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Global warming and the depletion of fossil fuels have created major pressure for scientists to seek alternative sources of energy and organic carbon. Biomass is a potential source from which many platform molecules can be derived. The development of sustainable technologies for producing these platform chemicals from renewable resources is very cha...
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... The generation of huge amounts of crude glycerol is one of the issues related to the usage of biodiesel. A mole of crude glycerol is generated for every three moles of biodiesel produced during the transesterification process [13]. This process accounts for about 10% of glycerol's overall output [14][15][16]. ...
... Because of the hydrothermal conditions of SCWR, organic compounds that cannot react in water except in the presence powerful base or acid catalyst can easily react. This is a result of SCWR producing a considerable amount of ions ([H + ] or [OH -]), which causes it to behave as an acid or base during the process [13]. Since reactions in supercritical water can be carried out in a single fluid phase, the SWR process has been explored both with and without a catalyst. ...
... The syngas stream was cooled down using two coolers (E-102 and E-103) connected in series, from 650 ℃ to 482.2 ℃ and from 482.2 ℃ to 35 ℃, respectively [13]. This was carried out to condense water out of the system. ...
Due to the large amount of crude glycerol produced as a by-product by the biodiesel industry, alternative technologies for converting glycerol to value-added fuels such as syngas have been proposed. By employing four main processes, the syngas could further be used to produce methanol. The first process is steam reforming (STR) where the crude glycerol is converted into syngas. The next step is a three-unit pressure swing adsorption (PSA) system which is employed to condition the syngas into the required stoichiometric ratio. The final two process are the methanol synthesis and methanol purification processes. The effects of STR temperature, steam-to-glycerol ratio (SGR), methanol synthesis temperature and pressure were all investigated. The results obtained shows that 0.29 kgMeOH/kgCG can be obtained through this process at STR of 650 ℃, SGR of 9, and methanol synthesis temperature and pressure of 250 ℃ and 80 bar respectively. In addition, a methanol production plant capacity of 6.8 tonnes/hr of crude glycerol feed for a 20-year plant life was investigated. The result from the economic analysis carried out shows that production of methanol from glycerol is economically feasible with net present value (NPV), return on investment, (ROI), discounted payback period (DPBP) and net production cost (NPC) of $74.2 million, 17%, 4.59 years, and 85₵/kgMeOH respectively. The sensitivity analysis results show that the revenue from sales of methanol and byproducts (hydrogen and methane), the manufacturing cost, the cost of raw materials, as well as fixed capital investment (FCI) were the most sensitive economic parameters.
... [135] The hydrogenolysis of the primary hydroxy group yields 1,2-PDO (also known as propylene glycol), a commodity chemical used in pharmaceutical and tobacco industry, in costumer care products, or as antifreeze. The current 1,2-PDO petrochemical production involves the selective hydrolysis of propylene oxide [136]. ...
... Propylene glycol (PPG) is produced by M/s Shell and Lyondell produced by acid or base catalysed ring opening of propylene oxide and approximately 80,000 tonnes/annum is being produced [ [148], [149]]. Shell and Degussa patented the conversion process of PPG produced from petrochemicals [ [149], [150]. ...
The enormous production of glycerol, a waste stream from biodiesel industries, as a low-value product has been causing a threat to both the environment and the economy. Therefore, it needs to be transformed effectively and efficiently into valued products for contributing positively towards the biodiesel economy. It can either be converted directly into competent chemicals or can be used as a feedstock/precursor for deriving valuable derivatives. In this review article, a technical evaluation has been stirred up, various factors and technologies used for producing value-added products from crude glycerol, Environmental and economic aspects of different conversion routes, cost factors and challenges of integration of the different routes for biorefinery have been reviewed and elaborated. There are tremendous environmental benefits in the conversion of crude glycerol via the biochemical route, the product and residue become eco-friendly. However, chemical conversions are faster processes, and economically viable if environmental aspects are partially ignored.
... Polysaccharides, monosaccharides and high carbon alcohols are structurally similar to glycols with hydroxyl group compared with ethylene and propylene [41]. Those two glycols can be produced from xylitol and sorbitol by hydrogenolysis under heating and in the presence of reducing agents [42,43]. Since xylitol and sorbitol are obtained from biomass, the conversion of both polyols to ethylene glycol and propylene glycol then becomes favorable. ...
Xylitol is one of the Top Value-Added chemicals from biomass released by DOE, with no petrochemical alternative. Industrially, this polyol is obtained by catalytic hydrogenation of xylose, a major component of hemicellulose. From xylitol it is possible to obtain various products, such as polyethylene glycol and ethylene glycol, and thus substitute fossil-based raw material. To reduce production costs and make the process environmentally friendly, it is necessary to reduce the stages of chemical conversion of lignocelluloses to xylitol. The present paper discusses the research advances focused on integrating several types of catalytic processes in a single container. The mechanism of catalytic hydrogenation of xylose to xylitol is detailed. The domain of the different parameters of the reaction will allow to increase the efficiency of the transformation of the biomass.
The increased energy demand and decreasing fossil resources have driven the research community to look into a sustainable, green process to meet the energy demands. India being one of the top producers of sugarcane derived sucrose, and conversion of surplus sucrose to value chemicals is always an advantage. 5%Ni-15%Ce/TiO2 catalyst is found to produce high yield of 1,2-PDO (~ 74%) under very mild reaction condition of 180 °C, 30 bar H2 for 3-h reaction time. The characterization of the catalyst by using various physicochemical methods indicates the synergy between Ni-Ce bimetal which enhances the selective production of glycol. The low temperature and pressure requirement and the advantage of being the one-pot process will always attract the future scope of commercialization.
Graphical Abstract
Electrochemical conversion of propene is a promising technique for manufacturing commodity chemicals by using renewable electricity. To achieve this goal, we still need to develop high-performance electrocatalysts for propene electrooxidation, which highly relies on understanding the reaction mechanism at the molecular level. Although the propene oxidation mechanism has been well investigated at the solid/gas interface under thermocatalytic conditions, it still remains elusive at the solid/liquid interface under an electrochemical environment. Here, we report the mechanistic studies of propene electrooxidation on PdO/C and Pd/C catalysts, considering that the Pd-based catalyst is one of the most promising electrocatalytic systems. By electrochemical in situ attenuated total reflection Fourier transform infrared spectroscopy, a distinct reaction pathway was observed compared with conventional thermocatalysis, emphasizing that propene can be dehydrogenated at a potential higher than 0.80 V, and strongly adsorb via μ-C═CHCH3 and μ3-η2-C═CHCH3 configuration on PdO and Pd, respectively. The μ-C═CHCH3 is via bridge bonds on adjacent Pd and O atoms on PdO, and it can be further oxidized by directly taking surface oxygen from PdO, verified by the H218O isotope-edited experiment. A high surface oxygen content on PdO/C results in a 3 times higher turnover frequency than that on Pd/C for converting propene into propene glycol. This finding highlights the different reaction pathways under an electrochemical environment, which sheds light on designing next-generation electrocatalysts for propene electrooxidation.
Production of 1,2-propanediol and 1,3-propanediol are identified as methods to reduce glycerol oversupply. Hence, glycerol hydrogenolysis is identified as a thermochemical conversion substitute; however, it requires an expensive, high-pressure pure hydrogen supply. Studies have been performed on other potential thermochemical conversion processes whereby aqueous phase reforming has been identified as an excellent substitute for the conversion process due to its low temperature requirement and high H2 yields, factors which permit the process of in-situ glycerol hydrogenolysis which requires no external H2 supply. Hence, this manuscript emphasizes delving into the possibilities of this concept to produce 1,2-propanediol and 1,3-propanediol without “breaking the bank” with expenses. Various heterogenous catalysts of aqueous phase reforming (APR) and glycerol hydrogenolysis were identified, whereby the combination of a noble metal, support, and dopant with a good amount of Brønsted acid sites are identified as the key factors to ensure a high yield of 1,3-propanediol. However, for 1,2-propanediol, a Cu-based catalyst with decent basic support is observed to be the key for good yield and selectivity of product. The findings have shown that it is possible to produce high yields of both 1,2-propanediol and 1,3-propanediol via aqueous phase reforming, specifically 1,2-propanediol, for which some of the findings achieve better selectivity compared to direct glycerol hydrogenolysis to 1,2-propanediol. This is not the case for 1,3-propanediol, for which further studies need to be conducted to evaluate its feasibility.
