Levuli̇ni̇k Asi̇t Üreti̇mi̇ İçi̇n Selülozun Sicak-Basinçli Suda Hi̇drotermal Muamelesi̇

Abstract

Abstract:In this paper, hot-pressurized water, operating above boiling point and below critical point of water (374. 15 °C and 22.1 MPa), was used as a reaction medium for the decomposition of cellulose to high-value chemicals, such levulinic acid. Effects of reaction temperature, pressure, time, external oxidant type and concentration on the cellulose degradation and product distribution were evaluated. In order to compare the cellulose decomposition and yields of levulinic acid, experiments were performed with and without addition of oxidizing agents (H 2 SO 4 and H 2 O 2 ). Analysis of the liqueur was monitored by HPLC and GC-MS at different temperatures (150 -280 °C), pressures (5-64 bars) and reaction times (30 -120 mins). Levulinic acid, 5-HMF and formic acid were detected as main products. 73% cellulose conversion was achieved with 38% levulinic acid yield when 125 mM of sulfuric acid was added to the reaction medium at 200 °C for 60 min reaction time.Keywords: Cellulose, levulinic acid, 5-HMF, hot-pressurized water Levulinik Asit Üretimi için Selülozun Sıcak-Basınçlı Suda Hidrotermal MuamelesiÖz: Bu makalede selülozu değerli kimyasallara, özellikle levulinik asite, parçalamak amacı ile suyun kaynama noktası üzerinde ve kritik noktası altında (374. 15 °C ve 22.1 MPa) çalışılan sıcak-basınçlı su, reaksiyon ortamı olarak kullanılmıştır. Reaksiyon sıcaklığı, basıncı, süresi, oksitleme ajanı çeşidi ve miktarının selülozun parçalanmasına ve ürün dağılımına olan etkileri incelenmiştir. Selüloz bozunma yüzdesi ve levulinik asit oluşum verimini kıyaslamak amacı ile deneyler hem oksitleme ajanı (H 2 SO 4 ve H 2 O 2 ) kullanarak, hem de kullanmayarak gerçekleştirilmiştir. Farklı sıcaklık (150 -280 °C), basınç (5-64 bar) ve tepkime sürelerinde (30 -120 dk.) oluşan likit ürünlerin analizleri HPLC ve GC-MS ile gerçekleştirilmiştir. Ana sıvı ürünler olarak levulinik asit, 5-HMF ve formik asit tespit edilmiştir. 125 mM sülfürik asit eklenerek 200 °C sıcaklıkta ve 60 dk boyunca gerçekleştirilen tepkime sonucunda, %73 selüloz bozunmuş ve %38 verimle levulinik asit elde edilmiştir.

Conversion of Biomass to Organic Acids by Liquefaction Reactions Under Subcritical Conditions

“…However, yield of levulinic acid has decreased to 14.3% for longer reaction times up to 120 min. The opposite case was observed for lower reaction temperature such as 150 • C. The yield of levulinic acid increased from 1.5 to 6.1% when the reaction was prolonged, however, it was still lower than the levulinic acid yield at 200 • C (Yüksel, 2016). According to Girisuta (2007), the highest levulinic acid yield was obtained at higher reaction temperature in a shorter time.…”

“…At this condition, initial amount of cellulose was 4 g and the remaining amount was 3.61 g. It could be concluded that this reaction temperature (150 • C) and pressure (5 bar) was not enough to breakdown of glicosidic bonds of cellulose. However, when temperature was 200 • C, whereas yield of desired product (levulinic acid) and degradation of cellulose was suddenly enhanced, the amount of 5-HMF in liquid product decreased to 1.7% (Yüksel, 2016). Thus, it could be concluded that cellulose could be degraded under hydrothermal conditions through two steps so liquid products were formed.…”

“…While water becomes a good solvent when its pressure and temperature approach its critical point, it is called as hot-pressurized water. It has a unique characteristic and its thermodynamic properties such as density, dielectric constant, viscosity, ion product, and solvating power could be tuned so that it becomes more effective on decomposition of cellulose (Savage, 1999;Yüksel, 2016).…”

“…For instance, if cellulose is used as a model compound, then high yield of carbon monoxide and char is observed. Additionally, C1 and C4 hydrocarbons were formed (Yüksel, 2016). Ehara and Saka (2005) investigated the treatment of cellulose in three different systems which are sub-and supercritical water and their combined system.…”

“…It can be said that levulinic acid is a versatile chemical and it is in the list of Top Value-Added Chemicals from Biomass. Pharmaceutical and flavoring agents, resins, herbicides, plasticisers, anti-freeze agents, and biofuel additives can be derived from levulinic acid (Yüksel, 2016). Based on the present knowledge, firstly, hexose sugars dehydrate and the intermediate product 5-hydroxymethylfurfural (5-HMF) forms.…”