane environment) is the highest amongst competitors when compared. This alone would undoubtedly benefit its downstream refining at the other end of the pipeline and thus lead to significantly reduced production cost for its end use. Moreover, the impressive increased gasoline fraction allows the accumulation of yet more evidence of the synergetic effect between bitumen and methane (under catalyst) with regards to the cracking and rearrangement of bitumen when obtaining desirable products. Several additional properties of the oil samples reported in Table 1 are further analyzed and compiled in Table 4 in order to better reflect the quality of the partially upgraded oils. As one of the most important criteria for judging the bitumen upgrading 15


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degree, densities of all the oil products are measured and included into Table 4 for inspection. Charged Ag-Mo-Ce/ZSM-5 under methane environment gives the lowest density oil product (equivalent to 15 at API density) and is supported by the reduced viscosity and diesel/gasoline fraction data as presented in Table 3. Such density reduction might originate from the increased hydrogen content and decreased contents of sulfur and nitrogen in the partial upgraded oil as shown in Table 5 according to the density-composition relationship description given by M. Gray, et al.[2]. Furthermore, Table 4 also reports less acidity of the partially upgraded oil as evidenced by the reduced TAN value making it less likely to corrode the inside of the pipeline and hence benefiting long term storage and transportation. Once again, as shown in Table 4, Ag-Mo-Ce/ZSM-5 under methane environment demonstrates the most promising results when compared to control samples, with an acidity value of 0.02 mg KOH/g (100 times smaller than the value for raw bitumen and 10 times smaller than its N2 counterparts). A further demonstration of the synergetic effect between methane and bitumen (when in the presence of a suitably charged catalyst) is given when comparing the acidity value above to those of oil samples that underwent a methane run without the addition of a catalyst. Table 4 also gives respective water contents, an increased water content is accompanied by the reduced total acid number when partial upgrading occurs under methane environment, particularly with the facilitation of Ag-Mo-Ce/ZSM-5 catalyst where highest water content (0.196 wt.%) is reached with the lowest TAN value at 0.02 16


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mg KOH/g. This is probably due to the hydrodeoxygenation reactions taking place between oxygen containing molecules (e.g. hydroxyl and carboxyl groups) in cracked bitumen and hydrogen formed from activated methane as illustrated in our previous publication.[24] Ag-Mo-Ce/ZSM-5 and it’s associated performance during partial upgrading of bitumen is further evident during comparison of heating values for oil products as in Table 4. The methane runs always yield oil products with higher heating value when its N2 counterparts are referred. The highest heating value (41.4 MJ/kg) is associated with the oil product received during partial upgrading of bitumen under methane environment when the Ag-Mo-Ce/ZSM-5 catalyst is charged, thus providing more indirect evidence of methane incorporation into the molecules of the partially upgraded oil whilst under the influence of a suitable catalyst. When evaluating the impact of catalytic methanotreating of bitumen, it is important to measure the asphaltene reduction, as this is the most difficult component to upgrade[2] as well as being the major contributor to bitumen viscosity. Hence, the asphaltene contents of various oil products have been measured and documented in Table 4. The oil product obtained from the catalytic methane run has the lowest asphaltene content (9.5 wt.%) and thus exhibits the highest asphaltene reduction (~57 %) when taking into account that the asphaltene content of raw bitumen is 22.04 wt.%. This is further evidence for the positive contribution of the Ag-Mo-Ce/ZSM-5 catalyst and methane as a combination to bitumen

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partial upgrading. The observed asphaltene reduction over Ag-Mo-Ce/ZSM-5 is more significant compared with Ag-Zn/ZSM-5 (reduced to 12.3%) in previous work[24], suggesting an enhanced asphaltene conversion capability. Table 5 allows for the inspection of saturation with regards to the atomic ratio of H/C. By elemental analysis of the oil products, this information was obtained and can be used to verify methane’s participation during partial upgrading. The catalytic methane run gives the highest atomic ratio of H/C at 1.70 and hence confirms the positive role that both methane and the catalyst play during upgrading. Given raw bitumen H/C atomic ratio of 1.48, the H/C atomic ratio difference is shown to be larger compared with the results obtained from Ag-Zn/ZSM-5 catalyst in previous work[24], indicating an improved catalytic performance. It is also noticed that the lowest O/C atomic ratio is witnessed when the Ag-Mo-Ce/ZSM-5 catalyst is charged under CH4 environment, suggesting enhanced oxygen content removal under this upgrading condition. Evidence of the occurrence of denitrogenating and desulfurization reactions, albeit on a small scale, can also be seen due to a small reduction of N and S content post partial upgrading of bitumen. 3.2 Mechanistic studies It is widely accepted that bitumen has a complex chemical composition and complicated molecular structure[2, 30] and thereby a variety of its model compounds are often adopted so as to trace the chemistry during upgrading. Bitumen is rich in molecules with phenyl groups. In some components including asphaltenes, polyaromatic units are 18


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present in the molecular structure. Compared with paraffin or olefin, phenyl group containing feedstocks would produce partially upgraded liquid product with much less variety in molecular structure since phenyl moieties are relatively stable and hence, difficult to alter structurally during partial upgrading. Therefore, it is prudent to include the phenyl ring in the model compound to better represent bitumen molecules. According to literature[31, 32], n-butylbenzene has an aromatic component as well as a saturated alkyl moiety, while remaining relatively simple in its molecular composition compared to other available candidates and is therefore used to represent bitumen in this report. Tables 6 and 7 show the results when n-butylbenzene is substituted in place of bitumen as a part of the liquid feedstock and the partial upgrading reactions conducted. Nothing of note is to be taken when looking at Table 6 for the liquid yield, gas yield and final pressure when the environment is changed from N2 to methane (no support or catalyst) and the same can be said for the liquid product distribution as seen in Table 7. This is also the case when only a support is introduced. Overcracking of n-butylbenzene is observed in Table 6 when the support is present by interpretation of the largest value for final pressure (6.0 MPa ~ 6.1 MPa) in addition to the largest value for gas yield (4.0 wt.% ~ 4.1 wt.%) and lowest liquid yield (95.9 wt.% ~ 96.0 wt.%) as well as in Table 7 by highest n-butylbenzene conversion (86.86 % ~ 87.66 %) and liquid product formation with lower carbon number compared to those from its counterparts with catalyst charged. In addition, Table 6 also witnesses the lowest final pressure at 400 oC (4.6 MPa ~ 4.7 MPa) from the runs in the absence of either the zeolite support or Ag-Mo-Ce/ZSM-5 19


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where moderate gas yield is observed, indicating the least n-butylbenzene conversion. The lowest gas yields coupled with the highest liquid yields belong to the runs when Ag-Mo-Ce/ZSM-5 catalyst is employed where the final reaction pressures at the reaction temperature (i.e., 400 oC) are neither the highest nor the lowest, which is especially true for the catalytic methane run. A possible explanation for this intriguing phenomenon may be, that for the conversions under Ag-Mo-Ce/ZSM-5, very light hydrocarbons, such as benzene, have been formed due to the catalytic activation of methane; these light molecules possess the ability to be in the liquid phase at room temperature and in the gaseous phase under high temperature conditions. Furthermore, the lowest gas yield (2.1 wt.%) from the catalytic methane run which is even lower than that from the control run (3.7 wt.%) provides us more confidence in methane incorporation into the liquid product. In order to identify how methane gets involved in the upgrading process, the liquid products collected from various runs as shown in Table 6 are further analyzed by GC-MS and the major liquid product distributions as well as the conversions of n-butylbenzene and methane are summarized in Table 7. Benzene production is detected from all the reported runs. Moreover, it is worth noting that higher benzene formation is clearly observed whenever methane is present in the gas environment and this enhancement effect becomes more and more notable when HZSM-5 support or particularly Ag, Mo, and Ce modified ZSM-5 is charged, suggesting that the methane aromatization reaction takes place to an escalating degree due to the involvement of the catalyst. This collaborates with the evidence that methane conversion as high as 6.65% when 20


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Ag-Mo-Ce/ZSM-5 is engaged. Non-oxidative conversion of methane to form benzene by aromatization has been reported by a number of parties group

[24]

[11, 12, 16, 33-38]

and our research

. A control experiment using solely methane and the catalyst is carried out,

where the conversion of methane is not observed, suggesting that the conversion of methane is enhanced by the presence of n-butylbenzene. Further, more information can be obtained from Table 7 when n-butylbenzene upgrading is performed over Ag-Mo-Ce/ZSM-5. Isopropylbenzene : styrene and n-propylbenzene : styrene ratios under N2 and the catalyst are 3.6 and 6.4 respectively, as opposed to 6.3 and 8.6 for the same respective ratios when under CH4 and the catalyst. A higher ratio for propylbenzne : styrene ratio under CH4 and catalyst (14.9) than for N2 and catalyst (10.0) clearly demonstrates methanes participation in saturating the olefinic side chain of styrene, which has also been observed in previous research, [24, 39] through the equation (1).

(1) To further verify the involvement of methane in the upgrading process, the major liquid products except for benzene collected over Ag-Mo-Ce/ZSM-5 listed in Table 7 under CH4 atmosphere are compared to the control group runs where N2 is employed as the gas feedstock by arranging the product distribution based on the carbon number (Figure 3). Toluene is the only product in the C7 category. Ethyl benzene and xylene as well as styrene are the products in C8 group. C9-C14 groups refer to aromatic derivatives 21


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with methyl, ethyl, propyl, butyl, pentyl groups, or their combinations as the substitute groups. Figure 3 witnesses the slightly lower liquid product formation with lower carbon number (C7-C8) followed by enhanced aromatics production with higher carbon number (C9-C14) when methane is introduced, suggesting that methane might participate in the upgrading reaction and get incorporated into the molecular structure of the upgraded oil, thus leading to the shift of carbon number of the formed liquid product to the higher end when N2 run is referred. The methane participation into the upgrading reaction is further confirmed by the direct evidence provided by the NMR spectra collected from the liquid product when isotope-labelled methane are employed in the reaction with n-butylbenzene. Deuterium-enriched methane, i.e., CD4, is therefore engaged as the methane source in this study. The 1H (Figure 4) and 2D NMR spectra (Figure 5) of the liquid product are acquired and compared with those of the non-isotopic enriched product in order to probe the incorporation of the hydrogen atoms from methane to the products. On the 1H NMR spectra displayed in Figure 4, the intensities of the peaks at 7.24 ppm due to the CHCl3 in the solvent are similar. The intensities of other peaks, however, are greatly suppressed when CD4 is employed as the methane source. The peaks between 6.9~7.8 ppm are due to the H atoms on the phenyl rings. The signals between 2.2~2.7 ppm can be assigned to benzylic H sites. Those appearing at the region below 1.5 ppm are attributed to H sites of the alkyl groups that are not bonded to phenyl rings directly. The ratios between the peak areas with respect to that of CHCl3 are shown in Table 8. The peak areas due to aromatics 22


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and benzylic H sites are greatly reduced in the isotopic labelled products, while the peak area due to H in alkyl groups is less significantly reduced, suggesting that the hydrogen from methane favor the aromatic and benzylic sites over the alkyl group hydrogen sites. This observation is also further confirmed by the 2D NMR spectra, where the NMR signals of the D atoms are observed at the aromatic (7~8 ppm) and benzylic (2.6 ppm) sites. The presence of these signals demonstrates the incorporation of hydrogen atoms from methane into the product molecules, particularly at the phenyl and benzylic hydrogen sites. 3.3 Catalyst characterizations Physical characteristics and properties of Ag-Mo-Ce/ZSM-5 were obtained so as to observe the evolution of the catalyst whilst upgrading n-butylbenzene. This was achieved by TEM, XPS and XRD and the data collated in the associated Figures (6-10). Figure 6 reveals an unchanged diffraction pattern for ZSM-5 post loading of the active metal as well as that during the reaction, the framework is very well maintained. The suppressed diffraction peak intensities might be due to the migration of metal species onto the crystalline planes of the structure. In addition, CeO2 diffraction peaks at 28.55o from (111) crystal plane and 33.08o from (200) crystal plane are identified over Ag-Mo-Ce/ZSM-5 at various stages in its life, which could be attributed to the high loading during catalyst preparation (10 wt.%). The presence of diffraction peak at 28.55o might be also derived from the formation of mixed metal oxide Ce(MoO4)2 as a new phase, which is supported

23


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by the co-existence of Mo and Ce signals in the Energy-dispersive X-ray (EDX) spectra focused at selected particles present in the TEM images of Ag-Mo-Ce/ZSM-5 catalysts collected at various life stages as shown in Figure 7-9. It is worth noting that these two identifiable diffraction peaks decrease in size and broaden after reaction, suggesting that these active metal oxide particles might either get partially reduced to a lower oxidation state during the upgrading process as a result of the reductive environment or that their dispersion is improved on both the external and internal support. On the other hand, Ag and Ag2O diffraction peaks are non-observable, likely due to a low loading of 1 wt.% as well as the possibility of a high dispersion. The morphology and particle size as well as elemental composition of fresh Ag-Mo-Ce/ZSM-5 are further investigated using TEM equipped with EDX spectroscopy. After a thorough examination of the charged catalyst sample, no silver concentrated particles are identified, implying that the loaded 1% Ag might be highly dispersed on the catalyst surface with very small particle size which is beyond the resolution limitation (1 nm) of the employed TEM instrument. Nevertheless, Mo and Ce abundant particles are easily observable with resort to the same machine. Figure 7 shows the TEM image of a single represented area of the catalyst and its associated EDX spectra after focusing on the circled particles spot. By combing the TEM image and EDX spectra, it can be deduced that molybdenum and cerium oxides are either co-existing as a new single crystal phase within one particle as identified by the XRD diffraction pattern or individually concentrated in two adjacent particles with an average particle size of 8 nm 24


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as demonstrated by the corresponding EDX spectrum in Figure 7c. Per the TEM images of the catalyst collected both before and after the upgrading reaction (not included), the channel structure of H-ZSM-5 remains intact even post reactions at high temperature and high pressure (N2 or CH4 conditions), which collaborates with the XRD results as reported in Figure 6. Nevertheless, as shown in Figure 8, the particle sizes (~18 nm at averaged value) of the spent Ag-Mo-Ce/ZSM-5 catalyst collected under N2 environment are much larger than those of the fresh catalyst when referring to Figure 7a, indicating that under N2 conditions, the loaded metal species tend to aggregate. Nonetheless, the severe active metal particles agglomeration is effectively lessened when CH4 is present, leading to smaller resulting particles of the spent catalyst with averaged size of 13 nm as evidenced by Figure 9, which indicates that CH4 condition is beneficial for the sintering prevention of loaded metal species and thereby makes positive contribution to the catalytic performance. In addition, the loaded active metal oxides also undergo partial reduction during the upgrading process, particularly under methane environment as evidenced by the reduced oxygen intensity and its related intensity to that of the Si intensity from the comparisons between Figure 7c and Figure 8b and between Figure 7c and Figure 9c. The lower oxidation state of the active species achieved under methane environment might also be closely related to its enhanced catalytic performance toward bitumen partial upgrading. In order to get an even better understanding of the element distribution as well as the oxidation state on the Ag-Mo-Ce/ZSM-5 catalyst surface, XPS has been employed for 25


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conducting specific scans at Ag 3d, Mo 3d, Ce 3d, O 1s, and C 1s regions, respectively, and the results are shown in Figure 10. As seen in Figure 10a, the notable reduction of concentration of silver on the surface can likely be attributed to the diffusion of silver into the inner pores of the zeolite support, as evidenced by the reduced peak intensities. Furthermore, surface silver is completely reduced from Ag+ to metallic silver during reaction, as witnessed by the peak shift from 368.0 eV to 368.3 eV when their standard binding energies are referred.[40] When taking the reductive reaction into consideration, such an observation is more than reasonable. By taking a closer look at the spectra obtained post reaction, it can be identified that silver presence is heightened on the surface of the catalyst after reaction with methane as opposed to the N2 run. This could be related to the greater performance seen under methane. As displayed in Figure 10b, majority of surface Mo exists in the fresh catalyst as oxidation state of 6+ corresponding to the presence of MoO3 after referring to its characteristic 3d5/2 binding energy at 232.6 eV. Moreover, it is also worth noting that there is an additional small peak present in the fresh sample spectra, which is centered at 228.3 eV implying the existence of metallic Mo at small concentration probably due to incomplete oxidation during catalyst synthesis. After upgrading reaction, in a similar matter, Mo concentration at the surface is also reduced, as seen by the reduced intensity of the peaks and is likely explained by the diffusion of Mo into the inner pores of the support. Furthermore, partial reduction of Mo during reaction can be seen due to the formation of a shoulder peak at a lower binding energy of 230.3 eV, indicating the 26


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existence of Mo4+ according to the characteristic binding energy of MoO2.[41] This reduced Mo valance might be due to the reducing reaction environment. The catalytic active center widely reported in literature work at higher temperatures such as 700 oC is molybdenum carbide species, like Mo2C, which is not observed in the XPS spectra of spent catalysts, indicating that the active molybdenum species exist as the molybdenum oxide species, such as MoO3 and MoO2, in this work. After closer inspection of the two spectra collected post reaction, it is also noticed that slightly higher amount of Mo species as active phase is still present on the catalyst surface after the reaction under methane environment than that from N2 run, which might attribute to its better performance. Figure 10c reports the 3d5/2 and 3d3/2 core level XPS spectra of cerium which contains many satellites. This peak splitting phenomenon (i.e., from two major peaks to seven observable individual peaks) can be interpreted from different aspects. A coupling between spin and angular momentum belonging to the single f electron and the 3d core hole named multiplet effect results in a broadening of the two major 3d peaks. In addition, the spatial extension of the 4f orbitals in cerium can strongly contribute to the hybrid orbital formed with O 2p orbitals, leading to some covalent feature of the Ce-O bonding and a partial 4f orbitals occupation and thus resulting in the 3d peak splitting. Moreover, a so-called final-state effect induced upon irradiation of X-ray during XPS signal collection can create a core hole which would disturb the valence electron arrangement and cause an electronic transfer from O 2p valence states to localized cerium 4f orbitals, 27


Energy & Fuels

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thus leading to the final formation of fine structures at three 4f states (i.e., 4f0, 4f1, and 4f2).[42] Upon upgrading reaction, the 3d3/2 4f2 peak becomes more visible and better separated from 3d5/2 4f0 peak, accompanied with the occurrence of a shoulder peak at 885.5 eV, particularly over the methane run, indicating the reduction of cerium from 4+ oxidation state to 3+ oxidation state.[42, 43] The formation of Ce4+/Ce3+ redox pair might make a significant contribution to the excellent coke formation resistance capability of the Ag-Mo-Ce/ZSM-5 catalyst due to its well-known OSC feature. The surface distribution of oxygen containing species is better observed when Figure 10d is referred. The overlapping peaks are clearly observed in the spectra collected over fresh catalyst. Four peaks are identified and located at 533.1 eV, 532.2 eV, 531.2 eV, and 530.4 eV, respectively, after performing peak deconvolution, indicating the presences of SiO2 from zeolite framework, hydroxyl groups,[41] molybdenum oxide, and cerium oxide on the catalyst surface when their characteristic binding energies are cited. Due to the aforementioned back diffusion of Mo and Ce species into the inner pores of the ZSM-5 support during the upgrading reaction, more SiO2 from the ZSM-5 framework gets exposed on the catalyst surface, leading to an enhanced peak intensity at 533.1 eV accompanied with significantly reduced peak intensities at lower binding energies. Deactivation of the catalyst during the upgrading of heavy oils has been attributed predominantly to carbon deposition. [44, 45] Thus, monitoring the Carbon 1s signal of solid samples from a variety of runs was deemed necessary. Figure 10e shows that a carbon signal is present for all the tested samples. Sample storage (CO2 adsorption and other C 28


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containing compounds) is a likely contributor to the residue carbon witnessed on the fresh catalyst surface. Post upgrading reaction over the catalyst and under methane and N2 environments, coke formation can be observed via the increased peak intensity in the spectra. Nevertheless, lower C 1s signal at binding energy of 284.8 eV is clearly observed in the spectra under methane environment when its N2 counterpart is referred, which is consistent with the coke yield results as reported in Table 1.

4. Conclusions As reported, the application and technical feasibility of using transition metals as active centers upon loading onto a zeolite support under methane environment and moderate conditions to obtain partially upgraded crude oil is demonstrated. The upgraded oil could be applied to pipelines for transportation without the need for expensive additional diluents. It has been observed that because of methane introduction into the system for the catalytic thermal cracking of bitumen, the quality with regards to flowability, acidity, density, heating value, distillated fractions as well as increased productivity is enhanced. Various techniques have been used to help confirm methane participation in the process of upgrading such as: CD4 use for 1H and 2D NMR characterization, an appropriately selected model compound and GC-MS analysis of the obtained liquid products. Varying performance was witnessed depending on the feed gas, catalyst and thermal cracking of bitumen which aided with the identification of their synergism. By identifying the high dispersion of Ag and Mo surface species in a reduced 29


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form and the Ce3+/Ce4+ redox pair formation for the minimization of coke formation, it is a possibility that these factors are closely related to the superb performance of Ag-Mo-Ce/ZSM-5 during partial upgrading. Promising future work lies with the investigation of modifying catalysts to further upgrade oil for gasoline and diesel production.

Acknowledgements We gratefully acknowledge the financial support from Imperial Oil and the Natural Sciences and Engineering Research Council of Canada (NSERC, CRDPJ/460752-2013) through the Collaborative Research and Development (CRD) program.

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References [1] Speight, J. G. Heavy Oil Production Processes, Gulf Professional Publishing, 2013. [2] Gray, M. R. Upgrading Oilsands, Bitumen, and Heavy Oil, University of Alberta Press, 2015. [3] Idriss, H. Platinum Metals Review, 2004, 48, 105–115. [4] Kolyagin, Y.G.; Ivanova, I.I.; Ordomsky, V.V.; Gedeon, A.; Pirogov, Y.A. J. Phys. Chem. C, 2008, 112, 20065-20069. [5] Guczi, L.; Koppány, Zs.; Sarma, K.V.; Borkó, L.; Kiricsi, I. Stud. Surf. Sci. Catal., 1997, 105, 861-868. [6] Xu, Y.; Lin, L. Appl. Catal. A, 1999, 188, 53-67. [7] Xu, Y.; Lin, L. J. Catal., 2003, 216, 386-395. [8] Cui, Y.; Xu, Y.; Lu, J.; Suzuki, Y.; Zhang, Z. Appl. Catal. A: Gen., 2011, 393, 348-358. [9] Alvarez-Galvan, M.C.; Mota, N.; Ojeda, M.; Rojas, S.; Navarro, R.M.; Fierro, J.L.G. Catal. Today, 2011, 171, 15-23. [10] Ha, V.; Sarioğlan, A.; Erdem-Şenatalar, A.; Taârit, Y. J. Mol. Catal. A: Chem., 2013, 378, 279-284. [11] Choudhary, T.V.; Aksoylu, E.; Goodman, D.W. Catal. Rev. Sci. Eng., 2003, 45, 151-203. [12] Choudhary, V.R. ;Kinage, A.K. ;Choudhary, T.V. Science, 1997, 275, 1286-1288. [13] Baba, T.; Sawada, H. Phys. Chem. Chem. Phys.,2002, 4, 3919–3923. [14] Baba, T.; et al. Micropor. Mesopor. Mat., 2007, 101, 142–147. [15] Baba, T.; Inazu, K. Chem. Lett.,2006, 35, 142-147. [16] Baba, T.; Abe, Y. Appl. Catal. A, 2003, 250, 265-270. [17] Anunziata, O.; Mercado, G.; Pierella, L.B. Catal. Lett., 2003, 87, 167-171. [18] Anunziata, O.; Cussa, J.; Beltramone, A. Catal. Today, 2011, 171, 36-42. [19] Wang, L.; Xu, Y.; Tao, L. Sci. China B, 1997, 40, 161-164. 31


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[20] Zhang, H.; Kong, A.; Ding, Y.; Dai, C.; Shan, Y. J. Nat. Gas Chem., 2011, 20, 243-248. [21] Anunziata, O.; Mercado, G.; Pierella, L.B.2nd Mercosur Congress on Chemical Engineering, 2005. [22] Ovelles, C.; Filgueiras, E.; Morales, A.; Scott, C.E., Gonzalez-Gimenez, F.; Embaid, B. Fuel, 2003, 82, 887-892. [23] Ovelles, C.; Filgueiras, E.; Morales, A.; Rojas, I.;Jesus, J.; Berrios, I. Energy Fuels, 1998, 12, 379-385. [24] Guo, A.; Wu, C.; He, P.; Luan, Y.; Zhao, L.; Shan, W.; Song, H. Catal. Sci. Technol., 2016, 6, 1201-1213. [25] He, P.; Song, H. Ind. Eng. Chem. Res., 2014, 53, 15862–15870. [26] He, P.; Shan, W.; Xiao, Y.; Song, H. Top. Catal., 2016, 59(1), 86-93. [27] Xiao, Y.; He, P.; Cheng, W.; Liu, J.; Shan, W.; Song, H. Waste Manage., 2016, 49, 304-310. [28] Tsaprailis, H. Properties of Dilbit and Conventional Crude Oils, Alberta Innovates, 2014. [29] Song, H.; Ozkan, U.S. J. Catal., 2009, 261, 66-74. [30] Speight, J. G. The chemistry and technology of petroleum, CRC press, 2014. [31] Savage, P. E.;Korotney, D. J. Ind. Eng. Chem. Res., 1990,29, 499-502. [32] Savage, P. E.; Klein, M. T. Ind. Eng. Chem. Res., 1987,26, 488-494. [33] Guo, X.; Fang, G.; Li, G.; Ma, H.; Fan, H.; Yu, L.; Ma, C.; Wu, X.; Deng, D.; Wei, M.; Tan, D.; Si, R.; Zhang, S.; Li, J.; Sun, L.; Tang, Z.; Pan, X.; Bao, X. Science, 2014, 344, 616-619. [34] Choudhary, V. R.; Mondal, K. C.; Mulla, S. A. R. Angew.Chem. Int. Edit., 2005, 44, 4381-4385. [35] Wang, L.; Tao, L.; Xie, M.; Xu, G.; Huang, J.; Xu, Y. Catal. Lett., 1993, 21, 35-41. [36] Wang, D.; Lunsford, J. H.; Rosynek, M. P. J. Catal., 1997, 169, 347-358.

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[37] Weckhuysen, B. M.; Wang, D.; Rosynek, M. P.; Lunsford, J. H. J. Catal., 1998, 175, 338-351. [38] Borry, R. W.; Kim, Y. H.; Huffsmith, A.; Reimer, J. A.; Iglesia, E. J. Phys. Chem. B, 1999, 103, 5787-5796. [39] He, P. ; Zhao, L. ; Song, H. Appl. Catal. B Env. 2017, 201, 438-450. [40] Moulder, J.F. ; Stickle, W.F. ; Sobol, P.E. ; Bomben, K.D. Handbook of X-ray Photoelectron Spectroscopy, Perkin-Elmer, 1992. [41] Choi, J.G. ; Thompson, L.T. Appl. Surf. Sci., 1996, 93, 143-149. [42] Normand, F.L. ; Hilaire, L. ; Kili, K. ; Krill, G. ; Maire, G. J. Phys. Chem., 1998, 92, 2561-2568. [43] Creaser, D.A. ; Harrison, P.G. Catal. Lett., 1994, 23, 13-24. [44] Absi-Halabi, M.; Stanislaus, A. Appl. Catal., 1991, 72, 193-215. [45] Rana, M.S.; Sámano, V.; Ancheyta, J.; Diaz, J.A.I. Fuel, 2007, 86, 1261-1231.

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Figure Captions

Figure 1. Stability test of (a) bitumen and oil products collected under (b) N2, (c) CH4, (d) CH4 with ZSM-5, (e) N2 with catalyst Ag-Mo-Ce/ZSM-5, and (f) CH4 with catalyst Ag-Mo-Ce/ZSM-5 Figure 2. Reference spot definition and visualization for compatibility and stability evaluation of oil samples Figure 3. The carbon number distribution in the liquid product samples collected over Ag-Mo-Ce/ZSM-5 at 400 oC and 3 MPa under CH4 and H2 environments Figure 4. 1H NMR spectra of the liquid products obtained from the reaction between n-butylbenzene and CH4/CD4 Figure 5. 2D NMR spectra of the liquid products obtained from the reaction between n-butylbenzene and CH4/CD4 Figure 6. XRD patterns of fresh and spent ZSM-5 and Ag-Mo-Ce/ZSM-5 after n-butylbenzene upgrading at 3.0 MPa and 400 oC for 20 min Figure 7. (a) TEM image of fresh Ag-Mo-Ce/ZSM-5 and (c) its corresponding EDX spectrum focused at the circled area in (b) Figure 8. (a) TEM images of spent Ag-Mo-Ce/ZSM-5 collected after catalytic n-butylbenzene cracking under the environment of N2 and (b) its corresponding EDX spectrum focused at the circled area in (a) Figure 9. (a) TEM images of spent Ag-Mo-Ce/ZSM-5 collected after catalytic n-butylbenzene cracking under the environment of CH4 and (c) its corresponding EDX spectrum focused at the circled area in (b)

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Figure 10. XPS spectra of Ag-Mo-Ce/ZSM-5 before and after n-butylbenzene upgrading at 3.0 MPa and 400 oC for 20 min under different environments at (a) Ag 3d, (b) Mo 3d, (c) Ce 3d, (d) O 1s, and (e) C 1s regions

Tables: Table 1. Performance of bitumen upgrading under various environments at 3.0 MPa and 400 oC for 20 min Table 2. Reference spot description for compatibility and stability evaluation of oil samples Table 3. Gasoline and diesel fractions of the oil samples collected before and after bitumen upgrading under various environments at 3.0 MPa and 400 oC for 20 min Table 4. Properties of the oil samples collected before and after bitumen upgrading under various reaction conditions at 3.0 MPa and 400 oC for 20 min Table 5. Elemental analysis results of oil samples collected before and after bitumen upgrading under various reaction conditions at 3.0 MPa and 400 oC for 20 min Table 6. Parameters of n-butylbenzene upgrading performance under various environments at 3.0 MPa and 400 oC for 20 min Table 7. Aromatics composition of liquid products and conversions of n-butylbenzene and methane at 3.0 MPa and 400 oC for 20 min Table 8. 1H NMR peak area ratio with respect to CHCl3 of the products from n-butylbenzene upgrading under CH4 and CD4 environment

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Table 1. Performance of bitumen upgrading under various environments at 3.0 MPa and 400 oC for 20 min Coke yield

Liquid yield

Viscosity

(wt.%)

(wt.%)

(cP at 25 oC)

---

---

---

848,080

-

N2

0.31

94.9

1,884

-

CH4

0.25

96.0

1,735

HZSM-5

CH4

0.87

91.5

1,664

Ag-Mo-Ce/ZSM-5

N2

0.24

95.1

734

Ag-Mo-Ce/ZSM-5

CH4

0.38

98.2

404

Trial

Atmosphere

Bitumen

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Table 2. Reference spot description for compatibility and stability evaluation of oil samples Reference Spot No.

Characterizing Features

1

Homogeneous spot (no inner ring)

2

Faint or poorly defined inner ring

3

Well-defined inner ring, only slightly darker than the background

4

Well-defined inner ring, thicker than the ring in reference spot Mo.3 and somewhat darker than the background

5

Very dark solid or nearly solid area in the center. The central area is much darker than the background

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Table 3. Gasoline and diesel fractions of the oil samples collected before and after bitumen upgrading under various environments at 3.0 MPa and 400 oC for 20 min Trial

Atmosphere

Gasoline

Diesel (wt.%)

(wt.%)

Total gasoline and diesel (wt.%)

Bitumen

---

0.3

11.8

12.1

-

N2

6.5

20.2

26.7

-

CH4

7.1

23.9

31.0

HZSM-5

CH4

6.9

24.8

31.7

Ag-Mo-Ce/ZSM-5

N2

6.7

27.1

33.8

Ag-Mo-Ce/ZSM-5

CH4

11.0

26.1

37.1

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Energy & Fuels

Table 4. Properties of the oil samples collected before and after bitumen upgrading under various reaction conditions at 3.0 MPa and 400 oC for 20 min Liquid Product Properties

Oil Sample Density

TAN

Water Content

Heating Value

Asphaltene

(g/cm )

(mg KOH/g)

(wt.%)

(MJ/kg)

content (wt.%)

Bitumen

1.0275

2.69

0.159

40.2

22.0

N2

0.9964

0.54

0.146

39.4

16.8

CH4

0.9892

0.23

0.163

40.9

16.2

CH4+ HZSM5

0.9774

0.25

0.172

40.8

14.7

N2+ Ag-Mo-Ce/ZSM5

0.9771

0.44

0.157

39.5

10.7

CH4+ Ag-Mo-Ce/ZSM5

0.9648

0.02

0.196

41.4

9.5

3

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Page 40 of 53

Table 5. Elemental analysis results of oil samples collected before and after bitumen upgrading under various reaction conditions at 3.0 MPa and 400 oC for 20 min Oil Sample

Carbon

Hydrogen

H/C

Nitrogen

Sulfur

Oxygen

O/C

(wt.%)

(wt.%)

Atomic

(wt.%)

(wt.%)

(wt.%)

Atomic

Ratio

Ratio (× ×10-3)

Bitumen

83.09

10.24

1.48

1.85

4.48

0.34

4.1

N2

83.96

10.45

1.49

1.73

3.58

0.28

3.3

CH4

84.14

10.57

1.51

0.95

4.05

0.29

3.4

CH4+ZSM-5

84.23

10.19

1.45

1.64

3.74

0.20

2.4

N2+ Ag-Mo-Ce/ZSM-5

83.86

10.94

1.57

1.04

3.89

0.27

3.2

CH4+ Ag-Mo-Ce/ZSM-5

83.57

11.84

1.70

1.02

3.38

0.19

2.3

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Energy & Fuels

Table 6. Parameters of n-butylbenzene upgrading performance under various environments at 3.0 MPa and 400 oC for 20 min Catalyst or support

Atmosphere

Final pressure (400ºC, MPa)

Gas yield (wt.%)

Liquid yield (wt.%)

-

N2

4.7

3.6

96.4

-

CH4

4.6

3.7

96.3

HZSM-5

N2

6.0

4.1

95.9

HZSM-5

CH4

6.1

4.0

96.0

Ag-Mo-Ce/ZSM-5

N2

5.8

2.8

97.2

Ag-Mo-Ce/ZSM-5

CH4

5.8

2.1

97.9

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Page 42 of 53

Table 7. Aromatics composition of liquid products and conversions of n-butylbenzene and methane at 3.0 MPa and 400 oC for 20 min Liquid Product Distribution/Conversion (wt%) Compound

ZSM-5,

ZSM-5,

Ag-Mo-Ce/ZS

Ag-Mo-Ce

N2

CH4

M-5, N2

/ZSM-5, CH4

3.30

7.23

10.10

19.94

26.68

25.14

22.84

0.88

1.16

1.52

1.37

Ethylbenzene

9.07

8.72

3.86

2.89

1.02

1.21

Styrene

14.58

12.29

0.06

0.16

0.86

0.64

Isopropylbenzene

--

--

6.62

6.56

3.10

4.05

N-propylbenzene

--

--

6.32

6.88

5.50

5.51

2.71

1.61

7.14

6.97

5.78

6.09

1-Ethyl-4-isoproylbenzene

--

--

2.03

1.76

6.77

5.91

Pentylbenzene

--

--

2.31

2.32

2.95

2.76

1,4-isopropylbenzene

--

--

0.47

0.52

8.23

9.20

1,4-dipropylbenzene

--

--

1.49

1.25

0.66

1.16

Hexylbenzene

--

--

0.84

0.78

0.74

0.81

1,1-diethylpropylbenzene

--

--

3.44

2.97

5.80

9.63

1,4-diisopropyl-2-methylbenzene

--

--

3.42

5.53

8.45

8.46

1,3-(1-methylpropyl)-benzene

--

--

0.35

0.46

1.15

1.44

10.70

10.90

86.86

87.66

47.13

58.04

--

--

--

1.02

--

6.65

N2

CH4

Benzene

1.03

Methylbenzene

Methylpropylbenzene

N-butylbenzene* Methane*

* Conversion -- Below detection limit or not applicable

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Energy & Fuels

Table 8. 1H NMR peak area ratio with respect to CHCl3 of the products from n-butylbenzene upgrading under CH4 and CD4 environment Sites

CH4

CD4

Decrease/%

Aromatics

7.0

2.6

63

Benzylic

2.7

1.1

59

Alkyl

4.2

3.4

19

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Page 44 of 53

(a)

(b)

(c)

(d)

(e)

(f)

Figure 1. Stability test of (a) bitumen and oil products collected under (b) N2, (c) CH4, (d) CH4 with ZSM-5, (e) N2 with catalyst Ag-Mo-Ce/ZSM-5, and (f) CH4 with catalyst Ag-Mo-Ce/ZSM-5

44


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Energy & Fuels

Figure 2. Reference spot definition and visualization for compatibility and stability evaluation of oil samples

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Figure 3.

The carbon number distribution in the liquid product samples collected over

Ag-Mo-Ce/ZSM-5 at 400 oC and 3 MPa under CH4 and H2 environments

46


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Energy & Fuels

Figure 4. 1H NMR spectra of the liquid products obtained from the reaction between n-butylbenzene and CH4/CD4

47


Energy & Fuels

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Figure 5. 2D NMR spectra of the liquid products obtained from the reaction between n-butylbenzene and CH4/CD4

48


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Energy & Fuels

Figure 6. XRD patterns of fresh and spent ZSM-5 and Ag-Mo-Ce/ZSM-5 after n-butylbenzene upgrading at 3.0 MPa and 400 oC for 20 min

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(a)

Page 50 of 53

(b)

(c)

Figure 7. (a) TEM image of fresh Ag-Mo-Ce/ZSM-5 and (c) its corresponding EDX spectrum focused at the circled area in (b)

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Energy & Fuels

(a)

(b)

EDX Area

Figure 8. (a) TEM images of spent Ag-Mo-Ce/ZSM-5 collected after catalytic n-butylbenzene cracking under the environment of N2 and (b) its corresponding EDX spectrum focused at the circled area in (a)

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(a)

Page 52 of 53

(b)

(c)

Figure 9. (a) TEM images of spent Ag-Mo-Ce/ZSM-5 collected after catalytic n-butylbenzene cracking under the environment of CH4 and (c) its corresponding EDX spectrum focused at the circled area in (b)

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Energy & Fuels

(a)

(b)

(d)

(c)

(e)

Figure 10. XPS spectra of Ag-Mo-Ce/ZSM-5 before and after n-butylbenzene upgrading at 3.0 MPa and 400 oC for 20 min under different environments at (a) Ag 3d, (b) Mo 3d, (c) Ce 3d, (d) O 1s, and (e) C 1s regions 53


Catalytic Bitumen Partial Upgrading under Methane Environment over

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