A study is carried out on chemical constitution of sulfur compounds in MTBE and their formation mechanisms. These sulfur compounds are classified into three types: common sulfur compounds, newly formed sulfur compounds, and high boiling sulfur compounds. Common sulfur compounds which include mercaptans, low molecule sulfides and disulfides, are directly from C4, one of the stocks for production of MTBE. The newly formed sulfur compounds, with one sulfur atom and five or more total carbon atoms in one molecule, are mainly tert-butyl methyl sulfide and tert-butyl ethyl sulfide, thioetherification products of thiols with butenes. Many high boiling sulfur compounds, including polysulfides such as dimethyl trisulfide, multisulfur heterocyclic compounds such as 3,5-dimethyl-1,2,4-trithiolane, and oxygen-containing sulfur compounds such as 2-methoxy-3-methylthio-butane, are also found newly formed in the processes of LPG refining and succedent etherification reaction for producing MTBE. Polysulfides are additional products of elemental sulfur to disulfides, and other high boiling sulfur compounds may be formed by thiols reacting with dienes.
In recent years, alcoholic fuels have been considered as an alternative transportation biofuel even in compression ignition engines either as blended in diesel or as premixed fuel in the case of dual-fuel configuration. Within this framework, the authors investigated the possibility to improve the combustion efficiency when ethanol is used in a dual-fuel light duty diesel engine. In particular, the study was focused on reducing the HC and CO emissions at low load conditions, acting on the most influential engine calibration parameters. Since this kind of investigation would require a significant number of runs, the statistical design of experiment methodology was adopted to reduce significantly its number. As required by the DoE approach, a set of factors (injection parameters, etc.) were selected. For each of them, two levels “high” and “low” were defined in a range of reasonable values. Combining the levels of all the factors, it was possible to evaluate the effects and the weight of each factor and of their combination on the outputs. The results identified the rail pressure, the pilot, and post-injection as the most influential emission parameters. Significant reductions of unburnt were found acting on those parameters without substantial penalties on the global engine performances.
In 2012, a new specification for synthetic fuels containing up to 7% biodiesel (FAME) was approved (CEN TS 15940). This specification allows the sale of neat paraffinic diesel, such as Gas-to-Liquids (GTL) diesel, to captive fleets in Europe. Several aspects are important in the final end-use application, including the stability of the fuel. The current study evaluated the stability of neat GTL diesel and FAME/paraffinic fuel blends via standard laboratory stability tests commonly used to study petroleum-derived fuels. The stability of GTL diesel, containing biodiesel, was evaluated using the Rancimat, PetroOxy, and ASTMD2274 tests. Selected samples were also evaluated using ASTM D5304. The Rancimat results indicated that FAME/GTL diesel blends performed similar to the FAME/petroleum derived fuel blends. In the PetroOxy test, the addition of more than 2 v/v% of a highly stable FAME resulted in an unexpected boost in the stability of the FAME/GTL diesel blend. The ASTM D2274 results were generally insensitive to the addition of FAME. The correlation between the PetroOxy and Rancimant tests was evaluated and found to be base fuel dependent. From this study it was concluded that GTL diesel (in blends with FAME) performed similar to petroleum-derived reference fuels in standard laboratory stability.
For the production of bioethanol from lignocellulosic biomass, it is important to optimise the thermochemical pretreatment which is required to facilitate subsequent liberation of monomeric sugars. Here, we report optimisation of pretreatment conditions for brewers spent grains (BSG) with the main objectives of (1) working at commercially relevant high solids content, (2) minimising energy and chemical inputs, and (3) maximising downstream sugar yields. Studies indicated there to be a play-off between pretreatment solids content, the usage of an acid catalyst, and pretreatment temperature. For example, yields of 80–90% theoretical glucose could be obtained following pretreatment at 35% w/v solids and 200°C, or at 140–160°C with addition of 1% HCl. However, at very high solids loadings (40–50% w/v) temperatures of 180–200°C were necessary to attain comparable sugar yields, even with an acid catalyst. The feasibility of producing bioethanol from feedstocks generated using these protocols was demonstrated (but not optimised) at laboratory scale.
The performance of a direct hydrocarbon phosphoric acid fuel cell, PAFC, was investigated using petroleum diesel, biodiesel, and n-hexadecane as the fuels. We believe this is the first study of a fuel cell being operated with petroleum diesel as the fuel at the anode. Degradation in fuel cell performance was observed prior to reaching steady state. The degradation was attributed to a carbonaceous material forming on the surface of the anode. Regardless of the initial degradation, a steady-state operation was achieved with each of the diesel fuels. After treating the anode with water the fuel cell performance recovered. However, the fuel cell performance degraded again prior to obtaining another steady-state operation. There were several observations that were consistent with the suggestion that the carbonaceous material formed from the diesel fuels might be a reaction intermediate necessary for steady-state operation. Finally, the experiments indicated that water in the phosphoric acid electrolyte could be used as the water required for the anodic reaction. The water formed at the cathode could provide the replacement water for the electrolyte, thereby eliminating the need to provide a water feed system for the fuel cell.
