Synthesis, Characterization, and Mechanism of Copolymer Viscosity

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Synthesis, Characterization, and Mechanism of Copolymer Viscosity Reducer for Heavy Oil Xiaobo Lv, Weiyu Fan, Qitian Wang, and Hui Luo Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.9b00217 • Publication Date (Web): 04 Apr 2019 Downloaded from http://pubs.acs.org on April 5, 2019

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Energy & Fuels

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Synthesis, Characterization, and Mechanism of Copolymer

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Viscosity Reducer for Heavy Oil

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Xiaobo Lv,† Weiyu Fan,*,† Qitian Wang,‡ Hui Luo†

4

†

5

China

6

‡

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Abstract: A functional copolymer viscosity reducer based on molecule dynamics (MD)

8

simulations was synthesized using monomers of mixed ester, 4-vinylpyridine, and styrene. The

9

possible structure and number of hydrogen bonds with in the complex structure of heavy oil were

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simulated and analyzed after the copolymer was added. Results showed that the number of

11

hydrogen bonds in asphaltene in the simulation structure decreased from 36 to 28 per unit volume

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with the addition of the copolymer. The original plane overlap structure of asphaltene was

13

damaged as soon as interactions occurred between the asphaltene and copolymer molecule. The

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system potential energy was higher with the addition of the copolymer, while the non-bond energy

15

difference of the two systems was not obvious. The stereo-hindrance effect of the copolymer

16

viscosity reducer molecules either broken or improved the interlocking structures of the asphaltene,

17

helping to decrease the viscosity of the heavy oil.

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Key words: Heavy Oil ， Copolymer Viscosity Reducer ， Solution Polymerization ， Molecular

19

Simulation

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1. Introduction

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The low molecular weighted hydrocarbon component of crude oil (especially heavy oil) accounts

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for 20% to 60% or less of the total oil content-far below that of light crude oil. Generally, there are

State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Qingdao.266580, Shandong,

China Petrochemical Lubricant Co., Ltd. Jinan Branch, Jinan 250101, P. R. China

ACS Paragon Plus Environment

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aggregations of interlocked network structures in heavy oil. Inside these structures, the

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hydrocarbon component is surrounded by asphaltenes, resins and kinds of paraffin clumped

3

together in the form of gel1 which is responsible for the density and viscosity of the oil and the

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resulting decline of flow behavior.2,3 The high viscosity and pour point of heavy oils have caused a

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series of operational and engineering challenges in the pipeline transportation of crude oil,

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particularly of heavy oil, for developmen and exploitation.1 Therefore, research into the viscosity

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and drag reduction of crude and heavy oils has become a difficult, yet attractive topic of

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research.4,5

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Across the world, pour point depressants are typically used for viscosity reducer in crude oil. In

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fact, viscosity reduction usually consists of both physical and chemical technologies.6 Oil-soluble

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polymer viscosity reduction technology, based on pour depressant technology, is relatively new

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and is yet to be used in most oil-producing countries. Research progress into this technology has

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been relatively slow, only recently starting in China. Currently, the viscosity reduction mechanism

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has no unified conclusion. It is generally considered that the viscosity reduction polymer

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molecules in the colloid structure of asphaltenes have the ability to form hydrogen bonds, and

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have strong permeability and dispersion effects.7,8 The original plane overlap structure is partly

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broken into aggregates by the polymer that form a new random packing structure. These new

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aggregate structures are loose in heavy oil, the stacking order is relatively low, and the elongation

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space is not large enough, thereby reducing the viscosity of heavy oils.9-11 Because of the

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differences characteristics of crude and heavy oils from different regions, oil-soluble functional

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copolymer viscosity reducers are focused on breaking or weakening the stability of the crude and

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heavy oil interlocking network structure, so as to improve flow behavior.12-14 Thus far,


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experimental comparisons have mainly been carried out on only four types of oil-soluble

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functional polymer viscosity reduction materials: condensation compounds, homopolymers of

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unsaturated monomers, copolymers of unsaturated-monomers, and polymeric surface active

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agents.15,16 Therefore, further research on oil-soluble functional polymer viscosity reduction

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materials for viscosity reduction is necessary.

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In this study, a molecular dynamics simulation is used to simulate the possible structure and

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number of hydrogen bonds existing within the complex structure of heavy oil. Based on the results

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of the molecular simulation, the molecular structure of a viscosity reducer was designed. A

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functional copolymer viscosity reducer based on mixed ester was synthesized using monomers of

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stearyl methacrylate, lauryl methlacrylate, methyl methacrylate, n-butyl acrylate, vinyl acetate,

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4-vinylpyridine, and styrene. Heavy oil was added to a copolymer, and then its structure and

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possible hydrogen bonds were simulated and analyzed. Interactions between the copolymer

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viscosity reducer and heavy oil glial asphaltene were confirmed from the perspective of molecular

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dynamics which provided the basis for the viscosity reduction mechanism.

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2. Background of Molecular Simulation

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2.1. Simulation of Hydrogen Bonds in Asphaltene. Asphaltene is the main constituent that

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affects the viscosity of heavy oil, however, low temperature promoting the crystallization of the

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paraffins mainly affects the pour point. In general, the higher the content of asphaltenes, resins,

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and paraffins in heavy oil, the higher the increase in viscosity. In fact, both differences and

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relationships exist between the viscosity and the pour point in terms of certain physical properties

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that affect the viscosity of heavy oil. Thus, asphaltene should be considered the main factors

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affecting viscosity reduction, but the effects of resin and paraffin and the self-aggregation


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behavior of the highly viscous contents of crude oil should not be ignored.17

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Asphaltene consists of alkyl branches made up of C, H, and O and the functional groups of

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heterocyclic polycyclic and aromatic hydrocarbons or naphthene. The molecules of asphaltene

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interact with each other to form hydrogen bonds as an interlocking network of complex

5

structures.18 The heterocyclic and polycyclic aromatic hydrocarbons overlap on the molecular

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surfaces of asphaltene and are fixed by the hydrogen bonds of the polar segment, piled into

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particles, and then accumulate into asphalt micelles of different sizes. The asphaltene molecules

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overlap on the surface of the resin molecules and are fixed by the hydrogen bonds in the

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heterocyclic and polycyclic aromatic hydrocarbons, which form the cover layer of the resin

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particles. The particles can also interconnect via hydrogen bonds and form micelles with a high

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molecular weight19, contributing to the high viscosity of heavy oil. Therefore, the main factors that

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affect heavy oil viscosity are the microstructure and the molecular inter-force properties of

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asphaltene and these would be key factors of viscosity and development of a drag reducer at the

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molecular level.20-22

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2.2. Molecular Design of Functional Copolymer. According to previous studies and hydrogen

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bond theories, 5,13,16,18 an ester-based compound has a high combining capacity to form hydrogen

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bonds, especially a compound containing an N atom like a pyridine ring. At the same time, when

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the copolymer was synthesized using 4-vinyl pyridine and ester-based compounds, both the

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benzene ring resonance effect and the reactivity ratio affected the polymerization degree and the

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structure of the copolymer.1,23 These effects resulted in either a breakdown or improvement of the

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polymerization progress to the proper interlocking network structure.24 Consequently, a more

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efficient functional copolymer for viscosity reduction materials could be synthesized.25,26


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3. Method and Simulation Details

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3.1. Simulation Details

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3.1.1 Simulation of Hydrogen Bonds in Asphaltene. The temperature of the simulation

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system was 303K, which was above the pour point of Shengli (China) heavy oil, which

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considerably decreased the effect of paraffins in the simulation system. In terms of the possible

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hydrogen bond types among asphaltenes, the studied molecular simulation model27-30 was

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established with proportions of 10:4:10:3:9:10:4:4:4:4:4:4 according to the ability of the alkyl

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fluorenol, alkyl benzfluorenol, alkyl benzfluorenone, abietic acid, alkyl anthracenecarboxylic acid,

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alkyl dibenzothiophenecarboxylic acid, 2-alkyl quinoline, benzquinoline, benzcarbazole, alkyl

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pyridine, benzthiophene, and alkyl thiophene, to form complex molecules by hydrogen bonds,

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some of the groups were displayed in Figure 1.

12 13 14

Figure 1. Structures of hydrogen bonds in the simulation system of asphaltene

Structures of representative asphltene molecules could be found in Figure S1. As a construction


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tool for the amorphous cells, the Materials Studio was adopted to build the molecular model. The

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hydrogen bond molecular system of asphaltene was simulated using the NVT system in the

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Compass force field, and the system’s molecular simulation was studied. The system was made up

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of C, H, O, N, and S to form 19 different atom types. The number of molecules was 70, the

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number of atoms was 2439, and the number of bonds was 2575.

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Next, 5000 steps of energy minimization were implemented with a minimizing tool (Smart

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Minimizer) at the convergence level (Medium). The molecular dynamics simulation was carried

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out at 303K by adopting the NPT system of the Dynamics tool in Discover Tools, and 10000 steps

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were implemented; the step length was 1.0 fs, and the information was stored every 50 steps. Then,

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hydrogen bonds were built according to the criterion of maximum hydrogen-acceptor distance:

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2.5Å, minimum donor-hydrogen-acceptor angle: 90º.

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3.1.2. Molecular Design of the Copolymer. The theoretical simulation model of the viscosity

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reducer could reduce the viscosity of heavy oil was mainly based on its composition of ester group,

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aromatic ring, pyridine ring, and alkyl chain.24,27 Therefore, the copolymer that with viscosity

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reduction

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lauryl methlacrylate, methyl methacrylate, n-butyl acrylate, vinyl acetate, 4-vinylpyridine, and

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styrene. The structure scheme was schematically illustrated in Figure S2. Styrene was added to

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adjust the polymerization degree and the interlocking structure of the polymer. Materials Studio

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simulated the molecular dynamics modelling of synthesis processes within functional copolymers

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of the viscosity reduction materials derived from mixed ester, styrene, and 4-vinyl pyridine

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monomers.

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function

could

be

synthesized

using

monomers

of

stearyl methacrylate,

The simulation factors were designed to be the same as the simulation of the hydrogen bonds in


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asphaltene.31 The system was made up of C, H, O, N, and S to form 21 different atom types when

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the viscosity reducer was added. The number of molecules was 71, the number of atoms was 3534,

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and the number of bonds was 3687.

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The construction tool for amorphous cells was adopted to build the simulation models, and 5000

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steps of energy minimization were implemented on the system. Then, a dynamics simulation was

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carried out using the Dynamics tool of Discover Tools at 348K, deemed the most suitable

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temperature for this solution polymerization reaction.32–34 The thermodynamic date of the

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synthesis was obtained from the simulation process.

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3.2. Synthesis of Copolymer Viscosity Reducer

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3.2.1 Experimental Reagents. The following substances were used in this research project:

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stearyl methacrylate (Tokyo Chemical Industry Co. Ltd.), lauryl methacrylate (ACROS), n-butyl

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acrylate (Beijing Yili Fine Chemical Co. Ltd.), methylacrylate (Sinopharm Shanghai Co. Ltd.),

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vinyl acetate (Tianjin Damao Chemical Co. Ltd.), styrene (Sinopharm Chemical Co. Ltd.),

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4-vinylpyridine (ACROS), AIBN (Shanghai Shisi Hewei Chemical Co. Ltd.), methylbenzene

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(Laiyang Kangde Chemical Co. Ltd.), dehydrated alcohol (Tianjin Fuyu Fine Chemical Co. Ltd.),

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and high-purity nitrogen (Ji’nan Deyang Special Gas Co. Ltd.).

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3.2.2 Synthesis and Characterizations. The main reactor consisted of a 250-mL five-necked

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flask equipped with a reflux condenser, a mechanical stirrer, and a heating system. The monomer

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ratio of styrene, 4-vinylpyridine, stearyl methacrylate, lauryl methacrylate, n-butyl acrylate,

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methylacrylate, and vinyl acetate was 3:1:3:3:3:3. All of the monomer reagents were added into

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the five-necked flask with toluene as the dissolvent. The reactor was heated to 60°C, and then, half

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the amount of the initiator AIBN was added. The temperature was increased to 75°C and


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maintained for 18 h with nitrogen protection. At the 9th h, the left initiator was added. After the

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polymerization had finished, the solution was cooled at room temperature and transferred to a

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beaker. The polymer was washed with dehydrated alcohol, separated, and then dried in the oven.

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The polymer had a yellow viscous liquid appearance.

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The copolymer synthesized based on ester, benzene and pyridine ring functional groups was

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studied by Vertex-70 Infrared Spectrometer (Bruker Company, Germany), Dawn Heleos Laser

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Light Scattering Spectrometer (Wyatt Company, USA), 515 Gel Permeation Chromatograph

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(Waters Company, USA), and DSC 822e Simultaneous Thermal Analyzer (Mettler Company,

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Switzerland). More importantly, the polymer was dissolved in kerosene acting as the viscosity

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reducer before it was added to 20 g of Shengli (China) heavy oil. To obtain the results in

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accordance with accurate rheological measurements, the crude oil was left standing for half an

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hour. Afterwards, the kinematic viscosity was measured with the RheoStress RS75 rotary

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rheometer (HAAKE Company, Germany). The measurements were carried out at 30°C for 180 s,

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and the test rotation speed was within 0-400 rpm.

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4 Results and Discussion

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4.1 Simulation of Hydrogen Bonds in Asphaltene. Figure 2 shows the molecular simulation

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of hydrogen bonds in the asphaltene, with and without the viscosity reducer molecules added.

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Figure 3 shows the local structures of hydrogen bonds in the asphaltene system (O…H, N…H, and

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S…H). In Figure 2, the dotted line represents hydrogen bonds, with 36 hydrogen bonds formed in

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the simulation structure of asphaltene per volume unit. However, the number of hydrogen bonds in

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asphaltene in the simulation structure decreased from 36 to 28 per unit volume with the viscosity

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reducer added as shown in Figure 2b. This was attributed to the copolymer viscosity reducer based


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on ester, benzene and pyridine ring functional groups having better oil solubility. On the other

2

hand, the electronegativity of the copolymer was higher than that of the hydrogen bond atoms in

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asphaltene of heavy oil. Thus, the combination of hydrogen bonds with the copolymer molecule

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could be forecasted first, and they either broke or improved the interlocking network structure.35,36

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This proved that number and the types of hydrogen bonds varied upon the addition of the viscosity

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reducer.

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Figure 2. Molecular simulation structure. a. hydrogen bond in asphaltene. b. hydrogen bonds in asphaltene with

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viscosity reducer copolymer added

10 11

Figure 3. The local structures of hydrogen bonds: a. O…H, b. S…H, and c. N…H

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Differences in temperature and simulation times of hydrogen bonds in asphaltene could be used

13

to evaluate the system energy absorbed from the environment. As displayed in Figure 4,


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significant discrepancies in heating rates were observed where the system with the added viscosity

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reducer exhibited a relatively low heating rate compared with the system with no added reducer

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before 3000 fs, although the simulation system temperature became stable after 3000 fs. This

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indicated that the original plane overlap structure of asphaltene was damaged as soon as

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interactions occurred between the asphaltene and the copolymer molecule after the viscosity

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reducer molecule was added to the heavy oil system.

7 8

Figure 4. The relationship between temperature and simulation time of molecular simulation of hydrogen bond in

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asphaltene. a. The molecular dynamics simulation system. b. The system with functional copolymer viscosity

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reducer

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The potential energy and non-bond energy of the system as a function of time are given in

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Figure 5. As can be seen in Figure 5a, the potential energy and the non-bond energy of the

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simulation system became stable from 3000 fs onwards. The potential energy was about 11500

14

kcal/mol, and the non-bond energy was about −800 kcal/mol. While in Figure 5b, it can be seen


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that the potential energy was about 12300 kcal/mol, and the non-bond energy was about −800

2

kcal/mol. The molecular dynamics simulation results suggest that the potential energy of the two

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systems (molecular dynamics simulation system and system with functional copolymer viscosity

4

reducer) significantly differed with simulation time at a temperature of 303K. The system

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potential energy of the system with the addition of the functional copolymer was higher than that

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of the system with no copolymer, however, the non-bond energy remained invariant. This

7

demonstrated that the interlocking structure of asphaltene changed with the existence of the

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copolymer viscosity reducer molecules.37 The distance expanded between the molecules of

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asphaltene in aggregations, indicating the molecular potential energy had increased. However, the

10

non-bond energy (static electricity and van der Waals force) difference between the two systems

11

was not obvious due to the hydrogen bond energy being relatively lower than bond energy, thus

12

the macroscopic interaction between the aggregations had no obvious change. 38,39

13 14

Figure 5. Potential energy and non-bond energy of systems as a function of time for hydrogen bond in asphaltene.


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a. The molecular dynamics simulation system. b. The system with functional copolymer viscosity reducer.

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4.2 Characterization of the Synthesized Copolymer. The chemical structure of the prepared

3

copolymer was studied through an FTIR spectral analysis. The spectrum of the copolymer is

4

shown in Figure 6. The copolymer spectra clearly show the peaks corresponding to both the

5

aromatic heterocycle and the bending =CH vibrations of the benzene ring of the polymerized

6

styrene at 1410–1586 cm−1 and 702 cm−1, respectively. The absorption peak at 3650~3500 cm-1

7

indicated a carboxyl from the dissociation reaction of acrylic ester in the polymerization process.

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A chain of unsaturated double bonds was not obviously detected in any spectrum. The ester

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groups absorption peak was at 1744 cm−1 and 1100 cm−1, corresponding to carbonyl and C–O,

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respectively. The characteristic strong absorption peak of –CH3, –CH2–, and CH stretching

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vibration of pyridine ring were at 2850~2950 cm−1. Furthermore, pyridine ring’s stretching

12

vibration and out-of-plane bending of aromatic rings were evidenced at 1500~1600 cm−1, and

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700~900 cm−1, respectively. –C–H stretching vibration absorption peak of aromatic rings at

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3100~3000 cm-1 could be also clearly evidenced. These suggesting that the copolymer based on

15

ester, benzene and pyridine ring functional groups had been obtained.

16 17

Figure 6. The infrared spectrum of the synthesized copolymer


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Dynamic light scattering (DLS) is a technique in physics that can be used to determine the size

2

distribution of small particles in suspension or polymers in solution. The polymer was dissolved in

3

tetrahydrofuran and was tested with a laser light scattering spectrometer. The dynamic light

4

scattering of the polymer is illustrated in Figure 7 where the three scatter areas represent different

5

grain diameters, as the polymer was synthesized using esters with different chain lengths. The

6

numerical integration reveals the average grain diameter of 23.6 nm.

7 8

Figure 7. Dynamic light scattering of the synthesized copolymer

9

A common means of expressing the chain length of a polymer is the degree of polymerization,

10

which quantifies the number of monomers incorporated into the chain.40 As with other molecules,

11

molecular size of a polymer may be also expressed in terms of molecular weight. Since synthetic

12

polymerization techniques typically yield a statistical distribution of the chain lengths, the

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molecular weight is expressed in terms of weighted averages, and the number-average molecular

14

weight (Mn) is most commonly used.41 In our study, the polymer was dissolved in tetrahydrofuran

15

and was tested using gel permeation chromatography. Figure 8 shows the scatter of the molecular

16

weight of the copolymer. Since a copolymer is a mixture compound which derived from more

17

than one species of monomer, the scatter curve showed a continuing distribution. The


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number-average molecular weight was 15079,42 the mass-average molecular weight was 29665,

2

and the diffusion coefficient was 1.9686, proving that the scatters of the molecular weight were

3

relatively concentrated.

4 5

Figure 8. Scatters of molecular weight of the synthesized copolymer

6

The glass-transition temperature Tg of a material characterizes the range of temperatures over

7

which this glass transition occurs. It is always lower than the melting temperature, Tm, of the

8

crystalline state of the material. Rubber elastomers are used above their Tg, that is, in the rubbery

9

state, where they are soft and flexible.41 Figure 9 shows the differential scanning calorimeter (DSC)

10

curve of the synthesized copolymer. The polymer was tested at temperatures ranging from –20°C

11

to 150°C in a nitrogen atmosphere. The glass transition temperature of the polymer was –18 ℃

12

shown in the inset. Furthermore, no new phase emerged between –15℃ and 140℃, illustrating

13

that the polymer had a suitable range of temperature for application above 0℃.


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Figure 9. DSC curve of the synthesized copolymer

3

The viscosity reduction effect of the functional copolymer on heavy crude oil is shown in

4

Figure 10. It can be seen that the kinematic viscosity of the heavy oil sample with kerosene was

5

737.37 mPa·s, the heavy oil with kerosene and the polymer (260 ug/g) sample was 227.27 mPa·s,

6

and the heavy oil with the kerosene and the polymer (463 ug/g) sample was 154.04 mPa·s. This

7

demonstrated that the ester-based benzene and pyridine ring functional group viscosity reducer

8

had a better effect on the Shengli (China) heavy oil, and the viscosity reducing effect improved

9

with an increase in the amount of polymer added. The rate of viscosity reduction reached 79% at

10

30 ℃

when the amount of the copolymer was 463 ug/g. This was because the comb-type

11

copolymer viscosity reducer adsorbed the small sheet-like micelles to accumulate on the surface of

12

the molecules, which reduced the number of small sheet-like micelles and extended the distance

13

between the micelle groups.23,43 On the other hand, the stereo-hindrance effect of the copolymer

14

viscosity reducer molecules either broke or improved the interlocking structures of the asphaltene.

15

Besides, the eutectic and the adsorption effects of the paraffin molecules with the long-chain

16

alkyls of the polymer contributed to the improved interlocking structure.16 Subsequently, the


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1

possibility of interactions between micelle aggregations decreased, reducing the viscosity of heavy

2

oil.

3 4

Figure 10. Visbreaking curve of the heavy oil with different proportion of viscosity reducer at 30℃. a. heavy oil

5

with kerosene. b. heavy oil with kerosene and polymer (260 ug/g). c. heavy oil with kerosene and polymer (463

6

ug/g)

7

The crude oil sample was also observed under a cold field scanning electron microscope (SEM,

8

JEOL JSM-7600F). Figure 11 shows the surface SEM images of the heavy oils with and without

9

the viscosity reducer added and illustrates that the state of aggregation changed significantly.44,45

10

The micelles showed in Figure 11A are probably the high viscosity condensed polar molecule

11

crystallizations which are the key facter that causing aggregation of asphaltene groups. However,

12

the micelles disappeared with the addition of viscosity reducer illustrated in Figure 11B. This

13

corresponded to the fact that the asphaltene micelles were adsorbed on the surface of the polymer

14

molecules upon the addition of the viscosity reducer which reduced the number of small sheet-like

15

micelles and extended the distance between the asphaltene groups, helping to decrease the

16

viscosity of the heavy oil. Combined with the result of the cold field scanning electron microscopy,

17

we believe that the heteroatoms of the designed copolymer viscosity reducer interacted with the H


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atoms of the hydroxy ions among asphaltenes, which is in accordance with the fact that the

2

original colloidal particles were atomized.7,8

3 4

Figure 11 A. A surface SEM image of the heavy oil. B. A surface SEM image of the heavy oil with the viscosity

5

reducer added

6

5 Conclusions

7

From the simulation of the structure and number of hydrogen bonds in heavy oil, we found that

8

the number of hydrogen bonds in asphaltene in the simulation structure decreased from 36 to 28

9

per unit volume at 303K when the viscosity reducer was added. This indicated that the polar

10

segment of the viscosity reducer molecules could insert themselves into the overlap structure of

11

asphaltenes and prevent the formation of hydrogen bonds. Therefore, the distance between the

12

molecules of asphaltene in aggregations expanded, and the molecular potential energy increased.

13

Since hydrogen bond energy is relatively lower than bond energy, the macroscopic interaction

14

between the aggregations had no obvious change, so the non-bond energy of the two-simulation

15

system remained invariant. The heating rate of the system with the viscosity reducer was relatively

16

lower than the system without the viscosity reducer, indicating that the original plane overlap

17

structure of asphaltene was damaged as soon as interactions occurred between the asphaltene and

18

copolymer molecule. Therefore, the viscosity of the heavy oil was decreased with the copolymer


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1

viscosity reducer.

2

According to the result of the MD simulation, we synthesized the copolymer viscosity reducer

3

and studied it through an FTIR spectral analysis, dynamic light scattering analysis, gel permeation

4

chromatography analysis and thermal analysis. The infrared spectrum of the copolymer at

5

1410–1586 cm−1, 1744 cm−1, 3450 cm−1 and a strong absorption peak around 3000 cm−1, suggest

6

that the copolymer based on ester, benzene and pyridine ring functional groups had been ottained.

7

The copolymer showed good performance for its proper average grain diameter (23.6 nm),

8

average molecular weight (15079), and mass-average molecular weight (29665). Besides, the

9

glass transition temperature of the polymer was −18℃ and no new phase emerged between –15°C

10

and 140°C so the polymer had a suitable temperature range for the application.

11

To validate the result of the simulation, the polymer viscosity reducer was added to Shengli

12

(China) heavy oil and observed under SEM. The kinematic viscosity of the heavy oil decreased

13

from 737.37 mPa·s to 154.04 mPa·s at 30℃ when the amount of copolymer viscosity reducer was

14

463ug/g. The viscosity reduction rate of heavy oil as high as 79%. The copolymer exhibited a

15

good viscosity reduction effect on the heavy oil, highlighting the potential for industrial

16

applications. The surface SEM images of the heavy oils, with and without the added viscosity

17

reducer, showed that the state of aggregation changed significantly, indicating that interactions

18

between the copolymer viscosity reducer and heavy oil glial asphaltene are in accordance with

19

confirmed facts from the perspective of molecular dynamics, the basis for the viscosity reduction

20

mechanism.

21

Author Information

22

Corresponding Author:


Page 18 of 23

Page 19 of 23 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

1

*Weiyu Fan

2

*Email: [email protected]

3

Author Contributions

4

The manuscript was written through contributions of all authors. All authors have given approval

5

to the final version of the manuscript.

6

Notes

7

The authors declare no competing financial interest.

8

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