Modifiers in Rhodium Catalysts for Carbon Monoxide Hydrogenation: Structivity Relationships

Modifiers in Rhodium Catalysts for Carbon Monoxide Hydrogenation:
Structivity Relationships - May 1989

1.	Introduction, Scope and Approach						1
	1.1	Synthesis Gas Reactions					1
	1.2	Oxygenates					4
	1.3	Scope					8
	1.4	Approach and Structure-Activity Relationships					8
	1.5	Organization of Dissertation					14
References							19
2.	Background						20
	2.1	Oxygenates					20
		2.1.1		Manufacture			20
				2.1.1.1.		Modified Fischer-Tropsch	20
				2.1.1.2.		Iso-Synthesis	20
				2.1.1.3.		Homologation	21
				2.1.1.4.		Co-Production with MeOH	21
				2.1.1.5.		Modified Rh Catalysts-Based Processes	23
		2.1.2		Uses			24
	2.2	CO Hydrogenation					24
		2.2.1.		Reaction Pathway			24
		2.2.2.		Effect of Support and Modifiers			28
		2.2.3.		Effect of Metal Percursor			28
		2.2.4.		Role of Additives in CO-Hydrogenation			32
		2.2.5.		Effect of Alkali Modifier			32
		2.2.6.		Role of Alkali Modifier			36
		2.2.7.		Effect of MO Modifier			40
	2.3.	Catalysts Preparation: Effect of pH					48
	2.4.	Characterization					50
		2.4.1.		Ion-Scattering Spectroscopy (ISS)			50
				2.4.1.1.		Problems with ISS on Particulates	52
				2.4.1.2.		Previous Work on Catalysts	53
		2.4.2.		Transmission Electron Microscopy			55
				2.4.2.1.		Sample Preparation	56
				2.4.2.2.		Operation of the Microscope	57
				2.4.2.3.		Analysis and Interpretation of Images	57
				2.4.2.4.		Techniques for Bimetallic Catalysts	60
		2.4.3.		Nuclear Magnetic Resonance Spectroscopy			61
				2.4.3.1.		Previous Work on Adsorbed ¹³CO	63
		2.4.4.		X-Ray Photoelectron Spectroscopy			72
				2.4.4.1.		Charge Correction with Insulating Materials	72
				2.4.4.2.		Oxidation State of Molybdenum	74
				2.4.4.3.		Quantitative XPS on Supported Catalysts	75
		2.4.5.		Infrared Spectroscopy			78
		2.4.6.		Electron Spin Resonance Spectroscopy			80
References							82
3.	The Delplot Technique: A New and Simple Method for Reaction Pathway Analyses						95
	3.1.	Introduction					95
		3.1.1.		Introduction			95
		3.1.2.		Rank of a Product			99
		3.1.3.		Time Scales			102
		3.1.4.		Rate-Limiting Steps			103
		3.1.5.		Overview			104
	3.2.	Basic Delplot: Products of Primary Rank					105
		3.2.1.		Development			105
		3.2.2.		Rules for Basic Delplot			108
	3.3.	Extended Delplot					111
		3.3.1.		Development			111
				3.3.1.1.		First Order Reactions	112
				3.3.1.2.		Non-First Order Kinetics	115
				3.3.1.3.		Characteristics of Delplot Intercepts	116
				3.3.1.4.		Series-Parallel Reactions: Effective Order of Reaction	116
		3.3.2.		Rules for Extended Delplot			119
		3.3.3.		Effective Rank of Product			120
				3.3.3.1.		Definition	120
				3.3.3.2.		Derivation of Effective Product Rank Equation (EPRE)	121
				3.3.3.3.		Application of EPRE	124
	3.4.	Application to Fischer-Tropsch Synthesis and Oxygenate Synthesis Reaction Networks					125
	3.5.	Miscellaneous Delplots					129
		3.5.1.		Non-Integer Rank Delplot			129
		3.5.2.		Product-Based Delplot			131
	3.6.	Identification of Reaction Steps					134
		3.6.1.		Introduction			134
		3.6.2.		Example			135
		3.6.3.		Overall Scheme			140
	3.7.	Separation of Regimes					140
		3.7.1.		Order of Magnitude Analysis			140
		3.7.2.		Singular Perturbation Analysis			145
	3.8.	Conclusions					150
References							152
4	Equipment and Experimental Methods						154
	4.1.	Flow Microreactor					154
	4.2.	Test Reactions					158
	4.3.	Analytical System					160
	4.4.	Static Chemisorption					160
	4.5.	Flow Chemisorption					161
	4.6.	X-Ray Diffraction					161
	4.7.	X-Ray Fluorescence Spectroscopy					161
		4.7.1.		Calibration			163
		4.7.2.		Effect of Particle Size on the Selection of Standards			163
	4.8.	X-Ray Photoelectron Spectroscopy					164
	4.9.	Temperature Programmed Methods					167
	4.10.	Electron Spin Resonance Spectroscopy					169
	4.11.	Ion-Scattering Spectroscopy					170
	4.12.	Transmission Electron Microscopy and EDX					170
	4.13.	Solid-State NMR Spectroscopy					170
	4.14.	Low Pressure IR					171
References							174
5	The Effect of Support, Modifiers and Catalyst Precursor in CO Hydrogenation						175
	5.1		Introduction				175
	5.2		Catalysts Preparation				175
	5.3		Results and Discussions				178
			5.3.1.		Rhodium Precursor		178
			5.3.2.		Support		182
			5.3.3.		Modifiers		184
					5.3.3.1.	Rh/Al₂O₃	184
					5.3.3.2.	Rh/SiO₂	188
					5.3.3.3.	Rh/TiO₂	192
					5.3.3.4.	Rh/Florisil	197
			5.3.4.		Alloying with Pd		198
			5.3.5.		Modification by Sodium		198
			5.3.6		Modification by Molybdena		201
5.4.	Conclusions						203
References							206
6	Performance of Sodium Modified Rhodium/Alumina Catalysts						207
	6.1.		Catalysts Preparation				207
	6.2.		CO Hydrogenation				208
			6.2.1.		Activity		208
			6.2.2.		Product Distribution		209
			6.2.3.		Effect of Catalysts Pretreatment		215
			6.2.4.		Selectivity and Productivity		218
	6.3.		Transport Limitations				219
	6.4.		Basic Delplot Analysis				219
	6.5.		Extended Delplot Analysis				233
	6.6.		Conclusions				234
References							238
7	Characterization of Sodium Modified Rhodium/Alumina Catalysts						239
	7.1.		Hydrogen Chemisorption				239
	7.2.		X-Ray Diffraction				242
	7.3.		Infrared Spectroscopy				243
			7.3.1.		Stability of Adsorbed CO Species		247
			7.3.2.		Effect of Temperature		247
			7.3.3.		Effect of Reaction		250
	7.4.		X-Ray Photoelectron Spectroscopy				250
			7.4.1.		Chemical State of Rhodium		253
			7.4.2.		Chemical State of Sodium		255
			7.4.3.		Silanization Studies		257
			7.4.4.		Photoelectronic Responses		259
	7.5.		Temperature Programmed Methods				266
			7.5.1.		Effect of Sodium on the Reducibility of Rhodium		166
			7.5.2.		Effect of Sodium on Hydrogen Adsorption in Rh-Na/Al₂O₃		272
	7.6.		Discussion				272
			7.6.1.		Reactivity		272
			7.6.2.		Location of Sodium Modifier		274
			7.6.3.		Chemical State of Rh and Na		275
			7.6.4.		Formation of Mixed Oxide		276
			7.6.5.		Ensemble Requirement		276
	7.7.		Conclusions				277
References							278
8	Performance of Molybdena Modified Rhodium/Alumina Catalysts						280
	8.1.		Catalyst Preparation				280
	8.2.		Performance Testing Results				282
			8.2.1.		Overall Activity and Selectivity		282
			8.2.2.		Product Distribution		284
			8.2.3.		Approach to Steady State		288
	8.3.		Transport Limitations				291
	8.4.		Delplot Analysis				291
			8.4.1.		Basic Delplot Analysis		293
			8.4.2.		Separation of Regimes		300
			8.4.3.		Nature of Reaction Steps		302
	8.5.		Power Law Fit				302
	8.6.		Activation Energies				303
	8.7.		Ethylene Hydrogenation				308
	8.8.		Conclusions				311
References							313
9	Characterization of Molybdena Modified Rhodium/Alumina Catalysts						314
	9.1.		X-Ray Fluorescence Spectroscopy				314
	9.2.		CO Chemisorption				315
	9.3.		X-Ray Diffraction				317
	9.4.		Transmission Electron Microscopy and Energy Dispersive X-Ray Analysis				322
			9.4.1.		Bright Field Images		322
			9.4.2.		Energy Dispersive X-Ray Analysis		327
	9.5.		In-Situ Infrared Spectroscopy				327
	9.6.		X-Ray Photoelectron Spectroscopy				331
			9.6.1.		Binding Energies		331
			9.6.2.		Relative Photoelectronic Response		333
			9.6.3.		Estimation of Particle Size		337
			9.6.4.		Effect of pH of the Solution on Molybdena Aggregation		341
	9.7.		Electron Spin Resonance Spectroscopy				342
	9.8.		Ion-Scattering Spectroscopy				346
	9.9.		Solid-State Nuclear Magnetic Resonance Spectroscopy				352
			9.9.1.		Chemical Shifts		352
			9.9.2.		Calculations		355
	9.10.		Discussions				358
	9.11.		Conclusions				371
References							372
10	Overall Conclusions and Recommendations						376
	10.1.		Overall Conclusions				376
	10.2.		Recommendations for Future Work				380
Appendix
A	Calculations of Possible Transport Limitations						382
	A.1		Mass Transfer				382
			A.1.1.		Axial Dispersion		382
			A.1.2.		Intraparticle Mass Transfer		385
			A.1.3.		Fluid to Particle Mass Transfer		385
	A.2		Heat Transfer				387
			A.2.1.		Fluid to Particle Heat Transfer		389
			A.2.2.		Intraparticle Gradients		390
References							392
B			Salient Features of the Theory of Relaxation of Nuclear Spins				393
			B.1.		Randomly Fluctuating Magnetic Field		393
			B.2.		Scalar Coupling of Spins		397
References							400