Hydrodeoxygenation of microalgae oil to green diesel over Pt, Rh and presulfided NiMo catalysts

Abstract

The catalytic characteristics, activity and selectivity of 1% Pt/Al 2 O 3 , 0.5% Rh/Al 2 O 3 and presulfided NiMo/Al 2 O 3 catalysts have been investigated in hydrodeoxygenation of microalgae (Nannochloropsis salina) oil to produce green diesel in a microreactor. Coke accumulation decreased in the order NiMo > Pt > Rh. The amount of formed coke over NiMo increased with reaction duration, while no on-stream time dependence was found over Pt and Rh. Rhodium was found to be very active for CH 4 production via hydrocracking at its fresh reduced state. The activity and selectivity of all three investigated catalysts were positively affected by increased reaction pressure, temperature, H 2 /Oil ratio and residence time. The selectivity of NiMo for hydrodehydration (DHYD) route was changed to Hydrodecarbonylation/Hydrodecarboxylation (DCO/DCO2) route at reduced H 2 /Oil ratio and residence time, while the selectivity of Pt and Rh for DCO/DCO2 route was not affected by reaction conditions. The highest hydrocarbon yield, 76.5%, was obtained over 1% Pt (310 o C, 500 psig, 1000 SmL/mL gas/oil ratio, 1.5s residence time), which is 13.8% higher than that over NiMo (360 o C, 500 psig, 1000 SmL/mL gas/oil ratio, 1s residence time). The 50 o C decrease in reaction temperature for Pt indicates a possible energy saving via heat supply. IntroductionOver the next few decades, as economies expand and evolve, the global energy demand for transportation is expected to continue to grow significantly. It is estimated that global demand for energy for commercial transportation will rise by 70 percent from 2010 to 2040. Due to its affordability, availability, portability and high energy density, liquid fuel, including gasoline, diesel, jet fuel and fuel oil, will remain the energy of choice for most types of transportation. Seventy-five percent of the heavy-duty transportation energy requirements are met by diesel fuel, due to its widespread availability and the robust ability of diesel engine technology to handle heavy loads. With an estimate of about 80 percent growth in heavy-duty transportation fuel requirements, demand for diesel is expected to grow sharply by about 75 percent from 2010 to 2040 [1]. Petroleum diesel is refined from crude oil, and approximately 12 gallons of diesel fuel can be produced from each 42-gallon barrel of crude oil [2]. The CO 2 emissions from diesel can be calculated based on its carbon content, 2,778 g per gallon diesel, 3 which is 10,084 g CO 2 per gallon diesel [3]. Therefore, the combination of continued crude oil depletion, the ever-growing need for renewable energy resource, and the CO 2 emission problem, are a motivation for research and development into advanced biofuels.It has been reported that the oleaginous feedstock, the main components of which are triglycerides and free fatty acids, has higher energy content than the lignocellulose[4].Microalgae, as a source of oleaginous feedstock for green diesel production is currently attracting attention of researchers. Green diesel, produced from hydrotr...

Fe/Indonesian Natural Zeolite as Hydrodeoxygenation Catalyst in Green Diesel Production from Palm Oil

“…In general, the consumption of H2 gas used to catalyzed palm oil decreased with time. This phenomenon is due to the added hydrogen gas consumed during the HDO reactions and automatically turned into several liquid and gas phases, such as: H2O, CO, CO2, CH4, and propane, as already published in previous papers [32]. The rate of H2 consumption obtained from this study using NZ and modification with Fe metal as heterogeneous catalysts can be seen in Figure 7.…”

The Catalytic Reduction of Carboxylic Acid Derivatives and CO2 by Metal Nanoparticles on Lewis‐Acidic Supports

“…Triglycerides and fatty acids from microalgae and jatropha are considered promising candidates for renewable resources of biofuels . The hydrogenation of triglycerides and fatty acids reduces their high content of oxygen and produces higher alkanes suitable as diesel fuels . Among the three hitherto reported methods for the deoxygenation of fatty acids, hydrodeoxygenation, which produces hydrocarbons without cleavage of C−C bonds in the fatty acids, is more atom‐efficient than decarbonylation and decarboxylation, which also cleave C−C bonds in fatty acids ,,.…”

Kinetic study of hydrodeoxygenation of palmitic acid as a model compound for microalgae oil over Pt/γ-Al2O3

“…As reported previously, microalgae oil contains mainly C14 to C20 fatty acids with C16 fatty acid being predominant in the Nannochloropsis salina strain, which is the workhorse of the algae industry. 5 Based on the experience on upgrading of vegetable oil, hydrotreating, which produces green diesel, is comparatively more advantageous than transesterification, the product of which is biodiesel. 6 Performance studies of hydrodeoxygenation (HDO), the most critical step in hydrotreating of microalgae oil [5][6][7] and vegetable oil [8][9][10] have been demonstrated over different catalysts.…”

“…This catalyst has been previously shown to have excellent performance in the HDO of microalgae oil, including inhibition of CH 4 and coke formation. 5 The objective of the current work is to establish a kinetic model with specified parameters that can be used in design of reactors for HDO of microalgae oil over Pt/γ-Al 2 O 3 , which makes both scientific and industrial contribution to the production of green diesel. In terms of complex reaction feedstocks, such as lingo-cellulosic biooils, the lumping kinetics approach can be used, in which the chemical species with similar chemical reactivity are grouped into pseudo-species, the so-called lumps.…”