Experimental Investigation on the Effect of Aliphatic Ionic Liquids on

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Experimental Investigation on the Effect of Aliphatic Ionic Liquids on the Solubility of Heavy Crude Oil using UV-Visible, FT-IR, and 13C-NMR Spectroscopy Sivabalan Sakthivel, Sugirtha Velusamy, Ramesh L Gardas, and Jitendra S. Sangwai Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/ef501086v • Publication Date (Web): 22 Aug 2014 Downloaded from http://pubs.acs.org on August 27, 2014

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Energy & Fuels

Research Article

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Experimental Investigation on the Effect of Aliphatic Ionic Liquids on the

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Solubility of Heavy Crude Oil using UV-Visible, FT-IR, and 13C-NMR

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Spectroscopy

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Sivabalan Sakthivel1, Sugirtha Velusamy1, Ramesh L. Gardas2, Jitendra S. Sangwai1,*

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1

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Gas Hydrate and Flow Assurance Laboratory, Petroleum Engineering Program,

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Department of Ocean Engineering, Indian Institute of Technology Madras, Chennai – 600

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036, India

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Ionic Liquid Laboratory, Department of Chemistry, Indian Institute of Technology Madras, Chennai – 600 036, India

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*Corresponding Author: Jitendra Sangwai: [email protected]; Phone: +91-44-

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2257-4825 (Office); Fax: +91-44-2257-4802

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1 ACS Paragon Plus Environment

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ABSTRACT

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Chemical treatment of aromatic heavier hydrocarbons are traditionally done by using

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cyclic aromatic non-polar solvents such as, benzene, xylene, and toluene which has

4

capability to dissolve asphaltenes. However, these aromatic solvents are volatile and

5

hazardous, and hence not advisable to use. Alternatively, lighter hydrocarbons such as,

6

heptane, hexane, etc., show lesser solubility. It is, therefore, crucial that these problems

7

require intelligent, cost-effective and innovative solutions. The present work investigates the

8

possible solution for the dissolution of heavy crude oil using the application of eight

9

aliphatic ionic liquids (ILs) along with five solvents, namely, toluene, heptane, decane, ethyl

10

acetate and hexane. Ionic liquids (ILs) based on [CH3COO]-, [BF4]-, [H2PO4]- and [HSO4]-

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as anions and with various cations such as, di- and tri- alkyl ammonium are considered. The

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enhancement in the solubility of heavy crude oil in solvent+ILs mixture is investigated

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using Ultraviolet Visible (UV-Vis) spectrophotometry, Fourier Transform-Infra Red

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spectroscopy (FT-IR) and

15

techniques. The absorbance of the sample solution (heavy crude oil+solvent+IL) is

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compared with the standard solution (heavy crude oil in neat solvent alone). It is observed

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that the dissolution of heavy crude oil is more in the solution with IL than with the solvent

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alone. Solubility of heavy crude oil in solvents increases to about 70 % in the presence of

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ILs. Hold-time study is also performed to understand the maximum time required for

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efficient dissolution of heavy crude oil. The hold-time study reveals that solubility of heavy

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crude oil in heptane increased to about 61 to 222 % in the presence of ILs, as compared to

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11 to 16 % in case of standard solution for a prolonged period of 30 days.

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C-Nuclear Magnetic Resonance (NMR) spectroscopic

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words:

Heavy

24

Key

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Spectrophotometry.

crude

oil;

Ionic

liquids;

Organic


solvents;

Solubility;

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1. INTRODUCTION

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Heavy crude oil is mostly composed of heavier hydrocarbons, particularly saturates,

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aromatics, resins and asphaltenes (commonly known as SARA). These hydrocarbon groups

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remain mostly in the dissolved state at high pressure high temperature (HPHT) reservoir

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conditions. At surface conditions, these high molecular weight components begin to

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separate from the bulk stream and accumulate in the form of solid leading to flow-assurance

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issues in production tubing and transportation. It is estimated that unconventional

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hydrocarbon reservoirs containing heavier crude oil are almost double in magnitude to that

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of the conventional hydrocarbon reservoirs.1 In addition, the production from conventional

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reservoir is on decreasing trends due to their maturity resulting in the increased production

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of heavier hydrocarbons. As the world’s demand for processed hydrocarbons continues to

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increase tremendously, there is a need to address the production challenges associated with

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heavy oil and matured reservoirs, although efforts have already been made to extract this

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heavy crude oil that was previously considered uneconomical to produce and process.2,3

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Oil and gas industries, in the recent past faces operational and technical challenges

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due to the deposition of higher molecular weight components of crude oil, increased skin

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factor near well-bore, resulting in decreased oil production from mature reservoirs and huge

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production losses. API (American Petroleum Institute) gravity is an inverse measure, based

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on relative density, of how heavy or light a crude oil is as compared to water. The

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definitions of heavy crude oil varies from region to region. In general, if the crude oil has an

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≤ 20 °API gravity, it is considered as heavy, while the crude oil with ≤ 10 °API, is termed as

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extra-heavy oil or bitumen. The greatest disadvantages of heavy and extra-heavy crude oil

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are their low API gravity, high contents of asphaltene, aromatics, wax and heavy metals.

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The asphaltenes and resins are the major polar fractions in the crude oil. These large and

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polar constituents have a condensed polyaromatic structure containing alkyl chains, 3 ACS Paragon Plus Environment

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heteroatoms (such as O, S, and N), and some metals.4 The presence of aromatics along with

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resins, asphaltene and saturates make production of these hydrocarbon a daunting task.5,6

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The produced hydrocarbon also magnifies the flow assurance issues in the reservoirs and at

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surface facilities. The current standards in the field of heavy oil production and management

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pose a severe environmental impact in view of the damage it could cause.

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Asphaltene precipitation and deposition during petroleum production takes place due

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to the changes in temperature, composition, pressure and flow regime leading to difficult

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transportation, refining, and processing.7 These asphaltene precipitations are the root cause

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for making oil production extremely complex and costly owing to the partial or complete

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plugging of the oil well and transportation pipelines.8 In petroleum industry, attempts to

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upgrade and refine heavy oil are encountered with serious problems arising due to

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asphaltenes which are responsible for the formation of coke-precursors.9 On many

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occasions, such accumulation renders the transportation pipeline unusable due to inability to

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take suction and dispatch crude oil for delivery. Beyond the need for additional refining,

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heavy crude oil requires new strategies and treatments for its extraction and enhancing its

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flow properties for better transportation. In fact, the consistency of the heavy crude oil

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increases to that extent that it remains in the form of hardened solid similar to the residue

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obtained from refining of light crude oil, unless not heated.10,11 It is customary to use heated

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oil or lower hydrocarbon fractions for dilution of the heavy crude oil12,13 and water,14,15

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dispersant formulations and elaborate oil circulation arrangement to soften the heavy crude

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oil. In the absence of such arrangements, heavy crude oil deposition in the transportation

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pipeline is removed using the common pigging process.16

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Enhanced oil recovery (EOR) techniques aim in producing the difficult to flow

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hydrocarbon fluid from the reservoirs. Nevertheless, the most commonly used EOR

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technologies are the thermal techniques, as they reduce the viscosity of heavy crude oil


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significantly. Current methods of extraction also include injection of air into the well so as

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to create fire to burn heavier hydrocarbons and degrade them into lighter components (in-

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situ combustion) which could be easily pumped out, open-pit mining, steam-injection and

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miscible solvent method.17,18 The objective of the techniques is to increase mobility of the

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heavy crude oil by reducing its viscosity to enhance the recovery or production of heavy

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crude oil. Steam generation costs and formation water critically affect the economics of the

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thermal technique. Miscible solvent method is energy effective, but its financial side

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depends on the solvent recovery.17,18 In the case of underwater transportation of heavy crude

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through heated pipelines, the operation becomes very difficult due to the cooling effect of

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the surrounding water and it also causes difficulty in maintaining substations and heating

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stations at certain intervals of distance for continuous heat to persist.19,20

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Chemical treatment of aromatic heavier hydrocarbons such as, asphaltenes, etc., are

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traditionally done by using cyclic aromatic non-polar solvents such as benzene, xylene, and

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toluene which has capability to dissolve asphaltenes.14,21 However, these aromatic solvents

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are volatile and hazardous, and hence not advisable to use.21 Alternatively, lighter

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hydrocarbons such as, heptane, hexane, etc., could be used, which however, show lesser

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solubility when compared with aromatic organic solvents. It is, therefore, crucial that these

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problems require intelligent, cost-effective and innovative solutions.

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The use of ionic liquids (ILs) have huge prospective as a good co-solvent along with

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solvents for heavy crude oil solubility and can be used for flow assurance mitigation and

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EOR applications for heavy oil reservoirs.15,22-25 ILs are organic salts possessing very low

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melting points.26 ILs possess good catalytic properties, negligible vapour pressure, high

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chemical and thermal stability, non-flammability, which in this manner makes them a

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worthy substitutes to volatile organic solvents. Additionally, the used ILs can be recycled

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using water15 and can also be reused plentiful times.14,27 Several ionic liquids are being


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employed for diverse kinds of work such as enhanced oil recovery, bitumen recovery,

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desulphurization, asphaltene degradation, etc.15,22-25,28 Ionic liquids thus show potential

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solution to tackle the energy and environmental challenges and to help facilitate the easy

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transportation of the heavy crude oil, reducing its deposition inside the pipeline and to

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enhance potential recovery of conditioned fuel.

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Recently, few researchers14,22,23,28 have studied the use of ILs to address various

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issues in the upstream oil and gas industry. A very good performance in the dissolution of

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asphaltenes has been observed using ILs as novel solvents.22 By increasing the charge

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density of the anionic part of ILs and by decreasing the chain length of the alkyl group,

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(cationic part) asphaltene association is found to be broken easily.22 Undeniably, there is still

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bountiful scope in the area of scheming specific ionic liquids which are capable to solubilise

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heavy crude oil by softening and making them pumpable. In recent times,23 room

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temperature

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[Et3NH]+[AlCl4]--Fe2+ and [Et3NH]+[AlCl4]--Cu+ have been used for upgrading heavy oil at

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the reservoir conditions by decreasing the viscosity. The results confirm that noteworthy

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improvement has been observed on upgradation of heavy oil at optimum temperature

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conditions of the oil reservoir. Among the ILs studied, [Et3NH]+[AlCl4]--Ni2+has been

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observed to exhibit better viscosity reduction than the rest ILs.23,29 Chloro-aluminate (III)

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ionic liquids/H3PO4 systems have established effective performance on asphaltic sand

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degradation.23,28 Additionally, ionic liquids such as, [EMIM]+[BF4]- and [BMMIM]+[BF4]-

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are found to be more proficient to enhance the recovery of bitumen from oil sands.

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Furthermore, the authors have compared these two ionic liquids with each other and have

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found that the IL, [EMIM]+[BF4]- to be more efficient than the other.15

ionic

liquids

such

[Et3NH]+[AlCl4]-,

as,

[Et3NH]+[AlCl4]--Ni2+,

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Ionic liquids, [BMIM]+[Cl]- and [BMIM]+[AlCl4]- behave as a better dissolution

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agents for asphaltene.22,24 [BMIM]+[BF4]- is found to be very capable in bitumen recovery


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from oil sand.14 Excellent solubility and wide range of catalytic properties of ILs have

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enabled their use in extraction, desulphurization, and scale re moval.25 The first step in the

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mechanism of the reaction of heavy oil and ILs is the reaction of organic sulphur from

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heavy oil with transition metal modified ILs to form the intermediate complex (S―›M+),

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which helps in weakening the C-S bonds, which is followed by the breaking of heavy oil

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molecules. The end result of this reaction is that, sulphur in the heavy oil escapes as H2S

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(gas) and thus, the content of the sulphur gets minimized in the heavy oil.24 These results

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indicate that the separation is easier by using ionic liquids rather than by using water. The

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interfacial tension and surface tension between bitumen and silica are reduced in the

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presence of ionic liquids, which enable their easy separation.15 Adhesion force between

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bitumen and silica are considerably smaller in the presence of ILs than in aqueous

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solution.30 In the same way, the contact angle between the bitumen oil and water droplets is

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∼90o, but in the case of bitumen oil and ionic liquid it is ~73o, suggesting that the separation

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of bitumen from sand is easier by using ionic liquids rather than water.30 Considering the

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solubility aspects of SARA oil fractions, most of the available literature focusses on

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asphaltenes rather than complex-solids formed within production wells, particularly on

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two general areas, the first being the fundamental aspects on solubility and flocculation31

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and the second is the identification of methods to enhance the solvent dissolution power,

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either by combination of solvents32 or by the addition of suitable chemicals.8

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In this work, the enhancement in the solubility of heavy crude oil in five different

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solvents in the presence of eight aliphatic ILs is investigated and compared with the

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solubility of heavy crude oil in the neat solvent alone. Ionic liquids (ILs) based on

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[CH3COO]-, [BF4]-, [H2PO4]- and [HSO4]- as anions and with various cations such as di- and

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tri- alkyl ammonium are considered. The details of ILs synthesized, along with structure,

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abbreviation and molecular weight of the ILs are given in Table 1. The solvents used are


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from the class of paraffinic, aliphatic-polar and aromatic solvents. These are hexane,

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heptane and decane from the paraffinic group and ethyl acetate from the aliphatic-polar

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solvents and toluene from the aromatic solvents. In the present work, the dissolution of

4

heavy crude oil using ionic liquids along with solvents is evaluated using different

5

experimental techniques such as, Ultraviolet Visible (UV-Vis) spectrophotometry, Fourier

6

Transform-Infra Red spectroscopy (FT-IR) and

7

spectroscopic techniques. The determination of the solubility of ionic liquids is performed

8

using the above said techniques based on their capabilities as demonstrated in previous

9

literatures.33,34 Hold-time studies are also done so as to acquire knowledge of the maximum

10

time required for the efficient dissolution of the heavy crude oil, both in the presence and

11

absence of ILs in the solvent heptane.

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C-Nuclear Magnetic Resonance (NMR)

12 13

2. EXPERIMENTAL SECTION

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2.1. Materials

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2.1.1. Heavy Crude Oil

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For the present study, heavy crude oil (referred as HCO henceforth unless specified)

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samples are provided by Oil India Limited (OIL), Assam, India. The HCO was found to be

18

more of a solid and highly viscous as compared to the conventional crude oil. The SARA

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properties and other details of HCO are summarized in Table 2.

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2.1.2. Ionic Liquids and Solvents In the present work, eight ILs, namely, [Et2NH2]+[H2PO4]-, [Et2NH2]+[HSO4]-,

23

[Et3NH]+[CH3COO]-,

[Et3NH]+[BF4]-,

[Et3NH]+[H2PO4]-,

24

[Pr3NH]+[HSO4]- and

[Bu3NH]+[HSO4]- (see Table 1) are synthesized and purified

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according to the methods available in literature35 and have been confirmed using 1H nuclear


[Et3NH]+[HSO4]-,

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magnetic resonance (1H NMR) spectroscopy. Preceding to their usage, all the ILs are dried

2

under severe agitation at 353 K under vacuum (0.1 Pa) for a minimum of 48 h to remove

3

volatile compounds and to reduce water content to negligible values. Table 3 provides the

4

list of starting materials used for the synthesis of ILs, their CAS number, source and purity.

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All the pure ILs are stored in sealed vials under N2 atmosphere.

6 7

2.2. Experimental Procedure

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2.2.1. Standard Solution Preparation

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Stock standard solutions of 1000 ppm of heavy crude oil in pure solvent (50 mg of

10

HCO in 50 mL of the corresponding solvent) are prepared without ILs and further dilutions

11

are made from it. To begin with, as a first step in the investigation, standard solutions, i.e.,

12

heavy crude oil with solvents at different concentrations (dilutions) are prepared and their

13

absorbances are recorded using UV-Visible spectrophotometer at fixed wavelength

14

corresponding to the λmax of HCO in the specific solvent considered and are provided in

15

Table 4 and the corresponding figures are shown in Figure S1 of the supporting information.

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These λmax values (as in Table 4) are obtained by running full scan spectra of different

17

concentrations of solution containing heavy crude oil in the specified solvent in the

18

wavelength range of 190-900 nm. For absorbance studies relating to standard solution of

19

heavy crude oil in toluene, the 1000 ppm solutions of heavy crude oil in solvent is diluted

20

for 10 ppm to 100 ppm (with an increment of 10 ppm). For the rest of the solvents (heptane,

21

decane, ethyl acetate and hexane) the concentrations of the solutions (with respect to heavy

22

crude oil) used are in the range of 10 ppm to 120 ppm (with an increment of 10 ppm). The

23

range with respect to toluene was kept to the minimum as much as possible to reduce the

24

amount of solvent being used as it is toxic, whereas, the toxicity for the rest of the solvents

25

is comparatively lesser and, therefore, a wider range was considered. The term


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1

concentration (in ppm) further referred herein refers to the concentration of the heavy crude

2

oil in the solvent only and not of the ionic liquid. Absorbance is measured for all the above

3

concentrations and the corresponding calibration plots are discussed in section 3.

4 5

2.2.2. Sample Solution Preparation

6

Sample solution preparation for dissolution studies are being considered for varying

7

ratios of heavy crude oil and ionic liquids in the weight ratios of HCO:ILs as, 1:1; 1:0.5 and

8

1:0.1. For HCO:ILs = 1:1, stock solution of 1000 ppm is prepared by dissolving 50 mg of

9

heavy crude oil and 50 mg of IL in 50 mL of the corresponding solvent. For HCO:ILs=1:0.5

10

and 1:0.1, similar procedure as described above is followed. The concentrations considered

11

in this work (i.e., 30, 50, 70 ppm for the case of toluene; 10, 30, 50 and 70 ppm for the rest)

12

are made by dilution from the stock solution. As mentioned above, three different weight

13

ratios of HCO to ILs (i.e., HCO:ILs =1:1, 1:0.5 and 1:0.1) are studied for all eight ILs

14

considered in this work. Further, for each ratio of HCO to ILs, four different concentrations

15

(i.e., 10, 30, 50, 70 ppm) are prepared in four different solvents (i.e., heptane, decane, ethyl

16

acetate and hexane) and three different concentrations (i.e., 30, 50, 70 ppm) are prepared in

17

toluene. Thus total of 456 sample solutions are prepared for this work, moreover each of

18

them are prepared thrice from their respective stock solution, for three trial studies. The

19

absorbance values for all of the sample solutions are recorded and are compared with their

20

respective standard solution and are used for the calculation pertaining to the dissolution of

21

heavy crude oil with solvent in the presence of ILs. The schematic of the experimental

22

procedure followed is shown in Figure 1. It is to be noted that the standard and sample

23

solutions for this study are freshly prepared and their absorbance are recorded on the same

24

day approximately within two hours of solution preparation. For hold-time study, the sample

25

solutions are stored in black chamber.


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2.2.3. Preparation of Sample for FT-IR and 13C-NMR Samples for FT-IR and

13

C-NMR analysis are prepared by decanting the dissolved

4

portion of HCO with solvent (filtrate) from the sample prepared for UV-Vis spectra,

5

followed by thoroughly washing the entire portion of the remaining residue to remove the

6

ionic liquid used. This portion of residue (obtained from the solutions containing 1:1 of

7

HCO: ILs) is dried using rota-vapour, followed by oven-drying for 2 hrs, both maintained at

8

70°C. Small amount of solid portion which is obtained, is then divided into two portions.

9

One portion is used for recording the 13C-NMR and the rest is used for recording the FT-IR

10

spectra by grinding it with potassium bromide (KBr). Ionic liquids used in the sample

11

solutions are recovered by the use of water which can be recycled and reused. The same

12

procedure is followed for all the five solvents considered in this study. Amount of sample

13

and KBr used is maintained uniform throughout this investigation.

14 15

2.3. Analytical Methods

16

The water content is measured by Analab Karl Fischer Titrator (Micro Aqua Cal100,

17

India) and with the use of Karl Fischer reagent obtained from Merck. The details of water

18

content determination using the said instruments is provided in our previous work.36 It is

19

observed that the water content of all the ILs involved in this study is below 2000 ppm. The

20

purity of the synthesized ionic liquids is determined using 1H-NMR. 1H and

21

(Brukar Avance, Switzerland). The standard absorbance values of heavy crude oil in the

22

presence of solvent and ILs are recorded using Ultraviolet-Visible (UV-Vis)

23

spectrophotometer (JASCO V-650, Japan; accuracy= ± 0.2 nm; wavelength range= 190 to

24

900 nm; optical path length= 10 mm) at fixed wavelength corresponding to the λmax of the

25

HCO in the solvent under consideration. FT-IR spectra are recorded on FT-IR


13

C-NMR

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spectrophotometer (JASCO FT-IR-4100, Japan; wavenumber range= 7800-400 cm-1;

2

wavelength range= 1282-25000 nm). The device has a maximum resolution of 0.9 cm-1 and

3

have 22,000:1 signal to noise ratio. 13C-NMR is performed in a similar manner as formerly

4

described in the literature,37 with the exception of employing ILs for 13C NMR analysis.

5 6

3. RESULTS AND DISCUSSION

7

At first, quantification for the dissolution of the heavy crude oil without ILs

8

(standard solutions) are carried out, followed by the quantification of the sample solutions

9

(heavy crude oil in solvents along with ILs) using UV-Vis spectrophotometric, FT-IR and

10

13

11

consequence of using ILs for the dissolution of the heavy crude oil with respect to time.

C-NMR techniques. Following this, hold-time study is also performed to understand the

12 13

3.1. Solubility Studies of Heavy Crude Oil without ILs

14

The softening of the heavy crude oil by manner of its dissolution in various solvents

15

(standard solutions) are carried out by measuring their absorbance using UV-Vis

16

spectrophotometer at the particular wavelength corresponding to the λmax of HCO in the

17

respective solvent concerned (as in Table 4). Figure 2 (a-e) shows the graphs of absorbance

18

of standard solutions against the concentration (in ppm) of the heavy crude oil in solvents

19

such as toluene, heptane, decane, ethyl acetate and hexane, respectively. These

20

concentration (in ppm) versus absorbance graphs are fitted with linear regression analysis

21

with regression coefficient (R2) to be greater than 0.99. The values of R2 obtained for

22

various standard solutions of heavy crude oil in pure solvents (without ILs) toluene,

23

heptane, decane, ethyl acetate and hexane are 0.9980, 0.9982, 0.9993, 0.9997 and 0.9995,

24

respectively.

25


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Energy & Fuels

3.2. Solubility Studies of Heavy Crude Oil with ILs

2

The solubility studies of the sample solutions with eight ionic liquids, five solvents

3

and with three different weight-ratios of HCO:ILs are done by measuring their absorbance

4

at a particular wavelength corresponding to the λmax of HCO in the respective solvent

5

concerned (as provided in Table 4). All the values corresponding to the absorbance runs are

6

consistent for three trials, and are within ± 0.001 of the reported values. The absorbance of

7

the sample solutions are compared with the respective concentration of the standard

8

solutions and the increase in the percentage solubility over standard solution (with

9

absorbance values of standard solution as the base reference) are calculated and plotted.

10

Figure 3 shows the UV-Vis absorption of the sample solution in comparison with the

11

standard solution in the solvent heptane with the weight ratio of HCO:ILs= 1:1. In Figure 3

12

(a)-(h) shows the efficiency of eight ILs in the dissolution of heavy crude oil following the

13

order,

14

[Et3NH]+[H2PO4]-, [Et3NH]+[HSO4]-, [Pr3NH]+[HSO4]- and

15

observations, showing the effect of eight ILs in the process of dissolution of heavy crude oil

16

for the weight ratio of HCO:ILs= 1:1 in the rest of the solvents, namely, toluene, decane,

17

ethyl acetate and hexane, are made and are provided in the Figures S2-S5 of supporting

18

information. Figures 4 to 8 show the percentage increase in solubility (with an accuracy of ±

19

0.1 %) with increase in the concentration of HCO in solvent (in ppm) for different weight-

20

ratios of HCO:ILs, showing the effectiveness of various ILs on the solubility of heavy crude

21

oil.

[Et2NH2]+[H2PO4]-,

[Et2NH2]+[HSO4]-,

[Et3NH]+[CH3COO]-,

[Et3NH]+[BF4]-,

[Bu3NH]+[HSO4]-. Similar

22

In the present investigation, the dissolution of heavy crude oil in toluene is observed

23

to be more efficient in the presence of [Et3NH]+[H2PO4]-. Minimum efficiency of less than

24

10 % is observe for the IL, [Et3NH]+[CH3COO]-. In case of the solvent heptane, the IL

25

[Et3NH]+[CH3COO]- exhibits the maximum efficiency of about 70 % for the dissolution of


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

heavy crude oil while with other ILs it shows an overall better performance of around 30 %.

2

For the case of the solvent decane, [Et3NH]+[CH3COO]- shows an efficiency to the

3

maximum of around 45 % in the dissolution of heavy crude oil and for the concentration of

4

10 ppm of heavy crude oil in decane, the ILs namely, [Et3NH]+[H2PO4]-, [Et3NH]+[BF4]-

5

and [Bu3NH]+[HSO4]- show around 50 % efficiency. In the case of ethyl acetate, the IL,

6

[Et2NH2]+ [H2PO4]- provides an efficiency of up to 32 % at 10 ppm concentration for 1:1

7

ratio of HCO:IL for the dissolution of heavy crude oil and the ILs, such as,

8

[Et3NH]+[HSO4]- and [Bu3NH]+[HSO4]- show better performance next to [Et2NH2]+[H2PO4]-

9

. Other ILs show C=O group present in the heavy crude oil. The peaks visible in the region of

6

120-140 ppm indicate the presence of aromatics in the crude heavy crude oil. It is observed

7

from Figure 13(b) that these peaks do not get vanished completely; indicating that there is

8

oil still present in the sample. In Figure 13 (c), the peaks due to the aromatics disappeared,

9

signifying the absence of oil after the treatment of heavy crude oil in heptane with the IL,

10

[Et3NH]+[CH3COO] -.

11

In general, from the present investigation, it is observed that the presence of ILs

12

along with solvents enhance the dissolution of heavy crude oil making it to be easily

13

pumpable and transportable through pipelines. This is more convincing from the

14

quantification of dissolution of heavy crude oil done by UV-Vis studies. The hold-time

15

study also provides reliable information for the use of appropriate ILs and solvents for

16

efficient softening of the heavy crude oil thereby preventing sludge deposition in storage

17

tanks, transportation pipelines and in the reservoirs. Qualitative analysis for the

18

determination of dissolution of heavy crude oil in solvents in the presence of ILs is

19

performed using FT-IR and 13C-NMR and is reported.

20 21

4. CONCLUSIONS

22

This study presents the detailed investigation on the enhancement of solubility of

23

heavy crude oil in various organic solvents with addition of aliphatic ionic liquid using UV-

24

Vis, FT-IR and 13C-NMR spectroscopic techniques. It is apt to say that a meagre 10 % of IL

25

for almost complete dissolution of heavy crude oil in organic solvent is adequate.


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Energy & Fuels

1

[Et3NH]+[H2PO4]- seems to exhibit good performance in the dissolution of heavy crude oil

2

in toluene, whereas in the case of heptane, decane and hexane [Et3NH]+[CH3COO]- shows

3

better performance and in ethyl acetate [Et2NH2]+[H2PO4]- gives better result. Comparing

4

the efficiency of solvents with respect to their enhancement in dissolution of heavy crude oil

5

follows the order as toluene> heptane> decane> ethyl acetate> hexane. The results of FT-IR

6

and 13C-NMR also support the results obtained using UV-Vis studies. The hold-time study

7

reveals that contact of heavy crude oil with heptane alone for a prolonged period (30 days)

8

dissolves about 16 % of heavy crude oil while in case of heptane+IL ([Et3NH]+[CH3COO]- )

9

it is increased by about 222 %. This work reveals that minimal usage of ionic liquids

10

(green solvents) is sufficient for dissolution of heavy crude oil, and its exploitation in large

11

scale for petroleum industries will provide room for environmentally friendly atmosphere.

12 13

ACKNOWLEDGMENTS

14

Financial support from Oil India Limited through grant CONT/HC/C-5/0931/2012 is

15

highly appreciated and acknowledged. We also thank Dr. Srinivasan V. Raju, General

16

Manager (R&D) and Mr. Prashant Dhodapkar, Chief Research Scientist, Research and

17

Development/Oil India Limited for technical support relating to the studies of heavy crude

18

oil (HCO).

19 20

SUPPORTING INFORMATION AVAILABLE

21

Full scan UV-Vis spectra- λmax of HCO in various solvents (Figure S1), UV

22

absorption showing the effect of ionic liquids on HCO in various solvents (HCO:ILs=1:1)

23

(Figures S2-S5), Full scan UV spectra of HCO in heptane, both in the absence and presence

24

of [Et3NH]+[CH3COO]- at different concentrations (Figure S6), 1H-NMR spectra of ionic


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

liquids (Figure S7-S14). This information is available free of charge via the Internet at

2

http://pubs.acs.org/.

3 4

REFERENCES

5

1. Hart, A. J. Petrol. Explor. Prod. Technol. 2013, DOI 10.1007/s13202-013-0086-6.

6

2. Hart, A. Int. J. Pet. Sci. Technol. 2012, 6, 79-96.

7

3. Ashrafizadeh, S. N.; Kamran, M. J. Petrol. Sci. Eng. 2010, 71, 205-211.

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4. Mohamed, R. S.; Loh, W.; Ramos, A. C. S.; Delgado, C. C.; Almeida, V. R. Pet. Sci.

9 10 11 12 13

Technol. 1999, 17 (7), 877-896. 5. Saniere, A.; Henaut, I.; Argillier, J. F. Oil Gas Sci Technol Rev IFP.2004, 59(5),

455-466. 6. Hart, A.; Shah, A.; Leeke, G.; Greaves, M.; Wood, J. Ind. Eng. Chem. Res. 2013, 52,

15394-15406.

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7. Ashtari, M.; Bayat, M.; Sattarin, M. Energy Fuels. 2011, 25, 300-306.

15

8. Permsukarome, P.; Chang, C.; Fogler, H. S. Ind. Eng. Chem. Res. 1997, 36, 3960-

16 17 18

3967. 9. Zhang, Y.; Takanohashi, T.; Sato, S.; Kondo, T.; Saito, I. Energy Fuels. 2003, 17,

101-106.

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10. Hasan, S. W.; Ghannam, M. T.; Esmail, N. Fuel. 2010, 89, 1095-1100.

20

11. Meyer, R. F.; Attanasi, E. D. U. S. Geological Survey Fact Sheet. 2003, 70-03.

21

12. Abdurahman, N. H.; Azhari, N. H.; Yunus, Y. M. Int. J. Eng. Sci. Innov. Techn.,

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2013, 2(5), 170-179.

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13. Yaghi, B. M.; Al-Bemani, A. Energy Sources. 2002, 24, 93-102.

24

14. Painter, P.; Williams, P.; Lupinsky, A. Energy Fuels. 2010, 24, 5081-5088.

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15. Li, X.; Sun, W.; Wu, G. Energy Fuels. 2011, 25, 5224-5231. 20 ACS Paragon Plus Environment

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1 2 3 4

Energy & Fuels

16. Mustaffa, N. B. M. Oil pipeline wax deposition inhibition using chemical methods.

B. Tech. Thesis, University Malaysia Pahang, 2010. 17. Burger J.; Robin M. 11th World Petroleum Congress, London, Aug. 28-Sept. 2,

1983; 3, 251-260.

5

18. Alomair, O. A.; and Almusallam, A. S. Energy Fuels. 2013, 27, 7267-7276.

6

19. Zaki, N.; Butz, T.; Kessel, D. Petrol. Sci. Technol. 2001, 19, 425-435.

7

20. Ali, M. A.; Nofal, W. A. Fuel Sci. Technol. Int. 1994, 12, 21-33.

8

21. De Boer, R. B.; Leerlooyer, K.; Eiger, M. R. P.; van Bergen, A. R. D. SPEPF, 1995,

9 10 11

5, 55-6l. 22. Yansheng, L.; Yufeng, H.; Haibo, W.; Chunming, X.; Dejun, J.; Yan, S.; Tianmin,

G. Chinese J. Chem. Eng. 2005, 13, 564-567.

12

23. Hong-fu, F.; Zhong-bao, L.; Tao, L. J. Fuel Chem. Technol. 2007, 35, 32-35.

13

24. Ze-xia, F.; Teng-fei, W.; Yu-hai, H. J. Fuel Chem. Technol. 2009, 37, 690-693.

14

25. Lu-Shan, W.; Qing, Y.; Fu-Lin, Z.; Ye-Fei, W.; Li-Na, M.; Yan-Ping, J. Chinese J.

15

Appl. Chem. 2005, 5, 603–604.

16

26. Kohno, Y.; Ohno, H. Chem. Commun. 2012, 48, 7119-7130.

17

27. Welton, T. Chem. Rev.1999, 99, 2071-2083.

18

28. Changjun, Z.; Chao, L.; Zhiyu, H.; Pingya, L. J. Chem. Ind. Eng. (China) 2004,

19 20 21 22 23

55(12), 2095-2098. 29. Nares, H. R.; Schacht-Hernandez, P.; Ramirez-Garnica, M.A.; Cabrera-Reyes, M. C.

SPE, 2007, 107837. 30. Hogshead, C. G.; Manias, E.; Williams, P.; Lupinsky, A.; Painter, A. Energy Fuels.

2011, 25, 293-299.

24

31. Wiehe, I. A.; Kennedy, R. J. Energy Fuels. 2000, 14, 56-59.

25

32. Deo, M. D.; Hwang, J.; Hanson, F. V. Fuel Process. Technol. 1993, 34, 217-228.


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33. Freire, M. G.; Neves, C. M. S. S.; Carvalho, P. J.; Gardas, R. L.; Fernandes, A. M.;

2

Marrucho, I. M.; Santos, L. M. N. B. F.; Coutinho, J. A. P. J. Phys. Chem. B, 2007,

3

111, 13082-13089.

4 5 6 7

34. Freire, M. G.; Carvalho, P. J.; Gardas, R. L.; Marrucho, I. M.; Santos, L. M. N. B.

F.; Coutinho, J. A. P. J. Phys. Chem. B, 2008, 112, 1604-1610. 35. Wang, C.; Guo, L.; Li, H.; Wang, Y.; Weng, J.; Wu, L. Green Chem. 2006, 8, 603-

607.

8

36. Chhotaray, P. K.; Gardas, R. L. J. Chem. Thermod. 2014, 72, 117–124.

9

37. Duan, P.; Savage, P. E. Energy Environ. Sci. 2011, 4, 1447-1456.

10 11 12 13

38. Painter, P. C.; Coleman, M. M.; Jenkins, R. G.; Whang, P. W.; Jr, P. L. W.;

Fuel.1978, 57, 337-344. 39. Painter, P. C.; Rimmer, S. M.; Snyder, R. W.; Davis, A. Appl. Spectrosc. 1981, 35,

102-106.

14 15 16 17 18 19 20 21 22 23 24 25 26 22 ACS Paragon Plus Environment

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Energy & Fuels

1 2 3 4 5 6 7 8 9

Table 1. List of synthesized ionic liquids Cation

H H N

Anion

H2PO4

HSO4

Name

Abbreviation

Diethylammonium phosphate

[Et2NH2]+[H2PO4]-

Molecula r weight (g mol-1) 171.13

Diethylammoniumsulfate

[Et2NH2]+[HSO4]-

171.22

[Et3NH]+ [CH3COO] -

161.24

Triethylammoniumtetrafluoro borate Triethylammonium phosphate

[Et3NH]+[BF4] -

189.00

[Et3NH]+[H2PO4]-

199.19

Triethyl ammonium sulfate

[Et3NH]+[HSO4]-

199.27

Tripropylammoniumsulfate

[Pr3NH]+[HSO4]-

241.35

Tributylammoniumsulfate

[Bu3NH]+[HSO4]-

283.43

[CH3COO]- Triethylammonium acetate

H N

BF4

H2PO4

HSO4

H N

H N

HSO4

HSO4

10 11

Table 2. SARA analysis and API gravity report


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

No. of trials

1

Composition S (%) Ar (%) R (%) 1 25.3 63.4 5.1 2 25.2 67.6 3.5 3 28.6 63.5 3.8 26.4 64.8 Average 4.1 + S: Saturates; Ar: Aromatics; R: Resins; A: Asphaltenes

Page 24 of 39

As (%) 6.2 3.7 4.2 4.7

API gravity 10.6 10.2 10.4 10.4

2 3 4 5 6

Table 3. List of chemicals used for the synthesis of ILs, their CAS number, source and purity

7

Chemical Name CAS No Source Acetic acid 64-19-7 Merck Diethyl amine 109-89-7 S D Fine-Chem Ltd o-phosphoric acid*a 7664-38-2 Merck Potassium bromide 7758-02-3 S D Fine-Chem Ltd Sulphuric acid 7664-93-9 Merck Tetrafluoroboric acid*b 16872-11-0 Spectrochem Tributyl amine 102-82-9 Spectrochem Triethyl amine 121-44-8 Rankem Tripropyl amine 102-69-2 Spectrochem *a - o-phosphoric acid in H2O; *b-Tetrafluoroboric acid in H2O

Purity (%) 99% 99% 85% 99% 98% 45% 99% 99.5% 98%

8 Table 4.λmax of the HCO in various solvents

9

Solvents CAS No. Source Purity λmax (nm) Decane 124-18-5 Aldrich 95% 227 Ethyl acetate 141-78-6 Rankem 99% 257 Heptane 142-82-5 Merck 99% 226 Hexane 110-54-3 Merck 99% 229 Toluene 108-88-3 Merck 99% 288 10 11 12 13 14

Table 5. Best of ILs based on their efficiency in the enhancement of dissolution of HCO in five solvents, with respect to 30 ppm concentration of heavy crude oil in the respective solvents (HCO:IL=1:1) Solvents Toluene Heptane Decane

Name of ILs Triethylammonium phosphate Triethylammonium acetate Triethylammonium acetate

Abbreviation of ILs

Increasing Percentage (%)

[Et3NH]+[H2PO4]-

58.60

[Et3NH]+[CH3COO] [Et3NH]+[CH3COO] -

58.61 44.55


Page 25 of 39

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

Ethyl acetate Hexane

Diethylammonium phosphate Triethylammonium acetate

[Et2NH2]+[H2PO4]-

21.91

[[Et3NH]+[CH3COO]-

31.19

1 2 3 4 5 6

Figure Captions

7

Figure 1. Schematic for the experimental procedure

8

Figure 2. Standard calibration curve (Linear fit) – UV absorption for the HCO in different solvents

9

such as (a) toluene, (b) heptane, (c) decane, (d) ethyl acetate and (e) hexane at different

10

concentrations (ppm)

11

Figure 3. UV absorption showing the effect of ionic liquids on HCO in heptane (HCO:ILs=1:1). (a)

12

Effect of [Et2NH2]+[H2PO4]- (b) Effect of [Et2NH2]+[HSO4]- (c) Effect of [Et3NH]+[CH3COO]- (d)

13

Effect of [Et3NH]+[BF4]- (e) Effect of [Et3NH]+[H2PO4]- (f) Effect of [Et3NH]+[HSO4]- (g) Effect of

14

[Pr3NH]+[HSO4]- (h) Effect of [Bu3NH]+[HSO4]-

15

Figure 4. Comparison of the efficiency of the said ILs in terms of increase in solubility of HCO in

16

toluene for solutions containing varying ratio of HCO:ILs at three different concentrations

17

(concentration (in ppm) of HCO in toluene). Base line of 0% solubility is for standard solution.

18

Figure 5. Comparison of the efficiency of the ILs in terms of increase in solubility of HCO in

19

heptane for solutions containing varying ratio of HCO:ILs at three different concentrations

20

(concentration (in ppm) of HCO in heptane). Base line of 0% solubility is for standard solution.

21


22

decane for solutions containing varying ratio of HCO:ILs at three different concentrations

23

(concentration (in ppm) of HCO in decane). Base line of 0% solubility is for standard solution.


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

Page 26 of 39

1


2

ethyl acetate for solutions containing varying ratio of HCO:ILs at three different concentrations

3

(concentration (in ppm) of HCO in ethyl acetate). Base line of 0% solubility is for standard solution.

4


5

hexane for solutions containing varying ratio of HCO:ILs at three different concentrations

6

(concentration (in ppm) of HCO in hexane). Base line of 0% solubility is for standard solution.

7

Figure 9. Comparison of the efficiency of all the said ILs in terms of increase in solubility of HCO

8

in all of the mentioned solvents involved in the present investigation containing varying ratio of 1:1

9

(HCO:ILs) at three different concentrations. Base line of 0% solubility is for standard solution.

10

Figure 10. Representation of the day- hold study for the standard solution (HCO in heptane) at

11

different concentrations.

12

Figure 11. Representation of the day- hold study for the sample solution (HCO in heptane with ILs)

13

at different concentrations.

14

Figure 12. FT-IR spectra of the crude HCO, solvent treated HCO and HCO treated with solvent

15

along with one best ionic liquid which gave the highest percentage increase in solubility as per UV

16

studies. (a) HCO, HCO+Toluene and HCO+Toluene+[Et3NH]+[H2PO4]-; (b)HCO, HCO+Heptane

17

and

18

HCO+Decane+[Et3NH]+[CH3COO]-; (d)HCO, HCO+EtOAc and HCO+EtOAc +[Et2NH2]+[H2PO4]-;

19

(e) HCO, HCO+Hexane and HCO+Hexane+[Et3NH]+[CH3COO]-

HCO+Heptane+[Et3NH]+[CH3COO]-;

(c)HCO,

HCO+Decane

and

20 21

Figure 13. 13C-NMR spectra of the HCO, heptane treated HCO and HCO treated with heptane along

22

with [Et3NH]+[CH3COO]-.

23 24

25 26 ACS Paragon Plus Environment

Page 27 of 39

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Energy & Fuels

1

2 3

Figure 1. Schematic for the experimental procedure

4

5

6

7

8

9


Energy & Fuels

3.0

1.5 1.0

1.5 1.0

0.5

0.5

0.0

0.0

0

20

40

60

80

100

1.5 1.0

0.0 0

20

40

60

80

100 120

Concentration (ppm)

(a)

(b)

3.0

HCO in decane 2.5 R2=0.9993 2.0 y=0.0219x

0.5

Concentration (ppm)

0

20

40

60

80

Absorbance

1.5 1.0 0.5

(c)

HCO in hexane 2.5 R2=0.9995 2.0 y=0.0237x 1.5 1.0 0.5

0

20

40

60

80

100 120

Concentration (ppm)

0.0

0

20

40

60

80

100 120

Concentration (ppm)

1

(d) (e) Figure 2. Standard calibration curve (Linear fit) – UV absorption for the HCO in different solvents

2

such as (a) toluene, (b) heptane, (c) decane, (d) ethyl acetate and (e) hexane at different

3

concentrations (ppm)

4

5

6

7

8

9

10


100 120

Concentration (ppm)

3.0

HCO in ethyl acetate 2.5 R2=0.9997 2.0 y=0.0123x

0.0

3.0

HCO in heptane 2.5 R2=0.9982 2.0 y=0.0195x

Absorbance

HCO in toluene 2.5 2 R =0.9980 2.0 y=0.006x

Absorbance

Absorbance

3.0

Absorbance

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

Page 28 of 39

Page 29 of 39

1.2 0.9 0.6

1.5 1.2 0.9 0.6

0.3

0.3

0.0

0.0

0

10 20 30 40 50 60 70

0

2.1

0.6

1.5 1.2 0.9 0.6

0.3

0.3

0.0

0.0

0

10 20 30 40 50 60 70

0

10 20 30 40 50 60 70 Concentration (ppm)

(d) 2.1

1.2 0.9 0.6 0.3

10 20 30 40 50 60 70

(c) 2.1

Standard Curve Et3NH HSO4

1.8 1.5 1.2 0.9 0.6 0.0

0


(f)

Standard Curve Bu3NH HSO4

1.8 1.5 Absorbance

1.5

0.0

(e)

Standard Curve Pr3NH HSO4

1.8

0

0.3

Concentration (ppm)

2.1

0.6

Concentration (ppm)

Absorbance

0.9

0.9

0.0

10 20 30 40 50 60 70

Standard Curve Et3NH H2PO4

1.8 Absorbance

Absorbance

1.2

1.2

(b)

Standard Curve Et3NH BF4

1.5

1.5

Concentration (ppm)

(a) 1.8

Standard Curve Et3NH CH3COO

1.8

0.3

Concentration (ppm)

2.1

2.1

Standard Curve Et2NH2 HSO4

1.8 Absorbance

1.5 Absorbance

2.1

Standard Curve Et2NH2 H2PO4

1.8

Absorbance

2.1

Absorbance

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

1.2 0.9 0.6 0.3

0


(g)

0.0

0


(h)

1

2

Figure 3. UV absorption showing the effect of ionic liquids on HCO in heptane (HCO:ILs=1:1). (a)

3

Effect of [Et2NH2]+[H2PO4]- (b) Effect of [Et2NH2]+[HSO4]- (c) Effect of [Et3NH]+[CH3COO]- (d)

4

Effect of [Et3NH]+[BF4]- (e) Effect of [Et3NH]+[H2PO4]- (f)Effect of [Et3NH]+[HSO4]- (g) Effect of

5

[Pr3NH]+[HSO4]- (h) Effect of [Bu3NH]+[HSO4]-

6

7

8


Energy & Fuels

1

70 Increase in solubility (%)

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

Page 30 of 39

60

Et2NH2 H2PO4

50

Et2NH2 HSO4

40

Et3NH CH3COO

30

Et3NH BF4

20

Et3NH H2PO4

10

Et3NH HSO4

0 1:1

1:0.5 30 ppm

1:0.1

1:1

1:0.5

1:0.1

50 ppm Concentration (ppm)

1:1

1:0.5 70 ppm

1:0.1

Pr3NH HSO4 Bu3NH HSO4

2 3


4

toluene for solutions containing varying ratio of HCO:ILs at three different concentrations

5

(concentration (in ppm) of HCO in toluene). Base line of 0 % solubility is for standard solution.

6

7

8

9

10


Page 31 of 39


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

70 60

Et2NH2 H2PO4

50

Et2NH2 HSO4

40

Et3NH CH3COO

30

Et3NH BF4

20

Et3NH H2PO4

10

Et3NH HSO4

0 1:1 1:0.5 1:0.1 1:1 1:0.5 1:0.1 1:1 1:0.5 1:0.1 1:1 1:0.5 1:0.1 10ppm

30ppm 50ppm Concentration (ppm)

70ppm


1 2

Figure 5. Comparison of the efficiency of the ILs in terms of increase in solubility of HCO in

3

heptane for solutions containing varying ratio of HCO:ILs at three different concentrations

4

(concentration (in ppm) of HCO in heptane). Base line of 0 % solubility is for standard solution.

5

6

7

8

9

10

11

12

13

14

15


Energy & Fuels

1


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

Page 32 of 39

50

Et2NH2 H2PO4

40

Et2NH2 HSO4

30

Et3NH CH3COO

20

Et3NH BF4 Et3NH H2PO4

10

Et3NH HSO4 0 1:1 1:0.5 1:0.1 1:1 1:0.5 1:0.1 1:1 1:0.5 1:0.1 1:1 1:0.5 1:0.1 10ppm


70ppm


2 3


4

decane for solutions containing varying ratio of HCO:ILs at three different concentrations

5

(concentration (in ppm) of HCO in decane). Base line of 0 % solubility is for standard solution.

6

7

8

9

10

11

12

13

14

15


Page 33 of 39

1


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

30 Et2NH2 H2PO4

25

Et2NH2 HSO4

20

Et3NH CH3COO

15

Et3NH BF4

10

Et3NH H2PO4

5

Et3NH HSO4

0 1:1 1:0.5 1:0.1 1:1 1:0.5 1:0.1 1:1 1:0.5 1:0.1 1:1 1:0.5 1:0.1 10ppm


70ppm


2 3

Figure 7.Comparison of the efficiency of the said ILs in terms of increase in solubility of HCO in

4

ethyl acetate for solutions containing varying ratio of HCO:ILs at three different concentrations

5

(concentration (in ppm) of HCO in ethyl acetate). Base line of 0 % solubility is for standard solution.

6

7

8

9

10

11

12

13

14

15


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

Page 34 of 39

60 Et2NH2 H2PO4

50

Et2NH2 HSO4

40

Et3NH CH3COO

30

Et3NH BF4

20

Et3NH H2PO4

10

Et3NH HSO4

0 1:1 1:0.5 1:0.1 1:1 1:0.5 1:0.1 1:1 1:0.5 1:0.1 1:1 1:0.5 1:0.1 10ppm


70ppm


1 2


3

hexane for solutions containing varying ratio of HCO:ILs at three different concentrations

4

(concentration (in ppm) of HCO in hexane). Base line of 0 % solubility is for standard solution.

5

6

7

8

9

10

11


Page 35 of 39


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

60 Et2NH2 H2PO4

50

Et2NH2 HSO4

40

Et3NH CH3COO

30

Et3NH BF4

20

Et3NH H2PO4

10

Et3NH HSO4

0 30

50

70

Toluene

30

50

70

Heptane

30

50

70

30

50

70

Decane Ethyl acetate Concentration (ppm)

30

50

70

Hexane


1 2

Figure 9. Comparison of the efficiency of all the said ILs in terms of increase in solubility of HCO

3

in all of the mentioned solvents involved in the present investigation containing varying ratio of 1:1

4

(HCO:ILs) at three different concentrations. Base line of 0 % solubility is for standard solution.

5

6

7

8

9

10

11

12

13

14


Energy & Fuels

3.0 2.5

Absorbance

2.0

Day 1 Day 2

1.5

Day 4 1.0 Day 10 Day 30

0.5 0.0 10

20

30

40

50 60 70 80 Concentration (ppm)

90

100

110

120

1 2 Figure 10. Representation of the day- hold study for the standard solution (HCO in heptane) at 3 different concentrations.

3 2.5 Absorbance

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

Page 36 of 39

2 Day 1

1.5

Day 2 1

Day 4 Day 10

0.5

Day 30 0 10 30 50 70 10 30 50 70 10 30 50 70 10 30 50 70 10 30 50 70 10 30 50 70 10 30 50 70 10 30 50 70 Et2NH H2PO4

Et2NH HSO4

Et3NH Et3NH BF4 Et3NH CH3COO H2PO4 Concentration (ppm)

Et3NH HSO4

Pr3NH HSO4

Bu3NH HSO4

4 5

Figure 11. Representation of the day- hold study for the sample solution (HCO in heptane with ILs)

6

at different concentrations

7


Page 37 of 39

Heavy Crude Oil (HCO) HCO+Toluene HCO+Toluene+Et3NH H2PO4

120

120

Heavy Crude Oil (HCO) HCO+Heptane HCO+Heptane+Et3NH CH3COO

120

60 40 20

Transmittance (%)

80

80 60 40

3500 3000 2500 2000 1500 1000

60 40

0

0

500

80

20

20

0

Heavy Crude Oil (HCO) HCO+Decane HCO+Decane+Et3NH CH3COO

100

100 Transmittance (%)

Transmittance (%)

100

3500 3000 2500 2000 1500 1000

-1

500

3500 3000 2500 2000 1500 1000 -1

-1

Wavenumber (cm )

Wavenumber (cm )

Wavenumber (cm )

(a) (b) Heavy Crude Oil (HCO) HCO+EtOAc HCO+EtOAc+Et2NH2 H2PO4

120 100

120

(c)

Heavy Crude Oil (HCO) HCO+Hexane HCO+Hexane+Et3NH CH3COO

100

Transmittance (%)

Transmittance (%)

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

80 60 40 20

80

60

40

20

0 3500 3000 2500 2000 1500 1000 -1

Wavenumber (cm )

(d)

500

0 4000

3500

3000

2500

2000

1500

1000

500

-1

Wavenumber (cm )

(e)

1

Figure 12. FT-IR spectra of the crude HCO, solvent treated HCO and HCO treated with solvent

2

along with one best ionic liquid which gave the highest percentage increase in solubility as per UV

3

studies. (a) HCO, HCO+Toluene and HCO+Toluene+[Et3NH]+[H2PO4]-; (b)HCO, HCO+Heptane

4

and

5

HCO+Decane+[Et3NH]+[CH3COO]-; (d)HCO, HCO+EtOAc and HCO+EtOAc +[Et2NH2]+[H2PO4]-;

6

(e) HCO, HCO+Hexane and HCO+Hexane+[Et3NH]+[CH3COO]-

HCO+Heptane+[Et3NH]+[CH3COO]-;

(c)HCO,

7

8


HCO+Decane

and

500

Page 38 of 39

77.419 77.163 76.909 62.428 60.350 57.672 53.040 53.011 52.983 39.034 38.802 34.188 32.776 31.995 29.735 29.439 29.093 27.988 25.879 22.722 20.612 20.180 19.047 18.111

1

139.850 136.045 130.259 128.366 128.214 127.000

(a) HCO in CDCl3

2

3

4

5

180

170

160

150

140

130

120

110

100

90

80

70

60

50

60

50

77.415 77.161 76.907

190

40

30

20

10 ppm

39.532 37.547 32.926 32.090 29.864 29.527 28.138 24.964 24.624 22.854 22.782 19.855 14.277

6

7

(b) HCO+Heptane 8

9

10

11 180

170

160

150

140

130

120

110

100

90

12

13

80

70

40

30

20

ppm

14.28

190

22.85

200

32.08 29.86

210

77.42 77.16 76.91

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

171.120

Energy & Fuels

(c) HCO+Heptane+[Et3NH]+ [CH3COO]-

14

15

16 200

190

180

170

160

150

140

130

120

110

100

90

80

70

60

50

40

30

20

10

ppm

17

18

19

Figure 13. 13C-NMR spectra of the HCO, heptane treated HCO and HCO treated with heptane along

20

with [Et3NH]+[CH3COO]-.


Page 39 of 39

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Energy & Fuels

1


Experimental Investigation on the Effect of Aliphatic Ionic Liquids on

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