Dehydroxylation of glycerol on nickel-containing catalysts: A method of utilization of glycerol in biodiesel production

The catalytic dehydroxylation of glycerol in a flow mode was studied. This is one of the methods for utilization of excess glycerol accumulated during the production of biodiesel fuel. Raney nickel and Ni-Cr₂O₃ were used as catalysts. The possibility of glycerol dehydroxylation on Raney nickel and Ni-Cr₂O₃ catalysts in flow units was studied for the first time. The Raney catalyst showed higher activity in glycerol dehydroxylation compared with Ni-Cr₂O₃. At 220°C and 2 MPa, the conversion of glycerol and the yield of 1,2-propanediol was 88 and 35% on Raney nickel versus 16 and 6.5% on Ni-Cr₂O₃, respectively. The reaction under the given conditions, however, formed large amounts of by-products: ethylene glycol, simple alcohols, and methane. At pressures of H₂ of over 2 MPa, the yield of the acetol by-product decreased considerably, ultimately increasing the efficiency of the process. The Raney catalyst can be used for the dehydroxylation of glycerol in flow units under relatively mild conditions (up to 240°C and 2 MPa).     

Glycerol Hydrogenolysis to 1,2-Propanediol by Cu/ZnO/Al2O3 Catalysts

The effect of preparation methods on the Cu/ZnO/Al₂O₃ catalyst structure and catalytic activity on liquid glycerol hydrogenolysis to 1,2-propanediol has been investigated. The physicochemical properties of the catalysts were characterized by BET, XRD, TG/DTA, NH₃-TPD and TPR. The experimental results showed that the catalyst prepared by an oxalate gel–coprecipitation had the highest activity. At 200 °C and 400 psi hydrogen pressure, the glycerol conversion and 1,2-propanediol selectivity catalyzed by the Cu/ZnO/Al₂O₃ catalyst prepared via oxalate gel–coprecipitation were 92.3 and 94.5 % respectively. It was found that the 1,2-propanediol selectivity was dependent on hydrogen pressure and the un-desired by-products were mainly due to the side reactions caused by the presence of the intermediate acetol.     

Glycerol Hydrogenolysis to 1,2-Propanediol by Cu/ZnO/Al2O3 Catalysts

The effect of preparation methods on the Cu/ZnO/Al₂O₃ catalyst structure and catalytic activity on liquid glycerol hydrogenolysis to 1,2-propanediol has been investigated. The physicochemical properties of the catalysts were characterized by BET, XRD, TG/DTA, NH₃-TPD and TPR. The experimental results showed that the catalyst prepared by an oxalate gel–coprecipitation had the highest activity. At 200 °C and 400 psi hydrogen pressure, the glycerol conversion and 1,2-propanediol selectivity catalyzed by the Cu/ZnO/Al₂O₃ catalyst prepared via oxalate gel–coprecipitation were 92.3 and 94.5 % respectively. It was found that the 1,2-propanediol selectivity was dependent on hydrogen pressure and the un-desired by-products were mainly due to the side reactions caused by the presence of the intermediate acetol.

     

Hydrogenolysis of glycerol with FeCo macrocyclic complex bonded to Raney Nickel support under mild reaction conditions

The hydrogenolysis of dilute glycerol solution to 1,2‐propanediol was studied in the presence of heterogeneous catalyst (FeCoL/Raney Nickel) having a heterodinuclear FeCo macrocyclic complex ionically bonded to Raney Nickel. Studies on the stability of the complex bonded to the support were carried out at different temperature as well as the effect of solvent to confirm that it was stable up to 600°C and 100 h of refluxing. In the hydrogenolysis of glycerol, the temperature has been varied from 165 to 220°C with an initial hydrogen pressure 0.35 MPa and the conversion increases from 1% to 36% with no gases evolving in this temperature range. The major product is 1,2‐propanediol which is formed with 80% selectivity. The initial water content (20–60%) in the feed was also varied and it was found that the conversion and yield of 1,2‐propanediol increases when the water content increases. Based on literature, a kinetic model was proposed and optimal rate constants determined using Genetic Algorithm (GA).     

Aqueous-Phase Hydrogenolysis of Glycerol to 1,3-propanediol Over Pt-H<Subscript>4</Subscript>SiW<Subscript>12</Subscript>O<Subscript>40</Subscript>/SiO<Subscript>2</Subscript>

Abstract  

Hydrogenolysis of glycerol to 1,3-propanediol in aqueous-phase was investigated over Pt-H₄SiW₁₂O₄₀/SiO₂ bi-functional catalysts with different H₄SiW₁₂O₄₀ (HSiW) loading. Among them, Pt-15HSiW/SiO₂ showed superior performance due to the good dispersion of Pt and appropriate acidity. It is found that Br?nsted acid sites facilitate to produce 1,3-PDO selectively confirmed by Py-IR. The effects of weight hourly space velocity, reaction temperature and hydrogen pressure were also examined. The optimized Pt-HSiW/SiO₂ catalyst showed a 31.4% yield of 1,3-propanediol with glycerol conversion of 81.2% at 200 °C and 6 MPa.     

Hydrogenolysis of Glycerol to Propanediol Over Ru: Polyoxometalate Bifunctional Catalyst

Ruthenium-doped (5 wt%) acidic heteropoly salt Cs_2.5H_0.5[PW₁₂O₄₀] (CsPW) is an active bifunctional catalyst for the one-pot hydrogenolysis of glycerol to 1,2-propanediol (1,2-PDO) in liquid phase, providing 96% selectivity to 1,2-PDO at 21% glycerol conversion at 150 °C and an unprecedented low hydrogen pressure of 5 bar. Rhodium catalyst, 5%Rh/CsPW, although less active, shows considerable selectivity to 1,3-PDO (7.1%), with 1,2-PDO being the main product (65%).     

纳米CuO/SiO_2催化甘油氢解制备1,2-丙二醇反应研究

采用共沉淀法制备了纳米CuO/SiO2催化剂,在固定床反应器上考察了纳米催化剂对甘油催化加氢制1,2-丙二醇（1,2-PDO）的催化活性。结果表明,在反应温度200℃,反应压力1.0 MPa,n（H2）∶n（甘油）=30∶1,液空速0.30 h-1的条件下,甘油转化率100%,1,2-PDO选择性98.71%。     

Direct Conversion of Glycerol into 1,3-Propanediol over Cu-H4SiW12O40/SiO2 in Vapor Phase

Using a SiO₂ supported copper and H₄SiW₁₂O₄₀ catalyst, it is demonstrated that glycerol can be directly converted to 1,3-Propanediol (1,3-PD) through vapor-phase process under pressure below 0.54 MPa, without employing environmentally harmful organic solvent. The formation of 1,3-PD is proved to proceed through the designed reaction pathway: (step 1) dehydration of glycerol to 3-hydroxypropanal on acid site of supported H₄SiW₁₂O₄₀ (step 2) hydrogenation of 3-hydroxypropanal on supported copper metal. The effect of temperature, weight hourly space velocity, pressure, and initial water content was investigated to obtain the optimum conditions. The glycerol conversion and products distribution greatly depended on these factors. Both the 1,3-PD and 1,2-Propanediol selectivity improved with increasing hydrogen pressure. At 210 °C, 0.54 MPa and 83.4% conversion, the selectivity of 1,3-PD was up to 32.1%, together with a 22.2% selectivity of 1,2-Propanediol. The cyclic acetal, an important kind of byproducts, was identified by Gas Chromatogram–Mass Spectrometer (GC–MS).     

Ni/NaX: A Bifunctional Efficient Catalyst for Selective Hydrogenolysis of Glycerol

Non-noble metal Ni/NaX catalyst was prepared and used in the hydrogenolysis of aqueous glycerol. Characterization by XRD, SAED, H₂ chemisorption, ICP and NH₃-TPD techniques disclosed that the proper strong acid sites were responsible for the high activity and selectivity. Over Ni/NaX catalyst, conversion of glycerol reached 86.6% with 94.6% selectivity to glycols including 1,2-proplyene glycol and ethylene glycol under 6.0 MPa H₂ pressure at 200 °C after 10 h reaction. Additionally, the effects of time, temperature, and H₂ pressure were investigated in detail.     

Polyol hydrogenolysis on supported Pt catalysts: Comparison between glycerol and 1,2-propanediol

Pt-based catalysts supported on TiO₂ and SIRAL 20 (Al₂O₃–20 wt.%SiO₂) were prepared and characterized by H₂ chemisorption, FTIR of adsorbed pyridine and 3,3-dimethyl-1-butene isomerization. The catalysts were evaluated for the transformation under aqueous phase of glycerol and 1,2-propanediol at 210 °C, under 60 bar as total pressure (H₂ atmosphere). Under similar conditions, 1,2-propanediol is easier converted than glycerol, indicating that in the glycerol transformation process in aqueous phase, the 1,2-propanediol reactivity is inhibited by the presence of glycerol. This behavior is explained by a strong adsorption of glycerol compared to 1,2-propanediol on the catalyst surface.     

Continuous production of 1,2‐propanediol by the selective hydrogenolysis of solvent‐free glycerol under mild conditions

BACKGROUND: The conversion of glycerol to value‐added derivatives is now critical, owing to the large surplus of glycerol from biodiesel production. The main objective of this work is to develop a novel process for converting solvent‐free glycerol to 1,2‐propanediol. RESULTS: Several catalysts were screened for aqueous‐phase hydrogenolysis of glycerol in an autoclave. The most effective catalysts (Ni/Al₂O₃, Cu/ZnO/Al₂O₃) were further tested for vapor phase hydrogenolysis in a fixed‐bed. Ni/Al₂O₃ did not prove as effective for the production of 1,2‐propanediol because of the high selectivity to CH₄ and CO. Over Cu/ZnO/Al₂O₃, glycerol was mainly converted to the desired 1,2‐propanediol and the reaction intermediate acetol. The production of 1,2‐propanediol was favoured at higher hydrogen pressure. At 190 °C and 0.64 MPa, near complete conversion of glycerol was achieved with 1,2‐propanediol selectivity up to 92%. In addition, a higher concentration (between 43.4% and 0.8%) of acetol was detected and an approximately stoichiometric relationship was found between acetol and 1,2‐propanediol. CONCLUSION: 1,2‐propanediol can be produced with high yields via the vapor phase hydrogenolysis of glycerol over Cu/ZnO/Al₂O₃. Furthermore, the mechanism of 1,2‐propanediol formation is suggested to proceed mainly through an acetol route over Cu/ZnO/Al₂O₃. Copyright © 2008 Society of Chemical Industry     

常压、无氢气添加条件下催化甘油转化制1,2-丙二醇

在常压、无氢气添加的固定床反应器上考察了Na2CO3负载型催化剂对甘油歧化制1,2-丙二醇的催化性能,并研究了负载量、反应温度和流速等对甘油水溶液歧化制1,2-丙二醇反应性能的影响。结果表明,5.0%Na2CO3/AC催化剂具有较高的活性,在反应温度300℃,甘油水溶液流速为2 mL/h的反应条件下,得到甘油的转化率为94.4%,1,2-丙二醇的产率为21.4%。用表面测试仪和傅里叶红外光谱对催化剂进行了表征。     

Conversion of oils to monoglycerides by glycerolysis in supercritical carbon dioxide media

Glycerolysis of soybean oil was conducted in a supercritical carbon dioxide (SC-CO₂) atmosphere to produce monoglycerides (MG) in a stirred autoclave at 150–250°C, over a pressure range of 20.7–62.1 MPa, at glycerol/oil molar ratios between 15–25, and water concentrations of 0–8% (wt% of glycerol). MG, di-, triglyceride, and free fatty acid (FFA) composition of the reaction mixture as a function of time was analyzed by supercritical fluid chromatography. Glycerolysis did not occur at 150°C but proceeded to a limited extent at 200°C within 4 h reaction time; however, it did proceed rapidly at 250°C. At 250°C, MG formation decreased significantly (P<0.05) with pressure and increased with glycerol/oil ratio and water concentration. A maximum MG content of 49.2% was achieved at 250°C, 20.7 MPa, a glycerol/oil ratio of 25 and 4% water after 4 h. These conditions also resulted in the formation of 14% FFA. Conversions of other oils (peanut, corn, canola, and cottonseed) were also attempted. Soybean and cottonseed oil yielded the highest and lowest conversion to MG, respectively. Conducting this industrially important reaction in SC-CO₂ atmosphere offered numerous advantages, compared to conventional alkalicatalyzed glycerolysis, including elimination of the alkali catalyst, production of a lighter color and less odor, and ease of separation of the CO₂ from the reaction products.     

Zirconia-supported niobia catalyzed formation of propanol from 1,2-propanediol via dehydration and consecutive hydrogen transfer

Vapor-phase catalytic dehydration of 1,2-propanediol was investigated over Zirconia-supported niobia catalysts. The catalysts exhibit selectivity favoring propanol (approximately 39%) at 85.0% 1,2-propanediol conversion at 290 °C under 1 atm N₂. The ZrNbO catalysts were analyzed by various techniques; the results indicated that the active sites were weak Brønsted acid sites. A dehydration and hydrogen transfer mechanism was also proposed.     

Vapor-phase hydrogenolysis of glycerol to 1,2-propanediol using a chromium-free Ni-Cu-SiO2 nanocomposite catalyst

A Ni-Cu-SiO₂ nanocomposite was studied as a catalyst for vapor-phase glycerol hydrogenation to produce 1,2-propanediol (1,2-PDO). Substitution of a small amount (3 wt%) of Ni for Cu is beneficial for decreasing the Cu particle size, which would be advantageous for attaining higher 1,2-PDO selectivity and higher glycerol conversion. 92% 1,2-PDO selectivity and 100% glycerol conversion were obtained at 220 °C, 30 bar, and a weight hourly space velocity of 0.5 h^− 1 over Ni(3)-Cu(77)-SiO_2, which were nearly identical to those obtained with the conventional copper chromite (CuO-Cr₂O₃) catalyst. Therefore, the present Ni(3)-Cu(77)-SiO₂ nanocomposite is regarded as a green and efficient catalyst for glycerol conversion into more valuable 1,2-PDO.     

Direct post-cracking of volatiles from coal hydropyrolysis: 1. Influence of post-cracking temperature

Direct post-cracking of volatiles from fixed-bed hydropyrolysis of bituminous coal at 580 °C and 1 MPa hydrogen pressure has been studied between 600 and 900 °C at residence times of 0.1 and 1 s. Results showed that post-cracking promotes the formation of gas, mainly methane, at the expense of oil yield. However, the oil composition was richer in benzene, toluene and xylenes (BTX fraction), in naphthalene and methylnaphthalenes, and poorer in phenol, cresols and xylenols (PCX) content. The optimum temperature for post-cracking under conditions investigated was ≈800 °C, but at this temperature the PCX yield was reduced by 40–60%. The PCX formation rate, from heavier phenols, was lower than the PCX dehydroxylation.     

Hydrogen generation from noncatalytic hydrothermolysis of ammonia borane for vehicle applications

Ammonia borane (AB) is a promising hydrogen storage material as it contains 19.6 wt % hydrogen. In this article, our recently developed hydrothermolysis approach to release hydrogen is studied over a wide range of AB concentrations (6–88 wt %), at pressure 14.7 and 200 psia, and temperature 85–135°C. It is shown that with increasing AB concentration up to 77 wt %, the H₂ yield increases, and that the role of thermolysis, when compared with hydrolysis, increases. The maximum hydrogen storage capacity, obtained at 77 wt % AB and T_reactor ～ 85°C along with rapid kinetics, was 11.6 and 14.3 wt % at pressure 14.7 and 200 psia, respectively. To our knowledge, on a material basis, the AB hydrothermolysis process is the first one to provide such high hydrogen yield values at near PEM fuel cell operating temperatures without use of catalyst, and thus is promising for use in fuel cell‐based vehicle applications. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Hydropyrolysis of 2,4-xylenol under pressure

The hydrocracking of 2,4-xylenol, chosen as a model compound for the hydropyrolysis of phenolic fractions was studied as a function of the following parameters: temperature, pressure, residence time and hydrogen partial pressure so as to determine the yield of light aromatic hydrocarbons (B T X) and the formation of light phenols (PC). These results, compared with those obtained by thermal pyrolysis, allow the determination of the experimental conditions under which the presence of hydrogen increases the yields of BTX, phenol and cresols instead of inducing the dehydroxylation of 2,4-xylenol. Under such conditions the amounts of solids and heavy liquid products are decreased. A postcracking temperature of 775 °C, a residence time less than 4 s, a total pressure of 1 MPa and a mole fraction of hydrogen of at least 0.25 lead to the highest yields of phenols and cresols; the yield of BTX increases with temperature, but is independent of pressure.     

Superacid coal chemistry. 2. Model compound studies under conditions of HF:BF3:H2 catalysed mild coal liquefaction

Selected model compounds representing coal structural entities were studied under the conditions of HF-BF₃-H₂ catalysed mild coal liquefaction. Bibenzyl and diphenylmethane gave near quantitative conversion at room temperature without added hydrogen. Biphenyl, however, required hydrogen pressure at 150 °C and gave a conversion of only ≈30%. Among the model compounds containing ether linkages, dibenzyl ether and benzyl phenyl ether gave quantitative conversion at room temperature without added hydrogen. Diphenyl ether in contrast was converted (≈70% yield) only under hydrogen pressure at 155 °C. Sulphur- and nitrogen-containing model compounds were also studied. At 95 °C in the absence of hydrogen, benzyl phenyl sulphide and dibenzyl sulphide gave over 95% conversion. On the other hand diphenyl sulphide and diphenyl disulphide required hydrogen pressure at 150 °C to give conversions of ≈95%. Quinoline gave a conversion of ≈20% under hydrogen pressure at 150 °C. The formation of condensation products in these conversion processes could be suppressed by the use of a good hydrogen donor, such as isopentane.     

Hydrogenolysis of Glycerol to Propanediols Over Highly Active Ru–Re Bimetallic Catalysts

Several supported Ru–Re bimetallic catalysts (Ru–Re/SiO₂, Ru–Re/ZrO₂, Ru–Re/TiO₂, Ru–Re/H-β, Ru–Re/H–ZSM5) and Ru monometallic catalysts (Ru/SiO₂, Ru/ZrO₂, Ru/TiO₂, Ru/H-β, Ru/H–ZSM5) were prepared and their catalytic performances were evaluated in the hydrogenolysis of glycerol to propanediols (1,2-propanediol and 1,3-propanediol) with a batch type reactor (autoclave) under the reaction conditions of 160 °C, 8.0 MPa and 8 h. Compared with Ru monometallic catalysts, the Ru–Re bimetallic catalysts showed much higher activity in the hydrogenolysis of glycerol, and Re exhibited obvious promoting effect on the performance of the catalysts. The supported Ru monometallic catalysts and Ru–Re bimetallic catalysts were characterized by N₂ adsorption/desorption, XRD, TEM-EDX, H₂-TPR and CO chemisorption for obtaining some physicochemical properties of the catalysts, such as specific surface areas, crystal phases, morphologies/microstructure, reduction behaviors and dispersion of Ru metal. The results of XRD and CO chemisorption indicate that the addition of Re component could improve the dispersion of Ru species on supports. The measurements of H₂-TPR revealed that the coexistence of Re and Ru components on supports changed the respective reduction behavior of Re or Ru alone on the supports, indicating the existence of synergistic effect between Ru and Re species on the bimetallic catalysts. The hydrogenolysis of some products (such as 1,2-propanediol, 1,3-propanediol, 1-propanol and 2-propanol) were also examined over Ru and Ru–Re catalysts for evaluating influence of Re–Re on the reaction routes during glycerol hydrogenolysis. The results showed that over Ru–Re catalysts, glycerol was favorable to be converted to 1,2-propanediol, but not favorable to ethylene glycol, while 1,2-propanediol and 1,3-propanediol were favorable to be converted to 1-propanol. The influence of glycerol concentration in its aqueous solution on the catalytic performance was also evaluated over Ru and Ru–Re catalysts.