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Ethylenediamine in Alkaline Cooking of Jute Stick for Producing Dissolving Pulp

M. Sarwar Jahan
Pulp and Paper Research Division, BCSIR Laboratories, Dhaka, Dr. Qudra-I-Khuda Road, Dhaka-1205, Bangladesh.

Halima Rahman
Pulp and Paper Research Division, BCSIR Laboratories, Dhaka, Dr. Qudra-I-Khuda Road, Dhaka-1205, Bangladesh.

Purabi Rani Samaddar
Department of Chemistry, Eden Girls College, Dhaka.

Mostafizur Rahman
Department of Chemistry, Eden Girls College, Dhaka.

Abstract/ Executive Summary:

Jute stick is the woody portion of jute plant. It remains as the leftover after extracting the fibre . The ratio of the stick to fibre is about 2.5:1. For producing dissolving pulp, prehydrolysis is carried out prior to pulping to remove hemicelluloses from the lignocelluloses. In this investigation ethylenediamine (EDA) was used with the cooking liquor to remove hemicelluloses from the jute stick. Increasing EDA charge in soda and kraft liquor decreased pentosans content in the pulp. EDA in kraft liquor showed lower kappa number and pentosans content than in the soda-liquor. Prehydrolysis further improved cellulose content and kappa number of jute stick pulp with the sacrifice of pulp yield. The bleachability of soda-EDA pulp was inferoior to the kraft-EDA and prehydrolysed soda-EDA in ECF bleaching sequences. The final brightness of soda-EDA pulp was 85.1% and kraft-EDA pulp 89.7%. Degraded cellulose (R₁₈ -R₁₀ ) in soda-EDA and kraft-EDA pulps was lower than prehydrolysed pulps. Dissolving pulp can be produced to 93% purity without prehydrolysis by reinforcing EDA in kraft liquor.

Keywords: Jute stick; Dissolving pulp; Ethylenediamine; Delignification; Pentosan dissolution

Location: Dhaka area.

Start Date:

End Date:

Program Area: Postharvest and Agro-processing

Commodity: Jute

Objectives:

To evaluate EDA in soda and kraft liquor for producing dissolving pulp from jute stick.

Methodology:

Jute stick was collected from the local market in Dhaka. It was sun-dried and cut to 2-3 cm in length. The moisture content of raw materials was determined according to TAPPI Standard Methods (T 18m-53). After determination of the moisture content of air dried raw materials equivalent to 250 gm o.d. (oven dried) was weighed separately in a polyethylene bag for subsequent cooking experiments. Jute stick contained about 39% α-cellulose, 18% hemicelluloses and 25% lignin with other minor ingredients. The prehydrolysis was carried out in an electrically heated stainless steel digester of 5 l capacity, rotating at 1 rpm. Water prehydrolysis was carried out at 170 °C for 1 h. The jute stick to liquor ratio was 1: 5. The time required to raise max temperature was 60 min. The liquor was drained after prehydrolysis. The total solid content in the prehydrolysis liquor (PHL) was determined gravimetrically by drying 10 mL sample at 105°C to constant weight. The dissolved lignin in the PHL was measured based on the UV/Vis spectrometric method at wavelength 205 nm (TAPPI UM 250). For sugar analysis, PHL was filtered to remove any solid particle with filter paper. A vial containing 1 mL of the PHL and 4 mL 4N sulfuric acid was sealed and autoclaved at 121 °C for 60 min. Component sugars and organic acids were analyzed by high-performance liquid chromatography (HPLC) equipped with refractive index and UV detection (Shimadzu, Columbia, MD), using the Aminex HPX-87H column (Bio-Rad, Hercules, CA). The column was operated with a 5 mM sulfuric acid mobile phase at a flow rate of 0.6 mL/min and oven temperature of 60 °C. Samples were filtered through 0.22 μm syringe filters prior to injection. The sugar contents in oligomeric form in the pre-hydrolysis liquor were calculated from the difference of the monomeric sugar contents between pre and post hydrolysis PHL. Pulps were bleached in D₀ E_p D₁ E_p D₂ bleaching sequences. The bleaching was done in polyethylene bag. The pH of bleach liquor was 2-2.5 in D_o . The bleaching continued to 45 min at 70 °C. Alkaline extraction was carried out with 2 % NaOH and 0.5% H₂ O₂ at 70 °C for 120 min. The consistency was 10 in all stages. In the D₀ , D₁ and D₂ stages ClO₂ charges were 2, 1 and 0.5%, respectively. The time of D₁ and D₂ stages were 120 min at 70°C. Pulp tests were performed according to the Standard Methods of the Technical Association of the Pulp and Paper Industry (TAPPI, Atlanta, GA): kappa number (T 236 cm-85); brightness (T 452 om-92); viscosity (T 230 om-89); carbohydrate (T249 cm00); α-cellulose (T 203 om-88); and alkali solubility S₁₀ and S₁₈ (T 235 cm-85). Alpha-cellulose is the pulp fraction resistant to a treatment in an aqueous solution containing 17.5% sodium hydroxide and indicates undegraded, high molecular weight cellulose content in pulp. Alkali solubilities S₁₀ and S₁₈ provide information on the low molecular weight carbohydrates (degraded cellulose and hemicellulose) in pulp. A 10% sodium hydroxide solution dissolves both degraded cellulose and hemicellulose (S₁₀ ) whereas hemicellulose is soluble in an 18% sodium hydroxide solution (S ₁₈ ). All pulp properties were analyzed in duplicate.

Source of Information: Bangladesh J. Sci. Ind. Res. 50(1), 7-14, 2015

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Presence of EDA in soda and kraft liquor improved delignification and pentosan dissolution. Kraft process exhibited better results. The purity (α –cellulose) of kraft-EDA pulp reached to 92.8% without prehydrolysis, which increased to 94.2% with the introduction of prehydrolysis step. Prehydrolysis step increased degraded cellulose percentage as observed by R₁₈ -R₁₀ (6.4 and 7.6 vs 7.1 and 9.0). Prehydrolysis step decreased viscosity of the produced pulp. It can be said that EDA in kraft liquor produced dissolving pulp without prehydrolysis step and the produced pulp can be used in rayon production.

Knowledge Management: Journal