Catalytic effect of alkali carbonates on CO_2 gasification of Pingshuo coal

Na2CO3, Li2CO3, and K2CO3 were used as additives to Pingshuo （PS） coal that was subsequently gasified under a CO2 stream. The catalytic gasification of coal samples by CO2 in the presence single or mixed alkali carbonates was investigated by thermogravimetric analysis. The experimental results indicate that the catalytic effect of Li2CO3 is significantly larger than that of Na2CO3 or K2CO3. The catalytic effect of the mixed, bi-metal carbonate containing Li2C03 and Na2C03, or Li2CO3, and K2C03, is related to the compo- sition of the catalyst and the proportion of the two components. The bi-metal carbonates having a mole ratio of 9：1 （lri：x） has the largest catalytic effect for PS coal gasification. A synergistic effect between Li and K, or Na, carbonate appears at temperatures greater than 1300 K. An un-reacted shrinking core model is suitable for kinetic analysis of catalytic gasification of coal samples in the presence of alkali carbonates. It is inappropriate, however, to evaluate the catalytic effect only by the activation energy obtained from the kinetic calculations.

Effect of Alkali Carbonate/Bicarbonate on Citral Hydrogenation over Pd/Carbon Molecular Sieves Catalysts in Aqueous Media

The efficient citral hydrogenation was achieved in aqueous media using Pd/CMS and alkali additives like K2CO3. The alkali concentrations, reaction temperature and the Pd metal content were optimized to enhance the citral hydrogenation under aqueous media. In the absence of alkali, citral hydrogenation was low and addition of alkali promoted to ~92% hydrogenation without reduction in the selectivity to citronellal. The alkali addition appears to be altered the palladium sites. The pore size distribution reveals that the pore size of these catalysts is in the range of 0.96 to 0.7 nm. The palladium active sites are also quite uniform based on the TPR data. The catalytic parameters are correlated well with the activity data.

Effect of alkali metals on the performance of CoCu/TiO_2 catalysts for CO_2 hydrogenation to long-chain hydrocarbons

CoCu/TiO_2 catalysts promoted using alkali metals（Li, Na, K, Rb, and Cs） were prepared by the homogeneous deposition-precipitation method followed by the incipient wetness impregnation method. The influences of the alkali metals on the physicochemical properties of the CoCu/TiO_2 catalysts and the catalytic performance for CO_2 hydrogenation to long-chain hydrocarbons（C_（5＋））were investigated in this work. According to the characterization of the catalysts based on X-ray photoelectron spectroscopy, X-ray diffraction, CO_2 temperature-programmed desorption（TPD）, and H_2-TPD, the introduction of alkali metals could increase the CO_2 adsorption and decrease the H_2 chemisorption, which could suppress the formation of CH_4, enhance the production of C_（5＋）, and decrease the hydrogenation activity. Among all the promoters, the Na-modified CoCu/TiO_2 catalyst provided the maximum C_（5＋） yield of 5.4%, with a CO_2 conversion of 18.4% and C_（5＋） selectivity of42.1%, because it showed the strongest basicity and a slight decrease in the amount of H_2 desorption;it also exhibited excellent catalytic stability of more than 200 h.

Electrochemical manufacturing of nanocarbons from carbon dioxide in molten alkali metal carbonate salts： roles of alkali metal cations

One simple and fast way to manufacture a useful product from CO2 is to capture the gas by, and then carry out electrolysis in molten alkali metal carbonates. Carbon electro-deposition in molten Li2CO3-Na2CO3- KaCO3 （molar ratio： 43.5：31.5：25.0） has been widely reported in literature. However, studies in each of the individual alkali metal carbonates either have received less attention or are simply lacking in literature. Electrochem- ical studies of these molten carbonates are important to understand their underlying processes and reactions during the electrolysis. In this work, cyclic voltammograms （CVs） were recorded in each of the above-mentioned molten alkali carbonate salts using a 0.25 mm diameter Pt wire working electrode. In molten Na2CO3 and K2CO3, the main cathodic reaction was likely the formation of alkali metal, while that in Li2CO3 was carbon deposition. The results also suggest that other competing reactions such as CO and alkali metal carbide formation are possible as well in dif- ferent molten salts. On the CVs, the anodic current peaks observed are mostly associated with the oxidation of cathodic products. Flake/ring/sheet-like structures and quasi-spherical particles were observed in the produced carbon. The morphology of the carbon contained both amorphous and graphitic structures, which varied with different electrolysis variables.

Experimental on C50 Ultra-high-early Strength Concrete

In this paper,C50 ultra-high-early-strength concrete was prepared with rapid-harden sulphoaluminate cement,alkali carbonate early strength agent,inorganic tribasic acid retarder and polycarboxylate water reducing agent. The properties testing results of C50 ultra-high-early-strength concrete indicated that the compressive strength at 12 h exceeded 37 MPa and at 3 d exceeded 59 MPa. Compared to the C50 ordinary reference concrete,the durability of C50 ultra-high-early strength concrete was investigated. The results indicated that C50 ultra-high-early-strength concrete had the same chloride ion permeability resistance,carbonization resistance and abrasion resistance to the C50 ordinary concrete. As to the sulfate resistance,the ultra-high-early-strength concrete was much better than the ordinary concrete.