Alireza Saraeian

Bio: Alireza Saraeian is an academic researcher from Iowa State University. The author has contributed to research in topics: Pyrolysis & Hydrodeoxygenation. The author has an hindex of 9, co-authored 17 publications receiving 283 citations. Previous affiliations of Alireza Saraeian include New Mexico State University.

A comprehensive review on biodiesel purification and upgrading

Abstract: Serious environmental concerns regarding the use of fossil-based fuels have raised awareness regarding the necessity of alternative clean fuels and energy carriers. Biodiesel is considered a clean, biodegradable, and non-toxic diesel substitute produced via the transesterification of triglycerides with an alcohol in the presence of a proper catalyst. After initial separation of the by-product (glycerol), the crude biodiesel needs to be purified to meet the standard specifications prior to marketing. The presence of impurities in the biodiesel not only significantly affects its engine performance but also complicates its handling and storage. Therefore, biodiesel purification is an essential step prior to marketing. Biodiesel purification methods can be classified based on the nature of the process into equilibrium-based, affinity-based, membrane-based, reaction-based, and solid-liquid separation processes. The main adverse properties of biodiesel – namely moisture absorption, corrosiveness, and high viscosity – primarily arise from the presence of oxygen. To address these issues, several upgrading techniques have been proposed, among which catalytic (hydro)deoxygenation using conventional hydrotreating catalysts, supported metallic materials, and most recently transition metals in various forms appear promising. Nevertheless, catalyst deactivation (via coking) and/or inadequacy of product yields necessitate further research. This paper provides a comprehensive overview on the techniques and methods used for biodiesel purification and upgrading.

Deoxygenation of biomass pyrolysis vapors: Improving clarity on the fate of carbon

Abstract: Deoxygenating biomass pyrolysis vapors prior to condensation would ideally yield chemically stable and petroleum-miscible streams comprised primarily of hydrocarbons that could be integrated into the existing refinery infrastructure. Both in-situ and ex-situ catalytic fast pyrolysis have shown promising results in terms of product quality, i.e., lower acidity, higher heating values, and product stability. However, these improvements come at the expense of carbon loss as CO, CO2, and coke, as well as cracking of larger molecules (potentially more valuable) into smaller molecules. It is thus of utmost importance to track the carbon, both product distribution and carbon yields, in order to obtain the full picture of deoxygenation efficacy. Despite potentially interesting results reported in the literature, it is unfortunately difficult to compare the true ability of various catalyst systems for deoxygenating biomass pyrolysis vapors primarily due to insufficient product characterization and data reporting. In this review paper, it is argued that results ultimately need to be reported in terms of carbon yields of individual products. This would enable an accurate accounting of where the carbon ultimately resides after processing, which is required for a more conclusive comparison between various systems. This information would enable the identification of effective catalytic systems for pyrolysis vapor deoxygenation and accelerate the advancement of catalyst design. Additionally, hydrodeoxygenation is discussed as a promising process in terms of carbon recovery. This article aims to propose a set of standard criteria for future reports on deoxygenation of biomass pyrolysis vapors by scrutinizing the existing literature.

Enhancing bio-oil quality and energy recovery by atmospheric hydrodeoxygenation of wheat straw pyrolysis vapors using Pt and Mo-based catalysts

Abstract: Atmospheric hydrodeoxygenation (HDO) of wheat straw fast pyrolysis vapors was studied as a promising route for the production of renewable liquid transportation fuels. The performance of TiO2-supported Pt (0.5 wt%) and MoO3 (10 wt%) catalysts was compared to an industrial Mo-based catalyst using a bench scale reactor operated at atmospheric pressure and up to high biomass-to-catalyst ratios (B:C). Mass and energy balances were complemented by detailed bio-oil characterization including advanced methods such as GC×GC-ToF/MS or -FID and 13C NMR. At 50 vol% H2, all three HDO catalysts effectively reduced the oxygen content of the bio-oils to ∼7–12 wt% (dry basis) compared to a non-catalytic reference (23 wt% O). MoO3/TiO2 was least efficient in conversion of acids (TAN = 28 mg per KOH), while Pt/TiO2 and MoO3/Al2O3 obtained oils with TAN ∼ 13 mg KOH/g (non-catalytic = 66 mg KOH/g). Compared to the TiO2-supported catalysts, the industrial Mo/Al2O3 catalyst produced higher yields of coke at the expense of condensed bio-oil. MoO3/TiO2 performed similar to Pt/TiO2 in terms of deoxygenation and energy recovery of condensed bio-oil, and by increasing the H2 concentration to 90 vol% the energy recovery of bio-oil increased to 39 and 42% at 8 and 10 wt% O (d.b.), respectively. Pt/TiO2 showed the highest selectivity to aliphatics and the lowest coke yields, e.g. the coke yield at B:C ∼ 8 was only 0.6 wt% of fed biomass. This study demonstrates that by using low-pressures of hydrogen and appropriate HDO catalysts, the quality of bio-oil can be improved without severely compromising its quantity (carbon yield) as observed under catalytic fast pyrolysis conditions.

Cadmium removal from aqueous solution by low-cost native and surface modified Sorghum x drummondii (Sudangrass)

Abstract: In an attempt to find inexpensive and effective biosorbents and modification methods, cadmium sorption ability of native Sorghum x drummondii, commonly called sudangrass, and its modified biomass was studied for the first time. From several modified biosorbents, 0.05 M NaOH-modified sudangrass performed the best and hence was used for further experiments. Both sorbents were characterized and various parameters were investigated on their sorption performance. Equilibrium time was reduced from 90 to 20 min after modification. Intra-particle diffusion and pseudo-second order kinetic models were found as best-fitting models for sudangrass and NaOH-modified sudangrass, respectively. Langmuir isotherm model described equilibrium data with the highest accuracy. Maximum monolayer adsorption capacity of cadmium onto sudangrass and NaOH-modified sudangrass was obtained as 1.52 and 7.76 mg g−1, respectively, showing a five-fold improvement for cadmium sorption. Sorption mechanism and thermodynamic investigations suggested that cadmium removal by modified sudangrass is a chemisorption and endothermic process, while cadmium removal by sudangrass is predominantly physisorption and exothermic. This study indicated that both native and modified sudangrass sorbents are capable of removing cadmium ions from aqueous solution with modified biosorbent having a much higher potential for this application.

Removal of cadmium from wastewaters with low-cost adsorbents

Abstract: Instead of using commercial activated carbon or ion exchange resins, researchers have worked on inexpensive materials, such as wastes from industry and agricultural operations due to their outstanding adsorption behavior toward heavy metal ions. Low-cost adsorbents are easily and locally available in large quantities. The modification of these materials could considerably increase their sorption capacity. In this review, the technical feasibility of various low-cost adsorbents for removal of Cd(II) from wastewaters has been discussed. Due to widespread cadmium contamination and its toxicity, there is considerable interest to remove it before discharge into wastewater streams. Several factors affecting an adsorption process such as pH, contact time as well as the reported maximum adsorption capacity values are summarized. The subsequent regeneration and reuse of adsorbents has been given considerable attention and some adsorption studies using real wastewater samples were also discussed.