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      • SCISCIESCOPUS

        Solvothermal liquefaction of alkali lignin to obtain a high yield of aromatic monomers while suppressing solvent consumption

        Riaz, Asim,Verma, Deepak,Zeb, Hassan,Lee, Jeong Hyeon,Kim, Jin Chul,Kwak, Sang Kyu,Kim, Jaehoon The Royal Society of Chemistry 2018 GREEN CHEMISTRY Vol.20 No.21

        <P>The unique physicochemical properties and high solubility of a wide range of biomass-derived feedstocks make sub- and supercritical alcohols promising media for thermochemical conversion to liquid fuels and value-added chemicals. Short-chain alcohols (C1-C3) not only hydrogenolyse a variety of recalcitrant feedstocks by donating <I>in situ</I> hydrogen, but also suppress the char formation by capping reactive intermediates. However, the beneficial features of supercritical alcohols also bring some demerits, such as their excessive decomposition and high consumption, which has been given cursory attention to date. Consequently, the aim of this study was to elucidate the role of sub- and supercritical alcohols as a hydrogen donor, their self-reactivity, their reactivity with the feedstock, the extent of their conversion under catalytic and non-catalytic conditions, and the detailed pathways to byproduct formation. Based on the solvent reactivity, the optimum conditions were investigated for the solvothermal liquefaction of recalcitrant alkali lignin to give a high yield of aromatic monomers with careful emphasis on the solvent consumption. The addition of formic acid instead of the more commonly used hydrodeoxygenation catalysts (<I>e.g.</I>, CoMo/Al2O3, Ru/Al2O3) can not only suppress ethanol consumption significantly (from 42.3-46.8 wt% to 7 wt%), but can also result in complete lignin conversion by providing an excess amount of active hydrogen. The reaction at 350 °C for a short duration of 60 min led to the complete decomposition of alkali lignin and afforded a high yield of aromatic derivatives (36.7 wt%), while at the same time, suppressing ethanol consumption (11.8 wt%) and the formation of ethanol-derived liquid products. The alkylation of lignin-derived phenolic intermediates at the expense of the solvent is a time-dependent reaction, instead of the primary stabilization reaction. Molecular dynamics simulations using dilignol molecules revealed that the ethanol-formic acid mixture reduced the activation and thermal energies required for the dissociation of C-C and C-O bonds in the lignin structure.</P>

      • The continuous conversion of oleic acid into light hydrocarbons over mesoporous zeolites

        ( Asim Riaz ),김준범,차진성,이인구 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1

        Coffee is one of the most consumed beverages in the world, which generates a large amount of residue called, spent coffee grounds (SCG). Due to its high lipid content (10-15 wt %), the SCG has a potential of producing 1.3 billion liters of biodiesel annually. Fast pyrolysis is commonly used for the liquefaction of solid SCG, which resulted in the production of fatty acid rich bio-crude. We examined the ability of mesoporous zeolites (SAPO-11, and MCM-41) for the catalytic cracking of oleic acid, as a model compound of fatty acids rich bio-crude in a continuous flow reactor. The oleic acid was fed into the reactor at the flowrate of 15 g/min, and the reactions were conducted at the temperature range of 400 to 500 °C. The GC-MS results showed that the oleic acid was completely converted into the hydrocarbons and aromatics rich oil over MCM-41 with maximum selectivity of 90 %, which mainly consisted of gasoline fractions (45 %).

      • Liquefaction of technical lignins in a continuous reactor

        ( Asim Riaz ),김준범,이인구 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1

        Lignin is the largest renewable source of naturally obtainable aromatic hydrocarbons; the efficient utilization of which has been acknowledged as the most logical alternative to the depleting fossil fuels. Owing to its notorious nature of structural complexity and being chemically recalcitrant, its processing has been proven quite challenging indeed. Therefore, much of the scientific research, for its conversion into valuable bio-based chemicals or fuels, has been limited to the lab-scale batch reactors. In this work, we investigated depolymerization of technical lignins in sub- and supercritical solvents using a continuous reactor. The concentrated sulfuric acid hydrolysis and Kraft lignin, with high lignin-to-solvent ratio (up to 30 wt%) were used as reactants. The reactor was designed to hold the pressure up to 350 bars at 400 °C and equipped with a continuously stirred feeder. The liquid and gas products were periodically collected and analyzed.

      • A Complete, Reductive Depolymerization of Concentrated Sulfuric Acid Hydrolysis Lignin into a High Calorific Bio-oil using Supercritical Ethanol

        Riaz, Asim,Kim, Jaehoon Korea Electric Power Corporation 2016 KEPCO Journal on electric power and energy Vol.2 No.3

        It is imperative to develop an effective pathway to depolymerize lignin into liquid fuel that can be used as a bioheavy oil. Lignin can be converted into liquid products either by a solvent-free thermal cracking in the absence air, or thermo-chemical degradation in the presence of suitable solvents and chemicals. Here we show that the solvent-assisted liquefaction has produced promising results in the presence of metal-based catalysts. The supercritical ethanol is an efficient liquefaction solvent, which not only provides better solubility to lignin, but also scavenges the intermediate species. The concentrated sulfuric acid hydrolysis lignin (CSAHL) was completely liquefied in the presence of solid catalysts (Ni, Pd and Ru) with no char formation. The effective deoxy-liquefaction nature associated with scEtOH with aid hydrodeoxygenation catalysts, resulted in significant reduction in oxygen-to-carbon (O/C) molar ratio up to 61%. The decrease in oxygen content and increase in carbon and hydrogen contents increased the calorific value bio-oil, with higher heating value (HHV) of $34.6MJ{\cdot}Kg^{-1}$. The overall process is energetically efficient with 129.8% energy recovery (ER) and 70.8% energy efficiency (EE). The GC-TOF/MS analysis of bio-oil shows that the bio-oil mainly consists of monomeric species such as phenols, esters, furans, alcohols, and traces of aliphatic hydrocarbons. The bio-oil produced has better flow properties, low molecular weight, and high aromaticity.

      • Characteristics of liquid products from zeolite cracking of oleic acid

        김준범,( Asim Riaz ),차진성,이인구 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1

        Coffee ground which is generated during coffee extraction is considered a good urban biomass for the production of advanced biofuel such as green gasoline via fast pyrolysis because of its high generation (more than 100,000 ton in Korea) and good quality (small particle size) as a feedstock. Since coffee ground contains a relatively high amount of fatty acids and the fatty acids remain in bio-oil after fast pyrolysis, it is necessary to conduct C-C cracking in order to maximize the yield of green gasoline in upgrading processes such as hydrodeoxygenation. In this work, liquid products from the cracking reactions over zeolites were evaporated at 200 °C and 80 mbar in rotary vacuum evaporator to obtained gasoline fraction. The highest yield of gasoline was obtained for the products from the cracking over MCM-41 at 500 oC. GC-MS analysis results show the composition of the gasoline fraction consisting of 70.5% hydrocarbons and 27.4% aromatics.

      • Metastatic Bone Disease as Seen in Our Clinical Practice - Experience at a Tertiary Care Cancer Center in Pakistan

        Qureshi, Asim,Shams, Usman,Akhter, Azra,Riaz, Sabiha Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.9

        Aim: Metastatic tumor of bone is the most common malignancy involving bone and is an important predictor of prognosis in advanced cancers. The prognosis depends upon the primary site of origin and the extent of disease. In current study, we present the pattern and distribution of metastatic bone disease seen in the leading cancer care center of Pakistan, Shaukat Khanum Cancer Hospital & Research Center (SKMCH & RC), Lahore. Materials & Methods: All cases of bony metastatic disease were included that presented in the Pathology Department, from Jan 2005 to July 2011. Patients of all ages and both sexes were included. Primary bone tumors, lymphomas, sarcomas and other malignancies were excluded. The data were recorded and analyzed with SPSS 16.0. Results: A total of 146 cases of metastatic bone disease were included in the study. Out of the total cases, 79 were male and 67 were female. Age range 25-82 years (median 52). Hip bone was the most frequent bone involved, with femur and vertebrae as second and third in the list. The commonest bone involved in males was vertebrae with 23 cases and in females was hip bone with 22 cases. Regarding primary site, cancers of breast, prostate and gastrointestinal tract were at the top of the list with prostate and breast being the most frequent primary sites of metastasis in males and females respectively. Conclusion: Bone metastasis is an important entity to consider in the differential diagnosis whenever a bony tumor especially carcinoma present in older age. Our data are comparable with international findings and the literature available regarding the site and distribution of skeletal metastatic lesions. A slight deviation noted was more common bony metastatic lesions with ovarian primaries in females and gastrointestinal tract cancers in males in our study.

      • SCISCIESCOPUS

        Understanding the relationship between the structure and depolymerization behavior of lignin

        Park, Jaeyong,Riaz, Asim,Insyani, Rizki,Kim, Jaehoon Elsevier 2018 Fuel Vol.217 No.-

        <P><B>Abstract</B></P> <P>Various lignin depolymerization methods have been proposed. Nevertheless, the relationship between the structure of lignin and its depolymerization behavior has not been widely investigated. Herein, six types of lignin samples were produced from oakwood (OW, hardwood) and pinewood (PW, softwood) using three different delignification techniques (ethanolsolv, formasolv, and Klason). The content of ether linkages in the OW-derived lignins was approximately three times higher than that in the PW-derived lignins because of the presence of the sinapyl alcohol unit in the former. The contents of ether linkages in the lignin isolated via the different methods followed the order: formasolv > ethanolsolv > Klason. The lignin samples were depolymerized in a mixture of supercritical ethanol (scEtOH) and formic acid at temperatures of 250–350 °C. At 350 °C, regardless of the lignin type, high conversion (>95%) and a high bio-oil yield (>81 wt%) could be achieved, demonstrating that the combined use of scEtOH-HCOOH was very effective for the depolymerization of various types of lignin. At the low temperatures of 250–300 °C, the lignin conversion and bio-oil yield were highly dependent on the amount of ether linkages; for example, at 300 °C, the use of OW-derived formasolv lignin resulted in a high bio-oil yield (86.2 wt%), whereas the use of OW-derived Klason lignin resulted in a very low bio-oil yield (27.9 wt%). The properties of the bio-oils produced from the different types of lignin were discussed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Oakwood lignin contains 3 times higher ether linkage than pinewood lignin. </LI> <LI> Formosolv lignin contains highest ether linkage among the three different lignins. </LI> <LI> Ethanolsolv, Formosolv and Klason lignins were depolymerized in scEtOH and HCOOH. </LI> <LI> High conversion of >95% and high bio-oil yield of >81 wt% were achieved at 350 °C. </LI> <LI> Bio-oil yield depends on amount of ether linkage in lignin sources at 250–300 °C. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

      • SCIESCOPUS

        Effective conversion of the carbohydrate-rich macroalgae (<i>Saccharina japonica</i>) into bio-oil using low-temperature supercritical methanol

        Zeb, Hassan,Riaz, Asim,Kim, Jaehoon Elsevier 2017 Energy conversion and management Vol.151 No.-

        <P><B>Abstract</B></P> <P>The use of supercritical methanol (scMeOH) for the liquefaction of the carbohydrate-rich macroalgae <I>Saccharina japonica</I> was investigated at low temperature (250–300°C). At 300°C, almost complete conversion (98.1wt%) and a high bio-oil yield (66.0wt%) were achieved. These values are higher than those achieved with supercritical ethanol (scEtOH, 87.8wt% conversion, 60.5wt% bio-oil yield) and subcritical water (subH<SUB>2</SUB>O, 91.9wt% conversion, 40.3wt% bio-oil yield) under identical reaction conditions. The superior liquefaction in scMeOH is attributed to the beneficial physical properties of scMeOH, including its higher polarity, superior reactivity, and higher acidity. The superior reactivity of scMeOH was evident from the larger amount of esters (54.6 area%) produced in scMeOH as compared to that in scEtOH (47.2 area%), and the larger amount of methyl/methoxy-containing compounds (78.6 area%) produced in scMeOH than that of ethyl/ethoxy-containing compounds (58.2 area%) produced in scEtOH. The higher bio-oil yield combined with its higher calorific value (29.2MJkg<SUP>−1</SUP>) resulted in a higher energy recovery of 135% for scMeOH as compared to those of scEtOH (118%) and subH<SUB>2</SUB>O (96%). When considering the amount of alcohol consumed during the liquefactions and the production of light bio-oil fractions that evaporate during bio-oil recovery, the higher methanol consumption (5.3wt%) than that of ethanol (2.3wt%) leads to similar bio-oil yields (∼51wt%).</P> <P><B>Highlights</B></P> <P> <UL> <LI> 98.1% carbohydrate-rich macroalgae was converted in scMeOH at 300°C. </LI> <LI> The conversion in scMeOH was higher than those of scEtOH (87.8%) and subH<SUB>2</SUB>O (91.9%). </LI> <LI> Higher energy recovery values of scMeOH than those of scEtOH and subH<SUB>2</SUB>O. </LI> <LI> High reactivity of scMeOH can be the reason for high conversion. </LI> <LI> Higher consumption of methanol than ethanol verified the high reactivity of scMeOH. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

      • KCI등재

        Effect of pyrolysis temperature on the physiochemical properties of biochars produced from raw and fermented rice husks

        Hafiza Sana,Riaz Asim,Arshad Zubaria,Zahra Syeda Tahsin,Akhtar Javaid,Kanwal Sumaira,Zeb Hassan,Kim Jaehoon 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.8

        This study investigated the slow pyrolysis behavior of raw rice husk (RRH) and fermented rice husk (FRH) in a fixed-bed reactor at temperatures in the range of 200–600 °C. The effects of pyrolysis temperature on the biochar yield, composition, and physiochemical properties were examined to evaluate the energy potential of biochars produced from RRH and FRH. The FRH-derived biochar produced at 600 °C was found to be more suitable than the RRH-derived biochar because of its higher carbon content (68.9% vs 42.1%), GCV (31.6 vs 24.1 MJ kg−1), and true density (1.94 vs 1.54 g cm −3). The slow pyrolysis in the high-temperature regime facilitated the formation of lignin-rich and aromatically condensed biochar, making it particularly useful for producing carbon-rich materials. Thus, slow pyrolysis can be a technically viable approach for producing high-energy-density solid fuels that can replace medium-ranking coals in co-firing.

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