Separation & Purification of Crude Glycerol

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    This article was downloaded by: [Universiti Kebangsaan Malaysia], [Wan Isahak] On: 11 October 2014, At: 00:22 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House 37-41 Mortimer Street, London W1T 3JH, UK

    Separation & Purification Reviews Publication details, including instructions for authors and subscription information:

    http://www.tandfonline.com/loi/lspr20

    Recovery and Purification of Crude Glycerol from

    Vegetable Oil Transesterification Wan Nor Roslam Wan Isahak

    ab , Zatil Amali Che Ramli

    b , Manal Ismail

    a , Jamaliah Mohd Jahim

    & Mohd Ambar Yarmo b

    a  Department of Chemical Engineering and Process, Faculty of Engineering and Built

    Environment, Universiti Kebangsaan Malaysia, Bangi, Malaysia b  School of Chemical Sciences and Food Technology, Faculty of Science and Technology,

    Universiti Kebangsaan Malaysia, Bangi, Malaysia

    Accepted author version posted online: 11 Feb 2014.Published online: 10 Oct 2014.

    To cite this article: Wan Nor Roslam Wan Isahak, Zatil Amali Che Ramli, Manal Ismail, Jamaliah Mohd Jahim & Mohd Ambar

    Yarmo (2015) Recovery and Purification of Crude Glycerol from Vegetable Oil Transesterification, Separation & Purification

    Reviews, 44:3, 250-267, DOI: 10.1080/15422119.2013.851696

    To link to this article: http://dx.doi.org/10.1080/15422119.2013.851696

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    Separation & Purification Reviews, 44: 250–267, 2015

    Copyright © Taylor & Francis Group, LLC

    ISSN: 1542-2119 print / 1542-2127 online

    DOI: 10.1080/15422119.2013.851696

    Recovery and Purification of Crude Glycerol from Vegetable Oil Transesterification

    Wan Nor Roslam Wan Isahak,1,2 Zatil Amali Che Ramli,2 Manal Ismail,1

    Jamaliah Mohd Jahim,1 and Mohd Ambar Yarmo2

    1 Department of Chemical Engineering and Process, Faculty of Engineering and Built Environment,

    Universiti Kebangsaan Malaysia, Bangi, Malaysia 2School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti

    Kebangsaan Malaysia, Bangi, Malaysia

    This article reviews the purification techniques involved in producing high-purity glycerol in

    the biodiesel industry. Utilization of glycerol by-products (contains less than 50 wt.% of glyc-

    erol and the remaining contents are water, salts, unreacted alcohol and catalyst) in biodiesel

    production affords greener and less costly processes. Research has focused on several purifi-

    cation steps that are capable of producing high-purity glycerol. Various new techniques for

    purifying glycerol promise better quality and lower cost and technologies are required to fulfil

    increasing worldwide demand. Neutralization, ultrafiltration, the use of ion exchange resins,

    vacuum distillation and other methods have been utilized in single or multiple stages. Recent

    studies have demonstrated that the combination of more than one technique produces high-

    -purity glycerol (>99.2%). Purifications cost can be as low as 0.149 USD$/kg. For many

    applications, high-purity glycerol is more useful. In some cases, it is even necessary, partic-

    ularly in the fields of hydrogen production, methanol production, pharmaceuticals and food

    additives.

    Keywords: Crude glycerol, purification, ion exchange resins, separation technique, ultrafiltra-

    tion, vacuum distillation

    BACKGROUND

    Glycerol, or glycerine, or 1,2,3-propanetriol, can be pro-

    duced from the transesterification or hydrolysis of natural

    fats, vegetable oils or petrochemicals (1). In Malaysian

    biodiesel processes, palm oil is the primary raw material

    from which glycerol is produced as a transesterification by-

    product. In these processes, palm oil is treated with methanol

    and a basic homogeneous catalyst. Alternatively, acidic, basic or enzymatic heterogeneous catalysts are used because

    of their ease of separation from the products.

    Received 19 August 2011, Accepted 30 September 2013.

    Address correspondence to Mohd Ambar Yarmo, School of Chemical

    Sciences and Food Technology, Faculty of Science and Technology,

    Universiti Kebangsaan Malaysia, Bangi 43600, Malaysia. E-mail:

    ambar@ukm.my

    Crude glycerol production from biodiesel conversion is

    increasing yearly. From 2008 to 20011, total worldwide

    crude glycerol output increased from 2.06 to 2.88 mil-

    lion tonnes (2,3). The global demand for glycerol was

    1,995.5 kilo tons in 2011 and is expected to reach

    3,060.4 kilo tons by 2018, growing at a Compounded Annual

    Growth Rate (CAGR) of 6.3% from 2012 to 2018 (4).

    The Malaysian palm-based oleochemical industry is grow-

    ing rapidly and produces products such as fatty acid methyl esters (FAMEs), fatty alcohols and crude glycerol (5,6).

    The abundant crude glycerol generated by this industry

    affords a great opportunity for scientists to explore new glyc-

    erol applications. High-purity glycerol finds wide use as

    an ingredient or processing aid in healthcare products, fuel

    additives, lubricants, personal care products, cosmetics and

    food (7,8).

    However, the glycerol produced as a by-product of trans-

    esterification from biodiesel processes is not pure enough for

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    GLYCEROL RECOVERY FROM VEGETABLE OIL   251

    direct use in high-tech applications. To overcome this prob-

    lem, numerous treatments are required to remove impurities.

    Moreover, the manufacturing and pharmaceutical indus-

    tries have increasingly demanded high-quality, food-grade

    glycerol because of its superior physical properties, low

    contamination and odorlessness (9).

    Therefore, an effective, efficient glycerol purificationprocess is needed to minimise production costs, minimise

    industrial waste and maximise the utility of biodiesel indus-

    trial processes. Because of the enormous demand for the

    production of glycerol from biodiesel waste, we have

    thoroughly reviewed vegetable oil transesterification and

    hydrolysis as a glycerol synthetic route. Various purifica-

    tion methods for producing high-purity glycerol are herein

    discussed, and some glycerol conversion processes are

    summarized.

    CHEMICAL COMPOSITION OF CRUDE GLYCEROL

    The factors that influence the quality of crude glycerol

    derived from biodiesel production processes include cata-

    lyst type and quantity, recovery methods, unreacted methanol

    and other impurities. For example, a crude glycerol extracted

    from sunflower oil biodiesel had a composition (w/w) of 

    30% glycerol, 50% methanol, 13% soap, 2% moisture,

    2-3% salts (primarily sodium and potassium) and 2–3%

    other impurities (7). In contrast, Hansen et al. (10) reported

    glycerol contents of 38 to 96% in a set of 11 crude glyc-

    erol samples collected from 7 different Australian biodiesel

    producers. Some of those samples contained more than 14% methanol and 29% ash. Because most biodiesel pro-

    duction uses low-grade methanol and homogeneous alka-

    line catalysts (sodium methoxide or potassium hydroxide),

    the quality of the afforded glycerol is poor (11). Saman

    et al. identified several contaminants in crude glycerol –

    methanol, soaps, catalysts, salts, non-glycerol organic matter

    and excessive water (12).

    Even when identical feedstocks were employed, the

    crude glycerol produced from alkali- and lipase-catalyzed

    transesterifications was reported to differ in purity (13).

    For biodiesel production that utilized homogeneous alka-

    line catalysts, the crude glycerol produced contained 5 to

    7% salts (14), making conventional purification techniques more costly. Heterogeneous processes using enzymes and

    solid metal-oxide catalysts have been promoted as a

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