57-55-6 Usage
Uses
Used in Chemical Industry:
Propylene glycol is used as an important raw material for unsaturated polyester, epoxy resin, and polyurethane resin. The use amount in this area accounts for about 45% of the total consumption of propylene glycol. Such unsaturated polyester is used extensively for reinforced plastics and surface coatings.
Used in Food Industry:
Propylene glycol is used as a hygroscopic agent, antifreeze, lubricant, and solvent. It reacts with fatty acid to give propylene ester of fatty acids, which is mainly used as a food emulsifier. It is also a good solvent for flavorings and pigments.
Used in Pharmaceutical Industry:
Propylene glycol is commonly used as solvents, softeners, and excipients in the manufacture of various types of ointments and salves.
Used in Cosmetic Industry:
Propylene glycol is used as a solvent and a softener due to its good mutual solubility with various spices. It is also used as a humectant, giving a pleasant feel with less greasiness than glycerin and serving as a solvent for antioxidants and preservatives.
Used in Tobacco Industry:
Propylene glycol is used as a moisturizing agent, antifungal agent, and lubricant for food processing equipment.
Used in Brewing and Dairy Industry:
Propylene glycol is used as an antifreeze and is also used in the manufacture of resins and as an emulsifier in food.
Used as a Solvent:
Propylene glycol is used as a solvent for flavors and colors that are insoluble in water. It is also used in beverages and candy.
Occurrence:
Propylene glycol has been reported found in several varieties of mushrooms, roasted sesame seed, oat groats, parmesan cheese, cocoa, pecans, and truffle.
Brand Names:
Sentry Propylene Glycol (Union Carbide); Sirlene (Dow Chemical)
Aroma Threshold Values:
Detection: 340 ppm
Physical and Chemical Properties
Propylene glycol is scientifically named as “1,2-propanediol”, and has a chemical formula of CH3CHOHCH2OH and a molecular weight of 76.10. There is a chiral carbon atom in the molecule. Its racemate is a hygroscopic viscous liquid and is slightly spicy. It has a specific gravity of 1.036 (25/4 °C), a freezing point of-59 °C, and a boiling point of 188.2 °C, respectively 83.2 °C (1,333 Pa). It is miscible with water, acetone, ethyl acetate and chloroform, and is soluble in ether. It is soluble in many essential oils, but is not miscible with petroleum ether and paraffin oil. It is relatively stable to heat and light, and is more stable at low temperatures. Its L-isomer has a boiling point of 187 to 189 °C and a specific optical rotation [α] of D20-15.0°. It can be oxidized at high temperatures to propionaldehyde, lactic acid, pyruvic acid and acetic acid.
Figure 1 the molecular structure of propylene glycol.
Propylene glycol is a diol having the general nature of the alcohol. It can react with inorganic and organic acids to generate mono-or di-esters. It reacts with propylene oxide to generate ether, with hydrogen halide to generate halohydrin, and with acetaldehyde to generate methyl dioxolane.
Medicinal property and application
Propylene glycol has good solubility and less toxicity and irritation, and is widely used as solvents, extraction solvents and preservatives for injections (eg. intramuscular injections, intravenous injections) and non-injectable pharmaceutical preparations (such as oral liquid, ophthalmic preparations, otic preparations, dental preparations, rectovaginal preparations, transdermal preparations, etc.). It is better than glycerol solvent and can dissolve many substances such as corticosteroids (sex hormone), chloramphenicol, sulfonamides, barbiturate, reserpine, quinidine, corticosterone acetate, tetrahydropalmatine sulfate, mechlorethamine hydrochloride, vitamin A, vitamin D, many volatile oils, most of the alkaloids and many local anesthetics.
Propylene glycol is similar to ethanol when used as a bacteriostatic agent, and its efficacy to inhibit mold is similar to glycerin and is slightly lower than that of ethanol. Propylene glycol is commonly used as a plasticizer for the aqueous film coating materials. Its mixture with equal amounts of water can delay the hydrolysis of certain drugs, and increase the stability of the preparation product. It is used as an antimicrobial preservative in 15% to 30% propylene glycol solution and semi-solid formulation, as humectants in about 15% propylene glycol topical formulation, and as solvent and co-solvent in 10% to 30% propylene glycol aerosol solvent, 10% to 25 % propylene glycol oral solution, 10% to 60% injectable formulation and 5% to 80% topical formulation.
[Stability and storage condition] It is very stable at room temperature, but is oxidized when left open at high temperatures (above 280 °C); has a chemical stability after mixing with 95% ethanol or water; can be sterilized by autoclaving or sterile filtration. Propylene glycol has hygroscopicity, and should be positioned at cool and dry place and stored in dark airtight container.
[Incompatibility] It has incompatibility with some oxidants (such as potassium permanganate).
The above information is edited by the lookchem of Jin Yinxue.
Content analysis
A 10μl sample is injected into the gas chromatograph, which has a thermal conductivity detector. The column is 1m × 6.35mm stainless steel column. The filler is polyethylene glycol 20M (Carbowax compound 20M) 4%, and the carrier is a 40/60 mesh sieved polytetrafluoroethylene (Chromosorb T) or similar material. Helium carrier gas has a flow rate of 75ml/min. Injector temperature is 240 °C; column temperature is 120 to 200 °C, temperature increment is 5 °C/min; final temperature is 250 °C. Under specified conditions, the residence time of propylene glycol is about 5.7 minutes, the residence time of three kinds of glycol isomers are respectively 8.2, 9.0 and 10.2 minutes. The area of each peak is determined using any proper method, and then the percentage of propylene glycol area is calculated and transformed into mass percentage.
Toxicity
FAO/WHO (2000): ADI is 0 to 25mg/kg.
LD50 is 22 to 23.9 mg/kg (mouse, oral).
GRAS (FDA, §184.1666, 2000).
Use limitation
FAO/WHO (1984): Cottage cheese, the cream mixture amount of 5g/kg (used alone or in combination with other carriers and stabilizers).
Japan (1998): Raw noodles, raw stuffing and cuttlefish smoked products ≤2%; skins for dumplings, steamed dumplings, spring rolls and wonton ≤1.2%; other food ≤0.6%.
GB 2760-96: pastry 3.0g/kg, chewing gum.
FDA, §184.1666 (2000): Alcoholic beverages 5%; frosting and candy 24%; frozen dairy 2.5%; flavoring agents, flavor enhancers 97%; nuts and nut products 5%; other food 2.0%.
Synthesis method
It can be obtained by hydrolysis of Propylene oxide:
CH3CHCH2+H2O[H+]→CH3CH(OH)CH2OH
Direct hydration
Propylene oxide and water are fed in a molar ratio of 1: 15, and react at 150-2000 °C, a pressure of 1.2-1.4 MPa for 30 minutes to obtain 16% aqueous solution of propylene glycol, which is subjected to evaporation to obtain the finished product.
Catalyzed hydrolysis
The reaction is performed under catalyzation of sulfuric acid or hydrochloric acid. 0.5% to 1.0% dilute sulfuric acid is added into 10% to 15% aqueous solution of propylene oxide, the mixture is hydrolyzed at 50 to 70 °C; the hydrolysate is neutralized and concentrated under reduced pressure, and refined to obtain the finished products.
The preparation method is a method in which propylene oxide is hydrolyzed to propylene glycol, and which can be carried out in the liquid phase. There are catalytic and non-catalytic processes in industry. Catalytic method is a method in which hydrolysis is carried out in the presence of 0.5% to 1% sulfuric acid at 50 to 70 °C. Non-catalytic process is carried out under high temperature and pressure (150 to 300℃, 980 to 2940kPa), and is used for production in domestic.
Acute toxicity
Oral-rat LD50: 20000 mg/kg; Oral-Mouse LD50: 32000 mg/kg
Irritation data
Eyes-rabbit 100 mg mild
Extinguishing agent
Dry powder, foam, sand, water.
Preparation
Manufactured by treating propylene with chlorinated water to form the chlorohydrin, which is converted to the glycol by
treatment with sodium carbonate solution. It is also prepared by heating glycerol with sodium hydroxide.
Indications
Propylene glycol solution (40% to 60%, v/vCH2CH[OH]CH2OH, propylene glycol)
applied to the skin under plastic occlusion hydrates the skin and causes desquamation
of scales. Propylene glycol, isotonic in 2% concentration, is a widely used vehicle
in dermatologic preparations. Hydroalcoholic gels containing propylene glycol or
other substances augment the keratolytic action of salicylic acid. Keralyt gel consists
of 6% salicylic acid, 19.4% alcohol, hydroxypropylcellulose, propylene glycol, and water and is an extremely effective keratolytic agent. Overnight occlusion is used
nightly until improvement is evident, at which time the frequency of therapy can
be decreased to every third night or once weekly. This therapy is well tolerated,
is usually nonirritating, and has been most successful in patients with X-linked
ichthyosis vulgaris. Burning and stinging may occur when applied to damaged skin.
Patients with other abnormalities of keratinization with hyperkeratosis, scaling, and
dryness may also benefit.
Production Methods
Propylene glycol generally is synthesized commercially by
starting with propylene, converting to the chlorohydrin, and
hydrolyzing to propylene oxide, which is then hydrolyzed
to propylene glycol. It can also be prepared by other
methods.
Air & Water Reactions
Water soluble.
Reactivity Profile
1,2-Propanediol is hygroscopic. 1,2-Propanediol is sensitive to excessive heat (tends to oxidize at high temperatures). 1,2-Propanediol can react with oxidizing materials. 1,2-Propanediol is incompatible with acid chlorides, acid anhydrides, chloroformates, and reducing agents. 1,2-Propanediol dissolves many essential oils. A mixture of 1,2-Propanediol with hydrofluoric acid and silver nitrate was put in a glass bottle which burst 30 minutes later.
Hazard
Toxic.
Health Hazard
Liquid may irritate eyes.
Fire Hazard
1,2-Propanediol is combustible.
Contact allergens
Propylene glycol is used as a solvent, a vehicle for
topical medicaments such as corticosteroids or aciclovir,
an emulsifier and humectant in food and cosmetics,
and as antifreeze in breweries, in the manufactures
of resins. It was present as an occupational sensitizer
in the color film developer Flexicolor?. Patch tests in
aqua are sometimes irritant.
Safety Profile
Slightly toxic by
ingestion, skin contact, intraperitoneal,
intravenous, subcutaneous, and
intramuscular routes. Human systemic
effects by ingestion: general anesthesia,
convulsions, changes in surface EEG.
Experimental teratogenic and reproductive
effects. An eye and human skin irritant.
Mutation data reported. Combustible liquid
when exposed to heat or flame; can react
with oxidizing materials. Explosive in the
form of vapor when exposed to heat or
flame. May react with hydrofluoric acid +
nitric acid + silver nitrate to form the
explosive silver fulminate. To fight fire, use
alcohol foam. When heated to
decomposition it emits acrid smoke and
irritating fumes.
Potential Exposure
Propylene glycol is used as a solvent;
emulsifying agent; food and feed additive; flavor, in manu-
facture of plastics; as a plasticizer, surface-active agent;
antifreeze, solvent, disinfectant, hydroscopic agent; coolant
in refrigeration systems; pharmaceutical, brake fluid; and
many others.
Carcinogenicity
Dewhurst et al. and
Baldwin et al. in studies on the carcinogenicity of
other chemicals used propylene glycol as the solvent. As a
result they tested propylene glycol alone for carcinogenic
activity in rats and mice. Dewhurst et al. used a single
injection of 0.2 mL, whereas Baldwin et al. gave rats
and mice three to five subcutaneous injections, amount not
specified. In neither case were tumors observed during a
period of about a year or 2 years .
Wallenious and Lecholm applied propylene glycol
to the skin of rats three times a week for 14 months but found
no tumor formation. Stenback and Shubik confirmed
these findings when they applied propylene glycol at undiluted
strength and as a 50 and 10% solution in acetone to the
skin of mice during their lifetimes.
No tumors have been reported in the lifetime dietary
feeding studies . In fact, Gaunt et al.
specifically state that no tumors were found in the rats.
Environmental Fate
Propylene glycol can be released into the environment via
industrial releases or by disposal of consumer products.
Propylene glycol is readily soluble in water and has a low
sorption partition coefficient (KOC), so has the ability to move
through soil and to leach into ground water. Because of low
vapor pressure (0.1 mmHg at 25°C) and high water solubility,
there is minimal volatilization to the atmosphere from
surface water releases as well as substantial removal of its
vapors by wet deposition. Its low octanol/water partition
coefficient (KOW) indicates that bioconcentration and biomagnification
should not happen. Propylene glycol is readily
degraded in surface water and soil, by chemical oxidation and
microbial digestion, with a short half-life (1–5 days) in
aerobic or anaerobic conditions. It is also rapidly degraded in
the atmosphere by photochemical oxidation, with a half-life
about 1 day. Although environmental releases can and do
occur (airports must monitor storm water runoff of deicing
solutions), human health effects are likely to be minor, at
least in comparison to effects from potential exposures in
clinical scenarios.
Purification Methods
Dry the diol with Na2SO4, decant and distil it under reduced pressure. [Beilstein 1 IV 2468.]
Toxicity evaluation
Propylene glycol has a low degree of toxicity in animals as well
as humans, such that very high doses are needed to elicit effects
in acute toxicity studies. The toxic effects of propylene glycol
appear to be similar in animals and in humans. Central
nervous system (CNS) depression, hematologic toxicity,
hyperosmolarity, metabolic acidosis, cardiovascular effects,
and renal toxicity encompass the main acute and subacute
syndromes for propylene glycol. Most of the effects of
propylene glycol can be ascribed to high concentrations of the
parent molecule or to the accumulation of D,L-lactate in the
blood. Due to its alcohol moiety, propylene glycol at very high
concentrations is the most likely reason for the CNS depression.
Also, because high concentrations of propylene glycol will
increase the osmolarity of the blood, the hyperosmotic effects
are likely due to the parent molecule. The cardiovascular and
renal effects may be a result of the hyperosmolarity in combination
with the metabolic acidosis. The acidosis itself results
from the accumulation of lactate (both D- and L-forms), which
has been well documented in both animals and humans.
Incompatibilities
Incompatible with oxidizers (chlorates,
nitrates, peroxides, permanganates, perchlorates, chlorine,
bromine, fluorine, etc.); contact may cause fires or explo-
sions. Keep away from alkaline materials, strong acids
(especially nitric acid), strong bases, permanganates,
dichromates; may cause a violent reaction.
Waste Disposal
Dissolve or mix the
material with a combustible solvent and burn in a chemical
incinerator equipped with an afterburner and scrubber.All federal, state, and local environmental regulations must
be observed.
Check Digit Verification of cas no
The CAS Registry Mumber 57-55-6 includes 5 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 2 digits, 5 and 7 respectively; the second part has 2 digits, 5 and 5 respectively.
Calculate Digit Verification of CAS Registry Number 57-55:
(4*5)+(3*7)+(2*5)+(1*5)=56
56 % 10 = 6
So 57-55-6 is a valid CAS Registry Number.
InChI:InChI:1S/C3H8O2/c1-3(5)2-4/h3-5H,2H2,1H3
57-55-6Relevant articles and documents
Hydrogenation of lactic acid to propylene glycol over a carbon-supported ruthenium catalyst
Jang, Hyuk,Kim, Sung-Hwan,Lee, Duwon,Shim, Sang Eun,Baeck, Sung-Hyeon,Kim, Beom Sik,Chang, Tae Sun
, p. 57 - 60 (2013)
Catalytic hydrogenation of lactic acid to propylene glycol is performed in a high-pressure batch reactor over ruthenium on various carbon supports (i.e., VulcanXC-72, ketjen black, CNTs, CNFs, and graphite) prepared using the incipient wetness impregnation method. The crystallinity of the synthesized catalyst is investigated via X-ray diffraction, and the particle sizes are determined using transmission electron microscopy. The surface areas of the synthesized catalysts are analyzed using the BET method; the catalytic activity correlates remarkably with the BET surface area. The yield of propylene glycol increases with pressure, and the highest yield is achieved at 130 C. The catalytic activity is strongly dependent on the type of support. Among the catalysts tested, Ru on ketjen black shows the highest yield of propylene glycol.
Effect of nickel on catalytic behaviour of bimetallic Cu-Ni catalyst supported on mesoporous alumina for the hydrogenolysis of glycerol to 1,2-propanediol
Yun, Yang Sik,Park, Dae Sung,Yi, Jongheop
, p. 3191 - 3202 (2014)
The catalytic conversion of glycerol to 1,2-propanediol by hydrogenolysis has potential use in the commercial biomass industry. However, the high hydrogen pressure required for the reaction is a major drawback. To overcome this limitation, in this study, we added nickel metal to a copper-based catalyst for both supplying hydrogen via aqueous-phase reforming (APR) of glycerol and improving selectivity for 1,2-propanediol in hydrogenolysis. The bimetallic Cu-Ni catalyst supported on mesoporous alumina (MA) was prepared by a sol-gel method. The prepared Cu-Ni catalyst contains ordered mesopores with high surface area and well-dispersed active sites, as confirmed by BET, TEM, XRD, and TPR. The 9Cu-1Ni/MA (molar ratio of copper to nickel: 9:1) catalyst showed the highest catalytic performance among the various xCu-yNi/MA catalysts in a low pressure of H2. The XPS results showed that the surface ratio of Ni to (Cu + Ni) and Cu0/(Cu0 + Cu2+) is closely related to catalytic performance, selectivity and yield. The effect of nickel on the hydrogen production was experimentally proven by the time-on-stream tests over monometallic (Cu) and bimetallic (Cu-Ni) catalysts in the absence of hydrogen. The optimum value of the ratio of Ni to Cu is varied with the conditions in the presence of H2. The reaction mechanism was proposed for the Cu-Ni bimetallic catalysts for hydrogenolysis with APR of glycerol. the Partner Organisations 2014.
A significant enhancement of catalytic activities in oxidation with H 2O2 over the TS-1 zeolite by adjusting the catalyst wettability
Wang, Liang,Sun, Jing,Meng, Xiangju,Zhang, Weiping,Zhang, Jian,Pan, Shuxiang,Shen, Zhe,Xiao, Feng-Shou
, p. 2012 - 2014 (2014)
Hydrophilic TS-1 (H-TS-1) with rich hydroxyl groups, which were confirmed by 29Si and 1H NMR techniques, exhibits much higher activities in the oxidation than conventional TS-1. This phenomenon is strongly related to the unique features of high enrichment of H2O2 on H-TS-1.
Hydrogenolysis of Glucose into Propylene Glycol over Pt/SiO2@Mg(OH)2 Catalyst
Gu, Minyan,Shen, Zheng,Zhang, Wei,Xia, Meng,Jiang, Jikang,Dong, Wenjie,Zhou, Xuefei,Zhang, Yalei
, p. 3447 - 3452 (2020)
One-pot selective conversion of glucose is a green approach compared with petroleum-based processes to produce 1,2-propylene glycol (1,2-PG), but its realization is hindered by various side reactions. Here we demonstrate a feasible strategy of Pt/SiO2@Mg(OH)2 core-shell catalyst to achieve the 1,2-PG yield of 53.8 % by a three-pronged promotion, including enhancement of the glucose-fructose isomerization and retro-aldol condensation (RAC), as well as re-conversion of by-product hexitol into 1,2-PG. We realized the in situ synthesis of the core-shell structure using a self-existent Mg(OH)2 base instead of an extraneous base in the hydrothermal process and it achieved a stable performance during reuse by protecting Pt from leaching.
Robust Iridium Coordination Polymers: Highly Selective, Efficient, and Recyclable Catalysts for Oxidative Conversion of Glycerol to Potassium Lactate with Dihydrogen Liberation
Sun, Zheming,Liu, Yaoqi,Chen, Jiangbo,Huang, Changyu,Tu, Tao
, p. 6573 - 6578 (2015)
Along with the rapid expansion of the biodiesel industry to deal with the world energy crisis, inexpensive glycerol is also produced in large scale as the main byproduct in biodiesel production via transesterification. Much attention has been paid to the development of environmentally benign technologies for the transformation of glycerol to valuable DL-lactic acid and its derivatives. Herein, a series of NHC-Ir coordination polymers were readily synthesized via reaction of some structurally rigid bis-benzimidazolium salts with iridium precursors under alkaline conditions and were successfully applied as robust self-supported catalysts in the oxidative dehydrogenation of glycerol to potassium lactate with dihydrogen liberation. Extremely high activity and selectivity were attained in open air under the mild reaction conditions even with ppm-level loadings of the catalysts, which were readily recovered after reaction by simple filtration and reused for up to 31 runs without obvious loss of activity or selectivity. Probably owing to the effective suppression of inactive binuclear iridium species in a homogeneously catalyzed reaction, the catalysts assembled via self-supported strategy exhibited high selectivity and productivity for potassium lactate, with up to 1.24 × 105 turnover numbers (TON) being attained even in large-scale reactions of neat glycerol at an elevated temperature. The high catalytic activity, recyclability, and scalability of the robust self-supported catalysts highlight their potential toward the development of practical technologies for transformation of glycerol to value-added chemicals.
Kinetics and mechanism of the catalytic hydration of propylene oxide
Shaikhutdinov,Petukhov,Sapunov,Kharlampidi,Petukhov
, p. 50 - 55 (2010)
The kinetics of propylene oxide hydration in the presence of bis(ethane-1,2-diol)molybdate is reported. A mathematical description of PO disappearance and propylene glycol formation is suggested. The most probable scheme for the process is presented. The basic kinetic constants are calculated.
Determination of intramolecular δ13C from incomplete pyrolysis fragments. Evaluation of pyrolysis-induced isotopic fractionation in fragments from the lactic acid analogue propylene glycol
Wolyniak, Christopher J.,Sacks, Gavin L.,Metzger, Sara K.,Brenna, J. Thomas
, p. 2752 - 2757 (2006)
Intramolecular carbon isotope ratios reflect the source of a compound and the reaction conditions prevailing during synthesis and degradation. We report here a method for determination of relative (Δδ13C) and absolute (δ13C) intramolecular isotope ratios using the volatile lactic acid analogue propylene glycol as a model compound, measured by on-line gas chromatography-pyrolysis coupled to GC-combustion-isotope ratio mass spectrometry. Pyrolytic fragmentation of about one-third of the analyte mass produces optimal fragments for isotopic analysis, from which relative isotope ratios (Δδ13C) are calculated according to guidelines presented previously. Calibration to obtain absolute isotope ratios is achieved by quantifying isotope fractionation during pyrolysis with an average fractionation factor, α, and evaluated by considering extremes in isotopic fractionation behavior. The method is demonstrated by calculating ranges of absolute intramolecular isotope ratios in four samples of propylene glycol. Relative and absolute isotope ratios were calculated with average precisions of SD(Δδ13C) 13C) 13C range of 2‰ for each position in each sample. Relative isotope ratios revealed all four samples originated from unique sources, with samples A, B, and D only distinguishable at the position-specific level. Regardless of pyrolysis fractionation distribution, absolute isotope ratios showed a consistent pattern for all samples, with δ 13C(3) > δ13C(2) > δ13C(1). The validity of the method was determined by examining the difference in relative isotope ratios calculated through two independent methods: Δδ13C calculated directly using previous methods and Δδ13C extracted from absolute isotope ratios. Deviation between the two Δδ13C values for all positions averaged 0.1-0.2‰, with the smallest deviation obtained assuming equal fractionation across all fragment positions. This approach applies generally to all compounds analyzed by pyrolytic PSIA.
Stability and regeneration of Cu-ZrO2 catalysts used in glycerol hydrogenolysis to 1,2-propanediol
Durán-Martín,Ojeda,Granados, M. López,Fierro,Mariscal
, p. 98 - 105 (2013)
A series of Cu-ZrO2 catalysts with different copper contents have been prepared by the coprecipitation method. Their catalytic behavior was studied for glycerol hydrogenolysis reaction to obtain 1,2-propanediol (1,2-PDO) joint to deactivation mechanism and regeneration protocols. A number of physical chemical techniques as X-ray diffraction (XRD), evolved gas analysis by mass spectrometry (EGA-MS), temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS) and chemical analysis have been used to characterize the precursors, activated and spent catalysts. Cu-ZrO2 catalysts with higher atomic ratio Cu/Zr showed higher selectivity while glycerol conversion values were not significantly changed. In terms of stability a decreasing of yield to 1,2-PDO due to a decrease of its selectivity was observed with the number of cycles. The main cause of deactivation was associated to the progressive formation of organic deposits on the surface of catalyst. A regeneration process highly efficient, where almost complete recovery of yield to 1,2-PDO shown by the fresh catalyst was reached, has been identified.
Selective hydrogenolysis of glycerol to propanediols on supported Cu-containing bimetallic catalysts
Zhou, Jinxia,Guo, Liyuan,Guo, Xinwen,Mao, Jingbo,Zhang, Shuguang
, p. 1835 - 1843 (2010)
Supported Cu-containing bimetallic catalysts were prepared and used to convert glycerol to propanediols. The effects of supports, metals, metal loadings, and impregnation sequences were examined. A synergistic effect was observed between Cu and Ag when they were impregnated on γ-Al 2O3. Characterizations revealed that the addition of Ag not only resulted in an in situ reduction of CuO, but also improved the dispersion of the Cu species on the support. A CuAg/Al2O3 catalyst with optimal amounts of Cu and Ag (Cu/Ag molar ratio 7:3, 2.7 mmol Cu+Ag per gram of γ-Al2O3) showed a near 100% selectivity to propanediols with a glycerol conversion of about 27% under mild reaction conditions (200 °C, 1.5 MPa initial H2 pressure, 10 h, (Cu+Ag)/glycerol molar ratio of 3/100). Compared with a commercial copper chromite catalyst commonly used for this reaction, the CuAg/Al2O 3 catalyst had much higher activity and did not need a reduction pretreatment.
Shape effect of ZnO crystals as cocatalyst in combined reforming- hydrogenolysis of glycerol
Hu, Jiye,Fan, Yiqiu,Pei, Yan,Qiao, Minghua,Fan, Kangnian,Zhang, Xiaoxin,Zong, Baoning
, p. 2280 - 2287 (2013)
Disk- and rod-shaped hexagonal ZnO crystals with various length-to-diameter aspect ratios were controllably synthesized via a facile solution route by adjusting the precursor concentration. The shape and the dimension of the synthesized ZnO crystals were observed by scanning electron microscopy (SEM). The wurtzite structure and the growth habit were determined by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) coupled with selected-area electron diffraction (SAED). It is found that with the lowering of the precursor concentrations, the ZnO crystals were elongated along the c-axis, and the diameter of the {001} planes was reduced, leading to shape evolution from hexagonal disk to prismatic rod. As a result, the ZnO crystals were different from each other in the proportion of the {100} nonpolar planes and the {001} polar planes. The well-defined ZnO crystals were used as the cocatalyst with skeletal Ni40Mo10 in the combined reforming-hydrogenolysis (CRH) of glycerol in the absence of adventitious H 2. A remarkable shape-dependent effect on the selectivity to the C3 hydrogenolysis products and the production rate of 1,2-propandiol (1,2-PDO) was identified. ZnO with a larger proportion of the nonpolar planes was more effective in the CRH of glycerol to the C3 products. An excellent linear relationship between the surface area of the {100} nonpolar planes and the production rate of 1,2-PDO was identified. This is attributed to the in situ enhancement of the Lewis acidity of the nonpolar planes of ZnO by chemisorbed CO2 from the reforming of glycerol, which greatly accelerates the dehydration of glycerol to acetol, the intermediate to 1,2-PDO.
