Hydroxyapatite Catalysts Research Articles

Formaldehyde Total Oxidation on Manganese-Doped Hydroxyapatite: The Effect of Mn Content

An aqueous impregnation method using manganese (II) nitrate precursor, followed by calcination at 400 °C, was carried out for the preparation of manganese doped hydroxyapatite catalysts (MnxHap; x = Mn wt.%: 2.5, 5.0, 10, 20, and 30 based on MnO2). Methods of characterization including inductively coupled plasma spectroscopy (ICP), N2 physisorption, X-ray Diffraction (XRD), Fourier-Transform Transmission Infrared (FT-IR), Raman, and Thermal gravimetric analysis (TGA/MS) analysis were used for the identification of Mn species and its surrounding environment. Raman spectroscopy indicated the presence of the ε-MnO2 phase for Mn20Hap and Mn30Hap in agreement with the XRD results and the presence of β-MnOOH species for Mn5Hap and Mn10Hap. The formaldehyde total oxidation was investigated on these catalysts and it was shown that Mn5Hap was the most active catalyst, achieving a normalized rate of formaldehyde (HCHO) conversion into CO2 per mole of Mn of 0.042 h−1 at a temperature of 145 °C. The well dispersed oxidized manganese species on Hap with a medium Mn AOS (average oxidation state) were mainly responsible for this performance. Since HCHO was retained on the surface of all catalysts during the catalytic test, the combined Diffuse Reflectance Infrared Fourier Transform spectroscopy (DRIFT) experiment at room temperature and thermodesorption (TD)-FTIR identified formate species as their oxidation consumed surface OH groups. A stability test and moisture effect study showed that the presence of water vapor has a beneficial effect on the performances of the catalyst.

One-pot transesterification of non-edible Moringa oleifera oil over a MgO/K2CO3/HAp catalyst derived from poultry skeletal waste

A hydroxyapatite (HAp) catalyst support from poultry’s bones was derived and then modified with MgO/K2CO3 to generate a heterogeneous catalyst to produce biodiesel from a non-edible Moringa oleifera oil. The catalyst properties were analyzed with SEM, EDX-Map, XRD, FTIR, and N2 adsorption–desorption. A design of experiments by response surface methodology (RSM) via central composite design (CCD) including catalyst loading (1–5 wt%), temperature (40–80 °C), reaction time (50–250 min), and methanol to oil ratio (0.346–0.81 w/w) optimized the biodiesel yield. The P-value and F-value of the model proposed were 677.129 and <0.0001, respectively, thus the predictive model can identify the operating conditions that maximize biodiesel yield (99.3%). These conditions were catalyst loading of 4 wt%, reaction time of 200 min, methanol to oil weight ratio of 0.69, at 70 °C. The environmental performance (E-factor) was obtained 0.98, which indicates low waste generated from the process. The reusability of the catalyst was evaluated in 9 consecutive runs. The catalyst lost up to 40% of its activity, depending on the recovery method. The produced biodiesel complies with EN14214 and ASTM D6751 standards. Therefore, this investigation showed that MgO/K2CO3 can be used as a potential heterogeneous catalyst to produce biodiesel from non-edible Moringa oleifera oil.

Influence of Surface Formate Species on Methane Selectivity for Carbon Dioxide Methanation over Nickel Hydroxyapatite Catalyst

AbstractAbsence of mechanistic understanding of carbon dioxide (CO2) methanation reaction on nickel hydroxyapatite (NiHAP) and the nature of nickel chemical state hampers the enhancement of catalytic activity and selectivity for such material. A varying amount of oleic acid (OA) addition on NiHAP is found to have a strong influence on the chemical state of nickel as evidenced from x‐ray spectroscopy (XPS) and x‐ray absorption spectroscopy (XAS). The chemical state of nickel influences the amount of surface intermediate species which affects methane formation as observed in infra‐red spectroscopy. This suggests that varying amount of OA can influence the chemical state of nickel which is important in influencing the type of reaction intermediates on the NiHAP surface. Langmuir‐Hinshelwood model is validated for proposed reaction mechanism for the better performing catalyst. The findings reported here is useful for designing a hydroxyapatite‐based catalyst for CO2 utilization.

High Performance and Sustainable Copper-Modified Hydroxyapatite Catalysts for Catalytic Transfer Hydrogenation of Furfural

Designing and developing non-noble metal-based heterogeneous catalysts have a substantial importance in biomass conversion. Meerwein-Ponndorf-Verley (MPV) reaction is a significant pathway for eco-friendly catalytic transfer hydrogenation (CTH) of biomass derived furfural into furfuryl alcohol. In this work, a series of copper-supported hydroxyapatite (HAp) catalysts with different copper loadings (2–20 wt.%) were prepared by a facile impregnation method and tested in the reduction of furfural to furfuryl alcohol using 2-propanol as a hydrogen donor. The structural and chemical properties of the synthesised catalysts were analysed by using various techniques (XRD, N2 sorption, SEM, TEM, UV-DRS, ICP, FTIR, TPR, TPD-CO2 and N2O titration). The effect of copper loading was found to be significant on the total performance of the catalysts. The results demonstrate that 5CuHAp catalyst possess highly dispersed copper particles and high basicity compared to all other catalysts. Overall, 5CuHAp exhibited highest conversion (96%) and selectivity (100%) at 140 °C at 4 h time on stream. The optimised reaction conditions were also determined to gain the high activity.

Transformation of carbohydrates to 5-hydroxymethylfurfural with high efficiency by tandem catalysis

Production of 5-hydroxymethylfurfural (HMF) is a pivotal step in biorefinery. However, the intrinsic HMF production efficiency in traditional catalytic systems are low owing to the side-reactions. Here we report the highly efficient transformation of carbohydrates to HMF via tandem catalysis in heterogeneous catalytic system. The combination of Al and Sn co-modified hydroxyapatite catalyst (Al/Sn-HAP) with ionic liquid exhibit a low activation energy of 68.4 kJ mol-1, affording HMF yields of 70.5 and 46.6% at glucose loading of 10 and 40 wt%, respectively. Compared with other catalysts, Al/Sn-HAP exhibits remarkably higher Lewis acid concentration, specific surface area and pore dimeter with slight Brønsted acid, as are beneficial for glucose isomerization. The efficient conversion of maltose, cellobiose and starch to HMF are achieved via the triple tandem pathway consisted of hydrolysis, isomerization and dehydration with inhibited side-reaction. Besides, the Al/Sn-HAP catalyst after regeneration can be reused without decrease of catalytic performance.

Comparative study of gas-phase “dehydration” of alkyl lactates and lactic acid for acrylic acid production over hydroxyapatite catalysts

Gas-phase “dehydration” of methyl (ML) and ethyl lactates (EL) for acrylic acid (AA) production was studied and compared with the dehydration of lactic acid (LA) over serial hydroxyapatite catalysts of varying compositions (HAPm-360, molar Ca/P ratio m = 1.58–1.68, calcination temperature: 360 °C). The product distribution from both lactic esters was found very similar to that from LA; AA but not methyl (MA) or ethyl acrylate (EA) also appeared as the prevailing product (> 50 mol% by selectivity) from both ML and EL. Compared with the reaction of LA, both esters showed much lower reactivity but higher AA selectivity. Among the two esters EL was less reactive but produced a higher selectivity for AA formation. Correlating the AA selectivity or yield with the catalyst surface acid-base property uncovers that a suitable balance between the surface acidity and basicity (or acidity/basicity ratio) is the key to the lactic ester-to-AA reactions. However, the optimum surface acidity/basicity ratio for producing the highest AA selectivity from both esters was higher than that from LA. These results suggest that the lactic ester-to-AA reactions proceeded by catalytic tandem processes involving a formation of LA (or adsorbed lactate) as the key intermediate at the catalyst surface. Acid-base catalysis responsible for these observations is discussed.

Preparation of KI/Hydroxyapatite Catalyst from Phosphate Rocks and Its Application for Improvement of Biodiesel Production.

The main aim of this work was to investigate the suitability of a KI/KIO3 impregnated hydroxyapatite (HAP) catalyst derived from natural phosphate rocks for biodiesel production. This study evaluated the effect of impregnation concentrations (1–6% w/w) on the catalyst performance in biodiesel production. The biodiesel was produced from waste cooking oil (WCO) under simultaneous esterification-transesterification reactions at 60 °C for 6 h. The results showed that the biodiesel yield increased by increasing impregnation concentration and the maximum yield (91.787%) was achieved at an impregnation concentration of 5% w/w. The KI/HAP catalyst showed better performance (91.78% biodiesel yield, 59.1% FAME yield and surface area of 13.513 m2/g) as compared to the KIO3/HAP catalyst (90.07% biodiesel yield, 55.0% FAME yield and surface area of 10.651 m2/g).

Selectively Chemocatalytic Conversion of Fructose to 1,2‐Propylene Glycol over Ru‐WOx/Hydroxyapatite Catalyst†

Summary of main observation and conclusionThe conversion of fructose to 1,2‐propylene glycol (PG) is an important process from cellulosic biomass to high‐value added chemicals. Herein, Ru‐WOx/hydroxyapatite (HAP) catalyst was employed for this reaction and reached up to 91.3% yield of PG at 180 °C, 1 MPa initial hydrogen for 8 h in water. On this catalyst, Ru and WOx were highly dispersed on HAP support and they interacted with each other to form a special catalytic center. The lack of isolated Ru or RuW alloy site led to a moderate activity for hydrogenolysis and hindered the further conversion of PG to propanol. The weak basic HAP support efficiently prevented the humin formation. This precisely controlled catalyst has potential in green PG production.

Waste quail beaks as renewable source for synthesizing novel catalysts for biodiesel production

In the current study, waste biomass (quail beaks) has been considered for synthesizing highly active hydroxyapatite (HAp) catalyst and used for biodiesel production. The produced HAp is characterized by several analytical techniques such as Thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), Hammett indicator-benzene benzoic acid titration method and BET surface area. TGA/DSC analysis confirmed the complete removal of organic matter from the raw quail beaks. The XRD results revealed that the crystallinity of HAp phase was enhanced by thermal calcination with crystallite size of 37.33 nm at 900 °C. FTIR results showed the peaks of phosphate (PO4−3) and hydroxyl groups (OH−1) belonging to HAp molecules. EDX analysis revealed the presence of calcium (Ca) and phosphorus (P) compositions were 28.5 and 11.4 wt %, respectively. Total basicity and BET surface area of the synthesized catalyst were found to be 12.9 mmol/g and 4.54 m2/g, respectively. Furthermore, the treated HAp at temperature of 900 °C was used for biodiesel production from canola oil, rapeseed oil and waste cooking oil. Thus, HAp was opted to be highly active for biodiesel production with promising reusability.

Kinetic Modeling of Alcohol Oligomerization over Calcium Hydroxyapatite

Guerbet coupling to oligomerize ethanol to heavy alcohols over a hydroxyapatite (HAP) catalyst is explored through the development and application of a reaction kinetics model that describes coupli...

Mn Supported on Ce Substituted Hydroxyapatite for VOC Oxidation: Catalytic Activity and Calcination Effect

The Mn supported on Ce substituted hydroxyapatite (HAp) catalyst was prepared by co-precipitation method and investigated for the low-temperature oxidation of toluene as a model component of VOC. The present work demonstrated the substitution of Ce in HAp in place of Ca. Furthermore, the effect of calcination temperature on oxidation activity of the catalyst was examined by calcining the catalyst at 400, 500 and 600 °C. The low-temperature calcination could favour the insertion of Ce in HAp, whereas higher calcination temperature could lead to the formation of separate CeO2 phase. The catalyst was characterized by using XRD, surface area, XPS, H2-TPR, ATR-FTIR techniques. The probable bonding between Ce and hexagonal HAp, which favors the oxidation of toluene at lower temperature has been explained with the calcination effect. The Ce substitution in HAp leads to the decrease in toluene activation energy which consequently increases the toluene conversion rate. The improvement in Mn2O3/Mn3O4 ↔ MnO2 redox cycle was observed due to the Ce substitution compared to unsubstituted Mn supported on HAp. The ATR-FTIR toluene adsorption study demonstrated the plausible mechanism of toluene oxidation. The activation of toluene on Ce substituted catalyst surface could proceed through the adsorption of the –CH3 group, whereas toluene adsorbed on unsubstituted catalyst surface through ortho, meta or para C–H bond.

New possibility of hydroxyapatites as noble-metal-free catalysts towards complete decomposition of volatile organic compounds

Initially established catalysis mechanism for the decomposition of VOCs on noble-metal-free hydroxyapatite catalysts.

Cobalt Incorporated Hydroxyapatite Catalyst for Water Oxidation

AbstractWe report the novel oxygen evolution reaction (OER) catalyst based on cobalt incorporated hydroxyapatite (CoHAP). Our catalyst is prepared on the surface of hydroxyapatite by ion exchange reaction in Co2+ aqueous solution. The cobalt content is approximately 1 wt. % based on ICP‐AES and XPS experiments. XRD, TEM, EDX experiments suggest that individual cobalt ions are adsorbed on the HAP surface in non‐aggregated manner. The cyclic voltammetry (CV) of CoHAP exhibits a weak oxidation peak at 1.10 V which is comparable to CV of in‐situ formed Co−Pi in previous literature. Tafel slope is approximately 80 mV/decade which is independent on the loading amount of CoHAP. The Faradaic efficiency is 94 % measured by quantitative analysis of O2 using gas chromatography. Bulk electrolysis verifies that CoHAP can be utilized OER catalyst at neutral pH with high stability. Our preparation method using hydroxyapatite as a solid phase phosphate source offers a new strategy to fabricate the OER catalysts.

Direct, Selective Production of Aromatic Alcohols from Ethanol Using a Tailored Bifunctional Cobalt–Hydroxyapatite Catalyst

Aromatic alcohols are essential components of many solvents, coatings, plasticizers, fine chemicals, and pharmaceuticals. Traditional manufacturing processes involving the oxidation of petroleum-de...

Propanol Amination over Supported Nickel Catalysts: Reaction Mechanism and Role of the Support

Ni-supported hydroxyapatite catalyst (Ni/HAP) was characterized and evaluated for propanol amination to propylamine at 423 K. The reaction proceeds via dehydroamination, a process that involves sequential dehydrogenation, condensation, and hydrogenation. Kinetic and isotopic studies indicate that α-H abstraction from propoxide species limits the rate of the dehydrogenation step and hence the overall rate of reaction. The rate of propanol dehydrogenation depends on the composition of the support and on the concentration of Ni sites located at the interface between Ni nanoparticles and the support. Ni/HAP is an order of magnitude more active than Ni/SiO2 and displays a higher selectivity toward the primary amine. The superior performance of Ni/HAP is attributed to the high density of basic sites on HAP, which are responsible for stabilizing alkoxide intermediates and suppressing the disproportionation and secondary amination of amines.

Comparative performance of copper and iron functionalized hydroxyapatite catalysts in NH3-SCR

Iron-functionalized hydroxyapatite (Fe/HAP, 2 < Fe wt% < 7) was prepared by ionic exchange and tested in the NOx reduction by ammonia (NH3-SCR). Iron dispersion, structure and acidity of the samples were investigated by UV–vis-DR spectroscopy, XRPD and ammonia titration. On Fe/HAP catalysts, NOx conversion started at higher temperatures and was always lower than on the reference Cu/HAP catalysts. Selectivity to N2 was remarkable (>95%) up to the attainment of maximum NOx conversion; for higher temperatures, selectivity declined due to the formation of N2O from NH3 over-oxidation. TPR-TPO cycles allowed to relate the redox properties of samples with their catalytic performances.

CATALYTIC ACTIVITY AND COKING RESISTANCE ON HYDROXYAPATITE FOR THE OXIDATIVE DEHYDROGENATION OF ISOBUTANE

Hydroxyapatite (HAp) samples were prepared from precursor solutions with different Ca/P molar ratios. The HAp samples were utilized as catalysts for the oxidative dehydrogenation (ODH) of isobutane. Also, the HAp samples were characterized by N2 and H2O adsorption-desorption measurements, X-ray diffraction, inductively coupled plasma optical emission spectrometry, thermogravimetry-differential thermal analyses, and temperature-programmed oxidation (TPO). The Ca/P molar ratio of the precursor solution had a major influence on the catalytic activity and coking resistance ability. The HAp catalyst prepared from the stoichiometric precursor solution [HAp (1.67)] showed the highest isobutene yield. Furthermore, the white color of HAp (1.67) remained unchanged during the ODH of isobutene, indicating the absence of coke on the surface of HAp (1.67) after the reaction and its higher coking resistance ability. The results of the TPO measurements showed that the HAp (1.67) catalyst possesses the strongest oxidation ability which is likely related to its higher coking resistance ability.

Efficient Ketose Production by a Hydroxyapatite Catalyst in a Continuous Flow Module

Ketose is a valuable industrial ingredient, but there is no effective synthetic method for ketoses. A hydroxyapatite (HAp)-loaded flow system was developed for atom-economical ketose preparation. T...

Insight into Deactivation Behavior and Determination of Generation Time of the Hydroxyapatite Catalyst in the Dehydration of Lactic Acid to Acrylic Acid

For the purpose of industrial applications, deactivation behavior of the hydroxyapatite catalyst was studied in the dehydration of lactic acid to acrylic acid. The hydroxyapatite catalyst shows stable acrylic acid selectivity with 140 h on stream. Obvious increases in acetaldehyde and lactide selectivities were observed from 140 to 250 h, which resulted in a decrease of sharp acrylic acid selectivity. The fresh and used hydroxyapatite catalysts were further characterized by techniques including N2 adsorption–desorption, X-ray diffraction, transmission electron microscopy, 13C cross-polarization magic-angle spinning nuclear magnetic resonance, thermal gravity analysis, and temperature-programmed desorption of CO2 and NH3. These results indicate that the mechanism of coke deactivation consists of two steps. One is the formation of aliphatic carbon by the deposition of low carbon products with 140 h; the other is the formation of aromatic coke by the condensation of lactide. Also, the best generated time of 140 h was determined.

Behaviour of Rh supported on hydroxyapatite catalysts in partial oxidation and steam reforming of methane: On the role of the speciation of the Rh particles

Rh/hydroxyapatite samples were prepared by impregnation and investigated for the partial oxidation (POM) and steam reforming (SRM) of methane. The catalysts were analysed by BET, XRD, DRS, XPS, H2-TPR, TEM, H2 chemisorption, CO2-TPD and NH3-TPD techniques. The characterisation results showed that, after calcination, Rh existed in three different forms in the samples: (i) large crystallites of Rh2O3 deposited on the surface of the catalysts, (ii) RhOx in small particles exhibiting strong interaction with the support and (iii) a phase of Rh2+ species which incorporated the hydroxyapatite framework.Operating in the POM and SRM processes the reduced Rh(x)/HAP catalysts resulted highly active and exhibited excellent stability at 973 K (for 30 h). This behaviour was explained by their high coke-resistance. The activity of the catalyst with the optimum loading (1%), in SRM, was compared with that of a commercial Rh/Al2O3 catalyst. The conversion and H2 and CO yields values achieved on the former were all close to those exhibited by the latter. This comparable behaviour was explained by suitable properties provided by the HAP support such as reducibility, lower surface acidity and larger pore sizes (ensuring a better diffusion of the reactants and the products during the SRM reaction). These properties seemed to compensate the low dispersion of the Rh active phase induced by its low specific surface area.