Conversion of Residual Palm Oil into Green Diesel and Biokerosene Fuels under Sub- and Supercritical Conditions Employing Raney Nickel as Catalyst

A comprehensive study of the thermal deoxygenation of palm residue under sub- and supercritical water conditions using Raney nickel as a heterogeneous catalyst is presented in this paper. Hydrothermal technology was chosen to replace the need for hydrogen as a reactant, as happens, for example, in catalytic hydrotreatment. Several experiments were carried out at different reaction temperatures (350, 370, and 390 °C) and were analyzed with different times of reaction (1, 3.5, and 6 h) and catalyst loads (5, 7.5, 10 wt.%). No hydrogen was introduced in the reactions, but it was produced in situ. The results showed the selectivity of biokerosene ranged from 2% to 67%, and the selectivity of diesel ranged from 5% to 98%. The best result was achieved for 390 °C, 10 wt.% catalyst load, and 3.5 h of reaction, when the selectivities equal to 67% for biokerosene and 98% for diesel were obtained. The Raney nickel catalyst demonstrated a tendency to promote the decarboxylation reaction and/or decarbonylation reaction over the hydrodeoxygenation reaction. Moreover, the fatty acid and glycerol reforming reaction and the water−gas shift reaction were the main reactions for the in situ H2 generation. This study demonstrated that a hydrothermal catalytic process is a promising approach for producing liquid paraffin (C11−C17) from palm residue under the conditions of no H2 supply.

Histamine Limits by Country: A Survey and Review

Histamine is a biogenic amine and a food safety hazard, and it is the only biogenic amine regulated by statute or HACCP Guidance. This paper reviews the regulations for histamine levels in fish in countries around the world, including maximum limits or levels and sampling procedures in different fish preparations. The maximum histamine levels, sampling plans, and fish products are listed. The country-by-country regulations for maximum histamine acceptance levels in some food products vary by a factor of 8, from 50 ppm in some countries to a maximum of 400 ppm in other countries. For similar food products, the maximum histamine levels vary by a factor of 4 (from 50 ppm to 200 ppm) in, for example, fresh tuna. The country-by-country sampling plans vary widely as well and these, too, are covered in detail. Molecules of histamine are formed from L-histidine molecules, an amino acid, by a decarboxylation reaction caused by a bacterial enzyme, histidine decarboxylase. Histamine can form in many different species of saltwater fish that have elevated levels of free L-histidine. Histamine formation is completely preventable, and these methods are described as well. Although there are multiple maximum histamine acceptance levels, rapidly chilling the fish immediately after harvest by any means available is the only method to stop the formation of histamine. Fishermen should rapidly chill the fish using ice, chilled seawater, dense cold brine, or air blast freezers as quickly as possible.

Synergistic Use of FTIR Spectroscopy and TG to Elucidate the Solid State THCA Decarboxylation Reaction Kinetics in THCA Standard and Cannabis Flower

<p>The decarboxylation of Δ9-tetrahydrocannabinolic acid (THCA) plays pivotal role in the potency of medical cannabis and its extracts. However, the literature data point out substantial variations in the process reaction rate and conversion efficacy due to variability of the temperature, heat transfer efficacy, raw material attributes, consequently resulting in incomplete decarboxylation, cannabinoid content decrease due to decomposition, evaporation, and possible side reactions. Our present work aims to draw attention to mid-infrared (MIR) spectroscopy for in-situ monitoring and decipher the THCA decarboxylation reaction in the solid state. The initial TG/DTG curves of THCA, for a first time outlined the solid-solid decarboxylation dynamics, defined the endpoint of the process and the temperature of the maximal conversion rate, which aided in the design of the further IR experiments. Temperature controlled IR spectroscopy experiments were performed on both THCA standard and cannabis flower by providing detailed band assignment and conducting spectra-structure correlations, based on the concept of functional groups vibrations. Moreover, a multivariate statistical analysis was employed to depict the spectral regions of utmost importance for the THCA→THC interconversion process. The principal component analysis model was reduced to two PCs, where PC1 explained 94.76% and 98.21% of the total spectral variations in the THCA standard and in the plant sample, respectively. The PC1 plot score of the THCA standard, as a function of the temperature, neatly complemented to the TG/DTG curve and enabled determination of rate constants for the decarboxylation reaction undertaken on several temperatures. Consequently, a progress in elucidation of kinetic models of THCA decarboxylation, fitting experimental data for both, solid state standard substance and a plant flower, was achieved. The results open the horizon to promote an appropriate process analytical technology (PAT) in the outgrowing medical cannabis industry.</p>

Synergistic Use of FTIR Spectroscopy and TG to Elucidate the Solid State THCA Decarboxylation Reaction Kinetics in THCA Standard and Cannabis Flower

<p>The decarboxylation of Δ9-tetrahydrocannabinolic acid (THCA) plays pivotal role in the potency of medical cannabis and its extracts. However, the literature data point out substantial variations in the process reaction rate and conversion efficacy due to variability of the temperature, heat transfer efficacy, raw material attributes, consequently resulting in incomplete decarboxylation, cannabinoid content decrease due to decomposition, evaporation, and possible side reactions. Our present work aims to draw attention to mid-infrared (MIR) spectroscopy for in-situ monitoring and decipher the THCA decarboxylation reaction in the solid state. The initial TG/DTG curves of THCA, for a first time outlined the solid-solid decarboxylation dynamics, defined the endpoint of the process and the temperature of the maximal conversion rate, which aided in the design of the further IR experiments. Temperature controlled IR spectroscopy experiments were performed on both THCA standard and cannabis flower by providing detailed band assignment and conducting spectra-structure correlations, based on the concept of functional groups vibrations. Moreover, a multivariate statistical analysis was employed to depict the spectral regions of utmost importance for the THCA→THC interconversion process. The principal component analysis model was reduced to two PCs, where PC1 explained 94.76% and 98.21% of the total spectral variations in the THCA standard and in the plant sample, respectively. The PC1 plot score of the THCA standard, as a function of the temperature, neatly complemented to the TG/DTG curve and enabled determination of rate constants for the decarboxylation reaction undertaken on several temperatures. Consequently, a progress in elucidation of kinetic models of THCA decarboxylation, fitting experimental data for both, solid state standard substance and a plant flower, was achieved. The results open the horizon to promote an appropriate process analytical technology (PAT) in the outgrowing medical cannabis industry.</p>

CO2(aq) concentration–dependent CO2 fixation via carboxylation by decarboxylase

Enzymatic carbon fixation is one of the most interesting processes in CO2 sequestration. A number of decarboxylases can catalyze the reversible decarboxylation reaction in vivo, while can strengthen the carboxylation...

Efficient non-noble Ni–Cu based catalysts for the valorization of palmitic acid through a decarboxylation reaction

The synergistic effect Ni–Cu in the bimetallic catalyst Ni–Cu/C improved the stability and reduction temperature as well as enhanced the catalytic activity for the decarboxylation of palmitic acid.

Asymmetric construction of six vicinal stereogenic centers on hexahydroxanthones via organocatalytic one-pot reactions

Inspired by the chemistry and biology of hexahydroxanthones, herein we report an organocatalytic Michael-Michael-Aldol-decarboxylation reaction that provides efficient access to biologically interesting fully substituted hexahydroxanthones bearing six contiguous stereogenic centers...

Experimental study of the hydrothermal reactivity of oxalic acid under high pressure

The thermal stability of organic acids has a close relationship with the formation mechanism of secondary pores in deep reservoirs. Experiments were conducted to investigate the thermal stability of oxalic acid under high pressure and the influence of K-feldspar on oxalic acid decomposition. The experiment temperatures were set in the range of 130-330°C and each experiment was performed for 72h under 60MPa. Results show that both temperature and K-feldspar have significant influence on the decomposition of oxalic acid. The oxalic acid decomposed slowly at temperatures less than 180°C, and most of the oxalic acid decomposed at temperatures between 180°C and 230°C. Besides, the decarboxylation reaction proceeded more slowly in the presence of K-feldspar than the mineral-free experiments, which is most likely attributed to the increasing pH caused by dissolution. In addition, because the decomposition rate of oxalic acid was low, the K-feldspar dissolution was not affected at temperatures lower than 230°C.