Kinetic studies of a number of interesting and significant reactions involving activation of hydrogen, olefins, oxygen and carbon monoxide by solutions of rhodium complexes containing sulphur and/or chloride ligands are described. The cis 1,2,3-trichlorotris(diethylsulphide)rhodium (III) complex, RhCl(EtS₃and the corresponding dibenzyl sulphide complex, RhCl₃(Bz₂S)₃in N,N -dimethylacetamide (DMA) solution were found to be effective catalysts for the homogeneous hydrogenation of maleic, fumaric and trans-cinnamic acids. The kinetic data are consistent with a dissociation of a sulphur ligand prior to the hydrogen reduction of rhodium (III) to rhodium (I). The rhodium (I) is stablized in solution by rapid complexing with the olefin to produce a Rh¹(olefin)(Ln) complex (L = auxiliary ligands) which then reacts with H₂ in a rate determining step to produce the saturated paraffin and rhodium (I). In some instances, more complex kinetics resulted when one of the auxiliary ligands in the Rh¹ (olefin)(Ln) complex dissociates prior to reaction with H(2); a unique apparent zero order in catalyst concentration has been observed. Isomerization was observed in the RhCl(EtS)₃catalyzed hydrogenation of fumaric acid and a mechanism involving rhodium (III) alkyl intermediate seems likely. The cyclooctene complex, [Rh(C8H14)₂C1], in DMA was found to be a convenient source for preparing rhodium (I) complexes "in situ" by adding the desired ligands, for example, chloride or diethyl sulphide. Kinetic data obtained using such solutions are in good agreement with the hydrogenation data obtained by starting from the corresponding rhodium (III) complexes. This result confirms that rhodium (I) intermediates are involved in the catalytic hydrogenation starting from rhodium (III) complexes. During studies to investigate the effect of solvent on catalytic hydrogenation of olefins by rhodium (III) complexes, dimethyl sulphoxide (DMSO) was found to be catalytically reduced by hydrogen to dimethyl sulphide and water in the presence of RhCl(EtS)₃ and RhCl‧3H2O. The kinetics were consistent with a rate determining heterolytic splitting of H₂ by Rh(III)(DMSO) to produce Rh[III](DMSO)H¯ which then decomposes to the products in a fast step. RhCl₃‧3H₂O also catalyzed the oxidation of DMSO to dimethyl sulphone using a mixture of oxygen and hydrogen. The solution of [Rh(C8H14)₂C1]₂ in DMA containing LiCl was found to be a versatile catalyst, for besides the activation of hydrogen and olefins, oxygen and carbon monoxide could also be activated. The formation of a rhodium (I) molecular oxygen complex, Rh(I)(O2) and a subsequent catalyzed oxidation of the DMA solvent and cyclooctene were studied in detail. The formation of the Rh(I)(O2) complex appears to be irreversible. An E.S.R. signal, possibly due to species such as Rh(II)(O2¯) was also observed. The kinetics of the oxidation suggest the equilibrium formation of the Rh(I)(O2) complex followed by a rate determining step to give the products. A free radical mechanism seems likely. Solutions of [Rh(C8H14)₂C1]₂ in LiCl/DMA readily reacted with carbon monoxide to form a Rh(I)(CO)₂ species. A solution of the oxygen complex was converted more slowly to the Rh(I)(CO)₂ species in a reaction whose observed rate was determined by the dissociation of the coordinated oxygen. Preliminary studies indicated that a mixture of CO and O₂ is converted catalytically to CO₂ by a solution of [Rh(C8H14)₂C1]₂ in LiCl/DMA. / Science, Faculty of / Chemistry, Department of / Graduate

Kinetic and spectroscopic studies on solutions of two iridium(I) complexes—trans-chlorocarbonylbis(triphenylphosphine)iridium(I), Ir(CO)Cl(PPh3)2, and μ-dichlorotetrakis (cyclooctene)-di-iridium(I) , [IrCl(C8H,14)2]2—are described, especially for reactions involving activa-tion of molecular H2, molecular O2, and olefins. The studies also illustrate the importance of solvent effects. The catalytic activity of Ir(CO)Cl(PPh3)2 for hydrogenation of maleic acid has been surveyed using a range of solvents—pyridine, dimethylsulfoxide (DMSO), dimethylacetamide (DMA), dimethylformamide (DMF), acetone, sulfolane, acetonitrile, nitromethane and formamide. Where activity is observed, the mechanism appears to involve activation of hydrogen by a square-planar four-coordinate Ir(I) olefin complex. The DMA, DMF and DMSO solvent systems, which are very similar in terms of coordinating ability and dielectric constant, do show catalytic activity and this results from the dissociation of a phosphine molecule from the iridium at some stage to form the required four-coordinate catalyst 1: [series of chemical reactions] The sulfolane system is more active than the DMA, DMF and DMSO systems, but shows much more complicated kinetics. The hydrogenation appears to proceed in part via the phosphine dissociation path outlined in the above scheme, but the major pathway involves a cationic inters mediate Ir (CO) (PPh3)2 (olefin)+, 2, formed via chloride dissociation from the five-coordinate olefin complex. Diethylmaleate is hydrogenated in sulfolane, however, primarily via the phosphine dissociation path. Solvents that are too strongly coordinating (pyridine) or too weakly coordinating (nitromethane) lead to catalytically inactive systems. The catalytic homogeneous hydrogenation of hexene-1, cyclooctene using DMA solutions of [IrCl(C8H14)2]2 involves a monomeric species. The strongly coordinating solvent or the added olefin are thought to cleave the chloride bridge in [IrCl^gH^^J^* The hydrogenation mechanism can be outlined as [series of chemical reactions] where Ir is a complex already containing coordinated olefin. Selective hydrogenation of cyclooctene in a mixture of cyclooctene and hexene-1, the catalytic isomerization of hexene-2 and the catalytic hydrogenolysis of molecular 02 to water, all using [IrCl(C8H 14)2]2 complex in DMA are described and discussed. Molecular 0 is activated by DMA solutions of [IrCl2(C8H14)2]2 containing excess chloride; the major species believed to be present in solution is [IrCl2(C8H14)2]2⁻ . The solution initially absorbs one 02 per iridium. Product characterization proved to be difficult but the solutions catalytically oxidize cumene likely via a hydroperoxide free radical intermediate and the data are discussed in terms of the following equilibria: [series of chemical reactions] During some preliminary studies to investigate possible activation of CO under mild conditions using Ir complexes in aqueous solutions, the iridium(III) dicarbonyl [Ph4As]⁺ [Ir(C0)2C14]⁻•2H20, and a new cluster carbonyl tentatively formulated [Ir(CO)2]n, were synthesized. / Science, Faculty of / Chemistry, Department of / Graduate

Rhodium(I)-bis(ditertiaryphosphine) complexes of the general formula Rh(P⁀P)₂Cl[P⁀P = Ph₂P(Ch₂)n PPh₂, n = 1-4, and (+)-diop (diop = 2,3-0 isopropylidene 2,3-dihydroxy-1,4 bis(diphenylphosphino)butane] have been prepared by treating [Rh(Ccyclooctene)C₂Cℓ]₂ with the appropriate ditertiaryphosphine. The n=1, and n=4 and diop species are five-coordinate in the solid state and in non-polar solvents, while the n=2 and 3 species contain ionic chloride. The cationic complexes Rh(P⁀P)₂ +X- were prepared from the Rh(P⁀P)₂ Cℓ species by adding AgX[X=SbF₆,PF₆,BF₄] . Reaction of the chloro complexes with borohydride has yielded the hydrides, H Rh(P⁀P)₂, for the n=2 and 3 diphosphines, and for (+)-diop. ¹H and ³¹P nmr, as well as visible spectral data, are presented: a solvent-dependent deshielding of ortho protons of the phenyl groups is observed in some of the complexes, and the ligand CH₂ protons are coupled to the rhodium in the Rh(Ph PCI^PPh^^ cation; the P atom in this bis(diphenylphosphino) ligand shows an unusual highfield shift on coordination to rhodium. Preliminary kinetic data for catalytic hydrogenation of methylene succinic0 acid or itaconic acid (IA) show that the cationic and hydrido complexes are more active than the corresponding chloro complexes, and that activity generally increases with increasing chain length of the diphosphine. The rhodium-bis(diop) complexes efficiently catalyze the asymmetric hydrogenation of a number of prochiral substrates, optical purities of >90% being obtained in the hydrogenation of N-acylaminoacrylic acids. Steric factors at the olefinic bond, and coordination of the -NHCOR group through the "^C=0 moiety, seem important in determining the hydrogenation rates. The rates are slower in the more strongly coordinating DMA compared to n-butanol-toluene mixtures. The solvent medium has little effect on the +degree of asymmetric induction, when using thre Rh[(+)-diop]2^ or HRh[(+)-diop]2 complexes, but reversal of product configuration is observed when using the Rh[(+)-diop]^Cl complex in DMA or in n-butanol-toluene mixtures. An unusual increase in optical purity of the product with increasing temperature has been observed in the hydrogenation of IA. Detailed kinetic and spectroscopic studies on the hydrogenation of IA catalyzed by HRh[(+)-diop] are explained in terms of a mechanism involving the formation of a metal alkyl via coordination of the olefinic substrate, followed by reaction with H2 to yield the saturated product (S.P.) and regenerated catalyst (equations [l]-[3]). A monodentate diop(diop*) is invoked: HRh(diop)2 _ HRh(diop)(diop*) [1] HRh(diop) (diop*) + olefin k Rh(diop) (diop*) (alkyl) [2] Rh(diop)(diop*)(alkyl) + > HRh(diop)(diop*) + S.P. [3] The initial hydride catalyst is slowly decomposed by protons of the acidic substrate to give Rh(diop)2+. To avoid this complication, a mechanistic study was carried out on the HRh(diop)2"Styrene-H2 system, which was found to proceed via the same mechanism as outlined in equations [l]-[3], A mechanistic study on the Rh(diop)2+BF^ -catalyzed hydrogenation of IA shows that the reaction proceeds mainly via the 'hydride' route: Rh(diop)2+ + H2 ^ Rh(diop)2H2+ [4] Rh(diop)2H2+ + IA v=^Rb(diop) (diop*) (H)2(IA)+ [5] Rh(diop) (diop*) (H)2(IA)+ > Rh(diop)2+ + S.P. [6] A complete inhibition of the hydrogenation by small amounts of added diop(diop:Rh>0.2) is tentatively attributed to formation of an inactive polymeric species: nRh(diop)2H2+ + diop > [Rh(diop)(diop*)H2+]n [7] The forward step of Reaction [4] was studied in detail in the absence of olefinic substrate. Spectroscopic and kinetic data are best explained in terms of dihydride formation via the consecutive reactions outlined in equation [8]: Rh(diop)„+ s . •> Rh(diop)(diop*)S+ ——• Rh(diop) (diop*) (H) „S+ [8] Rh(diop)2H2+ The dehydrogenation reaction was also studied. The reactions of [Rh(P~P)2]A complexes (A=C£,BF4) with C0,C>2,H2 and HC&(g) yield several new complexes. Thus the [Rh(P P)2XY] BF^ complexes rs rs r\ (P P = dpm,dpp;XY=CO, P P=dpm,dpe,dpp;XY=02, P P=dpp, (+)-diop: XY=H2, and rs P P=dpm,dpe,dpp;XY=HC&) were isolated and characterized. The solution 31 structures were determined using especially variable temperature P nmr spectroscopy. The formally six-coordinate rhodium(III) dioxygen and the dihydrido complexes were assigned cis geometries, whereas the HC£ complexes were more fluxional and cis geometries could only be assigned with certainty to the dpp complex; for dpm and dpe complexes, the limiting spectra could not be achieved even at -60°C. For the five-coordinate rhodium(I) CO complexes, the dpp complex has been assigned a TBP structure but the dpm complex is fluxional even at -60°C. Some stopped-flow kinetic data are presented for the addition of CO, 02, and B.^ to the Rh(P P>2 complexes. For the dpp system, the rate increased in the order CO>H2>02, although the reactions are not simple 1:1 single step additions, solvated species probably playing an important role (cf. equation [8]). / Science, Faculty of / Chemistry, Department of / Graduate

The purpose of this work was to investigate the catalytic activity in both hydrogenation and hydroformylation reactions of rhenium preparations which have not been previously characterized. Rhenium pentacarbonyl was prepared in good yield from rhenium heptoxide and carbon monoxide. The optimum conditions for preparation were 25 hours per gram of dry rhenium heptoxide at 250° under 3000 psig. (initial) of carbon monoxide. Rhenium chloropentacarbonyl was prepared in 62% yield from potassium chlororhenite and carbon monoxide at high temperatures and pressures. The iodopentacarbonyl was prepared in 29% yield from potassium perrhenate, methyl iodide, and carbon monoxide. The preparation of rhenium hydrocarbonyl was attempted using sever approaches; however, no indication of the hydrocarbonyl was observed. Hydrogenative decomposition of rhenium pentacarbonyl in benzene solutions yielded an active catalyst which upon analysis proved to be metallic rhenium. Other solvents besides benzene were used but in each case the catalyst appeared as a rhenium mirror which was difficult to remove from the container. The use of rhenium pentacarbonyl as a homogeneous hydrogenation catalyst failed in attempts to reduce hexene-1 and cyclohexanone. The hydrogenation was accomplished only when temperatures were used which were high enough to decompose the carbonyl (200-250°). The metallic rhenium catalysts were characterized against a variety of substrates. With the exception of styrene, the substrates were all reduced in the temperature range 160-200°. Comparatively, the most successful reductions were those of benzene (179/3350 psig. for 22 hours) and acetic acid (2000/4190 psig. for 16 hours). Notably, nitrobenzene required 198° for complete reduction. When activated charcoal was added to the rhenium pentacarbonyl-benzene solution, a slightly more active catalyst was obtained. However, milder conditions of hydrogenative decomposition were not achieved. The addition of iron, zinc, or tin to acidified solutions of ammonium perrhenate resulted in the formation of a "rhenium black" which exhibited catalytic activity in hydrogenation reactions. This catalyst was obtained in a quantitative yield when an excess of reductant was present at all times. Analysis of this catalyst (both quantitatively and qualitatively) indicated that this catalyst was a hydrated rhenium oxide, probably ReO_2•3H_2O or ReO_2•2½H_2O. The activity of these hydrated rhenium oxide catalysts was greater than that of the metallic rhenium catalysts in all cases. Using the hydrated rhenium oxide catalyst, the carbon-carbon double bonds of hexene-1, cyclohexene, and styrene were reduced at 90-130°/3400-3900 psig. Interestingly, the presence of this catalyst did not effect the reduction of cycloheptanone until a temperature of 167° was reached. The reduction of 2-propyn-1-ol at 163° yielded both saturated and unsaturated alcohol. Adam's catalyst resulted in total decomposition of this substrate at 250° with no reduction occurring at lower temperatures. Benzene was also reduced at relatively mild conditions (177°/3935 psig. for 14 hours) using a hydrated rhenium oxide catalyst; pyridine was reduced at 230°/4520 psig. in 22 hours. Acetic acid was reduced at a mild 156° in the presence of a hydrated rhenium oxide catalyst. This is comparable with other rhenium catalysts and much better than Adam's catalyst which will not reduce acetic acid at 250° and better than any other reported catalyst except those of rhenium. The catalysts prepared using iron as a reductant were more active than those which were obtained using zinc; however, this difference was not great in the reduction of most substrates. The hydrated rhenium oxide catalysts were used in the reduction of a series of bifunctional substrates which contained the possible combinations of carbon-carbon double bond, carbonyl, carboxyl, and nitro groups. These reductions were compared with Adam's catalyst in many cases. The olefinic bonds in allylacetone and 2-allylcyclohexanone were preferentially reduced using both the hydrated rhenium oxide catalyst and Adam's catalyst. However, the rhenium catalyst reduced crotonaldehyde to n-butanol while Adam's catalyst yielded n-butyraldehyde. The olefinic bonds in vinyl-acetic, maleic, crotonic, and undecylenic acids were reduced in preference to the carboxyl group using the rhenium oxide catalyst. Under milder conditions, Adam's catalyst also reduced vinylacetic acid to n-butyric acid as expected. The carbonyl group was reduced completely in the presence of the carboxyl group in levulinic acid using the rhenium oxide catalyst. The nitro group was reduced (in the presence of the rhenium catalyst) in preference to the carbon- carbon double bond, carboxylic, or carbonyl groups in m-nitrostyrene, p-nitrophenyl-acetic acid, and m-nitroacetophenone, respectively. The same results were obtained using Adam's catalyst in the reduction of m-nitroacetophenone. The ease of reduction of different groups using the hydrated rhenium oxide catalyst was in the order: aromatic ring < carboxyl < carbonyl < carbon-carbon double bond < nitro. The order was the same using Adam's catalyst except that the carboxylic acid group and aromatic system were not reduced at all in the latter case under conditions of 250°/4500 psig. for 24 hours. However, the order of ease of reduction using the rhenium catalyst in the reduction of mono-functional substrates was aromatic ring < carboxyl < nitro < carbon-carbon double bond < carbonyl. Thus, the nitro group exhibited a poisoning effect when present in bifunctional substrates. Generally, the activity of the catalysts prepared in this study are comparable with previously characterized rhenium catalysts. This applies especially to the reduction of benzene and acetic acid. Rhenium pentacarbonyl, rhenium iodopentacarbonyl, and rhenium hepta-sulfide were used as catalysts in the attempted hydroformylation of cyclohexene and hexene-1 . However, in the temperature range 30-260° no hydroformylation was observed other than that which resulted from iron impurities. However, increased hydrogenation of substrate and products occurred when a rhenium compound was added as a catalyst. Dicobalt octacarbonyl was prepared and used in the hydroformylation reaction for comparison. As reported, the yields of hydroformylated products was excellent.

Following the first liquid phase hydrogenation in the early part of the twentieth century, it was quickly recognized that catalytic reductions were convenient research and industrial tools. Through catalytic hydrogenations unsaturated compounds can be saturated, aldehydes transformed into alcohols, nitro groups changed into amines in one step and usually with nearly quantitative yields to mention only a few possibilities. The improvement of existing catalysts and the search for new catalytic materials has been an important phase of catalytic hydrogenation research. A good hydrogenation catalyst should be active toward a variety of substrates at relatively low temperatures, be selective in its action toward different functional groups, and should be resistant to "poisoning." However, one of the greatest deterring factors facing the research chemist as well as the industrial chemist in hydrogenations of organic compounds is the ease wit h which the ordinary active catalysts are poisoned. This poisoning, by a rather large variety of compounds, decreases the efficiency of the catalyst, even to a point where it becomes entirely inoperative. One method, in common use, of circumventing this problem is by the use of catalysts which are not affected by the presence of foreign substances. Two such catalysts that are in common use are molybdenum trisulfide and cobalt polysulfide. This resistance to poisoning is achieved at the expense of a marked decrease in the catalytic activity of these sulfide catalysts as compared to the more active and more easily poisoned platinum (Adams catalyst) or nickel (Raney nickel). From its position in the periodic table and from its electronic configuration the element rhenium (element number 75) and possibly some of its compounds, might well be expected to exhibit catalytic activity. Previous investigations have found this to be the case. Among other compounds and preparations of rhenium, rhenium heptasulfide has been found to be resistant to poisoning yet much more active than either molybdenum trisulfide or cobalt polysulfide. The purpose of this investigation was to establish the catalytic activity of other rhenium compounds, and in particular to investigate the activity of a compound closely related to rhenium heptasulfide, viz., rhenium heptaselenide. This evaluation was done by preparing rhenium heptaselenide and establishing the fact that it has catalytic activity. Once this was done attention was directed toward determining the method of preparation that would yield the most active catalyst. The next step was the trial of the catalyst with a variety of substrates; comparing the ease of reducibility of different functional groups and structural features. Having once extablished the catalytic powers of rhenium heptaselenide, attention was then turned toward an investigation of the poison resistance of the new catalyst. When these things were known a comparison and critical evaluation of rhenium heptaselenide as compared to Raney nickel, Adams' Catalyst, rhenium heptasulfide, molybdenum trisulfide and cobalt polysulfide were made.

The literature on the properties of quinazoline, with special attention to its preparation and its behavior on reduction, was reviewed. Quinazoline was prepared by a reaction sequence involving condensation of anthranilic acid with formamide to give 4-quinazolinone, followed by conversion of 4-quinazolinone to 4-chloroquinazoline by boiling with phosphorus pentachloride in phosphorus oxychloride, and then controlled hydrogenation of 4-chloroquinazoline. Quinazoline was hydrogenated using rhodium-on-alumina as catalyst under varied conditions. Four runs were made at low pressure (40-60 p. s. i. ) and room temperature; with aqueous hydrochloric acid; with anhydrous ethanolic hydrochloric acid; in glacial acetic acid; and under anhydrous neutral ethanol. In all these cases the only product found was 3,4-dihydroquinazoline, identified by its melting point and those of its HCl salt and picrate. Hydrogenation was also carried out at 2000 p. s. i. and 125 C. in anhydrous netrual ethanol. The bolatile products were identified as o-toluidine (2-24%), N^α-methyl-toluene-α, 2-diamine (20-66%), N^α, N^α-dimethyltoluene-α, 2-diamine (24-51%), and unidentified trace products (5-18%) (about 3% of total product is non-volatile). The N^α, N^α-dimethyltoluene-α, 2-diamine must result from reaction of N^α -methyltoluene-α, 2-diamine with methylamine produced by formation of o-toluidine; this reaction may be considered analogous to the conversion of alcohols to amines under similar conditions. The products were identified by gas chromatography, thin-layer chromatography, infrared and ultraviolet spectrometry, mass spectrometry, MNR spectrometry, elemental analysis and synthesis of authentic samples. The authentic samples of o-toluidine was obtained commercially. N^α-Methyltoluene-α, 2-diamine and N^α, N^α-dimethyltoluene-α, 2-diamine were both obtained by reaction of o-nitrobenzyl chloride with the appropriate amine, followed by catalytic reduction of the nitro group. Samples of several other possible products were also synthesized but the products were not found in the hynrogenation mixtures. N-Methyl- o-toluidine was obtained commercially. Toluene-α, 2-diamine and N^2-methyltoluene-α, 2-diamine (a new compound) were both prepared by the lithium aluminum hydride reduction of the corresponding amides, which were obtained by treating isatoic anhydride and N-methylisatoic anhydride, respectively, with aqueous ammonia. The synthesis of N-o-tolylmethanediamine was attempted by lithium aluminum hydride reduction of the corresponding urea and by a modified Mannich condensation, but it was found to be unstable.

Rhenium is a comparatively newly discovered element and its catalytic properties have been poorly characterized. Therefore, this study was made to investigate more completely the catalytic properties of rhenium and its compounds. A complete review of the literature has been made on the reductions of carboxylic acids and the use of rhenium and its compounds as contact catalysts. The primary aspect of this investigation is the reduction of carboxylic acids with main interest in rhenium heptoxide in situ prepared catalysts. Reductions on various solvents with ex sity prepared catalysts also were studied. There have been about one hundred and fifty catalytic reductions on thirty-eight different substrates using rhenium prepared catalysts. The compounds to be reduced were either reagent grade or distilled to insure reasonable purity. The substrate along with rhenium heptoxide for the in situ reductions was placed in a rocking bomb using a glass liner and charged with hydrogen to 2000 psi. (occasionally 300 psi.). The usual procedure was to maintain low initial temperatures and if no appreciable reduction was observed, the pressure drop being the criterion, successively higher temperatures were used until reduction occurred, if at all. Thus minimal conditions were assured.

No description available.

No description available.

The purpose of this research project was to evaluate the feasibility of producing hydrocarbons by liquid phase hydrogenation of carbon dioxide. Initial studies dealt with the evaluation of ruthenium (III) chloride over a wide range of reaction conditions. High conversions were observed and were found to vary with catalyst concentration, temperature and time. Conversion of carbon dioxide reached 73% after twenty-four hours at a catalyst concentration of 0.75g/mole of CO2 feed. The hydrogen to carbon dioxide ratio was found to have a significant effect on product distribution and amount of methane produced. For example, low ratios of H2/CO2 gave large amounts of high molecular weight hydrocarbons, while relatively more methane was formed at high H2/CO2 ratios. An attempt was made to determine whether the reaction was taking place in the gas phase or the liquid phase or both. A number of solutions were tested, with sodium hydroxide solutions exhibiting the best results. Since the carbon dioxide feed gas dissolves in this solution immediately to form carbonate species, it is assumed that the hydrogenation reaction takes place through a carbonate species in solution. This mechanism is supported by the observation that the carbonate molarity in solution strongly affected the conversion. The conversion of carbon dioxide over different molarities of sodium hydroxide was observed to exhibit a maximum at the concentration of sodium hydroxide, which give the maximum NaHCO3 concentration. Sodium carbonate and sodium bicarbonate solutions were also tested as starting reagents in the hydrogenation reaction. Conversion was found to be 10.68% for sodium carbonate and 15.88% for sodium bicarbonate, compared with 19% conversion of carbon dioxide under the same reaction conditions. These data suggest that the major part of the hydrogenation reaction takes place through a HCO3 species in solution. The rate of hydrogenation of sodium bicarbonate and sodium carbonate were found to be first order in catalyst concentration. A linear relationship was also found to exist between conversion of carbonate species and temperature in the range of 150-300°C. Three catalyst systems; RuCl3, Ru metal and 1% Ru supported on graphite were tested in the hydrogenation of carbon dioxide over sodium hydroxide solutions. One percent Ru on graphite exhibited the fastest rate at which equilibrium was achieved, with a 76-77% conversion of carbon dioxide to methane, and higher hydrocarbons being observed after 24 hours. Thea activity of Ru metal catalysts was observed to decrease during the course of the reaction, probably because of the loss of active catalyst sites, due to fusing of the catalyst on the surface of the glass liner. The rate of reaction between carbon dioxide and hydrogen over RuCl3 in the gas phase was found to be faster than the rate of this reaction in the liquid phase. In the gas phase reaction, equilibrium was achieved after 24 hours, with 89% conversion of carbon dioxide to methane and higher hydrocarbons, compared with 70% conversion in the liquid phase, under the same reaction conditions. One percent Ru supported on graphite exhibited a faster rate of reaction in the gas phase than in the liquid phase. But the rate of the reaction over Ru metal was faster in the liquid phase than in the gas phase. Table I summarized the comparison between the gas phase and the liquid phase hydrogenation reaction for the three catalytic systems under the same reaction conditions.