Methanol Substitution Research Articles

To achieve high methanol substitution ratio and clean combustion on a diesel/methanol dual fuel engine: A comparison of diesel methanol compound combustion (DMCC) and direct dual fuel stratification (DDFS) strategies

Diesel methanol compound combustion (DMCC) suffers from poor fuel economy at low load and knock at high load. A direct dual fuel stratification (DDFS) strategy in which diesel is injected before the top dead center (TDC) and methanol is directly injected after the auto-ignition of diesel has been proposed and investigated in previous research. In this study, a three-dimensional simulation model coupled chemical reaction kinetic mechanism is used to investigate and compare the DMCC and DDFS strategies. In the former strategy, the ratio of methanol energy to total fuel energy (Rm) is limited by inefficient combustion at low load, and although fuel economy can be improved by advancing diesel injection and increasing initial temperature, Rm still cannot exceed 30%. Moreover, Rm is limited by knock at high load; however, knock intensity can be suppressed by delaying diesel injection and increasing exhaust gas recirculation (EGR) rate, allowing Rm to reach values as high as 50%. In contrast, the latter strategy can yield Rm values as large as 90%, stable combustion, good fuel economy, and low emissions without intake air heating and EGR. In short, the DDFS strategy is a promising way of applying methanol to diesel engines.

Comparison in the effects of alumina, ceria and silica nanoparticle additives on the combustion and emission characteristics of a modern methanol-diesel dual-fuel CI engine

Methanol is widely used as a potential alternative source for diesel fuel and can reduce the CO, THC and smoke emissions of the CI engines. However, the lower cetane number and energy content of methanol hinder the high substitution of methanol over diesel fuel. Introducing nanoparticles as fuel-additive is an effective approach to cope with this issue. In the present work, the alumina, ceria and silica nanoparticles were separately mixed into methanol in mass proportions of 25, 50 and 100 ppm with the composite surfactant of sodium dodecyl benzene sulfonate and cetyl trimethyl ammonium bromide (1:1 mass fraction) to create the nanofluid. The nanofluid was then injected into the intake port to combust synergistically with the mineral diesel fuel injected by the other high-pressure injection system, generating the nanoparticle-assisted methanol-diesel fuel mode (NMF). The characteristics of combustion and pollutant emission of NMFs were investigated with 10%, 30% and 50% methanol substituted level (M10, M30 and M50, respectively), at 10–90% engine loads of a constant engine speed. The results showed that the substitution of methanol led to an extension in the ignition delay but a shortening of combustion duration than diesel fuel. The additional introduction of alumina and ceria nanoparticles in each dosage, and silica nanoparticles in 100 ppm dosage, into M10 slightly shortened the ignition delay at 10% load conditions. When dosed into M50 fuel, all the three nanoparticles in various dosages led to shortened ignition delay at 10–50% engine loads. Over the test conditions, the addition of nanoparticles all caused a distinct increase in the peak in-cylinder pressure for the methanol-diesel dual-fuel mode. However, the addition of nanoparticles exerted marginal influences on further reduction of CO, HC and smoke emissions, and even further elevated the NOx emissions for MDF mode by up to 40%. Moreover, the deterioration degrees of NOx emissions for alumina and ceria nanoparticle addition were higher than the silica nanoparticles, and elevated towards the higher nanoparticle dosage and lower engine load.

The kinetic substitution reactions and structural analysis of manganese(I) acetylacetonato complexes

The methanol substitution reactions in the manganese acetylacetonato complex, fac-[Mn(CO)3(acac)(CH3OH)], was kinetically investigated with a range of entering ligands including pyridine (Py), imidazole (Im) and 4-dimethylaminopyridine (DMAP). All the complexes were characterized by NMR, UV–vis and IR spectroscopy. Moreover, crystal structures of fac-[Mn(CO)3(acac)(CH3OH)] (1), fac-[Mn(CO)3(acac)(Py)] (2) and fac-[Mn(CO)3(acac)(DMAP)] (3) are reported. The substitution of methanol in fac-[Mn(CO)3(acac)(CH3OH)] (1) by DMAP is approximately 2 times faster than Py, and 1.7 times faster when compared to Im. The results correlate well with the pKa of the entering nucleophile where pyridine (Py) < imidazole (Im) < 4-dimethylaminopyridine (DMAP). The activation parameters for complex (1) were determined as ΔH≠=73.9 ± 0.6 kJ mol−1 and the entropy of activation ΔS≠=−28 ± 2 JK−1 indicating an interchange associative mechanism.

Experimental study on cycle-to-cycle variations in natural gas/methanol bi-fueled engine under excess air/fuel ratio at 1.6

In this study, the cycle-to-cycle variations in natural gas/methanol bi-fueled engines under excess air/fuel ratio at 1.6 was analyzed. In order to examine the impact of the methanol substitution ratio (MSR) on cyclic variability, four values of MSRs (MSR = 0%, 3.6%, 7.5%, and 11.5%) were selected under low load conditions. The results showed that the variations in the multicycle in-cylinder pressure traces decreased with the increase in MSR. In addition, the variations in peak in-cylinder pressure (Pmax), peak of pressure rise rate (dp/dϕ)max, 50% mass fraction burned (CA50), peak of averaged gas temperature (Tmax), and indicated mean effective pressure (IMEP) in 100 consecutive cycles decreased with the increase in MSR. Meanwhile, the higher was the MSR, the narrower was the range of frequency distribution of Pmax, (dp/dϕ)max, CA50, Tmax, and IMEP covered. In addition, the coefficient of variation in IMEP (COVIMEP) decreased with the increase in MSR for a specific spark timing. For instance, as MSR increased from 0% to 11.5%, the value of COVIMEP decreased from 2.25% to 1.28% when the spark timing was set to 46°CA BTDC. This is because methanol addition to natural gas leads to faster combustion with less cyclic variability.

Effect of injection strategy on a diesel/methanol dual-fuel direct-injection engine

Methanol direct-injection achieves direct injection of diesel and methanol in the cylinder by using two independent fuel injection systems. This yields an extremely high methanol substitution rate and extremely low pollutant emissions. Due to these advantages, three injection strategies are proposed to investigate this injection method: D/M mode and M/D mode are where methanol injection occurs later and earlier than diesel injection respectively while M/D/M mode is where methanol is injected once before and once after the diesel injection. In this paper, these strategies are investigated, and the optimal settings of each are obtained and compared at low load and high load. The results show that in D/M mode, fuel economy is optimized and knock intensity increases with advancement of fuel injection and decreased injection dwell. This mode also effectively prevents knock but is not conducive to fuel economy. The most suitable methanol injection timings are obtained in M/D mode, namely 20°CA before the top dead center (BTDC) at low load and 30°CA BTDC at high load. Moreover, at low load the higher the first methanol injection ratio is, the better the fuel economy becomes, while at high load continued increases in the first ratio are limited by knock. Ultimately, M/D/M mode is found to be the best injection strategy at low load and high load.

A comparative study of combustion and emission characteristics of dual-fuel engine fueled with diesel/methanol and diesel–polyoxymethylene dimethyl ether blend/methanol

In this study, a comparative study of the combustion characteristics and performances of a dual-fuel engine fueled with diesel/methanol and diesel–polyoxymethylene dimethyl ether blend/methanol was conducted. All the experiments were conducted on a heavy-duty common rail diesel engine at an engine speed of 1800 r/min. The engine loads were fixed at low, medium, and heavy loads, with the brake mean effective pressure at 0.42 MPa, 0.7 MPa and 0.9 MPa, respectively. Methanol substitution ratio (MSR) was defined as the torque output contributed by methanol to the total torque output, and in this study, three MSRs (0 %, 20 %, and 40 %) were defined. Diesel–polyoxymethylene dimethyl ether (PODE) blend was defined as P50 (50 % diesel and 50 % PODE by volume) to clarify the effect of PODE addition on engine performance. The results showed that the dual-fuel engine fueled with P50/methanol had a higher peak cylinder pressure, lower first peak heat release rate (HRR), and higher second peak HRR than the dual-fuel engine fueled with diesel/methanol. Both the ignition delay and combustion duration of the dual-fuel engine decreased when the pilot fuel injection changed from diesel to P50. Moreover, both NOx emissions and particulate matter produced by the P50/methanol engine were lower than those produced by the diesel/methanol engine for the specific MSR and engine load.

In-depth comparison between pure diesel and diesel methanol dual fuel combustion mode

Diesel Methanol Dual Fuel (DMDF) could achieve high efficiency and low emissions simultaneously at part of engine conditions, but the reason of this has not been clarified. In order to find the reason behind this phenomenon, Pressure-Volume (P-V) map, equivalence ratio (φ)-temperature (T) map and three-dimensional simulation software were used to compare diesel and DMDF mode, and two test conditions were selected to fulfill in-depth comparison of two combustion modes. Based on the analysis of P-V map, the reason of higher thermal efficiency at DMDF mode is as follows: lower cylinder pressure in compression stroke contributes to compression work reduction. Meanwhile, higher combustion rate of DMDF mode could reduce cylinder temperature and pressure in the late power stroke, which would further decrease exhaust loss and heat loss. Based on the analysis of φ-T map, higher methanol substitution percent could reduce the intersection area between cylinder φ-T map and nitric oxide & soot generation region. And after analyzing in-cylinder temperature, hydroxy mole fraction together with the equivalent ratio three-dimensional cloud map, it is found that the inhibitory effect of methanol on diesel low-temperature combustion prolongs diesel ignition delay, which helps to form the homogeneous charge in the cylinder. Under DMDF mode, fuel rich areas are significantly reduced, so is the maximum in-cylinder temperature. This is the key to achieve ultra-low nitrogen oxides and soot emissions for DMDF mode.

Parametric study on effects of methanol injection timing and methanol substitution percentage on combustion and emissions of methanol/diesel dual-fuel direct injection engine at full load

The effects of methanol injection timing (MIT) and methanol substitution percentage (MSP) on the combustion and emissions of a methanol/diesel dual-fuel direct injection engine were investigated, followed by a comparative analysis with the conventional methanol/diesel dual-fuel mode. A single-cylinder, air-cooled, naturally aspirated common rail diesel engine was modified into a dual-fuel direct injection engine with a methanol direct injection system. The engine was operated at a maximum torque speed of 2500 rpm and a mean effective pressure of 0.75 MPa. The engine performance was analyzed for different methanol/diesel fuel mixtures using four MSPs: 10%, 20%, 30%, and 40%. Meanwhile, the MIT was adjusted from −60 to −300 °CA after top dead center (ATDC). The results indicated that methanol addition and retarded MIT allowed the diesel injection timing to be properly advanced. A higher MSP increased the ignition delay (CA0-10) and decreased the combustion duration (CA10-90), leading to increases in the brake thermal efficiency (BTE), coefficient of variation of the indicated mean effective pressure (IMEP) (COVIMEP), and knock intensity (KI), along with increases in the total hydrocarbon (THC) and nitrogen oxide (NOX) emissions and decreases in the carbon monoxide (CO) and soot emissions. Additionally, for a specific MSP, the retarded MIT increased the peak cylinder pressure and decreased the maximum heat release rate. Concurrently, it decreased the CA0-10 and increased the CA10-90. Moreover, increases in the BTE, COVIMEP, and KI; decreases in the THC and CO emissions; and increases in the NOX and soot emissions were achieved using the retarded MIT.

Exploring the high load potential of diesel–methanol dual-fuel operation with Miller cycle, exhaust gas recirculation, and intake air cooling on a heavy-duty diesel engine

Legislations concerning emissions from heavy-duty diesel engines are becoming increasingly stringent. This requires conventional diesel combustion to be compliant using costly and sophisticated aftertreatment systems. Preferably, diesel–methanol dual-fuel is one of the suitable alternative combustion modes as it can potentially reduce the formation of nitrogen oxide and soot emissions which characterised the diesel mixing-controlled combustion. This is primarily due to the high latent heat of vaporisation and oxygen content of the methanol fuel. At high engine loads, however, the potential of diesel–methanol dual-fuel operation is constrained by the excessive combustion pressure rise rate and peak in-cylinder pressure, which limits both the engine efficiency and the percentage of methanol that can be used. For the first time, experimental studies were conducted to explore advanced combustion control strategies such as Miller cycle, exhaust gas recirculation, and intake air cooling for improving upon high load diesel–methanol dual-fuel combustion. Experiments were carried out at 1200 r/min and 18 bar indicated mean effective pressure on a single-cylinder heavy-duty diesel engine, which equipped with a high pressure common rail diesel injection, a methanol port fuel injection, and a variable valve actuation system on the intake camshaft. Results showed that the methanol energy fraction of a conventional diesel–methanol dual-fuel operation with a baseline intake valve closing timing was limited to 28%. This was due to the high combustion temperature at a high load which advanced the ignition timing of the premixed charge, resulting in high levels of pressure rise rate. The application of lower effective compression ratio and intake air temperature ( Tint) effectively decreased the compression temperature, which successfully delayed the ignition timing of the premixed charge. This allowed for a more advanced diesel injection timing to achieve improvement in the thermal efficiency and potentially enabled a higher methanol substitution ratio. Although the introduction of exhaust gas recirculation demonstrated very slight impact on the ignition timing of the premixed charge, a higher net indicated efficiency was observed due to a relatively lower local combustion temperature which reduced heat transfer loss. Moreover, the optimised diesel–methanol dual-fuel operation allowed a higher methanol energy fraction of 40% to be used at an effective compression ratio of 14.3 and Tint of 305 K and achieved the highest net indicated efficiency of 47.4%, improving by 3.7% and 2.6%, respectively, when compared to the optimised conventional diesel combustion (45.7%) and conventional diesel–methanol dual-fuel (46.2%). This improvement was accompanied with a reduction of 37% in nitrogen oxide emissions and little impact on soot emissions in comparison with the conventional diesel combustion.

High-pressure direct injection of methanol and pilot diesel: A non-premixed dual-fuel engine concept

In order to reduce the climate impacts, methanol produced from carbon-neutral methods plays an important role. Due to its oxygen content and high latent heat, methanol combustion can achieve low soot and NOx emissions. In the present study, direct injection (DI) of methanol is investigated in a non-premixed dual-fuel (DF) setup with diesel pilot. The present DF engine study is carried out via a specially-designed new cylinder head operating with a centrally located methanol injector and with an off-centered diesel pilot injector. The target is to inject methanol close to top dead center (TDC) in a similar fashion as in standard diesel combustion enabling robust operation with high efficiency. The ignition of the DI methanol is achieved with an almost simultaneously injected diesel pilot. The experiments were conducted in a single-cylinder heavy-duty research engine at a constant engine speed of 1500 rpm with a compression ratio of 16.5. The indicated mean effective pressure (IMEP) varied between 4.2 and 13.8 bar while the methanol substitution ratio was swept between 45 and 95%. In addition, the diesel pilot and methanol injection timings were varied for optimum efficiency and emissions. The introduced non-premixed DF concept using methanol as the main fuel showed robust ignition characteristics, stable combustion, and low CO and HC emissions. The results indicate that increasing both the load and the methanol substitution ratio can increase the thermal efficiency and the stability of combustion (lower COV) together with decreased CO and HC emissions.

Iron as electron donor for denitrification: The efficiency, toxicity and mechanism.

For the treatment of low C/N wastewaters, methanol or acetate is usually dosed as electron donor for denitrification but such organics makes the process costly. To decrease the cost, iron which is the fourth most abundant element in lithosphere is suggested as the substitution of methanol and acetate. The peak volumetric removal rate (VRR) of nitrate nitrogen in the ferrous iron-dependent nitrate removal (FeNiR) reactor was 0.70±0.04kg-N/(m3·d), and the corresponding removal efficiency was 98%. Iron showed toxicity to cells by decreasing the live cell amount (dropped 56%) and the live cell activity (dropped 70%). The toxicity of iron was mainly expressed by the formation of iron encrustation. From microbial community data analysis, heterotrophs (Paracocccus, Thauera and Azoarcus) faded away while the facultative chemolithotrophs (Hyphomicrobium and Anaerolineaceae_uncultured) dominated in the reactor after replacing acetate with ferrous iron in the influent. Through scanning electron microscope (SEM) and transmission electron microscope (TEM), two iron oxidation sites in FeNiR cells were observed and accordingly two FeNiR mechanisms were proposed: 1) extracellular FeNiR in which ferrous iron was bio-oxidized extracellularly; and 2) intracellular FeNiR in which ferrous iron was chemically oxidized in periplasm. Bio-oxidation (extracellular FeNiR) and chemical oxidation (intracellular FeNiR) of ferrous iron coexisted in FeNiR reactor, but the former one predominated. Comparing with the control group without electron donor in the influent, FeNiR reactor showed 2 times higher and stable nitrate removal rate, suggesting iron could be used as electron donor for denitrification. However, further research works are still needed for the practical application of FeNiR in wastewater treatment.

Synthesis, characterization and substitution reactions of fac-[Re(O,O′-bid)(CO)3(P)] complexes, using the “2+1” mixed ligand model

The solid state structures of six complexes {fac-[Re(Acac)(CO)3(PPhCy2)] (3), fac-[Re(Acac)(CO)3(PCy3)] (4), fac-[Re(Benzac)(CO)3(PPh3)] (7), fac-[Re(Tfaa)(CO)3(PPh3)] (10), fac-[Re(Hfaa)(CO)3(PPh3)] (13) and fac-[Re(Trop)(CO)3(PTA)] (15)}; acetylacetone = Acac, trifluoroacetylacetone = Tfaa, benzoylacetone = Benzac, hexafluoroacetylacetone = Hfaa and tropolone = Trop are reported. The complexes were synthesised in high yield and purity, using the “2 + 1” mixed ligand concept and the characterisation was done by spectroscopic methods IR, NMR, UV/Vis and elemental analysis. A kinetic study of the methanol substitution of fac-[Re(CO)3(Acac)(CH3OH)] (2), fac-[Re(CO)3(Benzac)(CH3OH)] (6) fac-[Re(CO)3(Tfaa)(CH3OH)] (9) and fac-[Re(CO)3(Hfaa)(CH3OH)] (12), by triphenylphosphine - PPh3, cyclohexyl diphenylphosphine - PPh2Cy, dicyclohexyl phenylphosphine - PPhCy2 and tricyclohexyl phosphine - PCy3 is performed. The reaction rates for 2, 6, 9 and 12 with PPh3 occurred in the following decreasing order: Benzac > Acac > Tfaa > Hfaa.

Experimental study of the active and passive regeneration procedures of a diesel particulate filter in a diesel methanol dual fuel engine

The diesel methanol dual fuel (DMDF) technology has been used in diesel engines to reduce the nitrogen oxides (NOX) and particulate matter (PM) emissions in past years. A combination of a diesel oxidation catalyst (DOC) and a diesel particulate filter (DPF) is applied on DMDF engines to meet severer emission standards in this study. The DOC was modified to produce adequate nitrogen dioxide (NO2) in the presence of the high hydrocarbon and carbon monoxide emissions formed by DMDF mode. During tests, the effect of methanol substitution ratio (MSR) and DOC inlet temperature on DOC performance was studied. Moreover, the effect of MSR on the active and passive regeneration of DPF was investigated. Results show that at high DOC inlet temperatures (>190 °C), the DMDF mode combined with DOC achieves the high DPF inlet temperatures and the high NO2/PM ratio, which is benefit for passive regeneration. During active regeneration, the initial regeneration temperature, the fuel penalty and the emissions of PM, particulate number (PN), NO2 and carbon dioxide (CO2) after the DPF at MSR40 are lower than those at MSR0. The emissions of methanol (CH3OH) and formaldehyde (HCHO) after the DPF at MSR40 are higher than those at MSR0. During passive regeneration, the regeneration rate at MSR40 is higher than that at MSR0, as well as the emissions of PN, CH3OH and HCHO after the DPF. While the NO2 and CO2 emissions after the DPF at MSR40 are lower than those at MSR0.

Controlling the phase of iron oxide nanoparticles fabricated from iron(III) nitrate by liquid flame spray

AbstractIron oxide nanoparticles were synthesized in a liquid flame spray process from iron(III) nitrate. The choice of chemicals and all other process parameters affects the crystallographic phase composition and the quality of the material. Adjustment of the solvent composition and the gas flow rates was used to control the phase composition of the produced particles. All samples consisted of pure maghemite (γ‐Fe2O3) or a mixture of maghemite and hematite (α‐Fe2O3). When using pure alcohols as solvents, the maghemite/hematite phase ratio could be adjusted by changing the equivalence ratio that describes the oxidation conditions in the flame zone. A large residual particle mode formed in the size range of ~20‐700 nm along with a dominant very fine particle mode (2‐8 nm). Both phases seemed to contain large particles. A partial substitution of methanol with carboxylic acids turned the hematite phase into maghemite completely, even though some of particles were possibly not fully crystallized. Residual particles were still present, but their size and number could be decreased by raising the heat of combustion of the precursor solution. 30 vol‐% substitution of methanol with 2‐ethylhexanoic acid was adequate to mostly erase the large particles.

Risk mitigation of biodiesel production through the replacement of methanol by ethanol in the production process

AbstractAlthough biodiesel is considered a safe substance for the environment, its production can be dangerous because it involves flammable and toxic substances, such as methanol. In addition to the risks associated with fire and explosions, methanol also implies a risk to the health of workers who are constantly inhaling this product, even in low concentrations. Despite all the associated risks, most Brazilian industries produce biodiesel from methanol. Aiming to find an alternative to make the production process of biodiesel safer, several research studies were carried out in which the advantages and disadvantages of methanol substitution for ethanol were raised. From there, it was found that the biggest advantage is actually making the production process safer. However, it has been found that this proposal is still not feasible because the production of biodiesel by an ethyl route raises the cost of production considerably. In view of the foregoing, it was concluded that the alternative presented is only feasible through measures that compensate for the increase in costs, such as fiscal incentives.

Comparative study on the laminar flame speeds of methylcyclohexane-methanol and toluene-methanol blends at elevated temperatures

Laminar flame speeds of methylcyclohexane (MCH)-methanol and toluene-methanol blends were experimentally determined with spherically expanding flame method in a constant volume bomb at atmospheric pressure, initial temperatures of 393 and 433 K, covering wide equivalence ratio range. The blending ratio of methanol in liquid volume varies as 0%, 20%, 40%, 60%, 80%, 100%. Nonlinear methodology was employed to remove the stretch effect in the data processing. Experimental results show that MCH-air flame propagates faster than toluene at the same condition. The addition of methanol into MCH and toluene results in acceleration of laminar flame speed especially at the rich mixtures. Since the published model suffers difficulty in reproducing experimental data, model refinements were carried out and the refined model yields better performance. Comprehensive analyses were developed regarding thermal and chemical kinetic properties. For MCH has lower adiabatic flame temperature than toluene and methanol addition into the two cyclic fuels decreases the adiabatic flame temperature, the thermal effect on laminar flame speed difference is negligible. Therefore, the effect of chemical kinetics was specifically discussed. MCH and toluene have different ring structures. The disintegration of aromatic ring plays as the limiting step in the high-temperature oxidation of toluene, resulting in low concentration of active radical pool and overall reactivity. However, the ring opening reaction of MCH occurs easily after the initial H-abstraction reaction, which favors the production of active intermediates and the enhancement of flame propagation. For the blending fuels, the analyses show that the laminar flame speed variation of the blends are primarily caused by the methanol substitution and the disturbance of reaction pathway through affecting the generation of important intermediates.

First kinetic data of the CO substitution in fac-[Re(L,L′-Bid)(CO)3(X)] complexes (L,L′-Bid = acacetylacetonate or tropolonate) by tertiary phosphines PTA and PPh3: Synthesis and crystal structures of water-soluble rhenium(I) tri- and dicarbonyl complexes with 1,3,5-triaza-7-phosphaadamantane (PTA)

fac-[Re(OH2)3(CO)3]+ reacts with acetylacetone (AcacH) at room temperature to yield fac-[Re(Acac)(CO)3(OH2)] (1) under aqueous conditions 1 was isolated and reacted with the monodentate ligand, 1,3,5-triaza-7-phosphaadamantane (PTA), to form fac-[Re(Acac)(CO)3(PTA)] (2) in a 9:1 ratio of water and methanol. The isolated complex 2 was further reacted with an excess of PTA ligand in a 9:1 ratio of water and methanol to yield the highly soluble cis-trans-[Re(Acac)(CO)2(PTA)2] (3). The complexes have been characterized by spectroscopic techniques IR, 1H, 13C and 31P NMR, as well as single crystal X-ray crystallography for 2 and 3. From the crystallographic results of 3, the formation of the cis-trans conformation was confirmed, while the 31P NMR results further established 3 as the sole product formed. A 31P NMR kinetic study, involving the methanol substitution of fac-[Re(CO)3(Acac)(CH3OH)] (4) and fac-[Re(CO)3(Trop)(CH3OH)] (TropH = tropolone) with PTA as entering monodentate ligand was also undertaken. The second-order rate constants (k1) for the forward reactions at 25.0 °C were respectively obtained as (35.9 ± 0.2) x 10−3 M−1 s−1 and (25.1 ± 0.8) M−1 min−1. In a preliminary 31P NMR kinetic investigation of the carbonyl substitution in fac-[Re(Acac)(CO)3(PPh3)] by PPh3, an estimated equilibrium constant (Kest) of ≈ 5.09 was calculated for the reversible reaction.

Ambient and high-pressure kinetic investigation of methanol substitution in fac-[Re(Trop)(CO)3(MeOH)] by different monodentate nucleophiles

Methanol substitution in the fac-[Re(CO)3(Trop)(MeOH)] complex (Trop- = tropolonate) was studied with a range of seven nucleophiles, namely pyridine (Py), 4-dimethylaminopyridine (DMAP), imidazole (Im), thiourea (TU), 1-methyl-2-thiourea (MeTU), bromide (Br-) and iodide (I-) at variable temperature, and at ambient and high pressure. The substitution products were characterized by NMR, IR and UV/vis spectroscopy, and by chemical analysis, and the crystal structures of two of these, namely fac-[Re(Trop)(CO)3(Im)] and fac-[Re(Trop)(CO)3(DMAP)], are reported. High-pressure kinetic studies with four of these entering nucleophiles in methanol at 25 °C on fac-[Re(Trop)(CO)3(MeOH)] yielded the following activation volumes, ΔV≠(kL), for the ligation by four nucleophiles as defined by kL (cm3 mol-1): Im: 9.0 ± 0.2; Py: 10.1 ± 0.2; TU: 10.0 ± 0.3 and MeTU: 14.5 ± 0.3. Since these experimental ΔV≠(kL) values were positive but smaller than expected, it was interpreted that these indicated a dissociative/dissociative interchange pathway for these substitution reactions. Kinetic studies at ambient pressure and variable temperature in methanol on fac-[Re(Trop)(CO)3(MeOH)] with a range of eight entering nucleophiles pointed more clearly to a dissociative pathway and yielded the following results, wherein a clear linear free-energy relationship (LFER) was established for the entering nucleophiles Py, DMAP, Im, TU, MeTU, NCS-, Br- and I-, within the following ranges: kL (ligation; M-1 s-1), 0.263 ± 0.001 to 0.765 ± 0.002; k-L (solvolysis; s-1), (0.07 ± 0.01) × 10-3 to 0.674 ± 0.001; KL (equilibrium; M-1); 1.06 ± 0.01 to 2000 ± 500; ΔH≠(kL) (kJ mol-1), 58.0 ± 0.7 to 76.1 ± 0.6, and ΔS≠(kL) (J K-1 mol-1); -55 ± 2 to 6 ± 3.

Study of the characteristics of PM and the correlation of soot and smoke opacity on the diesel methanol dual fuel engine

Methanol is regarded as an alternative fuel of diesel for reducing the particulate matter emissions on diesel engines. However, recent studies reveal that methanol has the different effects on particulate matter characteristics at high loads. In order to reduce particulate matter emissions further within the full operating range of the engine, the characteristics of particulate matter and the correlation between soot and smoke opacity were investigated on a turbocharged and intercooled diesel engine under diesel/methanol dual fuel mode. During the experiment, particulate characteristics are primarily exhibited by the characteristics of soot and particulate number. Results show that the engine-out soot and particulate number emissions increase with the increase of methanol substitution percent under high intake temperature at high loads. On the contrary, the engine-out soot and particulate number decrease with the increase of methanol substitution percent under low intake temperature at high loads. There is an applicable scope of methanol substitution percent that effectively reduces soot and particulate number emissions. Methanol substitution percent which is larger than 20% has a significant effect on the decrease of soot and particulate number. At low and medium loads, the effect of methanol substitution percent on soot and particulate number emissions is dependent on the start of injection. The effect of methanol substitution percent on the decrease of particles strengthens as the start of injection is away from the top dead center. The inflection point of particulate number and soot emissions moves forward with the increased methanol substitution percent. Compared to pure diesel mode, the strong correlation between soot and smoke opacity does not exist on diesel/methanol dual fuel mode. However, the correlation between soot and smoke opacity comes back in usage of the diesel oxidation catalyst or exhaust gas recirculation on diesel/methanol dual fuel mode. Most of nitrogen dioxide and unburned hydrocarbons are reduced by the diesel oxidation catalyst on diesel/methanol dual fuel mode.

Experimental investigation of methanol dissociated gas addition to gasoline in a spark ignition engine

This work investigates the performances and emission characteristics of a spark ignition (SI) engine fuelled with methanol dissociated gas and gasoline mixtures. The dissociation system for methanol was designed, methanol dissociated gas was blended to the gasoline up to 20% by volume, and experiments were conducted within a four-cylinder, four-stroke and water-cooled spark ignition (SI) engine. Performance tests were carried out via measuring brake thermal efficiency, equivalent specific fuel consumption, and exhaust emissions (CO, HC, NOx) with a constant speed of 2000 rpm at stoichiometric condition. The results indicate that an increase in methanol substituted ratio has slightly lowered the engine torque. The addition of methanol dissociated gas decreases the equivalent specific fuel consumption and increases the effective thermal efficiency from the economical point of view. And the exhaust emissions decrease by about 33% and 28% of the mean average values of CO and HC emissions when the proportion of methanol substitution was 20% comparing to pure gasoline. However, nitrogen oxide emission values increased with the adding of methanol dissociated gas.