Subscriber access provided by NEW YORK UNIV
Article
Hydrothermal Conversion of Russian Olive Seeds into Crude Bio-oil Using CaO Catalyst Derived from Waste Mussel Shells Kubilay Tekin Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.5b00724 • Publication Date (Web): 04 Jun 2015 Downloaded from http://pubs.acs.org on June 11, 2015
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
Energy & Fuels is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 28
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
Hydrothermal Conversion of Russian Olive Seeds into Crude Bio-oil Using CaO Catalyst Derived from Waste Mussel Shells
Kubilay Tekin* Department of Occupational Health and Safety, Karabük University, 78050 Karabük, Turkey
Graphical Abstract
*To whom correspondence should be addressed. Corresponding author. Tel.: +90 370 433 0202; fax: +90 370 433 0262 E-mail:
[email protected] (K. Tekin)
ACS Paragon Plus Environment
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 2 of 28
Abstract
Hydrothermal conversion studies were performed (bio-oil obtained under hydrothermal conditions) using Russian olive (Elaeagnus angustifolia L.) seeds as a waste biomass at different temperatures and different residence times. After the conditions where the highest yield of bio-oil were found, a mussel shell catalyst (which is a source of calcium oxide when calcined at T > 950 °C) was applied for first time for the hydrothermal conversion of biomass. To compare and evaluate the catalytic performance of the catalyst, the effects of the catalyst on product distributions, elemental contents and high heating values of products and bio-oils compositions were investigated. The use of the catalyst significantly increased the bio-oil and conversion yields. The bio-oils were analyzed by a gas chromatograph-mass spectrometer (GC-MS). Characterization studies of the catalyst were completed by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area analysis, and X-ray diffraction (XRD) analysis. This study exclusively focus on the bio-oil and solid residue yield in order to demonstrate the effects of the catalyst derived from a waste biomass. Suggestions for further studies are provided at the end of the conclusion section.
Keywords: Green Chemistry, Russian olive stone, Mussel shell, Bio-oil, Water, Natural catalyst, Hydrothermal conversion.
ACS Paragon Plus Environment
Page 3 of 28
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. Introduction
The principles of green chemistry are based upon sustainable development of products and processes. The most important objective of sustainable development is to eliminate negative effects of produced and used materials on human health and the environment. For this purpose, renewable sources should be used for the production of energy and carbon-based chemicals instead of the finite fossil fuels which are harmful to environment 1. Among the available renewable sources, biomass is the most attractive option for energy production because it is abundant, inexpensive and environmentally friendly. There are some known technologies used to convert biomass into biofuels or chemicals. These include hydrothermal processing, pyrolysis, aerobic and anaerobic degradations, fermentation, and enzymatic hydrolysis. The conversion of biomass into liquid fuels and/or valuable products via hydrothermal processing is an important thermochemical process and it adheres to the concepts of green chemistry. Hydrothermal conversion of biomass has been the subject of extensive research in recent years 2-5. The advantages of hydrothermal conversion include the following: applicability of the process for high-moisture-content biomass; ability to co-process biomass with waste materials; the use of lower temperatures than processes such as pyrolysis; and the high energy efficiency of the process 6. Also, the use of water as a reaction medium in hydrothermal processing is important for implementing green chemistry practices, as water is a unique and environmentally benign solvent. There are various types of biomass used in hydrothermal processing as a feedstock. Plants and plant-based wastes (including agricultural and fruit processing wastes) are the most common resources for the production of bio-oils and biofuels
6-10
. As is well known, lignocellulosic biomass has a heterogeneous and
recalcitrant structure. Thus, the efficient conversion of lignocellulosic biomass into bio-oil is quite difficult 11. In some studies edible feedstocks (sugars, vegetable oils, etc) are used as they can be easily and efficiently converted into bio-oils with high yields 12, 13. However, lignocellulosic biomass waste is a promising source for being most abundant and available source at almost no cost for the sustainable production of fuels. The Russian olive tree (Elaeagnus angustifolia L.) is native to southern Europe
ACS Paragon Plus Environment
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 4 of 28
and to central and eastern Asia. The appearance of the Russian olive fruit is similar to the olive (Olea europaea). The seed is considered as a waste product after the fruit is consumed. Consequently, the Russian olive seed is selected as a second generation biomass for this study.
Catalysts are used to increase bio-oil yield, decrease waste, reduce energy requirements and increase selectivity 14. There has been a steady increase in the number of research studies concerning the use of catalysts in the hydrothermal processing of biomasses
8, 15-20
. The need for a catalyst especially arises
in the hydrothermal conversion of a woody biomass. Although woody biomass is one of the most commonly used types of biomass, it provides low yields of bio-oils without a catalyst
17, 21
. Thus,
effective catalysts should be considered for use in the process. However, it is insufficient for a catalyst to only have the quality of effectiveness. According to the principles of green chemistry a catalyst should also be inexpensive, have less harmful effects on the environment, and be renewable as a biomass. The design and use of natural resources as catalysts is therefore important 22, 23.
Catalysts obtained from natural resources have already been used in some areas. Waste shells of mollusks and eggs
24
waste mussel shells
28, 29
, acid-treated quail egg shells
25
, mud crab shells
26
, waste capiz shells
27
, and
are some examples which have been used as catalysts for the production of
biodiesel. Mussel shells are one of the wastes of the fish industry and they primarily contain (95–99 wt%) CaCO3
30
. When a shell is treated with high temperature in air, the CaCO3 in the structure
decomposes to yield CaO via calcination reaction
31
. CaO is a solid base and it is used alone or with
other metal/metal oxides to improve bio-oil quality by reducing the carbon-oxygen bond and removing heteroatoms which results in a higher energy content reactions for biodiesel production
35
32-34
. It is mostly used in transesterification
. Razaei et al. used mussel shells as a catalyst in biodiesel
production. The shells were calcined in a furnace at 950, 1000 and 1050 °C and used in the presence of soybean oil and methanol. The conditions of the experiments were optimized using response surface methodology (RSM). Optimal conditions were found to be the following: calcination temperature of
ACS Paragon Plus Environment
Page 5 of 28
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
1050 °C; catalyst concentration of 12 wt.%; and methanol to soybean oil ratio of 24:1
28
. Hu et al.
obtained catalysts from freshwater mussel shells with the calcination-impregnation-activation method and they were used in the transesterification of Chinese tallow oil. After a shell was calcined at 900 °C for 4 h, it was activated in deionized water at 600 °C for 3 h. The transesterification reaction was performed with 12:1 methanol/oil ratio and 5% catalyst concentration for 1.5 h at 70 °C. Researchers found that the catalyst was active for 7 reuse with the biodiesel yield above 90% 29. While the process of obtaining biodiesel requires the activation of the mussel shell catalyst in water, there is no need for this activation step during hydrothermal processing because the process already takes place in water. The steps of the process are therefore reduced and energy is saved.
The focus of this research lies exclusively with the bio-oil and solid residue fractions – i.e. no gas- or aqueous phase analyses were carried out, nor were mass or carbon-balances pursued. The following research questions are answered in the present study: How can we derive great benefit from the use of lignocellulosic biomass, and how can we increase the bio-oil yields in the production of clean energy from biomass using a natural catalyst instead of synthetic catalysts. This study not only demonstrates for the first time Russian olive seed conversion in hydrothermal media, but it also shows that the applicability of mussel shells as a catalyst in hydrothermal conversion experiments for all biomasses.
2. Experimental 2.1. Materials
In this study Russian olives (Elaeagnus angustifolia L.) were purchased from Carrefour grocery store in the city of Karabük, Turkey and their seeds were used as a biomass source. The seeds were separated from the flesh of the Russian olive, washed with deionized water, and dried at 100 °C. After drying, the seeds were milled using a disc mill and sieved so that particle sizes
