Subscriber access provided by Penn State | University Libraries

Energy & Fuels is published by the American Chemical Society. 1155 Sixteenth StreetN.W., Washington, DC 20036Published by American Chemical Society. Copyright © American Chemical Society.However, no copyright claim is made to original U.S. Government works, or worksproduced by employees of any Commonwealth realm Crown government in the courseof their duties.

Article

A Novel Solution to Oil Spill Recovery; Using Thermo-degradable Polyolefin Oil Super-absorbent (oil-SAP)"

Xuepei Yuan, and T. C. Mike ChungEnergy Fuels, Just Accepted Manuscript • DOI: 10.1021/ef300388h • Publication Date (Web): 09 Jul 2012

Downloaded from http://pubs.acs.org on July 9, 2012

Just Accepted

“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are postedonline prior to technical editing, formatting for publication and author proofing. The American ChemicalSociety provides “Just Accepted” as a free service to the research community to expedite thedissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscriptsappear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have beenfully peer reviewed, but should not be considered the official version of record. They are accessible to allreaders and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offeredto authors. Therefore, the “Just Accepted” Web site may not include all articles that will be publishedin the journal. After a manuscript is technically edited and formatted, it will be removed from the “JustAccepted” Web site and published as an ASAP article. Note that technical editing may introduce minorchanges to the manuscript text and/or graphics which could affect content, and all legal disclaimersand ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errorsor consequences arising from the use of information contained in these “Just Accepted” manuscripts.

1

Energy & Fuels

A Novel Solution to Oil Spill Recovery; Using Thermo-degradable

Polyolefin Oil Super-absorbent (oil-SAP)

Xuepei Yuan and T. C. Mike Chung*

Department of Materials Science and Engineering,

The Pennsylvania State University

University Park, Pennsylvania 16802

* Author to whom all correspondences should be addressed (chung@ems.psu.edu)

Page 1 of 21

ACS Paragon Plus Environment

Energy & Fuels

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960

2

Abstract

This paper discusses a novel approach that may provide a complete solution to combating

oil spills. The technology is centered on a cross-linked polyolefin terpolymer (x-OS-DVB),

containing 1-octene, styrene, and divinylbenzene units, which is an oil super-absorbent (oil-SAP)

with aliphatic and aromatic side chains that have similar solubility parameters (oleophilic and

hydrophobic properties) with the hydrocarbons in crude oil. Some x-OS-DVB terpolymers, with

desirable morphology (amorphous, low Tg, and high free volume) and lightly cross-linked

(complete network) structure, show rapid oil absorption and swelling to reach a capacity 45

times of their weight. The capacity of oil uptake (swelling) is inversely proportional to the cross-

linking density. The combination of selective oil absorption (without water) and tough

mechanical strength offers buoyancy, stability, and easy recovery on water surfaces. The

recovered oil-swelled gel, containing more than 98% oil and 2% of x-OS-DVB, is suitable for

regular oil refining processes (an economic, no waste, and no pollutant approach). The bulk side

chains in x-OS-DVB result in relatively low ceiling temperature for depolymerization and zero

heating residue at 450o C, well below the first distillation step (>600o C) in oil refining.

Furthermore, polyolefins are the most inexpensive polymeric material, with a large production

capability around the world. Overall, this cost-effective new polyolefin oil-SAP technology shall

dramatically reduce the environmental impacts from oil spills and help recover one of our most

precious natural resources.

Page 2 of 21

ACS Paragon Plus Environment

Energy & Fuels

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960

3

Introduction

In light of the 2010 BP oil spill in the Gulf of Mexico—more than 20 years after the

Exxon Valdez disaster in Alaska—we still have no effective technology for removing,

recovering, and cleaning up oil spills or oil slicks from the surfaces of water bodies and

shorelines. Despite the government’s "all hands on deck" approach to combating the oil spill,

currently-used methods (booms and skimmers, dispersants, and in situ burning) are decades-old,

low-tech, and manpower-intensive, some with unknown environmental consequences. Based on

these current methods, most spilled oil is wasted and becomes pollutants in our air and waters.

Furthermore, any small fraction that is actually recovered generates a large quantity of solid and

liquid waste itself, from tons of soiled boom and other oily waste. It is treated as industrial waste

and buried at specially-designated dumps, some near residential neighborhoods. In fact, oil spill

accidents around the world are actually more frequent than the few highly-publicized cases in

United States. As shown in Figure S1, every few years there has been a major oil spill, due to

storage tanks and cracked pipes, oil tanker collisions or wrecks, even from war with delivery

destroying oil facilities. The Exxon Valdez spilled 11 million gallons oil into the Prince William

Sound, but even that case did not make the top ten list of the largest oil spills (the smallest spill

on the list was four times larger than that of Exxon Valdez). Indeed, more than 30 oil spills were

measured as larger and more devastating in the past 40 years.

There have been some reports discussing the sorption of crude oils, which is an attractive

approach to the actual removal of spilled oil. Two general sorption mechanisms include

adsorption (surface sorption) mechanism by employing porous or fibrous (high surface area)

materials and absorption (matrix sorption/swelling) mechanism by using cross-linked oleophilic

and hydrophobic materials [1]. The economic and environmental concerns surrounding oil spills

Page 3 of 21

ACS Paragon Plus Environment

Energy & Fuels

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960

4

encouraged many researchers to investigate natural sorption materials, such as multifarious

inorganic porous products (i.e. clay, talc, zeolites, silica aerogel, calcium fly ash, etc.) [2,3], and

organic biodegradable products (straw, hull, corncob, peat moss, sugarcane bagasse, wood/cotton

fibers, wool-based materials, silkworm cocoon waste, etc.) [4-10]. However, most of them show

limited oil sorption capacity and also absorb water, thus making the recovered solids unsuitable

for calcinations; most of them end up in the landfills. Meltblown PP pads and booms [11,12] are

the most commonly used oil sorbent materials, adsorbing oil in their interstices via capillary

action. Due to the weak oil-substrate interaction (adsorption mechanism), the fiber-based

adsorbers exhibit many disadvantages, including failure to maintain oil of low viscosity and easy

re-bleeding of adsorbed oil under a slight external force. There are also some reports disclosing

the usage of hydrophobic alkyl acrylate oil absorbents [13-16], such as cross-linked

styrene/acrylate, 1-octene/acylate, and octadecene/maleic anhydride copolymers. However, these

resins contain some hydrophilic polar groups and require an additional procedure for cross-

linking reaction after copolymerization. In addition, this method has the drawback of a long

absorbing time, especially for aliphatic hydrocarbon components. Some synthesized rubbers [17-

22], such as polybutadiene, butyl rubber, SBR, and EPDM, were also modified (grafting and

cross-linking) to achieve the network structure for oil absorption. However, the solution cross-

linking is hardly controlled; they usually require extensive solvent extraction to remove soluble

fraction. The resulting sol-free materials possess various degrees of cross-linking density,

reducing the overall oil swelling capability. Some methods, i.e. milling, electric-spinning, and

foaming of the oil absorbents to increase surface area, have also been applied to improve oil

absorbing speed. However, many materials [23-25], similar to that of meltblown PP, only

physically adsorb oil at the surface by capillary action. Recently, several papers applied the high

Page 4 of 21

ACS Paragon Plus Environment

Energy & Fuels

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960

5

surface area materials, including nanowire membranes [26], nanocellulose aerogels [27], carbon

nanotube aerogels [28], to increase oil adsorption capacity. The treatment of the recovered solid

materials is always a major concern, including waste disposal, recyclability, and biodegradability.

Overall, it is still a major scientific challenge to identify a suitable oil-SAP material that can

offer a comprehensive solution for combating future oil spills.

Experimental Section

Materials and Instrumentation

All O2 and moisture sensitive manipulations were carried out inside an argon filled Vacuum

Atmosphere dry box. 1-Octene, styrene, p-divinylbenzene (Sigma-Aldrich) were distilled over CaH2

under argon. Toluene (Wiley Organics) was dried via refluxing over sodium metal for 48 hours

under argon. TiCl3.AA (AA: activated by aluminum metal), AlEt2Cl (25 wt% in toluene) (Sigma-

Aldrich), and hexane, benzene, cyclohexane, petroleum (VWR) were used as received. Gasoline

(octane# 98) and diesel were purchased from a service station of Shell Oil Company. Meltblown PP

pads were kindly provided by Newpig Corporation in Pennsylvania.

All 1H spectra were recorded on a Bruker AM-300 instrument in chloroform-d at room

temperature. The thermal properties of the polymers were measured by differential scanning

calorimetry (DSC) using a Perkin-Elmer DSC-7 instrument controller with a heating and cooling

rate of 20o C/min under nitrogen. The molecular weight of the polymer was determined using a

Waters GPC. The columns used were Phenomenex Phenogel of 105, 104, 103, and 500 Å. A flow

rate of 0.7 ml/min was used, and the mobile phase was THF. Narrow molecular weight

polystyrene standards were used to estimate the molecular weight.

Synthesis of 1-octene/styrene/divinylbenzene Terpolymers

In a typical 1-octene/styrene/divinylbenzene terpolymerization reaction, 50 ml of toluene,

Page 5 of 21

ACS Paragon Plus Environment

Energy & Fuels

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960

6

5 ml of 1-octene, 5 ml of styrene and 0.2 ml of DVB were charged into a Parr 450 ml stainless

autoclave equipped with a mechanical stirrer in an argon-filled dry-box. The reactor was sealed

and moved out of the dry box, then purged with nitrogen gas at 25o C. About 0.101g of

TiCl3(AA) and 4ml of AlCl2Et (25 wt% in toluene) were added under nitrogen pressure to

initiate the polymerization. After agitation for 3 hours at elevated temperature (~45o C), the

reaction was terminated by adding 100 ml of dilute HCl solution in methanol. The polymer was

isolated by filtration and washed completely with methanol, then dried under vacuum for 8 hours.

About 4 g of OS-DVB terpolymer was obtained. The terpolymers were completely soluble in

common organic solvents, including toluene, THF, and decalin. They were analyzed by 1H NMR

and GPC to determine their molecular structures.

Oil Absorption Evaluation

Oil absorption tests were conducted following the standard method (ASTM F726-06)

using various oils. Typically, a piece of polymers around 0.2 g was put into gasoline. After

certain time, the sample was picked up with a tweezer and laid on a filter paper to remove the

excess gasoline before weighing it on a balance. Oil absorbency (g/g) was calculated by the

weight ratio between the absorbed oil to the origin dried materials. In order to study swelling

kinetics, the above measurements were carried out from time to time. In addition, the absorption

study was also extended to the individual crude oil components, including alkanes (such as

heptane), cycloalkanes (such as cyclohexane), and aromatic hydrocarbons (toluene and xylene),

respectively. Evidently, these amorphous x-OS-DVB based oil-SAP samples are very effective

absorbing both aliphatic (linear and cyclic) and aromatic hydrocarbon molecules, and their

capacities are basically controlled by cross-linking density (swelling ability), lower cross-linking

density higher swelling and absorption capacity.

Page 6 of 21

ACS Paragon Plus Environment

Energy & Fuels

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960

7

Results and Discussion

Our research approach has been focused around the design of a new oil super-absorbent

polymer (oil-SAP) that can simultaneously exhibit a combination of several essential properties,

including (a) high oil absorption capacity, (b) fast kinetics, (c) no water absorption, (d) buoyancy

and good mechanical strength for easy recovery from water surface, (e) the recovered oil/oil-

SAP mixture suitable in regular oil refining process, and (f) cost-effectiveness. The study has

been centered on new polyolefin-based oil-SAP polymers that are petroleum downstream

products, having similar solubility parameters (oleophilic and hydrophobic properties) with the

hydrocarbon components in crude oil, and low production cost. With a suitable polyolefin

structure and morphology, the polymer shall rapidly absorb oil (without water) and swell its

volume to accommodate a large quantity of absorbed oil. The resulting oil/oil-SAP mixture (pure

hydrocarbons) shall float on the water surface with good stability for easy recovery. In addition,

it is highly desirable that the oil-SAP polymer can be thermally decomposed back to low

molecular weight hydrocarbons (monomers) at <600o C during the first refining (distillation) step.

Therefore, the recovered oil/oil-SAP mixtures shall be suitable for regular oil refining processes

and resolving concerns regarding disposal, recyclability, biodegradability, and environmental

issues caused by the initial oil spill.

As illustrated in Scheme 1, a series of amorphous 1-octene/styrene/divinylbenzene (OS-

DVB) terpolymers (I) were systematically synthesized using a common heterogeneous Ziegler-

Natta catalyst that shows to be suitable for preparing high molecular weight OS-DVB

terpolymers with good control of composition and random structure, and only engaging mono-

enchainment for divinylbenzene (DVB). As will be discussed, a lightly cross-linked oil-SAP

material (an oil-swellable network) is crucial for achieving a high oil absorption capability,

Page 7 of 21

ACS Paragon Plus Environment

Energy & Fuels

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960

8

which requires a high molecular weight OS-DVB terpolymer (I) with few DVB cross-linker

units in every polymer chain. The resulting OS-DVB terpolymer (I), containing some pendent

styrene moieties (thermal cross-linkers), is completely processible (soluble) in forming various

product sizes and shapes (II). However, upon thermal heating (>220o C) it becomes a completely

insoluble network structure (III) by engaging in a Diels-Alder [2+4] inter-chain cycloaddition

reaction between two pendent styrene units in the adjacent polymer chains [28-30]. This solid-

state cross-linking reaction (effective and without any by-product) eliminates the requirement of

an expensive solution-removal of hydrocarbon-soluble fractions shown in many papers, in which

the cross-linking reactions were usually carried out in dilute solutions with a considerable

amount of intra-chain coupling activities.

CH3

+

(I)

(II)(III)

(CH2-CH)x (CH2-CH)y

OS

OS

CH2=CH

(CH2)5

CH=CH2

CH2=CHCH2=CH + (CH2-CH)z

CH3

(CH2)5

CH=CH2

Ziegler-Natta

catalyst

Processing

OS-DVB

productthermal cross-linking

oil-SAP

Scheme 1. Synthesis of cross-linked x-OS-DVB terpolymer material for oil absorption.

Page 8 of 21

ACS Paragon Plus Environment

Energy & Fuels

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960

9

Table 1. Synthesis and oil absorption evaluation of cross-linked 1-octene/styrene/divinylbenzene terpolymersa.

Run no.

Polymerization condition Absorption capacity (weight times)f

Monomer A/B/Cb

(ml)

Terpolymerc [A]/[B]/[C] (mole ratio)

Yield (g)

Mwd

(Kg/mol) Gele (%)

Gasoline Petroleum Diesel Toluene Hexane Benzene Cyclo- hexane

A-1 5/5/0.2 82.3/17.4/0.3 3.07 330 100 41.3 40.3 41.1 47.1 42.8 40.7 43.5 A-2 5/5/0.5 79.3/20.2/0.5 3.76 410 100 21.1 19.6 20.0 22.7 20.4 19.8 22.0 A-3 5/5/1 78.4/20.7/0.9 3.94 420 100 13.7 11.6 11.9 11.6 11.9 14.1 14.1 A-4 5/5/2.5 76.3/22.3/1.4 4.02 460 100 6.41 6.28 6.39 6.24 5.62 5.59 7.02 A-5 5/5/5 74.1/24.0/1.9 4.56 520 100 5.45 5.34 5.40 4.75 5.10 5.21 5.80 PPg - - - - - 9.21 9.71 9.09 10.0 8.10 10.4 11.3 a. Polymerization condition: TiCl3(AA)/AlCl2Et= 0.101g/4ml (25 wt% in toluene), 50 ml of toluene, 45o C for 3 h; Cross-linking condition: 240o C

for 2 h. b. A: 1-octene, B: styrene, and C: divinylbenzene. c. Determined by 1H NMR spectra. d. Measured by GPC with a standard polystyrene calibration curve. e. After thermal cross-linking reaction, the gel content was determined from the toluene-insoluble part after Soxhlet extraction. f. Absorption time: 24 hours g. Commercial meltblown PP pad (adsorption mechanism).

Page 9 of 21

ACS Paragon Plus Environment

Energy & Fuels

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960

10

Table 1 summarizes the experimental results of the terpolymerization reaction with 1-

octene, styrene, and divinylbenzene (DVB) using a heterogeneous Ziegler-Natta catalyst (i.e.

TiCl3(AA)/AlCl2Et; AA: activated by aluminum metal). This traditional Ziegler-Natta catalyst

shows an effective incorporation of both 1-octene and styrene co-monomers and mono-

enchainment of DVB to form the homogeneous OS-DVB terpolymer (I) solution with a rather

narrow molecular weight and composition distribution. In general, the terpolymerization results

are quite consistent with the previous observation in the copolymerization reactions between 1-

octene and styrene [31] and 1-octene and p-methylstyrene [32]. Although 1-octene exhibits

higher reactivity than styrenic monomers (styrene and p-methylstyrene), the styrenic

comonomers can be homogeneously incorporated in the copolymer with high molecular weight

and a broad range of copolymer compositions using heterogeneous Ziegler-Natta catalysts.

Figure S2 in the Supplemental Information shows a typical GPC curve of the terpolymer (run A-

1) with high molecular weight (Mw~330,000 g/mol) and relatively narrow molecular weight

distribution (Mw/Mn~2.1). As will be discussed, the DSC curves also show a sharp Tg that is

proportional to the styrene content, and the styrene and DVB contents are directly proportional to

the monomer feed ratios. The high OS-DVB terpolymers, containing more than 20 mol%

aromatic units (styrene and DVB), have been prepared without any detectable cross-linking

reaction. All resulting OS-DVB terpolymers were completely soluble in common hydrocarbon

solvents, such as hexane and toluene, at ambient temperature.

Figure 1 shows a typical 1H NMR spectrum of OS-DVB terpolymer (run A-5). There are

several aliphatic proton chemical shifts at 0.8 ppm, corresponding to CH3 in the 1-octene units,

and a band between 0.9 and 1.7 ppm, corresponding to CH2 and CH in the polymer backbone and

1-octene side chains. In the expanded region, there are three minor bands around 5.2 and 5.7 ppm

Page 10 of 21

ACS Paragon Plus Environment

Energy & Fuels

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960

11

(CH=CH2) and 6.7 ppm (CH=CH2), corresponding to the vinyl groups in the pendent styrene

groups (after mono-enchainment of DVB units). There is also a broad aromatic proton band

between 6.9 and 7.4 ppm (C6H4) from both styrene and DVB units. The integrated intensity ratio

between all three vinyl protons from the DVB units and the phenyl protons from both styrene and

DVB units determines the styrene and divinylbenzene mole ratio. The mole ratio of 1-octene was

determined by the CH3 chemical shift intensity at 0.8 ppm.

Figure 1. 1H NMR spectrum of an OS-DVB terpolymer (run A-5).

Figure 2 shows thermal properties of the OS-DVB terpolymers in Table 1, including

differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) measurements.

In Figure 2 (left), all DSC curves exhibit only one sharp Tg transition in the flat baselines. There

was no any detectable melting point up to 200o C. The Tg (-80o C) of poly(1-octene) linearly

increases with its aromatic comonomer content. All OS-DVB terpolymers (Table 1) exhibit low

Page 11 of 21

ACS Paragon Plus Environment

Energy & Fuels

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960

12

Tg’s (< -50 oC), even with 25 mol% of aromatic (styrene and DVB) content. The combination

implies a homogeneous terpolymer microstructure with a completely amorphous morphology

and high free volume. Figure 2 (right) shows TGA curve of an OS-DVB sample (run A-1).

Under an inert atmosphere, the OS-DVB terpolymer starts its thermal decomposition at 300o C

and rapidly decreases its weight around 400o C. At 450o C, the OS-DVB terpolymer was

completely decomposed without any residue, indicating the formation of volatile small

hydrocarbon molecules. Based on the mass spectrum, the main volatile components are the 1-

octene and styrene monomers, with their derivatives having the molecular size below C20.

Overall, the thermal decomposition profile resembles those of poly(1-octene) and polystyrene

hompolymers. The bulky side chains in 1-octene and styrenic monomer units weaken the C-C

bonds along the backbone, which may result in chain scission and the subsequent free radical

mediated depolymerization [33, 34] at a relatively low pyrolysis temperature. It is interesting to

note that the OS-DVB terpolymer (I) shall engage in rapid cross-linking activities during the

thermal process (>200o C). However, the resulting cross-linking structure appears to have little

effect to the overall thermal degradation.

Page 12 of 21

ACS Paragon Plus Environment

Energy & Fuels

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960

13

Figure 2. (left) DSC curves of four OS-DVB terpolymers (runs A-1, A-2, A-3, and A-4), (right)

TGA thermographs of an OS-DVB terpolymer (run A-1) under nitrogen atmosphere.

Before oil absorption evaluation, the OS-DVB terpolymer (I) solids were divided into

1/4" sized particles and then heated at 240o C under N2 for 2 hours to complete the cross-linking

reaction. The resulting x-OS-DVB samples (III) were subjected to a vigorous solvent extraction

by refluxing toluene for 36 hours to examine any soluble fraction that was not fully cross-linked

into the network structure. Evidently, all x-OS-DVB samples in Table 1 show no detectable

soluble fraction, even in the terpolymer (run A-1) with only 0.3 mol% DVB units (about 5 DVB

units per polymer chain), indicating a very efficient thermal cross-linking reaction under a

polymer melt state condition. The extensive chain entanglement among many polymer chains

significantly enhances the inter-chain Diels-Alder [2+4] cycloaddition reaction between two

pendent styrene units from adjacent polymer chains. The high molecular weight terpolymer with

narrow molecular weight and composition distributions certainly also helps in achieving the

complete network structure.

The resulting x-OS-DVB terpolymers (runs A-1 to A-5) were subjected to contact with

various oils and pure hydrocarbons in order to understand their oil absorption capability and

kinetics. Since crude oil is predominantly a mixture of aliphatic and aromatic hydrocarbons with

various molecular weights, and the exact molecular composition varies widely from formation to

formation. Thus, we decided to examine a broad range of petroleum products, including some

representative of pure aliphatic and aromatic compounds. Table 1 summarizes the experimental

results with several individual aliphatic and aromatic hydrocarbons (i.e. hexane, cyclohexane,

benzene, and toluene) and some common petroleum products (i.e. gasoline, petroleum, and

diesel). Figure 3 compares the oil uptake vs. time for five x-OS-DVB samples (runs A-1 to A-5)

with a crude containing approximately 70% volatile light oils and 30% non-volatile heavy oils.

Page 13 of 21

ACS Paragon Plus Environment

Energy & Fuels

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960

14

Figure 3. Oil uptake vs. time for a comparative set of x-OS-DVB samples (runs A-1 to A-5) with

a crude containing approximately 70% volatile light oils and 30% non-volatile heavy oils.

Seemingly, the oil absorbency and swelling capacity in x-OS-DVB is largely controlled

by cross-linking density, reversely proportional to the cross-linking density. There is a very

minor dependence on the absorbates—either the aliphatic or aromatic hydrocarbons, or even the

mixed oil products. All of the x-OS-DVB samples contain both aliphatic and aromatic side

chains with similar mole ratios, but with different cross-linking densities. The lowest cross-

linking density of x-OS-DVB (run A-1), with 82.3/17.4/0.3 1-octene/styrene/DVB mol%,

exhibits a high absorbent capacity and the largest degree of swelling, forming a softer and more

cohesive gel formation. Conversely, the x-OS-DVB sample with high cross-link density (run A-

5) shows lower absorbent capacity and swell. The gel strength is firmer and can maintain particle

shape, even under modest pressure.

Page 14 of 21

ACS Paragon Plus Environment

Energy & Fuels

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960

15

Figure 4. Oil up-take for (a) x-OS-DVB (run A-1) and (b) commercial meltblown PP pad.

Figure 4 compares the oil absorption performance of the x-OS-DVB sample (run A-1)

with a state-of-the-art meltblown PP pad that is fabricated from a nonwoven fibrous PP textile

with a highly crystalline polymer structure and porous morphology (high surface area). They

were examined side-by-side for comparison. The meltblown PP pads (adsorption mechanism)

show rapid oil adsorption in their interstices by capillary action, saturating at 10 times the weight

of uptake without any visible volume enlargement. The adsorption mechanism happens only on

the PP fiber surfaces (not inside the crystalline matrix), which is advantageous with fast kinetics

but with limited capacity, and the weak oil-PP interaction results in some adsorbed oil re-

bleeding under a slight external force. On the other hand, the lightly cross-linked oil-SAP sample

(run A-1), with amorphous morphology, gradually absorbs oil in its matrix, increasing its weight

Page 15 of 21

ACS Paragon Plus Environment

Energy & Fuels

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960

16

by more than 10 times within 10 minutes, and reaching 40 times its weight after 12 hours. Its oil

sorption capacity is superior (>4 times) to that of the state-of-the-art meltblown PP pad.

Figure 5. (a) The starting x-OS-DVB oil-SAP sample (run A-1), (b) after soaking with crude oil,

this swelled oil-SAP is floating on the surface of water, and (c) is picked up by a tweezer. The

background grid is used for the scale reference.

Figure 5 shows the action of this x-OS-DVB sample (run A-1) during the oil absorption.

The starting 1/4" sized oil-SAP sample (Figure 5 (a)) can effectively absorb crude oil from the

water surface with a large expansion of its volume (>40 times). Subsequently, the resulting

oil/oil-SAP mixture floating on water surface (Figure 5 (b)) is ready for collection and can be

picked up with a tweezer without leaking oil (Figure 5(c)). The combination of good mechanical

strength (cross-linked elastic structure) and a strong affinity between the oil and polymer matrix

assure its structure integrity and oil absorption stability. In a real-world context, it shall also be

stable under ocean environments (waves, wind, sunlight, etc.) and be easily removed from the

water surface. Had this material been applied to the top of the leaking well head in the Gulf of

Mexico during the 2010 spill, this oil-SAP could have effectively transformed the gushing brown

oil into a floating gel for easy collection, and minimized the pollution consequences to our air

and water.

Page 16 of 21

ACS Paragon Plus Environment

Energy & Fuels

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960

17

In addition to effective oil recovery, the resulting oil-swelled gel mixture can be treated

as crude oil, suitable for regular refining processes (distillation and cracking). The mixtures

contain no water and have nearly the same composition as original crude oil. During refinery, the

minor component (2-3%) of x-OS-DVB polymer will be thermally decomposed back to <C20

hydrocarbon molecules (typically existing in crude oil) without residue (Figure 2), well below

the typical crude oil refining temperature (>600o C). This process has multifarious benefits: it

eliminates the concern surrounding solid waste disposal, recyclability, and biodegradability, and

maintains our reservations of natural resources. Furthermore, polyolefin products are the most

inexpensive of polymeric materials, and are capable of large-scale production around the globe.

With conservative estimates, the production cost of new oil-SAP material comes below $2 per

pound in large-scale industrial production. One pound of oil-SAP, with a 40 times absorption

capacity, can recover more than five gallons of spilled oil (currently treated as a pollutant instead

of a useable resource) to regular crude oil that is worth more than $12 (based on $80/barrel).

In this study, we have developed a new oil-SAP technology based on polyolefin based x-

OS-DVB terpolymers that can be effectively prepared by a conventional Ziegler-Natta catalyst

and then thermally cross-linked into the oil-SAP materials. The combination of oleophilic and

hydrophobic properties with amorphous morphology, high free volume, and a cross-linked

network offers a desirable matrix for oil absorption and swelling. The oil uptake is inversely

proportional to the cross-linking density. Oil uptake with up to 45 times that of the polymer

weight and fast kinetics has been observed in a lightly cross-linked x-OS-DVB terpolymer.

Overall, this new oil-SAP technology exhibits a combination of benefits in oil recovery and

cleanup, including (i) high oil absorption capability, (ii) fast kinetics, (iii) easy recovery from the

water surface, (iv) no water absorption, (v) no waste in natural resources, and (vi) is cost-

Page 17 of 21

ACS Paragon Plus Environment

Energy & Fuels

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960

18

effective and economically feasible. This new oil-SAP technology shall fundamentally address

the multiple issues created by mega oil spills, whether seen from an environmental or economic

standpoint.

Acknowledgement

The authors gratefully acknowledge the financial support of this work by an NSF

Research Grant (CBET-1067554) and commercial feasibility study by Ben Franklin Foundation

under its Translational Research in Energy Support Program.

Supporting Information Available: Major oil spills and polymer structure characterization

(GPC and TGA curves) of OS-DVB terpolymers. This material is available free of charge via the

Internet at http://pubs.acs.org.

Page 18 of 21

ACS Paragon Plus Environment

Energy & Fuels

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960

19

Reference:

1. Karan, C. P.; Rengasamy, R. S.; Das, D. Indian J. Fibre & Textile Res. 2011, 36, 190-200.

2. Arbatan, T.; Fang, X.; Shen, W. Chem. Eng. J. 2011, 166, 787-791.

3. Karakasi, O. K.; Moutsatsou, A. Fuel 2010, 89, 3963-3970.

4. Chol. H. M.; Cloud, R. M. Environ Sci. Technol. 1992, 26, 772-776.

5. Teas, C.; Kalligeros, S.; Zanikos, F.; Stournas, S.; Lois, E.; Anastopoulos, G. Desalination

2001, 140, 259-264.

6. Inagaki, M.; Kawahara, A.; Konno, H. Carbon 2002, 40, 105-111.

7. Adebajo, M. O.; Frost, R. L.; Kloprogge, J. T.; Carmody, O.; Kokot, S. J. Porous Materials

2003, 10, 159-170.

8. Deschamps, G.; Caruel, H.; Borredon, M. E.; Bonnin, C.; Vignoles, C. Environ Sci. Technol.

2003, 37, 1013-1015.

9. Suni, S.; Kosunen, A. L.; Hautala, M.; Pasila, A.; Romantschuk, M. Marine Pollution Bull.

2004, 49, 916-921.

10. Sun, X. F.; Sun R.C.; Sun J. X. J. Mater. Sci. 2003, 38, 3915-3923.

11. Bayat, A.; Aghamiri, S. F.; Moheb, A.; Vakili-Nezhaad, G. R. Chem. Eng. Technol. 2005, 28,

1525-1528.

12. Wei, Q. F.; Mather, R. R.; Fotheringham, A. F.; Yang, R. D. Marine Pollution Bull. 2003, 46,

780-783.

13. Jang, J.; Kim B. S. J. Appl. Polym. Sci. 2000, 77, 903-913.

14. Atta, A. M.; Arndt, K. F. J. Appl. Polym. Sci. 2005, 97, 80-91.

15. Atta, A. M.; El-Hamouly, S. H.; AlSabagh, A. M.; Gabr, M. M. J. Appl. Polym. Sci. 2007,

105, 2113-2120.

Page 19 of 21

ACS Paragon Plus Environment

Energy & Fuels

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960

20

16. Farag, R .K.; EI-Saeed, S. M. J. Appl. Polym. Sci. 2008, 109, 3704-3713.

17. Shan, G. R.; Xu, P. X.; Weng, Z. X.; Huang, Z. M. J. Appl. Polym. Sci. 2003, 90, 3945-3950.

18. Ceylan, D.; Dogu, S.; Karacik, B.; Yakan, S.; Okay, O. S.; Okay, O. Environ Sci. Technol.

2009, 43, 3846-3852.

19. Essawy, H. A.; Essa, M. M.; Abdeen, Z. J. Appl. Polym. Sci. 2010, 115, 385-392.

20. Zhou, M. H.; Cho, W. J. J. Appl. Polym. Sci. 2002, 85, 2119-2129.

21. Zhou X. M.; Chuai, C. Z. J. Appl. Polym. Sci. 2010, 115, 3321-3325.

22. Fouchet, B. J. Appl. Polym. Sci. 2009, 111, 2886-2891.

23. Lin, C.; Huang, C. L.; Shern, C. C. Resource Conservation and Recycling 2008, 52, 1162-

1166.

24. Zhu, H.; Qiu, S.; Jiang, W.; Wu, D.; Zhang, C. Environ Sci. Technol. 2011, 45, 4527-4531.

25. Tanobe, V. O. A.; Sydenstricker, T. H. D.; Amico, S. C.; Vargas, J. V. C.; Zawadzki, S. F. J.

Appl. Polym. Sci. 2008, 111, 1842-1849.

26. Yuan, J. ; Liu, X. ; Akbulut, O. ; Hu, J. ; Suib, S. L. ; Kong, J. ; Stellacci, F. Nature Nanotech.

2008, 3, 332-336.

27. Korhonen, J. ; Kettunen, M. ; Ras, R. ; Ikkala, O. ACS Appl. Mater. Interfaces 2011, 3, 1813-

1816.

28. Gui, X. C.; Wei, J. Q.; Wang, K. L.; Cao, A. Y.; Zhu, H. W.; Jia, Y.; Shu, Q. K.; Wu, D. H.

Adv. Mater. 2010, 22, 617–621.

29. Chung, T. C. Functionalization of Polyolefins; Academic Press: London, 2002.

30. Lin, W. T. ; Shao, Z. ; Dong, J. Y. ; Chung, T. C. Macromolecules 2009, 42, 3750-3754.

31. Chung, T. C.; Lu, H. L.; Hong, S, Rubber Chem. and Technology 1999, 72. 283-298.

32. Fu, Z.; Zhu, L.; Deng, J.; Xu, J.; Wang, Q.; Fan, Z. J. Appl. Polym. Sci. 2011, 119, 677-684.

Page 20 of 21

ACS Paragon Plus Environment

Energy & Fuels

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960

21

33. Faravelli, T. ; Pinciroli, M. ; Pisano, F. ; Bozzano, G. ; Dente, M. ; Ranzi, E. J. Anal. Appl.

Pyrol. 2001, 60, 103-121.

34. Guaita, M. British Polym. J. 2007, 18, 226-230.

35. Yuan, X. P. ; Chung, T. C. Appl. Phys. Lett. 2011, 98, 62901-62903.

Table of Contents Graphic

A Novel Solution to Oil Spill Recovery; Using Thermo-degradable Polyolefin Oil Super-

absorbent (oil-SAP)

Xuepei Yuan and T. C. Mike Chung*

Page 21 of 21

ACS Paragon Plus Environment

Energy & Fuels

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960