Oxidative cleavage of lignin aromatics during chlorine bleaching of kraft pulp
Methanol liberation and methoxyl loss during chlorine bleaching of softwood kraft pulp were quantitatively investigated to estimate the degree of structural modification of lignin aromatics. An increase in the chlorine multiple led to enhanced methoxyl loss from lignin. Our result, using pH-adjusted chlorine water (pH 5.7), by which chlorination under oxidation-favorable conditions was achieved, strongly supported the importance of the oxidation reaction by chlorine during delignification and lignin degradation. It was also suggested that methanol can be produced not only via catalytic hydrolysis by chlorine but via oxidative cleavage of the ether bond as well. The infrared spectrum of chlorolignins suggested that chlorine oxidation can open aromatic rings to muconic acid derivatives without cleaving ether bonding of the methoxyl group. No straight relation between the methoxyl content and the kappa number of chlorinated pulps was shown. The methoxyl content of bleached kraft pulps subjected to successive chlorination and alkali extraction showed a good relation with the kappa number. This means that almost all the portions of the oxidatively modified lignin structure were successfully removed during these treatments, and the aromatic structures of residual lignin in chlorinated and alkali-extracted pulps were thought to remain intact.
Formation Characteristics of Chloroorganics from Hardwood Kraft Pulp during Chlorine Bleaching.
By chlorine treatment, residual lignin in hardwood kraft pulp became soluble in water more easily than that in softwood kraft pulp. Majority of adsorbable organic halide (AOX) and about half of total organic carbon (TOC) produced by chlorine treatment of hardwood kraft pulp was found to be present in a chlorination stage (C-stage) effluent rather than in an alkali extraction stage (E-stage) one, which makes a contrast to the significance of E-stage effluent of softwood kraft pulp. By oxygen treatment, a part of residual lignin in kraft pulp is converted to a part which is very reactive to chlorine, resulting in an increase of a delignification at C-stage
ANALYSIS OF SAUDI ARABIAN MARITIME TRANSPORTATION INDUSTRY
This paper analyses the past, present and future of the maritime transportation industry in the Kingdom of Saudi Arabia. Saudi Arabian seaborne trade and the shipping capacity are analysed for the past 15 years. Relationships between the declining Saudi shipping capacity and other economic measures are identified. Analysis of the Saudi Arabian maritime transportation is performed with respect to the world carrier fleets and models are developed to determine the theoretical shipping capacity required for transportation of the national seaborne cargo. Forecasts of the future shipping capacity requirement for the Kingdom are also presented. This paper illustrates the general approach for analysing a country's maritime industry and thus could help other researchers in that respect.