Heterogeneous catalyzed biodiesel production from Moringa oleifera oil

In this study, biodiesel was produced from Moringa oleifera oil using sulfated tin oxide enhanced with SiO₂ (SO₄²⁻/SnO₂-SiO₂) as super acid solid catalyst. The experimental design was done using design of experiment (DoE), specifically, response surface methodology based on three-variable central composite design (CCD) with alpha (α) = 2. The reaction parameters studied were reaction temperature (60 °C to 180 °C), reaction period (1 h to 3 h) and methanol to oil ratio (1:6 to 1:24). It was observed that the yield up to 84 wt.% of Moringa oleifera methyl esters can be obtained with reaction conditions of 150 °C temperature, 150 min reaction time and 1:19.5 methanol to oil ratio, while catalyst concentration and agitation speed are kept at 3 wt.% and 350-360 rpm respectively. Therefore this study presents the possibility of converting a relatively new oil feedstock, Moringa oleifera oil to biodiesel and thus reducing the world's dependency on existing edible oil as biodiesel feedstock.     

An ideal feedstock, kusum (Schleichera triguga) for preparation of biodiesel: Optimization of parameters

Kusum (Schleichera triguga), a non-edible oil bearing plant has been used as an ideal feedstock for biodiesel development in the present study. Various physical and chemical parameters of the raw oil and the fatty acid methyl esters derived have been tested to confirm its suitability as a biodiesel fuel. The fatty acid component of the oil was tested by gas chromatography. The acid value of the oil was determined by titration and was found to 21.30 mg KOH/g which required two step transesterification. Acid value was brought down by esterification using sulfuric acid (H₂SO₄) as a catalyst. Thereafter, alkaline transesterification was carried out using potassium hydroxide (KOH) as catalyst for conversion of kusum oil to its methyl esters. Various parameters such as molar ratio, amount of catalyst and reaction time were optimized and a high yield (95%) of biodiesel was achieved. The high conversion of the feedstock into esters was confirmed by analysis of the product on gas chromatograph-mass spectrometer (GC-MS). Viscosity and acid value of the product biodiesel were determined and found to be within the limits of ASTM D 6751 specifications. Elemental analysis of biodiesel showed presence of carbon, hydrogen, oxygen and absence of nitrogen and sulfur after purification. Molar ratio of methanol to oil was optimized and found to be 10:1 for acid esterification, and 8:1 for alkaline transesterification. The amounts of H₂SO₄ and KOH, 1% (v/v) and 0.7% (w/w), respectively, were found to be optimum for the reactions. The time duration of 1 h for acid esterification followed by another 1 h for alkaline transesterification at 50 ± 0.5 °C was optimum for synthesis of biodiesel.     

Reactive extraction and in situ esterification of Jatropha curcas L. seeds for the production of biodiesel

Jatropha curcas L. has recently been hailed as the promising feedstock for biodiesel production as it does not compete with food sources. Conventional production of biodiesel from J. curcas L. seeds involve two main processing steps; extraction of oil and subsequent esterification/transesterification to fatty acid methyl esters (FAME). In this study, the feasibility of in situ extraction, esterification and transesterification of J. curcas L. seeds to biodiesel was investigated. It was found that the size of the seed and reaction period effect the yield of FAME and amount of oil extracted significantly. Using seed with size less than 0.355 mm and n-hexane as co-solvent with the following reaction conditions; reaction temperature of 60 °C, reaction period of 24 h, methanol to seed ratio of 7.5 ml/g and 15 wt% of H₂SO₄, the oil extraction efficiency and FAME yield can reached 91.2% and 99.8%, respectively. This single step of reactive extraction process therefore can be a potential route for biodiesel production that reduces processing steps and cost.     

In situ production of fatty acid methyl ester from low quality rice bran: An economical route for biodiesel production

Low quality rice bran was used to produce fatty acid methyl ester (FAME) via in situ extraction, esterification and transesterification process. The effects of the acid and alkaline catalysts on the ester yield, esterification and transesterification process were studied. When 75 ml of absolute methanol, 150 ml of petroleum ether, 0.75 g of concentrated sulfuric acid and 0.71 g of sodium hydroxyl were used, 16.69% (w_FAME/w_{rice bran}) of FAME was obtained. The esterification rate and the transesterification rate reached 98.83% and 80.47%. Based on the proposed route, the production process of FAME (biodiesel) could be simplified and the production cost could be reduced.     

Biodiesel preparation,optimization, and fuel properties from non-edible feedstock,Datura stramonium L.

This is a study on the feasibility of biodiesel preparation from a new and promising non-edible feedstock, Datura stramonium L. oil (DSO). First, important physical–chemical properties, such as oil content of seed (21.4 wt%), acid value (7.93 mg KOH/g) and fatty acid composition of expressed oil, were determined. Second, under the optimal two-step catalyzed reaction conditions, the maximum fatty acid methyl ester (FAME) yield (87%) and FAME content of more than 98 wt% were obtained. Furthermore, the fuel properties of DSO biodiesel were determined and evaluated. Compared with Jatrpha curcas L. (JC) and beef tallow (BT) biodiesel, DSO biodiesel possessed the best kinematic viscosity (4.33 mm²/s) and cold filter plug point (?5 °C). Based on the results, D. stramonium L. was identified as a promising species for biodiesel feedstock.     

Alkoxylation of biodiesel and its impact on low-temperature properties

A property of biodiesel that currently limits its use to blends of 20% or less is its relatively poor low-temperature properties. Alkoxylation of the unsaturated portion of biodiesel offers the potential benefit of reduced cloud point without compromising ignition quality or oxidation stability. Conventional biodiesel was synthesised from canola oil and the alcohols methanol, ethanol and butanol, epoxidised in situ, and alkoxylated by acid-catalysed oxirane ring opening in the presence of the alcohol of the ester group. Optimal conditions for epoxidation were H₂O₂/biodiesel molar ratio of 2:1, acetic acid/biodiesel molar ratio of 0.2:1, 2 wt% H₂SO₄, 6 h reaction at 60 °C. Alkoxylation resulted in alkoxy substitution rates of 37.1% (methyl), 34.3% (ethyl) and 32.9% (butyl). Selectivity for alkoxy biodiesel was 89.0%, 82.7% and 81.7% for methoxy, ethoxy and butoxy biodiesel, respectively. The cloud point for methyl and ethyl biodiesel increased slightly, while a reduction of 1 K was achieved for butyl biodiesel. The presence of by-products negated much of the expected improvement in cloud point for butoxy butyl biodiesel. Further optimisation work is required to improve both conversion and selectivity if significant improvements in cloud point are to be achieved.     

A hybrid feedstock for a very efficient preparation of biodiesel

Biodiesel has been synthesized from karanja, mahua and hybrid {karanja and mahua (50:50 v/v)} feedstocks. A high yield in the range of 95-97% was obtained with all the three feedstocks. Conversion of vegetable oil to fatty acid methyl esters was found to be 98.6%, 95.71% and 94% for karanja, mahua and hybrid feedstocks respectively. The optimized reaction parameters were found to be 6:1 (methanol to oil) molar ratio, H₂SO₄ (1.5% v/v), at 55 ± 0.5 °C for 1 h during acid esterification for the three feedstocks. During alkaline transesterification, a molar ratio of 8:1 (methanol to oil), 0.8 wt.% KOH (wt/wt) at 55 ± 0.5 °C for 1 h was found to be optimum to achieve high yield for karanja oil. For mahua oil and the hybrid feedstock, 6:1 (methanol to oil) molar ratio, 0.75 (w/w) KOH at 55 ± 0.5 °C for 1 h was optimum for alkaline transesterification to obtain a high yield. High yield and conversion from hybrid feedstock during transesterification reaction was an indication that the reaction was not selective for any particular oil. ¹H NMR has been used for the determination of conversion of the feedstock to biodiesel.     

The addition of alkoxy side-chains to biodiesel and the impact on flow properties

Butyl biodiesel was synthesised from canola oil and subsequently epoxidised via the in situ peroxyacetic acid method converting 45% of the unsaturated portion. Alkoxy butyl biodiesel was synthesised under acid conditions with a range of both straight-chain and branched alcohols. Alkoxylation of butyl biodiesel with methanol, ethanol and n-propanol did not improve the cloud or pour point over that for conventional methyl biodiesel. Alkoxylation with alcohols larger than butanol including n-pentanol, n-hexanol and n-octanol produced cloud points that were 5 °C lower than that for methyl biodiesel. The lowest cloud point achieved was for 2-ethylhexoxy butyl biodiesel at −6 °C, representing a 6 °C reduction in cloud point over methyl biodiesel. Alkoxylation did not have a significant effect on the pour point of biodiesel. Alkoxylation of butyl biodiesel resulted in significant increases in viscosity. The kinematic viscosity generally increased with increasing alkoxy chain length and ranged from 6.67 mm² s⁻¹ for methoxy butyl biodiesel to 9.76 mm² s⁻¹ for ethylhexoxy butyl biodiesel, more than double the value for methyl biodiesel. The improved low-temperature properties of the longer-chain alkoxy biodiesel were most likely due to the protruding alkoxy chain, which also resulted in an increase in viscosity. The use of alcohols larger than pentanol does not provide significant benefit in terms of low-temperature properties, and results in an undesirable increase in viscosity.     

Engine performance, exhaust emissions and combustion characteristics of a CI engine fuelled with croton megalocarpus methyl ester with antioxidant

The use of biodiesel as a substitute for petroleum-based diesel has become of great interest for the reasons of combating the destruction of the environment, the price of petroleum-based diesel and dependency on foreign energy sources. But for practical feasibility of biodiesel, antioxidants are added to increase the oxidation stability during long term storage. It is quite possible that these additives may affect the clean burning characteristics of biodiesel. This study investigated the experimental effects of antioxidants on the oxidation stability, engine performance, exhaust emissions and combustion characteristics of a four cylinder turbocharged direct injection (TDI) diesel engine fuelled with biodiesel from croton megalocarpus oil. The three synthetic antioxidants evaluated its effectiveness on oxidation stability of croton oil methyl ester (COME) were 1, 2, 3 tri-hydroxy benzene (Pyrogallol, PY), 3, 4, 5-tri hydroxy benzoic acid (Propyl Gallate, PG) and 2-tert butyl-4-methoxy phenol (Butylated Hydroxyanisole, BHA). The fuel sample tested in TDI diesel engine include pure croton biodiesel (B100), croton biodiesel dosed with 1000 ppm of an effective antioxidant (B100 + PY1000), B20 (20% croton biodiesel and 80% mineral diesel) and diesel fuel which was used as base fuel. The result showed that the effectiveness of the antioxidants was in the order of PY > PG > BHA. The brake specific fuel consumption (BSFC) of biodiesel fuel with antioxidants decreased more than that of biodiesel fuel without antioxidants, but both were higher than that of diesel. Antioxidants had few effects on the exhaust emissions of a diesel engine running on biodiesel. Combustion characteristics in diesel engine were not influenced by the addition of antioxidants in biodiesel fuel. This study recommends PY and PG to be used for safeguarding biodiesel fuel from the effects of autoxidation during storage. Overall, the biodiesel derived from croton megalocarpus oil can be utilized as partial substitute for mineral diesel.     

A MALDI, TGA, TG/MS, and DEA study of the irradiation effects on PMMA

Poly(methyl methacrylate) (PMMA) (M_w=6.4×10³, PD=1.06) was irradiated under vacuum. The constant dose rate was 1.66×10⁴ rad/min at doses between 10 and 100 Mrad using a cobalt-60 source. The samples were then analyzed by matrix assisted laser desorption/ionization (MALDI), hyphenated thermogravimetric/mass spectrometry (TG/MS), and dielectric analysis (DEA), all novel methods for the analysis of polymers damaged by radiation. Gel permeation chromatography (GPC), nuclear magnetic resonance (NMR), and differential scanning calorimetry (DSC) were also used for analysis. This study evidenced main chain scission, the removal of ester side groups, and the production of monomer as a result of ionizing radiation.     

Study on phase structure and electrochemical properties of Ml1−xMgxNi2.80Co0.50Mn0.10Al0.10 (x = 0.08, 0.12, 0.20, 0.24, 0.28) hydrogen storage alloys

Phase structure and electrochemical properties of the Ml_1−xMg_xNi_2.80Co_0.50Mn_0.10Al_0.10 (x = 0.08, 0.12, 0.20, 0.24, 0.28) (Ml = La-rich mixed lanthanide) alloys were studied. X-ray diffraction (XRD) analysis and Rietveld refinement show that the alloys consist mainly of LaNi₅ and (La,Mg)Ni₃ phase. Due to variation in phases of the alloys, the maximum discharge capacity, the high rate dischargeability (HRD), and the low temperature dischargeability increase first and then decrease. The maximum discharge capacity increases from 322 mAh g⁻¹ (x = 0.08) to 375 mAh g⁻¹ (x = 0.12), and then decreases to 351 mAh g⁻¹ (x = 0.28) with increasing x. As the case of x = 0.20, HRD at 1200 mA g⁻¹ and discharge capacity at 233 K reaches 41.7% and 256 mAh g⁻¹, respectively. The cycling stability is improved by substituting La with Ml and B-site multi-alloying, and the capacity retention of Ml_0.72Mg_0.28Ni_2.80Co_0.50Mn_0.10Al_0.10 at the 200th cycle is 71%.     

Mitigation of NOx emissions from a jatropha biodiesel fuelled DI diesel engine using antioxidant additives

Biodiesel offers cleaner combustion over conventional diesel fuel including reduced particulate matter, carbon monoxide and unburned hydrocarbon emissions. However, several studies point to slight increase in NO_x emissions (about 10%) for biodiesel fuel compared with conventional diesel fuel. Use of antioxidant additives is one of the most cost-effective ways to mitigate the formation of prompt NO_x. In this study, the effect of antioxidant additives on NO_x emissions in a jatropha methyl ester fuelled direct injection diesel engine have been investigated experimentally and compared. A survey of literature regarding the causes of biodiesel NO_x effect and control strategies is presented. The antioxidant additives L-ascorbic acid, α tocopherol acetate, butylated hydroxytoluene, p-phenylenediamine and ethylenediamine were tested on computerised Kirloskar-make 4 stroke water cooled single cylinder diesel engine of 4.4 kW rated power. Results showed that antioxidants considered in the present study are effective in controlling the NO_x emissions of biodiesel fuelled diesel engines. A 0.025%-m concentration of p-phenylenediamine additive was optimal as NO_x levels were substantially reduced in the whole load range in comparison with neat biodiesel. However, hydrocarbon and CO emissions were found to have increased by the addition of antioxidants.     

Simultaneous determination of quality parameters of biodiesel/diesel blends using HATR-FTIR spectra and PLS, iPLS or siPLS regressions

Partial least-squares (PLS), interval partial least squares (iPLS) and synergy partial least squares (siPLS) regressions were used to simultaneous determination of quality parameters of biodiesel/diesel blends. Biodiesel amount, specific gravity, sulfur content and flash point were evaluated using spectroscopic data in the mid-infrared region obtained with a horizontal attenuated total reflectance (HATR) accessory. Eighty-five binary blends were prepared using biodiesel and two types of diesel, in concentrations from 0.2 to 30% (v/v). Fifty-seven samples were used as a calibration set, whereas 28 samples were used as an external validation set. All samples were characterized using the appropriated standard methods. The specific gravity values at 20 °C were in the range of 848.2-866.2 kg/m³. Flash point values lay between 47.0 and 79.5 °C. Sulfur content values varied from 312 to 1351 mg/kg. Raw spectra of the samples were corrected by multiplicative scatter correction (MSC) and were pre-processed using a mean-centered procedure. Algorithms iPLS and siPLS were able to select the most adequate spectral region for each property studied. For all the properties studied, the siPLS algorithm produced better models than the full-spectrum PLS, selecting the most important bands. The quantification of biodiesel was performed using two spectral regions between 650-1909 cm⁻¹ and 2746-3165 cm⁻¹, and an excellent correlation coefficient of R² = 0.9996 was obtained. The specific gravity was determined from the spectral region from 650 to 1070 cm⁻¹, which yielded a very good correlation coefficient of R² = 0.9987. The sulfur content was evaluated from the spectral regions of 1070-1491 cm⁻¹ and 2746-3165 cm⁻¹. A very good correlation coefficient of R² = 0.9995 was obtained, regardless of whether the samples were formulated with metropolitan or countryside diesel. Finally, the flash point was determined from the spectral region between 756 and 968 cm⁻¹ and a very good correlation coefficient of R² = 0.9982 was obtained.     

Development of a method to determine Ni and Cd in biodiesel by graphite furnace atomic absorption spectrometry

This paper proposes a low cost, simple, fast method for determining Ni and Cd in biodiesel samples by graphite furnace atomic absorption spectrometry (GFAAS). The method was evaluated in biodiesel from different sources. Tungsten was used as a permanent modifier and the samples were prepared in the form of microemulsions, by mixing about 0.5 g of biodiesel with 5 g of surfactant (Triton X-100) in volumetric flasks and completing the volume with HNO₃ 1% (v/v). The detection limits obtained for Ni and Cd in microemulsions were ≤0.9 and 0.1 μg L⁻¹, respectively. The relative standard deviation (% R.S.D., n = 12) was ≤8.20% for Ni (washed animal fat sample) and ≤4.71% for Cd (sunflower oil sample). Accuracy was checked based on addition and recovery experiments, which yielded recovery rates varying from 93% to 108% for Ni and from 98% to 116% for Cd. Sample preparation is rapid and easy, and the use of an inorganic standard for calibration makes this sample preparation procedure suitable for routine applications.     

Biodiesel production from Croton megalocarpus oil and its process optimization

Production of biodiesel from non-edible feedstocks is attracting more attention than in the past, for the purpose of manufacturing alternative fuels without interfering with the food chain. Biodiesel was produced using Croton megalocarpus oil as a non-edible feedstock. C. megalocarpus oil was obtained from north Tanzania. This study aimed at optimizing the biodiesel production process parameters experimentally. The parameters involved in the optimization process were the amount of the catalyst, of alcohol, temperature, agitation speed and reaction time. The optimum biodiesel conversion efficiency obtained was 88% at the optimal conditions of 1.0 wt.% amount of potassium hydroxide catalyst, 30 wt.% amount of methanol, 60 °C reaction temperature, 400 rpm agitation rate and 60 min reaction time. The properties of croton biodiesel which were determined fell within the recommended biodiesel standards. Croton oil was found with a free fatty acid content of 1.68% which is below the 2% recommended for the application of the one step alkaline transesterification method. The most remarkable feature of croton biodiesel is its cold flow properties. This biodiesel yielded a cloud and pour point of −4 °C and −9 °C, respectively, while its kinematic viscosity lay within the recommended standard value. This points to the viability of using croton biodiesel in cold regions.     

Biodiesel production through transesterification over natural calciums

Transesterification of palm kernel oil (PKO) with methanol over various natural calciums, including limestone calcite, cuttlebone, dolomite, hydroxyapatite, and dicalcium phosphate, has been investigated at 60 °C and 1 atm. The study showed that dolomite, mainly consisting of CaCO₃ and MgCO₃, is the most active catalyst. The calcination temperature largely affected the physicochemical properties, as evidenced by N₂ adsorption-desorption measurement, TGA, SEM and XRD, and the transesterification performance of the resultant catalysts. It was found that the calcination of dolomite at 800 °C resulted in a highly active mixed oxide. CaO was suggested to be the catalytically active site responsible for the methyl ester formation. Under the suitable reaction conditions, the amount of dolomite calcined at 800 °C = 6 wt.% based on the weight of oil, the methanol/oil molar ratio = 30, and the reaction time = 3 h, the methyl ester content of 98.0% can be achieved. The calcined dolomite can be reused many times. The analyses of some important fuel properties indicated that the biodiesel produced had the properties that meet the standard of biodiesel and diesel fuel issued by the Department of Energy Business, Ministry of Energy, Thailand.     

Vapor pressure measurements on saturated biodiesel fuel esters by the concatenated gas saturation method

The purpose of this work was to determine vapor pressures for saturated biodiesel esters at the low-temperature end of their liquid range. A “concatenated” gas saturation apparatus capable of simultaneous measurements on 18 samples was used for measurements on methyl palmitate, ethyl palmitate, methyl stearate, ethyl stearate, and eicosane (C₂₀H₄₂) over the temperature range 323.15 K-343.15 K. Eicosane, a linear alkane with a well known vapor pressure curve (in the same range as the biodiesel esters), was included as a control compound. Importantly, the measured vapor pressures for eicosane are in excellent agreement with reference values, which is good evidence of the low uncertainty of the measurements on the biodiesel esters. Over this temperature range, the measured vapor pressure ranges were 0.145 Pa-1.11 Pa for methyl palmitate, 0.0687 Pa-0.616 Pa for ethyl palmitate, 0.0159 Pa-0.183 Pa for methyl stearate, and 0.00704 Pa-0.0912 Pa for ethyl stearate. The combined standard uncertainty in the vapor pressure measurements ranged from 8% to 15%.     

Enhancement of pyrolysis gasoline hydrogenation over Pd-promoted Ni/SiO2-Al2O3 catalysts

Pyrolysis gasoline upgrading by hydrogenation and ring opening was investigated over highly loaded Ni catalysts supported on amorphous silica-alumina and incorporating promoters as Pd, seeking a higher aromatic reduction of this feedstock in order to meet stringent fuel regulations. The effect of Ni loading and Pd component on the activity of those systems was evaluated in a fixed bed reactor under the following operating conditions: T = 573 and 673 K, H₂:PyGas molar ratio = 10, P = 5.0 MPa, WHSV = 4 h⁻¹. The catalyst properties, measured by several characterization techniques (ICP-AES, XRD, N₂ adsorption-desorption isotherms, TPR, H₂-TPD, CO chemisorption, XPS, FTIR spectroscopy of adsorbed pyridine and NH₃-TPD), were related to their catalytic activity and selectivity. Interestingly, the increase in Ni loading from 24.4 to 33.2 Ni wt.% has a negative effect on both hydrogenation and ring opening activities, as it causes a drop in the BET surface area and a decrease in metal-support interaction, with a negative bearing on catalyst stability. On the other hand, the addition of Pd has a positive effect for hydrogenation, linked with the higher electronegativity of Pd⁰ species compared to those of Ni⁰, as well as with a greater stability of Pd-promoted catalysts during on-stream conditions. A linear correlation has been found between the total amount of desorbed H₂, as determined from H₂-TPD experiments on freshly reduced catalysts, and the initial turnover frequency.     

Ion-pairing effects and ion-solvent-polymer interactions in LiN(CF3SO2)2-PC-PMMA electrolytes: a FTIR study

FTIR spectroscopic investigations coupled with ionic conductivity and viscosity measurements on lithium imide (LiN(CF₃SO₂)₂)-propylene carbonate (PC)-poly(methyl methacrylate) (PMMA) based liquid and gel electrolytes over a wide range of salt (0.025-3 M) and polymer (5-25 wt.%) concentration range furnish a novel insight into the ion-ion and ion-solvent-polymer interactions. Vibrational spectral data for LiN(CF₃SO₂)₂-PC electrolytes reveal that the solvation of lithium ions manifests from Li⁺OC and Li⁺O (ring oxygens) interactions as the ν_s(CO), the ring breathing and the δ(CH) modes of the pentagonal solvent ring are strongly perturbed for all salt concentrations. The split of the ν(SO₂) mode (that appears at 1355 cm⁻¹ for the “free imide ion”) into two components at 1337 and 1359 cm⁻¹ confirms the existence of contact ion-pairs possessing two different stable optimized geometries wherein the Li⁺ ion coordinates in a bidentate fashion in liquid and gel electrolytes of 3 M LiN(CF₃SO₂)₂-PC strength. Perturbations observed for the ν_a(SNS) and ν_s(SNS) modes of the imide ion and the symmetric ring deformation mode of PC confirms the presence of ion-pairs in both 2 and 3 M electrolytes. Incorporation of even upto 25 wt.% of PMMA in a solution of LiN(CF₃SO₂)₂-PC of 3 M strength results in an insignificant conductivity decline (as σ₂₅>10⁻³ S cm⁻¹) which is simultaneously accompanied by a massive increase in its macroscopic viscosity (as η₂₅>10⁸ cSt). Gels containing 25 wt.% of PMMA exhibit a complex pattern of Li⁺-PMMA interactions through the carbonyl oxygen of its ester group which is evidenced from the perturbations observed for the ν_s(CO) mode of PMMA. Ionic conductivity decline that occurs at salt concentrations ≥1.25 M LiN(CF₃SO₂)₂-PC in both liquid and gel electrolytes, is therefore attributable to (i) ion-pairing phenomenon and (ii) an enhancement in the solution viscosity due to a high salt proportion.     

Synthesis and transport properties in La2−xAxMo2O9−δ (A = Ca, Sr, Ba, K) series

The La_2−xA_xMo₂O_9−δ (A = Ca²⁺, Sr²⁺, Ba²⁺ and K⁺) series has been synthesised as nanocrystalline materials via a modification of the freeze-drying method. The resulting materials have been characterised by X-ray diffraction (XRD), thermal analysis (TG/DTA, DSC), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The high-temperature β-polymorph is stabilised for dopant content x > 0.01. The nanocrystalline powders were used to obtain dense ceramic materials with optimised microstructure and relative density >95%. The overall conductivity determined by impedance spectroscopy depends on both the ionic radius and dopant content. The conductivity decreases slightly as the dopant content increases in addition a maximum conductivity value was found for Sr²⁺ substitution, which show an ionic radii slightly higher than La³⁺ (e.g. 0.08 S cm⁻¹ for La₂Mo₂O₉ and 0.06 S cm⁻¹ for La_1.9Sr_0.1Mo₂O_9−δ at 973 K). The creation of extrinsic vacancies upon substitution results in a wider stability range under reducing conditions and prevents amorphisation, although the stability is not enhanced significantly when compared to samples with higher tungsten content. These materials present high thermal expansion coefficients in the range of (13-16) × 10⁻⁶ K⁻¹ between room temperature and 753 K and (18-20) × 10⁻⁶ K⁻¹ above 823 K. The ionic transport numbers determined by a modified emf method remain above 0.98 under an oxygen partial pressure gradient of O₂/air and decreases substantially under wet 5% H₂-Ar/air when approaching to the degradation temperature above 973 K due to an increase of the electronic contribution to the overall conductivity.