Diol Products Research Articles

Selective Control of Catalysts for Glycerol and Cellulose Hydrogenolysis to Produce Ethylene Glycol and 1,2-Propylene Glycol: A Review

The bioconversion of cellulose and the transformation of glycerol can yield various diols, aligning with environmental sustainability goals by reducing dependence on fossil fuels, lowering raw material costs, and promoting sustainable development. However, in the selective hydrogenolysis of glycerol to ethylene glycol (EG) and 1,2-propylene glycol (1,2-PG), challenges such as low selectivity of catalytic systems, poor stability, limited renewability, and stringent reaction conditions remain. The production of diols from cellulose involves multiple reaction steps, including hydrolysis, isomerization, retro-aldol condensation, hydrogenation, and dehydration. Consequently, the design of highly efficient catalysts with multifunctional active sites tailored to these specific reaction steps remains a significant challenge. This review aims to provide a comprehensive overview of the selective regulation of catalysts for producing EG and 1,2-PG from cellulose and glycerol. It discusses the reaction pathways, process methodologies, catalytic systems, and the performance of catalysts, focusing on active site characteristics. By summarizing the latest research in this field, we aim to offer a detailed understanding of the state-of-the-art in glycerol and cellulose conversion to diols and provide valuable guidance for future research and industrial applications. Through this review, we seek to clarify the current advancements and selective control strategies in diol production from glycerol or cellulose, thereby offering critical insights for future investigations and industrial scale-up.

Origin of Manipulating Selectivity in Prins Cyclization by [Ga4L6]12- Supramolecular Catalysis through Host-Guest Interactions.

The host effect of the supramolecular [Ga4L6]12- tetrahedral metallocage on Prins cyclization reaction of the substrate by encapsulated citronellal has been investigated by means of molecular dynamics and quantum mechanics. The encapsulation process of the substrate into the [Ga4L6]12- cavity was simulated via attach-pull-release (APR) methods. Thermodynamic calculations and classical molecular dynamics simulations assessed the substrate's microenvironment inside the cavity, guiding DFT-level modeling of the reaction. DFT calculations show diol product predominance in acidic solution but high enol selectivity inside [Ga4L6]12-, consistent with experimental findings. [Ga4L6]12- alters the selectivity of the Prins cyclization reaction by inhibiting diol formation. The activation strain model-based decomposition analysis (ASM-DA) of the barrier difference among distortion and interaction terms indicates that the more positive interaction between a host and guest in the diol transition state than enol determines the product selectivity, particularly the fewer C-H···O and O-H···O hydrogen-bonding interactions. These theoretical insights could contribute to a deeper understanding of the nature of supramolecular catalysis and to further develop new supramolecular catalysts.

Conversion of limonene to limonene diol over activated carbon supported Ti catalyst

AbstractA series of activated carbon supported Ti-3,3′-ethylen bis(3,4-dihydro-2H-1,3-benzoxazine) complex catalysts (denoted Ti-Bz (0.25)/AC, Ti-Bz(0.37)/AC, and Ti-Bz (0.5)/AC) was evaluated in the conversion of limonene to limonene diol using H2O2 as oxidant. The opening of oxazine ring as a step to the titanium complex formation was highlighted, as far as we are aware, for the first time, by NMR analysis. A range of characterization methods, including SEM–EDS, nitrogen physisorption, ATR-FTIR, and XRD, showed that the procedure used in the preparation of these materials was reproducible. Parameters affecting the catalytic performances in the production of limonene diol, such as reaction temperature, amount of catalyst tested, and its catalytic stability, were studied. Ti-Bz (0.5)/AC was the most performant catalyst leading to limonene diol yield of 36.7%. The recyclability of the catalyst was evaluated along three catalytic consecutive tests that showed no significant difference of performance compared with that of fresh catalyst.

Investigation into the effect of the culture conditions and optimization on limonene-1,2-diol production from the biotransformation of limonene using Pestalotiopsis mangiferae LaBMicrA-505.

Different bioproducts can be obtained by changing operative condition of biotechnological process, and this bioprocess aspect is a significant approach to be adopted on industrial scale leading to the creation of new natural aroma. Thus, this study aimed to investigate the culture conditions and optimization of the biotransformation of limonene into limonene-1,2-diol using Pestalotiopsis mangiferae LaBMicrA-505 obtained from the Brazilian Amazon. The study started with the investigation of the establishment of culture, followed by optimization of the conditions for biotransformation of R-(+)-limonene to limonene-1,2-diol, using shake flasks. The fresh biomass of P. mangiferae LaBMicrA-505 obtained in liquid media supplemented with yeast-malt extract under with 72h (stationary phase) performed better diol productivity when compared to other biomasses. Finally, in the modeling of contour plots and surface responses of a central composite design, the use of 4g l- 1 biomass, 2% of the substrate at 24°C, 120rpm, and pH of 6.0 could maximize the production of limonene-1,2-diol, accumulated up to 98.34 ± 1.53% after 96h of reaction. This study contributed to identified operational condition for the R-(+)-limonene bioconversion scale-up. The endophytic fungus P. mangiferae LaBMicrA-505 proved to be a potent biocatalyst to biotechnologically produce limonene-1,2-diol, an aroma compounds with interesting bioactive features that up to now has been manufactured by extraction from plants with long and not environmentally friendly procedures.

Diols production from pyrolysis oil water‐soluble fraction

AbstractBACKGROUNDThe production of value‐added chemicals from pyrolysis oil or its fractions is of great significance for the valorization of biomass. Diols, including ethylene glycol (EG) and 1,2‐propylene glycol (1,2‐PG), are important bulk chemicals with widespread industrial applications. Here we investigated the production of diols from pyrolysis oil water‐soluble fraction (WS) using a hybrid catalyst (Ni + H2WO4).RESULTSFirstly, levoglucosan, glycolaldehyde and acetol, three main components in WS, were respectively selected as the single model compound, and their respective conversions into diols were investigated at different temperatures for different reaction times. The result showed the optimum reaction temperature and time were 180 °C and 2 h respectively, under which a EG yield of 53.8% and 1,2‐PG yield of 5.2% were obtained from levoglucosan conversion, a EG yield of 98.6% was obtained from glycolaldehyde conversion, and a 1,2‐PG yield of 98.5% was obtained from acetol conversion. The reaction pathway of levoglucosan conversion was analyzed. Secondly, the model mixture of levoglucosan, glycolaldehyde and acetol was used to simulate the real WS, and their conversion was investigated at different ratios of H2WO4 to Ni. The result showed the optimum catalyst composition was 0.15 g H2WO4 and 0.3 g Ni, under which a EG yield of 76.4% and 1,2‐PG yield of 38.4% were obtained. Thirdly, the real original WS was converted under the optimum reaction conditions and the result only gave a EG yield of 19.1% and 1,2‐PG yield of 25.8% (based on the carbon moles of main substrates), which were much less than the two yields of model mixture. That was related to the presences of other types of chemicals in original WS. After the original WS being adsorbed by activated carbon, the yields of EG and 1,2‐PG could be increased to 39.2% and 37.9%, respectively.CONCLUSIONThe presences of certain other types of chemicals (such as acids, furans, phenolics and cyclopentanones) in original WS inhibited the production of diols. The activated carbon adsorption could efficiently remove most of furans, phenolics and cyclopentanones in original WS and increased significantly the diols yields. © 2024 Society of Chemical Industry (SCI).

Engineering strategies for enhanced 1′, 4′-trans-ABA diol production by Botrytis cinerea

BackgroundCurrently, industrial fermentation of Botrytis cinerea is a significant source of abscisic acid (ABA). The crucial role of ABA in plants and its wide range of applications in agricultural production have resulted in the constant discovery of new derivatives and analogues. While modifying the ABA synthesis pathway of existing strains to produce ABA derivatives is a viable option, it is hindered by the limited synthesis capacity of these strains, which hinders further development and application.ResultsIn this study, we knocked out the bcaba4 gene of B. cinerea TB-31 to obtain the 1′,4′-trans-ABA-diol producing strain ZX2. We then studied the fermentation broth of the batch-fed fermentation of the ZX2 strain using metabolomic analysis. The results showed significant accumulation of 3-hydroxy-3-methylglutaric acid, mevalonic acid, and mevalonolactone during the fermentation process, indicating potential rate-limiting steps in the 1′,4′-trans-ABA-diol synthesis pathway. This may be hindering the flow of the synthetic pathway. Additionally, analysis of the transcript levels of terpene synthesis pathway genes in this strain revealed a correlation between the bchmgr, bcerg12, and bcaba1-3 genes and 1′,4′-trans-ABA-diol synthesis. To further increase the yield of 1′,4′-trans-ABA-diol, we constructed a pCBg418 plasmid suitable for the Agrobacterium tumefaciens-mediated transformation (ATMT) system and transformed it to obtain a single-gene overexpression strain. We found that overexpression of bchmgr, bcerg12, bcaba1, bcaba2, and bcaba3 genes increased the yield of 1′,4′-trans-ABA-diol. The highest yielding ZX2 A3 strain was eventually screened, which produced a 1′,4′-trans-ABA-diol concentration of 7.96 mg/g DCW (54.4 mg/L) in 144 h of shake flask fermentation. This represents a 2.1-fold increase compared to the ZX2 strain.ConclusionsWe utilized metabolic engineering techniques to alter the ABA-synthesizing strain B. cinerea, resulting in the creation of the mutant strain ZX2, which has the ability to produce 1′,4′-trans-ABA-diol. By overexpressing the crucial genes involved in the 1′,4′-trans-ABA-diol synthesis pathway in ZX2, we observed a substantial increase in the production of 1′,4′-trans-ABA-diol.

Highly efficient conversion of biomass-derived furanic compounds into alkyl diols by selective hydrogenolysis using non-noble metal catalysts with tunable surface oxygen vacancies

Production of alkyl diols from biomass-derived furanic compounds by hydrogenolysis is a promising route to the fabrication of bio-based polyesters and polyurethanes. However, it faces many challenges such as the use of noble metal catalysts, or low hydrogenolysis activity of the furan rings and poor product selectivity with non-noble metal catalysts. In this work, non-noble metal catalysts Cu-Co3O4 (CuCox) catalysts were modified by magnesium, obtaining CuCoxMgy catalysts with tunable surface oxygen vacancies (OV). The CuCoxMgy catalysts demonstrated greatly improved activity and selectivity (approx. 50 %), comparable to those of noble metal catalysts, in the hydrogenolysis of furfuryl alcohol into 1,5-pentanediol (1,5-PeD). The obtained CuCoxMgy catalysts are even superior to the noble metal catalysts in terms of production rate or productivity. Extensive characterizations including XAS, EPR and XPS revealed that magnesium significantly promotes the formation of Co2+-OV pair sites on the catalyst surface, which simultaneously activate furan ring and hydroxyl group in furfuryl alcohol, leading to the efficient and selective cleavage of the C2-O1 bond to form 1,5-PeD. The CuCoxMgy catalysts also exhibited high activity and selectivity in hydrogenolysis of various other biomass-derived furanic compounds towards ring-opening products.

Regulating the oxygen vacancy of M-WOx-MgOy catalysts (M = Ni, Pd, Pt, Ru) for the chemoselective conversion of glucose to diols

A series of M-WOx-MgOy (M = Ni, Pd, Pt, Ru) catalysts was prepared and their catalytic performances were systematically investigated in the chemoselective hydrogenolysis of glucose to diols. Among these catalysts, Ru-WOx-MgOy exhibited superior catalytic activity in the production of diols as well as ethylene glycol from glucose under mild reaction conditions. Then various Characteristic techniques including XRD, BET, FTIR, SEM, TEM, HAADF-STEM, XPS, NH3-TPD, and Pyridine-adsorbed DRIFTS were adopted to investigate the structural properties of these catalysts and correlate them with their catalytic performances. Based on these characterization results, it showed that the outstanding catalytic activity of Ru-WOx-MgOy catalyst was attributed to its higher content of oxygen vacancies, which served as the active acidic sites and greatly lowered the activation energy required for glucose conversion, thereby promoting the efficient production of diols.

Pseudomonas putida as a platform for medium-chain length α,ω-diol production: Opportunities and challenges.

Medium-chain-length α,ω-diols (mcl-diols) play an important role in polymer production, traditionally depending on energy-intensive chemical processes. Microbial cell factories offer an alternative, but conventional strains like Escherichia coli and Saccharomyces cerevisiae face challenges in mcl-diol production due to the toxicity of intermediates such as alcohols and acids. Metabolic engineering and synthetic biology enable the engineering of non-model strains for such purposes with P. putida emerging as a promising microbial platform. This study reviews the advancement in diol production using P. putida and proposes a four-module approach for the sustainable production of diols. Despite progress, challenges persist, and this study discusses current obstacles and future opportunities for leveraging P. putida as a microbial cell factory for mcl-diol production. Furthermore, this study highlights the potential of using P. putida as an efficient chassis for diol synthesis.

Asymmetric Partial Hydrosilylation of 2,2‐Difluoro‐1,3‐diketones with Chiral Frustrated Lewis Pairs

Comprehensive SummaryThe asymmetric partial reduction of 1,3‐diketones stands as a straightforward pathway to access optically active β‐hydroxyketones. In this paper, an asymmetric Piers‐type hydrosilylation of 2,2‐difluoro‐1,3‐diketones was successfully realized by using a frustrated Lewis pair of chiral borane and tricyclohexylphosphine as a catalyst, delivering a variety of α,α‐difluoro‐β‐hydroxyketones in high yields with up to 99% ee. Significantly, no over‐reduced diol products were observed even with an excess amount of silanes. The product can be conveniently converted to α,α‐difluoro‐β‐hydroxyester or 1,3‐anti‐diol via an oxidation with m‐CPBA or a reduction with DIBAL‐H without obvious loss of ee.

Screening Bacterial Strains Capable of Producing 2,3-Butanediol: Process Optimization and High Diol Production by Klebsiella oxytoca FMCC-197

In the present investigation, the potential of various newly isolated strains which belong to the Enterobacteriaceae family to produce 2,3-butanediol (BDO), an important bio-based compound, was studied. The most interesting strain, namely Klebsiella oxytoca FMCC-197, was selected for further investigation. Commercial (raw) sucrose or molasses, which are important agro-industrial surpluses, were employed as carbon sources for most of the trials performed. Different fermentation parameters (viz. incubation te4mperature, utilization of different carbon sources, substrate inhibition, aeration) were tested to optimize the process. Fermentations under non-aseptic conditions were also conducted to investigate the potential of growth of the strain K. oxytoca FMCC-197 to surpass the growth of other microorganisms in the culture medium and produce BDO. Besides BDO production, in trials in which molasses was employed as the sole carbon source, significant color removal was observed simultaneously with the production of microbial metabolites. The very high BDO concentration ≈115 g L−1 was reported in approximately 64 h during a fed-batch bioreactor experiment, using sucrose and molasses as carbon sources at 30 °C, reaching a conversion yield (YBDO) of 0.40 g g−1 and a productivity rate (PBDO) of 1.80 g L−1 h−1, while similar results were also obtained at 37 °C. The strain demonstrated remarkable results in non-previously sterilized media, as it produced 58.0 g L−1 in 62 h during a fed-batch bioreactor experiment, while the potential to decolorize molasses-based substrates over 40% was also recorded. From the results obtained it is shown that this wild-type strain can be used in large-scale microbial BDO production using various raw materials as fermentative substrates. The wastewater derived after BDO fermentation by K. oxytoca FMCC-197 can be disposed relatively safely into the environment.

Biosynthesis of chiral diols from alkenes using metabolically engineered type II methanotroph

Methanotrophs are environmentally friendly microorganisms capable of converting gas to liquid using methane monooxygenases (MMOs). In addition to methane-to-methanol conversion, MMOs catalyze the conversion of alkanes to alcohols and alkenes to epoxides. Herein, the efficacy of epoxidation by type I and II methanotrophs was investigated, and type II methanotrophs were observed to be more efficient in converting alkenes to epoxides. Subsequently, three (Epoxide hydrolase) EHs of different origins were overexpressed in the type II methanotroph Methylosinus trichosporium OB3b to produce 1,2-diols from epoxide. Methylosinus trichosporium OB3b expressing Caulobacter crescentus EH produced the highest amount of (R)-1,2-propanediol (251.5 mg/L) from 1-propene. These results demonstrate the possibility of using methanotrophs as a microbial platform for diol production and the development of a continuous bioreactor for industrial applications.

Hydrophobic tuning of PDMS-PVDF hollow fiber membranes for enhanced isopropanol recovery in pentane diol production process via pervaporation

BackgroundsThis study explores a use of crosslinked polydimethylsiloxane (PDMS) membranes for the selective pervaporation separation of isopropanol (IPA) from a mixture of 1,2 and 1,5 pentanediols (PeD). MethodsTwo crosslinkers, tetraethyl orthosilicate (TEOS) and 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FDTS), were used to prepare PDMS coating on inside of polyvinylidene fluoride (PVDF) hollowfiber membrane. Significant findingsSeparation performance of PDMS-FDTS membrane outperformed to that of PDMS-TEOS membrane. Both of the PDMS membrane systems resulted a high IPA selectivity, was attributed to the nonpolar nature of IPA and its strong interaction with hydrophobic PDMS chain. An operating conditions influenced the pervaporation performance, with higher feed temperature increasing flux but reducing IPA content in permeate. An increasing IPA content in the feed mixture increased flux while slightly decreasing the separation factor. Overall, PDMS-FDTS membranes demonstrated promising performance for selective IPA removal and yielded a flux in the range of 173 ± 15 g/m2h while maintaining the IPA content in permeate higher than 99.7% at 60 °C, which showed potential for industrial-scale applications due to its high flux and selectivity.

Plasma Electrochemistry for Carbon-Carbon Bond Formation Via Pinacol Coupling Reaction

Low-temperature, atmospheric-pressure plasmas in contact with liquids have attracted interest for various chemical applications including the degradation of organic pollutants,1 conversion of abundant feedstocks,2,3 and more recently, organic chemistry.4 Compared to other chemical approaches, plasma-liquid chemistry does not require a catalyst material, is electrified, and produces unique reactive species such as solvated electrons, one of the strongest chemical reducing species.5 Here, we present an application of plasma-liquid chemistry to the formation of carbon-carbon bonds via the well-known pinacol coupling reaction. Pinacol coupling is conventionally carried out by using an electron donating reagent such as magnesium to initially reduce a carbonyl group forming a ketyl radical anion species. A pair of these ketyl groups then react to form a vicinal diol, which in the presence of a proton donor such as water, leads to the final diol product. We show that the pinacol coupling reaction can instead be driven at a plasma-liquid interface without any catalyst. Our study was performed using a direct-current (DC) powered plasma formed between a metal electrode and liquid water surface similar to previous reports.2 Parametric studies were focused on methyl-4-formylbenzoate (MFB) as the substrate. We find that the faradaic efficiency of the pinacol product depends on the initial concentration, increasing from 20% to 80% as the concentration increased from 0.06 M to 0.18 M. For an initial concentration of 0.12 M and a constant operating current of 3 mA, a yield of 46% can be reached after 12 h. The experimental results were supported by a reaction-diffusion model, and a rate constant of 10^10 L-1 mol-1 s-1 was extracted from kinetic studies. In addition to the pinacol product, nuclear magnetic resonance (NMR) spectroscopy also indicated methyl 4-(dimethoxymethyl)benzoate, methyl 4-(hydroxymethyl)benzoate, and 4-(methoxycarbonyl)benzoic acid as side products. By carrying out scavenger control experiments, we show that the vicinal diol is produced by solvated electron reduction while these other side products are formed by reactions with other radicals or the solvent. The generality of the approach is demonstrated by extending to several other aromatic aldehydes and ketones.

Potential of Y. lipolytica epoxide hydrolase for efficient production of enantiopure (R)-1,2-octanediol

The recombinant Yleh from a tropical marine yeast Yarrowia lipolytica NCIM 3589 exhibited a high epoxide hydrolase activity of 9.34 ± 1.80 µmol min-1 mg-1 protein towards 1,2-epoxyoctane (EO), at pH 8.0 and 30 °C. The reaction product was identified as 1,2-Octanediol (OD) by GC-MS using EO and H2O18 as substrate, affirming the functionality of Yleh as an epoxide hydrolase. For EO, the Km, Vmax, and kcat/Km values were 0.43 ± 0.017 mM, 0.042 ± 0.003 mM min-1, and 467.17 ± 39.43 mM-1 min-1, respectively. To optimize the reaction conditions for conversion of racemic EO by Yleh catalyst to enantiopure (R)-1,2-octanediol, initially, Response Surface Methodology was employed. Under optimized reaction conditions of 15 mM EO, 150 µg purified Yleh at 30 °C a maximal diol production of 7.11 mM was attained in a short span of 65 min with a yield of 47.4%. Green technology using deep eutectic solvents for the hydrophobic substrate (EO) were tested as co-solvents in Yleh catalyzed EO hydrolysis. Choline chloride-Glycerol, produced 9.08 mM OD with an increased OD yield of 60.5%. Thus, results showed that deep eutectic solvents could be a promising solvent for Yleh-catalyzed reactions making Yleh a potential biocatalyst for the biosynthesis of enantiopure synthons.

Process design and comprehensive 3E analysis of low carbon diol production with and without heat integration

As an important chemical intermediate, the synthesis process of 1,4-butanediol is still energy-intensive and seriously polluting the environment. It is necessary to study its high efficiency and energy saving. The two step synthesis process of 1,4-butanediol: (1) ethynylation of formaldehyde reaction and separation, (2) hydrogenation of 1,4-butynediol reaction and separation are simulated. A sequential iterative optimization method is used to optimize the whole process of 1,4-butanediol production to obtain the best parameters which achieve the minimum annual total cost. In order to further explore the energy-saving process, the heat integration technology is introduced on the basis of the common process, and the annual total cost of the process is reduced by 28.30%. In addition, the exergy efficiency and environmental impact of common process and heat integration process are compared. The results showed that the exergy efficiency of the heat integration process is increased by 6.67% and the CO2, SO2 and NOX emission is reduced by 32.48%, 32.48% and 62.01% compared with the common process. Through the comprehensive analysis of the economy, exergy and environment of synthesis processes, it has important reference significance for the synthesis of 1,4-butanediol in industry.

One-pot synthesis of 2,5-bis(hydroxymethyl)furan from biomass derived 5-(chloromethyl)furfural in high yield

5-(Chloromethyl)furfural (CMF), as a new platform molecular, has become a hot topic in the field of biorefinery. Herein, the one-pot conversion of CMF to 2,5-bis(hydroxymethyl)furan (BHMF) in the water phase was demonstrated for the first time. A 91% BHMF yield was obtained over Ru/CuOx catalyst, and BHMF was mainly produced by the consecutive hydrolysis and hydrogenation of CMF with 5-hydroxymethylfurfural (HMF) as an intermediate. Kinetic studies revealed that the conversion of HMF to BHMF was the rate-determining step. Remarkably, the characterizations and density functional theory (DFT) calculations further revealed the lower electron density of Ru NPs in Ru/CuOx catalyst, resulting in a larger adsorption energy and a smaller free energy difference for the formation of alcohols. The present findings offered a new pathway for biomass-derived diol production through CMF as a potential source.

Epoxide hydrolase activity in the aqueous extracts of vegetable flours and application to the stereoselective hydrolysis of limonene oxide

The aqueous buffered suspensions of some vegetable flours were tested in the reaction with 1,2-epoxide deriving from (4R)- or (4S)-limonene as well as with the standard substrate methyl oleate epoxide and epoxide hydrolase activity was mainly detected in the flours from soybean, mung bean and red mung bean. A simple protocol was applied for obtaining a raw freeze-dried enzymatic preparation from flours, which maintained most of the activity of the fresh suspension and offered advantages in easy handling, reproducibility and stability over the time. Preferential hydrolysis of one of the diastereoisomers present in the starting (4R)- or (4S)-limonene oxide (cis/trans mixture) was observed and the reaction converged toward the formation of a predominant diol, resulting from the attack on the most (C1)- or less (C2)-substituted carbon of the oxirane ring depending on the cis/trans stereochemistry of the substrate. Biocatalyzed hydrolysis of (S)-limonene oxide proceeded at higher reaction rate compared to the (R)-isomer and with superior stereoconvergence toward a single diol product. The kinetic separation of the slow-reacting diastereoisomers of (R)- and (S)-limonene oxides was optimized by using the enzymatic preparations from red mung bean and soybean, respectively, and trans-(4R)-limonene oxide and cis-(4S)-limonene oxide were obtained in good yield and stereochemical purity.

Hydrodeoxygenation of C3–4 polyols to C3–4 diols over carbon-supported bimetallic MgCu@C catalysts prepared from ion exchange resin

The selective hydrodeoxygenation (HDO) of C3–4 polyols (glycerol and erythritol) to value-added diol products was investigated over a series of Cu-based catalysts, namely, carbon-supported monometallic Cu@C and bimetallic MgCu@C prepared by using a weakly acidic cation-exchange resin as the carbon support precursors. High metal loading (> 50 wt%) and small metal particle size (< 15 nm) were realized by the catalyst prepared from ion-exchange resin. The addition of Mg decreased Cu particle size (10.0–13.5 nm) and improved metal dispersion. The largest metal surface area was achieved for the MgCu@C catalyst with Mg/Cu molar ratio of 1/9. Furthermore, HDO of C3–4 polyols was performed over the prepared catalysts at relatively low temperature (180 °C) under low initial H2 pressure (1.2 MPa). Over the MgCu@C catalyst with a nominal Cu/Mg atomic ratio of 9/1, a C3 polyol conversion of 94.0 C mol% was obtained with a high selectivity towards 1,2-propanediol (94.3 C mol%), while a low erythritol conversion of 18.75 C mol% with a selectivity toward butanediols of 43.0 C mol% was achieved after 360 h reaction. The different effects of the Mg addition on catalytic activity to C3 and C4 polyol HDO were likely attributed to the different reaction mechanism. The dehydration-hydrogenation mechanism was proposed for C3 HDO over Cu@C and MgCu@C, in which the addition of Mg species promoted the dehydration of glycerol to produce hydroxyacetone followed by the hydrogenation of hydroxyacetone to 1,2-propanediol.

Chromium-catalyzed production of diols from olefins

Concrete materials and proportions are usually selected to obtain a group of required characteristics of fresh and hardened concrete, for a particular project application. Concrete mix design has major impacts on concrete porosity and water permeability; thus it is a key approach for obtaining watertight and durable concrete. Within this context, this chapter describes the process of material selection and concrete proportioning and summarizes concrete types, grades, and classes. It establishes the required general background of concrete mix design for engineers and researchers dealing with concrete waterproofing technologies and durability issues.