Synthesis of a magnetic-separated chitosan-palladium complex and its catalytic activity in the reaction of acrylic acid with iodobenzene

Progresses in chitin, chitosan, starch, cellulose, pectin, alginate, gelatin and gum based (nano)catalysts for the Heck coupling reactions: A review

Heck cross-coupling reaction (HCR) is one of the few transition metal catalyzed CC bond-forming reactions, which has been considered as the most effective, direct, and atom economical synthetic method using various catalytic systems. Heck reaction is widely employed in numerous syntheses including preparation of pharmaceutical and biologically active compounds, agrochemicals, natural products, fine chemicals, etc. Commonly, Pd-based catalysts have been used in HCR. In recent decades, the application of biopolymers as natural and effective supports has received attention due to their being cost effective, abundance, and non-toxicity. In fact, recent studies demonstrated that biopolymer-based catalysts had high sorption capacities, chelating activities, versatility, and stability, which make them potentially applicable as green materials (supports) in HCR. These catalytic systems present high stability and recyclability after several cycles of reaction. This review aims at providing an overview of the current progresses made towards the application of various polysaccharide and gelatin-supported metal catalysts in HCR in recent years. Natural polymers such as starch, gum, pectin, chitin, chitosan, cellulose, alginate and gelatin have been used as natural supports for metal-based catalysts in HCR. Diverse aspects of the reactions, different methods of preparation and application of polysaccharide and gelatin-based catalysts and their reusability have been reviewed.

Synthesis of the Graphene Supported Pd Composites as Catalyst for the Heck Reaction of Iodobenzene, Acrylic Acid and Triethylamine

Graphene-supported Palladium composites were prepared through irradiation of the mixture of K2C2O4, Pd and graphene oxide (GO) with UV light in the presence of ethylene glycol (EG). Since the two-dimensional sheet of GO has a huge surface area, the as-synthesized graphene supported Pd composites kept excellent catalytic activity. There is no reduction agents that were used in the process of synthesis of graphene supported Pd composites. The good yield of cinnamic acid could be obtained when using the as-synthesized graphene-supported Pd composites as a catalyst in the reaction of iodobenzene, acrylic acid and triethylamine in the water system. Furthermore, no obvious mass loss of catalyst could be observed when being used to catalyze the heck reaction multiple times.

Experimental design data for the zinc ions adsorption based on mesoporous modified chitosan using central composite design method

In the present study, new generation of silica-based mesoporous adsorbents were introduced for the removal of heavy metals with the aim of developing new adsorption technologies in water treatment. The magnetic nanoadsorbent, prepared by modification of SBA-15 with [3-(2-Aminoethylamino) propyl] trimethoxysilane (AEAPTMS)-functionalized chitosan, was applied for the removal of Zn²⁺ from aqueous solution. The synthesized Fe₂O₃@SBA-15-CS-AEAPTMS nanoadsorbent was thoroughly characterized using XRD, TEM, FTIR and BET analysis. In order to determine the optimum condition of Zn²⁺ adsorption on Fe₂O₃@SBA-15-CS-AEAPTMS (3 ml), the experiments were performed based on central composite design in a response surface methodology method. The obtained results were further studied using adsorption kinetic, isotherm and thermodynamic relations which revealed that Zn²⁺ adsorption was spontaneous and endothermic with enhanced adsorption efficiency achieved for higher contents of functional groups. In addition, according to the results, the adsorption process was best conformed to Langmuir isotherm (with R² > 0.99 and q_max = 107.21 mg g^-1) and pseudo second-order kinetic model (with R² > 0.999). The values of standard entropy (DS°) and activation energy (E_a) reduced as the initial concentration was increased and the dominant mechanism was found to be chemisorption.

Preparation of triethylene-tetramine grafted magnetic chitosan for adsorption of Pb(II) ion from aqueous solutions

In this paper, a novel triethylene-tetramine grafted magnetic chitosan was synthesized. The chemical structure and the percentage content of each element of chitosan and its derivatives were characterized by elemental analysis, infrared spectroscopy, solid state (13)C NMR, X-ray diffraction analysis and thermogravimetric analysis, respectively. Their surface topography was observed by the transmission electron microscope. The results of adsorption kinetics and adsorption thermodynamics showed the adsorption mechanism could be better described by the pseudo-second-order equation (R>0.999). The adsorption isotherm was well fitted by the Langmuir equation (R>0.999), and 0<R(L)<1. The maximum adsorption capacity was 370.63 mg/g at the optimized adsorption conditions, which were pH=6, T=298 K, t=1.5h, C(0)=200 mg/L and adsorbent dose is 500 mg/L. The rate-limiting step may be the chemical adsorption rather than mass transport. The adsorbent still exhibited very good adsorption performance after the fifth regeneration cycle. The mechanism for adsorption and desorption was discussed.