Gliserolün izobüten ile eterleşmesiyle yakıt katkısı üretimi

Etherification of glycerol with isobutene is an industrially promising reaction to produce glycerol tert-butyl ethers (GTBE) as renewable fuel additives. The desired ethers are the di-GTBE (DTBGE) and tri-GTBE (TTBGE) with better solubility in hydrocarbon fuels. In this thesis study, we have studied glycerol etherification with isobutene on solid acid catalysts in batch and flow reactor systems for the enhanced production of the desired ethers. Our literature review pointed out to the usability of the cost effective and commercial solid acid catalysts in this reaction. A thorough catalysts screening study was conducted, for the first time in literature, with over 70 solid acid catalysts including ion exchange resins, zeolites, mesoporous silica and heteropolyacids under identical conditions in a multiple batch reactor system. The commercial Amberlyst™ ion exchange resins and zeolite H-Beta yielded more than 80 wt% selectivity to DTBGE and TTBGE. Desired ether selectivity was observed to increase with increasing acid strength for zeolites and mesoporous silica supported heteropolyacids, ascertained by ammonia temperature programmed desorption (NH3-TPD) experiments. We modified Amberlyst 15™ ion exchange resin by partially exchanging the H⁺'s of its sulfonic acid sites with Na⁺. Acid strength of the remaining sulfonic acid sites increased with increasing Na⁺-exchange, determined by our Fourier Transform Infrared Spectroscopy (FTIR) based method, and was further validated by the density functional theory (DFT) calculations. Batch reactor measurements at high glycerol conversion illustrated the enhancement in the desired ether selectivity together with the suppression of isobutene dimerization with an increase in acid strength. Furthermore, a laboratory scale once-through fixed-bed tubular flow reactor was exploited for the first time in literature. The minimum eligible Amberlyst 15™ catalyst particle size without pressure drop was ascertained to be 250 microns. The estimated Mears and Weisz-Prater parameters indicated that the 250-425 micron particle size fraction had negligible external and internal mass transfer resistance throughout the whole glycerol conversion range. Flow reactor tests at differential glycerol conversion revealed the formation of DTBGE and TTBGE as primary products at high acid strength. Moreover these desired products were obtained at significantly faster rates in the flow reactor compared to the batch reactor. For instance, the corresponding rates of desired ether production in volume basis were 7400 gDTBGE + TTBGE × (Lcat × h)-1 and 66 gDTBGE + TTBGE × (Lreactor × h)-1, in the flow and batch systems, respectively. Data also demonstrated that the catalyst activity remained the same for an extended time-on-stream of at least two days. We then prepared fuel additive mixtures with different concentrations of GTBE. The density, water solubility and viscosity of the GTBE mixtures decreased with increasing TTBGE content, corresponding to a decrease in the number of hydroxyl groups. Blending 3.45 vol% TTBGE-rich (34 wt% TTBGE) GTBE in gasoline enhanced the octane number and reduced the vapor pressure. Power and emission tests in a gasoline engine dynamometer, performed for the first time in literature, indicated the commercial potential of GTBE as a replacement of the conventional gasoline oxygenate methyl tert-butyl ether (MTBE), due to the fact that their blends provided similar torque values, specific fuel consumption and mean emissions of CO2, CO, NOx and total hydrocarbon emissions (THC).